INFLUENCE OF APPLIED NITROGEN ON NITRATE
DISTRIBUTION IN SOIL PROFILES AND NITROGEN
UPTAKE BY CORN

Dissertation for the Degree of Ph. D.
MICHIGAN STATE UNIVERSITY
RUSSELL PAUL-SCHNEIDER
1975

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ABSTRACT

INFLUENCE OF APPLIED NITROGEN ON
NITRATE DISTRIBUTION IN SOIL PROFILES
AND NITROGEN UPTAKE BY CORN

BY

Russell Paul Schneider

Soil profile distribution studies were conducted on
two Michigan soils using two sources of nitrogen. Corn was
grown on a Hodunk sandy loam using four rates of N (0, 100,
200, 400 kg N/ha) added as urea. Significant yield increases

were obtained as the rate of application increased from 0-200

3
of greater than 200 kg N/ha created conditions for N0; leach-

kg N/ha. Soil profile NO levels indicated that the addition

3

prediction model was developed from soil test NOS-N in a 90

ing and possibly NO pollution of ground water. A yield
cm soil profile.
The second experiment was conducted on a Metea fine
sandy loam. The application of Ca(NO3)2 (0, 50, 100, 200, 400
kg N/ha) suggested that there is an optimum amount of NOS-N in
a 90 cm profile which will produce maximum corn yields.
A computer program was developed which will predict the

amount of N0; leached during a season. The program can be used

Russell Paul Schneider

to predict the amount of NOS-N present in order to predict

corn yields.

INFLUENCE OF APPLIED NITROGEN ON
NITRATE DISTRIBUTION IN SOIL PROFILES

AND NITROGEN UPTAKE BY CORN

BY

Russell Paul Schneider

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1975

To Ben and Helen

ii

ACKNOWLEDGEMENTS

Special recognition and appreciation is due to Dr.
Donald R. Christenson, committee chairman, for his guidance,
patience and understanding during this study. Gratitude is
also expressed to the committee members, Drs. P. E. Rieke,

M. L. Vitosh, A. R. Wolcott and C. J. Pollard for their
advice and consultation. Appreciation and thanks are
expressed to Drs. B. G. Ellis, A. E. Erickson, R. J. Kunze,
M. M. Mortland and the late J. F. Davis for their helpful
"hints" during the acquisition of this education.

Gratitude is extended to the Tennessee Valley Authority
for the financial assistance and enlightening experience
during this study.

Special thanks are extended to Dr. E. C. Doll, for his
interest, keen judgement and advice during the early portion
of this study.

Appreciation is extended to F. Rodammer and R. Voth for
their assistance in the development of the computer program,
and to Jan Schwinke for assistance in the laboratory analysis.

To Cathy and our two daughters I am especially grateful
for without their patience and adaptability this study would

never have been completed.

iii

TABLE OF

ACKNOWLEDGEMENTS . . .

LIST OF TABLES . . . .

LIST OF FIGURES. . . .

INTRODUCTION . . . . .

LITERATURE REVIEW. . .

Nitrate Pollution
Methods Used for Testing and Recommendations

for N. .

Problems Involved in Soi

Modeling of N03

METHODS AND MATERIALS.

Experiment 1. .
Experiment 2. .

RESULTS AND DISCUSSION

Experiment 1. .
Soil . .
Yield. .

Experiment 2. .
Soil . .
Yield. .
Computer

CONTENTS

1 Testing for N .

Leaching and Yield Responses.

SUMMARY AND CONCLUSIONS.

APPENDIX A . . . . . .

APPENDIX B . . . . . .

LITERATURE CITED . . .

iv

Page
.iii
, v
.vii
. l
. 3
. 3
. 4
. 6
. 8
. lO
. 10
. 13
. l7
. l7
. l7
. 22
. 27
. 27
. 3l
. 35
. 45
. 49
. 56
. 59

LIST OF TABLES
Table Page

1. Distribution of rainfall and irrigation during
1973 growing season . . . . . . . . . . . . . . . 12

2. Initial levels of NHZ-N and NOS-N in a 150 cm
profile of Metea fine sandy loam, May 1974. . . . l4

3. Distribution of rainfall and irrigation during
1974 growing season . . . . . . . . . . . . . . . 15

4. Effect of urea on soil pH 45 days after N
application, Experiment 1, 1973 . . . . . . . . . 20

5. Soil moisture in the profile at each sampling
period, Experiment 1, 1973. . . . . . . . . . . . 23

6. Effect of urea on corn yields, Experiment 1,
1973. O O O O O O I O O O O O I O O O O O O O O O 25

7. Effect of urea on soil NOS-N in an acre 90 cm
soil profile 45 days after N applications, 7
Experiment 1, 1973. . . . . . . . . . . . . . . . 25

8. Soil organic N at various sampling times,
Experiment 2, 1974. . . . . . . . . . . . . . . . 30

9. Soil moisture in the profile at each sampling
period, Experiment 2, 1974. . . . . . . . . . . . 32

10. Effect of Ca(NO3)2 on corn yields, Experiment
2, 1974 . . . . . . . . . . . . . . . . . . . . . 33

11. Effect of Ca(NO3)2 on total plant N at
harvest, Experiment 2, 1974 . . . . . . . . . . . 33

12. Effect of Ca(NO3)2 on soil NOS-N in an acre 90
cm soil profile 45 days after N application,
Experiment 2, 1974. . . . . . . . . . . . . . . . 34

13. Effect of Ca(NO3)2 on the amount of total
plant N derived from applied N, Experiment 2,
1974. . . . . . . . . . . . . . . . . . . . . . . 37

Table Page

A.l. Effect of urea on % moisture, NHZ-N and N03 N,
July 9, 1973 . . . . . . . . . . . . . . . . . . . 49

A.2. Effect on urea on % moisture, NHZ-N and NOS-N,
September 25, 1973 . . . . . . . . .'. . . . . . . 50
A.3. Effect of urea on % moisture, NHZ-N and NOS-N,
May 14, 1974 . . . . . . . . . . . . . . . . . . . 51

A.4. Effect of Ca(NO3)2 on % moisture, NHZ-N and
NO--N' may 24' 1974. O O O O O O O O O O O O O O O 52

3
A.5. Effect of Ca(NO3)2 on % moisture, NHZ-N and
NO—-N' JUly 8' 1974. o o o o o o o o o o o o o o o 53
3
A.6. Effect of Ca(NO3) on % moisture, NHZ-N and
NOS—N, september 36' 1974. O O O O O O O O O O 0 O 54
A.7. Effect of Ca(NO )2 on % moisture, NHZ-N and
NOS-N, May 12, I975. . . . . . . . . . . . . . . . 55

vi

LIST OF FIGURES
Figure Page

1. Vertical distribution of NH+-N due to applica-
tion of urea, Experiment 1, 1973 . . . . . . . . . l8

2. Vertical distribution of N0-—N due to the
application of urea, Experiment 1, 1973. . . . . . 21

3. Yield response curve resulting from the NO--N
in an acre 90 cm of soil after 45 days, Ex eri-
ment 1’ 1973 O O O O O O O I O O O O O O O O O O O 26

4. Vertical distribution of NO--N due to the
application of Ca(N03)2, Experiment 2, 1974. . . . 28

5. Flow chart followed to develop the computer
program, 1974. . . . . . . . . . . . . . . . . . . 38

6. Simulation versus actual NOS-N data, 1974. . . . . 44

vii

CHAPTER I

INTRODUCTION

In 1974, according to the Fertilizer Summary Data com-
piled by TVA, 9,157,200 tons of nitrogen fertilizer were used
by the American farmer. Population demands for greater food
production coupled with increased demands for agricultural
land have accelerated the use of N. The intensive utiliza-
tion of such fertilizer materials necessitates additional
responsibility to environmental protection.

A routine and necessary endeavor associated with crop
production is the application of essential plant nutrients to
the soil with fertilizers or manures. The application of most
nutrients is based on soil test determinations and field
correlations. Nitrogen is not one of these nutrients. 'Most
N recommendations are based on application rate studies which
do not relate to leaching probabilities or environmental
contamination. Nitrogen in its available form is very mobile
and consequently quite difficult to evaluate routinely.

A great deal of emphasis has been placed on commercial
fertilizers in recent years and nitrogen fertilizers specif-
ically. Environmentalists claim the eutrophication of many
lakes to be a direct result ofthe agricultural use of
fertilizers and the improper management of such materials.

The improper management by a few has led some extremists to

state that scientists and farmers have no regard for the
environment. Such statements, while having little merit,
attract the greatest attention by the media and are widely
accepted by many people. Scientists must therefore develop
new methods to evaluate fertilizer recommendations which
consider the impact on the environment as well as yield.
Realizing the many factors of nitrogen fertilizer
application and use efficiency, two major points were
3-

leaching losses, and 2) how

considered: 1) how can soil test NO N be used to predict

3

can scientists predict the amount of NO

crop yields while limiting NO

3
soil profile. With this background the following studies

leached through a

were conducted.

CHAPTER II

LITERATURE REVIEW

As the clamor for increased production grows louder so
does the outcry and outrage of environmentalists concerned
with nitrate pollution of lakes and streams (24). Some work—
ers (38) have gone so far as to state that soil scientists

have not been concerned with N0; losses that were economically

unimportant to the farmer but which could contaminate large

volumes of water. This statement is erroneous, but the

3

increased NO} levels in ground water as well as lakes and

streams do occur. The U. S. Department of Health, Education

problem of excess levels of NO in the soil does exist and

and Welfare set a drinking water standard of not more than

10 ppm NOS-N (46).

Nitrate Pollution

 

The concept that all fertilizer nitrogen must be bad
has caused a great deal of controversy in production agricul-
ture. In recent years Kohl et a1. (24) has stated that the
addition of fertilizer N was polluting lakes and rivers in
Illinois, and Viets (46) quoted Commoner as saying that there
should be an elimination of N use for the next 10 years.
Present research has shown scientific concern for the

pollution problem and in part corrective possibilities.

Bartholomew (7) has shown that No; pollution may occur at
either low or high application rates of N depending upon how

well plants utilize the nutrient. If corn yields were less

than 1 metric ton per hectare (T/ha), N03.pollution could
occur when 100 kg N/ha were added. However, if the corn
yields were 12 T/ha, then N additions would need to be about
400 kg N/ha to be pollutants. Realization of proper manage-
ment practices by producers in relation to the recommended

fertilizer additions can make a great deal of difference in

the amount of NO3 moving through the soil profile. Pratt et

31. (36) felt that drainage water would not be appreciably

affected by NO3 when proper management was used to maximize

production. Olsen and his co-workers (33) found that the
total amount of N0; in the soil profile was directly related
to the rate of N application and that NO

3
could be limited by avoiding excessive rates of fertilizer N.

in the ground water

3
during the winter and early spring was a process of leaching

More recently, Derici (14) has shown that the loss of NO

and not denitrification on a Hodunk sandy loam. Derici also

indicated the possibility of ground water pollution by NO

 

3
when application rates exceeded 186 kg N/ha.
Methods Used for Testing and Recommendations for N
Leibig's law of the minimum and the Mitscherlich
equation, log (A—y) = log A - cb, have been used by scientists

to relate soil test N or tissue test N to the N needs of agri-
cultural crops. Fitts (18, 19) and Stanford (44), worked on

incubation techniques which were quite successful for

predicting N fertilizer needs in Iowa soils. Several workers
(26, 43) have worked with A values, (A = B (l-y)/y) where A
is the amount of available soil N, B is the amount of added N
fertilizer and y is the fraction of N in the plant derived

from the fertilizer, to develop better soil test methods.

3

soil plus the N from organic sources. Legg (26) concluded

Stanford (43) calculated A values from N0 initially in the
that the A value constituted a precise standard for
characterizing N supplying capacities of soils but it has not
been utilized to any great extent. Hunter (23) felt that N
values, (N = B (l-y)/y) where N is the amount of indigenous
soil N available to plants, B and y are the same as described
in A value, were best for calculating N for sudan grass
production.

Soper gt gt. (39) found that the NOS-N content of the
soil to a depth of 120 cm gave the best correlatiOn with
yield in assessing nitrogen fertilization in barley. Spencer
and his co-workers (40) found that N uptake by corn was most
highly correlated with initial NOS-N in the 15-30 cm depth,
or initial NOS-N plus N released on incubation for 2 weeks
and total N in the 0-30 cm depth. They indicated that the
initial N0; had little effect on correlations between miner—
alizable N and N uptake by corn and sugar beets. Giles gt gt.
(22) has shown that soil NOS-N levels determined before
planting were useful in estimating the N requirement of sugar
beets. These same workers found that fertilizer N responses
were unlikely when soil NOS-N levels in the 0-60 cm depth

were greater than 130 kg/ha.

Lucas (30) has proposed that 40 pp2m of NOS-N in the

plow soil represents a critical level for estimating the N
available to corn during tasseling, silking and pollination.

Doll gt g1. (15) felt that in potato production additional
3-
ppm 10-12 weeks after emergence. Work in Missouri (29)

N fertilizer should be applied if soil NO N fell below 20
indicated that applications of N greater than 112 kg N/ha
exceeded the N needed in corn production while Derici (14)
obtained maximum yields in corn with 186 kg N/ha. Vitosh
(47) has shown maximum yields with 154 kg N/ha on clay loam
soils producing corn. Stanford (41) stated that the efficien-
cy of applied N was rate and time dependent and was also
influenced by growing conditions.

The evaluation of plant N has been used to predict N
needs. Baird gt gt. (6) found that the N in corn leaves
could not be used for predicting N fertilization.‘ Stanford
(41) maintained that the maximum attainable yield for corn
was associated with 1.2% N in the total dry matter. Stan-
ford concluded that the efficient use of N was not just an
uptake phenomenon but was also part of the NOS-N and NHZ—N

present in the soil initially, and the N mineralization

potential of the soil.

Problems Involved in Soil Testing for N

 

Allison (5) stated that it was impossible, or at least
impractical, to account for all gains and losses of N in a
single experiment under normal soil conditions. Evaluation

of NO3 leaching and mineralization during the growing season

have posed problems. According to Allison (4) leaching of
available nitrogen beyond the plant root zone seldom occurred

in cultivated, medium textured, humid soils unless the annual

3

occurred during the winter and early spring. Wolcott gt gt.

rainfall was above 127 cm. He felt the leaching of NO

(50) has also shown that annual accumulations of N0; were
largely moved out of the soil before the following season.
Stanford (41) felt that properly timed applications of N at

economically optimum levels for crop production would reduce

3
The failure to adopt a standard sampling depth may

the leaching of NO from the root zone.
cause problems. Onken and Sunderman (34) felt that samples
to a depth of 30 cm were sufficient for grain sorghum.

Giles (22) recommended 60 cm in sugar beets and Soper (39)
stated that 120 cm was best for barley. Due to mass flow and
diffusion patterns N0; tends to move in several directions,
the amount in any direction depending on soil texture.
Allison (3) stated that the chief avenue for loss of N in
normal agricultural practices was leaching, but leaching
seemed to be restricted by the clay content of the soil (31).
Wetselaar (48) and Boswell and Anderson (8) found that
nitrate would accumulate at the soil surface on drying which
would cause sampling problems. Another problem encountered
has been that associated with recycling of high N0; ground
water from shallow depths (1). The total amount of available

plant nutrients would be impossible to determine under such

conditions. Band applications of N at planting may cause

problems when soil testing in mid-season. Since the N was
concentrated in a band, root proliferation was greatest in
this region and leaching was minimized (35). Lateral move-

ment of N0; in the soil was restricted by banding and there—

fore the uniformity of the total soil-water system was
decreased.
Soil tests for N are difficult, sometimes misleading,

often controversial but necessary. Carter gt gt. (13) has

3

mineralizable N and NOS-N levels of a soil. Carter's idea

coincided with Stanford's (41) suggestions for optimum N

stated that a good soil test for NO should measure both the

use. They felt that the crop's needs must be known as well
as the amount of N mineralized during the season. They also
felt that the amount of residual mineral N present in the
root zone early in the season and the expected efficiency of

the crop available N supply was needed.

Modeling of NOELeachingand Yield Responses

 

The modeling of yield responses from N applications
has been studied in several areas of the country. Vitosh
EE.§l- (47) and Engelstad and Parks (17) developed yield
models for corn based on rates of spring applications of N.

A conclusive computer model, or more specifically a
leaching simulation computer program, has many integrated
pieces. The total system must include soil transformations,
environmental influences and plant characteristics. The
scientist must realize that minimal use efficiency has been

obtained with applied N (12, 25), and poor efficiency

3

3 but Wetselaar (49) found that NO3

moved about 3.8 cm when the soil was near 15 atmospheres

increased the probability of NO leaching. Free water has

been shown to remove NO

tension. Liao and Bartholomew (28) showed mass flow to con—
tribute more to corn nutrition than did diffusion in a soil

system. Foth (20) defined the root distribution patterns in
corn according to the time of year in a dynamic soil system.

Gardner (21) developed a leaching equation for N03 solutions.
The equation was based on leaching being a function of perco-
lated water and percolated effectiveness based on porosity and
water content (45). Mineralization also influenced the
development of leaching models. Legg and Allison (27) have
shown mineralization to be essentially constant regardless of
the rate of nitrogen addition. Stanford and Smith (42) found
that mineralization rates of soils were similar but crop
rotations played a major role in the amount of mineralization.
It has been indicated (32) that N applications did not in-
crease the rate of breakdown of soil organic matter. Duffy
gt gt. (16) developed a simulation model which predicted the
concentration of NO- in tile effluent based on many of the

3

afore mentioned concepts.

CHAPTER III

METHODS AND MATERIALS

Two field studies were conducted at the Michigan State
University soils farm during 1973 and 1974. Corn (Egg mgyg
L.) was utilized as an indicator crop to evaluate several N
rates with respect to soil test NOS-N and N recommendations
on corn. Incremental-soil samples were taken by depth four
times during each growing season to determine the profile

distribution of NHZ-N and NOS-N.

Experiment 1

 

The first experiment was conducted on a Hodunk sandy
loam (Cchreptic Fragiudalf). This soil series is a moderately
well-drained, gray-brown podzolic soil, developed on'a Calcar-
eous sandy loam glacial till, with a fragipan usually at 40-60
cm. Soil test results were as follows:pH(l:l soilzwater),
6.5; Bray P

50 kg/ha; NH OAc extractable K, 143 kg/ha.

l' 4
Initial NOS-N levels were found to be negligible throughout
the entire soil profile. Nitrogen treatments were arranged
in a randomized complete block design with four replications.
Urea was broadcast at rates of 0, 100, 200 and 400 kg N/ha
and disced into the soil. Funks hybrid (F—4444) was planted

June 1, 1973, in 71 cm rows with a band application of 200

kg/ha 0-26-26, 5 cm below and 5 cm to the side of the seed.

10

11

During the growing season, sprinkler irrigation was
utilized to maintain adequate moisture throughout the profile.
The distribution of rainfall and irrigation during the 1973
growing season is given in Table 1. Soil samples were taken
before the crop was planted, 45 days after the N application
(32 days after emergence), at harvest and finally in the
spring of 1974. Five holes per plot were taken with a 8 cm
soil auger to a depth of 180 cm initially, 150 cm at 45 days
and 180 cm at harvest and in the spring. Each increment for
each hole was screened through a .5 cm screen and sub-
sampled. Each sub-sample was placed in a plastic zip-lock
bag and then 5 drops of toluene were added to each sample to
restrict biological activity. The bags were then sealed and
frozen until the time of analysis.

Corn was harvested in late September, weighed and
sampled for moisture. All yield values were based on 15.5%
moisture.

The soil samples were analyzed for NHZ-N and NOS-N
using a micro-kjeldahl analysis outlined by Bremner (9). A
representative 1 9 sample of soil was suspended in 10 m1 of
2N KCl and directly steam distilled. The NH+-N was liberated

4
first using MgO and the NOS—N was reduced to NH3 with
Devarda's alloy. A 30 ml sample was caught in a 2% boric
acid solution containing a mixed indicator of bromocresol
green, methyl red and ethanol. The solution was titrated

using standard H2804.

12

Table 1. Distribution of rainfall and irrigation during 1973
growing season.

 

 

 

 

 

 

Date April May June July August September
cm
1 2.79 1.71 .13
2 .23 .38
3 .23 1.27 (2.54)9/
4 .23 1.14 (2.54)
5 .25
6 .25
7
8 1.78 1.91
9 .66 .64 1.14 .64
10 .66
ll
12 .l3
13
14 (2.54) (2.54)
15
16 .41 2.39
17 .58
18 .28 3.23
19 .23 .09
20 «
21 .29
22 2.31 2.23 .25
23 .25 .05
24
25 1.26
26 .38 .20
27 2.72 2.11 .80
28 .89 2.10
29 .10 1.27 (2.54)
30 .30 .25 .03
31 .54 .41 .13
Total 8.20 11.87 7.79 5.74 11.11 10.34
a/

— The values in parentheses are irrigation data.

l3

Experiment 2

 

The second field experiment was conducted on a Metea
fine sandy loam (Arenic Hapludalf). This soil series is a
well—drained, gray-brown podzolic soil, formed in water or
wind laid sands or loamy sands overlying loamy till. Soil
tests were as follows: pH (1:1 soi1:water) 7.0, Bray Pl

174 kg/ha, NH OAc extractable K 213 kg/ha.

4
On October 9, 1973, 400 kg N/ha as urea was broadcast
over the entire experimental area. The urea was disced into

the soil and rye (Secale cereale L.) was planted. In the

 

spring the rye was plowed under and soil samples from each
plot were taken to determine the NHZ-N and NOS-N in the soil
profile (Table 2). Nitrogen treatments were arranged in a
randomized complete block design with 4 replications.

Calcium nitrate was broadcast at rates of 0, 50, 100, 200 and

2

400 kg N/ha to all but 3.25 m located in the center of each

plot. The 3.25 m2 were treated with the same rates of N
except 1% atom excess 15N was applied as KlsNO3 plus Ca(N03)2
to give the desired rates. The entire area was hand raked to
incorporate the N without moving the 15N outside the desired
area. Pioneer hybrid 3780 was planted May 27, 1974, in 71 cm
rows without any band applied fertilizer.

During the growing season, sprinkler irrigation was
used to supplement the limited rainfall (Table 3). Soil

samples were taken at 45 days, harvest and in the spring of

1975 as described in Experiment 1.

14

Table 2. Initial levels of NHz-N and NOE-N in a 150 cm
profile of Metea fine sandy loam, May 1974.

 

 

 

Depth NHZ-N NOS—N
cm kg/ha kg/ha
0-15 9.8 12.6

15-30 13.0 12.8
30-45 10.0 13.8
45-60 11.6 22.6
60-75 6.6 25.2
75-90 10.0 20.6
909120 10.2 17.6
120-150 7.2 10.6

 

15

Table 3. Distribution of rainfall and irrigation during 1974
growing season.

 

 

 

 

 

 

Date May June July August September
cm
1 1.37 .81
2 1.40 .15 1.12
3 .05
4 .74 .05 /
5 .76 (3.18)-‘1
6 1.02
7 1.24 .18
8 .81
9 .33 .66
10 .05 1.42
11 1.78 .43 .30 .23
12 4.60(3.18)
l3
14 1.07
15
16 5.69 .10 (2.54) .41
17 .46
18 .41
19 (2.54)
20 .15 '
21 (3.18).38
22 .05
23 .08
24 .03
25
26 2.99
27 . .08 1.19
28 1.68 .08 2.03
29 (3.18) .08
30 1.04 .03
31
Total 11.79 5.23 12.24 19.08 6.99
g/

The values in parentheses are irrigation data.

16

The corn was harvested after a 120 day growing season,
weighed and sampled for moisture. All yield values were
based on 15.5% moisture. Total corn stalk and ear samples
were cut from each 15N treated plot and chopped with a con-
ventional silage chopper. The samples were forced air dried,

15

sub-sampled, and ground for total N and N determinations.

Total N was determined as outlined by Bremner (11) and 15N
was analyzed according to Bremner (10) by personnel at the
National Fertilizer Development Center, Muscle Shoals,
Alabama. The soil samples for each sampling period were
analyzed as specified in Experiment 1.

A yield model was established from the 1973 data and
a computer program was developed from the 1974 data which
computes the amount of NOS-N leached during a growing season.
The computer program data was compared to the actual soil

NOE-N data to evaluate the applicability of such a program

in an agricultural situation.

CHAPTER IV

RESULTS AND DISCUSSION

Experiment 1

 

ggtt

Soil samples were taken at the initiation of the 1973
study. These samples did not indicate the presence of any
NHz-N or NOS-N. The area utilized for the experiment had not
been fertilized for approximately 3 years and was considered
ideal for a N study.

The rapid hydrolysis and nitrification of urea, in
most soils, may be influenced by soil pH or microbiological
activity. Ammonium N determinations were made twice during
the 1973 growing season and in the spring of 1974 (Figure l).
The NHZ-N levels shown were greater than expected at the

July sampling. Only the application of 400 kg N/ha increased

the NHZ-N content significantly above the check (Table A.1).
The zero treatment and the applications of 100 and 200 kg N/

ha show similar NHz-N distribution in the soil profile (Figure

l). The application of 400 kg N/ha showed an increase in
+-
4

the high application of urea with the subsequent nitrification

. . +
NH N to a depth of 90 cm. The increase in NH4—N was due to

being inhibited. The inhibition was thought to have occurred

due to a rapid decrease in soil pH. Solubilized iron oxides

l7

NHI-N (ppm)

 

 

 

 

18

NHI-N (ppm)

 

 

 

     

 

O 5 IO I5 20 25 30 O 5 I0 I5 20 25 30
I5 I5
30[ 30‘
45’ 45~
60- 60-
E 75- ’g‘ 75- \
gem gem-f ”-9-73
3- 3 0 9—25-73
0 0 7- 9-73 0 A 5-I4—74
I20 » 0 9-25-73 (20 - l00 KgN/ho
A 5—(4-74
CHECK
I50 I50-
I80- I80-
NHI-N (ppm) NH,+-N (ppm)
0 5 l0 I5 20 25 30 0 5 I0 I5 20 25 30
I5 I5
30 30*
45A 45-
60- 60-
E 75 r E 75 -
£90" .7— 9—73 5 90’
_ _ G.
a 0 22:23: a
'2 _ _ 09- 5—73
\ 200 Kg N/ha I20 A 54444
400 Kg N/ho
|50- [50.
I80 - I80 -
. + . .
Figure 1. Vertical distribution of NH4-N due to application
of urea, Experiment 1, 1973.

19

were observed on the surface of the plots which received 400
kg N/ha. The rapid solubilization was caused by the pH
depression due to the acidifying effects of the added nitro-
gen (Table 4). The acidification arises from the protons

donated by the following reaction:

H20 - +
- — — - +
HZN C. NH2 rease H4NO C| ONH4-'---¥2NH3---—'INO2 H20 + H

0

There were slight differences in the NHZ-N soil profile dis-

tribution at the end of the growing season and May 1974

(Figure l). A great deal of NHZ-N was present in July and

subsequent nitrification later in the growing season increased

the amount of No; subject to leaching (Figure 2). The amount

of NO3 N found in the soil profile was quite high when

applications exceeded 100 kg N/ha. The NOS-N found in the

surface 30 cm 45 days after the application of 200 or 400 kg

N/ha showed that significant amounts of NO3

N were still
present (Table A.1).

Greater amounts of NOS-N were found to be present at
harvest than were found in July when applications exceeded
100 kg N/ha (Figure 2). The increase in the amount of NOS-N
in September indicated that nitrification had been delayed
early in the growing season. The amount of NOS-N present in
significant amounts (Table A.2) in September was subject to
leaching as some leaching had already occurred. The values

show that applications exceeding 200 kg N/ha are excessive and

the possibility of leaching increased. By the spring of 1974

20

Table 4. Effect of urea on soil pH 45 days after N applica—
tion, Experiment 1, 1973.

 

 

 

 

Treatment pH
kg N/ha
o 6 . 09/
100 5.7
200 5.3
400 4.3
a/

—-Values are means of 4 replications.

21

 

 

 

 

   
 

 

 

 

 

 

N03-N (ppm) N03-N (ppm)
0 IO 20 30 40 50 60 0 I0 20 30 40 50 60
IS
30-
45 —
60—
g .g 75—
.5 o 7— 9—73 5 90’ 07- 9—73
5} ° 9-25-73 E} 0 9—25—73
0 A 5—(4—74 ‘3 A 5—14—74
I CHECK '20 ' I00 KgN/ha
I |50~
I80 I80-
N03-NIppm) N03-NIppm)
0 IO 20 30 40 50 60 0 IO 20 30 40 50 60 70
m»
30-
45*
60—
E E 75.
.3 .3
s s 90'
a. G.
8 .7- 9-73 5’ 07—9—73
I20 — o seas—73 (20» ° 9‘25‘73
A 5-(4—74 A 5—(4-74
200 KgN/ha 400 Kg NH“!
(50 - |50r
|80 L |80

 

Figure 2.

 

Vertical distribution of NO--N due to the applica-

tion of urea, Experiment 1, 1973.

22

the NOS-N which was present in September had been lost from
the system. These results support the work of Allison (5)
showing that little NO} was leached during the summer and
that the removal of NOS occurred during the winter (50). The
loss of N could have been caused by denitrification or leach-
ing. The work by Derici (14), on the same soil type as used
by the author, using Cl- as a tracer indicated that No;
leaching from the soil profile was the most probable method
of N loss. The loss of N after the growing season could be
contributing to environmental contamination.

Water was a factor in the nitrification process as
well as the leaching process and as indicated (Table l)
irrigation was applied during the growing season. The %
moisture was determined at each sampling period (Table 5)
for each depth to determine whether the NOS-N concentration
was a function of soil drying. The data indicated that there
were significant differences in soil moisture with respect to
depth. There were no significant differences in the surface
45 cm where the NO--N concentration differences were greatest.

3

The values obtained show that the water served as a leaching

pathway but NO3 concentrations were not a function of soil

water.

The corn yield was significantly increased by the
addition of up to 200 kg N/ha (Table 6). The amount of N
added has often been considered to be the amount needed for

optimum yields in corn. Two questions must be asked:

23

 

 

 

 

 

Table 5. Soil moisture in the profile at each sampling
period, Experiment 1, 1973.
Depth Date
cm 7/9/73 9/25/73 5/14/74
% w/w
0-15 8.1 9.2 12.7
15-30 7.8 8.3 12.5
30—45 9.2 7.8 11.2
45-60 9.7 8.9 12.3
60-75 10.9 9.8 13.9
75-90 12.6 12.1 15.0
90-120 14.6 14.7 14.8
120-150 13.1 14.1 14.4
150-180 - - 14.3
L.S.D. .05 1.4 2.3 1.5

 

 

 

24

1) why is 200 kg N/ha critical, and 2) how is the critical

amount reflected in soil NOS-N levels?

The critical time for and maximum uptake of N occurs
from 30-45 days after corn emergence (2). This would seem to

be the appropriate time to evaluate soil NOS-N. Root penetra-

tion by corn is usually in the top 90 cm (20) and therefore

soil test levels to this depth seem desirable. In 1973 the
3-

was determined (Table 7). The values indicate that the

total amount of NO N in the top 90 cm of the soil profile

presence of approximately 76 ppm NOS-N in the top 90 cm of

the soil profile 45 days after N application produce maximum

yields. The 76 ppm NO3 N coincides with the application of

200 kg N/ha. This information showed that there was a

critical level of NO3 N associated with the application of N.
The critical factor was not the application rate (200 kg N/

ha), but rather the soil NOS—N content of 76 ppm. The eval-
3-
ing a yield model (Figure 3) based on the ppm NOS—N in a 90

uation of the critical soil NO N was completed by establish-

cm soil profile 45 days after the N applications. The
regression equation gave the best fit when compared to either

a linear or cubic equation. The summation of NOS-N was

--N with 15 cm depths or NH+-

3 4
N with 15 cm depths or in 90 cm. Yield predictions can

better than individual NO N plus

3-
2

be made with reasonable confidence Ul=.84, P=.05) using soil

+- _-

4 3

a yield model did not give adequate correlation coefficients.

NO

test NOS-N and yield. The use of NH N plus NO N to develop

25

Table 6. Effect of urea on corn yields, Experiment 1, 1973.

 

 

 

 

 

 

Treatment Yield
kg N/ha _ , bu/a I T/ha
0 28.73/ 2.3
100 88.7 ' 6.8
200 129.5. 10.2
400 123.4 9.7
L.S.D. .05 33.7 2.7
2[Values shown are means of 4 replications.

Table 7. Effect of urea on soil NOS-N in an acre 90 cm soil
profile 45 days after N applications, Experiment 1,

 

 

 

1973.
Treatment NOS-N —————— Yield
kg N/ha ppm bu/a’ T/ha
0 36.83/ 28.7 2.3
100 43.2 88.7 6.8
200 75.8 129.5 10.2
400 125.9 123.4 ' 9.7

 

a/

-Va1ues shown are means of 4 replications.

26

 

 

 

200 r-

l60 - °
3 I 20 -
B
E
.92
>- 80 _. y=-28.68+2.72x-.0Ix"-

o o a”: .84
40 -
0 1 1 J 1 1 l l 1 1 '
o 40 80 I20 I60 200
ppm NOS-N

Figure 3. Yield response curve resulting from the NO—-N in
an acre 90 cm of the soil after 45 days, Experi-
ment 1, 1973.

27

Experiment 2

 

§gtt

The field experiment in 1974 proved to be of interest
in several respects. Initially the author thought that
excessive levels of NOS-N could be established by the fall
application of 1000 kg urea/ha. The author felt that the
late application of urea would limit the amount of NOS-N
released in the fall. He also felt that the small amount
released would be utilized by the rye. The rapid growth of
the rye early in the spring probably immobilized some of the
applied N but the large amounts of soil profile NOS-N which
were expected were not detected in the analysis (Figure 4).
The urea was either readily hydrolyzed, nitrified to N0; and
leached or else the NO_ was denitrified. The vertical dis-

3
tribution of NO--N rarely exceeded 10 ppm. The No; pulse

3
shown from 45-90 cm was present initially and was assumed to
have originated from the fall applied urea. The additiOn of
the various N treatments were quite obvious at the July
sampling. Significant increases occurred in the surface 30
cm 45 days after N application (Table A.5) while treatments
greater than 100 kg N/ha showed increases below 30 cm. This

suggested the movement of some NO3 in association with the 8
cm of rain and irrigation water which had been applied
(Table 3). The pulse present initially from 45-90 cm was
still evident in July and in the 400 kg N/ha treatment

actually accentuated. Loading of the system the previous fall

had little influence on the movement of the spring applied N.

 

   
   

 

 

 

28

 

   

 

~03-~(ppm) ~03-N(ppm) '~o;-~(ppm)
0 l0 2.0 39 4O - 50 60 0 IO 20_ 30 40__50 60 0 IO 20 30 40 50 60 70
.E. ,_. i.
3 05—24-74 E 0 5-24—74 :63 ‘. 0 5—24—70
5 [jg—221: ‘ o '- 6—74 5 | o 7- 8-74
3 AS:I2:75 5‘ r o 9-36774 a :1 9—26—74
9 CHECK Q )5.) o 5-(2-75 5 I50 .- s—uz—rs
so I'g rm). . l00 lg Nlha
‘83) I80)
2'9 are!»
240.L 240A
I“ '
270 270L
NOS-N (ppm) N03~N (ppm)
I0 20_ 30 40___50 69 70 0 I0 20 30 40 50 60 7O ‘ I00 IIO I20
P—"V " '7' _ 'V ' ' ' " Y v T v v r *7 fl Y Ta
\/ 15 ”M‘-
/

   

0 5-24—74

A I20 °7-0-"
5 0 9-26-74
" 65—12-75
g '50 200 Kg mm
0
0

I80

2(0

240

270

Figure 4.

089” (cm)

2|0’

240 '

270

 
 

 

if

0 5—24-74
0 7- a-u
0 9—26~n
0 542-75
400mm“

2'

Vertical distribution of NOE—N during 1974 as due
to the application of Ca(N03)

Experiment 2, 1974.

29

After 120 days, the addition of greater than 100 kg
N/ha was changing the profile distribution of NOS-N (Figure

4). Where less than 100 kg N/ha was applied, NO3-N levels

were reduced to levels less than those found prior to N

application. The depletion suggested good crop utilization

3
subject to winter loss. The application of greater than 100

of the applied N as well as a reduction in the amount of NO

kg N/ha significantly increased the amount of NOS-N found in

the upper 60 cm (Table A.6). The leaching patterns observed

where 200 or 400 kg N/ha were applied show the leaching of

NO3 from one depth to another. The redistribution of N0;

was certainly prevalent in the surface 30 cm. The variabili-
ty of the soil profile was demonstrated by the non-uniformity
of the leaching patterns (Figure 4). Increased amounts of
NOS found deep in the soil profile suggest that the large
application of urea the previous fall increased the amount of

3

following spring as had been shown in Experiment 1. Samples

No'-N in the fall of 1974. However, this was lost by the

taken to a depth of 270 cm Show that NO3

had been completely
leached below this depth.

The addition of the excessive amount of urea and the
plowing of the rye made it necessary to evaluate the organic
N in the soil (Table 8). Significant differences were a
function of depth but not treatment. Very little difference
was found between sampling periods. It appeared that no N of

significance came from the organic N pool, but rather from

the N applied as fertilizer.

30

 

 

 

 

 

 

 

Table 8. Soil organic N at various sampling times, Experiment
2, 1974.

Depth Date

cm 5/24 7/8 9/26

PPm

0-15 693 716 670
15-30 573 591 549

30-45 251 304 248
45-60 238 267 ' 242

L.S.D. .05 85 57 ’55.

 

31

The moisture content was determined for all depths at
each sampling time (Table 9). Significant differences
occurred between depths but the % moisture was not considered

to be influencing the N03 concentration in the individual

increments due to drying.

2.19.1.6

The 1974 corn yield was excellent considering the late
start and the hot dry summer. The addition of N did not
significantly increase the yield of corn (Table 10) though a
yield increase did occur. The residual N from the fall
application was considered to be responsible for the yield
similarities. The application of 50 kg N/ha revealed a
significant increase in total plant N (Table 11). The total
plant N was not changed significantly where applications
exceeded 50 kg N/ha. The total plant N values obtained were
similar to those considered optimum by Stanford (41). The
yield model developed earlier (Figure 3) was used to predict
the 1974 corn yields. The NOS-N levels determined to a
depth of 90 cm 45 days after N application implied that yield
differences would be predicted. The yields were different
(Table 10) but not as predicted from the yield model. The
maximum yield predicted from the model using the 1974 NOS-N
values did correspond to the greatest amount of total plant
N. Comparison of the 1973 yield (Table 7) with the 1974
yield (Table 12) disclosed that the maximum corn yield
occurred when the NO--N content in 90 cm was between 76 and

3
82 ppm 45 days after N application.

32

Table 9. Soil moisture in the profile at each sampling
period, Experiment 2, 1974.

 

 

 

 

 

 

 

Depth Date
cm 5/24 7/8 9/26 5/12/75
% w/w
0-15 7.5 7.5 11.2 11.7
15-30 8.0 7.1 10.5 12.6
30—45 7.7 7.7 9.4 12.6
45-60 10.0 9.6 9.7 10.9
60-75 12.0 10.9 10.8 13.6
75-90 12.7 11.7 11.5 14.6
90-120 12.7 12.0 11.9 14.0
120-150 12.4 12.2 13.0 14.5
.s.0. .8 1.1 1.2 3.1

 

33

Table 10. Effect of Ca(NO3)2 on corn yields, Experiment 2,

 

 

 

 

 

1974.

Treatment Yield
kg N/ha ' bu/a T/ha
0 126.83/ 10.02
50 132.3 10.45
100 119.9 9.47
200 117.8 9.31
400 123.3 9.74
L.S.D. .05 n.s. n.s.

 

2/

Values shown are means of 4 replications.

Table 11. Effect of Ca(NO3)2 on total plant N at harvest,
Experiment 2, 1974.

 

 

 

 

Treatment Total Nitrogen
kg N/ha %
0 .983/
50 1.14
100 1.16
200 1.19
400 1.17
L.S.D. .05 .10
51/

Values shown are means of 4 replications.

34

Table 12. Effect of Ca(NO ) on soil NOS-N in an acre 90 cm
soil profile 45 days after N application, Experi-
ment 2, 1974.

 

 

 

 

Treatment NOS—N ——————— Yield
kg N/ha ppm bu/a T/ha
0 51.63/ 126.8 10.02
50 81.5 132.3 10.45
100 102.1 119.9 9.47
200 153.0 117.8 9.31
400 223.5 123.3 9.74
a/

— Values shown are means of 4 replications.

35

Computer Model

 

The use of the computer has gained widespread attention
in recent years in regard to ecological simulation. This
author concluded that given specific information a simulation
program could be developed which would predict the movement of

NO3 through the soil profile. There are several parameters
which must be considered: 1) plant uptake, 2) root biomass,
3) evapotranspiration, 4) denitrification, 5) nitrification,
6) leaching, 7) soil profile water, 8) water application, and
9) mineralization. The use of the afore mentioned parameters

can be made particularly when utilizing the following leaching

equation developed by Gardner (21) for nitrate solutions:

K-b
[co - (£—)1[1‘1§§£]T + 3,133 [11

0
II

where

c = amount of NO3 present at a specific depth

Co= amount of N added

B = rate of nitrification

K = proportionality constant of uptake versus Co

b = water content at a specific depth

qo= soil water content

x = depth in cm
The plant uptake curve for N by corn (2) was used to determine
the amount of N03 removed from the soil each day. The first
50 days the uptake follows the curve expressed by the follow-

ing equation:

36

y = .3e X/lO-l [2]
where

x = number of days

y = amount of uptake
The uptake from 50-60 days was expressed as:

y = x-l [3]
and from 60-120 days as:

y = 13.75 + .75x. [4]
The uptake was then determined according to the % root bio-
mass in each 15 cm increment of soil. The root biomass data
was obtained from work by Foth (20). The root biomass distri-
bution varies with time requiring recalculation of the root
distribution each day. The evapotranspiration parameter was
computed as an effective evapotranspiration percentage based
on pan evaporation in corn (37). The % evapotranspiration
loss from each layer was computed from the root biomass in
each layer and the total loss each day. Denitrification was
assumed to be a 10% loss per layer per day. The rate of
nitrification (B in the leaching equation) was assumed to be
a unity factor of .14. The amount of NOS added to the top
120 cm of the soil due to nitrification was .16 ppm per layer
per day. The soil water content was determined at the
beginning of the study and the field capacities of the various
depths were determined from soil surveys. The water content
was adjusted each day according to evapotranspiration and the

amount of water added each day. Once the water content

exceeded the field capacity leaching was assumed to have

37

occurred and Gardner's equation was utilized. The propor-
tionality constant K was determined from the 15N data. The
data indicated that as the amount of N applied increased, the
% of N in the plant derived from the applied N increased.
The 15N data suggested-that the plants obtained the major
portion of their N from somewhere other than the spring
applied N (Table 13).

A flow chart was constructed to aid in the development
of the computer program (Figure 5). The flow chart indicated

every step needed to develop the computer program contained

in Appendix B.

Table 13. Effect of Ca(NO3)2 on the amount of total plant
N derived from applied N, Experiment 2, 1974.

 

 

 

 

Treatment Fertilizer Derived
kg N/ha Plant N
%
0 9/
50 15
100 29
200 39
400 ' 48
a/

— Values shown are means of 4 replications.

38

MAIN PROGRAM
Start

. W
Read in H20 Data and
Pan Evaporation Data

 

W
Convert Inches
to Centimeters

Read Initial NO-
for Each Depth

Adjust Surface to
Amount of Applied
Material

Initialize Soil H 0
Content of Each Layer

Read in Saturation Content
of Each Layer

Convert Inches to Centimeters

120 Day Growing Season
Using a Do Loop ' ;

 

Figure 5. Flow chart followed to develop the computer
program, 1974.

Figure 5.

39

If
Day >27

J’Yes

If
Day) 32

J'Yes

If
Day) 35

[Yes

If
Day >41

‘lYes

If
Day >49

‘lYes

If
Day 767

J/Yes

Set % Root

I

70

Subroutine

No

NO

NO

NO

NO

NO

Biomass by Depth

Determine % Root Biomass
Per Depth By Day

Set % Root

GOTO

Biomass by‘—’

Depth

Set % Root

GOTO

Biomass by '

Depth

Set % Root
Biomass by
Depth

Set % Root
Biomass by
Depth

Set % Root
Biomass by
Depth

Set % Root
Biomass by
Depth

Call Evapotranspiration

GOTO

GOTO

GOTO

GOTO

70

7O

70

70

70

7d

 

40

Call Soil Water
Subro tine f

Check for Leaching

Adjust Soil H O in
Each Deptfi I

Call Uptake

Adjust Each Layer
for Uptake and Leaching

Adjust Each Layer A
for Denitrification

Adjust Each Layer
for Nitrification

 

If Print Data___
Nitrate=0 NO ' for the Day

1' Yes

Print Message

End

Figure 5. (Cont.)

Figure 5.

(Cont.)

41

SUBROUTINE UPTAKE

Determine
Uptake %
for
Day

Adjust

Layers
for

Uptake

End

SUBROUTINE LEACHER

Determine
Amount Leached
According to
Amount of S.W.C.
and Co

End

42

SUBROUTINE SOILWATER

Check for

NOI Layer 1

 

Yes

Update Soil Water
Content
for Layer 1
Considering Rain

 

L-—-’Update Soil Water
Content ¢
for Layers 1—12

 

Check for . (Call Leacher)
No Leaching Yes iObtain Amount
Leached
End

SUBROUTINE EVPTRNS

Convert
Evapotranspiration
in Pan Figure to
Field Figure

Determine Evap. Amount
Per Layer

End
Figure 5. (Cont.)

43

The prediction of the amount of NOS-N in any given 15
cm of soil proved to be quite interesting and of value. The
data from three sampling periods shows (Figure 6) that simu-
lation can be accomplished given knowledge of the total
system. The equation of the line (y = 4.61 + .94x) and the
subsequent r value (.83) show that variation does occur be—
tween actual and simulated data. The variation at low
concentrations was caused by the lack of data available for
actual mineralization values for the specific soil depths.

The assumptions used may not be valid for all situations
and possibly not for the soil in question depending on soil
variability. Mass flow has been shown to be the major influ-
ence on NO- leaching (4), but to assume that profile saturation

3

must be established to remove N0; is erroneous. Water poten—

tials must be determined to evaluate unsaturated flow as well
as the movement of water upward due to capillarity. Root

efficiency data would also increase the efficiency of the pro-

3

biomass. Expansion of the system could be made utilizing

gram, by predicting the amount of NO utilized by a given root
different sources of N, organic matter contents and the many
transformations involved in the system.

The author feels that a simulation program concept is
essential in a modern agricultural soil testing program.
Once a complete program has been developed any soil could be
evaluated for an entire growing season. The use of a yield
model similar to that discussed earlier (Figure 3) could be

made early in the season to predict the N needs of any crop.

44

240,
220 .
200 ~
I80 -

-N/h0

I60 ~

Kg N03
3
0

I20"
I00-

80"
60.;-

     

y= 4.6I+.94 X
’r=.83

SIMULATED

40-
20 - “a

 

I... .1 l . l l 1 J l 1 J l l I
O0 20 4O 60 80 I00 l20 I40 |60 |80 200 220 240
ACTUAL Kg NOg-N/ho

Figure 6. Simulation versus actual NOS-N data, 1974.

CHAPTER V

SUMMARY AND CONCLUSIONS

Field experiments were conducted in 1973 and 1974.

The initial N experiment was conducted on a Hodunk sandy loam
soil. The experimental site had had no N fertilizer applied
in recent years and was ideal for the study. Four rates of

N (0, 100, 200, 400 kg/ha) were broadcast as urea. The
experiment was conducted in an effort to determine the opti-
mum rate of N application in corn. Leaching characteristics
and a yield prediction model for corn based on NOS-N were
also included.

Several areas of significance developed from the
study. Significant yield responses were found as N applica-
tions reached 200 kg/ha. The application of N greater than
200 kg/ha did not increase corn yields. Profile distribution

of NO3 indicated that the application of N greater than 200
kg/ha was a potential environmental pollutant. The data
revealed that severe leaching occurred during the winter, and
not during the growing season. Soils similar.to those used
in this experiment must be monitored carefully to avoid
excessive N applications and leaching losses. The NHZ-N data

showed nitrification of urea was not as rapid as previously

thought. The application of 400 kg N/ha as urea also

45

46

magnified the acidification properties of the N carrier.
The pH of the soil was lowered to such an extent (6.0-4.3)
that nitrification was inhibited.

The experiment also indicated that a yield prediction
model based on soil test NOS-N was feasible. The soil test
NOS-N to a depth of 90 cm was found to give the best results
in relation to the observed corn yields. The total NOS-N in
90 cm corresponding to the highest yield was 75.8 ppm. This
level of NOS-N was determined 45 days after applying 200 kg
N/ha. The yield obtained suggested that an optimum NOS—N
content in the soil can be determined to predict the N
requirements of corn.

The data from the following spring disclosed that
minimum levels of N0; persist in the soil following winter
leaching and denitrification.

The second experiment was conducted on a Metea fine
sandy loam. The application of 1000 kg urea/ha served as a
residual N load in 1974. Five rates of N (0, 50, 100, 200,

400 kg/ha were broadcast as Ca(NO in association with 1%

3’2
atom excess 15N as K15N03. The experiment indicated that
residual N0; levels are of little value when trying to pre-
dict corn yields. Once again, the optimum time for determin-
ing the amount of NOS-N appeared to be 45 days after the
application of N. The maximum yield occurred when the NOS-N
content was 81.5 ppm. The work from Experiment 1 and 2
suggested that an optimum range does occur at the most active

time of N uptake by corn. The range appeared to be from

47

75-85 ppm. The yield model established in 1973 predicted
greater yields than were obtained in 1974. The model did
predict that the highest yield would occur where the greatest
total plant N occurred, however. The experiment showed that
the additional application of N did not affect the organic

15N indicated that given suffi-

soil N. The limited use of
cient amounts of soil N, corn utilizes more fertilizer N as

the amount of fertilizer N increased, even though the total
plant N was similar for all treatments.

The leaching patterns observed in 1974 showed that some
leaching occurred during the growing season but that the major
loss of N0; occurred during the winter and early spring.

The simulation model showed that a computer program can
be developed which will predict the NOS-N status of a soil
any time during the growing season. Agreement between simula-
tion data and field data was best when N applications were
greater than 100 kg/ha. The variation of points at the low
end of the simulation curve (Figure 6) indicated that work
must be done to evaluate the mineralization potential of the
soil. The model could also be utilized to a greater extent
if the rate of nitrification were known for specific soils.
Several refinements must be made in the model, but the data
disclosed that a computer simulation program predicting N0;
leaching was a workable concept. The values determined by

the computer could be used to make yield predictions based

on the yield model discussed previously.

48

The computer program simulation concept should involve
team research. The work of the soil physicist dealing with
water potentials and unsaturated flow must be considered.
Research should be conducted which determines the rate of
water movement with varying intensities of rain or irrigation.
An active leaching solution must be obtained as a function of
applied water. Plant physiologists must work in this area
to formulate the efficiency of roots exposed to various
nutrient concentrations. Their work should also include the
efficiency with varying degrees of root distribution. The
prediction of a realistic amount of nutrient uptake from
specific root distribution at a specific depth would be
invaluable in simulation work.

Several conclusions can be made from the work dis-
cussed: 1) Soil test NO--N can be used to predict corn yields;

3
2) the application of greater than 200 kg N/ha may be an

3-

optimum 30-45 days after corn emergence; 4) the application

environmental pollutant; 3) 75-85 ppm NO N in the soil is

of high rates of N to poorly buffered soils may reduce the pH

to such an extent that other nutrients are influenced; 5) a

computer program simulation can be developed to predict NO3

leaching; and 6) leaching of NO3

occurs mainly during the

winter and early Spring.

APPENDIX A

DATA

49

 

 

 

Table A.l. EffectIOf urea on % moisture, NHZ-N and
NOS-N, July 9, 1973.
Treatment Depth Moisture NHZ-N NOS-N
kg N/ha cm % ppm ppm
0 0-15 7.1 5.7 12.8
15-30 5.8 6.3 10.1
30-45 9.1 3.7 5.0
45-60 9.4 3.7 3.3
60-75 11.6 2.8 5.5
75-90 13.3 2.6 3.5
90-120 13.0 2.9 3.6
120-150 13.1 2.7 3.5
100 0-15 8.4 7.9 17.6
15-30 9.2 7.8 7.0
30-45 9.7 6.9 4.3
45-60 10.0 7.9 3.8
60-75 11.2 5.4 4.4
75-90 12.4 6.1 4.8
90-120 13.3 3.8 3.9
120-150 13.0 2.4 3.0
200 0-15 7.6 9.4 28.5
15-30 7.8 10.4 22.7
30-45 8.9 6.2 5.9
45-60 9.1 5.0 6.2
60-75 10.0 3.1 6.2
75-90 12.6 4.9 6.3
90-120 13.2 3.8 5.8
120-150 13.0 2.3 3.5
400 0-15 9.1 23.7 56.9
15-30 8.6 14.0 38.2
30—45 9.3 9.8 8.0
45-60 10.2 8.2 7.2
60-75 11.0 5.3 6.6
75-90 12.3 8.1 9.0
90-120 13.2 6.5 9.0
120-150 13.3 4.1 5.1
L.S.D. .05 (Depth) .8 n.s. 4.4
.05 (Treatment) n.s. n.s. 3.6
.05 (Depth within
treatment) n.s. 14.0 13.9
.05 (Treatment
within Depth) n.s. 28.1 21.3

 

50

. +
Effect of urea on % mOisture, NH4-

NOS-N, September 25, 1973.

Table A.2. N and

 

 

Treatment. Depth. Moisture NHZ-N NO--N

kg N/ha

CIT!

PPm

PPm

 

100

200

400

0-15
15-30
30-45
45-60
60-75
75-90
90-120

120-150

0-15
15-30
30-45
45-60
60-75
75-90
90-120

120-150

0-15
15-30
30-45
45-60
60-75
75-90
90-120

120-150

0-15
15-30
30-45
45-60
60-75
75-90
90-120

120-150

HF-P‘
LUUJO\O\HmO\m
OPQGDmFdOMQ\J

Ht-k‘

panopmcnoxmcn
O O

~4Khhh-ounhaq

HOKOKDkOkD
OQO‘UJNUJNN

Hr-PJH
pan

t-uahnbrahuytn

I—‘HQNU'IUJ-bq
O O O O O O .0 O
\OQOQUJO’NKDKO \OI—‘QWUUNNU‘I

Ht-

LflNNWLflbI—‘O
o o o o o o o o

UlI—‘umell—‘le

:bONI-‘prU'lO‘UI
O O O O O O O O
cowoqwmxow

I-'
wmwwwmoow 60.5.5004:qu
O O O O O O O C O C O O O I O
I-‘I-‘QU'lmubChKO \DNADVWWUT

NU‘I

Hk-F'
upmrac>oxo~1m

I C O O
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0‘
N
.b

56.3

Ht-
Pan
mcn

I-‘
moooq
O O O

O‘Nubxl

L.S.D. .05 (Depth) 1.5

.05 (Depth within n.s.
treatment)

.05 (Treatment n.s.

within Depth)

Stu
O O
mro
OCh
O O
oxm

('4
\l
(I)

n.s.

 

51

. +
Table A.3. Effect of urea on % mOisture, NH -N and

 

 

 

NOS-N, May 14, 1974. 4
Treatment Depth Moisture } NHZ-N NOS-N

kg N/ha cm % ppm ppm
0 0-15 12.5 7.7 7.2
15-30 12.6 5.8 4.2
30-45 11.3 4.1 2.0
45-60 11.8 3.4 2.9
60-75 13.2 3.1 2.8
75-90 14.0 3.1 3.0
90-120 12.3 1.5 1.4
120-150 13.6 4.2 1.2
150-180 13.2 1.2 2.3
0-15 12.9 5.5 7.8
15-30 12.8 5.0 6.5
30-45 11.7 2.8 4.0
45-60 12.4 2.4 2.7
60-75 13.6 3.2 1.9
75-90 14.9 2.0 1.9
90-120 15.5 1.3 2.4
120-150 14.9 1.0 1.6
150-180 14.8 3.1 1.0
0-15 13.1 7.9 6.2
15-30 12.3 5.5 4.8
30-45 11.5 3.6 3.1
45-60 12.8 2.4 3.4
60-75 14.3 ' 5.2 4.7
75-90 14.9 2.7 3.4
90-120 15.0 3.1 3.6
120-150 14.3 1.6 1.7
150-180 14.5 4.1 1.8
0-15 12.3 8.2 6.5
15-30 12.3 6.1 5.5
30-45 10.2 3.7 5.2
45-60 12.0 3.4 8.6
60-75 14.6 2.6 9.2
75-90 16.1 2.3 10.5
90-120 15.2 3.1 10.0
120-150 14.9 2.5 3.3
150-180 16.1 2.6 4.6
.05 (Depth) .9 1.4 2.0

 

52

 

 

 

Table A.4. Effect of Ca(NO3)2 on % moisture, NHz-N and
NO3-N, May 24, 1974.

Treatment Depth _ . Moisture NHI-N NOS-N
kg N/ha cm % ppm ppm
0 0-15 7.8 11.6 5.7
15-30 8.6 10.0 6.6

30-45 7.6 7.1 7.3

45-60 8.9 2.9 11.1

60-75 11.2 2.9 12.6

75-90 13.0 2.9 14.4

90-120 13.8 3.7 11.5

120-150 14.6 2.9 8.2

50 0-15 7.9 4.7 4.6
15-30 8.2 6.2 5.4

30-45 8.1 3.4 5.5

45-60 10.0 5.0 8.5

60-75 11.8 2.4 10.1

75-90 * 13.4 4.0 8.4

90-120 12.6 4.1 7.0

120-150 12.2 3.2 5.0

100 0-15 7.0 4.9 6.3
15-30 7.5 6.5 6.4

30-45 7.9 5.0 6.9

45-60 9.6 5.8 11.3

60—75 12.8 3.3 12.6

75-90 11.9 5.0 10.3

90-120 12.2 5.1 8.8

120-150 12.2 3.6 5.3

200 0-15 7 6 8.0 6.6
15-30 8.5 9.1 8.9

30-45 7.9 6.9 8.4

45-60 11.4_ 5.4 10.2

60-75 12.3 8.3 12.8

75-90 12.8 4.0 9.3

90-120 12.4 4.2 6.8

120-150 11.3 5.2 5.7

400 0-15 7.1 5.7 4.1
15-30 7.3 4.7 4.4

30-45 7.3 4.2 4.0

45-60 10.0 5.9 8.1

60-75 11.8 5.3 11.7

75-90 12.4 5.3 14.1

90—120 12.4 4.9 10.6

120-150 11.8 4.3 9.4

L.S.D. .05 (Depth) .8 n s. 2.0

 

53

 

 

 

Table A.5. Effect of Ca(NO3)2 on % moisture, NHZ-N and
NOS-N, July 8, 1974.

Treatment Depth Moisture NEE-N NOS-N
kg N/ha cm % ppm PPm
0 0-15 7.8 6.3 14.0
15-30 7.8 5.3 6.1

30-45 6.9 3.5 3.4

45-60 8.4 1.2 5.1

60-75 10.1 1.7 9.8

75-90 11.3 4.9 13.4

90-120 12.0 5.1 9.8

50 0-15 7.2 8.9 25.5
15-30 6.7 6.7 12.0

20-45 6.9 5.3 7.1

45-60 9.2 5.9 10.9

60-75 11.3 6.2 13.9

75-90 12.4 6.4 12.1

90-120 12.1 6.0 9.9

100 0-15 4.1 7.4 32.9
15-30 6.4 5.4 23.0

30-45 7.7 3.8 11.7

45-60 9.5 2.7 11.6

60-75 11.0 3.8 12.5

75-90 11.1 2.9 10.4

90-120 12.3 4.3 7.2

200 0-15 8.2 8.8 62.2
15-30 7.5 5.9 34.4

30-45 8.3 . 3.6 13.8

45-60 9.6 3.8 13.5

60-75 11.0 3.9 14.5

75-90 12.0 3.0 14.6

90-120 12.6 3.7 7.1

400 0-15 10.2 7.4 111.7
15-30 7.3 6.2 39.4

30-45 8.5 2.4 14.5

45-60 11.1 3.2 18.3

60-75 11.0 3.5 21.9

75-90 11.6 5.7 17.6

90-120 12.1 4.7 11.8

L.S.D. .05 (Depth) 1.1 1.6 7.0
.05 (Treatment) n.s. n.s. 6.4

.05 (Depth within n.s. n.s. 15.7

treatment)
.05 (Treatment n s. n.s. 24.5

within Depth)

 

54

Table A.6. Effect of Ca(NO3)2 on % moisture, NH+-N and

 

 

 

NOE-N, September 26, 1974. 4
Treatment Depth Moisture NHZ-N NOS-N
kg N/ha cm % ppm ppm
0 0-15 11.8 4.3 6.0

15-30 10.6 8.5 4.0

30—45 8.7 7.8 3.5

45-60 8.4 2.6 1.6

60-75 11.4 7.6 4.1

75-90 11.5 6.3 6.2

90-120 11.7 9.9 9.8

120-150 12.7 5.8 6.8

50 0-15 11.8 4.6 4.4

15—30 11.3 4.9 7.5

30-45 9.2 6.6 2.6

45-60 9.2 5.3 1.5

60-75 10.7 2.1 3.5

75-90 11.8 4.1 9.2

90-120 11.6 6.6 5.2

120-150 14.3 2.2 6.7

100 0-15 10.7 4.1 3.8

15-30 9.9 6 2 10.2

30-45 9.8 6.5 9.3

45-60 9.9 1.3 5.6

60-75 9.9 2.6 4.7

75-90 10.1 2.1 7.9

90-120 11.3 3.8 7.2

120-150 12.6 6.0 11.2

200 0-15 9.5 7.6 24.3

15-30 10.0 7.6 37.9

30-45 10.4 9.2 19.8

45-60 10.1 4.9 23.8

60-75 9.5 3.1 10.3

75-90 10.3 15.1 18.0

90-120 11.8 5.3 8.5

120-150 12.5 2.5 7.1

'400 0-15 12.1 6.0 9.8

15-30 10.8 8.8 54.7

30-45 8.9 3.2 29.9

45-60 10.9 5.9 21.3

60-75 12.6 5.4 21.3

75-90 13.7 8.0 9.5

90-120 13.2 15.1 27.3

120-150 13.1 8.5 12.0

L.S.D. .05 (Depth) 1.2 n.s. 6.5

.05 (Treatment) n.s. n.s. 5.1

.05 (Depth within n.s. n.s. 14.5
treatment)

.05 (Treatment n.s. n.s. 22.1

within Depth)

 

55

 

 

 

. 4-
Table A.7. Eftect of Ca(NO3)2 on % moisture, NH4-N and
NO3-N, May 12, 1975.

Treatment Depth Moisture NHz—N NOS—N
kg N/ha cm . % ppm ppm
0 0-15 11.8 7.4 5.4
15-30 12.0 3.4 1.0

30—45 12.8 1.7 4.1

45-60 13.6 6.2 1.0

60-75 14.0 2.7 1.4

75-90 16.0 1.0 3.3

90-120 14.4 2.8 1.7

120-150 13.8 1.0 3.8

150-180 14.9 3.7 1.0

180-210 14.7 3.2 1.0

210-240 15.8 1.0 1.1

240-270 16.0 4.3 1.0 '

50 0-15 11.1 9.7 6.4
15-30 13.3 5.5 7.2

30-45 12.1 3.0 1.0

45-60 11.9 7.5 3.8

60-75 11.7 4.5 3.8

75-90 11.7 1.7 1.7

90-120 14.0 6.2 1.4

120-150 17.1 7.6 7.5

150-180 14.2 1.0 4.4

180—210 13.6 1.0 4.1

210-240 15.6 1.4 6.7

240-270 14.5 3.1 2.1

100 0-15 11.5 6.7 1.4
15-30 12.2 4.7 1.0

30-45 13.4 3.4 1.0

45-60 14.1 2.8 1.0

60-75 14.8 1.0 3.5

75-90 16.1 2.1 7.1

90-120 12.3 9.1 5.5

120-150 14.2 1.1 7.4

150-180 12.3 2.3 1.0

180-210 10.6 1.7 1.0

210-240 11.3' 2.3 1.0

240-270 11.7 1.0 1.0

200 0-15 12.4 1.4 1.0
15—30 13.4 6.2 1.4

30-45 11.7 3.3 3.3

45-60 14.8 1.0 1.3

60—75 13.0 2.7 1.0

75-90 14.3 1.7 1.0

90-120 14.9 1.4 2.7

120-150 12.9 1.4 1.4

150-180 21.3 9.4 1.1

180-210 15.2 1.1 1.0

210-240 8.2 1.0 1.0

240-270 35.4 3.6 1.0

400 0-15 11.7 3.4 1.3
15-30 12.2 2.4 1.0

30-45 13.0 1.3 1.0

45-60 13.2 1.4 2.0

60-75 14.4 4.5 1.0

75-90 14.9 3.8 3.2

90-120 14.3 2.2 1.7

120-150 14.7 2.1 1.0

150-180 14.3 3.1 5.9

180-210 14.1 1.0 3.8

210-240 13.8 1.0 5.0

240-270 12.8 3.5 2.8

L.S.D. .05 (Depth) 3.1 n.s. n.s

 

APPENDIX B

COMPUTER PROGRAM

CDC 6500 FT" VSQC'PSCO OPT=1 OQ/OQI75 011026.590

COMPUTER P ROGRAM

LEACH

PPOGRAH

 

09/04/79 0 A1026. 590

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56

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1

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SCILHAT

SURPOUT IVE

 

09/0k/75

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LITERATURE CITED

 

10.

ll.

LITERATURE CITED

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Aldrich, Samuel R. and Earl R. Leng. 1965. Fertilizing
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Allison, Franklin E. 1966. The fate of nitrogen applied
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Allison, Franklin E. 1965. Evaluation of incoming and
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Allison, F. E. 1955. The enigma of soil nitrogen balance
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Baird, Bruce L., J. W. Fitts and D. D. Mason. 1962. The
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Bremner, J. M. 1965a. Inorganic forms of nitrogen. 12
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Bremner, J. M. 1965b. Isotope-ratio analysis of nitrogen
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Bremner, J. M. 1965c. Total nitrogen. In "Methods of

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Carter, J. N., M. E. Jensen and S. M. Bosma. 1974.
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Derici, Mehmet Rifat. 1975. Profile distribution of
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Duffy, J., C. Chung, C. Boast and M. Franklin. 1973.

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24.

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Soil Sci. Soc. Amer. Proc. 29:405-410.

 

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