• TABLE OF CONTENTS
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 Title Page
 Introduction
 Yield response and nitrogen uptake...
 Time and method of application...
 Comparison of fall application...
 Comparisons of early spring applied...
 Residual effects of applied...
 Fate of unutilized nitrogen
 Implication for fertilizer nitrogen...
 Literature cited






Title: Effects of nitrogen fertilizer application in agriculture
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 Material Information
Title: Effects of nitrogen fertilizer application in agriculture
Physical Description: Book
Language: English
Creator: Lathwell, D. J.
Bouldin, D. R.
Reid, W. S.
Publication Date: 1970
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Subject: Farming   ( lcsh )
Agriculture   ( lcsh )
Farm life   ( lcsh )
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Table of Contents
    Title Page
        Title Page
    Introduction
        Page 1
    Yield response and nitrogen uptake by corn
        Page 2
    Time and method of application of nitrogen
        Page 3
    Comparison of fall application and summer sidedress application of nitrogen on corn
        Page 4
        Page 5
        Page 6
    Comparisons of early spring applied nitrogen and summer sidedress application of nitrogen on corn
        Page 7
    Residual effects of applied nitrogen
        Page 8
        Page 9
        Page 10
        Page 11
    Fate of unutilized nitrogen
        Page 12
        Page 13
    Implication for fertilizer nitrogen management
        Page 14
    Literature cited
        Page 15
Full Text










EFFECTS OF NITROGEN FERTILIZER APPLICATION
IN AGRICULTURE
D. J. Lathwell, D. R. Bouldin and W. S. Reid
Reprinted from
Relationship of Anriculture to Soil and Wfafr Pll,-t:on
Proceedings of Conell University Conterence on Agri-
cultural Waste M nagement, held in Syracuse, N. Y.
January 19-21, 1970.
Conference sponsored by the New York State College of
Agricultu e. A Statutory College c the Ncwv 'ork State
University of Cornell University, Ithaca, N. Y.













Effects of Nitrogen Fertilizer Applications

in Agriculture

D. J. LATHWELL, D. R. BOULDIN, and W. S. REID

Professor of Soil Science, Associate Professor
of Soil Science, and Assistant Professor of
Soil Science, Respectively. Cornell University,
Ithaca, New York

Effective use of fertilizer N is now an essential part of modern agriculture. The
development of the fertilizer N.industry :has been an essential component in increased
crop production throughout the United States. Consumption of fertilizer N in the
United States in '1945 was 595,313 tons, 2,,685,572 tons in 1960, and by 1968 con-
sumption: hhad reached ; 6,538,112 tofisji~ In New', York. comparable figures are
21,353 tons in 1945, 45,522 tons in:,960. and in 1968.consumption of fertilizer N
reached 67,699 tons. The trends in both the United States and in New York show a
gradual increase in consumption from 1945 to 1960, and a more rapid increase in
consumption from 1960 to 1968. Thompson (1969) has shown this graphically
(Figure 1) for several Corn Belt States where N fertilizer rates on corn increased much
more rapidly after 1960 than before 1960. For the period 1967 to 1969, however,
little change occurred indicating that N consumption in the United States may well
have reached a plateau, especially in those states where fertilizer usage has been well
established.
Thompson (1969) also summarized the trends in yield of corn for the same Corn
Belt States (Table 1) and his data show that while the annual increase in corn yields
from 1930 to 1960 was about 0.8 bushels per acre per year, from 1960 to 1967 the
annual increase was around 3.0 bushels per acre per year. Interestingly, trends in corn
yields in New York as shown in Table 1 are very similar to those for the Corn Belt.
These observations demonstrate that corn yields in the United States and in New
York have increased as the use of N fertilizer has increased. While N fertilizer is only
part of the technology responsible for the increased corn yields, they could not have
been obtained without sufficient inputs of fertilizer N.
Based on Figure 1, N consumption increased at a rate of about 10 pounds per acre
per year from 1960 to 1967. At the same time corn yields increased at the rate of
about 3 bushels per acre per year. (Table 1). Thus, something over three pounds of N
added resulted in a one bushel increase in yield. Assuming that only the grain was
removed from the field, about one pound of the three pounds of N applied was
actually removed from the land in the crop. Thus, some two-thirds of the N applied
cannot be accounted for by crop removal. This then points up the problem of efficient
use of fertilizer N in agriculture. The data of Thompson (1969) indicate an average
application to corn in the Corn Belt of from 80 to 120 pounds of N per acre presently.
These figures are not too different from the rates applied to corn in New York and are
substantially lower than those applied to many vegetable crops in the state.
In the remainder of this paper we will examine the use of fertilizer N on corn and


Agronomy Dept. Paper No. 884.









TABLE 1
TREND IN YIELD OF CORN IF FIVE U.S. CORN BELT
STATES AND IN NEW YORK (THOMPSON, 1969)

State Yield Annual Increase Yield Annual Increase Yield
1930 1930-1960 1960 1960-1967 1967
Bu/A
Illinois 42.9 0.87 68.9 4.10 97.6
Indiana 41.1 0.77 64.3 3.07 85.8
Iowa 44.2 0.74 66.5 3.70 92.4
Missouri 25.0 0.81 49.4 2.95 70.1
Ohio 40.0 0.82 66.6 2.15 81.7
SNew York 30.0 0.87 56.0 3.00 77.0


Figure 1. Trend in use of N on corn in several mid-
western states. (Thompson 1969)


evaluate rate, method of application, and time of application on yield and efficiency
of use of applied N.

YIELD RESPONSE AND NITROGEN UPTAKE BY CORN
Response to applied N on corn at several sites in New York is given in Figure 2.
Twenty-one location years of data were available and the data were divided into the
highest seven (I), the middle seven (II), and the lowest seven (III) yields and response
curves for each set of data are plotted. As is typical of most data obtained from such
experiments, response to applied N increased as yields increased; that is response to N
was greater at Group I sites than at Group III sites. Likewise, these results show the
typical diminishing response with each additional increment of applied N. Usually the
point of greatest economic return to applied N is at some point below the maximum
yield obtained.









150-



125 C


St --------n




75-



50 -- -------------
The15 50 85 155 e
Fertilizer N added, Ib/A
Figure 2. Yield of corn grain plotted against fertilizer
N added for 21 location-years of data in New York.
The curve labeled I is the average of the 7 highest
yieldings experiments, the curve labeled II is the
average of the 7 intermediate yieldings experiments,
and the curve labeled III is the average of the 7 lowest
yielding experiments.


The N content of the above ground portion of the plants as shown in Figure 3
parallels the yield curves. As expected, the N content of the plants was higher at higher
yields. The figures shown on the graph show the percent of the applied N that was
recovered in the above ground portion of the plants. The recovery of applied N is
defined here as the increase in N content of the above ground dry matter expressed as
a percent of the fertilizer N applied. Two points are of considerable significance; first,
as the rate of applied N increased, the percentage recovery decreased and this was true
at each yield level. Secondly, at each rate of application of N the percentage recovery
increased as yields increased. For example, percentage recovery of 50 pounds of ap-
plied N was higher at Group I sites than at Group III sites. Thus, in these experiments
the percentage recovery ranged from a high of 83 percent at the lowest rate of applied
N at the highest yield (Group I), to a low of 10 percent at the highest rate of applied N
at the lowest yield (Group III).
These data are typical of most response as a function of rate experiments. They
illustrate vividly the diminishing response to each additional increment of input and
the rapidly declining efficiency of utilization of fertilizer N as the rate of application
increases. These data also illustrate the importance of higher yields in promoting the
efficiency of use of fertilizer N. Thus, manipulation of factors which increase yield
potential should increase the efficiency of applied fertilizer N and thereby enhance
economic returns from fertilizer application and reduce possible N loss to other en-
vironments.

TIME AND METHOD OF APPLICATION OF NITROGEN
Before about 1945 most fertilizer, including N, was applied to corn at planting in
a band. With higher rates of N, however, it is difficult, if not impossible, to apply all of
the fertilizer at planting. Other possibilities exist including broadcasting most of the N














150- II _H-- *
83% 18%
E" /Z 37%
4 -9%





50 --
15 50 85 155
Fertilizer N added, Ib/A
Figure 3. N content of the above ground dry matter of corn plotted
against fertilizer N added for 21 location-years of data in New York.
Curves I, II, and III correspond to the definitions given for Figure 2.
The numbers adjacent to the curves are the increases in N content re-
sulting from each increment of N expressed as per cent of the added
fertilizer N.

in the spring either before plowing or else disking in after plowing, but before the
planting operation. Applying N in a band as a sidedress application after corn emerges,
but before it enters its period of maximum growth and N demand has the potential to
enhance efficiency and minimize losses. In recent years efficient labor use and reduced
prices for off season purchase of N have resulted in much interest in fall application of
N for the corn crop grown in the subsequent season. In most instances, fall applied N
has been plowed under or injected into the soil. We will consider fall application,
spring application, and summer sidedress as well as plowdown, disk in, and band
application in our evaluation of the effectiveness of fertilizer N for corn.

COMPARISON OF FALL APPLICATION AND SUMMER SIDEDRESS
APPLICATION OF NITROGEN ON CORN
In a series of experiments made in the Southeastern United States (Pearson et al,
1961) and on a Honeoye silt loam in New York, (Lathwell et al, 1966) several N
sources were applied at a single rate in late fall for the corn crop planted the subse-
quent year. A response curve to N was evaluated by using ammonium nitrate as the N
source applied as an application split between banding at planting (20 lb/A) and the
remainder as a summer sidedress. As shown in Table 2, in New York the relative
effectiveness of fall applied N on corn yields was quite low and varied widely among
sources. The relative effectiveness of NH4NO3 was unusually low, but in other experi-
ments has not been inferior to other sources. The values given in Table 3 show that
percent recovery of N by corn on the Honeoye silt loam for sidedress N were quite
high and significantly higher than those found for the fall applied N.
As shown in Table 4, the data from experiments in the Southeast were compar-
able to that obtained in New York although the relative effectiveness of the fall
applied N was slightly higher (49 percent compared to 37 percent). Likewise, the
variability among sources was not nearly as great on the average, although within
locations there were differences among sources in some years.









TABLE 2
RELATIVE EFFECTIVENESS OF FALL APPLIED
N COMPARED TO SIDEDRESS APPLIED N ON
CORN YIELDS ON HONEOYE SILT LOAM IN
NEW YORK
(AVERAGE OF 3 YEARS OF DATA)
(Lathwell et al 1966)

Relative Effectiveness
of Fall Applied N
as Per Cent of
N Source Sidedress Applied N
NH4NO3 10%
NH3 31
Urea 62
Cyanamid 43
Mean 37


TABLE 3
PER CENT RECOVERY OF FALL AND SIDEDRESS APPLIED N
BY CORN ON HONEOYE SILT LOAM IN NEW YORK
(AVERAGE OF 3 YEARS OF DATA)
(Lathwell et al 1966)

Rate of N Per Cent N Recovery
Fall Sidedress NH4 NO3 NHa Urea Cyanamid
0 40 82
0 80 55
80 0 5 16 14 25


Wide variability among locations with regard to relative effectiveness of fall ap-
plied N was observed. Pearson et al, (1961) found that differences in rainfall did not
account for this variability. They, therefore, examined variations in soil texture and as
shown in Table 4, the effectiveness of fall applied N was not related to differences in
soil texture.
In an experiment on Romulus silt loam in New York, several rates of fall plow-
down N were compared to the same rates of N applied as summer sidedress. As shown
in Figure 4, yields from 60 to 120 pounds of N sidedressed were equal to those
obtained with 120 and 240 pounds of N plowed down in the fall respectively.
Similar experiments (14 in total) comparing fall applied N and summer side-
dressed N were also made in Nebraska (Olson et al, 1964). The results obtained in
Nebraska (Figure 5) are similar to those from New York where 40 pounds of N
sidedressed was equal to 80 pounds plowed down in the fall and 80 pounds sidedressed
was equal to 160 pounds of N plowed down in the fall. In these experiments at the
rates used, yields from fall plown N were always lower than from summer sidedress.
Olson et al (1964) found no difference between nitrate and ammonium forms of N in
their experiments.
Nitrogen recovery in the Nebraska experiments is given in Figure 5 and is similar
to that found in New York. The percentage recovery of applied N was higher at the
lower rates of application for the summer sidedressed N, but little effect of rate was









TABLE 4
RELATIVE EFFECTIVENESS OF FALL APPLIED N COMPARED TO
SPRING APPLIED N ON CORN YIELDS IN SOUTHEASTERN
(AVERAGE OF 4 YEARS OF DATA)
(PEARSON ET AL 1961 )


N Source

NH4NO3
NH3
Urea
NaNO3
(NH4)2 SO4
Mean


Relative Effectiveness
of Fall Applied N
as Per Cent of
Spring Applied NH4 NO3
53%
50
49
47
59
49


SOIL TYPE
Greenville Sandy Loam 69
Greenville Fine Sandy Loam 61
Cecil Sandy Loam 48
Decatur Clay Loam 46
Houston Clay 45
Ruston Sandy Loam 45
Tifton Sandy Loam 13


* Fall Plowdown
o Summer Sidedress


""15 45 75 135 255
Fertilizer N added, Ib/A
Figure 4. Yield of corn grain plotted against
fertilizer N added for an experiment in New
York on Romulus silt loam.



















1%



* Fall Plowdown
o Summer Sidedress


Fertilizer N added, lb/A
Figure 5. Yields of corn grain plotted against
fertilizer N added by two methods for 14 experi-
ments in Nebraska. Numbers adjacent to the
curves represent the increase in N content of the
above ground dry matter resulting from each in-
crement of fertilizer expressed as per cent of the
increment. (Olson et al 1964)


found for fall plow down N. At all rates, the recovery of N was lower for fall plow
down than for summer sidedressed N.
These data reported for several parts of the United States are typical of other
published data available. Welch et al (1966) have shown in their experiments on wheat
in Illinois that fall applied N was only about 67 percent as efficient as spring applied
N. Stevenson and Baldwin (1969) likewise found in Ontario that corn yields were
inferior with fall applied N compared to summer sidedressed N. In their experiments
no rate of fall applied N used gave yields as high as the optimum rate applied sidedress.
In addition, they found no differences among sources of N used. Thus, the available
evidence indicates that fall applied N is inferior to summer sidedressed N both from
the standpoint of yield response of corn and from percentage recovery of applied
fertilizer N. Also, different sources of N are not consistently different from one
another regardless of time of application.


COMPARISONS OF EARLY SPRING APPLIED NITROGEN AND SUMMER
SIDEDRESS APPLICATION OF NITROGEN ON CORN
In an experiment on Honeoye silt loam in New York, (Lathwell et al, 1966)
several sources of N were broadcast at one rate and plowed under in early spring and
compared to summer sidedressed N. As shown in Table 5, there was some decrease in
relative effectiveness of the early spring plowdown treatment, but not nearly so
marked as the decrease for fall application. Some variation in source was found, with
urea in this instance appearing inferior to the other sources. Percent recovery (Table 6)
of spring applied N was not greatly different from that of summer sidedressed N
except for urea at the 80 pound rate. Recovery from the 80 pound rate was signifi-
cantly lower than that for the 40 pound sidedress rate. In addition, there was no
difference in yield between the 40 and 80 pound sidedress rate of N.








TABLE 5
RELATIVE EFFECTIVENESS OF EARLY
SPRING APPLIED N COMPARED TO
SIDEDRESS APPLIED N ON CORN ON
HONEOYE SILT LOAM IN NEW YORK
(1 YEAR DATA)
(Lathwell et al 1966)

Relative Effectiveness of
Early Spring Applied N
as Per Cent of
N Source Sidedress Applied N
NH4NO3 84%
NH3 85
Urea 61
Cyanamid 97
Mean 83


TABLE 6
PER CENT RECOVERY OF EARLY SPRING AND SIDEDRESS APPLIED IN
BY CORN ON HONEOYE SILT LOAM IN NEW YORK
(1 YEAR DATA)
(Lathwell et al 1966)

Rate of N Per Cent N Recovery
Spring Sidedress NH4NO3 NH3 Urea Cyanamid
0 40 82
0 80 42
80 0 34 54 10 44


In another experiment on Lima silt loam (Figure 6) at low rates of N, summer
sidedress N was superior to spring plowdown. At the 120 pound rate, little difference
was found between times of application while at the highest rate, the yields from the
plowdown N was slightly higher than from the summer sidedressed N. When soil
samples were taken at sidedress time, however, only about 30 percent of the spring
applied N could be recovered in the upper 16 inches of soil regardless of rate of
application of N.
In the same experiments described earlier, Olson et al (1964) found that summer
sidedressed N was superior to spring applied N at all rates tested (Figure 7). These
results showed little difference between fall and early spring applied N. Likewise,
percentage recovery of spring applied N was only slightly higher than that for fall
applied N and substantially lower than the recovery of summer sidedressed N.
In contrast to the results reported here, Stevenson and Baldwin (1969) on fine
textured soils in Ontario found no difference in effectiveness of spring applied and
summer sidedressed N on corn. Thus, it appears that early spring applications of N
may be as effective as summer sidedress application under certain circumstances and
definitely inferior in other situations. There appear to be no particularly reliable
criteria to predict which condition may prevail.

RESIDUAL EFFECTS OF APPLIED NITROGEN
Even under the most favorable conditions of application, from 75 to 80 percent
of the applied N is recovered in the crop to which it is applied and more likely only 50
























6 Spring Plowdown
o Summer Sidedress


15 45 75 135 255
Fertilizer N added, Ib/A

Figure 6. Yield of corn grain plotted against fertilizer
N added by two methods for 2 years to Lima silt loam
in New York.






150-



125-
39%
<4 35%
-51%
058% 34%
0


* Spring Applied


Fertilizer N added, lb/A

Figure 7. Yield of corn grain plotted against fer-
tilizer N added by two methods for 14 experi-
ments in Nebraska. Numbers adjacent to the
curves represent the increase in N content of the
above ground dry matter resulting from each
increment of fertilizer expressed as per cent of
the increment. (Olson et al 1964)









to 75 percent will be recovered. Under less favorable times and methods of applica-
tion, recovery may fall as low as 10 percent and routinely is in the range of 25 to
35 percent. Under many circumstances, then, well over half the applied N is not
utilized by the crop to which it was applied. As shown in Table 7, on several soils in
New York, any spring applied N that had not been utilized by the corn crop to which
it was applied had disappeared from the upper 16 inches of soil by the following
spring. Thus, any residual effect from the unutilized N is improbable.
In a laboratory and greenhouse experiment, samples of a Williamson silt loam on
which 4 consecutive crops of corn receiving differential N fertilization had been grown
were collected. As shown in Table 8, there was no difference in the inorganic N
content of the soil as taken from the field or after being incubated for 60 days.

TABLE 7
INORGANIC NITROGEN IN THE UPPER 16 INCHES OF SOIL IN THE SPRING
FOLLOWING DIFFERENTIAL NITROGEN FERTILIZATION OF CORN
Inorganic N in
Surface 16" of
N Removed in Soil, in Spring
Year of Quantity of Corn Grain + Following Year
Location Application N Applied Stover of Application
lb/A
Langford Silt Loam 1966 135 136 22
Langford Silt Loam 1966 15 99 10
Dunkirk Silt Loam 1965 135 168 8
Dunkirk Silt Loam 1965 15 81 12
Lima Fine Sandy Loam 1966 135 185 32
Lima Fine Sandy Loam 1966 15 137 36
Romulus Silt Loam 1967 255 198 52
Romulus Silt Loam 1967 25 101 37
Howard Gravelly Loam 1967 135 166 44
Howard Gravelly Loam 1967 15 129 48


TABLE 8
RESIDUAL NITROGEN AS MEASURED BY LABORATORY AND GREENHOUSE
EXPERIMENTS IN SAMPLES OF THE SURFACE HORIZON OF A
WILLIAMSON SILT LOAM FROM SARATOGA COUNTY AFTER 4 YEARS
OF DIFFERENTIAL NITROGEN FERTILIZATION UNDER CORN

Total Nitrogen Greenhouse Experiment
Removed in
Fertilizer Nitrogen Grain + Stover
Applied 1965 +'66 1965 +'66 + '67 Yield of Oats
+ '67 + '68 + '68 Inorganic N in Soil in Greenhouse
lb/A Original Incubation gm/Pot1
700 646 13 41 1.86
60 539 12 46 1.92
1Nitrogen additions equivalent to 100# of N per 2 X 106 pounds of soil resulted in yields of 4.02
grams per pot with both sets of soil samples.









Likewise, yields of oats grown on these samples in the greenhouse were not different
indicating that no differences in residual N as a consequence of differential fertiliza-
tion were present. These data show that in this soil, at least, the unutilized fertilizer N
was not incorporated into a readily mineralizable organic form which could become
available to a subsequent crop.
In a field experiment to evaluate the residual effects of N on subsequent crops,
oats were planted on a Troy silt loam following three years of differential N fertiliza-
tion of corn. In this field experiment, no difference in oat yields was measured and the
N content of the crop was not different (Table 9). Thus, the residual effect of the
applied N was negligible on this soil and supports the results found by measuring the
inorganic soil N content and that released by incubation. These experiments indicate
that under the conditions found in New York, residual effects of applied N are un-
likely.
Under certain conditions some residual effects of applied N may be found. As
shown in Table 10, Pearson et al (1961) found a winter oat forage crop responded
substantially to N applied the previous spring to corn. Even in the second year, corn
showed some response to residual N, especially at the highest rate. They found, how-
ever, that fall applied N fertilizers increased the small grain forage yield following the
corn crop only slightly. In addition, carry-over to the second corn crop, planted some
18 months after fertilizer application, was negligible.


TABLE 9
RESIDUAL NITROGEN IN TROY SILT LOAM IN WASHINGTON COUNTY AS
MEASURED BY AN OAT CROP FOLLOWING 3 YEARS OF DIFFERENTIAL
FERTILIZATION OF CORN

Oat Crop 1968
Total Nitrogen
Removed in Inorganic N
Fertilizer Nitrogen Grain + Stover in Soil Be-
Applied, 1965 +'66 1965 + '66 fore Plant- Yield' N Content of'
+ '67 + '67 ing Oats Dry Master Oats
lb/A
525 446 25 8700 52
45 274 18 8600 58
1 Addition of 20# N/Acre to a portion of either set of plots increased yield to 9600# of dry matter
containing 64 pounds of N.


TABLE 10
RESPONSE OF SUCCESSIVE CROPS TO A SINGLE APPLICATION OF N AT
VARYING RATES MADE IN SPRING BEFORE FIRST CORN CROP PLANTED
[PEARSON ET AL 1961]

Increase in Yields over Check
Rate of N Applied
to First Corn Crop
in Spring Corn Bu/A Oat Forage lb/A Corn Bu/A
50 29.4 191 3
100 42.7 600 7
200 47.7 1600 19










Studies of residual effects of fertilizer N were undertaken in Nebraska and re-
ported by Olson et al (1964). Their results are shown in Figure 8, and reveal increasing
residual effects from increasing rates of applied N. Even more striking, however, was
the greater residual effect from sidedressed N compared to earlier times of application.
There was little yield response to N additions above 40 pounds per acre on these
irrigated soils in the year of application due to high initial levels of soil N. There was
considerable residual effect from the higher rates in the second year, especially where
N was sidedressed. Utilization efficiencies ranged from 20 to 50 percent over the two
years with the sidedressed N being most efficient at all rates of application. Olson et al
(1964) point out that any residual N in the year of treatment would have equal
opportunity for stable combination in the soil by the year after treatment regardless of
application time so that the differences in residual effectiveness of applied N reflect
losses that had occurred.


160 LBS. N
SD


YEAR RESPONSE

YEAR RESPONSE


80 LBS N
SO


Figure 8. Mean two year response of corn to
one application of fertilizer N on two irrigated
soils in Nebraska. (Olson et al 1964)

White and Pesek (1959) in Iowa soils showed that significant quantities of residual
N may be found after the growing of a corn corp. In their experiments the residual N
was found chiefly as nitrate and was located in the 6 to 21 inch layer. Little residual
ammonium N was found and the effects of residual N on nitrifiable forms of N was
negligible.
FATE OF UNUTILIZED NITROGEN

The data presented reveal that from 20 to 90 percent of the N applied to corn was
not utilized by the crop to which it was applied. Variable amounts of this N may be










recovered by subsequent crops. Both the data of White and Pesek (1959) and that of
Olson et al (1964) show that while residual effects of N are significant in some
situations, still some 50 percent or more of the applied N was not recovered in the
crops grown and thus, remained unaccounted for.
A possible fate of the applied N is immobilization into the organic fraction of the
soil. An evaluation of the data indicates, however, that this is not a likely fate for any
significant portion of the unutilized N. White and Pesek (1959) were unable to show
residual effects to other than the nitrate form. Likewise, in the data reported for the
Williamson silt loam from New York (Table 8), incubation tests showed no difference
in inorganic N mineralized as a result of previous N application. Bouldin and Lathwell
(1968), on a long term rotation experiment on Honeoye silt loam, were unable to
show any increase in the organic N content of this soil as a result of inorganic fertilizer
N application. They concluded that the N was lost from the soil system and therefore
not immobilized. From these results it seems unlikely that substantial net immobiliza-
tion of inorganic fertilizer N occurs.
Regardless of the form of inorganic N applied to soils, the evidence indicates that
it is converted rapidly to nitrate under most conditions (Lathwell and Peech, 1964).
Nitrate being an anion does not react with the soil and, thus, is not retained by the
soil. It, therefore, moves through the soil profile in the percolation water and can
ultimately reach the ground water. Johnston et al (1965) in California found the N
content of tile drainage effluent from fertilized irrigated soils to range from 1.8 to
62.4 ppm and the quantity found was correlated with that applied to the soils. Most of
the N lost in the drainage water was found to be nitrate in their studies. Their figures
showed that as much as 70 percent of an application of 240 pounds of N per acre
could be lost in the tile drain effluent.
Zwerman et al (1969) found that the tile drain effluent from a recently heavily
fertilized Honeoye silt loam could contain as high as 140 ppm N as nitrate following a
heavy rain. Their figures also indicate that large quantities of N can be lost in the
drainage water resulting from natural rain fall.
The classical lysimeter experiments of Bizzell and Lyon (1927) showed on
cropped soils losses of N in the range of 6 to 8 pounds per acre per year in the
percolate, while on bare soils they found losses ranging from 40 to 70 pounds per acre.
These soils, however, had received relatively little N fertilizer compared to present day
practices.
These data indicate large quantities of N can be lost from soils in the drainage
water. It is also apparent that once N has moved into the profile below the zone of
organic matter accumulation, it is quite stable and remains as nitrate indefinitely under
many conditions. The data of Herron et al (1968) in deep loess-derived soils in Ne-
braska showed that large amounts of nitrate could be stored within the surface 6 feet.
A large portion of the N was found in the zone between 1 foot and 6 feet and
apparently remained there as nitrate. Obviously this N would be available to any
subsequent crop which rooted to these depths. White and Pesek (1959) also found that
the N in Iowa soils below the plow layer remained as nitrate.
As long as the N remains as nitrate and escapes from the rooting environment of
plants, it is a potential pollutant of the environment. It may escape to the groundwater
where it may accumulate and pose a potential hazard to the health of humans if they
use the groundwater as a source of drinking water. On the other hand, nitrate may
escape to streams and other aquatic environments and cause sufficient enrichment of
the water to cause significant entrophication. This may reduce the usefulness of
streams and lakes sufficiently to be a serious environmental problem.
The third possible fate of unutilized inorganic N in agricultural soils is denitrifica-
tion. In this process nitrate is reduced to elemental nitrogen (N2), nitrogen dioxide
(NO ) or nitrous oxide (N20), of which the most significant is elemental nitrogen.









Denitrification is favored by anaerobic conditions where certain organisms are able to
use nitrate or nitrite in place of elemental oxygen. Readily decomposable organic
matter is essential for denitrification to occur also.
Allison (1955), in his study of N balance sheets, showed that in almost all experi-
ments "unaccounted for losses" occurred. Allison concluded from his study, which
included lysimeter data from Ithaca, New York, that these losses occurred as a conse-
quence of denitrification. Viets (1960) reported that some 60 percent of applied N
was not accounted for in crop removal or increased soil N at Brawley, California where
no leaching losses occurred. Olson et al (1964) also presented indirect evidence to
show that significant losses of N from Nebraska soils occurred as a result of denitrifica-
tion.
In evaluating our data from New York, we have concluded that some significant
portion of the applied fertilizer N is lost by denitrification. Our soils are high in
organic matter and a readily decomposable carbon supply is available. These soils are
also fairly impermeable so that water movement through them is rather slow. Under
these conditions, we believe that both aerobic and anaerobic zones can coexist in the
same soil. This may be particularly true after heavy rains in late spring and early
summer. In soild normally considered to be aerobic, significant losses of applied N by
denitrification can thus occur in local zones where the environment is anaerobic. As
pointed out by Black (1968), adjacent anaerobic and aerobic microenvironments have
the potential for continuous loss of N from the soil by denitrification.
It seems evident from these considerations that significant loss of N from soils
occurs by denitrification although actual quantities lost are not known with any
precision. Quantitative data on the magnitude of field losses of N by denitrification
would contribute greatly to our understanding of the fate of applied N in soils.
Meanwhile, only curde estimates can be made of the magnitude of the losses. We
estimate that losses by denitrification are at least as great as those by leaching in most
experiments and may be far greater than leaching losses in others. Nitrogen that
escapes from the soil as N2 merely mixes with the N2 already present in the atmo-
sphere and is so insignificant in quantity compared to the N2 content of the atmo-
sphere as to be undetectable. Unutilized fertilizer N that is lost from the soil system by
denitrification then does not contribute to environmental pollution.


IMPLICATION FOR FERTILIZER NITROGEN MANAGEMENT
Fertilizer N is necessary for efficient crop production throughout the world. Vast
increases in consumption of fertilizer N in the past decade are a reflection of this need.
The evidence summarized in this discussion shows that even under the most favorable
conditions some fertilizer N will not be utilized by the growing crop and, therefore,
may be lost to the environment.
We believe a careful economic analysis of application rates must be made since at
high rates little yield response to the final increments is obtained and the efficiency of
use is very low. Thus, rate of application must be adjusted to maximize return and
minimize loss to the environment.
From the data presented, proper timing of application appears to hold the most
promise of influencing the efficiency of applied fertilizer N. the longer fertilizer N
remains in the soil, the greater is the probability of loss by one mechanism or another.
Less N, therefore, will be required to produce the same yield the closer it can be
applied to the time of maximum demand by the crop. For corn summer sidedress
applications fit this requirement. The number of experiments made under the wide
variety of conditions examined here lead us to conclude that to get maximum effi-
ciency and to minimize environmental pollution most, if not at all, fertilizer N applied
to corn should be summer sidedressed.






206


For all crops to maximize efficiency of use and to minimize potential loss, fertil-
izer N should be applied as close as possible to the period of greatest crop demand.

LITERATURE CITED
1. Allison, F. E., 1955. The enigma of soil nitrogen balance sheets. Adv. Agron.
7: 214-250.
2. Bizzell, J. A., and Lyon, T. L., 1927. Composition of drainage waters from ly-
simeters at Cornell University. Proc. and Papers, First Internat. Cong. Soil Sci., II:
342-357
3. Black, C. A., 1968. Soil-Plant Relationships. Second Edition John Wiley & Sons,
Inc., New York.
4. Herron, G. M., Terman, G. L., Dreier, A. F., and Olson, R. A., 1968. Residual
nitrate nitrogen in fertilized deep loess-derived soils. Argon. J. 60: 477-482
5. Johnston, W. R., Ittihadiek, F., Daum, R. M., and Pillsbury, A. F., 1965. Nitrogen
and Phosphorus in Tile Drain Effluent. Soil Sci. Soc. Amer. Proc. 29: 287-289
6. Lathwell, D. J., and Peech, M., 1964. Interpretation of Chemical Soil Tests.
Cornell Univ. Agr. Exp. Sta. Bul. 995
7. Lathwell, D. J., Free, G. R., and Bouldin, D. R. 1966 Efficiency of Fall Applied
Nitrogen in New York for Corn and Small Grains. Agronomy Mimeo 66-13,
Cornell University, Ithaca, N. Y.
8. Olson, R. A., Dreier, A. F., Thompson, C., Frank, K., and Grabouski, P. H., 1964.
Using Fertilizer Nitrogen Effectively on Grain Crops. Nebra. Agr. Exp. Sta. Bul.
S. B. 479
9. Pearson, R. W., Jordan, H. V., Bennett, O. L., Scarsbrook, C. E., Adams, W. E.,
and White, A. W., 1961. Residual Effects of Fall- and Spring-Applied Nitrogen
Fertilizers on Crop Yields in the Southeastern United States. U. S. Dept. Agr.
Tech. Bul. 1254
10. Stevenson, C. K., and Baldwin, C. S., 1969. Effect of time and method of
nitrogen application and source of nitrogen on the yield and nitrogen content of
corn (Zea mays L.). Agron. J. 61: 381-384
11. Thompson, L. M., 1969. Weather and Technology in the Production of Corn in
the U. S. Corn Belt. Agron. J. 61: 453-456
12. Viets, F. G., Jr., 1960. Revovery of fertilizer nitrogen or irrigated and dryland
soils of the western United States. Proc. 7th Internat. Cong. Soil Sci., III: 486-493
13. Welch, L. F., Johnson, P. E., Pendleton, J. W., and Miller, L. B., 1966. Efficiency
of Fall-Versus Spring-Applied Nitrogen for Winter Wheat. Argon. J. 58: 271-274
14. White, W. C., and Pesek, J., 1959. Nature of Residual Nitrogen In Iowa Soils. Soil
Sci. Soc. Am. Proc. 23: 39-42
15. Zwerman, P. J., Greweling, H. T., Lathwell, D. J., and Steinhardt, F. P., 1969.
Nitrogen and Phosphorus Content of Drainage Water at Two Levels of Fertiliza-
tion. Agron. Abst. 104




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