WATER POLLUTION CONTROL RESEARCH SERIES  I 3O3OELY 5-72-11
                                     REC-R2- 72- II
                                     DWR NO. 174-14-
      BIO-ENGINEERING ASPECTS OF AGRI CULTU RAL DRAINAGE

            SAN JOAQUIN VALLEY, CALIFORNIA
  POSSIBILITY  OF REDUCING  NITROGEN  IN
  DRAINAGE  WATER BY ON FARM PRACTICES
                    JUNE 1972
ENVIRONMENTAL PROTECTION AGENCYtRESEARCH AND MONITORING
          UNITED STATES BUREAU OF RECL A M ATIO N

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          BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
                   SAN JOAQUIN VALLEY, CALIFORNIA


 The  Bio-Engineering Aspects of Agricultural Drainage reports describe
 the  results  of  a unique interagency study of the occurrence of nitro-
 gen  and nitrogen removal treatment of subsurface agricultural waste-
 waters of the San  Joaquin Valley, California.

 The  three principal agencies involved in the study are the Water
 Quality Office  of  the Environmental Protection Agency, the United
 States Bureau of Reclamation, and the California Department of
 Water Resources.

 Inquiries pertaining to the Bio-Engineering Aspects of Agricultural
 Drainage  reports should be directed to the author agency, but may
 be directed  to  any one of the three principal agencies.
                           THE REPORTS
It is planned that a series of twelve reports will be issued describ-
ing the results of the interagency study.

There will be a summary report covering all phases of the study.

A group of four reports will be prepared on the phase of the study
related to predictions of subsurface agricultural wastewater quality--
one report by each of the three agencies, and a summary of the three
reports.

Another group of four reports will be prepared on the treatment
methods studies and on the biostimulatory testing of the treatment
plant effluent.  There will be three basic reports and a summary
of the three reports.  This report, "POSSIBILITY OF REDUCING NITROGEN
IN DRAINAGE WATER BY ON FARM PRACTICES," is one of the three basic
reports of this group.

The other three planned reports will cover (1) techniques to reduce
nitrogen during transport or storage, (2) removal of nitrate by an
algal system, and (3) desalination of subsurface agricultural waste-
waters.

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          BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
                   SAN JOAQUIN  VALLEY, CALIFORNIA
                      POSSIBILITY OF REDUCING
                   NITROGEN IN  DRAINAGE WATER BY
                         ON FARM PRACTICES
                          Prepared by the

                United States Bureau of Reclamation
                 Robert J. Pafford,  Jr., Director
                             Region 2
The agricultural drainage study was  conducted under the direction
of:

Robert J.  Pafford, Jr., Regional  Director, Region 2
UNITED STATES BUREAU OF RECLAMATION
2800 Cottage Way, Sacramento, California 95825

Paul DeFalco, Jr., Regional Director,  Pacific Southwest Region
WATER QUALITY OFFICE, ENVIRONMENTAL  PROTECTION AGENCY
100 California Street, San Erancisco, California 94111

John R. Teerink, Deputy Director
CALIFORNIA DEPARTMENT OF WATER RESOURCES
1416 Ninth Street, Sacramento, California 95814
                             June 1972
        For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
                     Price 1.2B domeitio ponpald or $1 OPO BookMon

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           REVIEW NOTICE

This report has been revived by
the Water Quality Office, Environ-
mental Protection Agency and the
California Department of Water
Resources, and has been approved
for publication.  Approval does
not signify that the contents
necessarily reflect the views and
policies of the Water Quality Office,
Environmental Protection Agency, or
the California Department of Water
Resources.

The mention of trade names or
commercial products does not
constitute endorsement or recom-
mendation for use by either of the
two federal agencies or the Cali-
fornia Department of Water Resources.
                   ii

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                            ABSTRACT

A nitrogen balance study of the San Luis Service Area determined
that the average annual nitrogen contributions from all sources
other than residual soil nitrogen were approximately equal to the
nitrogen removal by crops and volatilization losses.  This would
indicate that, although in many instances the residual nitrogen
would replace some of the contributed nitrogen, especially fertil-
izers, animal and municipal wastes, the amount of nitrates moved
to the drains would be directly proportional to the amounts of
soluble, native nitrogen in the soil.

A soil sampling study at several sites throughout the area indica-
ted that there was a wide range in the concentrations of nitrates,
ammonia and organic nitrogen in the soils and subsoil.  There were
extremely high concentrations of nitrates in those soils located
on the interfan positions between the larger streams.

Fertilizer studies in lysimeters show that in medium to heavy
textured soils under normal irrigation and fertilizer management
practices very little nitrogen fertilizer is leached to the drains.
Nitrate type fertilizer contributed more nitrogen to the drainage
effluent than ammonia and slow release sulfur coated urea fertili-
zers.

It was concluded that the best possibilities to reduce nitrogen in
drains by on farm practices will be to establish Farm Advisory
Programs to encourage the most efficient farm management and
fertilizer practices and, if found feasible, to design drain systems
to promote denitrification and reduce the area swept by the drain
flow lines.
                                iii

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                           BACKGROUND

This report is one of a series which presents the findings of inten-
sive interagency investigations of practical means to control the
nitrate concentration in subsurface agricultural waste water prior
to its discharge into other water.  The primary participants in the
program are the Federal Water Quality Administration, the United
States Bureau of Reclamation, and the California Department of
Water Resources, but several other agencies also are cooperating in
the program.  These three agencies initiated the program because
they are responsible for providing a system for disposing of sub-
surface agricultural waste water from the San Joaquin Valley of
California and protecting water quality in California's water bodies.
Other agencies cooperated in the program by providing particular
knowledge pertaining to specific parts of the overall task.

The need to ultimately provide subsurface drainage for large areas
of agricultural land in the western and southern San Joaquin Valley
has been recognized for some time.  In 1954, the Bureau of Reclam-
ation included a drain in its feasibility report of the San Luis
Unit.  In 1957, the California Department of Water Resources initi-
ated an investigation to assess the extent of salinity and high
ground water problems and to develop plans for drainage and export
facilities.  The Burns-Porter Act, in 1960, authorized San Joaquin
Valley drainage facilities as a part of the California Water Plan.

The authorizing legislation for the San Luis Unit of the Bureau of
Reclamation's Central Valley Project, Public Law 86-488, passed in
June 1960, included drainage facilities to serve project lands.
This Act required that the Secretary of Interior either provide for
constructing the San Luis Drain to the Delta or receive satisfactory
assurance that the State of California would provide a master drain
for the San Joaquin Valley that would adequately serve the San Luis
Unit.

Investigations by the Bureau of Reclamation and the Department of
Water Resources revealed that serious drainage problems already
exist and that areas requiring subsurface drainage would probably
exceed 1,000,000 acres by the year 2020.  Disposal of the drainage
into the Sacramento-San Joaquin Delta near Antioch, California, was
found to be the least costly alternative plan.

Preliminary data indicated the drainage water would be relatively
high in nitrogen.  The Federal Water Quality Administration con-
ducted a study to determine the effect of discharging such drainage
water on the quality of water in the San Francisco Bay and Delta.
Upon completion of this study in 1967, the Administration's report
concluded that the nitrogen content of untreated drainage waters
could have  significant adverse effects upon the fish and recreation
values of the receiving waters.  The report recommended a three-
year research program to establish the economic feasibility of
nitrate-nitrogen removal.

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As a consequence, the three agencies formed the Interagency Agri-
cultural Wastewater Study Group and developed a three-year cooper-
ative research program which assigned specific areas of responsibil-
ity to each of the agencies.  The scope of the investigation in-
cluded an inventory of nitrogen conditions in the potential drain-
age areas, possible control of nitrates at the source, prediction
of drainage quality, changes in nitrogen in transit and methods
of nitrogen removal from drain waters, including biological-
chemical processes and desalination.
                             vi

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                          TABLE OF CONTENTS


Section                                                          Page

  I      Conclusion	    1

 II      Introduction	    3

III      Literature Review	    5

 IV      Methods and Procedure	    7

           Nitrogen Balance Study	    7

             Sources of Nitrogen Contribution	    7

               Nitrogen Fertilizers	    9
               Mineralization of Organic Nitrogen.	    9
               Irrigation Water	    9
               Rainfall	    9
               Leguminous Plants	    9
               Livestock	   10
               Municipal and Industrial	   10

             Nitrogen Losses from the Soil	   10

               Removal by Crops	   10
               Volatilization	   10
               Denitrif ication	   11
               Deep Percolation and Drainage	   11

           Lysimeter Studies	   11

           Transect Studies	   15

           Nitrate Concentrations in the Groundwater	   17

  V      Results and Discussion	   19

           Nitrogen Budget	   19

             General	   19

             Nitrogen Contributions	   21

               Fertilizers	   21
               Irrigation Water	   21
                 Wells	   22
                 Canal Water	   23
               Stream and Flood Flow	   23
               Leguminous Plants	   24
               Rainfall	   25
                                  vii

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                   TABLE OF CONTENTS (Continued)

Section                                                          Page
               Livestock	   25
               Municipal and Industrial	   26
             Nitrogen Losses	   27
               Removal by Crops	   27
               Volatilization of Ammonia Fertilizer	   27
               Denitrification	.   29
             Nitrogen Budget Summary	   29
           Transect Study	   30
             Nitrogen in the Soil	   30
             Nitrogen in the Substrata	   35
           Nitrogen in Groundwater	   55
             0-50 Foot Well Depth	   55
             50-150 Foot Well Depth	   61
             150-300 Foot Well Depth	   61
             300-600 Foot Well Depth	   61
             600-800 Foot Well Depth	   61
           Nitrogen Transformation and Movement in Lysimeters...   62
           Sources of Nitrogen to the Drain	   74
           Quantity of Nitrogen in the Drainage Effluent	   77
           Anticipated Changes in Nitrogen Sources	   77
             Fertilizer Usage	   77
             Future Crop Pattern	   78
             Leaching Native Nitrogen	   78
             Increase in Municipal and Industrial Waste	   79
           Control of Nitrogen at the Source	   80
             Farm Advisory Program	   80
               Soil Management	   80
               Fertilizer Management	   80
               Water Management	   81
               Crop Management	   81
             Specially Designed Farm Drain Systems 	   81
 VI      References	   82
                                 viii

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                              FIGURES

Number
 1      San Luis Service Area - Nitrogen Transect Sites	   8
 2      Layout Of Lysimeters - Nitrogen Movement Studies	  12
 3      Instrument Layout - Lysimeter Number 7	  14
 4      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  42
 5      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  43
 6      Distribution of N03-N, NH,-N and Organic -N by
          Sampling Depth	  44
 7      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  45
 8      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  46
 9      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  47
10      Distribution of NO-j-N, NH3-N and Organic -N by
          Sampling Depth	  48
11      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth.	  49
12      Distribution of NOs-N, NH3-N and Organic -N by
          Sampling Depth	  50
13      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  51
14      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  52
15      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	  53
16      Distribution of N03-N, NH3-N and Organic -N by
          Sampling Depth	 54
17      Movement of Nitrates in Soil Column	  72
18      Movement of Chlorides in Soil Column	  73
                                ix

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                             TABLES
Number                                                        Page
 1     Nitrogen Contributed by Fertilizer 1968	  22
 2     Total Nitrogen Contribution from Irrigation Water
         1968 and Ultimate	  23
 3     Average Annual Nitrogen Contribution by Local
         Streams	  24
 4     Nitrogen Contribution from Leguminous Plants - 1968...  25
 5     Nitrogen Contributions for Animals - 1968	  26
 6     Removal of Nitrogen by Harvested Crop - 1968	  28
 7     Nitrogen Budget - 1968	  30
 8     Quantities of Various Forms of Nitrogen at Transect
         Site as Determined from 1:1 Soil-Water Extracts	  31
 9     Minimum, Maximum and Average N03-N and Organic -N
         Concentrations at the Various Sites by Soil Type
         0-5 Feet	  34
10     The Average N07-N and Organic -N Content in Parts Per
         Million in tne 0-5 Foot Increment for the 5 Holes
         Within the Various Sites	.	  36
11     Summary of N03-N in Parts Per Million, Standard
         Deviations and Standard Error of Mean for the Five
         Holes at each Nitrate Site	  37
12     Average Pounds Per Acre and Total N in the Study Area
         in 0-5 Foot Soil Depth	  39
13     N03-N, NH3-N and Organic N in PPM and Pounds Per Acre
         Feet in the Soil Substrata	  40
14     Total N in the 5-40 Foot Substrata by Alluvial Fan....  41
15     Summary of Nitrate.Nitrogen and Standard Deviations
         in Milligrams per Liter for Wells and USER Geohydro-
         logic Observation Hole above the Corcoran Clay -
         0-50 Foot Depth	  56

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                        TABLES  (Continued)

Number                                                          Page

16       Summary  of Nitrate Nitrogen and Standard  Deviations
           in  Milligrams Per  Liter for Wells and USER Geohydro-
           logic  Observation  Holes above the Corcoran Clay  -
           50-150 Foot  Depth	    57

17       Summary  of Nitrate Nitrogen and Standard  Deviations
           in  Milligrams Per  Liter for Wells and USER Geohydro-
           logic  Observation  Holes above the Corcoran Clay  -
           150-300 Foot Depth	    58

18       Summary  of Nitrate Nitrogen and Standard  Deviations
           in  Milligrams per  Liter for Wells and USER Geohydro-
           logic  Observation  Holes above the Corcoran Clay  -
           300-600 Foot Depth	    59

19       Summary  of Nitrate Nitrogen and Standard  Deviations
           in  Milligrams Per  Liter for Wells and USER Geohydro-
           logic  Observation  Holes above the Corcoran Clay  -
           600-800 Foot  Depth	    60

20      Nitrogen Content and Percent of Fertilizer Nitrogen in
           Soil Extracts from "A" Depths, December 16, 1968 -
           August 8, 1969	   63

21      Nitrogen Content and Percent of Fertilizer Nitrogen in
           Soil Extracts from "B" Depths, December 16, 1968 -
           August 8, 1969	   63

22      Nitrogen Content and Percent of Fertilizer Nitrogen in
           Soil Extracts from "C" Depths, December 16, 1968 -
          August 8, 1969	   64

23      Nitrogen Content and Percent Fertilizer N in the Leachate
           December 16, 1968  - August 1, 1969	   64

24      Total Nitrogen Content of Soil Extracts,   Leachates and
          Percent Fertilizer N - for the Period December 13,
           1968 to August 18, 1969	  65

25      Recovery of Fertilizer Nitrogen from all Probes and
           Leachate for the Period - December 16,  1968 -
          August 18,  1969	  66

26      Nitrate -N Recovered in the Leachate of Soil Columns
          for the Period December 16,  1968 - August 18,  1969...  66
                                 xi

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                        TABLES (Continued)
Number
27      Recovery of Applied Fertilizer Nitrogen in the Barley
          and Grain Sorghum	    67
28      Recovery of Applied Fertilizer N in Barley, Grain
          Sorghum and Water Samples	    68
29      Recovery of Applied Fertilizer Nitrogen in the Nitrate
          and Organic Nitrogen Fraction from Two Lysimeters...    69
30      Summary of Applied 15N Collected in the Various
          Categories 	    70
31      Nitrogen Balance Sheet - Lysimeter Number 6	    75
                                xii

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                            SECTION I

                           CONCLUSIONS

1.  The major source of the nitrogen in the drainage effluent in
the San Luis Service Area is the nitrogen that is native to the
soils and subsoils.

2.  Under normal soil, cropping, irrigation and fertilizer condi-
tions of this area, only a small percentage of the applied fertil-
izer nitrogen will reach the drainage effluent; however, in a few
small areas of light soils, where excessive irrigation water and
fertilizers were applied or the fertilizer application is ill-placed
and timed, larger amounts of nitrogen may be leached into the
drainage water.

3.  There will be local areas of high nitrate concentration adjacent
to municipal sewage disposal plants and possibly near cattle feed
lots.

4.  The reduction of the quantity of nitrogen reaching the drains
by controls at the source could be implemented by:

    a.  An advisory program conducted by the Extension Service and
        other agencies to encourage:

        (1)  the most efficient rate, type, time and method of
             fertilizer applications.

        (2)  irrigation practices to control excess deep percola-
             tion of applied water.

        (3)  crop and soil management practices to minimize nitrogen
             losses.

    b.  If research studies on the design of drainage systems to
        reduce nitrogen in drainage effluent prove feasible, systems
        should be installed to:

        (1)  encourage denitrification by maintaining anaerobic
             conditions with submerged drains.

        (2)  reduce the area swept by the drain flow lines by
             decreasing the depth and spacing of tile lines.
                               (1)

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                           SECTION II

                          INTRODUCTION

As a result of the application of large quantities of water to
relatively slowly permeable stratified soils, the west side of the
San Joaquin Valley now has large areas with groundwater at rootzone
depths.  These areas, requiring drainage to maintain productivity,
will increase in size as more water is imported.  Wherever sub-
surface drains have been installed to control this groundwater, the
drainage effluent has had high nitrate concentrations.  Investiga-
tions were conducted to determine the source of this nitrogen, its
form and quantity in the soil, its distribution, and whether its
entry into the drains can be controlled or limited.

Large quantities of inorganic nitrogen fertilizers are applied
annually and the assumption prevails that fertilizer is the major
source of nitrates in the drainage water.  The study reported
herein was designed to evaluate this assumption and to derive, if
possible, practical answers regarding the role of on-farm practices
in controlling nitrate out-put from the agricultural lands.  This
portion of the study was confined to the San Luis Service Area, a
part of the west side of the San Joaquin Valley comprising about
669,000 acres.  The area is centrally located with respect to
present and ultimate drainage areas and was judged to be reasonably
representative of the major areas contributing to drainage.

This study examines the nitrogen budget and investigates methods
for reducing the quantity of nitrates in the drainage effluent by
modifications in type or use of fertilizers, farming practices, or
drainage techniques. To accomplish these objectives it was necessary
to:

    1.  Identify the major sources of soil or water nitrogen
        which contribute to the drainage effluent.

    2.  Determine the quantities of nitrates that these sources
        contribute to the drainage effluent.

    3.  Determine if control of nitrates at the source is needed
        and if so how can it be accomplished.
                               (3)

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                          SECTION III

                       LITERATURE REVIEW

 The source, movement and fate of.nitrogen in soils and water have
 been the subject of many studies.  Tisdale and Nelson (1) describe
 the various biochemical processes of the nitrogen cycle which occur
 in soils and their relation to soil fertility.

 Stout and Burau (2) compared the accumulation of mobile nitrogen
 in uncultivated fields with heavily irrigated fields in the Grover
 City-Arroyo Grande Basin.  They found that in permeable soils
 nitrate concentrations in the range of 100 p.p.m. would accumulate
 in the water percolating to the groundwater table, whether unculti-
 vated or cultivated, and with or without fertilization.   Doneen,
 (3) in a study of irrigated fields in the Firebaugh area, states
 that nitrate-nitrogen in the effluent is principally from three
 sources;  (1) soil organic matter;  (2) originally in the soil profile
 or ground water before irrigation,  and (3) fertilizers.   The losses
 of nitrates from the soil and groundwater are in three general
 categories:  (1) removed in the harvested crop,  (2)  by denitrifica-
 tion,  and (3) in the drainage water.

 Various studies by Terman (4),  Martin and Chapman (5),  and Harding
 (6) conclude that if ammonia or urea  types of fertilizer are applied
 to the surface.of warm,  moist alkaline soils  which are present  in
 this area,  there will be large losses of  the  nitrogen by volatiliza-
 tion in the form of NHs.  However,  if the fertilizer  is  placed  a
 few inches  below the soil surface either  by tillage or by dissolving
 in the  irrigation water  the  losses  can be minimized.

 Significant quantities of nitrogen, primarily in  the  form of NH,
 and NO,,  enter  the  soil  dissolved in  the  rain waters.  Studies  by
 Junge  (7),  Gambel .and Fisher  (8)  suggest  that in  the  San  Luis Area
 the average concentrations of these ions  are about 0.1 mg/1  each.
 They believe the major sources of these N-forms are from  the volatili-
 zation of the nitrogen from the soil  surface or from  industrial
 plants.

 Well water will continue to be a major source of irrigation water
 for the area.  The nitrate concentrations for waters from selected
 wells in the area were measured and are described by a U. S. Geo-
 logical Survey open file report (9).  The nitrate content of these
 wells ranged from 0 to 98 mg/1 with an average of about 2 mg/1.
 An analysis of the distribution of nitrates in the water strata
 above the Corcoran formation in the Sierran and Coast Range sediments
 is presented in a study by the Groundwater Section of the Geology
 Branch, U.S.B.R. in Sacramento (10).  The N03 concentration in these
 strata ranged from less than 1 to more than 542 mg/1.   There were
higher concentrations in the Coast Range Sediments than in the Sierran
and a reduction of concentrations with depth.
                            (5)

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Leguminous plants are a source of nitrogen to the soil.  Bartholomew
and Clark (11) and Erdman (12) found that under normal conditions
these plants fix from a few pounds to more than 300 pounds per acre
annually.  The majority of this nitrogen is used to produce the
crop which is harvested and is not returned to the soil.

The waste from animals can make an appreciable contribution to the
nitrogen supply of an area, especially when the animals are con-
centrated in feed or dairy lots.  Leohr (13) gives the waste
characteristics of various types of livestock and humans.   These
characteristics include the amount of nutrients and pollutants,
and the chemical and biochemical oxygen demand of the waste.  He
also presents possible methods to treat or dispose of the  waste.

The major loss of nitrogen from the soil occurs through the removal
of nitrogen by the crops.  Morrison's "Feeds and Feeding" (14) lists
the percent of nitrogen in the various crops from which the amount
of removal can be estimated.   The average nitrogen content of the
crops grown in this area varies from a high of 5.31 percent for
alfalfa seed to a low of .12  percent for vineyards.   The major crops,
cotton and grain, contain 2.92 and 1.39 percent, respectively.
                                (6)

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                           SECTION IV

                     METHODS AND PROCEDURES

This section describes the methods and procedures used in the
various phases of the nitrogen balance study.

                     Nitrogen Balance Study

A nitrogen balance study was made of the San Luis Service Area, the
boundary of which is delineated in Figure 1.  The budget is impor-
tant in that it is to be used to identify the quantities of nitrogen
which might be controlled through modified farm practices.

The nitrogen balance was made by comparing the estimated annual
contributions to the crop root zone of the soil with estimated
annual losses that could be identified.  Because of the many com-
plexities of the system, it is difficult to determine if the
quantities of nitrogen measured in the soil are at equilibrium with
the contributions and losses; however, available data indicate that
near equilibrium exists.  No attempt was made to extend the budget
through the substrata and groundwater, however, from data in the
study it is noted that in some areas the nitrogen increases down
to shallow groundwater, but is markedly less in the deep ground-
water.  Anticipated changes in the nitrogen regime are also dis-
cussed in this study.

Sources of Nitrogen Contribution

The major sources of nitrogen, other than the naturally occurring
mineral forms in the soils, that contribute to the system are:

     1.  Nitrogen fertilizers
     2,  Mineralization of organic nitrogen compounds
     3.  Irrigation water
     4.  Stream and flood flows
     5.  Rainfall
     6.  Leguminous plants
     7.  Livestock
     8.  Municipal and industrial wastes

Many authorities consider non-symbiotic nitrogen fixation to be a
contributor; however, very little is known about the quantities
supplied under field conditions because they are too small to be
measured (15).  Therefore, this source was not included in this
study.

The methods used to determine the contribution of each category are
listed below:
                               (7)

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                                           L EGEND

                                      - Son  Luis Service Area Boundary
                                     	Alluvial Fan  Boundaries
                                        - Nitrogen Transect  Sites
                                       GEOMORPHIC  AREAS
                                 Laguna Seca-Little Panoche Creek Interfan
                                 Little Panoche Creek Fan
                                 Little Panoche-Panoche  Creek interfan
                                 Panoche Creek  Fan
                                 Panoche -Cantua Creek  Interfan
                                 Cantua  Creek Fan
                                 Cantua - Los  Gatos Interfan
                                 Los  Gatos Creek Fan
                                 Los  Gatos Creek Interfan (South)
KETTLEMEN CITY
FIG.  I - SAN  LUIS  SERVICE  AREA
         NITROGEN TRANSECT  SITES
                           (8)

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     Nitrogen Fertilizers;  The quantity of nitrogen applied in the
fertilizer was determined for 1968 and estimated for the ultimate
development.  This determination was made from the amount applied
per acre to each crop and the total number of acres of the various
crops.  The average application rates were based on Farm Advisors
and fertilizer consultants recommendations and field sampling of
actual farming practices.  The amount applied depended on such factors
as soil type, crop history, crop involved and the judgement of the
grower.

The acreage devoted to the various crops in 1968 was determined from
a crop survey made by the State of California, Department of Water
Resources.  The projection of the acreage of the various crops under
ultimate development conditions was prepared by the U.S. Bureau of
Reclamation.

     Mineralization of Organic Nitrogen:  The mineralization of
organic nitrogen compounds is accomplished by various types of micro-
organisms.  The amount of ammonia and nitrates released by this process
depends upon many factors but in general the environmental factors
favoring the growth of most agricultural plants are those that also
favor the activity of the nitrifying bacteria.  The estimates of the
quantities of the mineral nitrogen released in these reactions were
based on data derived from the literature.

     Irrigation Water;  The quantity of nitrogen applied by the
irrigation water was determined from the amount of water applied
and the nitrate concentration of the applied water.  The water applied
was calculated from the farm irrigation requirement multiplied by
the acreage of each crop.  The nitrate concentration of the water
was determined by calculating the weighted average of the ground-
water and the canal water as taken from the chemical analyses of the
wells in the area (9) and from State of California, Department of
Water Resources data.

     Rainfall:  The amount of nitrogen supplied by rainfall was
determined from the average precipitation in the area as taken from
Weather Burau data and the nitrogen concentration in the rain water.
This value was derived from work by Junge (7) and Gambel and Fisher
(8).

     Leguminous Plants;  Certain plants in a symbiotic relationship
with various species of the Rhizobium bacteria will fix elemental
nitrogen.  Alfalfa and beans are the legumes grown in this area.
The amount of nitrogen fixed by these crops will vary greatly but
based on the work of Erdman (12), it is estimated that alfalfa will
fix an average of 194 pounds per acre and beans 40 pounds per acre
per year.  The acreage of these crops was determined from the 1968
crop survey and the estimated ultimate acreage was taken from Bureau
of Reclamation studies.
                               C9>

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     Livestock;  The nitrogen contribution by the livestock was
taken from the numbers of each type and the waste characteristics
of each species.  The number of cattle in the area was determined
from information supplied by the major feed lots of the area for
the 1968 season.  The sheep population was estimated from data
reported in the 1968 Fresno County Agricultural Report.  The number
of other livestock in the area is not significant.  The waste
characteristics of the animals were taken primarily from the work
of R. C. Loehr (13).

     Municipal and Industrial;  This area is sparsely inhabited with
the majority of the population centered in several small communities,
a number of large labor camps, and the Lemoore Naval Air Station.
There are a few agriculture oriented industries in the area.  Pop-
ulation figures were estimated from census data supplied by the
Fresno County Planning Department.  The amount of nitrogen waste
contributed by the inhabitants of the area was calculated from data
derived from work by Loehr (13).  The industrial wastes were deter-
mined from field estimates made in the various communities.

Nitrogen Losses from the Soil

The main categories of nitrogen loss in this area are:

     1.  Removal by crops
     2.  Volatilization
     3.  Denitrification
     4.  Deep percolation and drainage

Wind and water erosion is a major factor in nitrogen removal in
some areas, however, in the study area losses by such physical
removal are not significant because of relatively level lands, low
rainfall, and light winds.  The methods used in determining the loss
by each category are presented below:

     Removal by Crops;  The major loss of nitrogen is through removal
from the soil by the growing plants.  The quantity removed in this
way was calculated from the number of acres of each crop grown as
determined from the 1968 crop survey and the estimated amount of
nitrogen in the various plant materials as determined primarily
from Morrison's "Feeds and Feeding" (14).

     Volatilization:  The loss of nitrogen by volatilization of
ammonia and urea type fertilizers was calculated from the amount
of those fertilizers applied multiplied by 5 percent, the estimated
amount of N volatilized.  This value was determined from the lab-
oratory and field studies made on the subject (4)(5) correlated
with local soil conditions and farming practices.
                               (10)

-------
      Denitrification;   Elemental nitrogen gas and/or nitrous oxide
 are released through denitrification,  the biochemical reduction of
 nitrates  under anaerobic  conditions.   The conditions under which
 this process occurs  are so  variable and difficult to measure in the
 field that  no meaningful  estimate of the actual values can be made.
 Therefore,  for this  study,  it  is recognized that losses under certain
 conditions  could be  significant  but no numerical values were assigned.

      Deep Percolation and Drainage:  The nitrates that are present in
 the soil  system,  either native,  mineralized, or added, that are not
 removed by  the crop, volatilized, denitrified, or immobilized by
 conversion  to other  nitrogen compounds will move with the percolating
 water where eventually  they will either be picked up in the drains or
 moved into  the groundwater.  The rate  nitrates enter the drains or
 groundwater for any  given period would be the difference between the
 nitrates  contributed and  the amount immobilized or removed by processes
 other than  percolation  divided by the  time required to move the nitrates
 through the soil profile.

                        Lysimeter Studies

 Lysimeters  were operated  in Fresno at  the Bureau of Reclamation Soils
 Laboratory  to study  the movement of nitrogenous fertilizers in soil
 columns.  Eighteen columns made  of techite (fiber glass) pipe 15 inches
 in  diameter and 6.7  feet  in length were filled with four major soil
 types developed on the  westside  of the San Joaquin Valley of California
 from sediment of  the Coast Range Mountains.  Five columns were filled
 with Panoche fine sandy loam, a  recent alluvial, light textured, slightly
 saline soil.   Four columns were  filled with Panoche silty clay loam and
 three columns were filled with Panoche clay loam soils similar to the
 above soils  except somewhat finer in texture.  Three columns were filled
 with Oxalis  Clay, a fine textured soil, slightly to moderately compacted
 in the subsoil, and moderately saline.   Three columns were filled with
 Lethent sandy clay loam, a basin rim soil with medium textured surface
 over a moderately compacted fine textured subsoil with moderate to
 strong concentration of alkaline and saline salts.   The soils were screened,
 weighed, and placed in the columns ana tamped to approximately field
 density.

 The  surface and subsurface soil material of the Panoche fine sandy loam,
 and  the Oxalis clay soils were mixed in the lysimeters.   The soil material
 from the Panoche clay loam and the Lethent soils were placed in layered
horizons in the same sequence as in the natural condition.   A layout of
the  lysimeters is shown as Figure 2.
                                (11)

-------
    PANOCHE FSL
                         PANOCHE  CL
                           	^
                            NO 2
PANOCHE CL
                        PANOCHE FSL
                        PANOC
                                FSL
                         OXALIS CLAY
                                              PANOCHE FSL
                                              LETHENT SCL
 PANOCHE SI CL
  "	-v
   NO. 12


Non-cropped
                                              MNOCHE SI CL
                                                               JL
FIG.  2-LAYOUT  OF  LYS! METERS-NITROGEN  MOVEMENT  STUDIES
                           (12)

-------
The lysimeters were instrumented with tensiometers, soil extract
suction probes, and soil moisture and temperature cells.  These
instruments were placed in the  soil columns by drilling holes
through the sides of the lysimeters and inserting the instruments
near the center of the soil columns.  Generally four mercury type
tensiometers were located in each lysimeter at approximately 18,
30, 42, and 54 inch depths.  Three each of the soil extract suction
probes and the soil moisture and temperature cells were installed
at approximately 12, 24 and 60  inch depths.  A typical layout of
one lysimeter is shown in Figure 3.  When the lysimeters were filled,
sufficient water was applied to the columns to bring the soils to
field capacity and to start water draining from the lysimeters.
After the columns started to drain, water was added in 4-inch
increments every two weeks to leach the nitrates to a relatively
constant level.

Soil extracts were collected from the suction probes at varying
time periods, depending on the needs of the program, by applying
approximately 14 pounds of suction with a vacuum pump.  Samples
of the effluent draining from the bottom of the lysimeters were
collected on the same schedule as the soil extracts.

The volumes extracted from the probes and collected in the leach-
ates were recorded.  All of the samples were analyzed for nitrates,
electrical conductivity and pH.  Some of the samples were analyzed
for chlorides, ammonia, total nitrogen and percent excess *%.
(an isotope of nitrogen with a mass number of 15)

The leaching program was continued until December 1968.   At this
time, the nitrate concentrations in most of the lysimeters, although
varying with soil type, were reduced to a fairly constant level.
Barley was planted in the lysimeters and three different types  of
nitrogenous fertilizers were applied - (NH4)2S04 and KNOj, both
fast nitrogen release types,  and sulfur coated urea, a slow nitrogen
release type.   The fertilizers were applied at a rate equivalent
to 100 pounds N per acre or 1250 milligrams of N per lysimeter.
The (NH4)2S04 and the KNOs fertilizers were eniched with approxi-
mately 10 percent 15N and the urea with 28.2 percent 15N.   The
(NH4>2S04 was applied to two lysimeters filled with Panoche clay
loam and two filled with Oxalis clay.   The KN03 was applied to  two
soil columns of Panoche fine sandy loam and two of Lethent sandy
clay loam.   Sulfur coated urea was applied to two columns  of
Panoche fine sandy loam.   A control to which no fertilizers were
applied was maintained for each soil type.   Samples from the suc-
tion probes and the leachates were collected,  frozen and sent to
                               (13)

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                                      Tensionmeter

                                      Hg Surface
  Suction  Probes
        a
Soil Moisture Cells
           0.92'
1.87
   5.03'
            Soil Surface
                                 X
                        II
                                   1.21'
                           046
                                     3.29'
                                X
                         X
                                  4.18'
                                             5.21
                                                  6.13'
    FIG. 3-  INSTRUMENT LAYOUT  LYSIMETER  N0.7
                      (14)

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  the  University  of  Arizona  for analysis  of nitrate and atom percent
  excess  -^N,  the amount  of  lbN in  excess of tnat which occurs
  naturally.

  The  barley was  irrigated at approximately the rate that the farmers
  of the  area  use in their normal field operations.  The soils were
  at field capacity  when  seeded and additional applications of water
  totaling 19.2 inches were applied during the growing season.  The
  irrigation water applied was obtained from a well at the University
  of California Westside  Field Station near Five Points.  This water
  contained approximately 2 mg/1 of N03 and 1,000 mg/1 of total
  dissolved solids.

  After the barley was harvested in May, eight inches of water were
  applied to the  lysimeters.   This amount brought the soils to field
  capacity and started drainage from the columns.   The lysimeters
  were planted to sorghum without additional fertilization.   In
  addition to the preirrigation of eight inches a subsequent 25.4
  inches of water were applied during the growing season.   The sorohum
 was harvested in October 1969.

 Grain from the barley and sorghum  crops was  weighed and  analyzed
 separately from the straw or stover.   All  plant  samples  were  dried
 ground,  and analyzed for total nitrogen by standard micro-Kjeldahl'
 procedures.   After  titration, the  ammonia  was redistilled  and atom
 percent  excess -"N  determined.

 In addition to those  lysimeters  used  in the plant  studies,  four
 columns  filled with Panoche silty  clay loam were employed  to  study
 the movement  of  nitrogen salts in  a non-cropped, moist but  unsat-
 urated moisture  regime.  On January 20,  1969, Ca(N03)2 was applied
 to the soil columns at a rate equivalent to 100 pounds of nitrogen
 per acre.  At the same time, CaCl2 was applied as a  source of Cl to
 serve as a tracer element for the NO,.   Water was applied at the
 rate  of  four  inches every two weeks.   Samples of the soil extract
 were  collected from the  suction cups at  four depths in the column
 and the  effluent which passed through the column was collected from
 the bottom of the lysimeter.  The samples collected were analyzed
 for nitrates, pH, electrical conductivity and chlorides.   Addition-
 al analyses for  NH4, N02 and organic N were run on a number of the
 samples.  When it was evident that the first application of salts
 had moved through the columns NH4C1 was applied to the columns and
 the movement of  this salt monitored as it moved downward through
 the soil.  The moisture regime was monitored by four mercury type
 tensiometers in  each lysimeter at depths of approximately 12  24
 36, and 48 inches.                                              '

                         Transect Study

A  series of borings  was made along several lines transecting the
San Luis Service Area generally  from east to  west.   The purpose of


                              (15)

-------
this study was to determine the quantity and distribution of the
various nitrogen forms, by area and by depthj and to determine the
variability of nitrogen in soils of similar type within small areas,

Thirteen sites were selected along four lines transecting the area.
The sites were selected to be representative of the different soil
series, physiographic and-geomorphic positions.  The soil type,
physiographic position, and alluvial fan location of each of the
sites were as follows:
Hole No. Soil Type

  1      Oxalis SiC
  2      Lethent SiC
  3      Panoche C L
  4      Panoche SiC

  5      Oxalis C

  6      Lethent C

  7      Levis C

  8      Oxalis Si C

  9      Panoche Si C

 10      Lost Hills Si

 11      Panoche C L
 12      Panoche Si C
 13      Oxalis C
  Physiographic Position Geomorphic Position
  Basin Rim
  Basin Rim
  Recent Alluvial
  Recent Alluvial

  Basin Rim

  Basin Rim

  Basin Rim

  Basin Rim

  Recent Alluvial

C Older Alluvial

  Recent Alluvial
  Recent Alluvial
  Basin Rim
Los Gatos Creek Fan
Los Gatos Creek Fan
Los Gatos Creek Fan
Los Gatos Creek
  Interfan
Los Gatos Creek
  Interfan
Los Gatos Creek
  Interfan
Cantua-Panoche Creek
  Interfan
Cantua-Panoche Creek
  Interfan
Cantua-Panoche Creek
  Interfan
Cantua-Panoche Creek
  Interfan
Panoche Creek Fan
Panoche Creek Fan
Panoche Creek Fan
The locations of the sites are shown on Figure 1.  At each of the
sites, five holes were bored on a line 50 feet apart.  Three holes
were drilled to a depth of five feet, one hole to ten feet, and one
hole to the water table or 40 feet, whichever occurred first.  The
soil material in each hole was logged in the field for texture,
moisture, permeability, lime, mottling, compaction, structure and
temperature.

Two sets of soil samples were collected from each hole.  One of the
sets was stored in a freezer where it was kept frozen to prevent
bacterial activity until the laboratory analyses for the various
nitrogen constituents could be made.  The other set was delivered to
the Regional Soils Laboratory where determinations were made for
calcium, magnesium, sodium, carbonates, bicarbonates, sulphates,
chlorides, boron, gypsum, lime, pH, saturation percentage,   cation
exchange capacity, exchangeable sodium percentage and total dissol-
ved solids.  Analytical methods for these tests were based  on the
                                (16)

-------
 Bureau of Reclamation laboratory instructions. (15)

 Nitrogen analyses were made for nitrates, ammonia and total organic
 nitrogen.  The nitrates were determined by 'the specific ion meter
 ammonia by distillation and titrating with H2S04 and the total   '
 organic nitrogen by the standard micro-Kjeldahl procedure.

 Infiltration rate and hydraulic conductivity were determined at
 the site.  The bulk density and porosity were calculated from core
 samples taken with a split ring density sampler.   The infiltration
 rates were by means of a constant head, double ring infiltrometer.
 The hydraulic conductivities were determined by the auger hole
 and shallow well pump-in methods.

 A statistical analysis was made of  the nitrates,  ammonia,  and
 organic nitrogen data to determine  the variability of these various
 constituents within a small area of a similar soil type.   The
 arithmetic average,  the  standard deviation of the mean and the
 standard error of the mean were calculated for the data from the
 upper five feet of the thirteen sites.

 The mineral analyses and the tests  for the soil physical  properties
 were primarily made  to obtain  basic data  for a prediction  model
 study.

            Nitrate  Concentrations  in the  Groundwater

 Studies of  the  nitrate concentration in the  groundwater of  the area
 have been made  by various  agencies.   Included  in  these  studies are-
 work by the U.  S.  Bureau of Reclamation, U.  S. Geological  Survey
 and State of  California, Department  of Water Resources.  The Bureau
 of  Reclamation, California Department of Water Resources and West-
 lands Water District entered into a  cooperative agreement with the
 U.  S. Geological  Survey to collect and make chemical analyses of
 wells in the  Dos  Palos-Kettleman City area.  Between July 15 and
 September 20, 1968, water  samples were collected from 361 wells in
 the  area.  The analyses of the  samples provided the majority of the
 data for this study.  These analyses, along with the descriptive
 well data and well location are presented  in the U. S. Geological
 Survey open file report. (9)  These data were supplemented with an
 additional 180 samples collected and  analyzed by the Bureau of
 Reclamation's Fresno office.

 Employing data from the wells and the U. S. B. R.  geohydrologic test
 holes nitrate in parts per million was plotted above the Corcoran
 Clay by depth of well, geomorphic area and by the  Sierra or Coast
Range sediments.  The arithmetic mean and standard deviation was
 computed by well depth intervals 0-50, 50-150, 150-300, 300-600 and
 600-800 feet,  on the analyses of nitrates in wells above the Cor-
coran Clay.  Where the number of samples in any interval was less
than thirty, the standard deviation  was computed from the  mean


                               (17)

-------
using one sample less (N-l) than the number  used  to  obtain the
arithmetic mean (N).
                            (18)

-------
                             SECTION V

                       Results and Discussion

This section discusses the results and findings of the several field
and lysimeter investigations on nitrogen balance, residual nitrogen
in field soils and the movement of applied fertilizer nitrogen.

                          Nitrogen Budget

This nitrogen balance study was based on average soil, farming,  and
irrigation conditions in the area.  However, it should be recognized
that because of the large size and variable conditions of the area
many of the soils will deviate appreciably from the norm, therefore,
there will be local areas that will vary significantly from the
average values presented here.  Precise measurements cannot be ob-
tained under ordinary field conditions, nevertheless these data  do
supply information that is sufficiently quantitative to show the
magnitude of the main soil nitrogen losses and gains.

GENERAL

The nitrogen cycle consists of a series of continuous processes  in-
volving the plants, animals and micro-organisms of the soil and  air
through which the elemental nitrogen moves in the eco-system. The
processes involved as they effect the appearance of nitrogen in  the
drainage water is the concern of this study.  Knowledge of the
processes in the nitrogen cycle is essential to understanding and
dealing with nitrogen in the drainage effluent.

The ultimate source of nitrogen is the inert gas N2, which consti-
tutes about 78 percent of the earth's atmosphere.  In its elemental
form it is useless to higher plants therefore it must be converted
to usable forms.  Although it may be recycled and delivered in many
forms, the basic processes by which nitrogen is converted to usable
forms and gains entrance to the soils are:

     1.  Fixation by Rhizobia and other micro-organisms which live
         symbiotically on the roots of legumes and certain non-
         leguminous plants.

     2.  Fixation by free-living soil micro-organisms and perhaps
         by organisms living on the leaves of tropical plants.

     3.  Fixation as one of the oxides of nitrogen by atmospheric
         electrical discharges.

     4.  Conversion to ammonia, nitrate, urea by any of the various
         industrial processes for the manufacture of synthetic
         nitrogen fertilizers.


                                (19)

-------
Plants adsorb most of their nitrogen as NO-, or NIfy which in the
growth process of the plant are converted to an organic form.  Much
of this organic nitrogen is reincorporated into the soil by plowing
the plant material back into the soil or through the application of
animal manures to the soil.  These organic forms of soil nitrogen
occur as consolidated amino acids or proteins, free amino acids,
amino sugars and other complex, generally unidentified compounds.
These compounds decompose at various rates ranging from fresh crop
residues that are subject to fairly rapid decomposition to lignins
which are very resistant to decomposition.

Mineralization is the process by which organic nitrogen is converted
to inorganic or mineral nitrogen compounds.  Mineralization, through
the effect of various types of micro-organisms essentially takes
place in three step-by-step reactions:  aminization, ammonification
and nitrification.  These steps are represented schematically by the
following formula:

Aminization:  Proteins     R-NH2 + C02 + energy -+ other products
Ammonification:  R-NH2 + HO H -* NH^-i- R -* OH -* energy
Nitrification:  2NH  + 302  2NOo- + 2H20 + 4H +
                2N02 + 02 -* 2N03

These reactions will go to completion only if several environmental
factors are favorable.  Generally,  these are 1) adequate supply of
ammonium ion, 2) adequate population of nitrifying organisms,
3) adequate aeration, 4) favorable  soil moisture and temperature
conditions.  The most favorable conditions for these reactions to
take place occur in the plow zone of moist soils after they have
been disturbed and aerated by cultivation.

Nitrates and ammonium are the main  mineral nitrogen forms that exist
in the soil.  The nature of NH4 permits adsorption and retention
by soil collodial material, therefore, it is generally not subject
to removal by leaching waters.  Nitrate nitrogen is very mobile in
some soils and within limits moves  with the soil water, therefore,
under conditions of excess irrigation or rainfall, nitrates can be
leached through the soils and will .be concentrated in the subsoils
or the groundwater.

As there are processes for the accumulation of nitrogen in the soils,
there are processes by which it is  lost other than by leaching and
crop removal.  These losses occur when nitrogen gas, nitrous oxide
or ammonia are released because of  certain biological and chemical
reactions taking place on or in the soils.  The three primary
processes which cause these losses  are:

     1.   Denitrification:   The biochemical reduction of nitrates
         under anaerobic conditions.

     2.   Chemical reactions involving nitrates under aerobic
         conditions.
                               (20)

-------
     3.  Volatilization of ammonia gas from the surface of
         alkaline soils.

Although there are conflicting data and opinions, most soil scien-
tists believe that an appreciable amount of applied nitrogen is
lost in gaseous forms to the atmosphere.  Biological denitrifica-
tion is considered to be one of the more important processes
accounting for these losses and nitrogen, N2, is believed to be
the principle gas produced.  Where nitrate occurs in zones of poor
aeration, significant quantities of nitrogen can be lost by this
process.  Nitrogen balance studies have shown mineral nitrogen
losses of about 20 percent with cropping and 10 percent with fallow
(16).

Normally, ammonia losses resulting from surface volatilization can
be prevented or reduced greatly by placing the nitrogen fertilizers
several inches below the soil surface.

                     Nitrogen Contributions

The major sources of nitrogen, not considering that native to the
soils are:

Fertilizers

This is an intensively farmed area and to gain maximum yields large
amounts of nitrogenous fertilizers are applied.  These fertilizers
may be classified broadly as either "natural organic" or "chemical."
Today in terms of tonnage consumed, chemical sources of .nitrogen
are by far the most important of the fertilizer nitrogen compounds.
Most of the chemical fertilizers applied in this area are ammonia
derivatives.  Information supplied by local dealers indicates that
the amounts of the various types of fertilizers sold in the area
were distributed approximately as follows:
                                            Percent
     Ammonia (all forms)                       63
     Ammonium Sulfate                          16
     Urea                                       9
     Urea - ammonium compounds                  6
     Other solids (ammonium nitrate, calcium
       nitrate, ammonium phosphate)             6

The amount of nitrogen applied to the study area in 1968  based on
the acreage and the estimated application rate of each crop is
presented in Table 1.  The total nitrogen applied was calculated
to be 20,210 tons placed on 669,160 gross acres of which  556,875
acres were cropped.   This is equivalent to  an average application
of 73 pounds per productive acre or 64 pounds per gross acre.

Irrigation Water

Irrigation water is supplied to the area from deep wells,  the


                               (21)

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                              TABLE 1

              Nitrogen Contributed by Fertilizer 1968
                        San Luis Service Area
                                              Nitrogen Applied
                              Acres   Ibs. per AcreTotal Tons
Cotton
Cotton ( 50% ground cover)
Cotton (70% ground cover)
Grain
Sugar Beets
Sorghum
Saf flower
Field Corn
Misc. Field Crop
Dry Beans
Tomatoes
Melons
Lettuce
Carrots
Misc. Truck Crops
Alfalfa 8- Pasture
Alfalfa Seed
Rice
Deciduous Fruits & Nuts
Vineyards
Total Cropped Area
Non Cropped Area
Total
51,119
48,975
44,300
230,832
2,661
3,094
53,440
749
492
439
23,890
26,314
662
124
1,063
6,348
55,581
825
5,348
620
556,875
112,285
669,160
110
55
77
70
100
130
80
200
100
0
100
100
150
120
150
40
20
80
120
45
73
0
64
2,810
1,350
1,700
8,080
130
200
2,140
70
20
_
1,200
1,320
50
10
80
130
560
30
320
10
20,210
0
20,210
San Luis Canal and the Delta-Mendota Canal.  The relative amounts
of nitrogen contributed from these sources are listed in the follow-
ing paragraphs.

Wells

Prior to the importation of surface water from the San Luis Project,
this area was irrigated entirely by water pumped from deep wells.
In the future there will continue to be pumping from wells although
at a reduced rate.  In 1968 it was estimated that about 900,450 acre-
feet were supplied from wells.  Under ultimate development and a
complete distribution syste, it is estimated that 460,000 acre-feet,
the annual "safe yield", will be pumped each year.

The nitrate content, the only significant nitrogen form present,
was determined for water samples taken from 360 representative
irrigation wells which pump from depths of 200 to 3,000 feet.  The
nitrate -N concentration of these wells ranged from 0 to 10 mg/1
                                (22)

-------
 with the  average  about  0.5 mg/1.   In  1968 the nitrogen contributed
 by well water,totaled 610 tons  or  1.8 pounds per acre.  If  it is
 assumed that.the  nitrogen content  will not vary significantly in the
 future, the  460,000  acre-feet that will be pumped under ultimate
 conditions will contribute 310  tons of nitrogen annually.   This
 quantity  is  equivalent  to about 0.9 pounds per acre.

 A summary of the  contribution of nitrogen from the wells is included
 in Table  2.

                              TABLE 2

        Total Nitrogen  Contributions  from Irrigation Water
                        1968 and Ultimate
                      San Luis  Service Area
Source
Deliveries
Total Nitrogen
1968
AF
Wells
Canals
Totals
900
195
1,096
,450
,600
,050
Ultimate
AF
460
' 1,240
1,700
,000
,000
,000
mg/1
0.
0.

5
8

1968
Ibs/ac
1.8
0.6
2.4
tons
610
210
820
Ultimate
mg/1 Ibs/ac tons
0.5
0.8

0.9
4.0
4.9
310
1,350
1,660
Canal Water

The surface deliveries to the area are primarily from the San Luis
Canal with smaller amounts from the Delta-Mendota Canal.  The source
of water for both canals is the San Joaquin-Sacramento River Delta
near Tracy. ,There will be no significant differences in the nitro-
gen content between the two canals, therefore, the deliveries from
both are combined*for this study.  During the first two years of
operation of the,Sao Luis Canal, the weighted average of total N in
the wate? was 0,?8 mg/1.  This includes about 0.4 mg/1 of N03-N, 0.1
mg/1 of NH3-N ,and 0.3 mg/1 of organic N.  At this rate the total
nitrogen contribution to the area in 1968 by the 195,600 acre-feet
of canal diversions was 210 tons or an average of 0.6 pounds per
acre.  Under ultimate development, about 1,240,000 acre-feet will
be delivered annually to the service area from the two canals.
This quantity of water, assuming the N content remains constant^ will
add 1,350 tons or fy.O pounds per acre of nitrogen to the area.  The
total quantity of N contributed by the irrigation water was 2.4
pounds per acre in,1968 and will rise to 4.9 pounds per acre under
ultimate developm^ent. ! A summary of the contribution of nitrogen by
canal diversions arid groundwater pumpage is in Table 2.

Stream and "FJ&x* Flow

The several intermittent streams that flow into the area are a
source of nitrogen.  'These streams originate in the Coast Range
Mountains to the west and flow for only short periods in the winter

                                 (23)

-------
and spring following the more intense storms over their watersheds.
For planning purposes these streams are placed into four groups
which include a major stream and several lesser ones.  They are,
from north to south, the Little Panoche group, Panoche group,
Cantua group and the Los Gatos group.  The Ground water Section of
the Geology Branch of the Bureau of Reclamation at Sacramento has
calculated from the historical records the average flow contribution
of each of these groups.  The nitrogen content of the streams of
the various groups was based on tests made by U.S.B.R. Fresno Field
Division personnel.  Table 3 is a summary of these values.

                        TABLE 3

 Average Annual Nitrogen Contribution by Local Streams
                 San Luis Service Area
Stream
Quantity
AF
Los Gatos Group 2,000
Cantua Group 9,000
Panoche Group 14,000
Little Panoche Group 7,000

32,000
N Content
PPM
0.5
0.6
0.5
0.5
Total N
tons
1.3
7.3
9.5
4.7
22.8
Ibs/ac
.07
The 22.8 tons calculated for the area of 669,160 acres would be
equivalent to less than 0.1 pounds per acre.  Although a sizeable
amount it is not significant in the total budget.

Leguminous Plants

For many centuries the use of leguminous crops has been one of the
principal means of supplying nitrogen to the soil.  In this process
various strains of the Rhizobial bacteria growing in a symbiotic
relationship with a host plant will fix atmospheric' nitrogen in
nodules on the roots of the plant.  The amount of nitrogen fixed by
this process will vary with the type of crop, soil, climate and
moisture conditions.

Historically, leguminous native plants were the main contributors
of this type of nitrogen in the area, however, with,.kth'e intensive
cultivation of the area most of the native plants have been removed.
In their place, a number of cultivated legumes are grown.  The
largest acreage by far of leguminous crops is in alfalfa.  Beans,
the only other legume, are a relatively small acreage.  Alfalfa
seed, which fixes less nitrogen than alfalfa hay, is the major
alfalfa crop grown in the area.  The weighted average of the nitrogen
fixation in this area by the alfalfa seed and hay crops is estimated
at 145 pounds per acre.  There were 61,929 acres of alfalfa seed and
hay grown in the area in 1968.  This acreage at the estimated rate
of fixation would contribute about 4,500 tons of nitrogen to the area.
                             (24)

-------
The  estimated amount of fixation by beans is about 40 pounds per
acre.  At  this  rate, the 439 acres of beans grown would contribute
about  10 tons of nitrogen.

The  total  quantity of nitrogen fixed by leguminous crops in 1968
was  about  4,510 tons or 13.7 pounds per gross acre.  A summary of
the  nitrogen contribution by legumes is in Table 4.
                           TABLE 4

     NitrogenContribution from Legiminous Plants - 1968
                    San Luis Service Area
Crop

Alfalfa
Beans

Acres

61,929
439

N/Acre
Ibs
194
40

Total N
tons
4,500
10
4,510
Ave/Acre (1)
Ibs
13.6
0.1
13.7
(1)  Based on gross acreage of service area
Rainfall

Nitrogen compounds are present in the atmosphere and are returned
to the earth in rainfall.  This nitrogen is mainly in the form of
ammonia and nitrate with lesser amounts of nitrite, nitrous oxide,
and organic forms.  The presence of NO* has been attributed to its
formation during atmospheric electrical discharges but recent studies
suggest that only about 10 to 20 percent of the N03 in rainfall is
from this source (8).  The remainder is thought'to come from indust-
rial waste gases or from nitrogenous gases that escape the soil.

The amount of nitrogen that is returned to the soil in this manner
has been studied by a number of authors (7) (8).  The estimated
concentrations for this area are approximately 0.1 part per million
of NOj-N.  The average rainfall is about 6.6 inches per year.

The nitrogen contributed to the soil by the rainfall each year would
total 100 tons or 0.3 pounds per acre.

Livestock

The livestock population of the area in 1968 was estimated at 37,000
beef cattle and 135,000 sheep.  The cattle were concentrated in three
feed lots.  The sheep graze in the area for about half the year during
the fall and winter, and then are moved to higher lands outside the
district.  There are no appreciable numbers of other types of live-
stock within the area.
                               (25)

-------
The amount of waste nitrogen contributed by these animals was based
on the calculated daily waste excreted by the animals times the
number of days fed or pastured in the area.  The beef cattle con-
tributed a total of 1,890 tons or based on the gross area, 5.7
pounds per acre.  Although some of the manure is removed from the
feed lots and spread on other lands, much N will be concentrated
in the soils below and immediately adjacent to the feed lots.
The sheep are grazed over a relatively large acreage, as a result
their waste nitrogen will be distributed fairly evenly over the
area.  The total N contributed by the sheep was 910 tons or 2.7
pounds per gross acre.  The total for all the animals would be 2,800
tons or 8.4 pounds per acre.  A summary of the contribution by live-
stock is in Table 5.
                               TABLE 5

              Nitrogen Contribution for Animals - 1968
_ San Luis Service Area _ _

                               Nitrogen
Animal          Number      Ibs/day/animal        Tons/yr    Ibs/AC
Beef Cattle      37,000             .28V '         1,890      5.7

                                                     910      2.7
                                                   2,800      874
Sheep           135,300(1)          .09(3)           910      2.7
(1)  150 days/year pastured in area
(2)  9 Ibs dry manure/day @ 3.10% N
(3)  1.64 Ibs dry manure/day @ 5.4% N
Municipal and Industrial

This is primarily a rural area of relatively large farm operations.
Other than the Lemoore Naval Air Station, the. largest single
employer in the district, the population is concentrated in a few
small towns and several large farm labor camps.  The industries
are limited to a few agriculture related enterprises such as farm
equipment dealers, machine shops, trucking firms, and fruit and
vegetable packing plants.

The 1960 population as estimated from data supplied by Fresno
County Planning Office was 16,450 people and the 1968 population
17,400.  These population figures include the Lemoore Naval Air Base
and the towns of Mendota, Huron and Five Points.  In the work by
R. C. Loeher (13) it is estimated that the nitrogen contribution
of domestic waste is between 8-12 pounds per year .per.capita.  If
it is assumed that the average would be 10 pounds per capita the


                                (26)

-------
17,400 people would contribute 87 tons or about .3 pounds per gross
acre.  This nitrogen is not spread uniformly over the area but it
is concentrated in relatively small areas at the disposal plants
of the towns and camps.  The overall area covered by these popu-
lation centers is probably not greater than 3,300 acres.  If the
total quantity of nitrogen waste is prorated to this acreage, the
average would be about 53 pounds per acre.  It is obvious from this
that adjacent to the sewage disposal areas there can be relatively
high concentrations of nitrates introduced into the soils although
the overall total is small.

                          Nitrogen Losses

The main causes of the loss of nitrogen from the soil are removal
by crops, volatilization of nitrogen fertilizers and denitrification.

Removal by Crops

The major medium of nitrogen removal is through its uptake by the
crop and its ultimate removal by harvesting.  The quantity of ni-
trogen removed by this means was determined from the number of acres
of each crop as measured by the 1968 crop survey, the estimated
crop yields and the nitrogen content of the crop material.  These
latter values were determined in part from Morrison's "Feed and
Feeding" (14).  The amount removed was broken down into the materials
which are removed from the area and the plant residue that is nor-
mally returned to the soil.  At least a part of the nitrogen in
this latter material will again become available for plant growth
through mineralization.  Although the amount of nitrogen removed
by the various crops will vary, depending upon such factors as yield
levels, nutrient supply in the soil, fertilizer applied and manage-
ment practices, representative nitrogen uptake data for the various
crops in this area for 1968 are presented in Table 6.

The amount removed ranged from about 322 pounds in alfalfa hay to
37 pounds in beans.  The average of all the crops is 89 pounds per
acre.  This relatively low rate is due primarily to the high percent-
age of the area planted to barley which has a relatively low utili-
zation rate.

Volatilization of Ammonia Fertilizers .

Ammonium salts when applied to an alkaline soil will react to form
ammonia gas which if unconfined will be released to the air.  The
rate of this reaction will vary greatly with soil condition, pH,
temperature, moisture content and depth of placement.  Studies (4)
(6) have shown that when ammonium salts or ammonia gas are placed
on the soil surface more than 40 percent of the material can be
lost to volatilization, however, if it is placed several inches be-
low the ground surface essentially none of the ammonia is lost.  In
this area although there are small amounts of the fertilizer applied


                                (27)

-------
Crop
                                                 TABLE 6

                   Removal of Nitrogen by Harvested Crop - 1968 -  San Luis Service Area
                Seed,  Fruit or Fiber
  Acres         Crop Material  Removed
            Yield           Nitrogen
                        X N   lba/Ac.  Ton*
                     Leaves,  Stock or Stover
                     Crop Material Returned
                Yield           Nitrogen
                         IN   ibs/Ac.  Tons
    Total

Ibs/Ac.   Tons
^\
NJ
OD
%*













Cotton
Grain
Sugar Beets
Sorghusj
Safflower
Field Corn
Field Crops
Dry Beans
ToMtoes
Melons
Truck Crop*
Alfalfa Seed
Alfalfa & Pasture
Rice
Nuts
Vineyards
144,393
230,832
2.661
3,094
53,400
749
492
439
23,890
26,314
1,849
55,581
6,348
825
5,348
620
1.77
1.7
23.0
2.0
l.l
2.8
2.0
760
28
8
10
600
7
2.7
1000
9
bales
tons
tons
tons
ton
ton
ton
Ibs.
ton
ton
ton
Ibs.
ton
tons
Ibs.
ton
2.92
1.39
.22
1.81
2.61
1.34
1.60
3.66
.14
.50
.45
5.31
2.30
1.26
3.98
.12
67
47
101
72
57
75
64
28
78
80
90
32
322
68
40
22
4,840
5,425
135
110
1.535
30
15
5
935
1.050
85
880
1,020
30
105
5
15 cwt
34 cwt
150 cwt
48 cwt
26 cwt
67 cwt
48 cwt
9 cwt
370 cwt
110 cwt
132 cwt
40 cwt
--
54 cwt
180 cwt
180 cwt
1.80
.59
.43
.51
.94
.94
.51
.98
.14
.11
.30
2.30

.62
.22
.18
27
20
64
24
24
63
24
9
52
12
40
92
..
33
40
32
1,950
2,310
85
40
650
25
5

620
155
35
2,560

15
105
10
94
67
165
96
81
138
88
37
230
92
130
124
322
101
80
54
6,790
7,735
2,205
150
2,185
55
20
5
1,555
1,205
120
4,320
1,020
45
210
15
  Total
556,875
58   16,205
                                                                                 31    8,565
   89  25,650

-------
by airplanes, in the water or by broadcast methods the great bulk
of it is drilled to several inches below the soil surface.  Under
these conditions it is estimated that not more than 5 percent of
the fertilizer applied is lost.

Approximately 95 percent of 19,200 tons of the fertilizer applied
to the area in 1968 was in the ammonia or urea form which is subject
to volatilization.  If 5 percent of this amount is lost, it would
be equivalent to 960 tons or about 3 pounds per gross acre.

Denitrification

Studies have shown that there are losses of nitrogen from soil by
denitrification, the biochemical reduction of nitrates under anaer-
obic conditions (17)(16).  In calcareous soils such as are present
in this area the loss will primarily be in the form of nitrogen gas.
Water logging with its resulting exclusion of oxygen induces deni-
trification, therefore, in the areas of high water table and in the
presence of organic carbon there will be significant losses through
this process.  Lysimeter studies indicate that under optimum con-
ditions almost 100 percent of the nitrate -N present can be lost
through denitrification.  The specific quantity of nitrogen lost in
the field by this method in this area has been impossible to measure
therefore any attempt at this time to put a numerical value on
denitrification losses would be meaningless.

                      Nitrogen Budget Summary

A summary of the quantity of nitrogen contributed and removed from
the soil by the various processes is in Table 7.  This summary in-
dicates annual nitrogen losses, without attributing any value to
denitrification, are slightly greater than the total contributions.
Considering the accuracy of the measurements, for all practical pur-
poses there are probably no significant differences between the two.

The total nitrogen removed by the plant from the soil system, in-
cluding that portion in the plant material that may be returned to
the soil, was included as a nitrogen loss item.  Although some of
this is returned to the soil, it is in an organic form which must
be mineralized before it can be utilized by the plant or leached
by the percolating waters.

These values are based on an even distribution of nitrogen over the
entire acreage, however, in fact, this would not be true.  Also the
native nitrates and the organic nitrogen that is mineralized are not
included in the balance study.   Although the quantity of nitrogen moved
through the soils to the drains will be roughly equivalent to the con-
tribution from native nitrates and the mineralized organic nitrogen,
under actual field conditions these natural nitrogen sources will
replace some of the other types in the plant's nitrogen use.  There-
fore, a part of the nitrogen that is leached to the drain will come


                                 (29)

-------
                              TABLE  7

           Nitrogen Budget  1968  - San Luis Service Area
       Sources                                    Nitrogen

Nitrogen Contributions                           Ibs./ac.

Fertilizer                                         64.0
Irrigation Water                                    2.4
Stream Flow                                         0.1
Rainfall                                            0.3
Leguminous Plants                                  13.7
Livestock                                           8.4
Municipal & Industrial Waste                        0.3
                                                   89~I

Losses

Crop Harvest                                       89.0
Volatilization                                      3.0
Denitrification
from the applied sources, principally from the fertilizer.  The
amount of fertilizer leached will depend upon many factors, includ-
ing the type and amount of fertilizer, when and how applied, the
crop and root pattern, method and amount of irrigation, and the soil
type.

                          Transect Study

The objectives of the transect study were to determine the quantities
and the distribution of the various nitrogen forms, both with depth
and areawise and to determine the deviations in soils of similar
type within small areas.

Nitrogen in the Soil

The average content of NOj-N, NHj-N and organic N in parts per mil'
lion and the pounds per acre foot for each foot increment were deter-
mined from 1:1 soil-water extracts.  The quantities of the first
five foot increments of each site are listed in Table 8.

The data indicate that the total nitrogen in the top five feet of
soil at the various sites ranged from a low of 4321 pounds per acre
at site 7, a Levis soil, to a high of 8849 pounds per acre at site
12, a Panoche soil.  Of this quantity, the greatest portion by far
was the organic nitrogen.  The amount in this form ranged from 4140


                               (30)

-------
                             TABLE 8

    Quantities of Various Forms of Nitrogen at Transect Sites
           as Determined from 1:1 Soil-Water Extracts
Depth

Ft
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
  N03-N         NH3-N         Organic N

PPM  lbs/AF   PPM  lbs/AF    PPM  lbs/AF
                             520
                             405
                             306
                             213
                             259
                                     - Lethent Soil
          Total N

3.4
18.5
7.9
4.3
12.6


1.6
4.1
1.4
1.4
1.4


3.2
2.3
0.9
1.1
1.4


11.5
12.5
12.9
8.8
9.7

Site #1
12
67
28
15
45
167
Site #2
6
15
5
5
5
3T
Site #3
12
8
3
4
5
3T
Site #4
41
45
46
32
35
1W
T19S RISE S
6
3
3
3
4

T19
5
2
2
1
2

T19
6
5
4
3
3

T19
4
3
2
3
3

20
12
10
12
15
69
R19 S27
18
7
7
4
7
4T
R17 S20
22
18
14
11
11
76
R16 S15
14
- 11
7
11
11
54
                             633
                             282
                             229
                             222
                             222
2279
1015
 824
 799
 799
57T6
                         - Panoche Soil

                             350   1260
                             380   1368
                             224    806
                             273    983
                             280   1008
                                   54T5

                         - Panoche Soil
2303
1037
 836
 804
 807
5787
           1294
           1394
            823
            998
           1024
                             491
                             459
                             315
                             278
                             246
1768
1652
1134
1001
 886
1823
1708
1187
1044
 932
                                (31)

-------
                             TABLE 8 (Cont.)

Depth         N03-N          NHs-N         Organic N     Total N

Ft          PPM   Ibs/AF   PPM  Ibs/AF   PPM  Ibs/AF     lbs/AF

                 Site #5 T17 R16 S22 - Oxalis Soil

0-1         1.4    5        6     22     606   2182       2209
1-2         1.1    4        5     18     382   1375       1397
2-3         1.8    6        5     18     287   1033       1057
3-4         2.5    9        4     14     216    778        801
4-5         5.2   19        4     14     250    900        933
                  43              86           6268       397

                 Site #6 T16 R16 S22 - Lethent Soil

0-1        19.1   69        5     18     647   2329       2416
1-2         3.2   12        5     11     456   1642       1665
2-3         1.4    5'       3     11     388   1397       1413
3.4         1.6    6        27     368   1325       1338
4-5         2.5    9        27     295   1062       1078
                 101              54           7755       7910

                 Site #7 T15 R15 S26 - Levis Soil

0-1        14.4   52        5     18     442   1591       1661
1-2         8.4   30        3     11     258    929        970
2-3         6.8   24        3     11     175    630        665
3-4         3.6   13        2      7     147    529        549
4.5         2.3    8        27     128    461        476
                 127              54           4140       4"32"T

                 Site #8 T15 R14 S27 - Oxalis Soil

0-1         7.7   28        6     22     505   1818       1868
1-2        22.1   80        3     11     309   1112       1203
2-3        48.1  173        2      7     212    763        943
3-4        53.9  194        2      7     210    756        957
4-5       174.0  626        2      7     202    727       1360
                1101              5?           5176       633T

                 Site #9 T15 R13 S26 - Panoche Soil

0-1         6.6   24        4     14     444   1598       1636
1-2         2.7   10        3     11     312   1123       1144
2-3        11.1   40        3     11     214    770        821
3-4        14.2   51        4     14     160    576        641
4-5        22.6   81        2      7     149    536        624
                 206              57           4~6U3       4866
                                (32)

-------
                              TABLE 8 (Cent.)

 Depth         N03-N          NH3-N        Organic N       Total N

 E          PPM  Ibs/AF    PPM  Ibs/AF   PPM   Ibs/AF      lbs/AF

                  Site #10 T14 R12 S26 -  Lost  Hills Soil

 0-1        31.2   112       3     11     434    1562       1685
 1-2        35.2   127       2      7     247     889       1023
 2-3        42.7   154       2      7     182     655        816
 3-4        52.6   189       1      4     175     630        823
 4-5        55.3   199       1      4     163     587        790
                   781             33           4323       5l37

                  Site #11 T14 R12 S13 -  Panoche Soil

 0-1        43.1   155       3     11     401    1444       1610
 1-2        21.9    79       2      7     271     976       1062
 2-3         9.5    34       1      4     168     605        643
 3-4         8.1    29       1      4     150     540        573
 4-5         6.3    23       1    _4     149     536        563
                   320            30           4TOT       445T

                   Site  12  T13 R13 S23  -  Panoche  Soil

 0-1        14.2    51       4    14     660    2376       2441
 1-2         3.8    14       2      7      521    1876       1897
 2-3         3.2    12       1      4      481    1732       1748
 3-4         8.1    29       1      4      398    1433        1466
 4-5        11.1    40       1    _4      348    1253        1297
                   146            33            8670        8849"

                 Site #13  T12 R13 S25  - Oxalis Soil
0-1
1-2
2-3
3-4
4-5

17.6
2.9
5.9
0.9
0.9

63
10
21
3
3
ISO
7
4
2
- 4
4

25
14
7
14
14
7?
687
427
328
279
250

2473
1537
1181
1004
900
709T
2561
1561
1209
1021
917
72T9"
to 8670 pounds per acre.  Nitrate -N was the next largest constit-
uent with a range of 28 to 1101 pounds per acre.  The amount
of NH3 in the soil was low but rather consistent with a range of
30 to 86 pounds per acre.

Soil organic matter is the source of the organic nitrogen which
comprised more than 98 percent of the total nitrogen in some of the
sites.  Soil organic matter is an ill defined term used to cover


                                 (33)

-------
organic materials in all stages of decomposition from humus, which
is relatively resistant to further decomposition, to fresh crop
residues that are subject to fairly rapid decomposition.  Studies
have  shown that this organic nitrogen exists about 5-10 percent
in the form of nucleic acids; about 30 to 40 percent in the form of
proteins or its derivatives and about 10 to 15 percent as amino
sugar.  Most of the remaining nitrogen has not been characterized.
Although quite refractory some of this nitrogen can be converted by
bacterial action to NH3 and/or N03.


Although there were several exceptions, most often in the first five
feet  of soil, the nitrate nitrogen and organic nitrogen concentrations
were  greatest in the surface foot.  This is probably due to the higher
rate  of mineralization in the better aerated surface soil and residual
nitrates from fertilizer, the absorption of the NHj fertilizer by
the clay complex, and the result of the organic matter incorporated
into  the surface soils.

The distribution of the various nitrogen forms did not show any
distinct pattern in relation to soil series, physiographic position
or geomorphic area.  The minimum, maximum and average NO?-N and organic
N contents for several soil types and physiographic positions are
listed in Table 9.  The N03-N concentration in the seven basin rim
soils ranged from a minimum of one to a maximum of 100 with an average
of 14 parts per million.  These figures include one site which had
an extremely high concentration.  If this site is excluded the average
N03-N would be only five parts per million.

The N03-N concentration of five recent alluvial soils ranged from a
minimum of 2 to a maximum of 35 with an average of about 11 parts

                               TABLE 9

          Minimum, Maximum and Average NOs-N and Organic N
	Concentrations at the Various Sites by Soil Type, 0-5 Feet	
                     No. of     Minimum       Maximum        Average
                     Sites N03-N    Org.N   N03-N  Org.N  N03-N   Org.N
                                 p.p.m.        p.p.m.         p.p.m.
Soils
  Basin Rim
    Oxalis            4      2     250     100     412    20      349
    Lethent           2      1     297       5     511     4      379
    Levis             1      2     207      10     253     7      230

  Recent Alluvial
    Panoche           5      2     156      35     525    11      349

  Old Alluvial
    Lost Hills        1     22     225      94     248    42      240
                                 (34)

-------
 per million.  These data would indicate that there is about as
 much variation within the same soil type as there is between the
 different soil types and physiographic positions.

 The data as listed in Table 10 also indicates that there are vari-
 ations in the N03-N concentrations among the holes located at the
 same sites in similar soil material.  In some sites there were
 percentage differences ranging up to 800 percent and actual differences
 up to 70 parts per million of nitrogen.

 Statistical analyses were made on the variability of the nitrate
 values at each of the transect sites.  These determinations include
 the averages,  standard deviation and the standard error of the
 mean of the nitrate concentrations from the five borings at each
 site.  The results of these calculations are presented in Table 11.

 The organic nitrogen concentrations, although not exhibiting as
 great a percentage range as the N03-N,  varied considerably in
 actual values.  Again there was as great or greater variation among
 the sites of similar soil types as there was among the different
 soil types and physiographic position.   There were also differences
 among the five holes at the same site,  indicating significant
 variations within small areas.

 The NH3 content of the soil at  all of the sites  ranged from about
 1  to 7 parts per million.   These values were relatively consistent
 at all of the  sites.   There were no appreciable  differences between
 soil type or physiographic position*

 If it is assumed that the  concentrations determined for the  in-
 dividual sites are representative  of the whole area, the average
 and total quantity of nitrogen  in  the top five feet of  soil of the
 study area would be 6,142  pounds per acre of  2,056,660  tons  and is
 segregated as  shown in Table  12.

 Nitrogen in  the  Substrata
                    <
 The results  of the  laboratory analyses for the various  forms of
 nitrogen  in  the  substrata  of the transect  sites as expressed in
 parts per million and pounds per acre-foot are summarized in Table
 13.  The  substrata as used in this study is defined as those soil
 horizons  between 5 and 40  foot depths.

 Because of the apparent correlation between nitrogen concentration
 and the fan-interfan position, this was used as a basis to determine
 the total quantity of nitrogen in the substrata of the area.  These
 values were determined by multiplying the weighted average of the
nitrogen concentrations in the 5-40 feet depths of the sites
                             (35)

-------
CT>
                                                       TABLE  10

          The Average N03-N and Organic  N Content in Parts Per Million in the 0-5 Foot Depth for the 5 Holes
                                               Within the Various Sites
Site
No.
1
5
8
13
2
6
7
3
4
9
11
12
Hole #
Soil Series NO-^-N
Oxalis
it
ii
it
Lethent
ii
Lev is
Panoche
it
ii
ii
it
23
7
30
5
5
5
10
3
11
8
35
24
a
Org.N
250
211
308
371
327
452
207
382
394
200
197
466
NOi-N
5
2
49
4
1
5
10
1
4
25
13
3
b
Org.N
338
360
277
412
297
405
225
335
319
239
156
525
NOvN
6
2
68
5
1
5
2
2
16
9
10
5
c
Org.N
387
389
313
409
302
511
233
244
361
266
261
475
NO^-N
4
2
100
9
2
5
5
2
17
11
13
4
d
Org.N
352
379
269
391
310
304
231
310
411
261
241
440
NOi-N
5
2
60
6
1
8
8
1
8
18
18
5
e
Org.N
375
402
290
388
352
483
253
236
345
316
283
461
Average
NO^-N Org.N
8
3
61
6
2
5
7
2
11
18
18
8
340
371
291
394
318
431
230
301
366
256
228
483
       10    Lost Hills    22    238     42    248     94    225     24    265     35    225     42     240

-------
                              TABLE 11
 Summary of NOj-N in Parts per Million, Standard Deviations and
 Standard Error of Mean for the Five Holes at Each Nitrate Site
Depth
 Ft.
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5

CD 0"
(2) Om
         b            d            Avg.

      Site #1 T19S RISE S23 - Oxalis Clay
10
67
26
12
19

6
15
2
2
2

3
2
2
4
4

12
14
15
9
5

1
12
5
8
11
2
4
2
3
15
Site #2
1
1
1
1
1
Site #3
3
2
1
1
1
Site #4
2
2
1
7
9
Site #5
2
1
1
1
2
2
10
6
2
11
T19 R19
1
1
1
1
1
T19 R17
4
3
1
1
1
T19 R16
16
22
19
13
8
2
10
3
2
4
S27
1
2
2
1
2
S20
4
2
1
1
1
S15
16
19
16
12
25
T17 R16 S22 -
2
2
1
1
3
1
1
1
1
4
2
2
2
3
15
- Lethent
0
2
1
2
1
- Oxalis
3
1
1
1
1
- Panoche
13
6
15
4
2
4
19
8
4
13
Soil
2
5
1
1
1
Soil
3
2
1
1
1
Soil
12
12
13
9
10
Oxalis Soil
0
1
1
2
5
1
3
2
2
5
(1)
0"
                                               3
                                              27
                                              10
                                               4
                                               6
                                              2
                                              6
                                              1
                                              1
                                              1
                                              1
                                              1
                                              1
                                              1
                                              2
                                              6
                                              8
                                              7
                                              4
                                              9
                                              1
                                              6
                                              2
                                              3
                                              3
(2)
din
        4
       34
       13
        6
        7
       2
       7
       1
       1
       1
       1
       1
       1
       2
       2
       7
      11
       8
       5
      11
       1
       7
       2
       4
       4
Standard deviation of the mean, all values +
Standard error of mean (95 percent confidence interval)
                                (37)

-------
                             TABLE 11 (cent.)

                                                           CD     (2)
             a       b            d             Avg.     0[	     Pin

                   Site #6 T16 R16 S22 - Lethent Soil

 0-1         16      17     17     15     30      19       6      8
 1-2          25424311
 2-3          12121111
 3-4          22122211
 4-5          32222211
 0-1         16       20     7      13     16      14     5      6
 1-2         17       11     1       58       868
 2-3         11       10     1       2     10       756
 3-4          5        6125422
 4-5          3        21       23       211
 0-1          14      6      4      10     5       845
 1-2          24     28     16      29    15      22      7      8
 2-3          32     30     32     120    28      48     40     50
 3-4          29     48     67      42    85      54     22     27
 4-5          54    130    219     303   160     175     93    115
16
2
1
2
3

16
17
11
5
3

14
24
32
29
54
17
5
2
2
2
Site #7
20
11
10
6
2
Site #8
6
28
30
48
130
17
4
1
1
2
T15
7
1
1
1
1
T15
4
16
32
67
219
15
2
2
2
2
R15 S26
13
5
2
2
2
R14 S27
10
29
120
42
303
Site #9 T15 R13 S26 -
1
2
23
14
1

2
3
16
40
48
11
6
22
33
52
Site #10
4
26
46
50
48
8
2
7
13
18
T14
97
70
82
101
101
6
1
1
8
40
R12 S26
14
20
26
29
33
Site #11 T14 R12 S13 -
79
61
17
11
7
48
10
2
1
2
29
8
3
5
6
30
16
10
6
3
30
4
1
2
2
- Levis
16
8
10
5
3
- Oxalis
5
15
28
85
160
Panoche
11
1
4
3
2
19
3
1
2
2
Soil
14
8
7
4
2
Soil
8
22
48
54
175
Soil
7
2
11
14
23
6
1
1
1
1

5
6
5
2
1

4
7
40
22
93

4
2
10
11
23
- Lost Hills Soil
40
40
44
44
50
Panoche
30
15
15
17
13
31
32
43
53
57
Soil
43
22
9
8
6
40
33
25
26
52

21
22
7
6
5
0-1            J.     JLJ.     b       b     11      7      4      5
1-2            26211222
2-3           23     22     7       14     11     10     13
3-4           14     33    13       83     14     11     14
4-5            1     52    18      40      2     23     23     28
0-1          2      4       97       14     40      31     40     50
1-2          3     26       70       20     40      32     33     40
2-3         16     46       82       26     44      43     25     31
3-4         40     50      101       29     44      53     28     35
4-5         48     48      101       33     50      57     52     65
0-1          79     48     29      30     30       43      21     26
1-2          61     10      8      16     15       22      22     28
2-3          17      2      3      10     15        97      8
3-4          11      1      5        6     17        8       6      8
4-5           7      2      6        3     13        6       5      6


                                (38)

-------
                         TABLE 11 (cont.)
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
64
13
 8
14
23
18
 2
 1
 1
 1
                  b             d     e_         Avg.

               Site #12 T13 R13 S23 - Panoche Soil
 5
 3
 2
 3
 2
 1
 1
 7
12
 1
 1
 3
 8
 1
 1
 2
 9
12
14
 4
 3
 8
11
               Site #13 T12 R13 S25 - Oxalis Soil
14
 2
 1
 2
 2
15
 2
 5
 1
 1
19
 3
22
 1
 1
23
 5
 1
 1
 0
18
 3
 6
 1
 1
                                              (D
                                              0"
28
 5
 2
 4
 8
 4
 1
 9
 1
 1
                                              (2)
                                              Om
34
 6
 3
 5
 9
 5
 1
11
 1
 1
                             TABLE 12
              Average Pounds Per Acre and Total N in
            the Study Area in the 0-5 Foot Soil Depth
    N03-N          NH3-N
Ibs/ac.  Tons  Ibs/ac.   Tons
                       Organic N
                    Ibs/ac.      Tons
                                        Total N
                                  Ibs/ac.     Tons
  258   86,370    54   18,400   5,830   1,951,940 6,142    2,056,600
within the individual fans, or those sites most representative of
them, by the acreages of the fans.  The total nitrogen and pounds
per acre for each of the nitrogen forms on each alluvial fan are
listed in Table 14.

The total nitrogen in the substrata is 8,193,080 tons or about
24,490 pounds per acre.  Nitrate N accounts for 1,496,000 tons or
4,470 pounds per acre of the total.  The concentration of nitrate
N ranged from a low of 87 pounds at site 5, a Panoche soil on the
Los Gatos Creek fan to a high 28,353 pounds per acre at site 8, an
Oxalis soil on the Panoche-Cantua interfan.

The total organic N in the Substrata was 6,559,250 tons or an
average of 19,730 pounds per acre.  The concentration of the
                             (39)

-------
                              TABLE  13

            N03-N,  NH3-N  and Organic N  in PPM  and Pounds
                    Per Acre in  the  Soil  Substrata*
Site
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
Depth in
feet
5-40
5-12.5
5-40
5-32
5-40
***
5-6
5-40
5-40
5-40
5-40
5-30
5-10
N03-N
PPM**
3.7
1.5
0.7
41.4
13.4

1.6
205.0
135.8
60.5
2.0
12.3
1.8
Ibs.
467
40
87
4,019
1,693

6
28,353
17,105
7,642
252
1,106
32
NH3-N
PPM**
2.9
3.0
3.2
2.9
2.0

3.0
1.8
2.2
1.1
1.5
1.4
2.3
Ibs.
368
82
409
277
250

11
232
282
137
186
128
42
Organic N
PPM**
144
199
232
202
152

138
118
112
108
145
185
235
Ibs.
18,197
5,383
29,284
19,560
19,109

497
14,810
14,164
13,573
17,691
16,686
4,230
Total N
Ibs.
19,032
5,505
29,780
23,867
21,052

514
43,395
31,551
23,352
18,129
17,920
4,304
*  5-40 feet or to water table
** Based on Apparent Specific Gravity of 1.32
*** Water Table at 5 feet
individual sites ranged from a minimum of 13,573 to a maximum of
29,284 pounds per acre.  Although this is a large variation, the
percentage differences are relatively small when compared with the
variations that occur in the nitrate concentrations.

The distribution of the relative concentrations of N03-N, NH3-N and
organic N throughout the profile at all the transect sites is shown
in Figures 4 through 16.

The nitrate -N generally was greatest in the upper part of the sub-
strata, there were exceptions and the peak;  concentrations occurred
at any depth.

The ammonia concentrations were relatively low, generally less than
five parts per million.  Although percentage-wise there was a large
variation between sites, the differences in actual quantities when
compared to differences in the other forms were small.

Although the quantity of organic N decreased with depth, it was
still the dominant type except in site 8.  At site 9 organic
N was only slightly more than N03-N.  A few Substrata contained
                              (40)

-------
                                                   TABLE 14

                              Total H in the 5-40 foot Substrata by Alluvial Fan
       Geonorphic Area
                             Area
               MO3-M
                               Organic-N
                                           Total N
                             Acres    Ibs/Ac
                     Total
                     Tons
         Ibs/Ac
         Total
         Tons
       Ibg/Ac
           Total
           Tons
         Ibs/Ac
Total
Tons
Laguna Seca -
 Little Panoche I.F.*

Little Panoche Creek

Little Panoche -
 Panoche I.F.
Total (Ave)

*I.F. - Interfan
  9,970    7,642
38,080
137
680
13,573
67,640   21,352
106,400
 10,340      252       1,300    186

 63,090    7,642     241,050    137
                      960    17,691     91,480   18,129      93,740

                    4,320    13,573    428,140   21,352     673,510
Panoche Creek
Panoche-Cantua I.F.
Cantua Creek
Cantua-Los Gatos I.F.
Los Gatos Creek
South of Los Gatos
Creek I.F.
Ill
90
45
73
245
20

,230
,130
,380
,220
,460
,340

252
22,725
270
2,945
277
2,945

14
1,024
6
107
33
29

,030
.090
,130
,810
,990
,950

186
257
388
280
388
280

10,340
11,580
23,740
10,250
47,620
2,850

17,691
14,487
23,740
19,730
23,740
19,730

983,880
652,850
538,680
722,230
2,913,610
200,650

18,129
37,469
24,398
22,955
24,405
22,955

1,008,250
1,688.520
553,610
840,380
2,995,220
233,450

669,160    4,470   1,496,430
          290
         97,400    19,730  6,599,250   24,490   8,193,080

-------
                     SITE NO. I -OXALIS  SOIL
  4OOOi
                                          ORGANIC  N -
                                             N03-N-
   1000-
    500 -
i/l
.0
c   100-
 c
 o
c
1)
o

o
                         Dtpth in Feet



           FIG. 4-  DISTRIBUTION OF  N03-N, NH3-N  AND


           ORGANIC-N  BY SAMPLING DEPTH
                          (42)

-------
                  SITE NO. 2-LETHENT SOIL
  4000
   IOOO-
    300

-------
                   SITE NO. 3-PANOCHE SOIL
4000-1
 IOOO-
                      Depth in Feet
        FIG. 6-  DISTRIBUTION OF N03-N, NH3-N  AND
        ORGANIC-N BY SAMPLING DEPTH
                       (44)

-------
                        SITE NO. 4-PANOCHE SOIL
  4000-1
   1000-
    500 -
o
    IOO 
     50 -
c
o
o
c
o
      10 
      5 -
                                              ORGANIC N -


                                                  NH3-N-
'i'
             i'V'j'
-------
                  SITE  NO. 5-OXALIS SOIL
  4OOOi
   IOOO 
    500 -
o>
l_
o
c
o
c
4)
O

o
o
    100-
                                         OKGANtC N 


                                            NH3-N -


                                            NO3-N 
                         Dpth in Feet



          FIG. 8 -  DISTRIBUTION OF N03-N, NH3~N  AND

          ORGANIC-N  BY SAMPLING DEPTH
                         (46)

-------
                   SITE NO. 6-LETHENT  SOIL
  4OOOi
   1000
    500 -
O)

o
o
N
O
c
o
u

o
                                         ORGANIC N 


                                            NH3-N -


                                            N03-N 
                                    in
                                          I  T
                         Dpth in Feet
T I '
 in
 ro
n
 o
          FIG. 9-  DISTRIBUTION Of N03~N, NH3~N  AND

          ORGANIC-N BY SAMPLING  DEPTH
                         (47)

-------
                      SITE NO.  7- LEVIS  SOIL
   4OOOi
                                          ORGANIC N 
                                             N03-N-
   1000-3
    500 -$
QJ
u_
o
a
\

A
    100 - i
c
d
o
c
o
     10  -
      5 -:
                                I I  I I I I I
                         Dpth in Feet
                                    cvj
                                                      u>
          FIG. 10- DISTRIBUTION OF  N03~N, NH3~N  AND

          ORGANIC-N BY SAMPLING DEPTH
                          (48)

-------
                     SITE NO  8-OXALIS  SOIL
  4000 
   1000
    500 -
o>
b
c
o
o
c
o
   IOO
                        Dpth in Feet
          FIG. II -  DISTRIBUTION OF N03~N, NH3~N  AND

          ORGANIC-N BY SAMPLING  DEPTH
                        (49)

-------
                    SITE  NO.  9-PANOCHE SOIL
40001
                      Dpth  in Feet
        FIG. 12-DISTRIBUTION  OF NO-j-N, NH3-N  AND
        ORGANIC-N  BY  SAMPLING DEPTH "
                      (SO)

-------
                  SITE  NO.  10-LOST  HILLS  SOIL
  4000-1
   IOOO 
   300 -
0)


o
    100 :
     50 - :
c
o
o

o
     10- :
             m
                    r
                    o
                                          ORGANIC N -
                                     OJ
                         Dpth in Feet
                                                 rO
          FIG. 13-  DISTRIBUTION OF N03-N, NH3~N  AND


          ORGANIC-N  BY  SAMPLING DEPTH
                          (SI)

-------
                        SITE NO. II- PANOCHE SOIL
  4000-1
   1000 
    500 -
o
.0
c
o
c
4)
O
c
o
    100 
                                            ORGANIC N -


                                              NH3-N-


                                              N03-N 
                 VVi'fV'i'rTj'i I i i [ > i'1 i |
                          Dpth in Feet



           FIG. 14- DISTRIBUTION OF  N03-N, NH3~N  AND

           ORGANIC-N BY SAMPLING  DEPTH
                          (52)

-------
                    SITE  NO. 12 - PANOCHE  SOIL
  4000-1
                                          ORGANIC N 


                                             NH3-N -


                                             N03-N 
   IOOO
    500 -
o
JD
O
c
O
O
L-


C:
c
O
    100 
                         Dpth in Feet
          FIG. 15- DISTRIBUTION OF  N03-N, NH3~N  AND

          ORGANIC-N BY SAMPLING  DEPTH
                         (.53)

-------
                     SITE NO. 13- OXALIS  SOIL
  4OOO-1
   1000
    500 -
O
.0
o
c
o
c
4>
O
C
o
    IOO 
     10-
      5 -
                  J"
                         "
                          IT)
T
 ID
 eg
                                           ORGANIC N 

                                              NH3-N-


                                              N03-N 
                          Dpth in  Feet
M^

 ro
           FIG. 16- DISTRIBUTION OF  NO-j-N, NH3~N  AND

           ORGANIC-N BY SAMPLING DEPTH
                           (54)

-------
less than 10, however, normally they contained more than 100 parts
per million.  The organic N concentrations were higher on the
alluvial fans than on the interfans and in both fan and interfan
areas there is an increase in concentration from north to south.

Sites No. 8, 9, and 10 have unusually high concentrations of
nitrates.  They represent different soil series and physiographic
position.  However, they do have a common factor in that they are
located on similar geomorphic units; that is, interfan areas between
the larger streams, Little Panoche, Panoche and Cantua Creeks.  These
areas have been subjected to less surface flooding and consequently
there has been less leaching of the nitrates from the soil profile.
There is also the possibility that because less water has moved
through the soils there have been fewer saturated conditions there-
fore less denitrification has occurred to reduce the nitrate con-
centrations.

                      Nitrogen in Groundwater

About 25 percent of the ultimate water demand will be met from the
groundwater of the area, therefore, it is necessary to know the
amount of nitrate in this body of water in order to predict the
nitrate-nitrogen content of the agricultural drainage effluent.
Generally data from the wells above the Corcoran clay show a
decrease in the nitrate concentration with increasing depth.  The
wells which have their primary yields from the.Sierra sediments
have lower nitrate concentrations than those wells that produce
from the Coast Range sediments.

A description of nitrate concentrations in water above the Corcoran
clay by well depth interval as prepared by the Geology Branch, USER,
Sacramento is presented below:

0-50 foot well depth

As shown in Tables 15 through 19, the highest NC-3-N values appear to
be in the 0-50 foot depth on the Los Gatos-Zapatos interfan in Coast
Range material.  However, ,this concentration of 122 mg/1 N03-N is
based on an average of only two samples.  The 0-50 foot depth on the
Panoche-Cantua interfan has a mean of 52 mg/1 N03-N  in Coast Range
sediments based on 16 samples.  The standard deviation for the 52 mg/1
mean approached 68 mg/1 indicating a wide range of NC>3-N concentrations
within the 0-50 foot depth interval.

On the Panoche fan a mean NO^-N concentration of about 36 mg/1 in
Coast Range sediments was computed for 53 samples including a very
high NOr-N value (560 mg/1) reported for USER geohydrologic obser-
vation hole No. 14S/14E/28R2.  Excluding this high analysis, the mean
NO,-N content was 16 mg/1, with the next highest N03-N being 160 mg/1.
                            (55)

-------
                             TABLE 15

Summary a/ of Nitrate Nitrogen and Standard Deviations in Milligrams
per Liter for Wells and USER Geohydrologic Observation Holes Above the
Corcoran Clay - 0-50 Foot Depth
GEOMORPHIC UNITS
LOS BANGS CR. - L. PANOCHE INTERFAN
LITTLE PANOCHE FAN
LITTLE PANOCHE - PANOCHE INTERFAN
PANOCHE FAN
PANOCHE - CANTUA INTERFAN
CANTUA FAN
CANTUA - LOS GATOS INTERFAN
LOS GATOS FAN
LOS GATOS - ZAPATOS INTERFAN
MENDOTA - FIREBAUGH AREA
TOTAL SAMPLES ABOVE
CORCORAN CLAY: 244
0-50
No. of
analyses
1
5
3
53b/
52c/
1
16
14
7
40
16
2
1
2
160
Ft. well depth
Yield primarily from:
Sierran Coast Range
sediments sediments
10.2
18.5 + 14.0
7.6 + 4.6
25.9 4 76.3
15.6 4 24.8
1.0
52.5 + 67.6
6.1 + 9.3
22.7 + 29.6
30.1 + 77.3
2.4 * 4.0
122.4 (aver.)
U.I
0.9 (aver.)

a/Expressed as arithmetic mean plus or minus standard deviation.
B/Includes analysis from USER geohydrologic observation hole No.  14S/
  14E-28R2 with a nitrate nitrogen value of 562 mg/1.
c/Excludes analysis from USER geohydrologic observation hole No.  14S/
  14E-28R2.
                                 (56)

-------
                             TABLE  16

Summary of Nitrate Nitrogen and  Standard  Deviations in Milligrams
per  Liter for Wells and USER Geohydrologic Observation Holes Above the
Corcoran Clay -  50-150 Foot Depth
GEOMORPHIC UNITS
50-150 ft. well depth
Yield primarily from:
No. of Sierran Coast Range
analyses sediments sediments
LOS BANDS CR. - L. PANOCHE INTERFAN
LITTLE PANOCHE FAN
LITTLE PANOCHE - PANOCHE INTERFAN
PANOCHE FAN
PANOCHE - CANTUA INTERFAN
CANTUA FAN
CANTUA - LOS GATOS INTERFAN
LOS GATOS FAN
2 1.4 (aver.)
1 93.5
1 0.1
1 0.7
9 29.3 + 32.4
LOS GATOS - ZAPATOS INTERFAN
MENDOTA - FIREBAUGH AREA
3 0.5 4- 0.3
TOTAL SAMPLES ABOVE
  CORCORAN CLAY:  244
17
                               (5.7)

-------
                            TABLE 17

Summary of Nitrate Nitrogen and Standard Deviation in Milligrams per
Liter for Wells and USER Geohydrologic Observation Holes Above the
Corcoran Clay - 150-300 Foot Depth
GEOMORPHIC UNITS
     150-300 ft. well depth
             Yield primarily from;
  No. of    Sierran    Coast Range
analyses   sediments    sediments
LOS BANDS CR. - L. PANOCHE INTERFAN
LITTLE PANOCHE FAN
LITTLE PANOCHE - PANOCHE INTERFAN
PANOCHE FAN
     7
     1
51.0 + 117.2
                                             0.5
PANOCHE - CANTUA INTERFAN
                         .6
CANTUA FAN
CANTUA - LOS GATOS INTERFAN
LOS GATOS FAN
     2
                                             0.3
 6.8 (aver.)
LOS GATOS - ZAPATOS INTERFAN
MENDOTA - FIREBAUGH AREA
     6                  0.4 + 0.5
    18     0.3+0.2
TOTAL SAMPLES ABOVE
  CORCORAN CLAY:  244
    36
                               (58)

-------
                            TABLE 18

Summary of Nitrate Nitrogen and Standard Deviations in Milligrams per
Liter for Wells and USER Geohydrologic Observation Holes Above the
Corcoran Clay - 300-600 Foot Depth
300-600 ft. well depth
GEOMORPHIC UNITS
No. of
analyses
Yield primarily from:
Sierran Coast Range
sediments sediments
LOS BANOS CR. - L. PANOCHE INTERFAN
LITTLE PANOCHE FAN
LITTLE PANOCHE - PANOCHE INTERFAN
PANOCHE FAN
PANOCHE - CANTUA INTERFAN
CANTUA FAN
5
3
1
2
0.2 + 0.3
0.9 + 0.5
21.0
0.2 (aver.)
CANTUA - LOS GATOS INTERFAN
LOS GATOS FAN
LOS GATOS - ZAPATOS INTERFAN
MENDOTA - FIREBAUGH
1
8

1
2
10.6
1.4 + 2.6

0.1
0.1 (aver.)
TOTAL SAMPLES ABOVE
  CORCORAN CLAY:  244
23
                                (59)

-------
                       TABLE 19

Summary of Nitrate Nitrogen and Standard Deviation in Milligrams per
Liter for Wells and USSR Geohydrologic Observation Holes Above the
Corcoran Clay - 600-800 Foot Depth
GEOMORPHIC UNITS
     600-800- ft. well depth
               Yield primarily from;
 No. of    SierranCoast Range
analyses  sediments    sediments
LOS BANOS CR - L. PANOCHE INTERFAN
LITTLE PANOCHE FAN
LITTLE PANOCHE - PANOCHE INTERFAN
PANOCHE FAN
PANOCHE - CANTUA INTERFAN
CANTUA FAN
CANTUA - LOS GATOS INTERFAN
LOS GATOS FAN
     5                 0.2  0.5
     2    0.5 (aver.)
LOS GATOS - ZAPATOS INTERFAN
                       5.6
MENDOTA - FIREBAUGH AREA
TOTAL SAMPLES ABOVE
  CORCORAN CLAY:  244
     8
                               (60)

-------
 Little Panoche fan has a mean N03-N concentration of 18 iag/1 for
 five analyses with individual analyses ranging from 4 mg/1 to 40
 mg/1 in the 0-50 foot interval.

 Generally N03-N concentrations for the 0-50 foot depth in wells
 which obtain their yield from Sierran sediments is comparatively low,
 ranging from 0 to 14 mg/1 (Los Gatos fan).  Nitrate -N concentrations
 for USBR holes in Coast Range sediments in the interval are high,
 ranging from a trace up to 460 mg/1, as mentioned above.  About five
 holes had nitrates in excess of 225 mg/1.

 50-150 foot well depth

 In the 50-150 foot depth range, one analysis on the Panoche-Cantua
 interfan was 93 mg/1 in Coast Range sediments.  On the Los Gatos
 fan the average for this depth was 29 ppm in Coast Range sediments.
 On the other fans and interfans in this depth range, mean N03-N was
 less than 2 mg/1, based on a small number of analyses in both Coast
 Range and Sierran sediments.

 150-300 foot well depth

 In the 150-300 foot depth interval Panoche fan had a high concen-
 tration of nitrate in Coast Range sediments; based on seven analyses
 the mean NOj-N concentration was about 51 mg/1 with a standard
 deviation of 117 mg/1.  The range was from 1 to 320 mg/1.  For other
 fans and sediments concentrations in this depth range were as much
 as 7 mg/1 but were generally less than 1 mg/1.

 300-600 foot well depth

 In the 300-600 foot depth interval, N03-N concentrations are generally
 low, ranging from 0.1 to 2 mg/1, principally from Sierran aquifiers.
 Two wells in this depth zone producing from Coast Range sediments
 on the Cantua and Los Gatos fans had 22 and 10 mg/1, respectively
 of N03-N.

 600-800 foot well depth

 In the 600-800 depth interval,  nitrate was low in both Sierran and
 Coast Range sediments with the  highest NO,-N being 6 mg/1 in Coast
Range sediments on the Los Gatos-Zapatos interfan.

The average N03-N concentration, about 0.5 mg/1,  of the irrigation
water from the wells in the area is much less than the average
 concentration of water in the material above the  Corcoran as listed
 in Table 15 through 19.   This is particularly true of the water in
 all depths of the Coast Range sediments and in the 0-50 depth of
                             (61)

-------
the Sierran sediments, indicating that relatively small amounts of
irrigation water is obtained from these sources.  Also, as many of
the wells are drilled below the Corcoran clay to depths of 2,000
feet or greater they pick up most of their water from strata not
shown in this report.

      Nitrogen Transformation and Movement in Lysimeters

The movement of residual nitrogen and applied fertilizer nitrogen
in lysimeters was monitored under leaching and cropping regimes.

The initial N03-N levels of the soils ranged from 12 ppm in the
Panoche clay subsoil to 115 ppm in the Lethent clay loam surface.
The N03-N levels in leachates collected during initial leaching and
before fertilization ranged from 4,290 ppm in the Oxalis clay to
560 ppm in the Panoche fine sandy loam.  These high levels are
believed due primarily to the change in the environment of the soils
as a result of the screening, mixing and aeration during the filling
of the lysimeters.  These actions increased microbial activity which
encouraged mineralization of some of the native organic nitrogen
to nitrates.

After the high initial nitrate concentrations were recorded, a rapid
drop in the nitrate levels occurred as additional water moved through
the columns.  When sufficient water had been applied to reduce the
nitrate-N levels in the soil extracts from all sampling depths of
the soil columns to less than 10 ppm, the N03-N concentrations in
the leachates ranged from about 11 ppm for the Panoche fine sandy
loam to about 115 ppm for the Oxalis clay.  After the barley was
planted and the 15N enriched fertilizer applied, periodic samples
were collected of the soil extracts at three depths in the columns
and from the leachates.  Data resulting from the analyses of these
samples, based primarily on the atom percent excess 15N, are presented
in Tables 20 through 28.  These data are averages of values from
duplicate columns of each treatement.

Data for nitrogen content and the percentages which are attributable
to fertilizer nitrogen in the "A" depths, 9 to 18 inches, are presented
in Table 20.  These data show that at this depth the highest percent-
age of fertilizer nitrogen appeared in those soils to which KNOs
was applied.  In Panoche fine sandy loam and Lethent sandy clay loam,
respectively, 81 and 66 percent of the total nitrogen collected in
the soil extract was fertilizer nitrogen.  By comparison 14 and 27
percent of the nitrogen in the extract was fertilizer nitrogen when
(NH4)2S04 was applied to Panoche clay loam and Oxalis clay and when
sulfur coated urea was applied to Panoche fine sandy loam 25 percent
of the extract from "A" depth was fertilizer nitrogen.

This would indicate that much of the ammonia-N is adsorbed by the
                              (62)

-------
clay  complex of the  soil near the  soil  surface.  Since only  30 per-
cent  of  the sulfur coated urea was readily  soluble and the remainder
was treated to dissolve slowly, movement of nitrogen from the urea
fertilizer could be  expected to be approximately 30 percent  of N
movement from KN03 assuming appreciable -hydrolosis did not occur.
The data are in accord with these  proportions.  However, the system
is complicated by nitrogen release from sulfur coated urea, hydrolosis
of urea, nitrification and soil textural differences, therefore, the
apparent proportionality may have  resulted from compensating effects.

The nitrogen content and the percent fertilizer nitrogen in the soil
extract  at the "B" depths, 24 to 39 inches, are listed in Table 21.

                             TABLE 20
            Nitrogen Content and Percent of Fertilizer
            Nitrogen in Soil Extracts from "A" Depths
                December 16. 1968 - August 18, 1969
Soil Type  Fertilizer
Water Applied  Probe Depth  Total N Fertilizer N
     In            In         mg        W"^
Panoche CL
Panoche FSL
Lethent GL
Panoche FSL
Oxalis C
(NH4)2S04
KN03
KN03
S:Urea-N
(NH4)2S04
60.6
60.6
60.6
60.6
60.6
16
15
9
11
18
13.2
49.5
34.2
15.2
16.5
13.6
81.4
66.1
25.0
27.3
                             TABLE 21

            Nitrogen Content and Percent of Fertilizer
            Nitrogen in Soil Extracts from nBn Depths
                 December 16. 1968 - August 18, 1969
Soil Type  Fertilizer
Water Applied  Probe Depth  Total N Fertilizer N
     In            In         mg        %
Panoche CL
Panoche FSL
Lethent CL
Panoche FSL
Oxalis C
(NH4)2S04
KN03
KN03
S:Urea-N
(NH4)2S04
60.6
60.6
60,6
60.6
60.6
39
39
24
33
31
23.6
23.0
14.2
14.4
36.0
2.1
4.8
23.9
4.2
1.4
The percent of fertilizer N of the total N collected from the "BTI
depths was less than 4.8 with the exception of the Lethent clay loam.
The higher percentage of fertilizer N in the Lethent columns may have
been because the suction probes were higher in the columns.  These
low values for the other columns indicate that little movement of the
fertilizers occurred to depths of 31 to 39 inches.
                                (63)

-------
The nitrogen content and percent fertilizer N for the "C" depth are
shown in Table 22.  At the most, 4.5 percent of the N collected from
the probe came from the applied fertilizer.  The highest percentage
of fertilizer N was from the Lethent soil and least was from the
Panoche fertilized with sulfur coated urea.  These low values indicate,
as did those of the nB" depths, that a very small percentage of the
applied N moved through the soil columns.

                             TABLE 22

            Nitrogen Content and Percent of Fertilizer
                 in Soil Extracts from "C" Depths
	December 16, 1968 - August 18, 1969	
Soil Type  Fertilizer
Water Applied  Probe Depth Total N Fertilizer N
     In            In        mg        3T
Panoche CL
Panoche FSL
Lethent CL
Panoche FSL
Oxalis C
(NH4)2S04
KN03
KN03
S:Urea-N
(NH4)2S04
60.6
60.6
60.6
60.6
60.6
63
62
60
58
56
25.9
41.6
19.8
20.9
20.5
1.5
2.2
4.5
1.4
1.5
Both the total nitrogen removed in the leachate and the percent of
this total that was fertilizer nitrogen are listed in Table 23.  The
total N in the leachates ranged from 163 to 1010 milligrams, however,
of these amounts less than 1.5 percent was from the applied fertilizer
N.

                             TABLE 23

            Nitrogen Content and Percent Fertilizer
                     Nitrogen in the Leachate
                December 16 1968 - August 18 * 1969
Soil Type

Panoche CL
Panoche FSL
Lethent CL
Panoche FSL
Oxalis C
Fertilizer

(NH4)2S04
KNO,
KNOj
S:Urea-N
(NH4)2S04
Water Applied
In
60.6
60.6
60.6
60.6
60.6
Total N
mg
244
503
163
302
1010
Fertilizer N
%
0.5
1.3
0.7
0.8
0.2
The total nitrogen removed in the soil extracts and leachates and
the percentage of these values that were fertilizer nitrogen are shown
in Table 24.  Although the total N ranged from 231 milligrams in the
                              (64)

-------
 Lethent  clay  loam  to  1083 milligrams in the Panoche fine  sandy loam,
 only  a small  percentage of these totals were from fertilizer N.  The
 percentages of  fertilizer nitrogen  in  the  total removed varied from
 0.7 percent in  the Oxalis clay to 12.2 percent in the Lethent clay
 loam.  The higher  percentages of fertilizer nitrogen recovered from
 those columns using XN03 are due primarily to the large quantities
 extracted from  the "A" and "B" depths  in these soils.
      Total Nitrogen Content of Soil Extracts, and Leachates
          and Percent Fertilizer Nitrogen for the Period
_ December 13, 1968 to August 18. 1969 _

                              (Soil - Fertilizer)        Fertilizer
Soil Type        Fertilizer   _ N _            N _
                                       mg               % of Total N
Panoche CL
Panoche FSL
Lethent Cl
Panoche FSL
Oxalis C
(NH4)2S04
KN03
KN03
S:Urea-N
(NH4>2S04
307
619
231
353
1083
1.2
7.9
12.2
2.0
0.7
The fertilizer nitrogen recovered as a percentage of the total fer-
tilizer applied is shown in Table 25.  The largest percentage, 3.91,
of the fertilizer N recovered was from the Panoche fine sandy loam
soil treated with KN03 fertilizer.  The smallest percentage, 0.30
or 3.8 milligrams, was from the Panoche clay loam which was treated
with (NH4>2S04.  The most significant of these data are the amount
of N recovered in the leachates.  This is the quantity which under
field conditions would enter the groundwater.  The data show that
the largest percentage of fertilizer nitrogen was recovered from
the leachate of the light textured soil treated with KN03.  It was
a very small amount, representing 0.54 percent, 6.7 milligrams, of
the total fertilizer applied.  The least amount, 0.09 percent, 1.1
milligrams, was recovered from the Panoche clay loam soil that was
treated with
The total amounts of nitrate N in leachates from various soil columns
treated with fertilizers and similar columns in which no fertilizers
were applied are shown in Table 26.

The total NC>3-N removed varied in the fertilized columns from 1002
milligrams in the Oxalis clay to 28 milligrams in the Lethent clay
loam and in the control columns from 788 milligrams in the Oxalis
clay to 44 milligrams in the Lethent clay loam.  As noted in Table
25, the maximum amount of fertilizer nitrogen recovered in the
leachate was 0.54 percent or 6.7 milligrams from the Panoche fine
sansy loam soil treated with KN03.  Lesser amounts of fertilizer


                              (65)

-------
                              TABLE  25
          Recovery  of  Fertilizer Nitrogen  from All Probes
             and  Leachate for  the Period  -  December 16,
          	1968  -  August  18,  1969	
            Soil
 Fertilizer  Type
          Sample Depth
 A
B
Leachate
Total
                         mg   %    mg  %   mg  %    mg%
                                       mg
(NH4)2S04
KN03
KN03
S.'Urea-
(NH4)2S04
Pan.CL
Pan.FSL
Le. CL
Pan.FSL
Ox. C
0.14
3.22
1.81
0.30
0.36
                          1.8 0.04 0.5 0.03 0.4 0.09 1.1 0.30  3.8
                          K),3 0.09 1.1 0.07 0.9 0.54 6.7 3.91 48.9
                          22.6 0.27 3.4 0.07 0.9 0.10 1.2 2.24 28.1
                          3.8 0.05 0.6 0.02 0.3 0.18 1.3 0.56  7.0
                          4.5 0.04 0.5 0.02 0.3 0.16 2.0 0.58  7.3
                             TABLE 26

           Nitrate -N Recovered in the Leachate of Soil
           Columns for the Period - December 16, 1968 -
           	August 18. 1969*	
Soil Type

Panoche CL
Panoche FSL
Lethent CL
Panoche FSL
Oxalis C
Fertilizer

(NH4)2S04
KN03
KN03
S:Urea-N
(NH4)2S04
           Nitrate N in Leachate
           Control    Fertilized
mg
133
259
44
259
788
mg
143
431
28
233
1002
* Determined by measurements with the Orion Nitrate probe.
nitrogen were recovered from the other columns.  Although large
differences existed between the control and the fertilized columns
for two of the soils and treatments (Table 26) these differences
probably were due to analytical and soil variability rather than
contributions from the applied fertilizers.

The significance of these data showing relatively large amounts of
nitrogen removed from the columns is that only a very small percentage
came from the applied fertilizers.  Since the N in the leachate did
not originate from the fertilizer applied during the study and the
amount in the applied water was small, it had to come from the
nitrogen in the soil at the start of the study.

The percentages of applied fertilizer nitrogen recovered by cropping
are listed in Table 27.  The highest percentage recovery by the barley
was 73 percent from the Panoche fine sandy loam treated with KN03.
                                (66)

-------
The  lowest  recovery,  47  percent, was  from the urea treated Panoche
fine sandy  loam.   This was  probably due  to the  slow release rate of
the  sulfur  coated urea.   The  recovery rates  in  the other treatments
ranged from 63  to 65  percent.

                            TABLE 27

          Recovery of Applied Fertilizer Nitrogen in
                  the  Barley and Grain Sorghum
Fertilizer
(NH4)2S04
KN03
KN03
Urea-S
(NH4)2S04
Soil Type
Panoche CL
Panoche FSL
Lethent Cl
Panoche FSL
Oxalis C
Barley (%AFN)*
Straw
17.9
18.8
17.4
8.9
24.5
Grain
47.7
54.3
47.9
38.4
38.2
Total
65.6
73.1
65.3
47.3
62.7
Grain
Straw
1.00
0.78
0.76
3.75
1.60
Sorghum (5&FN)
Seed
1.87
2.89
1.51
9.78
1.45
Total
2.87
3.67
2.28
13.53
3.05
*Applied  fertilizer nitrogen
The percentage of recovery by grain  sorghum of the applied fertilizer
nitrogen was greatest,  13.5 percent, in the Panoche fine sandy loam
treated with the sulfur coated urea.  The large recovery rate in this
treatment was due to the great amount of residual N remaining in the
soil as a result of the slow release of N from sulfur coated urea.
The recovery rates in the other treatments ranged from 2.3 to 3.7
percent.

The percentages of the  applied fertilizer nitrogen recovered by
barley, grain sorghum and in the water samples collected between
December 16, 1968 and August 18, 1969 are listed in Table 28.  They
ranged from a maximum 80.6 percent in Panoche fine sandy loam treated
with KNOs to a minimum  of 61.4 percent in Panoche fine sandy loam
treated with sulfur coated urea.  The recovery from the other systems
ranged from 66.3 to 69.8 percent.  The high percentage recovery from
Panoche fine sandy loam soil treated with KN03 was probably because
the N03-N form of fertilizer.is more mobile in the soil and thus a
greater root surface would be available,,to absorb the nitrogen.

These data do not account for a minimum of 19.4 and a maximum of
38.6 percent of the applied fertilizer nitrogen.   No analyses have
been made to determine  the quantities that might be accounted for
by the following:  (1)  volatilization and denitrification, (2) tied
up in the plant roots,  (3) adsorbed on the clay complex,  (4) converted
to an organic N form by soil bacteria, (5) remained in solution in
the soil columns.                                    ,

A portion of the residual N could be leached from the columns at a
later date.  To check this, water is still being applied to the columns
and the leachate collected, however, as this is written no additional
data are available.
                              (67)

-------
                           TABLE 28

      Recovery of Applied Fertilizer Nitrogen in Barley,
               Grain Sorghum, and Water Samples
Fertilizer

(NH4)2S04
KN03
KN03
S:Urea-N
(NH4)2S04
Soil
Type

Panoche CL
Panoche FSL
Lethent CL
Panoche FSL
Oxalis C
Barley
*
65.6
73.0
65.3
47.3
62.1
Grain
Sorghum
%
2.87
3.67
2.28
13.53
3.05
Water
Samples
%
0.30
3.91
2.24
0.56
0.58
Total
X
68.77
80.58
69.82
51.39
66.33
After the barley and grain sorghum crops were harvested, soil samples
were taken from one of each of the paired lysimeters.  These samples
were analyzed for nitrate, organic N and amount of I^N.  he results
of these tests for two of the lysimeters, one filled with Panoche
FSL to which NO^ fertilizer had been applied and one with Panoche
Cl to which NH4 fertilizer had been added, are in Table 29.  The
amounts of N03-N remaining in the soils were small and relatively
consistent throughout the depths of the column.  The two columns
had essentially the same concentration and distribution of N03-N
indicating no difference as a result of the applications of different
types of fertilizers and soil textures.  Only about 0.8 percent of
the applied fertilizer remained in the soil in the nitrate form.

The majority of the applied nitrogen still in the soil was in the
organic form and the largest amount of the ISj^ representing the
applied nitrogen, remained in the top 15 centimeters of soil.  This
was because the returned crop residue was concentrated in this depth.
The nitrogen fertilizer that remained in the organic fraction was
25.9 percent of that applied to the Panoche CL and 19.9 percent in
the Panoche FSL.
The amounts of     collected from the various sampling categories
are listed in Table 30.  These data show that an average of approxi-
mately 56 percent of the applied nitrogen was adsorbed up by the
plants.  The greatest removal of fertilizer N by the crops was from
those lysimeters to which the nitrates were applied.  There was no
significant difference between the recovery of nitrogen in those
lysimeters applied with NH4 and urea.  The residual nitrogen in the
soil accounted for 13.1 to 30.5 percent or an average of about 24
percent of the applied nitrogen.  The largest percentage of this
fraction was found in those columns to which the ammonium type
fertilizer had been applied.  The quantity of the applied nitrogen
that was unaccounted for ranged from 12.4 to 24.5 percent.  This
amount, aside from any possible analytical error, was lost through
volatilization and denitrification.
                              (68)

-------
TABLE 29
Recovery
Depth
era
0-15
15-30
30-45
45-60
60-75
75-90
90-105
105-120
120-135
135-150
150-165
165-180
% Recovei
of Applied Fertilizer Nitrogen in the Nitrate and
Nitrogen Fraction from Two Lysimeters
Panoche CL (3) (NfUSO/i) Panoche FSL
NO-^-N
ppm
43
38
42
45
41
49
45
50
43
43
65
42
546
'V 0.8
Organic N
ppm
358
310
288
353
281
284
176
178
127
134
124
148

J-bN mg
22.2
4.2
1.7
0.8
0.6
0.5
0.4
0.1
0.5
0.4
1.0
0.5
1579"
25.9
NOx-N
ppm
41
48
47
35
49
42
43
44
37
50
45
56
537
.8
Organic
(6) (KN03)
Organic N
ppm I5N~rng
246
220
211
243
234
234
213
175
209
261
233
238

12.6
1.0
1.3
3.4
1.5
1.0
0.3
0.4
1.1
0.9
0.3
1.1
25.3
19.9
   (69)

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                                                TABLE 30
Summary of Applied ^JH Collected in the Various Categories
Lys #
18 ug 1%
NH4 %
11 ug 15N
Urea %
9 ug 15N
N03 %
6 ug 15N
N03 7.
3 ug 15N
vn 7
Wtl4 /a
Added
Fertilizer
+115,773
100%
+354,762
100%
+116,357
100%
+ 116,357
100%
+ 115,773
100%
Water (2)
Samples
-536
0.5
-1,911
0.5
-2,170
1.9
-4,471
3.8
-340
0.3
Barley
Thinnings
-3,956
3.4
-6,987
2.0
* *
"" ~
-1,261
1.1
-1,888
1.6
Harvested
Barley Crop
Net Removal
-49,145
42.4
-168,327
47.4
-67,665
58.2
-67,244
57.8
-60,085
51.9
Milo
Crop
Removal
-2,849
2.5
-32,262
9.1
-2,696
2.3
-3,614
3.1
-3,793
3.3
Residual
Soil
Nitrogen
-25,030
30.3
-95,920
27.0
-15,340
13.2
-22,760
19.6
-35,260
30.5
15N
% Unaccounted
Recovery for
24,257
79 21.0
49,355
86.1 13.9
28,486
75.5 24.5
17,007
85.4 14.6
14,407
87.6 12.4
1.  - ug - Micrograms




2.  - Includes leachate and suction probe samples

-------
 The conditions in the lysimeters will be  different  than  field  con-
 ditions.   In the lysimeters,  the root distribution  is  rather uniform
 throughout the soil area while in the field,  especially  in row crops,
 there would be areas between  the rows where the root density is
 relatively low.   Under these  conditions,  unless special  care is
 taken in  fertilizer placement, ie,  in bands near the plant, and to
 avoid excess irrigation there could be greater losses  of fertilizer
 nitrogen  than indicated in the lysimeter  studies.

 Other lysimeter  studies were  conducted on the movement of nitrogen-
 ous salts in unsaturated flows under non-cropped conditions.   Cal-
 cium nitrate and calcium chloride were applied to the  columns  and
 four inches of water added every two weeks.   Under  the aerobic
 conditions that  existed in the upper portion  of the column the NOs's
 and Cl's  moved with the percolating water.  However, under the ana-
 erobic conditions in the lower saturated  portion of the  column the
 nitrates  were changed to a different form of  N.  Although part of
 this nitrogen was probably changed  to an  organic form  in the cell
 material  of microorganisms, most investigators attributed low  re-
 coveries  primarily to denitrification (16).   Chlorides,  which  are
 not subject to change to gaseous form under these conditions,  were
 moved through the column with the percolating water and  collected
 in  the leachate.   The movements of  the nitrates and chlorides  in
 one of the lysimeters are plotted in Figures  17 and 18.

 It  can also be noted from these data that approximately  36 inches
 of  applied water  was required to move  the  chlorides through the six
 foot soil column.   The porosity of  these  soils is approximately
 50  percent,  therefore,  the equivalent  of  about one  pore  volume of
 water moved the nitrate and chloride  front through  the columns.

 A nitrogen balance  sheet was  prepared  on  one  lysimeter to gain  some
 insight on nitrogen gains and losses  that occurred.   The budget
 was  prepared on lysimeter number 6 which was  filled with Panoche
 fine  sandy loam soil and treated with KN03.  The measurements were
made  over  approximately  a  years  time, from December 13, 1968 to
 December 20,  1969,  during which one fertilizer application was made
 and  two crops, one  of  barley  and one of milo,  were grown and harvested.

The  sources  of nitrate-nitrogen available were the applied fertilizer,
 irrigation water, the  residual  nitrate in the soil at the start of
 the  study  and the nitrogen available as the result of mineralization
of the organic nitrogen.  One application of 1.27 grams of KN03
fertilizer which was  equivalent to 100 pounds of nitrogen per acre,
was added to the  soil.   The applied irrigation water,  which con-
tained about 0.5 parts per million of nitrate -N,  added 0.09 grams
of nitrogen or the  equivalent of about 7 pounds per  acre.  The
residual nitrate in the  soil column at the start of  the study was
calculated to be 1.06 grams or equivalent of 83 pounds per acre.
These three sources totaled 2.42 grams or equivalent to 190  pounds
of nitrate -N per acre.
                              (71)

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JAN.
 FEB.                MAR.               APR.
FIG. 17- MOVEMENT OF NITRATES IN SOIL COLUMN
MAY

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                                                            A	A LEACHATE
                                                            	V DEPTH - 1.70'
                                                            		8   "   - 2.73'
                                                            	C   "   -3.74'
                                                            	0	0	 D   "   -4.70'
                                                                LEACHATE
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       11.11   1  I   I   I  ..  I   t   I  I   I   II  I  I   I   I  I   i   I  I   1   I
            JAN.             FEB.            MAR.            APR.            M/V
                    FIG. 18 - MOVEMENT  OF CHLORIDES  IN  SOIL COLUMN
0

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The losses were due to the removal of nitrogen by the crops,
removal in the leachate, removal through sampling of the suction
probes, and the unaccounted for losses to be primarily the
result of denitrification and volatilization reactions.  The amount
removed by the barley and milo crops was 2.90 grams or the equivalent
of 226 pounds per acre.  A calculated 0.55 grams, the equivalent
of 43 pounds per acre, was removed in the leachate and 0.12 grams,
or 9 pounds per acre, was removed by the suction probes for sampling
purposes.  There was an unaccounted for loss of 14.6 percent of the
applied fertilizer which was 0.15 grams or 12 pounds per acre.   The
causes of these losses were not documented but it is postulated
that the major cause was denitrification and a minor cause was
volatilization of nitrogen compounds.  There were undoubtedly some
similar losses from the other sources of nitrates but this was  not
proven, therefore, no values were assigned to them.  The total
losses of nitrogen from all factors amounted to 3.7 grams or an
equivalent of 290 pounds per acre.

In addition to the losses, in order to balance the system, the
nitrates that remained in the soil column at the end of the study
must be accounted for.  These were measured to be 0.55 grams or 43
pounds per acre.  The losses plus these residual nitrates totaled
4.27 grams or 333 pounds per acre.  This amount compared to the
measured contributions of 2.42 grains or 190 pounds per acre gives
a difference of 1.85 grams or 143 pounds per acre.  It was assumed
that mineralization of the organic nitrogen compounds in the soil
was the major source of nitrates that made up this difference of
143 pounds per acre.  This amount is somewhat larger that much  of
the data cited in the literature.  It indicates the large reserve
of potential nitrates that are in most soils in the insoluble
organic forms.

The assumption was made for this study that nitrate -N is the only
soluble nitrogen form in the soil and water.  The measurements
indicated that although there were small amounts of ammonia and
nitrite the quantities would be insignificant in the overall balance.

A summary of the nitrogen balance is in Table 31.

                  Sources of Nitrogen to the Drain

The nitrogen that occurs in the drain effluent originates from  three
major sources:  (1) those sources that are native to the area or
occur naturally, (2) those that occur as a result of agricultural
activities and (3) those that occur from municipal and industrial
waste products.

The major source of native nitrogen to the drain will be that which
occurs naturally in the soils and substrata or the soil profile.
There may be small quantities of ammonia and nitrate present in
the drainage water but for all practical purposes the nitrogen  that


                                 (74)

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                              Table 31
                  Nitrogen Balance Sheet - Lysimeter #6
       Item

 Contribution

 Residaul N03-N (start)
 Applied Fertilizer Nitrogen
 Applied in Water
 Mineralization

       Total

 Removal

 Crop (barley and milo)
 Leachate
 Suction Probe
 Unaccounted for Losses

       Total

 Residual NOs-N    (end)

 Total Removal & Residual
gms
4.27
        Nitrogen
Ibs/AC

  83
 100
   7
 143

 333
                  226
                   43
                    9
                   12

                  290

                   43

                  333
 moves to the drain will  be  in  the nitrate form.  Nitrates are soluble
 and readily moved  with the  percolating waters.  If they are not
 intercepted by  the plant roots or reduced to a volatile gas,usually
 molecular nitrogen and/or nitrous oxide, they will eventually appear
 in the groundwater or drainage effluent.  The ammonia in the soil
 is normally adsorbed by  the soil base exchange mechanism and will
 not move with the  water.

 The largest quantity of  nitrogen in"the soils is in organic forms.
 Although these  forms are generally inert, mineralization takes place
 through  a three step process which converts organic N to nitrate by
 bacterial activity.  The bacteria are obligate aerobes which require
 molecular oxygen to produce nitrates therefore maximum nitrification
 will take place in the plow zone of the soil.   Nitrification will
 decrease  with soil depth and in areas of high water table usually
 no  nitrates will be formed.   Studies indicate (19)  that 40 to 80
 pounds of  nitrogen as nitrates may be produced each year in the  top
 five feet  of soil by this process.

 Data from the transect study indicated that the average quantity of
nitrate in the 0-5 foot depth of  soil was 258  pounds  per acre.   The
                              (75)

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rate that this nitrate will be moved to the drain is subject to
much speculation.  Under the most favorable conditions, that is
complete piston flow displacement, within about five years nitrates
in the top five feet of soil immediately above the drains would be
leached.  This estimate was based on a pore volume of six inches
per foot or 2.5 feet for the five foot solid profile and the
estimated drainage effluent of six inches per acre per year.  However,
from field experience and laboratory investigations, it is known
that complete displacement does not occur.  There is diffusion by
the salts into the smaller pores where they are isolated from the
percolating water moving through the larger pores.  Also under
cropped conditions evapotranspiration removes the moisture from
the upper soils thereby creating a moisture gradient upward and
reversing the direction of the water and salt movement.

Other factors that will influence the length of time it will take
the nitrates to reach, the drain are the drain spacing, the depth
of the drain, depth of soil barrier, and the hydraulic conductivity
of the soils.

Estimates of the nitrogen contributions of each of the various
sources were developed in the section on the nitrogen budget analysis.
The values are listed in Tables 1 through 7.  The analyses show that
on an overall basis the nitrogen added to the soil by fertilizers,
irrigation water, rainfall, stream flow, leguminous plants, animal
and municipal wastes were essentially in balance with the nitrogen
removed by the harvested crops and volatilization of nitrogen gases.
Regardless of the source of the nitrogen taken up by the plant,
whether from sources outside the soil or from the residual nitrogen
in the soil, the same amount of nitrogen would be available to be
leached to the drains.

It is obvious that where the nitrogen contributions are not evenly
distributed throughout the area, such as cattle, municipal and
industrial wastes, only a small part of the nitrogen from these
sources will be used by the crops.  As a result a larger percentage
of this nitrogen could be leached to the drains.

The beef cattle operations now are concentrated in three feed lots
in an area of about 500 acres.  Much of the waste from these lots
will be removed as manure and spread throughout the district and a
lesser amount will be lost by volatilization.  The remainder could
be a source of the nitrogen in the drainage water.  The amount of
nitrogen from this source that reaches the groundwater will vary
with the conditions present, such as rainfall, soil conditions, and
surface drainage.  Although no specific studies were conducted in
this area, other studies give some indications of the relative amounts
of nitrate moving through soil profiles toward the groundwater.  The
contributions of nitrogen from concentrated livestock feeding operations
were studied in the South Platte River Valley in Colorado (20).  The
average total nitrate-nitrogen to a depth of 20 feet in the soil
                               (76)

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profile averaged 1,436 pounds per acre as determined from 47 core
samples.  There was a great variability in these samples, ranging
from aljnost none to more than 5,000 pounds per acre..  Also the water
samples collected from under the feed lots had a greater concen-
tration of ammonium -N than those sampled from irrigated croplands.
The feedlot samples averaged about 4.5 ppm and the irrigated field
samples averaged only about 0.2 ppm.

The rainfall in the area cited above is about double that of the
San Luis area.  Undoubtedly there would be less movement of nitrogen
here but some areas near feed lots probably will have unusually
high nitrogen concentrations in the drains.

In a like manner, the areas adjacent to the municipal sewage disposal
systems would have large quantities of nitrate leached into a small
area.  The drains serving these areas would have unusually high
nitrate concentrations in the effluent unless some remedial actions
are taken to either transport them to other areas or install treat-
ment processes to remove the nitrogen before it reaches the ground-
water .

Quantity of Nitrates in the Drainage Effluent

The existing drains on the lands adjacent to the study area were
monitored at various times by the State of California Department
of Water Resources and the University of California at Los Angeles
to determine the quantity and seasonal distribution of the nitrate
concentration in the drainage effluent.  In the San Luis area where
no drains have been installed, the nitrate concentrations were
calculated from the Prediction Model developed by the University
of Arizona and the Bureau of Reclamation Engineering and Research
Center.

The data from the drains monitored in the San Joaquin Valley in-
dicated a range of N03-N in the effluents from 2 to 400 milligrams
per liter (21).  The annual flow weighted average of these drains
measured during 1966-1969 period was 19.3 mg/1.  During the period
for which data are available, there was no evidence that there has
been any significant reduction in the average annual nitrate concen-
trations in the drainage effluent.

            Anticipated Changes in Nitrogen Sources

Fertilizer Usage

The usage of fertilizer is expected to increase in the future how-
ever the rate of the increase is subject to.speculation.  Interviews
with Agricultural Extension Specialists indicate that they anticipate
little increase in the, per acre applications on the various crops
in the foreseeable future.  This prediction is based upon two major
premises:  (1) The rates now used appear to be an optimum balance
between costs and economic return and (2) The present emphasis on


                             (77)

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ecology and conservation will exert public pressure on the farming
community to prevent increased use of commercial fertilizers.

There will be changes in the cropping pattern toward more intensive
farming, the production of crops that require higher fertilizer
application, more double cropping and the development of the areas
which are now non-irrigated.  These changes will increase the amount
of fertilizer that will be applied under ultimate development from
the 1968 average application of about 60 pounds per acre to an
estimated 87 pounds per acre.  For the total area this would amount
to an increase from about 20,120 tons to 29,200 tons annually.

Future Crop Pattern

Before supplemental surface water was available, the farmers were
forced to adjust their crop patterns to accommodate a deficient
water supply.  Generally, this was accomplished by planting low
water requirement crops, winter crops and allowing some land to lay
idle or undeveloped.  As water from the San Luis Project becomes
available, the operator will be able to grow the crops which are
most economically feasible or that best fit  his farming program.

The major change in the crop pattern is expected to be the reduc-
tion in the acreage of barley and increases in alfalfa seed, vege-
tables and deciduous fruits and nuts.  There is also expected to
be an increase in the number of acres double cropped.  It is projected
that the lands which have not been developed for irrigation or have
been left idle will be prepared for cultivation and for the most
part will be irrigated each year.

Cattle production is expected to increase about in proportion to
the increase in the human population.  This production will be,
as it is now, primarily a feed lot operation.  This type of operation
will continue to concentrate the nitrogen waste in relatively small
areas and create local hot spots which could introduce high nitrate
concentration to the drains servicing these areas.

Sheep production in the area is based primarily in grazing off the
crop residues.  Barley stubble has been the major pasture source;
however, with the more intensive farming practices anticipated in
the future, the acreage of this crop will be cut drastically.  As
a result, it is expected that the number of sheep will drop cor-
respondingly.  The resultant total nitrogen waste from both sheep
and cattle will probably not increase appreciably over present levels.

Leaching Native Nitrogen

As explained in an earlier section, theoretically, the soluble
nitrogen could be leached from the top five feet of soils in a
minimum of five years, however, in actual practice it would undoubt-
edly be much longer.  Also it could take many years to move that
nitrogen that has been leached down into the subsoil near the mid-
point of the drain spacings to the drains.  The time required will


                              (78)

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depend  primarily upon the drain  spacing, the volume of leachate,
the  hydraulic  conductivity of the  soils, and the depth of the sweep
of the  flow  lines.  This leaching  time might be reduced by decreasing
the  length and depth of the flow lines by decreasing the drain
spacing and  depth.

The  study that monitored nutrients from tile drainage systems (21)
found that nitrates are not removed at as fast a rate as chlorides.
This would indicate that there is  a continuous replacement of nitrates
in the  system.  The source of this replacement could be the applied
nitrogen, primarily fertilizer,  or from the organic nitrogen in the
soil.   The analyses of the transect samples show that there is a
very large reservoir of residual organic nitrogen, a portion of which
under favorable environmental conditions can be mineralized to nitrates,
The  rate that  this organic nitrogen will be mineralized will depend
upon the amount of the material  present in the soil, the C:N ratio
and  environmental factors such as  amount of aeration, moisture and
temperature.   The water quality  systems model being developed in
connection with these studies are  expected to give some insight on
the  rate and the change in quantity over time of the nitrate miner-
alization under the various conditions present in the area.

Increase in  Municipal and Industrial Water

Some demographers predict (23) that this area will become absorbed
in a megalopolis (a sprawling population belt in which once clearly
defined urban  areas tend to blend  into each other) that will cover
most of Central and Southern California.  This may occur at some
very distant time, but for the foreseeable future no extreme change
from the present rural pattern of  relatively large farm operations
and  small towns is anticipated.

The  importation of an adequate irrigation water supply which will
permit  more  intensive farming and  the construction of the north-
south interstate highway through the area will give some impetus
to a population growth; however, this will be offset by the increased
mechanization of farm work and the resultant reduced demand for
farm laborers.

If it is assumed that the population growth of the area continues
at the  same  rate as the past ten years, although nationally the rate
is expected  to decrease, the population is estimated to reach about
25,000  inhabitants by 2010.

The  improved transportation facilities available as the result of
construction of the interstate highway will attract a number of new
and  different industries into the area but it is anticipated that
the  industry of the area will continue to be agriculturally oriented.
It is estimated that they will increase somewhat more rapidly than
the  total population because of the increased requirements for
mechanized equipment and services as a result of the greater farm
mechanization.


                             (79)

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The increased population and industrial growth will about double
the waste-nitrogen disposal requirement for the area to approximately
174 tons.  This amount will be spread over about twice the area;
therefore, the per acre application rate will remain about the same
as the present 53 pounds per acre.  The drainage effluent near the
feedlots and population centers may be high in nitrates unless some
corrective action is taken to remove them.

Control of Nitrogen at the Source

The principal means of controlling the quantity of nitrogen that
reaches the drains is by reducing the amounts of applied nitrogen,
primarily fertilizers, and native nitrogen that are leached through
the soils.  These sources can best be controlled by educational
programs to advise and encourage the most efficient farming prac-
tices and by the installation of specially designed farm drain systems.

Farm Advisory Program

The lysimeter studies show that under normal soil conditions and
good irrigation management practices, very little applied fertilizer
nitrogen reached the drain.  However, in actual farm practices where
the soils, crop, root pattern and cultural practices vary greatly,
a greater percentage of this applied nitrogen could possibly move
to the drain.

An advisory program conducted by the Agricultural Extension Service
and other agencies should be encouraged to advise growers on cul-
tural practices that would reduce the amount of nitrogen that moves
through the soil profile to the drains.  The areas in which these
agencies might give assistance to the farmers could include:

    Soil Management;  Although most of the soils in this area are
medium to fine textured there are sizeable areas of light textured
soils on the south end of the district.  It is especially important
that these light soils are managed properly to prevent excess leach-
ing.  Practices which could be encouraged to reduce losses might
include matching of crops to soil conditions.  Studies (20) have
shown that fields of deep rooted crops such as alfalfa have practi-
cally no nitrates below them.  An alfalfa crop in rotation with
shallow rooted crops possibly would prevent much of the nitrate
leached below the root zone of shallow rooted crops from reaching
the water table.

    Fertilizer Management:  Some types of fertilizers, especially
the nitrate forms, are fast release types which may be leached
fairly rapidly through the soil.  Other types such as ammonia forms
which are absorbed by the negatively charged ions in the clay part-
icles and specially treated urea forms which dissolve slowly in
the soil are less rapidly leached.  The effect of the rate of
release on the amount of nitrogen leached would be especially sign-
ificant in the light textured soils.  Other factors which would

                                 (80)

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 influence  the  rate  of  movement  of the nitrate through the soils
 are  the  amount,  time and  placement of the  fertilizer.  Under con-
 ditions- of rapid nitrogen movement it would be better to make a
 larger number  of smaller  fertilizer applications than one large
 application.   Also  there  would  be less losses if the fertilizers
 were placed in bands near the areas of greatest root density rather
 than being broadcast uniformly  over the field.

      Water Management;  Nitrate  -nitrogen  generally will move with
 the  percolating  water.  Irrigation applications should be adjusted
 to avoid excess  deep percolation and the resultant loss of nitrogen.
 Only enough water should  be applied to meet the evapo-transpiration
 requirements of  the crops and have adequate deep percolation to
 prevent  a  buildup of salts in the root zone.

      Crop  Management;  Various crops have  different nitrogen require-
 ments and,  as  mentioned above, different root depths which influence
 nitrogen utilization.  The amount of nitrogen leached to the drains
 might be reduced by growing the high nitrogen requirement plants
 on the fine textured soils.

 Specially  Designed Farm Drain Systems

 Once  the residual or applied nitrogen has moved below the root zone
 of the plant,  the only means to reduce the amount that will reach
 the  drain  is by  denitrification or by reducing the area that con-
 tributes to the  drain.

 Laboratory  studies (17) have shown that denitrification,  the reduc-
 tion  of  nitrates  to nitrogen gas which is dissipated to the atmos-
 phere, can take  place in  soils, therefore, under proper conditions
 it should occur  in the field.  The process normally takes place in
 the  saturated  soil near or at the water table as a result of the
 action of anaerobic bacteria.  Willardson, et al (23) are conducting
 studies  to determine if, when the drain lines are submerged contin-
 uously and an organic energy source present,  there is a reduction
 in the nitrate concentration of the effluent.   If these results
 prove positive, recommendations should be made that farm  drains be
 designed to maintain submerged conditions to encourage denitrification.

 The quantity of nitrates in the soils and substrata which can be
 leached to the drains is directly proportional to the depth of  the
 area  swept by the drainage flow lines.   Any action which  will reduce
 the depth of the flow line will reduce  the ultimate quantities  of
nitrate  in the drain.   The most feasible methods to do this is  to
decrease the drain tile depths and spacings.
                             (81)

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                           SECTION VI

                           REFERENCES

 1.  Tisdale, Samuel L. and Nelson, W. L., Soil Fertility and Fer-
     tilizers, 2nd Edition, Macmillan Co., New York, N. Y.,  1966.

 2.  Stout, Perry R. and Burau, R. G., "The Extent and Significance
     of Fertilizer Build Up In Soils as Revealed by Vertical Dis-
     tribution of Nitrogenous Matter Between Soils and Underlying
     Water Reservoirs.

 3.  Doneen, L. D., A Study of Nitrate and Mineral Constituents
     from Tile Drainage in the San Joaquin Valley, California, A
     Report to the Central Pacific River Basin Project, FWPCA,
     November 1966.

 4.  Terman, G. L., Volatilization Loss of Nitrogen as Ammonia from
     Surface Applied Fertilizers, Agrichemical West, December 1965.

 5.  Martin, J. P. and Chapman, H. D., Volatilization of Ammonia
     from Surface-Fertilized Soils, Soil Science Soc. Vol. 71, 1951.

 6.  Harding, R. B., Embleton, T. W., Jones, W. W., Leaching and
     Gaseous Losses from Some Nontilled California Soils, California
     Citrograph, July 1963.

 7.  Junge, Christian E., The Distribution of Ammonia and Nitrate
     in Rain Water Over the United States; Transactions, American
     Geophysical Union, Vol. 19, No.  2, April 1958.

 8.  Gambell, Arlo W. and Fisher, D.  W., Occurrence of Sulfate and
     Nitrate in Rainfall, Journal of  Geophysical Research, October
     15, 1964.

 9.  USDI, Geologic Survey, Description and Chemical Analyses for
     Selected Wells in the Dos Palos-Xettleman City Area, San Joaquin
     Valley, California, Menlo Park,  California, 1969.

10.  USDI, Bureau of Reclamation, Geology Branch, Nitrate Analyses
     from Wells and USER.  Geohydrologic Observation Holes in the
     San Luis Unit and Mendota-Firebaugh Areas.  Sacramento,  California,
     December 1969.

11.  Bartholomew, W. V. and Clark, F. E., Soil Nitrogen No.  10,
     Agronomy Series, Amer. Soc. Agron. 1965.

12.  Erdman, L. W., Legume Innoculation, What It Is - What It Does,
     USDA Farmers Bull. 2003, 1959.
                                (82)

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 13.  Loehr, Raymond C., Animal Wastes - A National Problem, Journal
      of the Sanitary Engineer Div., April 1969.

 14.  Morrison, Frank B., Feeds and Feeding, 21st Edition, the Mor-
      rison Publishing Co., Ithica, N. Y. 1948.

 15.  Reclamation Instructions, Release No. 577-1, U. S. Department
      of the Interior, Bureau of Reclamation, Office of the Chief
      Engineer, Denver, Colorado, 1967.

 16.  Allison, F. E., The Fate of Nitrogen Applied to Soil, Advances
      in Agronomy, Vol. 18, 1966, American Soc. of Agronomy.

 17.  Meek, B. D., Grass, L. B., and MacKenzie, A. J., Applied
      Nitrogen Losses in Relation to Oxygen Status of Soil, Soil
      Sci.  Soc. Proceedings, Vol. 33,  No. 4,  July-August 1969.

 18.  Stanford, G.,  England, C. B. and Taylor,  A.  W.,  Fertilizer Use
      and Water Quality, USDA, ARS 41-168,  October 1970.

 19.  Allison, F.  E., Porter,  J.  N., and Sterling, L.  D.,  The Effects
      of Partial Pressures of  02 on Denitrification in Soil - Soil
      Science Society of America Proceedings  -  24, 283,  1960.

 20.  Stewart,  B.  A., Viets, F. G.,  Jr.,  Hutchinson, G.  L., Kemper,
      W. D.,  Clark,  F.  F.,  Fairbourn,  M.  L. and Strauch, F.,  1967.
      Distribution of Nitrate  and Other Pollutants Under Fields  and
      Corrals in the Middle  South Platte  Valley of Colorado,  ARS
      41-134,  U.S. Dept.  of  Agric.,  Washington,  D.  C.

 21.  Nutrients From Tile  Drainage Systems, Calif.  Department of Water
      Resources, Agricultural  Wastewater  Studies Group,  San Joaquin
      Valley,  California,  December 1970.

 22.   The Evolution  of a Super-Urban Nation, Business Week, October
      17, 1970.

 23.   Willardson, L.  S., Meek,  B.  D., Grass, L.  B., Dickey, G. L.,
      and Bailey, J. W., Drain Installation for  Nitrate  Reduction,
      paper presented at ASAE  Winter meeting 1969.
* U. S. GOVERNMENT PRINTING OFFICE ;197351U-15V271*
                             (83)

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1
Accession fturnbcr
w
5

6
Organization
Title
PAQBI
2

Subject Field & Croup
05B, 05G
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
'Department of the Interior
Bureau of Reclamation
Fresno Field Division
Fresno, California 93721
M H tv of Red
ucins Nitroeen in Drainaee Water Bv On Farm -Practices
10

Authors)
Will! ford, John W.
Cardon, Doyle R.
16

21
Project Designation
13030 ELY
Wo
-------