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L I B R A R Y
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This is to certify that the

thesis entitled

UTILIZATION AND LOSS OF NITROGEN
FROM AN ORGANIC SOIL PROFILE
presented by

Jerry Burt Fitts

has been accepted towards fulfillment
of the requirements for

Doctor degree in Philgsgphx

 

Major professor

 

, _ .H --.. "r.— "wow-m

ABSTRACT

UTILIZATION AND LOSS OF NITROGEN
FROM AN ORGANIC SOIL PROFILE

By

Jerry Burt Fitts

The utilization and loss of N from an organic soil profile was
studied under field and greenhouse conditions. Seven field experiments

were initiated to determine the effects of N fertilizer materials and
3-

take in lettuce, carrots and spinach grown on a Houghton muck soil.

application rates on plant tissue yield, N0 N concentration, and up-

These effects were correlated to the different climatic conditions

which affected the soil NOS-N content.

The effect of moisture (field capacity, l/Z-saturated and

saturated) and temperature (10 C and ambient) on the leaching losses

of organic-N and N03 N from a virgin muck soil was studied in the

greenhouse under various soil management regimes.
The NOS-N concentration in plant tissue increased with increasing

soil N03 N concentration for all three crops. Soil NOS-N concentration

was increased by fertilization. But increased rainfall accompanied by

a high water table reduced the soil N03 N levels especially at high

fertilization rates. This was attributed to NOS—N leaching followed

by denitrification.

Jerry Burt Fitts

Maximum plant yield was obtained with addition of 180 Kg N/ha
and in many cases higher levels suppressed yields. Fall grown spinach
contained much more NOS-N than spring grown spinach.

In the greenhouse study, the soil NOS-N content was highest in
the field capacity moisture treatment and in the ambient (28 C)
temperature treatment, indicating the more favorable climatic conditions
for the biological breakdown of organic matter to NHZ-N and its sub-
sequent oxidation to NOS-N. Soil NHZ-N content was highest in the
saturated moisture treatment and in the ambient temperature treatment,
indicating the dependence of biological nitrification upon aerobic
climatic conditions.

The leachates from the cores under the field capacity moisture
treatment and 10 C temperature treatment contained the highest NOS-N
content. This indicates that biological denitrification in the lower
profile layers is decreasing the leaching losses of NOS-N from the
soil cores which had the highest soil NOS-N content.

Adding inorganic-N fertilizer materials to the soil core sur-
face and shortening the incubation period from 21 to 4 days greatly
increased the leachate NOS-N content.

The cores under the l/Z-saturated moisture treatment and 10 C
temperature treatment leached the highest total NO—-N. This is an

3

indication that the increased soil NOS—N content of the upper layers and

the increased water content of the lower layers of the l/2-saturated
profile causes an increased loss of total NOS-N.
The leachate organic-N content was highest from the saturated

moisture treatment and ambient temperature treatment, indicating the

Jerry Burt Fitts
incomplete breakdown of organic matter to NHZ-N and reduced organic
compounds. Additions of inorganic fertilizer nitrogen and shortening

the incubation period did not change the organic-N content in the

leachate.

UTILIZATION AND LOSS OF NITROGEN

FROM AN ORGANIC SOIL PROFILE

BY

Jerry Burt Fitts

A THESIS

Submi t ted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1972

To Betsy

I dedicate this thesis to my wife. Her
love, encouragement and sacrifice made

this work possible.

11

ACKNOWLEDGMENTS

I wish to express my sincere appreciation to Drs. B. D. Knezek
and B. G. Ellis for their guidance and patience during the course of
this study, and in the thesis preparation. Their personal concern,
encouragement, and willingness to help at any time made this work
possible.

The writer is also grateful to Drs. J. M. Tiedje and H. C. Price
for their suggestions during the investigation and thesis preparation.

Appreciation is extended to Mr. Tom Rooney, Mrs. Elizabeth
Shields, and Mrs. Betsy Bricker for their efforts in laboratory and
statistical analysis of data.

A note of appreciation is extended to Dr. J. F. Davis and
Mr. R. A. Gnagey for their suggestions and help concerning the field
experiments.

To the other faculty members and fellow graduate students in
the Crop and Soil Sciences Department who assisted during this study

go my profound thanks.

iii

LIST OF TABLES . . . . .

LIST OF FIGURES . . . .

INTRODUCTION . . . .

LITERATURE REVIEW . . .

Organic Soil-Forming Factors
Organic Soil Decomposition

Soil N Accumulation .

TABLE OF

Nitrogenous Compounds and Their

The Fate of NH3 and NO
EXPERIMENTAL PROCEDURE .

Field Experiments . .
Greenhouse Experiments

RESULTS AND DISCUSSION .

Field Experiments . .
Greenhouse Experiments
Moisture Treatment

3

CONTENTS

Transformations

in an Organic Soil

Temperature Treatments

Regimes . . . . .
SUMMARY AND CONCLUSIONS

Field Experiments . .
Greenhouse Experiments

LITERATURE CITED . . . .

APPENDIX . . . . . . . .

iv

Page

vii

w

P‘P‘
a~c>a>u1ua

20
23

25
25
47
47
57
66
75

75
75

78

85

LIST OF TABLES

Table Page
1. Chemical Composition of Peat Waters . . . . . . . . . . . . 6

2. Redox Potential and 02 Diffusion Rates at the
Surface of a Muck Soil as Affected by Temperature
and Moisture Levels after Evaporation Regime . . . . . . 54

3. Nitrogen Content of H O Leached Through a Muck
Profile as Affected by Temperature, Moisture
Level, and Regime Prior to N Fertilization . . . . . . . 67

4. Nitrogen Leached from a Muck Profile as Affected
by Temperature, Moisture Level, and Regime
Prior to N Fertilization . . . . . . . . . . . . . . . . 69

5. Nitrogen Content of H20 Leached Through a Muck
Profile as Affected by Temperature, Moisture
Level, and Regime . . . . . . . . . . . . . . . . . . . . 71

6. Nitrogen Leached from a Muck Profile as Affected
by Temperature, Moisture Level, and Regime . . . . . . . 73

1A. Carrot Yield and Tissue NOS-N Content as Affected
by N Rate and Sampling Date (1969) . . . . . . . . . . . 85

2A. Lettuce Tissue NOS-N Content as Affected by
N Rate (1969). o s o s s o o o s o o o o o s o o s a o o 86

3A. Spinach Yield and Tissue NOB-N Content as Affected
by N Rate (1969) o o s o s o o s s o o o s o o s o a o 87

4A. Spinach Yield and Tissue NO -N Content as Affected
by N Rates and Carriers (I969) . . . . . . . . . . . . 88

5A. Spinach Tissue NO -N Content and Soil NOS-N Content
as Affected by N Rates, Sampling Dates, and
$011 Depths (1970) O O O O O O O O O I O O O O O O O O O 89

6A. Spinach Tissue NOS-N Content, Yield, and 3011

NO3-N Content as Affected by N Rates, Sampling
Dates, and Soil Depths (Spring 1971). . . . . . . . . . 90

V

Table

7A.

9A.

10A.

11A.

Spinach Tissue NO--N Content, Yield, and Soil
NO -N Content as Affected by N Rates,
Sampling Dates, and Soil Depths (Fall 1971)

. Soil NOS-N and NHZ-N Contents from Greenhouse

Experiment, Prior to Applying N Fertilizer,

as Related to Temperature, Moisture, and

$011 Depth 0 I O O I O O O O O O O O O 0
Analysis of Varience for Table 2 . . . . . .
Analysis of Varience for Table 3 . . . . . .

Analysis of Varience for Table 5 . . . . . .

vi

Page

91

92
93
93

94

LIST OF FIGURES

Figure

1. Carrot NOS-N Content and Yield as Affected by N
Application Rates (1969) . . . . . . . . . . . .

2. Head Lettuce and Spinach Leaf NOS-N Content as
Affected by N Application Rates . . . . . . . . . . .

3. Leaf NOS-N Content and Yield of Spinach as
Affected by N Rates (1969). . . . . . . . . . .

4. Leaf NOS-N Content and Yield of Spinach as
Affected by N Rates (1969). . . . . . . . . . . . . .

5. Water Loss and Gain and Mean Temperature for
1969 O O O O O O O O O I O O O O I I O O O

6. Water Loss and Gain and Mean Temperature for
1970 O O O O O O O O O O O O O O O O O O O I O O

7. Soil NOS-N Content as Related to Sampling Date
and Application Rates . . . . . . . . . . . . . .

8. Soil NOS-N Content as Related to Sampling Date
and $011 Depth 0 O O O O O I O O O I O O O O O O O O

9. Leaf and Stem NO -N and Yields of Spinach as
Affected by N Rates (Spring 1971) . . . . . . . . . .

10. Leaf NOS-N Content, Sampled at Different Dates,
and Yield of Spinach as Affected by N Rates
(Fall 1971) O I O O O O O O O O O O O O I O O O

11. Soil NOS-N Content as Related to Sampling Dates
and N Rates 0 O O O O O O O O O O O O O O O O O O O O

12. Soil NO--N Content as Related to Sampling Dates
and 8011 Depth 0 O O I O O O O O O O O O O O I 0 0 O

13. Water Loss and Gain and Mean Temperature for 1971 . . .

vii

Page

26

28

3O

31

32

35

36

37

39

4O

42

43

44

Figure Page

14. NOS-N Content of Water Leached Through a Muck
Profile as Affected by Regimes and Moisture
Treatments 0 O O O C O C C O O O O O C C O O O O O O O O 48

15. Organic-N Content of Water Leached Through a
Muck Profile as Affected by Regimes and
Moisture Treatment . . . . . . . . . . . . . . . . . . . 49

16. Soil NHZ-N Content as Affected by Soil Depth
and Moisture Treatment . . . . . . . . . . . . . . . . . 51

17. Soil NOS-N Content as Affected by Soil Depth
and Moisture Treatment . . . . . . . . . . . . . . . . . 52

18. NO--N Leached from a Muck Profile as Affected
6y Regime and Moisture Treatment . . . . . . . . . . . . 53

19. Organic-N Leached from a Muck Profile as
Affected by Regime and Moisture Treatment . . . . . . . . 58

20. NO--N Content of Water Leached Through a Muck
grofile as Affected by Regime and Temperature
Treatment 0 I O O O O O O O O O O O O O O O O O O O O O O 59

21. Organic-N Content of Water Leached Through a
Muck Profile as Affected by Regimes and
Temperature Treatment . . . . . . . . . . . . . . . . . . 61

22. Soil NOS-N Content as Affected by Soil Depth
and Temperature Treatment . . . . . . . . . . . . . . . . 62

23. Soil NHz-N Content as Affected by Soil Depth
and Temperature Treatment . . . . . . . . . . . . . . . . 62

24. NOS-N Leached from a Muck Profile as Affected
by Regime and Temperature Treatment . . . . . . . . . . . 64

25. Organic-N Leached from a Muck Profile as Affected
by Regime and Temperature Treatment . . . . . . . . . . . 65

viii

INTRODUCTION

The element nitrogen (N) makes up approximately 0.03% of the
earth's crust and atmosphere (Sisler, VanderWerf, and Davidson, 1961).
Of this amount, 97.82% is found in fundamental rocks, 1.96% in the
atmosphere, and 0.2% in ancient sedimentary rock. Negligible amounts
are found in terrestrial humus, sea-bottom organic compounds, and
living organisms (Stevenson, 1965).

Julius von Sacks (1860) was the first to recognize that N
was necessary for plant growth. In a table of relative number of atoms
of essential elements in alfalfa, N is at the top of the list of those
elements that come from the soil or fertilizers, and is exceeded only
by hydrogen (H), carbon (C), and oxygen (0), all of which the plant
obtains from the atmosphere (Viets, 1961).

In soil-plant nutrition relations, N is unique. Too little N
limits yield and reduces quality. Worldwide, more crops are deficient
in N than any other nutrient. 0n the other hand, too much N can lower
yield, reduce quality, cause lodging, and can make forage toxic to
animals (Viets, 1965).

Recently, Kohl, Sheaver, and Commoner (1971) have presented
evidence indicating that fertilizer N is a major pollutant in the
nation's waterways, and have raised the question of the effect on

public health concerning excess N, in the form of nitrate (N03),

2

in these waters. In at least one state, regulations on the rate and
method of applying fertilizers have been proposed.1

In Michigan, for 1969-71, a yearly average of approximately
110,169 metric tons of N was applied to agricultural crOps. Fresh and
processed vegetables and potatoes received an average of 112 and 168
kilograms of N per hectare (Kg N/ha) respectively.2 In an extension
study in 1971, it was found that fresh market celery grown on organic
soils received from 168 to 269 Kg N/ha.3

This thesis reports the utilization and loss of N from an

organic soil profile under different field and greenhouse conditions.

 

1Controversy builds over fertilizer runoff. Chem. & Eng. News
Jan. 10, 1972. p. 17-18.

2Data from the Crop Reporting Service and the Michigan Depart-
ment of Agriculture.

3Fitts, J. B. The Nitrate Electrode: Its Use in Soil and
Plant Tissue Tests. 1971.

LITERATURE REVIEW

Organic Soil-Forming Factors

 

An organic soil, sometimes referred to as peat or muck, is
defined as a soil containing 20 to 30% or more organic matter, one
foot or more in depth. It is formed under water or during cool, wet
climatic conditions.

There are approximately 4.5 million acres of organic soils in
Michigan, an area equal in size to the state of New Jersey. Less than
5% of this acreage is presently farmed, although many of these soils
are suited for agricultural purposes and can be developed.

Climate, vegetation and parent material are the factors active
in the development process, called paludification, of an organic soil.

Glaciation is the most important climatic agent in the paludifi-
cation process. Three types of distribution patterns of organic soils
can be attributed to glacial action.

(A) Dendritic.--This group includes organic soil formed in
glacial beds, small depressions and low areas. An example is the
St. Johns area in Clinton County, Michigan.

(B) Lake Bed.--Re1ative1y large continuous areas were formed
as a result of filling in of a shallow lake. The Gun Swamp area in

Allegan County, Michigan is an example of this type.

4

(C) Tilting of the Earth's Surface.--An early outlet of the
Grand River in the vicinity of Grand Rapids, Michigan was closed be-
cause of tilting of the land surface, and a new channel was developed
to Grand Haven, Michigan. A large acreage of organic soils was formed
in this abandoned channel.

The type of vegetation also plays an important role in paludifi-
cation. The different plant associations which led to the organic
soil formation can be divided into four groups.

(A) B23§.--These peat soils are formed from acid tolerant plants

from the genera including Chamaedophne (leatherleaf), Vacinium

 

(blueberry), Ledum (Labrador-tea), Andromeda (bog-rosemary), Oxycoccus
(cranberry), Ericaceae (heath), and Sphagnum (moss).
(B) Marsh.--This group includes: Typha (cattails), Juncus

(rushs), Phragmites (reeds), Carex (sedges), and several genera of

 

grasses.

(C) Forest or Swamngeat.--Woody plants comprise this group.
Included are: La£i§_(tamarack), £1223 (spruce), Fraxinus (ash),
Ulmug (elm), éEEE (maple), Populus (poplar and aspen), Betula (birch),
Almug (alder), §211£.(W111°W) and others with an admixture of Calluna
(heather), Oxycoccus (cranberry), Andromeda (bog—rosemary),_ga£gx

(sedge), and Phragmites (sedge).

 

(D) Aquatic or Sedimentary Peat.--This group includes organic

 

 

matter from algae, Potamogeton (pondweed), Nymphaea (waterlily), and
other water plantain (Davis and Lucas, 1959).
Water has been referred to as the parent material of organic

soils. Weber (1903) pointed out that the mineral content of water

5
associated with paludification and plant associations determine the
organic soil properties. Based on the water mineral content, three
types of peat are recognized. (Table l.)

l. Eutrophic. The water associated in this soil group is high
in mineral nutrients, especially phosphorus (P), calcium (Ca), and
magnesium (Mg). This permits plants to grow that require relatively
high fertility levels.

2. Oligotrophic. This organic soil group formed under water
that is low in plant nutrients, thus restricting the plants to those
requiring low fertility.

3. Mesotrophic. This soil group is in between the eutrophic
and oligotrophic groups.

The organic soils which are agriculturally developed in Michigan
belong to the marsh plant association and the eutrOphic water parent
material. The classification of the organic soil which will be con-
sidered in this thesis is a Houghton muck. The 0-15 cm layer is fibrous
material, being developed from marsh plant association. The 15-107 cm
layer is finely fibrous and is a dark brownish yellow in color. The
overall soil profile ranges from 3 to 6 m in depth, and the pH range

is 6.0 to 6.4 (Davis and Lucas, 1959).

Organic Soil Decomposition

 

Decomposition of an organic deposit takes place even though the
peat may be submerged for indefinite periods in water and is completely
cut off from air. Under these conditions, the original cellulose

softens and the lignins turn yellow. These changes are probably due

Table l.--Chemical composition of peat waters.*

 

 

Highmoor or Transition or Lowmoor or

Constituent Oligotrophic mesotrOphic eutrOphic
peats peats peats

mg/l

Organic matter 249.2 73.7 170.5
Ignition residue 23.8 73.2 141.9
Nitrogen 3.6 2.5 2.7
CaO 1.6 22.7 58.7
MgO 0.6 3.9 9.2
K20 4.4 2.7 3.9
Na20 4.5 6.2 8.0
P205 0.6 1 0 1 3
$03 0.9 15.9 3.0
Fe203-A1203 0.5 5.2 6.0
8102 9.1 13.2 4.4
Cl 12.3 6.6 11.3

 

*Weber (1903).

7
to hydrolysis and decomposition by anaerobic organisms. This decom—
position is termed "dy formation."

When the organic material is exposed to air, a different decom-
position process, humification, takes place. The lignin, cellulose,
other carbohydrates and proteins are oxidized at different rates to
form humus. During humification the C:N ratio is reduced. When dy
is formed, the C:N ratio is not significantly changed. Peats, which
have been drained either naturally or artificially, show the humifica~
tion process best. Maximum humification takes place at the surface
with the maximum dy formation occurring below the permanent water
table, with a transition zone lying in between (Davis and Lucas,
1959).

Microorganisms play a very important role in the organic soil
decomposition. Waksman (1942) has stated that microbes contribute to
the chemical transformations leading to soil development and decomposi-
tion in at least three ways.

First during the early stages of plant residue decomposition,
certain groups, mainly fungi and actinomycetes on the soil surface
and bacteria below the surface, decompose cellulose, hemicellulose,
and some proteins.

Second, after the initial decomposition, facultative and obliga-
tive anaerobic bacteria further decompose the celluloses, proteins, and
other complexes. Major characteristics of this anaerobic decomposition
are:

l. Incomplete breakdown of substrate into organic acids, and

methane, H2 and 002 gases with low energy yield.

8

2. Inefficient assimilation of substrate carbon, with only
2 to 5% being incorporated into microbial tissue compared to 20-40%
assimilation in the third group below.

3. Low N requirement leading to a net accumulation of ammonium
(NHZ) in the soil (Patrick and Mikkelsen, 1971).

Thirdly, when an organic soil is drained and air is admitted,
fungi, aerobic bacteria, and actinomycetes become active in the decom-
position of the more resistant organic complexes, such as lignins.
These organisms are responsible for the biological oxidation or sub-
sidence of an organic soil. The final end products of decomposition
include: 002, H20, N03, sulfates (80:), and Other minerals.

Waksman and Stevens (1929) have reported that in high-lime peats
(pH 4.6 or above), the aerobic bacteria population diminished rapidly
with increasing soil depth. The anearobic bacteria population, however,

increased with soil depth.

Soil N Accumulation

 

Soil N may be represented diagrammatically as two opposing pro—
cesses, incoming and outgoing (Allison, 1965). Incoming processes that
were important for soil N accumulation include: biological fixation,
both symbiotic and non-symbiotic, of atmospheric N; atmospheric pre—
cipitation; and N leached from surrounding upland soils. Of these
three processes, biological fixation of atmospheric N is probably the
most important N source (Davis and Lucas, 1959; Stevenson, 1965).

Under a natural ecosystem, the soil N content approaches an

equilibrium value. The magnitude of this value depends upon several

9
factors: climate, vegetation, topography, physical characteristics
of the soil, and the activities of the microflora and microfauna
organisms. Of these factors, the soil microorganisms are the most
important in soil N accumulation. Soil N can be maintained at high
levels only when microbial activity is arrested during some period of
the year. Three factors (restricted drainage, low pH, and low tempera-
tures) are most important in restricting microbial (decomposition)
activities (Stevenson, 1965).

Using the formation of NOS-N as an indicator of organic soil
decomposition, the effects of these three factors can be seen.

Waksman and Purvis (1932) in a laboratory study using 20 g soil
samples having 67,200, and 300 percent moisture, obtained 22, 1.7, and
1.0 mg NOS-N respectively after a 20 day incubation period.

Work by Turk (1939) on two acid organic soils (pH 4.3 and 3.4)
showed that the nitrifying capacity of both soils was increased about
fourfold by liming.

Data from a Houghton muck soil showed that the NOS-N production
is related to temperature. Using an 8 week incubation period, 31 and
136 ppm NO--N were produced from 5 C and 22 C treatments, respectively.

3

One non—biological factor does influence the net release of NOS-N from
an organic soil. A low total N content, usually placed at 1.5% or
less, gives the organic soil an unfavorable C:N ratio, such that all
of the mineral N available is utilized by the microbial population,
thus there is no net accumulation of NOS-N. The total N content of

peat and muck soils varies between 0.3 and 4.0 percent. One organic

deposit 3 m in depth has been reported to contain 224 tons (m) N/ha.

10
Based on a period of 5,000 years for development, this is an average

yearly accumulation of 45 kg N/ha (Davis and Lucas, 1959).

Nitrogenous Compounds and Their Transformations
The N present in organic soils is practically all in organic

forms, although measurable quantities of NOS-N are present in drained

+

soils, and measurable quantities of NH4

may be found in flooded soils
(Davis and Lucas, 1959).

Based on the treatment of soils with hot acids, several investi-
gators have reported that 20 to 40% of the total N in most surface
soils is in the form of bound amino acids (Bremner, 1949; Cornfield,
1957; Keeney and Bremner, 1964; Kojima, 1947; Rendig, 1951; Sowden,
1956; Stevenson, 1954, 1956; Young and Mortensen, 1958). Another 5 to
10% is in the form of combined hexosamines (amino sugars), mainly
glucosamine and galactosamine (Bremner, 1958; Bremner and Shaw, 1954;
Keeney and Bremner, 1964; Sowden, 1959; Stevenson, 1957a, 1957b, 1957c).
As indicated by the present evidence, these amino acids and amino
sugars are not "free" in the soil, but their mode of linkage in soils
has not been established (Bremner, 1965, 1967).

Purine and pyrimidine derivatives have been reported, but current
evidence indicates that they account for less than 1.0% of the total N
in surface soils (Adams, Bartholomew, and Clark, 1954; Anderson, 1958,
1961). Other organic compounds containing N, such as choline, creatinine,
and allantoin, have been isolated, but there is no evidence to indicate
that these compounds contribute significantly to the total soil N

(Bremner, 1965). Identifiable (by acid hydrolysis) organic N forms

11
account for only 25 to 50% of the total N in organic soils, leaving a
substantial balance, including minor forms, of 45 to 70% unidentified
(Black, 1968).

Two terms are commonly used to describe soil N transformations:
N mineralization, and N immobilization. Mineralization refers to the
change of organic-N to mineral-N forms without distinction among the
several forms of mineral-N as end products. Immobilization refers to
the change of mineral-N forms to organic-N forms (Black, 1968).

The first step in microbiological mineralization of organic-N
is NH: formation. This transformation is carried out by many different
organisms during organic matter decomposition, either under anaerobic
or aerobic conditions.

The decomposition rate under anaerobic conditions proceeds at
a much slower rate than under aerobic conditions. This results in a
low N requirement in anaerobic metabolism, hence lower quantities of
net N immobilization and a more rapid release of NH: to the organic
soil (Acharya, 1935a, 1935b; Karim, 1948; Patrick and Mikkelsen, 1971).

Aerobic decomposition is much more rapid and is complete to the

end products of CO H 0, etc. It is carried on by bacteria, actino-

2’ 2

mycetes, and fungi, all of which are heterotrophic (requiring an organic
source of C). The optimum moisture level for these organisms is be-
tween 50 and 75% of the soil water-holding capacity. The temperature
range is from 2-60 C with a maximum activity occurring between 40-60 C.
The total N and C content of the organic substrate is very critical

in determining whether net N immobilization or mineralization will occur.

With a natural material of approximately 40% C, the critical N content

12

is approximately 1.5%, thus giving a critical C:N ratio of 20-30:1.
Thus, in substrates such as proteins with a C:N ratio below 20:1, net
N mineralization takes place. In substrates, such as carbohydrates with
a C:N ratio greater than 30:1, net N immobilization takes place
(Alexander, 1961; Bartholomew, 1965; Black, 1968; Davis and Lucas,
1959).

Under aerobic conditions, further N transformations take place
in the process of nitrification and NH: is oxidized to nitrite (N02)

and then to N03 by two specific bacteria genera, Nitrosomonas spp.

and Nitrobacter spp., respectively. These organisms are autotrophic

 

 

utilizing CO2 as a C source, and carrying on the N transformations as a
source of energy. The critical temperature values are from 5-40 C,
with an optimum range between 30-35 C. Optimum moisture levels are

between 1/2 to 2/3 soil water-holding capacity. The formation of NH:

is not greatly affected by soil pH, but the maximum oxidation of NH:

to NO3 occurs in a pH range of 7.0 to 9.0 (Alexander, 1961, 1965;

Black, 1968).
Any change in the soil environment such as water-logging, which

prevents 02 from diffusing into the soil profile, will cause faculta-

tive anaerobic bacteria to use NO as an electron acceptor for

3
metabolic processes instead of 02. This process is termed denitrifica—
tion and involves the biological reduction of N03 to nitrous oxide

(N20) and then to N2 gases. Both of these N forms are lost from the
soil to the atmosphere by volatilization (Skerman, Lack, and Millis,
1951; Skerman and MacRae, 1957a, 1957b). The denitrifying bacteria have

an optimum.activity temperature in the range of 60-65 C (Broadbent and

13

Clark, 1965; Nommik, 1956) and are directly dependent on the soil
moisture content. Several investigators have reported increased losses
of N as a function of moisture content up to 450% of the water-holding
capacity. Also, little N loss occurs if the moisture content is less
than 60% of water-holding capacity, even when other conditions are
very favorable for denitrification (Bremner and Shaw, 1958; Jannson
and Clark, 1952; Nommik, 1956). The rate of denitrification is pro-
foundly influenced by soil pH--being very slow in acid soils, and very
rapid in soils of high pH (Bremner and Shaw, 1958; Jansson and Clark,
1952) with an optimum range between 5.5-8.0 (Alexander, 1961).

Several investigators (Allison, Carter, and Sterling, 1960;
Broadbent, 1951; Broadbent and Stojanovic, 1952; Corbet and Wooldridge,
1940) have reported the occurrence of denitrification in aerated soils

and in controlled atmospheres containing some 0 An explanation of

2.

this phenomenon is that when the demand for biological O is high, the

2

diffusion rate of O2 to the denitrifying bacteria may be limiting to

the extent that the bacteria must utilize NO3 as an electron acceptor.
This condition might occur when a readily decomposable substrate is
being rapidly decomposed, and the micro—environment of the bacteria may
essentially become anaerobic even though the soil is well aerated by
ordinary standards (Broadbent and Clark, 1965). Skerman et a1. (1951)
have reported that an organism may use two alternative respiratory
pathways at the same time, provided that conditions are satisfactory
for both.

In recent years, several investigators (Allison, 1955, 1963;

Clark, Beard, and Smith, 1960; Clark, 1962; Gerretsen and de HOOp,

14
1957; Smith and Clark, 1960; Soulides and Clark, 1958; Tyler and Broadbent,
1960; Wahhab and Uddin, 1955; Wijler and Delwiche, 1954) have reported

evidence showing that biological or dissimilatory N0; reduction does

not adequately explain all the gaseous N loss from a soil. These addi-

tional losses appear to be greater in soils in which N03 has been

observed to accumulate following the addition of NH3 or NH3 releasing

materials. Since the chemical reactions involve both N0; and nitrous
acid (HNOZ) Clark (1962) designated these losses as chemo-denitrification
or N0; dismutation. There is much disagreement as to the exact chemi-
cal pathways involved and the factors influencing these pathways. The
prOposed pathways have been extensively reviewed by Broadbent and

Clark (1965). Since there is no reported accumulation of NOE-N in an
organic soil profile, chemo-denitrification is probably of no
significance.

The Fate of Nquand N0;
in an Organic Soil

 

Ammonia (NH3) N is produced at varying rates from organic matter
decomposition or it may be applied to the soil in the form of a chemical
fertilizer. Once in the soil, it readily reacts with any proton
donating substance to form the positively charged NH: ion (Mbrtland and
Wolcott, 1965). Under conditions favorable for biological oxidation,

+ - _

NH4 is quickly oxidized to NO2 and finally to N03

02, the mineralization of N from organic matter staps with the forma-

In the absence of

tion of NH2. Under anaerobic conditions, generally caused by water-

logging or flooding the organic soil, most of the NH: is adsorbed on

the negatively charged organic complex with a small amount remaining

15
in the soil solution. The NH: in soil solution is in a dynamic equi-
librium with that adsorbed on the cation exchange complex. Any with-
drawal from the soil solution, hence immobilization of N into organic
forms, causes a movement of NH: from the exchange sites (Patrick and
Mikkelsen, 1971). In actual practice, however, mineralization generally
exceeds immobilization and there are often measurable amounts of NH+

l,
in flooded organic soils (Davis and Lucas, 1959).

4
water-logged soil, NO

Whereas NH+ is insoluble in water and is quite stable in a

3 is soluble in water and is very unstable in a
flooded soil. Because of the negative charge, there is little adsorp-
tion onto the organic complex and almost all of the NOS-N is completely
dissolved in the soil solution. Nitrate moves readily in the flooded
soil: by diffusion, as a result of a concentration gradient in the
soil solution; and by mass flow, as a result of hydraulic pressure
(Patrick and Mikkelsen, 1971).

Nitrates may be applied to a flooded soil either by chemical
fertilizers or by a biological nitrification process which occurs in
the aerobic surface layer of the soil. Nitrate which remains in this
aerobic layer is stable, but is readily lost from the soil profile if
it is leached or diffused into the underlying anaerobic layer. The
main mechanism of loss is by biological denitrification which produces
N20 or N2 gas. Nitrates in flooded soils may be immobilized by incor-
poration into plant or microbial tissue. However, the requirement of
facultative anaerobic bacteria for electron acceptors is usually much

greater than any nutritional requirement for N. Therefore, very little

NOS-N is immobilized (Patrick and Mikkelsen, 1971).

16

Unlike the flooded soil, N03 in a drained ot aerobic soil is

quite stable. With heavy chemical fertilizer applications and/or a

rapid biological mineralization process, NO3 may build up to extremely
high concentrations in the soil. Extensive biological denitrification

may also occur if anaerobic conditions prevail in the soil micro-

environments. Because N03 is completely soluble in water, it is quite

mobile in the soil. It may be taken up (immobilized) by plant roots,

or it may be leached out of the soil profile and into the drainage
waters. Nitrate may also move upward in the soil profile and accumulate
at the soil surface (Black, 1968). This is caused by the upward move-
ment of water and its subsequent evaporation at or near the soil sur-
face (Gardner, 1965).

Of particular interest is the leaching loss of NOS-N from the

soil profile and into the drainage waters. The amount of NOS-N lost

by leaching depends upon two factors: the amount of water percolating
3-

in drinking water was first associated with a

through the soil, and the NO N concentration in the water (Stewart,

3

temporary but sometimes fatal blood disease, infantile methemoglobinemia,

1970). In 1945, NO

in infants (Winton, Tardiff, and McCabe, 1971). Based upon studies
concerning this disease, the 0.8. Public Health Service considers

water containing more than 10 ppm NOS-N as unsafe for drinking purposes.

However, Navone, Harmon, and Voyles (1963) have reported that several

cities use water with considerably higher levels of NOS-N and have had

no reported cases of infantile methemoglobinemia. In addition to the

health hazard, NOS-N in streams and lakes stimulates algae growth when

other nutrients are also available. MacKenthun (1965) has reported

17
that nuisance algae blooms occur in water when N levels in the water
are as low as 0.3 ppm.

How much NOS-N is leached from an organic soil profile? Data
by Erickson and Ellis (1971) obtained in 1969 from the Michigan State
University Muck Experimental Farm shows a maximum NOS-N concentration
of 2.8 ppm and a total of 109 cm of water/ha pumped from the Houghton
muck soil. This gives a total loss of NOS-N of 18.7 Kg/ha. Unpub-
lished data from 1972 has shown that as high as 25 ppm NOS-N may be
obtained during the winter months.

Soil temperature and moisture content are the two most important
environmental factors affecting leaching losses of N. In an Israeli
study (Avnimelech, 1971) the N0; produced in an organic soil reached
an optimum at field capacity_and increased markedly between 24 and 36 C.
The values obtained at field capacity were 7 and 17 ug NOS/g of soil
per day at 24 and 36 C, respectively. These conditions increased

NO3 in the soil to extremely high levels (1,000-10,000 ug NOS/g soil)

inducing salinity problems in crOp production.

The leaching loss of NOS-N from an organic soil profile can be
greatly reduced by controlling the water table and using submerged
tile lines in the drainage system. This allows the biological denitri-
fication process to take place, thus reducing the NO--N concentration

3
(Meek, Grass, and MacKenzie, 1969; Meek et al., 1970).

Plant uptake of N is almost exclusively in the N03 form although

some species, such as rice, and the soil microbial papulation prefer

NHZ-N. Since N0; is soluble in water and is mobile in the soil solution,
all of the NOS-N in the soil profile is available for plant uptake

(Black, 1968).

18

With large concentrations of NOS-N in the soil readily available

for plant uptake, plants tend to "gorge" themselves resulting in
3-

Millar, 1953). In many plants this accelerated uptake of NOS-N may

N in plant tissue have

soluble NO N being present in excess of assimilation needs (Cook and

3-

been reported to prolong vegetative growth and to delay flowering and

be quite harmful. High concentrations of NO

fruiting or tubering. Another problem with an excessive accumulation
of NOS-N in plant tissue is the injurious effects to animals and
humans when such tissue is ingested. But the toxicity of a given

amount of NOS-N varies tremendously, and an accurate diagnosis is

often difficult.

The amount of NOS-N present in plants at any given time is

dependent upon several factors:

1. The N03 content of a soil in the rooting zone of plants.

2. The plant species being grown and its stage of development.
3. Environmental conditions.
4. Herbicidial applications.

5. Effect of the method of harvesting and storing plant material.
3-

1. There is a large amount of N03 present in the soil.

Excessive NO N accumulation occurs in the plant when:

2. Some factor interferes with the normal NO3 reduction pro-
cesses in the plant. Several of these factors include:
a. Drought
b. Hail

c. Frost

d. Disease

19
e. Herbicide applications, such as 2,4-D.
f. Day length
These increases, however, are dependent upon the availability of NOS—N
in the soil (Cantliffe, 1972; Hanway, et al., 1963).

Recently, particular concern has been directed towards the NOS-N
content in several vegetables in relation to the occurrence of
methemoglobinemia in infants under 3 months of age (Phillips, 1968).
Of the vegetables used in processed baby foods, spinach (Spinacea
oleracea L.) probably accumulates the highest NOS—N concentrations.
Spinach petioles which were purchased from several supermarkets once
weekly for several months in 1970 in the Cornell University area con-

tained NO3 N ranging from 7,500 to 22,500 ppm (dry weight basis), with

an average of 12,900 ppm.‘ Data by Barker, Peck, and MacDonald (1971)
on the accumulation of NOS-N in spinach grown on two loam soils showed
that the most efficient NOS-N accumulation occurred with the chemical
fertilizers being broadcast before planting as opposed to sidedressing
the same amount of fertilizer one week before harvesting. There was
no significant difference in the N carrier on the broadcast treatments,
but KNO3 form of N resulted in a higher accumulation of N than did
NH4NO3 or urea forms. Further work by Barker and Maynard (1971a,
1971b) shows that low and high levels of N fertilization in sand cul-
tures restricted spinach plant growth, with a lower critical level of
4000 ppm NOE—N necessary for 100% relative growth. In addition, the
level of N fertilization and the length of plant exposure to this fer-

tilization level are important factors in the NOS-N accumulation.

 

4Minotti, P. L. 1971. Unpublished data, Department of Vegetable

Craps, Cornell University.

EXPERIMENTAL PROCEDURE

Field Experiments

 

In 1969, two field experiments were initiated to determine the
effect of inorganic N fertilizer materials on the tissue yield, NOS-N
concentration, and NOS-N uptake in several vegetable crops grown on a
Houghton muck soil.

The first experiment was a randomized complete block design
replicated eight times utilizing four application rates (0, 90, 180,
and 360 Kg N/ha) of NH4NO3. A11 plots received an initial broadcast
application of 1,120 Kg/ha of an 0-10-30 +2% manganese (Mn) fertilizer
prior to planting.

In one-half of the 0.01-ha plots (four replications) carrots
(Daucus carota L. var. 'Gold Pak') were planted on May 28. The N
treatments were applied by hand in two equal applications on July 2
and July 30. The carrots were sampled, 10 roots/plot, on July 30 and
September 15, and the samples were frozen for NOS-N analysis. Yields

were determined on September 15.

In the other half of the experiment, head lettuce (Lactuca sativa L.

 

var. 'Fulton') was planted on May 28 and the N treatments were applied
by hand in one application on July 2. The head lettuce was sampled,
10 heads/plot, on July 28. The heads were cut into quarters with one
quarter/head being frozen for NOS—N analysis. Due to heavy damage by

rain, hail, and bottom rot disease, yields were not determined.

20

21
Following the head lettuce crop, the N treatments were again
applied on the same area in one application. The land was plowed to a

depth of 15 cm, and spinach (Spinacea oleracea L. var. Hybrid No. 7,

 

Northrup, King and Co.) was planted on August 6. The spinach was
sampled, 10 leaves/plot, on September 19, and the samples frozen for
NOE-N analysis. Yields were determined on September 19.

After freezing, all crops were stored in a freezer at -l7.8 C.
The samples were analyzed for NOS-N on a wet weight basis using a
modified N0; reductase enzyme procedure developed by Lowe and
Hamilton (1967). The wet weight values were then converted to a dry
weight basis. The NOS-N uptake was calculated by multiplying the dry
weight yields by the NOE-N concentrations.

The second experiment in 1969 was a randomized complete block
design replicated six times utilizing two N carriers, NH4N03 and urea,
and five application rates, 0, 56, 112, 224, and 448 Kg N/ha. All
plots received a broadcast application of 1,120 Kg/ha of an 0-10-30 +
2% Mn fertilizer prior to planting. The N treatments were applied by
hand in a single application to the 0.001-ha plots. Spinach (Spinacea
oleracea L. var. Hybrid No. 7, Northrup, King and Co.) was planted on
August 6. The spinach was sampled, 10 leaves/plot, and frozen for
NOS-N analysis on September 19. Yields were also determined on
September 19. The NOS-N analysis was the same as in the first experi-
ment.

In 1970, the first experiment was continued to determine the

effect of repeated high inorganic N fertilizer applications on the

soil and tissue NOS-N concentration, yield, and NOS-N uptake. Soil

22
samples were taken at 15, 30, 46, and 61 cm depths on July 30,
August 13, and September 10 and analyzed for NOS-N. The same basic
fertilizer and N treatments were applied to the plots prior to planting.
3-
var. Hybrid No. 7, Northrup, King and Co.) was planted on August 4'in

Because of its high NO N accumulation, spinach (Spinacea oleracea L.

 

all replications. This seeding did not result in a satisfactory crop
stand. Two replantings did not improve the stands. The spinach was

sampled, 10 leaves/plot on September 13 and analyzed for NOS-N. The

NOS-N analysis in both the muck soil and spinach tissue was carried

3
of Myers and Paul (1968) and Paul and Carlson (1968).

out potentiometrically using the NO ion specific electrode procedure
In 1971, the first experiment was again continued. Soil samples

were taken at 15, 30, 46, and 61 cm depths on May 17, July 1, July 31,

and September 7, and analyzed for NOS—N. The same basic fertilizer and

N treatments were applied to the plots prior to planting. Spinach

(Spinacea oleracea L. var. 'Nore Green', Northrup, King and Co.) was

 

planted on May 14 in 8 replications. The spinach was sampled, 10 plants/
plot, for NOS-N analysis on June 24 and July 12. Yields were deter-

mined on July 7.

The N treatments were again applied and the plots plowed to a
depth of 15 cm prior to the second planting. Spinach (Spinacea
oleracea L. var. Hybrid No. 7, Northrup, King and Co.) was planted on
August 5, using only 4 replications. The spinach was sampled, 10 leaves/
plot, for NO--N analysis on September 1, l4, and 30. Yields were

3
determined on October 10. The NO

3 N analysis was by the same procedure

used in 1970.

23

Greenhouse Experiments

 

In the fall of 1970, a 2 X 3 X 5 factorial experiment replicated
four times was initiated in the greenhouse to study the leaching losses
of organic-N and NOS-N from a virgin muck soil. Twenty-four core
samples were obtained by driving cylindrical galvanized containers
(35.6 cm in diameter and 76.2 cm in length) into a virgin muck. The
containers with the soil cores were then moved to the greenhouse where
caps were fitted and sealed on the bottom of each container. After
capping, the cores were placed upright and flooded with distilled
water for two-week incubation periods. At the completion of each two-
week period, the cores were drained by means of a plastic hose which
was attached approximately 3 cm above the bottom of the core container.
The cores were flooded again and leachate from each core for each two-
week period was subsequently analyzed for organic-N and NO--N using

3
the semi-microkjeldahl procedure of Bremmer (1965a) and the NO- ion

3
specific electrode procedure of Myers and Paul (1968), respectively.
The two-week incubation periods were continued until the NOS-N con-
centration in all 24 leachates stabilized. After this stabilization
(check) period, three moisture treatments (field capacity, one-half
saturated, and saturated) and two temperature treatments (ambient and
10 C) were initiated. The moisture level in the containers that cor-
responded to field capacity was determined during the stabilization
period by observing the water level in the plastic hose upon draining
the cores. The saturated level was maintained at the surface of the
soil core. The one-half saturated level was the difference between the

field capacity and the saturated level. The core containers maintained

under the ambient temperature treatment were randomized on a greenhouse

 

 

bench

water

follc
ethyl
sheet
as Ni
4 da)
week
drair
re-es
for c
the ]
46 cm
by ti
but v
metrj
The c
the C

were

24
bench. The containers under the 10 C treatment were randomized in two
water baths which were constantly kept at 10 C.

In addition to the stabilization (check) incubation period, the
following regimes were initiated: covering the containers with poly-
ethylene sheets to prevent evaporation, removing the polyethylene
sheets to allow evaporation, broadcasting the equivalent of 112 Kg N/ha
as NH4NO3 on the core surface, and shortening the incubation period to
4 days. The second, third, and fourth regimes consisted of four three-
week incubation periods. After each three-week period, the cores were
drained, the amount of the leachate recorded, and the moisture levels
re-established. A sample of the leachate was collected and analyzed
for organic-N and NOS-N as previously described. Prior to broadcasting
the 112 Kg N/ha, the cores were sampled at three depths (15, 30 and
+

46 cm) for NOS-N and NHZ-N content. The NH4 N analysis was accomplished

by the semi-microkjeldahl method as previously described for organic-N
3-
metrically using the N0; ion specific electrode previously described.

but without the digestion period. The NO N was carried out potentio-
The oxidation-reduction potentials using the method of Brown (1935) and
the O2 diffusion rates using the procedure of Lemon and Erickson (1955)

were also determined prior to the surface application of 112 Kg N/ha.

RESULTS AND DISCUSSION

Field Experiments

 

Yield and NOS-N content of the 1969 carrot crop are shown in

Figure 1. The NOS-N content of plants sampled July 30 was increased

from 380 to 780 ppm N by the addition of 90 Kg N/ha five weeks after

planting (1/2 of the 180 Kg N/ha rate). Plant NOS-N content decreased

to 570 ppm N as a result of adding 180 Kg N/ha (1/2 of the 360 Kg

N/ha rate). The NOS-N content of plants grown without added N was

similar at both sampling times. But the NO

3-
on the 90 and 180 Kg N/ha treatments decreased even though the last half

N content of plants grown

of the fertilizer N was applied just two weeks prior to sampling.

Carrot yield from the 180 Kg N/ha rate (280 Kg/ha) was signifi-
cantly greater than the yield from the O and 360 Kg N/ha rates (226
and 222 Kg/ha respectively), but there was no statistical significance
between the yield from the 90 and 180 Kg N/ha rates. These data show
the growth effects of limited and excessive N on crop yield where
maximum yield was obtained from the 180 Kg N/ha rate.

The highest N application rate resulted in a significant increase
in carrot NOS-N uptake over the O and 90 Kg N/ha rates. There was no

statistical difference in the NOS-N uptake between the 180 and 360 Kg

N/ha rates.

25

26

---- No3‘—N July 3o

—- NO3--N Sept. 15

 

 

 

 

Yields

10 F
to /'

r4 ‘\~ '

I

x I ‘\\ /

a I ‘\ ’

a.

" I ' “\ H
‘54 ” / \ >4
“ I ' i 3.0 w
8 I / fl
0 I O Q
z ',,-J
I. K s '6
"1 F4
c> m
z 31

‘ 2.0
0 l J *0
O 90 180 360

N Rates, Kg/ha

Figure 1. Carrot NO --N content and yield as affected by N application
rates (1969).

 

 

 

with N

explar
Figure
by eve
leach;
the p
water
tion

and 0
these
after

appli

excee
76 cu
half
there
HenCe
inCre.

aPP11(

27

The lettuce NOS-N content is summarized in Figure 2. Although
not statistically significant, the reduction in NOS-N content at the
highest N application rate, which was apparent in the first carrot
sampling, is also evident here.

Since the lettuce and carrot studies were conducted concurrently
with N fertilizer being applied July 2 in both experiments, a possible
explanation for their effects may be found in the climatic data,

Figure 5. The rainfall for July, 1969 greatly exceeded the water loss
by evaporation; consequently, the N applied July 2 was subject to
leaching. The heavy rainfall also raised the water table to 45 cm in
3-
water table was subject to denitrification. The rate of denitrifica-

the plots in early July. Thus the NO N which leached to the ground

tion is known to increase with increasing soil NOS-N contents (Wijler

and Delwiche, 1954). Thus the highest N application rate could, under

these climatic conditions, result in less total NOS—N in the soil

after accelerated denitrification has occurred than for lower N

application rates which stimulated denitrification to a lesser extent.
During August of 1969 the water loss by evaporation greatly

exceeded water gain by rainfall. The water table was lowered to

76 cm in early August and remained there the entire month. The second

half of the fertilizer applied to the carrots on July 30 was not,

therefore, subjected either leaching loss or to intensive denitrification.

;-

increase which was directly related to increased N fertilizer

Hence, the plant NO N contents determined on September 15 showed an

application.

 

 

 

 

 

FiEUI

28

 

N037-N Spinach

—--— N03"-N Head Lettuce

H
O

 

 

Head lettuce N03‘-N content (1969) ppm X 103
Spinach leaf NO3'- N content (l970)ppm X 102

 

.i l .

0 90 180 360

N Rates, Kg/ha

Figure 2. Head lettuce and spinach leaf N03--N content as affected
by N application rates.

29
Figure 3 shows the data from the first spinach experiment in
1969. This experiment followed the lettuce with the N being applied
to the lettuce residue on August 3. The field was subsequently plowed

to a 15 cm depth. The plant NO N content at harvest of the 360 Kg

3
N/ha rate was significantly increased over the NOS-N content of the
180, 90, and 0 Kg N/ha rates. The reduced plant NOS-N content of the

highest N application rate, evident in the carrot and lettuce experi-
ments was not present in this data. This is agreement with the data of
the second carrot sampling.

The yields, however, showed a "leveling off" trend as the curve
approached the 360 Kg N/ha rate. But the plant yields of the 360 Kg
N/ha rate were significantly increased over the 90 and 0 Kg N/ha rates.
The difference between the 180 and 360 Kg N/ha rates were not signifi-
cant.

The NOS—N content of 27,700 ppm for the 360 Kg N/ha rate is

quite high. The use of this rate of N fertilization does not appear
to be justified since it only produced a 5 percent yield increase over

the 180 Kg N/ha rate while at the same time a 48 percent NOS-N content

increase occurred. The use of 180 Kg N/ha increased the yield 36 per-

cent over the check with only a 38 percent NOS—N content increase.

The data from the second spinach experiment conducted in 1969

are summarized in Figure 4. There were no differences in yields, plant

NOS-N contents, and NOS-N uptake as related to NH4N03 and urea fertilizer

sources; therefore, each point in Figure 4 is an average of both N

sources. Differences were noted in yields, NO3

N content, and NOS-N

uptake as related to N rates.

3O

 

 

 

 

25 F
40
M
l
O
r-l
*4 ‘7'

a c:
Q v-l
O.

. ><
u m
a .2
3 a
c :z
0
U n

“U
z .4
I Q)
l m a;
O
2:
EH
m
d)
c:
15 -_
-—- NO3 N
— - Yields
1 30
1’- t . 5
0 90 180 360

N Rates, Kg/ha

Figure 3. Leaf NO --N content and yield of spinach as affected by N
rates (I969)-

31

-3

Leaf NO3—-N content, ppm X 10

Yield, Kg/ha x 10'2

 

—— NO3 -N

20 ' --- - Yield

1

30

 

 

‘k

I L: l l

0 56 112 224 *‘43
N Rates, Kg/ha

Figure 4. Leaf NO --N content and yield of spinach as affected by N
rates (1969).

32

 

Mean.Temp
--- Rainfall

---- Evaporation

 

20 - 20
N
\ I
5 \ I \\ U
. / \
C \ I \
o / ‘\ .
11 I \ 2
m ‘ I '\\~ 3
'5 \ /’ \ ti
3 10 - \I \\ 3
:3 I N 3‘
I \ m

g I \ F‘

/ c
z ,I \ a
Is I Ill,” 2
.5 [I \ I’
g V \ /

 

 

 

Months

Figure 5. Water loss and gain and mean temperature for 1969.

33

At harvest, the spinach NOS-N content on the 448 Kg N/ha rate
was significantly increased over the 224, 112, 56, and 0 Kg N/ha treat-
ments, and the plants on the 224 Kg N/ha rate contained significantly
more NOS-N than those on the 56 and 0 Kg N/ha rates. Again, the high
NOS-N content (32,300 ppm) of the highest N application rate appears
excessive. And as noted previously, the lack of yield response does
not justify the use of the highest N increment.

Plant yields on the 448 and 224 Kg N/ha were significantly
increased over the yields of the 56 and 0 Kg N/ha rates. The yield
curve follows a normal growth curve in that the yields increase
linearly as N rates increase up to the 224 Kg N/ha rate. Beyond the
224 Kg N/ha rate, yields were not increased by increased N application

rates 0

The plant uptake of NOS-N was increased from 70 to 130 Kg/ha
by the addition of 448 Kg N/ha. Thus, 13 percent of the added N was
in the harvested crop in the N0; form. It is expected that additional
N would be present as amino acids and proteins.

In 1970, a spinach experiment was established with the same
treatments and on the same location as the first spinach experiment
grown in 1969. The N treatments were applied at planting but a poor
stand necessitated replanting. The plant NOS-N contents shown in
Figure 2 for this experiment were from the later re-planting of spinach
even though no additional fertilizer was added. All plant NOS—N contents
were lower in 1970 than in 1969 (for example, the high content in 1970
was 520 ppm as compared to 27,700 ppm for 1969). The 1970 lower values

likely occurred because of the length of time between fertilizer N

34
application and crop production. The plant NOS—N content of the 180 Kg
N/ha rate was significantly increased over the contents of the 90 and

0 Kg N/ha rates. But again lower NOS-N content was observed at the

highest N application rate. The reduced plant N0

3-

be attributed to increased rainfall which caused an increased leaching

N content may again

and denitrification loss from the soil profile (see Figure 6).
The soil NOS-N data of this experiment support the theory of

increased leaching and denitrification losses of soil NOS-N as related

to increased rainfall (see Figures 7 and 8). In all 1970 sampling

dates, the soil NOS-N content of the 360 and 180 Kg N/ha rates were

increased significantly over the 90 and 0 Kg N/ha rates, and, in the

last sampling, the 90 Kg N/ha rate had significantly higher soil NOS-N

N curves of the 360, 180, and

3-
90 Kg N/ha rates continued to increase linearly with each sampling

than the 0 Kg N/ha rate. The soil NO

date, whereas the 0 Kg N/ha rate began to "level off" with the last
sampling. Since the 0 Kg N/ha treatment had received no fertilizer N,
this "leveling off" may be attributed to either a decreased biological
nitrification or an increased biological denitrification (or a combina-
tion of both processes) caused by an increased rainfall which raised

the water table in the organic soil profile from below 76 cm up to less
than 51 cm below the soil surface. By the last sampling date, little
difference occurred in the soil NOS-N content between the 180 and 360 Kg
N/ha rates. On the first sampling date, prior to the fertilizer N
applications, the 0—15 cm depth had a slightly higher soil NOS-N con-

tent than other depths. Two weeks later, however, the 30-46 and 46-61 cm

depths had slightly higher soil NOS-N content than the 0-15 cm depth.

35

 

Mean Temp
-- - Rainfall

--- Evaporation

 

 

 

 

20 / q 20
B
U

/______.—__
a /’
g 10 '- ll” ‘ 10
H ’1
u ,a
CU ,”
H ”’
8. ” A
g I -\‘ K-
“‘ , / \
:3 / .
r-l \
'3
“-4
g 0 l J \\ 0
g J e July Aug. éfit.
Months

Figure 6. Water loss and gain and mean temperature for 1970.

C

Mean Temperature,

 

36

   

 

/
[I
If
/,'
300? I.
I s
‘//./
I .’
/ l
I I.
I, /
/ .’
I .I
I 'I
[I I
I, I" '
I /' /
E: l I 0
Ch I 0’ O
J I I /
C“ l I. a.
3 I - /
8 ’ / .
o I l' .
Z, 200 - / - /
I m I, I .0
.9. . / /
H O
.8 /
m 0
I
"——' 0 Kg N/ha
"" 90 Kg N/ha
""'l80 Kg N/ha
13o --—- 360 Kg N/ha
July 30 Aug. 13 Sept. 10

Figure 7.

Sampling Dates, 1970

Soil NO --N content as related to sampling date and

applicagion rates.

37

 

 

 

 

 

290 '
I
/
I I
I lo,
-I
.’I
.III
.’ I
a I
O.
o.
i?
a
o
4.)
a
o
o
2:
'I
g“ 200
H
-.-u
0
V)
cm
cm
----lS-3O cm
130 46-61 cm
01 i I
July 30 Aug. 13 Sept. 10

Sampling Dates, 1970

Figure 8. Soil NO3 -N content as related to sampling date and soil
depth.

38

This increased soil NOS-N content in the lower soil depths is attributed

to the increased rainfall which leached the N03 N out of the upper

profile layers and away from the root zone. At the last sampling date,
3-

same as that on the second sampling. This stabilization effect was

however, the soil NO N content of the 46-61 cm depth remained the

attributed again to the increased rainfall and water table which caused

an increased biological denitrification due to the anaerobic conditions.
3-
tinued to increase linearly with the third sampling, but in the same

The soil NO N content of the 30-46, 0-15, and 15-30 cm depths con-

order as with the second sampling. The soil profile NOS-N content of
each sampling date was: July 30, 598 ppm; August 13, 865 ppm; and
September 10, 1055 ppm.

A spinach experiment was conducted in Spring and Fall of 1971,
where the treatments utilized in 1969 and 1970, were again repeated in
the same locations. Therefore, by Fall of 1971 the individual treat-
ments had received four times the stated application rate applied over
a three year period. The data for the 1971 experiments are given in
Figures 9 and 10. The NOS—N content of the Spring 1971 plant tissues
are quite low in comparison to the 1969 results. This may be attributed
to the cool and dry spring (see Figure 13), insufficient irrigation
'water during May, differences in spring and fall spinach varieties, and
greater day length in the spring. The fact that the stem tissue NOS-N
content was considerably higher than the leaf tissue NOS-N content,
suggest that the latter two factors may be the most important. Both

the leaf and stem tissue contents of the 360 Kg N/ha rate were signifi-

cantly greater than those from the 180, 90, and 0 Kg N/ha rates.

39

“" NO '-N Stern

 

 

 

3
"" NO ‘-N Leaf
3
-— Yields
, ,/
'I
10 - 0’ - 10
N N
If: '3
N N
E. .2
O. \
. s?
u
5 2
u .3
8 :u
U
Z
I
I
m
o i
Z
c. --- d
‘i‘O---‘----o O ”“- -
o l i ' o

 

0 90 180 360
N Rates, Kg/ha

Figure 9. Leaf and stem NO -—N and yields of spinach as affected by
N rates (spring I971).

40
"”' N03‘-N (9/1)

—- Yields

""” N03'-N (9/14)

--- N03'-N (9/30)

on
to
.4
>4 N
N:
a H
m.
a. N
U m
r: .c:
a) \
‘4 00
c: M
0
° 6‘
2 H
l 0
In a:
O
z
4.:
m
a)
p-l

 

 

 

 

O 90 180 360

N Rates, Kg/ha

Figure 10. Leaf NO --N content, sampled at different dates, and yield
of spinach as affected by N rates (fall 1971).

41

Regarding NOS-N concentration of the stem, the 180 Kg N/ha rate had
significantly increased plant content over the 90 and 0 Kg N/ha rates,
and the content of plants from the 90 Kg N/ha rate were significantly
increased over the content from the 0 Kg N/ha rate.

The plant yields from this experiment were not statistically
different, although there was a decreasing trend from the 0 Kg N/ha
rate to the 360 Kg N/ha rate. The NOS-N uptake from the 360 and 180 Kg
N/ha rates was significantly increased over the 0 Kg N/ha rate uptake.
There were no statistical differences in the plant uptake from the
360, 180, and 90 Kg N/ha rates.

The NOS-N contents of the fall (late) spinach crop are more
"normal" than the previous two crops (see Figure 10). The first
sampling date had a higher tissue NOS-N content than did the last two
samplings. Although tissue contents of plants from the first sampling
were not statistically different, there was an increased plant tissue
content up to the 180 Kg N/ha rate. The tissue contents of the 90, 180,
and 360 Kg N/ha rates "leveled off" in the last two samplings, with the
contents of the 90 and 360 Kg N/ha rates being significantly increased
over the content of the 0 Kg N/ha rate in the last sampling. Large
amounts of irrigation water (see Figure 13) were applied to the experi-
ment. What effect this had on tissue NOS-N content is not known. The
plant yields were not significantly different, although the 360 Kg N/ha
rate yield was slightly decreased. The plant NOS-N uptake differences
between treatments were not significant.

Soil NOE-N content for 1971 is summarized in Figures 11 and 12.

The soil NOS-N content, as related to both depth and N application

42

 

 

 

800 P -—-° 360 Kg N/ha /
‘-—“ 180 Kg N/ha I
"" 90 Kg N/ha /
— 0 Kg N/ha /.
i /’ "\ -- ,/
E .- ,/\. \ .o/ ./
‘3 400 t / / \. \.. ./ /
2: ' ' \\/ '
';ri ////’ ‘\\' .I/’ ./
j -' ' \ / /
”-1 ° /
a // ,’\ /
1429 17 Julyl 1 Jul; 31 Sept: 7

Sampling dates, 1971

Figure 11. Soil NO --N content as related to sampling dates and
N rates.

-N content, ppm

3

Soil NO

43

‘w' 0-15 cm
--- 15-30 cm
""“" 30-46 cm

—-— 46-61 cm

600 -

300

 

 

_ l l cj
May 17 July 1 July 31 Sept. 7

Sampling dates, 1971.

Figure 12. Soil NO --N content as related to sampling dates and
soil depth.

44

coaumwwuuu !|In.
coaumuomo>m :III
Haemcfimm null.

ououmuonaoe new:

 

.Hnma now ououmuonaou some new aHmw new wood noumz

.ma ouowwm

 

 

mnuaox
.umvm .mp4 mwoh mosh mm:
1 \:III a o
_\
no
on
r
u
t
a
r
m. 0H
m
t
n
a
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ON ON

 

 

 

mo ‘ursS pus ssoI 1339M

45

rates, was quite low at the May sampling. In May, the soil profile
NOS-N content was 271 ppm, whereas; the September 1970 was 1055 ppm.
These observations are in agreement with the increased NOS-N content
in the drainage water from the MSU Muck Experiment Farm in the late
winter and early spring as opposed to the NOS-N content of the summer
drainage water. These observations indicate that some of the NOS-N
present in the soil in late fall is leached out of the profile and
that together with denitrification reduces NOS-N levels over winter.
With the May sampling, the soil NOS-N content of the 360 and 180 Kg
N/ha rates is significantly increased over the content of both the 90
and 0 Kg N/ha rates, and the content of the 90 Kg N/ha rate is signifi-
cantly increased over the content of the 0 Kg N/ha rate. The soil
NOQ-N content of the 46-61 cm depth is significantly greater than the
content of both the 0-15, and 15-30 cm depths, and the content of the
46-61 cm depth is significantly increased over the content of the
0-15 cm depth. Once again these data indicate the leaching losses of
soil NOS-N from the upper layers of the profile into the lower layers.
In the July 1 samples, the soil NOS-N content from all N
application rates and soil depths increased dramatically. The soil
NOE-N content was significantly increased when related to increased N
application rates, with the increases being in the order 0 < 90 < 180 <
360 Kg N/ha. The soil NOS-N content as related to depth was not
significantly different. However, there was an increased amount of
soil NO_-N in the 30-46 cm depth, indicating that biological denitri-

3
fication was still not an important factor in total soil NOS—N content.

46

The July 31 samples showed a decrease in soil NOS-N content in
all N application rates and with all soil depths. This decrease may
be attributed to an increased rainfall and decreased evaporation
(Figure 13). The biggest decrease occurred with the 360 Kg N/ha rate
and at the 30-46 and 46-61 cm depths (where anaerobic conditions are
most likely to occur). These data indicate that biological dentrifi-
cation is playing an important role in the total soil NOS-N content of
a profile. The soil NOS-N contents are still significantly different
in the same order as in the July 1 sampling, except that no significant
difference occurred between the 90 and 0 Kg N/ha treatment. The soil
NOS-N content of the 0—15 cm depth was significantly greater than the

soil NO3 N content of all the lower depths. No statistical differences

were noted between the soil NO3-N content of the lower depths, although
a decreasing trend is noted with increasing depth.

The September 7 samples showed a large increase in soil NOS-N
content as related to increased N applications, and at all soil depths,
reflected the additional fertilizer applications on August 5. These
increases were the largest with the 360 Kg N/ha application rate, and
the 15-30 cm soil depth, and may be attributed to an increase in evapora-
tion and a decrease in rainfall. Considerable irrigation water was
applied to the experiment during August. What effect the added water
had on soil NO--N content is not known. There were significant dif-

3

ferences in soil NO

3-
content increasing in the order 0 < 90 < 180 < 360 Kg N/ha. The area

N content in all N application rates, with the

receiving the 360 Kg N/ha rate had an average soil NOS-N content of

780 ppm. Soil NOS-N content of the 0-15 cm depth was significantly

47
greater than the content of both the 30-46 and 46-61 cm depths. The
soil NOS-N content of the 15-30 cm depth was also significantly in—
creased over the content of the 46-61 cm depth.

For each 1971 sampling date, the soil profile NOS—N contents
were: May 17, 271 ppm; July 1, 1452 ppm; July 31, 811 ppm; and
September 7, 1792 ppm. These values represent an overall increase in
soil NO--N content from 1970, which may be attributed to the decrease

3
in rainfall. Soil N0

3-

tion and decreased with increasing soil depth.

N content increased with increasing N applica-

Greenhouse Experiments

 

Moisture Treatments

 

The leachates from the field capacity treatment of the evapora-
tion, 112 Kg N/ha and four-day incubation regimes contained signifi-
cantly greater amounts of NOS-N than leachates from the 1/2 saturated
and saturated treatments under similar regimes. Differences were small
until evaporation from the column surface was allowed, and they became
very large only after N fertilization (see Figure 14). For example,
during the four-day regime the soil NOS-N content in the field capacity
treatment was 7.6 ppm as compared to 0.3 ppm in the saturated treatment.
The average difference was 2.68 ppm soil NOS-N for the field capacity
as compared to 0.36 ppm for the saturated treatment (see Table 5).

The leachate from the saturated treatment of the evaporation and
the 112 Kg N/ha regimes contained significantly more organic-N than
the field capacity treatment, and, in the 112 Kg N/ha regime, the

«organic-N contant of the saturated treatment was also significantly

greater than the 1/2-saturated treatment (see Figure 15).

48

7.0 ‘ '

-___- Field Capacity //
---- 1/2 Saturated /

Saturated

 

5.0 " ,’
/ I

I

I

  
   

 

 

 

E
a. . ,'
.r ,’
e
I
$3 I
I
8 I I
e l
' a, 3.0 F I
<3
2 o I
I
/ I
I
I
l I,
/ I'
I
' I
1.0
0‘ - 1 __u
Stab. No vap. Evdp. 112 Kg N/ha Short Incub.

Regime

Figure 14. NO --N content of water leached through a muck profile as
affected by regimes and moisture treatment.

49

—- Saturated

--- 1/2 Saturated

--' Field Capacity

 

Organic-N, ppm

 

 

 

é
L l L 1 _r
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.
Regimes

Figure 15. Organic-N content of water leached through a muck profile
as affected by regimes and moisture treatment.

50

The soil NH:-

cantly greater than the l/Z-saturated and field capacity treatments

N content of the saturated treatment was signifi-

at the 0-15 and 15—30 cm depths. There was no significant difference

in soil NH:-

still followed the order of saturated > l/2-saturated > field capacity

N content at the 30—46 cm depth, although the contents

(see Figure 16).

The soil NOS-N content of the field capacity treatment was
significantly higher than the l/2-saturated and saturated regimes
at the 0-15, 15-30, and 30-46 cm depths (Figure 18). The soil NOS-N
content of the 1/2—saturated treatment was also increased significantly
over the saturated treatment at the 0-15 cm depth (see Figure 17).

The oxidation—reduction (redox) potentials and the O2 diffusion
rates (see Table 2) are also significantly different when related to
the moisture treatment. At the soil surface, the field capacity and
1/2-saturated treatments had significantly increased potentials over
the saturated treatment indicating oxidizing conditions were present
at the soil surface. The O2 diffusion rate of the field capacity treat—
ment was significantly increased over the l/2-saturated and saturated
treatment at the soil surface. The 1/2-saturated treatment 02 dif-
fusion rate was also significantly increased over the saturated treat-
ment.

From these data, the moisture regimes have both an indirect and
direct effect upon the soil and leachate NOS-N content, and upon the
leachate organic-N content. The indirect effect is probably the more
important of the two. By controlling the water table in the soil, the
O diffusion through the soil profile is controlled, thus creating either

2
aerobic (02 present) or anaerobic (O2 deficient) conditions.

Figure 16 .

51

 

 

 

80"
60"
E
o.
0..
J
a O
o .
U
c:
o
. /
z 401-
+' '
Q’
e /
I-l
W4 0
o l
m /
,;,-"
\-. f
\v.”
’I 'o
20" I
,’ Saturated
/
I
7’ — 1/2 Saturated
—..—— Field Capacity
10.
{t J 1
0-15 15-30 30-46

Soil Depth, cm

Soil NH4+-N content as affected by
treatment.

soil depth and moisture

Figure 17.

-N content, ppm

Soil NO

3

6O

20

52

 

 

(82)
\
\
\ -—- Saturated
. -"- 1/2 Saturated
\
\ _— Field Capacity
\
\
\ .”’
\ /'
\,/"
L .1
0-15 15-30 30-46

Soil Depth, cm

Soil NO “-N content as affected by soil depth and moisture

treatme t .

53

(9.2)

 

 

 

 

6.0 '
-——-- Saturated
1/2 Saturated
—---- Field Capacity
on
8
v6
o
.c
o
m
o
H
z. I
| I
m
c>
2:
11
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.
Regimes
iFigure 18. NO "—N leached from a muck profile as affected by regime and moisture

tr atment s

54

Table 2.--Redox potential and 02 diffusion rates at the surface of a

muck soil as affected by temperature and moisture levels
after evaporation regime.

 

 

 

 

 

 

Redox potential 02 diffusion
mv gm X 108/cm2/min

Temperature
Ambient 324 30.2
10°C 315 28.5
LSD (0.05) n.s. n.s
Moisture
Field Cap. 412 43.4
1/2 Sat. 414 33.1
Sat. 131 11.7
LSD (0.05) 60 9.8

 

55
Under aerobic conditions, the heterotrOphic organisms break

down the organic-N compounds to NHZ, which is quickly biologically
3-
for the increased soil and leachate NOS-N content of the field

oxidized to NO N, the final oxidation product. This process accounts
capacity treatment.

The breakdown of organic-N compounds under anaerobic conditions
to NH: proceeds at a much slower rate. This process is less efficient
than under aerobic conditions, and not all of the organic—N is con-
verted to NHZ. Because of the reduced metabolism, the microbes do not
utilize all of the NH: produced, and thus, a net increase in the NH:
content in waterlogged or saturated organic soils results. This process
accounts for the increased soil NHZ-N and increased leachate organic—N
contents in the saturated treatment.

The 0-15 cm depth of the l/2-saturated treatment also had an
increased soil NOS-N content, but the leachate Nog-N content did not
significantly increase above the saturated treatment in the no-
evaporation and evaporation regimes, and was significantly decreased
below the field capacity treatment in the N treatment and reduced incu-
bation regimes. This is an indication that much of the soil NOS-N
that is leached out of the 0-15 cm depth of the l/2-saturated treat-

ment is biologically reduced (denitrified) to N O and N2 gases upon

2
reaching the anaerobic conditions at the water table.

The direct effect of the moisture treatment is twofold. When
surface evaporation is prohibited, moisture movement upward and loss

from the soil profile is greatly restricted. Without the upward move-

ment of water, the soil moisture content of the field capacity treatment

56
and upper layers of the 1/2-saturated treatment is probably reduced
below field capacity, and hence may be the limiting factor for microbial
population. If this is the case, then the oxidation of organic-N to
NOS-N would be reduced and the leachate content of NOS-N would also be
reduced. Another factor is the evaporation of water from the soil
surface. If evaporation is restricted, then the need to replenish the
water lost from the profile is decreased. Thus, there is also a
decrease in the volume of water that is leaching the profile. If this
is the case, then there would be less NO--N leached from the profile.

3

The total NOS-N and organic-N leached from the soil profile is
dependent upon the N content in the leachate and the leachate volume.
The average volumes for the moisture treatments were: field capacity
0.4 2; 1/2-saturated 1.6 2; and saturated 3.0 2. There were no
statistical differences in the NOS-N leached as related to moisture
treatment except in the four day incubation regime where the NOS-N
leached in the l/2-saturated treatment was significantly increased
over the losses of the field capacity and the saturated treatments (see
Figure 18). These data indicate that, in relation to moisture treat-
ment, minimum amounts of NOS-N are lost from an organic soil profile
if conditions permit denitrification to occur. The 1/2-saturated
treatment allowed for NOS-N production in the surface one half of the
profile and a sufficient volume of water to allow for the loss of much
of the NOS-N if denitrification does not occur. Although the field

capacity treatment allows for production of NOS-N in the profile, the

total volume of water loss is only one-fourth of that from the 1/2-

saturated treatment; thus, less total NOS-N is lost. The quantity of

57
NOS-N which leached from the profiles was greater during the short,
4 day incubation period because this did not allow sufficient time for
denitrification.

The leaching losses of organic-N were significantly affected by
moisture treatment. The amount of organic-N leached from the saturated
treatment was increased significantly over that leached from the 1/2-
saturated and field capacity treatments in all regimes, except in the
stabilization period. The amount of organic-N leached from the 1/2-
saturated treatment was significantly increased over that leached
from the saturated and field capacity treatments in the stabilization
regime, and was significantly increased over that leached from the
field capacity treatment in all other regimes (see Figure 19). These
data again indicate the differences between the anaerobic and aerobic
conditions and the biological processes occurring under these different

conditions.

Temperature Treatments

 

The 10 C treatment leachates of the no-evaporation regime con-
3-

mean) treatment in the no-evaporation (5% level) and the evaporation

tained significantly greater amounts of NO N than the ambient (28 C
(10% level) regimes. This trend continued in the 112 Kg N/ha and
shortened incubation regimes (see Figure 20).

The ambient treatment leachates of the stabilization and no-
evaporation regimes contained significantly greater organic-N amounts
than the 10 C treatment. This trend continued with the evaporation and

112 Kg N/ha regimes. The leachate from both temperature treatments

58

13.0 "

11.0 r- .

9.0 - /

 

oo
5 K / —- Saturated
'6 o
0 \ ---- lJ2-Saturated
. ./
.93, 7.0 " ) -—- Field Capacity
\
f ' \
ii \
a a
CU \ at”
0 \ l
5.0 P

 

 

 

1.0 "
i, i L, .4
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.
Regime

Figure 19. Organic-N leached from a muck profile as affected by regime and
moisture treatment.

59

--- 10C

_ Ambient temp.

 

 

 

 

I
P I
5.0 I
I
I
I
I
I
E
a. 3.0
.3
c
0
U
a
o
O
2:
I
I
m
‘o
:z
1.0
1 _l
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.
Regime
Figure 20. NO '-N content of water leached through a muck profile as affected

by regime and temperature treatment.

60
contain the same amounts of organic-N in the four day incubation
regime (see Figure 21).
+
The soil NBA-

significantly higher than the content of the 10 C treatment at the

N content of the ambient temperature treatment was

15-30 cm depth. The same trend was observed at the 0-15 and 30-46 cm
depths (see Figure 23).

The soil NOS-N content (see Figure 22) of the ambient temperature
treatment was significantly higher than that of the 10 C treatment at
the 0-15 cm depth. This trend continued at the 15-30 cm depth, but the
soil NOS-N content at the 30-46 cm depth was the same for both tempera—
tures.

There were no differences noted in the oxidation-reduction

potentials and 0 diffusion rates as related to the temperature

2
treatments.

From these data the temperature treatment directly effects the
soil microorganisms. The increased soil NHZ-N and NOS-N content of the
ambient treatment is due to the increased heterotrophic microbial
activity under both aerobic and anaerobic conditions, which continually
work to break down and oxidize the organic soil. The soil NHZ-N con-
tent of the saturated, ambient treatment interaction was increased at
both the 0-15 and 15-30 cm soil depths, and the soil NOS—N content of
the ambient, field capacity treatment interaction was also greater
at 0-15, 15-30, and 30-46 cm soil depths than any other temperature and
moisture interactions.

The increased NOS-N content of the leachate with the 10 C
treatment is an indication that the increased soil NOS-N in the ambient

61

 

 

 

 

4.0 f '
."” “\~
./ .
a. ,/
o.
o. 3 op-'-—O_'/
z:
I
U
'H
a
m
3° -- o c
C) 1
2.0J' --- Ambient Temp.
k
I 1 n 1 4
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.
Regimes

Organic-N content of water leached through a muck profile

Figure 21.
as affected by regimes and temperature treatment.

62

 

 

 

 

 

0-15 F
A ’ ”’
3'2 x
.r: I”
I.)
On ’a’
.8 15-30 F
I: —- 10 c
o
(O
--- Ambient temp.
30-46 1 L J 1
10 30 40 50
Soil N03'—N Content, ppm
Figure 22. Soil NO ”-N content as affected by soil depth and temperature
treatment.
—-— 10 C
---- Ambient temp.
0-15 r' \
\\
V \\
.x: \
u s
s- “
1: 15-30 " ”
H I
H
.2 /
I
I
I
I
30-46 . i / ' 4
30 40 50 60
Soil NH4+-N Content, ppm
Figure 23. Soil NH4+-N content as affected by soil depth and temperature

C rea tment .

63

temperature treatment is being denitrified to N20 and N2 gases. Again,
the heterotrophic bacteria responsible for denitrification in an
anaerobic environment are mesophilic microbes, and have a greater popu-
lation in the higher temperature treatment.

The increased organic-N content of the leachate with the ambient
temperature treatment is again due to the increased microbial activity.
Because there is no reducing organism, this differs from the N0--N data.

3
The total leaching losses of NO--N from the soil profiles are

3
not significantly different, although the losses of the 10 C treatment
are slightly greater than the ambient treatment (see Figure 24). The
total leaching losses of organic-N from the ambient treatment, however,
are significantly increased over the losses of the 10 C treatment in the
stabilization, no-evaporation, and evaporation regimes. This increased
loss from the ambient treatment is continued through the 112 Kg N/ha
regime. But there is no difference in the organic-N losses during the
four-day incubation regime (see Figure 25).

The greater loss of NOS—N at the lower temperature is in agree—
ment with field observations. Since the temperature of the soil profile
in the field is less than 10 C during the winter months denitrification
would be expected to progress slowly. Even in the summer months the
temperature at the water table will not greatly exceed 10 C suggesting

that denitrification will require a few days for completion. The

microbial breakdown of organic matter and subsequent oxidation to

3
Should heavy water be applied at this point N0

N0 would proceed rapidly at the high temperatures at the surface.

3
the profile so rapidly that denitrification could not occur.

could be leached from

64

--- 10 C

___. Ambient temp.

 

 

 

 

on
a
15‘
o
.z
0
m
m
H
2:
l
I
«1
<3
2:
1 .J
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.
Regime
Figure 24. NO '-N leached from a muck profile as affected by regime and

te erature treatment.

Organic-N leached, mg

Figure 25.

65

-———— 10 C

-—— Ambient temp.

 

 

 

3.0 f
0' l— I L _I
Stab. No Evap. Evap. 112 Kg N/ha Short Incub.

Regime

Organic-N leached from a muck profile as affected by regime and
temperature treatment.

66

Regimes

Comparing the average leachate NOS-N content of the stabiliza-
tion, no-evaporation, and evaporation regimes, the NOS—N content of
evaporation regime is significantly greater than the content of the
first two regimes. The average NOS-N content of the leachates from
the first three regimes for the 10 C treatment is significantly greater
than the content of the ambient temperature. The average leachate
NOS-N content of field capacity treatment was also significantly greater

than that of the l/2-saturated and saturated average contents (see

 

Table 3). The average leachate NOS-N content of the evaporation regime,
10 C, field capacity treatment, was significantly greater than the
contents of the other regime treatments.

The average leachate organic-N content of the stabilization,
no-evaporation, regimes are also significantly less than the evapora-
tion regime. The three regime average leachate organic-N content of
the ambient treatment is significantly increased over that at the 10 C.
The average organic-N content from the 1/2-saturated and saturated
treatments was significantly greater than that at the field capacity
treatment. There were no significant differences in the interactions
involving the temperature treatments. The average organic-N content of
the leachate under the evaporation regime of the saturated treatment
was significantly greater than all regime treatment contents, with the
exception of the contents under the evaporation regime of the 1/2-
saturated treatment.

During the first three regimes, the average leaching loss of
NO_—N during the 10 C treatment was significantly greater than the

3

loss of the ambient treatment. There was no significant difference

67

Table 3.--Nitrogen content of H20 leached through a muck profile as
affected by temperature, moisture level, and regime prior

to N fertilization.

 

 

 

 

 

 

 

 

NOS-N Organic-N
"‘PPm"’

Temperature
Ambient 0.065 3.17
10 C 0.277 2.46
LSD (0.05) 0.179 0.32
Moisture
Field Cap. 0.354 2.48
1/2 Sat. 0.089 2.97
Sat. 0.070 2.98
LSD (0.05) 0.220 0.39
323.132
No Treat. 0.095 2.54
No Evap. 0.073 2.58
Evap. 0.344 3.33
LSD (0.05) 0.220 0.39

 

68
in NOS-N loss as related to the moisture treatment. The average NOS-N
loss from the stabilization regime was significantly greater than the
loss from the no evaporation regime. The average NOS-N loss from the
evaporation regime was slightly greater than the loss from the no—
evaporation regimes. There were no significant interaction differences
noted between the three regimes and six treatments (see Table 4).

The average organic-N leaching loss from the ambient temperature
treatment during the first three regimes was significantly greater than
that from the 10 C treatment. The average organic-N leaching loss from
the saturated treatment during the three regimes was significantly
greater than either the l/2-saturated or the field capacity treatment,
and the l/2-saturated treatment loss was significantly greater than the
loss at field capacity. The stabilization regime average organic-N loss
is significantly greater than the average loss of the other two regimes,
and the organic—N loss of the evaporation regime is significantly in-
creased over the loss of the no-evaporation regime. The organic-N
leaching loss from the ambient temperature treatment of the stabiliza-
tion regime was greater than the loss from any other regime tempera-
ture treatment. The average organic-N loss from the evaporation
regime of the saturated treatment was significantly greater than the
average loss from all other regime treatments.

These data indicate that significant leaching losses of NOS-N
and organic-N can occur in the development of a virgin organic soil.
The increased losses from the stabilization regime are due to the in-

creased leachate volume. The increased losses during the evaporation

regime, over the no—evaporation regime, are due to the increased NOS-N

69

Table 4.--Nitrogen leached from a muck profile as affected by temperature,
moisture level, and regime prior to N fertilization.

 

 

 

 

 

 

 

NOS-N Organic-N
___m8_-_

Temperature
Ambient 0.132 .' 6.70
10 C 0.242 4.98
LSD (0.05) 0.089 0.80
Mbisture
Field Cap. 0.183 2.85
1/2 Sat. 0.183 6.05
Sat. 0.194 8.63
LSD (0.05) n.s. 0.99
m
No Treat. 0.266 7.05
No Evap. 0.096 4.56
Evap. 0.198 5.92

 

LSD (0.05) 0.109 0.99

 

70
and organic-N contents of the leachate. The role of biological denitri-
fication is again shown in the NOS-N loss as related to the temperature
treatments.

The 112 Kg N/ha addition and the reduced incubation regimes re-
sulted in an increased leachate Nog-N content and leaching loss;
whereas the organic-N content and loss remained the same as it was
during the evaporation regime. Summarizing the average leachate NOS-N
contents for all five regimes and six treatments (see Table 5), the
10 C treatment was significantly (10% level) greater than that from
the ambient temperature treatment. The NOS-N loss from the field
capacity treatment was significantly greater that from either the 1/2-
saturated or saturated treatments, and the l/2-saturated treatment
lost significantly more than the saturated treatment. The loss at
10 C under the field capacity treatment was slightly greater than all
other treatments. The losses during the short incubation regime were
significantly greater than those from all other regimes, and 112 Kg
N/ha regime lost significantly more than the first three regimes.
Losses under the short incubation regime and the 10 C treatment were
slightly increased over the other regime and temperature treatments.
The loss under the short incubation regime at field capacity was
significantly greater than the other regime and moisture treatments.
The losses under the short incubation regime at l/2-saturation, and
the 112 Kg N/ha regime at field capacity are significantly greater

than the remaining regime and moisture treatments. There were no

interaction differences between the five regimes and six treatments.

71

Table 5.-—Nitrogen content of H20 leached through a muck profile as
affected by temperature, moisture level, and regime.

 

 

 

 

 

 

 

 

NOS-N Organic-N
"'PPm"-

Temperature
Ambient 1.29 3.38
10 C 1.83 2.85
LSD (0.10) 0.52 LSD (0.05) 0.32
Moisture
Field Cap. 2.68 2.83
1/2 Sat. 1.64 3.12
Sat. 0.36 3.39
LSD (0.05) 0.76 0.40
Regime
Stabilization 0.10 2.54
No Evaporation 0.07 2.58
Evaporation 0.34 3.33
112 Kg N/ha 2.70 3.56
4 Day Incub. 4.59 3.57
LSD (0.05) 0.98 0.51

 

72

Summarizing the average organic-N content of leachates from all
five regimes and six treatments, the loss from ambient temperature
treatment was significantly greater than the 10 C treatment. The
losses from the saturated treatment were significantly greater than that
from the field capacity treatment. The losses from ambient temperature
saturated moisture treatment were increased, but not significantly
over all other temperature and moisture interactions. The organic—N
removed from the short incubation, 112 Kg N/ha, and evaporation regimes
was significantly greater than that from the no-evaporation and
stabilization regimes. There were no interaction differences between
the five regimes and six treatments.
3-

experiment, the losses from the 10 C treatment were greater than from

Considering the average N0 N leaching loss during the entire
the ambient treatment; the losses from the l/2-saturated treatment
were significantly greater than from either the field capacity or
saturated treatments (see Table 6). The losses from the 10 C,
1/2-saturated treatment interaction were also significantly greater
than all other temperature and moisture interaction treatments. The
loss from the short incubation regime was significantly greater than
the other five regimes, and the loss from the 112 Kg N/ha regime was
significantly greater than the loss from the first three regimes. The
losses from the short incubation regime with the 10 C treatment were
increased, over all other temperature and regime interactions. The
losses from the short incubation regime at l/2-saturation were signifi—

cantly greater than from all other moisture and regime interactions.

73

Table 6.-—Nitrogen leached from a muck profile as affected by tempera-
ture, moisture level, and regime.

 

 

 

 

 

 

 

 

NOS-N Organic-N
-__m8--_

Temperature
Ambient 1.37 6.60
10 C 1.86 5.38
LSD (0.05) n.s. 0.67
Moisture
Field Cap. 1.01 2.23
1/2 Sat. 2.75 5.82
Sat. 1.07 9.92
LSD (0.05) 0.87 0.82
m
Stabilization 0.27 7.05
No Evaporation 0.10 4.56
Evaporation 0.20 5.92
112 Kg N/ha 2.93 6.37
4 Day Incub. 4.58 6.05
LSD (0.05) 1.12 1.06

 

74
The losses from the short incubation regime at 10 C and 1/2-saturation
were greater than those from all other regimes and treatments.

The losses from the ambient temperature treatment were signifi-
cantly greater than those from the 10 C treatment. Organic N losses
from saturated treatment were significantly greater than losses from
either the l/2-saturated or the field capacity treatments, and the
losses from the l/2-saturated treatment were significantly greater
than those from the field capacity treatment. Losses from the ambient
temperature and the saturated moisture level were greater than all
other treatments. The no evaporation regime losses were significantly
less than the other four regimes, and the stabilization regime losses
were significantly greater than those from the evaporation regime.

The losses from the stabilization regime at ambient temperature were
significantly greater (10% level) than losses from the other regime
and temperature treatments. The losses from the evaporation, 112 Kg
N/ha, and short incubation regimes under the saturated moisture treat-
ment were significantly greater than the losses from all other regime
and moisture treatments. There were no interactions between the five

regimes and six treatments.

SUMMARY AND CONCLUSIONS

Field Experiments

 

Plant NOS-N concentration is increased with increasing soil NOS—N
concentration.

Soil NOS-N concentration is related to fertilizer N applied and to
soil moisture conditions. Increased rainfall and a high water
table caused an increased leaching loss of NOS-N from the upper
soil layers, and an increased biological denitrification loss in
the lower soil layers.

Plant yields increased with increasing soil N application rates

up to 180 Kg N/ha. However, yields were suppressed at 360 Kg N/ha
or higher N rates.

Fall spinach accumulated much more NOS-N in the tissue than did

Spring spinach.

Greenhouse Experiments

 

Soil NHZ-N concentration reached a maximum under saturated soil
moisture conditions with ambient (28 C) temperature. This may be
attributed to the occurrence of biological ammonification and the
suppression of biological nitrification under anaerobic conditions.
Maximum soil NOS-N accumulation occurred at field moisture capacity
and ambient (28 C) temperature indicating the high rate of
biological ammonification and nitrification under aerobic conditions.

75

76
The greatest leachate NOS-N concentration was present with the
field moisture capacity and 10 C treatment indicating that signifi-
cant dentrification occurred in the leachate water from the pro—
files highest in soil NOS-N content.
Maximum leachate organic-N content was present in the saturated
moisture and ambient temperature (28 C) treatment. This coincides
with the increased soil NHZ-N content of the same treatment.
Prior to fertilizer N application, the evaporation regime had
increased leachate NOS-N and organic N contents over the no-
evaporation and stabilization regimes, indicating the necessity
for water movement in the profile for increased leaching loss of
N to occur.
Application of 112 Kg N/ha greatly increased the leachate NOS-N
content over the evaporation regime indicating the important con-
tribution of fertilizer N towards NOS-N content of the leachate.
The N application did not increase organic N content of the
leachate over the content in the evaporation regime.
Reducing the incubation time following the N application also in—
creased the NOS-N content of the leachate above that from the
112 Kg N/ha regime. Reducing the incubation time reduces the loss‘
of NOS-N by biological denitrification. The reduced incubation
period did not increase the organic-N content of the leachate over
the evaporation regime.
The l/2-saturated and 10 C treatments resulted in the highest
amount of leachable NOS-N. The reduced incubation and 112 Kg N/ha
regimes resulted in the highest total NOS-N losses, respectively.

77
This high total value reflects the NOS-N concentration and volume
of leachate.
The saturated and ambient temperature (28 C) treatments caused the
highest leaching of total organic-N. The stabilization regime lost

the highest total organic-N. Again, this reflects the leachate

organic-N concentrations and volumes.

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Brc

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Car

C15

C12

Coc

C0]

C0:

Da‘

Ga

Ge:

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APPENDIX

85

Table lA.--Carrot yield and tissue NO
rate and sampling date (19

2-N content as affected by N

9).

 

 

 

 

N Rate Tissue NOS-N Yield
Kg/ha ---ppm X 10- --- Kg/ha X 10-3
Jul. 30 Sep. 15
O 3.7 3.7 2.3
90 4.0 3.4 2.7
180 7.8 5.1 2.8
360 5.7 8.3 2.2
LSD (0.05) 2.7 3.0 0.4
Average of 4 Reps.
Analysis of Varience
F Statistic
Source Tissue NOS-N Yield
Jul. 30 Sep. 15
N Rates 4.4* 5.0** 5.2**
Reps 1.1 0.8 1.7

**Significant at 0.01 level.

*Significant at 0.05 level.

 

fl II.

86

Table 2A.--Lettuce tissue NOS-N content as affected by N rate (1969).

 

 

 

N Rate Tissue NOS-N
Kg/ha ppm X 10-3
O 6.5
90 8.9
180 9.8
360 6.8
LSD (0.05) n.s.

 

Average of 4 Reps.
Analysis of Varience
F Statistic
Source Tissue NOS-N
N Rates 0.7

Reps 0.6

87

Table 3A. Spinach yield and tissue NOS-N content as affected by
N rate (1969).

 

 

 

N Rate Tissue NOS-N Yield
Kg/ha ppm X 10-3 Kg/ha X 10—

o 13.5 3.2

90 18.7 3.9

180 18.7 4.4

360 27.7 4.6

LSD (0.05) 6.9 0.4

 

Average of 4 Reps.
Analysis of Varience

F Statistic

Source Tissue NOS-N Yield
N Rates 6.3** l7.3**
Reps 0.3 1.9

**Significance at 0.01 level.

*Significance at 0.05 level.

88

Table 4A.--Spinach yield and tissue NOS-N content as affected by N
rates and carriers (1969).

 

 

 

 

 

 

 

N Rate Tissue NOS-N Yield
Kg/ha ppm X 10”3 Kg/ha X 10.-3
O 20.7 3.4
56 19.1 3.6
112 24.6 3.7
224 27.1 4.1
448 32.3 4.1
LSD (0.05) 4.7 0.4
N Carriers
NH4NO3 24.8 3.8
Urea 24.7 3.7
LSD (0.05) n.s. n.s.
Average of 6 Reps.
Analysis of Varience
F Statistic
Source Tissue NOS-N Yield
Rates (A) 10.1** 4.1**
Carriers (B) 0.0 0.7
A X B 1.0 0.1
Reps 2.5* 6.5**

**Significance at 0.01 level.
*Significance at 0.05 level.

89

Table 5A.--Spinach tissue NO--N content and soil NO--N content as
affected by N rates, sampling dates, and soil depths (1970).

 

N Rates Tissue NOE-N Soil NOS-N

 

Kg/ha ppm X 10-2 ppm

Jul. 30 Aug. 13 Sep. 10

 

 

 

 

0 2.3 125 171 184
90 3.5 123 180 241
180 5.2 164 250 313
360 4.0 186 264 317
LSD (0.05) 1.4 25 38 40
Soil Depth
0-15 159 214 272
15-30 151 187 269
30-46 151 235 283
46-61 138 229 230
LSD (0.05) n.s. n.s. n.s.

 

Average of 8 Reps.
Analysis of Varience

F Statistic

Source Tissue NOS-N Soil NOS-N
Jul. 30 Aug. 13 Sep. 10
Rates (A) 5.8** 12.5** 12.2** l9.7**
Depth (B) 1.0 2.5 2.5
A X B 1.2 0.5 1.4
Reps 5.1** 15.5** 6.5** 9.0**

**Significance at 0.01 level.
*Significance at 0.05 level.

 

 

 

 

Table

is.“

90

Table 6A.-Spinach tissue NOS-N content, yield, and soil NOS-N content
as affected by N rates, sampling dates, and soil depths
(Spring 1971).

 

 

 

 

 

N Rates Tissue NOS-N Yield Soil NOS-N
Kg/ha ppm X 10-2 Kg/ha X 10-2 ppm
Jun. 24 Jul. 12 Jul. 12 May 17 Jul. 1
(stem) (leaf)
0 1.0 2.6 0.4 9.2 44 139
90 1.3 6.2 0.4 8.0 59 264
180 1.3 8.3 0.7 8.5 86 463
360 1.6 10.5 1.3 6.0 82 586
LSD (0.05) 0.5 2.0 0.4 n.s. ll 60
22st);

0-15 57 350
15-30 65 361
30-46 79 389
46-61 71 353
LSD (0.05) 11 n.s.

 

Average of 8 Reps.
Analysis of Varience
F Statistic

Source Tissue NOS-N Yield Soil NOS-N
Jun. 24 Jul. 12 Jul. 12 May 17 Jul. 1
(stem) (leaf)
N Rate (A) 3.2* 26.0** 8.4** 0.8 23.6** 87.3**
Depth (B) 5.3** 0.7
A X B 0.9 0.2
Reps 3.1* 1.6 2.7* 1.62 16.5** 7.7**

**Significance at 0.01 level.
*Significance at 0.05 level.

91

Table 7A.--Spinach tissue NOS-N content, yield, and soil NOS-N content
as affected by N rates, sampling dates, and soil depths

(Fall 1971).

 

 

 

 

 

 

N Rates Tissue NOS-N Yield Soil NOS-N
Kg/ha ppm X 10-3 Kg/ha X 10-3 ppm
Sep. 1 Sep. 14 Sep. 30 Jul. 31 Sep. 7
0 6.7 0.5 0.9 2.6 87 159
90 7.0 2.5 2.9 2.5 112 318
180 9.3 3.3 1.9 2.8 264 534
360 8.2 2.6 2.8 2.2 348 781
LSD (0.05) n.s. n.s. 1.5 n.s 66 97
Depth
0-15 310 554
15-30 202 486
30-46 158 414
46-61 140 338
LSD (0.05) 66 97
Average of 4 Reps.
Analysis of Varience
F Statistic
Source Tissue NOS-N Yield Soil NOS-N
Sep. 1 Sep. 14 Sep. 30 Jul. 31 Sep. 7
Rates (A) 0.9 1.1 3.9* 0.7 28.4** 63.2**
Depth (B) 10.7** 7.5**
A X B 1.4 2.2*
Reps 1.6 1.5 1.9 0.5 9.1** 2.0

**Significance at 0.01 level.
*Significance at 0.05 level.

92

Table 8A.--Soil NOS-N and NH+-N contents from greenhouse experiment,

prior to applying N fertilizer, as related to temperature,
moisture, and soil depth.

 

 

 

 

 

 

 

 

Temperature Soil NOS-N Soil NHZ-N
---ppm---

Ambient 34.4 49.7
10 C 18.2 33.0
LSD (0.05) 11.9 11.4
Moisture

Field Capacity 55.7 22.7
l/2-Saturated 20.8 30.8
Saturated 2.4 70.5
LSD (0.05) 14.6 14.0
Depth

0-15 41.3 39.0
15-30 19.2 42.3
30-46 18.4 42.7
LSD (0.05) 14.6 n.s

Analysis of Varience
F Statistic

Source NOS-N NHZ-N
Temperature (A) 7.4** 8.6**
Moisture (B) 27.8** 26.9**
A X B 12.1** 2.4
Depth (C) 6.4** 0.2
A X C 2.2 0.8
B X C 1.8 2.7*
A X B X C 1.1 1.6
Reps 1.0 2.4

**Significance at 0.01 level.
*Significance at 0.05 level.

93

Table 9A.--Ana1ysis of variance for Table 2.

Source
Temperature (A)
Moisture (B)

A X B

Reps

**Significance at 0.01 level.

*Significance at 0.05 level.

F Statistic
Redox Potential
0.1
66.6**
0.9

1.3

Table lOA.--Analysis of varience for Table 3.

Source
Temperature (A)
Moisture (B)

A X B

Regimes (C)

A X C

B X C

A X B X C

Reps

**Significance at 0.01 level.

*Significance at 0.05 level.

F Statistic
NOS-N
5.7*
4.3*
3.5*
3.8*
3.5*
3.8**
3.4*

0.9

02 Diffusion
0.2
24.6**
0.1

0.2

Organic-N

l9.5**
4.2*
2.1

10.3**
1.1
2.8
0.4

3.7*

94
Table llA.--Analysis of varience for Table 5.

F Statistic

Source NOS-N Organic-N
Temperature (A) 2.9 10.8**
Moisture (B) 18.4** . 3.9*
A X B 0.9 1.0
Regime (C) 33.4** 8.1**
A X C 0.5 1.3

B X C 6.9** 1.4

A X B X C 0.7 0.3
Reps 4,4** 4.7**

**Significance at 0.01 level.

*Significance at 0.05 level.

   

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