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J? H PHYSICAL SCI. LIB.

Ly^ ^^ff j WATER POLLUTION CONTROL RESEARCH SERIES # 1 3030ELY 5-7

^V/A^flBI'^ REC-R2-72-

DWR NO. 174

^')1

BIO-ENGINEERING ASPECTS OF AGRI CULTU RAL DRAINAGE
SAN JOAQUIN VALLEY, CALIFORNIA

.V1AY14REC'U
NOV 1 3 1974
OEC 1 3 m4

_ 1975
gl^RECT)

rPOSSlBlLITY OF REDUCING NITROGEN

•OCT 4 ^^

DRAINAGE WATER BY ON FARM PRACT

Jan 5 1 37 7

IN
CES

JUNE 1972

NVIRONMENTAL PROTECTION AGENCY»RESEARCH AND MONITORIN

UNITED STATES BUREAU OF R ECL A M ATI O N

BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINftGE
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 sununary 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 fchre* planned xep^^s will, covei;>;. (p.) technique;^ to reduce
nitrogen dufing tranisport "ot Sto'rag^, (2) removal of nitVate by an
algal system, and (3) desalinatibn df subsurface agricultural waste-
waters.

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 Francisco, 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. Oovernment Printing Office, Washington, D.C. 20403
Price $1.26 domestic postpaid or $1 QPO Bookstore

REVIEW NOTICE

This report has been reviwed 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.

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,
anunonia 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 denitrif ication and reduce the area swept by the drain
flow lines.

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 larg6 areas
of agricultural land in the western and southern San Joaquin Valley
has been recognized for some time. In 19 54, 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 S^n 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 or tne 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.

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.

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 IQ-/

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

TABLE OF CONTENTS (Continued)

Section Page

Livestock 25

Municipal and Industrial 26

Nitrogen Losses 27

Removal by Crops 27*

Volatilization of Animonia Fertilizer 27

Denitrif ication 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

FIGURES

Number Page

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 NO3-N, NH3-N and Organic -N by

Sampling Depth 42

5 Distribution of NO3-N, NH^-N and Organic -N by

Sampling Depth 43

6 Distribution of NO3-N, NH,-N and Organic -N by

Sampling Depth 44

7 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 45

8 Distribution of NO,-N, NH3-N and Organic -N by

Sampling Depth 46

9 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 47

10 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 48

11 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 49

12 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 50

13 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 51

14 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 52

15 Distribution of NO3-N, NH3-N and Organic -N by

Sampling Depth 53

16 Distribution of NO3-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

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 NO3-N and Organic -N

Concentrations at the Various Sites by Soil Type

0-5 Feet 34

10 The Average NO3-N and Organic -N Content in Parts Per

Million in the 0-5 Foot Increment for the 5 Holes
Within the Various Sites 36

11 Summary of NO3-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 NO3-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 USBR Geohydro-

logic Observation Hole above the Corcoran Clay -

0-50 Foot Depth 56

TABLES (Continued)
Number Page

16 Sununary 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 50

20 Nitrogen Content and Percent of Fertilizer Nitrogen in

Soil Extracts from "A" Depths, December 16, 1968 -
August 8 , 1969 63

21 Nitrogen Content cind Percent of Fertilizer Nitrogen in

Soil Extracts from "E" 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

TABLES (Continued)
Number Page

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 -^% Collected in the Various

Categories 70

31 Nitrogen Balance Sheet - Lysimeter Number 6 75

xii

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 denitrif ication 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)

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
569,000 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)

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 NH3. 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 eacn.
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 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 NO^ 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)

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)

SECTION IV

METHODS AND PROCEDURES

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

Nitrogen Balance Stud y

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)

L EGEND

- Son Luis Service Area Boundary

- Alluvial Fon Boundaries

- Nitrogen Transect Sites

GEOMORPHIC AREAS
A.- Laguna Seca- Little Panoche Creek Interfan
B. - Little Panoche Creek Fan
C- Little Panoche -Panoche Creek Interfan
D- Panoche Creek Fan
E — Panoche -Contua Creek Interfan
F- Cantuo Creek Fan
G- Cantuo - Los Gatos Interfan
H- Los Gotos Creek Fan
I.- Los Gatos Creek — Interfan (South)

FIG. I - SAN LUIS SERVICE AREA
NITROGEN TRANSECT SITES

(8)

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 caJculating 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 ainount 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
I per year. The acreage of these crops was determined from the 1958
crop survey and the estimated ultimate acreage was taken from Bureau
of Reclamation studies.

(9)

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. Denitrif ication

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 1958 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)

Denitr if ication ; Elemental nitrogen gas and/or nitrous oxide
are released through denitrif ication, 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, aurid placed in the columns and 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 CL

PANOCHE FSL

LETHENT SCL

PANOCHE FSL

PANOCHE SI CL

OXALIS CLAY

PANOCHE FSL

LETHENT SCL

PANOCHE FSL

PANOCHE SI CL

OXALIS CLAY

PANOCH E FSL

LETHENT SCL

PANOCHE SI CL

OXALIS CLAT

A-

FIG. 2 -LAYOUT OF LYSI M E TERS - Nl TROGEN 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 -"^N.
(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 KNO? , 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 12 50 milligrams of N per lysimeter.
The (NH4)2S04 and the KNO3 fertilizers were eniched with approxi-
mately 10 percent ^^N and the urea with 28.2 percent ^^ti . The
(NH4)2S04 was applied to two lysimeters filled with Panoche clay
loam and two filled with Oxalis clay. The KNO3 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)

Tensionmeter
Hg Surface

} I I \ 1

.21

Suction Probes

Soil Moisture Cells

0.92

.87'

5.03'

Soil Surfoce

t/Mu^»mu%tMt

046

3.29'

4.18'

5.21

6.13'

FIG. 3- INSTRUMENT LAYOUT LYSIMETER NOT

' 14)

the University of Arizona for analysis of nitrate and atom percent
excess ^^H , the amount of -'-% in excess of that 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 NO3 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 sorghum
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 % 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 CI 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 , NO2 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 NH4CI 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 depth, 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

Physiographic Position Geomorphic Position

Oxalis SiC

Basin Rim

Los Gatos Creek Fan

Lethent SiC

Basin Rim

Los Gatos Creek Fan

Panoche C L

Recent Alluvial

Los Gatos Creek Fan

Panoche SiC

Recent Alluvial

Los Gatos Creek
Interfan

Oxalis C

Basin Rim

Los Gatos Creek
Interfan

Lethent C

Basin Rim

Los Gatos Creek
Interfan

Levis C

Basin Rim

Cantua-Panoche Creek
Interfan

Oxalis Si C

Basin Rim

Cantua-Panoche Creek
Interfan

Panoche Si C

Recent Alluvial

Cantua-Panoche Creek
Interfan

Lost Hills Si

C Older Alluvial

Cantua-Panoche Creek
Interfan

Panoche C L

Recent Alluvial

Panoche Creek Fan

Panoche Si C

Recent Alluvial

Panoche Creek Fan

Oxalis C

Basin Rim

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 H2SO4 and the total
organic nitrogen by the standard micro-Xjeldahl 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 inf iltrometer.
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 ty 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-1) 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 NH4 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, ammonif ication
and nitrification. These steps are represented schematically by the
following formula :

Aminization: Proteins — ► R-NH2 -t- CO2 + energy -+ other products
Ammonif ication: R-NH2 -<- HO H ^ NH4+-1- R -»- OH -^ energy
Nitrification: 2NH4 + 3O2 ^ 2NO2 ■*■ 2H2O + 4H +
2NO2 +02^ 2NO3

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, Denitrif ication: 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, N^ , 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) 5

The amount of nitrogen applied to the study area in 1958 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 569,160 gross acres of which 555,875
acres were cropped. This is equivalent to an average application
of 73 pounds per productive acre or 54 pounds per gross acre.

Irrigation Water

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

(21)

TABLE 1

Nitrogen Contributed by Fertilizer 1968
San Luis Service Area

Crop

Cotton

Cotton (50% ground cover)

Cotton (70% ground cover)

Grain

Sugar Beets

Sorghum

Saff lower

Field Corn

Misc. Field Crop

Dry Beans

Tomatoes

Melons

Lettuce

Carrots

Misc. Truck Crops

Alfalfa & Pasture

Alfalfa Seed

Rice

Deciduous Fruits & Nuts

Vineyards

Total Cropped Area
Non Cropped Area
Total

Acres lbs,

51,119

110

48,975

44,300

230,832

2,661

100

3,094

130

53,440

749

200

492

100

439

23,890

100

26,314

100

662

150

124

120

1,063

150

6,348

55,581

825

5,348

120

620

556,875

112,28 5

669,160

Nitrogen Applied
per Acre Total Tons

2,810

1,350

1,70C

8,080

130

200

2,140

1,200

1,320

130

560

320

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 to 10 mg/1

(22)

with the average about 0.5 mg/l. In 1968 the nitrogen contributed
by well water totaled 510 tons or 1.8 pounds per acre. If it is
assumed that the nitrogen content will not vary significantly in the
future, the 450,000 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

1958 and Ultimate

San Luis Service Area

Source

Deliveries

1958 Ultimate
AF AF

mg/1

Total Ni

1968
Ibs/ac cons

trogen

Ultimat
mg/1 Ibs/ac

tons

Wells

Canals

Totals

900,450

195,600

,095,050

460,000
1,240,000
1,700,000

0.5
0.8

1.8 610
0.6 210
2.4 820

0.5 0.9

0.8 4.0

4.9

310
1,3 50
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 San Luis Canal, the weighted average of total N in
the water was 0.8 mg/1. This includes about 0.4 mg/1 of NO3-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 1958 by the 19 5,500 acre-feet
of canal diversions was 210 tons or an average of 0.5 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 1,3 50 tons or 4.0 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 development. A summary of the contribution of nitrogen by
canal diversions and groundwater pumpage is in Table 2.

Stream and Flood 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)

stream

Quantity

N Content

Total N

PPM

tons

Los Gatos Group

2,000

0.5

1.3

Cantua Group

9,000

0.6 .

7.3

Panoche Group

14,000

0.5

9.5

Little Panoche

Group 7,000
32,000

0.5

4.7

22.8

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 Geologry 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

Ibs/ac

"TW

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.

Legtmiinous 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 the 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 legximinous 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

Nitrogen

Contri

but
San

ion from Legiminous Plants
Luis Service Area

- 1968

Crop
Alfalfa

Acres
61,929

N/Acre
lbs
194

Total N

tons
4,500

Ave/Acre (1)
lbs
13.6

Beans

439

0.1

4,510
(1) Based on gross acreage of service area

13.7

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 NOt has been attributed to its
formation during atmospheric electrical discharges but recent studies
suggest that only about 10 to 20 percent of the NO3 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 NO7-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 Icinds 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 - 1958
San Luis Service Area

Animal
Beef Cattle
Sheep

Number

37,000
135,300

(1)

Nitrogen
Ibs/day/animal

Tons/yr

Ibs/AC

.as'^"'

1,890

5.7

.09<^'

910
2,800

2.7
8.4

(1) 150 days/year pastured in area

(2) 9 lbs dry manure/day |3 3.10% N

(3) 1.64 lbs dry manure/day (a 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)

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(28)

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)(18). 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 Ser vice Area

Sources Nitrogen

Nitrogen Contributions Ibs./ac.

Fertilizer 64.0

Irrigation Water 2.4

Stream Flow 0.1

Rainfall 0.3

Legximinous Plants 13.7

Livestock 8.4

Municipal & Industrial Waste 0.3

89.2

Losses

Crop Harvest 89.0

Volatilization 3.0

Denitrification

92.0

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 NO3-N, NH3-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

5-N

I3-N

Org

anic N

Total N

PPM

Ibs/ftp

PPM

Ibs/AF

PPM

Ibs/AF

Site #1

T19S

R18E S 23

- Oxalis Soil

0-1

3.4

520

1872

1904

1-2

18.5

405

1458

1537

2-3

7.9

306

1102

1140

3-4

4.3

213

757

794

4-5

12.6

259

932

992

157

6131

6357

Site #2 T19 R19 S27 - Lethent Soil

0-1

1.6

533

2279

2303

1-2

4.1

282

1015

1037

2-3

1.4

229

824

836

3-4

1.4

222

799

804

4-5

1.4

222

799

807

5716

5787

Site #3 T19 R17 S20 - Panoche Soil

0-1

3.2

3 50

1260

1294

1-2

2.3

380

1358

1394

2-3

0.9

224

805

823

3-4

1.1

273

983

998

4-5

1.4

280

1008

1024

5425

5533

Site #4 T19 R15 S15 - Panoche Soil

0-1

11.5

491

1758

1823

1-2

12.5

4 59

1552

1708

2-3

12.9

315

1134

1187

3-4

8.8

278

1001

1044

4-5

9.7

245

886

932

199

6441

6594

(31)

TABLE 8 (Cont.)

Depth

3-N

NH3

-N

Organic N

Total N

PPM

lbs

/AF

PPM

Ibs/AF

PPM

Ibs/AF

Site

T17 R16

S22 -

Oxalis

Soil

0-1

1.4

606

2182

2209

1-2

1.1

382

1375

1397

2-3

1.8

287

1033

1057

3-4

2.5

216

778

801

4-5

5.2

19
43

14
86

250

900
6268

933
6397

Site

T16 R16

S22 -

Lethent Soil

0-1

19.1

647

2329

2416

1-2

3.2

456

1642

1665

2-3

1.4

388

1397

1413

3-4

1.6

368

1325

1338

4-5

2.5

9
101

7
54

295

1062
7755

1078
7910

Site

T15 R15

S26 -

Levis Soil

0-1

14.4

442

1591

1661

1-2

8.4

258

929

970

2-3

6.8

175

630

665

3-4

3.6

147

529

549

4-5

2.3

8
127

7
54

128

461
4140

476
4321

Site

T15 R14

S27 -

Oxalis

Soil

0-1

7.7

505

1818

1868

1-2

22.1

309

1112

1203

2-3

48.1

173

212

763

943

3-4

53.9

194

210

756

957

4-5

174.0

626

1101

202

727
5176

1360
6331

Site

T15 R13

S26 -

Panoche Soil

0-1

6.6

444

1598

1636

1-2

2.7

312

1123

1144

2-3

11.1

214

770

821

3-4

14.2

160

576

641

4-5

22.6

81
206

7
57

149

535
4603

624
4866

(32)

TABLE 8 (Cont.)

Depth

NO3-N

NH3-N

Organic N

Total N

PPM

Ibs/AF

PPM Ibs/AF

Ibs/AF

Site

#10

T14 R12 S26 -

Lost Hills Soil

0-1

31,2

112

3 11

434 1562

158 5

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

4323

5137

Site #11 T14 R12 S13 - Panoche Soil

0-1

43.1

155

401

1444

1610

1-2

21.9

271

976

1052

2-3

9.5

168

605

543

3-4

8.1

150

540

573

4-5

6.3

149

535

563

320

4101

4451

Site 12 T13 R13 S23 - Panoche Soil

0-1

14.2

660

2376

2441

1-2

3.8

521

1876

1897

2-3

3.2

481

1732

1748

3-4

8.1

398

1433

1456

4-5

11.1

348

12 53

1297

146

8670

8849

Site #13

T12 R13

S25

- Oxalis

Soil

0-1

17.6

687

2473

2561

1-2

2.9

427

1537

1561

2-3

5.9

328

1181

1209

3-4

0.9

279

1004

1021

4-5

0.9

250

900

917

100

709 5

7269

to 8570 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 85 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 NHt and/or NO3.

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 NH3 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 NO3-N and organic
N contents for several soil types and physiographic positions are
listed in Table 9. The NO3-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
NO3-N would be only five parts per million.

The NO3-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 NO3-N and Organic N

Concentrations at the Various Sites by Soil Type, 0-5 Feet

No . of Minimum Maximum Average

Sites NO3-N Org.N NO3-N Org.N NO3-N Org.N

p. p.m. p. p.m. p. p.m.

Soils

Basin Rim

Oxalis

250

100

412

349

Lethent

297

511

379

Levis

207

253

230

Recent Alluvial

Panoche

156

525

349

Old Alluvial

Lost Hills

225

248

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 NO3-N concentrations among the holes located at the
saune 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 NO3-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)

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(36)

TABLE 11

Summary of NO-r-N in Parts per Million, Standard Deviations and
Standard Error of Mean for the Five Holes at Each Nitrate Site

Depth
Ft.

b c d e Avg .
Site #1 T19S R18E S23 - Oxalis Clay

(1)

(2)

0-1
1-2
2-3
3-4
4-5

4
19

4
13

Site #2 T19 R19 S27 - Lethent Soil

0-1

1-2

2-3

3-4

4-5

Site #3

T19 R17

S20 -

■ Oxalis

Soil

0-1

1-2

2-3

3-4

4-5

Site #4 T19 R16 S15 - Panoche Soil

0-1

1-2

2-3

3-4

4-5

Site

T17

R16

S22 -

Oxalis

So:

0-1

1-2

2-3

3-4

4-5

(1)

- Standard

deviation of

the

mean, a

ill

values

-+-

(2)

- Standard

error s

3f mean

I (95

1 percent (

confidence

interval

(37)

TABLE 11 (cont.)

Depth

(1)

(2)

Ft.

Avg.

Site #6

T16

R15

S22 -

Lethent Soil

0-1

1-2

2-3

3-4

4-5

Site #7

T15

R15

S26 -

Levis

Soil

0-1

1-2

2-3

3-4

4-5

Site #8 T15 R14 S27 - Oxalis Soil

0-1

1-2

2-3

120

3-4

4-5

130

219

303

160

175

115

Site #9 T15 R13 S26 - Panoche Soil

0-1

1-2

2-3

3-4

4-5

Site #10 T14 R12 S26 - Lost Hills Soil

0-1

1-2

2-3

3-4

101

4-5

101

Site #11 T14 R12 S13 - Panoche Soil

0-1

1-2

2-3

3-4

4-5

(38)

TABLE 11 (cont.)

Depth

(1)

(2)

Ft.

Avg.

Site #12

T13 R13

S23 -

Panoche

)il

0-1

1-2

2-3

3-4

4-5

Site #13

T12 R13

S25 -

Oxalis ;

3oi

0-1

1-2

2-3

3-4

4-5

TABLE 12

Average Pounds Per Acre

and

Total

N in

the

! Study A]

rea in the 0-5

Foot

So:

Depth

N03-

-N

NH3-N

Organic

Total N

Ibs/ac.

Tons

Ibs/ac.

Tons

Ibs/ac.

Tons

i lbs/<

ac.

Tons

258

86,

,370

L8,400

5,830

9 51

,940 6,142

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 28,3 53 pounds per acre at site 8, an
Oxalis soil on the Panoche-Cantua interfan.

The total organic N in the Substrata was 6,559,2 50 tons or an
average of 19,730 pounds per acre. The concentration of the

(39)

TABLE 13

NO3-

-N, NH3-]

^ and Org

anic N in PPM

and Pounds

Per

Acre in

the Soil

Substrata*

Site

Depth in

NO 3

-N

3-N

Organic N

Total N

No.

feet
5-40

PPM**
3.7

lbs.
467

PPM**
2.9

lbs.
368

PPM**
144

lbs.
18,197

lbs.

19,032

5-12.5

1.5

3.0

199

5,383

5,505

5-40

0.7

3.2

409

232

29,284

29,780

5-32

41.4

4,019

2.9

277

202

19,560

23,867

5-40

13.4

1,693

2.0

250

152

19,109

21,052

***

5-6

1.6

3.0

138

497

514

5-40

205.0

28,353

1.8

232

118

14,810

43,395

5-40

135.8

17,105

2.2

282

112

14,164

31,551

5-40

60.5

7,642

1.1

137

108

13,573

23,352

5-40

2.0

252

1.5

186

14 5

17,691

18,129

5-30

12.3

1,106

1.4

128

18 5

16,686

17,920

5-10

1.8

2.3

235

4,230

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 NO3-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 NO3-N. A few Substrata contained

(40)

00 -» m

^^ ^ rsi

^ ^ CM

J (lb

6 «^ 4J

•^ -H CL.

(41)

SITE NO. I-OXALIS SOIL

4000-1

1000-

500

c 100-

5 -

ORGANIC N -

NH3-N-

NO3-N-

rnTT,

I p I I I J- r' 'i' r i' c rt t I j t 1 1 1 [ 1 » » » \ t ii 1 |r 1 i 1 [ ' i ' l' r f
D«pth in Feet

FIG. 4- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(42)

SITE NO. 2-LETHENT SOIL

4000-1

1000-

500

100 —

ORGANIC N -

NH3-N-

NO3-N-

■:

I ~ 'I'f'f'ri'i'i 1 1 1 1 I'l I I I I I 1 1 I I 1 1 1 1 1 II I 1 1 1 1 1 I 1 1 I I

Depth in Feet

FIG. 5 - DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC -N BY SAMPLING DEPTH

(43)

SITE NO. 3-PANOCHE SOIL

4000-1

lOOO-

500-

100

ORGANIC

N-i

NH,-N-

' p I 1 1 1 t t I rp ' r t I I ' I f i ' I j r I I I I 1 1 I » I I I I I I I 1 1 I

- N N M lO ♦

D«pth in Feet

FIG. 6- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(44)

SITE NO. 4-PANOCHE SOIL

4000—1

1000

500 -

100

ORGANIC N -

NHj-N-

NO3-N-

1 1 I I I'l'i- f i r ^' f r rt'i' rm 'i'f r i i'j ' ^ ^ '1 I I I I I 1 1 I 1 1 I I
o « o « 8 « 8

D«pth in Feet

FIG. 7- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(4S)

SITE NO. 5-OXALIS SOIL

4000-1

1000-

500

100-

ORGANIC N -

NHj-N-
NO3-N-

I p i T r ^ - vvv i 'f i n I I I I I n I I 1 1 1 1 1 I I I 1 1 I 1 1 I 1 1 I

D«pth in Feet

FIG. 8 - DISTRIBUTION OF NO3-N, NH^-N AND
ORGANIC-N BY SAMPLING DEPTH

(46)

SITE NO 6-LETHENT SOIL

4000-1

1000-

500

100-

50 -

10-

5 '■■:■

ORGANIC N -

NHj-N-

NO3-N —

• I ' l " > V > " | II I I ; I I I I I I I I >[ I I I I J I I I T I I I I I I I I I I J

« W |l» fO ^

D«pth In Feet

FIG. 9- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(47)

SITE NO, 7- LEVIS SOIL

4O00-T

1000-

500

100-

10-

5 -

ORGANIC N -

NHj-N-
NO3-N-

i' I ' f 1 I I I I I I I I I 1 I I I I I I I I I I I I I [ I I » I I I I » I I

2 !G 8 S 5{

D«pth in Feet

FIG. 10- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(48)

SITE NO. 8-OXALIS SOIL

4000—1

1000-

500

100-

10-

5 -

''"'■

ORGANIC N -

NH3-N-

NO3-N-

• 1 1 I I n I t'tr i' t I f I ' l I r I I I I I I I I 'l I I I I I I I I I I 1 1 1 '

D«pth in Feet

FIG. II - DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(49)

SITE NO. 9-PANOCHE SOIL

4000-1

1000 — >

500

100 —

10 —

5 -

-: 2f

ORGANIC N -

NHj-N-

NO3-N-

pTr i* !' r I I ' l I I I 1 1 I I I I 1 1 I I 1 1 1 1 1 I I I 1 1 I I I I 1 1 I

Dtpth in Feet

FIG. 12- DISTRIBUTION OF NO3-N, NH3-N AND
0R6ANIC-N BY SAMPLING DEPTH

(50)

SITE NO. 10 -LOST HILLS SOIL

4000-1

1000 -;

500

100 —

o 50 -

10-

5 -

ORGANIC N -

NHj-N-
NO3-N —

I — Ti' f t'i' TV vrf r vvfp ' v rfp ' fr r yff f T [ » 1 < 1 | 1 1 1 i "

Dtpth in Feet

FIG. 13- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC -N BY SAMPLING DEPTH

(SI)

SITE NO. II- PANOCHE SOIL

4000-1

1000-

500-

100 —

ORGANIC N -

NHj-N-
NO3-N-

I p'v t'f y ^ 'vi' i ' i ' i 'V i I y I I I 1 1 I I I I I 1 1 I I I 'v i-ri'i f t rv

D«pth in Feet

FIG. 14- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(52)

SITE NO. 12 - PANOCHE SOIL

4000-1

1000-

500

100-

10 —

5 -

ORGANIC N -

NH3-N-

NO3-N —

' {' ' I » 'I I ' I I I I [ I I I I [ I I I I [ I I I I J I I I T ] I I I I I I I I II

- N W {15 rO 'T

D«pth in Feet

FIG. 15- DISTRIBUTION OF NO3-N, NH3-N AND
ORGANIC-N BY SAMPLING DEPTH

(53)

SITE NO. 13- OXALIS SOIL

4000-1

1000-

5 -

ORGANIC N -

NH3-N-
NO3-N-

I p ' f l' f | Tf l T ^ I I I I I I I I I I I I I r [ I I I I I I I I I J I I I I I

Dtpth in Feet

FIG. 16- DISTRIBUTION OF NO3-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 denitrif ication has occurred to reduce the nitrate con-
centrations.

Nitrogen in Groundwater

About 2 5 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 NO3-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 NO3-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 NO3-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 NO3-N concentrations
within the 0-50 foot depth interval.

On the Panoche fan a mean NO-j-N concentration of about 36 mg/1 in
Coast Range sediments was computed for 53 samples including a very
high NO3-N value (560 mg/1) reported for USER geohydrologic obser-
vation hole No. 14S/14E/28R2. Excluding this high analysis, the mean
NO7-N content was 16 mg/1, with the next highest NO^-N being 150 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

0-50 Ft. well depth

Yield primarily from:
GEOMORPHIC UNITS No. of Sierran Coast Range

analyses sediments sediments

LOS BANCS CR. - L. PANOCHE INTERFAN

10.

LITTLE PANOCHE FAN

IB.

14.0

LITTLE PANOCHE - PANOCHE INTERFAN

4.6

PANOCHE FAN

53b/
52c/

2b,

15.

.9
.6

76.3
24.8

PANOCHE - CANTUA INTERFAN

52,

67.6

CANTUA FAN

9.3

CANTUA - LOS GATOS INTERFAN

22,

29.6

LOS GATOS FAN

40
16

t 4'

30,

77.3

LOS GATOS - ZAPATOS INTERFAN

122,

(aver. )

MENDOTA - FIREBAUGH AREA

1
2

(aver

0.1

TOTAL SAMPLES ABOVE
CORCORAN CLAY: 244

160

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 USBR 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

No. of
analyses

ft. well
Yield pr
Sierran

sediments

depth

imarily from:

Coast Range

sediments

LOS BANGS CR. - L. PANOCHE INTERFAN

LITTLE PANOCHE FAN

LITTLE PANOCHE - PANOCHE INTERFAN

PANOCHE FAN

1.4 (aver.)

PANOCHE - CANTUA INTERFAN

93.5

CANTUA FAN

0.1

CANTUA - LOS GATOS INTERFAN

0.7

LOS GATOS FAN

29.3 + 32.4

LOS GATOS - ZAPATOS INTERFAN

MENDOTA - FIREBAUGH AREA

0.5

+ 0.3

TOTAL SAMPLES ABOVE
CORCORAN CLAY: 244

(E7)

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

150-300 ft. well depth

Yield primarily from:"

No. of Sierran Coast Range

analyses sediments sediments

GEOMORPHIC UNITS

LOS BANCS CR. - L. PANOCHE INTERFAN

LITTLE PANOCHE FAN

LITTLE PANOCHE - PANOCHE INTERFAN

PANOCHE FAN

51,

+ 117.

PANOCHE - CANTUA INTERFAN

CANTUA FAN

CANTUA - LOS GATOS INTERFAN

LOS GATOS FAN

(aver.

)

LOS GATOS - ZAPATOS INTERFAN

MENDOTA - FIREBAUGH AREA

6
18

,3 + 0.2

+ 0.5

TOTAL SAMPLES ABOVE
CORCORAN CLAY: 244

(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

GEOMORPHIC UNITS

300-600 ft. well depth

Yield primarily from~
No . of Sierran Coast Range
analyses sedinents sediments

LOS BANGS CR. - L. PANOCHE INTERFAN

LITTLE PANOCHE FAN

LITTLE PANOCHE - PANOCHE INTERFAN

PANOCHE FAN

+ 0.3

PANOCHE - CANTUA INTERFAN

+ 0.5

CANTUA FAN

1
2

(aver

21
)

CANTUA - LOS GATOS INTERFAN

LOS GATOS FAN

1
8

+ 2.6

LOS GATOS - ZAPATOS INTERFAN

MENDOTA - FIREBAUGH

1
2

(aver.

)

TOTAL SAMPLES ABOVE
CORCORAN CLAY: 244

(59)

TABLE 19

Sununary of Nitrate Nitrogen and Standard Deviation in Milligrams per
Liter for Wells and USER Geohydrologic Observation Holes Above the
Corcoran Clay - 600-800 Foot Depth

GEOMORPHIC UNITS

600-

No. of
analyses

■800- ft. well depth

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

CANTUA - LOS GATOS INTERFAN

LOS GATOS FAN

5
2

0.2 + 0.5
0.5 (aver. )

LOS GATOS - ZAPATOS INTERFAN

5.6

MENDOTA - FIREBAUGH AREA

TOTAL SAMPLES ABOVE
CORCORAN CLAY: 244

(60)

Little Panoche fan has a mean NO3-N concentration of 18 mg/1 for
five analyses with individual analyses ranging from 4 mg/1 to 40
mg/1 in the 0-50 foot interval.

Generally NO3-N concentrations for the 0-50 foot depth in wells
which obtain their yield from Sierran sediments is comparatively low,
ranging from to 14 rag/1 (Los Gatos fan). Nitrate -N concentrations
for USER 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 -Cant ua
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 NO3-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 NO3-N concentration was about 51 mg/1 with a standard
deviation of 117 rag/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, NO3-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 rag/1, respectively
of NO3-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 NO3-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 NO3-N levels of the soils ranged from 12 ppm in the
Panoche clay subsoil to 115 ppm in the Lethent clay loam surface.
The NO3-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 NO3-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 1% 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 -'■% , 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 ferti3j.zer 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 KNO3
was applied. In Panoche fine sandy loam and Lethent sandy clay loam,
respectively, 81 and 65 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 loeim and Oxalis clay and when
sulfur coated urea was applied to Panoche fine sandy loam 2 5 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 KNO3 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

Wate

r Applied

Probe Depth

Total N

Fertilizer N

Panoche CL

(NH4)2S04

60.6

13.2

13.6

Panoche FSL

KNO3

60,6

49.5

81.4

Lethent CI

KNO3

60.6

34.2

66.1

Panoche FSL

S:Urea-N

60.6

15.2

25.0

Oxalis C

(NH4)2S04

60.6

16.5

27.3

TABLE

Nitrogen Content and Percent of Fertilizer
Nitrogen in Soil Extracts from "B" Depths
December 16, 1968 - August 18, 1969

Soil Type Fertilizer

Wate

r Applied

Probe Depth

Total N

Fertilizer N

Panoche CL

(NH4)2S04

60.6

23.5

2.1

Panoche FSL

KNO3

60.6

23.0

4.8

Lethent CL

Kri03

60.6

14.2

23.9

Panoche FSL

S:Urea-N

60.6

14.4

4.2

Oxalis C

(NH4)2S04

60.6

36.0

1.4

The percent of fertilizer N of the total N collected from the "B"
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 "B" depths, that a very small percentage of the
applied N moved through the soil columns.

TABLE 22

Nitrogen Content and Percent <

in Soil Extracts from "C

December 16, 1968 - August

Df Fertilizer
" Depths
18, 1969

Soil Type Fertilizer

Panoche CL (NH4)2S04
Panoche FSL KNO3
Lethent CL KNO3
Panoche FSL S:Urea-N
Oxalis C (NH4)2S04

Water Applied
In

60.6
60.6
60.6
60.6
60.6

Probe Depth
In

63
62
60
58
56

Total N
mg

25.9

41.6
19.8
20.9
20.5

Fertilizer N
%

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

KNO3

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 KNO3 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

% of Total N

Panoche CL

(NH4)2S04

307

1.2

Panoche FSL

KNO3

619

7.9

Lethent CI

KNO3

231

12.2

Panoche FSL

S:Urea-N

353

2.0

Oxalis C

(NH4)2S04

1083

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 KNO3 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 KNO3. 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 (NH4)2S04.

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 25.

The total NO3-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 KNO, . Lesser amounts of fertilizer

(65)

TABLE 2 5

Recovery of Fertilizer Nitrogen from All Probes

and Leachate for the Period - December 15,

1968 - August 18, 1969

Soil
Type

Sample

Depth

Fertilizer

Leachate

Total

(NH4)2S04

KNO3

S:Urea-

(NH4)2S04

Pan.CL
Pan.FSL
Le. CL
Pan.FSL
Ox. C

0.
3.

1.
0.
0.

,14
,22
,81
,30
,36

40.

22,

% mg

.8 0.04 0.5
,3 0.09 1.1
,6 0.27 3.4
,8 0.05 0.6
,5 0.04 0.5

0,
0,
0,
0,
0,

,03 0.4
.07 0.9
,07 0.9
,02 0.3
,02 0.3

% mg

0.09 1.1
0.54 6.7
0.10 1.2
0.18 1.3
0.16 2.0

0,
3,
2,
0,
0,

,30 3.8
,91 48.9
,24 28.1
,56 7.0
,58 7.3

TABLE 26

Nitrate -N Recovered in the Leachate of Soil

Columns for the Period - December 16, 1958 -

August 18, 1969*

Soil Type

Panoche CL
Panoche FSL
Lethent CL
Panoche FSL
Oxalis C

Fertilizer

(NH4)2S04

XNO3

KNO3

S:Urea-N

(NH4)2S04

Nitrate N in Leachate
Control Fertilized

133

143

259

431

259

233

788

1002

Determined by measurements with the Orion Nitrate probe,

nitrogen were recovered from the other columns. Although large
differences existed between the control arid 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 KNO3.

(66)

The lowest recovery, 4 7 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 Soil Type

Barley (%AFN)'

Grain Sorghum (%AFN)

Straw Grain Total Straw Seed Total

(NH4)2S04

Panoche CL

17.9

47.7

65.6

1.00

1.87

KNO3

Panoche FSL

18.8

54.3

73.1

0.78

2.89

KNO3

Lethent CI

17.4

47.9

65.3

0.76

1.51

Urea-S

Panoche FSL

8.9

38.4

47.3

3.75

9.78

(NH4)2S04

Oxalis C

24.5

38.2

52.7

1.60

1.45

*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 KNO3 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 59.8 percent. The high percentage recovery from
Panoche fine sandy loam soil treated with XNO3 was probably because
the NO3-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
.38.5 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 denitrif ication, (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

Soil
Type

Barley

Grain
Sorg-hum

Water
Samples

Total

(NH4)2S04

Panoche CL

65.6

2.87

0.30

SB. 17

KNO3

Panoche FSL

73.0

3.67

3.91

80.58

KNO3

Lethent CL

65.3

2,28

2.24

69.82

S:Urea-N

Panoche FSL

47.3

13.53

0.56

51.39

(NH4)2S04

Oxalis C

62.1

3.05

0.58

56.33

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 15n. The results
of these tests for two of the lysimeters, one filled with Panoche
FSL to which NO3 fertilizer had been applied and one with Panoche
CI to which NH4 fertilizer had been added, are in Table 29. The
amounts of NO3-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 NO3-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 l^N, 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 -^^H 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
I amount, aside from any possible analytical error, was lost through
volatilization and denitrification.

(68)

TABLE 29

Recovery of Applied Fertilizer Nitrogen in
Nitrogen Fraction from Two

the Nitrate and Organic
Lysimeters

Depth

Panoche CL (3) (NH4S0d)

Panoche FSL (6) (KNOg )

NO^-N
ppm

ppm

Organic N

-L^N mg

NO^-N
ppm

ppm

Organic N
-L^N mg

0-15

358

22.2

246

12.6

15-30

310

4.2

220

1.0

30-45

288

1.7

211

1.3

45-60

3 53

0.8

243

3.4

60-75

281

0.6

234

1.5

75-90

284

0.5

234

1.0

90-105

176

0.4

213

0.3

105-120

178

0.1

175

0.4

120-135

127

0.5

209

1.1

135-150

134

0.4

261

0.9

150-165

124

1.0

233

0.3

165-180

42
546

148

0.5
32.9

56
537

238

1.1
25.3

% Recovery

0.8

25.9

19.9

(69)

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(70)

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 N03'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 denitrif ication (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 KNOv. 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 KNO3
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 1.05 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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(-5)

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 225 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 grraras 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 grams 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)

Table 31

Nitrogen Balance Sheet - Lysimeter #6

Item

Contribution

Residaul NO3-N (start)
Applied Fertilizer Nitrogen
Applied in Water
Mineralization

Total

Removal

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

Total

Residual NO3-N (end)

Total Removal & Residual

Nitrogen

gms

1.06

1.27

.09

1.85

4.27

2.90
.55
.12
.15

3.72

.55
4.27

Ibs/AC

100

143

333

226

290

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 exchcmge 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)

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 im.mediately 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

f76^

profile averaged 1,435 pounds per acre as determined from 47 core
samples. There was a great variability in these samples, ranging
from almost 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 Reclajnation Engineering and Research
Center.

The data from the drains monitored in the San Joaquin Valley in-
dicated a range of NO3-N in the effluents from 2 to 400 milligrams
per liter (21). The annual flow weighted average of these drains
measured during 1956-1969 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)

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 1958 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)

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
2 5,000 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
iinechanization.

(79)

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

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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 denitrif ication or by reducing the area that con-
tributes to the drain.

Laboratory studies (17) have shown that denitrif ication, 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 denitrif ication.

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.

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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.

5. 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, 1954.

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

10. USDI, Bureau of Reclamation, Geology Branch, Nitrate Analyses
from Wells and USBR. 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)

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, 1957.

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 O2 on Denitrif ication 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.

ft v. S. GOVERNMENT PRINTING OFFICE :1 973 — 51 U-1 5lt/27'l

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Accession /Vi/mfccr

SiihjccI Field Sc Croup

05B, 05G

Department of the Interior
Bureau of Reclaraatlon
Fresno Field Division
Fresno. California 93721

SELECTED V/ATER RESOURCES ABSTRACVS
INPUT TRANSACTION FORM

, I Organic

Possibility of Reducing Nitrogen in Drainage Water By On Farm Practices

IQ Author^s)

Williford, John W.
Cardon, Doyle R.

1/ Project Designation

13030 ELY

Agricultural Wastewater Studies, 1971

Report No. REC-R2-71-11

Pages 83 Figures 18 Tables 31 Reference 23

Descriptors (Starred Fust) ^jjj^^rates, *Agricultur al waste, *Fertilizers , Lysimeters,
Sub-surface drainage. Denitrification, Ammonia, Crop production. Animal wastes,
Municipal wastes

25 I Identifiers (Starred Fii

*San Luis Service Area, California, *Nitrogen Budget,
Mineralization, Organic Nitrogen

27 ^^^"•'^' f^ 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 gaseous losses.
This would indicate that, although in many instances the residual-nitrates would replace
some of the contributed nitrogen, especially fertilizers, animal and municipal wastes,
the amount of nitrates moved to the drains would be proportional to the amounts of
soluble, native nitrates in the soil.

A soil sampling study at several sites throughout the area indicated that there were
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 shows that in medium to heavy textured soils under
normal irrigation and fertilizer management practices very little nitrogen is leached to
the drains. Nitrate type fertilizer contributed more nitrogen to the drainage effluent
than ammonia and slow release sulfur coated urea fertilizers.

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 to design drain systems to promote denitrification
and reduce the area swept by the drain flow lines.

Abstfjctcr

John W. Williford

In-liiuiion

U. S. Bureau of Reclamation

:STJSCE5 SC'E-1 7
,R T-.ICST OF T«e 1
OW O. C. 2CJ40

:leat

WATER POLLUTION CONTROL RESEARCH SERIES • 13030 ELY 05/71-12

REC-R2-ri-l2
DWR NO. I7A- IB

BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEY, CALIFORN lA

JUN 5 1975'
MAY 2 7 REC'D

SALINATION OF AGRICULTURAL TILE DRAINAGE

■ffSSth^-nf^iimMa*

MAY 1 97- I

UNIVERSITY OF CALIFORNIA
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VIRONMENTAL PROTECTION AGENCY»R ESEARCH AND MONITORING

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