EPA-600/2-78-082
April 1978
Environmental Protection Technology Series
DEVELOPMENT OF MANAGEMENT GUIDELINES
TO PREVENT POLLUTION BY IRRIGATION
RETURN FLOW FROM RICE FIELDS
**
I
$322
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Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environments! Protection Agency
Ada, Oklahoma 74820
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-082
April 1978
DEVELOPMENT OF MANAGEMENT GUIDELINES TO PREVENT POLLUTION
BY IRRIGATION RETURN FLOW FROM RICE FIELDS
by
Kirk W. Brown
Lloyd Deuel
Jack Price
Don DeMichele
William R. Teague
Texas A&M University
College Station, Texas 77843
Fred Turner
Mike Jund
David Chance
Texas A&M University
Agricultural Research and Extension Center
Beaumont, Texas 77706
Grant No. S-802008
Project Officer
Arthur G. Hornsby
Source Management Branch
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
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DISCLAIMER
This report has been reviewed by the Robert S. Kerr Environmental
Research Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was established to coordinate
administration of the major Federal programs designed to protect the quality
of our environment.
An important part of the Agency's effort involves the search for informa-
tion about environmental problems, management techniques and new technologies
through which optimum use of the Nation's land and water resources can be
assured and the threat pollution poses to the welfare of the American people
can be minimized.
EPA1s Office of Research and Development conducts this search through a
nationwide network of research facilities.
As one of these facilities, the Robert S. Kerr Environmental Research
Laboratory is responsible for the management of programs to: (a) investigate
the nature, transport, fate and management of pollutants in groundwater;
(b) develop and demonstrate methods for treating wastewaters with soil and
other natural systems; (c) develop and demonstrate pollution control tech-
nologies for irrigation return flows; (d) develop and demonstrate pollution
control technologies for animal production wastes; (e) develop and demonstrate
technologies to prevent, control or abate pollution from the petroleum
refining and petrochemical industries; and (f) develop and demonstrate tech-
nologies to manage pollution resulting from combinations of industrial waste-
waters or industrial/municipal wastewaters.
This report contributes to the knowledge essential if the EPA is to meet
the requirements of environmental laws that it establish and enforce pollution
control standards which are reasonable, cost effective and provide adequate
protection for the American public.
William C. Galegar
Director
Robert S. Kerr Environmental
Research Laboratory
111
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ABSTRACT
A three year field and laboratory study was conducted to determine the
influence of management practices on the quantity and quality of irrigation
return flow from rice paddies. Continuous and intermittent irrigation tech-
niques were used on replanted field plots which received either recommended
or excessive applications of fertilizer and four selected pesticides. Water
quality was evaluated with respect to fertilizer amendments, pesticides, pH
and total salt load. Pesticides monitored included propanil, molinate,
carbofuran, carbaryl and their respective metabolites.
Present water management practices result in large return flow volumes.
Occasionally concentrations of NH, exceeded drinking water standards. Los-
ses as nitrate were below such limits and the total nitrogen losses were a
small fraction of the fertilizer applied. A model was developed to simulate
the ionic constituency of the return flow.
Propanil was washed from the foliage into the flood water and dissipat-
ed within 24 hours. Evidence is given that carbaryl is washed from the
leaves by rainfall, thus providing available source to contaminate return
flow. As long as 8 days were required to dissipate residue resulting from
recommended applications. Retention times to assure low concentrations in
the irrigation return flow for carbofuran are of the order of 16 days.
Granular applied molinate necessitates a retention time of 4 days to assure
concentrations are within 10% of the TLM to fish. Laboratory studies were
conducted to assess the primary modes of dissipation of the above pesti-
cides.
It is suggested that through improved water management and knowledge
of dissipation rates, the quantity of irrigation return flow can be re-
duced and the quality can be improved.
This report was submitted in fulfillment of Grant No. S-802008 by
Texas A&M University, Soil and Crop Sciences Department under the sponsor-
ship of the U.S. Environmental Protection Agency, This report covers the
period January 1, 1973 to January 17, 1976.
IV
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TABLE OF CONTENTS
Foreword • .......... ill
Abstract *v
List of Figures x
List of Tables .............. xxi
Acknowledgements ...... xxxiii
Section 1: Introduction . ......... 1
Section 2: Conclusions 3
Section 3: Recommendations 5
Section 4: Experimental Design ....... 7
Section 5: Experimental Procedures ................. 9
Description of Field and Soil 9
Field Procedures 9
Source of Irrigation Water .................. 9
Management of Irrigation Water .... 10
Lysimeters ............... 16
Application of Nutrients and Pesticides .16
Sampling 17
Water 17
Soil Solution Sampling .... 19
Soil Sampling 19
Special Field Experiments and Measurements .......... 20
Propanil Foliar Study . 20
Simulated Rainfall Washoff 20
Withholding Irrigation Water 21
Bulk Density 22
Root Distribution 22
Organic Load 22
Sediment Load , . 22
Meteorological Measurements . 22
Analytical Procedures . ..... 22
Soil Extractions and Analyses . 22
Analysis of Water Samples ........ ....23
Propanil and TCAB .23
Molinate 24
Carbofuran, 3-keto Carbofuran,and 3-hydroxy Carbofuran ... 25
Carbaryl and 1-Naphthol 25
Laboratory Experiments , . ......26
Pesticide Dissipation • 26
Volatilization 26
Photodecomposition 26
Adsorption ..... ......... 28
Biological and Chemical Degradation .......28
-------
ABSTRACT
A three year field and laboratory study was conducted to determine the
influence of management practices on the quantity and quality of irrigation
return flow from rice paddies. Continuous and intermittent irrigation tech-
niques were used on replanted field plots which received either recommended
or excessive applications of fertilizer and four selected pesticides. Water
quality was evaluated with respect to fertilizer amendments, pesticides, pH
and total salt load. Pesticides monitored included propanil, mblinate,
carbofuran, carbaryl and their respective metabolites.
Present water management practices result in large return flow volumes.
Occasionally concentrations of NH, exceeded drinking water standards. Los-
ses as nitrate were below such limits and the total nitrogen losses were a
small fraction of the fertilizer applied. A model was developed to simulate
the ionic constituency of the return flow.
Propanil was washed from the foliage into the flood water and dissipat-
ed within 24 hours. Evidence is given that carbaryl is washed from the
leaves by rainfall, thus providing available source to contaminate return
flow. As long as 8 days were required to dissipate residue resulting from
recommended applications. Retention times to assure low concentrations in
the irrigation return flow for carbofuran are of the order of 16 days.
Granular applied molinate necessitates a retention time of 4 days to assure
concentrations are within 10% of the TLM to fish. Laboratory studies were
conducted to assess the primary modes of dissipation of the above pesti-
cides.
It is suggested that through improved water management and knowledge
of dissipation rates, the quantity of irrigation return flow can be re-
duced and the quality can be improved.
This report was submitted in fulfillment of Grant No. S-802008 by
Texas A&M University, Soil and Crop Sciences Department under the sponsor-
ship of the U.S. Environmental Protection Agency. This report covers the
period January 1, 1973 to January 17, 1976.
IV
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TABLE OF CONTENTS
Foreword iii
Abstract , iv
List of Figures , x
List of Tables xxi
Acknowledgements ..... xxxiii
Section 1: Introduction ..... ..... 1
Section 2: Conclusions . ..... 3
Section 3: Recommendations 5
Section 4: Experimental Design . ..... 7
Section 5: Experimental Procedures . . 9
Description of Field and Soil 9
Field Procedures ........... ..... 9
Source of Irrigation Water ....... ... 9
Management of Irrigation Water ... ....... 10
Lysimeters .16
Application of Nutrients and Pesticides .16
Sampling . 17
Water 17
Soil Solution Sampling ..... 19
Soil Sampling 19
Special Field Experiments and Measurements ..... 20
Propanil Foliar Study 20
Simulated Rainfall Washoff 20
Withholding Irrigation Water 21
Bulk Density 22
Root Distribution 22
Organic Load 22
Sediment Load 22
Meteorological Measurements 22
Analytical Procedures . ......22
Soil Extractions and Analyses 22
Analysis of Water Samples 23
Propanil and TCAB 23
Molinate * .... 24
Carbofuran, 3-keto Carbofuran,and 3-hydroxy Carbofuran ... 25
Carbaryl and 1-Naphthol . 25
Laboratory Experiments ...... . 26
Pesticide Dissipation . 26
Volatilization 26
Photodecomposition . 26
Adsorption ..... 28
Biological and Chemical Degradation . ..... 28
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Toxicity of Pesticides to Fish 28
Static Bioassays . ....•••• 32
Intermittent Flow Bioassays ..... 32
Toxicant delivery system ............•••• 32
Water delivery system 32
Mixing and separation system 39
Ion Equilibrium Studies 41
Section 6: Results and Discussion 43
Water Balance 43
Introduction • 43
Irrigation and Rainfall 44
Water Depth Data 45
Infiltration 47
Piezometer Data 53
Bulk Density 53
Moisture Content , 53
Root Distribution » 57
Meteorological Data 57
Estimated Evapotranspiration ..... . 57
Water Balance 70
Salts and Nutrients 75
Introduction 75
Electrical Conductivity 77
pH of the Water 80
Salts and Nutrients in the Water 83
Introduction 83
Cation Concentrations 91
Anion Concentrations 103
Treatment Effects 108
Cations 108
Anions 123
Salts in Soil Solution 123
Salts in the Soil Samples 133
Salt Balance . 133
Fate of Pesticides 136
Propanil 138
Residue Levels in the Paddy Water 140
Residue Levels of Metabolites ....... . 148
DCA 148
TCAB 150
Modes of Dissipation 150
Volatilization and photodecomposition 150
Adsorption 154
Biological degradation . 154
Molinate 154
Residue Levels in Paddy Water 154
Modes of Dissipation 164
Volatilization 164
Adsorption 165
Biological dissipation 168
Carbofuran 168
Residue Levels in Paddy Water 170
VI
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Residue Levels of Metabolites ............... 178
Modes of Dissipation . 178
Volatilization 178
Adsorption . 178
Biological degradation 183
Carbaryl 183
Residue Levels in the Paddy Water . ..... 185
Residue Levels of Metabolites . 189
Modes of Dissipation 194
Volatilization 194
Photodecomposition 194
Adsorption 194
Biological degradation 194
Carbaryl Summary 197
Pesticides in Canal Water 198
Toxicity of Pesticides to Fish 200
General 200
Bioassay Data 205
Organic Load 212
Rice Yields During the Study 214
Effect of Designed Treatment . 214
Effect of a Water Conservation and Pollution
Prevention Technique ....... 216
Model 216
A Model of Irrigation Return Flow 216
Development of the Program ...» 219
Solutions Available in the Literature 220
Analytical Solutions . 220
Numerical Solutions 220
Finite-Difference Methods ..... 220
Other Numerical Methods 222
Simultaneous Consideration of Several Solutes 222
The Use of Finite-Difference Solutions to the One
Dimensional Linear Convection-Diffusion
Equation 223
The Basic Equation and Boundary Conditions 223
Numerical Difficulties 224
Selected Finite-Difference Approximations 226
The explicit scheme 226
Chaudhari's scheme 228
Bresler's scheme 230
Stone and Brian's scheme 231
Second order explicit scheme ..... 231
Simulation Runs 234
Computer programs .... 235
Conditions and basis for comparison 235
Results of Comparisons 236
The explicit scheme 236
Performances of the other schemes 248
Summary • • ........... 254
Chemical Equilibrium Equations 254
Choice of a System 254
vii
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ions ........................ "4
Chemical interactions ...... ...» ......
Ions and interactions considered in the model ...»
Mathematical Description of Chemical Interaction:
Types of Equations ................
Ionic activity . . .............. « • '
Cation exchange ........ ......... •'
Ion-pairing ....... . .............
Conservation of charge among adsorbed cations . . . •
Total ion concentration ...............
Rearrangement of the System of Simultaneous
Equations .................... 26°
Iterative Solution of the Chemical Equilibrium
Equations ........ . ...........
Initial Estimates for Ci and v .............
977
Ion Transport Equations . ................. *' '
Physical Considerations .......... ....»• 277
978
The Ion-Flux Equations ................. z/0
The Finite-Difference Equations ............ 280
Calculation Procedure . ................ 290
Testing of the Model ..... » ............. 292
Introduction .................. .... 292
Simulation Runs Involving Two or Three Cations ..... 294
Effects chosen for observation ..... . ..... 294
Solution concentration pulses » . . . ........ 294
Simulated tests ........... . ....... 295
Results and Discussion ................. 295
Comparison of results from two-cation problems
with an independent numerical solution ...... 295
Effect of a second cation in the slug solution » . . 318
Effect of solution normality .. ....... ... 320
Effect of ionic activity ............. » 320
Effect of varying Q and CEC ............. 322
Effect of varying r, the mean pore velocity to
apparent diffusion coefficient ratio ....... 322
Effect of varying the exchange coefficients,
Ei2 and Ej3 ................... 323
Comparison of cation 2, cation 3 and anion 3
pulses ...... . ....... . ..... .. 324
Observed increases in pulse height ...... ... 325
Summary ...... . ................. 327
Conclusions ...................... 329
Determination of Equilibrium Coefficients ..... .... 330
Preliminary Experiment ................. 330
Experiment with Field Soil ............... 337
Evaluation of Exchange Coefficients ..... 0 ....... 348
Simulation of Irrigation Return Flow ........... 349
References ................. . „ ........ 354
Vlll
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Appendix A: Logs of Rainfall and Cultural Practices during
the 1973, 1974 and 1975 Growing Seasons 356
Appendix B: Climotogical Data during the 1973, 1974 and 1975
Growing Seasons 370
Appendix C: Detailed Chemical Analysis Methods for Soil,
Soil Solutions and Water Samples Taken from Rice
Paddies during the 1973, 1974 and 1975 Growing
Seasons 386
Appendix D: Daily Water Depths during 1974 and 1975 in
Each Plot 389
Appendix E: Minimum and Maximum Soil and Water Tempera-
tures in the Rice Paddies 396
Appendix F: Average Daily Water Balance in the Six Rice
Paddies for Each Irrigation Treatment for
1974 and 1975 Growing Seasons „ . „ 405
Appendix G: Analysis of Variance for Various Ions and
the Electrical Conductivity of the Rice
Paddy Water for the 1974 and 1975 Growing
Seasons 420
Appendix H: Concentrations of Individual Ions in Paddy
Water during 1973, 1974 and 1975 Growing
Seasons 441
Appendix I: Analysis of Variance for Molinate, Carbofuran and
Carbaryl in Rice Paddy Water during 1973, 1974
and 1975 Growing Seasons ....... 481
Appendix J: Analytical Solution to the One-Dimensional
Linear, Convection-Diffusion Equation 491
Appendix K: Transformation of the Chemical Equilibrium
Equations . ... 0 .... 0 493
Appendix L: Listing of the Model 499
Appendix M: Users Guide to the Model . . . . «, . „ . „ 547
Appendix N: Finite-Difference Verification of Partial
Derivations 559
Appendix 0: Analysis of Covariance for Adsorbed and Solution
Cation Concentrations ....<, 567
IX
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LIST OF FIGURES
1 View of the field before planting showing levees, stand
pipes ready for the installation of water stage recorders
and a lysimeter box behind the stand pipe located to the
left of the photograph ........ .....
2 View of field plots showing outflow weirs and the boardwalks
used for access to plots. A water stage recorder can
be seen in the upper right quadrant of the photograph* .... 12
3 Schematic diagram of two of the research plots showing
water control devices. ............••» ..... 13
4 A water flow regulating float valve, stilling chamber
and weir used to maintain continuous flow plots . ....... 14
5 Schematic diagram of water stage recorder mounting and
stilling well ......................... 15
6 Schematic of apparatus used to determine volatilization
potentials .......... . ....... . ........ 27
7 Apparatus for obtaining simulated flood water condi-
tions ............................. 29
8a A composite overall diagram of the intermittent flow
apparatus ........ ...... ..... ... ..... 33
8b Schematic diagram of the intermittent flow system showing
CA) the water delivery system, (B) the toxicant delivery
system, (C) the mixing and splitting apparatus and (D) the
exposure chamber and overflow tube. .............. 34
9 A schematic diagram of the toxicant delivery system and
metering device where: (1) is the toxicant reservoir
tank (20 I glass bottle), (2) is the toxicant head tank,
(3) is the toxicant over flow standpipe, (4) is the chem-
ical pump, (5) is the toxicant delivery tube manifold,
(6) is the toxicant metering device, (7) is a siphon
(5mm glass tube), and (8) is a siphon. .... ..... . . . 35
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10 A schematic diagram of the water head tank where: (1)
is the water head tank, (2) is the floatless toilet fill
valve, (3) is the overflow standpipe, and (4) is the water
delivery tube to water metering devices 36
11 A schematic diagram of water delivery system from the
water head tank to the six water metering devices where:
(1) is the water head tank, (2) is the floatless toilet
fill valve and (3) represents stopcocks 37
12 Schematic diagram of a dosing unit where: (1) is the
water delivery tube, (2) is the water metering device,
(3) is the water delivery device, (4) is the toxicant
metering device, (5) is the mixing chamber, (6) is the
flow splitting chamber, (7) is the standpipe, (8) is
a sleeve, (9) is the flow splitting chamber to exposure
tank delivery tube, and (10) is a stopcock. .......... 38
13 A diagram of the mixing and separation system where:
(1) is the mixing chamber, (2) is the U shaped siphon
tube, (3) is the flow splitting chamber, (4) is the
standpipe, (5) is the sleeve, (6) is the flow splitting
chamber to exposure tank delivery tube. ............ 40
14 Details of the water depth in an intermittently irrigated
plot. The line at 9.4 cm represents the depth of the
bottom of the 10° outflow weir 46
15 Seasonal patterns of water depth in intermittently irri-
gated plots during 1974. The date line represents the
bottom of the 10° outflow weir 48
16 Seasonal patterns of water depth in intermittently ir-
rigated plots during 1975. The date line represents
the bottom of the 10° outflow weir 49
17 Seasonal patterns of water depth in continuously irriga-
ted plots during 1974. The date line represents the bot-
tom of the 10° outflow weir 50
18 Seasonal patterns of water depth in continuously irrigated
plots during 1975. The date line represents the botton
of the 10° outflow weir 51
19 The loss of water due to leaching for all plots during
the 1974 and 1975 growing seasons. . 52
20 Depth of irrigation water in rice paddies during 1975
measured with piezometers. 54
21 Bulk density profile in the flooded rice paddies 55
XI
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22 Moisture content by volume on several dates at various
depths in the rice paddies
3
23 Root density, expressed as length of root per cm of
soil, as a function of depth for five sampling dates
during the growing season. ... ...»•••
24 Minimum and maximum water temperatures during the 1974
season • • •"
25 Minimum and maximum soil temperatures during the 1974
season ......•••••• "°
26 The water balance for the continuous irrigated plots
during 1974 71
27 The water balance for the impounded irrigated plots
during 1974 72
28 The water balance for the continuous irrigated plots
during 1975 73
29 The water balance for the impounded irrigated plots
during 1975 74
30 Electrical conductivity in ymhos/cm for water in im-
pounded plots and in the canal 78
31 Electrical conductivity in ymhos/cm for water in con-
tinuous flow plots and in the canal 79
32 Electrical conductivity averaged over treatment blocks
for plot water sampled in 1974, and results of Duncan's
multiple range test at a 5% level of significance 81
33 Electrical conductivity averaged over treatment blocks,
for soil solutions collected prior to permanent flood,
and for plot water sampled following permanent flood in
1975, and results of Duncan's multiple range test at a
5% level of significance 82
34 pH of water in continuous flow plots and in the canal, .... 84
35 pH of water in impounded plots and in the canal 85
36 Resultant pH averaged over treatment blocks, for soil
solution collected prior to permanent flood (4/30 - 6/5)^
and for plot water samples following permanent flood
(6/6 - 8/20) in 1973 86
XII
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37 Resultant pH averaged over treatment blocks, for soil
solution collected prior to permanent flood (4/30 - 6/5)
and for plot water samples following permanent flood
(6/6 - 8/20) in 1974 87
38 Resultant pH averaged over treatment blocks, for soil
solution collected prior to permanent flood (4/30 - 6/5)
and for plot water samples following permanent flood
(6/6 - 8/17) in 1975 88
39 Diagram of nitrogen pathways and transformations in
flooded rice soils 90
40 Concentration of NH, in ppm in continuous flow plots
and in the canal water 92
41 Concentration of NH in ppm in impounded plots and in
the canal water. .7 93
42 The top graph represents the NH.-N concentration in a
10 cm layer of water over a 10 cm layer of soil., after
pipetting (NH,)2SO, (at the rate of 84 kg N ha" ) into
the water layer. The lower graph represents the distri-
bution of the NH.-N within the same 10 cm layer of soil
32 days after 0 and 84 kgs N ha were applied to the
simulated floodwater. This experiment was conducted
under laboratory room condition in the absence of rice
plants 94
I |
43 Concentration of Ca in ppm in continuous flow plots
and in the canal water. 95
I 1
44 Concentration of Ca in ppm in impounded plots and
in the canal water 96
I i
45 Concentration of Mg in ppm in continuous flow plots
and in the canal, water. 97
I |
46 Concentration of Mg in ppm in impounded plots and in
the canal water 98
47 Concentration of K in ppm in continuous flow plots and
in the canal water 99
48 Concentration of K in ppm in impounded plots and in
the canal water 100
49 Concentration of Na in ppm in continuous flow plots
and in the canal water. ........ 101
50 Concentration of Na in ppm in impounded plots and in
the canal water. 102
xiii
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51 Concentration of S0= in ppm in contiuous flow plots and
in the canal water ..... . ................ *
52 Concentration of S0= in ppm in impounded plots and in
the canal water ........................
53 Concentration of Cl~ in ppm in continuous flow plots
and in the canal water .....................
54 Concentration of Cl in ppm in impounded plots and in
the canal water ........................ ^
55 Concentration on NO -N in ppm in continuous flow plots
and in the canal water .....................
56 Concentration of NC> -N in ppm in impounded plots and
in the canal water. .... .......... •
57 Concentration of NO- in ppm in continuous flow plots
and in the canal water. ... ....... ...» ...... HI
58 Concentration of N0_ in ppm in impounded plots and in
the canal water ............. . ........ »• 112
59 Concentration of 0-PO, in ppm in continuous flow plots
and in the canal water. . ................... 113
60 Concentration of 0-PO, in ppm in impounded plots and
in the canal water ................. . ..... 114
61 The amount of NH, per hectare in the floodwater during
1974. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance. ...... 115
62 The amount of NH, per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range test at a 5% level of significance ....... 116
I i
63 The amount of Ca per hectare in the floodwater during
1974. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance ....... 118
I t
64 The amount of Ca per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance ....... 119
65 The amount of Na per hectare in the floodwater during
1974. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance ....... 120
xiv
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66 The amount of Na+ per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance 121
I [
67 The amount of Mg per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance, 122
68 The amount of SO? per hectare in the floodwater during
1974. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance 124
69 The amount of SCT° per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range test at a 5% level of significance 125
70 The amount of Cl per hectare in the floodwater during
1974. The vertical bers represent the results of Duncan's
Multiple Range Test at a 5% level of significance 126
71 The amount of Cl per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance 127
72 The amount of N0~ per hectare in the floodwater during
1974. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance 128
73 The amount of NO per hectare in the floodwater during
1975. The vertical bars represent the results of Duncan's
Multiple Range Test at a 5% level of significance 129
74 Oxygen profile in flooded soil [after Patrick and
Mikkelsen (1971)] 139
75 Propanil recovered in the water immediately following
the flood as affected by the adsorbed foliar concentra-
tion prior to the flood application in 1974 143
76 Propanil recovered in the water immediately following
the flood as affected by the adsorbed foliar concentra-
tion prior to the flood application in 1975 144
77 Percent propanil remaining on rice foliage sampled in
protected plots at 0, 1, 2, 3, and 5 days following the
application 145
78 Concentration of propanil and DCA in soils sampled from
high rate plots immediately following the spray applica-
tion, just prior to flood, and 24 hours following the
flood application in 1975 149
xv
-------
79 Levels of DCA in rice paddies sampled 24 hours following
the flood application as affected by the dissipation of
propanil between the 12 and 24 hour sampling periods
in 1975 ............................. 151
80 Average DCA concentrations of the surface sediment and
flood water sampled from the 6 high rate plots at 24,
72, 168, and 336 hours following the permanent flood
application in 1975 ....................... 152
81 Sediment load with respect to time following the perma-
ment flood application in 1975 ............... • •
82 Adsorption coefficients of propanil and DCA calculated
at the corresponding sediment loads
83 Correlation of percent pesticide in solution and K^
values determined at a sediment load of 50 g/1 ......... 156
84 Average concentration of molinate in rice paddy water
sampled in 1973 ......................... 161
85 Average concentration of molinate in rice paddy water
sampled in 1974 ......................... 162
86 Average concentration of molinate in rice paddy water
sampled in 1975 ......................... 163
87 Adsorption coefficients of molinate at varying sedi-
ment loads . .. ........................ 166
88 The amount adsorbed and K, versus molinate concentra-
tion in water with a sediment load of 2.5 g/1 .......... 167
89 Average concentrations of carbofuran in rice paddy water
sampled in 1973 ................... . ..... 171
90 Average concentrations of carbofuran in rice paddy water
sampled in 1974 ......................... 172
91 Average concentrations of carbofuran in rice paddy water
sampled in 1975 ......................... 173
92 Adsorption coefficients of carbofuran, 3-keto and 3-
hydroxy carbofuran at varying sediment loads ..... ..... 182
93 Carbaryl concentrations in the floodwater just before
and at a series of times following a simulated rainfall
of 2.5 cm/hour ......................... 193
94 Adsorption coefficients of carbaryl and 1-naphthol at
varying sediment loads .......... ...... ..... 195
xvi
-------
95 Percent recoveries of carbaryl and 1-naphthol from flooded
Beaumont clay soil samples , and corresponding redox po-
tentials ............................ 196
96 Median tolerance limitation for propanil in the three
waters ........................ ..... 206
97 Median tolerance limitation for molinate in the three
waters ............ . ................ 207
98 Median tolerance limitation for carbofuran in the three
waters ............................. 208
99 Median tolerance limitation for carbaryl in the three
waters ............................. 209
100 Predicted C/Co profiles using the explicit scheme with
r = 8. The analytical solution is shown as the solid
line on both sides of the figure. X is the solution
with Az=0.2; g=0.75: (•) is the solution with Az=0.2;
B=0.25: ^ is the solution with Az=0.4; B=0.05: and
fijl is the solution with Az=0.4; B=0.4; and D replaced
by D+0.5-V2-At ......................... 237
101 Predicted C/Co profiles with r = 32 and Az <= 0.2. The
analytical solution is shown as the solid line on both
sides of the figure where fa] is the Crank-Nicolson scheme
with 3=0.25: x is the explicit scheme with B=0.025: and
is the explicit scheme with B=0>.25 ............ 238
102 Predicted C/Co profiles with r = 2, Az = 0.5, and g = 0.5.
The analytical solution is shown as a solid line ..... ... 239
103 Predicted C/Co profiles with r « 2, Az = 0.5 and B = 0.4.
o is the Chaudhari scheme and Q is the explicit scheme.
The analytical solution is shown as the solid line ....... 240
104 Predicted C/Co profiles with r = 2, Az = 0.4, and B <= 0.5.
o is the Chaudhari scheme and Q is the explicit scheme.
The analytical solution is shown as the solid line. . ..... 241
105 C/Co profiles calculated using the second order explicit
scheme where Q is B = 0.46 and | is B = 0.51 ........ 242
106 Predicted C/Co profiles with r - 2, Az = 0.5 and B = 1.75.
o is the Crank-Nicolson scheme and x is the Stone-Brian
scheme. The analytical solution is shown as a solid line. . . 243
107 Predicted C/Co profiles with r = 2, Az = 2 and B = 0.5.
o is the Chaudhari scheme, x is the Stone-Brain scheme,
Q is the explicit scheme, and 0 is the Crank-Nicolson
scheme. The analytical solution is shown as the solid line. . 244
xvi i
-------
108 Predicted C/Co profiles with r • 32 and Az - 0.125.
The Stone and Brian scheme, Chaudhari scheme, and second
order explicit scheme are shown on the left side for 6=1.
On the right side the Chaudhari scheme is shown for g=0.5
and the Crank-Nicolson scheme for 3=1. The analytical
solution is shown as a solid line on the right side 245
109 Predicted C/Co profiles with r = 32 and Az = 0.125.
The second order explicit scheme with 6=1.5 is shown
on the left. The Stone and Brian scheme with 0=1.75
is shown on the right •""
110 Predicted C/Co profiles with r » 32 and B = 0.5. The
Crank-Nicolson scheme and the second order explicit
scheme with Az=0.25 are shown on the left side. The
solution is shown as a solid line. The Chaudhari
scheme and Stone and Brian scheme with Az=0.5. are
shown on the right. The analytical solution is shown
as a solid line. ....... ...... 247
111 Schematic diagram of the finite difference grid 282
112 Simulated concentration pulses for cation 2 for condi-
tions of runs R-l, R-2 and R-3 297
113 Simulated concentration pulses for cation 3 for condi-
tions of runs R-4 and R-5. . 298
114 Simulated concentration pulse for cation 2 and for the
conditions of run R-6 299
115 Simulated concentration pulse for cation 3 for the condi-
tions of run R-7. 300
116 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-8 30l
117 Simulated concentration pulse for cation 2 for the condi-
tions of run R-9 3C2
118 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-10 303
119 Simulated concentration pulses for cations 2 and 3 for
the conditions of R-ll. 304
120 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-12 305
121 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-13. ......... 306
XVlll
-------
122 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-14 , 307.
123 Simulated concentration pulses for cations 2 and 3 and
anion 3 for conditions of run R-15. . 308
124 Simulated concentration pulses for cations 2 and 3 and
anion 3 for conditions of run R-16. 309
125 Simulated concentration pulses for cations 2 and 3 and
anion 3 for conditions of run R-17 310
126 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-18 311
127 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-19. .... ......... 312
128 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-20 313
129 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-21 314
130 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-22. 315
131 Simulated concentration pulses for cations 2 and 3 for
the conditions of run R-23. ......... 316
132 Simulated concentration pulses for cation 2 and anion 3.
The conditions are the same as run R-21 except that CL =
0.0, C = 0.1 and A = 0.2. Observation time is T =
400 minutes. . . . ?s. 326
133 Standard dilution curves for Na employing distilled
deionized ELO, and 1 1J BaCl™ as diluents for soil sam-
ple 1. . 331
134 Standard dilution curves for K employing distilled de-
ionized ELO, and 1 N[ BaCl. as diluents for soil sam-
ple 1. / l 332
I I
135 Standard dilution curves for Ca employing distilled
deionized ELO, and 1 1J BaCl- as diluents for soil sam-
ple 1. . 333
-l_ [
136 Standard dilution curves for Mg employing distilled
deionized H_0, and 1 N^ BaCl- as diluents for soil sam-
ple 1. . l 334
xix
-------
137 Linear correlation of calculated and experimentally
observed Na+ adsorbed for soil sample 1. . .
138 Correlation of calculated and experimentally observed
Ca++ adsorbed for soil sample 1. • • • • ..... * .....
139 Linear correlation of calculated and the experimentally
observed Mg"*^ adsorbed for soil sample 1, ....... .... 340
140 Correlation of calculated K adsorbed and that deter-
mined experimentally for soil sample 1. .... ........
141 Linear correlation of calculated and experimentally
observed adsorbed Na for soil sample 2. ....... ..... 345
142 Linear correlation of calculated and experimentally
observed adsorbed Ca for soil sample 2. ...•>.»••••• 346
143 Linear correlation of calculated and experimentally
observed adsorbed Mg for soil sample 2 .......... ... 347
144 Linear correlation of calculated and experimentally
observed adsorbed K for soil sample 2 . . . .......... 348
_l _ L
145 Simulated Ca concentration in floodwater from im-
pounded recommended plots during 1975. The data
points are the actual field data ................ 351
146 Simulated Cl concentration in floodwater from im-
pounded recommended plots during 1975. The data
points are the actual field data ................ 352
147 Simulated Na concentration in floodwater from im-
pounded recommended plots during 1975. The data
points are the actual field data ................ 353
xx
-------
LIST OF TABLES
Table Page
1 Soil Texture of Composited Samples for the 12
Research Plots 9
2 Rate of Fertilizers and Pesticides Applied Given
in kg/ha Active Ingredients , 17
3 Structural Chemical Formulas of the Pesticides and
Their Toxic Metabolites 18
4 Water Quality Parameters for Filtered Tap Water and
Paddy Water Used in the Bioassays 30
5 Fertilizer and Pesticide Applications to the Paddies
From Which Water Was Collected for the Bioassays ..... 31
6 Source and Purity of Pesticides Used in the Bioassay ... 31
7 Adjusted Intermittent Flow Dilution Rates Used in
the Bioassay 41
8 Measured Daily Evapotranspiration Rate, Calculated
Potential Evaporation, Class A Evaporation and Evap-
oration From a 60 cm Sunken Pan 63
9 Measured Daily Evapotranspiration Rate, Calculated
Potential Evaporation, Class A Evaporation and Evap-
oration From a 60 cm Sunken Pan. , 64
10 Measured Daily Evapotranspiration Rate, Calculated
Potential Evaporation, Class A Evaporation and Evap-
oration From a 60 cm Sunken Pan 65
11 Measured Daily Evapotranspiration Rate, Calculated
Potential Evaporation, Class A Evaporation and Evap-
oration From a 60 cm Sunken Pan 66
12 Measured Daily Evapotranspiration Rate, Calculated
Potential Evaporation, Class A Evaporation and Evap-
oration From a 60 cm Sunken Pan 67
xxi
-------
13 Measured Daily Evapotranspiration Rate, Calculated
Potential Evaporation, Class A Evaporation and Evap-
oration From a 60 cm Sunken Pan
14 Regression Equations and Correlation Coefficients
Between Measured Evapotranspiration (E^) » Calculated
Potential Evaporation (PQ) , Evaporation From a 61
cm Diameter Pan (Pfci) and Evaporation From a 122
cm Pan, Class A (P]_22) ...................
15 Total Calculated, Pan, and Measured Evapotranspi-
ration During the Period of Permanent Flood Given
in cm ............................ 69
16 Water Balance From Planting to Harvesting During
1974 and 1975 For Both Irrigation Treatments Given
in cm ............................ 76
17 Water Balance During the Period of Permanent Flood
for 1974 and 1975 For Both Irrigation Treatments
Given in cm .............. ........... 76
18 Associated Ions Added With Fertilizers During the
Three Years .......... , .............. 130
19 Ionic Concentration of Dialysate Averaged Within
Treatments Following the 24-hour Equilibration
Period in Top 1 cm of the Soil in 1974 ........... 131
20 Ionic Concentration of Dialysate Averaged Within
Treatments Following the 24-hour Equilibration
Period in Top 1 cm of the Soil in 1975 ........... 132
21 Inorganic Ions Extracted From the 0-5 cm Surface
Soil Sampled Preplant and Following the Harvest in
1973, 1974, and 1975 .................... 134
22 Salt Balance During the Rice Growing Season During
1974 and 1975 ........................ 135
23 Propanil Recovered in Water From Treated Rice Plots
Sampled 0 and 24 Hours Following the Flood in 1973 ..... 141
24 Propanil in Water From Treated Rice Plots Sampled
0, 3, 6, 12, and 24 Hours Following the Flood in
1974 ............................ 141
25 Propanil Recovered in Water From Treated Rice Plots
Sampled 0, 3, 6, 12, and 24 .Hours Following the
Flood in 1975 ........................ 142
xxi i
-------
26 Propanil Recovered on Foliage Sampled From Treated
Rice Plots 0 and 24 Hours Following Application in
1974 ............ . ............... 146
27 Propanil Recovered on Foliage Sampled From Treated
Rice Plots 0 and 24 Hours Following Application in
1975 ............................ 146
28 Average Plot Depths Within Treatment Blocks With
Respect to Time in 1975 ............. . ..... 147
29 Concentration of Molinate in Paddy Water Following
Its Application in 1973, and Statistical Significance
With Respect to Time .................... 158
30 Concentration of Molinate in Paddy Water Following
Its Application in 1974, and Statistical Significance
With Respect to Time .................... 159
31 Concentration of Molinate in Paddy Water Following
Its Application in 1975, and Statistical Significance
With Respect to Time .................... 160
32 Volatilization of Molinate From Water at 27°C and
Air Flow Rate of 8 ml/sec .................. 164
33 Column Leaching of a Molinate-Spiked Beaumont Clay
Soil with Distilled Water ................ . . 165
34 Effects of Time, Substrate Level, and Redox Poten-
tial on the Dissipation of Molinate in Flooded Soil
Samples Under Laboratory Conditions . All Flasks
Including Controls Were Spiked with 100 mg Molinate ..... 169
35 Concentration of Carbofuran in Paddy Water Following
Its Application in 1973, and Statistical Significance
with Respect to Time ....................
36 Concentration of Carbofuran in Paddy Water Following
Its Application in 1974, and Statistical Significance
with Respect to Time .................... 176
37 Concentration of Carbofuran in Paddy Water Following
Its Application in 1975, and Statistical Significance
with Respect to Time .................... 177
38 Concentration of 3-keto Carbofuran with Respect to
Time in Rice Paddy Water Sampled in 1973 .......... 179
39 Concentration of 3>~keto Carbofuran with Respect to
Time in Rice Paddy Water Collected in 1974 ......... 18°
XXlll
-------
40 Concentration of 3-keto Carbofuran with Respect to
Time in Water Sampled from Rice Plots in 1975 ....... 181
41 Carbofuran Recovered from Flooded Beaumont Clay
Soil Equilibrated 96 Hours at 27°C. . ...........
42 Effect of Reducing Conditions on the Dissipation
of Carbofuran and 3-keto Carbofuran in Flooded
Samples of a Beaumont Clay Soil .............. 184
43 Concentration of Carbaryl in Flood Water Following
Its Application in 1973, and Statistical Significance
with Respect to Time ............... ..... 186
44 Concentration of Carbaryl in Paddy Water Following
Its Application in 1974, and Statistical Significance
with Respect to Time. . . ................. 187
45 Concentration of Carbaryl in Paddy Water Following
Its Application in 1975, and Statistical Significance
with Respect to Time .................... 188
46 Concentration of 1-Naphthol in the Paddy Water
in 1973 .......................... 190
47 Concentration of 1-Naphthol in the Paddy Water
Sampled in 1974 ...................... 191
48 Concentration of 1-Naphthol in the Paddy Water
Sampled in 1975 ...................... 192
49 Effect of Sterilization on Carbaryl Recovered From
a Beaumont Clay Soil and Flood Water ............ 197
50 Background Levels of Pesticides in Canal H?0 Used
to Flood Experimental Plots in 1973 . . . . ........ 198
51 Background Levels of Pesticides in Canal H90 Used
to Flood Experimental Plots in 1974 .... ........ 199
52 Background Levels of Pesticides in Canal H?0 Used
to Flood Experimental Plots in 1975 ... . ........ 199
53 Toxicity of Propanil to Fish Reported in the Liter-
ature ........................... 201
54 Toxicity of Molinate to Fish Reported in the Liter-
ature ........................... 202
55 Toxicity of Carbofuran to Fish Reported in the Liter-
ature ........................... 203
xxiv
-------
56 Toxicity of Carbaryl to Fish Reported in the Liter-
ature ....»..,, 204
57 The 24, 48, 72, and 96 Hour TLM Concentration and
Their 95% Confidence Intervals in Paddy Water I in
Static Tests Given in ppm 210
58 The 24, 48 and 96 Hour TLM Concentrations and Their
95% Confidence Intervals in Filtered Tap Water in
ppm 210
59 The 24, 48 and 96 Hour TLM Concentrations and Their
95% Confidence Intervals in Paddy Water II in ppm 211
60 Average TOC, COD and BOD of Flood Water and Canal
Water at the Time of Final Drainage in 1973 ... 213
61 Average TOC, COD and BOD of Flood Water and Canal
Water at the Time of Final Drainage in 1974 213
62 Average TOC, COD and BOD of Flood Water and Canal
Water at the Time of Final Drainage in 1975 214
63 Rice Yields During the Study - Average of Three
Replications. .....,..,., 215
64 Concentrations of Ions in Fd.ee Foliage and Grain
and Values of Ki Used to Calculate Ion Uptake from
the Soil 218
65 C/Co Values for r«Az=4, After Ten Time Steps from
Two Runs Using the Stone and Brian Scheme ......... 252
66 Symbols Used for Different Phases of the Ions 258
67 Complete System of Equilibrium Equations. 259
68 Rearrangement of the Equilibrium Equations 261
69 Correspondence Between Symbols 279
70 Values of the Input Parameters Used in the Test
Runs 296
71 Characteristics of the Ion Pulses for the Runs
Listed in Table 70. The Parameters Given Include
the Relative Distance the Pulse Traveled (dr), the
Relative Pulse Height (hr), the Relative Tailing
Pulse Width at Half Length (SL) and the Relative
Lead Pulse Width at Half Height (Sr) 319
xxv
-------
72 Equilibria Solution and Adsorbed Cation Concentra-
tions, of a Beaumont Clay Soil, Established at Var-
ious Solution Cationic Treatments in Sample 1
73 Correlation Coefficients Determined for Adsorbed
Cation Concentrations as a Function of Correspond-
ing Solution Concentration in Soil Sample 1 336
74 Multiple Linear Regression Coefficients for the
Cations Adsorbed as a Function of Solution Concen-
trations in Soil Sample 1 337
75 Equilibria Solution and Adsorbed Cation Concentra-
trations of a Beaumont Clay Soil, Established at
Various Solution Cationic Treatments in Sample 2 342
76 Correlation Coefficients for Adsorbed Cation Con-
centrations as a Function of Corresponding Solution
Concentrations in Soil Sample 2... •• 343
77 Multiple Linear Regression Coefficients for the
Cations Adsorbed as a Function of Solution Concen-
trations in Soil Sample 2 344
78 Exchange Coefficients Calculated from the Ion Equi-
librium Studies on Samples 1 and 2 of Beaumont Clay .... 349
A-l Log of Rainfall and Cultural Practices for 1973 366
A-2 Log of Rainfall and Cultural Practices for 1974 367
A-3 Log of Rainfall and Cultural Practices for 1975 369
B-l Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas 1973
(April) 371
B-2 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1973
(May) 372
B-3 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1973
(June) 373
B-4 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1973
(July) 374
B-5 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1973
(August) 375
xxvi
-------
B-6 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1974
(April) 376
B-7 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1974
(May) 377
B-8 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1974
(June) 378
B-9 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1974
(July) 379
B-10 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1974
(August) ,380
B-ll Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1975
(April) 381
B-12 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1975
(May) 382
B-13 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1975
(June) 383
B-14 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1975
(July) 384
B-15 Summary of Climatological Observation at the Texas
Agricultural Experiment Station, Beaumont, Texas, 1975
(August) 385
D-l Water Depth at the End of Each Day During Permanent
Flood in 1974 (June 6 - July 4) 390
D-2 Water Depth at the End of Each Day During Permanent
Flood in 1974 (July 5 - August 2) 391
D-3 Water Depth at the End of Each. Day During Permanent
Flood in 1974 (August 3 - August 23) 392
D-4 Water Depth at the End of Each Day During Permanent
Flood in 1975 (June 5 - July 3) 393
XXVll
-------
D-5 Water Depth at the End of Each Day During Permanent
Flood in 1975 (July 4 - August 1)
394
D-6 Water Depth at the End of Each Day During Permanent
Flood in 1975 (August 2 - August 16). . 395
E-l Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (June 1 - June 30, 1973) 397
E-2 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (July 1 - July 31, 1973) 398
E-3 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (June 15 - June 30, 1974) 399
E-4 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (July 1 - July 31, 1974) 400
E-5 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (August 1 - August 19, 1974) 401
E-6 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (June 1 - June 30, 1975) 402
E-7 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (July 1 - July 31, 1975) 403
E-8 Soil and Water Temperature in Rice Paddy, Beaumont,
Texas (August 1 - August 31, 1975) 404
F-l Daily Water Balance for Rice Paddies with Continuous
Irrigation for May 1974, given in cm 406
F-2 Daily Water Balance for Rice Paddies with Impounded
Irrigation for 1974 given in cm 410
F-3 Daily Water Balance for Rice Paddies with Continuous
Irrigation for 1975 given in cm 413
F-4 Daily Water Balance for Rice Paddies with Impounded
Irrigation for 1975 given in cm 417
G-l Analysis of Variance for E.G. in Rice Paddy Water
Sampled in 1974 421
G-2 Analysis of Variance for E.G. in Rice Paddy Water
Sampled in 1975 422
G-3 Analysis of Variance for E.G. in Rice Paddy Water
Sampled in 1973 423
xxvi11
-------
G-4 Analysis of Variance for pH in Rice Paddy Water
Sampled in 1973 ....................... 424
G-5 Analysis of Variance for pH in Rice Paddy Water
Sampled in 1974 . c ............... . ...... 425
G-6 Analysis of Variance for pH in Rice Paddy Water
Sampled in 1975 ....................... 426
G-7 Analysis of Variance for NH, in Rice Paddy Water
Sampled in 1974 ....................... 427
G-8 Analysis of Variance for NH_ in Rice Paddy Water
Sampled in 1975 ...... ................. 428
I j
G-9 Analysis of Variance for Ca in Rice Paddy Water
Sampled in 1974 ....................... 429
I I
G-10 Analysis of Variance for Ca in Rice Paddy Water
Sampled in 1975 ....................... 430
i i
G-ll Analysis of Variance for Mg in Rice Paddy Water
Sampled in 1974 ....................... 431
I [
G-12 Analysis of Variance for Mg in Rice Paddy Water
Sampled in 1975 ....................... 432
G-13 Analysis of Variance for Na in Rice Paddy Water
Sampled in 1974 ....................... 433
G-14 Analysis of Variance for Na in Rice Paddy Water
Sampled in 1975 ....................... 434
G-15 Analysis of Variance for S0~ in Rice Paddy Water
Sampled in 1974 ....................... 435
G-16 Analysis of Variance for S0~ in Rice Paddy Water
Sampled in 1975 ....................... 436
G-17 Analysis of Variance for Cl~ in Rice Paddy Water
Sampled in 1974 .......................
G-18 Analysis of Variance for Cl~ in Rice Paddy Water
Sampled in 1975 ....................... 438
G-19 Analysis of Variance for N0~ in Rice Paddy Water
Sampled in 1974 ....................... 439
XXIX
-------
G-20 Analysis of Variance for N0~ in Rice Paddy Water
Sampled in 1975
H-l Analysis for Nitrate (ppm) for 1973 442
H-2 Analysis for Nitrate (ppm) for 1974 443
H-3 Analysis for Nitrate (ppm) for 1975 445
H-4 Analysis for Electrical Conductivity (micromhos)
for 1973 446
H-5 Analysis for Electrical Conductivity (micromhos)
for 1974 447
H-6 Analysis for Electrical Conductivity (micromhos)
for 1975 448
H-7 Analysis for pH for 1973 449
H-8 Analysis for pH for 1974 450
H-9 Analysis for pH for 1975 451
H-10 Analysis for Nitrite (ppm) for 1973 452
H-ll Analysis for Nitrite (ppm) for 1974 453
H-12 Analysis for Nitrite (ppm) for 1975 455
H-13 Analysis for Ammonium (ppm) for 1973 456
H-14 Analysis for Ammonium (ppm) for 1974 457
H-15 Analysis for Ammonium (ppm) for 1975 459
H-16 Analysis for Sulfate (ppm) for 1973 460
H-17 Analysis for Sulfate (ppm) for 1974 461
H-18 Analysis for Sulfate (ppm) for 1975 463
H-19 Analysis for Ortho-phosphate (ppm) for 1973 464
H-20 Analysis for Ortho-phosphate (ppm) for 1974 465
H-21 Analysis for Ortho-phosphate (ppm) for 1975 467
H-22 Analysis for Potassium (ppm) for 1973 468
H-23 Analysis for Potassium (ppm) for 1975 469
xxx
-------
H-24 Analysis for Magnesium (ppm) for 1973 470
H-25 Analysis for Magnesium (ppm) for 1975 471
H-26 Analysis for Calcium (ppm) for 1973 472
H-27 Analysis for Calcium (ppm) for 1975 473
H-28 Analysis for Chloride (ppm) for 1973 474
H-29 Analysis for Chloride (ppm) for 1974 475
H-30 Analysis for Chloride (ppm) for 1975 477
H-31 Analysis for Sodium (ppm) for 1973 478
H-32 Analysis for Sodium (ppm) for 1975 479
H-33 Analysis for HCC>3 (ppm) for 1975 480
1-1 Analysis of Variance for Molinate in Rice Paddy Water
Sampled in 1973 482
1-2 Analysis of Variance for Molinate in Rice Paddy Water
Sampled in 1974 483
1-3 Analysis of Variance for Molinate in Rice Paddy Water
Sampled in 1975 484
1-4 Analysis of Variance for Carbofuran in Rice Paddy Water
Sampled in 1973 485
1-5 Analysis of Variance for Carbofuran in Rice Paddy Water
Sampled in 1974 486
1-6 Analysis of Variance for Carbofuran in Rice Paddy Water
Sampled in 1975 487
1-7 Analysis of Variance for Carbaryl in Rice Paddy Water
Sampled in 1973 488
1-8 Analysis of Variance for Carbaryl in Rice Paddy Water
Sampled in 1974 489
1-9 Analysis of Variance for Carbaryl in Rice Paddy Water
Sampled in 1975 490
M-l Input Variables 548
M-2 Input Data Deck
xxxi
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N-l Derivative of G with Respect to Cation I at Third
Grid Point . . ik 561
N-2 Derivative of G with Respect to Cation 2 at Third
Grid Point . . 562
N-3 Derivative of G with Respect to Cation 3, 4* or 5*
at Third Grid Point 563
N-4 Derivative of G with Respect to Anion 1 at Third
Grid Point . . 564
N-5 Derivative of G with Respect to Anion 2 or 3* at Third
Grid Point . . 565
N-6 Derivative of G with Respect to 9 at Third Grid Point. . . . 566
liC
0-1 Analysis of Covariance of Adsorbed and Solution
Concentrations of Ions in Soil Sample 1 568
0-2 Analysis of Covariance of Adsorbed and Solution
Concentrations of Ions in Soil Sample 2 569
xxxii
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ACKNOWLEDGEMENTS
This study was supported by the Environmental Protection Agency Project
S802008; Dr. A. G. Hornsby, Project Officer; by the Texas Agricultural
Experiment Station, Dr. J. E. Miller, Director; through the Soil and
Crop Sciences Department, Dr. M, E. Bloodworth, Head; and the Texas Agri-
cultural Experiment Station at Beaumont, Dr. J. P. Craigmiles, Director.
The researchers are indebted to those mentioned above for their support and
encouragement during the project.
This work could not have been complete without the able assistance of
J. C. Thomas, Research Associate; M. D. Gerst, S. G. Jones, S. A. Smith
and J. B. Allison, Graduate Students; and D. Anderson, Laboratory Assistant.
XXXlll
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SECTION 1
INTRODUCTION
As a result of technical advancements, particularly the sophistication
of methodology and new instrumentation, the distribution and levels of
hazardous chemicals in our environment are being revealed. The simplest,
most expedient solution to chemicals in the environment would be to ban the
use of all potential pollutants. This would include virtually all soil
amendments and chemicals employed in agricultural production, without which
production would be seriously curtailed.
A more logical approach is to determine the longevity and mobility of
the chemicals used for agricultural production and to select those chemicals
and management practices which minimize pollution hazards. This project is
one such endeavor.
Rice is presently the third largest cash crop in Texas with approxi-
mately 578,000 acres irrigated rice grown yearly. Louisiana has approximate-
ly 588,000 acres in rice cultivation, Arkansas about 787,000 acres, and Cali-
fornia approximately 395,000 acres. The Texas Water Development Board has
predicted that by 2020, the acreage in rice will have doubled in Texas alone.
Fertilizer amendments and pesticides are essential for the production of
rice. However, fresh water supplies for urban use and the estuaries along
the coastal regions are relatively unbuffered geographically from the rice
growing areas. Some of the chemicals used are known to be toxic to animals,
fish and plants in low concentrations. Fish kills have been found on several
occasions in streams which flow through the rice growing areas. Although no
direct cause and effect relationship has been established, it has been sug-
gested that the fish were killed by pesticides released from the rice fields.
A good body of research has been done on the persistence and movement
of nutrients and pesticides in soils (see Lichtenstein, 1970; and Biggar and
Nielsen, 1967 for review). However, much of this work has been done on up-
land soils under laboratory conditions. The results provide some understand-
ing of extrinsic factors involved, but cannot generally be extrapolated to
field conditions due to unknown or unduplicated intrinsic soil factors. We
therefore, undertook a comprehensive field experiment to determine the
effects of different management regimes on the pesticide, nutrient and corre-
sponding water and salt balances under a flooded rice culture. Particular
emphasis was placed on monitoring potentially harmful constituents of the
irrigation return flow.
The specific objectives of the project were: a) to conduct field scale
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experiments on the nutrient, pesticide and water balance of rice fields with
particular emphasis on measurements of deep percolation and released water;
b) to sample and analyze the water entering and leaving the fields by the
various pathways for persistent and toxic pesticides and nutrients; c) to^
determine the effect of recommended and excessive application rates of nu-
trients and pesticides on the pollution hazard from rice production; d) to
use the data obtained to develop management practices which will minimize or
eliminate the pollution hazard; and e) to evaluate fish toxicity levels of
the pesticides employed.
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SECTION 2
CONCLUSIONS
1. Maintaining the flood depth to the top of the lowest level encourages
run-off and provides for inefficient use of the rainfall, which in some cases
could supply all the water required by the crop.
2. Continuous flow irrigation wastes much water and increases the prob-
ability that chemicals in the water will be lost in the irrigation return
flow.
3. Salts in the irrigation return flow were generally lower than in the
irrigation supply. A fact attributed to the high adsorption capacity of the
clay soil, relatively low initial soluble salt in the irrigation water, nu-
trient uptake by rice plants, and dilution of the flood water by significant
amounts of rainfall.
4. Salts or pesticides did not leach to any appreciable extent due to
the low saturated conductivities of the flooded clay soil. The water table
remained perched throughout the entire period of flooding.
5. Occasionally, the NH, concentration in the irrigation return flow
exceeded the drinking water standards. The total amounts of NH, lost were,
however, a very small fraction of that applied as fertilizer.
6. Nitrate-nitrogen concentrations in the flood water were consistently
below the lOppm NO--N upper limit for drinking water throughout the growing
season.
7. Nutrient levels were temporarily increased in the irrigation return
flow following fertilizer applications. Fertilizer applied in, the flood water
had a greater influence on the salt load of the return flow than similar
amounts either applied to dry soil just before flooding, or incorporated in
soil before planting.
8. Propanil found in the plot water was directly proportional to that
which was washed from the foliage by the flood; the flood being normally ap-
plied 24 hours following the propanil application. DCA was proportionate to
the propanil dissipated, but the average concentration was less than 200 ppb
at the recommended 3.4 kg/ha recommended propanil application. Concentrations
in irrigation return flow could exceed 10% of the 96 hours TLM to fish if a
rainfall large enough to cause overflow occurs within a few hours following
the establishment of the permanent flood.
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9. Best fit analysis of field data to the first order biological decay
equation and laboratory studies under flooded soil conditions suggested that
biological degradation was the principal mode by which molinate was dissi-
pated in the field experiment. Persistence at statistically significant
levels ranged from 96 to 384 hours following application, and generally was a
function of the application rate and flood water depth. Half-life values av-
eraged 96 hours in impounded plots and 54 hours in continuous flow plots over
the 3-year experiment.
10. The 3-year field experiment indicated that carbofuran was chemically
altered to something other than the toxic metabolites: 3-keto or 3-hydroxy
carbofuran and was rapidly dissipated from the plot water. However, persis-
tence of this chemical was extended due to a variable entry into the flood
water from a significant fraction of the broadcast application intercepted by
the rice foliage. Correspondence of residual carbofuran levels to rainfall
events indicated that some of the material lodged at the leaf-stem junction
of the rice plant was dissolved and washed into the plots by rain.
11. Concentrations of carbaryl in the paddy water corresponded to rain-
fall distribution. Once flushed from the leaf canopy, carbaryl was dissi-
pated within 48 hours by an adsorptive mechanism interacting with both bio-
logical degradation and chemical alteration. Amounts of 1-naphthol, a toxic
metabolite of carbaryl, reflected the rate of carbaryl applied, but was more
the result of contamination of the commercial material rather than a degrada-
tion product. 1-Naphthol was rapidly dissipated in the paddy water and there
was no evidence that it would extend the residual life of carbaryl under the
conditions associated with flooded rice cultivation.
12. Releasing flood water from a rice field 10 days before harvesting is
a common water management practice which serves to dry the soil and thereby
facilitate harvesting. The desirable dry soil conditions can be obtained by
withholding additional irrigations and allowing all flood water to evapotrans-
pire prior to harvest. Rice yields were not affected by allowing the soil to
dry in this manner prior to harvest. Since very little salt is leached
through this type of soil, run-off during the winter is needed to remove the
salt that would otherwise accumulate.
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SECTION 3
RECOMMENDATIONS
1. The practice of continuous flow irrigation should be eliminated.
2. Practices should be initiated to maintain the maximum amount of free-
board possible to take advantage of natural rainfall and to minimize overflow.
These should include the use of higher levees and careful control of irriga-
tion water to prevent flooding to depths deeper than needed.
3. Fertilizers should be applied to dry soil rather than to flood water
whenever possible to reduce the nutrient levels now attained in the return
flow and to increase efficiency of nitrogen fertilizer.
4. To minimize concentrations of propanil in the irrigation return flow,
no water should be released for at least 24 hours after flooding. This is
now the general practice, but efforts should be made to assure that it is ad-
hered to.
5. Irrigation water management and application of fertilizers or pesti-
cides should be coordinated so that applications are made when the flood water
depths are minimal. This will allow sufficient free board to retain rain-
water, thus minimizing contaminated return flow.
6. Flood water should be retained a minimum of 4 days following the rec-
ommended 3.4 kg molinate/ha application to insure that molinate concentra-
tions in the irrigation return flow are within an acceptable 3 ppm, or 10% of
the TLM to fish.
7. Although carbofuran was rapidly dissipated from flood waters, there
should not be a release from flooded rice fields for 16 days following a nor-
mal broadcast application of 0.56 kg/ha to insure that the fraction inter-
cepted by the rice foliage does not adversely affect the quality of irriga-
tion return flow.
8. Carbaryl applied as a foliar spray may be washed from the leaves by
a rain; this results in a variable source to the paddy water. Paddy water
should not be released for 8 days following an application of 1.12 kg/ha car-
baryl to the rice, or within 48 hours following a heavy rain prior to the
eighth day.
9. The wide range of retention times needed to assure low levels of the
various pesticides tested in the irrigation return flow indicates the need
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to establish such data on each pesticide in the aquatic rice environment.
10. Rice fields should be allowed to evapotranspire to desirable dry
conditions to facilitate harvesting rather than maintaining flood levels un-
til harvest. This simple procedure has merit from"a conservation point of
view, but also would minimize the movement of potential pollutants from the
fields.
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SECTION 4
EXPERIMENTAL DESIGN
A series of experiments to determine the impact of fertilizer and
pesticide application on the quality of irrigation return flow were conducted
in both the field and the laboratory. The experiments were also designed to
elucidate the mechanisms influencing the quality of irrigation return flow.
The field studies were conducted on a group of 12 small rice paddies
which were sealed to prevent lateral water movement between plots. Weirs,
water stage recorders and rain gauges were utilized to monitor the water
balance throughout each of the three cropping seasons. Insofar as possible,
all cultural practices and their scheduling were done the same way they would
be under normal field production. Pesticides were selected which were in
wide use at the time of the experiment and are representative of several
families of pesticides. Both recommended and excessive rates of both fertil-
izers and pesticides were utilized in the experiments. Two irrigation
schemes, continuous flow and impounded, were utilized. Three replications of
two application rates and two irrigation practices were applied to randomly
selected plots.
The pesticides were applied at the time they would normally be needed
whether or not the target organisms were present in sufficient numbers to
warrant application. It is suggested that the presence or absence of the
target organism should not effect the rate of dissipation of the pesticide
or its toxic metabolites.
Water samples were collected from all plots and from the adjacent feeder
canal throughout the season to be analyzed for salt and nutrient load in the
flood water. The sampling schedule was adjusted to provide more frequent
samples following significant events such as fertilizer applications or heavy
rainfall. Water samples were collected for analysis on a geometric time scale
following application of pesticides.
Special field tests including the use of an artificial rainfall simu-
la±trr to wash the pesticides from the foliage, foliage harvesting, variable
flood depths and withholding irrigation water as a means to reduce the volume
of return flow were implemented throughout the study as their need was deter-
mined.
Laboratory studies consisted of testing various mechanisms of dissipa-
tion of pesticides from the flood water, chemical equilibrium studies to
determine equilibrium rate constants, and fish toxicity studies to determine
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lethal dose levels of the pesticides. Insofar as possible, all data was sub-
jected to statistical analysis. A computer model was developed to allow the
equilibrium of salts between the soil and the flood water and to further
elucidate extrapolation of present data to other soils, irrigation water, and
climates.
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SECTION 5
EXPERIMENTAL PROCEDURES
DESCRIPTION OF FIELD AND SOIL
Twelve field plots were used at the Texas A&M Agricultural Research
and Extension Center near Beaumont, Texas. Plots were laid out on a rather
homogeneous Beaumont clay soil (Typic pelludert). One location was used for
the plots during 1973, and another location was selected for use during 1974
and 1975. The texture analyses for the surface and subsoil of composited
samples from the two locations are shown in Table 1. When the clay was
further fractionated, it was found that approximately 70% was less than 0.2y.
The CEC of the surface sample was 35 meq/lOOg. The pH ranged between 5-7 and
6.1 at a 1:2 soil-water ratio. Carson and Dixon (1972) reported that the
clay fraction of the Beaumont soil is montmorillonitic and greater than 50%
of the isomorphous substitution is in the tetrahedral sheet. The area chosen
for the experimental plots had not been cropped for three years.
TABLE 1. SOIL TEXTURE OF COMPOSITED SAMPLES
FOR THE 12 RESEARCH PLOTS
Year
1973
1973
1974 &
1975
1974 &
1975
Depth cm
0-15
15-28
0-15
15-28
Sand
%
31.5
27.9
33.3
32.7
Silt
%
16.8
14.6
14.7
19.2
Clay
%
51.7
57.5
47.0
48.1
Texture
USDA
Clay
Clay
Clay
Clay
FIELD PROCEDURES
Source of Irrigation Water
The Neches River was the source of the irrigation water used on the plots,
The water is taken from the river by the irrigation district and travels
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approximately 25 km through a series of canals before it reaches the experi-
mental area. The suspended load of the source varies from time-to-time with
a typical value of 0.2 g/1.
Management of Irrigation Water
Earthen levees were constructed along the boundaries of the plots, and
plastic barriers were interred to a depth of 90 cm within the dikes to retard
water from moving horizontally between plots. Views of the field plots are
shown in Figures 1, 2 and 3. The flooded surface area of the plots averaged
300 m2.
Two prepermanent flood irrigations, applied after planting and two weeks
later, were accomplished using 5 cm diameter plastic tubes to siphon water
from a feeder canal. The irrigations required to bring the plots up to full
flood and subsequent irrigations required to replenish the flood water were
also accomplished by siphoning. Only infrequently was it necessary to siphon
water into the continuous flow plots. Such irrigation was necessary when the
continuous flow system lagged behind the losses. Intentional irrigation of
the plots was continued until the flood water reached the bottom of the 10°
weir described below.
Plots for irrigation treatment were randomly selected. The continual
flow plots were supplied with water through an aluminum irrigation pipe con-
nected to a gate on the district canal. The water flowed through a float
valve into a stilling chamber behind a 10° weir. The level of the float
valve was adjusted to control the flow rate through the weir (Figure 4).
Two weirs and a water stage recorder were used to measure the outflow
water. A 45° weir was installed so that the bottom on the V was at the level
of the bottom of the plots. It was used to release the water from the two
prepermanent flood irrigations, as necessary to rapidly release water from
exceedingly heavy rainfall during the permanent flood, and to release the
final flood. At other times during the permanent flood, it was sealed. A
10° outflow weir was placed such that the bottom of the V was nominally 10 cm
above the mean bottom of the plot. Excess water from both continuous and
intermittent plots was released through the weir. A Stevens Model 68 water
stage recorder with special pulleys to increase the sensitivity to 0.05 cm
of depth was used to measure the water depth inside a stilling well made of
a 30 cm diameter, 120 cm long concrete tile. See Figure 5 for details. A
hole was drilled in the side of the tile below the water level. To further
damp oscillations in the water level which resulted from the influence of
wind, it was necessary to connect under water a 100 cm section of 2 cm dia-
meter hose to the hole in the side of the tile.
In 1973, the levees were constructed of soil and covered with black
plastic. It was apparent from the fluctuating water depths and the seeps
around the edges of the plots that water was leaking both between plots and
from the edges of the plots. In 1974, the plot location was moved some 100
meters from the location used in 1973. Before the new levees were con-
structed, a ditch digger was utilized to dig a 90 cm deep trench around each
of the 12 plots. A 150 cm wide piece of black plastic (Grifflon No. 45) was
10
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Figure 1. View of the field before planting showing levees, stand
pipes ready for the installation of water stage recorders
and a lysimeter box behind the stand pipe located to the
left of the photograph.
11
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Figure 2. View of field plots showing outflow weirs and the board-
walks used for access to plots. A water stage recorder
can be seen in the upper right quadrant of the photo-
graph.
12
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IRRIGATION CANAL
•to a depth of
_J meter surrounding
—all plots
Figure 3. Schematic diagram of two of the research plots showing water control devices.
-------
Figure 4. A water flow regulating float valve, stilling chamber
and weir used to maintain continuous flow plots.
14
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Hose
Figure 5. Schematic diagram of water stage recorder mounting
and stilling well.
15
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placed in the ditch and the soil was replaced. The levees were constructed
on either side of the strip of plastic which protruded from the ditch. During
the process, vibrating compactors and a pneumatic tamper were used to pack
the soil to insure a water-proof barrier. Subsequent tests conducted by ir-
rigating alternate plots indicated that the barriers were effective in pre-
venting leaks. The same plots were utilized during the 1975 season.
Several methods were used to measure the movement of water into the
profile. A water balance comparing the lysimeter data and the water loss
from the plots,was used to determine infiltration during the period the
paddy was flooded. Additionally, measurements of infiltration were made on
small plots isolated with metal frames and surrounded by water. Measurements
were made of the amount of water required to refill the covered isolated plot
to the original level. During 1975, three sets of piezometer tubes were
placed in the plots at a series of depths. Observations of water level in
these were recorded throughout the season.
Lysimeters
Lysimeters were installed each year near the center of each of the im-
pounded plots. They consisted of galvanized sheet metal boxes 30 cm tall and
100 cm square. They were installed by digging a square hole 10 cm deep.
After the bottom of the hole was smoothed, the lysimeter boxes were set in
place and the excavated soil was placed inside and packed back to nearly the
same volume. Because of the late start in 1973, the rice was hand trans-
planted into the lysimeters. Direct seeding was employed in 1974 and 1975.
In all seasons, the foliar canopy developed in the lysimeters was similar to
that in the adjacent field. A series of holes at different depths was located
in one side of each lysimeter box. These holes were fitted with stoppers
which remained in place except when one or more was removed for a brief time
to allow the flood water from the plot to resupply the water in the lysimeter.
A hose fitting was sealed into the lysimeter below the water level.
The other end of the hose was fitted into the bell end of a sealed 30 cm
diameter, 120 cm long tube which served as a stilling well and as a stand to
hold the water stage recorder.
Application of Nutrients and Pesticides
The plots were randomized with respect to application rates of the
nutrients and pesticides. Excessive rates of both were applied to the same
plots. The actual rates employed for the pesticides and fertilizers are
given in Table 2. Applications of nitrogen were split with 40% being applied
at planting time, 40% just before permanent flood, and 20% at panicle dif-
ferentiation. The excessive rates were employed in an attempt to increase
the sensitivity limits for the detection of metabolites. Structural chemical
formulas for the pesticides and their metabolites analyzed are given in Table
3.
16
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TABLE 2. RATE OF FERTILIZERS AND PESTICIDES APPLIED
Fertilizers
and
Pesticides
Nitrogen
as N
Phosphate
as P205
Potassium
as K20
Propanil
Recommended
134,40
44.80
22.40
3.36
Excessive
179.20
112.00
89.60
6.72
Molinate 3.35 11.20
Carbofuran 0.56 3.36
Carbaryl 1.12 5.60
Sampling
Water—
The irrigation water and the flood water in the plots were sampled on
a schedule designed to provide detailed information about changes following
events such as irrigation, heavy rainfall, and applications.
Samples were collected for salt and nutrient analyses from the two
floods applied early in each season just before the water was released.
In addition, samples were collected from the water ponded in the plots after
significant rainfall events prior to the permanent flood. Water samples
were taken after the permanent flood was established by dipping a fraction
of a 100 ml plastic sample bottle into the flood water at three or four lo-
cations along the boardwalk which was located down the center of the plot.
Samples were collected of the irrigation water more frequently during the
early part of the season particularly after fertilizer applications. The
samples were transported directly to the laboratory where they were analyzed
or in some cases, frozen and stored for later analysis.
Water samples for pesticide analyses were taken as soon after appli-
cation as possible and assigned a relative time of 0 hours. Subsequent
samples were generally taken 24, 48, 96, 192, 384, and 768 hours. Time 0
for propanil was approximately 24 hours following the application because
17
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TABLE 3. STRUCTURAL CHEMICAL FORMULAS OF THE PESTICIDES
AND THEIR TOXIC METABOLITES.
Pesticide
Structural formula
Propanil
O
NHCC2Hg
DCA
Cl
TCAB
Molinate
Carbofuran
3-Keto carbofuran
3-Hydroxy carbofuran
Carbaryl
l-Naphthol
Cl
Oo
Hfi-S-(
= CNHCH,
ff
OrCNHCH,
CH-
O=CNHCH.
= CNHCH.
18
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that was when the rice plots were flooded. Then sampling proceeded accord-
ing to the above schedule. Plots were already under permanent flood at the
time of application of the other chemicals.
The sampling technique entailed dipping a 1.85 £ wide-mouthed jar into
the plot at random points along the boardwalk until full. Care was taken
not to disturb the bottom sediment when collecting samples.
Water samples were taken to the laboratory, deaerated with N£, and ad-
justed between pH 5 and 6 with concentrated HCl, sealed with a teflon liner,
then packed in cartons for shipment by bus to the pesticide laboratory.
Water samples spiked with each of the pesticides were carried through the
above procedure to determine the losses that may have occurred in the delay
between sampling and final analysis. Upon arrival at the pesticide labora-
tory at College Station, the samples were placed under refrigeration until
they were extracted. Samples were normally extracted into their respective
solvents on the day of receipt. In some cases, when sampling schedules were
intensive, the samples were extracted in the laboratory at Beaumont, and the
refrigerated extracts were transported directly to College Station.
Soil Solution Sampling —
The original plan was to sample the solution of the soil profile by
using 76 cm long, 16 cm diameter aluminum access tubes. These were forced
vertically into the soil, the inner soil was removed, and the sides of the
aluminum tube was fitted with porous sampling filters at 5, 15.4, 30, and 61
cm below the soil surface as described by Hossner and Phillips (1973). This
approach to sampling the soil solution was not reliable because very little
or no water could be withdrawn from the tight, fine-textured, very slowly
permeable soil. In the few cases where adequate replicated samples of soil
solution were obtained, analysis for certain ions showed excessive variabi-
lity. Thus, the lack of sample, sample volume, and the excessive variation
within replications called for another sampling method.
Since water percolation studies showed that the movement of water
through the soil profile was very small, during 1974 the effort to charac-
terize the soil below 15 cm was abandoned and a concentrated effort was made
to collect soil solution samples from the top 15 cm of soil. At the begin-
ning of the 1974 season, rigid PVC tubes (1.5 cm in I.D.) were fitted with
plastic porous filters (4 cm long and 1 . 1 cm O.D.) and forced into the soil
to a depth of 10 to 15 cm. Again, difficulty was experienced in obtaining
adequate volume and with excessive variations between replications. There-
fore, during the end of 1974 and throughout the 1975 season when the flood
water was on the field, a dialysis tube method of sample collection was used.
Dialysis tubing (1.7 cm diameter by 15 cm long) was filled with distilled
water. These were placed in the plots and covered with approximately 1 cm
of soil After -24 hours of contact with soil solution, equilibrium had been
attained and the dialysis tubing was removed from the plots and analyzed for
and NC-3.
Soil Sampling — „ ^ , r
At the beginning of the experiment, soil samples were taken for xon
and nutrient analysis with a soil core sampler from 0 to 15, 15 to 30, 30 to
19
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45, 45 to 60, 60 to 76, and 76 to 91 cm depths in each plot to establish the
background ionic constituency. Additional soil-surface samples were taken
during the growing seasons. During the 1974 and 1975 seasons, only samples
of the soil surface were obtained because it became evident that water per-
colation was very slow and that the top 15 cm of soil was most important.
Soil samples were also collected with a split tube from each plot in
biweekly intervals at 2.5 to 5.0 and 17.5 to 20.0 cm depths to determine if
any of the applied pesticide moved down through the soil profile. An
aggregate of several small cores from each depth was placed in a 450 ml jar
and stored in a freezer. The samples were packed in dry ice and transferred
to the pesticide laboratory for subsequent screening of the primary pes-
ticides and/or metabolites. The samples were always kept frozen prior to
extraction.
Special Field Experiments and Measurements
Propanil Foliar Study—
After reviewing the 1973 propanil data, it was decided to initiate a
special study to ascertain the source of propanil in the plot water fol-
lowing the flood. A border plot adjacent to the regular plots was seeded
with rice. Ten metal frames 1.3 m^ were driven 5 cm into the soil in the
border plot. The entire border plot was sprayed with the excessive rate of
propanil. The areas within the frames were protected from rainfall with re-
movable plastic covers. These allowed air passage over the plots but were
broad enough to prevent rainfall from reaching them.
Two metal frames were chosen at random 0, 24, 48, 72, and 120 hours
following the spray application. Foliage samples were taken by completely
removing all the vegetation within a 0.2 m^ area in each frame. The foliage
samples were placed into 1.85 liter jars and rinsed with 1 liter canal water.
A 200 ml aliquot of the rinse was extracted for propanil by the procedure
previously discussed. Following the foliage sampling, the area within the
frames was flooded to a depth of 10 cm. A water sample was collected ap-
proximately one hour following the flood and analyzed for propanil.
Prior to the spray application, nine petri dishes with 50 g soil in
each were placed on the soil surface between the foliage in the border plot
to determine the amount of the spray reaching the soil surface. To increase
sensitivity, the soils in three petri dishes were aggregated to give one
sample.
Foliage samples were also collected from all of the regular plots imme-
diately following the spray application and 24 hours later just prior to the
flood. Sampling entailed exfoliation within a 0.2 n? area within each plot.
This gave a measure of the actual amount of propanil remaining on the plants
after spraying and just prior to flooding.
Simulated Rainfall Washoff—
Data collected during the first season indicated the possibility that
carbaryl was washed off from the foliage by rainfall, resulting
in an increase in concentration in the flood water, rather than a decrease
20
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as might be expected due to dilution effects. An experiment was thus de-
signed to determine the amount of carbaryl which could be washed from the
foliage by rains of different intensities and durations which occurred at 0,
1, 2, 4, and 7 days after pesticide application.
A rainfall simulator similar to that described by Morin et al. (1967)
was used to generate controlled rainfall events in the field. Briefly, the
simulator consists of a rotating nozzle which delivers the equivalent of 150
cm of rainfall per hour. A slit disk rotating at 200 rpm intercepts the
majority of the rain so that only specified amounts reach the plots. By
varying the slit width, the intensity can be adjusted from 0.5 to 24 cm per
hour. The rainfall simulator closely approximates the characteristics of
natural rainfall including drop size, distribution and impact energy. In
the field, canvas curtains were used to prevent the wind from shifting the
rainfall pattern which is uniform over a square area 1.3 m on a side. The
well water used in the rainfall simulator was free of compounds which would
interfere with detection of the pesticide.
Since the simulator could only cover a small area at one time, 25 cm
tall plot frames made of galvanized steel were driven 5 cm into the soil.
They surrounded a plot 1.3 m on a side and extended about 10 cm above the
flood level. During 1974 and 1975, the subplots were established in the
border plots not used in the main experiment, Carbaryl was sprayed on the
plots within a few days of the time it was sprayed on the main experiment.
Applications were scheduled so that the long -rainfall simulations could be
accomplished within a one or two day period. To prevent natural rainfall
from reaching the plots between application and simulated rainfall, plastic
tents were suspended above the plots. These were 2.5 m square and allowed
air and light to reach the plots but did not allow even wind-driven rain to
reach the plots. Measurements were made on three replications of all treat-
ments.
Samples of flood water in the plots were collected by dipping a 1.85
liter wide-mouth jar into the plots just prior to the simulated rainstorm
and again at 2, 4, 8, 16, and 30 minutes after the initiation of the storm.
Withholding Irrigation Water—
One management practice which would reduce the quantity of irrigation
water would be to stop adding irrigation water to the permanent flood late
in the season so that the water already present would be lost by evapotrans-
piration before the end of the season. The soil moisture reserve should be
sufficient during this period to insure a yield without the flood. By this
time in the season, competition from weeds which are normally kept down by
the flood should be minimal. An additional advantage is dryer soil during
harvesting.
Therefore in the 1975 season, irrigation of selected impounded plots
was stopped August 1. This date was selected to provide enough time for the
flood present to evaporate by the time the flood would normally be released.
21
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Bulk Density—
A pit was opened in the soil to a depth of 150 cm. Natural peds were
collected from a series of depths. These were preserved at field moisture
until the bulk density could be measured. Volume measurements were made by
water displacement after the peds were coated with wax as described by
Black (1965) in the Methods of joi! Analysis, Monograph No. 9 of the American
Society of Agronomy.
Root Distribution—
To achieve some idea of the distribution of roots in the rice paddy
before and during flooding, samples were collected by forcing 30 cm diameter,
30 cm long sleeves into the soil. These were sliced into layers, The roots
were separated from the soil by the use of both water spray, sieve shakers,
soil dispersants, and hand picking, Dry weight measurements were made.
Length to weight ratios were determined on selected samples.
Organic Load—
At the end of each year, 1.85 liter water samples were collected from
the plots just before the permanent flood was released. A sample was also
collected from the feeder canal at this time. These were analyzed for BOD,
TOG, and COD according to the methods outlined in Standard Methods for the
Examination of Water and Wastewater, 13th edition (1971).
Sediment Load—
The sediment load was determined on the water samples collected for
pesticide analysis. For each collection, three plots were selected at ran-
dom, the sediment in'the sample bottles was resuspended by vigorous shaking,
and a 50 ml sample was withdrawn. This was dried in an oven at 98°C, and
the residue was determined graviraetrically.
Meteorological Measurements
A standard set of meteorological data from a weather station located
1000 m from the field plots is given in Appendix B. It consists of minimum
and maximum air temperature, relative humidity, air passage, precipitation,
and evaporation from a class A pan and a sunken 60 cm diameter pan. Radia-
tion measurements from the Port Arthur Station were extrapolated where
necessary.
Because of the spacial variability of some storms, an additional
weighing rain gauge was located at the site of the field plots. The water
temperature and soil temperature were recorded continuously in selected plots
during the time they were flooded.
ANALYTICAL PROCEDURES
Soil Extraction and Analyses
Soil cores for the respective depths were air dried, ground, and
thoroughly mixed. Ten gram subsamples were then placed in centrifuge tubes
followed by one of the three extractants: 1) water to extract SO? and Cl~;
2) 1 N KC1 to extract NtiJ, N03 and NO^; or 3) 1,4 N KC1 adjusted to pH 4.2
22
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to extract PO^, Ca^, Mg , Na+, and K+. The procedures employed were ac-
cording to Methods of Soil Analysis Monograph No. 9 of the American Society
of Agronomy (Black, 1%5). Tubes were stoppered and placed on a reciprocating
shaker for at least five minutes. Suspensions were then centrifuged for four
minutes at 1200 EPM. The extract was decanted through Whatman No. 1 filter
paper for analysis. Analyses were performed within two days after extrac-
tion. Corrections were made for moisture content and final data was reported
on an oven-dry basis.
All cations except NIty were measured by atomic absorption or by flame
emission on a Jarrell-Ash spectrophotometer. Sample readings were compared
to corresponding values on standard curves prepared from serial dilutions
of commercially available "Flame" standards. All dilutions involving either
standards or samples were made with the respective sample extractant.
Ammonium and all anion concentrations were determined colorimetrically
employing a "Technicon Auto-Analyzer" (Model II) and accompanying strip
chart recorder. To ensure reliability of the chemical analyses, routine
control programs were used as described in the "Handbook for Analytical
Quality Control in Water and Waste Water Laboratories". The "Technicon"
automated procedures employed are detailed in Appendix C. The pH and E. C.
were determined on the water extracts. Conductivity was measured using a
wheatstone bridge, and pH using a pH meter.
Analysis of Water Samples
Analytical procedures for soil solutions were essentially the same as
those employed for the soil analyses, with the exception that distilled, de-
ionized H20 was employed as the diluent, in the samples and standard prepar-
ations. Aliquots of suitable volume were taken for the respective elemental
analyses. Samples were treated with two drops chloroform/100 ml and frozen
to preserve the samples. Water samples were thawed and filtered just prior
to the elemental analyses. Aliquots of the bulk water sample were employed
for NH^ and each anion. Cation concentrations were determined on the bulk
water sample. Nitrogen as NH^, NO^, and N0£ was analyzed first to prevent
errors due to nitrification/denitrification. This was just a precautionary
sequence since chloroform had been added to the water samples upon collec-
tion. The analyses of plot water were performed according to the same pro-
cedures used for soil samples.
Propanil and TCAB--
The procedure used for screening of propanil and TCAB was basically
that developed by Kearney et al. (1970) for rice soils. It was assumed that
an extractant adequate for soils would also be adequate for water.
Five hundred ml of a water sample were placed in a 1 liter separatory
funnel, followed by 200 ml of 1:1 acetone:benzene solution. The mixture was
shaken'for one minute. The aqueous phase was removed by washing with three,
40 ml volumes of 0.1 N NaOH, followed by three, 40 ml volumes of 2 N HC1.
The benzene layer was"dried into a 10 cm bed of anhydrous Na2S04 and trans-
ferred to 250 ml round bottom flask. Samples were reduced in volume on a
Rinco flash evaporator, then taken to dryness with a gentle stream of clean,
dry air. Five ml of hexane were pipetted into the flask, transferred to a
23
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stoppered test tube, and injected directly into the gas chromatograph (GC)
if no clean-up was indicated.
When indicated, samples were cleaned up on Florisil columns. These
were prepared by adding the following to glass columns: glass wool plug,
10 g deactivated Florisil, 1 cm anhydrous NaoSC^ and another glass wool plug.
Florisil, 100/200 mesh, was deactivated at 25°C for 24 hours in an atmosphere
of 30% relative humidity. This environment is established by placing a sat-
urated solution of CaCl2'6H20 in the bottom of a desiccator. Columns were
prerinsed with 50 ml n-hexane. Just as the last of the rinse penetrated the
column, the sample was added followed immediately with the first of two, 10
ml rinses of the flask. The columns were first eluted with 150 ml hexane at
a rate of 5 ml/min. This fraction contained the TCAB. Columns were eluted
with 100 ml 12% diethyl ether/petroleum ether which was discarded. Finally,
propanil was eluted with 200 ml 5% dichloromethane in benzene. This was re-
duced in volume to near dryness, then readjusted to a suitable volume and in-
jected into the GC.
Soil samples were handled in much the same manner as the water samples
with the only difference being an initial filtration of the acetone:benzene
before the washes. Also the sediment on the filter paper was washed with
two, 25 ml portions of the extracted solution. Soil samples and the 1974
and 1975 water samples did not require column clean-up since precautions were
taken in keeping the plastic used to provide the water barrier isolated from
the plot water.
All analyses were performed on a Barber Coleman GC model 5360 equipped
with a tritium source EC detector. The instrument column contained one part
5% DC 710 and two parts 15% QF-1 on Chromosorb W (80/100 mesh). The pyrex
glass column was 4 mm in diameter and 6 ft long. Inlet, column, and detector
temperatures were 225, 185, and 200°C, respectively. The carrier gas (N£)
flow rate was 90 ml/min.
Standards were added to water samples and carried through the above
procedure to determine percent recoveries. Standard recoveries for propanil
and TCAB were generally around 90%.
Limits of detection were calculated by taking the corresponding amounts
equivalent to twice the reagent blank at the appropriate retention time.
These values were 0.4pg/l for propanil, and 0.2yg/l for TCAB in the water
samples. Corresponding limits of detection for the soil samples were O.Olyg/
g and 0.003yg/g for propanil and TCAB, respectively.
Molinate—
Molinate was extracted from water samples using three, 50 ml portions
of n-hexane. This was followed by drying with Na2S04 and reducing the ex-
tract to approximately 2 ml. The sample was quantitatively transferred to
graduated test tube and reduced to a suitable volume with a gentle stream of
dry air. The basic procedure employed was that developed by the Stauffer
Chemical Co. research staff (Knarr, 1970; Schwab and Patchett, 1967).
Soil samples were extracted with 100 ml 20% diethyl ether in dichloro-
24
-------
methane. The extracts were filtered and dried with anhydrous Na2S04 prior
to being taken just to dryness. Samples were taken up in exactly 2 ml n-
hexane and injected into the GC.
All analyses were made on a Barber Coleman GC model 5360 equipped with
a flame thermionic detector. The platimum-iridium wire was coated with
rubidium and potassium sulfate. The column contained equal portions of 10%
DC 200 and 15% QF-1 on Gas Chrom Q (80/100 mesh). Inlet, column, and de-
tector temperatures were 225, 185, and 230°C, respectively. The carrier gas
(N2) flow rate was 90 ml/min. Air pressure was set at 30 psi. Hydrogen was
adjusted to give maximum sensitivity.
The detection limit was 0.3yg/l for molinate in water and 0.02yg/g in
soil samples. Percent recoveries were near 100% for fortified water samples
and near 90% for spiked soil samples.
Carbofuran, 3-keto Carbofuran, and 3-hydroxy Carbofuran—
The derivatization procedure developed by Butler and McDonough (1971)
was used to determine carbofuran and its metabolites. Five hundred ml of
water was extracted with three, 50 ml portions of dichloromethane. The di-
chloromethane was dried by passing it through a bed of anhydrous Na2S04 and
evaporated to approximately 2 ml in a Rinco flash evaporator set at 40°C.
The procedure called for the addition of 0.1 ml keeper solution (1 ml white
mineral oil in 100 ml Cl^C^) prior to reduction in volume. Following the
volume reduction step, the extract was quantitatively transferred to 15 ml
graduated test tubes for the derivatization described in the procedural
paper. Derivatization entailed reaction of the esterified pesticide with
trichloro-acetyl-chloride. This resulted in halogenation of the pesticide
for EC detection.
Soil samples were extracted with 100 ml of 20% diethyl ether in di-
chloromethane on a rotation shaking device for approximately two hours.
Samples were filtered on a buchner funnel, passed through anhydrous Na2S04,
reduced in volume, and then carried through the derivatization procedure.
Instrumentation was the same as previously described for propanil.
Recoveries of carbofuran, 3-keto carbofuran, and 3-hydroxy carbofuran from
fortified soil and water samples were greater than 80% and generally greater
than 90% in the water samples. Detection limits for carbofuran, 3-keto car-
bofuran, and 3-hydroxy carbofuran in water were 0.2yg/l, 0.2yg/l, and 0.5yg/l,
respectively. Corresponding limits for fortified soil samples were O.Olyg/g
for carbofuran, 0.02yg/g for 3-keto carbofuran, and 0.04yg/g for 3-hydroxy
carbofuran.
Carbaryl and 1-Naphthol—
The extraction procedure was essentially the same for carbaryl and 1-
naphthol as that described for carbofuran. The technique utilized to sepa-
rate carbaryl and 1-naphthol was that reported by Butler and McDonough (1970).
The 1-naphthol is partitioned into 0.1 N NaOH, following the dichloromethane
extraction. The NaOH layer containing the 1-naphthol was neutralized with
10 ml 6 N HC1 and re-extracted with dichloromethane. The separate extracts
were then carried through the derivatization procedure as previously mentioned
25
-------
in the carbofuran discussion.
The procedure for extraction of carbaryl and 1-naphthol from the soil
samples was exactly the same as that used for carbofuran. However, no
attempt was made to separate carbaryl and 1-naphthol because it was found
that the procedure employed adversely affected the recovery of carbofuran
from spiked water samples. There was too little material collected for
separate extractions, so it was decided to forego differentiation between
carbaryl and 1-naphthol.
Standard recoveries for carbaryl and 1-naphthol from water were ap-
proximately 100 and 90%, respectively. Recovery from soil fortification was
found to be near 90% for carbaryl and. near 80% for 1-naphthol.
Detection limits were about the same for carbaryl and 1-naphthol. The
detection limit in water was 0.2ug/l, and in soil was O.Olyg/g.
Instrumentation and instrument parameters were the same as for carbo-
furan .
LABORATORY EXPERIMENTS
Pesticide Dissipation
Volatilization—
The volatility of the four pesticides used in the field experiment was
determined in the laboratory using the procedure developed by Farmer et al.
(1972). The method entailed passing air over a known water surface into a
series of traps (Figure 6). The traps contained the appropriate extraction
solvent and were kept at a lower temperature than the volatilization chamber
to minimize losses from the traps,
Air passed over the water surface was dry at first then saturated with
water vapor to ascertain to what extent co-distillation with water occurred.
If co-distillation was a factor, then the vapor flux would be greater with
the dry air. The flow rates employed were 2 and 8 ml/sec. The vapor flux
was determined initially at 42°C. If duplicate determinations using the
highest flow rate showed no flux, no further assessments were made on the
pesticide with respect to volatility.
If the results were positive, volatilization indicated, then a series
of experiments were conducted to determine concentration effects and ad-
sorption effects when soil was added to the water. These experiments were
done at room temperature over an extended period of time.
Photodecomposition—
This mode was evaluated by exposing 300 ml distilled water containing
lOOyg of the specific pesticide to full sunlight. Duplicate samples were
placed in the laboratory for comparison. After four days exposure, the
water samples were extracted and analyzed for the appropriate pesticide.
It was surmised that distilled water would tend to maximize light
26
-------
A Air inlet from source
B Volatilization chamber
C Thermometer
D Vapor traps
Figure 6. Schematic of apparatus used to determine volatiliza-
tion potentials.
27
-------
effects since the plot was somewhat turbid.
Adsorption—
Adsorption coefficients were determined for each of the pesticides and
their respective metabolites. They were determined at various sediment loads
and concentrations. The pesticide was put into a 250 ml centrifuge tube, and
the carrier solvent was allowed to evaporate. Soil amounting to .5, 1, 2,
5, 10, 20, and 30 g was added to separate centrifuge tubes. This was fol-
lowed by 200 ml water. The tubes were stoppered and the contents agitated
on a reciprocating shaker for 30 minutes. Samples were centrifuged until
the water was clear.
The water was transferred to separatory funnels and extracted for the
appropriate pesticide. The percent recovered in the water was calculated
from standards carried through the same procedure but in the absence of soil.
Amounts adsorbed to the soil were determined by difference. Adsorption co-
efficients were calculated from the data. The resultant adsorption co-
efficient (Kd) was correlated to the percent pesticide in solution to assign
some relativity to the values.
Biological and Chemical Degradation—
Soil samples from the field plots were placed in flasks and saturated
with water to simulate the flooded rice paddies in the field (Figure 7).
Some of the flasks were steam sterilized and then spiked with the appropriate
pesticide to estimate non-biological degradation.
The effects of the quality of the reduced environment attained were
determined for carbofuran, 3-keto carbofuran, molinate, carbaryl, and 1-
naphthol. Carbofuran, molinate, and carbaryl were applied after the per-
manent flood under field conditions. The quality of the reduced environment
was varied by adding different amounts of sugar to the soil sample and aided
with different length air convection tubes. After equilibrating the flasks
for one week, pesticide was injected into the flasks with a syringe through
a rubber septum so that the equilibria would not be disturbed. The contents
of the flasks were extracted with appropriate solvent after an additional
equilibrium period of the pesticide with the reduced environment. Redox
potentials were measured in the soil and in the flood water prior to pest-
icide extraction. Potentials were measured with a pH meter using a sat-
urated calomel electrode and a shiny platinum electrode in combination.
Toxicity^gf Pesticides to Fish
The bioassays were conducted in an air conditioned laboratory at the
Texas A&M University Research Annex near Bryan, Texas. The test animals,
channel catfish (Ictalurus jmnct a tu s), were obtained from the Texas Agri-
cultural Experiment Station's Aquaculture Center. The average weight of the
six week old fish was .3 grams. The catfish were acclimated for a period of
at least seven days in aquariums at the test lab. The fish were treated with
actiflavine and 2% terramycin food as a general disease preventative five
days before the tests began. The fish were fasted for 48 hours prior to the
initiation of tests. Tests were conducted using tap water and rice paddy
water. The tap water originated from a well at the Texas A&M Research Annex
28
-------
Capillary Convection Tube
Figure 7. Apparatus for obtaining simulated flood water conditions.
29
-------
and was passed through one cubic foot of activated charcoal to remove
chlorine. Rice paddy water was collected from the Texas Agricultural Experi-
ment Station at Beaumont, Texas, by means of a gasoline powered submersible
pump. It was then transported to the test site in a 4800 liter epoxy coated
steel tank trailer. The paddy water was held out of doors in a 12,000 liter
tank for a period averaging one week before it was used in the tests. Water
samples collected on July 29 and 30 are designated paddy water II.
Water quality parameters for the three test waters are given in Table
4. General values are given for paddy water. Pesticide and fertilizer
treatments applied to the paddies from which the waters were taken are
given in Table 5. Static bioassays were conducted with the four pesticides
used in this study in the filtered tap and both paddy waters. The source
and purity of the compounds used are given in Table 6, In addition, an in-
termittent flow bioassay was conducted for carbofuran only using the filtered
tap water and water from paddy II.
TABLE 4. WATER QUALITY PARAMETERS FOR FILTERED TAP WATER AND
PADDY WATER USED IN THE BIOASSAYS
PH
Total salts
Electrical conductivity
Calcium
Magnesium
Potassium
Sodium
Carbonate
Bicarbonate
Sulfate
Chloride
Filtered Tap
Water
8.5
597.0 ppm
963.0 mhos
2.0 ppm
1 . 2 ppm
0.8 ppm
237.0 ppm
22.0 ppm
461.0 ppm
39.0 ppm
72.0 ppm
Paddy Water
6.4
-
250.0 mhos
2 . 0 ppm
2.0 ppm
2.0 ppm
10.0 ppm
-
120.0 ppm
10.0 ppm
40.0 ppm
30
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TABLE 5, FERTILIZER AND PESTICIDE APPLICATIONS TO THE PADDIES
FROM WHICH WATER WAS COLLECTED FOR THE BIOASSAYS
Paddy Water
Paddy Water II
5/4 Propanil 4/48 kg/ha
5/13 16-20-0 112 kg/ha
5/20 Propanil 3.36 kg/ha
Molinate 3.36 kg/ha
5/25 (16-20-0) 112 kg/ha
(21-0-0) 112 kg/ha
6/14 (21-0-0) 224 kg/ha
7/2 Benlate .56 kg/ha
7/7 4800 liters collected
7/12 4800 liters collected
4/23 (16-20-0) 224 kg/ha
(21-0-0) 112 kg/ha
5/19 Propanil 4.48 kg/ha
5/25 21-0-0 224 kg/ha
5/29 Carbofuran 3.36 kg/ha
7/29 4800 liters collected
7/30 4800 liters collected
TABLE 6. SOURCE AND PURITY OF PESTICIDES USED IN THE BIOASSAY
Common Name
Propanil
Molinate
Carbofuran
Carbaryl
Trade Name
Stam
Ordram
Furadan
Sevin
Manufacturer
Rohm Haas
Stauffer Chem. Co.
FMC Corp.
Union Carbide
% Purity
88.0%
93.3%
99.0%
100.0%
31
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Static Bioassays—
Static bioassays were conducted in accordance with the procedures des-
cribed in Standard Methods for the Examination of Water and Waste Water. Four
liter wide-mouth glass jars each containing three liters of water were used
as test vessels. The pesticide, administered as a single dose, was dissolved
in 3 mis of acetone before being introduced to the test water. Ten parts per
billion of Triton X-100, a surfactant, was added to the carbaryl treatment to
promote its dissolution. Ten test animals were introduced within 10 minutes
after the addition of the toxicant. The test vessels were aerated throughout
each test. Aeration was maintained at between 30 and 80 bubbles per minute.
Mortalities were recorded every 24 hours, and dead fish were removed as soon
as they were observed. Water temperature during the test was maintained at
23°C Ofl°C) by the room air conditioner. Treatments were replicated and the
data were analyzed by means of a probit procedure given by Barr et al. (1976).
Intermittent Flow Bioassays—
Bioassays were conducted on carbofuran with filtered tap water and paddy
water II only. A system was used which added a dose of 250 ml of water con-
taining toxicant at the proper concentration to each test vessel every five
minutes.
For the sake of simplicity, the intermittent flow apparatus may be sub-
divided into the toxicant delivery system, the water delivery system, and the
mixing and separation system. Overall schematics are shown in Figures 8a and
b; the individual components will be discussed in detail.
Toxicant delivery system—The level of the concentrated solution of
toxicant in the toxicant head tank was maintained by means of a pump (Chem
Tech Series 100 Model 015). Excess toxicant was returned to the reservoir
tank via an overflow stand pipe (Figure 9). The toxicant is delivered to the
five toxicant metering devices by means of a manifold made of 5 mm capillary
glass tubing. The toxicant metering device, which is similar to that de-
cribed by Chandler et al. (1974), consisted of 15 ml conical-centrifuge tube
that was fitted with two siphons and a capillary tube. The toxicant entered
the metering device through the capillary tube manifold from the toxicant head
tank. The toxicant rose to a level in the toxicant metering device determined
by the position of the toxicant metering device in relation to the level in
the toxicant head tank.
Water delivery system—The water head tank was made from a 20 liter
plastic bucket equipped with a floatless toilet fill valve (Figure 10).
Water pressure from the faucet was adequate to deliver the filtered tap water
to the water head tank. Rice paddy water was delivered to the water head
tank by means of a small roller type pump that was adjusted to maintain a
pressure of 1.7 bars. The test water was distributed to the six dosing units,
via PVC pipe and 10 mm glass tube (Figure 11). The flow to each of the water
metering devices was adjusted with a stopcock to approximately one liter per
five minutes. The water metering device was constructed from a one liter
Erlenmeyer flask equipped with a U-shaped siphon tube and a siphon break-tube.
The volume delivered was determined by the height of the U-shaped siphon tube.
The water metering device (Figure 12) is similar to part of the automatic
dosing apparatus described by Abram (1960). The water in the metering device
32
-------
u>
Figure 8a. A composite overall diagram of the intermittent flow apparatus.
-------
Figure 8b. Schematic diagram of the intermittent flow system showing
(A) the water delivery system, (B) the toxicant delivery
system, (C) the mixing and splitting apparatus and (D)
the exposure chamber and overflow tube.
34
-------
Ol
Figure 9. A schematic diagram of the toxicant delivery system and metering device where:
(1) is the toxicant reservoir tank (20 t glass bottle), (2) is the toxicant head tankj
(3) is the toxicant overflow standpipe, (4) is the chemical pump, (5) is the toxicant
delivery tube manifold, (6) is the toxicant metering device, (7) is a siphon (5mm glass
tube), and (8) is a siphon.
-------
U5
O\
Figure 10. A schematic diagram of the water head tank where: (1) is the water head tank,
(2) is the floatless toilet fill valve, (3) is the overflow standpipe, and (4) is the
water delivery tube to water metering devices.
-------
Figure 11. A schematic diagram of water delivery system from the water head tank to the six
water metering devices where: (1) is the water head tank, (2) is the floatless toilet fill
valve and (3) represents stopcocks.
-------
•-3
Figure 12. Schematic diagram of a dosing unit where: (1) is the
water delivery tube, (2) is the water metering device,
(3) is the water delivery device, (4) is the toxicant
metering device, (5) is the mixing chamber, (6) is the
flow splitting chamber, (7) is the standpipe, (8) is a
sleeve, (9) is the flow splitting chamber to exposure
tank delivery tube, and (10) is a stopcock.
38
-------
is siphoned into the water delivery device. The water delivery device con-
fof £ a **- r°Und b0tt°m flask ei^PPed with two siphon tubes (Figure
12). The function of the water delivery device was to divert a small portion
of water to the toxicant metering device. This small portion of water causes
the toxicant metering device to empty via its two siphon tubes and results in
the appropriate amount of toxicant being delivered to the mixing chamber.
The major portion of water from the water delivery device is siphoned directly
into the mixing chambers.
Mixing and separation system—The mixing and separation system consisted
of two major parts, the mixing chamber and the flow splitting chamber.
The mixing chamber (Figure 13) was made from a 2.5 liter crystallizing
dish equipped with a U-shaped siphon tube similar to the mixing cells de-
scribed by Mount and Warner (1965).
The mixing chamber was designed to siphon on half cycles, two liters of
test solution, in order to facilitate better mixing of the toxicant and di-
luent water.
The test solution (toxicant mixed with diluent water) siphons from the
mixing chamber to the flow splitting chamber. The flow splitting chamber,
similar to that described by Benoit and Puglisi (1973i consists of a two liter
beaker with four flow splitting siphons (Figure 13).
As the test solution rises slightly above the top of the sleeves in
each chamber, water is forced through the notches and down the standpipe.
This action creates a siphon which empties the flow splitting chamber and
delivers the test solution to each of four exposure tanks via the exposure
tank delivery tubes (Figure 13).
The test vessels, or exposure tanks, were 20 liter glass bottles with
the tops cut off. Ten mm drain tubes were installed at the 16 liter level.
The end of the drain tube in the exposure tanks was constricted to prevent
fish from entering the drain. The drain tubes were connected with rubber hose
to the central drain manifold that delivers the spent test solution to a tank
trailer for disposal.
The intermittent flow apparatus was adjusted to deliver different
dilutions of the toxicant. The dilutions used are given in Table 7.
The actual dilution factors were determined by operating the apparatus
for 24 hours using a flourescent dye (Rhodamine B) in the toxicant delivery
system. The concentration of dye in the exposure tanks was determined with
a fluorometer. The dye test showed the concentrations to be identical in each
of the four exposure tanks within each dosing unit. These dilution factors
were used to calculate the toxicant concentrations used in the actual test
treatments.
The intermittent flow bioassays were conducted with 10 catfish (Ictalurus
punctatus) in each 16 liter exposure tank. Mortalities were recorded every
12 hours and dead fish were removed as soon as they were observed. Tempera-
39
-------
—I
Figure 13. A diagram of the mixing and separation system where:
(1) is the mixing chamber, (2) is the U shaped siphon
tube, (3) is the flow splitting chamber, (4) is the
standpipe, (5) is the sleeve, (6) is the flow splitting
chamber to exposure tank delivery tube.
40
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TABLE 7. ADJUSTED INTERMITTENT FLOW DILUTION RATES
JJSED IN THE BIOASSAY
Unit Number
1
2
3 (control)
4
5
6
Volume of Toxicant
10
8
0
6
4
2
ml
ml
ml
ml
ml
Volume of
Diluent Water
990 ml
992 ml
1000 ml
994 ml
996 ml
998 ml
tures during the tests were 23°C (+2°C). Aeration was not needed since dis-
solved oxygen concentrations in the flowing systems were great enough. TLM
values were calculated for 24, 48, and 96 hour periods. The results were
subjected to the same analysis used for the data from the static bioassay.
Ion Equilibrium Studies
The primary objectives of the chemical equilibrium studies were to ob-
tain values of the exchange coefficients for Na+, K+, Ca"1"*", and Mg++ in a
Beaumont clay soil, and to determine the effect of concentration of various
cations on the exchange coefficients.
J-. I 1 I II 1^1 ..L
One normal stock solutions of K , Na , Ca , Mg , Ba , and Ntfy were
prepared from their respective Cl~ salt. These were standardized against
commercially available flame standards.
A preliminary experiment was conducted to ascertain the interference
levels between cations exchanged and the Ba4"4" exchanger in the subsequent
flame and atomic absorption spectrophotometric analyses. Calcium and mag-
nesium were determined by atomic absorption. Sodium and potassium were de-
termined by flame emission. Barium was the exchange ion of choice since it
does not normally occur on soil clay exchange sites. To evaluate possible
antagonisms by B3++, standard dilution series were prepared for each cation
employing distilled, deionized water as the diluent, and another using 1 N
BaClo. Instrument settings (slit width, wave length, etc.) were optimized
for the standards in H20 and were maintained the same for the standards in
BaCl2.
41
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Another preliminary experiment was conducted to determine optimum
shaking times for the equilibrium studies. Twenty gram samples of a Beaumont
clay soil were equilibrated for 0.5, 1.5, 3, 6, and 12 hours with 200 ml of
distilled 1^0 and a (50 + 50) ppm (K + Mg) solution on a reciprocating shaker.
Resultant suspensions were centrifuged at 1500 rpm for 10 minutes, then an
aliquot was collected to determine equilibrium solution concentrations of Na ,
K , Ca"1"1", and Mg"1"1". Analyses of the supernatant solution showed no difference
in the concentration of Na+, K+, Ca4^, or Mg++ with respect to time, suggest-
ing that equilibrium was attained within 30 minutes at the dilution employed.
An equilibrium experiment was conducted on a soil classified as a
Beaumont clay but was not collected within the plots. The experiment was not
replicated but included all possible combinations for a two to four cation
system. A 20-g subsample was weighed into a 250 ml centrifuge tube, followed
by the respective cation treatments, and adjusted to give a final volume of
200 ml. Salts for the amendments were prepared in distilled, deionized H^O,
Samples were shaken 30 minutes on a reciprocating shaker, then centrifuged
10 minutes at 1500 rpm. An aliquot of the supernatant was collected and
analyzed for Na+, K , Ca , and Mg~*"+. These data were reported in m moles/
liter based on a saturated soil solution. Percent water at saturation was
assumed to be 45%. Taking into account initial moisture, a 20-g soil sample
would, therefore, contain 0.00835 liters of solution at saturation. The sed-
iments were rinsed with two, 100 ml volumes of distilled water prior to being
extracted with 100 ml 1 N_ BaCl2. The volume was adjusted for the 1^0 remain-
ing following the rinses. Dilutions, when necessary, were made with 1 N^ BaCl2«
Cation concentrations were reported in meq/lOOg on an oven dry soil basis,
A second equilibrium study was performed on Beaumont clay soil samples
collected from the field study plot site. Duplicate 10 g soil samples were
amended with the various treatments and adjusted to a 100 ml final volume.
Handling from this point was the same as in the previous experiment. Solu-
tion concentrations were reported in m moles/liter of saturated soil solution.
Corresponding soil values were reported in meq/100 g oven dry soil.
42
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SECTION 6
RESULTS AND DISCUSSION
WATER BALANCE
Introduction
Several methods of managing flood water for rice cultivation are pres-
ently in use. In one, a flood may be maintained continuously from the time of
seeding to just prior to harvesting. The primary purposes of the continuous
flood is to control weeds and irrigate the crop. The availability of her-
bicides now allows procedures to use short floods (typically only 24 hours)
early in the season to water the crop. In this system a permanent flood is
established only after the crop has developed to a height such that approx-
imately half of the foliage will protrude above the water level. During the
period of permanent flood, water may be applied intermittently to resupply the
losses or a continuous small flow may be used to maintain the water level and
in some cases, maintain a continuously flowing stream through the paddy. Ir-
rigation return flow from rice fields may thus occur during release of water
when the fields are flooded and drained early in the season before permanent
flood. In addition to planned releases, heavy rainfall may wash over the
levees or necessitate a deliberate release to prevent erosion of the levees.
Most of the measurements of water balance in rice paddies have been made
during the permanent flood. Several approaches have been utilized. Lysi-
meters were used by Rung (1965) and many of the earlier researchers he cites.
Evans (1971) also used lysimeters to determine the evapotranspiration losses
of water. Microtneteorological measurements of the energy balance have been
made by Kumai and Chiba (1953) , the scientists of the Research Group of Evapo-
transpiration of Japan's National Institute of Agricultural Services (1967)
and Lourence and Pruitt (1971). Kato et al. (1965) utilized a leaf chamber to
compare the transpiration rates of upland and flooded rice.
The water balance of a rice field over a season may be written as:
where P = amount of precipitation
I = depth of irrigation
E = amount of water lost due to evaporation from the water surface and,
to a lesser extent, from wet foliage
43
-------
T = the loss due to transpiration
R = the loss by runoff
L = the percolation loss
As indicated by Rung (1965), L may be a combination of losses which occur
vertically below the root zone, or losses which result from lateral movement
through the soil or through earthen levees. The latter can result in mis-
leading results particularly where measurements are made on isolated field
plots.
Evaporation and transpiration rates will depend on canopy cover and
meteorological conditions, while L will depend on the properties of the soil.
Thus, the contribution of each of these will vary from one location to another
and even from one field to another. Many of the studies in the literature
have reported on several of the parts of the water balance, but none report
on all of the components in a controlled experiment.
Average seasonal transpirational losses (JCung, 1965) range from 0.12 to
9.8 mm per day, while losses to percolation range from 0.2 to 15.6 mm per day.
For individual days, Evans (1971) reported evapotranspirational losses as
great as 12.4 mm/day.
The piezometer data indicated that the wetting front had reached a
depth of 10 cm in six hours after flooding. The soil in the lysimeter boxes
was 10 cm deep, therefore, after the day on which irrigation was applied, no
water was required to fill the pores in the soil in the lysimeters and since
downward and lateral movement was prevented, subsequent losses in water were
taken to be ET.
Irrigation and Rainfall
The amount of water used to irrigate the field just after seeding, that
required to irrigate the crop between seeding and the permanent flood, and
that required to establish the permanent flood were calculated from the amount
of water required to saturate the surface soil plus the depth of water when
irrigation was completed. Water was applied to all plots by the use of siphon
tubes when the level dropped too low. When the level of water in the lysi-
meters became too low, the one or more stoppers were temporarily removed from
the wall allowing water to flow from the flooded plots into the lysimeter.
The rate of water delivery was rapid, generally requiring only a few minutes
to a few hours to return the levels in the plots to the bottom of the 10° out-
flow weir or reestablish a 10 cm flood in the lysimeters. The supply of water
to the continuous flow plots varied from time to time because of difficulty
with material obstructing the float valve. The valves were checked and cleaned
twice a week and the depth of. water flowing - through each weir was recorded at
these times. Linear extrapolations between these data were used to calculate
the rate of continuous flow irrigations for each plot.
Precipitation was measured in the recording rain gauge immediately ad-
jacent to the plots, but for certain storms, the amount of water received by
44
-------
different plots as shown by the depth records varied widely. For these oc-
casions attempts were made to utilize the best average. The detailed rainfall
data are shown in Appendix A for all three years.
,Sev<}ra?; extreme eve*ts required special attention. The 7.9 cm rain on
?oS /?? Cm raln °n July 31> 1974' and the 21'6 cm rain °n June 9,
1975, fell too rapidly to allow all the water to flow through the 10° weir.
The rainfall threatened to overtop the levees. This would have resulted in
water flowing from one plot to another and could have washed out some of the
levees making repair necessary and making later water control difficult.
During each of these storms, the 45° weirs were opened to allow the excess
water to drain off. Weirs were closed again soon after the storms were over.
These storms resulted in large losses from the fields but are not unlike what
occurs in large fields when large amounts of rain fall in a short period of
time. The lysimeters were also overtopped during this period, and in some
cases, a day or two passed before the level of water in the plots dropped be-
low the level of the top of the lysimeters. During these periods, the data
were adjusted as necessary.
During 1973, the rainfall was great enough and was well enough dis-
tributed so that very little supplemental irrigation was needed in the inter-
mittent plots. During both 1974 and 1975, the rainfall during June and the
first half of July was spaced, necessitating several irrigations. During
both years the rainfall in late July and August was greater than evapotrans-
piration, eliminating the need for irrigation.
Water Depth Data
The depths of irrigation water calculated from the water stage recorders
for all plots during 1974 and 1975 are shown in Appendix D, Tables Dl through
D6.
The water stage recorders provided resolution of 0.05 cm of water depth
or better so that the daily pattern of water loss from each plot was traced.
Detailed data for a several day period from one plot are shown in Figure 14.
This was an intermittently irrigated plot and during this time, no water was
flowing out of the weir. The line at 9-4 cm represents the level of the bot-
tom of the 10° weir.
Two problems occurred with the water data the first year which made it
impossible to calculate an accurate water balance. Despite our efforts to
compact and cover the earth levees with plastic, leaks occurred into, out of,
and between the plots. Although vertical infiltration in these clay soils is
very slow, apparently considerable movement occurred between the peds that
were scraped from the surface to make the levees. The second problem was the
lack of sensitivity of the water stage recorder. Steps were taken to correct
both of these problems before the second year of research. As a result of the
difficulties, a majority of the effort in interpreting the water balance and
its subsequent use to calculate the salt balance, was concentrated on the
1974 and 1975 data.
During the night, the water losses due to infiltration or evapotrans-
45
-------
E
o
O)
SAM
6PM
7/8
SAM
6PM
1
7/9
SAM
6PM
7/10
SAM
6PM
Time (hours)
Figure 14. Details of the water depth in an intermittently irrigated plot.
9.4 cm represents the depth of the bottom of the 10° outflow weir.
The line at
-------
piration were very small. The major decrease in water depth occurred during
the midday, and the slope again flattened during sunset. The 2 2 cm rain
which occurred as a brief shower, followed by a downpour, can be clearly seen.
The rapid drop just after the rain represents the water running out through
the 10° weir. 6
A continuous record of two plots, one each intermittently irrigated and
one each continuously irrigated for 1974 and 1975, are shown in Figures 15,
16, 17, and 18. The detail shown in Figure 14 cannot be seen on these figures,
The general seasonal patterns, however, are evident. During 1974, some out-
flow occurred early in the season for the intermittently irrigated plot as a
result of excessive rains or over-irrigating. By July 21, the level of water
was very low, and a large irrigation overflowing the weir was applied July 22.
During the rest of the season, the rain was great enough to keep water flowing
out at all times until the paddy was drained August 22.
The water level of the continuous flowing plot from 1974 was above the
bottom of the weir and flowing out throughout the flooded period except be-
tween June 16 and 21. Irrigation water was siphoned into the plot June 21
to bring the level above the bottom of the weir.
The difference on the diurnal pattern can be seen by comparing these
plots. For the intermittently irrigated plot when no water is flowing out
the weir, the level drops during the day due to evapotranspiration and re-
mained nearly constant or dropped slightly during the night. For the con-
tinuously irrigated plot, the water level drops slightly during the day, but
increases again during the night since the water continues to run into the
plots. A prolonged period of these oscillations uninterrupted by rainfall
can be seen in Figure 17 starting July 19.
The water depths were read at three hour intervals and utilized to cal-
culate the water balance.
Infiltration
Water loss was calculated from the water depth data in the impounded
plots and the lysimeter box data during 1974 and 1975. Periods typically
three to four days long during times when no water was flowing out of the
plots, between rainfalls, and irrigations were selected. The difference in
water loss between the plots and the lysimeter boxes during this time period
may be attributed to either infiltration or possibly, but less likely, to
evaporative losses from the earthen levees. Efforts were made to keep the
exposed levee surface surrounding the plots small, but it is estimated that
the soil surface was equivalent to about 1/6 of the water covered surface of
the plot. This could contribute significantly to water loss if the soil sur-
face was wetted from the flood water for extended periods of time.
The average water loss in excess of evaporation is shown in Figure 19
for 1974 and 1975. To further isolate the nature of the loss, the levees of
one plot were covered with plastic during the 1975 season only Water loss
from this plot is shown separately in the figure. Only small differences are
noted between the water loss from the plastic-covered plot and the average of
47
-------
-P-
00
7/» 1/22 1724 7/M 7/2« T/30 I/I «/S »/0 8/7
Figure 15. Seasonal patterns of water depth in intermittently irrigated plots during 1974.
The date line represents the bottom of the 10° outflow weir.
-------
to
19
I ! I I
*1e
Figure 16. Seasonal patterns of water depth in intermittently irrigated plots
during 1975. The date line represents the bottom of the 10° outflow weir.
-------
Ol
o
Figure 17. Seasonal patterns of water depth in continuously irrigated plots during
1974. The date line represents the bottom of the 10° outflow weir.
-------
22
21
20
19
I *
f "
8 i&
Si 15
22
21
20
19
18-
17
16
Figure 18. Seasonal patterns of water depth in continuously irrigated plots during
1975. The date line represents the bottom of the 10° outflow weir.
-------
.10-,
~2Q\
E
o
(A
0>
o
a
40H
.50
o 1974
XI975
6/10 6/20 7/1 7/10 7/20 7/30 8/1
TIME (dote)
Figure 19. The loss of water due to leaching for all plots
during the 1974 and 1975 growing seasons.
52
-------
those not covered. Field observations indicated that the soil surface did
dry out between rains. The dry surface layer thus apparently prevented sig-
nificant evaporative losses. The losses thus determined must then be attri-
buted to infiltration. During 1974, the infiltration rate decreased from
0.29 cm per day at the beginning of the season to 0.1 or less by the end of
the season. While the infiltration during 1975 was as great as 0.20 cm per
day soon after permanent flood, only on two occasions during the middle of
the season did it drop below 0.10 cm per day.
Piezometer Data—
The depth of the water measured by the piezometers in 1975 is shown in
Figure 20. The flood water wet the top 10 cm within a few hours and reached
20 cm within one day. Three more days were required to reach the 30 cm
depth, and each increment past that required considerably more time. By the
end of the season, the saturated zone reached only 70 cm. Piezometers to a
depth of 150 cm showed no water table through the entire period. These data
indicate that water movement into the profile was very slow and that through-
out the period of flooding the wetting front did not join with the water
table below. Since the most rapid transpiration is expected to be under sat-
urated conditions, it is suggested that the leaching of soluble salts or
other contaminants in the water from the flooded zone of the soil was negli-
gible during the period of the study.
Bulk Density—
Since the clay soil studied is well structured, it was of interest to
measure the bulk density as a function of depth. The data are also useful
for converting measurements including water content and root density from the
unit weight to the unit volume basis.
The profiles of the bulk density of natural wet peds taken at different
depths are shown in Figure 21. The greatest bulk density is found in the
surface sample. This is probably a result of the puddling and compacting
which results from the heavy equipment used during soil preparation, planting
and fertilizing. The bulk density decreases to a minimum value at 25 cm and
increases again slightly with depth below that level. The values below the
surface are typical of what would be expected for a vegetated shrinking-
swelling clay soil.
The greater bulk density at the surface did not appear to restrict in-
filtration immediately since the piezometer data and the calculated infiltra-
tion rate indicated that water moved most rapidly through the surface and
slowed down as it reached lower layers. It may have restricted the infiltra-
tion later by blocking pores as it swelled.
Moisture Content—
On several occasions, large soil cores were taken from the field. These
were portioned in depth increments and moisture content determined on a dry
weight basis. This data was converted to the percent moisture on a volume
basis shown in Figure 22. The wetting front had moved deeper than the 20 cm
depth well before the sample was taken on July 10. Thus, both the July 10 and
August 21 samples were from saturated soil. The range of values may be a re-
sult of soil variability in the vertical direction in the field. In both
53
-------
30-
6/5 6/6
100 flooding
starts
6/7
DATE
6/8
6/9
13 21
JUNE
5 13 21 29
AUGUST
DATE
Figure 20. Depth of irrigation water in rice paddies during 1975 measured with
piezometers.
-------
10
20
30
40
~ 50
60
70
80
90
100
BULK DENSITY (gm cm-3)
1.2 1.3 1.4 1.5
Figure 21. Bulk density profile in the flooded rice paddies.
55
-------
(%) Moisture
22 26 30 34 38 42 46 50 54
Q.
O
10
12
14
16
20
\
\
\
\
j
^
A
O 7-10-75
A 8-21-75
• 8-28-75
Figure 22. Moisture content by volume on several dates at
various depths in the rice paddies.
56
-------
cases, the moisture content at the surface was the greatest and decreased to
a depth of 2 cm. They were essentially constant below this level. The mois-
ture contents at the surface and the bulk density of 1.4 g cm indicates
that nearly all the pores were filled with water. While the soil below was
at potentials of zero and above, indicating saturation, the moisture content
indicated that a considerable fraction o- the pores was filled with air.
The sample on August 28 was taken several days after the flood had been
drained. The surface had dried, but changes in moisture content below 4 cm
were small.
Root Distribution—
Water, nutrients and ions are removed from the soil profile to roots. To
achieve a better understanding of the distribution of uptake and movement of
water and ions in the soil profile, we must have data on the distribution of
roots and the change in distribution with time. Replicated cores were, there-
fore, taken periodically throughout the 1975 season and dissected for root
distribution. The roots were separated and dried; the length to weight ratios
were developed for different layers; and the different sampling dates were
used to convert the weight to the length basis. The results expressed as
length of root per volume of soil are shown in Figure 23. Just before flood-
ing on June 4, the root distribution was very linearly decreasing from 4 cm/
cm at the surface. The density decreased linearly to a depth of 5 cm. Roots
had proliferated below this level by this date and extended down to 19 cm.
Subsequent distribution of root density did not differ greatly from the data
of June 28, with the exception that the root density near the surface in-
creased to as great as 20 cm/cm .
These results indicate that despite the abundance of water in the system,
the roots continue to proliferate after the field is flooded. Much of the
additional growth appears to take place during the first month after flooding.
Although the roots are denser in a thin layer near the surface, the majority
of these are found below the 2 cm depth representing a considerable sink for
nutrients and perhaps water within the profile.
Meteorological Data
The detailed meteorological data are given in Appendix B. This data will
be used to calculate an estimate of the evapotranspiration. The water and
soil temperature data are also given in Appendix E. A plot of the minimum and
maximum water and soil temperature data are given in Figures 24 and 25 for the 1974
season. The maximum temperatures were greatest during June and the first half
of July while the weather was clearer. The amplitude of the diurnal water tem-
perature cycle was typically 5°C while that of the soil temperatures was typi-
cally 3°. Both decreased with time as the maximum decreased. The water tem-
perature averaged 30° for the season. This temperature should be in the optimum
range for biological decomposition of most organic pesticides and is above the
temperature at which channel catfish can survive bacteriological infestations.
Estimated Evapotranspiration
The loss of water from the paddy by evaporation will have the result
57
-------
Ul
00
ROOT DENSITY (cm/cm3)
4 6 8 10 12
14
16 18
20
10
12
I'M
16 H
18
/
/
/
JUNE 4
JUNE 25
JULY 10
JULY 31
AUG 21
Figure 23. Root density, expressed as length of root per cm of soil, as a function
of depth for five sampling dates during the growing season.
-------
(Jl
40i
38
36
34
32
J)
3 30
"
28
26
24
20
a Water (mini
X Water (max.)
^ \ ?/l5 7/l9 ?/23 ?/27 \\ \ \ \2 8/|6
Time (date)
Figure 24. Minimum and maximum water temperatures during the 1974 season.
-------
o\
o
o
CD
40
38
36
34
32
28
26
24
20
O Soil min.
A Soil max.
Time (date)
Figure 25. Minimum and maximum soil temperatures during the 1974 season.
-------
of concentrating the salts in the water that remains. The amount of water
lost by this means is thus important in determining the quality of the irri-
gation return. Since detailed information is not available on a regional
basis, it is of interest to develop correlations between measured evapo-
transpiration, evapotranspiration calculated from meteorological data, and
that characterized by pan evaporation.
Several approaches may be used to calculate the evapotranspiration from
meteorological data. A combination equation, which takes into account wind
speed, radiation temperature, vapor pressure and crop characteristics was
developed by van Bavel (1966) as:
-A/yH + 2 B d
TF - - v a
o " A/Y + 1
where L = the latent heat of vaporization in cal/g
E = the potential evaporation in cm day
A = the slope of the saturation vapor pressure curve
Y = the psychrometric constant
H = the RN-S where RN is the net radiation and S is the heat stored in
the water and the soils both in cal/cm2/min at standard pressure
d = the vapor pressure deficit in mbars
3.
Bv is a wind dependent transfer coefficient given as:
"./
*a o
2
in g/cm /min/mbar, where:
p = the ambient pressure in mbar
e = vapor pressure
k = Von Karman's constant (0.40)
-3
p = air density in gm cm
3.
u = the windspeed in cm/sec
a
Z = the elevation above the surface at which the measurements were taken
in cm
Z = the roughness parameter in cm,
o
For the present study, RN was calculated from measured incident radiation
61
-------
using modification of the equation of Uchijima (1969) to take into account
the crop height. Net radiation is given as:
RN = (0.70 - .001753 DN) • IR
—2 —1
where IR = incident radiation in cal cm day
DN = the number of days after flooding of the paddy
The DN factor takes into account the growth and development of the rice crop,
S was taken as the change in heat stored in the water layer as calcu-
lated from the difference between the minimum and maximum water temperatures.
Changes in the heat stored in the soil were anticipated to be even smaller
than those in the water and were, thus, not taken into account. The rough-
ness length as a function of crop height developed by Monteith (1973) is
given as:
Z = 0.13 h
o
where h is crop height in cm.
Measured evapotranspiration, evapotranspiration calculated as described
above, and measured class A pan evaporation are given during the period of
permanent flood in Tables 8 to 13 and for 1974 and 1975, The regression equa-
tions and values of r are given in Table 14 (Barr et al., 1976). All the re-
gression equations had large positive intercepts and slopes which were much
less than 1.0. The r values were not significant. It was suspected that the
discrepancy between the times that the measured and meteorological and pan
data were taken may have had some influence on the poor relationship. The
measured data was the total water loss between midnight one day and midnight
the next, while the weather data and the pan measurements were supposed to be
made at 8:00 a.m. each day. While the minimum and maximum temperatures were
arranged so that they were used to calculate the potential evapotranspiration
on the appropriate days, it was not possible to adjust the wind record. On
some occasions, the observer did not record the data until as late as 10:00
a.m., adding to the discrepancies. The four sets of data for each year were,
therefore, summed over seven day periods to eliminate day-to-day fluctuations
and the regressions were run again. The correlation improved some, but the
regression equations still poorly predicted the measured evapotranspiration
rates. These results are in contrast with what would be expected from a rice
crop. One would suspect that the flooded rice would be closely approximated
by calculated potential and pan evaporation. These results are also different
from the report of Evans (1971) of an r value of 0.91 between pan evaporation
and measured evapotranspiration for flooded rice.
The reason for the poor correlation between the measured and calculated
values is not evident, and we may conclude that for our climate, daily losses
cannot adequately be reflected by calculated evapotranspiration or measured
pan evaporation.
When the water loss was summed over the entire period during which the
rice was flooded, the results shown in Table 15 were in better agreement.
62
-------
TABLE 8. MEASURED DAILY EVAPOTRANSPIRATION RATE, CALCULATED POTENTIAL
EVAPORATION, CLASS A EVAPORATION, AND EVAPORATION FROM A 60
CM SUNKEN PAN
Date
I
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Total
Mean
Measured EVTS
cm
.__
-
-
-
-
.18
.50
.66
.26
.47
.60
.52
.70
.57
.78
1.05
.95
.86
.86
.74
.45
.92
.82
1.01
1.00
.80
.86
.71
.66
.65
17.52
.7008
June, 1974
Calculated
E cm
o
0.46
0.49
0.60
0.61
0.68
0.36
0.54
0.44
0.28
0.67
0.46
0.59
1.04
0.68
0.75
1.07
0.77
0.64
0.70
0.62
0.55
0.89
0.53
0.49
0.30
0.56
0.62
0.63
0.63
0.64
18.29
0.61
Class A Pan
.22
.27
,27
.29
.32
.29
.23
.32
.27
.39
.27
.31
.35
.32
.34
.30
.34
.31
.29
.32
.33
-
-
.46
.40
.36
.33
.54
.16
.24
8.77
0.29
60 cm Pan
.20
.18
.15
.15
.24
.18
.18
.19
.18
.26
.17
.17
.24
.09
.11
.20
.21
.21
.20
.21
.21
.23
.31
.41
.33
.27
.24
.37
.12
.17
6.38
0.21
63
-------
TABLE 9. MEASURED DAILY EVAPOTRANSPIRATION RATE, CALCULATED POTENTIAL
EVAPORATION, CLASS A EVAPORATION, AND EVAPORATION FROM A 60
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Total
Mean
Measured EVTS
cm
.49
.74
.84
.78
.82
.61
.60
.25
.75
.69
.50
.70
.54
.57
.18
.33
.33
.70
.57
.67
.65
.81
.89
.68
.65
.76
.94
.62
.70
1.00
.20
19.56
0.631
July, 1974
Calculated
EQ cm
0.44
0.69
0.54
0.59
0.83
0.71
0.77
0.77
0.75
0.84
0.56
0.61
0.88
0.32
0.29
0.49
0.43
0.61
0.78
0.53
0.65
0.54
0.56
0.48
0.48
0.23
0,54
0.38
0,67
0.61
0.49
18.06
0.583
Class A Pan
.18
.31
.35
.33
.40
.25
.22
.24
.29
.33
.21
.33
.34
.28
.11
.23
.21
.27
.28
.30
.31
.34
.32
.28
.29
.41
.25
.33
.31
.40
overflow
8.94
0.29
60 cm Pan
.15
.19
.29
.19
.26
.19
.18
.15
.19
.21
.14
.27
.21
.22
.10
,14
.13
.19
.16
.28
.19
.22
,23
.21
.20
.33
.34
.26
.30
.32
overflow
6.44
0.21
64
-------
TABLE 10. MEASURED DAILY EVAPOTRANSPIRATION RATE, CALCULATED POTENTIAL
EVAPORATION, CLASS A EVAPORATION, AND EVAPORATION FROM A 60
CM SUNKEN PAN
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
,20
21
22
23
24
25
26
27
28
29
30
31
Total
Mean
Measured EVTS
cm
.53
.18
.30
.62
.64
.27
.40
.67
.50
.83
.56
.48
.49
.47
.28
.52
.64
.63
.69
.59
.52
.41
11.22
.51
August, 1974
Calculated
E cm
o
0.61
0.36
0.42
0.41
0.51
0.31
0.53
0.52
0.31
0.34
0.48
0.41
0.54
0.56
0.51
0.58
0.50
0.52
0.47
0.47
0.45
0.69
10.5
.477
Class A Pan
.25
.12
overflow
.21
.29
.12
overflow
.18
.31
.21
.28
.26
.29
.27
.20
.24
.26
.27
.29
.28
.23
.28
4.56
.207
60 cm Pan
.25
.10
.18
.14
.20
.09
overflow
.18
.20
.16
.23
.17
.27
.21
.18
.18
.19
.18
.20
.18
.18
.20
3.67
.167
65
-------
TABLE 11. MEASURED DAILY EVAPOTRANSPIRATION RATE, CALCULATED POTENTIAL
EVAPORATION, CLASS A EVAPORATION, AND EVAPORATION FROM A 60
CM SUNKEN PAN
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Total
Mean
Measured EVTS
cm
_
-
-
-
.14
.60
.55
.48
-
4.45
.27
.56
.72
.87
.75
.85
.95
1.01
.93
.80
.77
.54
.48
.50
.11
.23
.36
.58
.26
.36
18.12
.724
June, 1975
Calculated
E cm
o
0.43
0.57
0.60
0.69
0.67
0.82
0.42
0.51
0.13
0.31
0.26
0.55
0.58
0.93
0.62
0.80
1.08
0.81
0.72
0.78
0.52
0.58
0.85
0.50
0.21
0.31
.38
0.49
0.33
0.42
16.86
.562
Class A Pan
.34
.27
.33
.28
.34
.26
.16
overflow
overflow
.06
.24
.30
.38
.25
.34
.37
.31
.23
.13
.26
.27
.28
.20
.11
.10
.21
.20
.15
.21
.22
6.93
.231
60 cm Pan
.16
.17
.18
.17
.20
.14
.15
overflow
overflow
.08
.19
.20
.26
.18
.17
.20
.21
.17
.19
.19
.14
.20
.12
.12
.08
.11
.22
.12
.12
.15
4.65
.155
66
-------
TABLE 12. MEASURED DAILY EVAPOTRANSPIRATION RATE, CALCULATED POTENTIAL
EVAPORATION, CLASS A EVAPORATION, AND EVAPORATION FROM A 60
CM SUNKEN PAN
Date
Measured EVTS
cm
July, 1975
Calculated
E cm
o
Class A Pan
60 cm Pan
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Total
Mean
.47
.52
.14
.56
.81
.79
.75
.77
.88
.81
.32
.50
.59
.21
.13
.40
.36
.60
.73
.56
.71
.30
.15
.33
.47
.50
.68
.98
.46
.39
.84
16.81
.542
0.59
0.58
0.29
0.42
0.74
0.80
0.99
0.84
0.73
0.81
0.43
0.59
0.82
0.40
0.35
0.49
0.47
0.58
0.80
0.62
0.73
0.30
0.40
0.45
0.52
0.55
0.76
0.70
0.69
0.50
0.37
18.31
.591
.23
.07
.24
.30
.32
.34
.26
.26
.34
.19
.25
.30
.16
.13
.18
.18
.28
.36
.27
.28
.13
.14
.11
.24
.22
.33
.29
.28
.16
overflow
overflow
7.06
.235
.02
.19
.14
.17
.25
.21
.19
.19
.21
.15
.13
.17
.14
.08
.12
.10
.20
.18
.17
.17
.09
.10
.11
.11
,14
.16
.18
.21
.15
overflow
overflow
4.58
.153
67
-------
TABLE 13. MEASURED DAILY EVAPOTRANSPIRATION RATE, CALCULATED POTENTIAL
EVAPORATION, CLASS A EVAPORATION, AND EVAPORATION FROM A 60
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Total
Mean
Measured EVTS
cm
1.04
.34
1.27
.67
.85
.62
.34
.37
.52
.37
.48
.64
.66
.30
.51
-
—
-
-
-
-
-
-
-
-
-
-
-
-
8.98
.528
August, 1975
Calculated
E cm
o
0.63
0.50
0.47
0.25
0.41
0.38
0.57
0.53
0.44
0.32
0.48
0.37
0.49
0.55
0.58
0.38
0.44
0.51
0.33
0.28
0.38
0.20
0.30
0.51
0.42
0.30
0.13
0.20
0.36
0.36
0.36
7.79
.458
Class A Pan
.09
.37
overflow
_
.06
.27
.42
.36
.15
.24
.21
.25
.25
.28
.18
.21
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
3.34
.196
60 cm Pan
.14
.13
overflow
.12
.12
.21
,21
.18
.10
,14
.13
.13
.16
.20
.09
.17
.17
.15
.14
.11
.18
.21
overflow
.10
.12
.15
.16
.14
.08
-
-
2.23
.131
68
-------
TABLE 14. REGRESSION EQUATIONS AND CORRELATION COEFFICIENTS
BETWEEN MEASURED EVAPOTRANSPI RATION (EM), CALCULATED
POTENTIAL EVAPORATION (P0), EVAPORATION FROM A 61CM
DIAMETER PAN (P6l) AND EVAPORATION FROM A 122 CM
_ PAN. CLASS. A (Pi??) _
1974
= 0.341 + 0.495 • PQ r = 0.38*
- 0.626 + 0.171 • P r = 0.58*
= 0.739 + 0.240 • P r = 0.58*
1975
EM = 0.119 + 0.784 • P. r = 0.55*
M u
E.. = 0.340 + 0.371 • P.. r = 0.30*
M Ol
EM = 0.201 + 0.911 • P r = 0.41*
"^Significant at the 0.05 level.
During both years, the total calculated potential evapotranspiration closely
approximated the measured evapotranspiration. The 61 cm second pan gave the
second best approximation, being slightly high both years. The class A pan
deviated from the first for the measured total. During the 1974 season, the
class A total was 15% low, while during the 1975 season the class A pan total
was 51% low.
TABLE 15. TOTAL CALCULATED, PAN, AND MEASURED EVAPOTRANSPIRATION
DURING THE PERIOD OF PERMANENT FLOOD GIVEN IN CM
Calculated
Potential
Evapotranspiration
61 cm pan
122 cm pan
Measured
Evapotranspiration
1974
43.2
55.5
40.5
47.9
1975
39.8
42.0
28.9
40.2
69
-------
Water Balance
Details of the daily water balance averaged over all replications of
the irrigation treatments during 1974 and 1975 are given in Appendix F, Tables
Fl, F2, F3, and F4. The cumulative inputs and outputs for the time between
planting and harvesting are shown in Figures 26, 27, 28, and 29. The amounts
of runoff early in the season were calculated from data on the amount of water
required to wet the soil during the flooding or during and immediately after
the rainfall which were large enough to cause runoff. Since no measurements
of evapotranspiration were available before permanent flood, calculated po-
tential evapotranspiration was utilized to approximate the total loss between
planting and permanent flood.
During both years, the cumulative evapotranspiration increased nearly
linearly throughout the season. During 1974, the rate was 0.55 cm per day,
and during 1975 the rate was 0.6 cm per day. The rainfall during 1974 was
lower than during 1975. During 1974 the rainfall alone, had it been properly
spread over the season, would not have supplied the evapotranspirational
needs of the crop. The 1975 rainfall should have more than satisfied the
evapotranspirational losses provided it could have been retained on the field.
Most of the water from the two intense storms early in the season were lost to
runoff. The rain on May 28, 29, and 30 was nearly all lost since the per-
manent flood had not yet been initiated, and the levees were opened. Nearly
all of the 20 cm rain of July 9 was also lost since the water levels in the
paddies were high before the rain and most of it washed over the levees.
For the impounded flow irrigation systems during both years, the water
applied approximated the evapotranspirational losses. Thus, an amount nearly
equivalent to the rainfall was lost to runoff from the plots.
After the initial large runoff at the beginning of the 1975 season,
little water was lost as runoff from the plots until late in the season.
Even had the levees been large enough to retain the rainfall of July 9, most
of the water would have had to be released since the depth would have
the height of the young plants. As a result of several excess irrigations
throughout 1974 on the impounded plots, runoff losses accumulated slowly
throughout the season.
The continuous flow plots' water balances during both years are charac-
terized by water applications which far exceeded the evapotranspirational
losses throughout the season. During 1974 the cumulative irrigation plus
rainfall exceeded the evapotranspiration rate by a factor of 2.5 or more
throughout the season. This resulted in large runoff losses throughout both
seasons.
These plots were managed as best as possible to approximate the two
water management systems presently in use. It can readily be seen that both
systems result in excessive irrigation return flow. Continuous irrigation is
obviously a wasteful practice and increases the probability that chemicals in
the water will be lost in irrigation return flow. The impounded plot manage-
ment could have been improved by using smaller irrigations so that rainfall
could have been trapped and utilized rather than being lost. Data, to be dis-
70
-------
1974 CONTINUOUS
I40H
120
IQO-
& RMNFALL
O LEACHATE
X EVAPOTRANSPIRATION
• IRRIGATION
X TOTAL WATER
D RUNOFF
Figure 26. The water balance for the continuous irrigated plots during 1974.
-------
1974 IMPOUNDED FLOW
140-
120
100
-80
4 RAINFALL
o LEACHATE
X EVAPOTRANSPFATION
• IRRIGATION
X TOTAL WATER
n RUNOFF
xxxxx
wx
MAY
JUNE
JULY
Figure 27. The water balance for the impounded irrigated plots during 1974.
-------
1975 CONTINUOUS
140-
120
BO
a so
a.
LJ
5
60
40
20
A RAINFALL
0 LEACHATE
* EVAPOTRANSPRATION
• IRRIGATION
X TOTAL WATER
D RUNOFF x
**
»i _ .
^
*
'<
.-S
11
'0 20 30
10 20
JULY
30
19
Figure 28. The water balance for the continuous irrigated plots during 1975,
-------
1975 IMPOUNDED FLOW
140-
120
100
5 so
a
i
CL 60
UJ
o
4QJ
20-
6 RAINFALL
O LEACHATE
X EVAPOTRANSPIRATION
• IRRIGATION
X TOTAL WATER
O RUNOFF
KXWX
21 31 10 20 30 10 20 30
MAY JUNE JULY
9 19 29
AUG
Figure 29. The water balance for the impounded irrigated plots during 1975.
-------
cussed later, show that withholding water at the end of the season could have
reduced the irrigation needs and the irrigation return flow without lowering
the yield. While deep floods may be necessary to some fields during the early
part of the season to kill weeds, they may not be necessary in the fields that
do not have excessive weeds. In these cases, only enough water need be ap-
plied to completely wet the surface of the field. While it is impossible to
schedule pre-permanent flood herbicide applications the day before a heavy
rainfall, some of the pre-permanent flood rain could be used for irrigation if
the levees had been kept closed during this period.
The seasonal water balance for the entire growing season is given in
Table 16, while the balance during the flooded period is given in Table 17.
As mentioned above, a few of the values used to calculate the balance before
the permanent flood had to be estimated, thus more confidence can be placed in
the budget during the permanent flood. The inclusion of the pre-permanent
flood period does not change the distribution of the energy balance greatly
and thus, the balance from the entire season will be considered in detail,
Total irrigation exceeded rainfall in all plots during both years. The gross
excesses in application to the continuous plots are evident with over a meter
of irrigation water being used to supply crop needs of .59 and .53 meters,
Leachate varied from 6.5 to 12.8 % of the total water applied. The measured
losses accounted for 80.9 to 111% of the applied water throughout the entire
season. Storage changes in the profile were neglected and may have con-
tributed to some of the discrepancies, but considering the factors involved,
the agreement between gains and losses is reasonable, The water balance data
was used to calculate the salt balance which will be presented in a later
section.
SALTS AND NUTRIENTS
Introduction
It has long been recognized that an occasional purge of salts from the
plant root zone is required in some soils to control salinity (U.S. Salinity
Laboratory, 1954). Naturally, water of relatively high quality is needed
which may result in the degradation of the irrigation return flow, either by
increasing the concentration or by altering the composition of dissolved and
suspended constituents.
Although the load of naturally occurring salts in irrigation return flow
may contribute to degradation of ground and surface water quality, more ser-
ious problems can occur from fertilizer residues in drain waters. Nitrogen
and phosphorus stimulate aquatic plant growth in the conveyance and water
storage systems resulting in eutrophication. The full impact of irrigation
return flow on quality of water resources is not easily assessed because of
the difficulty of obtaining meaningful data relating quality of return flows
with past and present water resource quality in irrigated areas. Federal
legislation to establish a national policy for the prevention, control, and
abatement of water and pollution through enactment of the Federal Water Pol-
lution Control Act (Law, 1971) illustrates the concern for conserving and pre-
serving our water resources.
75
-------
TABLE 16. WATER BALANCE FROM PLANTING TO HARVESTING DURING 1974
AND 1975 FOR BOTH IRRIGATION TREATMENTS GIVEN IN CM
I intermittent I rrjlgation
1974 1975
Gains
Rainfall
Irrigation
Total
Losses
Runoff
% of total app.
Leachate
% of total app.
EVTS
% of total app.
Total
% of total app.
43.4
52.9
96.3
35.0
36.3
12.3
12.8
59.6
61.9
106.8
111.0
81.7
58.9
140.2
63.7
45.5
12.0
8.6
53.8
38.2
129.5
92.2
Continuous
1974
43.4
103.0
146.4
46.4
31.7
12.3
8.4
59.8
40.8
118.5
80.9
JE irrigation.
1975
81.7
104.1
185.8
101.5
54.6
12.0
6.5
53.8
28.9
167.3
90.0
TABLE 17. WATER BALANCE DURING THE PERIOD OF PERMANENT FLOOD FOR
1974 AND 1975 FOR BOTH IRRIGATION TREATMENTS GIVEN IN CM
Gains
Rainfall
Irrigation
Total
Losses
Runoff
% of total app.
Leachate
% of total app.
EVTS
% of total app.
Total
% of total app.
Intermittent
1974
27.6
43.6
71.2
26.2
36.8
12.4
17.3
45.6
64.0
84.0
118.1
Irrigation
1975
48.4
24.7
73.1
31.2
42.6
12.0
16.4
39.6
54.0
82.9
113.1
Continuous
1974
27.6
90.0
117.6
34.3
29.2
12.4
10.5
45.8
38.9
92.5
78.6
Irrigation
9175
48.4
77.9
126.3
73.7
58.3
12.0
9.5
39.6
31.4
125.3
99.2
76
-------
The leaching and removal of excess salts from the soil in irrigated areas
by drainage and surface water frequently cause an undesirable increase in
salinity of the irrigation return flow (Flaigg, 1953; Wilcox, 1962; Eldridge,
1963; Sylvester and Seabloom, 1963; Law et al. , 1970; Nightingale and Bianchi,
1974).
As McGauhey (1968) has summarized from several sources of data, most of
the studies dealing with the effect of irrigation return flow on salinity of
the receiving stream come from the areas of low rainfall in the western United
States and indicate that salinity of the receiving stream increases from 5 to
10.8 times due to irrigation. Even higher increases (20-fold) in salinity as
a result of irrigation return flow into the Sevier River in central Utah were
reported by Thorne and Peterson (1967).
Williams (1972) has measured changes in salinity of soil solution of two
flooded rice soils in Australia to characterize the physicochemical properties
of soil solution in flooded rice fields. However, this data was not conclusive
enough to allow an evaluation of the effect of rice culture on the salinity of
the irrigation return flow.
Ponnamperuma1s (1965) study of specific conductance revealed that the
ionic strength of soil solution increased following submergence until maximum
reduction is obtained after which conductance subsides. He noted that Ca and
Mg"*"1" in alkaline soils and Fe*"1" in acid soils make appreciable contributions
to the specific conductance of reduced soils. He suggested that these ions
are present as bicarbonates or soluble hydroxides because of a high correla-
tion between specific conductances and alkalinity.
Electrical Conductivity
Electrical conductivity (E.G.) values of the irrigation supply and plot
flood water, averaged over the respective treatments, are given in Figures
30 and 31 for data collected in 1973, 1974, and 1975, respectively. Analyses
of variance indicated that time of sample collection, fertilizer application
rate, and irrigation management had highly significant effects on mean E.G.
values in 1974 and 1975 (Appendix G, Tables Gl and G2). The data from 1973
are too sparse to indicate significant trends due to treatments, although
the means did vary significantly with time (Appendix G, Table G3).
The excessive fertilizer application rate resulted in higher E.G. values
in 1974 and 1975 (Figures 30 and 31). The detailed data are given in Appendix
H. Electrical conductivity values were greater under the impoundment irriga-
tion management. The continuous flow system either flushes significant a-
mounts of salt from rice paddies, or the salts are decreased by some other
mechanism at an accelerated rate in the continuous flow plots.
The highly significant first order interaction between time and irrigation
treatment in 1974 (Appendix G) is indicative of the former when one considers
this interaction was not significant in 1975. As previously mentioned, a
smaller percentage of the total water volume was exchanged under the con-
tinuous flow management scheme in 1975.
77
-------
4001
_ 300-
U
200
100-
1973 E.C. of the Paddy
Water (Impounded flow)
"30 % 6/l9 %9 \ 7/\9 7/
Samplinq Dates
1974 E.G. of the Paddy
Water (Impounded flow)
8/8
300-1
200
wo-
Recommended
Excessive
Canal
300
ZOO- >
% % ^9 ^9 7/l9 7/
Sampling Dates
1975 E.G. of the Paddy
Water (Impounded flow)
8/J8 8/28
— Recommended
Excessive
Canal
o
A
7'l9
Sampling Dates
Figure 30. Electrical conductivity in ymhos/cm for water in
impounded plots and in the canal.
78
-------
400
300
o
200
I
100
0 5/,n
1973 E.G. of the Paddy
Water (Continuous flow)
% 6/l9 6'29 7/9 7/l9 7/29
Sampling Dates
1974 E.G. of the Patty
Water (Continues flow)
300
zoo
300]
o
200
100
Recommended
Excessive
Canal
5/ fi/ 6/ 6^ 7y 7/
"730 '9 '19 ^29 '9 '19
Samphng Dates
1975 EC. of the Paddy
Water (Continuous flow)
Recommended
Excessive
— Canal
'20
0 %.
^» 6/29 7/9
Sampling Dates
7/29 % 8/l8
Figure 31. Electrical conductivity in ymhos/cm for water in
continuous flow plots and in the canal.
79
-------
A Duncans' multiple range test was conducted on E.G. values, averaged
over treatment blocks, to determine which means were significantly different
with respect to time in 1974 and 1975 (Figures 32 and 33).
The relatively high initial E.G. values are due to the pre-plant fertilizer
applications. The drastic decrease in E.G. noted for the sample average on
May 21, 1974 (Figure 32) corresponds to the 5 cm rain logged on May 20, 1974
(Appendix A). The extremely low E.G. value noted May 28, 1975 (Figure 33)
corresponds to a 10 cm rain (Appendix A). Peak E.G. values noted after June 6
and June 19, 1975 are analogous to the significant decreases in pH resulting
from the (^4)2804 applications. These data are completely consistent since
pH represents the negative log of the hydrogen ion concentration, and the
hydrogen ion is approximately five times more mobile in aqueous solutions than
any other ions belonging to the alkali metal or halogen families. Conductance
is a measure of the current carried by electrolytes. Faster ions carry the
larger load. Thus, small decreases in pH can induce relatively large increases
in electrical conductance; conversely, dilution of the hydrogen ion by rain,
which is essentially neutral in pH, would effect a decrease in E,C. as noted
above.
It is evident from these data that the increase in E.G. following fer-
tilizer application was primarily a temporary effect. The E.G. returned to
approximately that of the irrigation canal water within 15 days (Figures 30
and 31). Fertilizer incorporation into the soil and/or applied to dry soil
prior to flood, resulted in lower salt levels in the floodwater, as evidenced
by the fact that peak concentrations were about equal, although the pre-plant
and tillering application rates were twice the panicle differentiation appli-
cation rate.
The E.G. values of the irrigation source indicate a low salinity hazard
(as categorized by the U. S. Salinity Laboratory, 1954) and paralleled the
E.G. values for the Neches River, which has good quality water compared to the
other rivers within the Texas Rice Belt (Westfall et al., 1971). The E.G. of
the good irrigation water increased only slightly by the end of the growing
season as a result of irrigation of rice plots in this study. It is likely
that irrigation return flow from the experimental rice plots would have little
effect on increasing the salinity of the receiving stream. This observation
concerning the salt load of irrigation return flow from rice fields is in con-
trast to the 5- to 20-fold greater salt load of irrigation return flow in
Western States (McGauhey, 1968; Thome and Peterson, 1967).
pH of the Water
The pH of acid soils tends to increase to near neutrality after flooding;
whereas, alkaline soils decrease in pH to near pH 7.0. This phenomenon, which
helps explain chemical changes in flooded soils, was clearly defined in a re-
port by Ponnamperuma et al. (1966). They established that the pH of reduced
acid and alkaline soils high in iron were buffered near pH 7.0 by the Fe3(OH)g
-HoO-C02 system. The dominating effect of C02 on the pH of alkaline soils was
established by Bradfield (1941) and Whitney and Gardner (1943). Ponnamperuma
et al. (1966) related this C02 effect to the decrease in pH of reduced alkaline
soil and showed that the pH values of reduced alkaline and calcareous soils
are controlled by the partial pressure of C02 through the Na2C03-H20-C02 and
80
-------
00
0.30
0.25
0.20-
0.15
10
"0.10
0.05'
Data sampled
Figure 32. Electrical conductivity averaged over treatment blocks for plot water
sampled in 1974, and results of Duncan's multiple range test at a 5% level of
significance.
-------
00
to
0.30
in
O
0,25
0.20-
§ 0.15
0.10
o
ui
0.05
t
4/30
8/20
8/l8
Data sampled
Figure 33. Electrical conductivity averaged over treatment blocks, for soil solutions
collected prior to permanent flood, and for plot water sampled following perma-
nent flood in 1975, and results of Duncan's multiple range test at a 5% level
of significance.
-------
the CaC03-H2) buffer systems, respectively.
Irrigation and paddy water pH values for the continuous flow and im-
poundment irrigation management schemes are given in Figures 34 and 35, res-
pectively. The general trend was for the pH of the paddy water to increase
towards that of the irrigation water with time. It has long been established
that soils tend toward neutrality under saturated moisture regimes. Analyses
of variance indicated the change in pH with time was highly significant in
each of the three growing seasons (Appendix G, Tables G4, G5, and G6).
Resultant pH values averaged over treatment blocks for soil solution
collected prior to permanent flood and for plot water sampled following per-
manent flood, are given in Figures 36, 37, and 38.
Definite trends were noted in the 1974 and 1975 averages (Figures 37 and
38), due mainly to the more exhaustive sampling schedule employed in these
years. The arrows in Figures 37 and 38 represent the dates that (Nlty^SC^ is
an acidic salt. While the high rate fertilizer treatment resulted in generally
lower pH values, analyses of variance indicated that rate of application was
not significant at a 5% level in either 1974 or 1975 (Appendix G, Tables G5
and G6). Rate of application had a highly significant effect on resultant pH
values in 1973 but so were deviations with replication (Appendix G, Table G4).
The fact that the low and high rate had about the same effect on pH suggests
that the flood is tenuously buffered, a point further substantiated by the way
plot water deviations corresponded with irrigation canal water deviations
(Figures 35 and 36).
The impoundment irrigation scheme resulted in a significantly lower pH
in 1974 but imparted little variation on the treatment means in 1975. The
difference between the two years may be due to the fact that a smaller per-
centage of the total water volume was exchanged under the continuous flow
management scheme in 1975. Continuous flow plots had been made deeper in 1975
to investigate the influence of plot depth on propanil. Thus, the deeper plots
resulted in a larger total water volume, resulting in less impact from the 1
cm/day flow rate.
The peak in pH noted on June 10, 1975, between the two N applications, is
attributed to dilution of the HT ion in the flood. Rain in excess of 20 cm
was recorded within a 24-hour interval between June 9 and June 10, 1975.
The pH values of the irrigation return flow are certainly within accept-
able levels or criteria enacted for release into surface waters or imposed on
public drinking water supplies.
Salts and Nutrients in the Water
Introduction—
The general topic of irrigation return flow has been reviewed by the Utah
State University Foundation (1969). Skogerboe and Law (1971) have outlined
problems, possible solutions, and research needs associated with irrigation
return flows. The potential for controlling quality of irrigation return
flows has been studied by Law and Skogerboe (1972). Although Carman (1973)
83
-------
X
a.
7-1
6-
5.5
1973 pH of the Poddy
Water (Continuous flow)
Recommended
Excessive
-.-• Canal
'•X.
'X
4/30 5/20 6/10 6/30 7/10 8/10
1974 pH of the Paddy
Water (Continuous flow)
71
5.5
— Recommended
— Excessive
Canal
4/30 5/20
6/IO
6/30
7/IO
8/IO
a.
7i
6
5.5
1975 pH of the Paddy
Water (Continuous flow)
Recommended
Excessive
4/30 5/20
6/10 6/30 7/10
Sampling Dates
8/10
Figure 34. pH of water in continuous flow plots and in the
canal.
-------
-- Excessive
— Recommended
..... Canal
1973 pH of the*Pqddy
Water (Impounded flow)
4/30 5/20 6/10 6/30 T'20
3/10
—Excessive
— Recommended
Canal
1974
4/30 5/20 6/10 6/30 7/20 8/10
1975
Excessive
Recommended
Canal
X 6
a.
4/30 5/20
6/LO 6/30 7/20
Sampling Dates
8/10
Figure 35. pH of water in impounded plots and in the canal.
85
-------
6-
X
Q.
00
o\
I
I
I
-I
5/IO 5/20
7/l9 7/29 % 8/l
l8
TIME (date)
Figure 36. Resultant pH averaged over treatment blocks, for soil solution collected
prior to permanent flood (4/30 - 6/5) and for plot water samples following
permanent flood (6/6 - 8/20) in 1973. The heavy horizontal line indicates
when the plots were flooded. The results of DMR test at a 5% level of
significance are shown in the upper right section of the figure.
-------
X
Q.
03
5-
V 5/
'30 HO
5/ 5/
'20 '3(
6/ 6/ 6/ <
7 7/|9
^29 % 8y
fe 8/28
TIME (date)
Figure 37. Resultant pH averaged over treatment blocks, for soil solution collected
prior to permanent flood (4/30 - 6/5) and for plot water samples following
permanent flood (6/6 - 8/20) in 1974. The heavy horizontal line indicates
when the plots were flooded. The results of DMR test at a 5% level of
significance are shown in the upper right section of the figure.
-------
X
a.
do
oo
5
I I
4/30 5/IO
5/30
6/l9 6/29 7/9
TIME (date)
7/l9 7/29 % 8/l8 8/28
Figure 38. Resultant pH averaged over treatment blocks, for soil solution collected
prior to permanent flood (4/30 - 6/5) and for plot water samples following
permanent flood (6/6 - 8/17) in 1975. The heavy horizontal line indicates
when the plots were flooded. The results of DMR test at a 5% level of
significance are shown in the upper right section of the figure.
-------
has argued that water quality degradation through irrigation usage has been
overestimated, it is evident from the above reviews that irrigation usage can
reduce water quality by increasing sediment mass, salinity, or inorganic nu-
trient content of waters. These three water quality problems as related to
irrigation return flows will be considered separately.
Reviews of nutrient losses from soils indicated that nutrient loss to
drainage water is dependent on a number of factors (Barrows and Kilmer, 1963;
Soileau, 1969; Carman, 1970; Veits, 1971; Veits and Hageman, 1971;
Kilmer and Barber, 1974; Kilmer and Joyce, 1971; Kilmer, 1972). Factors that
increase surface water runoff, water percolation through soil, and fertili-
zation in excess of crop uptake tend to enhance the possibility of eutrophi-
cation and high nitrate in drinking water. In a considerable number of
studies, (Erickson and Ellis, 1971; Hanway and Laflen, 1974; Kilmer et al.,
1974; Gillian et al., 1974) the nutrient content of the drainage water from
fertilized land was low considering the level of naturally occurring nutrients
in soil and rainwater. In fact, Carman (1973) suggested that carbon in the
runoff from agricultural lands induced eutrophication, not the nutrients,
since most fresh water bodies already contain a sufficient nutrient level for
eutrophication. Thus, few situations likely occur where decreasing agricul-
tural nitrogen and phosphorus contribution would stop eutrophication.
Others, equally adamant to their position, suggest that runoff and ir-
rigation return flow percolated through soils fertilized in excess of crop
needs can contribute appreciably to pollution of water resources. As a result,
Law and Skogerboe (1972) have suggested potential methods for control of ir-
rigation return flow quality by altering water delivery systems, farm manage-
ment systems and changing water removal systems. Meek et al. (1970) and
Gilliam et al. (1974) have shown how controlling water tables under fertilized
fields can be used as a means of removing unused nitrogen through denitrifi-
cation and, thus, reduce the contribution of irrigation return flow to water
pollution.
Ammonia, nitrate, and nitrite concentrations in soil and soil solutions
are the result of the following processes and/or factors: (1) amount, time,
and method of nitrogen fertilizer application, (2) nitrification rate, (3)
denitrification rate, (4) rate of diffusion between soil and soil solutions,
(5) nitrogen immobilization by rice plants and microbes, and (6) nitrogen con-
tent of irrigation water. Nitrification, denitrification, and uptake of N by
rice plants are the primary processes governing N transformation in flooded
rice soils. A diagram illustrating N transformation in rice fields is given
in Figure 39. Generally nitrification and denitrification processes occurring
simultaneously in the oxidized and reduced layers, respectively, are believed
to be responsible for low N use-efficiency of 23 to 56% recovery of added N
(Patrick et al., 1971 and Westfall, 1972).
Although the mechanisms of N transformation are adequately understood, it
is difficult to quantitively account for theN added to rice fields. Generally
N is applied as (NH^)£S04 to reduce losses by denitrification and leaching.
Ammonium dissolution and adsorption to soils are shown in the equations given
below:
89
-------
VD
O
Floodwoter
Oiidiied
Layer
higher Eh
(aerobic)
Reduced
Layer
1
/
\
s
\
^— - V_ / \jo[l orwoter./
f r«Urn How
^^""~-f=^L___ INORGANIC —^
5^^ ~~---^ NITROGEN POOL iy/
/ ORGANIC NITROGEN POOL V^
^
t *
living
and
dead
/ 3 "t^^^x
^1 io
3
6
IO
NH
* 9
^
4 " "
7t
NH4'' 1
N03 f
9
7i
•0 NH4' -Iree froi
Mr
M^.
<;
, 2
T
-7
-*NO,
17L
1 f
NOj
7
2
,1 2
NO2
9
'
T r»:ll •
A"
\N
\
>
^
9 E
y
X
o :
Ul
a
2O
1 H itri f icol ion
2 Dentfr ification
3 Mine ro tiiafion
4 Immob i fixation
5 N fixation by algae
6 Ammonification
7 DiMus ion
8 Mass How
9 Leaching
1O Plant uptake
Figure 39. Diagram of nitrogen pathways and transformations in flooded rice soils,
-------
(1)
NH*(H20) + X [Soil] £ NH4 [Soil] + X+(H20) (2)
The equilibrium in equation (1) depicts the complete dissociation of (NH.) SO,
in HO, and equation (2), the sorption-desorption of NHf where soil is the
exchange complex, and X is another cation.
Cation Concentrations—
Ammonia was measured in the soil solutions collected prior to permanent
flood and in the plot water sampled following the flood application in 1973,
1974, and 1975. Data, reported as NIfy-N, for the continuous and impounded
flow irrigation systems are given in Figures 40 and 41, respectively. Peak
concentrations correspond to the N topdressing applied at tillering and panicle
differentiation stages of rice growth. The interval between these stages was
somewhat shorter in 1975 due to better climatic conditions. Ammonium was
rapidly diminished in the plot water following the peak, primarily due to Nlty
adsorption by the soil.
Evidence of the soils capacity to remove Nlfy-N from the floodwater is
presented in the laboratory experiment summarized in Figure 42. Ammonium
nitrogen applied at 84 kg/ha to the 10 cm flood diffused from the floodwater
into the soil, as indicated by the decrease in NH4-N in the simulated flood-
1 by
NH|
water, and increase in the NHj level of the soil. Although water movement
was restricted, NH^ concentrations were notably greater than that of the con-
trol to a depth of 4 cm. It should be noted that (Nlty^SO^ had been applied
to the floodwater in an aqueous phase so that movement to the soil and within
the soil was essentially by diffusion in the laboratory. Mixing of plot water
by thermal convection, irrigation activity, wind induced plant disturbances,
and the fact that granular (^4)2804 was deposited at the soil surface may
account for the more rapid NIfy dissipation in the field.
Perhaps the most conclusive evidence from NH4 adsorption by the soil was
the increase of Ca"1"1", Mg"^", K+, and Na concentrations in the plot water fol-
lowing the fertilizer applications. Calcium concentrations in 1973, 1974 and
1975 for continuous and impounded flow plots are given in Figures 43 and 44.
Corresponding data for Mg"1""1" are given in Figures 45 and 46. K+ data are
plotted in Figures 47 and 48; and Na concentrations are given in Figures 49
and 50. These data exemplify the exchange equilibria given in Equation 2.
The background levels of the various cations were much greater in the irriga-
tion water in 1973 than in either 1974 or 1975. This was due to the fact that
irrigation water was sampled in the feeder canal adjacent to the plots and in-
dicated a contamination during fertilizer application. The 1974 and 1975
irrigation water samples were collected from the main irrigation canal. Thus,
rather than base conclusions on obviously erroneous data, the remainder of
this discussion will entail the 1974 and 1975 results,
Increases in the K were of short duration and concentrations generally
91
-------
12.3-
4.9-
2.5
0-
9.9
7.4
4.9
2.5
o-
«
-M "* "Jft *'
5/10 5/20 5/30 <
<
*^ *£> » *
1973 NH4-N in the Poddy
Water (continuous flow)
l( Canal
£ jj] — Excessive
(\ s$\^ Recommended
''"^gf5* "*"4fej" * 'x x" *-B
5/9 6/19 6/29 7/9 7/19 7/29 8/8 8/IB
« 1974 NH4-N in the Paddy
,'i Water (continuous flow)
1
'it
S lW> Canal
b I/IT\ — Excessive
%^ 'jfe^Hr *•••'& x ^B
5/10 5/20 5/30 6/9 6/19 6/29 7/9 7/19 7/29 8/8 8/18
12.3
| 9.9
7.4
4.9 ^
2.5
0
1975 NH4-N in the Poddy
Water (continuous flow )
Canal
— Excessive
5/10 5/20 6/30 6/9 6/19 6/29 7/9 7/19 7/29 8/8
Sampling Dates
Figure 40. Concentration of NH, in ppm in continuous flow
plots and in the canal water.
92
-------
14.8'
12.3'
- 9.9
7.4'
f
4.9
2.5
0
7.4
|-
4.9
2.5)
i
1973 NH4-N in the Paddy
Water (impounded flow)
Canal
— Excessive
— Recommended
5/10 5/20 5/30 6/9 6/19 6/29 7/9 7/19 7/Z9 8/8 8/18
'; 1974 NH4-N in the Paddy
Water (impounded flow)
Canal
— Excessive
• - XX
5/K> 5/20 5/30 6/9 6/19 6/29 7/9 7/19 7/29 8/8 8/18
1975 NH4-N in the Paddy
Water (impounded flow)
Canal
— Excessive
—- Recommended
6/19 6/29 7/9 7/19 7/29 8/8 8/18
Sampling Dates
Figure 41. Concentration of NH, in ppm in impounded plots and
in the canal water.
93
-------
E
a.
a
6O
NH4~N in simulated floodwater
8 16 24
Days after application
32
*"*.
E4*
2
V
••**
3
X **
4M
2- 4
• ^
o
_ 5
"o
"> 6
%f
7
8
1
I
t
i
1
(' 1
i
i
I
NH4 N applied
1 control soil
7O 1OO 13O
NH^-N ppm in Soil
16O
Figure 42. The top graph represents the NH.-N concentration in
a 10 cm layer of water over a 10 cm layer of soil
after pipetting (NH^KSO^ (at the rate of 84 kg N
ha"-'-) into the water layer. The lower graph repre-
sents the distribution of the NH.-N within the same
10 cm layer of soil 32 days after 0 and 84 kgs N ha
were applied to the simulated floodwater. This ex-
periment was conducted under laboratory room condi-
tion in the absence of rice plants.
94
-------
80-
55-
50-
45-
40-
I-
10-
5-
0
40-1
if
1973 -Co" in the Paddy
Water (continuous flow)
* -water taken from levee ditches
Recommended
Excessive
Conal
Sampling Dates
1974-Ca** in the Paddy
Water (continuous flow)
Recommended
Excessive
Conol
Sampling Dates
X
1975 Ca*Yi the Paddy
Water Iconlinuous flow)
Conal
Excessive
Recommended
Sampling Dates
Figure 43. Concentration of Ca in ppm in continuous flow
plots and in the canal water.
95
-------
85-
50-
46-
40-
35-
' 25-
20-
15-
10-
320-
Q_
Q. 10.
1973-Co" in the Paddy
Water (impounded flow)
Recommend«4
— Excessive
Canal
Sampling Dates
1974 -Ca«* in the Paddy
Water (impounded flow)
l(fo ^Z9 % ^is %a % ^i»
Sampling Dates
1975 Cd"in the Paddy
Water (impounded flow)
"'IT
Carol
Excessive
Recommended
X A
O
Sampling Dates
'/I8 8/7
e/27
i I
Figure 44. Concentration of Ca in ppm in impounded plots and
in the canal water.
96
-------
» \ v
1973 Mg+tin the Paddy
Water (continuous flow)
a.
a.
5/35/9 i795/29 6/86/186/28 7/87/18 7/28 8/7 8/17 8/27
1974 Mg+*in the Paddy
Water (continuous flowjfr
*
l<* X //
* /
\ y
\ /.---'-Excessive
—Recommended
10
9
a
7-
1-
Q.
S 4-
3-
2-
I-
5/3 5/9 5/19 5/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/ff 8/27
Sampling Dates
1975 Mg"in the Paddy ]',
Water (continuous flow) > \
ft
I
-,-- Excessive
Recommended
Sampling Dates
Figure 45. Concentration of Mg in ppm in continuous flow
plots and in the canal water.
97
-------
1 I
CT>
2
1973 Mg^in the Paddy
Water (impounded flow)
.*••. .X
•'•—Excessive
—Recommended
-•••Conal
5/3 8/9 5/19 5/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
r
O>
1974 Mgt4in the Paddy
Water (impounded flow)
x x
Excessive
Recommended
Conal
6/3 5/9 5/19 5/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
Sampling Dates
1975 Mfl* in the Paddy
Water (impounded flow) |m--Canal
.
r >
6/307/K) 7/21
Figure 46. Concentration of Mg in ppm in impounded plots
and in the canal water.
98
-------
1973 K*in the Paddy
Water (continuous flow)
_. CESSIVE
— RECOMMENDED
-CANAL
5/3 5/19 6/8 6/28 7/18 8/7
& x l974 K+in1he Paddy
. ..Wafer(continuous inflow)
8/27
H
X
— EXCESSIVE
RECOMMENDED
CANAL
5'/l9 ' 6^8 ' 6>28 'T^ii""1 8/7"* 8/27
^ 1975 K in the FUddy
Water (continuous flow)
5/3 5/19 6/8 6/28 7/18 8/7 8/27
Figure 47. Concentration of K in ppm in continuous flow plots
and in the canal water.
99
-------
4, 1973 K in the Paddy
Water (impounded flow)
E
a.
52
O
— EXCESSIVE
- RECOMMEND
............. CANAL
\
5/3 5/19 6/8
5 1974 K^in the Paddy
Water (impounded flow)
H K
'—EXCESSIVE
^ ^
6/28' 7/18 8>7 S/27
-^COMMENDED
5/3 5/19 6/8 6/28 7/18 8/7
x» •
8/27
4
4 1975 Kin the Paddy
f ; Water (impounded flow)
RECOMMENDED
CANAL /
&
5/>l9
6/7
Figure 48. Concentration of K in ppm in impounded plots and
in the canal water.
100
-------
1973:-.No* in the Paddy
x x Water (continuous flow)
fL *
Water taken from
Levee Ditches
X x
i - 1
*'» 5/l8
30
5- *
3 20 t
+ *
1 - 1 - 1 - 1 i i
%l 6/2B V<* 7/l8 \» h
Sampling Dates
1974-Na* in the Paddy
Water (continuous flow)
— Recommended
— Excessive
Canal
1 - 1 i i i - 1 - 1 - 1
Me 6/28 7/s 7'\e 7>ia ^7 "% *
Sampling Dates
1975 No* in the Paddy
Water (Continuous flow)
t
- - Excessive
Recommended
Canal
/
8
Sampling Dates
'27
Figure 49. Concentration of Na in ppm in continuous flow plots
and in the canal water.
101
-------
0.30-
1973 - No* in the Paddy
Water (impounded flow)
Canal
Recommended
Excessive
Sampling Dates
1974 -No* in the Paddy
Water (impounded flow)
— Recommended
- Excessive
Canal
e 20-
Sampling Dates
1975 Na* in the Paddy
Water (Impounded flow)
-- Excessive
— Recommended
Canal
8/l7 8/27
Sampling Dales
Figure 50. Concentration of Na in ppm in impounded plots
and in the canal water.
102
-------
were lower in the plot water than in the irrigation canal water, suggesting
a strong affinity by the soil for K+ (Figures 47 and 48). Increases in Mg*"1"
(Figures 45 and 46) were small compared to the increases in Ca"*"1" (Figures 43
and 44) and Na+ (Figures 49 and 50). Thus, NH^ adsorbed appears to be at the
expense of Ca"^ and Na+. This is reasonable since Ca"1"1" predominates the ex-
change sites of Beaumont clay soil and Na+ is easily exchanged. Calcium and
sodium were diminished in the plot water following peak concentrations due in
part to dilution by irrigation and rain and the establishment of a new equili-
brium. However, the new equilibrium did not reflect readsorption of Ca and
Na+ at the expense of NH^ since concentrations of the latter were nil. following
the peaks (Figures 40 and 41). Amounts of Ca"1""*' and Na+ readsorbed were finite
since the concentrations remained higher than that of the canal 1^0 over the
remainder of the growing season, all of which is consistent with an NH^ fix-
ation mechanism in a Beaumont clay soil similar to that previously reported
for K+ (Carson and Dixon, 1972).
The tenacity with which NIfy is adsorbed may account for the low N re-
coveries and efficiency previously reported in rice soils (Patrick et al., 1971
and Westfall, 1972), more so than the nitrification-denitrification trans-
formation mechanism. Many of the fluctuations in the concentrations of cat-
ions in the plot water were induced by heavy rains.
Anion Concentrations —
Anionic concentrations were measured on soil solution samples collected
prior to permanent flood and in the plot water sampled following the permanent
flood in 1973, 1974, and 1975. Anions measured included SO^, Cl~, NO^, NOf
and Pof.
Sulfate was the associated anion with ammonium, and peak concentrations
in both continuous and impounded flow plots correspond to the application dates
(Figures 51 and 52, respectively). Plot water concentrations prior to the
second application indicate that much of the S05 applied preplant had been dis-
sipated from the surface water. It is reasonable to assume that the SOJ was
leached into the soil by rain and the two temporary flood applications. Water
percolating through the Beaumont clay soil was very slow following saturation
by the permanent flood. Sulfate applied at tillering and panicle differentia-
tion was more probably dissipated by sulfur reducing micro-organisms associated
with the reduced soil environment created by the flood. This is substantiated
by the faster dissipation rate later in the season (Figures 51 and 52).
Fluctuation in the concentrations, as previously noted, corresponds to heavy
rains. Chloride data for the continuous and impounded flow plots are given in
Figures 53 and 54, respectively. Concentrations of Cl~ in the floodwater
tended to parallel that of irrigation canal water, except following the pre-_
plant fertilizer application, and the N topdressings. The higher initial Cl
levels are the result of the Cl~ added as the associated anion with the K pre-
plant fertilizer. However, much of the Cl~ added preplant was leached into
the profile and was not reflected in the plot concentrations following the
permanent flood. Peaks associated with N topdres'sing are attributed to SO^
release from soil solution into the overburden flood by mass action. Plot
water concentrations returned to that of the irrigation water once equilibrium
was established and rain diluted that released from the soil solution. Nitrate
concentrations in rice floodwater for the three cropping seasons were greatest
103
-------
100.
- .o]
ns
cn
40.
20.
OJ
5/3
KXJl
I!*" 6°
O
(/) 40
20
100,
1973 S04 in the Paddy
Water (Continuous flow)
— Excessive
— Recommended
Canal
^f... >«
5/21 5/29 6/6 6/17 6/26 7/15 7/26 8/12 8/21
1974 S04 in the Paddy
Water (Continuous flow)
Excessive
Recommended
Canal
"5/3 5/275/296/6 «/»7 6/26 7/15 7/26 8/12 8/21
— 80.
j|60.
§40.
/ f\
(J)
20.
0-
fV
^f
N
°° tV
yv
^ n Y>r?
u t-m^
v *-A ^yf
f x> ^
r
t
' M
V. J / M t\
£/ S / p ^
PiU 9
AJu I 1 /i
>^>rh.-,
'^L ''^ - /
Water (Continuous flov
Excessive
\D A >• J*.H» HK «k VU>I **. -4
necommcnocu
HPrmn!
- - - - - \jUIIUI
5/3 5/215/296/66/176/26 7/15 7/26
Sampling Dates
8/12
8/21
Figure 51. Concentration of SO, in ppm in continuous flow plots
and in the canal water.
104
-------
(f)
100.
80.
: so.
4O
20
0.
A
O
1973 $04 in the Paddy
Water (Impounded flow)
— Excessive
— Recommended
Canal
5/3 5/215/296/6 6/17 6/26 7/15 7/26 8/12 8/21
1974 SG>4 in the Paddy
Water (Impounded flow)
5/3 5/21 5/29 6/6 6/17 6/26
Excessive
Recommended
Canal
8/21
E
a.
a.
100
80
60
V) 40
20
0
a
o o
1975 S04 in the Paddy
Water (Impounded flow)
Excessive
Recommended
Canal
5/3 5/215/296/6 6/176/26 7/15 7/26
Sampling Dates
8/12 8/21
Figure 52. Concentration of SOT in ppm in impounded plots and
in the canal water.
105
-------
400-1
200
100
1973 CI" in the Paddy
Water (continuous flow)
Excessive
•Recommended
Canal
SJ2
<•>
S/l 8/9 6/19 5>29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
Sampling Dales
60
— B0'
20-
10
£40
zo
10
1974 CI" in the Paddy
Water (continuous flow)
*
<*
V*
— Excessive
— Recommended
Canol
5/3 6/9 5/19 5/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
£ 1975 CI" in the Paddy
a ^ Water (continuous, flow)
-Excessive
—Recommended
Canal
e/35/9 B/19 5/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/\7 8/27
Sampling Dates
Figure 53. Concentration of CI in ppm in continuous flow plots
and in the canal water.
106
-------
400<
. 30O'
200'
IOO
1973 cr in the Paddy
Water (Impounded flow)
Recommended
5/.9 5/
29
ao
70-
60-
50
40-
30-
20-
10-
Sampling Dates
1974 Cr in the Paddy
Water (Impounded flow)
o Recommended
Excessive
Canal
5/35/9 5/19 5/28 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
Sampling Dates
60-
50-
40-
3O-
20-
ISfD
c, Water
o
' * \
° x- X
1^1 in me raoay
(Impounded flow)
X' fc&&
^vJvAj/ Excessive
»^« * Canol
Sampling Dates
Figure 54. Concentration of Cl in ppm in impounded plots and
in the canal water.
107
-------
in the continuous and impounded flow plots in May resulting from nitrification
of the preplant (NH^SO^ fertilizer (Figures 55 and 56, respectively). The
decrease in the NOo concentrations correspond to the temporary floods applied
for irrigation and weed control, which may have leached the nitrate into the
soil or diluted the already comparatively low levels. Peaks in N03~N occurred
each year immediately following the permanent flood and at panicle differenti-
ation. These smaller peaks are attributed to nitrification in the aerobic sur-
face layer of the flooded soils. The rapid dissipation of NOJ was attributed
to crop removal and denitrification stimulated by the reducing conditions.
Although the presence of N0= following the preplant fertilizer application
confirmed the nitrification process, concentrations in the plot water after
the permanent flood reflected that of the irrigation water and were generally
less than the latter, suggesting that NO., produced on nitrification of NH^+
and that introduced via the irrigation supply were rapidly denitrified (Fig-
ures 57 and 58).
Ortho-phosphate concentrations in the plot water reflected that of the
irrigation supply except in those samples collected immediately after P fer-
tilization (Figures 59 and 60). It is apparent that the initial increase
following P fertilization was only temporary, The very low concentrations are
indicative of a strong fixation such as precipitation reactions and specific
absorption. This is further evidenced by the fact that the high SO/= levels
did not release POJF from the soil solution.
Treatment Effects
Analyses of variance were determined for the cation and anion concentra-
tions of the floodwater samples collected in 1974 and 1975, to ascertain the
statistical significance of time with respect to sample collection dates,
irrigation management scheme, and fertilizer application rate. The data were
normalized to kg/ha prior to analyses of variance to circumvent the variation
imparted by plot water depth on concentration expressed in mg/liter. Data
obtained from samples collected in the 1973 growing season were excluded from
statistical interpretation since the irrigation supply water values were
erroneous, negating meaningful cause and effect relationships based on the
irrigation management schemes employed,
Cations— + ++ ++ +
Analyses of variance for NH4, Ca , Mg , and Na indicated that the
variability between the amounts per hectare in the plot water with respect to
sampling date was highly significant in 1974 and 1975, with the exception of
Mg44" in 1974 (Appendix G, Tables. G7, G8, G9, G10, Gil, G12, G13, and G14).
A Duncan Multiple Range Test (DMR) was employed to determine significance be-
tween sampling dates at the 57, level. It should be noted that this test was
determined on the amount per hectare averaged over treatment blocks at the
respective sampling dates. The detailed ion concentration data are presented
in Appendix H.
Ammonium applied preplant and incorporated into the surface was signifi-
cantly lower than that applied to the soil surface just prior to permanent
flood, although an average of 80 kg/ha was applied both times (Figures 61 and
62). Half as much NH^ was applied at panicle differentiation but resulted in
108
-------
1.6
I,
to
o
.8
c a
1973 NOj-N in the Paddy
Water (continuous flow)
Canal Water
— Excessive
— Recommended
5/1 8/9 5/19 5/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
rW. Sampling Dotes
1.5
}o
o
.5
1974 N03-N in the Paddy
Water (continuous flow)
Canal
— Excessive
— Recommended
5/3 5/9 5/19 8/29 6/8 6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27
Sampling Dates
1.0.
1975 N03-N in the Paddy
Water (continuous flow)
In0'5'
o
z
o
n
— Excessive
,. <*-7 — Recommended
1? fl >, Canal
- A ^ffl^Vf^rff. if-
5/0 5/19 6/8 6/28 7/18 8/7 8/S
Sampling Dates
Figure 55. Concentration of NCL-N in ppm in continuous flow
plots and in the canal water.
109
-------
1973 - N03-N in the Poddy
Water (impounded flow)
Sampling Dat«
I974-N03-N in the Paddy
Water (impounded flow)
1975 N03-N in the Paddy
Water (impounded flow)
«/» 7/ie
Sampling Dates
Figure 56. Concentration of NO.,-N in ppm in impounded plots
and in the canal water.
110
-------
1974 N02 in the Paddy
Water (Continuous flow)
Recommended
X Excessive
Canal
0.4-1
0.3
<\J
O 02
o.i-
0-
5/ZD 5/30 6/9 6/Z4 7/5 7/15 7/25 8/5
Sampling Dotes
1975 NC>2 m the Paddy
Water (Continuous flow)
Recommended
Excessive
Canal
8/21
5/3 5/10 5/20 5/30 6/9 6/19 6/29 7/9 7/19
Sampling Dates
Figure 57. Concentration of N0» in ppm in continuous flow
plots and in the canal water.
Ill
-------
5/3
0.41
0.3
0^0.2
Z
O.I-
1974 N02~m the Paddy
Water (Impounded flow)
Recommended
— Excessive
Canal
5/20 5/30 6/9 6/24 7/6
Sampling Dates
1975 NO2" in the Paddy
Water (Impounded flow)
Recommended
Excessive
Canal
X
a>
7/15 7/25 8/5
8/21
5/3 5/10 5/20 5/30 6/9
Sampling Dates
6/19 6/29 7/9
7/19
Figure 58. Concentration of N0_ in ppm in impounded plots
and in the canal water.
112
-------
3-
a.
>
g an
o i-b
1973 0-P04 in the Paddy
Water (Continuous flow)
0_ —Recommended
6 •
— Excessive
Recom
Canal
%| 5*29 6/7 6/l7 6/26 7/3 7/22
Sampling Dates
1974 0-P04in the Paddy
Water (Continuous flow)
Excessive
Recommended
Canal
5/3 5/21 5/29 6/6 6/17 6/26 7",5 7/26 8/12 8/21
Sampling Dates
1975 0-P04 in the Paddy
Water (Continuous flow)
W — Excessive
a Recommended
X ••••
5/3 5/21 5/29 6/6 6/17 6/26 7/15 7/26 8/12 8/21
Sampling Dates
Figure 59- Concentration of 0-PO, in ppm in continuous flow
plots and in the canal water.
113
-------
E 4
a.
o ,
o
CL
— 3-
1973 0-P04 in the Paddy
Water (Impounded flow)
5
a Q
Excessive
— Recommended
Canal
- A
7/3 7/22 8^
Sampling Dates
1974 0-P04 in the Paddy
Water (Impounded flow)
Recommended
Excessive
Canal
6/.7 6/26 7/3
Sampling Dates
o
1975 0-P04in the Paddy
Water (Impounded flow)
A Excessive
° Recommended
x Canal
5/3 5/21 5/29 6/6 6/17 6/26 7/15 7/26 8/12 8/21
Sampling Dates
Figure 60. Concentration of 0-PO in ppm in impounded plots
and in the canal water.
114
-------
DATE
Figure 61. The amount of NH, per hectare in the floodwater during 1974. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
•*•
I
17
16
15
14
13
12
II
10-
9
8
7
6
5
4
3
2
I-
TIME (date)
Figure 62. The amount of NH, per hectare in the flood water during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
statistically equivalent preflood and post flood peak plot water levels in
1974. The peak amounts per hectare at panicle differentiation were signifi-
cantly greater than the peak following the applications made just prior to
permanent flood in 1975. Thus, the more intimate contact of the NIL with the
soil resulted in less NH£ in the plot water.
I i j_
Amounts of Ca and Na in the plot water, although significant, did not
reflect the quantities of NH^ conserved in the soil following the preflood
application in either 1974 or 1975 (Figures 63, 64, 65, and 66). This indi-.
cates that a considerable portion of the (NH^SC^ solubilized on initiation
of the permanent flood may have been washed by the wetting front in too deeply
to affect amounts in the plot water. However, Ca++and Na in plot water fol-
lowing the panicle differentiation application generally reflect the differ-
ence between NH£ applied and NH£ in the plot water. For example, the amounts
of Ca"1"1" + Na"^ in the plot water were approximately 35 and 25 kg/ha in 1974
and 1975, respectively. Correspondingly, the difference between NHj applied
and NH£ in the plot water was 33 kg/ha in 1974 and 23 kg/ha in 1975. The
comparison in kg/ha does not conserve charge but is reasonably accurate since
the milliequivalent weights are similar.
i i
The DMR indicated that Mg amounts per hectare corresponding to the peak
levels for Ca and Na+ were significant in 1975 (Figure 67), and may indicate
some release by NHj. However, the insignificance of the 1974 data (Appendix
G, Table Gil) and the occurrence of a 22 cm rain on June 9, 1975, suggest
that variations in the plot water concentration may have been induced by the
higher background levels of the irrigation water (Figures 45 and 46). Sim-
ilarly, Ca"1"1" (Figures 43 and 44) and Na (Figures 49 and 50) background levels
in the irrigation water were higher in 1975 than in 1974. The influence of
the irrigation supply is further evidenced by the fact that the irrigation
treatment was highly significant in 1975 (Appendix G, Table G12). Continuous
flow resulted in greater Mg levels than the impoundment irrigation scheme.
The impact of NH£ on the Mg++ levels is lessened even more when one considers
that the application rate was not significant at a 5% level.
Generally, the irrigation management scheme employed significantly in-
fluenced the amount of cations in the plot water in 1974 and 1975 (Appendix
G, Tables G7, G8, G9, G10, Gil, G12, G13, and G14). The amounts of cations
were higher under impoundment management in 1974. Conversely, the amounts
were significantly lower in those plots under impoundment irrigation in 1975.
The apparent anomaly in the results is actually consistent with cause and
effect relationships previously discussed. Impoundment represents the more
static system which entails less recharge of canal HO influx. Correspondingly,
the impoundment irrigation scheme results in lower colloidal load, thereby
lessening the absorptive capacity of the water. The heavy rains of 1975,
however, tended to increase cationic concentrations of the background irriga-
tion supply but dilute those released from the soil into the plots. The net
result was an increase in cations for those plots under continuous flow ir-
rigation management in 1975 following the return to normal irrigation schedules.
Ammonium levels were significantly affected by irrigation management in
1974 but not in 1975 (Appendix G, Tables G7 and G8). Impoundment resulted in
higher levels with respect to time following application due to the low influx
117
-------
200
ISO
160
140
120
100
8
00
60
40
0
DATE
Figure 63. The amount of Ca per hectare in the floodwater during 1974. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 57° level of
significance.
-------
40
35
30
S
10
5
6/20
7/IO 7/20 7/30
DATE
Figure 64. The amount of Ca per hectare in the floodwater during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
O
18.0
170
160
ISO-
140
130
ISO
IID
100
6/20 6/30 7/IO
DATE
8/l9 8/29
Figure 65. The amount of Na per hectare in the floodwater during 1974. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
40
30
2O
+o 10
I
3l
6/30 7fo %0 7/
DATE
Figure 66. The amount of Na per hectare in the floodwater during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
I 4
3
o>
I-1
N>
to
*30 %
''29
DATE
Figure 67. The amount of Mg"1"1" per hectare in the floodwater during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
of colloids with the irrigation water compared to the continuous flow scheme.
However, irrigation was not the factor in 1975 due to the dilution of NHj and
colloids. The irrigation water was essentially free of Nflt thus negating the
infusion of NH^ in the plots under continuous flow management, as noted for
the other cations.
Fertilizer application rate generally had a highly significant effect on
plot water cationic concentration variability. As one would expect, the ex-
cessive application rate resulted in greater amounts in the plot water.
Anions--
Analysis of variance, determined for SO, , Cl~ and NO^ concentrations in
the floodwater in 1974 and 1975, indicated significant variability between
sampling dates both years (Appendix G, Tables G15, G16, G17, G18, G19, and
G20). _ The excessive application rate resulted in significantly greater 504
and Cl levels than was found at the recommended rate in 1974 and 1975, but
had no apparent affect on the amounts of NOo either year. Generally, amounts
of anions were significantly greater with time under the impoundment irrigation
scheme in 1974. Weather and the narrower time interval between applications
appeared to have negated the irrigation management affects in 1975, with the
exception of Cl • Chloride levels were higher in the continuous flow plots in
1974, but then so was the irrigation supply levels.
A DMR test was employed to determine statistical significance of the
anionic concentrations with respect to time. Significant peak amounts per
hectare of SO/ averaged over treatment blocks corresponded to the application
of (NH,)2SO, (Figures 68 and 69). The amounts in the paddy water at panicle
differentiation were either equivalent to or significantly greater than that
applied preflood although twice as much was applied preflood (Table 18).
Since Cl~ was only associated with the fertilizer applied preplant, peak levels
corresponding to preflood and panicle differentiation fertilizer applications
suggest a mechanism of displacement from soil solution to the floodwater by
SOT (Figures 70 and 71). A significant peak was noted for NO^ following the
preflood N topdressing (Figures 72 and 73). However, the NO^ peak may have
been due to nitrification of NH^ rather than displacement by SO^ from soil
solution. No corresponding increase in NOT accompanied the second N topdress
application. This was not unexpected since denitrification rates increase
only under more favorable reducing conditions.
Salts in Soil Solution
As indicated in the section on soil solution sampling, the highly imper-
meable soil caused difficulty in obtaining an adequate solution sample. Where
samples were obtained, the analyses varied tremendously within replications.
Thus, inadequate sample volume and variability with replications made it diffi-
cult to obtain and interpret the data. The primary purpose of this phase was
to evaluate nutrient losses by percolation through the soil. It was evident
from the inability to obtain soil solution samples, and from the water balance
studies that very little water moved below into the profile below the root
zone.
123
-------
70l
60
50
40
to
20
10
5/3J
/|0
$29
DATE
Figure 68. The amount of SO, per hectare in the floodwater during 1974. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
70i
60
CO
to
Ul
30
20
10
6/
IO
%0 7/IO
DATE
30
8/
Figure 69. The amount of SO, per hectare in the floodwater during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
50
40
o
30
20
O\
5/
X
6/
X
20 30 0 20
DATE
!/ 8/ 8/
'9 7I9 72
Figure 70. The amount of Cl per hectare in the floodwater during 1974. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
50i
40-
30-
20-
'3) MO %0 ^0 fa X20 X30
DATE
8/ 8/ 8/
/o *ia 'c
29
Figure 71. The amount of Cl per hectare in the floodwater during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
O .4
-C
\
O* 3
Z •'
JO
00
'31
'10
'20
730
20
30
'19
Y29
DATE
Figure 72. The amount of NO- per hectare in the floodwater during 1974. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
s igni f ic anc e.
-------
2
.1-
iro
Q .0
N>
VD
73I
5/20
S/30 7/lO 7/20
DATE
7/30
8/c
'19
'29
Figure 73. The amount of NO per hectare in the floodwater during 1975. The verti-
cal bars represent the results of Duncan's Multiple Range Test at a 5% level of
significance.
-------
TABLE 18. ASSOCIATED IONS ADDED WITH FERTILIZERS
DURING THE THREE YEARS.
, Associated ion added
Growth stage Fertilizer Associated RecOmmendedExcessive
of rice element anion/cation rate rate
Preplant NH4 S0= 184 246
K+ Cl~ 16 64
H2P04 Ca+ 13 33
S0= 3 7
Preflood NH* S0= 184 246
Panicle NH* S0= 92 121
Differentiation
Dialysis tubes containing distilled water were placed at 1 cm in each plot
on the+respective sampling dates, and allowed to equilibrate 24 hours to assess
the NH4 and NO-j levels of the soil solution in 1974 (Table 19). Calcium was
measured in the dialysate in 1975 in addition to NHt and N0~ (Table 20). Soil
solution concentrations generally reflect that of the bulk paddy water pre-
viously discussed. The higher NH4-N levels correspond to the preflood and
panicle differentiation N topdressings. There was no discernible difference
in the preflood application with respect to the amount applied, whereas the
concentrations reflected the amounts applied at panicle differentiation. This
indicates that much of the NH^-N applied preflood was leached below the soil
solution - plot water equilibria level and/or tightly adsorbed by the soil.
Ammonium levels 4 days after the first sampling period are much higher in 1975
compared to the same time interval in 1974. This may have been related to
the interim 22 cm rain.
The averaged NO" levels never exceeded 0.20 ppm indicative of low nitri-
fication and high denitrification rates.
Calcium soil solution concentrations were similar in magnitude to that
130
-------
TABLE 19. IONIC CONCENTRATION OF DIALYSATE AVERAGED WITHIN
TREATMENTS FOLLOWING THE 24-HOUR EQUILIBRATION
PERIOD IN TOP 1 CM OF THE SOIL IN 1974
Ionic Concentration (ppm)
Treatment*
X1R1
X1R2
Z2R1
I2R2
Z1R1
I,R0
1 2
I-R,
2 1
I0R0
2 2
XIRI
1 1
I,R0
1 2
I R
2 1
I0R0
2 2
Z1R1
1 1
T R
12
T R
21
T R
22
IjRj
T R
12
T T?
21
T R
22
Date NH.-N
4
6/10/74 6.45
8.01
7.83
8.67
6/14/74 0.15
0.17
0.05
0.21
6/28/74 4.61
8.08
4.28
6.18
7/5/74 0.36
0.19
0.13
0.21
7/26/74 0.09
0.11
0.14
0.12
NO.-N
3
0.03
0.02
0.19
0.20
0.03
0.04
0.03
0.10
0.03
0.02
0.03
0.06
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
*I. and !„ correspond to continuous flow and impoundment irrigation,
respectively; RI and R_ correspond to recommended and excessive
application rate., respectively.
131
-------
TABLE 20. IONIC CONCENTRATION OF DIALYSATE AVERAGED WITHIN
TREATMENTS FOLLOWING THE 24-HOUR EQUILIBRATION
PERIOD IN TOP 1 CM OF THE SOIL IN 1975
Treatment*
Z1R1
Z1R2
Z2R1
I R
2 2
Z1R1
Z1R2
Z2R1
I2R2
Z1R1
Z1R2
Z2R1
2 2
Z1R1
Z1R2
Z2R1
Z2R2
Z1R1
Z1R2
Z2R1
Z2R2
Z1R1
Z1R2
Z2R1
I2R2
Ionic
Date NH4-N
6/9/75 4.88
8.57
8.38
8.57
6/13/75 3.42
2.95
2.19
3.03
6/20/75 8.92
15.70
11.15
12.05
6/30/75 0.08
0.19
0.08
0.08
7/10/75 0.18
0.12
0.16
0.16
7/25/75 0.14
0.27
0.11
0.18
Concentration
N03-N
0.06
0.05
0.05
0.06
0.05
0.01
0.06
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
. 0.00
0.00
0.00
0.00
0.00
0.00
(ppm)
Ca++
16.60
32.70
32.00
22.70
19.20
18.30
19.00
22.60
14.50
34.80
49.00
62.20
20.80
22.70
22.50
22.00
15.73
4.15
4.07
4.30
21.50
23.60
30.00
21.23
1^ and I^ correspond to continuous flow and impoundment irrigation;
Rj and R,, correspond to recommended and excessive application rates,
respectively.
132
-------
of the paddy water. Unlike NH,, Ca remained at a relatively high concentra-
tion up to the July 10, 1975 sampling date. The small,but frequent rain prior
to this sampling date probably significantly curtailed the amount of irriga-
tion water needed to maintain the desired plot depth. The July 25, 1975
sampling date was preceded by several canal water irrigations and the con-
centrations reflect that of the irrigation supply suggesting that the flux
is from the water to the soil.
Salts in the Soil Samples
Surface soil samples were collected prior to the preplant fertilizer
applications and following the rice harvest in 1973, 1974 and 1975. These
were extracted and analyzed for NH, , Ca*"1", Kg*"1", Na+, K+, Cl~~, PO? and NCU
(Table 21). Due to the accelerated water sampling schedule adopted early in
the 1973 season, time did not permit processing the soil samples collected
at the different soil depths. It was evident that the floodwater was not
percolating through the soil profile, so efforts were directed towards
analysis of the floodwater.
It is evident from the soil data obtained that the difference in CEC
between soils used for the 1973 field experiment and that employed for the
1974 and 1975 field experiment, was largely reflected in the amounts of Ca
in the soil. Furthermore, the salts were evidently adsorbed and not readily
solubilized since the floodwater in no way reflected the magnitudes of salt
in the soil. This is further substantiated by the rather tenuous equilibria
between canal water and surface soil solution which fluctuated with compara-
tively small fertilizer inputs, rainfall, and the colloidal, loads of the
irrigation supply. The point being that the soil served more as a sink
rather than as a source.
The rice plant must also be considered as a sink. Although yields were
lower in the excessive rate plots in 1974 and 1975 (Table 22), the difference
in fertility rates was small and could have been reflected in the vegetative
matter produced. The lower rice yields incurred in the excessive rate plots
during 1974 and 1975 may have been induced by the untimely application of an
excessive rate of molinate. Flinchum et al. (1973) reported that 10 kg
molinate/ha applied in the floodwater within 4 days of the panicle differen-
tiation growth stage reduced yields by 1000 kg/ha. Yields were not affected
in 1973 when molinate was applied 11 days prior to panicle differentiation.
Correspondingly, there was a much greater net decrease in ionic soil consti-
tuency in the 1973 growing season, as indicated by the preplant and post-
harvest analyses (Table 21).
Salt Balance
The water balance data was utilized with the electrical conductivity to
calculate 'the overall salt balance for the two irrigation treatments from the
time of seeding to the drainage at the end of the season. For purposes of the
calculation, a conversion factor of 640 mg/1 per 1000 ymhos was used. The
salt load of each irrigation and all runoff was calculated for both continuous
and impounded irrigation. The results are shown in Table 22.
133
-------
TABLE 21. INORGANIC IONS EXTRACTED FROM THE 0-5 CM SURFACE SOIL SAMPLED PREPLANT
Sampling
Date
Preplant
Post Harvest
Preplant
Post Harvest
Preplant
Post Harvest
Cationic Constituency
Year NH*
ppm
1973 10.78
7.35
1974 11.40
8.71
1975 7.14
5.83
Ca"
ppm
6003
5172
3840
3900
3500
3268
Ms4*
ppm
722
489
487
660
345
411
Na+
ppm
163
170
228
276
238
280
K+
ppm
53.11
38.22
126.00
112.00
92.00
121.00
Anlonic
Cl"
ppm
552.6
447.9
144.0
193.0
196.0
190.0
Constituency
P°4
ppm
0.89
1.15
1.43
1.28
2.65
2.63
N0~
ppm
4.14
2.76
0.90
0.90
0.90
-
-------
TABLE 22. SALT BALANCE DURING THE RICE GROWING SEASON DURING 1974 AND 1975.
Year
Irrigation technique
Salt applied in Salt lost Salt gained
Irrigation water in runoff by flood
1974
1974
1975
1975
Impounded
Continuous
Impounded
Continuous
kg /ha
528
993
428
712
kg/ha
559
575
433
587.9
kg/ha
-31
417
-5
124
During 1974, the rainfall was less, and the salt concentration in the
irrigation water was greater than during 1975. During both years, the salt
uptake and outflow for the impounded plots were nearly identical. More salt
was applied to the impounded plots during 1974 than in 1975, but the greater
concentration of salts in the runoff during 1974 resulted in more salt being
removed from the impounded plots during 1975. The continuous flow plots re-
ceived much more water than the intermittent irrigated plots during both years.
Consequently, the amount of salt added to these plots was greater. A total of
993 kg/ha was applied during 1974 again as a result of the greater concen-
tration of salts in the irrigation water. The salt loss in the outflow from
the continuous flow plots during 1974 and 1975 was nearly identical, resulting
in a net gain of 417 kg/ha during 1974 and 124 kg/ha in 1975. Individual run-
off-producing storms during both years contributed significantly to the salt
losses. The salt concentrations decreased sharply in the paddies during a
heavy rain, but the large values of runoff conveyed large amounts of salt
from the field. Rainfall induced runoff which occurred before the permanent
flood was established, indicates that salt residues from irrigation could be
removed from the fields in the runoff of a few storms each year.
Since more salt-bearing water is added to the continuous flow plots than
is removed in the outflow during the growing season, it is apparent that this
management practice could lead to excess salt in the soil during years which
do not receive much rainfall between growing seasons. On the other hand, the
concentrations of salts in the outflow from these plots are less and the water
would more easily meet rigid quality standards. The final release water be-
fore harvesting carried only a small fraction of the cumulative salt lost
during the entire season; therefore, termination of irrigation several weeks
before harvest to minimize outflow from the fields would not greatly increase
the salt residue in the field.
135
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FATE OF PESTICIDES
Much has been done to elucidate the fate of several of the infamous
chlorinated hydrocarbon pesticides in soils, aquatic environments, plants,
and other bio-systems. Persistence has been measured in years for^this^class
of pesticides, whereas persistence in most other classes of pesticides is
measured in months or weeks (Kearney,et al., 1969).
Perhaps a better indication of persistence is the half-life, or time
required for a 50% decrease of the applied material. This is a better measure-
ment of residue because many compounds degrade most rapidly at first, but may
linger for a considerable period of time at insignificant levels. Johnson
and Stansbury (1965) reported the half-life of carbaryl to be approximately
eight days with complete degradation in 40 days. Tanji and his co-workers
(1974) reported that molinate incorporated in dry soil persisted for only
about three to five days in the subsequently applied flood water. However,
molinate persisted in seepage waters in small quantities for at least four
months.
The production of toxic metabolites upon degradation of the parent pest-
icide must also be considered when one evaluates persistence of some particular
compound. Some metabolites can have a deleterious effect on non-target organ-
isms more striking than the original pesticide (Corke and Thompson, 1970).
Whatever the effect, metabolites can, under some conditions, extend the re-
sidual life of a pesticide (Burge, 1972; Chisaka and Kearney, 1970; Karinen
et al., 1967).
There are several modes by which the bioactivity of a pesticide is di-
minished in a target zone. They include: volatilization, leaching, adsorp-
tion by soil colloids, chemical alteration or decomposition, microbial
degradation, and absorption by non-target organisms (Bailey and White, 1970;
Edwards, 1966; Newman and Downing, 1958; Reed and Orr, 1943; Valentine and
Bingham, 1974). These processes interact creating very complex systems by
which pesticides are dissipated. Due to the complexity of the systems, path-
ways of degradation are very difficult to elucidate, making it very difficult
to predict how a compound will react under a given set of conditions.
Volatilization is generally important for those chemicals with vapor
pressures greater than 10~3 mm Hg at room temperature (Weber, 1972). Vari-
ables affecting volatility are soil moisture, formulation, wind speed,
turbulence, temperature, and time (Farmer et al., 1972). Other
processes such as adsorption, greatly affect volatility (Ashton and Sheets,
1959).
Leaching of pesticides is of particular importance in sandy soils low in
organic matter. High solubilities in water and low adsorptivities are charac-
teristics of compounds susceptible to leaching (Newman and Downing, 1958).
Bailey and White (1970) reported that soil adsorption was largely de-
pendent upon the properties of the adsorbate molecule. Some of these prop-
erties are: acidity or basicity (pKa or pKb), water solubility, molecular
size, and polarizability. However, the clay and organic humus fraction gen-
136
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erally determines the adsorptive capacity of a soil. Martin and Haider (1971)
reported that humic acid is generally the most important constituent of soil
humus. Several authors (Bartha, 1971; Chisaka and Kearney, 1970; Getzin, 1973;
Helling et al., 1971; Kazano et al., 1972; Martin and Haider, 1971) have re-
lated adsorption to the humus fraction of the soil. They have demonstrated
that an actual chemical bond may be formed between the carboxyl group of humic
acids and the adsorbate molecule. While an important mechanism in soils in
general, many soils have very low organic matter content limiting its impact
on the total amount adsorbed. These soils would favor adsorption by the clay
fraction of the soil. Amounts adsorbed in the clay fraction are governed
largely by the total percentage of clay and dominant clay minerals. Clay
minerals are comprised mainly of 1:1 and 2:1 type clays. The 1:1 type clays
(e.g. kaolinites, halloysites) are comprised of an octahedral sheet and a
tetrahedral sheet. They are characterized as non-expanding, low in cation
exchange capacity (CEC) and low in total surface area. The 2:1 type clays
(e.g. micas, vermiculites, montmorillonites) are comprised of an octahedral
sheet sandwiched between two tetrahedral sheets. They are characterized by
their higher CEC and higher surface area. Some are classed as expanding,
such as the montmorillonites, while others are non-expanding such as the micas.
The vermiculites are intermediate in that they do expand to some degree but
not nearly as much as montmorillonites. Perhaps the most important property
with respect to adsorbance is their well defined interlayer spacing. Swoboda
and Kunze (1968) have shown that there are different types of sites available
for adsorption of organic molecules at the surface of clays. Much of the
surface of 2:1 clays is exposed within the associate interlayer. A small
interlayer spacing could exclude large pesticide molecules from a considerable
portion of the available adsorption sites, due to steric hindrances.
Weber (1972) defined a distribution coefficient for adsorbance of pest-
icides in the two phase soil:water system as given in the equation below:
K = amount adsorbed/kg of soil ,.,.>
d amount in solution/liter
He pointed out that this was a relative value certainly dependent upon the
available sites, competition of water for the sites, concentration of the
adsorbate, and other chemical and physical properties. Generally, a large K^
value indicates removal of the pesticide from solution by adsorbance to soil
colloids.
Adsorbance is integrally related to microbial degradation of pesticides
in that it tends to reduce the amounts available for degradation, particularly
when a compound is chemisorbed in the interlayer or bonded to the organic
fraction (Bartha, 1971; Chisaka and Kearney, 1970; Karinen et al., 1967;
Swoboda and Kunze, 1968). Newman and Downing (1958) and Edwards (1966) re-
ported that loss rate of pesticides following application was rapid at first
due to overlapping processes of volatilization, leaching, adsorption, etc.,
but that in the long term the loss rate was principally due to microbial de-
composition.
Microbial degradation is a very complex process influenced by many
137
-------
variables. Aldrich (1953) reported that small differences within the structure
of otherwise similar pesticides affected microbial degradation. Other authors
(Audus, 1951; Engvild and Jensen, 1969; Newman et al., 1952; Patrick and
Mikkelson, 1971) have demonstrated that previous treatment with a particular
pesticide affected the microbial decomposition rate of succeeding treatments.
Newman and his co-workers (Newman et al., 1952) showed that the enrichment
effect can carry over from one year to the next. Generally, microbial de-
composition increases with temperature, substrate level, and moisture in-
creases. As the soil becomes saturated with water, a condition created by
flooding in rice culture, the biological activity changes. Patrick and
Mikkelson (1971) have demonstrated that flooding quickly reduces the oxygen
content of the soil, since the diffusion of oxygen in air is much greater
than its diffusion in water. The oxygen profile in a flooded soil is given
in Figure 74. As the redox potential decreases in the soil, the aerobic
bacterial count decreases, and the anaerobic bacteria count increases.
Generally, any treatment to the flooded soil that stimulates microbial ac-
tivity tends to decrease the oxygen content even more, resulting in lower
redox potentials. This could reduce the oxidized layer at the surface of the
soil shown in Figure 74. Numerous changes occur in the chemical nature of
the flooded soil and perhaps the most important with respect to pesticides,
is the change in soil reaction. Acid soils become neutral to slightly
alkaline, and alkaline soils tend toward a neutral pH after submergence. Soil
reaction has been shown to greatly affect the process of chemical alteration
(Caro et al., 1973; Wauchope and Haque, 1973). According to Faust (1964),
photodecomposition would be insignificant under flooded soil conditions due
to the scattering of ultraviolet light by the water and suspended colloids.
Propanil
Propanil (3',4'-dichloropropionanilide) is a postemergence herbicide used
in rice cultivation to control barnyardgrass and other annual weeds (Hodgson,
1971; Smith, 1965). Several researchers have shown that biological degrada-
tion is the principal mode of dissipation of propanil from soils (Bartha et
al., 1967; Bartha and Prammer, 1967; Bordeleau and Bartha, I972a; Surge, 1972;
Burge, 1973; Plimmer et al., 1970; Rosen and Siewierski, 1971). Two toxic
metabolites, DCA (3,4-dichloraniline) and TCAB (3,3',4,4-tetrachlorazobenzene);
are formed from the biological degradation of propanil (Bartha and Prammer,
1967; Corke and Thompson, 1970; Weisburger and Weisburger, 1966). Propanil
is biologically hydrolyzed to the aniline moiety and further transformed to
TCAB. Other complex products derived by the metabolism of chloranilines have
been isolated in soil cultures under laboratory conditions (Plimmer et al.,
1970; Rosen and Siewierski, 1971). However, TCAB is the only complex aniline
derivative isolated from field soils treated at normal application rates of
propanil (Kearney et al., 1970).
Bordeleau and Bartha (1972a and b) determined that the biological trans-
formations of propanil involved microorganisms with peroxidase and aniline
oxidase enzymatic activity. Peroxidase was found to have the greatest effect
in soil cultures. The occurrence of substantial cell-free peroxidases in
natural soils has been documented (Bartha and Bordeleau, 1969). Burge (1973)
reported that propanil could be converted to TCAB, and that the condensation
of two DAC molecules to TCAB was not necessarily dependent upon peroxidase
138
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WATER SURFACE
vo
10
SOIL SURFACE
OXIDIZED LAYER
REDUCED LAYER
OXYGEN
CONCENTRATION
2468
OXYGE:; CONCENTRATION, PPM
*400
-250
10
Figure 74. Oxygen profile in flooded soil[Patrick and Mikkelsen (1971)]
-------
activity.
Chisaka and Kearney (1970) recovered a maximum of 41% of the activity
from soils treated with l^C-labeled DCA. They concluded that binding with
soil components depended on the soil type as well as the physical-chemical
nature of the chloraniline. Others (Bartha, 1971; Chisaka and Kearney, 1970;
Kearney et al., 1970) have reported difficulty in recovering DCA from the soil,
indicating that adsorption is an important reaction involving chloranilines
and pathways of degradation.
Considerable work has been done to elucidate the nature of propanil re-
sidues in soils under aerobic conditions, and it has been found that acyl-
anilides are generally bio-degraded rapidly in soils (Bartha, 1971; Burge,
1972; Chisaka and Kearney, 1970; Helling et al, 1971; Kearney et al., 1970;
Plimmer et al., 1970). However, it is not known what effect anaerobic con-
ditions of a flooded soil regime may have on the half-life of propanil or its
toxic metabolites. Bordeleau and Bartha (1972a and b) demonstrated that the
oxygen content has a pronounced effect on the peroxidase and aniline oxidase
enzymatic activity. Also, it is not known to what extent the heavy mont-
morillonitic clay soils common to the Texas rice belt would affect the de-
gradation of propanil, or if irrigation management practices currently
employed would affect degradation rates. The extremes in irrigation manage-
ment practices are impoundment (a static condition) and continuous flow
systems.
Residue Levels in the Paddy Water—
Concentrations of propanil in the plot water sampled in 1973 indicated
that it was dissipated within 24 hours following the flood application (Table
23). Propanil was not detected in the 48-, 96-, and 152-hour water samples.
A more rigorous sampling schedule was employed in 1974 and 1975 to determine
the rapidity with which propanil was dissipated in the plots (Tables 24 and
25). The data were normalized to kg/ha to eliminate the influence of variable
plot water depths and impaired any meaningful statistical interpretation of
the results.
Analyses of variance for the 1973, 1974 and 1975 data indicated that time
had a significant effect upon the concentration of propanil in the plot water.
A Student-Newman-Keul's range test (Steel and Torrie, 1960) as employed to
determine the statistical significance between average concentrations with
respect to time for the 1974 and 1975 data (Tables 24 and 25). Although the
propanil concentration was about constant or increased over the first 12 hours.
it did not persist at significant levels 24 hours following the flood applica-
tion. A zero residue level was used as the lower limit of the range test in
computing the persistence at 24 hours alluded to in the above statement.
The concentration of propanil was generally higher in those plots which
received the 6.8 kg/ha treatment. Differences between the normal and ex-
cessive rates were significant at the 1% level in 1974 and 1975.
Analyses of variance did not reflect discernible differences between the
irrigation schemes tested. This was probably due to the rapidity with which
propanil was dissipated from the flooded rice plots. No first order inter-
140
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TABLE 23. PROPANIL RECOVERED IN WATER FROM TREATED RICE PLOTS
SAMPLED 0 AND 24 HOURS FOLLOWING THE FLOOD IN 1973
Water mgt.
Impounded
Impounded
Flowing
Flowing
Experiment
Treatments
kg/ha propanil
3.4
6.8
3.4
6.8
Ave*tSNK(p=2), 0.692
Hours Following
0
kg/hat
1.608
2.210
1.442
2.343
1.901
a
Flood
24
0.001
0.001
0.002
0.002
0.002^
tValues represent mean of three replications.
*tAverages over entire experiment not followed by the same letter are signi-
ficantly different at the 5% level using a Student-Newman-Keul's range test.
TABLE 24. PROPANIL IN WATER FROM TREATED RICE PLOTS SAMPLED 0, 3, 6,
12 AND 24 HOURS FOLLOWING THE FLOOD IN 1974
Treatments
Water mgt .
Impounded
Impounded
Flowing
Flowing
kg/ha propanil
3.4
6.8
3.4
6.8
0
0.136
0.330
0.078
0.322
Hours Following Flood
3
0.070
0.242
0.090
0.249
6 12
kg/hat
0.041 0.167
0.249 0.105
0.087 0.091
0.236 0.241
24
0.008
0.008
0.011
0.005
Experiment Ave*tSNK(p=5) 0.113
0.217 0.163 0.153
a a a
0.151 0.008,
a t
tValues represent mean of three replications.
*tAverages over entire experiment not followed by the same letter are signi-
ficantly different at the 5% level using a Student-Newman-Keul's range test.
141
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TABLE 25. PROPANIL RECOVERED IN WATER FROM TREATED RICE PLOTS
SAMPLED 0. 3. 6. 12, AND 24 HOURS FOLLOWING THE FLOOD IN 1975
Treatments
Water mgt.
Impounded
Impounded
Flowing
Flowing
kg/ha propanil
3.
6.
3.
6.
4
8
4
8
0.
1.
0.
1.
0
817
036
440
108
Hours Following Flood
0.
1.
0.
1.
3
176
203
466
036
6
kg/hat
1
1
1
2
.267
.310
.327
.525
0
1
0
2
12
.822
.671
.989
.306
24
0.061
0.056
0.075
0.208
Experiment Ave*t SNK(p=5) 0.560
0.850
0.720 1.607, 1.447,
abb
0.100
tValues represent mean of three replications.
*t Averages over the entire experiment not followed by the same letter are
significantly different at the 5% level using a Student-Newman-Keul's
range test.
actions involving time, application rate and/or irrigation scheme were found
to be statistically significant, although these sources of variation were
extracted from the error term. Hierarchical interactions involving replica-
tions were not subtracted from the error term since differences between rep-
lications were not found to be significant.
Propanil recovered from the rice foliage just prior to flooding was
linearly correlated to that recovered in the water just after flooding in
both 1974 and 1975 (Figures 75 and 76). The amount of propanil in the plot
water in 1974 (Table 24) was considerably lower than in 1973 and 1975 (Tables
23 and 25). The lower values in 1974 were attributed in part to the 0.63-cm
rain, which washed the propanil from the plants about five hours following
application. Propanil, which was washed from the foliage samples collected
prior to flooding and 24 hours after the application, was significantly lower
than that washed from the foliage immediately following the spray in 1974
(Table 26). Differences were not detected in 1975 at the corresponding time
interval (Table 27). Not all of the propanil dissipated from the foliage
between the two sampling periods in 1974 can be attributed to the rain, since
a 28% decrease in concentration was found on the foliage sampled within the
plot frames which were protected from rain (Figure 77). There was an addi-
tional 52% decrease in the amount of propanil recovered in the foliar rinses
over the next four days, during which no rain reached the plots. The analysis
of variance of the foliar data in the 1975 experiment indicated that the
propanil concentrations were not significantly different at a 5% level between
the two sampling periods (Table 27).
142
-------
.500-,
.300-
<
.200-^
o
2 .100-
o.
Y- 0.018+ 0.328 (X)
r = 0.71
O
JOO .200 .300 .400 .500 -600 .700
Propanil Recovered on Foliage (kg/ha)
.800
.900
Figure 75, Propanil recovered in the water immediately following the flood as
affected by the adsorbed foliar concentration prior to the flood application in
1974.
-------
1.6
I o8
o
o
or
o
Q.
20.4
a
Y = 0.305 * 0.530 (X)
r = 0.73
0.4 OB 1.2 1.6
Propanil Rinsed From the Foilage (kg/ha)
2.0
Figure 76. Propanil recovered in the water immediately following the flood as af-
fected by the adsorbed foliar concentration prior to the flood application in
1975.
-------
90-
80-
70-
:eo-
50-
§
'30-
20-
10-
12345
Days Following Spray Application
Figure 77. Percent propanil remaining on rice foliage sampled
in protected plots at 0, 1, 2, 3, and 5 days fol-
lowing the application.
145
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TABLE 26. PROP ANIL RECOVERED ON FOLIAGE SAMPLED FROM TREATED RICE PLOTS
0 AND 24 HOURS FOLLOWING APPLICATION IN 1974
Water mgt.
Impounded
Impounded
Flowing
Flowing
Experiment
Treatments
kg/ha propanil
3.4
6,8
3.4
6.8
Ave* SM(p=2) 0.272
Hours
0
0.609
1.599
0.636
1.902
1.582.
a
Following Application
24
kg /hat
0.213
0.601
0.254
0.806
0.625^
b
fValues represent mean of three replications.
* Averages over entire experiment not followed by the same letter are signi-
ficantly different at the 5% level using a Student-Newman-Keul's range test.
TABLE 27. PROPANIL RECOVERED ON FOLIAGE SAMPLED FROM TREATED RICE PLOTS
0 AND 24 HOURS FOLLOWING APPLICATION IN 1975
Water mgt.
Impounded
Impounded
Flowing
Flowing
Treatments
kg/ha
3
6
3
6
propanil
.4
.8
.4
.8
Hours
0
0.453
1.930
0.590
1.483
Following Application
kg /hat
0
1
0
1
24
.433
.233
.333
.306
Experiment Ave* SNK(p=2) .360
1.114
0.826
t Values represent mean of three replications.
- Averages over entire experiment not followed by the same letter are signi-
ficantly different at the 5% level using a Student-Newman-Keul's range test.
146
-------
The trend indicated a decrease with time. Foliar absorption probably accounts
for the losses where rain was not a factor. Absorption studies in rice and
other plants support this as a plausible explanation. Propanil absorbed by
the plants would not have been washed off by the foliar rinses.
The quantity of propanil remained nearly constant during the first 12
hours following the flood in 1974 (Table 24). A statistically significant
increase in propanil was found between the experimental averages computed for
the three hour and six hour water samples in 1975 (Table 25). The increase
corresponded to a statistically significant increase in plot water depth
during the 12 hours following flooding (Table 28). Continuous flow plots
were flooded to a greater depth in 1975 to further investigate the influence
of plot water depth on the amounts rinsed from the foliage. The higher flood
levels resulted in higher propanil concentrations at the 24 hour sampling
period within the same application rate, although the differences were not
significant at the 5% level (Table 25).
TABLE 28. AVERAGE PLOT DEPTHS WITHIN TREATMENT BLOCKS
WITH RESPECT TO TIME IN 1975
Treatments
Plot Depth
Hours Following Flood
Water mgt.
Impounded
Impounded
Flowing
Flowing
kg/ha propanil
3
6
3
6
.4
.8
.4
.8
0
11
11
10
12
.92
.06
.86
.52
11
10
12
13
3
.52
.62
.71
.62
6
cm
11.
10.
14.
15.
34
40
44
06
12
11
10
17
17
.22
.32
.21
.28
24
10.80
9.77
15.15
17.47
Experiment Ave*SNK(p=5) 2,10
11.59 12.12 , 12.81 , 14.01.
a ab ab b
*Averages over the entire experiment not followed by the same letter are
significantly different at the 5% level using a Student-Newman-Keul's range
test.
Approximately 82% of the 6.8 kg/ha propanil application was recovered on
the soil and foliar surfaces sampled from the border plot immediately follow-
ing the spray application in 1974. Propanil recovered on the soil surface
and foliar canopy was 3.5 and 2.1 kg/ha, respectively. The low levels of
propanil recovered in the water immediately following the flood (Table 24)
suggests little contribution from that which had been sprayed onto the soil
surface and that which had been washed onto the soil surface by the rain.
147
-------
This is substantiated by the low numerical value of the Y intercept obtained
from the linear regression of propanil recovered on the rice foliage and that
recovered in the flood water in 1974 (Figure 75). The very dry soil surface
conditions which occurred at the time of propanil application in 1975, may
have retarded its dissipation since more than 50% of that intercepted by the
soil surface remained in the 0.0 to 0.5 cm soil samples collected 20 hours
after the application (Figure 78). The Y intercept for the linear regression
of propanil recovered in the water was 0.31 kg/ha (Figure 76) which was sub-
stantially larger than the corresponding value for the 1974 data. This
indicates that soil-borne propanil may have contributed significantly to the
flood water concentration in 1975.
Propanil was not detected in the soil samples collected at 2.5 to 5.0
and 17.5 to 20.0 cm depths 24 hours following the flood water application.
Residue Levels of Metabolites—
DCA—DCA could not be quantitatively recovered from fortified soil and
canal water samples using the following extractants: 95% ethanol, benzene,
hexane, acetone, acetone-water, dichloromethane, diethyl ether, and combina-
tions of the above. However, the chromatograms of L;l acetonerbenezene extracts
for propanil showed that a small peak, analagous to the retention time of the
DCA standard, occurred in all of the 24-hour water samples in 1973 and 1974.
A steam distillation technique for DCA analyses in soil and water was
developed prior to the 1975 experiment. The distilling apparatus consisted
of a Friedrichs condenser equipped with a 34/45 ground glass joint and an
accompanying 750 erlenmeyer flask. A 10-g soil sample and 150 ml of water
was added to the flask, followed by 30 ml 6 N^ KOH. It was necessary to add
150 ml distilled water to the soil samples. The sample flask, with attached
condenser, was heated on a combination magnetic stirrer-hot plate until 100-
ml distillate was collected. The distillate was extracted with three, 25-ml
volumes of hexane. Extracts were combined, dehydrated with anhydrous Na2S04
and reduced to a suitable volume for GC analysis. Generally 100% of the DCA
was recovered from fortified canal water samples. DCA recovered from forti-
fied soil samples rangre between 91 and 100%.
The above method may not be suitable for soils and water levels with
appreciable propanil levels. Burge (1973) employed an alkaline hydrolysis to
convert propanil to DCA in the procedure he used for propanil analysis.Inter-
ference from propanil was indicated in the present study. The mean DCA con-
centration (Figure 78) of the surface soil samples collected from the six
high rate plots immediately following the propanil application, was 32 ppnv or
20 ppm when the background level was subtracted. The propanil concentration
determined on separate sub-samples was 58 ppm. This suggests that DCA was
34% contaminant of the spray formulation relativeto the propanil concentration.
Laboratory analysis of the propanil formulation used in 1975 showed DCA to be
less than a 2% contaminant. No attempt was made to remove propanil prior to
the DCA steam distillation procedure. It appears that the alkiline conditions
of the procedure employed resulted in a 32% conversion of propanil to DCA.
The mean DCA concentration (Figure 78) reported for the soil sediment sampled
24 hours after the flood was valid, since very little propanil was present
in the sample to interfere with the DCA analysis.
148
-------
60
50
VO
.2 30-
o
O
c
o
o
10-
Flood Application
A DCA Background Level
PROPANIL Background Level
0 24
Hours Following Spray Application
48
Figure 78. Concentration of propanil and DCA in soils sampled from high rate plots
immediately following the spray application, just prior to flood, and 24 hours
following the flood application in 1975.
-------
DCA levels in the plot water sampled 24 hours following the flood appli-
cation were linearly correlated to propanil dissipated between the 12 and 24
hour sampling periods (Figure 79). Generally, the propanil concentration 24
hours after the flood was small compared to the DCA concentration, suggesting
that only a small positive error would have been incurred by the propanil in
the distillation procedure.
The relatively high background level of DCA probably came from the^de-
gradation of a uniform 3.4 kg/ha propanil application made two weeks prior
to the replicated experiment for weed control in the plots. The flood applied
24 hours following the propanil was drained after 24 hours, and the surface
was allowed to dry. The drier surface condition may have retarded the micro-
bial decomposition of DCA.
Although propanil was rapidly dissipated in the surface soil samples
(Figure 78), there was no corresponding increase in the DCA concentration.
A marked increase in the mean DCA concentration of the surface sediment of
the six high rate plots was observed 72 hours following the permanent flood
application in 1975 (Figure 80). There was a corresponding decrease in the
DCA concentration of the plot water sampled, which suggests that a large por-
tion of the DCA in the H20 was adsorbed to the suspended colloidal load, and
the surface sediment concentration increased as the suspended particles set-
tled. The average suspended sediment concentration was 0.53 g/1 24 hours
following the permanent flood application (Figure 81). This was diminished
to 0.18 g/1 72 hours following the permanent flood application. Subsequent
variations from one sampling date to another did not appear to be associated
with heavy rainfall or irrigations.
DCA was not detected in the soil sampled at 2.5 to 5.0 cm and 17.5 to
20.0 cm depths 24 hours following the flood water application.
TCAB—The biological condensation of DCA -> TCAB did not occur to any
appreciable extent, as only trace levels were found in the 24 hour samples
collected in 1973, and none were detected in any of the samples collected in
either 1974 or 1975. The probability of two DCA molecules and the right
organisms coming together was perhaps a factor lessened greatly by the dis-
persal of soil sediments and dilution created by the flood.
Modes of Dissipation—
Volatilization and photodecomposition—It has been shown that the vari-
able and relatively high levels of propanil found in the water immediately
following the flood reflected the quantities washed from the leaf canopy.
Significant losses by photodecomposition and volatilization were not indicated
by the data. The driest year with respect to leaf and soil surface prior to
application resulted in the greatest concentration present in the flood. Pro-
panil concentrations present in the water had remained almost constant or
increased during mid-afternoon heat and sunlight intensities, with most of
the loss incurred during the night. No propanil was lost from the spiked dis-
tilled water samples placed in the laboratory, or those exposed to direct
sunlight for four days. This further indicates that photodecomposition and
vaporization are not predominant factors in the dissipation.
150
-------
o
o
1000
900
800]
700
1,600
500
400
300
200
100
Y=-63.57 +0.45 (X)
r = 0.78
200 400 600 800 1000 I2OO 1400 1600 1800 20OO
Propanil Dissipated Between 12 and 24 Hour Sampling Periods (ug/1)
Figure 79. Levels of DCA in rice paddies sampled 24 hours following the flood appli-
cation as affected by the dissipation of propanil between the 12 and 24 hour sam-
pling periods in 1975.
-------
600
Q>
24
72 168
Hours Following Permanent Flood
Figure 80. Average DCA concentrations of the surface sediment and flood water sampled
from the 6 high rate plots at 24, 72, 168, and 336 hours following the permanent
flood application in 1975.
-------
Ur
U)
O.6
0.5
&
iz:
o> o.4
^Q
^5
o
*- 0.3
cz
3 0.2
O.I
j j
o
(0
C\j
1
i :
§ § § § i S
« 8 £55 8g
. to 10 to ^ —
1 1 III!
i 5 5
5
6/6 6/11 6/16 6/21 6/26 7/1 7/6 7/il 7/16 7/21 7/26 7/31 8/5
Days Following Permanent Flood Application
Figure 81. Sediment load with respect to time following the permanent flood
olication in 1975.
ap-
-------
Adsorption—Adsorption coefficients (Kd) were determined for propanil,
DCA and TCAB at different sediment loads (Figure 82). The Kd was found to
increase sharply at sediment loads less than 10 g/1. This was attributed to
a surface area increase resulting from dispersion of the clay fraction into
individual particles, exposing sites within the interlayer space. The TCAB
Kd values ranged from 200 to 600 and, consequently, are not shown in Figure
82. The relationship between Kd and percent pesticide in solution is graphi-
cally depicted in Figure 83. Adsorption coefficients determined at 50 g I"1
sediment load and corresponding percent pesticide (propanil, DCA, carbofuran,
3-keto, and 3-Hydroxy-carbofuran, molinate, carbaryl, 1-napthol) in solution
were found to be negatively correlated, r2 = 0.87, using an exponential func-
tion. Generally, the higher the Kd value, the lower the percent pesticide in
solution. Concentration did have some effect on the Kd values determined for
propanil and DCA (Figure 82). Values determined at 0.5 ppm pesticide were
generally greater than those determined at 0.2 ppm, especially at the lower
sediment loads. This is possibly due to the increased probability of the
pesticide being at a specific adsorption site at the higher concentration,
Biological Degradation—The authors submit that biological degradation
was the primary mode by which propanil was dissipated from the rice plots.
Propanil was probably adsorbed by the colloidal load of the water and brought
into contact with the soil microorganisms which degraded it to DCA.
Molinate
Residue Levels in the Paddy Water—
Molinate (S-ethylhexahydro-lH-azepine-1-carbamate) is a herbicide
commonly used to control broadleaved weeds in rice after the permanent flood.
Kaufman (1967) proposed that the degradation of thiocarbamates may proceed by
an initial hydrolysis at the ester linkage with the formation of mercaptan,
C02, and an alkylamine. Hydrolysis is followed by the subsequent degradation
of the mercaptan and alkylamine formed.
Molinate may be subject to volatilization due to its high vapor pressure
(10~3 mm Hg) and high water solubility (Ashton and Sheets, 1959; Weber, 1972).
Tanji et al. (1974) recently reported their results on experiments con-
ducted to determine the persistence and movement of molinate in field plots
under static, flow-through, and recycled water management systems. Molinate
applied in a preflood, preplant treatment was found to persist in the
water for about three to five days. Much of that lost appeared to have been
leached in the subsequent flood, as indicated by the much higher initial con-
centrations which resulted from the postflood application. Molinate persisted
for at least four months in seepage water, which suggested to the authors that
anaerobic conditions induced by submergence of the plots may have retarded
microbial degradation. Molinate applied as a post-flood treatment in the
static water management system remained at relatively high concentrations for
more than 10 days following the application. It was not determined what effect
a granular application would have in a post-flood water treatment.
Molinate in commercially available granular form was applied by broad-
cast over the entire plots. Applications succeeded the permanent flood by
154
-------
tn
o>
'o
0>
o
o
c.
o
H.
b
T3
80 T
70
60
50
40
30
20
10
O Propanil
• DCA
50 100
Sediment Load (g/l)
150
Figure 82. Adsorption coefficients of propanil and DCA cal-
culated at the corresponding sediment loads.
155
-------
(Jl
IOO
c
0
o
CO
_c
d>
CO
75
50
(/)
a!
^ 25
0>
Y = 85.l2e
r2= -0.93
-0.04 (X)
10
20 30
Adsorption Coefficient
40
50
Figure 83. Correlation of percent pesticide in solution and
at a sediment load of 50 g/1.
values determined
-------
10 days in 1973, and by 18 days in 1974 and 1975 (Appendix A).
The amounts of molinate in the rice paddy water averaged within each
treatment block with respect to time are shown in Figures 84, 85, and 86, for
1973, 1974, and 1975, respectively, The data were converted to kg/ha to
account for the variable plot water depths which influenced the concentrations
and impaired any meaningful statistical interpretation of the field results.
Concentrations in the flood water were approximately proportional to the
application rates (Tables 29, 30, and 31). The plots receiving excessive
rates contained about three times that found in the plots receiving the
recommended rate.
Maximum molinate concentrations were obtained at the 0-hour sampling
period in 1973 and 1974. However, the maximum occurred at the 24-hour
sampling period in 1975. The apparent disparity in the data may have resulted
from the shorter time differential between application and zero sample col-
lection in 1975.
Analyses of variance for the data collected in 1973, 1974 and 1975 are
given in Appendix I. Concentrations of molinate were significantly different
with respect to time at better than a 1% level in each of the three years
tested. A Student-Newman-Keul's range test (Steele and Torrie, 1960) was
employed to determine the statistical significance of differences between
average concentrations within treatment (Tables 29, 30, and 31). Molinate
did not persist at significant levels in any of the treatments after the 96
hour sampling period in 1973. The 768 hour average concentration was used as
the lower limit of the range test for computing persistence on a significant
basis. For practical purposes, it was essentially 0 since the maximum average
concentration at the 768 hour sampling period was 5 ppb in 1973. Generally,
persistence was two to four times longer in the 1974 and 1975 field experi-
ments.
Application rate was found to have a highly significant influence on plot
water concentrations all three years. Molinate persisted longer in plots
treated at the excessive rate, as indicated by the highly significant first
order interaction between time and rate of application (Appendix I, Tables
II, 12, and 13).
Concentrations of molinate were generally higher under the impounded
irrigation management scheme all three years, but the difference was statisti-
cally significant only in 1973. Correspondingly, a highly significant in-
teraction was noted between time and irrigation treatments in 1973; whereas,
the interaction was not statistically significant in 1974 or 1975.
A first order, three-way interaction between time, irrigation treatment,
and application rate was significant at the 5% level in 1973. This inter-
action was not significant in 1974 or 1975. Since differences due to replica-
tions were not significant in 1973 or 1974, and only barely significant at the
5% level in 1975, one would not expect higher-order interactions involving
replications to be significant.
The rainfall which occurred during the period when measurements were
157
-------
TABLE 29. CONCENTRATION OF MOLINATE IN PADDY WATER FOLLOWING ITS
APPLICATION IN 1973, AND STATISTICAL SIGNIFICANCE WITH
RESPECT TO TIME
Treatment
Block* Rep 0
I.R, 1 1.055
2 1.239
3 1.104
ave** 1.133a
I ,R2 1 3.319
2 4.128
3 3.064
ave 3.504a
I2R, 1 1.383
2 1.638
3 1.660
ave 1.560a
I?R? 1 6.638
2 4.213
3 7.234
ave 6.028a
0
0
0
0
2
3
2
2
1
1
1
1
4
4
5
4
H
24
.977
.617
.704
.766ab
.248
.363
.795
,802b
.023
.642
.523
.396a
.545
.225
.960
.910b
ours Following Application
0.
0.
0.
0.
1.
1.
1.
1.
0.
1.
1.
1.
3.
3.
4.
3.
48
535
396
191
374bc
238
574
438
417c
902
319
250
157ab
978
000
000
659c
kg /ha
96
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
2,
1.
2.
2.
228
362
049
231bc
500
613
604
572d
553
934
904
797bc
165
541
810
172d
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
192
331
193
068
197bc
081
083
052
072d
216
301
235
251c
699
544
398
547e
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
384
.000
.011
.001
.004c
.006
.005
.000
,004d
.038
.026
.045
,036c
.076
.094
.035
.068e
768
0.000
0.003
0.001
O.OOlc
0.000
0.000
0.000
0.000
0.000
0.005
0.008
0.004c
0.004
0.006
0.004
O.OOSe
* 1^ and I2 indicate continuous flow and impoundment irrigation treatments,
respectively. R. and R indicate recommended and excessive application
rates, respectively.
** Averages with different letter subscripts are significantly different at
the 0.01 level.
158
-------
TABLE 30. CONCENTRATION OF MOLINATE IN PADDY WATER FOLLOWING ITS
APPLICATION IN 1974, AND STATISTICAL SIGNIFICANCE WITH
RESPECT TO TIME
Hours Following
Treatment
Block* Rep
I R 1
1 i 2
3
ave**
I 1 Rr-l J-
1 2 2
3
ave
I'D 1
2 1 2
3
ave
2 2 2
3
ave
1
2
2
2
8
5
3
5
0
2
1
1
8
5
6
6
0
.967
.607
.443
»339a
.363
.663
.757
.928a
.588
.731
.397
.572a
.504
.756
.463
.908a
2
1
1
2
7
4
4
5
0
1
0
1
6
4
5
5
24
.466
.801
.924
.064ab
.000
.333
.343
.225a
.800
.680
.973
.151a
.000
,672
.967
,546b
Application
kg/ha
96
1
1
1
1
4
2
3
3
0
0
0
0
2
6
2
3
.672
.768
.386
.609b
.749
.456
.561
.589b
.008
.754
.202
.321b
.261
.305
.611
.726c
0
0
0
0
0
0
1
0
0
0
0
0
1
1
2
I
192
.538
.403
.342
.428c
.819
.669
.412
.967c
.329
.982
.450
.587b
.984
.828
J312
.941d
384
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
£.
0.
000
052
010
021c
028
070
110
069d
017
141
026
061c
819
370
403
^^-^v—
531e
768
0.000
0.000
0.000
0.000
0.001
0.000
0.004
0.002d
0.000
0.000
0.000
0.000
0.093
0.009
0.056
0.053e
* I, and !„ indicate continuous flow and impoundment irrigation treat-
ments, respectively. R, and R_ indicate recommended and excessive
application rates, respectively.
** Averages with different letter subscripts are significantly different
at the 0.01 level.
159
-------
TABLE 31. CONCENTRATION OF M01INATE IN PADDY WATER FOLLOWING ITS
APPLICATION IN 1975, AND STATISTICAL SIGNIFICANCE WITH
RESPECT TO TIME
Hours Following^ Application
Treatment
Block* Rep
I.R. 1
1 l 2
3
ave**
I R 1
2
3
ave
I2R 1
2
3
ave
I R 1
22 2
3
ave
0
.000
.001
.019
.007d
.030
.000
.027
.019d
.000
.001
.000
,0003c
.000
.001
.001
.OOlc
24
1.814
1.235
2.289
1.780a
4.853
6.755
4.186
5.265a
1.758
1.461
1.659
1.626a
6.756
4.416
3.309
4.827a
48
1.535
.983
1.446
1.321b
4.917
4.217
4.660
4.598a
1.756
1.162
1.691
1.536a
5.857
4.403
3_.254
4.505a
kg /ha
96
.859
.715
.809
.794c
3.549
3.177
3.272
3.333b
1.544
.802
1.516
1.287a
5.023
3.408
2.923
3.785a
192
.569
.032
.105
.235d
1.053
1.224
2.130
1.469c
.958
.484
.716
.719b
2.062
2.138
1.569
1.923b
384
.003
.000
.049
.017d
.385
.029
.459
.291d
.159
.052
.093
.lOlc
.960
.726
•JLl^L,
.867bc
768
.000
.000
.000
.OOOd
.005
.000
.001
.002d
.035
.006
.000
,014c
.113
.099
.037
,083c
* Ij and 1^ indicate continuous and impoundment irrigation treatments,
respectively. R and R indicate recommended and excessive application
rates, respectively.
** Averages with different letter subscripts are significantly different at
the 0.01 level.
160
-------
0\
d d a d rr> o"
X Continuous, Recommended
D Continuous, Excessive
O Impounded, Recommended
A Impounded, Excessive
384
Hours Following Application
768
Figure 84. Average concentration of molinate in rice paddy water sampled in 1973.
-------
to
Continuous, Recommended
O Continuous, Excessive
O Impounded, Recommended
A Impounded, Excessive
192 384
Hours Following Application
768
Figure 85. Average concentration of molinate in rice paddy water sampled in 1974,
-------
X Continuous, Recommended
Continuous, Excessive
O Impounded, Recommended
A Impounded, Excessive
Exp. Ave.
384
Hours Following Appfication
768
Figure 86. Average concentration of molinate in rice paddy water sampled in 1975.
-------
taken had no apparent influence on the concentration of molinate in the flood
water. Both molinate and carbofuran were applied as granular materials. The
greater solubility of molinate may have resulted in a more rapid dissolution
of that held in the sheath, diminishing the probability of secondary plot
water concentration peaks, as were observed for carbofuran.
Modes of Dissipation—
Molinate dissipation rates within the paddy water were approximately the
same for continuous flow and impounded irrigation schemes. The rate of loss
was about 20% per day corresponding to a half-life of about 2^ days. Since
some water flowed out of the continuous flow system lots each day, one would
expect an inherently higher dissipation rate for this management scheme.
The apparent incongruity may have induced greater dissipation rates by other
modes negating the effect of the flushing mechanism under continuous flow.
Volatilization—An experiment was conducted in the laboratory to evaluate
volatilization as a potential mechanism for loss of molinate from the plot
water (Table 32). Very little difference was found between the vapor flux
using air saturated with water vapor and unsaturated air, suggesting that co-
distillation with water was minimal. Little difference was noted in the
vapor flux with an almost four-fold increase in the molinate concentration.
However, the vapor flux was diminished considerably when soil was placed in
the flask prior to the molinate spike,
TABLE 32. VOLATILIZATION OF MOLINATE FROM WATER AT
27°C AND AIR FLOW RATE OF 8 ML/SEC
Sample
Concentration
Vapor Flux*
Volatilization
Potential**
Distilled HO
Distilled HO1"
Distilled H20
Distilled H20tt
_Ug/ml
2.0
2.0
7.8
7.1
jjg/cm /day
1.6
1.7
2.0
0.8
yg/plot/day
4.8 X 106
5.1 X 106
6.0 X 106
2.4 X 106
* Average of two determinations
2
** Calculated on the basis of a 300 m plot water surface
t Air not saturated with H_0 prior to being passed into chamber
tf Ten g soil added to 100 ml water prior to molinate spike
The potential loss from a plot 300 m was calculated using the vapor
flux values determined empirically (Table 32). A maximum of 6 g/day would
be lost from pure water under the conditions of the experiment. Only 2.4
g/day would be lost by vaporization from a surface the size of field plots
with colloids in the water. Both rates are only a fraction of the 30 g/day
164
-------
actually dissipated from the field plots. Temperatures in the water ranged
between 35°C during the day and 25°C during the night. The high daytime
water temperature would probably result in an increased vapor flux (Farmer
et al., 1972). But it is doubtful that the increase would overcome the nega-
tive effect of the colloidal load of the plot water. Thus, vaporization
would not be the primary mode of dissipation, but the cumulative loss over a
period of time may be significant under hot, windy conditions.
Adsorption—To evaluate this mechanism, adsorption coefficients were
measured at varying sediment loads (Figure 87). Molinate reacted similarly
to propanil with respect to the rapid increase in Kd at sediment loads less
than 10 g/liter. An extrapolation of the Kd obtained at 50 g/liter to the
percent pesticide in solution curve given in Figure 83 indicates that moli-
nate adsorption is reversible with water, since about 75% is in solution.
The amount adsorbed (numerator in Kd equation) and Kd were measured at in-
creasing concentrations of molinate at the 2.5 g/liter sediment load as
shown in Figure 88. Amounts of molinate adsorbed increased linearly with
increased concentration. However, Kd appears to have peaked at about 1 ppm
molinate, suggesting that a partitioning mechanism with water may be occurring.
It should be noted that only about 10% of the added molinate was adsorbed at
the 2.5 g/liter sediment load, even at the higher Kd values. However, the
percentage adsorbed increased with increased sediment load in the experiment
summarized in Figure 87. This may have been the result of increased organic
matter content with increased additions of soil to the centrifuge tubes.
A leaching experiment was conducted in which 20 g samples of a Beaumont
clay soil were spiked with 87 ug of molinate, then leached with 100 ml dis-
tilled water (Table 33). The soil had been pre-wet with distilled water, and
the molinate was applied evenly in 1 ml water after complete drainage of the
pre-rinse. The Beaumont clay became very tight in the columns during wetting
and it took more than 48 hours to leach 100 ml. The 70% of the molinate
leached from the soils closely approximated the 67% in solution averaged for
the adsorption experiment where 20 g of soil was thoroughly mixed with 200 ml
of water for 30 min on a reciprocating shaker.
TABLE 33. COLUMN LEACHING OF A MOLINATE-SHKED
BEAUMONT CLAY SOIL WITH DISTILLED WATER
Molinate Recovered*
Column Soil Leachate
ug ug
1 17.9 62.4
2 16.6 60.0
* An 87 ug spike was added to each soil column.
165
-------
25
20
c
'§ 15
o
O
g
B. 10
o
4
U
-------
60
50
(U
o
0>
o
o
o
40
30
20
10
Amount Adsorbed
24
16
12
Q
X
8
1234
Molinate Concentration (ppm)
Figure 88. The amount adsorbed and K^ versus molinate con-
centration in water with a sediment load of 2.5
g/1-
167
-------
Molinate would probably leach under conditions other than total satura-
tion associated with the permanent flood in rice culture (Tanji et al., 1974).
However, the downward net flux in most rice soils is essentially zero after
establishment of the permanent flood. No molinate was found at either the
2.5 to 5.0 cm depth or the 17.5 to 20.0 cm depth sampled in the field experi-
ment after the application. The leaching of molinate could be a problem if
applied to a soil in which downward movement of water does occur. The hazard
would become a function of distance between the surface and the ground water
and the adsorptive capacity of the soil.
At the lower sediment loads, only 10% of the molinate was actually ad-
sorbed. The net effect of the colloidal load may be precipitory in nature.
The adsorptive mechanism returns solubilized molinate to the soil surface
where it may be trapped by other soil particles carried on sedimentation or
adsorbed more tightly by humic acids associated with the organic fraction of
the soil. Adsorption cannot account for the dissipation rates of molinate
demonstrated in the field experiment, although chemical bonding to the or-
ganic fraction could have a significant influence on the amounts in solution.
A precipitory mechanism would tend to bring molinate into more intimate contact
with the microorganisms proliferating at the soil surface (Patrick and
Mikkelson, 1971).
Biological dissipation—Soil samples were placed under flooded conditions
and equilibrated for eight days prior to the molinate fortification to simulate
field conditions. Molinate dissipation was generally greater for the most
oxidized samples (Table 34). The redox range was not as encompassing as de-
sired but resulted in some discernible differences in molinate recovered.
Samples receiving no added substrate generally had the higher redox potential,
but required a longer period of time to dissipate molinate. Those treated
with 0.25 g sugar dissipated more molinate over an eight day period than those
not treated with sugar. It is surmised that the 0.25 g treatment induced
rapid proliferation of microbial growth followed by a depletion in the oxygen
content. It appears that the depletion rate of oxygen was a function of the
substrate level. Although decomposition of molinate was noted in only one of
the 16 hour samples treated with 1 g sugar, the soils were definitely becoming
more oxidized with time. No degradation was noted in the sterilized controls
after the 16 day incubation period.
Results in the field experiment are consistent with those obtained in the
laboratory experiment. Field plots were flooded eight days prior to the
molinate application in 1973; whereas, the plots were flooded 18 days prior
to the application in 1974 and 1975. The longer half-life of molinate in
1974 and 1975 may be due to a more reduced environment attained in the longer
interval between permanent flood and molinate application.
Carbofuran
Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methyl carbamate)
is a broad spectrum insecticide belonging to the N-methyl carbamate family of
pesticides. The two toxic metabolites reported for carbofuran are 3-keto
carbofuran (2,3-dihydro-2,2-dimethyl-3-keto-7-benzofuranyl-N-methyl car-
bamate) and 3-hydroxy carbofuran (2,3-dihydro-2,2-dimethyl-3-hydroxy-7-benzo-
168
-------
TABLE 34. EFFECTS OF TIME, SUBSTRATE LEVEL, AND REDOX POTENTIAL
ON THE DISSIPATION OF MOLINATE IN FLOODED SOIL SAMPLES
UNDER LABORATORY CONDITIONS*
Incubation Soil
Period Preparation
Days
1 Not Sterilized
Not Sterilized
Not Sterilized
Sterilized
8 Not Sterilized
Not Sterilized
Not Sterilized
Sterilized
16 Not Sterilized
Not Sterilized
Not Sterilized
Sterilized
Sucrose
Added
8
none
0.25
1.00
1.00
none
0.25
1.00
1.00
none
0.25
1.00
1.00
Rep
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
Molinate
Recovered
ug
89.1
98.4
99.5
97.8
96.7
91.5
94.3
92.9
85.2
77.2
72.9
88.3
92.8
89.7
30.8
69.2
85.7
52.9
90.0
58.9
89.1
Redox
Potential
mv
- 75
- 98
-425
-418
-450
-485
+ 10
-155
-120
- 75
- 68
-330
-285
+150
-145
-170
-190
-175
-260
-175
+ 60
* All flasks including controls were spiked with 100 mg molinate.
169
-------
furanyl-N-methyl carbamate) (Butler and McDonough, 1971),
Caro et al. (1973) followed the degradation of carbofuran in an actual
field experiment. They found that carbofuran disappeared from the soil by
first-order kinetics, the half-life ranging from 46 to 117 days in the broad-
cast and in-furrow applications, respectively. Degradation was greatly
accelerated in several localized areas within the treated watersheds, These
areas were found to have higher soil water contents, a generally higher pH
level, and a more clayey texture. The field receiving the broadcast appli-
cation had an average soil pH of 6.3, and the field employed for the in-
furrow treatment averaged pH 5.2. Although circumstantial, the data certainly
indicate that pH may drastically affect the dissipation rate of carbofuran.
From 0.5 to 0.2% of the carbofuran applied was lost in runoff water. Of that
lost, more was in solution than in the suspended soil particles. About 5 to
10% of the carbofuran applied was converted to 3-keto carbofuran, which dis-
appeared at about the same rate as the parent compound. Only sporadic trace
levels of 3-hydroxy were found in the soil samples.
14
Getzin (1973) determined the persistence of C carbonyl-labeled carbo-
furan and l^C ring-labeled carbofuran phenol on four soils ranging in pH from
7.8 to 5.9. The soil with pH 5.9 was an organic muck soil with 40% organic
matter. The half-life varied from three weeks in the pH 7.8 to more than 50
weeks in the organic muck soil. C02 was evolved in both sterilized and non-
sterilized soils fortified with 20 ppm of the carbonyl-labeled carbofuran
suggesting that hydrolysis was not due only to metabolic processes of micro-
organisims under the oxidized conditions of these experiments. Evolution of
1^C02 proceeded at a considerably slower rate using ring-labeled carbofuran
phenol. Approximately 25% of the carbofuran phenol was degraded within the
32-week experimental period. However, carbofuran was almost completely
hydrolyzed within 32 weeks in the two soils used in the ring-labeled phenol
experiment. Soil-bound residues of ring-labeled carbofuran phenol reached
a 70 to 80% maximum within two weeks after treatment, Thus, it appears that
carbofuran may be chemically altered to its phenol which is immediately bound
to soil constituents and slowly metabolized by microorganisms, Getzin (1973)
made no attempt to identify metabolites other than carbofuran phenol.
It is not known how carbofuran would react under the anaerobic conditions
of flooded rice culture. The half-lives reported in the experiment above
suggest that carbofuran may be a problem in rice culture.
Residue Levels in the Paddy Water—
The residual amounts of carbofuran found for the various treatments with
respect to time following application are plotted in Figures 89, 90, and 91
for the 1973, 1974, and 1975 data, respectively. Residual levels were highest
initially and decreased rapidly to less than 50% of the initial concentration
within 24 hours in 1973. Carbofuran residues in the water followed a different
dissipation pattern in 1974 and 1975. The amounts in the water were low
initially and highest in the 24-hour samples. It is possible that a time
differential between application and the zero-hour sampling period could ex-
plain the discord in the data initially. Carbofuran was applied in the flood
water in a commercially available granular form, and sufficient time may not
have elapsed for dissolution in 1974 and 1975. However, a time differential
170
-------
'5
8
.6-
5.4
o
8-2
(O
o
O
o o o o f>
11II II
X Continuous Recommended
D Continuous Excessive
O Impounded Recommended
A Impounded Excessive
96 192 384
Hours Following Application
768
Figure 89. Average concentrations of carbofuran in rice paddy water sampled in
1973.
-------
z.o
o
.c
CD
1
.—
c
•2 1.0-
o
"c
0)
f 1
ft
' \
1
i
1
f
1
1
1
\
]
\
\
\
\
\
\
t
X Continuous Recommended
O Continuous Excessive
O Impounded Recommended
A Impounded Excessive
193 384
Hours Following Application
768
Figure 90.
1974.
Average concentrations of carbofuran In rice paddy water sampled in
-------
2.0i
Si §
8$ ?
O 6 C>
§ §
X Continuous Recommended
D Continuous Excessive
O Impounded Recommended
A Impounded Excessive
96 192
386
768
Hours Following Application
Figure 91. Average concentrations of carbofuran in rice paddy water sampled in 1975.
-------
cannot explain the anomaly in the 24-hour samples. As much as 60% of that
applied at the excessive rate could be accounted for in 1974, 24 hours later.
Conversely, only about 30% of that applied in 1973 was present in the water,
and this maximum occurred in the zero-hour samples. Error in application
could perhaps account for the disparity in amounts recovered ,but cannot ex-
plain the trend noted in the 24-hour sample.
During 1973, no rain fell until later than 192 hours after application.
This and subsequent rains had little effect on the amount of carbofuran in
the flood water. This most likely occurred because the amount of carbofuran
on the foliage had decreased, and because the rains fell just after sampling,
allowing considerable time for dissipation before the next sampling. During
1974, a 1.24 cm rain fell just before the 192-hour sampling causing a second
peak in concentration. Subsequent rainfall resulted in no increase in the
amounts in the floodwater. In 1975 a 0.53 cm rain fell just before the 24-
hour sample was collected. Those samples had the greatest concentrations.
The concentration decreased markedly between the 24- and 48-hour samples.
Two rains totaling 0.79 cm were recorded between the 48- and 96-hour sampling
which may have washed additional material into the water resulting in a second
peak in three of the four treatments at 96 hours. The influence of subsequent
rainfall was again not evident.
The carbofuran had been applied as granular material, a fraction of which
may have lodged in the sheath of the rice foliage. The data presented here
indicates that some of the material probably dissolved in the rainfall and
washed into the plots.
Deviations between replications within treatments were not statistically
significant at the 0.05 level or better during any of the three years
(Appendix I, Table 14, 15, and 16). No significant difference was found be-
tween irrigation treatments. Application rate and time were found to have a
highly significant influence on the amounts of carbofuran in the paddy water
in each of the three years tested. The only significant interaction found
was that between application rate and time. As expected, higher rates re-
sulted in longer persistence of significant residue levels.
A Student-Newman-Keul's range test (Steel and Torrie, I960) was employed
to determine which average residue level concentrations were significantly
different with respect to time (Tables 35, 36, and 37). Only the zero-hour
concentrations were significantly different from that measured in the 768-
hour samples in 1973, with the exception of the excessive rate treatments.
For this treatment significance was extended into the 24-hour samples.
No significant difference was found with respect to time in the treat-
ment receiving the recommended application rate in 1974 (Table 36). The 24-
hour level and the peak at 192 hours were found to be significant at the 5%
level in the excessive application rate treatments in 1974.
Trends in the 1975 data corresponded well with those observed for the
1974 data. However, the peak occurred at 96 hours in 1975 (Table 37). Re-
sidue levels in the 192-hour samples were not significantly higher than the
minute quantities obtained at 768 hours. Relatively higher levels were ob-
174
-------
TABLE 35- CONCENTRATION OF CARBOFURAN IN PADDY WATER FOLLOWING
ITS APPLICATION IN 1973, AND STATISTICAL SIGNIFICANCE
WITH RESPECT TO TIME
Hours Following Application
Treatment
Block* Rep 0
I R 1 0.317
1 2 0.159
3 0.205
ave** 0.227 a
I.R. 1 0.547
1 2 1.130
3 1.050
ave 0.909a
I-R. 1 0.206
2 0.312
3 0.405
ave 0.308a
I0R_ 1 0.500
2 2
2 0.990
3 0.954
ave 0.815a
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
24
044
052
090
062b
186
302
263
250b
098
093
103
098b
200
275
191
222b
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
48
.009
.008
.050
.022b
.076
.058
.079
.071c
.052
.040
.069
.054b
.117
.102
.098
.106bc
kg/ha
96
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
002
001
014
006b
Oil
021
025
019c
050
058
025
044b
072
069
041
061c
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
192
.002
.002
.030
.Ollb
.008
.029
.003
.024c
.037
.004
.014
.018b
.072
.074
.039
.062c
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
384
.002
.006
.024
.Ollb
.005
.003
.002
.014c
.029
.009
.055
,031b
.023
.068
.013
.035c
768
0.001
0.001
0.016
0.006b
0.000
0.004
0.001
0.007c
0.016
0.007
0.005
0.009b
0.016
0.010
0.003
O.OlOc
* I1 and I? indicate continuous flow and impoundment irrigation treatments,
respectively. R, and R? indicate recommended and excessive application
rates, respectively.
** Averages with different letter subscripts are significantly different at
the 0.01 level.
175
-------
TABLE 36. CONCENTRATION OF CARBOFURAN IN PADDY WATER FOLLOWING
ITS APPLICATION IN 1974, AND STATISTICAL SIGNIFICANCE
WITH RESPECT TO TIME
Treatment
Block* Rej3
I R. 1
0.
0
043
2 0.407
3
ave**
I B, 1
2
_3
ave
Ift 1
2
3
ave
I IL 1
2
3
ave
o^
0.
0.
0.
£1
0.
0.
0.
0.
0.
0.
0.
£•
0.
232
227a
188
012
080
093a
468
012
050
lOla
224
077
251
184a
0
0
0
0
3
1
I
2
0
0
0
0
1
0
1
1
Hours
24
.197
.286
.229
.237a
.906
.462
.901
i i • • .
.423b
.263
.262
.540
.355a
.939
.738
.235
.304b
Following
kg/ha
96
0.
0.
(h
0.
0.
0.
.P-i
0.
0.
0.
0.
0.
0.
0.
CK
0.
051
025
094
057a
384
121
063
189a
004
024
004
Olla
013
029
069
037a
0
0
0
0
0
0
J3
0
0
0
0
0
1
0
o.
0
Application
192
.118
.147
.176_
.I47a
.890
.536
.467
,631c
.328
.467
.525
.440a
.280
.495
.J83
,786c
384
0.
0.
0.
— . *».
0.
0.
0.
£i
0.
0.
0.
0.
0.
0.
0.
0^
0.
015
032
123
057a
124
513
108
248a
026
137
094
086a
843
267
229
446a
768
0.000
0.000
0.000
O.OOOa
0.001
0.019
0.002
0.007a
0.012
0.049
0.001
0.021a
0.202
0.067
0.195
0.155a
* I and I „ indicate continuous flow and impoundment irrigation treat-
ments, respectively. R^ and R indicate recommended and excessive
application rates, respectively.
** Averages with different letter subscripts are significantly different
at the 0.01 level.
176
-------
TABLE 37. CONCENTRATION OF CARBOFURAN IN PADDY WATER FOLLOWING
ITS APPLICATION IN 1975, AND STATISTICAL SIGNIFICANCE
WITH RESPECT TO TIME
Hours Following Application
Treatment
Block* Rep
i
3
ave**
X1R2 I
3
ave
T2R1 \
3
ave
X2R2 \
3
ave
0
.001
.001
.001
.OOlb
.000
.000
.001
.0003c
.000
.001
.001
.0007c
.000
.000
.000
.OOOb
24
.260
.240
.173
.224a
1.814
1.210
1.425
1.483a
.192
.102
.250
.181a
1.124
2.072
.587
1.261a
48
.344
.142
.204
.230a
.913
.506
.279
.566bc
.188
.019
.205
.137ab
.552
.875
.649
.692ab
kg/ha
96
.142
.094
.190
.I42a
.941
.443
1.572
.985ab
.198
.089
.291
.193a
.489
.670
1.476
.878ab
192
.126
.003
.007
.045b
.423
.472
.516
.470bc
.172
.093
.091
.030bc
.309
.397
.630
.445ab
384
.002
.002
.056
.020b
.018
.450
.246
.238c
.118
.045
.096
.086abc
.700
.324
.375
.466ab
768
.001
.000
.000
.0003b
.002
.000
.035
.012c
.052
.007
.000
.020bc
.004
.006
.003
.004b
* I and 12 indicate continuous and impoundment irrigation treatments,
respectively. R, and R~ indicate recommended and excessive application
rates, respectively.
** Averages with different letter subscripts are significantly different at
the 0.05 level.
177
-------
tained in the I2&2 block 768 hours in 1974 aS comPared to 1975» althou§h the
plot water residues were comparable at corresponding sampling periods. Two
heavy rains in excess of 2.5 cm fell on the plots just three and four days
prior to the 768-hour sampling period in 1975, which may have resulted in the
difference.
Residue Levels of Metabolites—
Small amounts of 3-keto carbofuran were detected in the plot water
sampled following the application of carbofuran (Tables 38, 39, and 40). The
time lag between application of carbofuran and detection of the 3-keto carbo-
furan suggests the latter to be a dissipation product rather than a contami-
nant of the former. However, the minute amounts detected (less than 0.05 ppm
even of the excessive application rate) indicate that the 3-keto moiety would
not enhance the residual life of carbofuran to an appreciable extent under
flooded rice culture. Concentrations of 3-hydroxy carbofuran were never
detected in excess of minute trace levels.
Modes of Dissipation—
Volatilization,—Neither carbofuran nor 3-keto carbofuran were found to
volatilize to any appreciable extent in the laboratory. The 3-hydroxy meta-
bolite of carbofuran had a vapor flux of 1.8 yg cm~2 day'1 in unsaturated
(with respect to water) air. However, when the air was saturated with water
vapor prior to being passed into the volatilization chamber, the vapor flux
was diminished to 0.3yg cm~^ day" from distilled water at 27°C, with air
flow rate of 8 ml/sec. No relevance was attached to the vapor flux obtained
due to the low value in moist air and the fact that only trace levels of 3-
hydroxy were ever detected in the plots. It is doubtful that significant
amounts of carbofuran of 3-keto carbofuran would be dissipated from the paddy
water via a volatilization mechanism.
Adsorption—Carbofuran and 3-keto carbofuran reacted similarly to moli-
nate in that the K^ increased rapidly at sediment loads less than 10 g/1, but
greater than 90% of the pesticide was in solution (Figure 92). Carbofuran
and 3-keto carbofuran were different in that the K^ did not increase at in-
creasing sediment loads greater than 10 g/1. This suggests that carbofuran
was not adsorbed at specific sites and/or did not interact appreciably with
the organic fraction. Lack of adsorption was evidenced by the fact that
greater than 80% remained in solution at the highest sediment load of 150
g/1. The 3-hydroxy metabolite was adsorbed more tightly than carbofuran or
3-keto carbofuran. It is doubtful that adsorption had more than a precipi-
tory function in the dissipation of carbofuran from the field plots.
No carbofuran, 3-keto, or 3-hydroxy carbofuran was detected in the soils
sampled at 2.5 to 5.0 and 17.5 to 20.0 cm depths one, three, and five weeks
following its application.
The data collected in the field experiments in 1973, 1974, and 1975
suggest that carbofuran was rapidly dissipated to some degradation product
other than 3-keto or 3-hydroxy carbofuran. It is surmised that chemical
alteration may be the major mode of dissipation of carbofuran from the flooded
Beaumont clay soil, with biological degradation important over a longer time
span.
178
-------
TABLE 38. CONCENTRATION OF 3-KETO CARBOFURAN WITH RESPECT
TO TIME IN RICE PADDY WATER SAMPLED IN 1973
Hours Following
Treatment
Block* Rep
I R 1
1 X 2
3
ave
I R 1
2
3
ave
IoRi !
2 1 2
3
ave
I R 1
2
3
ave
96
ND**
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
.008
trace
.001
.003
kg /ha
192
ND
ND
ND
ND
ND
trace
ND
ND
ND
.004
ND
.001
.010
.005
.003
.003
Application
384
tracet
ND
trace
trace
ND
trace
ND
ND
trace
ND
trace
trace
.003
.004
trace
.002
768
ND
trace
ND
ND
trace
.001
trace
trace
trace
trace
trace
trace
trace
.001
ND
trace
* I. and !„ indicate continuous and impoundment irrigation; R.
and R? indicate recommended and excessive application rates
of carbofuran, respectively.
** ND refers to none detected.
t Trace refers to those amounts detected but which were too close
to the sensitivity limit to quantitate.
179
-------
TABLE 39. CONCENTRATION OF 3-KETO CARBOFURAN WITH RESPECT
TO TIME IN RICE PADDY WATER COLLECTED IN 1974
Hours Following Application
Treatment
Block* Rep
I
1 l 2
3
ave
I R 1
1 2 2
3
ave
I R 1
2 1 2
3
ave
I7R9 1
2
3
ave
kg/ha
384
trace**
trace
0.001
0.001
0.007
0.011
0.017
0.012
0.004
0.002
0.004
0.003
0.042
0.057
0.044
0.048
768
NDt
ND
ND
ND
ND
trace
trace
-------
TABLE 40. CONCENTRATION OF 3-KETO CARBOFURAN WITH RESPECT TO
TIME IN WATER SAMPLED FROM RICE PLOTS IN 1975
Treatment
Block* Rep
hRl 2
3
ave
I R 1
2
3
ave
X2R1 I
3
ave
I R 1
22 2
3
ave
Hours
48
ND**
trace
trace
trace
ND
trace
.001
trace
ND
ND
ND
ND
.003
.002
.003
.003
Following
kg/ha
96
tracet
ND
trace
trace
.003
.002
.005
.003
.001
trace
.002
.001
.006
.005
.011
.007
Application
192
trace
ND
ND
ND
.002
384
ND
ND
ND
ND
ND
.002 trace
.003
.002
trace
.002
.001
.001
.019
.006
.014
.013
ND
ND
ND
ND
ND
ND
.006
.002
ND
.003
* I. and !„ indicate continuous and impoundment irrigation manage-
ment schemes; R, and R_ indicate recommended and excessive
application rates of carbofuran, respectively.
** ND refers to none detected.
t Trace refers to those amounts detected but which are too close to
the sensitivity limit to quantitate.
181
-------
36
30
U)
o
0)
o
(J
s l8
• Carbofuran
O 3- Keto Carbofuran
X 3-Hydroxy Carbofuran
50 100
Sediment Load (g/l)
150
Figure 92. Adsorption coefficients of carbofuran, 3-keto and
3-hydroxy carbofuran at varying sediment loads.
182
-------
Biological degradation—Very little degradation of carbofuran was ob-
served in the unsterilized Beaumont clay soil samples incubated under flooded
conditions for 96 hours (Table 41). However, more than 20% of the carbofuran
could not be recovered in the sterilized soil samples. Steam autoclaving
caused the Beaumont clay soil to disperse, creating a significant colloidal
load. Since the entire contents of the flasks were extracted, the data
suggested that carbofuran was non-biologically altered to some other moiety
of carbofuran which was tightly bound to soil colloids. Others have recently
reported on the importance of chemical alteration of carbofuran to carbofuran
phenol with respect to soil adsorption (Caro et al., 1973; Getzin, 1973).
TABLE 41. CARBOFURAN RECOVERED FROM FLOODED BEAUMONT
CLAY SOIL EQUILIBRATED 96 HOURS AT 27°C
Treatment* Carbofuran Recovered**
7
to
Unsterilized 95
Sterilized 79
* Sterilized samples, steam autoclaved prior to 100
yg carbofuran spike,
** Average of four determinations.
Another experiment was conducted with flooded soils to assess the effects
of more reduced conditions than obtained in the above experiment. This was
accomplished by allowing flooded Beaumont clay soil samples to equilibrate
six weeks prior to the introduction of carbofuran and 3-keto carbofuran into
the system. The data shown in Table 42 indicate that more reduced conditions
favor the degradation of carbofuran and especially that of 3-keto carbofuran.
Although the redox potentials were positive, it may be more a reflection on
the length of equilibration than on oxidized conditions. Potentials were
obviously much lower at some point in the six week equilibration period as
evidenced by the rusty coating on the walls of the flasks. Perhaps the addi-
tion of carbofuran and 3-keto carbofuran tended to drive the highly equili-
brated systems to a more oxidized state.
Carbaryl
Carbaryl (1-naphthyl-N-methyl carbamate) is a broad spectrum insecticide
belonging to the N-methyl carbamate family of pesticides. Carbaryl has
several metabolites associated with its degradation, but 1-naphthol is the
most significant (Kazano et al., 1972; Wauchope and Haque, 1973). Bollag and
Liu (1971) have demonstrated that soil microorganisms vary considerably^in
their ability to degrade carbaryl and 1-naphthol, and that some metabolites
can be more deleterious to certain non-target organisms than the original
pesticide. Kaufman et al. (1970) determined that methyl carbamate pesticides
183
-------
TABLE 42. EFFECT OF REDUCING CONDITIONS ON THE DISSIPATION
OF CARBOFURAN AND 3-KETO CARBOFURAN IN FLOODED
SAMPLES OF A BEAUMONT CLAY SOIL
Sample Spike
80 ug
Carbofuran
Carbofuran
3-Keto*
3-Keto
Aeration
Open
Restricted
Open
Restricted
Redox
Potential
-hnv
115
75
165
130
Pesticide
Recovered
%
100
88
65
11
. . . - ......
* 3-Keto refers to 3-keto carbofuran.
are competitive inhibitors of soil micnobial enzyme systems which hydrolyze
other pesticides. It is not known if synergistic effects will occur between
the pesticides to be used in this study.
Wauchope and Haque (1973) evaluated the effects of pH, light intensity,
and temperature on carbaryl in the laboratory. They found the stability of
carbaryl and 1-naphthol to be greatest in weakly acidic solutions. Marked de-
creases in the stability were noted with increases in pH. At a constant pH
value of 10.0, first order half-lives were found to be 20 and eight minutes
at 25° and 35°C, respectively. The 1-naphthol derivative was more susceptible
to photodegradation than carbaryl. As indicated earlier, most rice soils
would be well below the pH levels employed in their experiments, However, the
pH of marine estuaries would be approximately that of sea water which has a
pH of 8.
Karinen et al. (1967) did investigate the persistence of carbaryl and 1-
naphthol in the marine estuarine environment. Their efforts indicated that
carbaryl and 1-naphthol were greatly affected by temperature and the presence
of mud. In plain sea water, the carbaryl concentration decreased 50% in 38
days at 8°C. Most of the decrease was accounted for by the production of 1-
naphthol. In the presence of mud, both carbaryl and 1-naphthol were dissipated
to less than 10% in the sea water in 10 days. They were found to be adsorbed
by the mud where degradation continued at a slower rate. Radioactive carbon
dioxide was produced in the aquaria spiked with ^C carbonyl-labeled and ring-
labeled carbaryl, indicating decomposition by hydrolysis of the carbamate and
oxidation of the ring had occurred. Some 60% of the total ^C activity could
not be accounted for, which the authors believed to have been evolved as
methane gas. Their primary evidence for this was the fact that carbaryl could
be detected in the mud for 42 days at low concentrations, and the 1-naphthol
persisted in significant quantities for only one day. It should be noted that
their recovery was based upon a combustion method of their dichloromethane and
acetone extracts. Their experiments with the aquaria containing mud indicate
184
-------
that anaerobic conditions prevailed at some point in the experiment since the
pH was 0.4 to 0.5 units lower than the control tank which contained only sea
water. No attempt was made to correlate the seemingly increased persistence
of carbaryl in the mud treated aquaria to the more reduced conditions. In a
side experiment they showed that 93% of the carbaryl was hydrolyzed in four
days at 28°C in sea water alone.
Kazano et al. (1972) conducted laboratory experiments with five acid
Japanese rice soils treated with ^C carbaryl-labeled carbaryl and l^C-l, 4,
5, 8-ring-labeled 1-naphthol. Their soils were maintained at 80% of the field
moisture capacity indicating aerobic conditions prevailed throughout the course
of their experiment. The carbaryl experiment was conducted at 25°C with a 32
day incubation period. 1-Naphthol was incubated under the same conditions
but for 60 days instead of 32 days. Persistence was found to be influenced by
soil type. The ^CC^ evolution ranged from 2.2 to 37.4% of initial radio-
activity for carbaryl. The bulk of the remaining activity was found to be
associated with the soil humus. The difficulty with which it was extracted
indicated to the authors that it was more chemically bound than just adsorbed.
They concluded that carbaryl was hydrolyzed to its phenol, 1-naphthol. C02
evolution in the 1-naphthol experiment followed the general scheme as that
for carbaryl in that the soils degraded in 60 days incubation as compared to
more than twice that for carbaryl in half the time. Once again the 1-naphthol
was found to be immobilized on humic substances in the soil. The anomaly in
their data was that the soil with,the least amount of organic matter (1.5%)
resulted in the least amount of COo evolved in the 1-naphthol experiment.
The soil with the lowest total CEC (9.8 meq/lOOg) and second lowest organic
matter content (3.3%) had the lowest C02 evolved in the carbaryl experiment.
This may have been a result of variable microbial populations.
Bollag and Liu (1971) reported that carbaryl could be degraded both chemi-
cally and biologically to 1-naphthol. A fungus, Fusarium solani, altered 1-
'naphthol rapidly under moist soil culture.
Residue Levels in the Paddy Water—
A commercially available formulation of carbaryl was foliarly applied
approximately three weeks prior to harvest in 1973, 1974 and 1975 (Appendix A) .
Generally, the amounts in the water were influenced by the rainfall dis-
tribution (Tables 43, 44, and 45). A 7.6 cm rain fell on the plots following
the 24-hour sampling in 1973, washing the carbaryl from the foliage and, as a
result, greatest amounts were measured in the 48-hour water samples. The peaks
in plot water concentrations noted at 40 and 96 hours in 1974 also followed
8.6 and 0.5 rains, respectively. The carbaryl dispersed more evenly over the
first four sampling periods in 1975 due to the corresponding rains incurred.
Rains in excess of 7.0 cm were recorded between the 24 and 48 hour sampling
periods in the regular field experiments in 1973 and 1974. Much of the residual
material could have been flushed from the foliage into the plots by this rain.
A rapid dissipation rate was indicated by the fact that the samples following
the storms were much less than the concentration applied. The amount of car-
baryl in the plot water sampled in 1975 peaked 28 hours following application,
then was dissipated rapidly over the next 20 hours such that the 48 hour
samples did not differ significantly from the 96 hour samples which were
185
-------
TABLE 43. CONCENTRATION OF CARBARYL IN FLOOD WATER FOLLOWING
ITS APPLICATION IN 1973, AND STATISTICAL SIGNIFICANCE
WITH RESPECT TO TIME
Hours
Treatment
Block* Rep
I.R. 1
11 2
3
ave**
I.R, 1
2
3
ave
I R 1
2
3
ave
I2R2 1
2
3
ave
0.
0.
0.
0.
0.
0.
°i
0.
0.
0.
0.
0.
0.
0.
0.
0.
0
160
055
095
103a
119
073
171
121a
085
103
147
112a
119
161
513
264a
0.
0.
0.
0.
0.
0.
CL
0.
0.
0.
0.
0.
0.
0.
0.
0.
24
117
031
034
06la
073
120
109
lOla
047
051
067
055a
121
115
109
115a
Following Application
kg/ha
48
0.
0.
0.
0.
0.
0.
Ch
0.
0.
0.
0.
0.
0.
0,
1.
0.
270
124
321
238b
650
642
672
655b
563
396
222
394b
815
694
004
851b
0.
0.
0.
0.
0.
0.
£1
0.
0.
0.
0.
0.
0.
0.
0.
0.
96
001
001
000
OOla
000
001
006
002a
001
002
000
OOla
573
000
000
191a
192
0.
0.
0.
0.
0.
0.
2i
0.
0.
0.
0.
0.
0.
0.
0.
0.
000
000
001
000
001
000
052
027a
000
000
000
000
000
000
000
000
384
0.001
0.000
0.000
0.000
0.002
0.000
0.001
O.OOla
0.002
0.000
0.000
0.001
0.001
0.001
0.000
O.OOlc
* Ij and I £ indicate continuous and impoundment irrigation treatments,
respectively. R and R^ indicate recommended and excessive application
rates, respectively.
** Averages with different letter subscripts are significantly different
at the 0.01 level.
186
-------
TABLE 44. CONCENTRATION OF CARBARYL IN PADDY WATER FOLLOWING
ITS APPLICATION IN 1974, AND STATISTICAL SIGNIFICANCE
WITH RESPECT TO TIME
Hours Following Application
Treatment
Block* Rep
I R 1
2
3
ave**
I R2 1
3
ave
I R 1
2 1 2
3
ave
I R
22 2
3
ave
0
0
0
0
0
0
0
0
0
0
_0
0
0
1
1
1
0
.198
.090
.052
.113a
.034
.175
.789
.333ab
.104
.146
.090
.113a
.717
.140
.875
.244a
0.
0.
0.
0.
0.
0.
°i
0.
0.
0.
o^
0.
0.
0.
1.
0.
24
051
072
095
073a
125
090
068
094ab
039
015
020
025a
173
659
807
880ab
kg/ha
40
0.
0.
0.
0.
1.
0.
£1
0.
0.
0.
°i
0.
1.
0.
0.
0.
498
032
007
179a
291
255
206
584a
161
069
038
089a
250
820
003
691b
0
0
0
0
0
0
£
"s
0
0
0
0
0
0
1
1
96
.251
.054
.034
.113a
.433
.677
.484
.531a
.496
.272
.082
.288a
.859
.623
.534
.005ab
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
168
.000
.001
.000
.OOOa
.000
.015
.000
.005b
.000
.000
.000
.OOOa
.002
.000
.473
.158c
240
0.000
0.000
0.000
0.000
0.000
0.000
0.000
O.OOOb
0.000
0.000
0.000
0.000
0.000
0.000
0.001
O.OOOc
* I1 and I indicate continuous and impoundment irrigation treatments,
respectively. RI and R9 indicate recommended and excessive application
rates, respecitvely.
** Averages with different letter subscripts are significantly different
at the 0.01 level.
187
-------
TABLE 45. CONCENTRATION OF CARBARYL IN PADDY WATER FOLLOWING
ITS APPLICATION IN 1975, AND STATISTICAL SIGNIFICANCE
WITH RESPECT TO TIME
Hours Following Application
Treatment
Block* Rep
I,R. 1
11 2
3
ave**
Z1R2 1
L 2
3
ave
I R 1
2 l 2
3
ave
T2R2 l
2
3
ave
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.102
.033
.029
.055ab
.079
.132
.112
,108b
.025
.027
.011
.021a
.220
.170
.066
.152b
kg /ha
21 28
0.
0.
0.
0.
3.
1.
0.
1.
0.
0.
0.
0.
2.
0.
ii
2.
490
437
056
328a
513
407
937
950ab
181
249
611
347a
368
871
476
572a
0
0
0
0
7
2
1
3
1
0
0
0
2
0
£
1
.038
.232
.127
.132ab
.722
.644
.110
.832a
.320
.024
.102
.482a
.927
.927
.300
.385ab
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
2.
ii
1.
48
065
204
090
120ab
242
194
201
212b
056
196
134
129a
670
119
760
516ab
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
Hi
0.
96
000
000
000
OOOb
000
000
000
OOOb
000
001
000
OOOa
006
000
625
210b
* I and I indicate continuous and impoundment irrigation treatments,
respectively. R^ and R indicate recommended and excessive
application rates, respectively.
** Averages with different letter subscripts are significantly
different at the 0.01 level.
188
-------
essentially zero.
The results of the rainfall simulation experiment are shown in Figure 93
for the 2.5 cm per hour test conducted in 1975. Results of 1974 followed
similar trends but were less complete. The initial concentrations represent
the residuals in the water at the specified time intervals after application.
All concentrations at this point were between 50 and 100 ppm. They were
generally ranked such that those with large intervals between application and
rainfall had the lowest background levels at the start of the tests. The con-
centration of carbaryl increased rapidly after rainfall started in the plots
which had been sprayed the same day. Within four minutes the concentrations
had reached their maximum, after which they remained relatively constant indi-
cating that washoff had been completed. By the end of four minutes, less than
two millimeters of rain had reached the plots. Thus, only a very small rain-
fall was necessary to rinse essentially all the carbaryl from the foliage.
The concentration reached at the end of four minutes of rainfall represented
approximately 10% of the carbaryl originally applied to the plots. Rainfall
events occurring one, two, four, and seven days after application did not re-
sult in nearly as great a final concentration in the floodwater. In all cases
complete washoff occurred ^within four to eight minutes after the beginning of
the simulated storm. Although the concentrations resulting from washoff gen-
erally decreased as the interval between application and rainfall increased,
the differences were small and resulted in no more than a doubling of the con-
centration found at the beginning of the storm, Although no rainfall reached
the plots, very heavy dew was present on the plants each night, and it is
possible that even after one night of dew, much of the residual pesticide may
have already been washed from the foliage.
Analyses of variance indicated that time of sampling collection and ap-
plication rate had a highly significant influence on carbaryl concentration
measured in the water for each of the three years tested (Appendix I, Tables
17, 18, and 19). Residues of carbaryl were found to be greater in those plots
under the impoundment irrigation scheme at a 5% level of significance in 1973
and at a 1% level of significance in 1974 (Appendix I), Irrigation treatment
had no effect on carbaryl concentrations in 1975 (Appendix I, Tables 17, 18,
and 19).
A second order interaction between time and rate of application was ob-
served at a 1% level of significance in 1973 and at a 5% level of significance
in 1975. This interaction simply suggests that residual carbaryl levels were
greater with respect to time at the excessive application rate. Irrigation
treatment and rate of application interacted to significantly affect the
carbaryl concentration in 1974.
Residue Levels of Metabolites—
The 1-naphthol metabolite was determined in the paddy water in each of
the samples collected in 1973, 1974 and 1975 (Tables 46, 47, and 48, respec-
tively). Amounts present reflect the rate of carbaryl applied. However, the
relatively high levels at the zero sampling period indicate that 1-naphthol
was present initially as a contaminant. A peak in 1-naphthol levels was found
corresponding to the carbaryl washed from the foliage after the rains. Thus,
it appears that the 1-naphthol present was not produced as a metabolite of
189
-------
TABLE 46. CONCENTRATION OF 1-NAPHTHOL IN THE
PADDY WATER IN 1973
Hours Following Application**
Treatment
Block* Rep
Vi \
3
X1R2 2
3
2 l 2
3
X2R2 1
3
0
0.009
0.004
0.003
0.005
0.020
0.040
0.009
0.017
0.033
0.041
0.008
0.013
24
0.000
0.000
0.001
0.003
0.003
0.001
0.001
0.003
0.004
0.006
0.002
0.007
kg/ha
48
0.001
0.003
0.004
0.007
0.004
0.005
0.002
0.007
0.002
0.020
0.033
0.011
96
0.000
0.000
0.000
0.000
0.001
0.000
0.000
0.000
0.002
0.013
0.000
0.000
192
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
* I, and I„ indicate continuous and impoundment irrigation treat-
ments, respectively. R and R2 indicate recommended and excessive
application rates, respectively.
** Application is with respect to carbaryl.
190
-------
TABLE 47. CONCENTRATI ON OF 1-NAPHTHOL IN THE PADDY
WATER SAMPLED IN 1974
Hours Following Application**
Treatment
Block*
X1R1
I R
I R
I0R~
2 2
Rep
1
2
3
1
2
3
1
2
3
1
2
3
0
.001
.002
.004
.000
.002
.051
.001
.005
.005
.013
.110
.001
kg/ha
24
.001
.001
.001
.001
.002
,001
.001
.000
,000
.008
.010
.005
40
.003
.002
.000
.012
.006
.002
.011
.001
.000
.001
.000
.003
* I1 and !„ indicate continuous and impoundment irrigation
treatments, respectively. R.. and R« indicate recommended
and excessive application rates, respectively.
** Application is with respect to carbaryl.
191
-------
TABLE 48. CONCENTRATION OF 1-NAPHTHOL IN THE PADDY
WATER SAMPLED IN 1975
Treatment
Block* Rep
JiRi 1
1 l 2
3
X1R1 1
1 2 2
3
I R 1
^ L 2
3
I R2 1
^ 2
3
Hours
0
.001
.000
.001
.001
,000
.001
.000
.001
.000
.014
.000
.001
Following
kg/ha
21
.001
.001
.001
.021
.044
.004
.000
.001
.019
.005
.065
Application**
28
.000
.001
.001
.009
.091
.006
.011
.000
.000
.035
.012
.009
48
.000
.002
.000
.006
.000
.001
.000
.000
.001
.000
.010
.009
I. and I- indicate continuous and impoundment irrigation
treatments, respectively. R and R indicate recommended
and excessive application rates, respectively,
** Application is with respect to carbaryl.
192
-------
400i
300
X DAY OF APPLICATION
•fr I DAY AFTER APPLICATION
O 2 DAYS AFTER APPLICATION
A 4 DAYS AFTER APPLICATION
D 7 DAYS AFTER APPLICATION
'A
D
•••B
12 16
Min.
20
2'4
28
Figure 93. Carbaryl concentrations in the flood water just
before and at a series of times following a simu-
lated rainfall of 2.5 cm/hour.
193
-------
carbaryl in the plots but was about a 2% contaminant of the commercial material.
1-Naphthol was rapidly dissipated in the paddy water and probably would not
extend the residual life of carbaryl under flooded conditions even if meta-
bolically produced.
Modes of Dissipation—
Volatilization—No measurable vapor flux was found for carbaryl or 1-
naphthol from distilled water at 27°C and air flow rate of eight ml/min. This
indicates that little would be lost by volatilization in the field.
Photodecomposition—This mechanism may account for some degradation of
carbaryl exposed to direct sunlight on the leaf canopy, but cannot account for
the dissipation from the plot water due to the protection of the rice canopy,
and the diffraction of the incident radiation by the collodial material in the
plot water.
Adsorption—As demonstrated for the other chemicals, the Kj for carbaryl
and 1-naphthol increased sharply at sediment loads less than 10 g/liter (Fig-
ure 94), which proves rather conclusively that the observed increase is not
dependent upon the properties of the adsorbate molecule but is a function of
some physical property assoicated with the sediment. Carbaryl and 1-naphthol
were adsorbed tightly at even the lowest sediment load with only 85 and 73%
in solution, respectively. This is similar to the tenacity demonstrated for
DCA, which may suggest a chemical type adsorptive mechanism.
Three hundred ml distilled water was added to eight, 100-g samples of
Beaumont clay soil previously spiked with 1 g sugar (Figure 95). Four of the
flasks containing the soil samples were capped with a cotton plug and auto-
claved for 30 minutes. All flasks were fortified with 100 ug carbaryl 48 hours
later. Carbaryl was injected into the autoclaved sample flasks with a syringe
to prevent contamination. Following a 96 hour incubation period, the soil and
water samples were separated by filtration and analyzed separately for earbarul
(Table 49). It should be noted that no attempt was made in this experiment, to
separate carbaryl and 1-naphthol from the respective soil and water samples
extracted. More than twice as much carbaryl was recovered in the H20 from the
sterilized samples. This was possibly induced by the sterilization since the
treatment dispersed the soil. The condition was noted throughout the 96 hour
incubation. Most of the water in the non-sterilized samples was decanted
prior to filtration, whereas all of the water in the sterilized samples had
been filtered. The net results were enhanced conditions for soil adsorption
in the sterilized samples, which suggests that the reduced conditions may have
retarded biological dissipation. Ordinary laboratory light of between 10 and
15 microeinsteins had no discernible affect on the amounts of carbaryl re-
covered in the experiment.
No carbaryl was detected in the soils sampled in the plots at either the
2.5 to 5.0 cm or 17.5 to 20.0 cm depths following its application in 1973, in-
dicating it had not moved to these zones in the soil profiles.
Biological degradation—Several flasks containing Beaumont clay soil were
placed under reduced conditions by flooding and were allowed to equilibrate 10
days prior to the 100 ug spike of carbaryl and 1-naphthol. This was followed
194
-------
150-
125
•O
•— 100
"c
'o
75
O
Q. 50
O
CO
25
\
O Carbaryl
• l-Naphthol
•
O
2.5 5.0 7.5
Sediment Load (g/l)
10.0
Figure 94. Adsorption coefficients of carbaryl and 1-naphthol
at varying sediment loads.
195
-------
100
s
I
u
•g
'o
In
&
• Carbaryl
O l-Naphthol
80
60
o
20
"b-
80 100 120
Redox Potential UMV)
140
Figure 95. Percent recoveries of carbaryl and 1-naphthol
from flooded Beaumont clay soil samples, and
corresponding redox potentials.
196
-------
TABLE 49. EFFECT OF STERILIZATION ON CARBARYL RECOVERED
FROM A BEAUMONT CLAY SOIL AND FLOOD WATER
Carbaryl Recovered
Treatment* Soil Water
Sterilized
Dark
Sterilized
Light
Not Sterilized
Dark
Not Sterilized
50.5
57.7
22.7
13.5
21.5
20.0
44.3
49.0
Light
* Two of the sterilized and two non-sterilized samples
were wrapped in tin-foil and placed in the dark for
the 96 hour incubation period.
by an additional 12 day equilibration period and subsequent extraction of the
contents of the flasks. Redox potentials were measured in the soil and flood
water just prior to extraction. The amounts of 1-naphthol recovered ranged
between 24 and 32% (Figure 95). Carbaryl recovered was higher and ranged
between 61 and 98%. The 98% recovered indicates that no degradation of carbaryl
occurred over the 12 day period at a redox value of +90 mv. The corresponding
soil redox potentials ranged between -475 and -490 mv, indicative of very re-
duced conditions. Thus, it appears that the redox potentials of the water may
be more of a governing factor in the dissipation of carbaryl than that of soil.
1-Naphthol dissipation did not appear to be hindered by the reduced conditions
attained Very low redox potentials could possibly retard the dissipation of
carbaryl, but it is doubtful that the potentials were sufficiently low under
the field conditions to retard degradation. The author submits that the high
rainfall incidence and, low substrate levels available in the plot water late
in the season would favor more oxidized conditions.
a fr» the foliage into the plots by the rain .here it
was dissipated in a relatively short period of time without the subsequent
-
c
than 5 0 g/liwr. The actual sediment load of the plot water was
in
197
-------
of the pesticide determines the optimum amount adsorbed. Even if substantial
conversion of carbaryl to 1-naphthol had occurred, it probably would not be
reflected in the irrigation return flow from a Beaumont clay soil due to the
adsorptive mechanism. The dissipation rate of 1-naphthol measured in the
laboratory in flooded soil samples was greater than that of carbaryl, further
suggesting that 1-naphthol would have little effect on the residual life of
carbaryl under normal rice culture.
PESTICLDES IN CANAL WATER
The canal water collected each time pesticide samples were collected from
the flood water was screened for the pesticides used in this study to determine
background levels. Samples were collected from the feeder canal adjacent to
the experimental plots in 1973. However, the main irrigation canal was sampled
in 1974 and 1975. The concentrations following the applications of the pesti-
cides are given in Tables 50, 51, and 52. Values in 1973 are biased by the
drifts in application due to the close proximity of the feeder canal. Con-
versely, no appreciable background levels were found in 1974 and 1975, indica-
ting that the materials which may have inadvertently reached the canal water
applied further upstream were not contaminating the water supply used for the
experiment.
TABLE 50. BACKGROUND LEVELS OF PESTICIDES IN CANAL H^O USED
TO FLOOD EXPERIMENTAL PLOTS IN 1973
Hours Following Application
Ug/liter
Pesticide
Propanil
DCA
TCAB
Molinate
Carbofuran
3-keto
3-hydroxy
Carbaryl
1-Naphthol
0
6.4
ND
ND
0.6
5.5
ND
ND
78.2
8.4
96
ND
ND
ND
Trace
1.4
ND
ND
11.0
9.3
192
-
-
-
ND
0.8
ND
ND
Trace
Trace
384
-
_
-
ND
1.3
ND
ND
ND
ND
768
-
—
-
ND
0.9
ND
ND
-
198
-------
TABLE 51. BACKGROUND LEVELS OF PESTICIDES IN CANAL H 0 USED
TO FLOOD EXPERIMENTAL PLOTS IN 1974 2
Hours Following Application
Pesticide
Propanil
DCA
TCAB
Molinate
Carbofuran
3-keto
3-hydroxy
Carbaryl
1-Naphthol
0
4.4
ND
ND
ND
ND
ND
ND
0.4
ND
96
-
-
-
ND
ND
ND
ND
ND
ND
yg/liter
192
—
-
-
ND
2.6
ND
ND
ND
ND
384
_
_
_
ND
14.5
1.2
ND
-
-
768
_
-
—
ND
ND
ND
ND
-
-
TABLE 52.
BACKGROUND
TO FLOOD
LEVELS OF PESTICIDES
EXPERIMENTAL PLOTS IN
IN CANAL H?0
1975
USED
Hours Following Application
Pesticide
Propanil
DCA
TCAB
Molinate
Carbofuran
3-keto
3-hydroKy
Carbaryl
1-Naphthol
0
11.
ND
ND
ND
ND
ND
ND
96
6
-
-
ND
0,8
ND
ND
Trace ND
ND ND
yg/liter
192
-
-
-
ND
ND
ND
ND
ND
ND
384
-
-
-
ND
Trace
ND
ND
ND
ND
768
-
-
-
ND
ND
ND
ND
-
—
199
-------
TOXICITY OF PESTICIDES TO FISH
General
The toxicity of many pesticides to fish is well known and well documented.
Some of the available data is summarized in Tables 53 to 56. This data, which
has been taken on treated or clarified tap water, may not be transferable to
rice paddy water which often containes particulate matter, microflora, nu-
trients, and salts. Few studies have been conducted, however, which evaluate
the toxicity of pesticides in irrigation return flow from rice paddies.
In 24 hour and 96 hour acute toxicity tests on three species of fish
(Mosquitofish, Channel catfish, and Bluegills), Carter and Graves (1973) found
carbofuran four, five and 73 times as toxic as carbaryl. They reported 50%
tolerance limits (TLSO's) ranging from 0,08 ppm to 2,03 ppm for carbofuran,
and TL50's from 1.4 to 11.5 ppm for carbaryl. The FMC Corporation (undated)
reported 96 hour 50% lethal concentrations (LCSO's) for carbofuran to Bluegill
(.24 ppm), Channel catfish (.21 ppm) and Rainbow trout (.28 ppm).
Young fish have been reported to be dramatically more susceptible to
carbaryl than are their elder counterparts. In two 96 hour tests on carbaryl's
toxicity to Mosquitofish, 0.5 g (Carter and Graves, 1973), and 65 g (Chaiyara
et al., 1975) the LCSO's were found to be 1.4 ppm and 31.8 ppm, respectively.
Macek and McAllister (1970) conducted tests on the relative .susceptibility
of 12 fish species to nine insecticides. They found channel catfish among
the least susceptible and carbaryl to be less toxic than the organochlorine or
organophosphorus insecticides tested.
The effects of long-term exposure to fathead minnows in carbaryl were
considered in tests run by Carlson (1972). He introduced the fish when they
were one to five days old and held them at constant concentrations for nine
months. His study showed the no-effect level of carbaryl to be .21 ppm while
reproduction was disrupted at .68 ppm.
Korn (1973) studied the uptake and persistence of carbaryl in Channel cat-
fish. Results indicated food-dosed fish eliminated residues rapidly, while
the water-dosed fish had not eliminated residues by the end of the 28 day test.
The water exposure levels were .25 ppm and 0.05 ppm. These levels produced
residues in the fish of 0.011 ppm and 0.002 ppm, respectively. Statham (1975)
studied biliary excretion products of carbaryl. He exposed rainbow trout to
.25 ppm carbaryl and found that in 24 hours the concentration of carbaryl in
the bile was 1000 times that in the water. Statham and Lech (1975) noted an
increase in the acute toxicity of several pesticides and herbicides to rainbow
trout by the addition of a sub-lethal concentration of carbaryl.
Chaiyara et al. (1975) determined the 96 hour LC50 for mosquitofish in the
herbicides propanil (9.46 ppm) and molinate (16.4 ppm).
Fabacher and Chambers (1974) determined percent mortality of insecticide-
susceptible mosquitofish when exposed for 24 hours to 10 ppm of various herbi-
cides. They found 50 to 100% mortality in the fish exposed to 10 ppm propanil
200
-------
TABLE 53. TOXICITY OF PROPANIL TO FISH REPORTED IN THE LITERATURE
n . Exposure
Organism Time
Mosquitofish pub
Lake emerald shiners
Mosquitofish
Hours
24
48
96
4
24
48
96
24
Exposure
TIP6
S
S
S
S
S
S
S
S
Concen-
trat ion
PPtn
11.3
11.0
9.46
13.5
7.5
7.5
7.5
10.0
End f
Point
LC50
LC50
LC50
TLM
TLM
TLM
TLM
50-100%
Death
Temp-
erature
-
-
-
70°F
70°F
70°F
70°F
21°C
Weight
15cm
65g
59mro
59mm
59mm
59mm
Source
Chaiyara (75)
Chaiyara (75)
Chaiyaia (75)
Swabey(1965)
Swabey(1965)
Swabey(1965)
Swabey(1965)
Fabacher(75)
"1" (LC50) Lethal Concentration to 50%
(TLM) Median Tolerance Limitation
-------
TABLE 54. TOXICITY OF MOLINATE TO FISH REPORTED IN THE LITERATURE
ho
O
1-0
Organism
Mosquitof ish pub
Catfish
Bluegill
Rainbow trout
Flathead minnow
Bluegill
Rainbow trout
Flathead minnow
Mosquitof ish
Rainbow trout
Bluegill
Exposure
Time
Hours
24
48
96
96
24
24
24
96
96
96
24
48
48
Exposure
Type
S
S
S
S
S
S
S
S
S
S
S
S
S
Concen-
tration
ppm
30.7
21.4
16.4
13.0
>37.0
>28.0
>42.0
18.8
6.97
26.0
10.0
.29
.48
End f
Point
LC50
LC50
LC50
LC50
TL50
TL50
TL50
TL50
TL50
TL50
0-10%
Death
LC50
LC50
Temp-
erature
-
-
-
60-62°F
18°C
13°C
18°C
18°C
13°C
18°C
21°C
12.8°C
23.9°C
Weight Source
3-4cm Chaiyara (75)
3-4cm Chaiyara (75)
3-4cm Chaiyara (75)
2g McGowan(1972)
1.5g Sleight(1972)
1.5g Sleight(1972)
.8g Sleight(1972)
1.5g Sleight0972)
1.5g Sleight(1972)
.8g Sleight (1972)
Fabacher(74)
Crosby (1966)
Crosby(1966)
t(TL50) Tolerance Limitation to 50%
(LC50) Lethal Concentration to 50%
-------
TABLE 55. TOXICITY OF CARBOFURAN TO FISH REPORTED IN THE LITERATURE
O
U)
Organism
Bluegill
Mosquitof ish
Channel catfish
Bluegill
Channel catfish
Rainbow trout
Exposure
Time
Hours
96
96
24
96
96
96
Exposure
Type
S
S
S
S
S
S
Concen-
tration
ppm
.08
.30
2.03
.24
.21
.28
Endf Temp-
Point erature
°C
TL50 23
TL50 24
TL50 26
LC50
LC50
LC50
Weight Source
.5 g Carter (1973)
.5 g Carter (1973)
10 g Carter (1973)
FMC Corp.
FMC Corp.
FMC Corp.
t(TL50) Tolerance Limitation to 50%
(LC50) Lethal Concentration to 50%
-------
TABLE 56. TOXICITY OF CARBARYL TO FISH REPORTED IN THE
LITERATURE
Organism E
Gambusia affinis
(Mosquitof ish)
Cy p r i n u s carp j o
("CaTpT ~~
Bluegill
Hosqui t of ish
Channel catfish
Channel catfisli
Bullhead
Goldfish
Flathe.ad minnow
(arp
Sun fish
Blucgill
Ba^s
Rainbow
Erovn
Perch
Channel catfish
Bluegill
Rainbow
Bluegill
Longnosc Killfish
Shiner perch
Kn^lish sole
Wliite mullet
3-spine stickleback
Flathead minnow
Harlequin fish
Lonynose killfi.sh
Goldfish
Tlathead minnows
3-spine stickleback
Exposure
Time
Hours
24
48
96
24
48
72
96
96
24
96
96
96
96
96
96
96
96
96
96
96
48
48
48
24
24
24
24
24
24
96
24
48
48
96
96
Exposur
Type
S
S
S
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
e Concen-
tration
ppn
60.0
35.0
31.8
13.51
11.74
10.36
5.9
1.4
11 .5
15.8
20.0
13.2
14.6
5.3
11.2
6.8
6.4
4.3
1.9
.74
19.0
2.5
2.0
3.4
1.75
3.9
4.1
4.25
6.7
13.0
6.8
1.75
15.0
9.0
3.99
End t
Point
LC50
I.C50
LC50
LC50
LC50
LC50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
TL50
EC50
F.C50
EC50
EC50
TLM
TLM
TLM
TLM
TLM
TLM
LC50
TLM
LC50
TL50
TLM
Temp-
erature
°C
-
-
-
28-32
28-32
28-32
23
24
26
18
18
18
18
18
18
18
18
18
18
18
24
24
13
24
-
-
-
-
20
_
-
_
-
-
20+. 5"
Weight Source
65 E Chaiyara ('75)
. 65 g Chaiyara ('75)
65 e Chaiyara ('75)
7-9c.ni Toor (1974)
7-9cm Toor (1974)
7-9cm Toor (1974)
.5 g Carter (1973)
.5 g Carter (1973)
10 j; Carter (1973)
.6-1. 7g Macek (1970)
.6-1. 7g Macck (1970)
.6-1. 7g Macek (1970)
.6-1.7g Macek (1970)
-6-1.7g Macck (1970)
. 6-1.7g Macck (1970)
.6-1. 7g Macek (1970)
.6-1. 7g Macck (1970)
.6-1.7g Macck (1970)
,6-1.7g Macek (1970)
.6-1.7r; Macek (1970)
Cope (1964)
Cope (1964)
Cope (1964)
Cope (1964)
Stewart(1967)
Stewart (1967)
Stewart(1967)
Stewart (1967)
Stewart (1967)
Stewart(19t 7^
Alabaster ('•;•"' l
Butler (1Q631
Havne (195S'1
Carlson(1973)
22-44mm Katz (19i.il)
f (TLM) Median Tolerance Limitation
(11.50) Tolerance Limitation to 50%
ILC5G) Lethal Concentration 10 50?;
(!"C50) Effective Concentration to 50%
(LD50) Lethal Dose to 5?
204
-------
and 0 to 10% mortality with the fish in 10 ppm molinate. In the same report,
LC50 s were found on mosquitofish from pesticide-contaminated drainage canals
adjacent to cotton, soybean, and rice fields. Their study indicated that
through selective mortality from insecticide contamination of the environment,
the toxic response of fish to other pollutants (such as herbicides) can change.
More work is needed to develop an understanding of the possible effects of
multibiocide interactions and their alteration of toxic responses in exposed
fish species.
Fish may be indirectly affected by any upset in the aquatic ecosystem.
Herbicides were viewed as a danger to fish by Holden (1972) since they destroy
the vegetation which is an important food. Holden also pointed out that the
zooplankton and insect larvae which are important food sources for fish are
often particularly susceptible to insecticides. Short duration exposure of
fish to potentially lethal concentrations of a pesticide may have "delayed
lethal effects." Alabaster (1969) exposed fish for 30 minutes to an herbicide
concentration lethal in eight hours, and the fish died a week later.
This study was undertaken to evaluate the toxicity of the four pesticides
used in the field and to fish in both filtered tap water and irrigation return
flow water.
Bioassay Data
Three sources of water were used in the bioassays. Tap water was used
in all tests, and water collected from two different paddys on different dates
were also used. As will be discussed later, the presence of-an unknown toxicant
was suspected in paddy water I, while no such contaminate was suspected in the
second collection of paddy water.
The 24, 48, and 96 hour TLM concentrations and the 95% confidence inter-
vals for each pesticide in each water are given in Tables 57 to 59 and Figures
96 to 99.
The TLM concentrations for propanil were greater in the filtered tap water
than in either of the paddy waters.
The TLM values for molinate at 24 hours did not differ between waters.
After 96 hours of exposure, the values in the filtered tap water and the paddy
water II were similar but had decreased substantially in paddy water I.
Molinate was the least toxic of the pesticides tested as reflected by the TLM96
values.
In all waters, carbofuran was the most toxic of the pesticides tested.
The TLM concentrations for carbofuran were determined in both the static and
intermittent flow systems. For the static tests with tap water, the TLMg6
values were greater than for the intermittent tests. No differences between
static and intermittent test results were evident in the paddy water II.
The increased toxicity in the intermittent flow tests with carbofuran
in filtered tap water may be attributed to the difference between constant
toxicant concentration in the intermittent test as compared to the single dose
205
-------
15
10
5
f\
O
o
o
o
o
o
o
o
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o
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o
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j •
3 '
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(j)
0
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o
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o
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o
A Control Water
B Paddy Water H
C Paddy Water I
B
48
il
f ~\
o
o
o
0
o
0
Set
3M,
96
TIME (hours)
Figure 96. Median tolerance limitation for propanil in the
three waters.
206
-------
40-
35-
30
-. 25
o.
^ 20-
1-
15
10-
5-
Q)
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0
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o
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o
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~^r
4
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t
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£
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B Paddy Water H
C Paddy Water I
H
II
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it A
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M
it
96
TIME (hours)
Figure 97. Median tolerance limitation for molinate in the
three water.
207
-------
o
00
I.J
1.0
i
Q.
r-
0.5
V
O
O
O
O
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o
o
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Q
TT JL
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6
o
o
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o
o
o
o
o
0
o
n
A Control Water
B Paddy Water E
C Paddy Water I
IIP
•
•H
* *
96
TIME (hours)
Figure 98. Median tolerance limitation for carbofuran in the three waters,
-------
MJi
6.0
5.0-
4.0-
3.0-
2.0-
i.o-
IV
•
O
o
o
o
o
o
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-*r
B
•
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s #
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£ #
* 4fc
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* *
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n J&
* *
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* £
TV 4fc
* *
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A Control W
B Paddy Wa
C Paddy Wat
rwi
B
__ A *«* ^
7^ ^ i^** "^^ °
£• 1 <5»
| £ A
24
48
TIME (hours)
96
Figure 99. Median tolerance limitation for carbaryl in the
three waters.
209
-------
TABLE 57. THE 24, 48, 72, AND 96 HOUR TLM CONCENTRATION AND THEIR 95%
CONFIDENCE INTERVALS IN PADDY WATER I IN STATIC TESTS GIVEN IN PPM
Pesticide
Propanil
Molinate
Carbofuran
Carbaryl
24-Hour
>5.00
34.01
(28.38-45.53)
.25
(.16-. 33)
6.02
(5.20-6.71)
48-Hour
1.34
(1.01-1.99)
15.67
(13.28-18.13)
.17
(.07-. 29)
1.53
(1.27-1.94)
72-Hour
0.82
(.66-1.18)
7.21
(5.50-8.63)
.16
(.14-. 17)
0.67
(.55-. 83)
96-Hour
0.43
(0-.59)
>5.00
.13
(.11-. 15)
.14
(.08-. 19)
TABLE 58. THE 24, 48 AND 96 HOUR TLM CONCENTRATIONS AND THEIR 95%
CONFIDENCE INTERVALS IN FILTERED TAP WATER IN PPM
Pesticide
Propanil
Molinate
Carbofuran
Carbofuran
Carbaryl
Flow
Static
Static
Static
Intermittent
Static
24-Hour
20.81
(19.68-22.44)
33.25
(31.82-34.96)
1.5
>.56
(.50-. 62)
6.71
(5.89-7.78)
48-Hour
14.51
(13.33-15.65)
33.24
(31.82-34.96)
1.42
(1.33-1.80)
.52
(.47-. 58)
1.30
(1.24-1.40)
9 6 -Hour
7,94
(6.99-8.85)
33.24
(31.82-34.96)
1.42
(1.29-1.70)
.51
(.46-. 56)
1.30
(1.24-1.70)
210
-------
TABLE 59. THE 24, 48 AND 96 HOUR TLM CONCENTRATIONS AND THEIR 95%
Pesticide
Propanil
Molinate
Carbofuran
Carbofuran
Carbaryl
Flow
Static
Static
Static
Intermittent
Static
24-Hour
16 ppm
—
41 ppm
-
.45
(.29-. 62)
1.60
(.67-1.99)
2.27
(1.60-3.54
48-Hour
4.03
(2.39-12.36)
35.47
(24.35-59.19)
.45
(.29-. 62)
1.60
(.67-1.99)
2.00
(1.34-3.16)
96-Hour
1.90
(1.63-3.24)
29.41
(19.73-46.41)
.37
(.25-. 51)
.48
(.32-1.27)
1.56
(0.76-2.13)
of concentrated toxicant in the static test. However, the results in paddy
water do not lend themselves to this explanation. Apparently the other factors
in the paddy water are more influential on the 96 hour TLM than the decrease
in toxicant concentrations in static systems.
The TLM's of carbaryl were nearly the same for the filtered tap water and
for paddy water II. Much lower concentrations, however, were toxic to the
fish in paddy water I.
In all cases, the TLM_, values in paddy water I were less than those
found in either the filtered tap water or paddy water II. In addition, an
average of only 75% of the fish in the paddy water I controls survived for 96
hours. The reasons for the greater toxicity of the pesticides in this water
and the loss of 25% of the fish in the controls was sought.
The presence of an unknown toxicant in paddy water I was suspected. An
organic chloride pesticide scan (Environmental Protection Agency, 1971) showed
no trace in paddy water I. The data presented elsewhere in this report suggest
that the propanil and molinate applied early in the season (Appendix A, Table
A3) would no longer be present in detectable amounts. Since benomyl had been
applied most recently, it was suspected as the cause of the greater toxicity
in paddy water I. Boiling paddy water I did not reduce the toxicity, thus, the
toxicant was temperature stable and did not vaporize readily. Analysis of
paddy water I for benomyl using a method capable of detecting levels of 0.5
ppm were negative. Since this is above the toxicity for rainbow trout re-
ported by E. I. duPont de Nemours and Company, Inc. (1974), it is possible
that the benomyl caused the loss of fish at 96 hours and the increasedtoxicity
of the other pesticides in the water. More study is needed on the interactive
211
-------
influences of pesticides and other chemical constituents of water on toxicity,
especially since overlapping and often simultaneous applications are often
made.
All fish survived 96 hours exposure to untreated paddy water II. Propanil
and carbofuran pesticides had lower TLM's in this water, while carbaryl and
molinate were not different from the filtered tap water. When both paddy
waters are considered, it is evident that for static situations the TLM's are,
on the average, lower than those in filtered tap water.
In the tap water, most of the mortality observed in tests with molinate
and carbofuran occurred within 24 hours after exposure. The toxic effects
continued to result in loss of fish through the 96 hour test for propanil and
carbaryl. In paddy water I, the loss of fish in molinate treatments continued
to increase with time of exposure. The mortality increases with time in paddy
water I and II were greater for those treatments where they were observed than
were found in the filtered tap water.
The coefficients of variability were generally greater in the paddy waters
than in the filtered tap water. This may result from variability in suspended
colloids.
The TLM values for molinate and propanil in the filtered water determined
in this study are consistent with those reported in other publications (Tables
53 and 54). However, the bioassays of carbaryl in this study show it to be
10 times more toxic to catfish, and carbofuran to be five times less toxic
than is reported in the literature (Tables 55 and 56). These differences may
be a result of the different ages of the fish used in the tests reported in
the literature.
ORGANIC LOAD
The values of TOC, COD, and BOD measured in the water at the end of each
season are given in Tables 60, 61 and 62. During 1975 the intermittently
irrigated plots were drained early to allow a study of the influence of water
practices on the yield. As a result, there were no results on half of the
plots. In lieu of this, the data from the border plots were used. For each
parameter, no statistically significant figures were found between the re-
plicated plots, and there is no indication that the volume in the release
water differed from the canal water sample. The values of each parameter for
both the plots and the canal water were nearly the same in 1973 and 1974, but
the TOC and COD were only half as large during 1975, while the BOD averaged
twice as much in 1975 as it did in 1973 and 1974. The difference from one
year to the next appears to be reflected to the canal water. This may in-
dicate that either the canal water is the source of the season-to-season
change, or that the canals are in the same environment as the paddies and
undergo the same microflora fluctuations as that when vegetation is blown
down or the water level is raised due to rain. The influence of those factors
on the average demand of the canals may be similar to those of the water in
the paddies.
212
-------
TABLE 60. AVERAGE TOG, COD AND BOD OF FLOOD WATER AND
CANAL WATER AT THE TIME OF FINAL DRAINAGE IN 1973*
TOG COD BOD
Treatment mg/1 mg/l mg/1
Impounded irrigation recommended
rates of pesticides and nutrients 28 61 2.2
Impounded irrigation recommended rates
of pesticides and fertilizers 25.3 57 1.6
Continuous flow irrigation
excessive rates of fertilizer and
pesticides 29 45.7 2.2
Continuous flow irrigation
excessive rates of fertilizer and
pesticides 26.7 45 1.6
Canal water 28 55 1.0
* No significant differences between results were found in any year,
TABLE 61. AVERAGE TOG, COD AND BOD OF FLOOD WATER AND
CANAL WATER AT THE TIME OF FINAL DRAINAGE IN 1974*
TOG COD BOD
Treatment mg/1 mg/1 mg/1
Impounded irrigation recommended
rates of pesticides and nutrients 29 47 2.1
Impounded irrigation recommended
rates of pesticides and fertilizers 23 52 2.2
Continuous flow irrigation
excessive rates of fertilizer and
pesticides 27 57 1>7
Continuous flow irrigation
excessive rates of fertilizer and
pesticides 21 48 1'6
Canal water 21 47 2'3
*No significant differences between results were found in any year,
213
-------
TABLE 62. AVERAGE TOC, COD AND BOD OF FLOOD WATER AND
CANAL WATER AT THE TIME OF FINAL DRAINAGE IN 1975*
TOC COD BOD
Treatment mg/1 mg/1 mg/1
Impounded irrigation recommended
rates of pesticides and fertilizers
Continuous flow irrigation
excessive rates of fertilizer and
pesticides
Border plots intermittent flow
irrigation recommended rates of
fertilizer and pesticides
Canal water
11
28
5.3
9.3 25.4 2.0
13 29.5 6.4
17 36 3.4
*No significant differences between results were found in any year,
In any event, more of the values are increased in the rice field,probably
because of the large surface area to which the water is exposed. In addition,
neither the BOD nor the COD exceeded the 30 mg/1 level. During 1973 and 1974
the COD levels exceeded 30 mg/1, averaging 51. They did not exceed this level
during 1975.
RICE YIELDS DURING THE STUDY
Effect of Designed Treatment
Irrigation treatment did not have a significant effect on rice yields
during the three year evaluation, but the excessive rate of fertilizer and
pesticide application did adversely effect yield in 1974 and 1975 (Table 63).
Yields from the plots receiving recommended rates of fertilizer and pesti-
cides were on a par with the yield from adjacent plots in which optimum cul-
tural practices were employed (the adjacent plots yielded 5500, 4652, 5043 kg/
ha during 1973, 1974 and 1975, respectively). The lower rice yields incurred
in the excessive rate plots during 1974 and 1975 may have been induced by the
untimely application of an excessive rate of molinate. Flinchum et al. (1973)
reported that 10 kg molinate/ha applied in the floodwater within four days of
the panicle differentiation growth stage reduced yields by 1000 kg ha .
During 1974 and 1975 the excessive rate plots received 11.2 kg molinate ha
(plus an excessive rate of carbofuran) within three days of panicle differen-
tiation. Yields were not affected in 1973 when the molinate was applied 11
214
-------
TABLE 63. RICE YIELDS DURING THE STUDY-AVERAGE OF THREE REPLICATIONS
NJ
I-1
Cn
Treatment
Irrigation
Continuous
Continuous
Intermittent
Intermittent
Fertilizer and
Pesticide
Recommended
Excessive
Recommended
Excessive
1973
(Kg/Ha)
5658 a
5918 a
5685 a
5476 a
1974
(Kg/Ha)
3895 a
2561 b
4554 c
2631 b
1975
(Kg/Ha)
4745 a
3250 b
5084 a
3540 b
Average
5684
3410
4154
1 Ib/ac = 1.1208 Kg/Ha
Yields followed by the same letter are not significantly different than other
values in that column.
-------
days prior to panicle differentiation. The delay in molinate application
during 1974 and 1975 was a result of an effort to postpone the collection of
molinate water samples until after completion of the propanil analysis when
the gas chromatograph and extraction could be done without delay. The fer-
tility aspects of the field experiments were sacrificed in order to maintain
high quality analytical capabilities for the pesticides.
Effect of a Water Conservation and Pollution Prevention Technique
Releasing the floodwater from the rice field 10 days before crop maturity
is a common water management practice which serves to dry the soil and thus
facilitate harvesting. The desirable dry soil condition at harvest could be
obtained by sparingly metering the irrigation water so that all the floodwater
is evapotranspired at about 10 days prior to harvest. Since the evapotrans-
piration technique of obtaining a dry soil would conserve water and reduce
the possibility of surface water pollution from irrigation return flow, the
effect of this technique on rice yields was evaluated in 1975. Two of the
intermittent plots were irrigated as usual while the other four received no
further irrigation 16 days prior to the anticipated day that the floodwater is
normally released to allow the soil to dry. The 16 days cut-off time was
chosen assuming an evapotranspiration rate of 0.56 cm/day and 10 cm depth of
floodwater. Water added to the plots by rainfall, which amounted to about 13
cm during the 16 day period, was released from the plots soon after the rains.
The evapotranspiration technique of obtaining a dry soil at harvest did not
reduce yields and, thus, could be used to conserve water and reduce the pos-
sibility of water pollution from irrigation return flow.
Substantial rainfall would prevent the evapotranspiration technique of
obtaining a dry soil from working ideally, but the technique appears to be an
effective guideline for conserving water and reducing the possibility of water
pollution caused by irrigation return flow from rice fields.
MODEL
A Model of Irrigation Return Flow
The quality of irrigation return flow which is released from the paddy
after a period of flooding, or that which leaches from the field below the
root zone, is a result of water and salt balance. The water balance includes
the quantity and frequency of irrigation, precipitation, the water lost by
evaporation, transpiration, runoff losses, and the movement into or through
the soil profile. The salt balance must include consideration of the initial
salt concentrations in the soil profile, the distribution of root water and
salt uptake, and the reaction exchanges and subsequent equilibrium concentra-
tions in the soil solution and on the exchange sites. In addition, fertilizer
applications and timing will influence the concentration of certain ions.
The large number of factors involved makes it difficult to keep track of
the concentrations of ions in the system without the use of a computerized
model. Several researchers have developed models to track the movement of
ions in the soil system. The flooded rice paddy, however, presents a set of
216
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circumstances which cannot be adequately handled by the available models. In
addition, advances in formulation and solution techniques are available which
should allow more precise and universally applicable solutions to certain
parts of the system.
A model was developed which allows the consideration of all factors men-
tioned above. The water balance part of the model may be written as:
AH=I+P-T-E-K-L-
where AH = the change in depth of water in the paddy
I = irrigation
P = precipation
T = transpiration
E = evaporation
R = runoff
L = leaching
In the model, parameters on the right are entered as variables on a daily basis.
and the change in water depth is updated once a year. Flood water of the quality
and amount specified may be added on any day. If so desired, once the initial
flood is established, the program will automatically irrigate the paddy to a
level of 10 cm when the water level drops to a level of 4 cm. Precipitation
is assumed to be free of ions and to have a simple diluting effect on the ions
in the floodwater. Evaporation from the water surface is assumed to have the
reverse effect. The transpired water is assumed to be taken up by the roots
within the soil profile. The uptake is simulated to occur over a 14-hour
period, with the total daily uptake being divided into hourly values by assum-
ing a sinusoidal distribution of uptake over the period. This helps to realis-
tically simulate the possibility of diffusion of ions from the soil to the
floodwater during periods of low or zero transpiration. The water that moves
into the profile to supply the transpiring stream is assumed to carry along
with it into the first layer of soil ions at the concentration found in the
floodwater. These ions subsequently redistribute from one layer to the next
according to the flux of water and the calculated concentrations in solution.
Root distribution fractions may be updated periodically during a particular
run in order to simulate root growth.
Uptake of each ion by the roots is assumed to be represented by:
Q. = K. • T
xiz i z
where Q = the sink strength corresponding to ion i at depth z
iz
K. = a proportionality factor
217
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T = the sink strength for water uptake by the roots at depth z
The values of K. used in the program were selected to assume a charge balance
for the ions taien up and to insure that the ion uptake over the entire season
approximates the uptake rates reported in the literature for rice crops. The
data utilized are shown in Table 64. A sensitivity analysis indicated that
reasonable variations in the values of the K.'s do not significantly influence
the final concentrations in the irrigation return flow.
TABLE 64. CONCENTRATIONS OF IONS IN RICE FOLIAGE AND
GRAIN AND VALUES OF Ki USED TO CALCULATE
ION UPTAKE FROM THE SOIL*
Ion
Ca
Mg
Na
K
NH,
Cl
S°4
N03
HC03
Concentration
%
0.17
0.17
0.30
2.00**
1.21**
.40
.24
4.58
4.32
Ki
g cm
8.10 •
8.10 •
1.44 •
9.60 •
5.75 •
1.92 •
1.15 •
2.20 •
2.07 •
-3
-6
10 °
10-b
io"5
io-5
io"b
io"b
ID'5
i
-------
low solubility, the release may be spread over several days. Throughout the
calculations, It is assumed that mixing of the floodwater resulting from air
flow, thermal gradient, and thermal diffusion is sufficient to render concen-
tration gradients within the floodwater negligible.
Other parameters needed include the initial concentration of ions in the
soil profile, the bulk density of the soil, and the cation exchange capacity.
The program keeps account of the water depth and utilizes subprograms SOIL
and BQUIL to calculate the flux of ions into or out of the soil surface as
well as to calculate the distribution of ions with time in the profile. A
detailed discussion of the development of these submodels will be considered
next.
Development of the Program
Applications of the theory of simultaneous movement of water and solutes
through porous media are numerous and diverse. They range from laboratory
studies of chromatography to prediction of post-application redistribution of
chemicals in fields and aquifers. Theories applicable to chromatographic
column operations appeared more than 30 years ago (deVall, 1943), but only in
the last 20 years have extensions and modifications been made to include the
complex behavior associated with solute movement in soil. These extensions
have corresponded to a large influx of information from laboratory and field
studies that have isolated various phenomena operative in transport processes.
These studies have verified that convective transport is the dominant mechanism
of solute transfer, except in cases of near-zero flow velocities. Molecular
diffusion and hydrodynamic dispersion have been identified as important modi-
fers of the solute space-time distribution resulting from convective transport
alone (Biggar and Nielsen, 1967; Kirda et al., 1973; Sadler et al., 1965).
Moreover, researchers have shown that a number of other factors may influence
the rate and extent of solute movement depending on the medium and/or conditions
under which the experiments were conducted. Among these additional factors
are: cation exchange (Dutt and Tanji, 1962; Rible and Davis, 1955; Lai and
Jurinak, 1972), anion exclusion (Dyer, 1965; Thomas and Swoboda, 1970; Smith,
1972) , vertically nonuniform density and/or viscosity distributions (Biggar
and Nielsen, 1967; Krupp and Elrich, 1969; James and Rubin, 1972), transient
flow conditions (Bresler and Hanks, 1969; Kirda et al., 1973; Bresler, 1973),
and zones of solution that are stagnant or slow moving with respect to the
bulk solution (Coats and Smith, 1964; Skopp and Warrick, 1974).
In addition to laboratory and field experimentation, mathematical models
have been developed to include the effects of one or more of the above-men-
tioned phenomena. Although earlier models were based on chromatographic plate
concepts (Biggar et al., 1966), many of the more recent ones were based on
solutions of convection-diffusion type equations (hereafter referred to as CDT
equations) with associated boundary and initial conditions. With comparatively
few exceptions, these solutions were developed to describe the transport of a
single solute under steady-flow conditions. No thorough investigation has
been made to determine the feasibility of extending finite-difference methods
to the simultaneous solution of several CDT equations. The objectives of the
development were, therefore:
219
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1. To compare the performance of selected finite-difference schemes in
solving CDT equations for conditions of: one solute, one-dimensional
steady flow, without sources or sinks.
2. To develop a method for extending one of the selected schemes to
simultaneous solution of two or more CDT equations.
3. To develop a subroutine, based on such an extension, that will simu-
late the convective-dispersive transport of selected ions in a soil
system where local chemical equilibrium is assumed.
Solutions Available in the Literature
Analytical Solutions—
Analytical (exact) solutions of CDT equations are expressed in closed-
form, infinite-series, or integrals and yield values of the dependent variable
(concentration) directly, given values of the independent variables (distance
and time). Parlange and Starr (1971) have provided a discussion of such solu-
tions for the linear, one-dimensional CDT equation for a variety of boundary
conditions. Reiniger and Bolt (1972) reviewed analytical solutions of problems
involving absorption of two exchangeable cations. Shamir and Harleman (1967)
presented a solution for the one-ion problem for layered media. Coats and
Smith (1964) solved the one ion problem for a CDT equation which contained a
capacitance term to account for dead-end pore volume, Skopp and Warrick (1974)
treated a similar problem by ignoring longitudinal dispersion and including
diffusion into a stagnant phase. Warrick et al. (1971) applied an analytical
solution to an infiltration problem involving one solute. These solutions are
all restricted in application to situations which approximately conform to
certain boundary and initial conditions required for their derivation. In
spite of this restriction, they are valuable tools when applicable because
little computational effort is required for their evaluation. Moreover, they
serve as checks on the performance of numerical solutions.
Numerical Solutions—
Where boundary and initial conditions are too complex or other complicating
factors preclude an analytical approach, it is necessary to adopt a numerical
procedure. Such procedures rely on estimates of a change in the spatial con-
centration profile over a time period: tl_
-------
such an approximation is made at each point of a grid network that divides the
space for which a solution is desired into discrete intervals, or rectangles,
depending on the dimensionality of the transport. Thus, a system of algebraic
equations results, including one approximating equation and one unknown for
each interior grid point of the network. The knowns in these equations are
the values of the concentration at each of the grid points at ti and boundary
values of the concentration at tj_ and tl + At. The unknowns are values of the
concentration at each interior grid point at t. + At. If the resulting system
of approximating equations is such that each can be evaluated independently,
the procedure is termed "explicit". If simultaneous solution of all of the
equations is necessary, the procedure is an "implicit" term.
Finite-difference schemes are mutually distinguished on the basis of the
particular approximations employed either for the space or time derivatives.
For example, the explicit scheme (not to be confused with the more general use
of the term above) utilizes second-order, central-difference approximations for
the space derivatives and a first-order, forward difference approximation for
the time derivative (Shamir and Harleman, 1967; Fried and Combarnous, 1971).
Although some use has been made of this scheme for solute transport problems
in soils (Lai and Jurinak, 1972; Kirda et al., 1973), it has been criticized
due to an apparent need for unreasonably small time and space increments to
insure stability of the computational procedure (Shamir and Harleman, 1967;
Fried and Combarnous, 1971).
A second finite-difference approach that has been utilized for solving
CDT equations is the Crank-Nicolson scheme, which is of second-order accuracy
of approximation with respect to both space and time derivatives (Stone and
Brian, 1963; Fried and Combarnous, 1971). The higher-order accuracy with
respect to the time derivative is achieved by use of Crank-Nicolson (centered-
in-time) approximations for the space derivatives. Peaceman and Rachford (as
reported by Stone and Brian, 1963) were apparently the first to use this ap-
proach to solving CDT equations. They found for large values of the velocity
to dispersion coefficient ratio (V/D) that small grid spacings were required
to prevent oscillations from developing in the simulated concentration profile.
Stone and Brian (1963) derived a finite-difference scheme on the basis
of optimal propagation velocity and decay of harmonics present in a sharp
concentration front. In its final form, the scheme they demonstrated utilizes
Crank-Nicolson approximations for the space derivatives, andaweighted-average
(over three spatial grid points) approximation for the time derivative. Their
weighting factors are used in conjunction with cycling over successive time
steps. They demonstrated that a scheme employing three time steps per cycle,
with predetermined values of the weighting factor used in each time step,
greatly reduced oscillations incurred by use of the Crank-Nicolson scheme for
the case: D = 0. Shamir and Harleman (1967) later extended the Stone-Brian
scheme to a special problem of higher dimension.
Chaudhari (1971) derived a finite-difference approximation which is ap-
proximately second-order in time for high V/D. Realizing the tendency for
high order schemes to develop oscillations for high V/D and large grid spacinga
he derived the scheme so as to produce an explicit computational procedure and
include a "brute-force" mechanism to prevent oscillations.
221
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Bresler (1973) followed Chaudhari's example and derived an approximately
second-order accurate scheme for treatment of solute transport phenomena under
transient flow conditions. The computational procedure for his scheme is im-
plicit and can be shown to reduce to the Crank-Nicolson approach for saturated
steady-flow conditions in a homogeneous medium.
Other Numerical Methods—
Carder et al. (1964) pointed out the approximate hyperbolic nature of CDT
equations for high values of V/D. Accordingly, they developed an approach
based on characteristic curves of a convective-transport equation (i.e. an
equation obtained by setting D = 0 in a CDT equation). Smajstrla et al. (1974)
extended the use of this "method of characteristics" to unsaturated, tnransient-
flow problems. A discussion of the basic computational procedure can be found
in their paper or in the paper by Carder et al. (1964).
Price et al. (1968) applied techniques based on variational methods to
the single solute problems and showed that the resulting schemes were of high
order accuracy (>3) with respect to space derivatives.
Simultaneous Consideration of Several Solutes—
Comparitively few attempts have been made to describe the simultaneous
movement of several solutes. In such cases, interactions among the solutes
and between various solutes and the porous medium must be considered. Dutt
et al. (1972b) demonstrated the use of simultaneous solution of chemical
equilibrium equations in a program they developed for predicting gypsum and
leaching requirements for sodium-affected soils. They assumed convective
transport only but accounted for cation exchange, ion pairing, and solubility-
precipitation reactions. Dutt et al. (1972a) utilized the same basic equili-
brium scheme as part of a simulation model for prediction of moisture and
fertilizer redistribution in field situations. They utilized the concept of
"mixing cells" to simulate the effects of dispersion and diffusion. This con-
cept is based on the artificial smearing of concentration fronts that occur
when plates or segments of finite thickness are utilized in simulating con-
vective transport.
Frissel and Reiniger (1974) used a similar approach in their model of
simultaneous transport of Ca, Na, Mg, and K with provisions for cation exchange
(all cations) and fixation of K. They gave a more quantitative description of
the effect of plate thickness on the artificial mixing introduced. For their
computational procedure, they utilized a computer simulation package, CSMP,
which provides subroutines for numerical integration and solution of non-
linear algebraic equations.
Lai and Jurinak (1972) utilized the explicit finite difference scheme to
provide solutions of a CDT equation containing a generalized non-linear ex-
change isotherm. The resulting scheme is applicable for the displacement of
one cation by another under restricted boundary and initial conditions.
DeWit and van Keulen (1972) used CSMP to solve a system of DCT equations for
one anion and two exchangeable cations.
An alternative approach to a problem involving the simultaneous solution
of two or more CDT equations was taken by James and Rubin (1972). They used
222
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a Galerkin method to solve three equations which included cation exchange re-
lationships.
The Use of Finite-Difference Solutions to the One Dimensional Linear
Convection-Diffusion Equation
The Basic Equation and Boundary Conditions —
In order to provide a starting point for the development of a more gen-
eral ion-transport model, it is helpful to first consider finite-difference
approximations that have been developed to obtain solutions of the problem
characterized by the single linear equation:
|£ = „ A . v • |£ , (4,
dZ
3
and associated boundary conditions. In Equation 4, C(M/L ) is solute concen-
tration; t(T) is time; z(L) is distance; V(L/T) is mean pore velocity (i.e.
the solution flux density q(L/T) divided by the volumetric moisture content
9(L3/L3));and D(L2/T) is the apparent diffusion coefficient of the solute.
Although the physical meaning of Equation 4 has been discussed at length in
the literature, e.g. Fried and Combarnous (1971), a brief account of the de-
rivation will help motivate the ensuing discussion.
In a homogeneous, inert, saturated, porous medium, the solute flux, Jsz,
in the z direction is assumed to obey:
Js = -D • <£) - D • <) + q ' C. (5)
z m
°z
In Equation 5, D (L2/T) is the molecular diffusion coefficient of the solute
for the porous medium and Dh(L2/T) is the hydrodynamic dispersion coefficient.
The first and second terms on the R-H-S of Equation 5 represent the contri-
butions of molecular diffusion and hydrodynamic dispersion, respectively, to
the total flux. The term qC constitutes the solute flux due to convectiye
transport. The equation of continuity (mass-balance) for one-dimensional flow
can be written:
or
JLieci a rn) + D,> -Ir] - ^ <6)
, »,!). as opposed to the
balance approach taken here.
The boundary conditions most often associated with Equation 4 for a
223
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column or profile of finite depth, LC> are of the form:
C(z,0) = f (z), 0 £ z £ Lc
C(0,t) = g(t), t >. 0
or
_D . |£| + V • C(0,t) = V • Q(t), t > 0
82 z = 0
and !£| = 0, t >_ 0.
z = L
c
More specifically, the conditions:
C(z,0) = C±, 0 <_ z <_ LC (7a)
C(0,t) = CQ, t > 0 (7b)
or sr
-D • 7p| + V ' C(0,t) = V-C , t > 0 (7c)
z = 0
and |^| = 0, t > 0 (7d)
dz z = L
c
have been convenient for comparison of numerical results with analytical so-
lutions (Bresler, 1973; Shamir and Harleman, 1967; and Brenner, 1962). E-
quation (7a) represents an initially uniform distribution of the solute
throughout the porous medium, while condition (7b) represents a constant con-
centration (infinite source or sink) condition at z = 0, and condition (7c)
constitutes an alternative constant flux condition at z = 0. The zero-
gradient condition (7d) at z = L implies that flux across this boundary is
due to convective transport alone. The use of (7d) in preference to a con-
stant flux condition has been discussed by Brenner (1962) and Danckwerts
(1953).
Numerical Difficulties—
As was indicated earlier, attempts to obtain approximations to solutions
of CDT equations by numerical means have not always achieved satisfactory
results. The foremost difficulty manifested by finite-difference solutions
has been a failure to properly describe the spreading of sharp concentration
fronts as they progress in time and space. In the absence of diffusion and
dispersion (i.e. convective transport only), it is easy to show analytically
that such fronts progress without smearing or spreading. To show the same
thing with a finite-difference solution is more difficult. Stone and Brian
224
-------
(1963) present graphs illustrating the oscillatory behavior of certain finite-
difference solutions for the case, D=0. Although in most physically meaning-
ful problems D is never absolutely zero, it can be appreciated that severe
difficulties may be encountered when the ratio V/D is very large. These
authors showed that this oscillatory behavior is related to poor propagation
and decay rate of the harmonics present in the simulated concentration front.
Even if the solutions do not develop oscillations, they may be plagued
by an artificial smearing which results from a numerically induced dispersion
(Stone and Brian, 1963 and Carder et al., 1964). A classical example of
numerical dispersion can be illustrated by a finite-difference approximation
to the convective-transport equation:
£--'•£ <•>
The method of Courant, Isaccson and Reese (Stone and Brian, 1963) is based on
an approximation to equation (8) of the form:
d+1- d rf - d
-J4 - * = V • X-\ X (9)
At Az
where i and j are positive integers and d is the solute concentration having
space and time coordinates (iAz, jAt). To show that artificial dispersion
8C
is implicitly included in the approximation to -V-^- in equation (9) , a
3C
Taylor's approximation to - can be written:
1 2
3 C
Solving for (|^0 yields the first-order correct approximation:
d z .
1 j d - d
C, L izl
V8z . Az
and the second-order correct approximation:
^C J _ CJ " tf-l. + Az . (3V + 0(^2) . (10b)
3z Az 2 3z2
Substituting equations (lOa) and (lOb) into equation (8) the result is:
(lla)
CJ
3t
and
225
-------
CJ
= v . _
3t Az ^
From these last two. equations it can be seen that the use of equation
(10a) to approximate (|^) , as is the case in equation (9), has the effect of
^ P A
adding the numerical dispersion term Dn< — ^ where Dn = v~~2' The result is
that the right-hand side of equation (9) provides a second-order correct ap-
proximation to the expression:
D
but only a first-order correct approximation to the right-hand side of equa-
tion (8) . Stone and Brian (1963) demonstrated the artificial smearing that
results when equation (9) is used to approximate equation (8) .
Selected Finite-Difference Approximations —
In order to gain experience with the numerical difficulties reported in
the literature and to provide a basis for selection of a scheme to extend to
the several-solute, non-linear case, five difference equations were studied
and compared with respect to efficiency and accuracy. The schemes selected
for the study are (a) the explicit scheme, (b) Chaudhari's scheme, (c) Bresler's
scheme, (d) Stone and Brian's scheme, and (e) a second-order (in time) explicit
scheme that has not appeared in the literature.
To facilitate discussion and comparison of the various difference equa-
tions, the following notations are introduced:
Vci> -
CJ+1
The explicit scheme—The basic approximating equation for the explicit
scheme can be written:
226
-------
- V.6z(c). (15)
The scheme derives its name from the fact that the concentrations Cj+1 at
each grid point^z are defined explicitly in terms of the concentrations
Ci-1' Ci» and ci • Tne equation corresponding to each grid point can be
evaluated independently and therefore does not require the simultaneous solu-
tion of the equations corresponding to all grid points. Two of the other
schemes to be discussed are also "explicit" in this sense.
Kirda et al. (1973) used an approximation based on the explicit scheme
for simulation of solute movement in soils under infiltration conditions.
Their difference approximation reduces to the explicit scheme (15) under
saturated, steady-flow conditions. Lai and Jurinak (1972) used a modified
version of the explicit scheme to simulate the displacement of one cation
species by another from a soil column. Their approximation is equivalent to
the explicit scheme (15) when their separation factor, ab, is unity.
3.
The explicit scheme has been criticized by Shamir and Harleman (1967)
and Fried and Combarnous (1971) . These authors contend that small values of
the grid spacing:
42 < a ,
are necessary to insure stability of the numerical computations. The former
authors derived equation (13) from the criteria:
A z < -5
Azz -
and
^ < 1. (18)
Az
The inequality (17) must be satisfied to prevent instability (Rictmeyer, 1957)
and condition (18) provides an accuracy of the decay factor of order (At).
Fried and Combarnous (1971) showed that the off-diagonal elements of the co-
efficient matrix associated with the system of approximating equations (15)
are negative if condition (16) is violated. They concluded from this that
violation of condition (16) would cause the scheme to be unstable.
In spite of their criticism of the scheme none of these authors pre-
sented evidence which would support their claim. Of those who used the ex-
plicit scheme, Kirda et al. (1973)_acknowledged the use of (16), but Lai and
Jurinak (1972) made no mention of it.
227
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Chaudhari's Scheme—Chaudhari (1971) developed a finite-difference ap-
proximation for simulation of multi-dimensional solute transport. The one-
dimensional version of his approximating equation can be written:
.Az.(CJ+1 - CJ.) = { (8-D - D*).,^1"1 *) + q._V(
At,
V. At
Az ,., i
Where D* = q. j •—r- (1— ). Chaudhari called the number D* a numerical
dispersion coefficient. This coefficient results from the use of a second-
order correct approximation to the derivative • •)•• ^ and an approximately
second-order correct approximation to —-—. Upon rearrangement Chaudhari's
equation can be represented for saturated, steady-flow conditions as:
A (A - (D + D**) • 62(C^) - V-6 -(C1!), (19)
t i z i z i
where
Although Chaudhari did not indicate that his scheme manifested any par-
ticular relationship to the explicit scheme, the only difference between the
explicit scheme (15) and Chaudhari scheme (19) is the coefficient of 62(CJ).
The number D** in the explicit scheme (19) can be derived in a straight- *
forward manner as follows.
Substituting equations (13) and (14) into equation (15) we have:
0(Az2). (20)
9r i
An alternative expression for (-vp-) . can be obtained by a second-order correct
Taylor's approximation: 1
228
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Substituting equation (21) into equation (20) and rearranging yields:
2
At ' 'zi - V-«B<^ - - + °^2> + O^2) . (22)
In order to estimate the value of )j, Chaudhari suggested using the fol-
St 1
lowing approximation, valid for V»D:
Differentiating both sides of equation (23) with respect to t and interchang-
ing the order of differentiation on the RHS yields:
and again making use of equation (23), we obtain the desired approximation:
(9_£) a V2(^|) = V2-52(c|) + 0(Az2). (24)
8t2 i 3zz i
Substituting equation (24) into equation (22) and combining terms yields:
= (D + I_|£).fi2(CJ) _ V6z(c|) + 0(Az2) + 0(At2) ,
which is equivalent to Chaudhari's solution (19) when terms of order greater
than two are ignored. Note that elimination of all terms of order 0(At) or
higher, in equation (21) would result in equation (15), i.e. the approximating
equation for the explicit scheme. The conclusion that may be drawn is that
any improvement manifested by use of Chaudhari's scheme equation (19) over
the explicit scheme equation (15) to approximate the CDT equation (4) is due
solely to the accuracy of approximation of 8C .
3t
229
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Bresler's scheme—Bresler (1973) proposed the use of the following
finite-difference approximation for simulation of solute transport under
transient flow conditions:
i i
,. 2 1-1
2Az
J+l
± ± C±+1
2Az
J4^ , j+1 j
y- (C± + C± -
1 Tr,^ . cr3+1 + r-h nJ
- 2Al [qi-H5 (Ci + Ci} ' qi
Where D' may be identified with 9 • D in previous discussion and:
• _u • • . . .1 • At • (6^+1 -0 ;))
jjj.-a = Az ..j-Hs i i-Hs i i'
9 M-U' O
^ _L^^2 O
The quantity N._j2 is a numerical dispersion coefficient derived in a manner
similar to that ilsed by Chaudhari (1971) to derive D*. Without the numerical
dispersion coefficient, the approximation is only first-order correct for
both the time and space derivatives. For saturated steady-flow conditions,
Bresler's difference equation reduces to:
At(Ci} =
CJ
rp, 4. •,.• x2/i i\ j r / i i\ are Crank-Nicolson, or cen-
The quantities 6^( r ) and 6 ( )
z z z Z
o C ^ SC "^
tered-in-time approximation to the space derivatives (——) and (r—) , res-
*\ ^ » o Z* ,
3z i i
pectively. Although Bresler's scheme (25) is second-order correct both in
230
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time and space, its use has been criticized due to oscillations which develop
in simulated concentration profiles near sharp concentration fronts for large
V/D (Stone and Brian, 1963). It is interesting to note also that Chaudhari
(1971) chose an explicit procedure in order to prevent oscillation by a
brute force mechanism, whereby he transferred overshoot occurring in regions
of oscillation into regions where the concentration varies within acceptable
limits. Although Bresler followed Chaudhari's example in the derivation of
his numerical dispersion coefficient, he did not mention the possibility of
oscillations occurring. Nor did he acknowledge the earlier criticism of the
use of Bresler's scheme (25) by Stone and Brian (1963).
Stone and Brian's scheme—Stone and Brian (1963) presented the following
approximation to equation (4) as an alternative to equation (25) :
CJ CJ+1 + cj
~> -V<6(J^ - ->' (26)
where n cyclically takes on the values 0.1250, 0.4145 and 0.4605 during suc-
cessive time steps. In other words, at t=0, n has the value 0.1250, at
t = At, n is given the value 0.4145, etc. The basic equation they used, from
which equation (26) can be derived, contains five weighting factors in addi-
tion to n- Equation (26) is the result of substituting their recommended
values for the other weighting factors. We also note that n in equation (26)
corresponds to 0 in their equation (16) . Their choice of C-] + C .
a2c
to approximate — r- was based on the success of previous use of Crank-Nicolson
3z
approximations in solving diffusion equations. Choices of the weighting fac-
tors, as well as the cyclic use of z, were based on optimal propagation
velocities and proper decay of harmonics present in sharp concentration
fronts. Their theoretical deviation of n included the assumption, D=0.
The authors presented graphs showing the superiority of their method
over the Crank-Nicolson approach, represented by Bresler 's scheme equation
(25), for D = 0. Shamir and Harleman (1967) made test runs with Stone and
Brian's scheme for V/D = 10 and 100 but made no comparison with the Crank-
Nicolson approach for these values of V/D.
Second order explicit scheme— In addition to the above approximations,
which have been derived from equations appearing in the literature, an addi-
tional difference approximation was investigated. The approximation can
231
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easily be derived, beginning with equation (22), and does -not require the as-
sumption (23). Equation (22) can be expressed in the form:
_ CJ
2 2
At ui 2 at
where:
0(Az) + 0(At), (27)
_ V6 (C). (28)
To obtain -— ^- in equation (27), both sides of equation (28) can be differen
tiated with respect to t to yield:
+ G,) - TT- • (G^.. - G^ .)
' -
1 , .. .
. 2 i-l i i+l' 2Az x+1 i-l
Az
The desired approximation scheme is therefore:
At . r_D_ j j j
G - 2 G + G
At ~ i 2
(29)
"
Since G. is a function of the concentrations at time t, C"? -, C~l, and C~! , ;
the approximation scheme is explicit. It is formally second-order accurate
in space and time by virtue of (27).
Since the scheme has not previously appeared in the literature, the es-
sential steps in an efficient computational procedure are presented below.
Equations (7a), (7b), and (7d) are the assumed boundary and initial condi-
tions.
232
-------
(1) Define the coefficients A, B, A', and B' as follows:
Az
v' = £•=• • A
L 2 '
and
and
' - At
- ——
(2) Define the initial and surface boundary concentrations;
Ci = Cr for i = 2, . . . , M ,
Cl = Co '
GI = o .
The following steps are carried out for each successive time step.
(3) Define:
B'Ci '
and
G. , = F - F ,
1-1 i-l i
DFi-l
DFM = (A' + B') '
M
i = 3, 4, . . . , M
(4) Update the concentrations for i = 2, 3, . . . , M-l:
233
-------
_ + G_ + DF_ + DF i = 2, 3, . . . , M-l
111 i+l
and
p(new) _ r(new)
C^C
In step (4), the condition — =0, where L = (M-3/2)'Az, is approxi-
o Z C
z=L / N
c (sc)
/neW' = C ^neW . Bresler (1972) discusses this
mated by the equality, C/j' = C . Bresler (1972) discusses this
approximation in more detail. The definition of DF in step (3) is a result
of the equality of C and C .. for all times.
The second-order explicit scheme therefore requires four multiplications
per interior grid point per time interval (steps 2 and 3). In comparison, the
explicit scheme (15) and Chaudhari's scheme (19) require at least two multi-
plications per grid point per time interval (Carnahan et al. , 1969). The
Crank-Nicolson approach (25) and Stone and Brian's scheme can both be ar-
ranged for solution by inversion of a tri-diagonal matrix and probably re-
quire at least four or five multiplications per grid point per time interval,
depending on the algorithm used to invert the associated matrix (Carnahan et
al., 1969). The use of Bresler' s scheme and Chaudhari's scheme as originally
presented would require more computational effort due to the necessity of re-
calculating the coefficients of the concentrations for each time interval.
Chaudhari (1971) suggested using a transfer-of-mass mechanism to prevent os-
cillations from appearing in the numerical solutions generated by his scheme.
The use of this mechanism would also increase the computational effort some-
what .
Simulation Runs—
The characteristics of a numerical method which are probably the most
important to a potential user are the amount of time and effort required for
programming and the actual computer simulation time required to achieve a
given degree of accuracy for a particular type of problem. If the numerical
procedure is to be extended to a new type of problem, a judgment must also be
made as to the probability of success or failure of the potential extension.
For the present study it was desired to determine whether one or more of
the procedures investigated were superior in solving the CDT equation (4),
with the boundary conditions (7a), (7b), and (7d) for a range of V/D found in
soils. Based on the literature review, it would be expected that the explicit
scheme would perform unsatisfactorily compared to some of the other schemes.
However, the limitation on grid-spacing, which is uniquely associated with
this scheme, is part of the reason for investigating the explicit scheme.
The analysis carried out earlier showed that the only difference between the
explicit scheme and Chaudhari's scheme (equation 19) is related to time step
size and not to grid-spacing. The final test, of course, must be in terms of
numerical results generated by use of the two schemes.
234
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Bresler (1972) purported to have developed a finite-difference approxi-
mation which eliminates numerical dispersion. He presented graphs showing
near-perfect agreement between results obtained by the use of his scheme and
those obtained from an analytical solution presented by Brenner (1962), for
saturated, steady-flow conditions. However, he did not give any indication
of the time step sizes of grid-spacings necessary to achieve his results.
Moreover, he failed to indicate the fact that his scheme reduces to the Crank-
Nicolson approach (25) for these conditions.
Stone and Brian's scheme (26) apparently has more to offer for high
values of V/D, at least from a theoretical point of view, than either the
Crank-Nicolson approach or Chaudhari's scheme (equation 19). The reason is
that Stone and Brian included weighting factors in their scheme which result
in reduced oscillations in the numerical solutions for high V/D. However,
comparisons of the performance of these schemes for low values of V/D have
not been made. Since the derivations of both Stone and Brian's scheme and
Chaudhari's scheme included the assumption, D = 0, it was desired to check
their performance relative to that of the Crank-Nicolson approach for values
of V/D of 10 or less.
The second-order explicit scheme has the same theoretical accuracy of
approximation as the Crank-Nicolson approach, but has an explicit rather than
an implicit computational procedure. Moreover, it is not based on approxi-
mation (23), and can readily be extended to non-linear systems. Tests were
thus run to determine if its performance is similar to that of the Crank-
Nicolson approach, as theory indicates.
Computer programs—The explicit scheme, Chaudhari's scheme, Stone and
Brian's scheme, the Crank-Nicolson scheme, and the second-order explicit
scheme were programmed in F0RTRAN for the purpose of making computer simula-
tion runs. The systems of equations corresponding to Stone and Brian's
scheme and the Crank-Nicolson scheme (25) were arranged in tri-diagonal matrix
form, and the algorithm outlined by Carnahan et al. (1969) was used to invert
the tri-diagonal matrices. A transfer-of-mass mechanism, as suggested by
Chaudhari (1971), was included in the programming of Chaudhari's scheme. The
method outlined on page 231 was the basis for the program corresponding to
the second-order explicit scheme. The boundary and initial conditions given
in equation (7a) , (7b) , and (7d) were incorporated into the programs in a
manner similar to that suggested when the second-order explicit scheme was
presented on page 231 .
Conditions and basis for comparison,—In order to compare the performances
of the finite-difference approximations, computer runs were made for various
values of the quantities Az, r = V/D, and g = V-At/Az. The velocity, V, was
0.01 cm min"1 for all runs, so that varying 3 was equivalent to varying the
time step size At, provided Az was held constant. However, it is more mean-
ingful to express the relative magnitude of the time step size in terms of g
because interpretation of results can be extended to a broader spectrum of
conditions. Note that g = 1 is equivalent to the time interval required for
the solvent to move a distance, Az, at the velocity, V. It has already been
suggested,that the numerical results obtained from some of the schemes are
235
-------
sensitive to the value of Az used in conjunction with a particular value of r.
Finally, since the computational effort required for a given scheme on a par-
ticular problem is related to time step size and grid spacing, conclusions can
be drawn about the relative efficiency of the various schemes by considering
the values of Az and B in conjunction with the number of computations per grid
point per time step required for each scheme.
The quality of the results obtained from the various schemes was deter-
mined by comparison with results from the analytical solution presented in
Appendix J. Comparisons were made for T ^ 0.5, where T = V-t/L xhe column
length, L , was either 10 cm or 20 cm for all of the runs.
Results of Comparisons—
The discussion of the performances of the finite-difference schemes is
divided into two parts. The first part is confined to the explanation of the
behavior of the explicit scheme, Figures 100 and 101. The second part con-
sists of observations on the performances of the remaining schemes for values
of r = 2, Figures 102 to 107, and r = 32, Figures 108-110.
The explicit scheme—In Figure 100, results obtained from the explicit
scheme are plotted along with results obtained from the analytical solution
(solid line), for r = 8, Three of the cases presented were obtained by using
the approximation scheme (15), the representative equation for the explicit
scheme. For the fourth case, the apparent diffusion coefficient was in^-
creased by the amount D** = 0.5«V2«At; so that equation (19) is the basis for
the results for this case. Of the four cases, the worst performance is mani-
fested for the conditions, Az= 0.2 and B = 0.75. Since Az= 0.2 < 2'D/V =
0.25, the inequality (16) is satisfied for this case. In addition, since
D-At/Az2 = (|) • (-i) • (^1|£.) = (i) • (5) • (0.75) = || < 0.5, the criterion
(17) is also satisfied.
For the conditions Az = 0.2 and B = 0.25, a vast improvement resulted
from the reduction in time step size. For the two cases for which Az = 0.4,
the inequality (16) is violated. The results obtained for Az = 0.4 and 3=
0.05 are a significant improvement over the results for Az = 0.2 and g = 0.75.
This is undoubtedly due to the smaller time step size used in the former case,
which is •=•!•=- the size of the time step size used in the latter case.
The best results presented in Figure 100 correspond to use of the cor-
rection to the apparent diffusion coefficient by substituting (D -I- D**) for
D in the explicit scheme (15). The value of 3 = 0.5 represents an increase
by a factor of 10 over the time step size used for the conditions, B = 0.05
and Az = 0.4. Nevertheless, the results indicate an improved performance,
which is due to the correction to the apparent diffusion coefficient.
In Figure 101 results are presented for the explicit scheme and the
Crank-Nicolson scheme for V/D = 32 and Az = 0.2. For these values of r and
Az, Az > 2-D/V = 0.0625, so that the condition given in equation (16) is vio-
lated. The results from the explicit scheme exhibit severe oscillations for
236
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DEPTH fcM) g.0 3P 4T0 SO 6D 7.0
\\
3.0 4.0 50 6.0 7.0 DEPTH (CM)
Figure 100. Predicted C/Co profiles using the explicit scheme
with r = 8. The analytical solution is shown as
the solid line on both sides of the figure. X is
the solution with Az = 0.2; B = 0.75: 0 is the
solution with Az = 0.2; 3 = 0.25: ^ is the solu-
tion with Az = 0.4; 3 = 0.05: and [»] is the solu-
tion with Az = 0.4; 3 = 0.4; and D replaced by
D + 0,5-V2*At.
237
-------
3iO 4>0 5.0 &0 7.0
3.0 4.0 5.0 6.0 DEPTH (cM)
Figure 101. Predicted C/Co profiles with r = 32 and Az = 0.2.
The analytical solution is shown as the solid line
on both sides of the figure where [¥] is the Crank-
Nicolson scheme with $ = 0.25: x is the explicit
scheme with 8 = 0.025: and (*)is the explicit
scheme with B = 0.25.
238
-------
• CRANK - NICOLSON
X STONE - BRIAN
8 10 12 14
DEPTH (cm)
16 18 20
Figure 102. Predicted C/Co profiles with r = 2, Az = 0.5, and
3 = 0.5. The analytical solution is shown as a
solid line.
239
-------
8 10 12 14
DEPTH (cm)
16 18
Figure 103. Predicted C/Co profiles with r = 2, Az = 0.5 and
8 = 0.4. o is the Chaudhari scheme and f~j is the
explicit scheme. The analytical solution is shown
as the solid line.
240
-------
° CHAUDHARI
°2ntRDER EXPLICIT
8 10 12 14
DEPTH (cm)
Figure 104. Predicted C/Co profiles with r = 2, Az = 0.4, and
3 = 0.5. o is the Chaudhari scheme and Q is the
explicit scheme. The analytical solution is shown
as the solid line.
241
-------
a 2 ORDER EXPLICIT 5= .99
2 ORDER EXPLICIT ,8=1.01
8
10 12 14
DEPTH (cm)
16 18 20
Figure 105. C/Co profiles calculated using the second order
explicit scheme where Q is 6 = 0.46 and | is
3 = 0.51.
242
-------
• CRANK - NICOLSON
X STONE - BRIAN
8 10 12 14
DEPTH (cm)
Figure 106. Predicted C/Co profiles with r = 2, Az = 0.5 and
B = 1.75. o is the Crank-Nicolson scheme and x is
the Stone-Brian scheme. The analytical solution
is shown as a solid line.
243
-------
o CHAUDHARI
X STONE - BRIAN
a 2nd ORDER EXPLICIT
• CRANK - NICOLSON
8 10 12 14
DEPTH (cm)
16 18 20
Figure 107. Predicted C/Co profiles with r = 2, Az = 2 and
P = 0.5. o is the Chaudhari scheme, x is the Stone-
Brian scheme, Q is the explicit scheme, and •
is the Crank-Nicolson scheme. The analytical solu-
tion is shown as the solid line.
244
-------
3.0 4.0 5.0 6.0 70 8.0
nd
D 2 ORDER EXPLICIT
• CRANK- NICOLSON
o X STONE- BRIAN
o CHAUDHARI
5.0 6.0
7.0
DEPTH (cm)
Figure 108.
Predicted C/Co profiles with r = 32 and Az = 0.125.
The Stone and Brian scheme, Chaudhari scheme, and
second order explicit scheme are shown on the left
side for 8=1. On the right side the Chaudhari
scheme is shown for 3 = 0.5 and the Crank-Nicolson
scheme for 8=1. The analytical solution is shown
as a solid line on the right side.
245
-------
2.0 3.0 4.0
D 2 ORDER EXPLICIT
4.0 5.0 6.0 7.0 DEPTH (cm)
Figure 109. Predicted C/Co profiles with r = 32 and Az = 0.125.
The second order explicit scheme with $ = 1.5 is
shown on the left. The Stone and Brian scheme
with B = 1.75 is shown on the right.
246
-------
2.0 3.0 4.0 5.0 6.0 70 8.0
D 2ND ORDER EXPLICIT
• CRANK- NICOLSON
STONE - BRIAN
o CHAUDHARI
O.I
4.0 50 6.0 70 DEPTH (cm)
Figure 110. Predicted C/Co profiles with r = 32 and 3 = 0.5.
The Crank-Nicolson scheme and the second order ex-
plicit scheme with Az = 0.25 are shown on the left
side. The solution is shown as a solid line. The
Chaudhari scheme and Stone and Brian scheme with
Az = 0.5 are shown on the right. The analytical
solution is shown as a solid line.
247
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3 = 0.25. On the other hand, the results for 3 = 0.025 are almost identical
to those from the Crank-Nicolson scheme for 3 = 0.25. The oscillations
should not be confused with instability, since the oscillations in all cases
were found to be less pronounced as the solutions progressed in space and
time. (For a discussion of this type of oscillation, see Shamir and Harleman,
1967. For a discussion of instability, see Carnahan et al., 1969).
The following conclusions can be drawn regarding the behavior and use of
the explicit scheme. First of all, the criterion on grid-spacing (16) is
misleading. The scheme is not necessarily unstable when (16) is violated, as
has been suggested by Fried and Combarnous (1971) and Shamir and Harleman
(1967). Two stable solutions were presented for cases where (16) was viola-
ted. Moreover, cases were presented showing that the quality of results was
better when (16) was violated and a relatively small time step was used than
when (16) was satisfied but a larger time step was used. The implication is
that good results should not be expected from use of the explicit scheme just
on the basis that (16) and (17) are satisfied.
Secondly, the explicit scheme manifests a performance which is much in-
ferior to that of schemes utilizing second-order (equation 25) or approxi-
mately second-order (equation 19) accurate finite-difference approximations
to the time derivative in the CDT equation (4). Cases were presented showing
that results of better quality were obtained using Chaudhari's equation (19)
than those obtained using the explicit scheme, although the time step size
used with the explicit scheme was a factor of 10 smaller. These results are
significant since no more computational effort is required for Chaudhari's
scheme (19) than for the explicit (15) on a grid point per time step basis.
Finally, the inferiority of the explicit scheme is well-founded in
theory, in as much as the difference in equation (15) and (19) is related to
time step size and not to grid-spacing. The extreme sensitivity of the ex-
plicit scheme to time step size, which is indicated in Figures 100 and 101,
substantiates this theoretical difference,
Performances of the other schemes—The results obtained from runs using
the Crank-Nicolson and Stone and Brian schemes, for r = 2, Az = 0.5, and 3 =
0.5, are shown in Figure 102. Results for the Chaudhari and second-order ex-
plicit schemes, for the same values of r and Az and for 3 = 0.4 and 0.5, re-
spectively, are presented in Figures 103 and 104, respectively.
It is evident from Figure 102 that the Stone and Brian and Crank-Nicolson
schemes yield close approximations to the analytical solution for 3 = 0.5-
The second-order explicit scheme yields correspondingly good results for
3 = 0.4, but the results from Chaudhari's scheme exhibits more deviation from
the analytical solution than those from the other schemes. For 3 = 0.5, re-
sults from the Chaudhari scheme exhibit severe oscillations in the frontal re-
gion, while those from the second-order explicit scheme manifest less pro-
nounced oscillations about the analytical solution.
In order to understand the reason for this seemingly strange behavior of
Chaudhari's scheme and the explicit scheme, it is helpful to reconsider the
248
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relationship between the two. It was pointed out earlier that the only dif-
ference in the basic approximating equations for the two schemes is the value
of the coefficient of 6 (C ) appearing in both the explicit and Chaudhari's
scheme 15 and 19. The inequality (17) which must be satisfied to insure sta-
bility of the explicit scheme, can be translated to the following inequality
for Chaudhari's scheme:
JD + D**) . At .
. 2 -
Az
which can also be expressed in terms of r, 3, and Az:
Az
+ 0.5) <_ 0.5 . (30)
Since -- •-' .• > 0, an immediate consequence of (30) is the strict inequality:
3 < 1 .
The maximum value of 3 which satisfies (30), for r = 2 and Az = 0.5, is g =
0.41. Therefore, the use of ,3 = 0.5 with these values of r and Az is a vio-
lation of (30). The transfer-of-mass mechanism included in the programming
of Chaudhari's scheme curtails uncontrolled oscillations outside of the
frontal region, even if (30) is violated. However, the approximation to the
analytical solution in the frontal region degenerates as a result of the vio-
lation.
It might also be expected that the second-order explicit scheme should be
restricted with respect to time step size as a result of the explicit computa-
tional procedure associated with the scheme. Empirical observations from a
number of runs revealed that the oscillatory behavior illustrated in Figure
104 occurs when D • At/Az = 3/(r-Az) 2 0.5- Further evidence of this phenom-
enon is presented in Figure 105, for r = 2, Az = 1 and 3^1. One graph cor-
responds to 3 = 0.99 (3/(r-Az) = 0.495), while the other graph corresponds to
3 = 1.01 (3/(r-Az) = 0.505}. The degeneration of the approximate numerical
results with increasing 3/(r-Az), for 3/(r-Az) : 0.5, was also observed for
the values of r and Az used for Figure 104. Due to small differences in the
time step sizes, At, used to produce the two solutions in Figure 105, the re-
sults presented there do not correspond to exactly the same simulated time.
However, observations were made for other simulated times and for the same
values of r, Az, and B. For 3/(r-Az) = 0.505, the oscillations became more
pronounced with increasing time, while for 8 = 0.495, the oscillations tended
249
-------
to smooth out with increasing time. While these observations do not consti-
tute "proof" of instability of the second-order explicit scheme for g/(r*Az) >
0.5, they are indicative of a certain sensitivity of the results to the mag-
nitude of this ratio.
Results from the Crank-Nicolson and Stone and Brian schemes, for Az = 0.5,
r = 2 and g = 1.75, are presented in Figure 106. Very little adverse effect
was caused by the increase in g from 0.5 to 1.75, for these two schemes, al-
though, the results from the Stone and Brian scheme exhibited an overshoot of
0.3% at z = 2 for the larger value of 6. An overshoot of 0.6% was observed
for the Crank-Nicolson scheme for $ = 2 (not shown).
The results for all four schemes, for r = 2, g = 0.5 and Az = 2, are
presented in Figure 107. The effect of increasing Az can be observed by com-
paring Figure 107 with Figures 102 and 103. The deviations from the analyti-
cal solution are evident for the higher value of Az. In addition, minor
overshoots of 0.5% and 1.0% occur for the second-order explicit and Crank-
Nicolson schemes, respectively. Since the time step size, At, was also in-
creased by a factor of four in order to hold g constant, it might be thought
that the poorer quality results in Figure 107 are due partially to the in-
crease in time step size. However, runs made for Az = 2.0 and r = 2.0 and
for the same time step sizes used for Figures 102 and 103 resulted in no sig-
nificant improvements for any of the schemes.
The results from the Stone and Brian, second-order explicit, and Chaud-
hari schemes, for, r = 32, Az = 0.125, and g = 1.0 are presented on the left
in Figure 108. The symbols on the right of Figure 108 correspond to the
Chaudhari scheme, for g = 0.5, and the Crank-Nicolson scheme, for g = 1.0.
The results from the Crank-Nicolson scheme exhibit an overshoot of 0.5% Co
at z = 3.5. The response of the Chaudhari scheme, for g = 1.0, has the ap-
pearance of a step-function: C/Co = 1.0, for 0.0 <_z <_5.0, and C/Co = 0.0,
for z >_ 5.0. This response is another manifestation of the violation of (30)
for Chaudhari's scheme.
The effect of increasing 8 to 1.5, for the second-order explicit scheme,
and to 1.75, for the Stone and Brian scheme, is shown in Figure 109. The
quality of fit for the Stone and Brian scheme, for this value of g, is about
the same as that of the Crank-Nicolson scheme for g = 1.0, both having over-
shoots of 0.5%. The results from the second-order explicit scheme, for g =
1.5, also show some decrease in quality from the corresponding results for g
= 1.0, although no overshoot occurred for either value of g. Results from
the second-order explicit scheme, for g = 1.75 (not shown), exhibited rather
severe oscillations.
Finally, the results corresponding to the Crank-Nicolson and second-
order explicit schemes, for r = 32, Az = 0.25, and g = 0.5, are presented in
Figure 110. Also shown there are results from the Stone and Brian and Chaud-
hari schemes, for Az = 0.50. In this case, the quality of fit for the Stone
and Brian scheme is better than for the second-order explicit and Crank-
Nicolson schemes even though the grid spacing and time step size used for the
former scheme are both twice as large as those used for the latter two
250
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schemes Although the results from the Chaudhari scheme show no overshoot,
the deviation from the analytical solution in the frontal region is rather
severe. Runs were also made with the Stone and Brian scheme for r = 32 and
Az - U.^i (not shown). No overshoot was present for 3 = 0.5. For 3 = 1.0,
the quality of results, including overshoot, was about the same as that for
Az = 0.5 and 3 = 0.5.
Assessing the relative efficiency and accuracy of the four finite-
difference schemes, excluding the explicit scheme, is not as straightforward
as the comparison of the performance of the explicit scheme with that of the
others. However, at least some rather qualitative assessments can be made on
the basis of the figures presented. To aid in this discussion, attention is
first directed to an aspect of the finite-difference approximation schemes
presented in equations (15), (19), (25), (26), and (29), which has not here-
tofore been pointed out. Each of these approximations can be expressed in
the general form:
~
» r
although the analytical expression for f varies somewhat from scheme to
scheme. The fact that all of the schemes are similar in their general func-
tional form is not as important from the present point of view as the fact
that, for a particular scheme, different solutions resulting from the same
values of 3 and r-Az have something in common. The similarity between such
solutions exists in terms of the grid point number, i, and time step number,
j, rather than in terms of the total distance to a grid-point, i«Az, or the
total time spanned from t = 0, j'At. In other words, with a particular
scheme, and for a grid-network with a sufficient number of grid points so
that the lower boundary exerts negligible influence on the concentration C^j
after j time steps, any two approximations to the solution of the CDT equa-
tion (4), with the conditions given in (7a) , (7b) and (7d) produced from the
same values of 3 and r«Az, will be identical after j time steps at all grid
points, k, such that k <_ i. To illustrate what is meant, the results from
the Stone and Brian scheme, with r = 32, Az = 0.125, and 3 = 0.5, are com-
pared in Table 65 with results using the same scheme with 3 = 0.5 but with
r = 2.0 and Az = 2.0. The results for the first 10 grid points and after 10
time steps are identical for the two pairs of r and Az. By utilizing this
translational quality of the schemes, it is possible to glean additional in-
formation from the results which are presented in Figures 102-110.
First of all, the Crank-Nicolson and Stone and Brian schemes appear to
have some advantage over the second-order explicit and Chaudhari' s schemes
for low values of r-Az, due to a greater flexibility in the choice of 3 for
the former two schemes. For r«Az = 1, and for 3 = 1.75, the results of these
two schemes showed little decreases in quality from the corresponding results
for 3 = 0.5. The maximum value of 3 for the Chaudhari scheme is 0.41 (for
r-Az = 1), by virtue of equation (30), and that for the second-order explicit
scheme appears to be approximately 0.5. The translational property discussed
above indicates that the oscillatory behavior of the second-order explicit
scheme illustrated in Figures 104 and 105 would occur for 3/r«Az * 0.5 and
251
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TABLE 65. C/CO VALUES FOR r-Az=4, AFTER TEN TIME STEPS FROM TWO RUNS USING
THE STONE AND BRIAN SCHEME.
r-o
Ln
Grid Point
1
2
3
4
5
6
7
8
9
10
r=2
Z
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
Az=2.0 r=32
C/Co
1.0000
0.9996
0.9895
0.9404
0.8110
0.5953
0.3519
0.1614
0.0569
0.0158
C/Co
1.0000
0.9996
0.9895
0.9404
0.8110
0.5953
0.3519
0.1614
0.0569
0.0158
Az=0.125
Z
0.000
0.125
0.250
0.375
0.500
0.625
0.750
0.875
1.000
1.125
-------
for r-Az = 1 0 and r-Az = 2, regardless of the value of r. However, the
values of C/Co presented in these figures would be shifted to shorter simu-
lated times and distances for higher values of r.
The results presented in Figures 107 and 110 indicate that the Stone and
Brian and Chaudhari schemes resist overshoot for higher values of r«Az (i.e.
r-Az = 4, 8, and 16, respectively, corresponding to Figures 107, 109 and 110,
respectively) than do the Crank-Nicolson or second-order explicit schemes. It
is interesting to note that the value of r-Az which produced oscillations in
the observed C/Co profiles for the Crank-Nicolson, Stone and Brian, and
second-order explicit schemes was higher for the cases where r - 32 than for
those where r = 2. Shamir and Harleman (1967) pointed out the tendency of
overshoot in solutions produced by the Stone and Brian scheme to die out as
the simulated concentration front progresses in space and time. This same
tendency can be observed for the other two schemes from the present analysis.
The results for r = 2 and Az = 2 can be viewed as an early observation (i.e.
after 10 time steps) from any run for which B * 0.5 and r-Az = 4. The results
for r = 32 and Az = 0.125 can be viewed as a later observation (i.e. after 80
time steps) from the same run, assuming the provision of a sufficient number
of grid points. Overshoot would occur in the early observation for the Crank-
Nicolson and second-order explicit schemes but would not be present for the
later observation. Overshoot would be absent in both corresponding observa-
tions. Overshoot would be absent in both corresponding observations of
results from the Stone and Brian scheme.
Chaudhari1s scheme provides results which are free of overshoot for
large values of r-Az. It is difficult to assess the relative merit of this
characteristic from the present analysis since the deviation from the analyti-
cal solution in the frontal region was noticeably worse than that for the
Stone and Brian scheme for r = 2, Az - 2, and g = 0.5 and for r = 32, Az = 0.5
and g = 0.5. The scheme is certainly a simple alternative to the explicit
scheme, due to the similarity of the explicit scheme equation (15) and Chaud-
hari' s scheme equation (19). The transfer of mass mechanism for preventing
overshoot can apparently be used to best advantage when only qualitative re-
sults, free of overshoot, are required. In such cases large values of r«Az
can be used and the restriction on g due to (30) is not as severe as for
smaller values of r-Az. However, in any case, g must be less than 1.
The Crank-Nicolson scheme appears to be somewhat more sensitive to over-
shoot for higher values of r-Az (r-Az = 4) than either the second-order ex-
plicit or the Stone and Brian scheme. For r = 2, Az = 2, and g = 0.5, the
overshoot for the Crank-Nicolson scheme was slightly greater than for the
second-order explicit scheme. While for r = 32 and Az = 0.125, results for
the former scheme exhibited overshoot for g = 1.0, whereas the results for
the latter scheme showed no overshoot for 6 = 1.5. In resisting overshoot,
the Stone and Brian scheme exhibited at least a factor of 2 advantage in the
magnitude of r-Az, with g = 0.5, over both of the other schemes. However,
increasing g to 1.0 or increasing r-Az by an additional factor of 2, for g =
0.5, resulted in overshoot in the observed results for this scheme.
25:
-------
Summary—Five finite-difference schemes were investigated. Predicted values
of C/Co produced by the various schemes were compared to results from the ana-
lytical solution presented in Appendix J. The explicit scheme, represented by
equation (15), was found to be inferior to schemes possessing a second-order
(or approximate second-order) accurate approximation to the time derivative in
equation (4). Time steps required to produce an accuracy comparable to that
obtained by use of Chaudhari's scheme equation (19) or of that using the
Crank-Nicolson scheme were smaller by a factor of 10 for the explicit scheme.
The scheme produced stable solutions even when condition (16) was violated.
It was pointed out that all of the schemes are functions of the two di-
mensionless quantities, 3 = V-At/Az and r«Az, where r = V/D. It was demon-
strated that this property allows observations on the qualitative aspects of
numerical results from a particular scheme to be applied to other numerical
results which are generated from the same values of these two quantities.
It was demonstrated that larger values of 3 (^1.75) could be used with
the Stone and Brian and Crank-Nicolson schemes than with the Chaudhari or
second-order explicit schemes (3 > 0.5) for low values of r*Az (=1.0). For
higher values of r*Az, the Crank-Nicolson scheme was found to be more sensi-
tive to increases in 3 than the second-order explicit scheme, and the Stone
and Brian scheme was found to lose some of its advantage in this respect.
However, the Stone and Brian and Chaudhari schemes both produced solutions
which were free of overshoot for values of r«Az, a factor of 2 higher than
those for which overshoot occurred for the other two schemes. The deviation
from the analytical solution in the frontal region was found to be more pro-
nounced for Chaudhari's scheme than for the Stone and Brian scheme at the
higher values of r*Az.
Chemical Equilibrium Equations
Choice of a System—
Ions—In today's environment a large number of different chemicals are
applied to soils of various textures and under a variety of climatic condi-
tions. It would therefore be difficult to even discuss all of the chemical
interactions that might be important, given the right situation. There are,
however, certain cations and anions which are present in almost all soils.
For example, the exchangeable bases: calcium, magnesium, sodium and potassium
are included in many soil chemical analyses and in many instances occupy most
of the effective cation exchange capacity of soils. An additional cation
which is important in agricultural soils is ammonium, a constituent of certain
nitrogen fertilizers, e.g. (NH.) SO,. The anion chloride is present in appre-
ciable amounts in many irrigation waters and is also applied to soils as a
companion anion in fertilizer applications of potassium. Sulfate is present
in some irrigation waters and is applied in fertilizers as a nutrient addi-
tive. These same cations and anions are very often chosen for laboratory
column studies for the reasons outlined above.
Chemical interactions—Clay particles or platelets are present to some
extent in virtually all soils and play a major role in their chemistry and
fertility. The clay particles carry a net negative charge which serves to
254
-------
attract cations. The cations which neutralize this negative charge are in
equilibrium with the cations which remain in solution. The process by which a
soil system achieves equilibrium with respect to cations neutralizing the
negative charge of the clay (adsorbed cations) and those in solution is cation
exchange. Cation exchange is important both in the soil storage of cations
and in the distribution of cations between the solution and adsorbed phases.
Another ion interaction which can be important when calcium and/or mag-
nesium and sulfate are together in soil solutions is that of ion-pair forma-
tion (Dutt et al. 1972a). Ion pairs of calcium and sulfate or magnesium and
sulfate are formed; the extent of ion pairing is determined by an equilibrium
relationship between the paired and unpaired ions in solution.
Ions and interactions considered in the model—The ions chosen for in-
clusion in the model are: calcium (Ca"H-)} magnesium (Mg"1^") , sodium (Na+),
potassium (K+), ammonium (NH,+), sulfate (SO,= ), chloride (Cl~), and bicar-
bonate (HCO ~). The choice of bicarbonate instead of nitrate, which may be
important for some applications, perhaps seems arbitrary. However, the deci-
sion to use HCO,," was partly based on an intended application of the model,
for which this ion is important. Moreover, it will subsequently become clear
that the monovalent anions, as well as the cations, can easily be replaced by
other species for varied application of the model. The chemical interactions
considered are those of cation exchange and ion-pairing.
Mathematical Description of Chemical Interaction: Types of Equations—
To describe the equilibrium phenomena discussed above, the basic equa-
tions presented by Dutt, et al. (1972b) for cation exchange, ion-pairing and
ionic activities were chosen for the present work. However, the numerical
approach to the solution of the system of equations differs from the approach
taken by these authors. A brief account of the types of equations is given
below.
Ionic activity—Dutt et al. (1972a,b), ignoring the effects of tempera-
ture and ionic radius, used the following equation to define the activity,
(C.), of ion i, whose molar concentration is C.^:
(C±) - y± ' ci
where
y. = exp{-1.17 ' Z^ ' u/ 1 +u)} ,
and
U =
The quantity u is the ionic strength, Z, is the valence of ion j, and the sum
is over all ions in solution. The coefficient YI is termed the activity
255
-------
coefficient for ion i. It is clear from equation (31) that only two activity
coefficients are mathematically distinguished for solutions containing only
monovalent and divalent ions. These are:
Y = Y = exp{-1.17 *
for monovalent ions, and:
4
Yd - Y
for divalent ions.
Cation exchange—The equations utilized for cation exchange are of two
types, one which describes exchange between two cations of the same valence,
and one which describes exchange between divalent and monovalent cations.
The former can be written:
VY2 = E12 ' (V/(C2> = E12 ' VC2 <32>
In equation (32) Y and Y represent the adsorbed phase concentrations of
ions 1 and 2 , respectively, and E-^ is a constant exchange coefficient whose
value is characterized by the soil and the particular cations 1 and 2.
For exchange between a divalent cation, ion 1, and a monovalent cation,
ion 3, the following (Gapon) equation is used:
VY3 = WV^V = E13 ' Y ' C1/C3 (33)
In (33) the units of Y and Y- are arbitrary, but the value of E. ~ is depen-
dent on choice of units for C^ and C^. For subsequent discussion C.. and C,
will be assumed to have units (moles/liter) or (millimoles/cm ) and the ex-
change coefficient for divalent-monovalent exchange reactions will have units
(moles/liter)'5. The dimensionality of the exchange coefficient in this case
illustrates the empirical nature of the equation. Nevertheless, much success
has been achieved with its use •
-------
trations C^ {Ca } and A , {SO }. Letting D,, » -i- and using the defini-
Rll
tion of activities for divalent ions, the above equation can be written:
Conservation of charge among adsorbed cations—The negative charge on the
soil which is neutralized by adsorbed cations is assumed to be a fixed quan-
tity at a given depth in the soil and is usually expressed as cation exchange
capacity (CEC meq/100 gm soil). If Q (meq/100 gm) of cation i is adsorbed
then:
Z Q1 = CEC
If Y. is the adsorbed quantity of ion i expressed in units of (moles/liter),
based on the volumetric water content 9 (cm3 water/cm3 soil) and bulk density
p, (gm dry soil/cm3 soil), then assuming unit density for water, we have:
Ed. • Y = CEC
a. = 100 • Z. • 6/p,
l ib
Total ion concentration—In a finite volume of moist soil, V (cm ), at
equilibrium, the total amount, T. (mmoles), of ion i .present is-a fixed quan-
tity, regardless of the amounts of the ion which are in various phases (ad-
sorbed, solution, etc.)- If T- is divided by the volume of water V (cm3)
present in the finite volume or moist soil,, another fixed quantity is the
result:
CilT, = T./V
iT i w
3
where C._ is the total concentration (mmoles/cm ) of ion i at the specified
moisture content V /V . Moreover, we have:
C. + Y. + EX.j - C1T (35)
where C. = (mmoles of ion i unpaired)/V
i w
Y = (mmoles of ion i adsorbed)/V
i w
X . = (mmoles of cation i paired with anion j)/Vw .
These quantities can be expressed equivalently in units of either (moles/
liter) or (mmoles/cm3).
257
-------
TABLE 66. SYMBOLS USED FOR DIFFERENT PHASES OF THE IONS
Ion
ca«
Mg"
4.
Na
K+
NH/
S°4=
cr
HC03~
Solution Adsorbed
Cl Yl
C2 Y2
C3 Y3
C4 Y4
r Y
C5 Y5
A —
*2
A3
Ion Pairs Total
Xll C1T
X21 C2T
C3T
C4T
C5T
Xll» X21 A1T
A2T
A3T
-------
Description
Mass Balance
Cation-Exchange
Conservation of
Charge (Adsorbed
Cations)
Ion-Pairs
Activity Coefficient
C + V -4- V - r
"I ~ I. T A,- ~ L
1 1 11 IT
C2 + Y2 + X21 - C2T
C3 + Y3 - C3T
C4 + Y4 - C4T
C5 + Y5 = C5T
Al + Xll + X21 - A1T
A2 - A2T
A3 ' A3T
(V 3T
Yl 1 Y2 = E12-7C^ = E12- VC2
Yi ^ Y|* = En' (r \ = En* C.^/C. *Y
Y1 / Y4 - - y OIX-T
Y1/Y5- =E15'C>5-Y
5
J=iaiYi = CEC
where a. = lOO'Z^.^'0/f^
-I
Xl1 KllCaS04 ^l^V0!!^!^
X21 =D2l'Y8'C2'Al
Y = exp(-1.17u/(l+u))
(36)
(37)
(38)
(39)
(40)
(41)
(42)
(43)
(44)
(45)
(46)
(47)
(48)
(49)
(50)
(51)
where u=/2 (C1+C2+A1)+.
259
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The ions included in the model are shown in Table 66 together with the
symbols used to represent the various phases in which the ions occur. The
complete system of equilibrium equations is discussed in Table 67.
Rearrangement of the System of Simultaneous Equations—
Theoretically, the system of equations (36) through (51) could be solved
simultaneously, by numerical means, in its present form. However, if some
of the dependent variables in the system can be obtained explicitly in terms
of the remaining variables, the number of equations that must be solved si-
multaneously can be reduced by back-substitution. The advantages of a back-
substitution approach for a system that must be solved by an iterative tech-
nique (e.g. a general non-linear system) are as follows:
(1) Iterative techniques require an initial estimate for each unknown in
the system of simultaneous equations to be solved. Each back-sub-
stitution reduces the possibility of a "bad" estimate. This in turn
reduces the probability that a large number of iterations will be
required for convergence.
(2) If the system of equations constitutes a mathematical model of a
physical system, such as the chemical equilibrium system, knowledge
of the system may be used to reduce computational effort.
For example, any physically meaningful solution of the system of chemi-
cal equilibrium equations will be such that 0 <_ C- <_ CIT. In other words,
only non-negative concentrations are meaningful and in no case can the solu-
tion concentration, CL , exceed the total concentration C--. By bounding the
variables which are obtained by an iterative technique, the effort expended in
obtaining a solution can be reduced. In addition, situations which might lead
to an abortion of the solution procedure can be avoided in this manner. In
practice, the bounding of the variables is more straightforward for a system
of fewer unknowns.
To reduce the system of equations (36) through (51), all of the depen-
dent variables were obtained as functions of C.. and y« These two variables
occur frequently in the system, whereas the other variables occur in at most
four of the equations. The back-substitution scheme is presented in Appendix
K. The rearranged system of equations which results from the back-substitu-
tion process is presented in Table 68, along with the equations from (36)
through (51) used to obtain each new equation. Each equation in the system
(36) through (51) was used at least once to obtain the new system (52) through
(67).
Inspection of Table 68 reveals the following:
(a) In all of the equations except (54) and (61) variables are either
defined directly in terms of C-^ and Y or i-n terms of other variables which are
dependent only on C-^ and y« In other words, if the root values of C]_ and y
are available, then the entire system is essentially solved.
260
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TABLE .68. REARRANGEMENT OF.THE EQUILIBRIUM EQUATIONS
Equations from the Original System
(36) - (51) Used to Define a New The New System
Equation
(41), (50), AX = /(-BBB + BBBZ - 4'AAA-CCC)/(2-AAA), (52)
(37), (44), AAA = Y8 '
(49), (36). BBB = [l+D..
J.JL O,
'F^-V3
12 2i _
1 IT
ccc - * • r
(49), (36) YX = C1T - Cl • (L + D11 • Y8 • A1) (53)
(48), (50) Y,-{a. + T_ + Tr + Tr + T_ ) = CEC (54)
(37), (44), (38), TC = a2'C2T^Yl + E12 '
(45), (39), (46), 2
(40), (47) Tc = a3-C3T/[Y1 + Y - E13
+ Y ' E14
+ Y ' E15
(continued)
-------
TABLE 68. (Continued)
(50), (37) C = (E19/a0) ' C • T_
(44) Z -^ 2 X C2
(38) , (45) C3 = (E13/a3) • Y • C* • TC
(39), (46) C4 = (E14/a4) • Y • C^ • TC
4
(40), (47) C5 = (E15/a5) • y • C* • TC
(42) A2 = A2T
£ (43) A3 = A3T
(51) Y = EXP [-1.17 • y/(l + y)]
y = /Z'CC-j+C^A^ + 0.5- (C3+C4+C5+A2+A3)
(49) Xn = Dn • Y8 • Cj • AJ_
(50) X21 = D21 . Y8 . c2 - A;L
(50), (37), (44) Y2 = (Y1/a2) • TQ
(38), (45) Y3 = (Y1/a3) • TC
(55)
(56)
(57)
(58)
(59)
(60)
(61)
(62)
(63)
(64)
(65)
(Continued)
-------
TABLE 68. (Continued)
(39), (46) Y4 = (Y1/a4) ' TC <66>
(40), (49) Y = (Y/a) • T
u>
-------
(b) Equations (52) through (61) constitute a system of equations which is
independent of the remaining equations.
(c) For a given, fixed value of y, (52) through (54) can be solved inde-
pendently of the remaining equations.
The observations (a), (b) , and (c) which serves as guidelines for the
general approach to the solution of the chemical equilibrium equations, will
be considered next.
Iterative Solution of the Chemical Equilibrium Equations —
The complexity of the system (52) through (67) and the presence of a
transcendental equation precludes any closed-form solution procedure and ne-
cessitates the use of an iterative procedure. A Newton-Raphson technique was
chosen as the basis of the solution algorithm for the following reasons: (1)
The criteria for convergence of the scheme are not severely limiting (House-
holder, 1953); (2) It converges with high order, i.e. with few iterations for
good initial estimates of the unknowns; (3) The partial derivatives required
for the Newton-Raphson approach can be used both to provide estimates of the
unknowns for successive solution steps and to calculate quantities needed to
solve the transport equations.
The Newton-Raphson scheme for solving a single equation or a system of
simultaneous equations can be found in Householder (1953). However, a brief
description of the procedure for obtaining an approximation to a root, X , of
the equation:
f
-------
pointed out in the previous section that all of the equations in the system
(52) through (67) except (54) and (61) define other variables in terms of C±
and Y- By making appropriate substitutions into (54) and (61), two equations
which contain only the unknowns C^ and y would result. Since this would con-
stitute a system of two equations ^n two unknowns, that system could be re-
solved to obtain roots, C.. and y > assuming a solution exists.
Moreover, if equation (54), after appropriate substitutions, could be
solved for C^ in terms of y, then additional substitutions could be made to
reduce (61) to an equation in the single variable y. This can be done since
equations (52) through (54) constitute an independent system for a given value
of y (see observation (3) of 5'd). The solution procedure can be described
as follows. Initial estimates, C,^^ and y^> are made for C^® and y^ from
equations (52) and (53). These values are then substituted into (54) to yield
an expression of the form:
F3°° ' VC10°.Y°>-+VC1°0' W^Ccf.Y0)}
- CEC .
From Table 67 it can be seen that if F =0, then the equations (52)
through (54) are all satisfied. If F °° ^J0, a new estimate of C^t C^10, is
made according to:
C,10 = Cl°0 + dCl°° (68)
where:
The superscripts indicate evaluation in terms of C and y • The subscript,
Y, indicates that y is held constant for the differentiation of F_ with
respect to C, . This process is continued until F^ Z 0 for some j. The
value of CiJO is taken as the desired approximation to the root C-, = Ci(y ).
The accuracy of the approximation is controlled by an appropriate convergence
criterion.
Assuming the error of approximation is negligible, we have at this point
values A^0 = A1(C*0,y°), Y-f° = Y^C-^O, Y°) , and C^0 = C-^y0). The quan-
tities C0 , C_ , C, , and C- are then evaluated from equations (54) through
2 3 4 -* *Q *0
(58) and substituted along with A2T, A.^, C^ , and A± into (61) to yield
an expression of the form:
F,° - y° - EXP{-1.17 '
265
-------
where U°= [2 • (C0*0) + 0.5 -
,
according to:
Again, it is apparent that if F. = 0Jf.then the entire system of equations
(55) through (67) is satisfied. If F, ^ 0, a new estimate of y» Y1* is m
Y° + dY° , (69)
where:
dY°
A new estimate of C is provided according to:
C/1 = C/0 + OCj/ay)0 • dY° , (70)
where
The entire process is repeated until F,1 ~ 0 for some i. The meaning and use
of the notation will be further clarified below, but for the present, the pro-
cedure can be seen to consist of two Newton-Raphson algorithms, one nested
within the other. The inside algorithm provides C-j in terms of a current
value of Y> while convergence in the outside iteration loop amounts to solv-
ing the entire system of equations.
The step-wise procedure followed to obtain a solution of the equilibrium
equations is listed below. For the sake of brevity, the superscripts i, j,
etc. are dropped.
(1) Provide initial estimates of CL and j.
(2) Evaluate A-^ from (52). Note that solving for A-j_ is equivalent to
satisfying the equation:
where F.^ = AAA'A^ + BBB^ + CCC.
(3) Calculate (3A../3C-.) according to:
1 1 Y
In order to illustrate the use of notation, this step is carried out in more
detail. Differentiating equation (52), we have:
266
-------
and
,3CCCv
X \,Y
Note that (-rr—)_
Finally, we have:
and:
3F,
Since F.= 0 from the previous step, we have:
9F, 3F. 3F-, 3A,
or:
3A. 3F
l 3F
(4) Evaluate Y in terms of A , C , and Y from (53).
V
(5) Calculate (TTT-)V according to:
cHj- Y
267
-------
(6) Evaluate !„ , Tn , T_ , and Tn from equation (54) .
c2 c3 c4 c5
3Tc 3Tc 8Tc 9Tc
(7) Obtain the derivatives (— ^)y, (— -^ (— i)^ and (^)y .
3T
2
For example, (TT; — ) is calculated as:
oC... y
3T 3T 9T a. 3T
2 2 2 1 2 3Y
(8) Evaluate the function, F .
SF
(9) Calculate the derivative (3) , .
s-rrr- Y> according to:
8C1
3F
(10) Evaluate dC.. as in equation (68).
(11) Calculate the term:
T = Y • (|TC I + |TC | + |TC ( + |TC I + o^} + CEC .
If |dC..|/T is sufficiently small, proceed to step (12). Otherwise, make a
new estimate for C.. as in equation (68) and return to step (2).
9C1
(12) Calculate —^— . Since at this point F- = 0, we have:
9F3 9F3 9C1 9F3
SY ~ 3c * ^ 3Y SY GI ~ '
and therefore:
9C1 9F3 9F3
f\,, "" *"' V, ^*./ C< i \ r\n ) '
(13) Using the chain rule, obtain —r— according to:
268
-------
8Y. 8TC? 9TC.
(14) In a similar fashion, calculate the derivatives —~- . —. -„ ••,
3y ' 3y ' 3y '
, _ .
(15) Evaluate C2, C3, C^, and GS from equations (55) through (58)
3C7 3C, 3C. 3C-
(16) Calculate , , and .
(17) Evaluate the function F, .
3F
(18) Calculate •— .
dy
(19) Calculate dy as in equation (69), and check for convergence.
(20) If |dy| is too large, obtain new estimates for y and C- as in equa-
tions (68) and (70) .
Initial Estimates for C, and y —
It was previously indicated that all of the variables in equations (51)
through (67), which correspond to solution or adsorbed phase concentrations,
can be evaluated in terms of C-, and y for given values of the total concen-
trations, cation exchange capacity, water content, bulk density, and the ex-
change and dissociation constants. It was further indicated that initial es-
timates, C-^ and yO, are required for the iterative solution technique pre-
sented in the previous section. Certain guidelines, which were followed for
the selection of these initial estimates, are given below. Two cases are
presented:
The first case corresponds to a "rough guess" estimate for C-^ and y .
Since a physically meaningful solution of the system, (51) through (67), is
such that:
o i c1 < c1T ,
the initial estimate, C , should satisfy:
o < c.00 < c1T ,
— 1 — 11
269
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It can be seen from equation (61) that y always satisfies the dual in-
equality.
exp(-1.17) = 0.310 < y ±1.0 .
Consequently, an ind
ity.
Consequently, an initial estimate, y » should also satisfy this inequal-
In the second case it is assumed that the system (51) through (67) has
already been solved in terms of CIT, C2T C5T, AIT, A2T, A3T, and 6.
Another solution of the system is desired in terms of C +AC- , C-T+AC9T, . .
. , C5T+AC5T, A1T+AA1T, A2T+AA2T, A3T+AA3T, and 0+A0 where AC1T> AC2T, etc.,
are small changes of the total concentrations and water content from their
original values. If:
1 ~ 1 IT' 2T' ' " ' ' 51' IT' 2T' 3T' '
and
(old) _ , . .
i T ^ IT" 2T' " * ' ' "5T* IT* 2T' 3T' *
are the values of C-^ and y which satisfy the system (51) through (67) for the
original values of the total concentrations and water content, and:
, „ ,!' C2T+AC2T 6+A6)
and
y(new) = y(C1T + AC1T, C2T + AC2T, . . . , 6 + A9)
are the corresponding quantities for the final values, then Taylor's approxi-
mations yield:
/ \ / u\ 5 3C. (old) c 9C, (old)
(new) (old) , ^ , 1. ' 5 i
AL - L Li ~.L*\l?r ' ^*T
1 J. 1 -1=1 ot-.™ 1 1
(old)
AAJT + ( *A9
and
270
-------
Therefore, for small changes, AC.-, etc., good initial estimates for C-
and Y(neW) are:
0 (old)
Cl Cl + AC1'
and
(72)
(new)
Y° = Y^""*' +
Initial estimates of this type are particularly useful when the total concen-
trations and/or water content are time-dependent with rates of change slow
enough so that equilibrium between the various ion phases can be assumed. A
particular application is given at a later point in the discussion. The step-
wise procedure which was followed to obtain the derivatives of GI and Y with
respect to C.T, for j = 1, 2, . . . , 5, is as follows:
9F1
(1) Calculate (-JT-—) . Note: The notation used here is similar
to that used in the previous section. The only difference is that the total
concentrations and water content are now considered to be independent vari-
ables in the system. However, the symbols for total concentrations C9 , C_T,
Z. J. j J.
C, , GC , AI , A_ , A~T and for the water content, 9, are omitted from the
list or subscripts. One or more of the symbols y , A.. , C.. , and Y are in-
cluded in a subscript when the indicated differentiation is to be carried out
holding the listed variables constant. By using the definition of F.. from
above and the definitions of AAA, BBB, and CCC from equation (52) we have:
(1+DU.Y -C ) -
3A
(2) Calculate (——)p . Using the fact that F. = 0 for values of
oC -iT 1 ' Y -L
A., which satisfy equation (52), we have:
8F
271
-------
Rearranging the above equation yields:
8F
The quantity ( ) is calculated during the iterative solution procedure
1 l'^
for equations (51) through (67) . If this value is stored during the itera-
9A
tive solution process it need not be recalculated to evaluate (,-r-z — )n
9cjT C^Y
This is also true of all derivatives with respect to A. , Y , C- and y which
appear below.
3Y
(3) Calculate (-)
9Y1
(4) Evaluate (-g— ) ^ accord±ng to.
9Y
3TC2 9TC3
(5) Calculate (-^—) , (-r^—)
"^jrj, A^» ^L-J^J '-'^jY -JT 1' 1 '
9TC2 3TC3 3TC4
(6) Calculate (Si) (-Si) () and
9TC2
For example, the expression for (-rr — )
dtj.i '
272
-------
3T y 3T 3A 3T 3Y
/_J^£\ _ /• u/s . / AN . /_k£\ . f •L--'\
3CjT ci'Y i i' ci'Y JT ci'Y 3Yi Ar ci'Y 8cjT
3F3
(7) Calculate C) according to:
3F 8T 3T 8T 9T
/ 3 \ _ y . r / ^^\ . /__ ^J.\ , / _. V^\ i /
' U; ; + ;
TC3 + TC4 + TC5>
(8) Calculate (——) , using the expression:
JT Y
» 3F
•
9A1 8Y1 8TC2 3TC3 ST
(9) Using the quantities (-, ( (), ( (
3TC5
and (-TT;—) from the iterative solution procedure calculate
3CX Y
oX_ i oX
f\ fi *\TT ^ T1 .IT^ f^/i i^^
dA^ di.. C2 C3 ( ) and ( }
3C. Y' 3C Y' 3C Y' 3C Y jT Y jT
For example:
3A, 3An 3A, 8C,
273
-------
3C 3C. 3C, 3C
(10) Calculate (^M , (^7TL-)V, (ar~)v, and (T~-)Y . For example,
iT iT ' iT ' iT
from equation (55) we have:
E12
r — / -L^'\ • p • T
L2 " ^2 ; 1 C2 '
Differentiating with respect to C.,_ yields:
3C E 2 3T 3C
Y+ Tc2 • fe
9A 3A3
(11) Evaluate (^7; — ) and (•-• — •) . By virtue of equations (59) and (60)
3CJT Y 3CJT Y
we have:
and
SA
3
3 A. 3 A 3 A
)y = 0, for J 1 2, (jj-^ = 0, for J * 3, (^
•J 1 J
Moreover, (-— )y = 0, for J 1 2, (- = 0, for J * 3, (- = 1 and
3T
(12) Calculate ( •" ) according to:
3CJT
8C1 8C2 9A1
< + (> - - 0.5
274
-------
(13) Calculate (-r^—) using the expression:
,4, _ r -1.17i .. 9u
3Y
(14) Calculate -7^— according to:
3C.T
3F 3F
*CJT=" ('*v>/(^r)'
(15) Calculate -r^— by applying the chain rule:
3C.. 3C, 3C,
For some values of j , not all of the calculations indicated above are re-
quired. For example, from equation (52), it can be seen that AI is not ex-
3A
plicitly dependent on C-^. Therefore, (-rr; — ) _ = 0 so subsequent calcula-
3A1 3T 9C3T C1'Y
tions involving (-77; — ) as a multiplicative factor are not required and
3C3T ClsY
were not included in the operational form of the procedure. The above out-
line shows the general sequence which was followed to obtain derivatives of
C. and Y with respect to total anion concentrations as well as with respect
to total cation concentrations.
9C±
It will subsequently be shown that all derivatives of the form — — ,
3C.T
9Ci 9Ai 9Ai
•57 — , r^ — , and — — are required for another purpose. These can all be
275
-------
obtained from quantities which result from the above procedure by straight-
forward application of the chain rule. For example:
3A 9A 9A
-*• _ / -*- \ i f -*-\
3C. 9A,
Derivatives of the form •—- and •—• were obtained using the same general pro-
, 96 OD
cedure.
The nested Newton-Raphson procedure for solving the system of chemical
equilibrium equations was programmed in F0RTRAN entitled SUBROUTINE EQUIL. A
listing of the program is given in Appendix L and the F0RTRAN names of quan-
tities discussed in this section are given in Appendix M. A number of tests
were made to insure that the calculations and programming had been performed
correctly. Among the tests performed were:
(1) a test to indicate that the method used indeed provided solutions to
the original system of equations (36) through (51),
(2) finite-difference approximations to the partial derivatives to indi-
cate that the partial derivatives were calculated and programmed correctly,
and
(3) counts of the number of iterations required for convergence for dif-
ferent values of the parameters in the equations. The results of the tests
indicated under (2) are discussed in Appendix N.
A final note is that Frissel and Reiniger (1974) indicated that the
Newton-Raphson scheme, as embodied in the simulation program, CSMP, failed to
converge for a system of equations of the Gapon type when the percentage of
adsorbed divalent cations was less than 50. No such difficulties have been
encountered with the present approach. There are two requirements that cer-
tainly must be met for convergence with the scheme presented here. They are:
(i) CIT > o .
and 5
(2) I a.'C > CEC.
1=1 ! 1T ~
If C = 0, the function F cannot be defined. If condition (2) is not met,
there are insufficient cations to satisfy the cation exchange capacity re-
quirement and equation (54) cannot be satisfied.
276
-------
Ion Transport Equations
The one-dimensional convection-diffusion equation (4) was derived ear-
lier from mass-balance considerations for steady-flow conditions in a homo-
geneous, inert, saturated porous medium. Five cations and three anions have
been selected for study. They were presented along with a system of related
chemical equilibrium-equations (36) through (51). In the present section a
mass balance approach is used to derive a system of finite-difference equa-
tions which can be used in conjunction with appropriate boundary and initial
conditions to characterize the concentrations of these eight ions as functions
of depth and time in a soil profile. The second-order explicit scheme al-
ready presented will be extended to the multi-ion case for this purpose.
The second-order explicit scheme was previously shown to possess the im-
portant advantage of a second-order accurate approximation to the time deriva-
tive, !£ , which appears in equation (4), It will be shown subsequently that
31
the second-order accuracy is retained when an extension of the scheme is made
to a non-linear, multi-ion system. Extensions of the Crank-Nicolson scheme
to non-linear, systems have been made but require iteration across time steps
(Carnahan, et al. 1969). Apparently, no extension of the Stone and Brian
scheme has been made to multi-ion systems, although the original investiga-
tors indicated some use of the scheme for non-linear, single ion systems
(Stone and Brian, 1963).
Physical Considerations—
The developments considered so far assumed that the primary mechanisms
of transport of an ion are convection, diffusion, and hydrodynamic dispersion.
Accordingly, a convective component of flux was defined as the product of the
volumetric moisture flux, q, and the ion concentration, C. In addition,
there was a diffusive flux component: -D • 3C, where D was defined as the
3 3l a
sum of the molecular diffusion coefficient, D , and the hydrodynamic disper-
sion coefficient, D, . Because of the assumptions of homogeneity, saturation,
and steady-flow, it was possible to treat the moisture flux, the water con-
tent, and the apparent diffusion coefficient as constant parameters. The
non-interacting, inert nature of the system led to a linear partial differen-
tial equation for its characterization.
For the present case the assumptions of homogeneity, saturation and
steady-flow are relaxed for greater generalization. Thus q and 6 are al-
lowed to vary with depth and time. Unlike the inert medium considered pre-
viously, the medium considered in this chapter is assumed to interact chemi-
cally with the ions in solution, so that two distinct ion phases, the ad-
sorbed phase and solution phase, are included (indirectly) in the analysis.
Of these two phases, only the solution phase is assumed to be mobile, so the
primary mechanisms of transport are again convection, diffusion, and disper-
sion. The apparent diffusion coefficients are different for different ions
due to differences in the molecular diffusion coefficients. Also, since the
apparent diffusion coefficients are dependent on the moisture content, they
are treated as tijae- and depth-dependent parameters. The admission of dif-
ferent diffusion coefficients for different ions could lead to artificially
277
-------
large charge separations occurring in the system if the force which dis-
courages such separations is ignored. Therefore, an additional component of
flux is included in the analysis to simulate the effects of electric poten-
tial gradients on the total flux.
The Ion-flux Equations—
There were ten solution-phase concentrations discussed in the develop-
ment of the chemical equilibrium equation. Different symbols were used for
cations and anions due to fundamental differences in the mathematical treat-
ment of these ions and their equilibrium relationships. For discussion of
the transport processes and subsequent programming, it is expedient to stan-
dardize the symbolism to be used in this development. The correspondence
between the symbols used previously and those to be used in the present de-
velopment are shown in Table 69,
For ions 3, 4, . . . , 7 (Column 3 of Table 69), which have only one
solution phase component, the equation which describes the convective com-
ponent of flux, j£. , is similar to the corresponding equation (5):
c»i
JCi = q Ci' i = 3' 4' ' ' ' * 7 * (73')
However, the additional solution components Xn.. and X?1 are associated with
ions 1, 2, and 8. Thus the appropriate convective fluxes for these ions are
given by the equations:
(74)
4 = -
JC2 = q •
' (C-L + Xu) ,
(c2 + xn) ,
(75)
VJi- i, i, J.
and
JC8 - 1 ' (C8 + Xll + X21> • (76)
The quantities in parentheses in equations (74), (75), and (76) are the total
solution concentrations of ions 1, 2, and 8, respectively. Thus, as the soil
solution moves, it transports not only the unpaired ions in solution, but
also the ion pairs whose concentrations are X1. and X--, for CaSO ^ and
MgSO,°, respectively.
The equations of diffusive flux for ions 3, 4, . . . , 7 are:
Jri = "Dri '
U1 Ul
where D-,. is the sum of the molecular diffusion coefficient for ion i and the
hydrodynamic dispersion coefficient for the soil system. The equation used
here to define D is based on a concept tested by Kirda et al. (1973) in a
study of chloride1transport under infiltration conditions. The defining
equation can be written:
278
-------
TABLE 69. CORRESPONDENCE BETWEEN SYMBOLS
Previous Use Ion
Cl <*"•
c2 Mg4*
C3 Na+
C4 K+
S M4+
A2 cr
A3 HC03~
An SO ~
1 4
o
X.n Ca SO.
11 4
X^ Mg S04°
Present Use
Cl
C2
C3
C4
C5
C6
C7
C8
X
11
X21
279
-------
D = 0.6 • e • D . + e • x • |v|s (78)
Ci i"1
where D . is the molecular diffusion coefficient of ion i in free solution, X
and c are parameters of the system, and v = q/9 is the mean pore velocity as
a function of depth and time. The 0.6 is a tortuosity factor. For ions 1,
2, and 8, the contributions of Xu and Xn to the diffusive fluxes are in-
cluded in the following equations:
(79)
3Z '
JC2 " ~DC2 ' 3~Z "X21 3Z
and
n « 11 21
JC8 = -°C8 ' 3T - DX1! ' "IT ~ DX21 ' IF" ' (80)
The influence of electric potential on the simultaneous flux of ions hav-
ing different diffusion coefficients has been discussed by deWit and van Keulen
(1972). According- to their analysis, the flux of ion i due to an elec-
tric potential gradient can be defined in terms of weighted average of con-
centration gradients. The equation used to describe this component of flux
is :
JCi = Dci ' v± ' 5 • Ci, i = 1, 2, . . . , 8, (81)
where
8 8C. 8
5 = { E V • Dc . —J-}/{T, V. . D_. • Cj} .
j=l J UJ ^ j=i J °3
Equations (73) through (81) describe the components of instantaneous
flux for ions 1 through 8 as functions of depth, time, concentrations, and
concentration gradients. It must be remembered that the depth and time de-
pendencies are due to depth- and time-dependent parameters occurring in the
equations. The total flux of the ions can therefore be represented by the
equation:
JCi = JCi + J?i + JCi> ± " *• 2 ..... 8 '
The Finite-difference Equations —
The problem for present consideration is similar in the following re-
spects to the initial-boundary value problem considered earlier. In both
cases it is desired to obtain predictions of concentration values in the
280
-------
interior of a one-dimensional soil column or profile as a function of depth in
the column and time elapsed from some starting time. This is to be accom-
plished with a knowledge of the concentration distribution (s) within the
column at the starting time and a knowledge of the concentration (s) and/or
fluxes at the boundaries of the column. The fundamental mathematical tools
available for solution of the problem are the equations describing ion flux
and a mathematical description of mass conservation.
Figure 111 illustrates the setting in which the ion transport equations
are to be derived. A schematic design of a one-dimensional soil profile of
depth L is presented and is divided into compartments of thickness Az , ex-
cept for the surface compartment which has thickness Az/2. The symbols,
C.T, , represent the total concentration of ion i at a depth Z = (k-1) • Az
1 J-tC
and time t.
The mass density p.(Z,t) (moles/cm soil) of ion i at any time t and
depth Z in the profile can be represented by:
P_.(z,t) = ciT(z,t) • e(z,t) ,
where C (Z,t) and 9(Z,t) are the continuous total concentration and water
content distributions, respectively, in the column. Therefore the total mass
j_ j_ "L
M. of ion i in the k compartment at time t is given by:
where A is the cross-sectional area of the column and:
_ Z = (k-%) • Az
8CIT = A • Az ' f 9(Z't) ' CiT(Z»^ dZ
IT A Az z = (K_3/2) iTAz
is the average density for the k compartment. Assuming that 0 • C, varies
smoothly as a function of Z, and that Az is sufficiently small, then to a
close approximation:
MiT ~~ A ' Az ' 6k ' CiTk •
Differentiating the above equation with respect to t yields the approxi-
mate instantaneous mass rate of change for the compartment at time t:
,8M«\t „ , A
-------
Soil surface: z=0
"ill
Az
,t kth
JiTk-l com-
partment
z = (k-l)Az
ct
iTk+1
z = Lr
JiTM-l
Figure 111. Schematic diagram of the finite difference grid.
282
-------
where (JT-)£ i and (Jr.)5,i,, represent the flux of ion i at the top and bottom
of the compartment, respectively, as indicated in Figure 111. Since the rate
of change of mass of ion i in the compartment at time t is equal to the net
flux of ion i into the compartment multiplied by the compartment cross-
sectioned area, we have:
A • Az • — j~= = A '
in the absence of sinks and sources. The above equation can be expressed in
the equivalent form:
where:
C
^t 1 T t T t i.Tk
Gik = ~t
ek
As is indicated by equations (73) through (82), a precise evaluation of
the total fluxes (J^.)t and (Jp.jfjj would require knowledge of the con-
Li -
, _j^
centrations, C., and of l?he partial derivatives, 9C./9Z, at time t and at the
upper and lower boundaries of compartment k. For practical reasons it is
desirable to approximate these quantities in terms of the concentrations,
C., at the midpoints of the compartments. The following equations provide
the desired approximations:
cfc - cc
,TT t ^t ik ik-1 t . ,,t , ^t rt
(JCi>k-% ' -°Ci kJa -- ~z - + V% ci k-Ja + Dci kJa ' vi • ?k-%
ci k-Jg' i = 3) 4 ..... 7) (84)
ct _ ct
lk x
ci k-
183
-------
t _ t
D11 , . Il k -11 k~1 + D^ni , ' Vn 5? ! ' C!T . ! Cgs^
X11 k-% Az Clk-lg 1 k^s 1 k-% , <-°-3''
,TT nc . ^2k "2k-l , _t . /rt t
(JC0 k-3j = "DC2 k-Js ^ qk-% (C2 k-Js + X21 k
-
21 k 21 k-1 , _t „ _t . rt
- * C2 k~J
and t t
CTT ^ - nfc . °8 k " C8 k-1 t .,t t t
(JC8 k-Js ~ C8 k-3s Az • qk-% (C8 k-% + Xll k-% + X21 k-
-
11 k ll k-1 t
~
Xll k-Js Az X21 k-Jg 21 k 21 k-1
Az
C8 kJs 8 8 k-% '
The terms on the right-hand sides of (84) - (87) which are subscripted with
k-% are evaluated as follows :
(88)
Where Y- = 6XP t-1." • U / (1 + y)] and
284
-------
Finally, we have:
• 0.6 • D i + A] • [2 • q£ j,/(e£ 1 + 0Jp] (89)
(5-20)
Equations (84) - (87) are spatial approximations where second-order Taylor's
approximations have been utilized for partial derivatives of the form . ik.
t T,t 8Z
and for the concentrations C., , . The equations defining (J_.), i ,
Ik-Js T t 2
which would correspond to (84) - (88) for (Jc-)k_^ , need not be written down
since they can be obtained by replacing k with k+1 in (84) - (88).
At this point, sufficient information has been provided to enable a
rough approximation of the total concentrations at time t + At using values
of the total concentrations at time t. The sequence of operations that would
be required to accomplish the approximation is: (1) Use the previously
presented Newton-Raphson procedure to evaluate the solution concentrations
C., in terms of C , and Q, for i = 1, 2, . . . 8, and k = 1, 2, . . . , M.
ILK. 11K. K
(2) Use the resulting values of C., to evaluate the total fluxes at the com-
T t
parttnent boundaries, (Jr.), i, for k = 2, 3, . . . , M. (3) Substitute the
L"IL iC—^
total fluxes into equation (83) to evaluate G . (4) Substitute
IJX
~ CiTk^At f°r ^3CiTk/3t')t ln e4uation (83a) and solve the resulting
equation for C._ . However, as is the case for the explicit scheme, approx-
imating (9c1Tk/9t)t wltn (CiT]lCt ~ Cixk^At ls °nly first-°rder correct. In
order to achieve the desirable second-order accuracy demonstrated previously
for the single-variable, linear equation, the derivative must be carried one
rlP t"
step further. A Taylor's approximation to the time derivative, ( iTk)
9t
which appears on the left-hand side of equation (83), can be written:
SC t Ct+At - C* S2f
( iTk)t = LiTk CJTk At . / CiTk, . _,. 2,
~TT At --- 2 (~7^~) 0(At } '
Letting t denote the time at the beginning of a time step, t <_ t <_ t + At,
and substituting G^P. for (3C , , )t<3 from equation (83a) , we have to a close
1K
approximation:
r\ C t*
285
-------
The term in brackets in equation (90) is an approximation to the value of
Gt for t = t0 + At/2, i. e.:
J\p t
t o+At/2 t + At . ik, o ^ (91)
ik ik 2 3t
Two approaches may be taken to evaluate G*+ : U) Evaluate (3Gik/9t) °
ik
and Gto and substitute directly into the above expression or (2) Define an
iK.
auxiliary function, G.5 , such that G.5 +At/2 = G^°+At/ and use the auxil-
j_/\t- /7
iary function to approximate G.° . The second alternative may appear un-
warranted, but the reasons for suggesting such an approach will subsequently
be discussed. Attention is not directed toward obtaining an expression for
ik/9t , to be used in the first approach.
From equations (83b) through (89), it can be seen that G is dependent
lie
on the following time-dependent variables: C.T, ; C., , C,,-, and C., .. , for
j = 1, 2, . . . , 8; 9k, ek_r 6k+1; qk_!g;and q^; and 3ek/3t. However,
there is a hidden dependence of G., on 9, , 9,_1 , and 9, .. due to the depen-
dence of the solution concentrations on 6 in the chemical equilibrium equa-
tions (51) through (67). Consideration of the above time-dependencies re-
8Gik 'o
suits in the following expression for (— — ) :
o t
3G t 9G., t 3C. t , 3G. t 39
o \-o . . 8Glk 'o k^o . 3Gik /o
1=k~L
36 i t
In equation (92) all derivatives of the general form, 3Gik/3( ), can be
readily obtained by applying conventional rules for differentiation to the
286
-------
. m f\ T f\
defining equations for G., and the total fluxes, (Jc-)k_^ and (Jc-)i,44-> If
it is assumed that the solution concentrations are in equilibrium with the
total concentration at time t, as is the case here, the derivatives of the
t
form (9C.../8C _- ) can be obtained in the manner outlined in Section 5. The
'o fco
derivatives (9C -/8t) can be evaluated from equation (83a) in terms of G , ,
and the time-rate of change of water content (99-. /8t) could normally be ob-
tained from any numerical solution of the one-dimensional moisture-flow equa-
tion used to supply the water contents 9,. The derivatives (3q, ^/3t) and
n 9 r»
(8 0k/8t ) , however, may not, in. general, be available and would have to be
calculated or estimated at the expense of additional effort. This difficulty
can be avoided by defining an auxiliary function G^f- which is identical to
t "t
G., except that G., is defined in terms of the values of the water contents
IK. IK. r.
at the middle of a time step. G.. may be represented as follows:
liC
't _ f t t t t t0+At/2
bik ^ik^iTk' Ljk' °jk-l' Ck+l' Vl
t0+At/2 to+At/2 t0+At/2 t0+At/2
9k-l ' Vl ' qk-4g ' \4% ,
for j = 1, 2, . . . , 8 and for t <_ t <_ t + At. The argument list is used
't ° ° t
to indicate that G is defined by equation (83b) except that 0, and
(86 /8t)t in equation (83b) are replaced by Q^o+^/2 and (3e /st)to+At/2
"• . K, K,
and that the coefficients D x which appear in equations (84) through (89)
, . i rt L*1K~^
are replaced by DQ°k_i • With this in mind it can be seen that over the
time step t f_ t <_ t + At, G., is time-dependent only by way of its depen-
O O I.K.
dency on the concentrations C^', and C.,, for j=l,2, . . . ,8. Moreover,
G^ agrees with G^ when t = tQ + At/2, i.e. G^o+At/2 = G^°+At/2. Since an
approximation to G is required only for t = t + At/2, a Taylor's approxi-
mation to Go can be used effectively to approximate G ° , as
follows :
t0+At/2 = 't0+At/2 = 't0 At .
Ik ik Uik + 2
287
-------
3C... t 36, t ,
- ° • (-—) °» +0(At2). (93)
Due to the treatment of 0,, q, 19 q, ,, , and 90k/8t as constants over the time
K k."^ K"^5 r\ o
step, the derivatives 3q ^/9t, 3qk+^/3t, and 3 9k/3t do not appear in the
above equation. However, an additional problem arises due to the appearance
of (3C T1/8t)to = GCo in addition to G.f0. Strict substitution of 0^° for
nTl nl ik , nl
(3CnT1/3t) o would require the evaluation of both G . and G for all n and 1.
** *• n Tit" t"
This difficulty is avoided by -substituting G^0 for (——-) ° rather than G^,
The argument for doing this is that, due to the equality of Gnl° with
Gto and the differentiability of both functions, an upper bound for the
nl
absolute value of the error which arises from this substitution is (neglect-
ing terms of order greater than 1 in a Taylor's expansion of the two func-
tions) proportional to At. Using the term (3G . /3C , )fc° ' (3C ,/3t)to to
t+At/2
illustrate the effect of the substitution on the approximation to G ,
we have:
•"*- A*- -ilr r\ i-
/•"I ^* ^ I t-1 I- t / -L-IV\ \J / _ ^ .» \ ,
9 '«• A-I-
terms} + 0(AtZ) = G.° + &• -
0(At2) = G'fc° + ~2 ' {(jT^") ' (G-'° + °(At) + °ther
+ other
terms} + 0(At2) ,
so that the order of accuracy of the approximation to GM is not im-
't 't t *
paired by substituting G^o and G^° for-(3C±Tk/3t) ° and (3C /3t) o ,
respectively, in equation (93).
288
-------
•*t
The water content and flux terms which are required to evaluate G. ° and
t/2 t0+At/2 t0+At/2 t0+At/2 (3ek/3t)t0 t0+At/2 d X
lk k~l ' k ' k+1 ' vdek/dt; , qk_1 , and
+At/2 ~ _
q, °j . These quantities are readily available from many numerical solu-
tions of the moisture flow equation or may be easily approximated from other
quantities that would be available from such solutions.
Finally, the equation used to obtain C ° , can be written:
X .L iC
where:
.
t0
3C.. t 30. t
> ° ' °>} • (95)
k -t
We note that, for 9n = constant, ~- = — ~* = — —^ = - ^ = 0 and G.. ° =
K. ot at at _ L- IK
t
G.° so the use of equations (94) and (95) are equivalent to using equations
(90) through (92) for steady-flow conditions.
For purposes of computation, equation (95) can be represented in the al-
ternative, but equivalent, form:
ftp t"
3G., t 361 t
> ° • °} • (96)
The following equations are used to approximate constant concentration
boundary conditions at Z = 0 (k = 1) :
t+At t
289
-------
and
for t >_ 0 and i = 1, 2 8. To approximate a zero-gradient condi-
tion foe". /9ZL , = 0) at the lower boundary, the following equations are
i Z—L
used:
Ct0+At = Ct0+At
and
G t ^--IT-I 9
x M iM~ X
for t >_ 0 i = 1, 2, ... 8.
Calculation Procedure—
Given below is a brief outline of the calculation procedure for advanc-
ing the total concentrations, C , , in time,
(1) Set t = 0.
(2) Supply values of the total concentrations C.—, , for i = 1, 2, . .
. , 8 and k = 2, 3 M-l and of the solution concentrations
Cil' Xlll' X211, for i - 1, 2, , . . ,8.
(3) Supply values of e£+At/2, q^t/2, and (99./9t)t for k = 2, 3, . .
. , M. k ^ k
(4) Calculate the coefficients D~" according to equation (89) .
Similarly, calculate D At/2 " "
(5) For k = 2, 3, . . . , M-l, calculate cjk, X^lk, and X*^ in terms
of CiTk and 9fc according to the procedure outlined previously.
Also, calculate all derivatives of the form (9C.,/9C, , ) and
^ IK j Tk
(9C., /99k) as described previously.
(6) Calculate the quantities (jj.)?, for k = 2, 3 ..... M accord-
^ t t
ing to equations (84) through (89) except that D x , D^ l
Cik— -^ XHk — ^
D 2 , _j^, and qk_^ in those equations are replaced by D ., / ,
DXllk-^' °X21-3- ' and qk-^- ' resPectively' Also calculate the
290
-------
following derivatives:
and 8{(J .), j ]
for k = 2, 3, . . . , M; i = 1, 2, . . . , 8; and j = 1, 2, . . . ,
8.
(7) For k = 2, 3 M-l, calculate G., and the derivatives of
G.t with respect to CjTk, C.^, CjTfcfl. 9k, 9^. and «
For example:
r a A
ilk , kst+At/2
,t+At/2
\
and ,
3CjTk-i
(8) For k = 2, 3 ..... M-l and i - 1, 2, . . . , 8, calculate
G., according to equation (95) and update the total concentrations:
t+At t t+At/2
CiTk ' CiTk + At Gik
(9) Set t = t + At.
(10) For steady-flow conditions, repeat steps (5) through (9) until t
reaches a desired maximum value. For transient flow conditions
repeat steps (3) through (9) until t reaches a desired maximum
value .
The above sequence of calculation was programmed in F0RTRAN. The re-
sulting program, exclusive of the calculations of solution concentrations and
derivatives of solution content ratios [step 5], is entitled SUBROUTINE SOIL.
291
-------
A listing of the program can be found in Appendix L.
Testing £f_ the Model
Introduction—
A computer model was constructed to simulate the simultaneous transport,
by combined convection and diffusion processes, of five cations and three
anions in a soil-water system. Instantaneous, local, chemical equilibrium
among the various ions, and between the ions and the soil matrix, was assumed
for the development of the model. The specific equilibrium phenomena con-
sidered were those of cation exchange and ion pairing. The effects of solu-
tion ionic activity on chemical equilibrium were also considered. The mathe-
matical equations used to describe the equilibrium are similar to those pre-
sented by Dutt, et al. (1972b). No consideration was given to interactions
between anions and the soil matrix or to solubility-precipitation reactions.
The method used to solve the system of chemical equilibrium equations was dis-
cussed previously.
The primary mechanisms of ion transport which were considered in the
development of the model are those of convection, molecular diffusion, and hy-
drodynamic dispersion. To counter-balance the effects of different molecular
diffusion coefficients at low flow velocities, an additional (emf-induced)
component of flux was included in the development. The equation which was
used to describe this component of flux is similar to that used by deWit and
van Keulen (1972). The mathematical equation used to describe the effects of
diffusion and dispersion as a function of moisture content and mean pore ve-
locity is based on an approach taken by Kirda, et al. (1973) . No considera-
tion was given to the effects that non-uniform solution density would have on
the transport process. In order to predict the total concentrations of the
eight ions as functions of time and depth in a soil profile, finite-differ-
ence equations were developed from considerations of total flux mass-balance.
It was previously shown that calculational procedure used to solve these equa-
tions requires evaluation of partial derivatives of solution concentrations
with respect to total concentrations but does not require iteration across
time steps since the procedure is explicit.
Structurally, the computer model consists of two subroutines, SOIL and
EQUIL, and a prompting program. The prompting program serves as a vehicle
for reading in system parameters, initiating the execution of SUBROUTING SOIL,
and printing out calculated information at specified times. SUBROUTINE SOIL
provides estimates of the total concentrations of the eight ions at each point
of a finite-difference grid at time t + At based on values of the solution
concentrations and partial derivatives of solution concentrations with respect
to total concentrations at time t. The calculation of solution concentra-
tions and partial derivatives, as functions of the total concentrations, is
carried out in SUBROUTINE EQUIL.
In previous discussion the variables which denote solution and adsorbed
phase concentrations were identified with eight specific ions: Ca4"1", Mg"*"*",
Na+, K+, NH^+, S0^~ , Cl~, and HCO ~ However, the model takes on a more
292
-------
general character if the mechanisms which distinguish the roles of these ions
are identified. The monovalent anions, Cl and HCO ~, are assumed to inter-
act chemically with the remaining ions only through their influence on the
activity coefficient y. This can be seen from equations (31), (43), and (51).
The monovalent cations Na+, K , and NH,+ are distinguished from the divalent
cation, Mg"1"*", by their valences, by the type of cation exchange equation used
to describe their interaction with Ca"1"1" (see equations (44), (45), (46), and
(47) ), and by their lack of interaction with S0,~. The monovalent cations
are mutually distinguished only by the values of the exchange coefficients
E...,, E..,, and E..,-. The divalent cations are mutually distinguished by the
values of the inverse dissociation constants, D-- and D-_, and by the value
of the exchange coefficient E „.
In the transport part of the model the ions are mutually distinguished
by their valences and diffusion coefficients. The ions Ca , Mg , and S0,=
are distinguished from the others due to assumed transport of ion pairs con-
taining these three ions, as can be observed from equations (85) through (87).
The above observations were taken into account in the programming of the
computer model. The ion valences, exchange coefficients, inverse dissociation
constants, and molecular diffusion coefficients are included in the list of
input parameters for the computer model which appears in Appendix M. The
total numbers of divalent cations, monovalent cations and monovalent anions
for a given run, as well as an indicator as to the presence or absence of the
divalent anion, S0,=, are also included in the list. The model can be used
with reasonable efficiency for simulations of the simultaneous transport of
as few as two cations and no anions. For runs using fewer than five cations
or three anions, extraneous calculations that would normally be performed in
SUBROUTINE SOIL, with zero values for concentrations of ions not considered,
are entirely skipped. The calculations of unnecessary partial derivatives in
SUBROUTINE EQUIL are also avoided in these cases. Only the Newton-Raphson
procedures for obtaining C.. and y in SUBROUTINE EQUIL are carried out with
zero values of the total concentrations of ions which are considered absent
for a particular run.
The assumption of a unit ionic activity coefficient is sometimes made
when soil solution concentrations are low. Provisions were made in the pro-
gram so that this assumption can be used if so desired. In such cases, only
one pass is made through the outside (y) loop of the Newton-Raphson procedure
for calculating solution concentrations in SUBROUTINE EQUIL.
The use of the model for cases where fewer than eight ions are consi-
dered, or where unit activity coefficients are assumed, is further discussed
in Appendix M. A complete list of required input for the model can also be
found there.
In order to avoid unnecessary repetitive calculations of solution con-
centrations, flux terms and partial derivatives of solution concentrations as
functions of the total concentrations, provisions were made in the computer
program to skip these calculations at grid points where the predicted change
in all total concentrations over a time step is less than some predetermined
293
-------
value. Shamir and Harleman (1967) suggested the use of a similar device in
conjunction with the Stone and Brian scheme. The approach used for the pres-
ent model is outlined in Appendix M.
Simulation Runs Involving Two or Three Cations—
Effects chosen for observation—From the preceding discussion it is evi-
dent that there are a large number of system parameters whose combined influ-
ence on simulations produced by the model could be tested. For the present it
was decided to examine the effects of varying some of the parameters in cases
where only two or three cations and from zero to two anions were considered
simultaneously in an assumed homogeneous soil column under steadyflow condi-
tions. Specific parameters and effects chosen for observation are: (a) soil
cation exchange capacity, CEC, (b) soil moisture content, •&, (c) the mean-pore
velocity to apparent diffusion coefficient ratio, r, (d) the cation exchange
coefficients, E,2 and E,-, (e) the effect of the solution activity coefficient,
Y, through its influence on the cation exchange relationship equation (56),
and (f) the magnitude of the total cation concentration of the soil solution.
Solution concentration pulses—Solution concentration pulses were used as
the means of manifesting the influence of these parameters and effects on sim-
ulated results. The following example illustrates the type of pulse which was
used for this purpose. A homogeneous soil column, having bulk density, p, ,
moisture content, -0-, and cation exchange capacity, CEC, is assumed to initial-
ly contain adsorbed cations of only one species, cation 1. Thus there are CEC
meq/lOOg or Q =p • CEC/(20O-9-) moles/liter of cation 1 occupying the cation ex-
change complex of the soil. In addition there are C,T moles/liter of cation 1
uniformly distributed in the soil solution. It is further assumed that there
are A2 =2- C, ^ moles/liter of monovalent anion 2 in the initial soil solution.
At time t=0, a slug of solution of different ionic constituency is introduced
into the column at the soil surface and is allowed to begin to displace the
original soil solution at a constant velocity, V=q/-9-. The depth of the slug,
in cm H20, is V-t , where t is the time that the slug solution is assumed to
be in contact with the soil surface. The slug solution is to be void of ca-
tion 1 and is assumed, instead, to contain C2g moles/liter of divalent cation
2 and C3g moles/liter of monovalent cation 3. In addition there are either
A2S=2:C2S+C3S moles/1:i-ters °f monovalent anion 2 or A~ =2-C2s+C3s moles/liter
of anion 3 present in this solution. At time t , the slug is followed by a
solution of the same ionic constituency as the Original soil solution and
the displacement process is continued at the velocity, v.
The geometric shape of the concentration profiles of cation 2 and 3 with-
in the soil column for times greater than t will depend on a number of fac-
tors, including the magnitude of t , the re?ative preference of the cation
exchange complex for cations 1,2 afid 3, and the original concentrations of
the respective cations in their respective solutions. However, provided vt
< LC, the graphs of C2 and C3 versus depth in the column will have a pulse- P
shape. The simulation of such pulses offers a rather stringent test of
the performance of the model due to the existence of concentration fronts at
the leading and trailing edges of the pulses. In addition, the effects of
294
-------
varying parameters can be observed on the height, spread and symmetry of a
pulse at a given time of observation.
Simulated tests — For each simulation run made, a column length, L , of
approximately 20 cm was used. The exact column length can be computed from
the grid spacing, Az, and the number of grid points, M, which were used for a
particular run, according to: L = (M-3/2) • AZ. See Figure 111. For most
of the runs, the value of M used was 80.
The velocity, V, was established at 0.01 cm/min for all of the runs by
adjusting the uniform volumetric moisture flux, q, so that V = q/9 = 0.01.
The pulse time, t , was 300 minutes and results corresponding to simulated
times of 400 and 1600 minutes were observed for each run.
Particular values of the velocity to apparent diffusion coefficient
ratio, r, were established by using D . = 0, for cations 1, 2, and 3 and
anions 2 and 3, 6 = 1.0 and A = r in equation (78). For each run, the time
step size, At, was chosen to establish a desired value for the quantity,
3 = V • At/AZ.
The values of C.^, A2][, A , C2 , C^ g, A , E12 , E13> 9, CEC, r, AZ and
3 which were used for the runs .for which results are presented » are shown in
Table 70 along with the run numbers R-l through R-23. The runs for which the
effects of solution activity were considered are indicated by a C under the
column headed y- Those runs for which a 1.0 occurs in this column were made
with y = 1«0 for all depths and all times.
Results and Discussion —
The calculated values of the solution concentration corresponding to ca-
tions 2 and 3 and anion 3 were normalized and plotted as C«/C« , CL/C_ , and
A /A versus depth in the soil column. The resulting graphs are shown in
Figures 112 through 131. In each of these figures, C/C~ represents
C /C_ , or A, /A~<,, depending on which ions were included for the run correr-
sponding to that figure. Figure 112 corresponds to runs R-l through R-3,
Figure 113 corresponds to R-4 and R-5 and Figures 114 through 131, respective-
ly, correspond to runs R-6 through R-23 .
Comparison of results from two-cation problems with an independent nu-
merical solution — For runs R-l through R-8, which were made with only cations
1 and 2 or cations 1 and 3 present, the calculated values were compared with
results obtained from the numerical solution which is presented in Appendix
J. The approach to solving a two-cation problem with this alternate method
is fundamentally different from the approach which was outlined in Section 6
for solving multi-ion problems, because a finite-difference approximation to
only one (as opposed to two) partial differential equation is required. All
results from the independent numerical solution were obtained using a grid-
spacing of 0.2 cm and a time-step size of 10 minutes (B = 0.5).
Runs R-l through R-5 (Figures 112 and 113) were made with 9 = 0.5, CEC = 10.0,
Y = 1.0, r = 10.0, E - = E _ = 1.0, and C^ = 0.13. Runs R-l, R-2, and R-3
295
-------
TABLE 70. VALUES OF THE INPUT PARAMETERS USED IN THE TEST RUNS
Run
Rl
R2
R3
R4
R5
R6
R7
R8
R9
RIO
Rll
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
C1I
0.130
It
II
t!
M
0.050
"
0.025
"
0.050
"
"
ii
0.100
II
0.050
0.100
0.050
it
0.100
II
It
II
C2s
0.0
11
ff
0.130
It
0.050
0.0
"
0.025
0.050
0.025
0.050
"
0.050
ii
0.025
0.050
0.025
n
0.050
tt
"
"
C3s
0.260
"
"
0.0
11
"
0.100
0.050
0.0
0.100
0.050
0.100
"
0.100
It
0.050
0.100
0.050
ti
0.100
II
II
It
A2I
0.0
II
It
tl
II
It
It
II
II
II
II
11
II
II
0.200
0.100
0.200
0.0
n
n
n
"
"
A2s
0.0
"
"
"
"
11
"
n
tt
"
ti
11
n
n
n
11
it
it
ti
"
n
n
11
A3I
0.0
It
"
It
II
11
II
II
II
II
II
II
tt
tl
tl
tf
II
11
It
It
It
II
tl
A3s E12
0.0 1.0
II II
II II
tl II
It It
II It
II It
II It
II II
II It
11 It
tl II
tt II
II II
0.20 "
0.100 "
0.200 "
0.0
ti it
0.5
2.0
0.0
" "
E13 e
1.0 0.50
n n
n n
n it
n n
n n
M n
ii n
ti ii
n n
11 n
n n
" 0.25
11 0.50
tt ii
n n
n n
n n
it n
n n
n tt
0.5
2.0 "
CEC
10.0
n
"
11
"
tt
n
ii
it
n
n
20.0
10.0
ii
n
n
11
tt
"
ii
n
ii
n
Y
1.0
it
"
"
it
it
ii
n
tt
ii
n
n
tt
tt
c
It
tl
1.0
tt
tl
11
II
II
r
10.0
II
II
tt
II
tt
It
11
It
II
tl
It
II
II
11
tt
5.0
it
20.0
10.0
"
"
tt
Az
1.0
0.5
II
1.0
0.5
0.25
tt
"
ti
"
it
n
"
ti
"
tt
"
11
n
it
it
n
it
6
0.1
"
0.2
0.1
0.2
0.5
11
it
ii
"
n
n
n
tt
"
"
11
tt
11
"
"
it
"
-------
AZ = I.O, AT =10
AZ=0.5, AT =5
AZ=0.5 , AT = 10
INDEPENDENT SOLUTION
10 15
DEPTH (cm)
20
Figure 112. Simulated concentration pulses for cation 2 for conditions of runs R-l,
R-2 and R-3.
-------
vO
00
D AZ= 1.0 , AT= 10.0
• AZ= 0.5 , AT=IO.O
INDEPENDENT SOLUTION
3. a
10
DEPTH (cm)
15
20
Figure 113. Simulated concentration pulses for cation 3 for conditions of runs R-4
and R-5.
-------
I.CH
0.5-
o CATION 2 (DIVALENT)
INDEPENDENT SOLUTION
10
DEPTH (cm)
15
20
Figure 114. Simulated concentration pulse for cation 2 and for the conditions
of run R-6.
-------
I.Oi
0.5-
o
o
7Co
CATION 3 (MONOVALENT)
INDEPENDENT SOLUTION
10
DEPTH (cm)
15
20
Figure 115. Simulated concentration pulse for cation 3 for the conditions
of run R-7.
-------
I.Ch
0.5-
yCo
a CATION 3 (MONOVALENT)
INDEPENDENT SOLUTION
10
DEPTH (cm)
15
20
Figure 116. Simulated concentration pulses for cations 2 and 3 for the conditions of
run R-8.
-------
1.0
0.5
C/Co
0
CATION 2 ( DIVALENT)
INDEPENDENT SOLUTION
0
10
DEPTH (cm)
15
20
Figure 117. Simulated concentration pulse for cation 2 for the conditions
of run R-9.
-------
u>
o
1.01
0.5
7Co
0
a CATION 3 (MONOVALENT)
o CATION 2 (DIVALENT)
a a
°oa
10
DEPTH (cm)
15
20
Figure 118. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-10.
-------
UJ
o
I.Oi
0.5-
CD
0 o
o o
o
o
o
on
ao
D
D
D
D CATION 3 (MONOVALENT)
o CATION 2 ( DIVALENT)
10
DEPTH (cm)
15
20
Figure 119. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-ll.
-------
UJ
o
Ln
I.On
0.5-
o-
oo
D CATION 3 (MONOVALENT)
o CATION 2 ( DIVALENT)
O D
10
DEPTH (cm)
15
20
Figure 120. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-12.
-------
OJ
o
1.0
0.5H
'Co
00
a CATION 3 ( MONOVALENT)
O CATION 2 ( DIVALENT )
o a
o a
10
DEPTH (cm)
15
20
Figure 121. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-13.
-------
O
—4
i.Ch
0.5-
'Co
CP0
° O
o o
a CATION 3 (MONOVALENT)
o CATION 2 ( DIVALENT )
o a
10
DEPTH (cm)
15
20
Figure 122. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-14.
-------
1.0
0.5-
O
00
0
o°o
o o
Q
O
O
„ O
a CATION 2 ( DIVALENT )
o CATION 3 ( MONOVALENT)
A ANION 3 ( MONOVALENT)
A
A
A
A
A
A
A
A
A
A
A
A
10
DEPTH (cm)
15
20
Figure 123. Simulated concentration pulses for cations 2 and 3 and anion 3 for con-
ditions of run R-15.
-------
I.Ch
0.5-
U)
o
0
O
00
a CATION 3 ( MONOVALENT )
O CATION 2 ( DIVALENT )
& ANION 3 ( MONOVALENT)
A
A
A
A
A
A
A
A
A
A
A
A
10
DEPTH (cm)
15
20
Figure 124. Simulated concentration pulses for cations 2 and 3 and anion 3 for con-
ditions of run R-16.
-------
1.0
0.5
0
o
o
o
o
o
0°°
O ,-, n O
8
D CATION 3 (MONOVALENT)
o CATION 2 ( DIVALENT )
A ANION 3 (MONOVALENT)
A
A
A
A
A
A
A
A
A
A
D
D
D n „
10
DEPTH (cm)
15
20
Figure 125. Simulated concentration pulses for cations 2 and 3 and anion 3 for con-
ditions of run R-17.
-------
0.5-
'C.
n CATION 3 ( MONOVALENT)
o CATION 2 ( DIVALENT )
n
D
a
a
o a
0 a
D
a
o
D
a
a
D
a n
10
DEPTH (cm)
15
20
Figure 126. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-18.
-------
0.5
o
o o
o
a CATION 3 { MONOVALENT)
o CATION 2 (DIVALENT)
ft
a
a
a
a
a
a
a
D
a
a
o
ODD
10
DEPTH (cm)
15
20
Figure 127. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-19.
-------
I.Oi
0.5-
oo
o
o
o
o
o
a
a
n
n
o n
crip
n CATION 3 (MONOVALENT)
o CATION 2 (DIVALENT)
D
10
DEPTH (cm)
15
20
Figure 128. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-20.
-------
T = 400
o
1.0
0.5
'Co
o
T=I600
°°°0
o
° D
3 O n
cP
a o
a
a
rff
O CATION 3 (MONOVALENT)
o CATION 2 ( DIVALENT )
o
o
D
D
o
10
DEPTH (cm)
15
20
Figure 129. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-21.
-------
1.01
0.5-
C/r
OD
a a
a
o
o
a
D
a
a CATION 3 (MONOVALENT)
o CATION 2 ( DIVALENT)
10
DEPTH (cm)
15
20
Figure 130. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-22.
-------
01
i.o-
0.5
0
o°o
o
Q CATION 3 (MONOVALENT)
o CATION 2 (DIVALENT)
D
10
DEPTH (cm)
15
20
Figure 131. Simulated concentration pulses for cations 2 and 3 for the conditions
of run R-23.
-------
were made with C =0.13 and cation 3 absent. For runs R-4 and R-5 cation
2 was omitted ana C£s was 0.26. The results from R-l are for AZ = 0.5. There
is reasonable agreement between the results obtained from the model and those
from the independent method, although there is an insufficient number of
points to adequately define the simulated pulse configuration after 400 min-
utes of simulated time. For the larger value of AZ, the pulses simulated
with the model show considerable smearing and deviation from those obtained
by the independent method. Run R-3 was made with 8 = 0.2. The results indi-
cate almost no sensitivity to 8 in this range.
Similar sensitivity to grid spacing, A z, can be observed in Figure 113
for runs R-4 and R-5 with monovalent cation 3. For AZ = 1.0 and 8=0.1
(R-3) the agreement between the model predictions and the independent method
predictions is poor. Much better agreement can be seen for AZ = 0.5 and 8 =
0.2.
Runs R-6 and R-7 were made with C.., = 0.05. For run R-6, C™ was 0.05
with C- absent and for R-7, C«_ was 0.10 with C~ absent. Runs R-S and R-9
were made with C = 0.025. For R-9 €23 was 0.025 and for R-8, C was 0.05.
For each of these runs AZ was 0.25 and 8 was 0.5. In each case there is ex-
cellent agreement between the results calculated with the model and those ob-
tained from the independent solution method as can be observed in Figures 114
through 117 .
Due to the good agreement between model predictions, for AZ = 0.25 and
8 = 0.5, and those obtained independently, and to the reasonably detailed
pulse definitions obtained with AZ = 0.5, these values were selected for the
remaining runs.
To aid in the analysis of the various effects which were investigated,
smooth curves were drawn through the calculated C- /C2cj CQ/CQO anc* A.,/A_^
points which represent the pulses which appear in Figures 114 through 127.
From these graphs estimates were made of the values of certain dimensionless
numbers, which" to quantify certain characteristics of the simulated pulses
that can be observed qualitatively from the figures. The relative pulse
heights were calculated according to:
h = C /C
r max o
where C represents the estimated maximum at the time of observation value
of C , S^ or A_, and CL represents the correspond
C2S' C3S' or ATS in t*ie incomin8 slug of solution.
The relative distance traveled by each pulse was calculated according
to:
D,. = (D + Vtp/2)dq = (d + d^ /2)/d_
re & c up a
max max
where d is the value of the z coordinate where pulse height was deter-
cmax
317
-------
mined. The distance, d , is the distance traveled by an imaginary point in
the soil solution from time, t - 0, up to the time of observation. For V -
0.01 cm/min. and time of observation = 1600 min., dg has the value of 16.0
cm. The distance, d /2 = Vtp/2, allows t /2 minutes for the center of the
original solution slug to reach the columnPsurface. For all of the runs with
Vt /2 = 1.5 cm., two other numbers were recorded to indicate the relative
symmetry and spread of the pulses. The relative half-pulse widths SR and SL
were calculated according to:
SL=tdc -(dc >L"
-------
TABLE 71. CHARACTERISTICS OF THE ION PULSES FOR THE RUNS LISTED IN TABLE 70. THE PARAMETERS GIVEN IN-
CLUDE THE RELATIVE DISTANCE THE PULSE TRAVELED (d ), THE RELATIVE PULSE HEIGHT (h ) , THE RELA-
TIVE TAILING PULSE WIDTH AT HALF LENGTH (S_) AND THE RELATIVE LEAD PULSE WIDTH ATrHALF HEIGHT
Cation 2
Run
R 6
R 7
R 8
R 9
RIO
Rll
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
d
r
0.35
0.25
0.35
0.34
0.24
0.24
0.47
0.48
0.33
6.48
0.35
0.33
0.40
0.55
0.47
0.47
hr
0.35
0.27
0.37
0.39
0.29
0.29
0.50
0.51
0.39
0.37
0.30
0.50
0.41
0.60
0.51
0.49
SL
0.73
0.53
0.70
0.67
0.53
0.53
0.80
0.80
0.66
0.97
0.87
0.57
0.83
0.73
0.77
0.83
S
0.73
0.53
0.70
0.67
0.53
0.53
0.80
0.80
0.66
1.07
0.87
0.57
0.57
0.97
0.77
0.83
d
r
0.59
0.44
0.66
0.64
0.49
0.49
0.73
0.66
0.59
0.68
0.67
0.62
0.73
0.70
0.62
0.83
Cation 3
h
r
0.49
0.44
0.43
0.52
0.39
0.39
0.56
0.55
0.50
0.41
0.39
0.66
0.56
0.54
0.54
0.58
SL
0.83
0.67
1.03
0.97
0.87
0.87
1.07
0.93
0.97
1.40
1.40
0.67
1.07
1.07
0.87
1.23
S
r
1.47
1.43
1.60
1.23
1.27
1.27
1.30
1.17
1.17
1.50
1.53
1.13
1.30
1.37
1.00
1.43
Anion 3
d h ST S
r r L r
1.00 0.62 1.53 1.53
1.00 0.62 1.53 1.53
1.02 0.47 1.97 2.00
-------
The asymmetry of the cation 3 pulse, in the absence of cation 2(R-7), is
due to the preferential adsorption of cation 1 over cation 3. Lai and
Jurinak (1972), using simulated concentration fronts to illustrate the ef-
fects of preferential adsorption on solution profiles of one cation entering
a soil column which was initially saturated with a different cation, demon-
strated that the fronts tend to be more diffuse when the original cation is
adsorbed in preference to the influent cation. The leading edge of the ca-
tion 3 pulse is somewhat analogous to such a front and is therefore more dif-
fuse than the trailing edge of the pulse.
A comparison of Figures 118 and 114 and of d , h , SL> and SR for runs
R-10 and R-6 show that the presence of cation 3 has little effect on the ca-
tion 2 pulse for the conditions of those runs. For run R-6, d = 0.35, h =
0.35, S = 0.73, and S = 0.73. The corresponding values for the cation 2
pulse from run R-10 are 0.35, 0.37, 0.70, and 0.70, respectively. In both
cases, the cation 2 pulse is apparently symmetric, and there is no difference
in the values of d obtained for the two runs. The symmetry of the cation 2
pulses reflects the non-preferential adsorption of cation 1 over cation 2,
and vice-versa. This quality is "built-in" to all runs for which E 2 = 1.0,
since from equation (44) it can be seen that the ratio of the adsorbed phase
concentrations, Y /Y is equal to the ratio of solution concentrations,
C /C , when the exchange coefficient E.. „ is unity.
Effect of solution normality — The conditions for runs R-l through R-23
(Table 70), excluding runs R-10, R-12, and R-13, are such that the total
cationic concentrations, expressed in meq/ml, of the initial soil solution is
equal to the total cationic concentration of the slug solution. For example,
for run R-ll, the total cationic concentration of the initial soil solution
is C = 2 • 0.050 = 0.100 meq/ml.
The effect of varying C can be observed by comparing the pulses shown
in Figure 119 (run R-ll) wit ft those presented in Figure 122 (run R-14) . For
run R-14, C is 0.200 meq/ml. The values of d , h , S , and S , for cation
2, are 0.34^ 0.39, 0.67, and 0.67, respectively, for run R-ll and 0.47, 0.50,
0.80, and 0.80, respectively, for run R-14. For cation 3, the values of d ,
hr, SL, and S are 0.64, 0.52, 0.97, and 1.23, respectively, for run R-ll,r
and 0.73, 0.5&, 1.07, and 1.30, respectively, for run R-14. Thus, for both
cations, the effect of increasing C is manifested by increases in each of
the four parameters. Since increasing C , with other factors constant, re-
sults in an increase in the proportion o£ ions present in the solution phase,
as well as an increase in the total mass of each ion, the result is a more
solution-phase dominated system. The increases in the proportion of cations
2 and 3 which are present in the solution phase are reflected by the in-
creases in h , S^ and SR for the cation 2 and cation 3 pulses. The decreased
effect of cation adsorption on the pulses for the larger value of C is also
reflected in relative distances of travel for the two pulses which are closer
to unity for C^ = 0.2 meq/ml than for C =0.1 meq/ml.
Effect of ionic activity— The effects of ionic activity are included in
the model through two mechanisms. One such mechanism is the influence of the
activity coefficient, y, on the ion-pair concentrations X and X , as
indicated by equations (49) and (50) . The other is the influence of y on the
320
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exchange relationships between cation 1 and cations 3, 4, and 5, as can be
seen from equations (56) through (58). The effects due to the latter mechan-
ism can be observed by comparing Figure 119 (run R-ll) with Figure 124 (run
R-16) and Figure 122 (run R-14) with Figure 123 (run R-15). For runs R-ll
and R-16, the total cationic concentration is 0.1 meq/ml, with C. = 0.05
moles/liter, C2g = 0.025 moles/liter and C = 0.05 moles/liter. Run R-ll
was made with y n£ld constant at 1.0 for all depths and times. For run R-16,
anions 2 and 3 were included with A? =0.1 moles/liter and A_ = 0.1 moles/
liter to provide a total anionic concentration of 0.1 meq/ml for both the
original soil solution and the incoming slug solution. The activity coeffi-
cient, Y» was calculated according to equation (61) for run R-16.
For cation 2, the values of d , hr, S , and S are 0.34, 0.39, 0.67,
and 0.67, respectively, for run R-ll, and 0.33, 0.39, 0.66, and 0.66, respec-
tively, for run R-16. Hence,for the conditions which are common to runs R-ll
and R-16, the assumption of unit ionic activity (run R-ll) results in a ca-
tion 2 pulse which differs little from the pulse simulated with the effects
of activity included. For cation 3, d , h , S , and S are 0.64, 0.52, 0.97,
and 1.23, respectively, for run R-ll, and 5.59, 0.50, U.97, and 1.17, respec-
tively, for run R-16, indicating slight decreases in d and h , no change
in ST and a decrease in S for the case where y is calculated.
L K
For higher values of total cationic and anionic concentrations, 0.20
meq/ml for runs R-14 and R-15, the effect of ionic activity on the cation 3
pulse is more pronounced. Run R-14 was made with y = 1«0 for all depths and
times. For run R-15, y was calculated as a function of the solution concen-
trations. The values of dr, h , S , and S are 0.73, 0.56, 1.07, and 1.30,
respectively, for run R-14, and the corresponding values for run R-15 are
0.66, 0.55, 0.93, and 1.17, respectively, indicating lower values for d ,
h , and S when y is calculated rather than held constant. These effects are
qualitatively similar to those observed from runs R-ll and R-16, where the
total cationic and anionic concentrations are both 0.1 meq/ml. The value of
S is lower for y calculated than for y held constant at 1.0. Since this ef-
fect on S is reversed from that observed for runs R-ll and R-16, there is
apparently some interaction between the level of solution concentrations and
the effect of solution activity on S .
lj
For cation 2, the values of dr> hr, SL> and SR are essentially the
same for both runs R-14 and R-15, again indicating little observable effect
of solution activity on the cation 2 pulse.
The lower values of relative pulse height and relative distance of
travel of the cation 3 pulses which were observed for runs R-15 and R-16 are
indicative of decreased preferential adsorption of cation 1 over cation 3
when y is calculated as opposed to having the constant value, 1.0. The coef-
ficient, y, occurs in the numerator of the right-hand side of equation (33),
which determines the ratio of concentrations in the adsorbed phase, Y-i/Yo as
a function of C-^/CL. A reduction in the magnitude of y, for particular
values of CL and C-f therefore results in a reduced value of Y1/Y3» Since
for all non-zero values of the solution concentrations of ions which are pre-
sent the value of y is less than 1.0 (see equation 61), the preferential ad-
sorption of cation 1 is diminished when y is calculated rather than assigned
321
-------
the constant value, 1.0. Nevertheless, the effects of ionic activity on the
cation 3 pulse are small compared to the effects of changing the total ca-
tionic concentration by a factor of two.
Effect of varying 6 and CEC When only cations 1, 2, and 3 are consi-
dered simultaneously, equation (54), which expresses conservation of charge
on the soil cation exchange complex, can be written:
2 • Y, + 2 • ¥„ + b ' CEC
2 3 100-6
This equation constitutes the only mechanism through which influence of the
cation exchange capacity, CEC, is included in the model. The moisture con-
tent, 9, influences model results through equation (88) and also through its
effect on the combined diffusion and dispersion coefficient, D ., as can be
seen from equation (78). However, for steady-flow conditions, where 0 is
constant with depth and time, the value of 6 may be changed without affecting
the value of the apparent diffusion coefficient, D ,/0, provided the volu-
metric flux, q, is also adjusted so that v = q/6 ritnains the same. Therefore,
for runs made with the same value of V, differences in results from runs
using different values of 6 are due to equation (88). Moreover, the value of
6 by some multiplicative factor should produce the same difference in results
between two runs as increasing the value of CEC by the same factor.
The effect of increasing CEC from 10.0 to 20.0 meq/lOOg, for 6 = 0.50,
can be observed by comparing Figure 120 (run R-12) with Figure 118 (run R-10).
The effect of decreasing 6 from 0.50 to 0.25, for CEC = 10.0, can be seen by
comparing Figure 121 (run R-13) with Figure 118. The values of C T, C?c,,
and C_ are 0.05, 0.05, and 0.10, respectively, for all three runs.
JO
The values of d , h , S , and S for run R-10 (CEC = 10.0 and 0 = 0.50)
are 0.35, 0.37. 0.70^ an§ 0.70, respectively, for cation 2, and 0,66, 0.43,
1.03, and 1.60, respectively, for cation 3. The corresponding values for
both runs R-12 (CEC =20.0 and 9 = 0.50) and R-13 (CEC =10.0 and 6 = 0.25)
are 0.24, 0.29, 0.53, and 0.53, for cation 2, and 0.49, 0.39, 0.87, and 1.27
for cation 3. Thus an increase in CEC, with 0 constant, or a decrease in 0,
with CEC and V constant, produces effects which are qualitatively similar to
effects due to changes in the total cationic concentration, C , which were
pointed out earlier. A reduction in 0, with CEC and C constant, represents
both a reduction in total mass for the three ions in tne system and a reduc-
tion of the ratio of the ion masses in the solution phase to those in the ad-
sorbed phase. An increase in CEC represents both an increase of the total
mass of each ion and an increase of the ratio of the ion masses in the ad-
sorbed phase to those in the solution phase. Thus decreasing 0 or increasing
CEC results in a more adsorbed-phase dominated system, whereas decreasing C
also results in more adsorbed-phase dominated systems. ^
Effect of varying r, the mean pore velocity to apparent diffusion coef-
ficient ratio—The effect of varying the mean pore velocity to apparent dif-
fusion coefficient ratio, r, can be observed by comparing the pulses shown in
Figures 126 (run R-18) and 127 (run R-19) with those presented in Figure 119
322
-------
(run R-ll). For all three runs the value of (L , C , and C are 0.050,
0.025, and 0.050 moles/liter, respectively. For run R-ll (r = 10.0), the
values of d , hr> SL> and SR are 0.34, 0.39. 0.67, and 0.67, respectively,
for cation 2, and 0.64, 0.5Z, 0.97, and 1.23, respectively, for cation 3.
The corresponding values for run R-18 (r = 5.0) are 0.35, 0.30, 0.87, and
0.87, respectively, for cation 2, and 0.67, 0.39, 1.40, and 1.53, respective-
ly, for cation 3. For cation 2, the increase d due to changing r from 10.0
to 5.0 represents only 3.0% of the value of d corresponding to r = 10. For
cation 3 the percent increase in d is 4.7. Changing r has a much greater
effect on the relative heights and relative half-widths of the pulses than on
their relative distances of travel. Due to the decrease in r from 10.0 to
5.0 there is a 23.0% reduction in h and an increase of 23.0% for both S and
SR for cation 2. For cation 3 there is a decrease in h of 25.0%, an in-
crease in S of 44.4% and an increase in S,, of 24.4%. r
J-i K
For run R-19 (r = 20.0), the values of d , h , S , and S are 0.33, 0.50,
0.57, and 0.57, respectively, for cation 2, and 0^62, 0.66, 0.67, and 1.13,
respectively, for cation 3. Changing r from 10.0 to 20.0 results in a 3.0%
reduction in d for cation 2 and a 3.1% reduction in d for cation 3. For
cation 2 a 28.2% increase in h and a 15% decrease in § and S resulted from
the change in r from 10.0 to 20.0. For cation 3, the corresponding percent
increases in h was 46.2. The values of ST and S were decreased by 31.1%
and 8.1%, respectively.
Thus, for both cations 2 and 3 the results of changing r are manifested
primarily by changes in relative pulse height and in the relative half-widths
of the pulses. The most diffuse (lowest r, and highest ST and S ) pulses were
obtained for the lowest value of r, as would be expected, due to the greater
influence of apparent diffusion for low values of r.
Effect of varying the exchange coefficients, E^ and E^—As was previous-
ly indicated, the mass-action equation (44) and the Gapon equation (45) are
such that cations 1 and 2 are adsorbed preferentially over cation 3, when the
values of the exchange coefficients, E^2 and E^, are both 1.0. The effect of
varying £,„ can be observed by comparing Figures 128 (run R-20) and 129 (run
R-21) with Figure 122 (run (R-14). For each of the three runs the values of
C,T, C?_ and CL are 0.10, 0.05 and 0.10 moles/liter, respectively. The values
of E12 for runs R-14, R-20 and R-21 are 1.0, 0.5 and 2.0, respectively.
With E,? = 1.0 (run R-14), the values of d , hr, SL and S- are 0.47, 0.50,
0.80 and 0.80, respectively, for cation 2, and for cation 3, their respective
values are 0.73, 0.56, 1.07 and 1.30. The corresponding values for E-2 =0.5
(run R-20) are 0.40, 0.41, 0.83 and 0.57, for cation 2, and 0.73, 0.55, 1.07
and 1.30 for cation 3. The decrease in the values of E12 thus had no observ-
able effect on the cation 3 pulse in terms of the four calculated parameters.
The decrease in E19 from 1.0 to 0.5 is manifested in the cation 2 pulse
by decreases in h , d , and S and by an increase in S_. The more diffuse
trailing edge (Figure 128) is due to the preferential adsorption of cation 2
over cation 1, for £-„ < 1.0. The increased influence of adsorption for the
323
-------
lower value of E . is also reflected in the decreased relative height and
relative distance of travel of the cation 2 pulse.
The effect of varying EI. can be observed by comparing Figures 110 (run
R-22) and 131 (run R-23) witfi Figure 122 (run R-14). For E = 0.5 (run
R-22), the values of d,., h,., ST , and S^ are 0.47, 0.51, 0.77, and 0.77, re-
spectivel
cation 3.
R-22), the values of d , h , S , and S are 0.47, O.il, u.//, ana u.//, re-
spectively, for cationr2, and 0.62, 0.54, 0.87, and 1.00, respectively, for
For E = 2.0 (run R-23), the values of d , h , SL, and S are 0.47,
0.49, 0.83, and 0.83, respectively, for cation 2 and 0.83, 0.58, 1.23, and
1.43, respectively, for cation 3. Just as the variation of E^~ had little
effect on the cation 2 pulse, the variation of E • produced only small changes
in the observed characteristics of the cation 2 pulse. On the other hand,
decreasing E from 1.0 to 0.5 produced significant decreases in d , h , S^,
and S for the cation 3 pulse, while increasing £.„ from 1.0 to 2.0 had the
opposite effect on each of the cation 3 pulse characteristics.
Comparison^ c>f_cation 2, cation 3 and anion 3 pulses—For all of the runs,
R-l through R-23, the relative distances of travel, d , for the cation 2 pulse
are less than the corresponding value for the cation 3 pulse. In all cases
d for both pulses is less than 1.0. The cation 2 pulses are generally sym-
metric, with S /S = 1.0, while the cation 3 pulses are skewed to the right,
with S /S < 1.0). Exceptions to the symmetry of the cation 2 pulses were
noted for values of E ^ 1.0. With one exception (E-_ = 2.0) the relative
heights of the cation 2 pulses are less than the relative heights of the ca-
tion 3 pulses.
For the conditions of runs R-15 through R-17, the characteristics of the
two cation pulses can be compared with those of anion 3 pulses. Run R-16
(Figure 124) was made with lower values of initial soil solution and slug
solution concentrations (C = 0.05,0- = 0.025, C = 0.05, and A- = A =
0.1) than those used for run R-15 (C ^ = 0.1, C =0.05, C = 0,17 and
A2I = A3S = °'2)' but with the same value of r U = 10.0) for both runs.
Run R-17 (Figure 125) was made with the same values of initial soil solution
and slug solution concentrations as run R-15 (Figure 123) but with r = 5.0
instead of 10.0. The values of the ion pulse characteristics for each of the
three runs can be found in Table 71.
It is evident from Figures 122 through 124 that the anion 3 pulses are
further advanced and have greater spread and greater relative heights than
either of the cation pulses. The value of d for the anion 3 pulse is 1.0
for runs R-15 and R-16 and 1.02 for run R-17^ indicating that the apparent
velocity of the anion 3 pulse, as determined by the position of the peak con-
centration, is about the same as the mean solution pore velocity. The
slightly higher value of dr for run R-17 indicates a shift similar to that
observed for the cation 2 and cation 3 pulses. Indeed, for r = 10.0 d is
0.33 for cation 2 and 0.70 for cation 3, while for R = 5.0 d for cation 2
is 0.35 and 0.72 for cation 3. r
None of the characteristics of the anion 3 pulse show any sensitivity to
the differences in concentrations between runs R-15 and R-16, whereas it was
324
-------
previously indicated that the cation pulses are strongly affected by such
differences.
Reducing r from 10.0 (Figure 122) to 5.0 Figure 124) resulted in changes
in the anion 3 pulse which are qualitatively similar to the changes observed
in the cation pulses for the same reduction in r. The relative height of the
anion 3 pulse decreased from 0.12 to 0.47. The relative half-widths in-
creased from SL = 1.52 and SR = 1.52 to 1.97 and 2.00, respectively.
Observed increases in pulse height—Shown in Figure 128 are results cor-
responding to run R-21 for cations 1 and 2 after 1600 minutes of simulated
time and for cation 2 after 400 minutes of simulated time. The predicted
relative pulse height for cation 2, corresponding to 400 minutes,, is greater
than 1.0, indicating a temporary local increase in the concentration of ca-
tion 2 above C« for this run. At first, it was thought that the indicated
increase in concentration was numerically induced by the computational pro-
cedure in a manner similar to the overshoot observed and discussed earlier
for finite-difference solutions to equation (4). However, it was previously
shown that overshoot associated with finite-difference approximations to
equation (4) is sensitive to the grid-spacing, AZ, and/or the time step size,
At, used in conjunction with a particular value of r = v/D. Additional runs
made with varying combinations of smaller values of At and AZ than those used
for run R-21 failed to verify that numerically induced overshoot was the
cause of the increased concentration observed for run R-21. Runs with AZ =
0.125 and $ = 0.05 produced results very similar to those shown in Figure 126
(AZ = 0.25 and g = 0.5), and in no case was the maximum predicted concentra-
tion after 400 minutes less than that indicated in Figure 126.
An additional run was made with C~,, = 0.1 moles/liter, €„„ = 0.0 moles/
liter, A? = 0.2 moles/liter and A = 8.2 moles/liter and with the values of
all the other parameters identical to those used for run R-21. The cation 2
and anion 3 pulses observed after 400 minutes of simulated time are shown in
Figure 132. The relative heights of both pulses are less than 1.0. If the
excessive value of the concentration of cation 2 observed in Figure 126, for
C = 0.05 moles/liter, was due to poor response of the finite-difference ap-
proximations to the discontinuity in concentrations at t = 0_, and Z = 0, the
adverse effect should have been more pronounced with C- = 0.10 moles/liter.
Moreover, the effect should have also been observed in the anion 3 pulse.
Also, the results for cation 2 shown in Figure 131 were found to agree with
results obtained from the independent numerical solution to the two-cation
problems represented by that run.
For the conditions of run R-21, observations of the cation 2 and cation
3 pulses after each time step from t = 0 up to t = 400 minutes indicated that
h for the cation 3 pulse also exceeded 1.0 at early times. These observa-
tions indicate that similar phenomena may have occurred for the conditions of
some of the other runs but were simply not observed.
A plausible explanation of the temporary increases in concentrations of
cations 2 and 3 can be given as follows: as the solution containing cations
2 and 3 enters the soil column, the two influent cations begin to replace
cation 1 on the exchange complex, and the solution concentrations of both
325
-------
1.0
0.5-
'Co
A
A
A
o
A
o
A
A
O
O
A
A
O
O
A
A
A
A,
O CATION 2 (DIVALENT)
A ANION 3 (MONOVALENT)
0
10
DEPTH (cm)
15
20
Figure 132 Simulated concentration pulses for cation 2 and anion 3. The conditions
are the same as run R-21 except that C3s = 0.0, C^ = 0.1 and A3s = 0.2. Observa-
tion time is T = 400 minutes.
-------
cations begin to increase at shallow depths in the column. Since cation 3 is
less preferred on the exchange complex than cation 2, its solution concentra-
tion approached C--, the slug solution concentration, more rapidly than the
concentration of cation 2 approaches C2c-
Provided the pulse time t is long enough, the concentration of cation 3
eventually reaches C-g. Whether the concentration of cation 3 continues to
increase after it reaches €-„, or instead, begins to decrease depends not
only on the flux gradient but also on release or adsorption of cation 3 on
the exchange complex. The adsorption of cation 3 on the exchange complex,
at the expense of cation 3, provides a potential source of cation 3 to the
solution. Thus the solution concentration of cation 3, at a given depth in
the column, may continue to rise even when C- > C™. However, such a rise
cannot continue indefinitely since the exchange complex source is limited and
since diffusion and/or dispersion effects oppose increases of C- above C3g.
Summary—
Several simulation runs were made using the computer model of ion trans-
port and chemical equilibrium. Simulated concentration pulses were used to
compare results obtained from the model with results obtained from an inde-
pendent numerical method of solution of two-cation problems. The model
results agreed with results from the independent method.
Qualitative assessments were made of the effects of changes in the values
of certain model parameters on the simulated concentration pulses. To aid in
this analysis, four pulse characteristics: relative distance of travel, dr,
relative pulse height, h , and relative half-widths of the pulses, SL and SR,
were defined and calculated for each simulated pulse. Specific effects con-
sidered were: effect of a second cation in the slug solution, effect of total
cationic concentration, effect of solution activity, effect of mean pore ve-
locity to apparent diffusion coefficient ratio? effect of cation exchange ca-
pacity and volumetric moisture content^ and effect of exchange coefficients.
For the runs made, the greatest changes in the relative distance of tra-
vel, d , for the cation 2 pulse occurred as a result of varying the total cat-
ionic concentration (fid = 0.13, where Ad represents the absolute value of
the. change in dr due to the change in concentration), CEC or -9- (Ad = 0.11),
and E12 (Adr = .08). Little or no change in dr for the cation 2 pulse resulted
from changing E13 (Adr = 0.0), including the effect of the activity coeffi-
cient, Y(Adr = 0.01), including cation 2 in the incoming slug solution (Ad =
0.0), or changing 4 (Adr = 0.01).
The greatest changes in d for the cation 3 pulse occurred as a result of
varying CEC and -9- (Adr = .17) ^changing the total cationic concentration (Adr
= 0.09) and including cation 2 in the incoming slug solution (Ad = 0.07).
Smaller changes in d^_ resulted from changes in E12 (Adr = 0.03), changes in r
(Adr = 0.03), and including the effects of y(Ad = 0.03).
327
-------
The greatest changes in relative height for both the cation 2 and cation
3 pulses occurred as a result of varying r (Ahr = .11 for cation 2 and Ahr
.14 for cation 3). Varying the total cationic concentration had an equally
pronounced effect on the height of the cation 2 pulse (Ahr = 0.11) but a
smaller effect on the height of the cation 3 pulse (Ah = 0.06).
No change in the relative height of the cation 2 pulse resulted from in-
cluding the effects of y in the model at either level of total cationic and
anionic concentrations used. Little or no change in h^ for the cation 3 pulse
resulted from changing EI;J (Ahr = 0.021), changing EU, (Ahr = 0.02), or in-
cluding the effects of y at the low level of total cationic and anionic con-
centrations (Ah = 0.01). The effects on h on other changes were interme-
diate between the extremes indicated above for both cations.
The factors which produced the greatest changes in the half-widths of
the cation 2 pulses were a change in the total cationic concentration (ASL =
ASR = 0.13), a change in CEC or -0- (SL = SR = 0.17), a change in r (ASL = ASR
= 0.2) and a change in E1 „ (AS, = 0.03 and AS-. = 0.23). Among the factors
-L/ L K
having the greatest effects on the half-widths of the cation 3 pulses were
changes in r (AS, =0.43 and AS D = 0.30), changes in CEC or -6- (AS, =0.16
Li K 4-1
and AS = 0.33), changes in E, _ (AST = 0.20 and AS,, = 0.30), including cation
K. J. j l-i .K
2 in the slug solution (ASL =0.20 and ASR = 0.13) and changing the total
cationic concentration (AS = 0.14 and ASn = 0.17).
L K
By comparison, including the effects of y resulted in no change in S or
SR for cation 2 and resulted in only small changes in S and SR for cation 3
(ASL = 0.03 and A SR = 0.07 at the low level of solution normality and AS. = 0.07
and ASR= 0.03 at the high level of solution normality). Including cation 2 in
the incoming slug solution also produced little change in either S or S for
cation 2 (AsL = SR= 0.03), as did changing E13 (ASL = ASR= 0.03). Changing EU
likewise produced only small changes in S and SD for cation 3 (AS =0 and AS =
0.07). L R L R
For most of the runs, the cation pulses were nearly symmetric having
equal SL and S values. Asymmetric cation 2 pulses resulted when values of the
exchange coefficient, E^, were different from 1.0. For EU = 0.5, the cation 2
pulses were skewed to the left with SL > SR. For E =2.0, the cation 2 pulses
were skewed to the right, with SL < SR. On the other hand, the cation 3 pulses
were asymmetric and skewed to the right (S > S ) for all of the runs made.
nul,J°« r°th Catl°n*2 a^ 3' the respective heights and half-widths of the
pulses were appreciably affected by changes in r, whereas the relative dis-
tance of_travel was only slightly perturbed by changes in r. In contrast!
changes in the total cationic concentration and changes in CEC or * resulted
328
-------
in appreciable changes in all four of the calculated pulse characteristics
for both cations. Similarly, including cation 2 in the slug solution with
cation 3 resulted in appreciable changes in d , h , S and SR for cation 3.
On the other hand, the addition of cation 3 to the slug solution containing
cation 2 had little effect on any of the cation 2 pulse characteristics.
Comparisons among divalent cation (cation 2), monovalent cation (cation
3), and monovalent anion (anion 3) pulse characteristics revealed that the
anion pulse was characterized by the greatest distance of travel and greatest
spread (highest values of S and SR) of the three ion pulses. The cation 2
pulse was generally characterized by the shortest distance of travel, small-
est relative height, and least spread of the three ions. The only observed
exception to the above general trend occurred for the case, EI„ = 2.0, where
the cation 2 pulse had a greater relative height (but smaller distance of
travel) than the cation 3 pulse.
For the conditions of one of the runs, it was found that the relative
heights of the cation 2 and cation 3 pulses each exceeded 1.0 for short per-
iods of time. The results from additional test runs indicated that the tem-
porary increases in pulse height were due to some interaction between cations
2 and 3, rather than due to numerical overshoot.
Conclusions—
From the results of the simulation runs, the following conclusions were
drawn:
(1) Based on comparison of model results with those from an independent
method, the combined multi-equation and chemical equilibrium approach
(represented by the model) provides a valid solution procedure for
multi-ion transport problems where chemical equilibrium can be assumed.
(2) The comparatively minor effects of the presence of the monovalent
cation (3) on the characteristics of the divalent cation (2) pulse indi-
cates that the presence (in small quantities) of less preferred cations
may have a negligible effect on the transport of more strongly adsorbed
cations for certain applications. However, the effects of strongly ad-
sorbed cations on the movement of less preferred cations probably can-
not be ignored.
(3) The relatively minor responses of both cation pulses to the inclu-
sion of a calculated activity coefficient indicate that a precise deter-
mination of the activity coefficient is probably unnecessary when only the
effect on adsorption is important. This is not necessarily true for in-
stances where ion pairing or solubility-precipitation mechanisms are
important.
(4) The effects of apparent diffusion were shown to be important with
respect to the height and spread of both cation pulses for the runs for
which the velocity to apparent diffusion coefficient ratio was varied.
(5) Since varying the exchange coefficient for either of the cations
(monovalent or divalent) produced only minor changes in the characteristics
329
-------
of the pulse for the ion not associated with that coefficient, the ac-^
curacy of exchange coefficients for cations other than those being moni-
tored in a given experiment may not be critical.
The above conclusions (2) - (5) are tentative due to the limited number
of runs which have been made. They are strictly applicable only to the type
of transport problem represented by the runs. However, the conclusions drawn
from this set of runs are indicative of further investigations that may prove
fruitful with respect to information about multi-ion transport phenomena. A
different type of transport problem which should receive attention in the
future is a pulse problem where the slug solution contains only one cation
but where the soil initially contains two cations in varying ratios.
Determination of Equilibrium Coefficients
Preliminary Experiment—
The preliminary experiment on a Beaumont clay (sample ^_) t£ ascertain
Ba interferences indicated considerable antagonism for Na , K and Ca
analyses (Figures 133, 134 and 135, respectively^ However, Mg was not
greatly affected by the high concentration of Ba (Figure 136). Cation com-
positions on the soil were determined by comparison to standard dilution
curves using BaClj as the diluent to circumvent laborious corrections. This
was justified due to the linearity of the interference with increased cation
concentration. Solution concentrations were determined by comparison to the
standard dilution curves employing water as the diluent. It was assumed that
the salts, other than Ba, comprising the solution matrix were too low in con-
centration to interfere with the respective cationic analyses.
Solution and adsorbed cation concentrations at equilibrium for the
various treatments are given in Table 72. The solution concentrations shown
here were adjusted to 46% moisture by weight from the moisture contents used
in the experiment. The effective CEC of the soil can be expressed as the
sum of the individual cations adsorbed. Total cations summed over the 17
treatments averaged 47.38 meq/lOOg with a standard deviation of 1.23 meq/lOOg.
The small standard deviation indicates that the 4 cations measured adequately
described the cationic distribution for the soil. Also there was a complete
conservation of charge; or, an equivalent increase in one cation necessitated
an equivalent decrease of one or more of the other cations.
Generally, an increase in the solution concentration due to a treatment
input resulted in an increase in the amount adsorbed. Correlation coeffi-
cients were positive and relatively high except for Ca. The negative and
relatively low value for Ca suggested that adsorbed Ca decreased with in-
creased solution Ca. An inspection of the data (Table 73) shows that even
when Ca was applied at the 100 ppm level the increase on the exchange complex
was quite small. The greatest increase occurred at the 100 ppm treatment of
Na, K and Ca. Due to the relatively high correlation values, an analysis of
covariance was determined to evaluate the significance of the different
treatments on adsorbed cations (Appendix 0). Results of this test indicated
that no real differences existed for the cations adsorbed at the different
solution concentrations, although the error for adsorbed values was adjusted
for differences in the solution values. Thus, the variability between solu-
330
-------
20
QL
Q.
15
O
o
10
5-
BaCl,
5 10 15
Percent Transmittance
20
25
Figure 133. Standard dilution curves for Na employing distilled deionized HO, and
1 N_ BaCl_ as diluents for soil sample 1.
-------
OJ
i40
CL
2 30
E
05
8
O 20
10
BaCU
10 20 30 40 50
Percent Transmittance
60
70
80
Figure 3.34. Standard dilution curves for K
1 N_ BaCl,j as diluents for soil sample 1,
employing distilled deionized HO, and
-------
OJ
401
30
o
20
10
20 30 40 50
Percent Transmittance
60
70
j I
Figure 135. Standard dilution curves for Ca employing distilled deionized HO, and
1 N BaCl« as diluents for soil sample 1.
-------
10
8
IN BaCI2
o H20
234 56 78
Percent Transmittance
10
11
Figure 136. Standard dilution curves for Mg employing dis-
tilled deionized H20, and 1 N_ BaCl2 as diluents
for soil sample 1.
334
-------
TABLE 72. EQUILIBRIA SOLUTION AND ADSORBED CATION CONCENTRATIONS, OF A BEAUMONT CLAY SOIL,
TABLISHED AT VARIOUS SOLUTION CATIONIC TREATMENTS IN SAMPLE 1
ES-
LO
U)
Ul
Solution Cations
Treatment
ppm
none
50 Na + 50 K
100 Na + 100 K
50 Na + 50 Ca
100 Na + 100 Ca
50 Na + 50 Mg
100 Na + 100 Mg
50 K + 50 Ca
100 K + 100 Ca
100 K + 100 Mg
50 Ca + 50 Mg
100 Ca + 100 Mg
100 Na + 100 K +
100 Mg
100 Na + 100 Ca +
100 Mg
100 Na + 100 K +
100 Ca
100 K + 100 Ca +
100 Mg
100 K + 100 Na +
100 Ca +
100 Mg
Na
K
Ca
Mg
Na
mmoles/liter
8.48
30.81
54.14
11.11
67.06
38.38
60.60
9.60
11.34
11.11
9.69
13.13
67.67
67.47
58.88
13.64
59.59
0.77
6.98
15.64
2.33
3.64
3.34
4.36
10.04
18.21
19.72
3.40
3.99
19.64
4.72
19.70
22.09
21.97
1.04
8.12
16.93
13.51
41.18
27.55
52.37
19.14
44.37
53.94
43.50
98.60
57.42
95.70
46.40
98.89
101.79
1.55
5.24
8.34
6.79
14.07
16.98
40.74
9.31
13.58
44.14
25.71
58.69
47.04
58.20
17.95
53.35
39.29
0.41
1.65
2.88
2.54
2.30
1.33
2.59
0.36
0.28
0.29
0.36
0.20
2.26
2.28
2.66
0.18
2.63
Exchangeable Cations
K
Ca
Mg
Total
meq/lOOg
0.56
1.59
2.51
0.49
0.44
0.45
0.40
1.39
2.40
2.22
0.45
0.42
2.34
0.39
2.33
2.23
2.24
29.16
28.53
27.74
30.64
30.76
26.78
24.56
29.95
30.47
24.38
27.95
25.61
24.11
25.87
32.76
25.59
24.38
15.34
15.01
14.73
14.87
14.22
18.31
20.52
14.64
14.26
19.96
17.52
18.91
19.95
18.96
11.02
19.39
20.65
45.47
46.78
47.86
48.54
47 .72
46.87
48.07
46.34
47.41
46.76
46.28
45.14
48.66
47.50
48.77
47.39
49.90
-------
tion values was too great even with the adjustment. The reason for this was
probably due to the fact that Na, K and Mg were adsorbed at the expense of Ca
only to a point. That point was determined by the amounts of Ca released,
and the competitiveness of Ca for readsorption.
Multiple linear regressions were determined for a specific cation ad-
sorbed as a function of the solution concentrations, as described by the
following equation:
Y (cation adsorbed) = bo + b^ + b^ + bjX-j + b^x^
where:
x = Na in solution
•*• +
x~ = K in solution
^ I I
x~ = Ca in solution
I [
x = Mg in solution.
TABLE 73. CORRELATION COEFFICIENTS DETERMINED FOR ADSORBED
CATION CONCENTRATIONS AS A FUNCTION OF CORRESPOND-
ING SOLUTION CONCENTRATION IN SOIL SAMPLE 1
Cationic Specie Correlation Coefficient
Na 0.83
K 0.94
Ca -0.58
Mg 0.78
A summarization of these calculations is presented in Table 74. Sodium ad-
sorbed was positively affected by Na in solution and negatively affected by
Mg in solution. However, the low regression coefficient for Na in solution
suggests that Na is not preferentially adsorbed in the soil except for a few
exchange sites. This is completely consistent with what was observed in the
natural cationic distribution with no treatment. Although the Na solution val-
ue was much greater than any of the other 4 cations, it was adsorbed by less
than 1.0% of the exchange sites. Converesely, K adsorbed appeared to be large-
ly a function of K in solution with a small active competition from Ca. The
magnitude of the K adsorbed was approximately 2.4 meq/lOOg at the 100 ppm K
treatment levels regardless of the other cations in combination, suggesting a
site specificity for K in the Beaumont clay soil at about 5% of the effective
CEC (Table 72). However, only 1% of the exchange sites were occupied by K in
the natural soil (Table 72, no treatment). This is probably due to the low solu-
tion values which prevail in the area, and points out the need for K fertiliza-
tion.
Calcium, as shown in Table 72, was positively affected by Ca in solution,
336
-------
but negatively affected by K and Mg in solution, particularly that of Mg.
Magnesium adsorbed was largely a function of the Mg in solution, tempered
somewhat by the K and Ca solution levels. Naturally occuring ratios
TABLE 74. MULTIPLE LINEAR REGRESSION COEFFICIENTS FOR THE CATIONS ADSORBED
AS A FUNCTION OF SOLUTION CONCENTRATIONS IN SOIL SAMPLE 1.
Cation adsorbed
Y
Na
K
Ca
Mg
bo
0.562
0.464
30.393
14.433
X1(Na in
solution)
bl
0.038
0.000
-0.006
-0.003
X2 (K in
solution)
b2
-0.002
0.119
-0.029
-0.022
X3(Ca in
solution)
b3
-0.001
-0.007
0.055
-0.035
X4(Mg in
solution)
b4
-0.014
-0.001
-0.181
0.167
(Table 72, no treatment) appear to be inconsistent with the results of the
equilibrium experiment. Calcium occupies 64% of effective CEC compared to
34% for Mg, yet the solution values are essentially the same. The equili-
brium study suggests that Mg would be preferentially adsorbed, or at least
more strongly adsorbed than Ca. Perhaps Ca comprised a much greater percen-
tage of the primary minerals from which the soil was weathered, and with very
little K or Mg in solution, the ratio has remained high for Ca.
Adsorbed values for the various cations were calculated by the equations
summarized in Table 74, and correlated with the values experimentally ob-
served (Figures 137 - 140). The good correlations suggest that the equations
adequately describe the equilibrium obtained under laboratory conditions.
Experiment with Field Soil—
The second equilibrium study was conducted on Beaumont clay soil (sample
2) collected within the field plot area. Treatments consisted of various
concentrations of monovalent cations (Table 75), since this better approxi-
mated fertilizer amendments employed in the field study. These values were
adjusted to 46% gravimetric moisture content.
As noted in the previous experiment, the total cations adsorbed re-
mained relatively constant over the various treatments and averaged 20,55
meq^lOOg with a standard deviation of 1.26 meq/lOOg. Samples receiving the
NH, treatments were not used in the average since NH^+ was not determined
and obviously occupied some of the exchange sites.
Cationic concentrations of Na and K in solution were highly correlated
to the corresponding amounts adsorbed (Table 76). Calcium and magnesium were
negatively correlated indicative of the fact that they were exchanged by the
337
-------
2.5
o>
02.0^
1.5
OJ
(jj
00
o
S 10
in
.0
O
Y=-0.08+I.07(X)
r= 0.98
0 0.5 1.0 1.5 2.0 25 3.0
Calculated adsorbed Na+( meq loog)
Figure 137. Linear Correlation of calculated and experimentally observed Na+ adsorbed
for soil sample 1.
-------
16
14
8
n
O
13
Y=-0.53-H.04
r= 0.79
13 14 15
Calculated adsorbed Ca+M meq/!00g)
16
Figure 138. Correlation of calculated and experimentally ob-
served Ca "^adsorbed for soil sample 1.
339
-------
4.CH
Y=-0.3I+I.09(X)
r= 0.66
g 3.0
•o
0)
.O
k
o
10
•o
o
t>
«
>
ZO
2.0 3.0
Calculated adsorbed Mg++(meq/ioO)
4.0
Figure 139. Linear correlation of calculated and the experi-
mentally observed Mg"*"1" adsorbed for soil sample 1.
340
-------
6Di
5.0
"8
•e
o
in
Y- -0.03+ 0.99 (X)
r = 0.99
1.0 2.0 3.0 4.0
Calculated adsorbed K^(meq/joog)
5.0
Figure 140. Correlation of calculated K adsorbed and that
determined experimentally for soil sample 1.
341
-------
TABLE 75. EQUILIBRIA SOLUTION AND ADSORBED CATION CONCENTRATIONS OF A
BEAUMONT CLAY SOIL, ESTABLISHED AT VARIOUS SOLUTION CATIONIC
TREATMENTS IN SAMPLE 2
Solution Cations
Treatment Na+ K+ Ca"*"4" Mg"1"1
ppm mmoles/liter
none
80 Na +
120 Na +
160 Na +
240 Na +
130 K+
260 K+
390 K+
40 Na +
65 K+
85 Na +
325 K+
60 NH +
4
120 NH*
180 NH.+
4
1
41
62
88
132
2
3
3
24
54
2
3
2
.88
.90
.11
.73
.12
.96
.25
.25
.63
.22
.46
.94
.56
0.
1.
1.
2.
2.
30.
72.
124.
11.
86.
1.
2.
2.
64
39
57
03
38
23
68
43
24
05
98
50
67
1.42
3.97
7.71
9.35
13.38
21.09
41.95
58.96
11.45
54.42
16.04
34.58
46.49
1.00
1.51
2.27
2.83
4.25
5.00
8.69
10.77
3.31
9.92
4.11
7.18
9.35
Adsorbed Cations
h Na + K+ Ca++ Mg+"
meq/100 g
0.31
1.77
1.77
2.22
2.66
0.10
0.09
0.08
0.44
0.58
0.12
0.11
0.09
0.21
0.15
0.12
0.12
0.13
1.67
3.27
4.55
0.65
3.95
0.10
0.07
0.06
13.37
15.82
15.66
15.46
15.36
15.10
13.93
13.06
15.66
13.52
15.66
14.64
13.62
3.74
3.83
3.83
3.66
3.57
3.48
3.23
2.89
2.55
2.98
3.69
3.40
3,06
*" Total
17.63
21.57
21.38
21.46
21.72
20.35
20.52
20.58
19.30
21.03
34:
-------
Na and K treatments.
An analysis of covariance was determined to evaluate the significance of
the Na, K, and NH, treatments on the adsorbed cations (Appendix 0, Table 0-2).
Results indicated that the treatments had no significant influence on the ad-
sorbed cation distribution. This suggests that the solution values must ex-
ceed those obtained in this study to influence the distribution, where diva-
lent cations dominate the base saturation.
TABLE 76. CORRELATION COEFFICIENTS FOR ADSORBED CATION CONCENTRATIONS AS A
FUNCTION OF CORRESPONDING SOLUTION CONCENTRATIONS IN SOIL SAMPLE 2
Cationic Specie Correlation coefficient
Na+ 0.93
K+ 0.99
Ca"*" -0.72
Mg++ -0.64
Multiple linear regression analyses were determined for each cation ad-
sorbed as a function of the solution concentrations. These data are sum-
marized in Table 77. Adsorbed Na increased with increased Na+ and K"1" in
I i I .
solution but decreased as the solution Ca and Mg"*"1" increased. This sug-
gests that at the level of Na applied in this study there would be consi-
derable antagonism or competition from exchanged Ca"1"1" and Mg . This is con-
sistent with what one would expect due to differences in valence. However,
it appears incongruent with the trends observed for K. The coefficients ob-
tained for the solution cations suggest that K+ adsorption pivoted around
Ca"1"* desorption, but with considerable competition with Mg""" for adsorption
sites. The coefficients from the multiple linear regressions suggested con-
siderable antagonism of Ca"*""1" by Mg"*""*", and vice versa upon exchange by the
monovalent treatments' ions.
Values for the adsorbed ions were calculated using the coefficients
(Table 76) and solution concentrations (Table 75) and linearly correlated to
those actually observed (Figures 141, 142, 143, and 144). The calculated
values for Na and K adsorbed agreed closely with the observed values. Cal-
culated values for Ca and Mg deviated considerably from those observed, sug-
gesting that the equations developed do not adequately describe sorption-
desorption trends for the divalent cations, and precludes the extrapolation
of these equations to the field results.
343
-------
TABLE 77. MULTIPLE LINEAR REGRESSION COEFFICIENTS FOR THE CATIONS ADSORBED
AS A FUNCTION OF SOLUTION CONCENTRATIONS IN SOIL SAMPLE 2_
Cation Adsorbed
y bo
Na+ 0.737
K+ 0.116
Ca4'1" 14.509
Mg++ 3.844
S1(Na in
solution)
bl
0.023
-0.007
0.003
0.003
X2(K in
solution)
b2
0.025
-0.003
-0.018
0.001
X (Ca in
solution)
b3
-0.042
0.095
-0.071
0.038
X4(Mg in
solution)
b4
-0.125
-0.075
0.451
-0.296
EVALUATION OF EXCHANGE COEFFICIENTS
The concentrations of ions in the solution in equilibrium with the soil
samples and the concentrations on the exchange sites were used to calculate
the exchange coefficients. For calcium-sodium exchange, the coefficients
were calculated by a least squares fit to the following equation:
Ca ,
abs
Na ,
abs
where:
Y = e 1.171/2(Ca+Na)+ .5(Na+K) + Cl
Corresponding equations were used for Ca-K, one Ca-NH,. For the Ca-Mg ex-
change the following relation was used:
Ca , Ca ,
abs _ sol
Mg , .
abs sol
Solution concentrations utilized to calculate these values were not ad-
justed for moisture content. The values used to calculate the Ca-NH ex-
change were calculated by differences from the data shown in Table 77.
The exchange coefficients and correlation coefficients for both soil
samples are given in Table 78. Obvious differences occur between the ex-
change coefficients for the two samples of the same soil. The Kca-K was
344
-------
30i
O 2.5
o 2.0
v*
2
1.5
.5
.5 1.0 1.5 2.0 2.5
Calculated Adsorbed Na (meg/IOOg)
3.0
Figure 141. Linear correlation of calculated and experimentally
observed adsorbed Na for soil sample 2,
345
-------
30
§
Q
•^.
o»
O 28
•o
27
26
25
24
24 25 26 27 28 29 30
Calculated Adsorbed Ca (meg/IOOg)
Figure 142. Linear correlation of calculated and experimentally
observed adsorbed Ca for soil sample 2.
346
-------
201
o
o
--,
o>
-------
OJ
.ft-
00
O 2.5i
Q
O)
2.0
0)
.Cl
b
_Q
O
1.5
1.0
.5
.5 1.0 1.5 2.0 25
Calculated K Adsorbed (meg/IOOg)
Figure 144. Linear correlation of calculated and experimentally observed adsorbed
K for soil sample 2.
-------
twice as large in sample 1 as it was in sample 2, while K was twice as
large in sample 2 than it was in sample 1. Only the value! of K are in
reasonable agreement between the two soils. The correlations were highly
significant for all but the KCa_M coefficients. The poorer correlations for
these exchanges may be attributecFto the narrow range of exchanges which were
investigated.
The exchange coefficients for sample 2 were utilized in the present cal-
culations since this soil was collected from the field of interest.
TABLE 78. EXCHANGE COEFFICIENTS CALCULATED FROM THE ION EQUILIBRIUM STUDIES
_ ON SAMPLED 1 AKD 2 OF BEAUMONT CLAY. _
Soil 1 r
KCa-Na = I'°7 (m/£) 0.964**
K. v =0.231 (m/S,) 0.945**
L 3. —lx
KCa-Mg = °'851 0'212
Soil 2 r
K^ .. - 0.526 (m/i)*5 0.889**
Ca-Na
KCa-K = 0.539 (m/lfi 0.958**
KCa-Mg
*Significant at the 1% level.
**Significant at the 5% level.
Simulations of Irrigation Return Flow
After the SOIL and EQUIL parts of the model were thoroughly tested, they
were utilized in the paddy model to simulate the changes in ion concentra-
tions in the flood and irrigation return flow water. The input data required
for the model are listed in Appendix M. For these simulations the actual
data collected in the field was used insofar as possible. The simulation
was conducted utilizing data from the top 24 cm of soil. The bulk density
and soil-water content data shown in Figures 21 and 22 were used as was the
root distribution shown in Figure 23. Values of Ki calculated from data in
the literature shown in Table 64 were used. The recommended fertilizer rates
as given in Table 2 were used. The beginning salt contents of the surface
349
-------
soil for the 1975 season given in Table 21 were used. Since detailed data
were not available for each cm increment, the same values were used in each
depth increment. The ions from the fertilizer application at the time of
planting were spread through the top 5 cm of soil at the beginning of the
calculations. Eighty percent of the fertilizer applied just prior to the
flood was put in the solution in the first soil increment. Twenty percent
was dissolved in the flood water at the beginning of the simulation. This
was done to simulate the distribution which resulted as the salts dissolved
from the crystals on the soil surface and were leached directly into the
soil. The water balance during the 1975 season for the intermittent flow
plots given in Appendix F were utilized in the simulation. Evaporation
from the water surface was assumed to be 25% of the evapotranspiration
initially and decreases to 10% as the crop canopy developed.
The largest changes in the concentration of ions in the water followed
fertilizer application, therefore emphasis was placed on simulating these
changes. A series of simulations were run but only a few samples of the re-
sults will be shown here to demonstrate points of agreement and disagreement
between the data and the model.
The results of a simulation using the 1974 data from the impounded re-
commended rate plots are shown in Figures 145-147 during the period when the
plots were flooded.
The general agreement between the simulation and the concentration of
the Ca"^", Na , and Cl" shown in the figures is good. The model adequately
simulated the increase of Ca and Na early in the season and the dilution
which occurred after heavy rainfall such as that of June 9, The release of
Ca and Na+ when the second fertilizer application was made on June 19 is
also well simulated. The influence of several rainfalls which occurred later
in the season can be seen in the simulation but sampling was not frequent
enough to pick up the small fluctuations. The model did not simulate height
of the peak in Ca*"*" concentration which occurred at panicle differentiation
application. The chloride concentration was closely simulated throughout
the season except for the period between June 20 and 24 when the simulation
was about one-third greater than measured values.
Similar success was achieved with magnesium and sulfate. The agreement
between the nitrate concentration and that simulated was not very good un-
doubtedly because of the nitrogen transformation for which the mechanisms are
now being investigated by others.
The utility of the model for simulating the water quality is evident.
The concentration of specific ions in the return flow resulting from rainfall
overflow or from deliberate release of water can be simulated at any time
throughout the season. Efforts should be made in the future to use the model
to simulate the quality of irrigation return flow from different soils under
different climatic and irrigation management regimes.
350
-------
IO
DAY NO.
20
Figure 145. Simulated Ca concentration in floodwater from impounded
recommended plots during 1975. The data points are the
actual field data.
351
-------
50
O "
0.
Q.
IO+
10
DAY NO.
20
Figure 146. Simulated Cl concentration in floodwater from impounded
recommended plots during 1975. The data points are the
actual field data.
352
-------
20+
+
(0
z
a.
o.
104
10
DAY NO.
20
Figure 147. Simulated Na concentration in floodwater from impounded
recommended plots during 1975. The data points are the
actual field data.
353
-------
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Rictmeyer, R. D. 1957. Difference Methods for Initial Value Problems. In-
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362
-------
Schwab, G. W. and G. G. Patchett. 1967. Ordram Residue Method for Rice and
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14
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363
-------
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-------
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365
-------
APPENDIX A
Logs of Rainfall and Cultural Practices During the
1973, 1974 and 1975 Growing Seasons
TABLE A-l. LOG OF RAINFALL AND CULTURAL PRACTICES FOR 1973
Date
April 30
May 9
May 23
May 24
May 25
May 31
June 1
June 4
June 5
June 6
June 7
June 8
June 9
June 11
June 12
June 13
June 15
June 24
June 26
July 2
July 3
July 4
July 5
July 6
July 8
July 10
July 25
July 26
July 27
July 30
August 1
August 5
August 6
August 7
August 8
August 13
August 16
August 21
August 24
Rain at
plots (cm)
0
0
0
0
0.76
0.13
0.13
0
0
6.22
0.81
0.38
1.31
5.59
2.03
0.56
0
0.89
0
0..25
0.13
i.02
0.25
7.87
0.13
0.15
0.81
1.27
1.27
0
7.75
0.13
0.13
2.03
0.13
0.64
0.89
0
44.26
Event
Preplant fertilizer; rice planted
Rice emergence
Applied 3.4 kg/ha propanil to all plots
Flooded plots
Drained plots
Applied propanil treatments
Applied tillering nitrogen and permanent flood
Applied carbofuran and molinate
Panicle differentiation nitrogen applied
Applied carbaryl treatment
Plots drained
Plots harvested
366
-------
TABLE A-2. LOG OF RAINFALL AND CULTURAL PRACTICES FOR 1974
Date
April 29
April 30
May 1
May 3
May 4
May 5
May 9
May 10
May 20
May 21
May 25
May 26
May 27
May 28
May 29
May 30
May 31
June 1
June 5
June 6
June 10
June 14
June 20
June 21
June 24
June 26
July 1
July 6
July 14
July 15
July 16
July 17
July 30
July 31
August 2
August 3
August 7
August 12
August 13
August 14
August 15
August 18
August 21
August 22
Rain at
plots (cm)
0
0
1.55
T
0
0.91
1.65
1.96
5.31
T
0.48
0.64
0
0
0
1.27
0.89
1.14
0
0.10
T
0.64
1.79
0. 69
1.24
0.23
1.14
0.15
0.15
0.84
0
8.26
0.46
2.67
2.69
0.69
0.23
0.30
0.25
5.08
0
T
Event
Preplant fertilizer; rice planted
Plots flushed for first time
Plots drained
Rice emergence
Applied 3.4 kg/ha propanil to all plots
Flooded plots
Drained plots
Applied propanil treatments
Applied tillering N-permanent flood
Applied carbofuran and molinate
Panicle differentiation, nitrogen application
Applied carbaryl treatments
Plots drained
(continued)
367
-------
TAELE A-2. (Continued)
Date
Rain at
plots (cm)
Event
August 25
August 26
August 28
August 29
August 30
August 31
September 1
September 3
September 4
September 8
September 9
September 10
September 12
September 13
September 14
September 15
September 16
0.84
3.51
0.99
1.17
0.03
1.12
0.25
0.28
0.51
0.51
42
60
68
Recommended rate plots harvested
Excessive rate plots harvested: 3W, 5W, 6W, IE,
2E, 4E
368
-------
TABLE A-3. LOG OF RAINFALL AND CULTURAL PRACTICES FOR 1975
Date
April 29
April 30
May 2
May 6
May 7
May 8
May 11
May 13
May 15
May 21
May 22
May 23
May 24
May 28
May 29
May 30
June 1
June 5
June 6
June 9
June 10
June 15
June 19
June 21
June 23
June 24
June 25
June 26
June 28
June 30
July 2
July 3
July 10
July 11
July 13
July 14
July 28
July 29
July 30
JuJy 31
August 1
August 3
August 4
August 5
August 7
August 8
August 17
Rainfall at
plots (cm)
2.26
0.05
0.30
0.46
4.39
0.46
0.46
0.58
10.26
3.56
5.26
5.2.6
21.59
0.76
0.64
0.23
T
0.53
0.36
0.43
0.79
0.15
0.51
0.38
0.20
1.73
0.25
0.51
3.56
0.53
0.41
3.78
3.51
0.43
4.06
1.50
0.25
1.27
.05
Event
Preplant fertilizer
Rice planted and flooded
Rice emergence
Applied 3.4 kg/ha ptopanil to all plots
Flood applied
Flood drained
Applied propanil treatments 3.4 kg/ha and
Applied tillering N and permanent flood
Panicle differentiation nitrogen applicati
Applied carbofuran and molinate
Applied carbaryl treatments
Harvest
369
-------
Appendix B
Climatological Data
during the
1973, 1974 and 1975
Growing Seasons
370
-------
TABLE B-l. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT. TEXAS, 1975 (APRIL)
Month
APRIL
Day
1
2
3
4 ~|
5
6
7
8
9
10
11
12
13
Air
Temperature
win tv.ax
51
52
50
43
40
45
49
45
39
78
78
78
70
Relative
Humidity
Ttu'.n max
30
*~28
30
48
63 38
66 [ 30
58 f 78
98
100
98
96
90
98
98
67 56 j 98
70 I 64 | 99
~35 }~ 59 | 27 92
39
49
54"
14 j "
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29 I
30
31
total
r.ecn
64
64
60
57
71
70
70
69
™70
71
68
59
53
49
I 59
h 64
1664
55,5
65 1
~55"
-7T~
/»
78
70
22
~33
36 "
**<+
33
"•9"0~~
85
68 | 86
98
98"
100
96
98
9$ '
99
99
75 60 99
75 1 89
76 j 90
75 87 ,
78
80
L 8i
86
75
74
75
77
2187
72.9
77
71
72 "^
46
52 1
38
"34"
56
LJ7
195
97
98
98
93
98
92
Pan
Evaporation
2 4
.14 .25
.11 .22
.11 .15
.22 .28
.16 .22
.12 .13
.07 .09
.05 .04
i .22 .19
.16 .23
.14 .19
.12 .15
.07 .18
. UO .
-------
TABLE B-2. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1975 (MAY)
Month
MAY
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 ,
16
17
18
19
20
21
22
23
24
25
26
27
28 .
29
30
31
coca I
ir.scn
Air
Temperature
min max
69
64
56
51
54
68
63
60
62
61
67
63
58
55
57 i
51 ~1
58
~5T
67
•71"' "
67
67
73
71
77
f-Tr-
78
74
75
i_J7
76
82
87
85
"83 ""1
86
74 _j
78
79
78
80
""as
85
84
85
~55 1
87
87
71 1 89
69 88
69 88
61
60
60
93
Relative
Humidity
min Ylt9b£
73
86
84
40
34
50
86" '
69
32
46
nfg
54
80
30
34
'"so
26
42
42
59
58
52
5TT
55
97
-9-9- i
99
97
98
98
99
98
98
96
96
96
97
92
70
92
[ 98
98
95
93
97
95 ^
95
94
47 94
56
66
26
83 39
87
66 89
1950 2561
62.9
82.6
34
32
95
95
96
98 1
Pan
Evaporation
2 4
.09 .17
.02 .16
overf 1. .23
.21 .24
.16 .27
.16 .25
overf 1. .17
.08 .09
.08 .25
.16 .27
.11 .24
.11 .27
.11 .18
.18 .28
.14 .26
.18 .27
.17 .28
.14 .27
.17 .25
.15 .29
.14 .18
.15 .35
.14 .25
,_.14 .28
.13 .24
.17 .28
.13 .22
.19 .28
.20 .31
98 .12 .20
98
1566 i 2961
50.5
95.5
.19 .20
4.12 7.48
0.13 0.24
Precipitation
inches
TRACE
1.13
1.01
0
0
0
0.96
0.05
0
0
0
TRACE
0.92
0
0
0
0
0
0
0
0
0
0
0
0
0.27
0
0
0
0
0.04
4.38
0.14
Wind
miles /day
168.9
113.2
102.9
73.6
56,7
120.3
Attno-*
sphere
P.C.
Cl.
Cl.
C.
C.
_JL,c.
136.4 1 Cl.
62.3 1 P.C.
21.6
29.0
60.0
C.
C.
C.
61.0 r..
124.0
__
78.7 i C.
56.9 i P.C.
47.4 | C.
44.9
73.9
79.2
118.9
42.6
102.0
80.9
80.0
63.4
75.2
132.1
61.7
70.0
17.6
49.9
2405
77.6
C.
P.C.
C.
P~.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
Cl.
P.C.
C.
P.C.
C.
* H-haze, C-clear, F. C.-partifllly cloudy, Cl- cloudy
372
-------
TABLE B-3.
SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS. 1975 fJUNEI
Month
JUNE
Day
1
2
3
A
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
total
moan
Air
Temperature
Tiiin max
70
75
74
75
66
64
64
66
68
69
"~ 69
67
74
/h
/3
75
74
73
73
72
70
71
70
71
73
70
70
73
74 "
73
2131
71.0
87
88
88
88
89
88 H
81
~S1 1
83
85
"87 "
84
"8T
82
b8
89
89
90
90
90
90
84
87
89
90
87
Relative
Humidity
min max
66
58
58
62
58
62
58
35
67
70
60
76
77
80
66
63
57
U62
60
60
53
54 _j
46
52
52
62
91 45
91
44
92 ( 52
90
48
i
2626 1763
87.5
58.8
99
96
94
94
96
99
96
90
99
99
98
9?
99
W
96
96
95
95
96
96
99
96
96
98
98
r 97
96
96
96
96
2899
96.6
Pan
Evaporation
2 4
.09 .17
.16 .29
.19 .35
.14 .25
.15 .29
.30 overfl.
.11 .21
I .17 .31
TIB ~7l5
.24
.09 .19
overflow
.05 .22
"".04 "."05 "
.09 .19
.13 .27
.15 .25
.15 .26
.16 .27
.14 .27
.15 .30
.10 .08
.17 .25
.08 .22
.12 .16
.10 .16
. 15 . 30
.18 .33
.15 .31
.16 .32
4.09 6.42
0.14 0.214
Precipitation
inches
0.05
0.03
0
0
0
1.40
0
0
0.56
0.57
2.06
0.86
0.18
0
0
0
0
0
0
0.94
0
0
0
0.11
0
0
0
0
0
5.84
0.19
Wind
miles/day
64.3
111.6
144.4
104.1
94.8
Attiio-*
sphere
P.C.
P.C.
P.C.
P.C.
P.C.
110.6 Pel.
52.2
49.3
53.5
48.5
41.2
82.5
56.3
71.5
61.9
70.4
67.8
35.1
89.4
60.6
54.9
76.5
48.1
18.6
32.8
28.3
40.1 1
70.0
86.3
53.2
1988.8
66.3
P.C.
c.
P.C.
Cl.
Cl.
Cl.
Cl.
Cl.
P.C".
P.C.
P.C.
P.C.
P.C.
P.C.
P.C,
--
Cl.
Cl.
Cl.
P.C,
P.C.
P.C.
P.C.
c.
* H-haza, C-clear, I>. C.-partially cloudy, Cl-cloudy
373
-------
TABLE B-4. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1973 (JULY)
Month
JULY
Day
1
2
3
4
5 n
6
7
S I
9
10
11
12
13
14
15
16
17
IS
19
20
21
22
23
24
Air
Temperature
ir.in max
73
VS
74
74
7'2
71
69
73
73~
72
74
*75~
74
/ j.
73
75
75
73~
/3
75
74
76
"74 "
73
P74
_.
2C
29
30
31
total
Tr.cen
72
7] '
74
91
92
91
92
Relative
Humidity
min nax
44
4/
57
57
9'2"": 52"'
92
~8I
81
89
92
92
92
90
31
91
92
~5l
'91 ' '
93
9
-------
TABLE B-5. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1975 [AUGUSTl
Month AUGUST
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
T /
XH-
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
total
mean
Air
Temperature
tnin max
72
72
70
[_66
69
74
"74
7 11
71
70
70
74
73
70
70
72
72
74
73
73
71
70
65
69
69
70
68
70
71
70
72
2195
91
84
88 j
87 1
87
85
88
89
85"
90
92
92 j
88
30
87
84
82
83
189
92
91
93
91
LJ4
91
90
91
sin
94
Relative
Humid ity
min max
58
80
53
50
48
64
60
lie""1
72
58
44
L 491
62
,- *
Dt
72
64
i~~ 78^
86
58
1 46
46
46
32
1 39
44
42
44
96
97
95
96
95
96
96
98
98
96
98
98
98
38
99
98
97
99
98
98
96
Pan
Evaporation
2 4
overflow
.06 .07
.11 .19
.22 .33
.17 .23
.11 .23
.10 .18
.07 .20
.05 .09
.12 .16
.15 .28
.15 .23
.08 .11
.13 .20
.09 .10
.07 .07
.06 .08
.04 .04
.08 .16
.16 .25
.17 .30
95 .19 .31
96
95
96
.21 .31
.19 .28
.19 .24
97 ' .18 .33
99 ! .31 overfl
54 96
"60~T 98l
94 | 54
94 48
2764 1733
70.8 189.2 55.9
_9_7J
98 I
.17 .20
.17 .23
.15 .19
.13 .24
3007 4.08 5.83
97
0.13 0.19
Precipitation
inches
3.82
0.09
0
0
0
0.58
• 0
. 0.75
0.08
0
0.04
TRACE
0.04
0
0.32
0.03
0.04
0.22
0
0
0
0
0
0
0
o
1.11
Wind
miles /day
51.2
52.8 •
35.4
75.4
30.0
31.4 .
47.0
31.7
11.4
19.8
20.8
26.9
9.3
21. 7
14.6
11.4
9.9
35.6
31.1
18.7
39.8
39.0
31.4
24.6
27.0
32.6
45.4
0 38.9
0.20
0.02
0
7.34
0.24
41.1
30.5
33.9
970.3
31.3
Atmo-
sphere
P.C.
Cl.
P.C.
P.C.
Cl.
P.C.
P.C.
Cl.
P.C.-
1 — P.C,
P.C
Cl.
P.C.
P.O..
Cl.
Cl.
Cl.
Cl.
Cl.
P.C.
c.
P.C.
c.
c.
c.
c.
Cl.
P.C.
P.C.
c.
P.C.
* H-'rta&e, C-eJeax, P. C.-partially r.loudy, Cl-cloudy
375
-------
TABLE B-6. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1974 (APRIL)
Month APRIL
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
i't
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
total
men
Mr
Temperature
min wax
68
56
69
58
43
43
63
57
45
51
68
70
72
65
54
46
50
52
56
48
71
63
6JLJ
58
53
55
83
82
82
87
~72
W
75
Relative
llunidity
rain wax
60
70
45
26
26
20
11
77 ; 60
78 27
73
76
•76
30
57
76
83J 70
35 b8
74 | 40
60_j
77
75
78
96
70
96
98
98
98
82
96
30
) 93
73
98
90
98
98
y /
78
99
321 98
44
49
48
79 i 66"1
81
85
r 74j
64
76 74
81
34
77 L 42
60 i 77 50 j
97
98
96
97
96
99
98
93
r 98
97
60"! 80 58 ( 98
65
65
1746
58.2
Pan
Evaporation
2 4
.11 .21
.06 .12
.14 .25
.15 .28
.23 .26
.23 .31
.20 .32
.05 .14
.22 .37
.14 .25
.11 -14
.02 .07
.06 .15
.12 .21
.18 .25
.10 .05
• 11_ .3.8
.14 .25
.16 .28
• 18 .30
.07 .14
.09 .15
overflow
.08 .17
.16 .28
.14 .24
.16 .25
.12 .22
Precipitation
inches
0
0.01
0
0
0
0
0
0
0
0
0
0.03
0
0.02
0.13
0.46
0
0
0
0
0
0
1.81
0
0
0
0
Wind
miles /day
75.2
125.2
149.9
66.1
97.5
70.9
135.3
92.0
106.1
55.3
207.1
209.7
100.0
78.1
98.6
18.1
38.6
59.4
62.9
165.7
184.4
139.7
103.9
70.4
53.7
46.7
74.6
Atwo-*
sphere
P.C.
P.C.
P.C.
c
P.C.
c
P.C.
Cl
c
£_.
Cl
—
P.C.
P.C.
Cl
P.C.
c_
c
P.C.
—
P.C.
Cl
c
c
—
0 113.0 i P.C.
82 ! 59 i 931 .13 .21 1 0 98.]
82
2359
78.6
64 ( 98
1
1515
50.5
.11 .21
2853 ^ 4C03 6.32
95.1 j 0.13 0.21
0
89.4
2.46
0.08
2986.6
99.6
P.C.
P.C.
* H-haze, C-cle.ar, ?. C.
cloudy, Cl-cloudy
376
-------
TABLE B-7. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1974 (MAY)
Month
MAY
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
total
cean
Air
Temperature
min max
66
64
66
66
63
60
55
60
62
62
63
67
62
74
75
73
72
69
68
69
70
70
65
67
69
71
65
66 j
7f1
74
71
2076
67.0
82
73
Relative
Humidity
min max
64
97
84 64
87
84~
79
79
81
85
85
75
81
88
85
85
84
85
87
88
88
78
83
85
87
88
88
88
86
60
1 62
56
47
43
54
60
72
70
50
54
72
80
78
67
62
57
94
86
68
58
58
58
50
44
98
100
100
98
98
99
98
100
100
99
99
98
98
98
98
98
98
98
98
98
99
99
98
100
98
99
96
97
Pan
Evaporation
2 4
.10 .19
.06 .02
.07 .22
.12 .22
.10 .16
.08 .13
.12 .18
.12 .23
.12 .20
overflow
overf low
.09 .11
.16 .29
.22 .38
.12 .22
.10 .14
.12 .23
. 18 . 31
.20 .29
.20 .32
overf 1 .22_ ._.
.11 .19
.13 -22
.16 .26
.15 .24
.14 .26
.19 .34
.17 .28
37 j 49 98! .20 .32
90
88
56
98
59 98
.18 .30
.24 .38
1
2613 i 1929 305l! 4.67 6.85
84.3
62.2
98. 4j 0.15 0.22
Precipitation
inches
0
0.61
0
TRACE
0
0.36
0
0
0
0.65
0.77
0
0
0
0
0
0
0
L 0
0
2.09
TRACE
0
0
0
0.19
0
0
0
0
0.50
5.17
0.17
Wind
miles /day
61.9
40.7
61.6
79.6
48.7
61.1
49.2
47.5
23.6
99.4 .
7^.7
'44.0
35.9
Ib4.5
125.9
132.2
127.7
110.0
63.0
65.7
90.8
7S.1
65,5
45.5
54.7
78.5
70.4
47.7
86.1
87.5
138.6
2345.1
75.6
Atmo-*
sphere
P.C.
P.C.
P.C.
Cl
Cl
P.C.
P.C.
P.C.
P.C.
Cl
c_
CL__
— j^;'
P.C.
P.C.
P.C.
P.C.
Cl.,.
P.C.
P.C.
c
P..CL.
P._£_.
P^O..
P.C.
P.C.
* H-haze, C-cl.ear, P. C.-partially cloudy, Cl-cloudy
377
-------
T\BLE B-8. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1974 (JUNE)
Month
JUNE
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
33
trccal
r.ean
Air
Temperature
min max
66
68
66
69
72
76
77
78
77
71
65
69
69
Ob
69
70
72
73
7T
71
71
70
71
68
59
58
58
60
62
64
2060
83
87
8G
87
89
88
87
a8
88
90
83
90
90
69
91
!_ 92
Relative
Humidity
mi n max
79
55
50
48
56
62
66
74
78
72
82
47
54
bl
46
44
93 (~ 391
STf-ST
^1 | 46
i_ 91
92
91
93
95
85
83
| 50
49
52
L 45
r 40
h 36)
33
8~b 28
85 1 23
99
97
98
98
98
98
97
97
97
98
Pan
Evaporation
2 4
.17 .17
.20 .22
.18 ,27
.15 .27
.15 .29
.24 .32
.18 .29
.18 .23
.19 .32
.18 .27
98J .26 .39
97
98
99
98
96
97
97
9/
98
97
98
96
96
73
.17 .27
.17 .31
.^4 .35
.09 .32
.11 .34
.20 .30
.21 .34
.21 .31
.20 .29
.21 .32
.21 .33
.23
.31 --
.41 .46
97! .33 .40
98
84
.27 .36
Precipitation
inches
O.fifi
o
0
0
0
0.04
0
' TRACE
0
0.01
TRACE
0
0
0.13
0
0
0
0
0
0
0
0.08
0
0
0
0
0
.24 .33 0
88 | 26 f 80 | .37 .54
87
2659
68,7 J88.6
28
1494
49.8
92
2863
95.4
.12 .16
6.38 8.77
0.21 0.29
0
0
0.92
0.03
Wind
miles/day
qfi.<;
RI^O
39. S
38.4
79.2
171.2
181, 1
184.7
168.8
100.1
48.8
39.9
43.6
82.3
47.4
60.1
60.1
66.4
55.1
66 . 1
40.7
63.6
75.8
..115.7
131.0
98.1
70.5
38.1
67.9
Attno-*
sphere
P.P.
r
p.p.
r.
p.r.
P.C.
. .E.C.
C
Cl
Cl
C
Cl
P.C.
P.C.
P.C.
C
Q
C
C
C
P.C.
p.c.
P_.C.
P.C.
Fj.
C
C
c .
29.0 C
2414.7
80.5
r '
K-hale, C-ciear, P. C.-partial ly cloutlv, Cl-cloudy
378
-------
TABLE B-9. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1974 (JULY)
Month
JULY
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
23
29
30
31
total
Tacr.n
Air
Temperature
min tnax
71
70
71
72
74
72
70
70
69
69
70
69
71
"71
70
70
68
70
71
73
75
73
73
76
76
75
74
72
73
69
2216
71.5
90
90
90
92
95
93
93
90
3'j
91
92
39
93
96
95
8<
90
89
91
93
94
95
96
95
94
92
93
Relative
Humidity
mitt max
54
52
54
43
42
37
43
44
64
50
24
55
42
"39'
42
83
5" 2
56
45
40
52
41
44
43
42
52
52
[ 97 r 42
96
95
95
2864
92.4
96
99
95
94
95
92
99
98
97
97
97
96
97
99
99
99
99
90
9QJ
98
98
98
98
98
97
99
99
Pan
Evaporation
2 4
.17 .24
.15 .18
Precipitation
inches
0
D.3R
.19 .31 0
.29 .35
0
.19 .33 0
. 26 . 40 0
L .19 .25
.18 .22
.15 .24
.19 .29
.21 .33
.14 .21
.27 .33
. 21 . 34 1
.22 .28
.10 .11
.14 .23
.13 .21
.19 .27
.16 .28
. 28 . 30
.19 .31
.22 .34
.23 .32
.21 .28
.20 .29
.33 .41
0.06
0.02
0.46
0
0
TRACE
0
0.09
0.34
0.04
0.07
0.29
0
0
0
0
0
0
0
0
0
Wind
miles /day
54.0
^1,4
74.5
74.4
93.7
41.8
36.1
54.9
39.2
44.8
27.6
66.0
47.5
57.2
38.4
50.8
51.3
46.3
34.7
46.2
46.1
32.o
57.4
55.2
43.7
81.6
14 5 . 0
99 j .34 .25 0 49.8
40 98
35
36
1470
47.4
98
96
.26 .33
.30 .31
.32 .40
t
3021 6.44 8.94
97.4 0.21 0.29
0.12
0
0
1.84
0.06
27.1
60.2
83.9
1713.4
55.3
Atn-iO-*
sphere
P.C.
p.p
P.C.
P.C.
P.C.
P.C.
Cl
P.C.
P.C.
c
c
P.C.
P.C.
Cl
Cl
Cl
c
c
P.C.
c
c
c
P.C.
Ul
P.C.
P.C.
Cl
p.c..,
P.C.
» H-haze, C-clear, P. C.-partially cloudy, 'Cl-cloudy
379
-------
TABLE B-10. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1974 (AUGUST)
Month
AUGUST
Day
1
2
3
4
5
6
7
8
9
10
11
32
•,'.3
15 '
Air
temperature
min wax
67
69
68
70
67
67
71
73
90
88
85
92
87
88 1
84
82
75 89
74
72
1 90
.___
Relative
Humidity
min max
54
61
99
99
58 99
42
99
50 , 99
32 98
^~SS
82
""62"
60
71 1 93 ] --
71 j 92
50
69 ' 92 ! 50
70
16 72
91
90 1
17 j 72 S3
18 j 72
19 1 72
20 72
21
22
70
70
23 ! 72
24
25
26
28
2y
3U
31
7JL_
72
93
-93—1
95
" 93
_9_5_J
as j
91
.91 1
73 [ 80 .
71
74 '
88 1
92 i
73 ! 87 I
73 I 89
73 1
*-~.->i 2206
1
ir. ran
2787
1
71.2 89. 9 i
52 J
56 1
50
54 "
50
36
46
46.
3Q
50
99
99
"HsI
98
97
99
Pan
Evaporation
2 4
overflow
.25 .25
.10 .12
.18 overflow
.14 .21
i .20 .29
.09 .12
overflow
.18 .18
.16 .21
.23 .28
.17 .26
93 .27 .23
99 j .21 .27
99 I -18 .20
98 i .18 .24
98
98
98
96
98
98
98
52 99
93
.19 .26
.18 .27
.20 .29
t .18 .28
.18 .23
.20 .28
.17 .23
.20 .30
99 overfl.22
60 98 ! .12 .23
62 99 .13 .22
78 | 99 1 .12 .21
60
167 J
98 .16 .23
99 .11 .44
i
1663 3051
4.88 6.92
53. 7j 98.4, 0.16 0.22
1'recipitation
inches
3.40
0.04
0.22
1.07
0
0
0.03
1.22
0
0.09
0
0
0.49
0.06
0.31
0,15
0
0
0
0
0
_.._ TRACE
0
0
0.33
1.38
0
0.39
0.46
6.01
0.44
i
10.09
0.32
Wind
miles/day
59.0
27.1
40.3
37.0
32.7 i
, 47.6
27.4
40.5
50.2
94.2
45.4
23.5
14.9
56 .0
34.7
19.2
21.2
35.5
25.0
34.8
34.9
35.0
37.8
63.3
152.2
43.7
31.5
Atmo-
sphere
P.C.
Cl
P.C.
P.C.
P.C.
P.C.
Cl
Cl
._ P.C.
Cl
ElG...
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
c
P.C.
c
c_.
Ci
Cl
P.C.
P.C.
4~9.1 r P.C.
70.2
44.9
1370.4
44.2
Cl
Cl
* H-haze, C-cleay, P. C.-partially Cloudy, ci-cloudy
380
-------
TABLE B-ll. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION. BEAUMONT. TEXAS. 1975 (APRIL)
Month
H 1
Day
1
2
3
4
5
6
7
8
9
10
n
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
total
mean
Air
Temperature
min max
51 78
46 .. 78
36 64
40, .251
.07 .14
.06 overflow
.16 .31
Precipitation
inches
Trace
.02
.00
.00
.00
.00
.89
.45
.02
.66
.00
.00
1.76
.03
.00
.00
.00
.01
.00
.00
.62
.00
.00
.00
.00
.00
.00
.01
•65
.89
Wind
miles/day
54.0
151.0
66.0
87.0
68.0
64.0
121.0
76.0
74.0
110.0
87.0
55.0
125.0
38.0
32.0
176.0
150.0
109.0
77.0
98.0
78.0
100.0
118.0
104.0
96.0
136.0
129.0
65.0
70.0
62.0
Atmo-*
sphere
ci.
ci.
Cl.
' cl.
' cl.
ci.
cl.
P.C.
Cl.
P.C.
Cl.
Cl.
Cl.
Cl.
Cl.
c.
P.C.
c.
P.C.
P.C
Cl.
Cl.
P.C.
P.C.
P.C.
Cl.
P.C.
Cl.
Cl.
Cl.
H= haze, C= clear, P.C.= partially cloudy, Cl.= cloudy
381
-------
TABLE B-12. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1975 (MAY)
Month
May
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
IS
19
20
21
22
23
24
25
26
27
28
29
30
31
total
mean
Air
Temperature
min max
62- 85
65 83
74 84
65 84
67 83
75 84
68 86
66 85
69 87
66 82
65 84
64 87
67 84
64 82
63 76
62 79 .
60 85
63 84
69 84
72 85
75 88
70 86
71 87
69 85
68 88
69 89
68 89
66 84
67 87
65 80
64 79
Relative
Humidity
min max
44 94
56 91
57 94
51 94
62 94
68 96
62 96
54 94
42 94
54 95
52 98
44 95
55 96
46 84
56 99
54 98
33 97
46 97
60 98
67 98
57 98
50 97
50 97
60 99
54 97
48 99
46 97
62 99
62 99
80 99
34 96
Pan
Evaporation
2 4
.12 .14
.13 .19
.12 .23
.13 .20
.09 .17
.08 .15
.17 .24
.13 .21
.16 .33
.08 .05
overflow
.15 .22
.17 .23
.13 .23
.14 .17
.11 .18
•13 .25
.18 .24
.15 .23
.11 .16
.16 .13
•18 .29
.15 .24
.17 .20
•16 .27
.25 .30
.14 .31
overflow
overflow
Overflow
•30 .33
Precipitation
inches
.00
.02
.00
.00
.00
.00
.12
.18
.00
.00
1.73
- .00
.18
,00
,18
.00
.00
.00
.00
.00
.00
.00
.00
.23
.00
.00
.00
4.04
1.40
2.07
.00
Wind
miles/day
29.0
117.0
87.0
77.0
112.0
100.0
97.0
98.0
60.0
32.0
60.0
33.0
61.0
58.0
88.0
59.0
21.0
37.0
68.0
114.0
78.0
81.0
69.0
75.0
71.0
47.0
49.0
71.0
74.0
76.0
66.0
Atmo-*
sphere
Cl.
P.C.
Cl.
Cl.
P.C.
Cl.
P.C.
P.C.
CL.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
t~ .
P.C.
P.C.
Cl.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C:
Cl.
P.C.
P.C.
H= haze, C= clear, P.C.= partially cloudy, Cl.= cloudy
382
-------
TABLE B-13.
SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT. TEXAS. 1975 (JUNE)
Month
Day
1
2
3
4
5
5
7
8
9
10
n
12
13
14 H
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
total
mean
Air
Temperature
min max
58 83
64 86
66 87
72 89
76 89
75 92
73 90
73 89
78 86
70 81
71 81
71 92
72 90
75 89
77 86
76 89
78 89
76 89
75 89
74 92
71 92
72 90
69 90
71 86
72 84
71 83
72 89
69 88
69 88
70 92
Relative
Humidity
min max
39 QR
44 qq
45 qR
57 QR
58 QR
52 qfi
60 qR
54 Qfi
78 TOO
70 97
75 qq
48 97
50 96
52 93
60 98
65 98
53 98
62 97
60 99
L 43 96
46 99
48 99
50 99
58 99
77 99
70 99
52 98
49 ' 99
58 98
I 50 99
Pan
Evaporation
2 4
.21 .35
.16 .34
.17 .27
.18 .33
.17 .28
.20 .34
.14 .26
.15 .16
overflow
overflow
.08 .06
.19 .24
.20 .30
.26 .38
.18 .25
.17 .34
.20 .37
.21 .31
.17 .23
.19 .13
.19 .26
.14 .27
.20 .28
.12 .20
.12 .11
.08 .10
.11 .21
.22 .20
.12 .lb
.12 .21
Precipitation
inches
2.07
.00
.00
.00
.00
.00
.00
Trace
8.50
.53'
.02
.00
.00
.00
.17
.00
.00
.00
.00
.00
.09
.00
.12
.11
.27
.04
.01
.13
Trace
.15
Wind
miles/day
33.0
36.0
49.0
101. 0
82.0
" 107 ."ff
19.0
63.0
82.0
52.0
40.0
26.0
36.0
111.0
91.6
129.0
149.0
1 l.-i.O
bb.O
57.0
22.0
46.0
102.0
41.0
2b.O
33.0
33.0
3b.U
jy.u
Jb.U
Atmo-*
sphere
c
c
c
c
P.C.
P.C.
P.C.
P.C;
1 "cl •
cl '
CI
Cl
c
P.C.
c
P.C.
P.C.
n p
- . - .
P.C.
P.C.
P.C.
P.C.
P.C.
Cl
Cl
Cl
Cl
P.C.
P.C.
P.C.
V haze, C= clear, P.C.= partially cloudy, Cl.= cloudy
383
-------
TABLE B-14. SUMMARY OF CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION, BEAUMONT, TEXAS, 1975 (JULY)
Month
Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19 "
20
21
22
23
24
25
26
27
28
29
30
31
total
mean
Air
Temperature
m1n max
68 86
72 89
74 82
70 90
72 91
73 90
73 92
73 92
75 93
76 91
72 86
70 91
71 91
69 87
72 83
70 87
72 88
73 90
74 90
73 94
73 95
76 87
/b 91
72 89
12 91
12 12
12 y /
it y 3
7 j yi
71 •»!
f J O'J
Relative
Humidity
min max
56 99
46 98
61 98
46 95
46 96
44 95
40 96
42 95
39 99
55 99
70 99
51 99
40 99
68 99
64 99
57 99
62 99
61 99
50 99
50 99
4K 99
69 99
65 99
60 99
58 99
60 99
48 99
56 99
63 99
64 99
75 99
Pan
Evaporation
2 4
.15 .22
• '•. U2 . 23
— .19 .07
.14 .24
.17 .30
.25 .32
.21 ,34
.19 .26
.19 .26
.21 .34
.15 .19
.13 .25
.17 .30
.14 .16
.08 .13
.12 .18
.10 .18
.20 .28
.18 .36
.11 .27
.17 .28
.09 .13
.10 .14
.11 .11
.11 .24
.14 .22
.16 .33
.18 .29
.21 .28
.15 .16
overflow
Precipitation
inches
.12
.00
.18
.00
.00
.00
.00
.00
.00
.18
.55
.00
.15
.07
.03
.00
Trace
.00
.00
.00
Trace
0.1
0.6
.00
.00
.05
.00
. 3b
.40
.11
. JS
Wind
miles/day
60
50
31
34
56
62
76
82
54
83.8
60.3
40.3
62.8
btf.b
46.7
39.9
52
*i J
63.2
40.3
46.7
34.4
40.6
42.8
38.1
Ar. 3
49.2
bJ.I
bO.a
b>l.b
53.8
Atmo-*
sphere
P.C.
P.C.
P.C.
c
P.C.
P.C.
c
P.C.
P.C.
c
P.C.
Cl
P.C.
P.C.
Cl
P.C.
P.C.
P.C.
P.C.
P.C.
Cl
c
P.C.
P.C.
c
P.C.
P.C.
P.C.
P.C.
Cl
P.C.
H= haze, C= clear, P.C.= partially cloudy, Cl.= cloudy
384
-------
TABLE B-15. SUMMARY CLIMATOLOGICAL OBSERVATION AT THE TEXAS AGRICULTURAL
EXPERIMENT STATION. BEAUMONT. TEXAS. 1975 (AUGUST)
Month
Day
1
2
3
4
5
6
7
8
5
10
11
12
13
14
15
16
17
18
W
20
Zl
22
23
24
25
26
27
28
29
30
31
total
mean
Air
Temperature
min max
71 90
71 86 ±
73 84
72 87
71 87
71 89
73 91
68 89
69 86
72 85
73 91
73 91
72 93
73 93
73 94
74 90
73 92
73 92
73 92
73 95
74 92
74 90
"74 ' " 86 '
76 86
72 89
73 87
VI 90
71 91
/J 90
12 " 'Hb
Relative
Humidity
mi n max
63 99
71 99
71 99
72 99
65 99
60 99
56 99
58 99
68 99
69 99
54 99
57 99
54 99
51 99
53 99
60 99
56 99
59 99
53 99
50 98
63 98
60 99
64 99
86 99
75 99
75 99
65 58
57 98
66 98
08 9B
Pan
Evaporation
2 4
overflow
.14 .09
.13 .37
overlfow
.12
.12 .06
.21 .27
.21 .42
.18 .36
.10 .15
.14 .24
.13 .21
.13 .25
.16 .25
.20 .28
.09 .18
.17 .21
.17 .27
.15 .18
.14 .22
.11 .19
.18 .28
.21 .23
overflow
.10 .17
.12 .25
.15 .27
.16 .25
.14 .19"
.03 .04
Precipitation
inches
1.49
Trace
.26
2.16
1.10
.00
.13
.40
.02
.00
.00
.00
.00
.00
.00
.00
.05
.00
.00
.00
.00
.57
.38
1.13
.26
.31
.00
.00
.00
.00
Wind
miles/day
73.3
54.8
50.2
58.1
39.9
27.6
45.4
49.5
57.8
31.4
28.9
25.1
29.8
34.2
35.1
25.5
26.2
J/.2
23.4
23.3
28.3
63.8
44.5
47.5
46.8
66.5
73.4
44. £
35.9
43.7
Atmo-*
sphere
P.C.
P.C.
P.C.
P.C.
Cl
P.C.
P.C.
Cl
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
P.C.
Cl
P.C.
Cl
P.C.
p"7c~:
Cl
*H= haze, C= clear, P.C.- partially cloudy, Cl." cloudy
385
-------
APPENDIX C
DETAILED CHEMICAL ANALYSIS METHODS FOR SOIL, SOIL SOLUTIONS AND WATER
SAMPLES TAKEN FROM RICE PADDIES DURING THE 1973, 1974 AND 1975 GROWING SEASONS
Methods
Chemical analysis methods for soils, soil solutions, and water samples
were those found in Methods of Soil Analysis, Monograph No. 9, ASA, Diagnosis
and Improvement of Saline and Alkali Soils, USDA Handbook 60, and Standard
Methods for Examination of Water and Wastewater, American Public Health Asso-
ciation, Inc. Nutrient ion analysis was performed by either autoanalyzer,
atomic absorption, or flame emission.
Soil Extractions
The following extraction procedures were used in the determination of
NH , NO ~ NO ~, PO ~ , SO ~2, and Cl~. All extracts were analyzed using a
Technicon Autoanalyzer.*
N0,+, NO ~ and NO ~
An equilibrium extraction using IN KC1 was used to extract all soil sam-
ples for NH, , NO-", and NO ~. Ten grams of soil were placed in a 250 ml
centrifuge tube and 100 ml of IN KC1 was added. The tubes were stoppered and
placed on a reciprocating shaker (150 cycles/min.) for exactly 5 minutes. The
suspension was then centrifuged for 4 minutes at 1200 RPM and the supernatant
was poured off through a Whatman No. 1 filter. Corrections for soil moisture
were made and results were reported on an oven dry basis.
Example: TT _ ,
* amt. HO lost
-,— 7 r~z 7—I c „ ... x 100 = % moisture
(amt. of sample) - (amt. of H^O)
10 - (10 X % H20 as decimal) = dry wt.
100 X ppm = dry ppm
*Mention does not constitute endorsement.
386
-------
An extract using 1.4N NH^OAc was used to determine P_ in soil samples.
Ten grams of soil were placed in a 250 ml centrifuge tube and 50 ml of 1.4N
NH,OAc was added. The centrifuge tubes were placed on a reciprocating shaker
(150 cycles/min.) for 15 minutes. The suspension was centrifuged at 1200 RPM
for 4 minutes and the supernatant filtered with Whatman No. 1 filter paper.
Samples were analyzed within 2 days after extraction. Appropriate moisture
corrections were made and final data were reported on an oven dry basis.
Example: 10 - (10 X % H20 as a decimal) = dry wt.
50 .
dry wt. X Ppm = dry ppm
S0~2 and Cl~
Ten grams of soil were weighted out into a 250 ml polyethelene bottle
and 100 ml of de-ionized water were added to each bottle. The bottles were
then placed on a reciprocating shaker for 5 minutes at 150 cycles/min. The
suspension was centrifuged at 3,000 RPM for 30 minutes and the supernatant
was filtered through 2 thicknesses of Baroid Low Pressure filter paper. No
suction was used in the filtering process. The filtrate was analyzed within
2 days after extraction. Corrections were made for moisture and final data
reported on an oven dry basis .
Example: 10 - (10 x % H20 as decimal) = dry wt .
100
dry wt.
pH and E.G.
x ppm = dry ppm
Conductivity was measured using a wheatstone bridge, and pH by a pH
meter. The suspension from the water extract procedure used in the determi-
nation of SO ~2 and Cl~ was also used to determine pH and E.G.
Ca+2. Mg+2
Calcium and Magnesium analysis was made using atomic absorption. The
1.4N NH OAc extracts used in PO ~3 analysis were also used for the analysis
of these two cations. Moisture corrections were made and results reported on
an oven dry basis.
Na+
Potassium and Sodium analysis was made using flame emission. The 1.4N
NH,OAc extract was also used in this analysis. Results were reported on an
4 , ,
oven dry basxs.
387
-------
Water Samples and Soil Solution Analysis
All water and soil solution samples were analyzed for nutrient ions
Lor
V
using the autoanalyzer, atomic absorption, or flame emission. The auto-
analyzer was used to determine NH, , NO ~, NO ~, PO/ , SO, , and Cl~ using
Technicon Methods. Results were reported in ppm.
Documented procedures for the analyses were:
Nitrate and Nitrite
Ortho Phosphate
Chloride
Sulfate
Ammonia
Industrial Method No. 100-70W
June, 1973 Preliminary
Industrial Method No. AAII
94-70W
June, 1971
Industrial Method No. AAII
99-70W
June, 1971
Industrial Method No. 118-71W
December, 1972 Preliminary
Industrial Method No. AAII
98-70W
June, 1971
388
-------
Appendix D
Daily Water Depths During
1974 and 1975 in Each Plot
389
-------
TABLE D-l. WATER DEPTH AT THE END OF EACH DAY DURING PERMANENT FLOOD IN 1974
(JUNE 6 - JULY 4)
Plots
Date
June 6
June 7
June 8
June 9
June 10
June 11
June 12
June 13
June 14
June 15
June 16
June 17
June 18
June 19
June 20
June 21
June 22
June 23
June 24
June 25
June 26
June 27
June 28
June 29
June 30
July 1
July 2
July 3
July 4
IE
9.6
10.0
10.7
11.9
10.3
9.3
8.9
8.6
8.6
6.8
5.3
3.8
2.6
0.8
9.8
9.6
8.6
7.5
9.5
8.4
7.2
6.0
11.0
10.1
9.3
10.1
9.3
8.4
7.6
2E
7.8
9.9
11.8
11.7
9.1
8.4
8.0
8.1
6.8
4.9
3.4
2.1
1.1
0.1
5.7
5.8
5.1
4.2
3.9
2.8
1.7
1.9
4.9
4.9
4.8
6.2
6.3
6,2
6.3
3E
9.8
8.3
9.1
11.3
10.1
9.1
8.6
8.3
8.3
6.6
4.9
3.0
1.4
0.2
11.2
10.9
9.8
8.8
11.9
10.5
9.4
8.3
11.7
10.6
9.7
10.6
9.6
8.6
7.4
4E
7.2
9.5
9.8
10.5
10.9
9.6
9.1
9.2
8.4
6.5
5.1
4.0
3.6
3.6
9.8
13.2
13.2
13.1
10.8
8.3
7.3
7.1
7.0
6.6
6.3
8.0
8.1
7.8
7.8
5E
10.8
9.1
8.1
8.7
9.8
9.0
8.7
8.9
9.7
8.3
6.8
5.5
4.2
2.6
9.5
9.3
8.5
7.7
9.8
8.7
7.7
6.7
12.4
11.2
10.3
11.2
10.1
9.2
8.6
6E
1.8
1.8
3.0
4.3
2.2
3.8
5.9
7.0
6.3
4.4
3.1
1.6
1.2
1.6
7.5
9.0
8.6
8.4
9.2
8.7
8.1
7.5
7.4
7.2
7.1
8.3
8.5
8.3
8.0
1W
9.5
12.4
12.1
11.8
12.0
12.2
12.4
12.7
11.7
10.3
9.3
7.9
7.3
7.1
9.5
10.6
10.5
10.3
9.9
9.8
9.9
10.5
10.8
10.6
10.7
12.2
11.6
11.2
11.1
2W
7.2
6.8
8.5
8.5
8.8
8.8
9.0
9.3
9.3
7.7
6.3
2.7
0.0
0.0
6.2
5.2
3.3
1.8
6.8
5.3
3.9
2.6
8.1
7.2
6.5
7.2
6.5
5.5
4.7
3W
8.2
8.6
11.8
12.1
13.1
13.2
13.3
13.2
13.3
11.9
10.3
9.0
8.2
7.0
13.0
13.0
12.1
11.2
13.8
12.8
11.9
11.0
14.1
13.3
13.5
13.4
12.7
11.9
11.2
4W
2.2
2.2
2.2
2.2
2.1
2.2
2.1
2.2
1.2
0.0
0.0
0.0
0.0
0.0
0.5
3.1
3.8
4.1
4.1
2.9
2.1
2.9
3.2
3.4
3.7
4.3
2.8
3.1
4.9
5W
11.5
11.1
13.9
14.7
15.5
15.8
15.7
15.7
15.4
12.7
12.4
9.9
9.1
7.9
6.9
6.9
6.0
5.1
11.0
9.5
8.6
7.4
11.6
10.5
9.6
10.1
9.0
8,0
7.7
6W
3.1
6.3
8.4
8.7
9.0
8.6
8.4
8.1
6.7
4.9
3.5
2.2
1.7
1.3
0.5
1.3
1.4
1.4
1.3
1.9
2.6
3.8
4.5
5.0
5.7
7.6
7.4
7.3
7.1
-------
TABLE D-2. WATER DEPTH AT THE END OF EACH DAY DURING PERMANENT FLOOD IN 1974
(JULY 5 - AUGUST 2)
Plots
Date
July 5
July 6
July 7
July 8
July 9
July 10
July 11
July 12
July 13
July 14
July 15
July 16
July 17
July 18
July 19
July 20
July 21
July 22
July 23
July 24
July 25
July 26
July 27
July 28
July 29
July 30
July 31
August 1
August 2
IE
6.6
6.1
5.6
7.2
6.5
5.8
5.3
9.9
9.3
9.9
9.8
9.5
9.8
9.1
8.5
7.8
7.1
15.4
14.8
14.1
13.3
12.3
11.4
10.7
14.1
13.2
7.0
6.1
6.3
2E
6.8
7.7
8.2
10.6
10.5
10.1
9.9
10.9
10.6
11.6
10.7
10.2
10.6
9.8
9.8
9.6
9.4
9.2
9.2
9.1
9.3
9.4
9.5
9.8
9.8
9.8
10.0
10.1
10.8
3E
6.5
5.9
5.2
6.7
6.0
5.1
4.5
6.6
6.1
6.6
6.6
6.3
6.7
6.0
5.3
4.5
3.6
3.1
2.1
6.2
5.6
4.6
3.7
2.9
8.2
7.2
9.0
8.2
8.4
4E
8.0
8.7
9.2
10.7
9.3
8.7
8.7
9.0
9.5
10.7
10.1
9.6
9.8
9.1
8.9
8.5
8.1
8.0
8.1
8.2
8.3
8.4
8.3
8.4
8.4
8.5
11.1
9.8
10.1
5E
7.7
7.4
6.8
8.6
8.2
7.5
6.9
10.4
9.7
8.7
7.8
6.9
6.7
4.7
3.2
1.6
0.0
13.0
14.1
13.4
12.5
11.5
10.6
9.8
11.1
12.1
16.0
13.4
12.9
6E
8.2
8.5
8.7
10.8
9.9
9.8
9.8
9.7
9.6
10.2
10.0
9.9
10.3
10.2
9.9
9.5
9.4
9.4
9.3
9.1
9.2
9.0
8.8
8.7
8.6
8.4
14.1
8.4
7.3
IV
11.3
11.5
11.4
16.3
12.5
11.7
11.5
13.9
12.6
12.3
12.6
12.7
13.4
12.9
12.4
12.1
11.8
13.9
12.4
12.0
12.0
12.0
12.2
12.2
11.9
12.0
12.0
12.5
13.4
2VJ
3.8
3.0
2.5
8.5
8.6
7.8
6.8
8.2
7.3
7.7
7.6
7.3
7.7
7.2
6.5
5.7
4.8
9.7
11.2
10.5
9.7
8.6
7.4
6.4
9.4
7.9
7.8
6.7
6.4
3W
10.3
9.9
9.4
13.4
12.7
12.0
11.6
12.5
11.9
12.6
12.3
12.1
12.6
11.9
11.4
10.7
9.8
14.1
13.3
12.6
12.0
11.3
10.5
9.8
13.5
12.7
11.0
10.6
10.9
4W
4.9
4.4
4.3
5.7
4.1
3.3
2.9
2.4
2.3
3.3
3.3
3.1
3.9
3.8
3.9
4.2
4.4
4.2
4.0
3.8
3.9
4.5
5.4
5.4
5.8
5.9
3.0
5.5
6.2
5W
6.7
6.3
5.7
6.6
5.9
5.2
4.7
8.8
8.2
8.7
8.8
8.5
9.0
8.3
7.5
6.6
6.4
5.1
4.0
9.8
10.8
11.3
11.6
12.3
13.6
13.2
9.1
9.9
11.8
6W
7.4
7.0
6.9
8.3
7.0
6.4
6.3
6.1
5.9
6.5
6.7
7.3
8.2
7.5
6.7
6.3
5.9
2.2
0.8
3.8
4.8
5.4
5.7
6.3
8.2
8.0
4.3
4.7
7.1
-------
TABLE D-3. WATER DEPTH AT THE END OF EACH DAY DURING PERMANENT FLOOD IN 1974
(AUGUST 3 - AUGUST 23)
00
Plots
Date
August 3
August 4
August 5
Augus t 6
August 7
August 8
Augus t 9
August 10
August 11
August 12
Augus t 13
Augus t 14
August 15
August 16
August 17
August 18
August 19
August 20
August 21
August 22
August 23
IE
9.3
8.9
8.3
7.9
9.3
7.4
6.5
5.8
5.2
5.5
4.8
4.9
4.8
4.2
3.5
2.8
2.1
1.3
1.0
0.0
0.0
2E
13.5
11.5
10.7
10.6
13.0
11.3
10.7
10.3
10.2
10.7
10.4
10.4
10.4
10.1
9.8
9.7
9.5
0.0
0.0
0.0
0.0
3E
11.4
10.8
10.1
9.7
11.1
10.6
10.2
9.6
8.9
9.0
8.5
8.7
8.6
7.8
7.1
6.5
5.9
5.2
0.0
0.0
0.0
4E
12.4
10.1
8.9
8.8
11.1
10.1
9.5
9.1
9.4
10.1
9.7
9.8
10.1
9.7
9.4
9.1
9.1
9.3
0.0
0.0
0.0
5E
14.6
13.9
12.6
12.0
14.1
12.5
11.8
11.1
10.6
11.1
10.7
10.9
10.8
10.1
9.3
8.7
8.1
7.4
6.4
0.0
0.0
6E
9.5
7.6
6.6
6.4
9.2
7.5
6.7
6.2
5.9
6.5
6.2
6.6
6.3
5.8
5.5
5.3
5.1
5.0
0.0
0.0
0.0
1W
16.6
14.7
13.3
13.1
14.9
13.5
13.1
12.9
12.6
12.1
11.3
11.4
11.4
11.5
11.3
11.1
11.3
11.1
10.5
0.0
0.0
2W
9.1
7.9
6.6
5.9
8.7
8.0
7.2
6.3
5.3
5.2
4.1
3.8
3.3
2.5
1.5
0.4
0.0
0.0
0.0
0.0
0.0
3W
13.8
13.4
12.6
12.2
13.1
10.9
10.6
10.0
9.4
9.7
9.2
9.4
9.4
8.6
7.8
7.2
6.4
5.9
5.4
0.0
0.0
4W
7.3
6.4
6.3
6.5
6.9
6.7
6.4
6.3
6.4
6.9
6.6
6.8
7.1
7.2
7.2
7.2
7.1
7.2
0.0
0.0
0.0
5W
16.1
14.5
13.5
13.6
13.8
11.5
10.7
10.1
9.8
10.5
10.2
10.6
10.6
9.7
9.3
9.1
8.7
8.8
0.0
0.0
0.0
6W
10.1
9.8
8.9
8.9
9.2
6.8
6.0
5.4
5.2
6.1
5.7
6.1
6.0
4.9
4.5
4.3
4.0
4.1
0.0
0.0
0.0
-------
TABLE D-4. WATER DEPTH AT THE END OF EACH DAY DURING PERMANENT FLOOD IN 1975
(JUNE 5 - JULY 3)
u>
Plots
Date
June 5
June 6
June 7
June 8
June 9
June 10
June 11
June 12
June 13
June 14
June 15
June 16
June 17
June 18
June 19
June 20
June 21
June 22
June 23
June 24
June 25
June 26
June 27
June 28
June 29
June 30
July 1
July 2
July 3
IE
12.0
9.6
7.8
6.2
20.8
15.3
13.1
11.8
10.5
9.4
9.0
8.0
6.9
5.4
12.3
10.9
10.0
9.3
13.1
13.0
13.1
13.3
12.9
13.2
12.9
12.6
12.0
12.1
12.3
2E
14.6
16.5
15.8
15.1
21.7
17.8
15.9
15.1
14.8
14.7
15.4
15.3
15.1
14.6
14.2
14.5
14.8
15.3
15.1
14.6
14.6
15.3
15.5
16.2
16.5
17.0
17.1
16.3
16.2
3E
12.0
10.8
9.6
8.7
25.8
22.2
16.8
14.3
13.0
11.7
11.3
10.3
8.9
7.5
12.4
11.1
10.0
8.9
11.1
10.7
10.6
10.6
10.1
10.3
9.9
9.7
9.0
9.0
9.3
4E
15.9
15.5
13.2
12.4
22.3
15.9
14.2
13.3
13.1
13.4
14.4
13.4
12.5
12.0
11.8
12.0
12.8
13.4
12.5
12.0
12.4
12.9
12.5
14.7
15.3
13.8
12.4
11.9
13.2
5E
7.4
6.4
5.4
4.6
20.2
14.7
11.7
9.5
8.3
7.1
6.8
5.8
4.5
3.4
7.2
6.0
5.0
4.3
7.3
7.1
7.3
7.5
7.0
7.2
7.0
6.7
6.2
6.2
6.5
6E
18.4
19.0
17.4
16.9
23.7
19.0
17.7
17.0
16.7
16.5
16.7
16.2
15.5
15.1
15.6
15.7
16.0
16.2
16.0
15.6
16.4
17.4
17.2
17.6
17.0
16.6
16.9
18.0
18.1
1W
13.2
15.3
14.6
14.5
18.8
17.4
15.5
14.1
13.2
12.2
12.1
11.4
10.4
9.7
12.1
12.5
12.8
12.8
13.0
13.1
13.5
14.2
14.3
15.3
15.1
15.4
15.2
15.0
15.4
2W
29.1
26.9
25.7
24.7
22.1
19.0
16.8
15.6
14.7
13.5
13.2
12.4
11.3
10.2
13.4
12.5
11.7
11.0
13.9
13.8
13.9
14.2
13.6
13.8
13.4
13.1
12.5
12.5
12.6
3W
10.2
9.2
8.3
7.7
19.0
13.7
11.4
10.0
9.0
8.0
7.9
7.3
6.3
5.3
8.8
7.9
7.3
6.7
8.3
8.3
8.6
8.9
8.4
8.7
8.3
8.1
7.6
7.9
7.7
4W
1^.3
16.3
14.7
14.3
19.8
16.7
15.2
14.6
14.3
14.1
14.9
14.6
14.0
13.8
13.5
13.5
13.8
13.9
13.3
13.1
13.5
14.3
14.3
15.0
14.8
14.4
13.4
13.7
14.3
5W
9.7
10.4
9.5
8.7
20.6
14.6
12.2
10.8
9.7
8.7
8.5
7.7
6.6
5.6
9.2
8.4
8.0
7.5
10.2
10.1
10.4
10.6
10.1
10.4
10.0
9.8
9.2
9.2
9.5
6W
14.4
12.1
8.9
7.4
20.1
13.2
8.4
6.0
5.3
4.3
4.1
3.2
2.0
11.6
12.2
12.6
13.1
13.3
13.2
11.6
10.6
10.7
10.6
11.6
12.3
12.7
13.4
14.1
14.6
-------
TABLE D-5. WATER DEPTH AT THE END OF EACH DAY DURING PERMANENT FLOOD IN 1975
(JULY 4 - AUGUST 1)
Plots
Date
July 4
July 5
July 6
July 7
July 8
July 9
July 10
July 11
July 12
July 13
July 14
July 15
July 16
July 17
July 18
July 19
July 20
July 21
July 22
July 23
July 24
July 25
July 26
July 27
July 28
July 29
July 30
July 31
August 1
IE
11.8
10.9
10.1
13.2
12.4
11.2
10.4
12.6
12.0
11.6
11.9
11.7
11.2
11.9
11.3
10.4
9.8
8.9
10.9
10.7
10.3
9.8
9.2
8.3
12.8
12.9
13.3
15.7
18.1
2E
16.0
15.8
15.8
15.4
14.9
14.9
14.8
16.6
16.3
15.8
15.4
14.5
13.6
13.5
12.9
12.3
11.9
13.2
13.1
13.0
12.9
12.6
12.2
11.6
13.2
13.3
13.7
16.8
19.0
3E
8.6
7.8
6.7
11.2
10.4
9.3
8.4
10.4
9.8
9.3
9.7
9.4
8.9
10.9
10.2
9.2
8.5
7.7
10.5
10.3
9.9
9.2
8.6
7.9
12.7
12.7
13.1
16.4
18.9
4E
14.9
15.2
15.4
14.0
12.7
11.8
11.2
12.8
11.9
11.3
11.5
10.8
10.3
10.6
11.1
11.1
11.8
11.7
11.9
11.9
11.8
11.6
11.5
10.7
11.5
11.8
11.8
14.8
16.4
5E
6.0
5.1
4.3
9.0
8.1
7.2
6.4
8.3
7.7
7.3
7.5
7.4
6.9
9.4
8.5
7.6
6.9
6.0
8.1
7.8
7.4
6.8
6.2
5.4
8.3
8.3
8.7
12.5
15.5
6E
17.5
17.1
16.9
16.4
16.3
16.3
16.0
17.8
17.6
17.3
16.9
16.0
15.7
15.4
15.3
14.9
14.3
14.6
15.0
15.4
15.4
15.3
15.1
14.7
15.1
15.5
16.2
18.9
20.8
1W
15.6
15.5
15,2
15.4
15.4
14.0
13.4
14.6
13.6
12.8
13.1
12.8
12.4
12.1
11.8
11.0
10.3
13.7
13.5
13.6
13.7
13.4
12.6
12.2
13.3
13.7
14.0
17.3
18.7
2W
12.0
11.1
10.1
14.8
13.7
12.7
11.7
13.5
12.9
12.5
12.6
12.4
11.9
15.1
14.3
13.3
12.4
11.3
15.4
14.6
13.3
12.3
11.1
9.9
14.6
14.2
14.2
17.6
20.4
3W
7.2
6.3
5.3
11.6
9.9
8.6
7.6
9.4
8.6
8.1
8.3
8.2
7.7
11.2
9.9
8.7
7.9
7.1
11.6
10.7
9.8
9.1
8.3
7.5
11.1
11.0
11.0
15.1
18.1
4W
13.6
13.0
12.5
12.6
13.3
13.3
13.2
14.8
13.7
13.3
13.7
13.8
13.4
13.0
12.2
11.4
10.5
12.1
12.2
12.6
12.5
12.4
12.2
11.5
14.0
14.1
14.4
17.1
18.9
5W
8.9
8.1
7.1
12.0
10.7
9.5
8.6
10.4
9.7
9.3
9.6
9.3
8.8
11.1
10.2
9.2
8.5
7.7
12.0
11.2
10.4
9.7
9.1
8.4
11.5
11.8
12.0
15.4
18.1
6W
14.4
14.4
14.6
14.5
13.7
12.8
12.6
13.9
12.9
12.5
12.5
11.7
11.0
10.7
11.9
10.1
9.6
10.1
8.8
7.7
8.7
12.2
11.2
10.1
10.8
11.3
11.3
13.6
15.4
-------
Ul
TABLE D-6. WATER DEPTH AT THE END OF EACH DAY DURING PERMANENT FLOOD IN 1975
(AUGUST 2 - AUGUST 16)
Plots
Date
August 2
August 3
August 4
August 5
August 6
August 7
August 8
August 9
August 10
August 11
August 12
August 13
August 14
August 15
August 16
IE
14.9
14.2
16.6
16.6
14.9
7.6
8.6
8.3
7.9
7.5
7.1
6.7
6.2
5.6
5.3
2E
16.0
15.5
18.2
17.9
15.9
15.3
16.1
15.3
14.8
14.5
13.8
13.3
13.1
12.9
12.8
3E
15.5
14.9
16.5
16.5
14.6
5.4
5.1
4,9
4.5
4.0
3.4
2.8
2.1
1.3
0.7
4E
13.1
12.4
17.2
15.5
13.9
13.6
14.6
14.0
13.8
13.8
13.3
13.5
13-7
13.2
12.9
5E
12.9
12.1
13.5
12.4
11.3
2.2
3.3
3.1
2.7
2.1
1.7
1.2
0.4
0,0
0.0
6E
17.2
16.1
19.7
19.1
17.4
17.1
17.9
17.0
36.7
16.5
16.7
16.9
17.0
17.1
17.3
1W
15.1
14.7
18.0
17.5
15.7
15.0
15.7
14.9
14.4
14.3
14.3
14.2
14.2
14.0
13.9
2W
17.4
16.6
17.8
18.1
16.1
9.3
9.9
8.9
7.8
6.7
5.7
4.6
3.5
2.3
0.7
3W
15.6
15.4
17.1
14.3
11.6
3.7
4.3
3.9
3.5
3.0
2.3
1.7
1.2
0.5
0.0
4W
15.5
14.7
17.8
17.3
15.1
14.4
14.8
14.1
13.7
13.5
13.8
13.8
13.9
13.8
13.8
5W
14.9
14.9
14.8
14.8
12.2
5.7
6.6
6.4
6.0
5.4
4.9
4.3
3.8
3.2
2.8
6W
11.6
10.7
14.9
14.3
12.5
11.9
12.4
11.8
11.5
11.4
11.3
11.0
10.5
10.0
9.8
-------
Appendix E
Minimum and Maximum Soil and
Water Temperatures in the Rice Paddies
396
-------
TABLE E-l. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BEAUMONT, TEXAS (JUNE 1 - JUNE 50. 1973)
June 1 - June 30, 1973
June
of
1973
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
A
MIN.
27.78
27.78
26.67
26.67
26.67
26.61
26.39
24.44
25.89
26.67
27.22
26.67
27.50
27.67
27.67
27.22
29.61
Soil (°C)
MAX.
31.94
32.22
32.22
32.78
31.67
31.39
28.78
30.00
30.00
32.22
30.00
32.78
32.50
32.11
31.67
32.22
31.56
MEAN
30.17
29.06
29.22
29.11
29.06
28.72
27.06
27.28
28.00
29.00
28.72
29.56
30.00
29.83
29.61
29.50
29.00
Water (°C)
HIS. MAX.
27.22
26.67
26.39
26.11
26.39
25.72
25.28
25.89
25.00
26.39
26.94
26.11
27.22
27.22
27.22
26.78
26.33
33.89
33.61
34.17
34.17
33.06
34.44
28.28
30.94
30.72
33.89
31.39
36.11
34.39
34.33
33.17
34.22
33.17
MEAN
30.28
29.39
29.44
29.39
30.06
30.33
26.39
27.22
28.n
-------
TABLE E-2. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BEAUMONT, TEXAS (JULY 1 - JULY 31, 1975)
July 1 - July 31, 1973
July
of
1973
1
2
3
4
5
6
7
8
9
10
11
12
13
14
i5
ID
17
18
19
20
21
22
23
24
25
26
27
28
29
3C
31
A
Soil (°C)
MIN. MAX.
27.67
28.33
30.56
28.33
27.78
26.11
25.56
24.56
_
26.67
30.17
30.83
30.00
30.00
30.00
_
29.44
29.44
30.00
30.11
30.00
30.00
29.44
29.94
30.00
29.56
30.00
30.00
30.00
-
29.06
33.33
32.50
32.67
32.67
31.33
29.33
27.50
30.00
_
32.22
32.22
31.56
31.11
31.11
31.11
_
30.56
31.39
31.39
31.28
31.11
31.11
30.44
31.11
31.11
30.22
30.56
31.00
30.83
-
29.28
MEAN
30.28
30.50
30.72
30.72
29.44
27.44
26.44
26.11
_
29.89
31.17
31.17
30.67
30.61
30.56
_
30.00
30.56
30.89
30.89
30.72
30.56
30.17
30.50
30.33
30.00
30.22
30.50
30.56
-
30.06
Water (°C)
MIN. MAX.
27.22
28.22
30.44
28.33
27.50
26.00
24.61
24.22
26.11
28.78
28.83
27.78
27.61
27.78
_
26.67
27.78
28.17
28.56
28.44
28.72
27.67
26.67
29.67
27.22
26.94
28.89
28.61
-
27.78
35.56
33,33
33.89
34.61
32.22
28.89
27.67
32.22
„
34.44
34.33
32.22
32.50
32.78
32.78
_
31.11
34.44
34.44
34.44
33.33
33.22
32.27
33.33
31.39
31.11
33.17
32.33
32.78
-
32.56
MEAN
30.61
30.89
31.78
31.44
29.44
27.28
26.00
26.89
30.17
31.06
30.11
30.06
23.33
29.72
29.44
30.61
31.61
31.50
31.06
30.33
29.78
30.22
29.72
29.06
29.83
30.72
31.39
_
29.78
MAX. = Daily Maximum; MIN. = Daily Minimum; The table means were comput-
ed from six daily interval chart readings of continuous recordings; A. =
Monthly Average.
398
-------
TABLE E-3. SOIL AND WATER TEMPERATURE IN RICE PADDY
BEAUMONT, TEXAS (JUNE 15 - JUNE 30, 1974)
June 15 - June 30, 1974
June
of
1974
15
16
17
18
39
20
21
22
23
24
25
26
27
2.8
29
30
A.
Soil ( °C)
MEN. MAX.
27.78
27.78
26.67
26.67
26.67
26.61
26.39
24.44
25.89
26.67
27.22
26.67
27.50
27.67
27.67
27.22
26.85
31.94
32.22
32.22
32.78
31.67
31.39
28.78
30.00
30.00
32.22
30,00
32.78
32,50
32.11
31.67
32.22
31.53
MEAN
30.11
29.06
29.22
29.11
29.06
28.72
27.06
27.28
28.00
29.00
28.72
29.56
30.00
29.83
29.61
29.50
28.99
Water ( °C)
MIN. MAX.
27.22
26.67
26.39
26.11
26.39
25.72
25.28
24.44
25.00
26.39
26.94
26.11
27.22
27.22
27.22
26.78
26.32
33.89
33.61
34.17
34.17
33.06
34.44
28.28
30.94
30.72
33.89
31.39
36.11
34.39
34.33
33.17
34.22
33.17
MEAN
30.28
29.39
29.44
29.39
30.00
30.33
26.39
27.22
28.06
29.22
28.89
30.44
30.33
30.28
29.61
29.67
29.31
MAX. = Daily Maximum; MIN. = Daily Minimum; The table means
were computed from six daily interval chart readings of
continuous recordings; A = Monthly Average.
399
-------
TABLE E-4. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BEAUMONT, TEXAS (JULY 1 - JULY 51, 1974)
July 1 - July 31, 1974
July
of
1974
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
A.
Soil (°C)
MIN. MAX.
27.67
28.33
30.56
28.33
27.78
26.11
25.56
24.56
-
26.67
30.17
30.83
30.00
30.00
30.00
-
29.44
29.44
30.00
30.11
30.00
30.00
29.44
29.94
30.00
29.56
30.00
30.00
30.00
-
-
29.06
33.33
32.50
32.67
32.67
31.33
29.33
27.50
30.00
_
32.22
31.56
32.22
31.11
31.11
31.11
-
30.56
31.39
31.39
31.28
31.11
31.11
30.44
31.11
31.11
30.22
30.56
31.00
30.83
_
-
31.14
MEAN
30.28
30.50
30.72
30.72
29.44
27.44
26.44
26.11
-
29.89
31.17
31.17
30.67
30.61
30.56
-
30.00
30.56
30.89
30.89
30.72
30.56
30.17
30.56
30.33
30.00
30.22
30.50
30.56
-
-
30.06
Water (°C)
MIN. MAX.
26.72
28.22
30.44
28.33
27.50
26.00
24.61
24.22
-
26.11
28.78
28.83
27.78
27.61
27.78
-
26.67
27.78
28.17
28.56
28.44
28.72
27.67
26.67
29.67
27.22
26.94
28.89
28.61
_
-
27.66
35.56
33.33
33.89
34.61
32.22
28.89
27.67
32.22
-
34.44
34.33
32.22
32.50
32.78
32.78
-
31.11
34.44
34.44
34.44
33.33
33.22
32.22
33.33
31.39
31.11
33.17
32.33
32.78
_
-
32.77
MEAN
30.61
30.89
31.78
31.44
29.44
27.28
26.00
26.83
-
30.17
31.06
30.11
30.06
23.33
29.72
-
29.44
30.61
31.61
31.50
31.06
30.33
29.78
30.22
29.72
29.06
29.83
30.72
31.39
_
-
29.78
MAX. » Daily Maxirnum; MIN. <• Daily Minimum; The table means
were computed from aix daily interval chart readings of
continuous recordings; A. » Monthly Average.
400
-------
TABLE E-5. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BEAUMONT, TEXAS [AUGUST 1 - AUGUST 19, 1974)
August 1 -August 19, 1974
Aug.
of
1974
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
A.
Soil (°C)
MIN. MAX.
28.89
28.67
28.78
28.33
28.33
-
-
_
27.78
28.33
28.78
28.94
28.72
_
28.33
28.33
28.06
28.06
28.33
28.44
30.56
29.44
29.78
29.83
29.44
-
-
-
28.89
29.06
29.89
30.00
29.17
_
29.33
28.89
28.61
28.89
29.44
29.41
MEAN
29.83
28.67
29.33
29.17
28.88
-
-
-
28.56
28.89
29.28
29.44
28.94
-
28.72
28.67
28.33
28.17
28.83
28.91
Water ( °C)
MIN. MAX.
26.67
26.11
26.67
25.39
25.61
-
-
-
25.44
25.67
26.67
27.83
26.67
-
25.56
26.11
25.56
25.56
26.39
26.13
30.28
29.67
30.00
30.00
29.44
-
-
-
28.33
30.00
31.67
31.39
30.00
—
27.50
26.67
26.67
28.33
31.11
29.40
MEAN
28.28
27.17
28.61
28.00
27.50
-
-
-
26.00
27.22
29.22
29.24
28.06
—
26.44
26.39
26.06
26.22
28.28
27.51
MAX. «• Daily Maximum; MIN. = Daily Minimum; The table means
were computed from six daily interval chart readings of
continuous recordings; A. = Monthly Average.
401
-------
TABLE E-6. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BEAUMONT, TEXAS (JUNE 1 - JUNE 50, 1975)
June 1 - June 30, 1975
June
of
1975
1
2
3
4
5
6
7
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
A
MIN.
_
_
-
_
-
-
-
—
25.67
25.28
26.67
27.50
26.67
26.67
27.22
27.78
27.78
28.00
27.72
27.17
26.94
26.94
25.56
25.50
«.
w
-
26.78
Soil (°C)
MAX.
_
_
_
_
-
-
I
_
26.11
27.50
28.89
29.28
28.78
28.33
28.39
28.61
28.89
29.44
29.00
28.39
28.22
27.50
26.39
26.11
_
_
-
28.17
MEAN
_
_
_
_
_
-
_
25.89
26.22
27.67
28.44
27.56
27.44
28.06
28.11
28.33
28.78
28.50
28.11
27.67
27.33
26.00
25.83
_
27.50
MIN.
_
_
_
_
_
-
_
26.11
24.72
26.39
27.39
26.11
26.67
27.22
26.61
27.17
27.67
26.67
25.83
25.72
25.83
24.61
24.44
^_
26.11
Water (°C)
MAX.
_
_
_
_
-
~
26.22
28.33
30.56
30.89
28.44
29.33
29.89
29.00
29.39
29.78
29.50
28.44
28.06
27.22
25.78
25.67
28.56
MEAN
_
_
_
^
..
-
~
26.11
26.56
28.56
29.22
27.44
28.06
28.56
28.00
28.39
28.67
28.22
27.44
26.89
26.67
25.39
25.17
"
~
27.44
MAX. - Daily Maximum; MIN. - Daily Minimum; The table mean.s
were computed from six daily interval chart readings of
continuous recordings; A. ™ Monthly Average,
402
-------
TABLE E-7. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BBAUMONT, TEXAS (JULY 1 - JULY 31, 1975)
July 1 - July 31, 1975
July
of
1975
1
2
3
4
5
6
7
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
A
Soil (°C)
MIN. MAX.
-
27.50
26.94
26.22
26.33
26.11
26.06
25,83
26.06
26.11
26,33
26.67
-
-
-
25.89
26.33
26.39
26.33
-
-
_
-
26.33
-
27.78
27.78
26.89
27.00
27.00
26.39
26.17
26.22
26,67
27.22
27.22
-
-
-
26.67
26.83
26.94
27.22
-
-
-
-
26.94
MEAN
-
27.67
27.33
26.67
26.72
26.44
26.17
26.06
26.17
26.33
26.67
27.06
-
-
-
26.22
26.61
26.67
26.78
-
-
-
-
26.61
Water (°C)
MIN. MAX.
-
27.22
26.17
25.22
25.56
25.22
25.28
25.00
25.06
25.00
25.33
26.00
26.11
-
-
24.44
25.00
25.11
25.22
26.11
-
-
25.17
25.44
-
27.72
27.72
26.78
27.33
26.94
26.11
26.00
26.39
26.89
27.78
27.78
27.78
—
—
26.11
26.44
26.67
26.89
26.83
—
—
26.00
26.89
MEAN
-
27.44
27.00
26.11
26.39
25.94
25.67
25.33
25.72
25.94
26.56
26.95
26.94
-
-
25.17
25.78
26.00
26.11
26.56
—
—
25.67
26.17
MAX - Daily Maximum; MIN. «• Daily Minimum; The table means
were computed from six daily interval chart readings of
continuous recordings; A. =• Monthly Average.
403
-------
TABLE E-8. SOIL AND WATER TEMPERATURE IN RICE PADDY,
BEAUMONT, TEXAS (AUGUST 1 - AUGUST 31, 1975)
August 1 - August 31, 1975
August Soil (°C) Water (°C)
of
1975 MIN. MAX. MEAN MIN. MAX. MEAN
1 - - 25.00 26.11 25.61
2 - 24.69 25.89 25.33
3 - 25.00 25.56 25.39
5 - -
6— «. — —
— "•
7 - -
8 - - - -
9 - -
10 - - -
11 - - -
12 - -
13 - -
14 - -
!5 _ _
16 - -
17 __ _ _
18 - -
19 - -
20 - -
21 - -
22 - -
23 - -
24 - - - -
25 - -
26 - -
27 - -
28 - -
29 - -
30 - -
31 __ _ _
A - 24.94 25.83 25.44
MAX. = Daily Maximum; MIN. = Daily Minimum; The table means
were computed from six daily interval chart readings of
continuous recordings; A. = Monthly Average.
404
-------
Appendix F. Average daily water balance in the
six rice paddies for each irrigation treat-
ment for 1974 and 1975 growing seasons.
405
-------
TABLE F-l. DAILY WATER BALANCE FOR RICE PADDIES WITH CONTINUOUS IRRIGATION FOR MAY 1974,
GIVEN IN CM
o
o\
Date
May 1
May 5
May 9
May 10
May 11
May 20
May 21
May 22
May 23
May 25
May 26
May 30
May 31
Inflow Irrigation
13.00
MAY TOTALS 13.00
June 1
June 2
June 3
June 4
June 5
June 6
June 7
June 8
June 9
June 10
June 11
June 12
June 13
June 14
June 15
June 16
June 17
June 18
14.00
0.90
0.90
0.90 0.48
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
Total
Irrigation
13.00
13.00
14.00
0.90
0.90
1.38
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
lUin
1.55
0.91
1.65
1.96
5.31
0.48
0.64
1.27
0.89
14.66
1.14
0.10
0.64
Total
Water
1.55
0.91
1.65
1.96
5.31
13.00
0.48
0.64
1.27
0.89
27.66
1.14
14.10
0.90
0.90
1.38
0.90
0.90
0.90
1.54
0.90
0.90
0.90
0.90
Runoff
0.50
2.10
9.50
12.10
0.02
0.21
0.41
0.59
0.45
0.38
0.32
0.31
0.51
0.08
0.02
0.00
0.00
Leachate
0.00
0.00
0.00
0.00
0.00
0.60
0.60
0.58
0.53
0.47
0.44
0.42
0.39
0.36
0.34
0.33
0.30
0.27
Evapo-
transpiration
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.66
0.60
0.53
0.70
0.54
0.78
1.05
0.95
0.86
Total
Loss
0.62
0.81
1.65
1.12
0.92
1.42
1.27
1.40
1.41
1.20
1.40
1.25
1.13
(continued)
-------
TABLE F-l. (Continued)
Date
June 19
June 20
June 21
June 22
June 23
June 24
June 25
June 26
June 27
June 28
June 29
June 30
JUNE
TOTALS
July 1
July 2
July 3
July 4
Jyly 5
July 6
July 7
July 8
July 9
July 10
July 11
July 12
July 13
July 14
July 15
July 16
July 17
July 18
Inflow Irrigation
0.90
0.90 4.48
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90 0.66
0.90
0.90
27.00 19.62
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90 0.58
0.90
0.90
0.90
0.90
0.90
0.90
Total
Irrigation
0.90
5.38
0.90
0.90
0.90
0.90
0.90
0.90
0.90
1.56
0.90
0.90
40.32
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
1.48
0.90
0.90
0.90
0.90
0.90
0.90
Rain
1.79
0.69
4.36
1.24
0.23
1.14
0.15
0.15
0.84
Total
Water
0.90
7.17
1.59
0.90
0.90
0.90
0.90
0.90
0.90
1.56
0.90
0.90
44,68
2.14
0.90
0.90
0.90
0.90
1.13
0.90
0.90
0.90
0.90
0.90
1.48
0.90
2.04
1.05
1.05
1.74
0.90
Runoff
0.00
0.05
0.42
0.47
0.47
0.52
0.21
0.09
0.09
0.14
0.12
0.13
6.01
0.23
0.28
0.23
0.25
0.33
0.33
0.32
1.19
0.65
0.42
0.35
0.69
0.45
0.55
0.52
0.57
0.60
0.54
Leachate
0.27
0.25
0.24
0.22
0.20
0.19
0.18
0.16
0.15
0.14
0.13
0.12
7.88
0.13
0.12
0.12
0.12
0.11
0.11
0.11
0.10
0.10
0.10
0.10
0.10
0.09
0.09
0.09
0.09
0.09
0.09
Evapo-
transpiration
0.86
0.92
0.82
1.01
1.00
0.80
0.86
0.71
0.66
0.65
J4.Qfi
0.49
0.74
0.84
0.78
0.82
0.62
0.60
0.25
0.76
0.70
0.51
0.70
0.54
0.57
0.18
0.33
0.33
0.70
Total
Loss
1.13
0.30
0.66
1.61
1.49
1.72
1.39
1.05
1.10
0.99
0.91
0.99
28.94
0.85
1.14
1.19
1.15
1.26
1.06
1.03
1.54
1.51
1.22
0.96
1.49
1.08
1.21
0.79
0.99
1.02
1.33
(continued)
-------
TABLE F-l. (Continued)
00
Date Inflow Irrigation
July 19 0.90
July 20 0.90
July 21 0.90
July 22 0.90 0.68
July 23 0.90 0.15
July 24 0.90 0.58
July 25 0.90
July 26 0.90
July 27 0.90
July 28 0.90
July 29 0.90
July 30 0.90
July 31 0.90
TOTALS 27.90 1.99
August 1 0.90
August 2 0.90
August 3 0.90
August 4 0.90
August 5 0.90
August 6 0.90
August 7 0.90
August 8 0.90
August 9 0.90
August 10 0.90
August 11 0.90
August 12 0.90
August 13 0.90
August 14 0.90
August 15 0.90
August 16 0.90
Total
_ . . Rain
Irrigation
0.90
0.90
0.90
1.58
1.05
1.48
0.90
0.90
0.90
0.90
0.90
0.90
0.90 8.26
29.89 12.01
0.90
0.90 0.46
0.90 2.67
0.90
0.90
0.90
0.90 2.69
0.90
0.90
0.90
0.90
0.90 0.69
0.90 0.23
0.90 0.30
0.90 0.25
0.90
Total
Water
0.90
0.90
0.90
1.58
1.05
1.48
0.90
0.90
0.90
0.90
0.90
0.90
9.16
41.90
0.90
1.36
3.57
0.90
0.90
0.90
3.59
0.90
0.90
0.90
0.90
1.59
1.13
1.20
1.15
0.90
Runoff
0.44
0.38
0.34
0.49
0.42
0.32
0.27
0.29
0.36
0.38
0.56
0.48
1.03
14.26
0.80
0.50
1.17
0.99
0.82
0.56
1.28
0.75
0.54
0.45
0.42
0.49
0.44
0.59
0.44
0.44
Leachate
0.09
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
2.91
0.08
0.08
0.08
0.08
0.08
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
Evapo-
transpiration
0.57
0.67
0.65
0.81
0.89
0.68
0.65
0.76
0.94
0.62
0.70
1.00
0.20
19.60
0.53
0.18
0.30
0.62
0.64
0.27
0.40
0.67
0.50
0.83
0.56
0.48
0.50
0.47
0.28
0.52
Total
Loss
1.10
1.13
1.07
1.38
1.39
1.08
1.00
1.13
1.38
1.08
1.34
1.56
1.31
36,77
1.41
0.76
1.55
1.69
1.54
0.90
1.75
1.49
1.11
1.35
1.05
1.04
1.01
1.13
0.79
1.03
(continued)
-------
TABLE F-l. (Continued)
Date Inflow Irrigation
August 17 0.90
August 18 0.90
August 19 0.90
August 20 0.90
August 21 0.90
August 22 0.90
TOTALS 19.80
Total
Irrigation
0.90
0.90
0.90
0.90
0.90
0.90
19.80
Rain
5.08
12.37
Total
Water
0.90
5.98
0.90
0.90
0.90
0.90
32.17
Runoff
0.40
0.37
0.34
0.29
0.19
1.77
14.04
Leachate
0.07
0.07
0.07
0.07
0.07
0.07
1.59
Evapo-
transpiration
0.64
0.63
0.69
0.59
0.52
0.41
11.23
Total
Loss
1.11
1.07
1.10
0.95
0.78
2.25
26.86
-p-
o
VD
-------
TABLE F-2. DAILY WATER BALANCE FOR RICE PADDIES WITH IMPOUNDED IRRIGATION FOR 1974 GIVEN IN CM
Date Irrigation
May 1
May 5
May 9
May 10
May 11
May 20
May 21
May 22 9.27
May 23
May 25
May 26
May 30
May 31
MAY TOTALS 9.27
June 1
June 6 10.3
June 7
June 8
June 9
June 10
June 11
June 12
June 13
June 14
June 15
June 16
June 17
June 18
June 19
June 20 7.74
Rain
1.55
0.91
1.65
1.96
5.31
0.48
0.64
1.27
0.89
14.66
1.14
0.10
0.64
1.79
Total Water
1.55
0.91
1.65
1.96
5.31
9.27
0.48
0.64
1.27
0.89
23.93
10.40
0.64
9.53
Runoff
0.5
2.1
6.2
8.8
0.04
0.97
0.24
0.55
0.58
0.60
0.59
0.59
1.04
0.41
0.19
0.70
0.02
0.01
0.34
Leachate
0.60
0.60
0.58
0.53
0.47
0.44
0.42
0.39
0.36
0.34
0.33
0.30
0.29
0.27
0.25
Evapo-
transpiration
0.13
0.66
0.60
0.53
0.70
0.57
0.78
1.05
0.95
0.85
0.86
Total
Loss
0.77
0.67
1.48
1.08
1.04
1.64
1.53
1.68
1.97
1.53
1.57
1.32
1.17
1.14
0.59
(continued)
-------
TABLE F-2. (Continued)
Date Irrigation
June 21
June 22
June 23
June 24 4.70
June 25
June 26
June 27
June 28 4.71
June 29
June 30
JLTJE TOTALS 27.45
July 1
July 2
July 3
July 4
July 5
July 6
July 7
July 8
July 9
July 10 0.0
July 11
July 12 4.65
July 13 0.22
July 14 0.0
July 15
July 16
July 17
July 18
July 19
July 20
July 21
July 22 5.87
Rain Total Water
0.69 0.69
4.70
4.71
4.36 30.67
1.24 1.24
0.23 0.23
0.0
4.65
0.22
1.14 1.14
0.15 0.15
0.15 0.15
0.84 0.84
5.87
Runoff
0.49
0.31
0.21
0.35
0.20
0.28
0.18
0.57
0.53
0.35
10.34
0.36
0.36
0.25
0.17
0.11
0.08
0.06
0.26
0.33
0.25
0.18
0.48
0.25
0.26
0.24
0.27
0.25
0.22
0.17
0.13
0.08
0.82
Leachate
0.24
0.22
0.20
0.19
0.18
0.15
0.15
0.14
0.13
0.13
7.90
0.13
0.12
0.12
0.12
0.11
0.11
0.11
0.10
0.10
0.10
0.10
0.10
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.08
0.08
0.08
Evapo-
transpiration
0.92
0.82
1.01
1.00
0.80
0.86
0.71
0.66
0.65
15.11
0.49
0.74
0.84
0.78
0.82
0.62
0.60
0.25
0.76
0.69
0.51
0.70
0.54
0.57
0.18
0.33
0.33
0.70
0.57
0.67
0.65
0.81
To till
Loss
0.73
1.45
1.23
1.55
1.38
1.24
1.18
1.42
1.32
1.13
31.81
0.98
1.22
1.21
1.07
1.04
0.81
0.77
0.61
1.19
1.04
0.79
1.28
0.88
0.92
0.51
0.69
0.67
1.01
0.83
0.88
0.81
1.71
(continued)
-------
TABLE F-2. (Continued)
Date Irrigation
July 23
July 24 0.58
July 25 1.57
July 26
July 27
July 28
July 29 3.26
July 30
July 31
JULY TOTALS 16.15
August 1
August 2
August 3
August 4
August 5
August 6
August 7
August 8
August 9
August 10
August 11
August 12
August 13
August 14
August 15
August 16
August 17
August 18
August 19
August 20
August 21
August 22
AUGUST TOTALS
Rain
8.26
12.01
0.46
2.67
2.69
0.69
0.23
0.30
0.25
5.08
12.37
Total Water
0.58
1.57
3.26
8.26
28.16
0.46
2.67
2.69
0.69
0.23
0.30
0.25
5.08
12.37
Runoff
1.65
1.19
0.70
0.48
0.29
0.16
0.48
0.75
0.83
12.11
0.35
0.22
0.62
0.77
0.54
0.40
0.87
0.42
0.27
0.19
0.12
0.10
0.10
0.12
0.09
0.06
0.02
0.00
0.00
0.00
2.13
7.39
Leachate
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
2.91
0.08
0.08
0.08
0.08
0.08
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
1.59
Evapo-
transpiration
0.89
0.68
0.65
0.76
0.94
0.62
0.70
1.00
0.20
19.59
0.53
0.18
0.30
0.62
0.64
0.27
0.40
0.67
0.50
0.83
0.56
0.48
0.49
0.47
0.28
0.52
0.64
G.63
0.69
0.59
0.52
0.41
11.22
Totnl
Loss
2.63
1.95
1.43
1.32
1.31
0.86
1.26
1.83
1.11
34.62
0.96
0.48
0.99
1.47
1.26
0.74
1.34
1.16
0.84
1.09
0.75
0.65
0.66
0.66
0.44
0.66
0.73
0.70
0.76
0.66
0.59
2.61
20.20
-------
TABLE F-3. DAILY WATER BALANCE FOR RICE PADDIES WITH CONTINUOUS IRRIGATION FOR 1975 GIVEN IN CM
Rate of Intermittent Total
Date Inflow Irrigation Irrigation
May 1
May 2
May 3 9.4 9.4
May 4
Kay 5
May 6
May 7
May 8
May 9
May 10
May 11
May 12
May 13
May 14
May 15
May 16
May 17
May 18
May 19
May 20
May 21
May 22
May 23
May 24
May 25
May 26
May 27
May 28 8.43 17.83
May 29
May 30
May 31
Rainfall
.05
.05
.30
.46
4.39
.46
.46
.58
10.26
3.56
5.26
Total Total
HO Runoff Leaching Evts Loss
.05 .05
9.4
.05
.30
.46
4.39 1.2
.46
.46
.58
18.69
3.56
5.26
MAY TOTALS
9.37
18.77
25.83
43.66
1.7
(continued)
-------
TABLE F-3. (Continued)
Date
June 1
June 2
June 3
June 4
June 5
June 6
June 7
June 8
June 9
June 10
June 11
June 12
June 13
June 14
June 15
June 16
June 17
June 18
June 19
June 20
June 21
June 22
June 23
June 24
June 25
June 26
June 27
June 28
June 29
June 30
JUNE
TOTALS
Rate of
Inflow
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
24.44
Intermittent Total
Irrigation Irrigation
7.43 .94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
1.35 2.29
1.07 2.01
.47 1.41
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
10.32 27.33
Rainfall
5.26
21.59
.79
.64
.23
.53
.36
.43
.79
..15
30.77
Total
V
5.26
8.37
.94
.94
.94
22.53
1.7
.94
.94
.94
.94
1.58
.94
.94
2.29
2.01
1.41
1.17
.94
.94
1.47
1.30
1.37
.94
1.73
.94
1.09
65.50
Runoff
.13
2.06
.42
.50
19.98
4.99
1.85
.57
.43
.37
.44
.43
.31
.22
.19
.21
.24
.34
.31
.25
.40
.43
.49
.52
.76
.72
37.56
Leaching
.60
.60
.58
.53
.47
.44
142
.39
.36
.34
.33
.30
.29
.27
.25
.24
.22
.20
.19
.18
.16
.15
.14
.13
.13
7.91
Evt8
.14
.60
.55
.48
.14*
.32*
.27
.56
.72
.87
.75
.85
.95
1.01
.93
.80
.77
.54
.48
.50
.11
.23
.36
.59
.26
.36
14.14
Total
Loss
.27
3.26
1.57
1.56
20.65
5.78
2.56
1.55
1.54
1.60
1.53
1.61
1.56
1.52
1.39
1.26
1.25
1.10
0.99
0.94
0.69
0.82
1.00
1.25
1.15
1.21
59.61
(continued)
-------
TABLE F-3. (Continued)
Date
July 1
July 2
July 3
July 4
July 5
July 6
July 7
July 8
July 9
July 10
July 11
July 12
July 13
July 14
July 15
July 16
July 17
July 18
July 19
July 20
July 21
July 22
July 23
July 24
July 25
July 26
July 27
July 28
July 29
July 30
July 31
JULY
TOTALS
Rate of Intermittent
Inflow Irrigation
.94
.94
.94
.94
.94
.94
.94 .22
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94 .45
.94
.94
.94
.94 2.13
.94 1.42
.94
.94
.94 .79
.94
.94
.94 .44
.94
.94
.94
29.14 5.45
Total
Irrigation
.94
.94
.94
.94
.94
.94
1.16
.94
.94
.94
.94
.94
.94
.94
.94
.94
1.39
.94
.94
.94
3.07
3.30
.94
.94
1.73
.94
.94
1.38
.94
.94
.94
35.53
Rainfall
.51
.38
.20
1.73
.25
.51
3.56
.53
.41
3.78
11.86
Total
H20
.94
1.45
1.32
.94
.94
.94
1.16
.94
.94
1.14
2.67
.94
1.19
1.45
.94
.94
1.39
.94
.94
.94
3.07
3.30
.94
.94
1.73
.94
.94
4.94
1.47
1.35
4.72
47.39
Runoff
.88
.66
.62
.72
.73
.80
.60
.49
.36
.28
.52
.56
.41
.34
.26
.18
.12
.10
.07
.04
.07
.13
.15
.16
.14
.10
.06
.07
.16
.28
.89
10.95
Leaching
.13
.12
.12
,12
.11
.11
.11
.10
.10
.10
.10
.10
.09
.09
.09
.09
.09
.09
.09
.08
.08
.08
.08
.08
.08
.08
.08
.08
,08
.08
.08
2.91
Total
Evts Loss
.47 1.48
.52
.14
.56
.81
.79
.75
.77
.88
.81
.32
.50
.59
.21
.14
.40
.36
.60
.73
.56
.71
.30
.15
.33
.42
.50
.68
.98
.46
.39
.84
16.67 1.48
(continued)
-------
TABLE F-3. (Continued)
Rate of Intermittent Total
Date
August 1
August 2
August 3
August 4
August 5
August 6
August 7
August 8
August 9
August 10
August 11
August 12
August 13
August 14
August 15
August 16
August 17
TOTALS
Inflow Irrigation Irrigation
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
15.98
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
.94
15.98
Rainfall
3.5
.40
4.1
1.5
.25
1.27
.05
11.07
Total
H20
4.44
.94
1.34
5.04
2.44
.94
1.19
2.21
.94
.94
.94
.94
.94
.94
.94
.94
.99
27.05
Runoff
1.10
1.08
.50
1.59
1.49
.97
.59
.69
.65
.49
.47
.39
.41
.39
.40
.35
3.4
14.96
Leaching
.08
.08
.08
.08
.08
.07
.07
.07
.07
.07
.07
.07
.07
.07
.07
.07
.07
1.24
EVTS
1.04
.34
.55
.71
.67
.85
.62
.34
.37
.52
.38
.48
.64
.66
.30
.51
8.98
Total
Loss
1.18
2.20
.92
2.22
2.28
1.71
1.51
1.38
1.06
.93
1.06
.84
.96
1.10
1.13
.72
.92
35.54
* estimated from climatological data
-------
TABLE F-4. DAILY WATER BALANCE FOR RICE PADDIES WITH IMPOUNDED IRRIGATION FOR 1975 GIVEN IN CM
Date Irrigation
April 30
APRIL TOTALS
May 2
May 3 12.4
May 4
May 6
May 7
May 8
May 11
May 12
May 13
May 15
May 24
May 28 11.4
May 29
May 30
MAY TOTALS 23.8
June 1
June 5 10.40
June 6
June 7
June 8
June 9
June 10
June 11
June 12
June 13
June 14
June 15
June 16
June 17
Rain
2.26
2.26
0.05
0.30
0.46
4.39
0.46
0.46
0.58
10.26
3.56
5.26
25.78
5.26
21.59
0.76
0.64
Total Water
2.26
12.4
0.05
0.30
0.46
4.39
0.46
0.46
0.58
21.66
3.56
5.26
51.84
10.40
21.59
0.76
0.64
Runoff
9.4
2.1
11.3
7.2
2.1
32.1
0.37
0.97
0.58 r
0.48
16.7
4.20
0.73
0.20
0.07
0.02
0.00
0.00
0.00
Leachate
0.60
0.60
0.58
0.53
0.47
0.44
0.42
0.39
0.36
0.34
0.33
0.30
Evapo-
transpiration
0.14
0.60
0.55
0.48
0.13*
0.32*
0.28
0.56
0.72
0.87
0.75
0.85
0.95
Total
Loss
11.3
7.2
2.1
20.6
0.51
2.17
1.73
1.54
17.36
4.99
1.45
1.18
1.18
1.29
1.09
1.18
1.25
(continued)
-------
TABLE F-4. (Continued)
Date Irrigation
June 18
June 19 4.33
June 20
June 21
June 22
June 23 2.57
June 24
June 25
June 26
June 27
June 28
June 29
June 30
JUNE TOTALS 17.30
July 1
July 2
July 3
July 4
July 5
July 6
July 7 5.71
July 8
July 9
July 10
July 11
July 12
July 13
July 14
July 15
July 16
July 17 3.09
July 18
July 19
July 20
July 21
July 22 3.72
Rain
0.23
0.53
0.36
0.79
0.15
30.31
0.51
0.38
0.20
1.73
0.25
0.51
Total Water
4.33
0.23
2.57
0.53
0.36
0.79
0.15
45.47
0.51
0.38
5.71
0.20
1.73
0.25
0.51
3.09
3.72
Runof f
0.00
0.01
0.01
0.00
0.00
0.02
0.01
0.00
0.01
0.01
0.00
0.00
0.00
24.39
0.00
0.00
0.00
0.00
0.00
0.00
0.06
0.05
0.01
0.00
0.01
0.01
0.00
0.00
0.00
0.00
0.04
0.04
0.01
0.00
0.00
0.05
Leachate
0.29
0.27
0.25
0.24
0.22
0.20
0.19
0.18
0.16
0,15
0.14
0.13
0.13
7.91
0.13
0.12
0.12
0.12
0.11
0.11
0.11
0.10
0.10
0.10
0.10
0.10
0.09
0.09
0.90
0.09
0.09
0.09
0.09
0.08
0.08
0.08
Evapo-
transpiration
0.01
0.93
0.80
0.77
0.54
0.48
0.50
0.11
0.23
0.36
0.58
0.26
0.36
13.13
0.47
0.52
0.14
0.56
0.81
0.79
0.75
0.77
0.88
0.81
0.32
0.50
0.59
0.21
0.13
0.40
0.36
0.60
0.73
0.56
0.71
0.30
Total
Loss
0.30
1.21
1.06
1.01
0.76
0.70
0.70
0.29
0.40
0.52
0.72
0.39
0.49
45.47
0.60
0.74
0.26
0.68
0.92
0.90
0.92
0.93
0.99
0.91
0.43
0.61
0.68
0.30
0.22
0.49
0.49
0.73
0.83
0.64
0.79
0.43
(continued)
-------
TABLE F-4. (Continued)
Date Irrigation
July 23
July 24
July 25
July 26
July 27
July 28 4.02
July 29
July 30
July 31
JULY TOTALS 16.54
August 1
August 2
August 3
August 4
August 5
August 6 1.22
August 7
August 8
August 9
August 10
August 11
August 12
August 13
August 14
August 15
August 16
August 17
AUGUST „
TOTALS
Rain
3.56
0.53
0.41
3.78
11.86
3.51
0.43
4.06
1.50
0.25
1.27
0.05
11.07
Total Water
7.58
0.53
0.41
3.78
28.40
3.51
0.43
4.06
1.50
1.22
0.25
1.27
0.05
12.29
Runoff
0.04
0.02
0.00
0.00
0.00
0.02
0.06
0.09
0.47
0.98
0.88
1.06
0.60
1.20
0.75
0.47
0.09
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.22
6.27
Leachate
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
3.72
0.08
0.08
0.08
0.08
0.08
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
1.24
Evapo-
transpiration
0.15
0.33
0.42
0.50
0.68
0.98
0.46
0.39
0.84
16.66
.»___
1.04
0.34
1.27
0.67
0.85
0.62
0.34
0.37
0.52
0.37
0.48
0.64
0.66
0.30
0.51
8.98
Total
Loss
0.27
0.43
0.50
0.58
0.66
1.08
0.60
0.56
1.39
20.56
0.08
1.12
0.42
0.08
1.35
0.74
0.92
0.69
0.41
0.44
0.59
0.44
0.55
0.71
0.73
0.37
0.58
10.22
* estimated from climatological data
-------
Appendix G. Analysis of variance for various ions
and the electrical conductivity of the rice
paddy water for the 1974 and 1975 growing
seasons.
420
-------
TABLE G-l. ANALYSIS OF VARIANCE FOR E.G. IN RICE PADDY WATER SAMPLED IN
1974
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Rate
Times x Irri-
gation x Rate
ERROR
TOTAL
Sum of Squares
.038
4.637
0.245
.119
.684
.195
.008
.231
7.885
Df Mean Square
2 .0190
20 .2320
1 .2450
1 .1190
20 .0340
20 .0100
1 .0080
20 .0120
189 .0090
274
F-Value
Exp.
2.13
25.42**
26.86**
13.15**
3.75**
1.07
0.88
1.26
**Significant at the 1% level.
421
-------
TABLE G-2. ANALYSIS OF VARIANCE FOR E.G. IN RICE PADDY WATER SAMPLED IN
1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Rate
Times x Irri-
gation x Rate
ERROR
TOTAL
Sum of Squares Df
0.033 2
9.403 21
0.142 1
0.165 1
0.259 21
0.335 21
0.0029 1
0.201 21
1.861 186
12.404 275
Mean Square
.0170
.4480
.1420
.1650
.0120
.0160
.0029
.0096
0.010
F-Value
Exp.
1.63
44.74**
14.19**
16.54**
1.23
1.59
0.29
0.96
** Significant at the 1% level.
422
-------
TABLE G-3. ANALYSIS OF VARIANCE FOR E.G. IN RICE PADDY WATER SAMPLED IN
1973
Source Sum
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Rate
Times x Irri-
gation x Rate
ERROR
TOTAL
of Squares
0.047
6.992
0.008
0.048
0.141
0.076
0.002
0.104
1.154
8.576
Df Mean Square
2 .0235
8 .8740
1 .0080
1 .0480
8 .0176
8 .0095
1 .0020
8 .0130
70 .0160
107
F-Value
Exp.
1.45
53.00**
0.49
2.94
1.07
0.57
0.12
0.79
**Significant at the 1% level.
423
-------
TABLE G-4. ANALYSIS OF VARIANCE FOR pH IN RICE PADDY WATER SAMPLED IN
1973
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x rate
Irrigation x
Rate
Times x Irri-
gation x Rate
ERROR
TOTAL
Sum of Squares Df
0.493 2
7.969 8
0.002 1
0.458 1
0.509 8
0.296 8
0.285 1
0.314 8
3.097 70
13.424 107
Mean Square
0.247
0.996
0.002
0.458
0.063
0.037
0.285
0.039
0.044
F-Value
Exp.
5.57**
22.51**
.05
10.34**
1.43
0.83
6.44**
0.88
**Significant at the 1% level.
424
-------
TABLE G-5. ANALYSIS OF VARIANCE FOR pH IN RICE PADDY WATER SAMPLED IN
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
0.252
36.660
.345
.088
1.027
0.693
0.050
Df
2
20
1
1
20
20
1
Mean Square
0.126
1.833
0.345
0.088
0.051
0.350
0.050
F-Value
Exp.
2.20
37.83**
7.36**
2.76
1.05
0.69
0.32
Rate
Times x Irri- 0.797 20 0.039 0.82
gation x Rate
ERROR 9.127 188 0.048
TOTAL 49.041 273
** Significant at the 17, level.
425
-------
TABLE G-6. ANALYSIS OF VARIANCE FOR pH IN RICE PADDY WATER SAMPLED IN
1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Sum of Squares
0.304
30.522
0.000
0.000
1.391
Df Mean Square
2 0.152
21 1.453
1 0.000
1 0.000
21 0.066
F-Value
Exp.
3.43*
32.87**
0.00
0.01
1.49
Times x Rate 1.033 21 0.049 1.11
Irrigation x 0.054 1 0.054 1.23
Rate
Times x Irri- 0.591 21 0.028 0.64
gation x Rate
ERROR 8.224 186 0.044
TOTAL 42.122 275
**Significant at the 1% level.
426
-------
TABLE G-7. ANALYSIS OF VARIANCE FOR NH. IN RICE PADDY WATER SAMPLED
IN 1974 3
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
10.548
1957.795
49.057
34.866
152.960
154.909
0.979
Df
2
18
1
1
18
18
1
Mean Square
5.274
108.766
49.057
34.866
8.497
8.606
0.979
F-Value
Exp.
1.00
20.62**
9.29**
6.61**
1.61
1.63
0.02
Rate
Times x Irri- 72.547 18 4.030 0.76
gat ion x Rate
ERROR 791.354 150 5.276
TOTAL 3225.017 227
**Significant at the 1% level.
427
-------
TABLE G-8. ANALYSIS OF VARIANCE FOR NH, IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Rate
Times x Irri-
Sum of Squares
30.577
3492.074
2.622
67.737
243.014
287.798
0.007
177.671
Df Mean Square
2 15.288
17 205.416
1 2.622
1 67.737
17 14.295
17 16.929
1 0.007
17 10.451
F-Value
Exp.
2.23
29.97**
0.38
9.88**
2.09*
2.47**
0.00
1.52
gation x Rate
ERROR
973.140
142
6.853
TOTAL
5274.640
215
**Significant at the 1% level.
428
-------
TABLE G-9. ANALYSIS OF VARIANCE FOR Ca
IN 1974
IN RICE PADDY WATER SAMPLED
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
58.639
2159.029
356.674
110.752
368.948
497.503
242.011
Df
2
17
1
1
17
17
1
Mean Square
29.319
127.001
356.674
110.750
21.702
29.264
242.014
F -Value
Exp.
0.84
3.67**
10.31**
3.20
0.62
0.84
7.00**
Rate
Times x Irri-
gation x Rate
557.373
17
32.786
0.94
ERROR
4839.623
140
34.568
TOTAL
9190.555
213
**Signifleant at the 1% level.
429
-------
TABLE G-10. ANALYSIS OF VARIANCE FOR Ca IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
48.834
8621.322
264.218
268.523
860.927
392.687
0.096
Df Mean Square
2 24.417
17 507.137
1 264.218
1 268.523
17 50.643
17 23.099
1 0.096
F-Value
Exp.
0.73
15.24**
7.94**
8.07**
1.52
0.69
0.00
Rate
Times x Irri-
gation x Rate
693.093
17
40.770
1.22
ERROR
4992.327
150
33.282
TOTAL
16142.028
223
430
-------
TABLE G-ll. ANALYSIS OF VARIANCE FOR Mg
IN 1974
IN RICE PADDY WATER SAMPLED
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
4367.308
59069.807
523.106
907.059
35278.452
42826.360
3993.058
Df
2
18
1
1
18
18
1
Mean Square
2183.654
3281.656
523.106
907.059
1959-914
2379.242
3993.058
F-Value
Exp.
0.92
1.38
0.22
0.38
0.82
1.00
1.68
Rate
Times x Irri-
gation x Rate
44192.420
18
2455.134
1.03
ERROR
346357.889
146
2372.314
TOTAL
537515.459
223
431
-------
TABLE G-12. ANALYSIS OF VARIANCE FOR Mg IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
0.187
173.372
8.250
1.952
11.531
2.603
0.000
Df
2
15
1
1
15
15
1
Mean Square
0.094
11.558
8.250
1.952
0.769
0.174
0.000
F-Value
Exp.
0.16
20.50**
14.63**
3.46
1.36
0.31
0.00
Rate
Times x Irri-
gation x Rate
1.510
15
0.101
0.17
ERROR
76.660
136
0.563
TOTAL
276.067
201
432
-------
TABLE G-13. ANALYSIS OF VARIANCE FOR Na IN RICE PADDY WATER SAMPLED
IN 1974
Source
Reps
Times
Irrigation
Treatment
Application
Kate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
7910.780
139436.298
132729.969
12603.507
149598.794
23396.803
22112.470
Df
2
19
1
1
19
19
1
Mean Square
3955.390
7338.752
132729.969
12603.507
7873.621
1231.411
22112.470
F-Value
Exp.
1.24
2.31**
41.86**
3.97**
2.48**
0.38
6.97**
Rate
Times x Irri-
gation x Rate
38837.172
19
2044.062
0.64
ERROR
485084.014
153
3170.483
TOTAL
11011709.813
234
433
-------
TABLE G-14. ANALYSIS OF VARIANCE FOR Na+ IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
9.162
6617.023
192.518
179.084
532.172
221.337
18.191
Df
2
14
1
1
14
14
1
Mean Square
4.580
472.645
192.518
179.084
38.012
15.810
18.191
F -Value
Exp.
0.28
29.58**
12.05**
11.21**
2.37**
0.98
1.13
Rate
Times x Irri-
gation x Rate
68.242
14
4.874
0.30
ERROR
2045.158
128
15.977
TOTAL
9882.890
189
434
-------
TABLE G-15. ANALYSIS OF VARIANCE FOR S04 IN RICE PADDY WATER SAMPLED
IN 1974
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
1296.353
65210.916
18146.730
4941.365
16191.520
6314.462
2683.289
Df
2
18
1
1
18
18
1
Mean Square
648.177
3622.829
18146.730
4941.365
899.529
350.803
2683.289
F-Value
Exp.
2.40
13.42**
67.22**
18.30**
3.33**
1.29
9.94**
Rate
Times x Irri-
gation x Rate
2326.252
18
129.236
0.47
ERROR
41031.287
152
TOTAL
158142.176
229
435
-------
TABLE G-16. ANALYSIS OF VARIANCE FOR SO, IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
2134.479
48979.978
28.361
2365.755
4326.011
2500.639
1147.517
D f
2
13
1
1
13
13
1
Mean Square
1067.240
3767.691
28.361
2365.755
332.770
192.357
1147.517
F-Value
Exp.
3.16*
11.17**
0.08
7.02**
0.98
0.57
3.40
Rate
Times x Irri-
gation x Rate
4065.745
13
312.750
0.93
ERROR
40445.400
120
337.045
TOTAL
105993.889
177
436
-------
TABLE G-17. ANALYSIS OF VARIANCE FOR Cl~ IN RICE PADDY WATER SAMPLED
IN 1974
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
260.445
14327.552
4693.635
1801.951
5252.609
3131.578
1133.952
Df Mean Square
2
19
1
1
19
19
1
F -Value
Exp.
0.87
5.07**
31.55**
12.11**
1.86*
1.10
7.62**
Rate
Times x Irri-
gation x Rate
1782.309
19
0.63
ERROR
14392.266
164
148.733
TOTAL
56776.198
245
437
-------
TABLE G-18. ANALYSIS OF VARIANCE FOR Cl IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
138.941
32411.395
2654.925
537.074
5796.739
862.619
292.664
Df
2
13
1
1
13
13
1
Mean Square
69.471
2493.184
1654.925
537.074
445.903
66.355
292.664
F-Value
Exp.
0.59
21.41**
22.80**
4.61*
3.83**
0.56
2.51
Rate
Times x Irri-
gation x Rate
1066.162
13
158.936
1.36
ERROR
13969.717
120
116.44
TOTAL
58730.239
177
438
-------
TABLE G-19. ANALYSIS OF VARIANCE FOR N0~ IN RICE PADDY WATER SAMPLED
IN 1974
Source
Reps
Times
Irrigation
Treatment
Application
Rate
Times x
Irrigation
Times x Rate
Irrigation x
Sum of Squares
0.007
2.821
0.299
0.018
1.249
0.150
0.007
Df
2
19
1
1
19
19
1
Mean Square
0.004
0.149
0.299
0.018
0.066
0.008
0.007
F -Value
Exp.
0.67
25.88**
52.16**
3.22
11.46**
1.37
1.36
Rate
Times x Irri-
gation x Rate
0.035
19
0.001
0.31
ERROR
0.952
166
0.005
TOTAL
5.540
247
439
-------
TABLE G-20. ANALYSIS OF VARIANCE FOR N03 IN RICE PADDY WATER SAMPLED
IN 1975
Source
Reps
Times
Irrigation
Treatment
Application
Kate
Times x
Irrigation
Times x Rate
Irrigation x
Rate
Sum of Squares
0.049
1.530
0.017
0.016
0.146
0.030
0.000
Df
2
10
1
1
10
10
1
Mean Square
0.025
0.153
0.017
0.016
0.015
0.003
0.000
F-Value
Exp.
4.05*
25.27**
2.78
2.65
2.41*
0.51
0.02
0.87
Times x Irri-
gation x Rate
0.053
10
0.005
ERROR
0.581
96
0.006
TOTAL
2.424
141
440
-------
APPENDIX H
CONCENTRATIONS OF INDIVIDUAL IONS IN
PADDY WATER DURING 1973, 1974 AND 1975 GROWING SEASONS
441
-------
TABLE H-l. ANALYSIS FOR NITRATE (PPM) FOR 1973
-O
K3
Date
May 1
May 3
Hay 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
0.9
0.7
1.4
1.5
0.2
0.3
0.5
0.3
0.1
0.0
0.1
0.0
0.0
0.1
0.1
0.1
0.0
0.0
0.0
0.0
Reconmended
Standard
Deviation
+0.3
+0.1
+0.9
+0.7
+0.1
+0.4
+0.3
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.4
0.7
0.9
2.5
1.3
0.3
0.3
0.5
0.3
0.0
0.0
0.1
0.0
0.1
0.2
0.1
0.1
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.3
+0.1
+0.3
+3.0
+0.7
+0.3
+0.4
+0.2
+0.1
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.7
0.8
1.1
1.6
0.2
0.3
0.3
0.2
0.1
0.0
0.0
0.0
0.1
0.2
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.1
+0.2
+0.5
+0.1
+0.2
+0.3
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.7
0.7
1.1
3.2
2.0
0.0
0.3
0.4
0.2
0.0
0.1
0.0
0.0
0.1
0.2
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.2
+0.1
+0.2
+1.5
+0.7
+0.0
+0.4
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
. —
0.1
0.2
0.1
0.9
0.1
0.1
0.0
0.0
0.0
0.0
0.1
—
0.0
0.0
0.1
—
-------
TABLE H-2. ANALYSIS FOR NITRATE (PPM) FOR 1974
Date
May 3
Hay 3
May 21
May 29
June 6
June 7
June 8
June 8
June 10
June 10
June 14
June 17
June 24
June 24
June 26
June 27
June 27
June 28
June 28
June 29
July 1
July 3
July 3
July. 5
July 8
July 8
July 11
July 15
July 17
July 22
July 24
July 26
July 29
Impounded
Mean
4.4
2.0
2.0
0.1
0.4
0.2
0.6
0.5
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
—
0.0
0.0
—
0.0
0.0
Recommended
Standard
Deviation
+4.0
+0.9
+0.8
+0.1
+0.3
+0.1
+0.1
+0.1
+0.2
+0.0
+0.0
+0.0
+0.0
+0.0
H
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
1.5
3.4
2.0
0.2
0.1
0.3
0.4
0.6
0.5
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
—
—
0.0
0.0
0.0
__
0.0
0.0
Excessive
Standard
Deviation
+0.7
+2.2
+0.5
+0.0
+0.1
+0.2
+0.3
+0.1
+0.1
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
HO.O
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
—
—
40.0
+0.0
HO.O
40. 0
40.0
Continuous
Mean
1.0
1.7
2.3
0.1
0.1
0.1
0.2
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
—
0.0
0.0
—
—
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.3
+0.7
+0.4
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
—
+0.0
—
+0.0
+0.0
—
—
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.8
1.4
1.8
0.3
0.1
0.2
0.1
0.2
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
o.o
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.3
+0.3
+0,8
+0.2
+0.1
+0.1
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
0.1
1.0
0.1
0.0
0.1
0.1
___
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
—
0.0
0.0
-__
0.0
0.0
0.0
0.0
0.0
(Continued)
-------
TABLE H-2. (Continued)
Date Impounded
Mean
August 2 0.0
August 5 0.0
August 12 0.0
August 15 0.0
August 16 0.0
August 19 0.0
August 21 0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
0.0
0.0
0.0
0.0
0.0
-------
TABLE H-3. ANALYSIS FOR NITRATE (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 23
June 26
June 30
July 7
Impounded
Mean
0.4
0.6
0.7
0.3
0.5
0.1
0.1
0.1
0.0
—
0.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.1
+0.0
+0.2
+0.2
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.4
0.6
1.2
0.2
0.4
0.1
0.1
0.1
0.1
0.2
0.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.1
+0.1
+0.5
+0.2
+0.0
+0.0
+0.0
+0.0
+0.1
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.3
0.6
1.1
0.2
0.3
0.1
0.1
0.1
0.0
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.1
+0.1
+0.6
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.4
0.6
0.7
0.3
0.3
0.1
0.1
0.1
0.0
0.1
0.2
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.1
+0.1
+0.2
+0.2
+0.1
+0.1
+0.1
+0.0
+0.0
+0.0
+0.2
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
0.2
0.2
0.0
0.1
0.1
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-------
TABLE H-4. ANALYSIS FOR ELECTRICAL CONDUCTIVITY (MICROMHOS) FOR 1973
Date Impounded
Mean
May 2, 1973
May 3
May 7
Mav 12
June 15
July 12
July 27
August 8
August 13
180.0
192.0
191.3
356.7
153.3
121.3
143.7
144.7
124.7
Recommended
Standard
Deviation
+57.0
+66.5
+53.3
+125.8
+ 5.8
+ 8.1
+ 7.8
+31.4
+22.3
Impounded
Mean
172.3
190.0
212.3
423.3
163.3
145.7
166.3
143.7
136.3
Excessive
Standard
Deviation
+17.5
+20.0
+23.2
+32.1
+15.3
+33.0
+38.6
+24.0
+23.1
Continuous
Mean
164.3
186.7
204.3
383.3
183.3
131.7
121.0
119.3
89.0
Recommended
Standard
Deviation
+37.7
+51.6
+31.7
+90.7
+66.6
+10.7
+ 8.5
+10.0
+5.6
Continuous
Mean
219.7
239.7
234.3
403.3
140.0
123.0
114.7
119.0
85.0
Excessive
Standard
Deviation
+50.6
+46.2
+37.0
+40.4
+ 0.0
+ 6.2
+ 5.5
+ 3.5
+ 7.5
Canal
Water
140.0
112.0
187.0
110.0
81.0
-------
TABLE H-5. ANALYSIS FOR ELECTRICAL CONDUCTIVITY (MICROMHOS) FOR 1974
Date
Impounded
Mean
May 3,1974 214.0
May 3
May 21
May 29
June 6
June 7
June 8
June 8
June 17
June 24
June 26
June 27
June 28
June 29
July 1
July 8
July 15
July 22
July 29
August
August
August
August
225.3
113.3
137.3
212.7
285.0
189.0
211.0
181.0
122.7
273.0
255.7
191.7
201.0
186.3
198.3
163.7
181.3
5 136.7
12 167.0
19 205.7
21 192.3
Recommended
Standard
Deviation
+21.4
+22.4
+ 5.5
+11.0
+17.5
+17.4
+48.7
+68.4
+38.7
+ 5.0
+67.1
+20.1
+14.4
+33.0
+20.6
+20.2
+ 4.5
™
+ 2.9
+10.7
+ 7.8
+ 4.7
+31.6
Impounded
Mean
219.7
308.3
148.3
131.3
220.3
309.7
223.0
223.3
182.3
141.3
215.0
280.7
216.3
181.3
219.3
214.3
173.0
173.3
.190.3
136.3
161.0
189.0
184.3
Excessive
Standard
Deviation
+47.1
+95.8
+30.0
+ 4.2
+ 8.7
+25.9
+19.1
+41.4
+34.7
+32.7
+20.0
+29.0
+41.2
+27.2
+21.0
+17.2
+12.1
+15.3
+ 7.6
+ 5.8
+ 3.7
+ 0.0
+26.3
Continuous
Mean
249
199
124
153
228
194
128
137
130
116
195
227
216
202
193
151
157
153
152
131
156
151
156
.3
.3
.0
.0
.3
.3
.7
.0
.0
.3
.3
.7
.0
.7
.0
.7
.3
.0
.7
.7
.0
.3
.3
Recommended
Standard
Deviation
+67.9
+24.6
+23.5
+10.1
+46.8
+47.9
+ 2.1
+ 9.6
+ 4.6
+ 6.5
+30.6
+36.8
+ 6.9
+10.8
+24.9
+ 2.9
+ 4.7
+ 2.6
+ 6.8
+ 3.5
+ 0.0
+ 8.0
+ 9.5
Continuous
Mean
216.
227.
133.
146.
263.
260.
121.
134.
132.
112.
243.
327.
226.
238.
241.
163.
154.
154.
160.
131.
159.
153.
184.
7
3
0
3
7
7
7
0
3
0
0
7
0
7
0
3
3
7
0
7
7
7
7
Excessive
Standard
Deviation
+35.8
+25.0
+ 8.7
+18.8
+17.9
+77.5
+13.6
+ 6.1
+ 7.8
+ 1.7
+21.4
+41.3
+96 . 2
+19.0
+45.9
+15.3
+ 5.9
+ 4.2
+ 0.0
+ 1.5
+ 0.6
+ 7.6
+26.4
Canal
Water
118.0
150.0
115.0
132.0
159.0
125.0
130.0
135.0
116.0
133.0
130.0
130.0
135.0
139.0
135.0
142.0
125.0
130.0
141.0
139.0
135.0
143.0
-------
TABLE H-6. ANALYSIS FOR ELECTRICAL CONDUCTIVITY (MICROMHOS) FOR 1975
00
Date
Impounded
Mean
April 30JL975 230.0
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 10
June 12
June 16
June 19
June 19
June 20
June 22
June 23
June 26
July 7
July 14
July 21
August 4
August 15
207.0
193.7
213.3
60.7
168.3
180.0
225.7
227.7
71.7
76.7
110.0
81.7
91.7
203.3
181.7
164.3
126.0
138.0
131.0
170.7
110.0
106.7
Recommended
Standard
Deviation
+70.0
+19.0
+30.4
+19.0
+ 5.0
+27.5
+17.4
+ 9.3
+19.1
+ 5.8
+ 5.8
+13.2
+14.4
+10.4
+ 5.8
+12.6
+25.0
+ 8.5
+10.4
+ 4.6
+10.1
+13.9
+ 7.6
Inpounded
Mean
306.7
258.0
224.7
291.3
58.7
141.0
151.0
?37.3
217.7
73.3
76.7
98.3
73.3
a 10.0
253.3
213.3
203.0
151.0
348.3
150.0
173.3
140.7
122.3
Excessive
Standard
Deviation
+76.4
+18.4
+15.6
+J02.7
+ 9.0
+16.5
+45.0
+15.7
+50.0
+ 7.6
+ 5.8
+12.6
* 5.8
+26.5
+61.1
+25.2
+34.6
+20.1
+ 7.6
+26.5
+23.6
+34.1
+ 7.5
Continuous
Mean
215.3
210.7
184.3
216.3
32.0
121.7
140.3
142.7
178.3
61.7
70.0
101.7
71.7
96.7
236.7
180.0
151.3
124.7
142.7
123.0
158.7
118.3
108.3
Recommended
Standard
Deviation
+28.6
1 9.0
+26.6
+38.1
+ 8.7
+10.4
+45.0
+32.9
+58.0
+ 5.8
+ 0.0
+16.1
+10.4
+ 5.8
+70.9
+60.8
+24.9
+28.6
+16.2
+ 1.0
+25.5
+ 5.5
+10.1
Continuous
Mean
242.0
252.0
244. 3
275.3
53.0
213.3
108.0
175.0
165.3
76.7
73.3
87.7
70.0
83.3
216.7
196.7
155.3
128.3
144.3
140.7
162.0
119.3
113.3
Excessive
Standard
Deviation
+25.2
+27.1
4-1 L L
• .I4* • *f
+75.7
+20.0
+59.2
+23.6
+34.0
+58.6
+12.6
+ 5.8
+10.8
+10.0
+ 2.9
+58. 6
+55.1
+69.3
+30.6
+16.0
+16.3
+20.7
+ 9.1
+ 8.5
Canal
Water
122.0
160.0
83.0
1CO.O
90.0
82.0
100.0
115.0
65.0
100.0
50.0
60.0
70.0
80.0
85.0
1C1.0
118.0
120.0
120.0
140.0
101.0
78.0
-------
TABLE H-7. ANALYSIS FOR pH FOR 1973
Date
May 2
May 3
May 7
May 12
June IS
July 12
July 27
August 8
August 13
Impounded
Mean
6.0
6.1
6.3
6.7
6.4
6.4
6.7
6.3
6.2
Recommended
Standard
Deviation
+0.1
+0.2
+0.2
+0.2
+0.2
+0.0
+0.1
+0.1
+0.2
Impounded
Mean
5.8
5.9
6.3
6.8
6.3
6.4
6.6
6.3
6.3
Excessive
Standard
Deviation
+0.0
+0.3
+0.5
+0.5
+0.2
+0.1
+0.1
+0.2
+0.1
Continuous
Mean
6.0
6.3
6.6
7.2
6.6
6.4
6.5
6.2
6.1
Recommended
Standard
Deviation
+0.1
+0.1
+0.2
+0.5
+0.1
+0.1
+0.2
-+0.1
+0.1
Continuous
Mean
5.7
5.8
6.2
6.7
6.5
6.3
6.4
6.2
6.1
Excessive
Standard
Deviation
+0.3
+0.5
+0.1
+0.4
+0.0
+0.1
+0.1
+0.1
+0.0
Canal
Water
—— -.
__ H
7.2
6.5
6.8
6.5
6.3
-------
TABLE H-8. ANALYSIS FOR pH FOR 1974
Date
May 3
May 3
May 21
May 29
June 6
June 7
June 8
June 8
June 17
June 24
June 26
June 27
June 29
June 28
July 1
July 8
July 15
July 22
July 29
August 5
August 12
August 19
August 21
Impounded
Mean
6.6
7.2
5.9
6.2
6.4
6.2
6.0
6.0
6.0
6.1
6.2
6.3
5.8
6.3
5.9
5.9
6.5
6.7
6.6
6.7
6.7
6.7
Recommended
Standard
Deviation
+0.2
+0.2
+0.3
+0.1
+0.1
+0.1
+0.0
+0.1
+0.1
+0.2
+0.1
+0.1
+0.3
+0.1
+0.3
+0.2
+0.1
+0.0
+0.0
+0.1
+0.0
+0.1
Impounded
Mean
7.5
7.1
6.1
6.3
6.4
6.2
6.0
6.0
6.0
6.1
6.2
6.2
5.4
6.4
5.8
5.7
6.3
6.6
6.7
6.5
6.7
6.7
6.7
Excessive
Standard
Deviation
+1.1
+0.2
+0.2
+0.0
+0.2
+0.1
+0.0
+0.1
+0.1
+0.1
H3.1
+0.1
+0.7
+0.1
+0.2
+0.2
+0.1
+0.1
+0.1
+0.0
+0.1
+0.0
+0.1
Continuous
Mean
7.1
6.0
6.2
6.6
6.2
6.1
6.1
6.1
6.1
6.3
6.5
5.9
6.4
5.9
6.3
6.5
6.7
6.8
6.6
6.8
6.8
6.6
Recommended
Standard
Deviation
+0.2
+0.3
+0.1
+0.2
+0.1
+0.0
+0.1
+0.1
+0.3
+0.1
+0.1
+0.2
+0.3
+0.2
+0.1
+0.1
+0.0
+0.1
+0.1
+0.1
+0.0
+0.1
Continuous
Mean
6.8
7.2
5.9
6.3
6.5
6.3
6.1
6.1
6.0
6.2
6.2
6.6
5.8
6.4
5.6
6.3
6.4
6.6
6.7
6.6
6.7
6.8
6.7
Excessive
Standard
Deviation
+0.2
+0.1
+0.2
+0.0
+0.2
+0.1
+0.1
+0.1
+0.0
+0.0
+0.0
+0.3
+0.5
+0.1
+0.6
+0.0
+0.1
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
Canal
Water
7.0
7.5
6.0
6.3
6.8
6.3
6.4
6.3
6.3
6.6
6.7
6.6
6.8
7.0
7.0
6.8
7.2
6.9
6.8
6.9
7.0
6.9
-------
TABLE H-9. ANALYSIS FOR pH FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 10
-> June 12
[f] June 16
June 19
June 19
June 20
June 22
June 23
June 26
July 7
July 14
July 21
August 4
August 15
Impounded
Mean
6.5
6.2
5.4
5.9
6.2
6.2
6.2
5.8
5.7
6.4
6.0
6.0
6.5
6.4
6.1
5.7
5.8
6.1
6.4
6.3
6.3
6.1
6.6
Recommended
Standard
Deviation
+0.2
+0.1
+0.1
+0.1
+0.8
+0.1
+0.1
+0.0
+0.1
+0.1
+0.1
+0.1
+0.0
+0.1
+0.2
+0.2
+0.4
+0.2
+0.1
+0.2
+0.2
+0.3
+0.1
Impounded
Mean
6.4
6.2
5.3
5.7
6.1
6.2
5.9
5.7
5.8
6.4
6.0
5.9
6.4
6.5
6.0
5.7
5.5
5.9
6.3
6.2
6.7
6.3
7.0
Excessive
Standard
Deviation
+0.1
+0.1
+0.1
+0.1
+0.2
+0.1
+0.1
+0.1
+0.2
+0.0
+0.1
+0.1
+0.1
+0.2
+0.3
+0.2
+0.3
+0.3
+0.0
+0.0
+0.2
+0.1
+0.2
Continuous
Mean
6.4
6.2
5.4
5.9
5.6
6.3
6.1
5.9
5.9
6.5
6.2
6.2
6.4
6.4
6.0
5.3
5.4
6.0
6.3
6.1
6.6
6.3
6.5
Recommended
Standard
Deviation
+0.1
+0.0
+0.1
+0.1
+0.3
+0.1
+0.3
+0.1
+0.0
+0.0
+0.1
+0.0
+0.1
+0.0
+0.2
+0.4
+0.6
+0.1
+0.1
+0.1
+0.1
+0.1
+0.0
Continuous
Mean
6.4
6.2
5.3
5.8
6.1
6.1
6.0
6.0
6.0
6.5
6.1
6.2
6.5
6.5
6.0
5.5
5.4
6.0
6.3
6.1
6.6
6.3
6.8
Excessive
Standard
Deviation
+0.2
+0.1
+0.1
+0.1
+0.3
+0.2
+0.3
+0.1
+0.1
+0.2
+0.1
+0.1
+0.1
+0.0
+0.3
+0.4
+0.8
+6.2
+0.1
+0.1
+0.2
+0.1
+0.4
Canal
Water
6.6
6.4
6.3
6.3
6.5
6.3
6.5
6.5
6.6
6.6
6.6
6.9
6.7
6.5
6.4
6.5
6.7
6.3
6.2
6.9
6.9
6.8
-------
TABLE H-10. ANALYSIS FOR NITRITE (PPM) FOR 1973
Date
May 1
May 3
May 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
Impounded
Mean
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
±0.0
±D.O
±0-1
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
±0.0
Impounded
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
OiO
0.0
0.0
0.0
Excessive
Standard
_ Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuoue
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.1
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0,0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
____.
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-------
TABLE H-ll. ANALYSIS FOR NITRITE (PPM) FOR 1974
Date
Hay 3
May 3
May 21
May 29
June 6
June 7
June 8
June 8
June 10
June 10
June 14
June 17
01 June 20
<•*> June 24
June 24
June 26
June 27
June 27
June 28
June 28
June 29
July 1
July 3
July 3
July 5
July 8
July 8
July 11
July 15
July 17
July 22
July 24
July 26
July 29
Impounded
Mean
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
—
0.0
___
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+JD.O
+0.0
+0.0
+0.0
+0.0
+C.O
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
_„
+0.0
+0.0
Impounded
Mean
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0-0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
„„
_-_
0.0
0.0
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.1
0.0
0.0
0.0
o.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0,0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
TO.O
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
ft 0
U . \J
0.0
0.0
Ofl
• u
0.0
0.0
n n
U . \J
0.0
0.0
0.0
0.0
0.0
0.0
On
• U
On
• V
0.0
On
• u
0.0
-—-
0.0
Ort
• U
On
• U
0.0
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
0.0
0.1
0.0
0.0
0 .0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
c.o
0.0
0.0
0.0
0.0
(Continued)
-------
TABLE H-ll. (Continued)
Date
August 2
August 5
August 12
August 15
August 16
August 19
August 21
June 20
Impounded
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Canal
Water
0.0
0.0
— ._
0.0
o.n
-p-
Ul
-------
TABLE H-12. ANALYSIS FOR NITRITE (PPM) FOR 1975
Ul
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 10
June 12
June 16
June 19
June 19
June 20
June 22
June 23
June 26
July 7
Impounded
Mean
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.0
0.0
0.3
0.1
0.0
0.1
0.1
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.0
0.0
0.4
0.1
0.0
0.1
—
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.2
+0.0
+0.0
+0.0
Continuous
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.0
0.0
0.2
0.1
0.0
0.1
0.1
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.1
Continuous
Mean
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.0
0.0
0.3
0.1
0.0
0.1
0.2
Excessive
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.1
Canal
Water
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.1
0.4
July 14
-------
TABLE H-13. ANALYSIS FOR AMMONIUM (PPM) FOR 1973
Date
May 1
May 3
May 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
0.1
0.1
0.3
0.1
0.0
0.1
5.2
7.0
4.9
0.9
0.2
0.8
2.9
5.0
2.6
0.3
0.1
0.2
0.0
0.1
0.1
Recommended
Standard
Deviation
+0.0
+0.2
+0.1
+0.2
+0.1
+0.1
+1.2
+1.0
+1.2
+0.6
+0.1
+0.5
+0.8
+3.0
+0.5
+o.d
+0.1
+0.2
+0.0
+0.0
+0.0
Impounded
Mean
0.2
0.4
0.3
0.1
0.0
0.0
16.8
9.7
8.7
0.8
0.6
1.1
3.1
7.3
1.3
0.1
0.2
0.0
0.1
0.1
Excessive
Standard
Deviation
+0.2
+0.1
+0.1
+0.1
+0.1
+0.0
+1.3
+4.9
+0.0
+0.1
+0.5
+0.6
+1.0
+1.0
+0.1
+0.0
+0.0
+0.0
+0.0
Continuoue
Mean
0.1
0.3
0.2
0.0
0.0
0.1
17.7
7.9
2.6
0.4
0.1
0.4
3.1
4.0
1.7
1.1
0.1
0.1
0.0
0.0
0.1
Recommended
Standard
Deviation
+0.0
+0.2
+0.0
+0.0
+0.0
+0.0
+1.4
+0.6
+0.3
+0.1
+0.1
+1.3
+0.9
+0.6
+1.6
+0.0
+0.1
+0.0
+0.0
+0.0
Continuous
Mean
0.2
0.1
0.4
0.2
0.0
0.1
17.7
9.3
4.0
0.2
0.1
0.2
2.0
7.4
4.1
0.9
0.0
0.1
0.1
0.0
0.1
Excessive
Standard
Deviation
+0.2
+0.1
+0.1
+0.3
+0.0
+0.0
+0.5
+0.9
+0.1
+0.0
+0.1
+1.7
+1.5
+1.1
+0.3
+0.0
+0.0
+0.1
+0.0
+0.1
Canal
Water
0.2
0.2
5.0
2.1
0.2
0.1
0.1
0.1
-------
TABLE H-14. ANALYSIS FOR AMMONIUM (PPM) FOR 1974
Date
Impounded
Mean
May 3,1974 2.0
may 3
May 21
May 29
June 6
June 7
June 8
June 8
June 10
June 10
June i4
June 17
June 20
June 24
June 26
June 27
June 27
June 28
June 28
June 29
July 1
July 3
July 3
July 5
July 8
July 8
July 11
July 15
July 17
July 22
July 24
July 26
July 29
August 2
August 5
1.7
0.5
0.1
2.2
9.1
3.9
5.1
2.7
6.2
0.2
0.1
—
0.1
10.1
6.5
4.3
2.1
0.8
0.4
0.2
0.2
0.1
0.1
0.1
0.2
0.1
0.1
0.1
0.0
Recommended
Standard
Deviation
+1.2
+0.6
+0.1
+0.0
+3.4
+1.4
+1.1
+2.5
+2.1
+2.1
+0.2
+0.1
+0.0
+4.7
+2,2
+2.1
+0.9
+0.2
+0.2
+0.1
+0.1
+0.0
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Moan
1.3
3.4
0.7
0.1
_ —
10.5
6.9
6.9
2.6
7.9
0.1
0.1
2. .2
0.1
4.6
9.0
6.2
2.3
2.1
0.4
0.4
1.2
0.2
0.1
0.2
0.5
0.2
0.1
0.1
0.1
0.1
Excessive
Standard
Deviation
+0.3
+1.8
+0.1
+0.0
_•_-__
+2.3
+0.8
+0.8
+1.2
+3.3
+0.1
+0.0
+2.8
+0.0
+0.7
+1.0
+1.4
+0.7
+1.0
+0.2
+0.3
+1.5
+0.1
+0.0
"
+0.1
+0.3
+0.0
H
+0.0
+0.0
+0.1
Tp.O
Continuous
Mean
0.9
1.8
'0.7
0.2
4.4
2.5
3.0
1.0
5.8
0.2
0.1
0.1
3.8
1.0
6.0
4.6
3.5
3.5
1.0
0.3
0.4
0.1
«__
0.2
0.1
0.3
0.1
0.1
0.1
0.0
Recommended
Standard
Deviation
+0.3
+0.1
+0.1
+0.0
+3.4
+1.2
+0.4
+0.6
+1.0
+0.3
+0.0
+0.0
+1.9
+0.8
+2.5
+3.5
+1.5
+1.5
+1.2
+0.2
+0.4
+0.0
+J0.1
+0.0
+0.2
+0.0
+0.0
+0.0
+0.1
Continuous
Mean
0.9
2.1
0.6
0.1
8.6
3.5
2.6
0.6
8.6
0.1
0.1
0.1
8.5
1.1
12.9
8.1
5.3
4.1
1.0
0.3
2.9
0.2
0.1
0.1
0.1
0.1
0.2
0.1
0.1
0.1
0.0
Excessive
Standard
Deviation
+0.3
+0.5
+C.2
+0.1
«._._ —
+3.8
+0.7
+0.8
+0.1
+2.7
+0.2
+0.0
+0.0
+2.6
+0.0
+2.8
+2.5
+1.1
+4.1
+0.8
+0.1
+2.7
+0.1
+0.0
+0.1
+0.0
+0.0
+0.1
+0.0
+0.0
O.A n
' U . U
IP-0
(Continued)
Canal
Water
0.1
0.3
0.0
0.0
On
. u
0.2
0.3
0 0
w • \J
0 1
\J • J.
n i
\J • -L
0.2
0.3
0.3
n ?
\j * t.
n i
-------
TABLE H-14. (Continued)
Date
Augus t
August
August
August
August
Impounded
Mean
12 0.0
15 0.2
16 0.0
19 0.0
21 0.0
Recommended
Standard
Deviation
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.0
0.0
0.1
0.1
Excessive
Standard
Deviation
+0.0
+0.0
+0.1
+0.0
Continuous
Mean
0.0
0.3
— —
0.0
0.0
Recommended
Standard
Deviation
+0.0
+0.1
____
+0.0
+0.0
Continuous
Mean
0.0
0.2
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.0
+0.1
+0.0
+0.0
+0.0
Canal
Water
0.0
0.1
0.1
-p-
Ln
OO
-------
TABLE H-15. ANALYSIS FOR AMMONIUM (PPM) FOR 1975
VD
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
July 25
August 4
Impounded
Mean
1975
1.6
2.1
0.6
0.8
0.4
5.8
4.0
3.5
2.6
1.0
2.2
0.2
0.0
1.8
3.3
10.9
2.0
0.7
0.3
0.1
0.2
0.2
0.1
0.0
0.2
0.1
Recommended
Standard
Deviation
+1.0
+0.5
+0.1
+0.4
+0.1
+1.1
+0.8
+0.7
+0.0
+0.2
+1.7
+0.0
+0.0
+0.9
+0.8
47.2
+0.4
+0.3
+>).2
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
3.0
3.3
1.5
1.7
0.2
4.2
3.2
6.5
3.2
8.6
1.6
1.8
3.0
0.2
0.0
2.8
3.8
10.8
2.5
1.0
0.3
0.3
0.2
0.1
0.1
0.0
0.2
0.1
Excessive
Standard
Deviation
+0.8
+0.2
+0.4
+1.9
+0.1
+1.2
+2.3
+2.4
+2.3
+1.3
+0.4
+0.5
+0.4
+0.0
+0.0
+1.6
+0.8
+3.7
+0.8
+0.3
+0.1
+0.3
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
1.6
1.9
0.9
0.7
0.2
2.9
3.3
2.7
2.0
4.9
0.6
3.4
0.2
0.0
3.1
3.0
2.5
0.1
0.2
0.1
0.2
— _
0.1
0.0
0.1
0.1
Recommended
Standard
Deviation
+0.1
+0.1
+0.4
+0.2
+0.0
+0.9
+2.5
+1.7
+1.0
+1.1
+0.1
+3.3
+0.0
+0.0
+0.2
+1.0
+1.1
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
2.8
3.3
0.9
2.0
0.3
_— — •
3.6
1.1
8.6
1.0
0.8
3.0
0.2
0.0
1.9
4.0
16.9
2.3
0.6
0.2
0.1
0.2
0.2
0.1
0.0
0.3
0.1
Excessive
Standard
Deviation
+0.8
+0.8
+0.3
+1.1
+0.1
+1.6
+1.1
+3.1
+0.3
+0.3
+2.8
+0.0
+0.0
+0.6
+1.6
+5.8
+0.8
+0.8
+0.1
+0.0
+0.1
+0.0
+0.0
+0.0
+0.2
+0.0
Canal
Water
0.1
0.1
— —
0.0
0.1
0.1
0.0
0.2
0.0
—
0.1
0.1
0.2
0.0
0.1
0 .1
0.1
0.0
0.0
0.3
0.0
0.0
0.3
-------
TABLE H-16. ANALYSIS FOR SULFATE (PPM) FOR 1973
CTv
O
Date
Hay 1
May 3
Hay 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
35.7
39.2
47.3
81.8
43.8
20.3
35.7
39.0
35.7
8.7
3.7
22.3
15.0
25.3
56.6
50.1
28.8
29.8
6.0
4.7
5.3
Recommended
Standard
Deviation
+6.7
+8.5
+4.4
+0.3
+3.1
+1.9
+4.8
~~
+0.5
+0.6
+0.6
Impounded
Mean
27.3
33.3
49.2
86.7
38.5
22.7
50.5
44.3
60.8
5.5
8.8
26.9
34.7
77.1
47.6
20.2
47.8
5.7
4.5
5.5
Excessive
Standard
Deviation
+8.1
+2.8
+8.1
+4.6
+0.5
+3.8
___
+0.6
+1.5
+0.9
Continuous
Mean
30.3
36.8
45.1
63.6
27.8
42.2
48.2
50.7
27.5
4.7
3.3
25.7
9.3
12.5
19.6
34.4
22.3
23.0
5.9
3.8
7.5
Recommended
Standard
Deviation
— -
+8.4
+9.9
+2.4
+7.7
+4.3
+1.0
+1.5
+1.9
+6.9
+1.0
+0.0
+0.4
+0.3
+2.1
Continuous
Mean
39.5
50.3
57.8
89.3
35.3
25.3
60.8
36.7
27.7
1.7
4.3
16.7
12.2
29.3
36.8
23.3
15.0
12.8
4.7
3.6
6.5
Excessive
Standard
Deviation
+9.7
+8.3
+4.0
+4.0
+0.8
+0.6
+2.9
+2.4
+0.4
+9.0
+6.3
+0.8
+0.3
+0.5
Canal
Water
7.3
8.0
35.0
3.0
14.0
5.0
4.0
4.0
3.0
4.5
7.5
2.0
24.0
8.5
3.5
8.0
-------
TABLE H-17. ANALYSIS FOR SULFATE (PPM) FOR 1974
Date
May 3
May 3
May 21
May 29
June 6
June 7
June 8
June 8
June 10
June 10
June 14
June 17
June 20
June 24
June 24
June 26
June 27
June 27
June 28
June 28
June 29
July 1
July 3
July 3
July 5
July 8
July 8
July 11
July 15
July 17
July 22
July 24
July 26
July 29
Impounded
Mean
58.0
42.0
26.7
17.0
26.3
50.0
47.3
56.0
41.3
..— —
44.3
— — __
58.3
81.7
45.3
43.3
65.7
52.3
— — —
4.3
50.3
18.7
— —
— _
0.0
7.0
Recommended
Standard
Deviation
«__
+6.7
+3.6
+6.5
» — _
+0.6
_ — _
+2.5
+1.5
+5.8
____
+0.0
+2.0
Impounded
Mean
51.3
86.0
31.0
21.7
36.7
57.0
67.7
71.3
51.0
—. — .
55.0
51.7
_— —_
—_ _
33.0
53.3
B*— —
33.7
55.3
75.7
65.0
_
4.0
48.3
25.0
71.3
17.3
—
0.0
7.0
Excessive
Standard
Deviation
+7.0
+7.8
+1.2
+7.0
+4.2
__ «
..— —
+7.0
__—
41.0
—
+2,0
_
+8.7
__ —
+4.6
— — —
+0.0
+1.7
Continuous
Mean
44.3
24.7
15.3
32.0
36.3
20.0
23.3
12.7
21.3
16.7
39.0
57.0
44.0
30.7
50.7
17.7
27.7
— —
_— __
11.7
_
12.3
87.3
1.7
10.7
Recommended
Standard
Deviation
+3.8
+2.5
+ 8.5
+6.0
+ 4.2
+4.0
™"
+5.5
+ 0.6
~"~
— ____
+ 4.4
— —
__«.
+ 1.5
+1.5
_._.— _
+3.2
— — M.
+2.9
+1.5
Continuous
Mean
83.7
63.3
23.7
21.7
38.0
43.3
28.3
21.0
12.7
25.7
19.7
79.7
nil
61.0
89.3
51.0
14.7
29.7
12.7
11.7
82.7
0.0
7.7
Excessive
Standard
Deviation
+3.1
+4.0
+5.5
+5.6
+5.5
+9.5
+2.9
+2.1
+5.7
II™
+7.0
+2.1
+2.1
+0.6
+0.0
+2.1
(Continued)
Canal
Water
18.0
12.0
8.0
8.0
8.0
5.0
12.0
10.0
16.0
16.0
13.0
13.0
13.0
Ifi n
J.U • U
17.0
20.0
15.0
16.0
0.0
13.0
-------
TABLE H-17. (Continued)
Date Impounded
Mean
August 2
August 5
August 12
August 16
August 19
August 21
7.0
6.0
3.3
7.3
Recommended
Standard
Deviation
+1.0
+1.0
+1.2
-. _
+4.0
Impounded
Mean
6.3
5.0
2.7
— _
6.3
Excessive Continuous
Standard
Deviation
+0.6
+1.7
+1.2
"""• •
+4.2
Mean
6.7
9.3
9.3
_._
21.7
Recommended Continuous Excessive
Standard
Deviation
+1.2
+1.2
+1.2
— _
Mean
6.7
7.0
8.3
7.3
Standard
Deviation
+0.6
+1.0
+0.6
____
+3.8
Can.il
Water
12.0
13.0
____
-------
TABLE H-18. ANALYSIS FOR SULFATE (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
Impounded
Mean
47.4
52.8
26.3
24.8
14.1
13.8
26.0
28.8
28.5
15.5
74.5
20.3
15.3
21.5
48.5
34.9
41.3
30.8
17.7
11.8
Recommended
Standard
Deviation
+4.7
+9.1
+4.2
+2.3
+4.9
+5.0
+2.6
*.
+2.2
+1.3
+3.8
+2.4
+9.0
+4.2
+7.2
+2.3
+3.0
Impounded
Mean
77.4
65.7
55.7
40.2
11.7
10.0
28.3
44.0
18.5
14.8
83.8
13.0
14.5
29.5
51.5
44.5
68.6
37.3
18.3
16.2
Excessive
Standard
Deviation
+9.9
•
+1.6
+5.3
_
+2.4
+1.2
+7.8
+3.1
+0.4
_
_
+5.4
— .--
Continuous
Mean
41.7
54.1
44.9
34.5
10.9
11.8
25.3
22.8
23.3
11.3
7.5
82.0
10.6
10.0
22.9
42.0
_____
26.3
44.0
32.5
_-.__
13.5
____
10.1
Recommended
Standard
Deviation
+7.1
+4.4
__
+1.2
+5.1
+3.9
+0.8
+4.0
+3.6
+2.3
+6.0
__— —
+8.8
+1.3
+0.1
Continuous
Mean
63.1
69.5
31.2
42.3
11.3
37.3
15.1
26.0
20.0
14.5
9.8
61.8
10.5
10.8
17.3
50.3
30.3
46.8
28.0
_____
12.3
10.2
___..
Excessive
Standard
Deviation
+0.8
+7.5
+10.0
+4.6
+3.3
+6.0
+1.9
+4.2
__
+0.4
+0.6
Canal
Hater
9.9
10.5
4.5
14.3
3.0
7.5
9.0
11.3
6.8
3.0
13.5
9.0
7.5
11.3
6.0
6.0
16.5
10.5
15.5
-------
TABLE H-19. ANALYSIS FOR ORTHO-PHOSPHATE (PPM) FOR 1973
Date
May 1
May 3
May 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
1.9
0.2
___
0.2
0.5
0.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+1.7
+0.1
+0.2
+0.3
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Impounded
Mean
0.2
__
0.1
0.5
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Deviation
+0.1
+0.1
+0.4
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
2.1
0.3
0.1
0.5
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
O.'O
0.0
0.0
0.0
0.0
Recommended
Standard
Deviation
+0.1
+0.2
+0.1
+0.2
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
Continuous
Mean
2.5
0.1
0.1
0.4
0.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Excessive
Standard
Devotion
+0.5
+0.0
+ 0.1
+0.2
+0.0
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
Canal
Water
.
»— —
0.7
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
-------
TABLE H-2Q. ANALYSIS FOR ORTHO-PHOSPHATE (PPM) FOR 1974
Oi
Date
May 3
May 3
May 21
May 29
June 6
June 7
June 8
June 8
June 10
June 10
June 14
June 17
June 20
June 24
June 24
June 26
June 27
June 27
June 28
June 28
June 29
July 1
July 3
July 3
July 5
July 8
July 8
July 11
July 15
July 17
July 22
July 24
July 26
Impounded
Mean
1.7
1.6
0.0
0.0
0.0
0.6
_ —
0.3
0.2
0.2
0.2
0.3
0.1
0.1
0.1
0.2
0.1
3.9
0.1
1.1
0.2
0.1
0.0
0.1
—
—
0.0
Recommended
Standard
Deviation
+0.5
+0.4
+0.1
+0.1
+0.0
+0.2
+0.1
___- .
+0.1
+0.2
+0.1
+0.4
+0.1
+0.1
+0.1
+0.1
+0.1
+5.0
+0.1
+1.8
+0.1
+0.0
+0.0
••'
+0.1
+0.1
Impounded
Mean
2.2
4.6
0.0
0.0
0.1
0.4
0.3
0.5
0.1
0.1
2.2
0.3
0.1
0.2
0.1
0.2
0.1
0.2
0.4
0.1
0.3
0.1
0.0
0.1
0.2
0.1
0.1
Excessive
Standard
Deviation
+0.5
+4.7
+0.1
+0.1
+0.1
+0.1
+0.0
+0.4
+0.1
+0.2
+1.6
+0.2
+0.1
,
+0.1
+0.0
+0.0
+0.1
+0.2
+0.4
+0.1
+0.2
+0.0
+0.0
+0.0
+0.2
+0.1
+0.1
Continuous
Mean
1.1
1.3
0.0
0.1
0.1
0.4
0.4
0.5
0.1
0.2
0.3
0.0
0.2
0.1
0.1
0.2
0.2
0.1
0.1
0.2
0.1
0.2
0.1
0.2
0.2
Recommended
Standard
Deviation
+0.6
+0.3
+0.1
+0.1
+0.1
+0.1
+0.1
+0.7
+0.1
+0.1
H
+0.3
+0.1
+0.1
+0.1
+0.1
+0.3
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
+0.3
Continuous
Mean
2.4
2.2
0.0
O.C
0.1
0.5
0.4
0.4
0.1
0.3
0.2
0.1
0.1
1.3
0.2
0.2
0.3
0.1
0.3
0.2
0.1
0.2
0.1
0.0
0.1
—
0.1
0.2
0.1
Excessive
Standard
Deviation
+0.5
+0.7
+0.0
+0.1
+0.1
+0.1
_» —
+0.1
— — — _
+0.3
+0.1
+0.1
+0.3
+0.1
+0.0
+1.7
+0.1
+0.3
+0.4
+0.1
+0.4
+0.1
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.1
Canal
Water
1.1
1.1
0.0
0.0
0.0
0.4
—
0.5
2.7
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.0
0.1
0.2
(Continued)
-------
TABLE H-20. (Continued)
Date
July 29
August 2
August 5
August 12
August 15
August 16
August 19
August 21
Impounded
Mean
0.0
0.2
0.3
0.3
0.2
0.1
0.2
0.2
Recommended
Standard
Deviation
+0.1
+0.2
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
Impounded
Mean
0.1
0.0
0.3
0.2
0.1
0.2
0.5
Excessive
Standard
Deviation
+0.1
+0.1
+0.2
+0.1
+0.0
+0.1
+0,5
Continuous
Mean
2.2
0.1
0.2
0.2
0.3
_ —
0.4
0.2
Recommended
Standard
Deviation
+3.7
+0.2
+0.1
+0.2
+0.1
+0.4
+0.1
Continuous
Mean
0.0
0.0
0.2
0.3
0.3
0.1
0.2
0.3
Excessive
Standard
Deviation
+0.1
+0.0
+0.1
+0.2
+0.1
+0.0
+0.1
+0.2
Canal
Water
0.1
0.2
0.3
0.4
1.0
-------
TABLE H-21. ANALYSIS FOR ORTHO-PHOSPHATE (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
g; June 12
^i June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
July 25
August 4
Impounded
Mean
1.4
0.9
0.2
0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.1
0.1
0.0
0.2
0.2
0.1
0.1
0.2
0.3
0.2
0.2
0.3
Recommended
Standard
Deviation
+0.6
+0.4
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.1
__ —
Impounded
Mean
0.7
0.5
0.2
0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.1
0.0
0.2
0.2
0.1
0.1
0.2
0.3
0.2
0.3
0.2
— _
Excessive
Standard
Deviation
+0.5
+0.1
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.2
+0.0
_
— —
Continuous
Mean
1.1
1.0
0.3
0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.1
0.1
0.0
0.2
0.2
0.1
0.1
0.2
0.3
0.2
0.3
0.2
—
Recommended
Standard
Deviation
+0.1
+0.2
+0.2
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+0.1
— — -
Continuous
Mean
0.5
0.4
0.4
0.1
0.1
0.2
0.3
0.3
0.1
0.1
0.1
0.3
0.0
0.2
0.2
0.1
0.1
0.2
0.3
0.2
0.3
1.1
•
Excessive
Standard
Deviation
+0.1
+0.2
+0.3
+0.0
+0.0
+0.0
+0.1
+0.3
+0.0
+0.0
+0.0
+0.4
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.0
+0.1
+1.5
Canal
Water
___
0.1
0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.1
0.1
0.0
0.2
0.2
0.1
0.1
0.2
0.3
0.2
0.2
0.3
-------
TABLE H-22. ANALYSIS FOR POTASSIUM (PPM) FOR 1973
Date
May 1
May 3
May 7
May 12
May 18
Kay 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
2.0
1.6
1.6
2.2
2.5
1.4
2.1
1.0
2.3
1.3
1.4
1.4
0.3
0.6
0.7
0.5
0.4
0.4
2.2
2.2
3.1
Reconmended
Standard
Deviation
+0.1
+0.0
+0.0
+0.7
+0.3
+0.5
+0.5
+0.2
+0.1
+0.2
+0.3
+0.6
+0.2
+0.2
+0.2
+0.1
+0.1
+0.1
+0.4
+0.1
+0.2
Impounded
Mean
2.3
1.7
1.8
2.1
2.8
1.5
2.6
2.1
3.3
1.7
1.7
1.5
0.6
1.2
0.9
1.0
0.5
0.4
2.4
2.3
3.3
Excessive
Standard
Deviation
+0.4
+0.3
+0.5
+0.4
+0.3
+0.5
+0.3
+0.3
+0.4
+0.5
+0.5
+0.9
+0.2
+0.8
+0.5
+0.3
+0.1
+0.1
+0.3
+0.5
+0.2
Continuous
Mean
2.0
1.6
1.5
1.4
2.7
2.0
2.7
1.1
2.9
2.1
2.1
2.0
0.8
1.2
1.1
1.1
0.7
1.5
3.5
1.8
2.6
Recommended
Standard
Deviation
+0.1
+0.1
+0.1
+0.2
+0.5
+0.5
+0.6
+0.7
+0.3
+0.1
+0.1
+0.2
+0.4
+0.4
+0.7
+0.7
+0.2
+0.0
+0.9
+0.0
+0.2
Continuous
Mean
1.8
1.8
1.4
2.5
2.8
1.9
2.2
2.2
2.6
2.4
2.2
2.3
1.0
0.7
0.9
1.5
1.1
1.5
3.2
2.1
3.1
Excessive
Standard
Deviation
+0.3
+0.3
+0.3
+0.3
+0.1
+0.7
+1.6
+0.8
+0.5
HO .1
+0.2
+0.1
+0.2
+0.2
+0.7
+0.6
+0.2
+0.3
+0.3
+0.5
+0.3
Canal
Water
____
____
______
___
___
___
.
-------
TABLE H-23. ANALYSIS FOR POTASSIUM (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
July 25
August 4
August 15
Impounded
Mean
3.2
3.0
2.6
3.3
1.3
2.8
3.1
3.7
4.0
-
1.5
-
3.1
0.9
1.2
1.1
1.7
5.0
1.7
1.1
1.0
1.6
1.5
1.4
1.6
0.5
1.3
2.9
2.4
Recommended
Standard
Deviation
+0.5
+0.4
+0.3
+0.3
+0.2
+0.5
+0.8
+0.4
+0.5
-
+0.3
-
+1.3
+0.2
+0.1
+0.1
+0.3
+2.1
+0.2
+0.4
+0.1
+0.2
+0.3
+0.2
+0.9
+0.2
+0.1
+0.1
+0.5
Impounded
Mean
4.6
4.1
3.3
5.0
1.5
2.4
2.8
4.2
3.5
4.7
1.8
1.6
4.4
1.2
1.1
1.0
1.5
5.3
1.5
1.1
0.8
1.5
1.1
1.9
1.5
1.4
1.2
3.2
4.1
Excessive
Standard
Deviation
+0.6
+0.3
+0.0
+0.6
+0.2
+0.1
+0.7
+0.1
+0.7
+0.3
+0.1
+0.4
+0.8
+0.1
+0.2
+0.2
+0.3
+2.0
+0.1
+0.2
+0.3
+0.3
+0.3
+0.9
+0.8
+0.5
+0.2
+0.5
+0.4
Continuous
Mean
3.4
3.0
2.5
3.2
1.2
2.1
2.8
2.7
3.3
3.6
1.3
1.2
4.5
1.1
1.1
1.0
1.7
1.4
0.8
1.1
1.6
1.6
2.1
1.3
1.4
0-9
4.2
2.7
Recommended
Standard
Deviation
+0.3
+0.1
+0.3
+0.4
+0.2
+0.2
+0.8
+0.3
+0;8
+0.6
+0.1
+0.1
+0.7
+0.1
+0.4
+0.3
+0.4
+0.6
+0.7
+0.3
+0.6
+0.1
+0.5
+0.8
+1.0
+0.3
+1.5
+0.7
Continuous
Mean
4.0
3.8
3.4
4.6
1.3
3.1
2.2
3.3
2.8
5.0
1.5
1.4
3.8
1.3
0.9
1.1
1.6
3.7
1.4
1.0
0.8
1.8
1.9
1.4
1.4
4.4
3.9
Excessive
Standard
Deviation
+0.5
+0.6
+0.6
+0.6
+0.2
+0.9
+0.2
+0.3
+0.4
+0.8
+0.1
+0.2
+0.4
+0.2
+0.1
+0.3
+-Q.1
+2.7
+0.6
+0.7
+0.5
+0.5
+0.8
+1.2
+0.6
+0.8
+1.5
Canal
Water
1.8
1.5
-
1.5
2.5
1.5
1.7
1.6
2.0
_
1.0
1.8
-
1.2
1.2
1.5
1.7
1.6
1.5
2.4
2.1
2.6
2.3
2.0
3.9
-------
TABLE H-24. ANALYSIS FOR MAGNESIUM (PPM) FOR 1973
Dace
Hay 1
May 3
May 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
1.9
2.9
3. it
6.0
3.7
1.9
1.9
0.8
2.2
1.3
1.6
1.6
1.1
1.3
2.2
2.7
2.6
1.9
2.7
2.6
3.1
Recommended Impounded
Standard Mean
Deviation
+0.7
+0.7
+0.7
+1.9
+1.4
+0.6
+0.4
+0.2
+0.1
+0.2
+0.3
+0.4
+0.8
+0.4
+0.6
+0.3
+0.3
+0.2
+0.2
+0.4
+0.7
3. '4
2.4
3.5
7.0
3.6
1.8
2.3
1.5
2.9
1.4
1.7
1.3
1.8
2.2
2.2
2.7
3.1
2.4
2.8
2.8
3.1
Exceastve
Standard
Deviation
+1.6
+0.8
+1.3
+1.0
+0.9
+0.3
+0.1
+0.5
+0.6
+0.5
+0.4
+0.9
+1.0
+0.9
+1.1
+0.6
+1.2
+0.3
+0.4
+0.5
+0.5
Continuous
Mean
2.3
2.9
3.2
5.7
2.8
2.3
2.5
0.9
2.6
2.0
2.2
2.1
0.9
1.3
1.3
2.5
2.1
2.5
2.4
1.7
2.4
Recommended
Standard
Deviation
+1.0
+0.4
+0.6
+1.6
+0.2
+0.5
+0.7
+0.5
+0.4
+0.2
+0.1
+0.1
+0.4
+0.3
+1.0
+2.2
+0.2
+0.2
+0.3
+0.0
+0.1
Continuous
Mean
2.7
2.9
3.0
7.0
3.6
2.2
2.2
1.8
2.2
2.1
2.1
1.3
1.1
0.8
0.9
1.8
2.1
2.5
2.2
1.7
2.4
Excessive
Standard
Deviation
+0.1
+1.2
+0.7
+0.8
+1.7
+0.7
+1.7
+0.9
+0.4
+0.2
+0.4
+0.8
+0.1
+0.3
+0.7
+0.4
+0.1
+0.1
+0.1
+0.2
+0.1
Canal
Water
-------
TABLE H-25. ANALYSIS FOR MAGNESIUM (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
July 25
Augus t 4
Impounded
Mean
2.9
1.7
3.1
3.0
0.7
1.0
0.9
2.0
0.3
3.5
1.2
1.1
0.8
1.6
5.9
2.0
1.4
2.0
3.7
1.7
4.2
2.4
1.8
4.9
2.0
Recommended
Standard
Deviation
+1.4
+1.0
+0.6
+0.4
+0.2
+0.2
+0.3
+0.2
+0.2
+2.3
+0.1
+0.2
+0.1
+0.1
+5.7
+0.1
+0.4
+0.1
+1.3
+0.4
+0.7
+0.3
+0.2
+0.6
+0.2
Impounded
Mean
4.8
1.9
4.4
4.3
0.7
1.1
0.8
1.8
1.4
4.2
0.4
0.7
4.4
1.1
0.9
0.7
1.8
6.0
2.4
1.9
2.1
3.6
1.7
3.7
2.7
1.7
5.0
1.9
Excessive
Standard
Deviation
+4.6
+1.6
+1.7
+1.7
+0.1
+0.3
+0.2
+0.2
+0.1
+1.8
+0.2
+0.1
+0.9
+0.1
+0.0
+0.3
+0.2
+5.4
+0.5
+0.9
+0.2
+1.3
+0.1
+1.3
+0.5
+0.4
+0.6
+0.1
Continuous
Mean
1.4
0.8
2.9
3.2
0.4
1.2
0.8
1.3
2.0
3.2
0.2
0.8
1.2
0.1
0.1
1.7
2.2
1.5
1.9
3.9
1.6
2.9
2.2
1.8
5.0
2.0
Recommended
Standard
Deviation
+0.4
+0.1
+0.5
+0.8
+0.1
+0.1
+0.3
+0.2
+0.6
+2.1
+0.2
+0.0
+0.2
+0.1
+0.2
+0.7
+1.0
+0.5
+0.5
+2.0
+0.3
+1.2
+0.2
+1.1
+1.0
+0.2
Continuous
Mean
3.9
2.1
7.1
3.9
0.5
1.4
0.8
1.6
1.8
5.8
0.2
0.7
3.5
1.0
1.1
0.7
1.6
10.4
2.4
1.7
1.8
4.1
1.9
2.4
1.5
4.4
2.0
Excessive
Standard
Deviation
+2.9
+0.4
+5.5
+1.3
+0.3
+0.5
+0.6
+0.4
+0.3
+2.3
+0.1
+0.0
+0.9
+0.1
+0.2
+0.3
+0.4
+7.4
+0.9
+1.0
+0.2
+1.3
+0.4
+0.6
+0.2
+0.2
+0.3
Canal
Water
2.5
0.7
1.25
1.7
0.9
1.1
1.1
2.6
0.5
1.3
_ — —
0.6
0.8
0.8
1.0
1.0
1.0
1.5
2.2
1.0
__«
1.5
-------
TABLE H-26. ANALYSIS FOR CALCIUM (PPM) FOR 1973
Date
May 1
Hay 3
May 7
May 12
Hay 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
17.9
27.1
30.1
46.7
29.7
19.5
14.9
8.1
20.7
11.0
15.1
8.4
9.2
15.6
22.2
22.2
23.5
13.9
16.8
13.6
19.0
Recommended
Standard
Deviation
+5.7
+6.4
+3.8
+4.2
+2.0
+1.9
+1.6
+0.6
+2.7
+4.5
+5.5
+3.6
+3.0
+2.3
+2.4
+0.4
+2.3
+4.1
+5.1
Impounded
Mean
28.6
22.5
30.5
52.3
30.7
19.6
17.6
14.2
23.0
13.1
16.2
10.3
13.9
23.1
25.2
21.1
27.8
18.1
18.1
15.9
17.2
Excessive
Standard
Deviation
+5.9
+8.8
+5.1
+7.8
+1.2
+4.7
+4.5
+5.9
+4.1
+2.8
+7.3
+7.7
+2.9
+5.4
+6.5
+3.8
+3.8
+3.5
+1.9
Continuous
Mean
20.1
29.0
29.2
44.2
25.1
22.8
19.9
10.8
16.8
13.2
15.1
13.0
6.2
10.5
8.0
18.2
14.3
13.0
11.0
8.8
13.2
Recommended
Standard
Deviation
+7.9
+5.4
+5.4
+9.9
+1.1
+2.6
+5.9
+2.5
+2.0
+1.7
+0.1
+0.9
+2.5
+1.5
+5.6
+1.7
+2.0
+1.3
+0.6
+1.1
Continuous
Mean
25.0
27.2
25.6
56.1
28.9
20.5
17.4
17.0
16.0
12.8
13.5
11.6
7.7
8.6
7.2
11.8
14.2
12.6
9.2
9.0
12.5
Excessive
Standard
Deviation
+2.2
+ 4.4
+9.2
+5.0
+7.9
+3.2
+0.6
+1.1
+1.6
+0.4
+3.8
+7.0
+1.8
+0.8
+0.7
+1 .3
+1 .0
+1.8
Canal
Water
-------
TABLE H-27. ANALYSIS FOR CALCIUM (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
July 25
August 4
Impounded
Mean
18.8
9.3
15.0
15.0
3.2
5.7
6.2
10.0
2.1
19.3
6.7
6.2
5.2
10.5
43.2
13.7
9.2
10.3
21.8
7.9
20.6
9.6
8.9
22.7
9.0
Recommended
Standard
Deviation
+4.5
+4.0
+3.9
+2.4
+1.2
+1.3
+2.0
+0.6
H
H
+1.7
H
H
+0.8
+1.0
+0.5
+0.8
H
+4.2
+2.5
+0.6
+4.5
+0.8
+2.2
+1.4
+0.2
+3.1
+1.5
Impounded
Mean
18.8
9.3
18.4
22.4
5.7
5.8
5.8
9.5
10.5
22.7
2.4
4.1
22.6
6.0
5.5
4.7
12.5
38.2
14.8
12.7
11.4
22.2
9.3
18.9
12.1
7.3
24.5
9.2
Excessive
Standard
Deviation
+8.1
+3.5
+2.9
H
+2.0
+1.4
+2.0
+0.6
+2.6
+
+0.9
+0.3
+6.1
+0.5
+0.0
+1.5
+2.3
+
+6.0
+4.8
+1.6
+3.5
+0.8
+6.7
+3.4
+2.4
+3.1
+1.0
Continuous
Mean
8.2
7.3
14.2
14.6
4.7
6.8
6.7
6.2
8.2
16.6
1.7
4.5
19.1
6.2
5.6
5.5
11.4
14.7
9.0
9.6
21.5
14.5
9.1
10.0
28.8
8.3
Recommended
Standard
Deviation
+2.3
+2.1
+2.5
+3.5
+1.0
+1.5
+2.3
+0.9
+2.9
H
+1.2
+0.3
H
+1.2
+0.5
+0.9
+4.1
+
+5.5
+1.4
+2.4
+8.9
+
+4.2
+0.7
+5.7
+
+1.2
Continuous
Mean
22.5
11.8
22.7
20.6
6.2
7.9
5.8
7.9
7.6
32.7
1.2
4.0
18.3
5.4
5.8
4.4
10.1
61.8
16.1
10.7
9.8
21.5
8.3
10.7
7.6
20.4
8.9
Excessive
Standard
Deviation
+3.8
+8.1
+8.3
+0.8
+3.4
+2.5
+2.2
+2.4
+
TO. 4
+0.3
+5.8
+0.7
+0.8
+1.8
+3.1
+5.0
+5.9
+2.2
+2.3
+1.8
H
+2.3
+2.1
+2.8
+2.2
Canal
Water
10.0
5.0
5.8
8.5
5.0
8.0
5.2
6.5
3.0
5.7
3.3
4.8
5.3
6.5
5.3
6.5
18.3
7.0
6.0
6.7
-------
TABLE H-28. ANALYSIS FOR CHLORIDE (PPM) FOR 1973
Date
May 1
May 3
May 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Ifean
88.0
59.7
91.0
99.0
79.0
Recommended Impounded
Standard Mean
Deviation
+6.0
96.0
99.0
+7.9
+6.8
+9.0
Excessive
Standard
Deviation
+8.1
+7.9
Continuous
Mean
98.0
84.0
97.0
79.0
87.0
Recommended
Standard
Deviation
+4.6
+4.6
Contionuous
Mean
93.7
96.0
53.0
78.7
91.0
90.0
Excessive
Standard
Deviation
9.0
6.0
4.0
Canal
Water
93.0
99.0
-------
TABLE H-29. ANALYSIS FOR CHLORIDE (PPM) FOR 1974
Date
May 3
May 3
May 21
May 29
June 6
June 7
June 8
June 8
June 10
June 10
June 14
June 17
June 20
June 24
June 24
June 26
June 27
June 27
June 28
June 28
June 29
July 1
July 3
July 3
July 5
July 8
July 8
July 11
July 15
July 17
July 22
July 24
July 26
July 29
Impounded
Mean
79.2
32.7
8.9
37.3
37.5
55.3
37.9
52.6
48.4
41.3
40.7
31.3
28.9
35.6
37.2
35.1
41.3
37.4
34.0
39.7
66.7
36.7
42.4
43.4
Recommended
Standard
Deviation
+3.7
+4.2
+2.9
+3.3
+4.1
+5.3
+2.0
+4.5
+2.8
+8.6
+1.1
+1.3
+2.5
+2.9
+1.9
+1.0
+4.0
+1.5
+2.6
+1.3
Impounded
Mean
57.4
53.8
16.4
28.9
40.5
53.7
50.7
54.3
49.7
44.7
41.7
35.5
35.2
38.4
41.1
34.9
41.5
39.2
37.6
38.5
37.8
43.3
42.8
42.8
Excessive
Standard
Deviation
+2.3
+3.4
+4.6
+1.2
+6.0
+1.7
+4.6
"~
+3.2
+6.4
+5.5
+3.7
+4.7
+7.4
+1.7
+6.6
+4'. 3
+ .8
+2.9
+2.1
+4.6
+4.8
+2.8
Continuous
Mean
49.9
55.5
5.9
28.1
47.3
48.3
34.5
44.6
40.5
37.2
35.2
33.2
35.1
35.2
39.7
35.3
47.2
38.5
35.8
39.6
35.7
38.9
40.4
35.0
Recommended
Standard
Deviation
+2.7
+8.9
+3.8
+1.5
+ .7
+2.3
+1.3
_
+2.0
+3.0
+ .6
+6.0
+ .6
+ .8
+2.8
+3.2
+5.2
+1.5
+2.7
+2.6
+1.3
Continuous
Mean
39.0
60.0
7.8
33.1
37.8
50.1
45.5
44.5
40.4
33.5
33.3
32.2
36.3
36.8
40.4
36.7
39.2
38.0
37.5
50.0
35.2
37.2
39.5
36.3
Excessive
Standard
Deviation
+ ,8
+1.4
+1.2
+9.2
+ .5
+ .8
i-2.6
+1.3
+ .5
+1.1
+ .3
+2.2
+ .9
+3.0
+ .9
+1.3
+0.0
+ .2
+ .3
+3.5
+2.0
Canal
Water
39.5
48.7
20.5
27.7
35.3
42.4
42.8
40.3
36.0
31.4
31.5
31.5
32.0
39.0
34.0
33.0
34.0
31.0
31.5
(Continued)
-------
TABLE H-29. (Continued)
Date
August
August
August
August
August
August
August
2
5
12
15
16
19
21
Impounded
Mean
35.6
31.7
36.8
36.3
Recommended
Standard
Deviation
+ .9
+2.5
+1.2
+8.6
Impounded
Mean
32.3
30.9
35.0
35.2
Excessive
Standard
Deviation
+1.4
+2.7
+2.6
+7.5
Continuous
Mean
31.3
33.4
25.2
Recommended
Standard
Deviation
+ .6
+ .5
+3.4
Continuous
Mean
28.1
30.1
34.2
35.5
Excessive
Standard
Deviation
+1.1
+2.9
+ .3
+8.7
Canal
Water
30.0
23.5
-------
TABLE H-30. ANALYSIS FOR CHLORIDE (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
Impounded
Mean
46.6
42.6
9.7
35.7
12.7
31.4
31.7
22.2
19.5
11.8
17.5
9.7
11.4
12.4
10.5
21.1
8.9
9.8
17.5
10. .8
32.7
33.8
33.5
Recommended
Standard
Deviation
+2.2
+1.8
+2.2
+3.6
+2.1
+2.5
+4.8
+1.7
+1.1
+9.0
+1.2
+ .6
+1.9
+1.7
+2.4
+4.6
+1.3
+3.7
+3.9
+8.1
+6.0
Impounded
Mean
62.1
53.9
20.0
36.8
13.9
32.1
30.4
28.2
37.3
12.2
16.7
20.5
8.4
10.8
13.5
9.9
22.3
9.5
9.6
16.3
11.7
33.0
30.8
32.4
Excessive
Standard
Deviation
+1.2
+7.3
+3.2
+ .8
+2.5
+8.5
+1.6
+1.2
+3.8
+1.8
+3.7
+1.0
+2.5
+2.8
+2.5
+3.9
+3.1
+5.3
+4.0
+7.3
Continuous
Mean
45.3
43.5
14.9
29.9
6.2
31.3
31.3
30.8
21.3
30.2
12.1
15.2
30.8
12.4
13.7
14.5
10.1
9.9
11.3
18.1
14.0
44.0
35.6
35.7
Recommended
Standard
Deviation
+4.6
+ .6
+7.2
+8.9
+3.3
+ .9
+2.6
+1.5
+3.2
+4.2
+1.9
+8.3
+3.2
+3.4
+ .6
+2.1
+2.0
+5.1
+1.2
+7.4
+9.0
+2.1
Continuous
Mean
56.1
51.1
12.7
45.9
32.?
28.2
24.3
16.4
36.9
14.2
15.5
13.8
10.0
10.4
14.2
17.6
28.8
9.0
13.6
17.1
17.4
38.3
36.8
Excessive
Standard
Deviation
+1.9
+1.9
+4.7
+1.0
+4.8
+4.7
+7.1
+4.1
+ .8
+6.9
+4.2
+3.2
+1.8
+3.3
+7.0
+4.1
+7.6
+2.9
+7.7
Can.il
Water
36.8
36.4
8.5
32.1
30.5
19.9
25.9
6.3
12.00
16.00
12.1
16.50
1H.20
8.3
21.0
21.8
30.5
37.2
32.6
-------
TABLE H-31. ANALYSIS FOR SODIUM (PPM) FOR 1973
oo
Date
May 1
May 3
Hay 7
May 12
May 18
May 28
June 5
June 6
June 8
June 12
June 15
June 15
June 26
June 27
June 28
June 30
July 4
July 12
July 27
August 13
August 20
Impounded
Mean
15.5
17.5
16.1
25.8
23.7
16.6
7.3
6.6
13.3
8.1
13.7
7.9
8.4
10.3
9.5
17.6
15.2
8.4
14.5
12.9
14.1
Recommended
Standard
Deviation
+2.7
+7.6
+3.9
+7.3
+5.9
+0.8
+2.2
+3.2
+1.6
+2.7
+3.1
+5.8
+3.8
+1.3
+3.1.
+1.6
+1.2
+1.4
+1.8
+2.4
Impounded
Mean
15.8
13.3
12.5
58.9
25.3
14.5
9.8
12.5
19.2
8.7
13.9
8.0
12.5
13.7
8.0
15.0
15.1
10.0
14.9
13.2
15.3
Excessive
Standard
Deviation
+1.6
+1.5
+2.9
+9.8
+2.6
+2.2
+4.0
+6.7
+3.3
+4.5
+4.5
+7.5
+3.1
+1.8
+5.1
+3.0
+2.6
+6.1
+2.6
+3.5
Continuous
Mean
14.1
17.2
14.9
42.8
21.7
20.7
8.5
6.9
16.2
11.2
15.3
11.9
5.0
6.2
5.2
12.5
14.0
9.5
12.6
9.2
12.3
Recommended
Standard
Deviation
+2.4
+3.0
+4.8
+0.9
+1.9
+0.7
+4.7
+3.1
+1.1
+0.4
+0.9
+1.6
+2.0
+3,6
+0.9
+0.9
+0.4
+0.5
Continuous
Mean
13.6
17.1
12.9
27.3
19.5
17.0
7.5
12.7
11.8
11.3
13.6
10.4
5.2
2.9
3.4
8.1
9.0
8.7
11.3
9.0
12.4
Excessive
Standard
Deviation
+0.9
+7.9
+2.7
+3.2
+7.8
+4.3
+5.1
+5.4
+3.9
+0.5
+1.8
+1.3
+0.3
+1.4
+2.8
+2.0
+1.9
+0.2
+0.9
+0.9
+0.3
Canal
Water
-------
TABLE H-32. ANALYSIS FOR SODIUM (PPM) FOR 1975
Date
April 30
May 1
May 12
May 21
May 28
June 5
June 6
June 7
June 9
June 9
June 10
June 12
June 13
June 16
June 19
June 19
June 20
June 20
June 22
June 23
June 26
June 30
July 7
July 10
July 14
July 21
July 25
August 4
Impounded
Mean
19.8
17.3
11.8
17.7
5.2
14.4
11.0
12.9
13.9
-
4.5
-
15.5
8.3
7.6
6.8
7.1
18.0
8.4
8.1
8.3
11.7
11.4
26.9
11.3
.-
16.8
9.2
Recommended
Standard
Deviation
+3.4
+2.0
+2.0
+1.0
+0.8
+1.3
+2.3
+1.3
+1.4
-
+0.3
-
+8.2
+0.9
+1.2
+0.5
+0.4
+5.5
+0.7
+1.5
+0.4
+2.8
+1.4
+4.1
+1.9
-
+0.9
+1.2
Impounded
Mean
22.4
19.6
10.3
20.6
5.0
13.7
11.3
12.5
13.7
20.2
4.4
3.9
20.7
7.0
6.0
8.2
7.8
17.7
11.0
10.3
8.9
9.2
12.1
26.0
12.3
-
18.9
10.0
Excessive
Standard
Deviation
+2.4
+1.9
+0.3
+3.4
+0.7
+0.8
+2.4
+0.5
+1.5
+6.1
+0.7
+1.8
+7.7
+2.1
+0.3
+1.4
+1.9
+6.2
+1.6
+2.2
+0.6
+8.0
+0.4
+4.2
+2.9
-
+1.0
+1.1
Continuous
Mean
21.0
17.3
10.1
18.6
2.8
12.9
10.1
10.3
11.5
17.8
4.3
5.8
19.3
8.6
6.6
6.5
7.1
-
9.5
7.9
7.9
14.0
11.1
22.9
11.9
-
16.6
10.5
Recommended
Standard
Deviation
+4.4
+2.6
+1.4
+2.1
+1.1
+0.2
+1.5
+0.6
+1.2
+7.3
+0.6
+0.2
—
+1.3
+1.0
+0.9
+2.0
_
+2.7
+3.3
+1.8
+5.4
+1.7
+2.9
+0.6
_
+2.3
'+0.4
Continuous
Mean
19.5
15.3
11.4
18.4
5.0
15.6
9.9
10.7
12.6
24.2
5.0
4.8
10.3
6.8
6.2
6.6
7.2
17.8
8.7
8.4
7.8
13.8
13.1
-
-
-
17.0
9.6
Excessive
Standard
Deviation
+1.6
+2.1
+0.5
+2.7
+2.2
+1.9
+0.5
+1.2
+2.0
+5.5
+0.8
+0.3
_
+0.6
+2.3
+0.7
+2.1
+5.3
+1.9
+0.8
+1.3
+2.1
+0.8
_
-
_
+1.0
+0.5
Canal
Water
9.0
21.0
-
9.5
10.2
12.8
9.1
8.3
11.9
-
4.4
9.3
-
4.3
5.8
7.0
6.4
_
7.5
8.2
11.0
_
-
_
10.3
.i
_
10.8
-------
TABLE H-33. ANALYSIS FOR HCO_ (PPM) FOR 1975
00
o
Date Impounded
Mean
April 30
May l
I ICJ J i
May 12
May 21
May 28
June 5
June 6 — -
June 7
June 9
June 10
June 12
June 16
June 19
June 19
June 20
June 22
June 23
June 26
July 7
July 14
July 21
August 4
August 15
Recommended Impounded
Standard Mean
Deviation
213.5
— — • n n
\i . U
0.0
101.7
87.4
435.1
144.4
4.1
20.3
26.4
38.6
59.0
132.2
150.5
59.0
28.5
136.2
185.0
427.0
555.1
374.1
Excessive Continuous Recommended Continuous Excessive
Standard Mean Standard Mean Standard
Deviation Deviation Deviation
• ri n __
+p.o
"___ _ — — _
+33.6
— - ___
+7.0
+21.4
+21.4
+9.3
+21.4
+33.6
+39.7
+49.3
+88.9
+89.9
+56.4
Canal
Water
239.6
207. 4
170.8
16-'. . 7
]4i-.. 4
13A.2
225.7
IK. 3
9.1 .5
85.4
1
-------
Appendix I. Analysis of variance for molinate,
carbofuran and carbaryl in rice paddy
water during 1973, 1974 and 1975 growing
seasons.
481
-------
TABLE 1-1. ANALYSIS OF VARIANCE FOR MOLINATE IN RICE PADDY WATER
SAMPLED IN 1973
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
6
1
1
6
6
1
6
54
83
MS
0.071
18.011
14.250
34.215
1.428
5.945
4.535
0.484
0.185
F
0.92
97.43**
77.09**
185.08**
7.72**
32.15**
24.53**
2.60*
* Significant at the 5% level.
** Significant at the 17. level.
482
-------
TABLE 1-2. ANALYSIS OF VARIANCE FOR MOLINATE IN RICE PADDY WATER
SAMPLED IN 1974
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
5
1
1
5
5
1
5
46
71
MS
0.878
36.796
0.003
74.004
0.488
10.634
4.050
0.307
0.776
F
1.31
47.42**
-
95.36**
0.63
13.70**
5.22*
0.39
* Significant at the 5% level.
** Significant at the 1% level.
483
-------
TABLE 1-3. ANALYSIS OF VARIANCE FOR MOLINATE IN RICE PADDY WATER
SAMPLED IN 1975
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f .
2
6
1
1
6
6
1
6
54
83
MS
1.014
24.644
.492
49.653
0.241
6.236
.002
.053
.306
F
*
3.31
A*
80.53
1.61
**
162.26
0.79
20.38 **
.01
.17
*Significant at the 5% level,
**Significant at the 1% level,
484
-------
TABLE 1-4. ANALYSIS OF VARIANCE FOR CARBOFURAN IN RICE PADDY
WATER SAMPLED IN 1973
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
6
1
1
6
6
1
6
54
83
MS
0.017
0.483
0.007
0.299
0.001
0.141
0.003
0.004
0.007
F
2.42
70.44**
1.05
43.54**
0.13
20.52**
0.48
0.60
* Significant at the 57, level,
** Significant at the 1% level,
485
-------
TABLE 1-5. ANALYSIS OF VARIANCE FOR CARBOFURAN IN RICE PADDY
WATER SAMPLED IN 1974
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
5
1
1
5
5
1
5
46
71
MS
0.420
1.999
0.000
3.572
0.178
1.329
0.115
0.060
0.131
F
3.19
15.19**
—
27.15**
1.35
10.11**
o.a?
0.46
* Significant at the 5% level.
** Significant at the 1% level.
486
-------
TABLE 1-6. ANALYSIS OF VARIANCE FOR CARBOFURAN IN RICE PADDY
WATER SAMPLED IN 1975
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
6
1
1
6
6
1
6
54
83
MS
.012
.9871
.0005
3.9911
.0204
.525
.0007
.0176
.057
F
.21
17.32**
.01
70.02**
.36
9.21**
.01
.31
* Significant at the 5% level.
** Significant at the 1% level.
487
-------
TABLE 1-7. ANALYSIS OF VARIANCE FOR CARBARYL IN RICE PADDY
WATER SAMPLED IN 1973
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
5
1
1
5
5
1
5
46
71
MS
0.016
0.492
0.058
0.229
0.016
0.080
0.017
0.005
0.010
F
1.62
49.19**
5.83*
22.91**
1.60
8.00**
1.68
0.51
* Significant at the 5% level,
** Significant at the 1% level.
488
-------
TABLE 1-8. ANALYSIS OF VARIANCE FOR CARBARYL IN RICE PADDY
WATER SAMPLED IN 1974
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R
T X I X R
Error
Total
d.f.
2
5
1
1
5
5
1
5
46
71
MS
0.064
0.521
0.759
2.573
0.131
0.225
0.719
0.097
0.104
F
0.61
5.03**
7 . 32**
24.80**
1.27
2.17
6.94*
0.93
* Significant at the 5% level,
** Significant at the 1% level.
489
-------
TABLE 1-9. ANALYSIS OF VARIANCE FOR CARBARYL IN RICE PADDY
WATER SAMPLED IN 1975
Source
Reps
Times (T)
Irrigation (I)
Rates (R)
T X I
T X R
I X R'
T X I X R
Error
Total
d.f.
2
4
1
1
4
4
,1
4
38
59
MS
1.584
5.309
.001
15.973
1.228
3.170
.055
1.837
.990
F
1.60
5.36**
—
16.13**
1.24
3.20*
.06
1.86
*Significant at the 5% level.
**Signifleant at the 1% level.
490
-------
APPENDIX J
ANALYTICAL SOLUTION TO THE ONE-DIMENSIONAL
LINEAR, CONVECTION-DIFFUSION EQUATION
To provide a basis for comparison of the approximate numerical solutions,
an analytical (exact) solution is presented in this appendix. The problem to
which the solution applies is defined by equations (4), (la), (7b) , and the
boundary condition at Z = °°:
lira
Z -*• » C(Z,t) = 0, t > 0 (J-l)
The boundary condition (J-l) differs from the one for a finite column, but
results obtained from use of (J-l) are identical to those obtained by use of
(7d) for times, t, such that the concentration at Z = L has not been per-
turbed from its initial value.
The solution to the problem thus defined has been presented by Shamir
and Harleman (1967) and Nielsen, et al. (1972). It can be expressed in the
form:
V" Z
For moderate values of the term -=r— , equation (J-2) can be evaluated on a
computer using machine subroutines to obtain values for the erf c (.Z.!.Y.'JL) and
v-7 VZ 4-D-t
exp(-~-) functions. For large values of -g-Cl60) , the exponential could not
be evaluated directly. It was therefore necessary in such cases to resort to
an asymptotic approximation to the term erfc(±J — 1£-) .
4-D-t
According to Carslaw and Jaeger (1959), the following asymptotic ex-
pansion can be used to evaluate erfc(x) for large x.
2
~X
, , , . e ,1 1 , f nn-l
erfc(x) + -^— • (- -- 3 + ••• M)
491
-------
The error |E| which results from terminating the series after n-1 terms is
bounded according to the inequality:
n ' 2n . X2n+l
The advantage of using the asymptotic expansion is derived from combining
the arguments of the exponential functions appearing in equations (J-2) and
V* Z Z + V*T
(J-3). When this is done the product p = exp(-~) • erfc ( ^D.T' ') can be
expressed:
f2..rl _ _L + ,, jisn-1. l'3...(2n-3)-i
x 2>x3 ' 2n-l . X2n-l
where
V-t-Z , v V-t + Z
w = / r, • " and X = . _, ^ .
4-D« t 4-D11
V* Z
The asymptotic expansion was used to evaluate p when —— _>_ 150. The
error term |E| was also evaluated to insure that the approximation was valid.
A F0RTRAN program was written in accordance with the procedure described
above. Solutions generated from the program were used to develop the solid
line curves in Figures 100 through 110.
492
-------
APPENDIX K
TRANSFORMATION OF THE CHEMICAL EQUILIBRIUM EQUATIONS
The back-substitution scheme used to transform equations (46) - (51) to
equations (52) - (67) is presented in this appendix. In addition, the con-
ditions under which A^ can be properly defined by the quadratic formula (52)
are investigated.
Before proceeding with the back-substitution scheme it is helpful to
first define the following terms:
T - , (54a)
v 4- fr 4- w • n • v° • \ \ • r
21 Y V
T , (54b)
.2
(540
V C
T
C5 '
YI + y • E15 • Cl2
Solving for C,, in equation (38) and substituting the result into
equation (45) yields:
Y1/Y3 = YE13 ' Cl /(C3T - Y3) •
whereupon solving for Y- results in the expression:
i _ Lt _ m X -t
Y, = «—r = T ' Tc3 • (65)
~\ *y Ct-. wj
J V4-V*Pir, ^
Yl + Y E13°l J
493
-------
Following a similar procedure with equations (39), (46), (40) and (47) yields:
Y ' C. Y
Y + — r - — ' TC4 (66>
and
Back-substituting equations (65), (66) and (67) into equations (45), (46)
and (47), respectively, produces C~, C, and C,-:
C3 ' <5> ' (YC1^ ' TC3 (56)
C4 • (> ' (> ' TC4 (57)
4
S = <> • ' TC5 ' (58)
Substituting equation (50) into equation (37) and solving the resulting equa
tion for CL, we get:
(C0
C2 =
Y '
Substituting tn® right-hand side of the above equation into equation (44)
and solving for Y,., produces:
Yl ' C2T Yl
Y = i £i = -i - T (64)
^ Ysf'F +F -n •v°«A1>«r 9
Yl CE12 + \2 D21 Y Al} Cl 2
Substituting equation (64) into—(44) and solving for C? yields:
C2 - ^ ' Cl • TC2 ' (55^
Inspection of equations (54a) through (58) and (64) through (67) reveals
494
-------
that Y2, C2, Y3, C3, Y^, C^, YS, and GS are defined as functions of Y , A-,
GI( and Y- It will now be shown that Y can be obtained as a function of A ,
C , and Y and that A.^ can be obtained as a function of C and Y> only.
Substituting equation (49) into equation (36) provides Y.. as a function
of A,, GI and Y=
Y1 = C1T - GI • (1 + Du - Y8 • Ax) . (53)
Substituting equations (49) and (50) into equation (41), we get:
A1T = Al d + Y8 ' Dn C1 + Y8 • D21 • C2) .
Finally, substituting equations (53) and (55) into the above expression
and using the definition of T „ from equation (54a), we get:
D • E1? • C
A^ = AI ' {1 + Y8C1 [Du + -21 12 ^ —]} ,
(K-l)
which defines A as implicit function of C- and Y«
Multiplying both sides of (K-l) by the denominator of the quotient term
results in a quadratic equation in A.. , Upon rearrangement, the quadratic may
be expressed as:
F = AAA • A + BBB ' A + CCC = 0 ,
where
AAA = Y8 • (1 + D1n ' C, • Y8) ' OX,-, - ~) ,
BBB =
and
C
1T
CCC = A • (-^- - .c - D .
IT E E C
This quadratic may be solved for A by the quadratic formula:
-BBB ± BBB2 - 4 ' AAA • CCC ,,-„.
Ai T ' (52)
495
-------
provided (a) an unambiguous choice of sign can be made, (b) the discriminant,
d = BBB2 - 4 : AAA : CCC, is non-negative, and (c) AM ± 0.
To facilitate the discussion of conditions (a), (b), and (c), the fol-
lowing additional notation is introduced:
k = (1 + Du ' CL ' Y8 ,
= JL • n - CIT^ _
*^o r> \^- ~ r /"•*•»
3 E12 °1
and
k4 - y8 ' °21 ' C2T '
Using this notation we have:
AAA — ™»tr * If /A
£\An. Ix- IS,.- / A- ,_ ,
BBB = -k • k» + k, + k_ ,
and
The inverse dissociation constants D and D , as well as the exchange
coefficient, EI?, are always positive numbers. The total concentrations C9T
and A are non-negative, and since it is required that Q < GI <_ CIT for
equation (61) to be solvable, ^ and C.,™ are positive. In practice, C- is
forced to be positive in the programmed version of the iterative solution
technique. Finally, examination of equation (61) reveals that exp(-1.17) <_
y <_ 1. With this information it is evident that the following inequalities
are always satisfied:
k3 - ~
3
496
-------
and
CCC <_ 0 .
The conditions (a), (b), and (c) must be investigated for the cases: (1) k
> 0, (2) k. < 0, and (3) k = 0. '
Since -kn • k_ > 0 and k. > 0, we have:
1 j 4
d >_ (-k • k + k)2 + 4
so that condition (b) is met. The term -4 ' • A • C = 4 • k • k • k < 0,
/~~ f\ -L ^ j
and therefore |BBBJ = BBB >_ /d. Since BBS is the sum of three non-negative
terms, it is non-negative, i.e. BBB >_ 0. In addition, AAA = k • k_/A is
negative so that
-BBB + /d
2 • AAA
is non-negative regardless of the choice of sign. However, it is desirable
that A -> 0 as A -> 0. Since the product 4 ' AAA • CCC + 0 as A -»• 0, /d~->
BBB as A-,™ -> 0. Therefore a (+) sign in front of the radical will result in a
zero-limit for AI? when AIT -> 0. The minus sign in front of the radical yields:
A -*- -BBB/AAA 4 0, as A -*• 0.
It can be concluded from the above that the (+) sign is the proper choice in
this case.
Case 2; k < 0
In this case, -4 • AAA • CCC = 4 • k • k • k > 0, so d > 0. Moreover,
AAA > 0 and |fiBB| < /d so that A will be non-negative if the (+) sign is used
and negative if the (-) sign is used. Again, the proper choice is the (+)
sign.
497
-------
Case 3: k = 0
Dll
This case can arise in two ways. Either A must be zero or (D9_ - r—)
IT IL b12
must be zero. The situation where A1 ->• 0 was discussed under Case 1. In
Dll
the event that the term (D0, - -—) = 0, AAA = 0, so any discussion of the
21 E12
quadratic formula would be superfluous. The defining equation (52) for A. is
linear in A for this case so the computational procedure requires special-
ized treatment.
The final step in the overall transformation scheme is to obtain (54) by
substituting (52), (53), (54), and (58) into (48). The equations (42), (43),
(49), (50), and (51) appear unmodified in the new system as equations (59),
(60), (62), (63), and (61), respectively. This completes the description of
the back-substitution process used to obtain Table 67.
498
-------
APPENDIX L
LISTING OF THE MODEL
499
-------
Ul
o
o
0001
0002
0003
OOO4
000 5
0006
0007
oooa
0009
ooto
0011
0012
0013
0014
0015
0016
0017
0018
0019
0020
0021
0022
OO23
O024
002S
0026
0027
0028
0029
OO3O
0031
0032
0033
0034
0035
0036
OO37
Cl .C2.C3.C4.C5.AI.A2.A3
101
13OO
13O1
DIMENSION VTMOLC(8)»OUNPAD<8>.aUANIRf 8>
DIMENSION ISOL<8>
COMMON K»I tClT.C2T.C3T.C4T.CSt* At T.A2T.A3T
COMMON CSTOS(8I ,OUTFUO<8> ,P ASTO< 8) .CADD< 8 >
COMMON ISTO.SOSTO(B>.DELPA(8>.CSTO<8)
COMMON X1K2S). X2K2S). DX1H22S). DX2K225I
COMMON AMPEV.QTOT.TIMAX. ICHG
COMMON DRAINl.SWATf 2SI.TAUO
COMMON RIONRT(8).WTMOL<8I*IPERC< 25) . IFERTC 8 ) . IRCONC<8)
COMMON DELT.DELZ.DIFCOF.DIFEXP
COMMON VALH8J.DIFUSI8). IDAY
COMMON NDON.NOON1 ,ML1 .MLND.MLNDO1
COMMON DIFX1.DIFX2
COMMON MLON.NOERl.NIONl.MLIN
COMMON ALP2.AL.P3.ALP4.ALP5.E12.E13.Et4.E15.Oll.D21
COMMON ITHET.NOER.NSULF.NDICAT.NMONCA.NMONAN.NION.M
COMMON CT<225).THETA1( 2SI.RHO8I 25 I.DCCC 1800 I
COMMON DGAMAt 2251 ,DGAMA8< 2251 .DELC<225I .CEC<2S»
COMMON IFLAGC 2S).GAMA( 25) ,C< 200 ).GAMA8< 25)
COMMON IGAM. ML2 . TEMX
COMMON V1K25)
COMMON H
REAOI5. 1011 M.NDICAT.NMONCA.NSULF.NMONAN.ITHET
REAO(5*10n IGAM. ML2. ICHG
FORMAT<10I3»
TEMX a 1.17202
WRITE(6.1300IM.NDICAT.NMONCA.NSULF.NMONAN. IT NET
**I2.«
ITMET «
I3)
NMONCA
«.I3>
FORMAT*X/10X.*M a «.I3.« NDICAT :
I «NSULF a «.I3.« NMONAN a «.I3,»
WRITE(6.130£»IGAM.ML2.ICHG
FORMATC/5X.»PRINT-OUT INTERVALS OF CONCENTRATIONS •
1*IGAM a *.I3.* ML2 = **I3.* ICHG «
NION a NDICAT4-NMONCA4- NMONAN4-NSULF
NDER * NION
IFtlTHET.NE.OJ NDER * NION+1
NDON1 * NION*NDER
NOON a NDON1-NDER
ML I = M-l
MLND a ML1«NDER
.I2.
-------
0038
0039
0040
00*1
0042
0043
0044
OO4S
0046
0047
0048
0049
0050
0051
0052
0053
0054
0055
0056
OOS7
OOS8
0059
0060
0061
0062
0063
0064
0065
0066
0067
0068
0069
0070
0071
0072
0073
0074
MLNOO1
MLON *
NOER1
Ml ONI
ML IN *
* *L1*NDONI
ML1*NDON
= NDER-1
= NION-1
MLt*NION
CVAL1U )* I = !.N10N>
(OIFUSTIMAX
1311 FORMAT
WRITE(6.1312>TPRIN
1312 FORMAT(/5X.« PRINT-OUT INTERVALS OF CONCENTRATIONS (DAYS).4X.TPRIN
1 = «.Et6.4)
READ(S,102> DELT.O1,DELZ,TPULSE
READ(5.102) E12.E13.E14.E15.CEC1
BEAO(S.103) tCEC
206 FORMATS///' VALENCE AND DIFFUSION COEFFICIENT OF EACH ION*/)
DO 240 1=1.NICN
VV = VALK I )
DO = OIFUSCI)
240 J*RITE(6.207I I.VV.OO
207 FORMATC/10X.' ION*.13.SX.F6.2.E12.4)
DIFX1.DIFX2
-------
O
K>
0075
O076
OO77
O078
OO79
0080
0081
OO82
0083
OO84
008S
0086
0087
ooae
0089
OO90
OO91
O092
OO93
0094
0095
OO96
OO97
OO98
0099
0100
OtOl
0102
O1O3
OI04
0105
0106
0107
0108
01O9
0110
0111
0112
2*5 FORMAT
DZ10OO = OEL.Z*THETA1<2)
TP * 0*0
GAMO =0.9
IF
-------
Ln
O
0113
0114
OtlS
0116
0117
0118
0119
0120
0121
0122
0123
0124
0125
0126
0127
0128
0129
013O
0131
0132
0133
0134
0135
0136
0137
0138
O139
0140
0141
0142
0143
0144
0145
0146
0147
0148
11
20
1331
1332
1333
1335
1336
1337
1338
1339
1340
JK1 -
JK =
JK3 =
IK1 -
= JK1+I
JK+1
: JK3+NDON1
•• IK1+NION
DO 2O 1=2,NION
C< I) * 0.0
READ!5.101) NDAYS.NOPT
WRITE!6.1331)NOAYS
FORMAT!//SX.«* DAYS OF SIMULATION«.Z8X»»NDAYS * «»I3I
WRIT El6•1332 >NOPT
FORMAT!SX,** OF OPTIONS*«36X.«NOPT * ••13)
READ(5.102) (RIONRT!!>.[«1.NION»
READ<5.102) !*TMOL.1*1.NION )
READI5.1O2) SUNTIM,OAYLNG
WRITE!6.1333)
FORMAT!//* FACTOR FOR ION •*E16.4)
WRITE(6.1340)OAVLNG
FORMAT
WRITE!6.252)
252 FORMAT!//25X,»MOLECULAR WEIGHTS OF IONS1//)
WRITE (6. 1350)
1350 FORMAT!IX.• CA MG NA K
U NH4 CL HC03 SO4 •/*
-------
Ul
o
-p-
0149
OtSO
0151
0152
O133
0154
0155
OI56
O1S7
O156
0159
0160
0161
0162
0163
0164
41*5
O166
0167
0168
0169
O17O
0171
0172
0173
0174
0175
0176
0177
0178
0179
0180
0181
0182
0183
0184
0185
WRITE(6.251 HWTMOLf I).1=1.NION)
WRITE(6.253) DAYLNG
253 FORMAT(//10X.*DAYLENGTH(HRS) = '.F4.1/I
FACSOL = l.OE-02 / (THETAK2) * DELZ )
SINTOT a 0.0
RPI = 3.141592
CONS = RPI/(120«*DAYLNG>
TAUO - RPI/(DAYLNG*60.OI
NOEL * DAYLNG*60.0/DELT
TJ a -DELT/2.0
00 30 J*l.NOEL
TJ - TJ+OELT
TAUJ = TAUO*TJ
30 SINTOT -= SINTOT* SIN* TAUJ)
AMP = 1./4SINTOT*OELT)
HSOIL = 0.5*THETA1<1>*OELZ
H = HSOIL
QTOT * O.O
00 10 1*1.NION
RIONRT(I) • RtONRTCI}/WTMOL(I>
|0 WTMOLC * WTMOLCI»*100.0
DO 1000 IDAY = 1.NOAYS
REAO(5,104» fIPERCCKI.K^l.Ml
REAOtS.lOSt IROEP. IPREC. HHJAIN. IEVAP. ITRANS. « fFERTd D.I 1 - 1.
INIONl.fIRCONC(Il).11 » l.NION)
REAO<5.105UISOL( I). 1*1. NION)
REAOCS.104} IRUNOF
104 FORMATf20I4l
105 FORMAT*3X.2113)
HRITE(6.201)
201 FORMAT*//////////25X.»NEW OAY«//I
WRITE(6.134S>
1345 FORMAT(//« FERTILIZER ADDED AT CRID PT. 1 IKGHA-1 DAV-1».J1=1.8>
HRITE(6*1351I
1351 FORMAT*//* AMT. OF FERTILIZER AT SECOND CELL GRID PT.2 IKGHA-1> (I
1 SOLI•»
WRITE (6.13521 (ISOL(I I. I * 1.81
1352 FORMAT (817)
-------
o
Ul
0186
0187
0188
0189
0190
0191
O192
0193
0194
0195
0196
0197
0198
O199
0200
0201
0202
0203
0204
O205
O206
0207
02O8
0209
0210
0211
0212
0213
0214
0215
0216
0217
0218
0219
RUNOF = IRUNOF * 0*1
DRAIN = IDRAINOO.l
ORAIN1 = DRAIN/ 1440.0
OTDRA = OELT*DRAIN1
PRECIP - IPREC*0*1
EVAP = IEVAP*0.1
TRANS = ITRANS*0.1
DEPIR = IRDEP*0.1
IF(NOPT.EQ.l) GO TO 2500
IF<(H-HSOIL).LT .4 .0 ) OEPtR «
2500 CONTINUE
WRITE16.256) IDAV
FORM AT CSX,* DAY = •• 13. SX . 'LEACHED
10.O-H+HSOIL
EVAPORATION
TRANSP
256 FORM AT CSX,* DAY = •• 13. SX . 'LEACHED RAINED
1IRATION IRRIGATION RUNOFFtALL IN CMt*/>
WRITE C6.2S7I DRAIN. PREC IP. EVAP. TRANS. DEPIR. RUMOF
257 FORMAT (22X ,F4. 2 ,4X ,FS .2 .9X.F4 .2 * I 1 X.F4 .2. 10X. F5.2. 8X .FS. Z/ / \
WRITE* 6. 254)
254 FORMATI//25X. 'PERCENTAGE OF TRANSPIRATION EXTRACTED FROM LAYERS'/I
WRITE<6.255) C IPERC4K) ,K=1 ,MC1 >
255 FORMAT«/10X.IO 151*
AMPTR = AMP*TRANS
AMPEV = AMP*EVAP
HO = H
H = HO * DEPIR + PRECIP - RUNOF
HI * HQ-HSOIL
H2 = H-HSOIL
WRITE(6.258> HI ,H2
258 FORMAT(/10X»*DEPTH OF PADDY WATER BEFORE AND AFTER TODAYS PRECIP A
I NO IRRIG* •F6.2.5X.F6.2.*CM*/X)
Kll = NION + 1
DO 2000 1=1 .NION
SOL 2 » ( FACSOL * ISOL(I)} / WTMOLf I >
CT(Kll) > CT(Kll) + SOL 2
Kll = Kll + 1
QUANIR(I) - 0. 1*DEPIR*IRCONC< I )
OUANAD = OUANIRf I)*IFERT< I )
-------
0220
0221
0222
0223
0224
0225
0226
0227
0226
0229
0230
0231
0232
0233
0234
0235
0236
O23T
0238
0239
024 O
0241
0242
0243
0244
0245
0246
0247
0248
0249
0250
0251
0252
0253
0254
0255
0256
0257
0258
DELC1 * ((HO-H)*CT/H
CTII I = CT
265 FORMAT(//IOX.'CONCENTRATION OF IONS IN TODAYS IRRI6.
NRITE(6.255KIRCONC.1=1.NION)
DO 3000 K=l,M
SWATtKl = 0.01*IPERC(K)*AMPTR
IF
-------
Ln
O
0259
0260
0261
0262
0263
0264
0265
0266
0267
0268
0269
0270
0271
0272
0273
0274
0275
0276
0277
0278
0279
0280
0281
0282
0283
0284
0285
0286
0287
0288
0289
0290
0291
0292
0293
0294
AT END PREVIOUS DAV
QUNPAD(I) = C(II*WTMOL(I>*1000.0
60 DELPAt I ) = VTMOL(I)*
T21 = 1000.*X21<1)*WTMCL<2)
QUNPAD(l) = QUNPADt D+Tll
OUNPAD<2) ~ QUNPAD(2)+T21
QUNPAD(NION) = QUNPADt NION)+T1H-T21
IK = NICN+t
DO 65 K-2.ML1
DELC
262 FORMAT(//5X.< NET GAIN.1=1.NION)
TP = TP*1.0
IF
-------
Ul
o
oo
0295
0296
0297
0298
0299
0300
0301
0302
0303
03O4
O305
0306
0307
0308
0309
0310
0311
0312
0313
0314
031S
0316
0317
0318
0319
0320
0321
0322
0323
0324
0325
0326
0327
0328
0329
0330
033 \
0332
0333
IM2 = IM1+NION1
WRITE<6.203MC< I ) , 1= I M 1 . I M2 )
2O01 IM1 = IMI+NICN
203 FO«MAT(/8<2X,E12.4.2X1»
WRITE<6.246>
246 FORMAT<1H1//40X,«ION TOTALS*//)
WRITE<6.202>
IM1 = 1
OO 2002 K=1.M
IM2 = IM1 +NICN1
WRITE<6,203) < CT
2002 IMl = IM1*NION
IK = *NION+1
DO 964 K=ML2.ML1
KK1 = ( K-I )*NION+1
KK2 = KK1
VIP - Y1KK)
IF(NDICAT.EQ.II GO TO 2003
KK2 = KK2*1
V2P = YIP* C*SQ«T(C
IF{NMQNCA.EQ.2> GO TO 2004
KK2 = KK2+1
Y5P = Y1P*C»KK2>/(E15*GAMRTC>
2004 CONTINUE
GAP = GAMA(K)
XIP = Xll«Kl
X2P = X21(K)
KK1 = KKl-fNION
CHG =0*0
963
OO 963 1=1.NION
CHG = CHG*VAL1(I)*C
-------
0334 IFL as IFLAG(K>
0335 964 CONTINUE
0336 lOOt CONTINUE
0337 QTOT =0.0
0338 1000 CONTINUE
0339 STOP
0340 END
Ui
o
-------
Ln
M
O
OO01
0002
0003
0004
0005
0006
0007
0008
0009
0010
00 I I
0012
0013
0014
0015
0016
ooi r
0018
0019
O020
0021
O022
0023
0024
0025
0026
0027
0026
0029
0030
0031
0032
0033
0034
0035
0036
0037
OO38
0039
SUBROUTINE SOIL
DIMENSION DTOEN1 < 9 ) .DTDEN2 ( 9 ) .DTNUMK 9) .OTNUM21 9)
DIMENSION VAL2(8).OSTR1<9).DSTR2(9)
DIMENSION DFL<9).CAVt9>.DXSI 1(9>.DKSI2(91
DIMENSION DXIIAl (9>*DX11A2(9 ) ,OX11Gt{9).DX11G2{9»
DIMENSION OX21A1(9),DX2lA2(9).DX21G1(9)*DX2IG2(9)
DIMENSION DOFLU 72),ODFL2( 72)
DIMENSION THETA2(25 I,DTMET(25 ),DEC(25 >,THEINV(25 I
DIMENSION COF3<25 I.COF4K25 >.COF42(25 )
DIMENSION FLC(200).G(225>,TCTHE(200 >
DIMENSION DTHDT<25 1.0(26 ). DZlI(9) ,DZ12(9>.ZZZ(9 )
DIMENSION DC<200>.COF4<200 ).COF1(200)
DI MENSICN DCC1 (1800» . DCC2(I800 I.DFLC1 ( 1800 ) .DFLC2<1800 )
DIMENSION DG1(1800)»OG2(18001,OG3(18001
DIMENSION SNKION(200)
COMMON K.I.C1T.C2T.C3T.C4T.C5T.A1T.A2T.A3T.C1
COMMON CSTOS<8).OUTFLO(8).PASTO(8),CAOD(8)
COMMON ISTO.SOSTO(8>.DELPA(8).CSTQ(8)
COMMON Xlt( 25).X21( 25).DX 11(225).DX21<225)
COMMCN AMPEV.OTOT.TIMAX.ICHG
COMMON ORAIN1.SWATI 25>.TAUO
COMMON RIONRT<8).WTMOL(8).IPERCf 25).IFERTf6).IRCONC(81
COMMON DELT.DELZ.OIFCOF.DIFEXP
COMMON VALI(8).DIFUS(8).IDAV
COMMON NOON.NDON1,ML1.MLND.MLNOOt
COMMON DIFX1.DIFX2
COMMON MLON.NDER1.NION1.MLIN
COMMON ALP2.ALP3.ALF4.ALP5.E12.E13.E14.E1S.D11.D21
COMMON ITHET.NDER.NSULF.NDICAT.NMONCA.NMONAN.NION.M
COMMON CTC225).THETA1( 25).RHOB( 25).OCC<1800)
COMMON DGAMA(225)»DGAMA8(22S).DELC(225>.CECC25)
COMMON IFLAG( 25).GAMA{ 25).C(200),GAMA8C25)
COMMCN IGAM. ML2, TEMX
COMMON V1 I< 25)
COMMON H
TIM s 0.0
DHDT = -ORA INI
OT? a OELT/2.0
DZINV = 1,/DELZ
C2.C3.C4.CS.Al.A2.A3
-------
0040
0041
O042
0043
0044
0045
0046
0047
0048
0049
0050
OOS1
0052
0053
0054
0055
0056
0057
0058
0059
0060
0061
OO62
0063
0064
0065
0066
0067
0068
0069
0070
0071
0072
0073
0074
C
c
GAM1 = 1.0
GAMS =1.0
DGAMll =0.0
OGAM12 - 0.0
OGAM81 =0.0
DGAM82 =0.0
XSI ~ 0.0
XSI1 = 0.0
TXSI1 =0.0
DZINV2 = OZINV*O2INV
***************************************
***************************************
DO 2 t=l.NION
VAL2CI) a VAL1 ( I )+VALl (I )
C
C
2020 CONTINUE
0(M) = DRAIN!
TAU = TAUOMTIM+DT2)
FAC1 * SIN
DHOTO = DHDT
DHDT - <-AMPEV*FACl-O
-------
Ul
0075
0076
0077
0076
0079
0080
ooat
0082
0083
0084
0085
0086
0087
0088
0089
0090
0091
0092
0093
0094
0095
0096
0097
0098
0099
0100
0101
0102
0103
0104
0105
0106
0107
0108
0109
0110
0111
0112
0113
DTHETC1) = +THETA2OZINV
TZ1 = 0.66*THETA
TZ5 = 1./THETA
TZ2 = OIFCOF*THETA*(TZ4*TZ5)**DIFEXP
TZ3 = DZINV2
OEI_C(KND> = THETA2 = 0.0
OC(IKl) = DIFUSd )*TZ1+TZ2
COFKIK1) - VALK I )*DC( IK1J
COF4(IKl) = -OC(IK1»*TZ3
4 IKl = IKH-1
DIXIt = OIFX1*TZI*TZ2
01X21 = DIFX2*TZH-TZ2
COF4KK) = -OIX11*TZ3
45 COF42(K) = *OIX2l*TZ3
II = NICN
OO 46 1=1.NION
II = 11+1
46 CQF41II) = 2.0*COF4(I1)
COF41C2) - 2.0*COF4l<2>
COF4212) = 2.0*CQF42(2)
-------
Ul
0114
0115
0116
OUT
0118
0119
O120
0121
0122
0123
0124
0125
0126
0127
0128
0129
0130
0131
0132
0133
0134
O13S
0136
0137
0138
0139
014O
0141
0142
0143
0144
0145
0146
0147
O148
0149
01SO
0151
0152
2000 CONTINUE
THETS - THETAK 1 )
THETAK1) = THETS1
CALL EOUIL
THETAK1) = THETS
Jl = I
00 6 K=1.ML1
DO 61 1=1 *NICN
OO 61 J=l ,NDER
OCCKJ1) » 0.5*DCC(J1)
OCC2(J1) = VAL2CI I*OCC1( Jl)
61 Jl = Jl+1
6 CONTINUE
IF(NSULF.EQ.O» GO TO 51
KI = 1
K2 = 2
K3 = NION
Jl = 1
J2 = 1
JKl = 1
JK2 = NDER+1
JK6 - NDCN+I
DO 57 K=l .ML1
IF I = IFLAG(K)
IF(IFt.EQ.O) GO TO 55
ZZ = GAMA8(K)*C
-------
0153
OI54
0155
0156
0157
O1S8
0159
0160
0161
0162
0163
0164
0165
0166
0167
0168
0169
0170
0171
0172
0173
O174
0175
0176
0177
0178
0179
0180
0181
0182
0183
0184
0185
0186
c
c
c
c
c
DO 56 J-ltNOER
DX2UJ2) = 021*
-------
Ul
0187
01S8
0189
0190
0191
0192
0193
0194
0195
0196
0197
0198
0199
0200
0201
0202
0203
0204
0205
0206
0207
0208
0209
0210
0211
0212
0213
0214
0215
0216
0217
0218
0219
0220
0221
Jl = J-NION
6006 C« J> = C( Jl >
BOUNDARY CONDITIONS END
***************************************
IM1 = 1
2050 CONTINUE
DO 501 K=2,M
KMINl = K-l
It = IFLAG(K)
IF(I1.EQ.O> GO TO 501
IFCK.NE.2) GC TO 62
Ul = 1
DO 63 1=1 .NICN
DO 63 J=l.NDER
IJ2 = U1+NDON1
DCC1 f Ul ) = DCCdJl I
DCCK IJ2) = 0.0
DCC2(IJli = VAL2( I )*DCC1 ( Ul )
OCC2UJ2) =0.0
63 Ul = Ul+1
62 CONTINUE
DO 50 J= l.NDER
DSTRKJ) = 0.0
DSTR2
-------
0222
0223
0224
022S
0226
0227
0228
0229
0230
0231
0232
0233
0234
0235
0236
0237
0236
0239
02*0
0241
0242
0243
0244
0245
0246
0247
0248
0249
02SO
O251
0252
0253
02S4
0255
0256
0257
02S8
0259
0260
CAV(I) = 0.5*J
IFCK.EQ.2) CAV( I I = C(1K2>
TO = VAL2< l»*CAV< I >
STR = STR+TD
DFU< M = COF4-C
IJ = (1-1I*NDER+I
IJ1 = IJJ+IJ
00 100 J=1.NOER
U2 = IJ1-NOON1
DSTRKJ) = CSTRK J >*OCC2( I Jl >
DSTR2O) = OSTR2( J ) *-DCC2 ( IJ2 )
DTOENl(J) = OTDENIC J)*DC( IK1)*DCC2< Ul )
= OTDEN2C J )*OC( IKI >*OCC2< U2J
= COF4(IKI)*DCC
OTOEN2( J)
DDFL HUt
OOFL2( IJ)
OTNUMJ(J)
DTNUM2(J»
IJI * IJi+I
10O IJ = IJ+1
IKI = IKl*t
110 CONTINUE
IF(ICHG.EQ.l) GO TO 196
XSI1 = l./TDEN
TXSI I = -XSI14XSI1
XSI s TNUM*XSI1
196 CONTINUE
OO 200 J= UNDER
OXSIlt = TXSt1*DTOEN1(J)
DXSI12 = TXSII*OTDEN2(Jl
OXSIHJ) - TNUM*DXSU 1 *XSI l*OTNUMl( J)
OXSI2(J) = TKUM*DXSI12*XSIl*DTNUM2
-------
Ul
0
XltA = Otl«ZI*CAV(lt
XllG - COF4KK) •( Xt 1(K)*K1 I (KMIN1 I
OO 22O J=1.NOCR
JMJ z JNJ-NOCNI
JJI = JU-NOONl
JK2 "= JK!»ND£H
IFflGAM.EO.I > GO TO 223
OUl = TO»OSTRI(J)
OU2 - TU«OSTR2(JI
DUII s TU2«OU1
OUI2 - TU2«OU2
DGAM11 ~ GAM«DUtt
OGAM 12 = GAM1*DUI2
GAM7e*OGAM|t
GAM78«OGAM12
OGAM8I
OGAM82
CONTINUF
DZU(J) =
DZ12(J> -
OXtlAI(J) =
OXIIA2(J> a
OXltGlfJ) =
OXIlGZiJ) =
JNJ = JNJ»!
Jl J = JlJ*t
.JKt - J»Ct+l
GAM8*OCC1(JNJ)«CAV(NION)*OGAM8I
GAM8*OCCI(J*J|*CAV< NIONI•OGAM82
= Ott*(OZII
-------
Ul
M
OO
OJOO
0301
0302
030J
0304
0 30 r.-
0306
0307
0303
0309
0310
Oil 1
031?
031 3
0314
03lb
0316
031?
0318
0319
0320
0321
0322
0323
032*
0325
0326
0327
0328
0329
0330
0331
0 33?
0333
0334
0335
0336
033?
0338
0339
U- < NL-I'-A' .f-'Q.O) C.O "1 210
X?1A - O? 1 *Zl *CAV<2 >
JK 1 •= JK.I I
OO 221 JM ,NOER
JK? - JK.1-NUFR
OX21AKJI = 021 * (OZl 1 ( J)*CAV(2 ) + Zt *OCC1 ( J2J» I
OX21A2U) = 021 *+Zl*DCC H JJ2) )
OXSIGKJ) - COF42
JK I JK1 M
2?1 J2J = J?l»l
?lf) CONT INUE
I Kl = I K3+1
OO 300 1 = 1 tIMION
TXtl = COF3 *XS I
FUCtlKl) = DFL( D-fTXIl *CAV( I)
IJ = ( I-l )*ND£R'H
Ul = I JJ*I J
OO 310 J=1,NOER
IJ? = IJl-NOONl
OTXIll = COFl I I Kl)*DXSIl( J»
OTXI12 = COFK I Kt )*OXSI2( J)
DFLCHIJ1I = OOFLI ( IJ >+TXl l*OCCH Ul »+CftV« I >*OTXI 11
OFUC2(IJ1I = OOFL2< U)+TXI 1OOCC1 ( I J2 >+CAV( I)*DTXI12
IJ = lJt-1
110 Ut = I Jl +1
IK 1 = IK1*1
300 CONT INUF
(F(K.NE.2» GO TO 65
I Jl = I
DO 66 1=1 .NION
DO 66 J=l tNOER
IJ2 = 1JI«-NDCN1
DCCKIJ1) = 0-.9*DCCl IJ I »
OCCKIJZ) = 0.5*OCC
-------
Ul
0340
O3«l
0342
0343
0344
0345
0346
0347
0346
0349
0350
0351
0352
0353
0354
0355
0356
035T
0356
0359
036O
0361
0362
O363
0364
0365
0366
0367
0368
O369
0370
0371
0372
0373
0374
0375
O376
0377
0378
65 CONTINUE
IF(NSULF.EQ.O) GO TO 501
TZt = X1IG+COF3*COF3( K>*OX11A1 < J)
OTZ12 = OX11G2CJ)*COF3(K»*OX1IA2(J)
DFLCUJ1KJ = OFLCt ( JIKI-fOTZl I
DFLC2(J»K> = OFLC2I JIKI4-DTZ12
OFLCKJNK) = D«-LCI ( JNK)«-OT21l
OFLC2CJNK) = DFLC2C JNK)«-OTZ12
J1K = JlK-fl
500 JNK = JNK+l
IF(NDICAT.EQ.t) GO TO 501
JNK = JNKK
K2K = IK3+2
TZ2 = X21G+COF3CK)«X21A
FLC(K2K) = FLC(K2K)+TZ2
FLC( KNK ) = FLC+COF3*DX2lA2(J)
OFLCKJ2K) = OFLCl ( J2K)*OTZ21
DFLC2O2K) = OFLC2< J2KI4-OTZ22
OFLCKJNK) * DFLC 1 ( JNK >*OTZ21
OFCC2
-------
Oi
K>
O
0379
0380
0381
0382
0383
0384
03B5
0386
0387
0388
0389
0390
0391
0392
0393
0394
0395
0396
0397
0398
0399
0400
0401
0402
0403
0404
0405
0406
0407
0408
0409
0410
0411
0412
0413
0414
0415
0416
041 7
041 8
uu 65o I - i . ivi UN
TCTHE(tK) - CT< IK)*DTHDT*NDER+t
II = U+l-1
00 51 1 J=l ,NDER
IJ1 = IJ4-NDCN1
DGl(IJ) = COFH1*DFLC2< Ul >
DG2< I JJ = 0.0
DG3(U) = COFHI *DFLC1< U 1 )
511 I J = IJ+1
510 OGKtl) = DGK I I >*COFH2
00 670 K=2.VL1
KMINI = K-l
KP1 = K+l
II = IFLAG(K)
13 - IFLAG< KP1 )
IF(I 1 .EO.O .AND. I2.EQ.O ) GO TO 670
IKK = ( K-l )*NION
IK2 = (K-t )*NDER+1
I JK1 = IKK*KOER*l
IK1 = IKK+1
IK3 = IK1+NION
OO 600 1 = 1 .MCN
G = THEINV(K>*(FLCI IKl )-FLC< IK3)-SNKION(
I JK3 = IJK14-NDON1
I IK = IJKH-I-1
DO 660 J- 1 .NOER
DGKUK1) = THE I NV(K) *(DFLC1 < I JK1 >-DFLC2( IJK3 3 >
DG2(IJKl) = THE INV« K)*DFLC2( IJK1 >
Df,3(IJKl) = -THFINV -TCTHE{ IKl
-------
0419
0420
0421
0422
0423
0424
0425
0426
0427
0428
0429
0430
0431
0432
0433
0434
0435
0436
0437
0438
0439
0440
0441
0442
0443
0444
0445
0446
0447
0448
0449
0450
0451
0452
0453
0454
0455
0456
0457
llK) = DG1 < t tK >-DTHOT ( K >
IK1 = IK 1*1
IK2 = IK2 + 1
IK3 = IK3+1
600 CONTINUE
670 CONTINUE
JMI = MLND+I
JM2 = JM!+NDER1
DO 680 J=JVl.JM2
Jl = J-NDER
680 G( J) = G(Jl )
II = JMl
12 = ML IN
DO 897 [ = 1 .NION
OUTFLO( I» = OUTFLO< M+G< I 1)
II = 11*1
12 = 12*1
S97 CSTO(I) = C5TO( I )+C( 12>
IF
X2TT = X2 1 (MLI )
CSTO( t> = CSTCH1J+XITT
CSTO<2) = CSTO< 2X-X2TT
CSTO(NION» = CSTO(NION)*X1TT+X2TT
896 CONTINUE
CH = 1.OE-8
JKll = NDER^l
UK = NDONH-1
IK = NION*1
DO 800 K=2,MLl
IK 1 « {K-l »*NDERvl
DO 801 I=1iNION
TT = 0.0
JKl = JK1 1
JK2 = JKl-NDER
JK3 = JKH-NDER
DO 802 J=1,NOER
TT1 = DGl
-------
Ln
M
NJ
0458
0459
0460
0461
0462
0463
0464
0466
0467
0468
0469
0470
0471
0472
0473
0474
0475
0476
0477
0478
0479
0480
0481
0482
0483
0484
0485
0436
0487
0488
0489
0«90
0491
0492
049-3
TT3 =
TT -
! JK =
JK1 =
DG3 ( I J*.
TTl •(•TT2
1 JK+ 1
JK1+1
JK
TT3
JK2 = JK2+1
802 JK3 = JK3+1
OELC(IK) = OELT*(G< tKl )+DT2*TT )
CT(tK) = CT( IK) *DELC( IK»
f Kl = I Kl *1
801 IK = IK+1
JK1 1 = JK 1 1 +NDFR
800 CONTINUE
IJ = 1
Jl = 1
DO 803 I - l.NICN
TT = 0.0
DO 804 J=l .NDER
J3 = Jl *-NOER
TT1 = DG1 ( IJ)*G( Jl )
TT3 = OG3( I J>*G( J3>
TT = TT+TTH-TT3
I J = I J + l
804 Jl = Jl+l
Jl = 1
OELC( I J = OELT*(G(I )+OT2*TT )
803 CT( I ) = CT( I )+DEl_C( I )
I Ml = MLIN+1
IM? = IM1+NION1
DO 701 1= IM1, IM2
II = I-MON
701 CT( I » = CT( II )
H = H*DT2*OHDT
TIM = TIM«-DELT
IF(T IM.GE .T IMAX-1 .E-61 RETURN
GO Tt 2020
END
-------
Ul
N3
0001
0002
0003
0004
0005
0006
0007
0008
0009
0010
0011
0012
0013
0014
0015
0016
0017
0018
0019
0020
0021
0022
0023
0024
0025
0026
0027
0028
0029
0030
0031
0032
0033
0034
0035
0036
0037
0038
0039
5002
SUBROUTINE ECUIL
DIMENSION DCCSC72)
COMMON K.I,C1T.C2T,C3T.C4T.C5T,A1T,A2T,A3T,CI.C2.C3.C*.C5.A1.A2.A3
COMMON CSTOS(8).OUTFLOJ8).PASTO<8>,CADD<8>
COMMON ISTO.SOSTO<6)«OELPA<8).CSTO(8)
COMMON Xll( 25) .X21 I 25).OX 11(225).OX21C225)
COMMON AMPEV.QTOT.TIMAX.ICHG
COMMON DRAIN!.SWAT{ 25>.TAUO
COMMON RIONRT«8»«WTMOL<8).IPERC< 25 I * I PERT(8>. tRCONCl8)
COMMON DELT.DELZ.DIFCOF.DIFEXP
COMMCK VALl(6>.DIFUS<8»,ICAY
COMMON NOONiNDONl.MLl*MLND.MLNOO1
COMMON OIf-XI.OIFX2
COMMON MLON.NDER1 .NIOM1 .MCIN
COMMON ALP2.ALP3.ALP4.At.P5.£12.E13,E14.E15.0t 1,021
COMMON ITHET.NDER.NSULF.NOICAT.NMONCA.NMONAN.NION.M
COMMON CT<225),THETZ< 25).RMOZ< 25».OCC(1800)
COMMON OGC225».DG8(225».OELC(225).CEC1«25 )
COMMON IFLAC< 25).GAMA( 25).C<200).GAMASf25)
COMMON IGAM. ML2. TEMX
COMMON Yt t (25)
COMMON H
GAMLIN = EXP(-TEMX»
ML I = l«"«-l
DO SOOt K=ML3,ML1
It = IFLAG(K)
tF(tl.EQ.O) GO TO 5001
KOER = JK-1)*NDER
JK = KDER+1
KON =
-------
0040
0041
0042
0043
0044
0045
0046
0047
0048
0049
0050
0051
0052
0053
0054
0055
0056
0057
0058
0059
0060
0061
0062
0063
0064
0065
0066
0067
0068
0069
0070
0071
0072
0073
0074
007b
0076
0077
0078
IF(C10 .LT.0.0) CIO = 0.5 * C(KK>
CEC = CEC1(K)
THETA - THETZ
-------
0233 BETSG = £15
0234 F32G - A1*SET2G
0235 F33G = C1*F32G
O236 F33GC1 = F33G*F 33A1 *A1G
0237 F37GCI = Y1GCI+F33GC1
0238 F34GC1 * BET3G*CIRT
0239 F3SGC1 - BET4G*C1*»T
0240 F36GC1 = BET5G»C1PT
0241 F38GC1 = VIGC1+F34GC1
0242 F39GC1 = YIGC1+F3SGC1
0243 F301GC = VIGC1+F36GC1
0244 TC2GCI = OTC2*F37GC1
0245 TC3GC1 = DTC3*F38GCt
0246 TC4GC1 = OTC4*F39GC1
0247 TC5GC1 = DTC5*F301GC
0248 F3GC1 = VI»(TC2GC1+TC3GC1+TC4GC1+TCSGCI»+F310*YlGC1
O249 OF3C1I « 1./DF3C1
0250 OC1G = -F3GCl*OF3CtI
0251 OA1G = AIG*DA1C1*DC1G
0252 OY1G = Y1GC1 + OYlCt*OCtG
O253 OTC2G = TC2GC1+DTC2C1*DC1G
0254 DTC3G = TC3GC1*OTC3Cl*OClG
0255 OTC4G = TC4GCI*OTC»Cl*DClG
0256 OTCSG = TCSGC1+DTC5CI*OC1G
02S7 GAC1 = GAM1*C1RT
0258 GAMRTC = GAM1*C1RT1
0259 OGAC1G = Cl RT-fGAMRTC*DClG
0260 FC22 = FC2l*Cl
0261 FC32 = FC31*GAC1
0262 FC42 - FC41*GAC1
0263 FC52 = FC5l»GACl
0264 C2 = FC22*TC2
0265 C3 = FC32*TC3
O266 C4 = FC42*TC4
O267 C5 = FCS2*TC5
0268 OFC22G = FC2I*DC1G
0269 OFC32G = FC3t*OGAClG
0270 OFC42G = FC41*DGAC1G
0271 OFC52G = FCS1*DGAC1G
-------
0272
0273
027*
0275
0276
0277
0278
0279
0280
0281
0282
02 83
0284
0285
0286
0287
0288
0289
0290
0291
0292
0293
0294
0295
0296
0297
0298
0299
03OO
0301
0302
03O3
0304
0305
0306
C
c
C
c
DC2G = TC2*DFC22G+KC22*OTC2G
OC3G = TC3*OFC32G+FC32*OTC3G
DC4G s TC4*CFC42G+FC42*DTC4G
OC5G * TC5*OFCS2G+FC52*OTCSG
Ul = 2.*(Cl * C2 * All
U2 = .S*(C3 + C4 * C5 » A2T * A3T>
U3 * Ul «• U2
OU1G - 2.*(DC1G * DC2G «• DAIG)
DU2G = .5 * (OC3G «• OC4G * DC5G )
OU3G = OU1G «• DU2G
U = SORT(U3)
UPS = 0.5/U t
DUG = UP5*DU3G
US = I. /(I. 4- U)
U5U5 * -US*U5
OU5G = U5US*OUG
U6 * TEMX * US
OUG6 = TEMX * OUG5
U4 a U • U6
OU4G = U*DU6G * U6*OUG
EKPU - EKP(«U4>
OEXPUG = -expu*ou4G
F4 = GAM1 - EXPU
OF4G - - DEXPUG «• 1.0
IFtlGAM.EO.I ) GO TO 550
T2 - ASStGAMll * ABS
IF(ABS(F4/T2).LT.l.E«5> GO TO 550
DC AMI ~ -F4/DF4G
GAMOLO = GAM1
GAM1 = GAM1 * OGAM1
IF(GAMI.LT.GAMLIM) GAM1 = .5*
IF(GAMl .GT.i .0 ) GAM1 = .5*
-------
Ul
OJ
0107
0308
0309
0310
0311
0312
031 3
0314
0315
0316
0317
0318
0319
0320
0321
0322
0323
0324
032S
0326
0327
0328
0329
0330
0331
0332
0333
0334
0335
0336
033 T
0338
03J9
0340
0341
[F(C1 .LT.0.0 »
rF
Cl -= .5*
C
C
C
C
500 CONT INU6
WRITE(6,
551 FORMAT( /
STOP
550 CONTINUE
************
551 >
/25X,1 FLAGG«//»
****************************
* CALCULATION OF DERIVATIVE OF Fl WITH
* CONSTANT
************
QF4GI =
F17C1T =
F18CIT =
F1041T =
BBBC1T =
CCCC 1 T =
F1C1T =
AC1TCG =
YIC1 T =
YCITCG =
TC2A1 =
TC2Y1 =
TC3Y1 =
TC4Y1 =
TC5Y 1 =
T2C1CG =
T3CICG =
T4C1CG =
****************************
1 ./DF4G
F16
F17C1T
F14*F1BC1 T
F1041T
- AJT*F18CIT
A1*BBBCIT * CCCC IT
-FtClT*FtAM
1 .
Y1CIT * VIA1*AC1TCG
DTC2*F33A1
DTC2
OTC3
DTC4
OTC5
TC2A1*AC1TCG * TC2Y1*YC1TCG
TC3Y1*YC 1TCG
TC4Y1*YC1TCG
T5CICG = TC5Y1*YC1TCG
F3101T -
F311 1 T =
F3CIT =
T2C1CG * T3C1CG * T4C1CG +
Y1*F3101T + F310*YC1TCG
F3111T
C1C1TG = -F3CIT*OF3C1 I
A1C1TG = AC1TCG + A1C1*CIC1TG
VIC1TG = YC1TCG * OY1C1*C1C|TG
T2CITG = T2C1CG+OTC2C I*C1C1TG
TTCtTG = T3C1CG+DTC3CI *C1 C1TG
T4CI TG =
T4CICG*OTC4CI *C 1 C 1 TG
RESPECT TO
; C». GAM1
T5C1CG
-------
0342
0343
0344
034S
0346
0347
0348
0349
0350
0351
0352
0353
0354
0355
0356
0357
0358
0359
0360
0361
0362
0363
0364
0365
0366
0367
0368
0369
0370
0371
0372
0373
0374
0375
0376
0377
0378
0379
0380
T5C1TG = T5CICG+DTCSC1*CIC1TG
C2C1 = TC2*FC2l
C3C1 = TC3*FC31*GAMRTC
C4CI = TC4*FC41*GAMRTC
C5C1 = TC5*FC5l*GAMRTC
C2TC2 = FC22
C3TC3 •* FC32
C4TC4 = FC42
CSTC5 = FC52
C2CITG = C2C1*CIC1TG + C2TC2*T2C1TG
C3CITG = C3C1*C1C1TG + C3TC3*T3C1TG
C4C1TG = C4CI*C1C1TG * C4TC**T*CITG
C5C1TG = C5C1*C1C1TG * C5TCS*TSC1TG
U1C1TG = 2.0 * (C1CITG 4- C2C1TG «• AtClTG)
U2CITG = 0.5* (C3CITG «• C4C1TG «• C5C1TG)
U3C1TG = U1C1TG *• U2C1TG
UC1TG = UP5*U3C|TG
USC1TG = U5U5*UC1TG
U6C1TG = TEMX * U5C1TG
U4C1TG = U*U6C1TG * UCITG * U6
EXIUDG = -EXPU*U4C1TG
F4C1TG = -EXIUDG
GAMC1T = -F4C1TG*DF4GI
IF( IGAM.EQ. 1) GAMC1T = 0.0
DC1C1T = C1CITG + DC1G*GAMC1T
= A1C1TG + DAIG*GAMCIT
= Y1C1TG + DYlG*GAMCtT
= C2C1TG * DC2G*GAMC1T
- C3C1TG + OC3G*GAMCIT
DC4G*GAMCIT
OC5G*GAMC1T
OA1CIT
OV1C1T
OC2C1T
OC3C1T
OC4C1T
OC5C1T
DA2C1T
DA3C1T
IKK
= C4C1TG
= C5C1TG
= 0.0
= 0.0
KCN-H
JKK = KDER«-1
DCCS< 1 ) = DC1C1T
OCCS(2) = OC2C1T
DCCS< 3) = DC3CI T
OCC5(4) = DC4C1T
-------
UJ
0381
0382
0383
0364
0385
0386
0387
0388
0389
0390
0391
0392
0393
0394
0395
0396
0397
0398
0399
0400
0401
0402
0403
0404
0405
O406
0407
0408
0409
0410
0411
0412
0413
0414
0415
0416
0417
0418
0419
OCCS -
OCCS<7) =
OCCS(8) =
OGtJKKl :
DG8(JKK>
C( IKK > =
OC5CIT
DA2C1T
OA3CIT
OA1C1T
GAMC1T
= GAM78*GAMC1T
Cl
JKK = JKK+1
KK1 = JKK
IKK = IKK+1
Kl = 9
K2 = 10
K3 = 11
K4 = 12
K5 = 13
K6 = 14
K7 = 15
K8 = 16
IF(NDICAT.EO.l> GO TO 7001
FI 9C2T = O21
FI022T = F19C2T
F1032T = GAM6*F1022T
F19C2T = 021
F1022T = F19C2T
BBBC2T = F1032T
F1C2T = Al*BSaC2T
AC2TCG = -FIC2T*FIA1I
YC2TCG = Y1AKAC2TCG
TC2C2T * ALP2*F37I
T2C2CG = TC2A1*AC2TCG
T3C2CG = TC3Y1*VC2TCG
T4C2CG = TC4Yl*YC2rCG
T5C2CG = TC5Y1*YC2TCG
F3102T = T2C2CG * T3C2CG * T4C2CG * T5C2CG
F3112T = Y1*F3102T * F310*YC2TCG
F3C2T = F3112T
C1C2TG = -F3C2T*DF3C1I
A1C2TG = AC2TCG * A1C1*C1C2TG
Y1C2TG = VC2TCG +DY1C 1*C1C2TG
TC2Y1*YC2TCG
TC2C2T
-------
On
OJ
-P-
0420
0421
0422
0423
0424
0425
0426
0427
0428
0429
0430
0431
043?
O433
O434
0435
O436
0437
0430
0439
0440
O441
0442
0443
0444
0445
0446
0447
0448
0449
0450
0451
0452
0453
0454
0455
0456
0457
0458
T2C2TG = T2C2CG*OTC2C1*C1C2TG
T3C2TG = T3C2CG + DTC3C1*CIC2TG
T4C2TG = T4C2CG+DTC4C1*C1C2TG
TSC2TG = T5C2CG«-DTC5Cl*CIC2TG
C2C2TG = C2C1*C1C2TG + C2TC2*T2C2TG
C3C2TG « C3C1*CIC2TG «• C3TC3*T3C2TG
C4C2TG « C4CI*CIC2TG «• C4TC4*T4C2TG
C5C2TG = C5CI*CIC2TG * C5TC5*T5C2TG
U1C2TG = 2.C*(C1C2TG «• C2C2TG * A1C2TG)
U2C2TG = .5* = C2
-------
Ln
0459
0460
0461
0462
0463
0464
0465
0466
0467
0468
0469
0470
0471
0472
0473
0474
0475
0476
0477
0478
0479
0480
0481
0482
0483
0484
0485
0486
0487
0488
0489
0490
0491
0492
0493
0494
0495
0496
0497
Kt
K2
K3
K4
K5
K6
KT
K8
JKK
=
=
=
=
=
=
=
=
17
18
19
20
21
22
23
24
= JKK+1
KK1 = JKK
IKK = IKK+I
7001 CONTINUE
IF(NMONCA.EQ.O) GO TO 7002
TC3C3T = ALP3*F38I
T3C3CG = TC3C3T
F3103T = T3C3CG
F3113T = Vl*F3103T
F3C3T = F3113T
C1C3TG = -F3C3T*DF3C1I
A1C3TG = A1C1*CIC3TG
Y1C3TG =OY1C1*C1C3TG
T2C3TG = OTC2C1*C1C3TG
T3C3TG = T3C3CG+DTC3C1*CIC3TG
T4C3TG = OTC4C1*C1C3TG
T5C3TG = OTC5C t*CIC3TG
C2C3TG = C2C1*C1C3TG + C2TC2*T2C3TG
C3C3TG = C3C1*C1C3TG 4- C3TC3*T3C3TG
C4C3TG = C4CI*C1C3TG * C4TC4*T4C3TG
C5C3TG = C5C1*C1C3TG + C5TC5*T.5C3TG
UIC3TG = 2.*(CiC3TG + C2C3TG + AIC3TG)
U2C3TG = .5*(C3C3TG * C4C3TG * C5C3TG)
U3C3TG = U1C3TG * U2C3TG
UC3TG = UP5*U3C3TG
U5C3TG - U5U5*UC3TG
U6C3TG = TEMX * U5C3TG
U4C3TG = U*U6C3TG + UC3TG*U6
EX3UDG = -EXPU*U4C3TG
F4C3TG = -EX3UOG
GAMC3T - -F4C3TG*DF4GI
-------
0498
0499
0500
OS01
0502
0503
0504
0505
0506
0507
0508
0509
0510
051 1
0512
0513
0514
0515
0516
0517
0513
0519
0520
0521
0522
0523
0524
0525
0526
0527
0528
0529
0530
0531
0532
0533
0534
0535
0536
OY1G*GAMC3T
OC2G*GAMC3T
DC3G*GAMC3T
DC4G*GAMC3T
OC5G*GAMC3T
IF ~ OA1C3T
DG(JKK) = GAMC3T
OG8(JKK)
C
-------
Ln
UJ
0537
0538
0539
0540
0541
0542
0543
0544
0545
0546
0547
0543
0549
OS50
0551
0552
0553
0554
O55S
0556
0557
0558
0559
0560
0561
0562
0563
0564
0565
0566
0567
0568
0569
OS 70
0571
0572
O573
0574
0575
Y1C4TG =DY1C1*C1C4TG
T2C4TG = DTC2C1*C1C4TG
T3C4TG = OTC3C1*C1C4TG
T4C4TG = T4C4CG+OTC4C1*C1C4TG
T5C4TG = OTC5C1*C1C4TG
C2C4TG = C2C1*C1C4TG + C2TC2*T2C4TG
C3C4TG = C3C1*C1C4TG «• C3TC3*T3C4TG
C4C4TG = C4C1*C1C4TG * C4TC4*T4C4TG
C5C4TG = C5CI*C1C4TG * C5TC5*T5C4TG
U1C4TG = 2.MC1C4TG * C2C4TG + A1C4TG)
U2C4TG = .5*tC3C4TG + C4C4TG + C5C4TGI
U3C4TC = U1C4TG * U2C4TG
UC4TG = UP5*U3C4TG
U5C4TG = U5U5*UC4TG
U6C4TG = TEMX * U5C4TG
U4C4TG = U*U6C4TG * UC4TG*U6
EX4UDG = -EXPU*U4C4TG
F4C4TG = -EX4UOG
GAMC4T = -F4C4TG*DF4GI
IF = OC3C4T
DCCS(K4) = OC4C4T
OCCS(KS) = DC5C4T
DCCSCK6) = OA2C4T
DCCS
-------
0576
0577
0578
0579
0580
0581
0582
0583
05S4
0585
0586
0587
C( IKKI = C4
Kl
K2
K3
K4
K5
K6
K7
K8
KKI
KB + 1
Kl+1
K2+1
K3 + 1
K4+1
K5 + 1
K6-H
K7+1
= KK1
IKK = IKK+1
IF(NMONCA.FO.Z)
GO TO 7002
Ul
w
cx>
0588
0589
0590
0591
OS92
OS93
0594
0595
0596
0597
0598
0599
0600
0601
0602
0603
0604
0605
0606
0607
0608
0609
0610
0611
0612
0613
TC5C5T = ALP5*F301I
TSC5CG = TC5C5T
F3105T = T5C5CG
F3115T = Y1*F3105T
F3C5T = F31 1ST
CICBTG » -F3C5T*OF3C1I
A1C5TG = AlCl * CIC5TG
V1C5TG =DYtCl*ClC5TG
T2C5TG = DTC2C1*C1C5TG
T3C5TG = OTC3C1*CIC5TG
T4C5TG = OTC4CI*C1C5TG
T5C5TG = T5C5CG*OTC5CI*C1C5TG
C2C5TG * C2C1*C1C5TG * C2TC2*T2C5TG
C3C5TG = C3CI*C1C5TG * C3TC3*T3C5TG
C4CSTG = C4C1*C1C5TG * C4TC4*T4C5TG
C5C5TG = C5C1*CIC5TG * C5TC5*T5C5TG
U1C5TG = 2.*(C1C5TG + C2C5TG + AIC5TG)
U2C5TG = .5*tC3C5TG •»• C4C5TG + C5C5TG)
U3C5TG * U1C5TG * U2C5TG
UC5TG = OP5*U3C5TG
U5C5TG = U5U5*UC5TG
O6C5TG = TEMX * U5C5TG
U4C5TG = U*U6C5TG + UC5TG*U6
EX5UOG = -EXPU*U4C5TG
F4C5TG = - EX5UDG
GAMC5T = -F4C5TG*DF4GI
-------
OJ
0614
0615
0616
0617
0618
0619
0620
0621
0632
0623
0624
0625
0626
0627
0628
0629
0630
0631
0632
0633
0634
0635
0636
O637
0638
0639
0640
0641
0642
0643
0644
0645
0646
0647
0648
0649
06SO
0651
0*5?
700?
IF(IGAM.EO.l) = DC1C5T
DCCS
-------
Ln
-P-
O
0653
065*
0655
06S6
0657
0658
0659
O660
O661
0662
0663
0664
0665
0666
0667
0668
0669
0670
0671
0672
0673
0674
0675
O676
0677
0678
0679
0680
0681
0682
0683
0684
0685
0686
0687
0688
0689
0690
0691
U4A2TG = U6*UA2TG + U * U6A2TG
EXA2TG = -EXPU*U4A2TG
F4A2TG = - EXA2TG
GAMA2T = -F4A2TG*DF4GI
IF(IGAM.EQ.I> GAMA2T = 0.0
DCIA2T =
OC2A2T =
DC3A2T =
DC4A2T =
DC 5A 2 T =
DA1A2T =
DVIA2T =
DA2A2T =
DA3A2T =
OCCS(K1 I
OCCS
DG(KKl) :
DGStKKl)
C(IKK1 =
OC1G * GAMA2T
DC2G*GAMA2T
OC3G*GAMA2T
OC4G*GAMA2T
OC5G*GAMA2T
OA1G*GAMA2T
DYIG*GAMA2T
1 .0
0.0
= OCIA2T
= OC2A2T
= OC3A2T
= OC4A2T
= DC5A2T
= DA2A2T
= OA3A2T
- DAIA2T
•- GAMA2T
= GAM780GAMA2T
A2T
KI = K8+I
KKI = KK1*l
IKK = IKK+t
Kt = K8+t
K2 = Kl*l
K3 = K2-M
K4 = K3+1
K5 = K4+1
K6 = K5+1
K7 = K6+1
K8 = K7+I
IF(NMONAN.EQ
U2A3TG = .5
U3A3TG = U2A3TG
1) GO TO 7005
-------
0692
0693
0694
0695
0696
0697
0693
0699
0700
0701
0702
0703
0704
0705
0706
0707
0708
0709
0710
071 I
0712
0713
0714
0715
0716
0717
0718
0719
0720
0721
0722
0723
0724
0725
0726
0727
0728
0729
0730
UA3TG = UP5*U3A3TG
USA3TG = U5U5*UA3TG
U6A3TG = TEMX * U5A3TG
U4A3TG - U6*UA3TG + U * U6A3TG
EXA3TG = -EXPU*U4A3TG
F4A3TG = - EXA3TG
GAMA3T = -F4A3TG*DF4Gl
IF(IGAM.EO.I) GAMA3T = 0.0
DC1A3T =
OC2A3T -
OC3A3T =
OC4A3T =
OC5A3T =
OA1A3T =
OV1A3T =
OA2A3T =
DA3A3T =
OCCSCKl)
DCCS
OCCS
OCCS
DCCSIK7)
DCCS(K8>
DG(KKt
DC1G*GAMA3T
OC2G*GAMA3T
DC3G*GAMA3T
DC4G*GAMA3T
DC5G*GAMA3T
DA1G*GAMA3T
OY1G*GAMA3T
0.0
1 .0
= DC1 A3T
= DC2A3T
= DC3A3T
= OC4A3T
= DC5A3T
= OA2A3T
= OA3A3T
= OA1A3T
= GAMA3T
7005
OGS(KKl) = GAM780GAMA3T
C(IKK) = A3T
Kl = K8+1
K2 = KI * 1
K3 = K2+1
K4 = K3+1
K5 =
K6 =
K7 = K6 + 1
K8 = K7H
KK1 = KKl-H
IKK = IKK+l
CONTINUE
-------
-p-
t-o
0731
0732
0733
0734
0735
0736
0737
0738
0739
0740
0741
0742
0743
0744
0745
0746
0747
0748
0749
0750
0751
0752
0753
0754
0755
0756
0757
0758
0759
0760
0761
0762
0763
0764
0765
0766
0767
0768
0769
If (NSULF.EQ.O ) GO TO 7006
FIA1T = -F18-F105*A1
AIA1T = -F1A1T*FIA1I
AAITCG = A1A1T
YAITCG = V1AI * AAITCG
T2A1CG = TC2A1*AA|TCG 4- TC2Y1*YA1TCG
T3AICG = TC3V1*YA1TCG
T4AICG = TC4Y1*YA1TCG
T5A1CG = TC5Y1*YA!TCG
TISMCG = T2A1CG * T3A1CG 4- T4A1CG 4- TSA1CG
T1SYCG = Yl * TISMCG * F310 * YAITCG
F3AICG •= T1SYCG
CIAITG = -F3A1CG*DF3C1 I
A1AITG = AAITCG 4- A1CI*C1A1TG
YIAITG = YAITCG 4-DY 1C I *C1 Al TG
TC2AIG = T2AICG4-DTC2C1 *Cl A1TG
TC3A1G - T3A1CG+DTC3C1*CIAITG
TC4A1G = T4AICG4-DTC4CI*CI Al TG
TC5AIG = T5A1CG4-OTC5C1*C1AITG
C2AITG = C2C1*CIA1TG 4- C2TC2*TC2A1G
C3AITG = C3CI*CIAITG 4- C3TC3*TC3A1G
C4AITG = C4C1*CIA1TG 4- C*TC4*TC4A1G
C5AITG = C5C1*C1AITG * C5TC5*TC5A1G
U1A1TG = 2.0 * (CIAITG * C2A1TG 4- A1A1TG)
U2AITG = .5* (C3A1TG 4- C4AITG * C5AITG)
O3A1TG = UIA1TG * U2AITG
UAITG = UP5*U3AITG
U5A1TG = U5U5*UA1TG
U6A1TG = TEMX * U5A1TG
U4A1TG = U6*UAITG 4- U * U6A1TG
EXA1TG = -EXPU*U4AITG
F4A1TG = - EXA1TG
GAMA1T = -F4AITG*OF4GI
IF< 1GAM.EQ.1 ) GAMA1T = 0.0
DCIA1T - DC1G*GAMA1T 4- CIAITG
DC2A1T = DC2G*GAMA1T 4- C2A1TG
OC3A1T = DC3G*GAMA1T 4- C3AITG
OC4A1T = OC4G*GAMA1T 4- C4A1TG
DC5A1T = OC5G*GAMA1T 4- C5A1TG
-------
OT70
0771
0772
0773
077*
0776
0777
0778
0779
0780
0761
0782
0783
0784
0785
0786
0787
0788
0789
O790
0791
0792
0793
079*
0795
0796
0797
0798
0799
0800
0801
0802
0803
0804
0805
0806
0807
0808
OA1A1T =
OY1A1T =
OA2A1T =
OA3A1T =
OCCStKt 1
OCCS ( K2 >
OCCS
DCCS
-------
0809
0810
0811
0812
0813
0814
0815
0816
0817
0818
0819
0830
0821
0822
0823
0824
0825
0826
0827
0828
0829
0830
0831
0832
0833
0834
0835
0836
0837
0838
0839
0840
0841
O842
0843
0844
0845
0846
0847
FC51TH = -
C3TMG « U1THG+U2THG
UTHG = UP5*U3THG
U5THG = U5U5*UTHG
U6THG = TEMX * U5THG
U4THG = U*U6THG+U6*UTHG
EXTHG = -EXPU*U4THS
F4THG = -EXTHG
GAMTH s -F4THG*OF4GI
IFCIGAM.EQ.l) GAMTH = O.O
OC1TH a ClTt-G+DClG*GAMTH
OA1TH = AlTHG+DA1G*GAMTH
OC2TH - C2THG+DC2G*GAMTH
DC3TH = C3THG*DC3G*GAMTH
-------
Ln
-f>
Ui
0848
0849
0850
0851
0852
0853
0854
0855
0856
0857
0858
0859
0860
0861
0862
0863
0864
0865
0866
0867
0868
0869
0870
0871
0872
0873
0874
0875
0876
0877
0878
0879
0880
0881
0882
0883
0884
0885
0886
OC4TH = C4THG+DC4G*GAMTH
DC5TH = C5THG+OC5G*GAMTI'
DA2TH = 0.0
DA3TH = 0.0
= OCITH
= DC2TH
= OC3TH
= DC4TH
= OC5TH
= DA2TH
= DA3TH
= OA1TH
= GAMTH
= GAM78*GAMTH
DCCStKl)
OCCS(K2)
OCCS < K3 )
OCCS(K4)
OCCS
DCCS
KUS = KIJS + NDER
KIJ = KIJS
IFCNDICAT.EQ.l) GO TO 6002
KKK = 2
JIK = KKK-8
OO 4002 Il=l,NDER
KIJ = KIJ+l
JIK = JIK ••• 8
4002 DCC(KIJ) = OCCS(JIK)
KI JS = KI JS+NDER
Kl J = KUS
6002 IF(NMCNCA.EO.O) GO TO 6005
KKK = 3
DO 4010 III = l.NMONCA
JIK = KKK-8
DO 4003 11=1.NOER
-------
0887
0888
0889
0890
0891
O892
O893
0894
069$
0896
0897
0898
0899
0900
0901
0902
0903
0904
0905
O906
0907
0908
O909
0910
0911
0912
0913
0914
0915
0916
KIJ = KIJ+1
JIK = JIK + 8
4003 DCC(KIJ) * OCCS(JIK)
KIJS = KIJS+NDER
KIJ = KIJS
4010 KKK = KKK + 1
6005 IF(NMONAN.EQ.O) GO TO 6007
KKK = 6
DO 4020 II=ltNMONAN
JIK = KKK- 8
OO 4004 I 11 = 1 .NOER
KI J = KI J + l
JIK = JIK + 8
4004 DCC(KIJ) = OCCS(JIK)
KIJS * KIJS+NDER
KIJ « KIJS
4020 KKK s KKK4-1
6007 IF(NSULF.EQ.O) GO TO 6008
KKK - 8
JIK = KKK-8
DO 4005 I I 1=1. NOER
KI J = KU + 1
JIK = JIK + 8
4005
6008
50O1
OCC(KIJ)
CONTINUE
Yll(K) -
GAMA(K)
GAMA6(K>
CONTINUE
RE TURN
= OCCS(JIK)
VI
GAM1
= GAMS
-------
APPENDIX M
USERS GUIDE TO THE MODEL
The purpose of this appendix is to provide the user of the paddy model
with instructions for operation. A list of the required input variables is
provided in Table M-l. The organization of the input data is shown in Table
M-2 where the data is divided into sets, with each data set corresponding to
a FORTRAN READ statement in the computer program. Also shown in Table M-2
are the units where applicable, data type, the number of cards in each data
set, and the displacement of the important input data on each card.
A brief summary of the calculations in the important program is given so
the logic can be traced.
547
-------
TABLE M-l. INPUT VARIABLES
-p-
00
M
DELZ
NDICAT
NMONCA
NSULF
NMONAN
ITHET
= ND. Grid Points Profile depth = ^ Bdy Cond at z = (M-3/2)*DELZ :
(M-3/2)*DELZ cm ~" C = C 1 J 9C.
Grid Spacing (cm) I
dz | z=:
i i i i
= no. divalent cations (=2 for Ca + Mg ) (max = 2) (min = 1)
= no. monovalent cations (max = 3) (min = 0)
= 1 if SO, present = 0 if not
= no. monovalent anions (0-2)
= 1 if changes in H00 content are accounted for either in soil or paddy water.
IGAM
ML2
I CHG
VALI(I)
DIFUS(I)
DIFX1
DIFX2
_
includes changes in H for paddy H«0.
= 1 if GAMA (activity coef) = 1
= 0 if GAMA calculated in EQUIL
= 1 if changes in surface concentration are calculated
= 2 if concentrations at surface constant for the run
= 0 if diffusion to chg gradients are calculated
= 1 if diffusion to chg gradients are ignored
= valence of ion I (2 <_ I £ NION = NDICAT + NMONCA + NSULF + NMONAN)
= soil diffusion coefficient for ion i
= diffusion coefficient for CaSO, , MgSO,
= diffusion coefficient for CaSO ° MgSO °
(continued)
-------
TABLE M-l. (Continued)
DIFEDE
DIFEXP
TIMAX
TPRIN
IF TPRIN = 3
Dll' D21
DELT
F F F
h!2' E13' *V
E15
CEC(K)
RHOB(K)
THETAI (K)
CT(IK)
NDAYS
NOPT if = 1,
DAYLNG
apparent diffusion coefficient for ion i = .6*0*DIFUS(I)+0*DIFCOF*(q/e)**DIFEXP
apparent diffusion coefficient for ion i = .6*0*DIFUS(I)+0*DIFCOF*(q/9)**DIFEXP
length of run in subroutine SOIL before return to MAIN, in this case TIMAX =
1440 min = no. rain in a day
no. days run before printout
printout occurs at end of day 3 = beginning of day 4
inverse of dissociation constants for CaSO, and MgSO, , respectively.
time step size for SUBROUTINE SOIL
exchange coefficient for exchange between cation 1 and cations 2, 3, 4, 5, respect-
ively; must not = 0.
cation exchange capacity ( in center at z - (K-l) * DELZ)
bulk density
H_0 content
intial total ion concentrations (mmoles/cm ) at H_0 content THETAI(K)
no. days for run
irrigation occurs to 10 cm depth when the paddy H_0 depth falls to or below 4 cm -
occurs only at start of new day
no. daylight hours/day (continued)
-------
TABLE M-l. (Continued)
01
On
3
RIONRT(I) = mg/cm ion uptake coefficient
WTMOL(I) = molecular weight of ion i
IPERC(K) = percentage of total trans, taken up from layer K
IRDEP = depth (units of 1 cm) of irrigation on a given day
IPREC = rainfall (units of 1 cm)
IDRAIN = deep perculation (.1 cm) total for day
IEVAP = evaporation (.1 cm) total for day
ITRANS = transpiration (.1 cm) total for day
o
IFERT(I) = fertilizer application (kg/ha) of ion i
IRCONC(I) = concentration (mg/1) of ion i in irrigation H-0
-------
TABLE M-2. INPUT DATA DECK
Card ft
1
1
1
1
1
1
Variable
M
NDICAT
NMONCA
NSULF
NMONAN
ITHET
Columns
1-3
4-6
7-9
10-12
13-15
16-18
Format
13
12
12
13
13
13
Definition
number of grid points
number of divalent cations
number of monovalent cations
0 if sulfate absent;
1 if sulfate present
number of monovalent ahions
0 for steady flow;
Units
1 if water contents vary with time
2
2
2
3
3
3
3
3
4
4
4
5
5
5
5
6
6
IGAM
ML2
ICHG
VALI(I),
(1=1)
VALI(I),
(1-2)
VALI(I),
(1=3)
VALI.(I) ,
(1=4)
VALI(I),
(1=5)
VALI (I) ,
(1-6)
VALI (I),
(1-7)
VALI (I),
(1=8)
DIFUS(I)
(1=1)
DIFUS(I)
(1=2)
DIFUS(I)
(1-3)
DIHJS(I)
(1-4)
DIFUS(I)
(1-5)
DIFUS(I)
(1-6)
1-3
4-6
7-9
1-16
17-32
33-48
49-64
65-80
1-16
17-32
33-48
, 1-16
, 17-32
, 33-48
, 49-64
, 65-80
, 1-15
13
13
13
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.4
E16.5
E16.4
at any grid point
0 for concentration-dependent
activity coefficient
1 if not concentration-de-
pendent
1 for unit activity coefficient
1 if change-induced Ifux is ignored;
0 otherwise
valence of ion I*
valence of ion I
valence of ion I
valence of ion I
valence of ion I
valence of ion I
valence of ion I
valence of ion I
diffusion coefficient of ion I
diffusion coefficient of ion I
diffusion coefficient of ion I
diffusion coefficient of ion I
diffusion coefficient of ion I
diffusion coefficient of ion I
2 -1
cm min
2 -1
cm min
2 -1
cm mm
2 -1
cm min
2 -1
cm min
2 -1
cm min
* Ions are as follows:
sulfate, sodium.
calcium, magnesium,potassium,ammonium, chloride, bicarbonate,
(continued)
551
-------
TABLE M-2. (Continued)
Card f
6
6
7
7
8
8
8
8
9
9
10
10
11
11
11
11
12
12
12
12
12
12
Variable
DIFUS(I),
(1=7)
DIFUS(I),
(1-8)
DIFX1
DIFX2
DIFCOF
D1FEXP
TIMAX
TPRIN
Dll
D21
DELT
DELZ
E12
E13
E14
E15
CEC(K),
(K=l)
CEC(K),
(K-2)
CEC(K),
(K=3)
CEC (K ) ,
' (K=4)
CEC(K),
(K-5)
CEC(K),
(K-6)
Columns
17-32
33-48
1-16
17-32
1-16
17-32
33-48
49-64
1-16
17-32
1-16
33-48
1-16
17-32
33-48
49-64
1-10
11-20
21-30
31-40
41-50
51-60
Format
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(E16.4)
(F10.4)
(F10.4)
(F10.4)
(F10.4)
(F10.4)
(F10.4)
Definition
diffusion coefficient of ion I
diffusion coefficient of ion I
diffusion coefficient for
diffusion coefficient for
MgS04
parameter used in calculation
of hydrodynamic dispersion
parameter used in calculation
of hydrodynamic dispersion
total simulated time
sucessive print-outs of con-
centrations
inverse of diffusion coeffi-
cient for Ca S04
inverse of diffusion coeffi-
cient for MgSO,
time step size
grid spacing
Exchange coefficient for
mass-action relationship
Exchange coefficient for
Gapon relationship
exchange coefficient for
Gapon relationship
exchange coefficient for
Gapon relationship
cation exchange coefficient
at grid point K.
cation exchange coefficient
at grid point K
cation exchange coefficient
at grid point K
cation exchange coefficient
at grid point K
cation exchange coefficient
at grid point K
cation exchange coefficient
at grid point K
Units
cm min
2 -1
cm min
2 * -1
cm min
2 _i
cm min
min
days
1 mol
,
1 mol
min
cm
"> \f
(mol 1 K
,
(moi rzr
9 If
(mol I"''/5
meqdOOg)'1
«
meq(100g)~
4
meq(100g)~
meq(100g)~
4
meqdOOgr-1
meq(lOOg)"
(continued)
552
-------
TABLE M-2. (Continued)
Card #
12
12 •
13
13
13
13
13
13
13
13
14
14
14
14
14
14
14
14
15
15
15
15
15
15
15
15
Variable
CEC(K),
(K-7)
CEC(K),
(K-8)
CEC(K),
(K-9)
CEC(K),
(K-10)
CEC(K),
(K-ll)
CEC(K),
(K-12)
CECOO,
(K-13)
CEC(K),
(K-14)
CEC(K),
(K-15)
CEC(K),
(K-16)
CEC(K),
(K-17)
CEC(K),
(K-18)
CEC(K),
(K-19)
CEC(K),
(K-20)
CEC(K),
(K-21)
CEC(K),
(K-22)
CEC(K),
(K-23)
CEC(K),
(K-24)
RHOB(K),
(K-l)
RHOB(K),
(K-2)
RHOB(K),
(K-3)
RHOB(K)
(K-4)
RHOB(K),
(K-5)
RHOB(K),
(K-6)
RHOB(K),
(K-7)
RHOB(K),
(K-8)
Columns Format Definition Units
61-70 (710. 4) cation exchange coefficient meq(lOOg)
71-80
1-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
1-10
11-20
21-30
31-40
41-50
51-60
61-70
at grid point K
/ ^
/
/
71-80
-3
1-10 (F10.4) bulk density at grid pt. K gm cm
11-20
21-30
31-40
41-50
51-60
61-70
71-80
s >
/ v
/
-1
(continued)
J53
-------
(Continued)
Card If
16
16
16
16
16
16
16
16
17
17
17
17
17
17
17
17
18
18
18
18
18
18
18
18
19
Variable
RHOB(K),
fV^Q\
IK=S ;
RHOB(K),
(K-10)
RHOB(K),
(K-ll)
RHOB(K),
/V=1 9 ^
VK.=J./;
RHOB(K),
(K=13)
RHOB(K),
(K=14)
RHOB(K),
(K=15)
RHOB(K),
(K-=16)
RHOB(K),
(K=17)
RHOB(K),
(K-18)
RHOB(K),
(K-19)
RHOB(K),
(K-20)
RHOB(K),
(K-21)
RHOB(K),
(K-22)
RHOB(K),
(K-2 3)
RHOB(K),
(K-24)
THETAl(K)
(K-l)
THETAl(K)
(K-2)
THETAl(K)
(K-3)
THETAl(K)
(K-4)
THETAl(K)
(K-5)
THETAl(K)
(K-6)
THETAl(K)
(K=7).
THETAl(K)
(K-8)
THETAl(K)
(K-9)
Columns Format Definition Units
1-10 (F10.4) bulk density at grid pt. K gm
11-20
21-30
31-40
41-50
51-60
61-70
71-80
1-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
cm"3
V '•L' V '
3 -3
, 1-10 (F10.4) water content at grid point cm cm
, 11-20
, 21-30
, 31-40
, 41-50
, 51-60
, 61-70
, 71-80
, 1-10
>
K
^ >
»
' •+,
f
(continued)
554
-------
TABLE M-2. (Continued)
Card #
19
19
19
19
19
19
19
20
20
20
20
20
20
20
20
21
21
21
21
21
22
22
22
Variable
THETAl(K)
(K=10 )
THETAl(K)
THETAl(K)
(K=12)
THETAl(K)
(K-13)
THETAl(K)
(K-14)
THETAl(K)
(K-15)
THETAl(K)
(K-16)
THETAl(K)
(K=17)
. THETAl(K)
(K=18)
THETAl(K)
(K=19)
THETAl(K)
(K=20)
THETAl(K)
(K=21)
THETAl(K)
(K-22)
THETAl(K)
(K=23)
THETAl(K)
(K-24)
CT(IK),
(IK=1)
CT(IK),
(IK=2)
CT(IK).
(IK-3)
CT(IK),
(IK-4)
CT(IK),
(IK-5)
CT(IK),
(IK-6)
CT(IK),
(IK=7)
CT(IK),
(IK-8)
Columns Format Definition Units
3 -3
, 11-20 (F10.4) water content at grid point cm cm
, 21-30
, 31-40
, 41-50
, 51-60
, 61-70
, 71-80
, 1-10
, 11-20
, 21-30
, 31--40
, 41-50
, 51-60
, 61-70
, 71-80
K
• «
t
1-16 (E16.4) total concentration of ion IK mole 1
17-32
33-48
49-64
65-80
1-16
17-32
33-48
>
at grid point K
' \
' \
/
(continued)
555
-------
TABLE M-2. (Continued)
Card #
69
69
70
70
70
70
70
71
71
71
72
72
72
72
72
73
73
73
74
74
75
75
75
75
75
Variable
NDAYS
NOPT
RIONRT(I)
(1=1)
RIONRT(I)
(1=2)
RIONRT(I)
(1=3)
RIONRT(I)
(1=4)
RIONRT(I)
(1=5)
RIONRT(I)
(1=6)
RIONRT(I)
(1=7)
RIONRT(I)
(1-8)
WTMOL(I),
(1=1)
WTMOL(I),
(1=2)
WTMOL(I),
(1-3)
WTMOL(I),
(1=4)
WTMOL(I),
(1=5)
WTMOL(I),
(1=6)
WTMOL(I),
(1-7)
WTMOL(I),
(1=8)
SUNTIM
DAYLNG
IPERC (K) ,
(K-l)
IPERC (K) ,
(K=2)
IPERC (K),
(K-3)
IPERC (K),
(K-4)
IPERC (K),
(R-5)
Columns Format Definlation Units
1-3 (13) number of day bar simulation days
4-6 (13) number of options
1-16 (E16.4) factor bar ion (I) uptake by mg cm (H20)
, 17-32
, 33-48
, 49-64
, 65-80
, 1-16
, 17-32
, 33-48
roots (ion)
N/ S
/ ^
-1
1-16 (E16.4) gram mol. wt . of ion (I) per gm mole
17-32
33-48
49-64
65-80
1-16
17-32
33-48
mol of ion (I)
1
1
Nr •*, ^
1-16 (E16.4) sun up time hours
17-32 (E16.4) length of daylight period hours
1-4 (14) percentage of total transpira-
tion taken up from layer K
5-8
9-12
13-16
17-20
\
f
•\
/
(continued)
556
-------
TABLE M-2. (Continued*)
Card «
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
77
77
77
77
77
77
77
Variable
IPERC (K),
(K-6)
IPERC (K),
(K-7)
IPERC (K),
(K-8)
IPERC (K),
(K-9)
IPERC (K),
(K-10)
IPERC (K),
(K-ll)
IPERC (K),
(K-12)
IPERC (K) ,
(K-13)
IPERC (K),
(K-14)
IPERC (K),
(K-15)
IPERC (K) ,
(K-16)
IPERC (K),
(K=17)
IPERC (K).
(K-18)
IPERC (K),
(K-19)
IPERC (K),
(K=20)
IPERC (K),
(K=21)
IPERC (K),
(K-22)
IPERC (K) ,
(K-23)
IPERC (K),
(K-24)
IRDEP
IPREC
IDRAIN
IEVAP
ITRANS
IFERT(Il)
(11=1)
IFERT(Il)
(11=2)
Cplumns
21-24
25-28
29-32
33-36
37-40
41-44
45-48
49-52
53-56
57-60
61-64
65-68
69-72
73-76
77-80
1-4
• ',5-B
9-12
13-16
4-6
7-9
10-12
13-15
16-18
19-21
22-24
Format
(14)
•v
-
>^
(13)
(13)
(13)
(13)
(13)
(13)
(13)
Definition Units
percentage of total transpira-
tion taken up from layer K
V
x
depth of irrigation nun day_^
precipitation rate mm day_^
drainage rate mm day_^
evaporation rate mm day_^
transpiration rate mm day^
amount of fertilizer ion (11) kg ha day
added to grid point 1 _^
amount of fertilizer ion (11) kg ha day
added to grid point 1
(continued)
557
-------
TABLE M-2. (Continued)
Card *
77
77
77
77
77
77
77
77
77
77
77
77
77
77
78
78
78
78
78
78
78
78
79
**
Variable
IFERT(Il)
(11=3)
IFERT(Il)
(11=4)
IFERT(Il)
(11=5)
IFERT(Il)
. (H-6)
IFERT(Il)
(11=7)
IFERT(Il)
(11=8)
IRCONC(Il)
(11=1)
IRCONC(ll)
(11=2)
IRCONC(Il)
(11=3)
IRCONC(Il)
(11-3)
IRCONC(Il)
(11=4)
IRCONC(Il)
(11=5)
IRCONC(Il)
(11=6)
IRCOHC(Il)
(11-7)
ISOL(I),
(1=1)
ISOL(I),
(1=2)
ISOL(I),
(1=3)
ISOL(I),
(1=4)
ISOL(I),
(1=5)
ISOL(I),
(1-6)
ISOL(I),
(1=7)
ISOL(I),
(1=8)
IRUNOF
Columns Format Definition Units
-1 -1
, 25-27 (13) amount of fertilizer ion (11) kg ha day
, 28-30
, 31-33
, 34-36
, 37-39
, 40-43 \
added to grid point 1
/
\
/ \
,,
_1
, 43-45 (13) concentration of ion (11) in ir- mg 1
rigation water
, 46-48
, 49-51
, 52-54
, 55-57
, 58-60
, 61-63
, 64-66 J
/
>
/ ^
S
4-6 (13) amount of fertilizer ion (I) •• kg ha"1
7-9
10-12
13-15
16-18
19-21
22-24
25-27
added to grid point 2
^ x!
' \
f
1-4 (14) amount of runoff Turn day"
** Cards #74-79 (6 cards) are within a do loop; each set of 6 cards are read after
the program runs for that day and progresses to the next day (by one day) and then
reads the data set (next 6 cards) for the next day.
558
-------
APPENDIX N
FINITE-DIFFERENCE VERIFICATION OF PARTIAL DERIVATIONS
The computational procedure used to solve the system of chemical equili-
brium equations requires the calculation of a number of partial derivatives.
In addition, the numerical scheme used to solve the transport equations also
requires the calculation of the derivatives of certain functions with respect
to the ion totals C , 1=1,2, .... 8. For transient flow conditions
the derivatives of these functions with respect to 9 are required.
To insure that the computational procedure had been programmed correctly,
these partial derivatives were evaluated using the programmed procedure and
then compared with finite-difference approximations to the corresponding de-
rivatives. Favorable comparison, after some corrections were made, indicated
consistency between calculated function values and calculated values for the
partial derivatives.
In order to carry out these comparisons, values were first assigned to
each of the parameters and soil-and moisture-dependent variables in both SUB-
ROUTINE SOIL and SUBROUTINE EQUIL and to each of the independent variables
'"'iTk' ^2Tk' " " ' ' '"'STk' ^llk' ' * * ' 3Tk' ^°r = ' '* '""' S
value or each function ror which a test was desired, for example G' , was
calculated in terms of the assigned values of the parameters and total con-
centrations. If a test of the derivatives with respect to C~ , was desired,
then the derivatives of each function with respect to C were also evalu-
ated. Then only the value of C2T. was changed by a small amount, ACOTk'
while the remaining independent variables retained their original values. The
functions and their corresponding derivatives were again evaluated in terms
of C + AC , and finally, finite-difference approximations to each of the
partial derivatives were calculated. For example,
£G13(C2Tk + AC2Tk> - G13(C2Tk)]/AC2Tk
was the finite-difference approximation calculated for 8G13/8C2xk> For a
sufficiently small change in the independent variable (in this example,
AC ), the finite-difference approximation would be expected to be in rea-
sonable agreement with the calculated values of the partial derivatives at
the end-points (e.g. C and C , + AC ). That this is the case can be
seen from Tables N-l through N-6. The first column in each table corresponds
to the calculated value of the derivative of the indicated function at the
left end-point and the third column corresponds to derivative values at the
right end-point. The center column contains values of the finite-difference
approximations.
559
-------
Although each of the functions of the total concentrations was checked
individually, Tables N-l through N-6 contain only derivatives of the G..
functions. In all cases, it can be seen that the calculated finite-differ-
ence lies numerically between the values of the derivatives calculated for
the end-points.
560
-------
TABLE N-l. DERIVATIVE OF G.. WITH RESPECT TO CATION 1 AT THIRD GRID POINT
ik
Derivative _
CIT = 0.11 F.D. Check CIT = 0.12
1 -1.158 x 10~3 -1.153 x 10~3 -1.145 x 10~3
2 -1.452 x 10~4 -1.328 x 10~4 -1.123 x 10~4
3 1.010 x 10~4 1.119 x 10~4 1.209 x 10~4
4 1.010 x 10~4 1.119 x 10~4 1.209 x 10~4
5 1.010 x 10~4 1.119 x 10"4 1.209 x 10~4
6 -2.229 x 10~4 -2.033 x 10~4 -1.853 x 10~4
7 -7.356 x 10~4 -7.124 x 10~4 -6.887 x 10~4
8 -7.356 x 10~4 -7.124 x 10~4 -6.887 x 10"4
561
-------
TABLE N-2. DERIVATIVE OF G.. WITH RESPECT TO CATION 2 AT THIRD GRID POINT
ik
i =
Derivative
C2T = 0.05 F.D. Check C£T = 0.06
1 -2.750 x 10~4 -2.349 x 10~4 -1.065 x 10~4
2 -9.170 x 10"4 -9.393 x 10~4 -9.582 x 10~
3 2.104 x 10~5 3.676 x 10~5 5.068 x 10~5
4 2.104 x 10~5 3.676 x 10~5 5.068 x 10"5
5 2.104 x 10~5 3.676 x 10"5 5.068 x 10~5
6 -2.229 x 10~4 -2.047 x 10~4 -1.879 x 10~4
7 -7.356 x 10~4 -7.124 x 10~4 -6.888 x 10~4
8 -7.356 x 10~4 -7.124 x 10~4 -6.888 x 10~4
562
-------
TABLE N-3. DERIVATIVE OF G., WITH RESPECT TO CATION 3, 4* OR 5* AT THIRD
GRID POINT
i =
Derivative
1
2
3
4
5
6
7
8
*
C
1
7
-1
7
7
3T
.253
.384
.358
.903
.903
-1.114
-3
-3
.678
.678
0.05
x 10"5
x 10"6
x 10~3
x 10~5
x 10"5
x 10~4
x 10~4
x 10~4
For cation 4,
For cation 5,
F
1
9
-1
7
7
-1
-3
-3
.D.
.659
.196
.357
.970
.970
.090
.628
.628
rows 3 and 4
rows 3 and 5
Check
x 10~5
x 10~6
x 10~3
x 10~5
x 10~5
x 10~4
x 10~4
x 10~4
should be
should be
C
2
1
-1
8
8
-1
—3
-3
3T
.063
.095
.355
.031
.031
.067
.579
.579
0.
x
x
X
X
X
X
X
X
06
10
10
10
10
10
10
10
10
-5
-5
-3
-5
-5
-4
-4
-4
interchanged .
interchanged.
563
-------
TABLE N-4. DERIVATIVE OF GM WITH RESPECT TO ANION 1 AT THIRD GRID POINT
ik
i =
Derivative ___
A = 0.03 F.D. Check A^ = 0.04
1 -5.755 x 10~4 -5.448 x 10~4 -5.147 x 10"4
2 -2.247 x 10~4 -2.141 x 10"4 -2.036 x 10"4
3 -1.626 x 10"4 -1.591 x 10~4 -1.553 x 10~4
4 -1.626 x 10~4 -1.591 x 10~4 -1.553 x 10~4
5 -1.626 x 10"4 -1.591 x 10~4 -1.553 x 10"4
6 -1.982 x 10~3 -1.933 x 10~3 -1.881 x 10~3
7 7.356 x 10~4 7.329 x 10~4 7.276 x 10~4
8 7.356 x 10~4 7.329 x 10"4 7.276 x 10~4
564
-------
TABLE N-5. DERIVATIVE OF G WITH RESPECT TO ANION 2 OR 3* AT THIRD GRID
POINT
i =
1
2
3
4
5
6
7
8
A
A2T ~
-2.018
-9.423
-1.507
-1.507
-1.507
1.114
-1.837
3.678
For an:
0.075
x 10"4
x 10~5
x 10~4
x 10~4
x 10~4
x 10~4
x 10"3
x 10~4
Lon 3, rows
Derivative
F.D. Check
-1.995 x 10"4
-9.314 x 10~5
-1.488 x 10~4
-1.488 x 10"4
-1.488 x 10"4
1.103 x 10~4
-1.817 x 10~3
3.631 x 10~4
3 7 and 8 should be in
A2T
-1.972
-9.205
-1.469
-1.469
-1.469
1.092
-1.798
3.585
.terchangec
0.085
x 10"4
x 10~5
x 10"4
x 10~4
x 10~4
x 10~3
x 10~3
x 10"
i.
565
-------
TABLE N-6. DERIVATIVE OF G.. WITH RESPECT TO 6 AT THIRD GRID POINT
ik
Derivative
6 = 0.49 F.D. Check 6 = 0.50
1 -1.722 x 10"4 -1.677 x 10~4 -1.632 x 10~4
2 -7.687 x 10"5 -7.493 x 10~5 -7.302 x 10~5
3 -2.483 x 10~5 -2.308 x 10~5 -2.144 x 10"5
4 -2.483 x 10"5 -2.308 x 10~5 -2.144 x 10~5
5 -2.483 x 10"5 -2.308 x 10~5 -2.144 x 10~5
6 -6.817 x 10~5 -6.522 x 10~5 -6.241 x 10~5
7 -2.182 x 10"5 -2.120 x 10~5 -2.059 x 10""5
8 -2.182 x 10"5 -2.120 x 10~5 -2.059 x 10"5
-------
Appendix 0
Analysis of Covariance
for Adsorbed and Solution
Cation Concentrations
567
-------
TABLE 0-1. ANALYSIS OF COVARIANCE OF ADSORBED AND SOLUTION CONCENTRATIONS
OF IONS IN SOIL SAMPLE 1
Analysis of Covariance of Equilibrium Data
Source of
Variation
Total
Cations
Treatments
Error
df
51
3
12
36
Sum of Products y Adjusted for x
x,x x,y y,y df SS MS F
51,394.22 960.42 1732.89
5,361.28 -99.86 1674.48
12,144.51 162.67 7.69
33,888.43 897.61 50.72 35 26.94 .77
Treatment
and Error 48 46,032.94 1060.28
Treatments
Adjusted
58.41 47 33.99
12 7.05 .59 .76
568
-------
TABLE 0-2. ANALYSIS OF COVARIANCE OF ADSORBED AND SOLUTION CONCENTRATIONS
OF IONS IN SOIL SAMPLE 2
Analysis of Covariance of Equilibrium Data
Source of
Variation
Total
Ions
Treatments
Error
Treatments
and Error
Treatments
Adjusted
Sum of Products Y Adjusted for X
df XjX X Y Y Y df SS MS F
67 44,929.86 7,036.26 8,643.76
3 9,711.9 6,688.66 8,364.09 2
16 17,211.21 141.52 6.02 15
48 18,006.76 206.08 273.65 47 271.30 5.77
64 35,217.97 347.60 279.67 63 276.24
0 16 4.94 .31 NS
_ E(xv)2 „.. ,0 (206. 08)2
Eyy ' Exx ' "71>3° " 18,006.76
cvv E(xy)2_ _ (347. 6)2
Syy " ~Sxt~ " 276'24 35,217,97
F Table 16, 47 df = 2.40
There was no real difference on the cation adsorbed at the different treat-
ments when adjusted for Y on X.
569
-------
TECHNICAL REPORT DATA .
d Instructions on the reverse before completing)
-EPORT NO.
EPA-600/2-78-082
3. RECIPIENT'S ACCESSION-NO.
L£ AND SUBTITLE
DEVELOPMENT OF MANAGEMENT GUIDELINES TO PREVENT
POLLUTION BY IRRIGATION RETURN FLOW FROM RICE FIELDS
5. REPORT DATE
April 1978_j.gsuin8 date
6. PERFORMING ORGANIZATION CODE
AUTHOR^) Kirk IV. Brown, Lloyd Deuel, Jack Price, Don
Je'nchele, iVilliam R. Teague. Fred Turner, Mike Jund,
David Chance, TAMU Agri. Res. fT Ext. Center, Beaumont
8. PERFORMING ORGANIZATION
9. PERFORMING ORGANIZATION NAMt AND ADDRESS
fexas Agricultural Experiment Station
College Station, Texas 77843
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Lab.-Ada, OK
Office of Research and Development
"U.S. Environmental Protection Agency
Ada, Oklahoma 74820
10. PROGRAM ELEMENT NO.
1BB770
11. CONTRACT/GRANT NO.
S-802008
13. TYPE OF REPORT AND PERIOD COVERED
FINAL
14. SPONSORING AGENCY CODE
EPA/600/15
15. SUPPLEMENTARY NOTES
In cooperation with Texas Agricultural Extension Service at Beaumont
'i6. ABSTRACT A three year field and laboratory study was conducted to determine the influ-
ence of management practices on the quantity and quality of irrigation return flow from
rice paddies. Continuous and intermittent irrigation techniques were used on replanted
field plots which received either recommended or excessive applications of fertilizer
ind four selected pesticides. Water quality was evaluated with respect to fertilizer
itnendments, pesticides, pH and total salt load. Pesticides monitored included propanil
nolinate, carbofuran, carbaryl and their respective metabolites.
Present water management practices result in large return flow volumes. Occasion-
illy concentrations of NH exceeded drinking water standards. Losses as nitrate were
jelou such limits and the total nitrogen losses were a small fraction of the fertilizer
ipplied. A model was developed to simulate the ionic constituency of the return flow.
Propanil was washed from the foliage into the flood water and dissipated within 24
tours. Evidence is given that carbaryl is washed from the leaves by rainfall, thus
providing available source to contaminate return flow. As long as 8 days were required
to dissipate residue resulting from recommended applications. Retention times to assur<
Low concentrations in the irrigation return flow for carbofuran are of the order of 16
iays. Granular applied molinate necessitates a retention time of 4 days to assure con-
:entrations are within 10% of the TLM to fish.
It is suggested that through improved water management and knowledge of dissipation
•ates, the quantity of irrigation return flow can be reduced and the quality improved.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Irrigation
Pesticides
hater Quality
Water Pollution
Agronomy
SoiJ Water
:;ST=P SL'T' 3\ STATE ME \ .
Release to Public
b.IDENTIFIERS/OPEN ENDED TERMS
Irrigation Return Flow,
Rice irrigation,
Pesticide residue,
Propanil, Carbofuran,
Molinate, Carbaryl,
Salt balance
|1S. SECURITY CLASS (Tins Report)
\ Unclassified
]2D. SECURITY CLASS (This page)
Unclassified
COSATl Field/Group
98/C
98/D
21. NO. OF PAGES
604
22. PRICE
,-^ 2220-1 (9-73;
570
•1^ U. S. GOVERNMENT PRINTING OFFICE: 1978-757-140/6811 Region No. 5-11
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