EPA-600/2-77-158
August 1977
Environmental Protection Technology Series
THE CONTROL OF NITRATE
AS A WATER POLLUTANT
Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environmental 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
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The nine series are:
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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
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This document is available to the public through the National Technical Informa-
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EPA-600/2-77-158
August 1977
THE CONTROL OF NITRATE AS
A WATER POLLUTANT
by
Allen R. Swoboda
Texas ASM University
Texas Agricultural Experiment Station
College Station, Texas 77843
Project S-800193
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 Re-
search 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 recom-
mendation for use.
ii
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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
information 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.
EPA's 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
wastewaters 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 pollu-
tion 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
iii
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ABSTRACT
This study was based on the premise that the most logical approach to re-
ducing nitrate leaching in soils was to limit the amount of nitrate in the
soil solution at any one time. Methods of limiting the concentration of ni-
trate in the soil solution while maintaining an adequate supply of available
nitrogen for plant growth are reported.
Timing of nitrogen application was found to be a very effective means of
reducing nitrate leaching. When nitrogen was applied in the fall as much as
3-fold more nitrate was found to have leached below 60 cm in the soil by June
as compared to applications made in March. A nitrification inhibitor, N-
Serve, was found to be very effective in reducing the amount of nitrate leach-
ed. Slow release sulfur coated ureas and treatment of nitrogen fertilizers
with N-Serve were found to be effective means of reducing leaching losses of
nitrate when fertilizers were applied in the fall or winter.
Losses.of 0.5 and 3.6% of nitrogen applied as fertilizer occurred in
runoff waters when normal rates of nitrogen were applied to a grassland water-
shed. Lysimeter studies indicated that from 0.04 to 6% of the applied
fertilizer nitrogen could be leached below 120 cm in a silt loam soil
depending on the source of nitrogen.
This report was submitted in fulfillment of Project S-800193 by the
Texas Agricultural Experiment Station under the sponsorship of the Office of
Research and Development, Environmental Protection Agency. Work was com-
pleted as of January 31, 1976.
iv
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vii
Acknowledgements x
1 Introduction 1
2 Recommendations 3
3 Conclusions 4
4 Microbial Immobilization and Release 6
Laboratory incubation 6
Plant uptake and leaching losses from microbial
immobilized nitrogen 9
5 Nitrification Inhibitors 16
Procedure 16
Results 17
6 Timing and Source of Nitrogen Application 28
Procedure 28
Results 33
7 Nitrogen Applications to a Grassland Watershed 81
Procedure 81
Results 82
8 Field Lysimeters 99
Procedure 99
Results 100
References Ill
Appendix 113
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FIGURES
Number Pag
1 Nitrate-N concentration in Norwood silt loam soil incubated at
19° C for 71 days with and without addition of Ca(N03>2 7
2 Nitrate-N concentration in Norwood silt loam soil incubated at
19° C for 71 days after adding various amounts of carbon, as
sucrose, and 100 ppm N as Ca (N(>3) 2 8
3 Accumulative loss of N03-N in effluent from Lakeland sand col-
umns treated with different ratios of carbonrnitrogen as suc-
rose and Ca0*03)2 12
4 Accumulative loss of NC^-N in effluent from Lakeland sand col-
ums treated with different ratios of carbon:nitrogen as oil
and Ca(N03>2 13
5 Accumulative nitrate-N in effluent from columns of Norwood
silty clay loam maintained at high moisture level 18
6 Accumulative nitrate-N in effluent from columns of Norwood
silty clay loam maintained at low moisture level 19
7 Nitrate in oat tissue from 3 harvests grown under high mois-
ture conditions 21
8 Nitrate in oat tissue from 3 harvests grown under low moisture
conditions 22
9 Yield of oats from 3 harvests grown under high moisture con-
ditions 23
10 Yield of oats from 3 harvests grown under low moisture con-
ditions 24
11 Nitrogen efficiency nomogram of protein nitrogen in oats
grown under different moisture conditions and nitrogen
sources 26
12 Concentration and cumulative N03-N found in drainage from
Lysimeter 1 during 1974 and 1975 and fertilized with
NH4C1 and NH4C1 treated with N-Serve 102
13 Concentration and Cumulative NC^-N found in drainage from Ly-
simeter 2 during 1974 and 1975 and fertilized with NH4C1 103
14 Concentration and cumulative N03~N found in drainage from Ly-
simeter 3 during 1974 and 1975 and fertilized with NHAC1
treated with N-Serve and NltyCl ... 104
15 Concentration and cumulative N03~N found in drainage from Ly-
simeter 4 during 1974 and 1975 and fertilized with Ca(N03)2 -...105
16 Concentration and cumulative N03-N found in drainage from Ly-
simeter 5 during 1974 and 1975 and fertilized with SCU-20 1°6
vi
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TABLES
Number Page
1 Rates of nitrogen and carbon added to 1000 g Norwood Silt loam
in immobilization study 9
2 Amount of nitrogen and carbon as sucrose or oil, applied to
Lakeland sand columns planted in Sudan grass 10
3 Yield of forage from four harvests of sudan grass grown on
Lakeland sand and treated with sucrose, oil, and CaCNO-)^ ^
4 Nitrogen uptake by four harvests of sudan grass grown on
Lakeland sand treated with sucrose, oil, and Ca(NCO2 15
5 Yield and nitrogen content of sudan grass roots grown in pots
of Lakeland sand treated with sucrose, oil, and Ca(NO_)_ 15
6 Nitrogen treatments applied at the rate of 400 kg/ha prior to
planting oats 17
7 Nitrogen balance sheet for oats grown under high moisture
treatment 27
8 Nitrogen balance sheet for oats grown under low moisture
treatment 27
9 Dates that various fertilizer N sources were applied to the
Houston Black clay and Norwood silt loam experiment loca-
tions : 30
10 Fertilizer treatments applied at the Houston Black clay and
Norwood silt loam experiment locations 30
11 Acitvities and dates related to grain sorghum grown on treated
plots to monitor N efficiency 32
12 Dates soil samples were taken from the Houston Black clay
and Norwood silt loam experiment areas, and the various
fertilizer treatments sampled 32
13 Average initial exchangeable N concentration for Houston
Black clay* and Norwood silt loam experiment locations 34
14 Total N03-N and ITCty-N in 120-cm profiles of Houston Black
clay after receiving 134 kg-N/ha. Sampling date, February
8, 1974 35
15 Concentrations of N03~N in profiles of Houston Black clay
after receiving 134 kg-N/ha. Sampled February 8, 1974 37
16 Total NOo-N and NH^-N in 120-cm profiles of Houston Black
clay after receiving 134 kg-N/ha. Sampled January 21, 1975 .... 38
17 Concentrations of N03~N and NH^-N in 120-cm profiles of
Houston Black clay on January 21, 1975 after receiving 134
kg-N/ha 40
18 Total NOg-N and NH^-N in 150-cm profiles of Norwood silt loam
on February 6, 1974 after applying 134 kg-N/ha on November
16, 1973 and December 19, 1973 43
vii
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19 Concentrations of NC^-N in 150-cm profiles of Norwood silt
loam when sampled February 6, 1974, after receiving 134
kg-N/ha in November and December 44
20 Total of the N03-N, ffl^-N, and Urea-N in 150-cm profiles of
Norwood silt loam on January 27, 1975, after receiving 134
kg-N/ha 45
21 Concentrations of N03~N and NH^N in 150-cm profiles of Nor-
wood silt loam on January 27, 1975, after receiving 134
kg-N/ha 47
22 Total of the N03-N and NH4-N in 120-cm profiles of Houston
Black clay on May 29, 1974 after receiving 134 kg-N/ha 49
23 Concentration of NC^-N and NH^-N in 120-cm profiles of Hour
ston Black clay after receiving 134 kg-N/ha prior to sam-
pling on May 29, 1974 51
24 Total N03-N and NH4~N in 120-cm profiles of Houston Black
clay on June 6, 1975 after receiving 134 kg-N/ha 55
25 Amount of NO^-N present below 60 cm of depth in 120 cm pro-
files of Houston Black clay that had received 134 kg-N/ha
prior to sampling on June 6, 1975 56
26 Concentrations of N03-N and Nfy-N in 120-cm profiles of Hou-
ston Black clay on June 6, 1975 after receiving 134 kg-N/ha .... 58
27 Total of the NCU-N and NH4-N in 150-cm profiles of Norwood
silt loam on June 4, 1974 after being treated with 134 kg-
N/ha 61
28 Concentrations of N03~N and NH4-N in 150-cm profiles of Nor-
wood silt loam after receiving 134 kg-N/ha prior to sam-
pling on June 4, 1974 63
29 Concentrations of N03-N and NH4-N in 150-cm profiles of Nor-
wood silt loam on May 21, 1975 after receiving 134 kg-N/ha 67
30 Amount of N03~N present below 60 cm of depth in 150-cm pro-
files of Norwood silt loam on May 21, 1975 that had re-
ceived 134 kg-N/ha 71
31 Concentrations of N03-N and NHA-N in 150-cm profiles of Nor-
wood silt loam on May 21, 1975, after receiving 134 kg-N/ha .... 73
32 Grain sorghum yields in 1974 on Houston Black clay fertilized
with 134 kg-N/ha of various N sources 74
33 Grain sorghum yields in 1974 on Norwood silt loam fertilized
with 134 kg-N/ha of various N sources 75
34 Protein N in grain sorghum plants on May 22, 1974 growing on
Houston Black clay fertilized with 134 kg-N/ha at various
times 76
35 Protein N in grain sorghum plants on June 7, 1974 growing on
Norwood silt loam fertilized with 134 kg-N/ha at various
times 77
36 Grain sorghum yields in 1975 on Houston Black clay fertilized
with 134 kg-N/ha of various N sources 78
37 Grain sorghum yields in 1975 on Norwood silt loam fertilized
with 134 kg-N/ha of various N sources 79
38 Daily rainfall on grassland watershed at Riesel, Texas in 1974 ... 83
39 Concentrations of N03~N in runoff water from grassland water-
shed at Riesel, Texas in 1974 85
viii
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40 Total runoff and nitrogen lost in runoff from 7.7-ha grassland
watershed in 1974 86
41 Daily rainfall on grassland watershed at Riesel, Texas in 1975 .... 87
42 Total runoff and nitrogen lost in runoff from 7.7-ha grassland
watershed in 1975 90
43 Concentration of N03~N in runoff water from 7.7-ha grassland
watershed at Riesel, Texas in 1975 91
44 Concentration of NO^-N in shallow wells in 7.7-ha grassland
watershed at Riesel, Texas in 1974 92
45 Concentration of NC>3-N in shallow wells in grassland watershed
at Riesel, Texas in 1975 93
46 Yield of coastal bermudagrass and N uptake in spring and sum-
mer of 1974 following spring application of 90 kg-N/ha to
watershed 94
47 Yield of Coastal bermudagrass and N uptake in fall of 1974
following fall application of 90 kg-N/ha to watershed 94
48 Yield of Coastal bermudagrass and N uptake in spring and sum-
mer of 1975 following applications of 90 kg-N/ha to watershed ... 96
49 Soil profile nitrogen in watershed at various times after ap-
plying 90 kg-N/ha as NItyNOs on March 5, and September 27, 1974 .. 97
50 Soil profile nitrogen in samples taken at various times from
watershed during 1975 98
51 Fertilizer treatments applied to field lysimeters 101
52 Yield and nitrogen content of grain from lysimeters .... * 101
53 Concentrations of N03~N in soil of lysimeters on October 2, 1974 .. 109
54 Concentration of N03-N in soil of lysimeters on May 23, 1975 109
55 Concentration of N03~N in soil profile of lysimeters on August
7, 1975 110
ix
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ACKNOWLEDGEMENTS
Several individuals were instrumental in the completion of this investi-
gation. The results and collection of data for this study are the results of
efforts of individuals other than the project director. Special thanks go
to Mr. Dennis P. Landua, Mr. Kenneth P. Banks, and Mr. WeIdon H. McFarland
who were responsible for the collection of most of the field and laboratory
data. For the chemical analysis of collected samples appreciation is extend-
ed to Miss Judy Massey and Mrs. Pamela Walker.
For use of facilities and cooperation at the Blacklands Experimental
Watershed thanks go to Dr. Earl Burnett of the Agricultural Research Service
with the U. S. Department of Agriculture. Appreciation is also extended to
Miss Patty Gates for doing much of the bookkeeping and typing for this re-
port and to Mrs. Mary Jo Grimes for typing this report.
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SECTION 1
INTRODUCTION
Nitrate occurrence in ground water aquifers in Texas is widespread
(George and Hastings, 1951). George and Hastings (1951) surveyed 20,000 wells
in 101 Texas counties and found that 15% or 3,000 of the wells contained
over 4.5 ppm N03-N. Runnels County, in the west central part of the state,
is well known for its high nitrate containing groundwaters. Jones (1973)
investigated the unusually high concentrations of nitrates in the ground-
waters in Runnels county and concluded that most of the groundwater contam-
ination was caused from natural nitrates in the area and was not caused by
the activities of man.
In 1969, 38 domestic water wells in Central Texas were analyzed for ni-
trates (Swoboda, 1969). Eleven of these wells were found to contain over
10 ppm N03~N which is the maximum level established by the U. S. Public
Health Service (1962) for drinking water. The N03~N concentrations of the 38
wells tested ranged up to 332 ppm. All eleven wells which were found to con-
tain excessive nitrate levels were located under heavy montmorillonitic clay
soils. Thomas and Swoboda (1967) and Kissel et al. (1973) reported that
anions such as nitrate can be readily leached in montmorillonitic soils under
proper moisture conditions.
This study was undertaken to:
A. Quantitate the amount of nitrate lost from the soil under various con-
trolled environmental conditions.
B. Develop practical farming methods which reduce the amount of nitrate
which is lost from the soil by leaching and runoff.
C. Develop certain guidelines for the optimum use of nitrogen fertilizers
while limiting the amount of nitrate entering our natural resources.
Since it is well documented that nitrates can readily move through soils
which do not have a significant anion adsorptive capacity, the basic premise
of this study was to devise methods of maintaining fertilizer nitrogen in
the NH4 form as long as possible. The NH^ form of nitrogen can be adsorb-
ed by the negatively charged sites on the clay and restrict its movement
through the soil. Three basic methods of maintaining the applied fertilizer
nitrogen in the NH^ form were investigated. The first method investigated
was microbial immobilization and release. This technique provides a natural
slow release source of nitrogen which would limit the amount of NO3 present
in the soil at any one time. The second technique investigated was the in-
hibition of the nitrification process in soils by treatment of fertilizer
with a specific microbicide. This method would delay the conversion of NH^
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to N(>3. The third method was the use of slow release or slowly soluble
nitrogen source which should limit the amount of NH^ and NOg which is pre-
sent in the soil at any time. Also investigated was the timing of applica-
tions of various nitrogen sources prior to planting on the movement of N03
through the soil.
To determine the effect excessive rainfall has on the loss of fertil-
izer nitrogen in runoff waters, a grassland watershed was fertilized and the
runoff water monitored for N03« Movement of N03 into shallow groundwater
aquifers in the watershed was also investigated.
Nitrate movement through a soil was quantitated by using 5 lysimeters
to collect percolating soil water. The lysimeters were fertilized with 3
different sources of nitrogen and the percolating water was collected
throughout the year and analyzed for NH^ and
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SECTION 2
RECOMMENDATIONS
The two most important factors to consider in relation to limiting the
loss of fertilizer nitrogen by leaching are the rate of application and the
time of application. Nitrogen should not be applied at rates exceeding eco-
nomic plant response. This is normally no more than what the plant can take
up from the soil in a 2-3 week period. The nitrogen should be applied as
near to the time of plant use as possible.
If it is necessary to apply more nitrogen than what the plant can take
up in a 2-3 week period it is advisable to apply the nitrogen at different
times. This is especially true for small grains and improved pastures.
Leaching losses are directly related to the amount of rainfall which
occurs. It is advisable not to apply high rates of nitrogen just prior to
an expected rainy period. Nitrogen should not be surface applied prior to a
high rainfall season. This can result in nitrogen being lost in runoff wa-
ter as well as leaching waters.
Nitrogen should not be applied between October and February whenever
possible. When fall or winter applications are necessary, a nitrification
inhibitor such as N-serve will reduce the amount of nitrogen being leach-
ed as N03» Slow release nitrogen sources such as sulfur coated urea are
also recommended when fall or winter applications are necessary. Whenever
possible an ammonium or urea source of nitrogen should be used rather than
a nitrate source. This is especially true for fall or winter applications.
Ammonium is not nearly as subject to leaching losses as nitrate.
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SECTION 3
CONCLUSIONS
1. The addition of a carbon source with fertilizer nitrogen was effective
in reducing the concentration of N03 in the soil solution by microbial im-
mobilization. However, the recovery of applied nitrogen by plants was not
increased and the amount of nitrogen lost by leaching was not appreciably
reduced.
2. A nitrification inhibitor, N-Serve, was found to be very effective in
reducing the amount of N03~N lost from leaching columns treated with am-
monium and the inhibitor. Forage yields of oats were increased slightly by
the addition of the inhibitor and the concentration of NC^ in the plant tis-
sue was reduced considerably.
3. In field studies, time of nitrogen application had a significant effect
on the amount of nitrate leaching in the soil. Generally 10-30% more nitro-
gen was found in soil profiles during the growing season when the fertilizer
was applied at the time of planting as compared to fall or winter applica-
tions. In addition, 2-3 times more nitrogen had leached below 60 cm by
June from the fall application as compared to applications at the time of
planting.
4. Slow release sulfur coated ureas (SCU) were effective sources for re-
ducing the amount of nitrate leaching. Although more nitrogen remained in
the upper part of the soil profile during the growing season with the use of
SCU*the yield of grain sorghum was not increased.
5. The nitrification inhibitor, N-Serve, was effective in maintaining fall
and winter applied nitrogen in the NIfy form for a substantial period of
time. Addition of N-Serve to the N source resulted in up to 307. less N03
leaching.
6. Runoff losses of nitrogen from fertilizer applied to a grassland water-
shed were insignificant. In 1974, 0.57. of the applied nitrogen was detected
in the runoff water and 3.6% of the 180 kg/ha applied in 1975 was detected
in the runoff water.
7. Concentrations of N03 in shallow wells located in the watershed ferti-
lized twice each year with 90 kg/ha of nitrogen were appreciable following
the initial rains following fertilization. Concentrations as high as 61
ppm N03-N were detected in the well waters.
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8. Lysimeter studies indicated that even though NO^-N concentrations as high
as 32 ppm were present in the effluent below 120 cm of soil the total amount
of nitrogen lost by leaching was low. Concentrations of N03-N generally
ranged from 0-3 ppm in the effluent from the lysimeters. The greatest leach-
ing losses (67,) occurred when CaONOg^ was applied to the soil. Leaching
losses from the application of 168 kg-N/ha as NH^Cl or SCU-20 ranged from
0.04 to 2.17. over a two year period.
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SECTION 4
MICROBIAL IMMOBILIZATION AND RELEASE
LABORATORY INCUBATION
Soil microbes require nitrogen in their metabolic processes. The nitro-
gen utilized by these microbes will be immobilized and not available to
plants or be free to leach through the soil. As the microbes slowly die and
their bodies decompose, the nitrogen again becomes available to plants. This
temporary immobilization of nitrogen by microbes provides a possible slow re-
lease source of nitrogen which would reduce the chances of it being leached
through the soil. Incorporating a carbon source with fertilizer nitrogen
should stimulate the microbial population in the soil and immobilize a con-
siderable amount of applied nitrogen. By proper timing of fertilization
with nitrogen mixed with a carbon source, nitrogen could become available to
growing plants at a rate sufficient to maintain maximum yeilds.
Procedure
One kilogram of Norwood silt loam soil was added to two liter plastic
containers. Nitrogen as Ca(N03)2 and sucrose were thoroughly mixed with each
soil as indicated in Table 1. Duplicates of each treatment were incubated at
19°C for 71 days at near field capacity. Soil samples of approximately 20
gms were taken from each container every 2 to 3 days with a cylindrical
probe. The moist samples were extracted immediately with 0.2 tl I^SO^ or were
frozen until they could be extracted. Nitrates were determined in the ex-
tract by the phenoldisulfonic acid method and ammonium by steam distillation.
Results
The microbial population in the soil which was stimulated by the addi-
tion of carbon and nitrogen did reduce the amount of soluble nitrate in the
soil. Figure 1 shows the amount of nitrate nitrogen in the soil when no
nitrogen or carbon was added (ck), and when 100 ppm of nitrogen as Ca(N03>2
was added (0:1). The amount of nitrate in solution at any time was much
greater when nitrogen was added than in the check treatment. The N03~N
concentration in the check sample ranged from 9 to 25 ppm. In the sample
receiving 100 ppm N, the NO--N concentration ranged from 38 ppm to 139 ppm.
The addition of carbon, as sucrose, reduced the soluble nitrate concen-
tration considerably, especially at the high rates of carbon (Fig. 2). The
addition of 500 ppm carbon (5:1) reduced the N03~N concentration to 60 ppm
after 2 days. The N03~N increased to 102 ppm after 8 days and decreased
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mg
N03-N
V
o-o
o
JO Check
10
70
80
Figure 1.
20 30 40 50 60
DAYS AFTER N APPLICATION
Nitrate-N concentration in Norwood silt loam soil incubated at 19°C for 71
days with or without addition of
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ppm
N03-N
00
100
10
20
30
4O
50
60
70
DAYS AFTER N APPLICATION
Figure 2.
Nitrate-N concentration in Norwood silt loam soil incubated at 19°C for
71 days after adding various amounts of carbon, as sucrose, and 100 ppm
N as Ca(N03>2.
80
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TABLE 1. RATES OF NITROGEN AND CARBON ADDED TO 1000 G. NORWOOD SILT LOAM IN
IMMOBILIZATION STUDY
Treatment
No.
1
2
3
4
5
6
7
8
9
10
Carbon*
(gms.)
0
0
0.5
1.0
3.0
6.0
0.5
1.0
3.0
6.0
Nitrogen*
(gms.)
0
0.1
0.1
0.1
0.1
0.1
0
0.0
0.0
0.0
C:N
Ratio
____
5:1
10:1
30:1
60:1
""
* Carbon added as sucrose and nitrogen added as
continually until it reached 35 ppm after 29 days of incubation and again in-
creased sharply. There appeared to be three cycles of high concentrations
followed by low concentrations. The same trend seemed to occur when the
carbon: nitrogen ratio of the soil amendment was increased to 10:1, although
the concentrations were slightly lower. When the ratio was increased to
30:1 or 60:1, the NOo-N concentration decreased from 55-86 ppm after 1 day
to less than 10 ppm after 8 days. The concentration remained below 10 ppm
for the remainder of the 71 days of incubation except for one sampling date
in which the concentration reached 12 ppm.
The addition of a carbon source with nitrogen fertilizers did reduce the
amount of nitrate in the soil solution. The availability of this nitrogen
to plants under leaching conditions was investigated under greenhouse con-
ditions.
PLANT UPTAKE AND LEACHING LOSSES FROM MICROBIAL IMMOBILIZED NITROGEN
The objective of this experiment was to determine if microbial immobili-
zation of nitrogen could be utilized as an effective means of reducing the
leaching of nitrates while maintaining optimum yields.
Procedure
Lakeland sand was placed in 15 cm diameter polyvinyl chloride (PVC) col-
umns to a depth of 27.5 cm. The columns had sealed bottoms with a drain
for effluent collection. The columns were leached with sufficient distilled
water until no nitrate was present in the effluent. Nitrogen and carbon
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were surface applied on May 11,1973, at the rates indicated in Table 2.
There were 3 replications for each treatment. Nitrogen was applied as
Ca(N03)2 at a rate equivalent to 224 kg-N/ha. Carbon was supplied as either
sucrose or motor oil. The sucrose analyzed 37.6% carbon and the oil 83.4%
carbon. After the carbon sucrose and nitrogen were applied, they were cover-
ed with an additional 2.5 cm of soil to give a total depth of 30 cm.
TABLE 2. AMOUNT OF NITROGEN AND CARBON AS SUCROSE OR OIL, APPLIED TO LAKE-
LAND SAND COLUMNS PLANTED IN SUDAN GRASS
Treatment
No.
1
2
3
4
5
6
7
8
9
10
Carbon
Source
P^B
sucrose
sucrose
sucrose
sucrose
oil
oil
oil
oil
Carbon
(gins.)
0.0
0.0
2.05
5.10
12.30
24.60
2.05
4.10
12.30
24.60
Nitrogen
(gins.)
0.0
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
C/N
Ratio
__
5:1
10:1
30:1
60:1
5:1
10:1
30:1
60:1
The pots were allowed to incubate 14 days in a greenhouse maintained be-
tween 20° and 30°C. On May 24, 1973, sweet sudan grass (Sorghum vulgare
sudanenese) was planted at the rate of 40 seeds per column. Potassium, phos-
phorus, and zinc were applied to each pot at rates equivalent to 224, 112,
and 2.2 kg/ha, respectively, on June 4, 1973. The sudan was replanted on
June 11, 1973, due to poor germination at the high rates of applied carbon.
Water was applied at the rate of 5 to 7 cm per week as required to ob-
tain leaching. Leachate was analyzed for nitrate and ammonium after total
volume of leachate was recorded.
Forage yields were harvested on July 2, August 14, October 1, and No-
vember 7, 1973. Phosphorous, equivalent to 112 kg/ha,was applied on July 25,
1973, and on August 3, 1973, K, P, and Zn were again applied to each pot at
the same rates as the initial application. To correct a nitrogen deficiency
evidenced in the second cropping, nitrogen was again applied on September 5,
1973, to the nitrogen treated pots at. a rate equivalent to 224 kg-N/ha as
Ca(N03)2« Following the final forage harvest, soil samples were taken from
each pot and root weights were obtained. Root yields were obtained by re-
moving the entire soil and placing it on a screen table and washing the soil
from the roots. The forage and roots were dried at 55°C. Total nitrogen
was determined in the forage and root tissue by Kjeldahl digestion and dis-
tillation.
10
-------
Results
The high rates of sugar and oil restricted germination after the 14 day
incubation period. Seedlings were removed from all treatments and sorghum
replanted 32 days after applying carbon and nitrogen.
The cumulative losses of nitrate-N in the drainage effluents are shown
in Figures 3 and 4. The addition of carbon with the nitrogen fertilizer
did tend to reduce the amount of nitrates lost in the leaching during the
first 60 days. Whereas, when sucrose was added to give C/N ratios of 5:1
and 10:1, the amount of nitrogen lost, respectively, was only 65 and 93% as
much as when no sucrose was added. More nitrates were lost at the 30:1
C/N ratio than when no carbon was added. This could be caused by a high
osmotic pressure of the solution caused by the addition of sucrose which
limited the buildup of a suitable microbial population. More nitrates ap-
pear to have been lost at the 30:1 C/N ratio than when no carbon was added.
The high loss shown in Figure 3 is the result of one replication having an
extremely high effluent concentration. The other two replications of the
30:1 treatment had leaching losses similar to the 60:1 treatment.
Forty-one grams of nitrogen were reapplied to the pots 96 days after the
initial application. The nitrate in the effluent increased sharply. How-
ever, the amount lost from the 30:1 treatment was much less than from the
treatment receiving no sucrose. The reduction in nitrate loss over the 117
day growing period by the addition of sucrose was 22, 5, 7, and 21% by the
5:1, 10:1, 30:1, and 60:1 treatments, respectively.
The addition of oil as a carbon source appeared to decrease nitrate
leaching similar to sucrose. After the initial application of nitrogen and
carbon, the low C/N ratio applications caused less loss of N than the higher
ratios (Fig. 4).
Nitrate losses were reduced 6.5% by the C/N treatments of 5:1 and
10:1. The 30:1 and 60:1 treatments both increased the amount of N loss over
the treatment receiving no carbon. After the second addition of nitrogen,
all carbon treatments reduced nitrate leaching. It appears that the detri-
mental effect of the high rates of oil on the microbial population has been
overcome after being in the soil for 96 days prior to the second application
of nitrogen. The reduction in nitrate leaching caused by the addition of
oil and two nitrogen applications was 50, 19, 26, and 9% for the 5:1, 10:1,
30:1, and 60:1 treatments, respectively.
The addition of carbon did not affect forage yields of the sudan grass
except at the higher levels of added carbon. The addition of carbon to
give a C/N ratio of 5:1 appears to increase yields of the first harvest
(Table 3) for both the sucrose and oil treatments. The first forage harvest
indicated that the carbon treatments at the C/N ratios of 30:1 and 60:1 had
a detrimental effect on plant growth. However, the second, third, and fourth
harvestsdid not indicate a reduction in yield due to the large addition of
carbon. The total yields of the four harvests were not reduced by the ad-
dition of sucrose or oil except at the 60:1 level.
11
-------
90
8O
70
60
mg
50
40
30
20
10
SUCROSE
pa 30:1
i-j
/
IO 20 30 40 50 60 70 80 90 100 110 120
DAYS AFTER N APPLICATION
Figure 3. Accumulative loss of NC>3-N in effluent from Lakeland sand
columns treated with different ratios of carbon:nitrogen
as sucrose and C
12
-------
90,-
OIL
* 60:1
nna 30:1
-- 0:1
5:1
-* 60= I
DO 30:|
10 20 30 4O 50 60 70 80 90 100 110 120
DAYS AFTER N APPLICATION
Figure 4. Accumulative loss of NOo-N in effluent from Lakeland
sand columns treated with different ratios of carbon:
nitrogen as oil and
13
-------
TABLE 3. YIELD OF FORAGE FROM FOUR HARVESTS OF SUDAN GRASS GROWN ON LAKE-
LAND SAND AND TREATED WITH SUCROSE, OIL, AND Ca(N03)_.
N
Treatment
Source
C/N
1st
Harvest
2nd
3rd
4th Total
0.0
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.0
0.0
2.05
4.10
12.30
24.60
2.5
4.10
12.30
24.60
sucrose
sucrose
sucrose
sucrose
oil
oil
oil
oil
5:1
10:1
30:1
60:1
5:1
10:1
30:1
60:1
0.90
14.8
17.8
15.9
8.5
2.6
16.9
14.8
14.4
8.3
2.10
5.3
5.6
5.5
7.4
11.9
5.0
4.8
4.8
6.1
1.08
21.4
19.3
18.4
28.0
21.6
19.2
19.6
21.2
19.9
.47
2.8
2.6
2.5
4.1
2.6
2.8
2.6
3.3
.46
4.6
44.3
45.3
42.3
48.0
38.7
43.9
41.8
43.7
34.8
The uptake of nitrogen by the plants was not increased by the addition
of carbon (Table 4). The oil treatments actually reduced the amount of ni-
trogen taken up.
Although the addition of carbon did not stimulate forage production, it
did increase the amount of roots produced. The higher rates of carbon, gen-
erally, produced more roots than the lower rates (Table 5). The yield of
roots was increased by 198% in the case of the 60:1 sucrose treatment. The
roots of the plants receiving the higher carbon treatments appeared to con-
tain more of the total nitrogen taken up, even though they had a lower nitro-
gen content.
Microbial Immobilization of nitrogen did tend to decrease the amount of
NO^ movement through soils, although it did not increase plant response or
nitrogen uptake. It does not appear that this technique would be very prac-
tical for reducing the amount of nitrate leaching in soils.
14
-------
TABLE 4. NITROGEN UPTAKE BY FOUR HARVESTS OF SUDAN GRASS GROWN ON LAKELAND
SAND TREATED WITH SUCROSE, OIL, AND Ca(NO ) .
Treatment
N
&
0.0
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
C
luo
0.0
0.0
2.05
4.10
12.30
24.60
2.05
4.10
12.30
24.60
Source
sucrose
sucrose
sucrose
sucrose
oil
oil
oil
oil
C/N
5:1
10:1
30:1
60:1
5:1
10:1
30:1
60:1
1st
14
216
261
213
106
50
178
168
158
111
Harvest
2nd
12
28
32
30
33
55
26
24
28
29
3rd
mr. V
mg N
14
167
108
153
170
195
147
143
156
114
4th
4
25
23
24
30
24
23
24
29
23
Total
44
436
424
420
339
324
374
359
371
277
TABLE 5. YIELD AND NITROGEN CONTENT OF SUDAN GRASS ROOTS GROWN IN POTS OF
LAKELAND SAND TREATED WITH SUCROSE, OIL, AND
Treatment
N
0.0
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
0.41
C
0.0
0.0
2.05
4.10
12.30
12.30
24.60
2.05
4.10
12.30
Source
__
sucrose
sucrose
sucrose
sucrose
sucrose
oil
oil
oil
C/N
__
^_
5:1
10:1
30:1
30:1
60:1
5:1
10:1
30:1
Yield
gms.
4.7
32.8
34.6
43.6
45.4
45.4
65.0
40.5
33.5
32:3
Nitrogen
mg.
26.4
165.6
197.3
250.1
179.3
179.3
314.1
214.8
185.6
189.9
%
.56
.50
.57
.57
.39
.39
.48
.53
.55
.59
15
-------
SECTION 5
NITRIFICATION INHIBITORS
Nitrate is the water soluble form of nitrogen most prevalent in soils
and is subject to leaching. Ammonium, which is also very prevalent in soils,
is seldom leached in soils due to its cationic naturei but is readily taken-
up by plants. However, ammonium is readily nitrified in agricultural soils
to nitrate which can be lost by leaching. Nitrification inhibitors, which
would limit or prevent the conversion of ammonium to nitrate, should be very
effective in preventing leaching losses of nitrates.
This study was undertaken to determine if N-Serve, 2-chloro-6(trichloro-
methyl)-pyridine, a nitrification inhibitor produced by the Dow Chemical Com-
pany, would be effective in restricting the nitrification of ammonium and
thereby limiting -the movement of nitrogen in soils under greenhouse and field
conditions.
PROCEDURE
Soil columns 25 cm in diameter and 45 cm in depth were used. Each col-
umn contained 22 kg of Norwood silty clay loam soil. Drainage outlets were
placed in the bottom of each column for collection of effluent samples.
Treatments were applied in triplicate as shown in Table 6. The check
received no nitrogen or N-Serve while the calcium nitrate and ammonium sul-
fate treatments were applied at the rate of 400 kg-N/ha in a band 5 cm be-
low the soil surface and oats (Avena sativa) were planted in two rows, one
on each side of the fertilizer band on February 8, 1973. Twenty-five seeds
were planted in each row. A total of 1.96 g N was applied to each column.
Calcium sulfate was applied with the calcium nitrate to equal the amount of
sulfate added in the ammonium sulfate. N-Serve was applied as a percentage
of total nitrogen applied, and mixed with the ammonium sulfate just prior to
application. Phosphorus and potassium had been mixed into the top 10 cm at
the rate of 44 kg P/ha as triple super phosphate and 166 kg K/ha as muriate
of potash. The plants were grown in a greenhouse.
Two different moisture regimes were maintained throughout the experi-
ment. Periodic weights were taken on the columns to determine their moisture
status. Particle size distribution was determined by the Bouyoucos Hydro-
meter Method. Moisture release characteristic curves were determined using
the pressure plate technique. The high moisture treatment received water
whenever the weight of the soil was equivalent to that at a 1 bar moisture
16
-------
TABLE 6. NITROGEN TREATMENTS APPLIED AT THE RATE OF 400 KG/HA PRIOR TO
PLANTING OATS.
Treatment Nitrogen Source
1
2
3
4
5
Check
Ca(N03)2
(NH4)2S04
(NH4)2S04
(NH4)2S04
+0.5% N-Serve*
+1.0% N-Serve*
* N-Serve was added as a percentage of the total nitrogen applied.
tension. The low moisture received water whenever the moisture tension drop-
ped to 15 bar moisture tension. Water was applied to above field capacity
to insure some degree of leaching and collection of effluent samples. Ef-
fluent samples were analyzed for nitrate using the Orion specific ion ni-
trate electrode in a buffer solution as described by Milham, Awad, Paull, and
Bull (1970). Oats were harvested on March 6, April 9, and May 10. The first
two cuttings were clipped at a 5-cm height to induce tillering. The final
oat harvest included all above ground plant tissue.
Following the third cutting of oats, sweet Sudan grass (Sorghum vulgare
sudanense) was planted in the same manner as the oats. No additional fer-
tilizer was applied. Sudan was harvested on June 19, and all above ground
plant tissue was taken for yield and nitrogen analysis. Plant tissue was
dried in a forced draft oven at 55°C then ground to pass a 60 mesh sieve.
Nitrates were determined on the plant tissue using the same method as given
previously. Protein-N was determined by digesting plant tissue in concen-
trated sulfuric acid along with selenized Kjeldahl granules and determining
the ammonia by micro Kjeldahl.
Initial and final soil samples were dried at 55°C and ground to pass a
10 mesh sieve. Soils were extracted using 0.2 N K2S04 and 0.05 N H2S04 solu-
tion. Ammonium was determined by the Kjeldahl method and nitrates determin-
ed using the nitrate electrode method.
RESULTS
During this experiment, water was applied to the high moisture treat-
ment 8 times and 6 times to the low moisture treatment. Rainfall was un-
usually high during this period which accounted for more cloudy days than
would normally be expected during this season.
Figures 5 and 6 show the cumulative nitrate nitrogen collected in the
17
-------
Treatment
00
mg
N03
700
600
500
400
300
200
100
* T
* *
T
*
* T
V i
* 1 *
| * * * *
^
, i 1 -J
T NH4
NH4
^ NH4
Che<
NH4 *l.0% N-Serve
20
40
60
80
Figure 5.
DAYS AFTER M APPLICATION
Accumulative nitrate-N in effluent from columns of Norwood silty clay loam
maintained at high moisture level.
-------
mg
600 r
500
400
300
200
100
Total
* * 474
* T V 404
^C <+> ^ ^ 340
^ V 300
<* I
jr
M 159
»
N03
NH4
NH4*
NH +
Check
0.5%N-Serve
1.0 %N- Serve
20 40 60 80
DAYS AFTER N APPLICATION
Figure 6. Accumulative nitrate-N in effluent from columns of Norwood silty clay loam
maintained at low moisture level.
-------
effluent samples from the different treatments. Each point represents an
average over 3 replications. Under both moisture regimes total nitrate lost
in the effluent was highest under the nitrate treatment and lowest in the
ammonium treatments treated with N-Serve.
Nitrate-N lost from the high moisture treatment, where nitrate and am-
monium were applied, was 326 and 245 mg greater, respectively, than that col-
lected from the low moisture treatments. Nitrate loss was only slightly
higher in the high moisture treatment over the low moisture where ammonium
was applied with N-Serve. Where N-Serve was applied with ammonium, the
nitrate lost by leaching started to level off at 35 days while it took 68
days under the low moisture regime. In relation to the amount of total ni-
trogen applied, approximately 30% was lost in the leachate from the nitrate
treatment while only 10% was lost from the ammonium with N-Serve treatment
in the high moisture regime.
Figures 7 and 8 show the percent NO^ in the plant tissue (oats) for each
harvest and each moisture treatment. The nitrate and untreated ammonium
treatment was not significantly different in the first cutting and NO3 in the
plant tissue from these treatments was approaching 1.0% which is a very cri-
tical level and could be expected to cause death of animals feeding on such
forages. Nitrate accumulation was prevented by the addition of N-Serve to
the ammonium fertilizer. Although both the 0.5% and 1.0% N-Serve treatments
had low accumulation of NO^, the 1.0% N-Serve treatment was the only treat-
ment in which the nitrate-N was less than 0.5% in the plant tissue in both
moisture treatments. Nitrate in the plant should ideally be less than 0.5%.
Even in the second cutting nitrate-N in the plants grown on nitrate and am-
monium (untreated) contained between 0.4 and 0.5% NC^-N. The N-Serve treat-
ed ammonium again significantly reduced the accumulation on nitrate in the
plants.
As can be seen in the graph, nitrate in the plant tissue was reduced by
the higher rate of N-Serve in both moisture treatments. In the third har-
vest the values were very low and the accumulated nitrate remained highest
in the nitrate treatment and all values were slightly higher in the low mois-
ture treatment. Even though the nitrate in the plant was much lower where N-
Serve treated ammonium had been applied to the soil this did not reduce
protein production or yield.
Figures 9 and 10 show the yield data for each harvest under high and
low moisture. In the high and low moisture treatment the yield for the ni-
trate treatment was always lower than the ammonium with N-Serve treatment.
In the low moisture treatment there was no significant difference between
any of the nitrogen treatments. However, the total yield in the ammonium
with N-Serve treatments was slightly higher than where no N-Serve was ap-
plied. It should be pointed out that the reason for the large increase in
yield for the third harvest was due to taking all the above ground material
whereas in the first two harvests the plants were clipped at a 5-cm height.
Yield was considerably less under low moisture for all treatments in the
second and third harvest except for the check.
20
-------
ro
I.VJ
0.8
0.6
N03-N
0.4
0.2
-
-
(
:K
mm*
\
MG
mm*
*
NH
mm
'4
NH4
o
(a
#
2
i
CO
s
NH4
b
#
CO
i
r
Ck
JO
mm
3NH4
NH4
PI m4
^ ? NH4 NH4
3 ? N03 SP 1-
2 j Ck pf NH4 |S IS
Figure 7.
I 2 3
HARVEST
Nitrate in oat tissue from 3 harvests grown under high moisture conditions.
-------
N>
(O
1.0
0.8
0.6
N03-N
0.4
0.2
~
-
_
Ck
(1
H
JO
M
3
ry
IK
4
.
NH4
0
bi
*
i
M
i
i^
NO,
NH4
b
#
z
to
n
Ck
n
^
JH
MM
4
NH4
P
Ol
* NH4
** ^^
5 * n ^
Z IklLJ JPP »||_1
nin4 T o» ran ^
^ « A v^ f^*^
3 PL I 1 f~+ |5l
CK i i n IP!
HARVEST
Figure 8. Nitrate in oat tissue from 3 harvests grown under low moisture conditions.
-------
N>
60
50
40
grams
Forage
30
20
10
Ck
v*k _
n n
NH4
NH4
NO,
Ck
n
Ul
NH4
NH4 N"4
NH4
NO 3
Ck
I 2 3
HARVEST
Figure 9. Yield of oats from 3 harvests grown under high moisture conditions.
-------
N3
50
40
30
grams
of
Forage
20
10
NH4NH4NH4
3 r-n r-i
Ck
NH4NH4
NH4§z 3?
"V3 n ?-. rn
mill if
NO NH4
3 NH4 ^
Ck
n
PI
NH4
I
HARVEST
Ul
Figure 10. Yield of oats from 3 harvests grown under low moisture conditions.
-------
Percent protein was not significantly different among nitrogen treat-
ments in either moisture regime. The check had significantly lower protein
in all harvests. Percent protein was higher in all treatments except the
check of the third harvest in the low moisture treatment as compared to the
third harvest of the high moisture treatment.
The efficiency with which nitrogen was utilized to synthesize protein
is illustrated in Figure 11 for all treatments. Efficiency was 10% higher
for all the ammonium treatments than the nitrate treatment. The average
percent protein is much higher in the low moisture treatment because percent
protein was similar or slightly higher in certain harvests than that in the
high moisture. In this graph it would seem that ammonium without N-Serve
would be just as efficiently used. However, it should be emphasized that this
treatment lost more nitrate in the effluent and had higher concentration of
nitrate in the plant tissue than did the ammonium with N-Serve.
Sudan grass was planted on May 15, 1973, to determine if any residual ni-
trogen remained in the soil. No additional fertilizer was applied. Moisture
treatments were the same as when oats were grown. All of the above ground
forage was harvested on June 19, 1973. During this period, nitrate in the
effluent was below the level of detection for most samples and not signifi-
cant in the samples that were recordable. In the high moisture treatment, the
yield in all treatments was not significantly different from the check. Pro-
tein nitrogen and nitrate nitrogen was also extremely low and not signifi-
cantly different from that found in the check. In the low moisture treatment,
there seemed to be more residual nitrogen remaining after the final oat
harvest.
The nitrogen balance sheet is given for the high and low moisture in
Table 7 and 8, respectively. Nitrogen analysis is not recorded for the su-
dan phase in the high moisture treatment because none of the values were
significant enough to report. The values reported in each category are aver-
ages over 3 replications minus that found in the check.
In the high moisture treatment, the nitrate lost in effluent under the
nitrate treatment was perhaps the most striking disadvantage of the nitrate
application. The nitrate lost in the ammonium without N-Serve treatment was
also considerable. This was true for both moisture treatments. However,
the nitrate and ammonium treatments alone lost almost half as much nitrate
in the low moisture treatment.
Total nitrate accumulated in the plant was also higher where nitrate
was applied in the high moisture treatment while nitrate was slightly high-
er for the ammonium without N-Serve treatment under low moisture. In both
moisture regimes addition of N-Serve decreased the amount of nitrate in the
plant tissue.
Another important aspect of this study was to find that a higher per-
centage of nitrogen was utilized for protein nitrogen. The nitrate treat-
ment was lowest followed by ammonium alone. Both N-Serve treatments gave
the highest totals in both moisture treatments.
25
-------
to
%N
IN
PLANT
TISSUE
3.0
2.5
2.0
1.5
LOW *
MOISTURE
HIGH
MOISTURE
* NO 3
NH4
^ NH4*0.5%N-Serve
NH4+ I.O%N-Serve
20
30
40
50
RATIO FORAGE
g N APPLIED
Figure 11. Nitrogen efficiency nomogram of protein nitrogen in oats grown
under different moisture conditions and nitrogen sources.
-------
TABLE 7. NITROGEN BALANCE SHEET FOR OATS GROWN UNDER HIGH MOISTURE
TREATMENT.
Treatments
NH4
+0.5%N-S
NH4
+0.5%N-S
NH4
+1.0%N-S
mg
Effluent N03-N 608
Plant (oats) N03-N 93
Protein N (Oats) 957
467
95
1082
169
76
1172
197
50
1153
TABLE 8. NITROGEN BALANCE SHEET FOR OATS GROWN UNDER LOW MOISTURE TREATMENT.
Treatments
N03
NH4
NH4
+0.5%N-S
NH4
+1.0%N-S
mg
Effluent N03-N 316
Plant (Oats) NOo-N 127
Protein N (Oats) 861
Plant (Sudan) NO,-N 3
Protein N (Sudan) 41
Total N recovered as
Protein N 902
245
78
1109
1
19
1128
179
72
1111
2
31
1142
141
62
1107
5
83
1190
These results indicate that nitrification inhibitors could possibly re-
duce the amount of nitrate leaching through soils under field conditions.
27
-------
SECTION 6
TIMING AND SOURCE OF NITROGEN APPLICATION
Field plots were established in the fall of 1973 to determine the effect
timing of applying nitrogen fertilizers has on the uptake of nitrogen by
grain sorghum. Fertilizer was applied as much as five months prior to plant-
ing. The properties of readily soluble and slowly soluble nitrogen sources
were utilized to determine the effect these sources have on the movement of
nitrates through the soil. The effectiveness of a nitrification inhibitor on
preventing the movement of nitrogen through the soil was also determined.
PROCEDURE
The field plot locations were established on two soil types, Houston
Black clay (Udic Pellustert) and Norwood silt loam (Typic Udifluent) . Plots
established on Houston Black clay were located at the Blackland Research
Center near Temple, Texas* Norwood silt loam plots were initiated on the
Brazos River flood plain at the Texas Agricultural Experiment Station re-
search farm near College Station, Texas. Overall size at each experiment
location was 0.57 ha and consisted of 231 plots. Plots were arranged in a
randomized block design with individual plots being 4.0 m by 6.1 m. Plots
consisted of 4 rows.
The year prior to initiation of this experiment, corn (Zea mays) was
planted on the College Station location to eliminate the first year effect of
cultivation. Prior to this time, this area had been pasture. The beds were
not significantly disturbed during the entire course of the experiment.
The Houston Black clay location had been in a 3-year rotation for many
years. The usual rotation was grain sorghum (Sorghum vulgare) followed by
cotton (Gossypium hirsutum L.) followed by winter oats (Avena sativa) .
Previous crop grown on this location Immediately prior to the establishment
of this experiment was winter oats. Following incorporation of the winter
oat residue by discing, the land was bedded on 100- cm centers. The beds
received only a minimum amount of disturbance during the experiment .
Two readily soluble N fertilizers, (N^^SO^ and urea, and two slowly
soluble N fertilizers, sulfur-coated urea-20 (SCU-20) and sulfur-coated
urea-30 (SCU-30), were selected to determine what effect N source might have
on N03~N movement. The units 20 and 30 refer to the percentage of N which
dissolves in hot water (38°C) during a 7-day incubation period. These fer-
eilizers were applied in a band approximately 15-cm below the soil surface.
A tractor powered, conveyer-belt type fertilizer applicator was employed to
28
-------
place fertilizer below the center of the bed. This resulted in the band
being 5 to 10 cm below seed placement depth. Rate of application was 134
kg-N/ha with individual plots receiving only one application per year.
Fertilizer applications were made monthly, if weather permitted, starting in
October of each year and continuing through March. The N sources which were
applied and dates of application are shown in Table £ Fertilizer placement
on the March application date (planting date) was not directly in the center
of the bed. Placement was 10 cm to the side of the bed center. Grain
sorghum was planted immediately following N application. Sidedress treat-
ments, in which one-half of the N was applied at the time of planting, were
also made using this placement location. The second one-half of the side-
dress applications, which were made just prior to the boot stage of the grain
sorghum, were subsurface band applied, approximately 5 cm deep and 25 cm to
the side of the plants. To evualuate whether nitrifying or denitrifying
conditions exist at lower depths in these soils during winter months, a deep
placement of (NH4>2S04 with and without N-Serve was made approximately 25 cm
below the top of the beds at each application time. By applying these
fertilizers monthly, an evaluation was made of the effect timing of applica-
tion had on each N source.
A nitrification inhibitor, 2-chloro-6 (trichloromethyl)-pyridine, (N-
Serve), was evaluated to determine its effectiveness in retarding nitrifica-
tion under field conditions. Each N source was applied with and without an
N-Serve treatment (Table 10). To treat the fertilizer, N-Serve was mixed at
a rate equilvalent to 170 of the N content. N-Serve was mixed with the fert-
ilizer one day prior to actual application of each fertilizer.
Grain sorghum (Sorghum vulgare) was planted each year at both locations.
Table 11 lists the dates and activities related to the management of the
crop during the growing season. Top Hand (Conley Seed Company), at 9.4
kg/ha, was the grain sorghum variety planted on April 3, 1974, at the College
Station location. Excel 606 was planted at the Temple location at 9.6 kg/ha
on March 21, 1974. At planting, propazine was applied to assist in weed
control. Each location was cultivated twice during early to midgrowth
stages. In 1975, Pioneer 846 was planted on both locations at 7.9 kg/ha.
The planting date for College Station was March 12 while the date for Temple
was March 25. Propazine was again applied and followed by cultivation as
needed. Planting and cultivation was accomplished using conventional farm
equipment.
As sorghum plants approached the boot stage, tissue samples were taken
to determine protein content. This was accomplished by taking the entire
above ground portion of two plants from each plot. Samples were dried at
55°C, then ground to pass a 30 mesh sieve. A 0.5 g subsample was then
digested in sulfuric acid for protein N content (Jackson, 1958). The
digested samples were distilled by a micro-Kjeldahl unit, into boric acid
which was later back-titrated with standardized sulfuric acid. Crude protein
calculations were made by multiplying N content by 6.25.
Grain yield data were collected to determine efficiency of each treat-
ment. When moisture content of the maturing grain reached a level below 14%,
two rows, 3.35 m long, were hand harvested from each plot. Heads vere placed
29
-------
TABLE 9. DATES THAT VARIOUS FERTILIZER-N SOURCES* WERE APPLIED TO THE
HOUSTON BLACK CLAY AND NORWOOD SILT LOAM EXPERIMENT LOCATIONS.
Houston Black clay
Norwood silt loam
1973-1974
November 16
December 19
February 13
March 21 (at planting)
March 21 (%) +
June 6 (%)
1974-1975
October 18
November 19
December 20
February 21
March 25
March 25 (%) +
May 19 (%)
November 19
December 17
February 18
April 3 (at planting)
April 3 (%) +
May 22 (*)
October 18
November 19
December 20
February 21
March 12
March 12 (%) +
May 20 (%)
(1^4)2804, urea, sulfer-coated urea-20 and sulfur-coated urea-30
TABLE 10. FERTILIZER TREATMENTS APPLIED AT THE HOUSTON BLACK CLAY AND
NORWOOD SILT LOAM EXPERIMENT LOCATIONS.
Treatments
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Urea
Sulfur-coated urea (SCU-20)
Sulfur-coated urea (SCU-30)
(NH4)2S04 + N-Serve
Urea + N-Serve
SCU-20 + N-Serve
SCU-30 + N-Serve
(NH4)2S04 (deep placement)
(NH4)2S04 (deep placement)
Control
N-Serve
30
-------
in burlap bags and stored until thrashed. At this time, seed weights were
taken for yield calculations and subsamples for protein analysis were taken.
Monitoring of NO^-N movement through soil profiles was accomplished by
taking soil core samples. Houston Black clay samples were taken to a depth
of 120 cm, while Norwood silt loam samples were taken to 150 cm. A hydrau-
lically powered 5-cm diameter core tube was used to take the samples. Each
soil core was sectioned into the following increments: 0-15 cm, 15-30 cm,
30-60 cm, 60-90 cm, 90-120 cm. Each subsample was placed in individual paper
bags for drying. Two soil cores were taken from each plot. The 5-cm soil
core was taken directly through the center of the bed. This resulted in
sampling the area immediately in and below the fertilizer band. Even though
only 134 kg-N/ha was applied the concentration of N in the core sample was
considerably larger. This does not indicate that N throughout the soil pro-
file is as concentrated as the area near the band.
Initial soil samples were taken at random over both locations prior to
initiation of the treatments. Table 12 contains soil sampling dates.
As the soil samples were collected, they were placed in small paper bags
and dried at 55°C in a forced air oven as soon as possible. There were times
during the spring sampling period when enough ovens were not available to
dry all the samples immediately. To alleviate this problem, the remaining
samples were allowed to air dry under a high speed fan. Outdoor environ-
mental conditions were such the samples dried within 12-24 hours.
After drying, the soils were ground to pass a 20 mesh sieve. A 40.0 g
portion of each sample was extracted with 50 ml, of 0.2 N K2S04. The samples
were placed on a mechanical shaker for 30 minutes before being filtered
through a 10-cm Buchner funnel containing Whatman 42 filter paper. The
extracted solution was immediately refrigerated to 2°C to await further
analysis.
Nitrate N determinations were made on all soil samples using a modifi-
cation of the phenoldisulfonic acid (Bremner, 1965) method. Rather than
drying aliquots of the extracts in a beaker over a hot plate, as described in
the original procedure, the aliquots were dried in a forced draft oven at
55 C overnight. Further investigation revealed temperatures as high as 120°C
could be used to speed up drying time without causing loss of N03-N. Drying
at 120 C allowed extract aliquots to be dried directly in 100 ml volumetric
flasks. This permitted the omission of several time consuming transfer
steps.
After addition of the phenoldisulfonic acid to the dried extract in the
volumetric flasks, a small amount of distilled water was added to generate
heat. The color was developed by making the solution basic with 1.2 N KOH
and bringing to volume. The colorimetric determination was made using a
Spectronic 20 at a wavelength of 420 mu.
Ammonium N concentrations were determined on all soil profiles to a depth
of 60 cm during the winter sampling periods. At this time, NH^-N concentra-
tions were much higher than during the spring sampling period. After a
31
-------
TABLE 11. ACTIVITIES AND DATES RELATED TO GRAIN SORGHUM GROWN ON TREATED PLOTS TO MONITOR N
EFFICIENCY.
Activities
Planting: Grain sorghum was planted.
Tissue samples: Plant tissue samples were
taken at pre-boot to determine protein
content.
Harvest: Yield data was collected and sub-
samples taken for protein analysis.
Date Houston Black Slay
1974
1975
1974
1975
1974
1975
March 21
March 25
May 21
June 4
July 22
August 8
Norwood silt loam
April 3
March 12
June 7
May 21
August 6
July 23
u>
Ni
TABLE 12. DATES SOIL SAMPLES TORE TAKEN FROM THE HOUSTON BLACK CLAY AND NORWOOD SILT LOAM EXPERIMENT
AREAS, AND THE VARIOUS FERTILIZER TREATMENTS SAMPLED.
Houston Black clay
Sampling dates Treatments sampled *
Norwood silt loam
Sampling dates Treatments sampled *
1974: Feb. 7
1975: Jan. 21
1974: May 22
1975: June 6
Winter
Nov., Dec.
Oct., Nov., Dec.
Spring f
1974: Feb. 7
1975: Jan. 27
1974: June 4
1975: May 21
Winter
Nov., Dec.
Oct., Nov., Dec.
Spring f
* All treatments applied at the application periods indicated were sampled.
t At this sampling, all application periods and treatments were sampled.
-------
complete check of several profiles sampled in the spring, it was determined
NH^-N needed to be run on only the upper 30 cm. The deep placement treat-
ments were analyzed for NIfy-N to a depth of 60 cm during every sampling
period.
To determine NH^-N concentration (Bremner, 1965), a 10 ml aliquot of the
extracted solution was added to a micro-Kjeldahl unit (Labcon Co.)- Five ml
of 10 N NaOH was added to raise the pH of the distilling solution. Distil-
lation was allowed to continue until approximately 20 ml of the distillate
had been collected in a boric acid-indicator solution. The resulting solu-
tion was then titrated with standardized sulfuric acid.
An analysis was made to determine urea concentrations remaining in the
sulfur-coated prill in the SCU-20 and SCU-30 treatments. This was accom-
plished following Keeney and Bremner's (1967) procedure for urea determina-
tion. The extracted urea was hydrolized by urease to NH^-N. The Ntfy-N was
determined by the above described micro-Kjeldahl procedure.
RESULTS
Soil core samples were taken periodically to determine the relative
amounts of N03~N leaching. Two soil cores were obtained from each plot
during each sample period. These cores were taken through the center of the
bed. Since the fertilizer was band applied, the core obtained was of the
soil directly above and below the applied N. This resulted in very high N
concentrations in the core segments that were from the immediate area of the
band. This sampling technique will give an .indication of the amount of N
that had leached from the band into the lower depths of the profile, but will
not give an estimate of the total amount of N in the entire profile of the
soil. The measurements obtained should indicate the maximum NC>3-N concen-
tration in the soil profile.
To determine the inherent N level of the plot areas, initial samples
were taken to a depth of 150 cm at the College Station location and 120 cm
at the Temple site. The College Station samples were collected November 20,
1973, while the Temple samples were taken November 23, 1973. Eleven soil
profiles were analyzed at each site. The average of these determinations is
given in Table 13. The exchangeable N level for the 150-cm profile at
College Station was 45.9 kg-N/ha. Ammonium N constituted 167. of the N
present. The maximum average N03-N level (2.5 ppm) occurred at the 0-15 cm
depth, while the minimum (1.3 ppm) occurred at the 60-90 cm depth. No NIty-N
was found below 30 cm. Above this depth only very small amounts of Nlty-N
(1.6 ppm) were detected.
The Houston Black clay site initially contained an average of 32.7 kg/ha
exchangeable N. The maximum average NOj-N concentration (2.1 ppm) occurred
at the 0-15 cm depth. The lower depths (60-120 cm) had a very limited amount
of N03-N present (0.9 ppm). The N03-N level for the 120-cm profile was only
20.8 kg-N/ha. The NH^-N concentration for the upper 60 cm of the profile
averaged less than 2 ppm. Below this depth no NH^-N was detected. The
fraction constituted 37% of the exchangeable N present.
33
-------
TABLE 13. AVERAGE INITIAL EXCHANGEABLE N CONCENTRATION FOR HOUSTON BLACK
CLAY AND NORWOOD SILT LOAM EXPERIMENT LOCATIONS.
Depth
(inches)
Houston Black clay *
N03-N NH4-N
Depth
(inches)
Norwood silt loam t
N03-N NH4-N
0
6
12
24
30
6
12
24
30
48
ppn,
2.1
1.4
1.2
0.9
0.9
1.8
0.9
1.2
0
6
12
24
30
48
6
12
24
30
48
60
2.5
1.6
1.5
1.3
2.3
1.6
1.4
1.6
Total kg-N/ha
32.7
45.9
* Sampled November 23, 1973
t Sampled November 20, 1973
Leaching and Nitrification During Fall and Winter
Houston Black Clay- 1974--
The various N sources were band applied, at 134 kg-N/ha, to a selected
group of plots on November 19, and to a second group on December 17, 1973.
The October application period was omitted due to adverse weather conditions
which occurred during that month. The treated plots were sampled February 8,
1974, to determine the degree of leaching and nitrification during the fall
and winter.
Relative amounts of exchangeable N are exhibited in Table 14.
Generally, plots treated with a readily soluble N source contained larger
amounts of exchangeable N. The only significant difference amoung sources
was between the readily soluble and slow release forms. Due to slow dissolu-
tion rate of sulfur-coated urea, substantial amounts of applied N had not
been released into the soil solution at the time of sampling. Although
samples were not analyzed for urea, it is evident that considerable amounts
of unhydrolyzed urea were present. This would explain low exchangeable N
levels found in plots treated with sulfur-coated urea.
34
-------
TABLE 14. TOTAL N03-N AND NH4-N IN 120-CM PROFILES OF HOUSTON BLACK CtAY
AFTER RECEIVING 134 KG-N/HA. SAMPLING DATE, FEBRUARY 8, 1974
(deep)
Average
Time of application
November
December
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N -Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-serve
NOs-N*
429
143
636
270
180
103
192
124
511
227
NH4-N
21
329
213
455
152
440
62
348
43
129
Sum
450
473
849
725
333
543
253
473
552
356
N03-N
267
67
220
99
136
180
156
63
217
67
NH4-N
167
22
76
31
38
87
78
124
190
110
Sum
431
90
296
130
174
268
234
187
408
177
281
179
501
147
92
239
Control
38
18
56
40
35
75
Average of six profiles consisting of five sampling depths
Amounts of exchangeable N present (Table 14) were significantly affected
by time of application. Average exchangeable N for November applied treat-
ments was 501 kg-N/ha while December treatments contained 239 kg-N/ha. No
apparent reason for the 53% decrease can be obtained from data collected.
Nitrate is the major form of N susceptable to denitrification. If deni-
trification caused the observed differences, then a major portion of the
November applied N should have been denitrified. One plausible explanation
why the November applied N was not denitrified could be it was immobilized
and was present in an organic form when the December applied N, which was
35
-------
nitrified, was subjected to denitrifying conditions. Another point to con-
sider is the effect of N-Serve. Losses in December treatments tended to be
greater when N-Serve was included. N-Serve decreased NC>3-N and increased
NH/-N. This factor would tend to indicate that denitrification was not the
major source of N loss.
As discussed earlier, volatilization could be involved in the N loss
that occurred. Ammonia is the major form of N lost in this manner. Since
N-Serve was highly active during December, addition of N-Serve could have
caused a substantial increase in N loss due to volatilisation. However, it
has also been reported (Jansson, 1958) that NH^-N is more readily immobilized
by microorganisms than N(>}-N. Since total N was not determined in these
soils this could not be verified.
Although N-Serve had little effect on amounts of exchangeable N present
at the February sampling of the November application, it did reduce the
amount of soluble N found in the December sampling. However, N-Serve was
highly effective in maintaining the N in the NH^-N form (Table 14). The
result of this highly significant effect is apparent in Table 15. When N was
maintained in the NHA-N form very little leaching occurred. This is evident
by observing relative amounts of N(>3-N below 60 cm in (NH/^SO^ + N-Serve
treatments. Average content of the latter treatment was 1.2 ppm while the
former contained 6.1 ppm N03-N.
When considering leaching, the readily soluble N forms exhibited the
greatest amount of leaching. The least amount of leaching occurred in the
sulfur-coated urea plots that were treated with or without N-Serve. The
latter treatments exhibited NC^-N levels at 60-120 cm depths very similar to
those observed in control plots.
Houston Black Clay-1975
During the second year of the study applications of fertilizer were made
October 18, November 19, and December 20, 1974. Each treatment again re-
ceived 134 kg-N/ha. The following January 21, 1975, soil cores were taken
to a depth of 120 cm on treated plots. In addition to N03-N and Ittfy-N
analysis, urea N was determined on samples from plots treated with sulfur-
coated urea.
The data collected during this time interval is very similar to the 1974
data. However, some differences were obtained and will be discussed.
Total exchangeable N values are listed in Table 16. Source of N had a
significant effect on resulting N values only when readily soluble sources
were compared. As previously discussed, differences were due to the dissolu-
tion rate of sulfur-coated urea. During 1974, no urea N analysis was per-
formed on soil samples obtained from the slow release treatments:; however,
in 1975, this analysis was made. There was no significant difference between
the dissolution rate of SCU-20 and SCU-30 during this sample period. There-
fore, they will be considered jointly. These results indicate that approx-
imately 54% of the urea N had not hydrolyeed from the sulfur-coated prills.
This percentage value is obtained by considering the initial concentration
of urea N in the fertilizer band and the area of the soil sampling tube.
36
-------
TABLE 15. CONCENTRATION OF N03-N IN PROFILES OF HOUSTON BLACK CLAY AFTER RECEIVING 134 KG-N/HA.
SAMPLED ON FEBRUARY 8, 1974
co
Depth
cm
Am Sul
Am Sul
+ N-s*
Urea
Urea
+N-s
SCU-20
SCU-20
+ N-s
SCU-30
SCU-30
+ N-s
Am Sul
(deep)
Am Sul +
N-s (deep) Control
Application date:. November 19,
0- 15
15- 30
30- 60
60- 90
90-120
48.6
90.4
14.4
4.6
7.7
21.2
28.2
4.6
1.5
1.0
135.8
105.8
17.7
2.7
0.5
43.1
48.7
11.0
1.8
1.5
42.2
27.1
3.2
2.1
0.4
8.3
14.3
2.3
1.4
0.8
41.0
33.6
4.8
0.8
1,4
1973
25.7
17.1
3.4
1.7
1.2
107.6
64.8
16.1
5.2
6.4
36.6
37.3
10.1
1.7
2.0
5,7
3.9
2.0
0.9
0.8
Application date: December 17,
0- 15
15- 30
30- 60
60- 90
90-120
72.1
31.1
5.3
1.2
1.2
8.5
11.6
3.4
0.8
0.7
45.4
28.9
9.7
0.6
1.0
10.7
11.4
7.9
1.5
1.5
30.6
18.1
3.5
1.5
1.5
58.1
10.5
2.8
, 1.7
1.3
40.1
20.7
2.7
0.9
0.6
1973
7.5
8.9
3.1
1.9
0.7
9.2
60.0
11.2
1.6
1.0
3.5
14.0
2.9
2.0
1.4
3.5
3.9
3.0
1.3
0.9
* N-s = N-Serve
-------
TABLE 16. TOTAL N03-N AND Nfy-N IN 120-CM PROFILES OF HOUSTON BLACK CLAY
AFTER RECEIVING 134 KG-N/HA. SAMPLED ON JANUARY 21, 1975*
October
Time of application
November
December
Treatment
Am Sul
Am Sul -f N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve
(deep)
Average
N03-N
478
123
391
131
183
85
259
235
498
120
250
NH4-N
0
102
0
73
34
21
18
91
0
49
39
N03-N
319
137
404
97
158
93
474
421
340
131
257
Nfy-N
34
73
3
31
5
73
18
124
14
66
44
N03-N
73
72
285
82
87
118
73
107
59
72
103
NH4-N
175
269
133
385
89
40
68
84
138
142
152
* The control for this sample date averaged 73.9 kg-N/ha
Since less N was released, it is reasonable to assume less exchangeable N
would be present in the soil solution at sampling time. The collected data
agrees with this assumption.
Nitrogen source influenced N03-N leaching. Urea and (NH4)2S04 were not
significantly different as an N source nor was SCU-20 and SCU-30, consequent-
ly, they can be considered jointly. By comparing N03-N leaching for the
readily soluble sources, a considerable difference is observed. In the
October applied readily soluble treatments, the soil below 60 cm contained
16.6 ppm N03-N while the slow release forms contained only 12.1 ppm (Table
17).
38
-------
The various times of fertilizer application had only limited effect on
resulting total exchangeable N levels per profile. The average of all treat-
ments applied in October is 289 kg/ha exchangeable N. November and December
treatments contained 301 and 255 kg/ha exchangeable N, respectively (Table
16). It is interesting to note the lowest average value obtained was from
the December applied treatments. This unusually low December value was also
observed in 1974.
Nitrate N leaching was influenced by time of application. Generally,
the longer the time interval, from fertilizer application to sampling, the
greater the amount of leaching. Maximum time of application effect was ob-
served on readily soluble sources not treated with N-Serve. These treatments
averaged 16.9, 12.2, and 7.0 ppm NOyN below 60 cm for October, November,
and December application periods, respectively (Table 17). When nitrifica-
tion was inhibited by addition of N-Serve or a slow release source was
applied, time of application did not substantially influence the amount of
NOg-N below 60 cm. Overall, December applied treatments exhibited the least
N03-N below 60 cm. This fact may be only indirectly releated to time of ap-
plication, since the total exchangeable N level of December applied treat-
ments was always lower than the other application dates.
N-Serve caused several significant effects on the N content and distri-
bution in the various profiles. Generally, the N-Serve effect was very simi-
lar to the results reported in 1974. Briefly, N-Serve decreased leaching and
decreased nitrification. In all cases, adding N-Serve to the fertilizer
treatment decreased the amount of NO-j-N present below 60 cm (Table 17). The
maximum N-Serve versus leaching effect was in the readily soluble treatments.
These sources applied in October, November, and December averaged 16.9, 12.2,
and 7.0 ppm N03-N below 60 cm, respectively. When these sources were treated
with N-Serve, respective N03~N levels were 11.9, 9.3, and 5.8 ppm. This is
a decrease in leaching of 30, 24, and 17%, respectively. When N-Serve was
included in sulfur-coated urea treatments, the decrease in leaching was not
as dramatic.
N-Serve effect on leachability can be directly related to nitrification.
In plots treated with (NH^JSO^ 90% of the exchangeable N present at sam-
pling was in the N03~N form. When N-Serve was included in this treatment
only 65% of the exchangeable N was as N03~N. When this source was applied
in October, no NH^-N was present at sampling. When N-Serve was included,
55% still remained in NH^-N. Other sources responded similarly. This data
indicated N-Serve was active as a nitrification inhibitor for the duration
of this test.
The addition of N-Serve to the readily soluble N sources resulted in
less exchangeable N being present at sampling. In the October and November
application periods, N-Serve decreased exchangeable N by 51 and 56%, re-
spectively, while in the December period, it increased exchangeable N by 20%.
This could be explained by the fact Nlty-N is more readily immobilized by
microorganisms as reported by Jansson (1958). This effect was not observed
in 1974. Another possible cause could be NH.-N volatilization. Since the
NH4-N was held in high concentration near the fertilizer band, volatiliza-
tion could have ocdurred. No data has been collected to substantiate this
39
-------
TABLE 17. CONCENTRATION OF N03~N AND NIty-N IN 120-CM PROFILES OF HOUSTON
BLACK CLAY ON JANUARY 21, 1975, AFTER RECEIVING 134 KG-N/HA
Treatment
and
depth
cm
Am Sul
0- 15
15- 30
30- 60
60- 90
90-120
Am Sul + N-Serve
0- 15
15- 30
30- 60
60- 90
90-120
Urea
0- 15
15- 30
30- 60
60- 90
90-120
Urea 4- N-Serve
0- 15
15- 30
30- 60
60- 90
90-120
SCU-20
0- 15
15- 30
30- 60
60- 90
90-120
SCU-20 + N-Serve
0- 15
15- 30
30- 60
60- 90
90-120
SCU-30
0-15
15- 30
30- 60
60- 90
October
N03-N
NH4-N
Time of application
November
N03-N
NH4-N
December
N03-N
BH4-H
11.0
31.7
59.5
20.1
14.5
2.5
4.4
11.5
6.2
8.5
9.0
16.6
48.5
19.5
13.7
3.6
3.9
9.7
8.7
9.5
4.3
7.8
17.0
13.7
7.5
1.5
1.5
6.5
6.5
6.0
8.2
10.3
26.2
17.2
0
0
0
ND
ND
44.7
2.0
1.2
ND
ND
0
0
0
ND
ND
34.4
0
0
ND
ND
13.0
2.8
0
ND
ND
9.9
0
0
ND
ND
6.9
0
0.8
ND
18.3
45.4
25.5
9.0
10.2
2.6
6.1
8.5
8.0
7.7
21.6
25.1
44.2
15.7
14.2
14.7
8.8
25.2
12.5
9.2
5.6
8.2
13.7
9.0
8.6
2.2
3.6
18.0
10.7
9.5
15.1
16.7
27.5
12.5
13.0
3.1
0
ND
ND
31.8
2.4
0
ND
ND
1.6
0
0
ND
ND
27.1
4.1
0
ND
ND
2.5
0
0
ND
ND
32.4
2.0
0
ND
ND
8.4
0
0
ND
7.4
2.2
4.0
3.5
5.2
3.4
2.4
4.5
4.0
6.1
18.2
3.9
38.5
12.7
6.7
3.0
2.1
4.0
5.5
7.7
3.9
2.2
5.5
6.0
6.5
2.3
12.2
5.5
7.5
8.2
4.4
2.0
4.2
4.5
82.5
0
0
ND
ND
86.7
40.1
0
ND
ND
62.6
0
0
ND
ND
171.2
10.5
0
ND
ND
42.2
0
0
ND
ND
18.7
0
0
ND
ND
27.8
0
2.1
ND
40
-------
Table 17. (Continued)
Treatment
and
depth
cm
SCU-30 (Continued)
90-120
SCU-30 + N-Serve
0- 15
15- 30
30- 60
60- 90
90-120
Am Sul (deep)
0- 15
15- 30
30- 60
60- 90
90-120
Am. Sul + N-Serve (deep)
0- 15
15- 30
30- 60
60- 90
90-120
Control
0- 15
15- 30
30- 60
60- 90
90-120
October
NC-3-N
10.
2.
5.
24.
16.
8.
2.
27.
70.
22.
13.
1.
3.
9.
10.
6.
0
1
1
3
1
7
2
5
5
2
0
3
4
7
5
5
NH4-N
ND
42.8
0
0
ND
ND
0
0
0
ND
ND
11.7
6.2
2.6
ND
ND
Time of application
November
N03
58
1
4
15
11
8
15
28
38
15
6
2
3
13
8
8
NO,-N
2T6
2.3
1.3
0.9
0.9
-N
.7
.8
.9
.8
.3
.0
.2
.6
.0
.7
.2
.2
.0
.0
.0
.2
NH4-N N
ppm-
ND
56.5
2.1
0
ND
ND
4.0
2.8
0
ND
ND
17.2
14.1
0
ND
ND
NH4-N
23.1
0.3
0.9
ND
ND
December
1
5
20
2
5
4
5
3
2
3
2
5
1
2
5
4
5
-N
.7
.0
.4
.1
.8
.0
.8
.7
.5
.5
.0
.7
.1
.5
.7
.2
NH4-N
ND
39.4
0
0
ND
ND
59.9
5.0
0
ND
ND
55.9
11.0
0
ND
ND
statement. However, it must be remembered the fertilizer N was applied
several centimeters below the soil surface. This N-Serve effect was not ob-
served in sulfur-caated urea treatments.
Norwood Silt Loam-1974
Fertilizer applications were made November 16 and December 19, 1973, on
the Norwood silt loam plots. The October application period was omitted due
to adverse weather conditions which prevented entrance into the plot area.
Treated plots were sampled to a depth of 150 cm on February 6, 1974.
The results obtained for the November and December application were
similar to those obtained from the Houston Black clay location during the
41
-------
same time interval. The effect of N source was not detectable except be-
tween readily soluble and the slow release forms. The readily soluble forms
resulted in higher exchangeable N (Table 18) levels in the profile. Also,
movement of N03-N to the lower depths of the profile (Table 19) was greater
for the readily soluble treatments.
Whether the N was applied in November or December did not affect the
amount of soluble N found in the profiles during February for the readily
soluble sources. There was somewhat more N03-N in the profiles fertilized
in November with the readily soluble forms not treated with N-Serve (Table
18). This is a result of a longer period for nitrification to occur.
When considering leaching, the concentration of N03~N at 60-90 cm was
greater in all the November treated plots as compared to control plots or
the December treatments (Table 19). This indicates some leaching of N03~N
to at least 90 cm had occurred in the 82 days prior to February 6. Concen-
trations of N03-N below 60 cm in plots fertilized in December were similar
to the control plots at similar depths. There was a slight increase in
N03-N concentration in the 30-60-cm depth. This signifies little or no move-
ment of N03-N below 30 cm between December 19, 1973 and February 6, 1974,
in the Norwood silt loam soil. This limited amount of leaching can be at-
tributed to the small amount of rainfall received in December and January.
During this period only 11.5 cm of precipitation fell. No substantial rain-
fall had been received since October, therefore, the soil was dry and when
precipitation did occur no runoff or deep percolation resulted.
In every N-Serve treatment, regardless of N source, N03~N concentrations
were lower than in non-treated plots (Table 18). For the November appli-
cation treatments, the N03-N level in the profiles treated with N-Serve
averaged 101 kg-N/ha for all sources. For the same application period, but
without the N-Serve treatments, the N03-N levels averaged 201 kg-N/ha. N-
Serve resulted in a 50% reduction in NO-j-N content and a corresponding 54%
increase in NH^-N. Movement of N to the lower depths of the profile (Table
19) was also reduced by the addition of N-Serve. However, since no sub-
stantial amounts of leaching occurred in any of the treatments, the difference
caused by N-Serve was not significant.
Norwood Silt Loam-1975
During the second year of the study, fertilizer applications were made
on October 18, November 19, and December 20, 1974. The following January
27, 1975, soil samples were taken to a depth of 150 cm.
The source of N, as has been the case in previous sections, exhibited
a significant effect only when the readily soluble and slow release sources
are compared. The readily soluble sources averaged 779 kg/ha of exchange-
able N while the slow release forms averaged 578. When the various sources
are compared as to leachability, (NH^^SO^ and urea leached more than sulfur-
coated urea. These differences are directly due to dissolution rate. The
slow release sources maintained less N in the soil solution thereby decreas-
ing the potential for N03-N leaching.
42
-------
TABLE 18. TOTAL N03-N AND NH.-N IN 150-CM PROFILES OF NORWOOD SILT LOAM ON
FEBRUARY 6, 1974, AFTER APPLYING 134 KG-N/HA ON NOVEMBER 16, 1973,
AND DECEMBER 19, 1973.
Time of application
November December
Treatment
N03-N
NHA-N
Sum
N03-N
NH4-N
Sum
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (dei
274
114
264
127
120
80
181
75
166
ep) 109
170
599
396
1210
1203
302
410
253
101
1826
444 153
713
660
1337
1323
382
591
328
267
1935
113
151
130
102
59
85
76
161
88
147
450
632
792
179
249
911
627
232
727
300
563
783
922
281
308
996
703
393
815
Average 151 647 798 112 495 606
Control 90 217 307 80 224 304
Much of the sulfur-coated urea remained in the undissolved prill as in-
dicated by the high N values found in 1974 (Table 19). Averaging the re-
sults of this sampling period indicates that 1,245 kg urea-N/ha was present
at sampling on January 27, 1975. This urea was apparently still in undis-
solved prills and was unavailable for hydrolysis.
Time of application influenced the amount of exchangeable N present
and the degree of leaching. The total exchangeable N (urea N included) pre-
sent in the 150-cm profiles is shown in Table 20. The treatments applied in
October, November, and December averaged 1,010, 1,416, and 895 kg-N/ha,
43
-------
TABLE 19. CONCENTRATION OF N03-N IN 150-CM PROFILES OF NORWOOD SILT LOAM WHEN SAMPLED FEBRUARY 6, 1974,
AFTER RECEIVING 134 KG-N/HA IN NOVEMBER AND DECEMBER
Depth
eta
Am Sul
Am Sul + N-s
Urea
Urea 4-N-s
SCU-20
SCU-20 + N-s
SCU-30
SCU-30 + N-s
Am Sul
(deep)
Am Sul -f
N-s (deep)
Control
Application date: November 16, 1973
0- 15
15- 30
30- 60
60- 90
90-120
120-150
38,5
17.8
8.4
11.8
4.0
8.8
11.9
12.8
5.2
3.2
2.5
2.1
21.6
37.7
13.7
8.4
3.6
3.1
5.4
10.4
7.1
6.3
4.4
2.5
9.6
13.4
6.7
3.3
3.2
1.9
2.8
5.5
4.3
2.7
3.3
3.2
19.5
22.8
7.2
4.6
3.6
3.9
19.5
22.8
7.2
4.6
3.6
3.9
4.6
15.0
13.9
5.5
3.7
4.1
5.1
9.8
5.5
2.7
3.2
5.2
4.0
8.4
5.3
2.9
2.6
3.1
Application date: December 19, 1973
0- 15
15- 30
30- 60
60- 90
90-120
120-150
27.3
16.6
4.5
3.7
2.0
1.9
8.6
7.3
3.9
2.8
5.4
5.1
28.3
17.4
3.4
2.4
2.5
2.3
18.7
14.5
6.4
2.8
2.0
1.2
9.8
10.2
3.3
3.6
3.3
2.9
2.8
4.2
2.9
2.8
1.7
2.3
10.2
7.3
2.8
2.8
2.8
1.8
5.0
5.9
3.8
2.9
2.4
2.1
8.8
20.0
7.9
3.4
3.6
6.1
9.0
4.6
3.6
2.4
2.0
5.0
5.1
6.9
3.8
3.5
2.8
1.8
-------
TABLE 20. TOTAL OF THE N03-N, NH4-N, AND UREA-N* IN 150-CM PROFILES OF
NORWOOD SILT LOAM ON JANUARY 27, 1975, AFTER RECEIVING 134 KG-N/HA
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N- Serve
SCU-20
SCU-20 + N- Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (de<
Time
October
562
465
737
771
1307
2535
2230
961
194
ep) 346
of application
November December
_ ___ _Vrr_\T /Vio _________
1230 739
781 690
981 837
814 737
2261 994
2607 927
2387 1624
2035 1104
540 783
521 519
Average
844
645
852
774
1520
2023
2080
1367
506
462
Average 1010 1416 895 1107
Control 87
* The presence of urea was determined on the SCU's only
respectively. Those fertilized in December contained 11% less than their
October counterpart and 37% less than those fertilized in November. The
1974 data also indicates the December application averaged significantly
less than the other application periods sampled in January. It is interest-
ing to point out the average exchangeable N level for the November and
December treatments sampled in 1974 was 702 kg-N/ha, while in 1975 these
sample plots contained an average of 1,155 kg-N/ha. This is an increase
of 60%. This indicates some of the N fertilizer applied the previous year
was still present in the profile in 1975.
45
-------
The relative amounts of leaching that occurred due to the various times
of application is demonstrated in Table 21. The October applied fertilizer
had moved a greater distance into the soil profile than those more recently
applied. To demonstrate this, one may compare the relative amounts of NC^-N
below 60-cm in the October and December applied urea treatments. The former
contained 8.8 ppm N03~N below 60-cm while the latter application period
averaged only 2.5 ppm.
The various concentrations of NIfy-N in the profiles indicate the effect
of N-Serve on the treatments. When N-Serve was not mixed with the N source,
the fraction of the exchangeable N that was in the NH.-N form at the time of
sampling was 16%, 32%, and 58%, respectively, for the October, November, and
December application dates. When N-Serve was included the respective NH^-N
percentages were 70, 71, and 70. This indicates the activity of N-Serve
was substantial even after being in the field for 101 days. By maintaining
the N mainly in the NH^-N form, N-Serve caused a significant decrease in
leaching in the treatments applied in October. This effect is exemplified
in the October applied (Nlfy^SO^ treatment which averaged 9.5 ppm N03~N
below 60-cm without N-Serve and 4.1 ppm with N-Serve. Since the amount of
leaching in the November and December applied treatments was limited, the
N-Serve affect was not apparent.
Leaching and Nitrification During Spring
Houston Black Clay-1974
Fertilizer applications were made at the Houston Black clay site on
November 16 and December 19 in 1973, and February 13, March 21, and as a
split application on March 21 and June 6 in 1974. The March applications
were made at the time the grain sorghum was planted. Soil samples were taken
on all treated plots May 29, 1974.
The influence of N source on exchangeable N contained in the various
profiles can be viewed in Table 22. Source effect is best illustrated when
considered independent of time of application. If viewed in this manner,
(NH/^SO^ and urea are insignificantly different in all respects. Compared
to these sources SCU-30 averaged 16% less exchangeable N present in the pro-
file at sampling. Sulfur-coated urea-20 averaged 57% less exchangeable N
present. This would be expected since it is the least soluble of the N
sources. The differences between SCU-30 and the readily soluble sources are
due to their respective dissolution rates. During the winter sampling, no
significant differences between SCU-20 and SCU-30 were observed. However,
during the May, 1974 sampling, a sizeable difference was disclosed. Ap-
parently the relative dissolution rates of these two slow release sources
differ only slightly during periods when the soil temperatures are low, but
become quite different during warmer weather. Since SCU-30 appeared more
similar to (1^4)2804 and urea than to SCU-20 (Table 22), one may conclude
the dissolution rate of SCU-30 was greatly enhanced by the warmer spring
temperatures. These statements of probable cause cannot be substantiated
since no urea analysis was performed on samples taken in 1974 to determine
the amount of N remaining in the sulfur-coated prills.
46
-------
TABLE 21. CONCENTRATION OF N03-N AND NH/pN IN 150-CM PROFILES OF NORWOOD
SILT LOAM ON JANUARY 27, 1975, AFTER RECEIVING 134 KG-N/HA
Time of application
October November December
Depth
cm
Am Sul
0- 15
15- 30
30- 60
60- 90
90-120
120-150
Am Sul + N-Serve
0- 15
15- 30
30- 60
60- 90
90-120
120-150
Urea
0- 15
15- 30
30- 60
60- 90
90-120
120-150
Urea + N-Serve
0- 15
15- 30
30- 60
60- 90
90-120
120-150
SCU-20
0- 15
15- 30
30- 60
60- 90
90-120
120-150
SCU-20 + N-Serve
0- 15
15- 30
30- 60
60- 90
N03-N
NH4-N
N03-N
NH4-N
N03-N
NH4-N
ppm
73.3
79.9
25.0
12.6
7.2
8.6
7.7
32.1
11.2
4.8
4.1
3.3
132.3
83.4
23.6
7.3
8.9
10.2
13.9
9.3
4.3
6.3
3.1
2.9
39.6
42.6
7.6
6.0
3.6
4.6
6.5
8.1
4.8
4.1
5.5
0
0
0
0
1.5
111.7
9.4
0
0
0
0
7.3
5.3
0.9
0
0
0.6
252.1
17.8
1.2
1.5
1.7
5.6
43.3
0.5
0
0
0
0
250.8
3.9
0
0.7
123.0
127.1
23.6
11.5
14.6
7.4
25.3
45.3
8.1
6.1
9.2
6.5
151.4
76.0
12.9
16.5
7.3
6.8
15.7
35.0
21.2
7.1
5.2
4.2
36.7
24.3
10.2
5.7
3.7
2.4
5.8
7.9
6.3
4.6
127.9
58.1
0
0
0
0
147.3
64.7
0
0
0
3.4
94.8
26.0
0
0
0
0
189.1
35.8
2.7
0
3.5
0
58.6
1.3
0
0
0
0
95.0
2.1
0
0
48.9
10.5
5.8
9.6
11.4
8.9
20.4
10.2
11.8
11.2
10.5
7.9
115.0
24.5
4.0
1.6
3.6
2.3
19.1
12.1
6.3
7.2
9.2
8.1
34.9
17.1
10.0
8.2
5.0
5.9
10.6
6.3
2.4
2.5
124.2
16.7
2.0
0
9.0
17.9
154.5
1.0
0
0
16.3
2.9
194.0
10.2
0
4.2
0
0
209.1
5.1
0
0
8.5
2.2
53.8
2.2
0
0
7.1
1.2
72.6
0.5
1.6
0
47
-------
Table 21. (Continued)
October
Depth
cm
SCU-20 + N-Serve
90-120
120-150
SCU-30
0- 15
15- 30
30- 60
60- 90
90-120
120-150
SCU-30 + N -Serve
0- 15
15- 30
30- 60
60- 90
90-120
120-150
Am Sul (deep)
0- 15
15- 30
30- 60
60- 90
90-120
120-150
Am Sul 4- N-Serve (deep)
0- 15
15- 30
30- 60
60- 90
90-120
120-150
Control
0- 15
15- 30
30- 60
60- 90
90-120
120-150
N03-N
NHA-N
Time of application
November
N03-N
December
NH4-N N03-N
NH4-N
-ppm --.__________
6.1
3.7
115.7
144.1
9.5
5.6
5.8
6.1
6.3
18.3
10.3
6.0
9.4
8.5
4.3
5.4
6.7
10.9
8.7
5.8
22.3
20.8
8.3
4.3
2.9
2.7
0.9
1.7
83.4
2.0
ND
ND
ND
ND
189.0
9.6
0
0
0
0
3.0
0.5
1.5
1.2
1.5
1.5
59.1
59.1
4.2
0
0
0.7
3.0
2.4
53.7
41.6
17.4
6.2
48.0
4.2
5.0
8.8
4.8
5.0
5.4
5.3
44.9
72.9
39.1
7.9
4.1
5.0
10.1
5.5
6.1
6.3
6.5
4.1
12.4
6.8
2.3
2.0
1.3
1.4
0
0
72.7
0
0
0
53.6
10.2
165.5
3.9
0
0
0
0
5.5
5.6
0
0
0
0
100.2
65.2
1.3
0
1.1
0
2.8
1.9
ND
ND
ND
ND
1.6
1.6
82.4
29.1
7.5
3.6
3.6
2.5
14.2
11.5
7.3
4.9
6.2
4.4
39.9
41.4
6.5
4.0
6.8
4.5
16.1
15.5
3.6
3.4
2.8
2.1
0
1.3
219.8
2.5
14.8
0
1.0
0
107.2
0
0
1.6
0
0
88,2
136.2
0
0
0
0
129,8
46.8
0
0
0
0
48
-------
TABLE 22. TOTAL OF THE N03-N AND Nfy-N IN 120-CM-PROFILES OF HOUSTON BLACK
CLAY ON MAY 29, 1974 AFTER APPLYING 134 KG-N/HA
Treatment*
Time of application
Nov. Dec. Feb. March
Sidedresst
Average
trr, W /Vi «
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
406
402
473
403
169
278
479
290
394
492
379
222
239
271
204
104
56
289
128
267
270
205
580
325
664
420
385
174
473
278
420
367
408
479 176
289
521
338
156
185
256
302
500
334
336
121
172
139
26
93
164
99
249
176
141
373
275
420
301
168
157
332
219
366
328
294
* The inorganic N level in the control plots was 33 kg-N/ha
t The cidedress treatment had received only one-half (67 kg-N/ha) the
prescribed amount of N at sampling.
The readily soluble forms exhibited the maximum amount of leaching fol-
lowed by SCU-30, then SCU-20. An example of comparative amount of leaching
can be seen in the March applied treatments. Plots treated with readily
soluble forms averaged 7.1 ppm N03-N below the 60-cm depth. Sulfur-coated
urea-30 and SCU-20 averaged 6.5 and 3.9 ppm N03~N, respectively.
Time of application had no significant effect on exchangeable N levels
except in December applied treatments. December applications averaged 40%
49
-------
less soluble N in the entire profile than the other application periods.
When the December applied group was sampled in February, the results were
very similar to those discussed above. It is interesting to compare amounts
of exchangeable N present in the profiles in February to the amount present
in May, for November and December times of application. In February, the
November applied group contained 501 kg/ha exchangeable N. The following
May this group contained 501 kg/ha exchangeable N. This is a decrease of
24%. The December applied treatments contained an average of only 239 kg/ha
exchangeable N in February and 205 kg/ha exchangeable N in May. This is a
decrease of 14%. Since N uptake by the crop accounted for sizeable portions
of the exchangeable N loss in both instances,it appears only small amounts of
the exchangeable N present in February was removed from the soil solution by
means other than crop utilization. It appears the most favorable period for
N losses would be prior to January and February. If application date is
compared independent of N source, no noticeable differences in degree of
leaching are obtained other than for the December application period (Table
22).
The data in Table 23 indicates more NC^-N is present in the lower 60 cm
of the profiles of the treatments which had received the latest application
of N. For example, the average NO^-N concentration in the 60-120 cm depth of
the (NH^^SO^ treatment was 4.8 ppm when the N was applied in November, but
was 9.6 ppm when the N was applied in March. This same trend was evident in
most of the other treatments. It appears the reason for this was more total
N in the profiles of the latter application dates which was subject to leach-
ing. Much of the earlier applied N had leached through the lower depths by
the May sampling date as evident by the higher concentrations present at
these depths in January (Table 17).
Generally, N-Serve caused a decrease in exchangeable N present at sam-
pling. If N-Serve is considered independent of time of application and N
source, it is apparent a 23% decrease in exchangeable N occurred by the ad-
dition of N-Serve. If N-Serve is considered versus time of application, more
explanatory results are obtained. In the readily soluble N treatments the
percent decrease in exchangeable N caused by N-Serve in the November, -Decem-
ber, February, and March application periods is 8, 10, 40, and 37, respect-
ively. This demonstrates the earlier applications of N-Serve caused only
small decreases in exchangeable N levels while the latter months of appli-
cation the decrease became large. Some of the decrease may be due to the
fact NH^-N is immobilized more rapidly than N03~N (Jansson, 1958). It may
also be due to NH4-N volatilization. No real conclusion can be drawn on this
observation from the collected data.
That N-Serve significantly decreased N03~N leaching is best exemplified
in the readily soluble treatments (Table 23). The respective decreases in
N03-N content at 60-120 cm caused by N-Serve in the November, December,
February and March times of application are 29%, 23%, 69%, and 60%. Some of
this decrease may be due to the corresponding decreases in exchangeable N
content when N-Serve was added. However, even when this data is considered
jointly, N-Serve effected a substantial decrease in leachability of the
applied fertilizer.
50
-------
TABLE 23. CONCENTRATION OF N03-N AND NH4-N IN 120-CM PROFILES OF HOUSTON BLACK CLAY AFTER RECEIVING
134 KG-N/HA PRIOR TO SAMPLING ON MAY 29, 1974
Treatment
and
depth
cm
Am Sul
0
15
30
60
90
Am Sul
0
15
30
60
90
Urea
0
15
30
60
90
Urea +
0
15
30
60
90
- 15
- 30
- 60
- 90
- 120
+ N- Serve
- 15
- 30
- 60
- 90
- 120
- 15
- 30
- 60
- 90
- 120
N- Serve
- 15
- 30
- 60
- 90
- 120
November
N03-N
NH4-N
Time of application
December February
N03-N
NH4-N
N03-N
NH^-N
March
N03-N
NH4-N
51.1
50.8
20.2
5.7
3.8
65.2
39.8
16.1
4.5
1.8
43.1
68.6
41.4
5.2
3.1
58.2
46.5
27.0
4.9
1.4
0
0
10.0
ND
ND
26.0
3.6
0
ND
ND
0
0
0
ND
ND
8.2
0
0
ND
ND
23.0
36.1
12.6
4.7
2.1
37.1
31.7
10.2
4.2
2.2
35.1
48.0
13.1
4.2
2.7
42.2
15.4
4.7
2.2
1.7
0.9
0
0
ND
ND
4.6
0
0
ND
ND
0
0
0
ND
ND
15.6
0.6
0
ND
ND
86.0
99.2
24.1
7.8
3.9
52.2
35.4
7.2
2.8
1.5
83.2
114.8
34.8
10.7
3.7
65.1
31.5
5.3
2.0
1.6
0
0
1.0
ND
ND
34.6
0
0
ND
ND
0
0
0
ND
ND
73.1
0
0
ND
ND
33.4
75.6
33.2
13.1
6.0
25.6
30.1
9.0
3.2
1.7
38.9
87.2
43.4
6.1
3.2
32.8
40.3
10.1
4.2
2.2
0.6
0
0
ND
ND
75.1
17.8
2.4
ND
ND
0
0
0.6
ND
ND
44.1
0.8
0
ND
ND
-------
Table 23. (Continued)
Ul
N)
Treatment
and
depth
cm
SCU-20
0
15
30
60
90
SCU-20
0
15
30
60
90
SCU-30
0
15
30
60
90
November
N03-N
NH4-N
Time of application
December February
N03-N
NH4-N
N03-N
NH4-N
March
N03-N
NH^-N
- 15
- 30
- 60
- 90
- 120
4- N-Serve
- 15
- 30
- 60
- 90
- 120
- 15
- 30
- 60
- 90
- 120
13
14
7
4
2
24
10
6
3
2
70
38
12
4
1
.4
.2
.6
.1
.2
.0
.1
.8
.9
.0
.1
.5
.0
.8
.8
18.3
2.1
0
ND
ND
64.3
0
0
ND
ND
67.4
0.7
0
ND
ND
5.2
9,3
9.9
4.0
2.2
7.7
3.0
3.4
2.3
0.7
49.4
32.3
14.6
5.4
1.7
0
0
0
ND
ND
1.4
0
0
ND
ND
4.2
0
0
ND
ND
77.9
14.1
9.8
4.3
2.8
6.6
3.1
3.7
2.4
1.4
97.5
36.1
19.1
5.2
3.0
46.0
0
0
ND
ND
53.2
0
0
ND
ND
23.0
0
0
ND
ND
11.
16.
9.
4.
3.
2.
6.
5.
3.
2.
18.
44.
13.
7.
5.
6
9
6
7
2
8
0
1
2
5
0
0
2
2
9
2.2
3.9
0
ND
ND
42.2
9.5
0
ND
ND
0
0
0
ND
ND
SCU-30 + N -Serve
0
15
30
60
90
- 15
- 30
- 60
- 90
- 120
28
16
5
1
1
.0
.8
.9
.9
.4
66.5
0
0
ND
ND
30.5
5.3
2.7
1.6
0.7
9.5
0
0.8
ND
ND
28.0
9.5
5.3
2.9
2.1
66.0
0
0
ND
ND
6.
18.
5.
3.
1.
8
7
0
5
9
78.2
10.3
0
ND
ND
-------
Table 23. (Continued)
OJ
Treatment
and
depth
cm
November
N03-N
NH4-N
Time of application
December February
N03-N
NH4-N N03-N
______ _ppm-.
NH^-N
March
N03-N
NH4-N
Am Sul (deep)
0 -
15 -
30 -
60 -
90 -
Am Sul +
0 -
15 -
30 -
60 -
90 -
Control
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
N-Serve
15
30
60
90
120
15
30
60
90
120
38.9
62.4
27.9
7.5
2.0
77.1
63.4
24.9
5.5
2.2
0
0
0
ND
ND
13.9
0
0
ND
ND
6.2
30.8
31.0
7.0
2.9
20.6
41.9
15.9
5.7
2.8
N03-N
1.5
2.2
1.8
1.5
1.6
0
0
0
ND
ND
6.2
2.9
0
ND
ND
NH4-N
1.5
0
0.1
ND
ND
2.2
60.3
33.7
18.8
7.2
8.5
40.2
20.4
5.0
2.7
0
0
0
ND
ND
1.5
57.4
0
ND
ND
63.0
68.2
32.7
8.7
4.6
36.4
36.0
5.7
8.2
2.1
0
0
0
ND
ND
25.6
19.2
0
ND
ND
-------
Houston Black Clay-1975--
During the second year of this study, fertilizer treatments were applied
on October 18, November 19, and December 20, 1974, and on February 21 and
March 25, 1975. A split application was made on March 25 (at planting) and
May 19. The treated plots were sampled to a depth of 120 cm on June 6, 1975.
The total N03-N and NH4-N found in the 120-cm profiles are listed in
Table 24. The March applied treatments contained 357. more inorganic N than
the October applied treatment. The November applied group was also consider-
ably lower than the other times of application. If the amounts of exchange-
able N present in the soil at the June 6 sampling period are compared to the
amounts present at the January sampling period (Table 16), it is evident N
loss or immobilization occurred after the earlier sampling date. In June* the
October applied group contained 317. less (198 kg-N/ha) exchangeable N than
was present in January (289 kg-N/ha). The November applications averaged 44%
less. Those applied in December contained equal amounts of exchangeable N at
both sampling dates. The decrease in soluble N concentrations in the soil
from January to June can be attributed to diffusion out of the fertilizer
band and sampling zone, immobilization by microorganisms, as well as denitri-
fication, leaching and plant uptake. The fact there was no difference in N
levels for the December treatment would tend to indicate the decrease in
soluble N occurred soon after the January sampling date while the N in the
December application treatment was mainly in the NH4-N form (Table 16) and
not as subject to the loss mechanisms mentioned above.
During the 1974 spring sampling, N-Serve caused a decrease in exchanger
able N in almost all cases (Table 22). The data in Table 24 indicates N-
Serve had no significant effect on exchangeable N levels. If N-Serve is
considered independently of N source and time of application, versus total
exchangeable N» the resulting values are 258 kg-N/ha exchangeable N for the
N-Serve treatments and 259 kg-N/ha for the non-N-Serve treatments. The
results are similar if time of application is included in this comparison.
The differences obtained in 1974 were large and consistent. Because the
observations of this sample period are not comparable to those of 1974 » one
may conclude that environmental factors seriously influenced the results.
Table 25 demonstrates the amount of N03-N that had moved to a depth of
60 to 120 cm in the profiles. Observing the data organized in this fashion
gives a good indication of the amount of downward movement that had occurred
during the various time intervals. When N-Serve is considered as a treat-
ment independent of N source, it can be shown that the addition of N-Serve
resulted in less N03~N leaching. Plots not treated with N-Serve contained an
average 78 kg N03-N/ha in the 60-120 cm depth while N-Serve treated plots
contained 34% less or 51 kg-N/ha. At this sampling period, the check plots
contained only 11 kg/ha N03-N in the 60-120 cm depth.
The more soluble N sources (urea and (NHA^SO^) resulted in more N03-N
leaching than the sulfur-coated ureas. The former sources averaged 59, 71, 72,
89, and 194 kg-N/ha below 60 cm, respectively, for the March, February,
December, November, and October application periods. This indicates more
leaching occurred the longer the fertilizers were in the soil. The maximum
amount of leaching occurred with the October treatment while the least
54
-------
TABLE 24. TOTAL N03-N AND NH4-N IN 120-CM PROFILES OF HOUSTON BLACK CLAY ON JUNE 6, 1975 AFTER RECEIV-
TNI* 1 xA irf^w'M/TiA
ui
ING 134 KG-N/HA
October
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve
(deep)
Average
Control
N03-N
355
206
181
211
86
125
174
161
182
191
187
NH4-N
0
42
0
2
28
10
16
11
2
0
November
N03-N
222
101
136
207
102
87
137
205
165
187
11 155
N03-N
41
.3
NH4-N
0
22
8
4
14
32
23
40
0
7
15
NH4
0
December
N03-N
NH4-N
kg-N/ha--
216 0
212
387
371
102
92
180
163
274
209
221
-N
14
0
171
56
40
0
34
0
61
38
February
N03-N
190
174
332
162
152
84
162
186
295
133
187
NH4-N
3
62
0
88
67
24
55
41
38
106
48
March
N03-N
262
136
286
170
80
61
337
89
295
151
187
NH4-N
0
132
2
106
2
70
76
95
2
130
61
Average
(sum)
250
220
266
298
138
125
232
205
251
235
222
-------
TABLE 25. AMOUNT OF N03~N PRESENT BELOW 60 CM OF DEPTH IN 120-CM PROFILES
OF HOUSTON BLACK CLAY THAT HAD RECEIVED 134 KG-N/HA PRIOR TO
SAMPLING ON JUNE 6, 1975
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve
(deep)
Average
Control
No N-Serve
N-Serve
Oct.
264
67
100
72
40
41
78
44
111
58
90
Time
Nov.
102
57
76
79
51
46
73
98
99
65
75
11
78
51
of application
Dec.
63
50
82
68
28
39
52
31
73
43
53
Feb.
kg-N/ha--
84
37
58
46
42
38
49
39
80
39
51
March
39
43
79
48
42
38
78
43
77
39
53
Average
107
51
79
63
41
40
66
51
88
49
64
56
-------
occurred in the March applied treatments. This data agrees well with that
collected in 1974 during the same time interval.
In the SCU treatments, the amount of N03~N present below 60-cm was ap-
proximately equal for all months of application. The average amount was
50 kg N03-N/ha. This indicates the application of SCU resulted in about 34%
less N03-N moving into the lower depths of the profile than for the more
soluble N sources.
The relative amounts of N03-N and Nfy-N found in the profiles in June
are listed in Table 26. The effect of N-Serve on the nitrification of fer-
tilizer applied NH^-N was substantial for a relatively long period of time.
The percent of the inorganic N that was in the NH4-N form was relatively
constant for all treatments which did not receive N-Serve. In the non-N-
Serve treated plots approximately 8% of the inorganic N present was NH^-N
regardless of the month applied. This indicates the fertilizer applied
NH^-N was nitrified rapidly in the absence of N-Serve. When N-Serve was
applied the percent Nfy-N present was 47.8% for the March treatment, while
the February, December, November, and October treatments contained 32.17.,
21.6%, 13.3%, and 6.3%, respectively. The NH^-N content of the October
treatment was essentially the same as the treatment without N-Serve. Ammo-
nium N content differences began to appear in the November applied treatment
and increased as the application date moved closer to the sampling date.
This indicates N-Serve affected nitrification for at least 207 days, but less
than 228 days.
A urea analysis was performed on all the sulfur-coated urea treated
plots. The results of this data were erratic but do give an indication that
a considerable amount of the SCU applied was still hydrolyzed and in the
sulfur-coated prill at sampling time in June. The average urea content in
the soil profiles of the October, November, and December applied treatments
was 300 kg-N/ha. The February and March treatments averaged 353 kg-N/ha.
The overall average for the SCU-20 treatment was 458 kg urea N/ha, while the
SCU-30 treatments only contained 184 kg-N/ha. This signifies SCU-20 is much
more insoluble than SCU-30 since the SCU-20 plots contained 2.4 times more
urea-N.
Norwood Silt Loam-1974
Fertilizer applications were made to preselected plots of Norwood silt
loam on November 19, and December 17,1973, and on February 18, April 3, and
a split application on April 3, and May 21, in 1974. The April applications
were made at planting. On June 4, two soil cores were taken from each plot
to a depth of 150 cm.
Exchangeable N levels (Table 27) were significantly affected by N
source. When N source is considered independent of time of application, the
N content of plots treated with readily soluble sources averaged 426 kg-N/ha.
The SCU-30 source was similar with an average 415 kg-N/ha. The SCU-20 treat-
ments were significantly lower with an average of only 280 kg-N/ha. This is
approximately 30% less than the SCU-30. This data is similar to that
obtained in the Houston Black clay during the same time interval. Both
locations indicated the dissolution rate of SCU-30 increased substantially
57
-------
TABLE 26. CONCENTRATIONS OF N03-N and NH^-N IN 120-CM PROFILES OF HOUSTON BLACK CLAY ON JUNE 6, 1975
AFTER RECEIVING 134 KG-N/HA '
m
00
Treatment
and
depth
cm
Am Sul
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
October
N03-N
4.4
4.6
10.5
37.3
26.9
NH4-N
0
0
ND
ND
ND
Time of application
November December February
N03-N
4.4
12.6
17.4
14.4
10.3
NH4-N
0
0
0
ND
ND
N03-N
ppm-
6.3
23.1
23.7
9.9
5.5
NH4-N
0
0
0
ND
ND
N03-N
4.6
50.8
30.5
11.7
8.7
NHA-N
1.2
0
0
ND
ND
March
N03-N
13.5
49.5
18.9
8.5
7.5
NH^-N
0
0
0
ND
ND
Am Sul + N-Serve
0 -
15 -
30 -
60 -
90 -
Urea
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
15
30
60
90
120
20.4
46.8
25.5
9.5
6.8
3.6
20.3
7.5
12.9
11.3
18.7
0
0
ND
ND
0
0
0
ND
ND
7.8
16.6
16.8
7.9
5.9
4.9
5.9
9.0
10.2
8.2
10.2
0
0
ND
ND
3.7
0
0
ND
ND
18.4
29.0
14.8
7.3
4.9
21.4
48.3
38.0
13.1
6.9
6.5
0
0
ND
ND
0
0
0
ND
ND
15.8
20.7
13.4
4.5
4.4
8.5
70.3
28.2
8.6
5.6
24.7
3.3
0.7
ND
ND
0
0
0
ND
ND
29.3
12.6
9.0
5.0
5.4
8.8
46.5
21.9
12.0
7.1
62.1
0
0
ND
ND
0.3
0.7
0
ND
ND
Urea + N-Serve
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
14.1
18.8
16.6
9.7
7.9
1.0
0
0
ND
ND
6.0
16.7
19.4
11.0
8.1
1.7
0
0
ND
ND
41.9
51.7
25.4
10.6
5.9
69.3
11.5
0
ND
ND
11.3
24.5
9.8
4.9
6.3
38.4
2.9
0
ND
ND
18.0
18.6
10.8
5.4
6.2
49.9
0
0
ND
ND
-------
Table 26. (Continued).
VO
Treatment
and
depth
cm
SCU-20
0 -
15 -
30 -
60 -
90 -
October
N03-N
NH.-N
4
Time of application
November December February
N03-N
NH4-N
N03-N
NH4-N
N03-N
NH^-N
March
N03-N
NH4-N
. -----ppm
15
30
60
90
120
5.6
4.2
6.1
5.1
4.6
13.4
0
0
ND
ND
5.4
5.2
6.9
6.3
6.0
6.7
0
0
ND
ND
15.7
6.7
6.4
3.8
3.1
26.2
0
0
ND
ND
13.9
19.4
9.7
5.3
4.9
21.8
9.6
0
ND
ND
6.1
10.6
9.3
5.5
4.7
1.5
0
0
ND
ND
SCU-20 + N-Serve
0 -
15 -
30 -
60 -
90 -
SCU-30
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
15
30
60
90
120
8.2
13.0
9.5
5.7
4.3
5.8
8.0
16.2
9.4
9.6
4.7
0
0
ND
ND
7.4
0
0
ND
ND
3.5
6.8
4.5
5.3
6.0
9.2
3.7
8.7
10.3
7.6
15.2
0
0
ND
ND
10.8
0
0
ND
ND
9.0
6.4
4.8
4.4
5.2
5.1
19.4
18.4
7.1
5.6
18.7
0
0
ND
ND
0
0
0
ND
ND
5.0
5.5
5.5
4.7
4.7
96.7
12.2
1.0
5.8
6.2
9.8
0
0.8
ND
ND
25.8
0
0
ND
ND
3.3
3.1
2.3
4.4
4.7
40.5
33.2
24.9
10.2
8.8
31.9
0
0.5
ND
ND
36.1
0
0
ND
ND
SCU-30 + N-Serve
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
13.5
17.4
12.7
5.8
4.8
10.1
0
0
ND
ND
7.9
10.3
16.5
14.9
8.9
19.1
0
0
ND
ND
26.0
19.0
8.8
4.3
3.3
13.0
0
1.5
ND
ND
10.1
21.1
19.7
5.3
4.2
18.2
1.1
0
ND
ND
5.8
7.8
4.2
4.7
5.8
44.2
0.5
0
ND
ND
-------
Table 26. (Continued).
Treatment
and
depth
cm
October
N03-N
NH4-N
Time of application
November December February
N03-N
NH^-N
N03-N
NH4-N
N03-N
NHA-N
March
N03-N
NHA-N
Am Sul (deep)
0 -
15 -
30 -
60 -
90 -
Am Sul +
0 -
15 -
30 -
60 -
90 -
Control
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
N -Serve
15
30
60
90
120
15
30
60
90
120
5.9
3.4
12.5
15.7
11.1
(deep)
6.6
28.3
14.1
7.5
6.6
1.0
0
0
ND
ND
0
0
0
ND
ND
3.5
4.8
11.9
14.8
9.2
4.7
16.3
18.8
9.1
6.7
N03-N
5.2
4.2
2.5
1.6
1.1
0
0
0
ND
ND
0.8
2.5
0
ND
ND
4.0
34.2
29.0
10.2
7.6
8.9
39.6
15.4
6.3
4.1
0
0
0
ND
ND
20.2
8.4
0
ND
ND
3.4
34.4
32.8
12.0
7.4
6.5
20.7
8.7
4.6
4.9
17.9
0
0
ND
ND
32.9
17.0
0
ND
ND
9.2
37.9
31.3
10.3
8.4
15.9
20.5
8.3
4.5
5.0
0.8
0
0
ND
ND
54.0
6.7
0.4
ND
ND
NH4-N
0
0
0
ND
ND
-------
TABLE 27. TOTAL OF THE N03-N AND NH4-N IN 150-CM PROFILES OF NORWOOD SILT
LOAM ON JUNE 4, 1974, AFTER BEING TREATED WITH 134 KG-N/HA
Time of application
Treatment Nov. Dec. Feb. April Average
Am Sul
Am Sul + N-Serve
Urea
Urea + N- Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
Control
310
477
332
469
188
403
229
644
253
338
397
433
471
358
322
238
401
353
246
316
178
332
421
.419
777
265
269
282
488
531
569
247
405
403
487
478
403
314
149
362
469
636
347
405
392
464
486
365
252
309
358
472
444
278
399
114
during the spring while SCU-20 was influenced only slightly by warmer
temperatures.
Time of application did not markedly influence exchangeable N concentra-
tions except in the December treatments. The December applied group, as has
been the case in all previous samplings, contained less exchangeable N. For
the June 4 sampling period, it contained an average of 21% less soluble N than
the other application treatments. Since this type of relationship was pre-
sent throughout this study, it is apparent there are some undesirable clima-
tic conditions which made the application of N fertilizers in December
undesirable.
If the influence of time of application on exchangeable N level is
determined on individual N sources, the results are as follows. The exchange-
able N levels resulting from the application of (^4)3804 or urea was
61
-------
.influenced only slightly by time of application on the Norwood silt loam in
1974. When applied in November these treatments averaged 397 kg-N/ha which
was only 10% less than the amount observed in the April applied group. The
SCU-30 treatments acted similar to the above mentioned readily soluble forms.
N-Serve effect on exchangeable N level was erratic, depending on time of
application. Generally, N- Serve did not influence the total amount of
soluble N found in the profiles. However* when time of application is in-
cluded in the N-Serve examination, . the results are quite different . When N-
Serve was applied with the N in November, a considerable higher amount of
soluble N (36%) was found. When applied with the fertilizer at the December,
February, and April application dates, no influence on the total amount of
soluble N in the profiles was observed. The significant loss of N from the
non-treated N sources applied in November may be attributed to 5.2 cm of
rainfall which occurred within 10 days of .application. The rains were light
and over an extended period of time which could have created denitrifying
conditions in the soil.
Table 28 lists the relative depths of N03-N and NH.-N in the profiles of
Norwood silt loam in 1974. The plots receiving a N application during the
winter months (November and December) had a higher N03-N concentration in the
lower depths of the profile than plots fertilized in the spring. This can be
demonstrated by viewing the (NH^^SO^ treatments versus time of application.
The average amounts of N03~N found in the 60-150 cm depths for the (1^4)2804
treatment applied in November, December, February, and April were 7.8, 5.9,
4.6, and 2.7 ppm, respectively. When N-Serve was added, the respective NC^-N
contents at these lower depths were 4.4, 3.8, 3.5, and 12.2 ppm. The April
treatment was excessively high (12.2 ppm) due to a very high NC^-N level
was much more reasonable. Nitrate N leaching from the applied fertilizer was
found to be lower for the SCU's than for the more soluble (NlSC and urea.
When all the treatments applied were averaged, it was found that 88% of
the inorganic N was in the NC^-N form. The remaining 12% was NH4-N. For
those plots treated with N-Serve and for those treated without N-Serve, the
fraction of the inorganic N that was in the NH4-N form was 20% and 6%, re-
spectively. When the effect of N-Serve was considered versus time of appli-
cation, it was noted the percent NB^-N in the November, December, February,
and April application periods were 10.2%, 13.2%, 26.7%, and 56.7%, respec-
tively. When N-Serve was not included in the treatment, there was no signifi
cant difference between the Nfy-N percentages indicating nitrification is
rapid in Norwood silt loam.
Norwood Silt Loam-1975
During the second year, the various N sources were band applied at 134
kg-N/ha on October 18, November 19, and December 20, 1974 and on February
21, and March 12, 1975. Also, a split application was made March 12, and
May 21. Soil samples were taken to a depth of 150 cm on May 21, 1975.
The NC>3-N and NH^-N concentrations throughout the treated profiles are
listed In Table 29. Nitrate N leaching has occurred to some extent in all
62
-------
TABLE 28.
CONCENTRATIONS OF N03-N AND NH4-N IN 150-CM PROFILES OF NORWOOD SILT LOAM AFTER RECEIVING
*34 KG-N/HA PRIOR TO SAMPLING ON JUNE 4, 1974
Treatment
and
depth
Am Sul
0 -
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
November
N03-N
17.1
45.7
14.5
9.5
8.6
7.2
NH4-N
2.3
3.6
0
ND
ND
ND
Time of application
December February
N03-N
73.7
68.4
15.5
9.1
2.7
2.4
NH4-N
PP
3.2
1.3
0
ND
ND
ND
N03-N
66.7
76.2
15.5
3.1
4.4
0
NHA-N
4.3
2.8
2.1
ND
ND
ND
April
N03-N
59.0
105.0
5.4
2.5
3.0
2.6
NH4-N
o
o
o
ND
ND
ND
Am Sul + N- Serve
0 -
15 -
30 -
60 -
90 -
120 -
Urea
0 -
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
15
30
60
90
120
150
103.2
72.4
13.4
3.4
3.0
2.5
67.9
31.0
11.9
6.0
4.1
3.2
2.3
3.6
0
ND
ND
ND
5.5
3.3
0
ND
ND
ND
85.5
85.1
9.9
3.2
3.0
2.7
68.7
47.2
9.6
7.0
5.0
4.5
4.3
10.9
0
ND
ND
ND
0.3
1.8
0
ND
ND
ND
70.1
72.5
9.4
2.5
3.5
2.0
234.2
77.4
10.4
4.4
4.4
4.1
11.0
7.3
1.4
ND
ND
ND
3.5
4.0
1.2
ND
ND
ND
49.9
28.0
50.1
3.7
3.5
3.7
98.7
84.1
10.0
5.5
2.7
2.1
26.8
6.6
o
ND
ND
ND
2.0
1.5
0
ND
ND
ND
-------
Table 28. (Continued).
Treatment
and
depth
cm
Urea +
0
15
30
60
90
120
SCU-20
0
15
30
60
90
120
SCU-20
0
15
30
60
90
120
November
N03-N
NH4-N
Time of application
December February
N03-N
NH4-N
N03-N
NH^-N
April
N03-N
NH4-N
N-Serve
- 15
- 30
- 60
- 90
- 120
- 150
- 15
- 30
- 60
- 90
- 120
- 150
+ N -Serve
- 15
- 30
- 60
- 90
- 120
- 150
123.7
50.1
9.2
4.1
2.9
3.7
45.7
24.6
6.1
3.5
3.0
2.2
88.2
53.1
5.5
4.5
2.0
2.9
4.1
4.6
0
ND
ND
ND
2.3
0.4
1.0
ND
ND
ND
15.1
2.4
1.2
ND
ND
ND
44.1
34.6
7.4
4.0
3.2
2.2
29.2
30.2
5.4
5.0
8.1
3.2
97.0
38.9
7.5
3.2
2.4
2.9
30.9
9.7
0
ND
ND
ND
2.5
8.1
0
ND
ND
ND
19.8
2.3
0
ND
ND
ND
60.7
35.4
4.4
3.0
2.1
1.7
41.7
31.6
6.4
5.4
5.5
4.9
60.1
20.6
5.1
3,7
3.2
2.1
3.6
2.4
0.7
ND
ND
ND
5.3
1.5
2.0
ND
ND
ND
21.5
3.5
0
ND
ND
ND
64.0
48.4
5.2
2.9
2.9
2.7
61.4
39.7
3.1
3.1
3.4
2.5
8.2
12.5
4.1
3.0
2.6
3.0
38.4
12.7
0
ND
ND
ND
22.4
1.2
0
ND
ND
ND
21.7
2.8
0
ND
ND
ND
-------
Table 28. (Continued).
Treatment
and
depth
SCU-30
0 -
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
November
NC-3-N
48.6
24.6
6.5
4.6
3.2
0
NH4-N
3.1
3.9
ND
ND
ND
ND
Time of application
December February
N03-N
71.6
37.7
12.4
6.1
3.1
4.1
NH4-N
1 Ppn
6.7
0.4
0
ND
ND
ND
N03-N
1--
138.6
54.5
11.4
2.6
2.6
1.6
NH4-N
1.5
0
0
ND
ND
ND
April
N03-N
93.0
37.7
3.0
2.9
2.7
2.9
NH4-N
2.4
15.4
o
ND
ND
ND
SCU-30 + N -Serve
0 -
15 -
30 -
60 -
90 -
120 -
Am Sul
0 -
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
(deep)
15
30
60
90
120
150
212.1
36.6
5.1
3.2
2.4
2.4
26.6
38.9
10.4
7.1
5.4
3.5
24.4
1.6
1.9
ND
ND
ND
0,8
0
1.0
ND
ND
ND
30.9
38.6
8.5
3.1
3.Q
3.0
11.7
40.5
28.7
5.6
4.9
9.5
6.7
5.5
0
ND
ND
ND
0.8
1.4
ND
ND
ND
ND
163.0
42.5
7.0
3.2
3.1
2.4
65.5
147.4
17.0
3.2
2.4
2.5
7.8
4.8
1.0
ND
ND
ND
1.2
4.9
0
ND
ND
ND
37.2
14.5
3.9
3.1
4.1
9.0
138.0
126.5
3.9
2.5
3.2
8.6
103.5
27.2
o
ND
ND
ND
o
0
n
\J
ND
ND
ND
-------
Table 28. (Continued).
Treatment
and
depth
November
N03-N
NH4-N
Time of application
December February
N03-N
NH4-N
Am Sul + N-Serve (deep)
0 -
15 -
30 -
60 -
90 -
120 -
Control
-
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
15
30
60
90
120
150
72.9
38.4
6.4
4.9
4.0
4.0
4.1
3.9
1.0
ND
ND
ND
N03-N
9.0
6.5
4.6
3.5
5.0
4.4
2.2
22.5
8.9
11.5
4.4
5.0
0
1.4
0
ND
ND
ND
N03-N
ppm
NH4-N
1.3
1.3
0 8
ND
ND
ND
9.1
12.4
5.2
4.7
4.4
3.4
NH4-N
18.5
42.3
0
ND
ND
ND
April
NOa-N
17.6
42.1
6.0
3.1
3.5
2.5
NH4-N
46.6
28.2
o
ND
ND
ND
-------
TABLE 29. CONCENTRATIONS OF N03-N AND NIfy-N IN 150-CM PROFILES OF NORWOOD SILT LOAM ON MAY 21, 1975,
AFTER RECEIVING 134 KG-N/HA.
Treatment
and
depth
cm
Am Sul
0 -
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
October
N03-N
4.5
17.2
17.9
18.6
13.0
10.5
NH4-N
1.8
1.4
ND
ND
ND
ND
Time of application
November December February
N03-N
4.5
21.6
8.0
13.8
10.7
9.3
NH4-N
3.6
2.2
ND
ND
NB
ND
N03-N
7.1
17.3
25.6
16.4
14.5
6.5
NH4-N
ppm-- -
1.9
0
ND
ND
ND
ND
NOs-N
5.3
17.7
16.3
16.5
12.6
7.4
NH4-N
40.9
0
ND
ND
ND
ND
March
N03-N
53.7
72.9
11.8
12.1
8;6
9.9
NH4-N
0
0
ND
ND
ND
ND
Am Sul + N-Serve
0 -
15 -
30 -
60 -
90 -
120 -
Urea
0 -
15 -
30 -
60 -
90 -
120 -
15
30
60
90
120
150
15
30
60
90
120
150
36.2
17.9
8.5
8.0
7.5
7.3
4.5
17.2
17.9
18.6
13.0
10.5
4.3
0
ND
ND
ND
ND
1.8
1.4
ND
ND
ND
ND
18.9
40.5
14.0
8.5
9.5
10.4
4.5
21.6
8.0
13,8
10.7
9.3
4.6
9.2
ND
ND
ND
ND
3.6
2.2
ND
ND
ND
ND
61.8
20.8
9.3
7.2
, 6.1
9.6
7.1
17.3
25.6
16.4
14.5
6.5
9.4
0
ND
ND
ND
ND
1.9
0
ND
ND
ND
ND
16.1
31.7
9.1
9.4
7.8
6.1
5.3
17.7
16.3
16.5
12.6
7.4
43.4
36.2
ND
ND
ND
ND
40.9
0
ND
ND
ND
ND
13.4
19.7
21.2
13.1
10.3
8.0
53.7
72.9
11.8
12.1
8.6
9.9
35.2
14.9
ND
ND
ND
ND
0
ND
ND
ND
ND
ND
Urea + N-Serve
0 -
15 -
15
30
51.8
25.9
1.4
0
9.6
20.9
2.5
0
26.4
26.9
64.0
ND
30.2
23.5
106.4
100.0
16.6
25.4
120.9
7.4
-------
Table 29. (Continued).
00
Treatment
and
depth
cm
October
N03-N
NH4-N
Time of application
November December February
N03-N
NH4-N
N03-N
NH4-N
N03-N
NH4-N
March
N03-N
NH4-N
ppm .
Urea 4- N-Serve
30 -
60 -
90 -
120 -
SCU-20
0 -
15 -
30 -
60 -
90 -
120 -
60
90
120
150
15
30
60
90
120
150
(cont.)
4.4
8.3
6.2
5.9
27.0
15.4
8.6
10.0
6.4
7.0
ND
ND
ND
ND
2.7
1.7
ND
ND
ND
ND
12.6
7.0
10.1
8.1
10.9
10.9
11.3
10.0
9.7
6.7
ND
ND
ND
ND
0
0
ND
ND
ND
ND
5.2
6.1
6.9
8.0
45.5
20.4
10-, 8
9.4
7.4
7.6
ND
ND
ND
ND
44.4
0
ND
ND
ND
ND
12.3
10.8
29.2
10.8
29.9
12.4
8.0
5.8
5.9
7.6
ND
ND
ND
ND
11.7
0
ND
ND
ND
ND
5.9
4.8
4.6
3.1
6.6
5.5
3.8
4.2
4.2
2.6
ND
ND
ND
ND
6.1
0
ND
ND
ND
ND
SCU-20 + N-Serve
0 -
15 -
30 -
60 -
90 -
120 -
SCU-30
0 -
15 -
30 -
60 -
90 -
15
30
60
90
120
150
15
30
60
90
120
27.5
11.2
5.0
6.9
6.0
5.2
4.3
2.8
7.2
11.1
10.7
7.0
0
ND
ND
ND
ND
5.4
0.9
ND
ND
ND
32.2
11.0
6.9
5.4
5.6
4.3
31.9
24.7
9.9
10.6
9.0
41.5
0
ND
ND
ND
ND
10.6
6.7
ND
ND
ND
14.8
5,2
2.6
3.2
5.9
4.1
22.2
23.6
10.0
8.1
9.5
16.9
2.3
ND
ND
ND
ND
2.6
0.7
ND
ND
ND
33.9
12.0
5.1
4.0
3.5
4.1
41.5
21.1
8.6
8.6
8.1
31.1
20.1
ND
ND
ND
ND
16.0
2.4
ND
ND
ND
12.6
12.3
5.7
5.2
5.9
1.4
33.8
24.6
5.9
9.8
9.5
131.7
4.1
ND
ND
ND
ND
17.5
0
ND
ND
ND
-------
Table 29. (Continued)
Treatment
and
depth
Time of application
October
N03-N NH4-N
November December
N03-N
NH^-N N03-N
Nlty-N
February
N03-N
NH4-N
March
N03-N NH4-N
SCU-30 (cont.)
120 - 150
7.9
ND
8.2
ND 4.8
ND 8.A
ND
9.4
ND
SCU-30 + N-Serve
0-15
15 - 30
30 - 60
60 - 90
90 - 120
120 - 150
Am Sul (deep)
0 - 15
15 - 30
30 - 60
60 - 90
90 - 120
120 - 150
22.5
23.9
9.4
7.8
8.6
4.6
10.6
0.5
ND
ND
ND
ND
28.4
18.0
9.0
6.3
9.1
7.5
2.4
2.3
3.6
3.7
3.4
5.1
Am Sul + N-Serve (deep)
0-15 2.4
15 - 30 2.7
30-60 3.7
60-90 6.2
90 - 120 7.8
120 - 150 6.9
1.1
0
ND
ND
ND
ND
1.0
ND
ND
ND
ND
ND
3.4
6.8
6.9
7.9
6.5
9.0
16.1
18.9
11.8
12.1
8.3
1.5
8.0
0
ND
ND
ND
ND
24.7
11.8
8.0
7.4
5.5
6.5
10.9
1.9
ND
ND
ND
ND
33.9
12.0
5.1
4.0
3.5
2.8
31.1
20.1
ND
ND
ND
ND
1.5
0
ND
ND
ND
ND!
7.5
34.6
24.3
14.4
15.2
11.2
4.4
0
ND
ND
ND
ND
42.3
38.3
9.3
5.3
6.4
6.7
9.0
8.1
4.3
7.4
8.8
9.9
8.2
0
ND
ND
ND
ND
30.0
13.6
11.9
19.6
8.0
9.2
4.3
7.4
ND
ND
ND
ND
8.6
15.9
12.2
5.9
6.4
6.8
20.8
24.1
ND
ND
ND
ND
24.1
17.8
5.2
3.3
6.7
6.0
47.5
28.8
ND
ND
ND
ND
15.4
9.2
8.3
7.3
6.0
6.3
61.2
6.5
ND
ND
ND
ND
0
0
ND
ND
ND
ND
8.0
7.9
ND
ND
ND
ND
-------
Table 29. (Continued).
Treatment
and
depth
cm
Time of application
October November
N03-N
NH4-N N03-N NH4-N
December
N03-N
01
NH4-N
>m
February March
N03-N
NH4-N N03-N
NH4-N
Control NOs-N NH/-N
0-15 6.6 0
15-30 4.8 0
30 - 60 4.8 ND
60 - 90 3.6 ND
90 - 120 3.3 ND
120 - 150 3.0 ND
-------
treated plots. This is exemplified in Table 30 which lists the amount of
N03~N present below 60 cm but above the sampling depth of 150 cm. The con-
trol plots in this experiment averaged 42 kg NC^-N/ha between 60-150 cm.
However, the overall average amount of NO^-N between 60-150 cm in the treated
plots was 99 kg-N/ha. This is more than two times greater than the amount
present in the control plots.
Time of application seemed to have little effect on the amount of
present at these lower depths. The October treated plots contained 96 kg
N03~N/ha between 60-150 cm, while March treated plots contained 99 kg-N/ha.
The effect of N-Serve on N03~N leaching is also apparent in Table 30. The
non-N-Serve treated plots contained 87 kg N03~N/ha at this depth.
TABLE 30. AMOUNT OF N03-N PRESENT BELOW 60 CM OF DEPTH IN 150-CM PROFILE OF
NORWOOD SILT LOAM ON MAY 21, 1975, THAT HAD RECEIVED 134 KG-N/HA.
Time of application
Treatment Oct. Nov. Dec. Feb. March
Am Sul 173 139 154 150 126
Am Sul + N-Serve 94 117 94 96 129
Urea 95 104 81 104 131
Urea + N-Serve 85 104 86 209 52
SCU-20 96 109 101 80 45
SCU-20 + N-Serve 75 63 54 48 52
SCU-30 123 115 92 104 118
SCU-30 + N-Serve 87 94 80 42 108
Am Sul (deep) 50 96 168 76 152
Am Sul + N-Serve (deep) 86 90 79 66 81
Average 96 103 99 97 99
Control 42
No N-Serve 112
N-Serve 87
71
-------
The slow release sources maintained a lower concentration of N03-N below
60 cm than the more soluble forms of N. Profiles treated with the soluble N
forms contained 109 kg N03~N/ha while the SCU's contained 34% less or 72 kg-
N/ha.
The data in Table 31 depicts total N03~N and NH^-N remaining in the 150-
cm profiles of Norwood silt loam on May 21, 1975. The average amounts of
soluble N of all treatments applied in October, November, December, February,
and March were 210, 243, 274, 355, and 319 kg-N/ha, respectively. The
October treatments contained 65% of the amount present in the March
treatment.
Effect of N-Serve on nitrification rate of fertilizer applied NH^-N can
be demonstrated by comparing relative amounts of NH^-N and NC^-N present in
the profiles. Six percent of the exchangeable N was in NH^-N on May 21 for
the non-N-Serve treated plots, regardless of application date. This
indicates nitrification was very rapid in this soil. In the N-Serve treated
plots, the percent of the exchangeable N present that was in the NH^-N form
was 4.8, 12.1, 23.7, 44.7, and 43.6, respectively, for the October, November,
December, February, and March treatments. This indicates there was some
effect from N-Serve even in the November treatments which were applied 195
days prior to sampling.
Crop Response
Grain Yield in 1974
Houston Black clayGrain sorghum yields were not effected by additions
of N. Generally, on the Blacklands soils of Texas, maximum response to N by
grain sorghum is obtained when it is grown on the same land the previous
year. Oats were the previous crop grown on the plot area used in this study.
The lack of adequate rainfall in June and July also limited response to N
applications and were responsible for low yields (Table 32). A poor stand of
plants was obtained for the plots treated with (NH^SO^ The reason for
the lack of germination is not known. Soil NH^-N levels, which are known to
affect germination, were not unusually high in soil samples taken on February
6 (Table 18). Germination was affected even when the w was applied in
November.
The plots treated with N-Serve or receiving SOU as the source of N
tended to have slightly higher yields, but the increase was not significant.
Norwood silt loamGrain yields were limited in 1974 due to the late
season drought period. Rainfall during June and July was only 6.0 cm. There
was a 45-day period during these two months when only 1.1 cm of rainfall fell
as light showers.
No response to N applications was distinguishable (Table 33). Even
though a difference in soil N was determined for the various N sources and
times of application grain sorghum did not respond to these differences.
Close observation of the data in Table 33 indicates the plots treated with
N-Serve or SCU produced more grain than those receiving the readily soluble
sources. However, plots which received no N also produced more grain than
72
-------
TABLE 31. CONCENTRATION OF N03-N and NH4~N IN 150-CM PROFILES OF NORWOOD SILT LOAM ON MAY 21, 1975,
AFTER RECEIVING 134 KG-N/HA
UJ
October
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul 4- N-Serve
(deep)
Average
Control
N03-N
293
244
199
267
222
177
167
224
92
112
NH4-N
7
9
3
3
9
15
7
24
2
2
210
N03
85
Time of application
November December February
N03-N
228
301
221
220
201
183
275
230
135
213
-N
NH4-N
12
29
5
5
0
88
37
17
3
25
243
N03-N
303
308
117
221
285
107
x 230
190
357
181
"V
NH4-N
kg-N/ha--'
4
20
4
136
94
41
7
27
9
95
274
NOs-N
266
235
257
374
202
166
271
161
285
176
NH4-N
87
169
6
438
25
108
39
109
17
162
355
March
N03-N
443
287
262
166
87
128
266
192
293
167
NH4-N
0
106
3
272
-13
288
37
144
0
34
319
-------
TABLE 32. GRAIN SORGHUM YIELDS IN 1974 ON HOUSTON BLACK CLAY FERTILIZED WITH
134 KG-N/HA OF VARIOUS N SOURCES
Time of application
Side-
Treatment Nov. Dec. Feb. March dress Average
kg/ha
Am Sul 3377 2496 1891 2697 3060 2704
Am Sul + N-Serve 3197 3619 2881 2984 3497 3232
Urea 3362 4166 2088 3144 3258 3204
Urea + N-Serve 3724 3353 3278 2675 2710 3148
SCU-20 3362 3352 3441 2371 3217 3149
SCU-20 + N-Serve 3417 3428 3440 3056 3295 3327
SCU-30 3832 2766 3076 2930 3025 3126
SCU-30 + N-Serve 3344 3447 3473 2308 2869 3088
Am Sul (deep) 3007 3123 2498 2593 2805
Am Sul + N-Serve (deep) 3119 3650 3017 2264 3674 3145
Average 3413 3328 2970 2693 3120 3525
Control 3139 3445 3119 2792 3152 3129
those receiving the readily available N sources. None of the yield differ-
ences were significant.
Nitrogen Uptake in 1974--
Houston Black clayThe concentration of N in the plant tissue was af-
fected by N application on the Houston Black clay even though grain yields
were not affected. The grain sorghum which did not receive any N fertilizer
averaged 1.867. N, whereas, those plants which were fertilized averaged-2.347..
There was no difference in plant uptake of N between plots treated with read-
ily soluble forms of N, but they contained more N than the sulfur-coated urea
treated plants. The average N content in the plants fertilized with the
soluble forms of N was 2.43% as compared to 2.23 % for the SCU fertilized
plant (Table 34).
74
-------
TABLE 33. GRAIN SORGHUM YIELDS IN 1974 ON NORWOOD SILT LOAM FERTILIZED WITH
134 KG/HA 6F VARIOUS N SOURCES
Treatment
Time of application
Nov. Dec. Feb. March
Side-
dress
Average
1>«. /Un
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
Control
3793
3573
2871
2447
5303
2882
2863
3144
2636
2699
3221
4285
1940
3151
1575
2866
2565
2083
3818
2994
2285
1351
2463
2432
1938 3037
2582
2574
3266
3017
2690
3143
2656
2587
3929
2838
3009
2656
2386
2023
2828
2874
3036
2456
2835
3135
2774
3091
2902
2136
2370
2054
2659
3174
2899
2684
2785
3413
2808
3441
2722
2820
2355
2731
3274
2741
3152
2781
2626
2905
2811
3252
Application time had no effect on N uptake. The sidedress application
which appears to contain less N, had received only one-half as much N as the
other application treatments.
Norwood silt loam Nitrogen application influenced the concentration of
N in the plant tissue of the plants grown on the Norwood silt loam even
though it did not affect grain yields. As shown in Table 35, there was essen-
tially no difference in protein content of the grain sorghum between sources
or times of application. The only difference was when no N was applied.
Average protein N of sorghum which did not receive N was 1.967>, whereas,
those receiving 134 kg-N/ha was 2.30%. Plant samples were taken on June 7,
1974. This was the pre-boot stage and prior to the drought period which
occurred in June and July. Sampling prior to the drought may explain why
there was a difference in N content between the grain sorghum receiving
75
-------
TABLE 34. PROTEIN N IN GRAIN SORGHUM PLANTS ON MAY 22, 1974, GROWING ON
HOUSTON BLACK CLAY FERTILIZED WITH 134 KG-N/HA AT VARIOUS TIMES
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
Control
Nov.
2.45
2.47
2.61
2.37
2.39
2.19
2.35
2.32
2.41
2.42
2.40
1.91
Time of application
Dec. Feb. March
2.54
2.34
2.46
2.37
2.15
2.33
2.46
1.98
2.18
2.50
2.33
1.94
%N
2.42
2.42
2.43
2.41
2.37
2.14
2.23
2.17
2.58
2.47
2.36
1.74
2.48
2.42
2.41
2.44
2.21
2.37
2.18
2.28
2.43
2.41
2.36
1,91
Sidedress
2.39
2.30
2.30
2.83
2.12
2.06
2.06
2.28
2.46
2.50
2.33
1.82
an application and the control plots, but no difference in grain yields nor
in protein content of the harvested grain.
Grain Yield in 1975
Houston Black clayThe average grain yield for the 1975 season on the
Houston Black clay pots was 3,336 kg/ha. There was a significant difference
(0.05% level) only at the December time of application, the average yield of
all treatments applied in October, November, December, February, March, and
sidedress were 3,436, 3,394, 2,990, 3,487, 3,469, and 3,577 kg/ha,respec-
tively (Table 36). The average yields are similar regardless of time of
application. This data agrees with the soil data which indicated December
treatments were always lower in exchangeable N.
There was also a significant treatment effect. The N-Serve treated
sources were all significantly greater than the control, while the non-N-Serve
76
-------
TABLE 35. PROTEIN N IN GRAIN SORGHUM PLANTS ON JUNE 7, 1974, GROWING ON
NORWOOD SILT LOAM FERTILIZED WITH 134 KG-N/HA AT VARIOUS TIMES
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
Gontrol
Nov.
2.14
2.86
2.66
2.35
2.40
2.77
2.55
2.46
2.32
2.29
2.48
2.39
Time of application
Dec . Feb . March
2.54
2.34
2.46
2.37
2.15
2.33
2.46
1.98
2.18
2.50
2.33
1.94
%w_.
2.42
2.50
2.40
2.41
2.32
2.00
2.35
2.17
2.58
2.47
2.36
1.74
2.48
2.42
2.41
2.44
2.22
2.37
2.18
2.28
2.43
2.41
2.36
1.91
Sidedress
2.39
2.30
2.33
2.33
2.12
2.06
2.06
2.28
2.46
2.50
2.27
1.83
treatments were not. It is interesting that every N source applied exhib-
ited an increase in grain yield when treated with N-Serve. The SCU-20 +
N-Serve treatment exhibited the greatest yield with (NH4)2S04 + N-Serve
following with the second highest yield.
Norwood silt loam--Grain yields were not affected by the addition of N
(Table 37).No significant difference was obtained among the treatments or
the times of application.
Nitrogen Uptake in 1975
Plant tissue and grain samples were collected at both locations for
crude protein analysis. The soil data indicated the exchangeable N level on
most treatments were more than sufficient to maintain a normal level of N in
77
-------
TABLE 36. GRAIN SORGHUM YIELDS IN 1975 ON HOUSTON BLACK CLAY FERTILIZED WITH 134 KG-N/HA OF VARIOUS N
SOURCES.
-4
00
Treatment
Oct.
Time of application
Nov. Dec. Feb.
March
Sidedress
Average
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
Control
3676
2681
3524
3450
3355
3529
3299
3659
3698
3490
3436
2629
3029
3546
3040
3586
3490
3507
3152
3563
2854
3676
3344
2437
1841
3746
1987
2944
3394
3754
2910
3169
2775
3377
2991
2854
3152 3169
3698
3265
3282
3563
4053
3529
3828
3304
3192
3487
3000
3659
3732
3642
3715
3563
3619
3248
3192
3152
3469
2702
3901
3788
3450
3923
3507
3845
3619
3980
3265
2437
3572
2831
3128
3521
3166
3471
2363
3709
3355
3575
3181
3221
3269
3269
-------
TABLE 37. GRAIN SORGHUM YIELDS IN 1975 ON NORWOOD SILT LOAM FERTILIZED WITH 134 KG-N/HA OF VARIOUS
N SOURCES
Treatment
Am Sul
Am Sul + N-Serve
Urea
Urea + N-Serve
SCU-20
SCU-20 + N-Serve
SCU-30
SCU-30 + N-Serve
Am Sul (deep)
Am Sul + N-Serve (deep)
Average
Control
Oct.
2631
1919
1880
1936
2527
1956
1834
2137
1930
1544
2029
1430
Time of application
Nov. Dec. Feb.
1826
2041
1768
1647
2170
1662
1910
1730
1273
2199
1823
1941
1753
2214
2072
1933
2385
2104
1643
1892
2047
\
1683
1973
1651
. - - -Iro- -N /Vi a -
1357
1537
1600
1730
1630
1986
1144
1564
2047
2156
1675
1545
March
1464
1622
1010
1389
1073
1607
1670
1620
1481
1891
1483
2197
Sidedress
1118
1775
2326
1640
1831
1704
1780
1872
2148
2159
1835
1581
Average
1692
1851
1776
1713
1936
1837
1664
1803
1821
1939
1939
1803
-------
the plant. Therefore, before extensive efforts were-initiated to analyze all
treatments, a selected group was examined to determine if there was any
reasonable difference among treatments. Sixty samples were analyzed from
each research location. It was concluded the only significant differences
in protein content in the tissue samples were between the control and treated
plots. No significant response was obtained in the grain protein data.
Therefore, the remainder of the samples was abandoned.
80
-------
SECTION 7
NITROGEN APPLICATIONS TO A GRASSLAND WATERSHED
A 7.7 ha (19.1 ac) grassland watershed was selected to study the fate of
nitrogen applied to a typical watershed. The site was located on the
Blacklands Experimental Watershed at Riesel, Texas, in Falls County. The soil
was Houston Black clay and the site has an established sod of Coastal
bermudagrass. Nitrate concentrations were determined in runoff waters, water
wells within the watershed and in soil samples taken in the watershed. Uptake
of nitrogen by bermudagrass was also determined.
PROCEDURE
In August of 1973, four shallow wells were installed down to and into
semi-permeable C-horizon of the soil. The wells were installed by digging a
trench approximately 75-cm in width and 2.5 m in length and about 30-cm into
the C-horizon. A slotted 10-cm diameter PVC pipe was placed vertically in
the trench. The trench was then back-filled with about 45~cm of 15-mm pea
gravel and then covered with the original soil. The1 depth of the wells varied
from 1.8 to 2.5 m depending on the depth to the C-horizon. Water samples
were collected from the wells by manual sampling.
A Chickasha sediment sampler (Miller, et al., 1969) was constructed and
installed at a weir already present in the watershed runoff channel; The
sampler was designed to automatically collect water samples at various
prescribed times during runoff flow. The sampler was installed during
December of 1973.
Volume and rate of runoff flow were determined utilizing a water stage
recorder. Nitrate levels in the water samples collected were determined by
the phenoldisulfonic acid method. Records of when water samples were taken
were recorded on the water stage recorder so that amounts of nitrate losses
could be calculated from volume of flow data.
Five forage cages 1.5 m in diameter were installed on the watershed to
determine forage production. A 0.8 nr area was harvested from each cage to
estimate the forage production on the watershed and to determine nitrogen
uptake. Cattle were allowed to graze the remainder of the watershed.
Protein nitrogen was determined in the harvested forage by Kjeldahl
distillation.
Soil samples were collected periodically to a depth of 150-cm using a
power driven soil corer. Nitrates and ammonium were determined in the soil
by the phenoldisulfonic acid method and by distillation, respectively.
81
-------
The watershed was managed similar to methods used by farmers In the
area. Fertilizer was surface applied twice each year at a rate of 90 kg-N/ha
using NH4N03. In 1974, the fertilizer was applied on March 5 and Septemeber
27. In 1975» the fertilizer was applied on March 16 and May 7.
RESULTS
Rainfall during the spring and early summer of 1974 at the 7.7 ha water-
shed at Riesel was much below normal. The total rainfall from January
through July was only 29.3 cm. However, rainfall during the later part of
August through November was exceedingly heavy (Table 38). The total rainfall
received at the watershed site for 1974 was 103 cm.
Ninety kilograms per hectare of nitrogen as NltylK^ was broadcast on the
solid surface of the watershed on March 5 and again on September 27 in 1974.
Nitrates in Runoff Water During 1974
Ten major runoff producing storms occurred during 1974. Several runoff
events occurred during the early part of the year, but the majority of the
runoff occurred in late summer and during the fall. Several runoff events
were not of sufficient magnitude to activate the sampler, and on at least
two occasions the sampler malfunctioned and did not collect any samples. The
first runoff samples were collected on February. 21, prior to fertilization.
Nitrate concentrations in the runoff water were low with no levels above 0.7
ppm N03-N occurring (Table 39). The total amount of runoff was 0.80 cm and
the total N03-N lost was only 0.027 kg/ha (Table 40). The second runoff
producing storm occurred 39 days after applying the 90 kg/ha of nitrogen.
Nitrate-nitrogen concentration in the runoff water from the April 13 storm
was much higher than in the earlier runoff. Concentrations of N03-N as high
as 7.2 ppm were measured. The highest concentrations of nitrate in the run-
off water occurred in the 7th sample collected. The first water collected
contained the lowest level of nitrate and the concentration increased until
the peak concentration was reached and then started to decrease when runoff
flow ceased after the 9th sample collected, at which time concentration of
N03-N in the runoff water was 4.2 ppm. The total runoff was 1.02 cm and the
total amount of N03-N lost in the runoff water was only 0.42 kg/ha. The
average concentration in the runoff water during the entire event was 3.9 ppm
N03-N. Rainfall during the summer was not sufficient to cause any major
runoff events. Twenty runoff samples were collected from the second runoff
event in September. The concentration of N03~N in the runoff was essentially
nil (Table 39). The total amount of nitrogen lost from the watershed in the
runoff was only 0.030 kg/ha.
Fertilizer was again applied to the watershed on September 27 when the
water content of the soil was near field capacity. A runoff producing
storm did not occur until the last of October, although 1.72 and 0.38 cm of
rainfall had occurred on October 4 and October 24, respectively (Table 38).
The concentration of N03-N in the runoff water following the September appli-
cation of nitrogen was appreciably higher than in the runoff water proceeding
the application. However, the highest concentration found in any of the
samples collected was only 2.3 ppm (Table 39). The total amount of nitrogen
82
-------
TABLE 38. DAILY RAINFALL ON GRASSLAND WATERSHED AT RIESEL, TEXAS IN 1974
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.
Monthly
Totals
Jan.
0.02
0.10
0.02
0.02
0.02
0.02
0.58
0.10
0.88
0.63
0.83
1.03
0.72
4.97
Feb. March April May June
3.00
0.05
2.12
0.05 0.60
0.80 0.43
2.48
0.22 ' 0.60
2.85
0.25 0.75
0.32
1.08
1.93
0.60
1.15
0.28
0.72
2.50 3.50 7.48 5.60 1.20
83
-------
TABLE 38. (Continued)
Day July Aug.
Sept. Oct.
Nov. Dec.
1.
2.
3. 0.28
4.
5.
6.
7. 0.82
8.
9.
10.
11. 0.12
12.
13.
14. 0.53
15. 0.20
16. 1.35
17.
18.
19.
20.
21.
22. 3.85
23.
24.
25. 0.32
26. 0.95 5.10
27. 0.25
28. 2.13
29. 1.55
30. 2.18
31. 0.95
Monthly 4.10 16.48
Totals
Yearly Total
-_.«-, -_ 1, ,||| - -m -» . n mmm-_mm>mm-> --w^- -_
1.70
1.72
0.90
2.48
1.42
3.18
0.90
2.38
10.22
0.40
0.08 0.38
0.25
0.08
1.35
3.45
8.92
23.99 15.82
103.02
0.02
0.70
0.42
1.83
0.05
0.17
1.20
8.12
0.62 0.52
0.55
0.10
0.90 0.10
0.10
0.30
13.61 3.77
84
-------
TABLE 39. CONCENTRATION OF N03~N IN RUNOFF WATER FROM GRASSLAND WATERSHED AT
RIESEL, TEXAS IN 1974
Sample
No,
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
Feb. March*
21 13.
1974 1974
0.7 1.8
0.3 2.2
0.3 2.8
0.3 3.4
0.3 4.6
0.1 7.0
0.3 7.2
0.3 7.0
4.2
Sept. Sept.
3 17
1974 1974
0 0.1
0
0.1
0
0
0
0
-
-
-
-
-
y
-
0.1
0
0
0
0.1
0
1.0
0.2
0
0
0
0
0
Oct.*
30
1974
1.6
2.2
2.2
2.3
0.5
0.3
0.3
0.2
0.2
0.2
0.2
0.2
0.3
0.1
0
0.2
0.2
0.1
0.2
Nov.
23
1974
0.5
0.3
0.3
0.3
0.2
0.3
0.3
0.2
0.2
0.3
0.2
0.2
0.2
0.1
0.2
0.3
0.2
0.1
0.2
90 kg/ha of nitrogen as
1974
was applied on March 5 and September 27,
85
-------
TABLE 40. TOTAL RUNOFF AND NITROGEN LOST IN RUNOFF FROM 7.7-HA GRASSLAND
WATERSHED IN 1974
Date of Runoff
Tannar-u 1 R _ 9Q
February 21 - 23
March 20 - 22 *
April 13 - 14
Mav 1-2
MA v 5-7
Con^ornhoT* 1 fl 1 **
September 16 - 19
October 30 - November 2 *
November 4-13
November 23 - 27
Kf nvaniK av 0 Q ^ O
T}0f*^niH0T" S 1 S
n»r»*imKo'r 7 A ^1
Runoff
(cm)
1 S9
0.80
n os
1.08
1 00
n so
9 Oft
10.00
6.58
1.42
5.15
Ons
0 88
OM
Nitrogen lost
(kg /ha)
0.027
0.424
0.030
0.301
0.001
0.125
Totals 31.13 0.908
* Nitrogen at the rate of 90 kg/ha was applied on March 5 and September 27,
1974
removed from the watershed by the 6.6-cm runoff was only 0.30 kg/ha.
Subsequent runoff events during the fall of 1974 removed very little
nitrogen from the watershed *and * the concentrations in the runoff water were
very low.
The total amount of runoff in 1974 was 31.1 cm and the amount of NOo-N
lost from the watershed was somewhat over 0.9 kg/ha. The total amount of
nitrogen lost in the runoff could not be estimated exactly due to mal-
functions of the sampling equipment on several occasions. However, it is
estimated that less than 1.0 kg/ha of nitrogen was lost from the watershed in
1974. This is about 0.57. of the nitrogen applied to the watershed. The
average concentration of N03~N in the runoff water for the entire year would
be 0.3 ppm if it is assumed that 1.0 kg/ha of NO^-N was lost from the water-
shed in 1974.
Nitrates in Runoff Water During 1975
Rainfall recorded during 1975 at the grassland watershed is given in
Table 41. The total recorded is slightly below average for the area while
the monthly distribution was relatively normal throughout the year. During
86
-------
TABLE 41. DAILY RAINFALL ON GRASSLAND WATERSHED AT RIESEL, TEXAS IN 1975
Day
Jan.
Feb.
March
April
May
June
1. 0.62
2. 5.30
3. 1.12 0.28
4.
5.
6.
7.
8.
9. 0.60 0.35
10.
11. 1.25
12. 0.55
13. 2.25
14.
15.
16. 0.35
17. 0.70 0.55
18.
19.
20.
21.
22.
23. 0.30
24.
25.
26.
27.
28.
29.
30.
31.
Monthly 2.40 8.04 3.78
Totals
0.22
0.52
0.72
0.30
0.48
'
0.65 0.10
0.80
0.30
0.82
1.60
5.68
3.08
1.75 1.55
2.38 2.62
6.32 17.25
0.32
0.38
0.48
5,52
2.15
1.68
0.22
10.75
87
-------
TABLE 41. (Continued)
Day July Aug. Sept. Oct. Nov. Dec.
1. 0.22 1.45
2. 1.10
3. 0.45
4.
5.
6.
7. 0.12
8. 0.08
9. 0.30 2.08
10. J.
11.
I2i 0.50
13.
14.
15. 0.38
16. 2.08
17.
18.
19.
20. 1.70
21. 0.38
22. 0.38 0.48 1.08
23. 1.10
24. 0.90
25. 1.90
26.
27. 0.72
28.
29. 0.38
30.
31.
Monthly 1.48 4.50 6.82 4.98
Totals
Yearly Total 74.52
88
3.18
0.25
0.45
3.40
0.92
4.55 3.65
-------
May and June this watershed received the largest rains for single storms and
overall totals for the month. These occurred after two applications of
nitrogen had been made. Nitrogen was applied as ammonium nitrate at the rate
of 90 kg-N/ha on March 16 and May 7, 1975.
During 1975 there were ten runoff producing storms (Table 42). Runoff
samples were collected from four of these events. The sampling equipment
malfunctioned on two of the events and the other four events produced insuf-
ficient runoff to sample. The storms from which samples were collected
occurred on February 2, May 24, May 29, and June 28. The nitrate-nitrogen
concentrations found in water samples taken during these storms are given in
Table 43. The storm on February 2, occurred more than a month prior to the
first nitrogen application. Nitrate nitrogen was 0.4 ppm in the first sample
with each successive sample containing a lower concentration. There were no
significant runoff producing storms between the first and second nitrogen
applications. The next runoff storms were recorded on May 24 and 29. This
was 17 and 22 days, respectively, after the second nitrogen application. Due
to sampler malfunction 16 samples were not collected from the runoff produced
by the storm on May 24. Although 1.1 and 1.0 ppm nitrate nitrogen were
recorded in the first two samples, this is much lower than that recorded
during the April storm in 1974. The concentrations in the samples taken
during the May 29 and June 28 storms were only slightly higher than in the
runoff from the February storm and were similar to the concentrations found
in 1974 which occurred prior to fertilizer application. These samples which
were lost could have been higher in nitrates than the first two samples since
this was the case in the previous year during a similar storm. However, this
is somewhat unlikely since there occurred 6 days' of light to moderate showers
(Table 41) totaling 4.1 cm of rainfall between the time of last application
and the runoff producing storm of May 24. This amount of rainfall would prob-
ably be sufficient to leach the nitrates several centimeters into the soil
and thereby prevent appreciable losses in the runoff waters. In addition,
favorable growing conditions probably resulted in considerable plant uptake
of the fertilizer nitrogen. Due to extremely dry conditions during the last
half of the year no runoff was recorded. The total amount of nitrogen lost
due to runoff storms was 6.46 kg/ha. This amounted to only 3.67. of the
fertilizer applied.
Nitrates in Shallow Water Wells During 1974
Nitrate concentration in the four shallow wells located within the grass-
land watershed indicated that some leaching of applied nitrogen was occurring.
Table 44 gives the levels of NO--N in the wells at various times during 1974.
Only Well 1 contained water throughout the year. Wells 2, 3, and 4 contained
water only after heavy rains or during extended wet periods during the fall
and winter. As previously indicated, nitTagen fertilizer was applied on March
5 and September 27.
Nitrate levels in the well waters prior to fertilizer application were
relatively low. Well 2 had a somewhat higher concentration ranging from 1.0
to 2.1 ppm N03-N. However, following nitrogen application, the concentrations
in Well 2 increased to 61 ppm NOj-N after the first rainfall which caused
percolation into the wells on April 1. The nitrate level did not increase
89
-------
TABLE 42. TOTAL RUNOFF AND NITROGEN LOST IN RUNOFF FROM 7.7-HA GRASSLAND
WATERSHED IN 1975
Date of Runoff
January 1-5
January 9-19
February 1-8
March 13-14
March 17-20 *
April 28-30 *
May 23 - 24
May 28 - 29
June 27 - 29
December 24-26
Totals
Runoff
(cm)
0.38
0.98
5.12
1.15
0.02
0.10
4.72
1.90
1.02
0.18
15.57
Nitrogen lost
(kg /ha)
1.21
____
2.67
1.58
1.00
6.46
Nitrogen fertilizer was applied at the rate of 90 kg/ha on March 16 and
May 7, 1975
significantly in Well 1 on the April 1 sampling date. Rainfall in March and
April was not sufficient to cause percolation into all wells, as demonstrated
by the lack of water in Wells 3 and 4. The lack of rainfall could explain
the low concentration of N03-N in Well 1 and the high concentration in Well
2. Well 1 always contained a considerable amount of water. If a small
amount of nitrate and water leached into the purged water table in Well 1, it
would be diluted and the concentration in the well water would not change
significantly. However, if the same amount of nitrate and water leached into
Well 2, the result would be a high nitrate concentration. This was probably
the case for Well 2 which was dry in March and had a high NOo-N concentration
on April 1.
Over 5 cm of rainfall fell during the first week of May causing addition-
al percolation. The N03-N concentration in Well 1 increased significantly to
9.7 ppm, whereas the concentration in Well 2 was diluted to 20 ppm by May 7.
On this date Well 3 contained some water but the concentration of nitrates
was below 1 ppm.
The concentration in Well 1 dropped to zero by June 1 and remained very
low throughout the summer. The other wells were dry throughout the summer.
Well 2 contained some water on September 6 following heavy rains and had a
concentration of 16.5 ppm N03~N. Well 1 contained 2.3 ppm at this time.
Fertilizer nitrogen was applied again on September 27. Only 1.72 cm of
rainfall fell from September 27 until October 23. This caused no appreciable
90
-------
TABLE 43. CONCENTRATION OF N03-N IN RUNOJT WATER FROM 7.7-HA GRASSLAND
WATERSHED IN RIESEL, TEXAS IN 1975
Feb. May May June
Sample 2 24 29 28
No. 1975 1975 1975 1975
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
0.4
0.3
0.3
0.3
0.3
0.2
0.3
0.3
0.3
0.3
0.1
0.2
0.3
0.1
0.2
0.1
0.1
0.1
0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
1.1
1.0
0.1
'
i
i
|
4-1
O
1
ll
*
(-1
-------
TABLE 44. CONCENTRATION OF N03-N IN SHALLOW WELLS IN 7.7-HA GRASSLAND
WATERSHED AT RIESEL, TEXAS IN 1974
Well-
Date 1 2
October 16, 1973
March 5, 1974
April 1, 1974 *
May 7, 1974
June 1, 1974
June 20, 1974
September 6, 1974
September 13, 1974
November 8, 1974
November 20, 1974
November 27, 1974
December 13, 1974
0.1
0.5
9.7
0.0
0.1
2.3
0.4
14.4
6.0
4.5
2.8
1
1.0
2.1
61.0
20.0
d
d
16.5
d
18.8
d
5.4
6.2
0.2
0.3
d
0.2
d
d
d
d
22.6
d
d
7.1
0.2
d
d
d
d
d
d
d
2.8
d
d
1.6
* 90 kg/ha of nitrogen as NH4N03 was applied on March 5 and September 27,
1974
d well was dry
Nitrates in Shallow Water Wells During 1975
The concentrations of NO^-N in the shallow wells on January 2, 1975 were
rather high (Table 45). Samples collected in December of 1974 also contained
rather high concentration of N03-N (Table 44). This indicates that the
nitrogen which was applied in September of 1974 was still affecting the water
in the wells and that enough rainfall had not occurred to dilute the nitrates
in the water. Well 1 which contained water throughout 1974 contained only
1.7 ppm as compared to 12 ppm in Well 3. It is evident that the nitrates
leached into Well 1 were diluted by the larger quantity of water present in
this well.
The concentrations in Wells 1 and 4 decreased to almost negligible levels
by February 5. This was caused by 9.5 cm of rainfall which occurred since
the previous sampling date. The concentrations in Wells 2 and 3 decreased
about threefold during the same period, but still contained 2.7 and 3.4 ppm
N, respectively. The NO^-N levels remained low until the first of May which
corresponded to the first appreciable rainfall (Table 41) following the
initial application of nitrogen in 1975. On May 1, N03-N concentrations in
the wells had increased to levels ranging from 5.7 to 11.2 ppm. On June 11
and July 3, concentrations of 33 and 20.5 ppm NOg-N, respectively, were
recorded in samples taken from Well 1. These values are extremely high and
92
-------
TABLE 45. CONCENTRATION OF N03-N IN SHALLOW WELLS IN GRASSLAND WATERSHED AT
RIESEL, TEXAS IN 1975
Well
Date 1 2
January 2, 1975
February 5, 1975
February 25, 1975
February 27, 1975
March 16, 1975 *
April 14, 1975
May 1, 1975
May 7, 1975 *
May 27, 1975
June 11, 1975
July 3, 1975
July 28, 1975
1.7
0.3
0.0
0.2
0.6
0.8
6.0
5.3
6.0
33.0
20.5
4.0
8.0
2.7
d
2.8
3.8
d
11.2
d
10.2
d
d
d
iu~-«
12.0
3.4
d
d
d
d
9.9
d
11.2
d
d
d
1.3
0.1
1.2
1.8
1.0
d
5.7
d
3.7
0.4
0.2
d
* 90 kg/ha of nitrogen was applied as NH.NO- on March 16 and May 7, 1975
d well was dry
show the potential hazard which could occur in this soil after nitrogen
applications. It is possible that these rains were adequate to produce
leaching, but not large enough to cause appreciable dilution. Well 1
consistently contained more water than any of the other wells, and in fact,
contained water throughout the year. It seems possible that Well 1 could
have collected water from a larger area of the watershed thus accumulating
a high concentration of nitrates when conditions were ideal. It is apparent
that duration and intensity of each storm causes different amounts of leach-
ing of nitrates depending on time and previous weather and soil conditions.
Due to the dry conditions during the last half of 1975, rainfall was inade-
quate to induce leaching.
Nitrogen Uptake by Forage
Forage production on the watershed was limited in 1974 due to the lack
of rainfall during much of the growing season. Only 23-cm of rainfall fell
on the watershed from March 1 through August 21. Very little forage was
produced during the summer months as indicated in Table 46. The average
total forage yield from 3 harvests was 2584 kg/ha. The amount of nitrogen
taken up by the forage was only 27.3 kg/ha. This is only 30.5% of the 90
kg/ha of the nitrogen applied.
93
-------
TABLE 46. YIELD OF COASTAL BERMUDAGRASS AND N UPTAKE IN SPRING AND SUMMER OF
1974 FOLLOWING SPRING APPLICATION OF 90 KG-N/HA TO WATERSHED
April 7
1974
Plot Yield N
Uptake
1 1609 11.4
2
3 2200 25.1
4 1431 19.0
5 1160 12.2
Ave. 1600 17.0
Harvest Date
June 20 September 6 Total
1974 1974
Yield N Yield N Yield N
Uptake Uptake Uptake
493 4.5 559 5.4 2661 21.3
775 8.1 483 6.6 1258 14.7
644 6.6 601 6.2 3446 37.9
407 4.4 271 3.4 2109 26.8
575 6.2 385 4.8 2120 23.2
578 5.9 460 5.3 2638 28.2
TABLE 47. YIELD OF COASTAL BERMUDAGRASS AND N UPTAKE IN FALL OF 1974 FOLLOW-
ING FALL APPLICATION OF 90 KG-N/HA TO WATERSHED
November 20, 1974 - Sampling
Plot
1
2
3
4
5
Yield
kg /ha
721
1057
1176
932
1583
Protein
% N
2.34
1.56
1.65
1.78
1.51
Date
N Uptake
kR/ha
16.9
16.5
19.4
16.6
23.9
Ave.
1094
1.70
18.7
94
-------
The yield of forage from the fall application of N was only 1094 kg/ha
{Table 47) with a nitrogen uptake of only 18.6 kg/ha. This represents an
uptake efficiencey of only 20.8%.
Four dippings of forage were taken at monthly intervals from the water-
shed in 1975 (Table 48). The average total yield was 5968 kg/ha of Coastal
bermudagrass with 116 kg/ha of nitrogen utilized as protein over the entire
growing season. The first two clippings were after nitrogen had been applied
at the rate of 90 kg/ha. Nevertheless, these applications did not seem to
promote significant growth over that observed in the check pasture adjoining
this watershed. However, there was a visual difference in color. The
Coastal bermudagrass was noticeably greener where nitrogen had been applied.
Data for the first three harvests indicates a small yield. Each harvest
should have yielded over 3000 kg/ha of forage under good growing conditions;
however, due to the small amount of rainfall and poor nitrogen utilization in
the first two growing periods,this potential was not obtained.
On a total basis more than 116 kg of nitrogen should have been recovered
as protein nitrogen in the Coastal bermudagrass. Since 180 kg of nitrogen
was applied per hectare, the 116 kg only represents a 65% recovery not
counting native nitrogen available in the soil profile.
Nitrates and Ammonium in Soil Profiles
Very little nitrogen was found in the soil profiles except for the top
30~cm of soil when sampled soon after nitrogen application. No ammonium was
found in the soil following the spring application of ammonium nitrate. How-
ever, an average 25.8 kg/ha of nitrate-nitrogen was found in the top 30 cm of
soil 17 days after the application of 90 kg/ha of nitrogen (Table 49). Very
little inorganic nitrogen was found in the soil on May 7 and June 20. Essen-
tially all the nitrogen found in the soil on March 22 was either utilized by
the growing bermudagrass or immobilized in the soil. It is unlikely that any
significant amount of nitrogen leached through the soil since only 16.2 cm of
rainfall fell from the time of nitrogen application until the soil samples of
May 7 were taken. However, Table 44 indicates that some nitrogen had leached
into the shallow wells, and the soil samples taken on March 22 indicate that
some nitrogen had moved down to 45-60 cm.
An appreciable amount of ammonium was found in the top 30-cm of soil
following the fall application of nitrogen. The ammonium persisted for at
least 55 days following application (Table 49). Nitrate concentrations were
also very high in the top 15 cm of soil on October 17, three weeks after
application. However, only 1.7 cm of rainfall had fallen since the date of
application. The dry soil surface in the upper part of the sail profile
probably prevented the uptake of nitrogen from the upper 15 cm of soil. The
nitrate indicated to be present from 60-120-cm was found in only 1 of 5
profiles sampled. Four profiles had no detectable levels of nitrate.
Rainfall between October 17 and the next sampling date on November 20
amounted to 18 cm. Considerable percolation of water occurred during the
first week in November. All four of the shallow observation wells contained
water on November 8. The well water also contained considerable amounts of
95
-------
TABLE 48. YIELD OF COASTAL BERMUDAGRASS AND N UPTAKE IN SPRING AND SUMMER OF 1975 FOLLOWING
APPLICATIONS OF 90 KG-N/HA TO WATERSHED
VO
Harvest Date in 1975
May 7
Plot
1
2
3
4
5
Yield
1611
1735
1859
1718
1138
N-Uptake
37.3
44.0
43.9
45.6
27.8
June 17
Yield
1583
2244
1382
2098
1903
N -Up take
32.7
51.9
32.5
51.9
40.9
July
29
Yield N -Uptake
1599
1816
2060
1805
1643
16.4
23.4
29.7
28.1
22.8
September 8
Yield
802
792
911
661
846
N -Up take
9.7
10.2
12.0
9.7
11.5
Total
Yield
5583
6586
6211
6282
5529
N -Up take
95.5
129.5
118.0
135.3
103.0
Ave,
1612
39.8
1842
41.9
1784
24.1
802
10.6
6005
116.5
-------
TABLE 49. SOIL PROFILE NITROGEN IN WATERSHED AT VARIOUS TIMES AFTER APPLYING
90 KG-N/HA AS NH4N03 ON MARCH 5 AND ON SEPTEMBER 27, 1974
Dates Sampled in 1974
March 22 *
Depth
(cm)
0- 15
15- 30
30- 45
45- 60
60- 75
75- 90
90-105
105-120
Total
NH4
0.0
1.8
0.0
0.0
0.0
0.0
0.0
0.8
N03
19.4
6.4
3.8
3.4
1.2
0.3
0.2
34.7
May
NH4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
7
N03
4.7
1.6
0.6
0.3
0.1
0.2
0.4
7.9
June 20
NH4
0.
0.
0.
0.
0.
0.
0.
0.
0.
g/hi
0
0
0
0
0
0
0
0
0
N03
1.1
0.4
0.0
0.0
0.0
0.0
0.0
0.0
1.5
Oct.
NH4
7.2
4.3
0.0
0.0
0.0
0.0
0.0
0.0
11.5
17 *
N03
36.3
0.2
0.0
0.0
2.2
2.2
2.4
2.4
45.7
Nov.
NH4
16.5
6.3
0.0
0.0
0.0
0.0
0.0
0.0
22.8
20
N03
2.4
1.1
0.4
0.4
0.4
1.1
1.1
0.4
7.3
* 90 kg/ha of nitrogen as NH.NO. was applied on March 5 and September
27. * J
nitrates (Table 44). The soil samples taken on November 20 (Table 49) also
indicate that some movement of nitrates had occurred since the last sampling.
Four of the five profiles samples contained some nitrate down to 120 cm.
About 34 kg/ha of N03-N was removed from the soil profiles between sampling
dates. Plant uptake of N was only 18.6 kg/ha (Table 46). Nitrogen in runoff
water during this period was less than 0.6 kg/ha. The 15.0 kg/ha of nitrogen
was not necessarily lost by leaching. Immobilization was probably a major
factor attributing to the disappearance of nitrate between October 17 and
November 20.
Soil profile data gives some insight as to what might have happened to
some of the nitrogen applied the previous year. Soil samples taken in
February of 1975 (Table 50) show an insignificant amount of nitrogen carried
over in the profile from the previous year. This agrees with the low amount
of nitrogen found in the wells during February and March of 1975 (Table 45).
97
-------
TABLE 50. SOIL PROFILE NITROGEN IN SAMPLES TAKEN AT VARIOUS TIMES FROM
WATERSHED DURING 19?5
Dates Sampled in 1975
Depth (cm)
Feb.
NH4-N
25
N03-N
May
NH4-N
1
N03-N
May
NH4-N
27
N03-N
0- 15
15- 30
30- 60
60- 90
90-120
120-150
150-180
Total
5.6
0.0
0.0
0.0
0.0
0.0
0.0
5.6
0.9
0.3
0.3
0.0
0.0
0.0
0.0
1.5
11.8 3.9
0.0
0.0
0.0
0.0
0.0
0.0
11.8
2.1
2.8
30.0
0.0
0.0
0.0
38.8
15.2
0.0
0.0
0.0
0.0
0.0
0.0
15.2
5.8
11.2
2.0
0.2
0.2
0.0
0.0
19.6
The high NH, and N03 levels found in the samples taken on May 1 were probably
due to the March nitrogen application and to some native nitrogen production
due to mineralization. The high nitrate value recorded in the 60- to 90-cm
sample was due to a high concentration found in only one of the three samples
taken. This could indicate a possible accumulation zone where one of the
cores was taken. The sample with the high N©3 concentration was taken from
the top of the C horizon which in this soil is predominantaly semipermeable
caliche. This sampling date corresponds with the date when high concen-
trations of N03-N were found in the well samples (Table 45).
The May 27 samples contained a similar amount of ammonium and nitrate as
that found in the May 1 samples. However, no samples contained large concen-
trations of either nitrogen form to indicate accumulation. The soil cores
do indicate some leaching of nitrates through the soil profile.
98
-------
SECTION 8
FIELD LYSIMETERS
To determine the quantity of nitrates which leaches through the soil from
different sources of nitrogen, five fertilizer treatments were applied to
five lysimeters. Nitrate movement through the soil was determined by measur-
ing N03~N in the soil profile and in the drainage effluent. Nitrogen uptake
from the various treatments by grain sorghum was also determined.
PROCEDURE
Five "natural" drainage lysimeters were installed in Norwood silt loam
near College Station, Texas, to determine the extent of nitrate movement
through the soil from various sources of nitrogen. The lysimeters were con-
structed by welding two 1.2 x 2.4 m and two 1.2 x 1.2 m steel plates together
to form a rectangular box with the top and bottom open. The inside dimen-
sions of the boxes were 105-cm wide, 225-cm long and 120-cm deep. The boxes
were placed on top of the soil where they were to be installed and concrete
weights slowly placed on the boxes until they started moving into the soil.
As the boxes moved into the soil, the soil around the outside wells was ex-
cavated with a backhoe and shovels to reduce the friction between the soil
and the walls. Weight was added until the lysimeters had been pushed to a
depth of 120 cm and the top edge of the walls were about 3 cm from the soil
surface. The weights were then moved.
An excavation was then made on one side of the lysimeter in order to push
the bottom of the lysimeter in place. A steel guide frame was made which wag
used to guide the bottom plate of the lysimeter while it was pushed into
place. A 0.625-cm steel plate 1.2 x 2.4 m was placed on the guide frame in
the excavation next to the lysimeter. Two 10 ton hydraulic jacks were used
to push the steel plate under the lysimeter. After pushing the bottom plate,
the space between the walls of the lysimeter and the bottom plate ranged from
0 to 3 cm. In order to seal the bottom to the lysimeter walls a steel strap
was welded around the walls at the bottom of the lysimeter and to the bottom
plate.
An underground room was constructed on one side of the lysimeters to col-
lect drainage samples and'make redox-readings at different depths. The rooms
were 1.2 x 2.4 m and 1.5 m high and made of cinder blocks. The top of the
room which was made of 0.615-cm steel plate was 30 cm below the soil surface.
To install the drainage ports, 2-cm holes were drilled along the bottom
of one side of the lysimeter 30 cm apart. A soil probe 1.25 cm in diameter
99
-------
was used to pull a soil core the entire width of the lysimeter. Drainage
tubes,consisting of 1.25-cm porous cylindrical tubes cemented over slotted
9 mm stainless steel tubes 120-cm long, were inserted into the core holes
along the bottom of the lysimeters through the drilled holes. The ends of
the stainless steel tubes were passed through rubber stoppers which were
inserted into the drilled holes in the side of the lysimeters to prevent
leakage around the drainage ports. The drainage ports were connected by
means of Tygon tubing and tension of 10 cm of water was maintained on the
drainage tubes by means of a vacuum system connected to glass collection
bottles.
Areas the same size as the lysimeters were established adjacent to the
lysimeters to serve as duplicates and to allow for the collection of soil
samples. Each lysimeter and its duplicate size area was located in the
center of a plot 6.75 m wide and 7.5 m long. These plot areas were treated
similar to the lysimeters.
The fertilizer treatments applied to each lysimeter in 1974 and 1975 are
shown in Table 51. The treatments were applied at the rate of 168 kg-N/ha
or 41 gms per lysimeter in both years. The fertilizer was applied at
planting. Placement of the fertilizer was approximatly 7 cm below and 5 cm
to the side of the seed. Grain sorghum (Sorghum vulgare) was planted in 25-
cm rows in both 1974 and 1975. At maturity, grain and forage was harvested,
weighed, and analyzed for nitrogen. After collecting a forage subsample for
analysis, the remaining litter was returned to the soil.
Rainfall measurements were taken at a nearby weather station.
RESULTS
Grain Sorghum Yields
Grain sorghum yields and N-contents are given in Table 52. Yields from
the lysimeters and the duplicate adjacent areas were used to determine
statistical relationships between treatments. There was a considerable
amount of variability between the lysimeter and their duplicate adjacent
plots. There was no significant difference in yields between treatments
within years. However, the grain yields in 1974 were significantly greater
than the yields in 1975. In 1975, there was also a significant difference
in %N in the forage between treatments. However, there-was no significance
between any grain yield or forage yield in 1974.
Nitrate Leaching
Leaching of nitrate through the lysimeter from the various sources of
nitrogen fertilizers is shown in Figures 12-16. Very little N03~N was found
in the effluents in 1974. Only the 3(^3)9 treatment (Fig. 15) resulted in
significant NO..-N concentrations in the effluents in 1974. The highest N03-N
concentration in 1974 was only 0.68 ppm in November, seven months after the
application of Ca(NOo>2« Generally, the concentrations w*»re less than 0.5 ppm
and the largest amount leached through any of the lysimeters was 123-rag from
lysimeter 2 which was fertilized with NltyCl. However, the majority of this
100
-------
TABLE 51. FERTILIZER TREATMENTS APPLIED TO FIELD LYSIMETERS
Fertilizer treatments
Lysimeter
I
II
III
IV
V
1974
NH^Cl NH^Cl
NH4C1
NH4C1 + N-Serve
Ca(N03)2
SCU-20
1975
+ 1% N-Serve
NH4C1
NH4C1
Ca(N03)2
SCU-20
TABLE 52. YIELD AND NITROGEN CONTENT OF GRAIN FROM LYSIMETERS
Lysimeter
I
II
III
iv
V
i
ii
in
IV
V
Yield
Grain
4842
4183
4990
4509
4444
3023
2779
2726
2769
2367
1974
(kg/ha) N-content (%)
Forage
*
*
*
*
*
7084
4642
3459
6279
5844
Grain
1.78
1.64
1.78
1.53
1.59
1975
1.25
1.17
1.10
1.09
1.05
Forage
0.64
0.75
0.78
1.02
0.48
0.93
0.81
1.05
0.81
0.76
* Forage yield not determined
101
-------
ppm
N03-N
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5-
0
Fertilizer
Applied
NH4CI
5
2000
1600
1200
Total
N03-N
Leached
(mg)
800
400
Dec. Feb. Apr. Jun. Aug. Oct. Dec. Fefat Apr. Jun. Aug. Oct. Dec.
I 1974 I 1975 I
Figure 12. Concentration and cumulative N03-N found in drainage from Lysimeter 1
during 1974 and 1975 and fertilized with NH4C1 and NH4C1ttreated
with N-Serve.
-------
o
U)
5.0 -
4.5 -
4.0 -
3.5 -
3.0 -
ppm 25-
N03-N '
2.0 -
1.5 -
1.0 -
0.5 -
0
^
i
, ,x--x
n. p 1 .
Fertilizer
Applied -
~? ^^V
NH4CI
^^^^^^^^^^^^i^^^^^NMMlM^b^lM^MHl
NH4 Cl
9 .f*"* 472 mg
,^-"y '
-2000
- 1600
- 1200
Total
N03-N
Leached
800
400
o
Dec. Feb. Apr. Jun. Aug. Oct. Dec. Feb. Apr. Jun. Aug. Oct Dec.
I 1974 | 1975 I
Figure 13. Concentration and cumulative NOs-N found in drainage from
Lysitneter 2 during 1974 and 1975 and fertilized with NH^Cl.
-------
5.0 --
4.5 --
4.0 --
3.5 --
3.0-
ppm
N03-N
Fertilizer
Applied
NH4ClfN-Serva
x
,.x-«~*l252mg
X
t
!
2.0--
1,5 --
1.0 --
0.5-
*p i i i i i i i i i i ! i i i i i i i i i i i i i
Dec. Feb. Ape Jun. Aug. Oct. Dec. Feb. Apr. Jun. Aug. Oct. Dec.
| 1974 | 1975 j
Figure 14. Concentration and cumulative N03~N found in drainage from
Lysimeter 3 during 1974 and 1975 and fertilized with NH4C1
treated with N-Serve and
. . gy . .
T 2000
-- 1600
1200
Total
N03-N
Leached
(mg)
800
-- 400
-------
13
o
Ul
5.0-
4.5-
4.0-
35-
3.0-
,2.5-
1
2.0-
1.5-
1.0-
0.5-
Q
1
Ht
M
m
«
I
9
Dec. Feb. A
Fertilizer
. Applied -
*^ 0 >v
s'' N^
r
Co(N03)2
0
p--x
l-l fte*'*"^
^ ^ A. ^
l i ^^^^^^^^^^^^^^^^^^^^^^^^^^^^P^^^^^^^^^r^^^^^^^^
pr. Jun. Aug. Oct. Dec. Feb.
1974 |
^^ ^^
/JHC-X 2759mg
/
x" ^
K
I
/
i
r
i
't
X
1
/ Ca(N03)2
i
i
i
IOC
f
1
1
1
.
Apr. Jun. Aug. Oct. Dec.
1975 1
[3000
2000
.
-1600
- 1200
Total
N03-N
Leached
(mg)
- 800
- 400
0
Figure 15. Concentration and cumulative NOj-N found in drainage from
Lysimeter 4 during 1974 and 1975 and fertilized with
.,-.
-------
o
ON
5.0
4.5--
4.0--
3.5--
3.0--
ppm
N03-N "
2.04-
IJ5 - -
1.0--
T2000
Fertilizer
Applied
SCU-20
SCU-20
'-*'**
- -1600
1200
Total
N03-N
Leached
(mg)
f 800
-- 400
Dec. Feb. Apr. Jun. Aug. Oct. Dec. Feb. Apr. Jun. Aug Oct. Dec.
I 1974 I 1975
Figure 16. Concentration and cumulative NO^-N found in drainage from
Lysimeter 5 during 1974 and 1975 and fertilized with SCU-20.
-------
occurred in December of 1973, prior to fertilization. The percent of nitrogen
fertilizer lost by leaching through the lysimeters ranged from 0.04% from the
SCU-20 to 0.23% from the Ca(N03>2. The very low level of leaching in 1974 is
attributed to the low amount of rainfall received after the application of
fertilizer. The maximum amount of leaching effluent collected from the time
of fertilization to the end of December in 1974 was only 3.6 cm from lysi-
meter 4. The least amount of effluent collected during this same period of
time was 0.9 cm from lysimeter 5. Drainage through the five lysimeters was
different due to heterogeneity in the soil profiles. Being an alluvial soil,
there was considerable variability in the texture of the soil with depth.
A supplemental study was undertaken to determine the variability of the soil
profiles with respect to moisture retention, bulk density, and texture. The
results of this investigation are given in the Appendix.
Leaching was insignificant during the first part of 1975 due to below
normal rainfall. However, heavy rains in May and June caused increased
water movement which,caused the concentration of N03 in the effluents to
increase significantly. Concentrations between 1-3 ppm were common in the
effluents collected in May through August of 1975. The NH^Cl treatments
with or without N-Serve additions generally resulted in lower N03-N
concentrations in the effluent. The Ca(N03)2 treatment was the only fertil-
ization practice which resulted in concentrations greater than 6 ppm
occurring in the leach at a Three samples were collected from this treatment
in August and September which had concentrations of 13, 32, and 16 ppm
(Figure 15). The last effluent sample collected in September from lysimeter
2 and fertilized with NH^Cl (Figure 13) had a N03-N concentration of 5.5 ppm
which may indicate that high concentrations of nitrate were beginning to move
through this lysimeter.
The total amounts of nitrogen leached during 1975 was relatively low.
The greatest amount of nitrogen lost by leaching in 1975 was 2.48 gms from
the Ca(NOq)2 treatment which amounts to 6.0% of the nitrogen applied in 1975.
The leaching losses from the other treatments ranged from 0.78% to 2.1% of
the nitrogen applied. The actual amount of N03-N lost from each fertilizer
treatment during the two years is shown in Figures 12-16.
It is believed that some of the N03 leached in 1975 was from fertilizer
applied in 1974. It is apparent from the data shown that leaching was
occurring over six months after fertilizer was applied in 1975 and some
leaching was occurring almost a year after it was applied in 1974. The 2.48
gms of nitrogen reported leached in 1975, probably was not all from the
nitrogen applied in 1975. The low amount of leaching water which occurred in
1974 was probably not sufficient to move the 1*03 through the entire 120-cm
profile in 1974. When the heavy leaching rains in the late spring and summer
of 1975 occurred, the nitrates which remained in the lower profile from 1974
were probably leached together with some of the nitrogen applied in 1975.
Nitrogen-15 was applied in 1974 and 1975 to two of the lysimeters to deter-
mine the contributijo-.s from year to year but the concentrations of N03 and
N-15 in the effluent were too low to determine this effect.
107
-------
Soil Nitrates
Soil samples were collected on October 2, 1974, May 23, 1975, and Au-
gust 7, 1975, from the plots adjacent to the lysimeter. The results of these
samplings are shown in Tables 53-55. Ammonium was not detected in any of the
samples at any sampling time. Soil N03-N concentrations were extremely low
in the October 1974 sampling (Table 53). Nitrate concentrations in effluents
in the summer and fall of 1974 were also very low indicating that very low
concentrations would be expected in the soil profiles. Since leaching of
nitrates was not significant in 1974 and only about 20% of the applied N
was found in the grain sorghum, and since no nitrates were found in the soil
profile six months after fertilizer application, it is apparent that im-
mobilization of much of the fertilizer N occurred in 1974.
Following the application of nitrogen in March of 1975, soil samples
were taken on May 23. The concentrations of N03~N in the soil profiles were
rather high, except for lysimeter 3 which was fertilized with NH4C1. The
concentrations between 90-105-cm were considerably lower, indicating that
movement of N03 had not reached this depth and that leaching effluents should
not contain much N03. The effluents collected from the lysimeters after the
application of fertilizer were on May 3. Figures 12-16 indicated that the
effluent concentrations the first of May were indeed low.
Figure 14 and Table 54 indicate that some of the N applied as NItyCl had
leached from lysimeter 3 as N03 by the later part of May. The concentration
of N03 in the effluents in May was relatively high with values between 1.8
and 2.5 ppm. The soil samples from the plot treated with NIfyCl and being
adjacent to lysimeter 3 indicated that very little nitrate remained in the
soil above 105-cm on May 23. The high nitrate concentrations found in the
other profiles on May 23 (Table 55) indicate that leaching of these nitrates
could be significant if sufficent rainfall occurred to cause drainage before
plant uptake or immobilization removed the N03 from the soil solution. Heavy
rains did indeed occur in June, July, and August. Figures 12-16 indicate the
extent of leaching which did occur during this period.
Soil samples taken following the heavy rains (Table 55) indicate that
most of the N03 had been leached lower in the soil and a considerable amount
leached from the soil. However, much of the decline in soil N03 concentra-
tion can be attributed to plant uptake.
108
-------
TABLE 53. CONCENTRATION OF N03-N IN SOIL OF LYSIMETERS ON OCTOBER 2, 1974
Lyslmeter
Depth (cm)
1
2
3
4
5
ppm
0
8
15
22
30
45
60
75
90
- 8
- 15
- 22
- 30
- 45
- 60
- 75
- 90
-105
0.
1.
0.
0.
0.
0.
0.
0.
1
0
3
3
1
-
1
1
1
0.
0.
0.
0.
0.
0.
0.
0.
0.
2
1
1
1
1
1
2
1
2
0.
0.
0.
0.
0.
0.
0.
0.
0.
4
3
3
2
2
2
2
2
2
0.
0.
0.
0.
0.
0.
0.
0.
0.
2
2
2
2
2
2
3
2
1
0.
0.
0.
0.
0.
0.
0.
0.
2
3
2
1
1
2
3
2
Each value is an average of two samples
TABLE 54. CONCENTRATION OF N03-N IN SOIL OF LYSIMETERS ON MAY 23, 1975
Lysimeter
Depth (cm) 1
ppm
0
8
15
22
30
45
60
75
90
- 8
- 15
- 22
- 30
- 45
- 60
- 75
- 90
-105
0.
0.
0.
5.
19.
18.
2.
-
9
6
6
8
1
3
5
1
3
11
37
26
36
26
18
9
.5
.6
.5
.1
.9
.8
.6
.2
.6
0.
1.
0.
0.
0.
2.
3.
2.
2.
5
6
9
6
8
6
1
3
2
0
11
30
18
36
25
10
3
4
.6
.6
.9
.6
.3
.2
.5
.9
.8
2.
2.
4.
10.
24.
11.
8.
5.
2.
7
6
6
1
6
1
3
4
0
Each value is an average of two samples
109
-------
TABLE 55. CONCENTRATION OF N03-N IN SOIL PROFILE OF LYSIMETERS ON AUGUST 7,
1975
Depth (cm)
0-8
8-15
15 - 22
22 - 30
30 - 45
45 - 60
60 - 75
75 - 90
90 -105
1
0.9
0.8
0.9
1.2
1.2
1.0
1.9
2.8
- »
2
3.1
5.5
7.2
10.4
8.1
5.0
2.3
12.1
.
Lysimeter
3
ppm N03-N
0.6
0.8
0.9
0.6
0.8
0.8
0.9
0.8
«»»
4
1.5
1.6
1.3
1.9
4.7
10.5
16.7
26.9
MM
5
2.1
2.1
2.1
2.5
1.6
0.9
1.0
*^^*
Each value is an average of two samples
110
-------
REFERENCES
1. Bremner, J. M. Inorganic Forms of Nitrogen. In: C. A. Black (ed.)
Methods of Soil Analysis. Amer. Soc. of Agron., Inc., Madison,
Wisconsin, 1965. Part 2, pp. 1179-1237.
2. Day, P. R. Particle Fractionation and Particle-Size Analysis. In:
C. A. Black (ed.) Methods of Soil Analysis. Amer..Soc. of Agron.,Inc.,
Madison, Wisconsin, 1965. Part 1, pp. 545-567.
3. George, W. 0., and W. W. Hastings. Nitrate in the Ground Water of Texas.
Amer. Geophys. Union, 32: 450, 1951.
4. Jackson, M. L. Soil Chemical Analysis. Prentice-Hall, Inc., Englewood
Cliffs, New Jersey, 1958.
5. Jansson, S. L. Tracer Studies on Nitrogen Transformation in Soil with
Special Attention to Mineralization-Immobilization Relationships. Kgl.
Lanthbruks-Hogskol Ann., 24:101-361, 1958.
6. Jones, D. C. An Investigation of the Nitrate Problem in Runnels County,
Texas. EPA-R2-73-267, Environmental Protection Technology Series.
U. S. Printing Office, Washington, D. C., 1973.
7. Klute, A. Water Capacity. In: C. A. Black (ed.) Methods of Soil
Analysis. Amer. Soc. of Agron., Inc., Madison, Wisconsin, 1965. Part 1,
pp. 273-278.
8. Keeney, D. R., and J. M. Bremner. Determination and Isotope-Ratio
Analysis of Different Forms of Nitrogen in Soils: Urea. Soil Sci. Soc.
Amer. Proc., 31:317-321, 1967.
9. Kissel, D. E., J. T. Ritchie, and E. Burnett. Chloride Movement in
Undisturbed Swelling Clay Soil. Soil Sci. Soc. Amer. Proc., 37:21-24,
1973.
10. Milham, P. J., A. S. Awad, R. E. Paull, and J. H. Bull. Analysis of
Plants, Soils, and Waters for Nitrate by Using an Ion-Selective
Electrode. Analyst., 95:751-757, 1970.
11. Miller, G. E., P. B. Allen, N. H. Welch, and E. D. Rhoades. The
Chickasha Sediment Sampler. ARS 41-150, U. S. Dept. Agri. Res. Serv.,
1969.
12. Swoboda, A. R. Unpublished Data. Texas A & M University, 1969.
Ill
-------
13. Thomas, 6. W., and A. R. Swoboda. Anion Exclusion Effects on Chloride
Movement in Soils. Soil Sci., 110:163-166, 1967.
14. U. S. Public Heath Service. Drinking Water Standards. 956-47-50, U. S.
Dept. Of Health, Education and Welfare. Public Health Service
Publication, 1962.
112
-------
APPENDIX
Undisturbed soil samples were taken around the 5 lysimeters described
in Section VIII to determine the particle size distributon, bulk densities
and moisture retention characteristics of the soil profiles. Eleven profiles
were sampled to depths of 141-154 cm. Undisturbed cores were taken approx-
imately every 3-10 cm with a core sampler fitted with a brass cylinder sleeve
5 cm in diameter and 3.75 cm in length.
Moisture retention characteristics were determined on each sample by the
method described by Klute (Klute, 1965). Basically* the method consists of
placing the undisturbed cores on a porous plate in a specially designed
pressure cell. The cores are saturated with water by wetting from the bottom.
The samples are allowed to drain by applying desired air pressure to the top
of the soil core. After drainage ceases the cell and soil core are weighed
and a slightly higher air pressure applied until drainage again ceases. The
cell is weighed to determine moisture loss caused by the added air pressure.
This process is repeated until a pressure of 1 bar is reached. Pressure
increments of 0.1 bar were used in this study.
Bulk density of the soils were determined by drying the undisturbed soil
cores used in the moisture retention study at a temperature of 110 C.
Using the weight of soil contained in the known volume of the cylinder
sleeves the bulk density was determined.
Particle size distribution was determined on the undisturbed soil cores
by the Hydrometer Method as described by Day (Day, 1965). The same soil
samples which were used for the water retention and bulk density
determinations were used for this determination.
113
-------
225cm 225 cm
225 cm
«I
3 llyi 4| 6
160 cm+
J
u7.
106 cm
Ly« ' '*'
10
APPENDIX A
Location of profiles with respect to lysimeters which were sampled for texture, bulk density,
and moisture retention.
-------
APPENDIX B
TABLE B-l. PARTICLE SIZE ANALYSIS AND BULK DENSITIES OF SOIL SAMPLES FROM
PROFILES IN LYSIMETER PLOTS
Profile
Location
1
2
3
*J
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
10
11
12
13
1
j.
2
3
4
5
6
7
Depth
(cm)
6-9
13 - 16
21 - 24
30 - 33
42 - 45
49 - 52
61 - 64
74 - 77
92 - 95
104-107
112-115
120-123
126-129
142-145
150-153
(-D- 2
7-10
17 - 20
28 - 31
39 - 42
48 - 51
61 - 64
81 - 84
94 - 97
102-105
121-124
137-140
149-152
L 7
H /
12 - 15
19 - 21
25 - 28
34 - 37
38 - 41
51 - 54
%
Sand
35
27
29
15
69
60
64
27
61
25
16
50
60
32
49
29
23
38
34
38
65
64
62
14
46
34
65
39
35
22
14
29
65
%
Silt
55
60
58
69
lost-
28
35
25
60
28
55
66
35
30
34
30
47
54
38
59
33
27
26
27
51
41
36
25
48
41
65
54
66
21
%
Clay
10
13
13
16
.__
3
5
11
13
11
20
18
15
10
34
21
24
23
24
7
29
8
10
11
35
13
30
10
13
24
13
32
5
14
Bulk
Density
1.42
1.57
1.63
1.48
_________
1.32
1.41
1.42
1.66
1.40
1.52
1.50
1.51
1.53
1.10
1.56
1.59
1.48
1.46
1.45
1.43
1.44
1.45
1.51
1.51
1.49
1.44
1.45
1.45
1.67
1.55
1.54
1.51
115
-------
Table B-i. (Continued)
Profile
Location
3
4
5
6
Sample
No.
8
9
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
5
6
7
8
9
10
11
12
1
2
3
4
5
6
7
8
9
10
11
Depth
(cm)
59 - 62
72 - 75
87 - 90
99 -102
110-113
120-123
132-135
143-146
(-2)- 1
8-11
22 - 25
32 - 35
43 - 46
56 - 59
74 - 77
84 - 87
99 -102
116-119
128-131
138-141
151-154
4-7
15 - 18
30 - 33
48 - 51
60 - 63
71 - 74
81 - 84
96 - 99
110-113
120-123
128-131
141-144
(_5)_(_2)
6-9
20 - 23
28 - 31
40 - 43
56 - 59
69 - 72
82 - 85
100-103
110-113
120-123
Sand
57
54
64
16
33
73
50
50
49
49
15
51
48
33
55
28
27
35
67
19
38
35
72
16
71
77
50
40
40
44
38
35
52
24
40
23
14
52
76
52
28
42
22
Silt
35
43
25
59
52
19
40
45
36
33
_____! nd
* ~ iOS 1
50
34.2
31.3
40
37
54
49.3
52
25.5
63
38
41
19
59
18
17
31
52
40
33
52
34
33
46
47
49
62
34
21
35
52
38
48
Clay
8
3
11
25
15
8
10
5
15
18
35
15
21
27
8
18
23
13
8
18
24
24
9
25
11
6
19
8
20
23
10
31
15
30
13
28
24
14
3
13
20
20
30
Bulk
Density
1.36
1.32
1.46
1.48
1.66
1.45
1.48
1.45
1.43
1.59
1.43
1.47
1.43
1.45
1.37
1.69
1.48
1.52
1.49
1.53
1.44
1.54
1.48
1.48
1.42
1.47
1.49
1.35
1.42
1.49
1.52
1.41
1.32
1.67
1.50
1.44
1.43
1.43
1.48
1.53
1.47
1.45
1.57
116
-------
Table B-l. (Continued)
Profile Sample
Location No .
6 12
13
7 1
2
3
4
5
6
7
8
9
1 />
10
11
8*
1
2
3
4
5
6
7
8
9
10
11
12
9 1
2
3
4
5
6
7
8
9
10
10 1
2
3
4
5
6
7
8
Depth
(cm)
129-132
145-148
6-9
18-21
36 - 39
45 - 48
59 - 61
70 - 73
84 - 87
100-103
104-107
mt O/.
IJq.
141-144
(c\ / o\
-5)-( Z)
4-7
14 - 17
25 - 28
43 - 46
58 - 61
74 - 77
90 - 93
100-103
114-117
122-125
140-143
6-9
14 - 21
34 - 37
44 - 47
59 - 62
76 - 79
95 - 98
107-110
122-125
141-144
(-3)- 0
8-11
24 - 27
35 - 38
49 - 52
64 - 67
81 - 84
94 - 97
%
Sand
34
46
44
48
46
26
24
59
67
46
42
32
40
40
84
39
82
64
73
60
55
33
36
42
16
38
29
31
30
40
28
33
37
40
77
38
26
56
29
93
96
%
Silt
50
48
49
35
33
51
60
21
20
32
40
44
41
52
10
53
12
26
17
27
37
40
40
40
56
36
43
60
67
38
47
48
46
38
12
41
63
39
57
0
2
%
Clay
16
6
12
17
21
23
16
20
13
22
18
24
19
8
6
8
6
10
10
13
8
27
25
18
28
26
28
9
30
22
25
19
17
22
11
21
11
5
14
7
2
Bulk
Density
1.43
1.53
1.49
1.51
1.49
1.43
1.34
1.50
1.35
1.53
1.34
1.50
1.69
1.58
1.50
1.40
1.48
1.51
1.48
1.46
1.43
1.52
1.50
1.37
1.57
1.44
1.48
1.44
1.62
1.46
1.47
1.52
1.66
1.50
1.53
1.37
1.55
1.47
1.39
117
-------
Table B-l. (Continued)
Profile
Location
10
11
Sample
No.
9
10
11
12
1
2
3
4
5
6
7
8
9
10
11
Depth
(cm)
102-105
116-119
128-131
140-143
(_4)_(_1)
11 - 14
25 - 28
38 - 41
60 - 63
69 - 72
86 - 89
96 - 99
109-112
120-123
138-141
Sand
57
52
49
62
44
65
67
40
57
66
46
56
52
32
33
Silt
32
33
31
24
46
23
29
55
30
24
45
28
30
60
57
Clay
11
15
20
14
10
12
4
5
13
10
9
16
18
8
10
Bulk
Density
1.55
1.49
1.30
1.47
1.35
1.12
1.40
1.52
1.32
1.45
1.48
1.51
1.48
1.52
1.42
118
-------
APPENDIX C
Mositure Retention Curves of Soil Samples from
Profiles at Various Locations Around Lysimeters.
Location numbers refer to locations shown in
Appendix A. Retention curve numbers refer to
soil sample numbers described in Appendix B.
119
-------
Location I
e
O.I
0.2 03 0.4 0.9 O.6 0.7
Pi
(Bars)
0.8 0.9
e
.7-
.ft
.5
.4
.3
Location I
V ** *"L*^ ^ < J .
f ^^^* *
.1
(Bart)
120
-------
Location I
6
0:2 09
0:4 0:5 o:s 0.7
Pi
(Ban)
0.8 0'9 1.0
121
-------
.7
.6
.5
Location 2
e
.3
.2
.1,.
- J
0 O.I 0.2 03
0.4 as 0.6 0.7 0.8 0.9
Pi
(Bars)
1.0
6
.7-
.6
.5
.4
.3.
Locat ion 2
.1 -
"o!i 8(2 S5 o!? Si oS ST Si
P|
(Bars)
o
122
-------
Location 2
123
-------
.7
.6
Location 3
.5
6
.3
.2
.1,
.rr
0 0.1 0.2
03 0.4 a5 0.6 0.7
Pi
(Bart)
0.6 0.9 1.0
Location 3
6
"oli 82 SS oft 8*5
(Bars)
1:0
124
-------
Location 3
e
0.1 0.2 03
0.4 0.5 0.6 0.7
Pi
(Bars)
0.8 0,9 1.0
125
-------
.7
Location 4
e
.5
.4
.3
.2
.1
0 O.I 0.2 03
0.4 0.3 0.6 0.7
Pi
(Bars)
0.6 0.9 1.0
6
.7
.6
.5
.4
.3
Location 4
.1
oSid2 o!a oU o'.s ole ol.7 rfe o!s i!o
(Bars)
126
-------
.7
.6
J5
e
.3.
.2
.1.
Location 4
12
I. -I. JL J. -I.
I
0 O.I 012 03 0.4 0.5 0.6 0.7 0.8 0"9 1.0
(Bo'rs)
127
-------
Location 5
6
0 O.I 0.2 03 0.4
as 0.6 0.7 0.6 0.9
Pi
(Bars)
1.0
6
.7
.6
.5
.4
.3
Locot ion 5
.1
*
o oa 0.2 0.3 0.4 0.5 0.6 0.7
(Bars)
128
o
-------
Location 5
0.1 0,2 03
0.4 0.5 0.6 0.7
Pi
(Bars)
0.8 0.9 1.0
129
-------
Location 6
e
o o.i
0.2 03 0.4 0.5 0.6 0.7
Pi
(Bars)
0.8 0.9
Location 6
6
0.3 0.4 o.s o.e
P|
(Bars)
0.9 1.0
130
-------
Location 6
0.2 03
0.4 0.5 0.6 0.7
Pi
(Bars)
0.6 0,9 1.0
131
-------
Location 7
e
0.2
03 0.4 0.5 0.6
Pi
(Bars)
0.7 0.6 0.9 1.0
Location 7
e
8
-------
.7
.6
Location 7
e
.3..
.1..
ii
0.6 07 0.8 0,9 1.0
Pi
(Bart)
133
-------
.7
.6
.5
Location 8
e
.3
.1,,
i i j_ i i j_ i j
0 O.I 0.2
03 0.4 as o.e
Pi
(Bart)
1.
0.7 0.6 0.9 1.0
Location 8
e
"Si SE S3S5 SsSe
P|
(Bart)
o
134
-------
Location 6
e
135
-------
.7
.6
.5
Location 9
e
\
.3
.2
0 O.I 0.2 03 0.4 a5 0.6 0.7
Pi
(Bart)
0.6 0.9 1.0
Location 9
6
5 otl SS o?4 o'.s ote Sr 6^8 S
136
-------
Location 10
e
0 O.I 0.2 03
0.4 0.5 0.6 0.7
Pi
(Bors)
0.8 0.9 1.0
Location IO
6
0 O.I O2 0.3 0.4 0.8 O8 O7 O8 0.9 1.0
137
-------
Location 10
e
0.1
138
-------
.7
Location II
.6
.5
e
.3
.1 .
i- J
0 0.1 0.2 03
0.4 0.5 0.6
Pi
(Bors)
0.7 0.6 0.9 1.0
Location II
6
0.9 0.4 0.5 0.6
0.7 Cf.6 0.9 1.0
-------
.7
.6
JB-
Location II
e
.£
.1.,
II
"oS 3s35"
PI
(Bort)
o!§ ols i!o
140
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
I. REPORT NO.
EPA-600/2-77-158
3. RECIPIENT'S ACCESSION-NO.
.TITLE AND SUBTITLE
The Control of Nitrate as a Water Pollutant
5. REPORT DATE
August 1977 issuing date
6. PERFORMING ORGANIZATION CODE
r. AUTHOR(S)
Allen R. Swoboda
8. PERFORMING ORGANIZATION REPORT NO.
, PERFORMING ORGANIZATION NAME AND ADDRESS
Soil & Crop Sciences Department
Texas Agricultural Experiment Station
Texas A&M University
College Station, Texas 77843
10. PROGRAM ELEMENT NO.
1HB617
11. CONTRACT/GRANT NO.
S-800193
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
EPA/600/1S
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
This study was based on the premise that the most logical approach to reducing
nitrate leaching in soils was to limit the amount of nitrate in the soil solution at
any one time. Methods of limiting the concentration of nitrate in the soil solution
while maintaining an adequate supply of available nitrogen for plant growth are re-
ported.
Timing of nitrogen application was found to be a very effective means of reducing
nitrate leaching. When nitrogen was applied in the fall as much as 3-fold more
nitrate was found to have leached below 60 cm in the soil by June as compared to ap-
plications made in March. A nitrification inhibitor, N-Serve, was found to be very
effective in reducing the amount of nitrate leached. Slow release sulfur-coated ureas
and treatment of nitrogen fertilizers with N-Serve were found to be effective means
of reducing leaching losses of nitrate when fertilizers were applied in the fall or
winter.
Losses of 0.5 and 3.6% of nitrogen applied as fertilizer occurred in runoff water
when normal rates of nitrogen were applied to a grassland watershed. Lysimeter
studies indicated that from 0.04% to 6% of the applied fertilizer nitrogen could be
leached below 120 cm in a silt loam soil depending on the source of nitrogen.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Nitrogen
Nitrates
Leaching
Nitrification Inhibitor
Urea
Soil
02D
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
151
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
141
U. S. GOVERNMENT PKIMTIHG OFFICE- 1977-757-056/6515 Region No. 5-11
------- |