• TABLE OF CONTENTS
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 Abstract
 Introduction
 Procedures
 Results
 Discussion
 Reference
 Acknowledgement
 Tables






Group Title: Agronomy research report - University of Florida Agronomy Department ; AY 92-05
Title: Rye or crimson clover and N fertilizer management to optimize corn ear leaf area, dry weight, and N concentration
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Permanent Link: http://ufdc.ufl.edu/UF00056114/00001
 Material Information
Title: Rye or crimson clover and N fertilizer management to optimize corn ear leaf area, dry weight, and N concentration
Physical Description: 19 leaves : ill. ; 28 cm.
Language: English
Creator: Henderson, Aaron B
Gallaher, Raymond N
University of Florida -- Agronomy Dept
Publisher: Agronomy Department, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1992?]
 Subjects
Subject: Crimson clover -- Fertilizers -- Florida   ( lcsh )
Rye -- Fertilizers -- Florida   ( lcsh )
Plants -- Effect of nitrogen on   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Aaron B. Henderson and Raymond N. Gallaher.
Bibliography: Includes bibliographical references (leaves 12-13).
General Note: Caption title.
General Note: Agronomy research report - University of Florida Agronomy Department ; AY 92-05
 Record Information
Bibliographic ID: UF00056114
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 62581963

Table of Contents
    Abstract
        Abstract
    Introduction
        Page 1
        Page 2
    Procedures
        Page 3
        Page 4
    Results
        Page 5
        Page 6
    Discussion
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Reference
        Page 12
    Acknowledgement
        Page 13
    Tables
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
Full Text

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Agronomy Research Report AY-92-05
:'. ..... Of F oriJ ,
Rye or Crimson Clover and N Fertilizer MaWagement-to-Op-timize Corn
Ear Leaf Area, Dry Weight, and N Concentration


Aaron B. Henderson and Raymond N. Gallaher
Participant in Student Science Training Program and Professor of
Agronomy, respectively, Agronomy Department, Inst. Food and Agri.
Sci., University of Florida, Gainesville, FL 32611.


ABSTRACT
Growth and nutrition of corn (Zea mays L.) are dependent upon
having a sufficient area of the leaves in relation to the land on
which they are growing. Nitrogen nutrition and management schemes
influence the corn plant's leaf area, and subsequently, growth and
yield. Ear leaf N concentration, area, and weight will benefit if
cover crops [crimson clover (Trifolium incarnatum L.) and rye
(Secale cereale L.)] and specific management schemes are utilized.
The objective of this research was to determine the best management
practice (BMP) of using rye or crimson clover and N fertilizer to
optimize corn ear leaf area, dry weight and N concentration. Each
cover crop is manipulated under each different management scheme
which includes the type of tillage (no-tillage vs. conventional)
and the amount of applied inorganic N fertilizer. The corn plants
on each separate plot were analyzed by picking the top ear leaf off
five plants and determining the total leaf area, dry weight, and N
concentration. Under clover management, no-tillage mulch was
proposed to be the most economical requiring only 57 kg N/ha to
meet the sufficiency level of 2.70% N required for healthy corn.
Under rye, no-tillage mulch was found to be the BMP based on
expected economics as well as conservation benefits. Too little N
and improper management will result in reduced corn yield, reduced
production for export sales, loss of profits, waste of resources,
and inefficiency. Too much N again results in inefficiency as well
as potential ground water pollution. If corn could be produced in
its ideal conditions with minimum tillage and N application,
resources would be maximized and efficiency increased with less
labor and less expense.









INTRODUCTION
With the growing dilemma of maximizing crop production to feed
the ever-increasing populace on this planet, consideration must be
given to discovering methods which increase efficiency. Farmland
must be utilized for growing crops on a year-round basis. The
practices of minimum tillage will aid in conserving the land and
other resources while practicing multiple cropping for food
production.1

The term multiple cropping refers to growing more than one
crop on the same plot of land in one 12-month period. Succession
cropping is one of the most commonly practiced types of multiple
cropping. This type of cropping describes the growing of two or
more crops in succession on the same soil in one year.1 Double
cropping, a type of successive multiple cropping, was used in this
experiment. Two crops were grown in succession, one in the
fall/winter and one in the spring/summer.

Minimum tillage, a conserving method of land and resources,
refers to disturbing the soil as little as possible to produce a
crop. Conventional tillage, the most commonly practiced method, is
a sharp contrast to minimum tillage, for it employs the use of
tillage implements such as plows to mix and turn over the land to
deposit seeds of a crop. No-tillage, a form of minimum tillage, is
defined as the opening of a slot in the soil only sufficiently deep
and wide to properly deposit and cover the seeds.1 Advantages of
no-tillage include the reduction of erosion, conservation of
resources (land, water, and fuel), the increase of field use,
reduction of labor and production costs, and efficient use of
time.2

A cover crop, or the first crop in a double cropping
system, is planted in the fall and then sacrificed in the spring
for the summer crop corn (Zea mays L.). A cover crop can be useful
for the cash-crop corn because it provides essential elements to
the soil. However, the method in which the soil is tilled is also
an essential factor that can affect crop yield. Along with the two
different types of tillage (no-tillage vs. conventional), there are
different manipulations of the cover crop such as forage, green
manure, and mulch.

Forage is used as feed for rumen animals. The cover crop is
removed from the land leaving only the roots behind. The risk of
erosion is reduced since the roots hold the soil in place.
However, 90% of the plant is removed for animal feed and therefore
the N supply available for the succeeding crop is minimal. The
main benefit of using the cover crop as forage is that it is
profitable for the farmer to sell or use the crop for livestock
feed.









Green manure is composed of organic matter which includes the
sacrificed cover crop. Green manure reduces runoff and erosion
while improving the degree of soil aggregation. Green manure is
best used to increase the organic matter content of the soil,
contributing essential elements to the soil.

Mulch is composed of the killed winter cover crop, compost,
leaves, residues, as well as inert materials such as sand and
pebbles. Mulch prevents water loss from the soil by evaporation
and keeps the soil moist and cool. Decaying mulch can serve to
hold more plant nutrients as well as the addition of nutrients to
the soil.3

The use of a legume as the cover crop has certain benefits to
the soil and crop which follows. The legume has a symbiotic
relationship with N-fixing bacteria. The bacteria live on the
plant's roots, absorbing the vital photosynthate (i.e. glucose)
that it requires from the plant, while converting the N in the
atmosphere (N,) into NO, or NO2, the sources of essential N for the
plants. The cover crop crimson clover (Trifolium incarnatum L.) is
a legume, although rye (Secale cereale L.) is not. Rye has the
benefits of making an excellent mulch.

Nitrogen is the single most important fertilizer element and
is required in the largest quantities for crop growth.4 Legumes
are one source of organic N that can be used as a cover crop to be
sacrificed for corn in a double cropping system. A second source
of N is inorganic N fertilizer which is applied in the form of
ammonia NH, in the compounds of NH4NO3 or NH4SO4. However, there
exists a limit to how much N a crop can absorb and utilize. Too
much N may induce K* deficiency, a vital mineral needed for
photosynthesis and proper regulation of turgor pressure and
stomata.5 Skeletal soils, like those in Florida, need heavy inputs
of N, thus increasing the demand for expensive inorganic N
fertilizer. A cover crop must be utilized to offset the need for
N. The corn crop has a sufficient level of N if the concentration
in the ear leaf at early silking and tasseling is between 2.70% and
4.0% N.6 A proper balance between the right cover crop, the right
manipulation of the cover crop, and the right amount of inorganic
N fertilizer will lead to the ideal conditions for corn growth at
the lowest cost.

In order to discover the most efficient methods to grow the
best crop, a number of null hypotheses have been created.
I. The cover crops of crimson clover or rye will not satisfy
the N requirements of corn, nor affect the ear leaf area, ear leaf
weight, or ear leaf N concentration.
II. Inorganic N fertilizer will not be needed in any amount
to meet the N requirements of corn (under the influence of the
cover crops), nor affect the ear leaf area, ear leaf weight, or ear
leaf N concentration.









III. Management schemes used on the cover crops will not
affect the ear leaf area, ear leaf weight, or ear leaf N
concentration of corn.

Growth and nutrition of corn is dependent upon having a
sufficient leaf area, the area of the leaves in relation to the
land on which they are growing. Nitrogen nutrition and management
schemes influence the corn plant's leaf area, and subsequently,
growth and yield.

Each cover crop is manipulated under each different management
scheme which includes the type of tillage (no-tillage vs.
conventional), the type of cover crop sacrifice (forage, green
manure, or mulch), and the amount of applied inorganic N
fertilizer. Two different plots of land, each with one of the two
cover crops planted in the fall, were divided into five sections of
different management schemes which were further subdivided into
five sections of different applied amounts of inorganic N
fertilizer. Each of these individual sections are repeated four
times to insure reliable data. The corn plants in each separate
section were analyzed by picking the top ear leaf off five random
plants and determining total leaf area, dry weight, and N
concentration.

Too little N and improper management will result in reduced
corn yield, reduced production for export sales, loss of profits,
inefficiency, and waste of resources. Too much N again results in
inefficiency as well as possible ground water pollution. If corn
could be produced in its ideal conditions with minimum tillage and
N application, resources would be maximized and efficiency
increased with less labor and less expense.

The objective of this research was to determine the best
management practice of using rye or crimson clover and N fertilizer
to optimize corn ear leaf area, dry weight and N concentration.


PROCEDURES
Two different species (crimson clover, rye) of cover crops
were planted in October 1991 on two separate plots of land. In
April 1992 the winter cover crop was manipulated according to five
different management schemes within each plot of land to nourish
the summer crop corn.

Each plot was divided into five main plots with each main plot
subjected to different manipulations of the cover crop. The
manipulations were as follows: (A) conventional tillage and
subsoil/forage of the winter crop, (B) conventional tillage and
subsoil/green manure of the winter crop, (C) no-tillage and
subsoil/mulch of the winter crop, (D) no-tillage and subsoil/forage
of the winter crop, and (E) conventional tillage and subsoil/fallow
(control). Furthermore, each of the above main plots were divided









into subplots with varying amounts of 0, 67, 134, 201, and 268
kg N/ha inorganic N fertilizer. Each of the 25 different subplots
(five different main plots multiplied by five different amounts of
N fertilizer) were replicated four times to insure reliable data.
All these subplots were randomly placed within the main plot. A
border row of untreated plants were on each side of the plot.

The samples were collected by removing the top ear leaf from
five random plants in each subplot and placed in a paper bag that
was marked with the cover crop, date, and plot number. Table 1 is
an example of the randomized setup of a main plot. The plot number
was determined by three factors: replication number (1-4),
manipulation type (tillage/subsoil 1-5), and the amount of added
amount of N fertilizer (1-5).

Table 1. Example of the randomization of a field plot of corn
following either crimson clover or rye
--------------NORTH DIRECTION----------------
134* 132 135 131 133



152 151 153 155 154



141 145 142 143 144



113 114 111 112 115



125 121 124 122 123

* 1 no.=replication no.1; 2d no.=management scheme; and
3rd no.=nitrogen rates.

All corn ear leaf samples were put through a leaf area index
meter (L1-3100). The sum of the five ear leaf areas represented
the leaf area for that subplot treatment. The samples were then
placed back in their bags and dried in a forced air oven at 70 C
for 24 hours and weighed on an analytical balance (Mettler PN 2210)
for dry matter weights. Then, all five leaves from each subplot
were ground in a Wiley mill to pass through a 2.00 mm stainless
steel screen. These ground samples were stored in air tight,
sterile plastic bags until they were analyzed. The tops of the
bags were opened and placed in a forced air oven at 70 C for four
hours then removed and resealed to insure no water contamination.









The Kjeldahl method for N determination was used to determine
ear leaf N concentration.7 After weighing 100 mg of leaf tissue,
3.2 g of catalyst (9:1 ratio of K2SO4:CuSO4) and 10 ml of sulfuric
acid (H SO4) were added and mixed with a centrifuge and then placed
in an aluminum digestion block.8 One ml of H202 was added to each
test tube to digest foaming compounds. After that was finished,
another ml was added and the samples were digested for six hours.
Each sample was brought to 75 ml volume with deionized water,
stored in plastic bottles, and analyzed on a Technicon II Auto
analyzer to determine N concentration.

Ear leaf area, dry weight, and ear leaf N concentration were
typed into a spreadsheet (Quattro Pro9) for manipulation and
transformation on a micro computer. Statistical analysis was
performed for a split-plot experimental design using MSTAT'0.
Harvard Graphics11 was used to plot relationships between changes
in leaf area, dry weight, N concentration, and applied N rates.


RESULTS
Crimson clover was one of the cover crops used to determine
the best management practice to optimize factors of corn growth.
Corn ear leaf area, dry weight, and N concentration are distinctly
affected by the various management schemes using clover and varying
amounts of N fertilizer.

Corn ear leaf area (Table 2 and Figure 1) increased (on the
average) as the amount of N fertilizer increased under all clover
management schemes up to 201 kg N/ha applied N fertilizer. With no
applied N fertilizer (0 kg N/ha) conventional-tillage forage was
the best with a leaf area of 2838 square cm while the fallow
(control) was the worst at 2160 square cm. With no applied N the
management scheme of conventional-tillage forage was 23.9% better
than the fallow scheme. At the maximum amount of applied N
fertilizer (268 kg N/ha) no-tillage mulch was the best method with
a leaf area of 3574 square cm while no-tillage forage was the worst
method with a leaf area of 3286 square cm. Thus, no-tillage mulch
was 8.1% better at that N level. All leaf areas were averaged
according to N level and management scheme. These averages
represented the leaf areas of 20 subplots (Table 2). Thus, on the
average, the leaf area was 26.4% better at the highest level of
applied N of 268 kg N/ha than at the 0 kg N/ha level for all
management schemes.

Corn ear leaf dry weight (Table 3 and Figure 2) increased (on
the average) as the amount of N fertilizer increased under all
clover management schemes up to 201 kg N/ha applied N fertilizer.
With no applied N fertilizer (0 kg N/ha) conventional-tillage green
manure performed the best while the fallow (control) performed the
worst. In fact, the conventional-tillage performed 30.7% better
than the fallow. At the highest level of applied N fertilizer (268
kg N/ha) no-tillage mulch performed the best with 21.88 g while no-









tillage forage was the worst method at 19.50 g. This translates to
a 10.9% higher weight for no-tillage mulch than no-tillage forage
at the 268 kg N/ha level. On the average, the dry weight was 38.4%
better at the highest level of applied N of 268 kg N/ha than at the
0 kg N/ha level for all management schemes (Table 3).

Corn ear leaf N concentration (Table 4 and Figure 3) increased
(on the average) as the amount of N fertilizer increased under all
clover management schemes all the way up to the 268 kg N/ha applied
N fertilizer level. With no applied amount of N fertilizer
conventional-tillage green manure had a ear leaf N concentration of
2.53% while no-tillage forage had a N concentration of 1.64% Thus
at this level conventional-tillage green manure was 35.2% better
than no-tillage forage. In fact the conventional tillage green
manure is only 0.17% N concentration under the 2.70% sufficiency
level6 with no applied inorganic N fertilizer. At the highest
level of applied N fertilizer (268 kg N/ha) conventional tillage
green manure again performed the best with 3.23% N while no tillage
mulch was the worst with 2.99% N although there existed only a 7.4%
difference between the two and both had exceeded the sufficiency
level. On the average, the N concentration was 38.8% better at the
268 kg N/ha level of applied N than at the 0 kg N/ha level for all
management schemes. On the average conventional-tillage green
manure had the highest N concentration, no-tillage mulch was
intermediate, and conventional-tillage forage, no-tillage forage,
and fallow had the lowest average N concentrations at all N levels
(Table 4).

Rye was the other cover crop used to determine the best
management practice to optimize corn growth. Corn ear leaf area,
dry weight, and N concentration were all uniquely affected by each
management scheme and varying amounts of N fertilizer.

Corn ear leaf area (Table 5 and Figure 4) increased (on the
average) as the amount of N fertilizer increased under all rye
management schemes up to 201 kg N/ha applied N fertilizer. With no
added N (0 kg N/ha) no-tillage mulch performed the best with a leaf
area of 2201 square cm while fallow performed the worst with 1607
square cm. Thus, with no applied N, no-tillage mulch was 27.0%
better than the fallow. At the highest level of applied N (268 kg
N/ha) no-tillage mulch again was the best at 3161 square cm while
no-tillage forage was the worst at 2777 square cm. At this level,
no-tillage mulch was 12.2% better than no-tillage forage. All leaf
areas were averaged according to N level and management scheme.
These averages represent the leaf areas of 20 subplots (Table 5).
Thus, on the average, the leaf area was 34.9% better at the highest
level of applied N of 268 kg N/ha than at the 0 kg N/ha level for
all management schemes. On the average, the 67 kg N/ha and 134 kg
N/ha levels of N were the same (Table 5).









Corn ear leaf dry weight (Table 6 and Figure 5) increased (on
the average) as the amount of N fertilizer increased under all rye
management schemes up to the 201 kg N/ha applied N fertilizer.
With no applied N fertilizer (0 kg N/ha) no-tillage mulch, the
best, performed 35.6% better than fallow, the worst. At the
highest level of applied N (268 kg N/ha) no-tillage mulch performed
the best with a weight of 20.83 g while no-tillage forage was the
worst at 19.12 g although the difference between the two was only
8.2%. On the average, the dry weight was 47.0% better at the
highest level of applied N that at the 0 kg N/ha level for all
management schemes. On the average, the dry weight at the 67
kg N/ha and 134 kg N/ha level of applied N were the same (Table 6).

Corn ear leaf N concentration (Table 7 and Figure 6) decreased
(on the average) from the 0 kg N/ha to 67 kg N/ha levels of N
fertilizer and increased (on the average) from the 67 kg N/ha all
the way to the 268 kg N/ha level of applied N fertilizer for all
rye management schemes. With no applied N fertilizer, no-tillage
mulch had the best ear leaf N concentration of 2.48% while fallow
had the worst of 1.77%. Thus with no applied N, no-tillage mulch
was 28.6% better than the fallow. In fact, at this level, no-
tillage mulch is only 0.22% N concentration under the 2.70%
sufficiency level6. At the 268 kg N/ha level of applied N
fertilizer no-tillage mulch had the best N concentration of 3.18%
while no-tillage forage was the worst with 2.96% N although both
were above the sufficiency level and there existed only a 6.9%
difference between the two. On the average, the N concentration
was 28.2% higher at the highest level of applied N fertilizer of
268 kg N/ha than at the 0 kg N/ha for all management schemes. On
the average, the N concentration was 7.7% higher at 0 kg N/ha than
at 67 kg N/ha for all management schemes (Table 7).

DISCUSSION
A 2.70% sufficiency level of N concentration in the ear leaf
of a corn plant is required for a healthy plant.6 Different cover
crops can be sacrificed and different management schemes utilized
to try to help provide the required N to the corn. In any event,
applied inorganic N fertilizer must be used in some amount to reach
this level. The amount of inorganic N fertilizer required to reach
this sufficiency level is critical for economic reasons (Table 8).

For crimson clover, no-tillage mulch required only 57 kg
N/ha, the least N fertilizer, while no-tillage forage required 179
kg N/ha, the most (Table 8). That means no-tillage forage required
68% more N fertilizer than no-tillage mulch to reach the same
sufficiency level of 2.70% N6. For management schemes under the
rye cover crop, conventional-tillage forage required the least N
fertilizer (143 kg N/ha) while no-tillage forage required the most
(230 kg N/ha). That translates to 37.8% more inorganic N
fertilizer required for no-tillage forage than for conventional-
tillage forage to reach the 2.70% N sufficiency level6.









Table 8. Amount of fertilizer nitrogen required for a
sufficiency level of 2.70% N in corn ear leaves.
(Kg N/ha) FERTILIZER
COVER CROP MANAGEMENT NECESSARY FOR SUFFICIENCY
Crimson CT-Forage 144
clover CT-Green manure 91
NT-Mulch 57
NT-Forage 179
Fallow (control) 119

Rye CT-Forage 143
CT-Green manure 151
NT-Mulch 170
NT-Forage 230
Fallow (control) 191


Economically, the less N fertilizer required for the corn crop
to reach the 2.70% N sufficiency level6, the less cost for the
farmer to produce the crop. If we assume that the farmer must buy
the N fertilizer at $0.66 per kg, then, under the clover cover
crop, it costs this farmer $40.92/ha more to achieve the
sufficiency level required for a healthy crop under the control
(fallow) rather than no-tillage mulching of the clover. It would
cost that farmer $80.52 more to achieve the sufficiency level under
no-tillage forage rather than no-tillage mulch. Thus, no-tillage
mulch is the best management practice (BMP), assuming that the
farmer has no livestock to feed.

If the farmer could not afford any N fertilizer when using a
clover cover crop then the BMP would be conventional-tillage green
manure. In this no added N situation, conventional-tillage green
manure provided 2.53% N concentration in the ear leaves, only 0.17%
less than the sufficiency level of 2.70% N6. Under conventional
tillage the cover crop (in the form of green manure) is immediately
exposed to the soil, releasing the organic N in the green manure to
the soil where micro-organisms can convert it into absorbable NO3.
Thus the N in the cover crop is maximized at the 0 kg N/ha level of
applied N fertilizer. However, only after 57 kg inorganic N/ha, at
a $37.62 cost to the farmer ($0.66 per kg N) the farmer would reach
the sufficiency level with less labor, conservation of land and
fuel (for plow, etc.), reduction of erosion, and increased
efficiency under no-tillage mulch. He would most likely earn that
$37.62 back with less wear on his plows and land, as well as less
labor for himself and field workers.

Under the influence of the rye cover crop, the farmer must pay
$31.68 more to achieve the sufficiency level required for healthy
corn under the control (fallow) then under conventional-tillage
foraging of the rye. He would also receive the benefits of the
forage which he could sell off or use for his own livestock.
However, under a conventional-tillage system, he works harder than









under no-tillage as well as running the risk of ruining his soil,
and shortening the life of his machinery. Thus, under rye
influence, the conventional-tillage forage may look profitable in
the near future, but in the long run the farmer may expose the soil
to erosion and decrease its productivity capacity for future
generations. No-tillage mulch would be the method of choice if the
farmer wished to conserve both soil and money. In order to produce
a crop under the control (fallow) the farmer would have to spend
$13.86 more to reach the sufficiency level of corn than under no-
tillage mulch.

If the farmer could not afford any N fertilizer under rye, the
BMP would be no-tillage mulch. In this no added N situation, no-
tillage mulch has the largest leaf area (Table 6) as well as a
2.48% N concentration (Table 9), only 0.22% away from the 2.70% N
sufficiency level6. The rye is not a legume, and thus under
conventional tillage management, there is no symbiotic bacteria
converting the N to NO3 and releasing it to the soil. Thus, under
rye, the benefits of a mulch are the strongest as well as the
management treatment of no-tillage.

As far as N concentration is concerned the farmer, under rye
cover crop, with no applied N is better off than the farmer who
adds 67 kg N/ha. This drop in average N concentration from 0 kg
N/ha to 67 kg N/ha (Table 8) can only be explained by a dilution
effect. Without the N-fixing bacteria converting N to NO3 under a
legume, corn under rye is so N starved that it only takes a little
N to "jumpstart" an explosive growth (37.1% in dry weight, Table 7)
that spreads the N throughout the new, large ear leaf which dilutes
the N concentration in the leaf. Thus, it takes a large amount of
inorganic N fertilizer under all methods to bring the N
concentration up to the sufficiency level in the newly expanded
leaf.

Corn ear leaf areas, dry weights, and N concentrations can be
used as diagnostic tools to predict corn yield. Thus, the
assumption is made that the larger the leaf area and the heavier
the dry weight the larger the corn yield will be. The estimated
leaf areas and dry weights varied at this 2.70% N6 sufficiency for
each management scheme under each cover crop (Tables 9,10).









Table 9 Estimated leaf area with minimum amount of fertilizer
nitrogen to reach 2.70% sufficiency level
ESTIMATED LEAF AREA
(square cm)
COVER CROP MANAGEMENT AT 2.70% SUFFICIENCY LEVEL
Crimson CT-Forage 3299
clover CT-Green manure 3076
NT-Mulch 3106
NT-Forage 3311
Fallow (control) 3174

Rye CT-Forage 3115
CT-Green manure 2957
NT-Mulch 2924
NT-Forage 2832
Fallow (control) 2915


At this sufficiency level the estimated leaf areas under the
crimson clover and rye management schemes varied only slightly and
were all statistically equal (Table 9).

Table 10 Estimated ear leaf dry weight with minimum amount of
fertilizer nitrogen to reach 2.70% sufficiency level
ESTIMATED DRY
WEIGHT (g)
COVER CROP MANAGEMENT AT 2.70% SUFFICIENCY LEVEL
Crimson CT-Forage 20.19
clover CT-Green manure 17.92
NT-Mulch 15.46
NT-Forage 19.54
Fallow (control) 18.58

Rye CT-Forage 20.88
CT-Green manure 19.02
NT-Mulch 18.09
NT-Forage 19.25
Fallow (control) 18.87


The estimated dry weights at the sufficiency level, however,
varied far more than the leaf areas (Table 10). The estimated dry
weight of the conventional-tillage forage scheme under clover was
20.19 g at the 2.70% N sufficiency level6 while the no-tillage
mulch weighed 15.46 g. That means that conventional-tillage forage
weighed approximately 23.4% more than no-tillage mulch at the same
sufficiency level. However, the farmer might receive greater
benefit using no-tillage mulch because it costs less to reach the
sufficiency level. Although the dry weight may be less at that
level, it costs the farmer under conventional-tillage forage $57.42
($0.66 per kg N) more than the no-tillage mulch to reach the
sufficiency level.









However, if the farmer has livestock to feed, then he may
elect to sacrifice the cover crop as forage and use that to feed
them. Or he may elect to sell off the forage for profit. In this
situation, conventional-tillage forage required only 144 kg
inorganic N/ha fertilizer while the no-tillage forage required 179
kg N/ha to reach the N sufficiency level at which they both had
equal dry weights. Thus it would cost the farmer $23.10/ha more in
N fertilizer to maintain a healthy crop under no-tillage forage
than conventional-tillage forage. However, factoring in wear and
tear on the machinery and the extra labor that conventional-tillage
carries, as well as the erosion prevention and soil conservation
benefits that no-tillage offers, the no-tillage foraging of the
clover could be the BMP in the long run.

The estimated dry weight of the conventional-tillage forage
scheme under rye was 20.88 g at the sufficiency level while the no-
tillage mulch weighed 18.09 g. That means that at the same
sufficiency level, the leaves under the conventional tillage forage
scheme would weigh approximately 13.4% more than those under the
no-tillage mulch scheme. No-tillage mulch may cost $17.82 more in
N fertilizer and be slightly smaller in dry weight at the
sufficiency level than conventional-tillage forage, but the farmer
saves money in the benefits of no-tillage. If the farmer needed
that forage, then no-tillage forage would be a better method then
conventional-tillage forage. The cost to the farmer would be
$57.42 more in N fertilizer to maintain a healthy crop under no-
tillage forage than under conventional-tillage forage. Yet, in the
long run, factoring soil conservation, resource conservation, and
labor, no-tillage could and be the BMP if the farmer plans to sell
off the forage or use it to feed his livestock.

The first hypothesis proved partially incorrect. The cover
crops of crimson clover and rye alone did not satisfy the N
requirements of corn. On the average, the cover crop of rye did
not affect the corn ear leaf area, dry weight, or N concentration.
However, crimson clover did affect the ear leaf N concentration
(Table 5). When the cover crop clover was left on the plot in form
of green manure or mulch, there was a higher N concentration as
opposed to the fallow (no cover crop), and forage (cover crop taken
off the plot). However, the clover had no significant effect on
the average ear leaf area and dry weight.

The second hypothesis proved completely incorrect. Inorganic
N fertilizer was needed to meet the N requirements of corn (Table
8). The inorganic N fertilizer increased, on the average, the ear
leaf area, ear leaf weight, and ear leaf N concentration of the
corn under crimson clover cover. The fertilizer also increased the
ear leaf area, and dry weight of corn ear leaf under rye cover but
due to the dilution effect the ear leaf N concentration under rye
did not increase with the first addition of N fertilizer but did
increase thereafter.









The third hypothesis proved partially incorrect. The
management schemes used on the rye cover crop had no effect, on the
average, on the ear leaf area, weight, or N concentration. The
same was true for clover except that the management schemes did
have an effect on ear leaf N concentration. The conventional-
tillage green manure and the no-tillage mulch schemes had a higher
average N concentration then the other schemes.

There are many different scenarios that farmers find
themselves in. One may have livestock to feed, another may want to
sell off the forage, while a third may not have access to or funds
to attain N fertilizer to supplement his corn crop. However, based
on resource conservation as well as producing healthy, N sufficient
corn, under the crimson clover cover crop at the lowest cost
overall, no-tillage mulch would be the BMP.

Rye as a cover crop, is very effective in recovering soil
nitrate.2 Rye provides for very low nitrate leaching which means
far less risk of ground water pollution. Based on land
conservation as well as producing healthy, N sufficient corn, under
the rye cover crop at the lowest cost overall, the best management
scheme would be no-tillage mulch.

Our world is becoming more environmentally conscious everyday.
We are beginning to see into the future and what will happen unless
we take care of our earth. No longer do we use goods and throw
away the containers, we recycle. Thus, we should do the same with
our soil from which our food grows. No-tillage is the best
management scheme for the long-term farmer. Its benefits far
outweigh its disadvantages. No-tillage reduces nitrate leaching
under corn systems which reduces the risk of ground water
pollution.13 Thus, while conserving some resources such as fuel and
soil, no-tillage farming protects others.

REFERENCES

1. Gallaher, Raymond N. (1980). Multiple cropping Minimum
Tillage. MMT-1, IFAS, University of Florida.

2. Gallaher, Raymond N. (1983). Minimum Tillage: Pollution
Solution. BMP, IFAS, University of Florida.

3. Gallaher, Raymond N. (1980). Value of Residues, Mulches or
Sods In Cropping Systems. MMT-5, IFAS, University of
Florida.

4. Olson, R.A. and D.H. Sander. (1988). Corn production. in,
Corn and Corn Improvement. Ed. G.F. Sprague, and J.W.
Dudley. Number 18 in the Agronomy series. American
Society of Agronomy, Inc., Crop Science Society of
America, Inc., and Soil Science Society of America,
Madison, wisconsin, USA. pp. 639-686.










5. Personal communication with Dr. Raymond N. Gallaher.

6. Jones, J. Benton, Jr., Harry A. Mills, and Benjamin Wolf.
(1991). Plant Analysis Handbook. Micro-Macro
Publishing, Inc. Athens, Ga.

7. Jones, J. Benton, Jr. (1991). Kjeldahl Method for Nitrogen
Determination. Micro-Macro Publishing, Inc. Athens, Ga.

8. Gallaher, Raymond N., C.O. Weldon, and J.G. Futral. (1975).
An aluminum block digester for plant and soil analysis.
Soil Sci. soc. Amer. Proc., 39: 803-806.

9. Quattro Pro, ver. 1.0. (1989). A spreadsheet software
program. Borland International, Inc. Scotts Valley, CA.

10. MSTAT, ver. 4.0. (1985). Microcomputer statistical
program. Michigan State University.

11. Harvard Graphics, ver. 2.0. (1987). Software Publishing
Corporation. Mountain View, CA.

12. Hargrove, W.L., J.W. Johnson, J.E. Box, Jr., and P.L. Roymer.
1992. Role of Winter Cover Crops in Reduction of Nitrate
Leaching. In proc. of the 1992 Southern Conservation
Tillage Conference. M.D. Mullen and B.N. Duck, Tennessee
Agricultural Experiment Station, Institute of Agriculture,
The Univ. of Tennessee, Knoxville, pp. 114-119.

13. Tyler, D.D., G.V. Wilson, J. Logan, G.W. Thomas, R.L. Blevins,
W.E. Caldwell, and M. Dravillis. 1992. Tillage and Cover
Crop Effects on Nitrate Leaching. In proc. of the 1992
Southern Conservation Tillage Conference. M.D. Mullen and
B.N. Duck, Tennessee Agricultural Experiment Station,
Institute of Agriculture, The Univ. of Tennessee,
Knoxville, pp. 1-5.

ACKNOWLEDGEMENTS

The authors appreciate Mr. James R. Chichester for laboratory
and computer assistance and Mr. Howard C. Palmer for leaf
collection assistance. Funding for this research came from a grant
from the Tennessee Valley Authority, a grant from Pioneer Hi-Bred,
International, Inc. and the Agronomy Department, Institute of Food
and Agricultural Sciences, University of Florida.










Table 2. Corn ear leaf area affected by clover-tillage management
and N fertilizer. (Average of five ear leaves)
Nitrogen level (kg/ha)
Management 0 67 134 201 268 Average
----- Square centimeter/5 leaves ------
CT-forage 2838 3258 3293 3333 3383 3221 v

CT-Green manure 2834 3043 3136 3236 3395 3129 v

NT-Mulch 2488 3214 3162 3405 3574 3169 v

NT-Forage 2274 2724 3158 3386 3286 2961 v

Fallow 2160 3044 3212 3521 3495 3086 v

LSD=169
Average 2519 c 3057 b 3192 b 3376 a 3422 a
CV=7.96%
CT-forage = Clover harvested for forage followed by conventional
tillage soil preparation. CT-Green manure = Clover turned under
with conventional tillage. NT-Forage = Clover harvested for forage
followed by direct seeding with in-row subsoil no-tillage planter.
NT-Mulch = Direct seeding in clover with in-row subsoil no-tillage
planter. Fallow = No winter cover crop, area kept clean tilled as
a control treatment. Values in rows within each management
treatment not followed by the same letter (a,b,c,d,e) are
significantly different at the 0.05 level of probability according
to LSD. Values in columns not followed by the same letter
(v,w,x,y,z) are significantly different according to Duncan's
multiple range test.


Corn ear leaf area affected by tillage-
clover management and N fertilizer


0 60 100 160 200 250 300
Kg/ha Nitrogen
- CT Forage CT Green Manure NT Muloh
-- NT Forage F- Fallow


Figure 1









Table 3. Corn ear leaf weight affected by clover-tillage
management and N fertilizer. (Average of five ear leaves)
Nitrogen level (kg/ha)
Management 0 67 134 201 268 Average
------------ Grams/5 leaves -----------
CT-forage 14.54 19.39 20.05 21.00 20.85 19.17 V

CT-Green manure 15.58 17.47 18.73 20.40 20.55 18.55 v

NT-Mulch 12.35 16.01 17.76 20.54 21.88 17.71 v

NT-Forage 11.22 15.22 18.30 20.15 19.50 16.88 v

Fallow 10.79 17.53 18.89 21.76 21.85 18.16 v

LSD=1.27
Average 12.90 d 17.12 c 18.75 b 20.77 a 20.93 a
CV=7.96%
CT-forage = Clover harvested for forage followed by conventional
tillage soil preparation. CT-Green manure = Clover turned under
with conventional tillage. NT-Forage = Clover harvested for forage
followed by direct seeding with in-row subsoil no-tillage planter.
NT-Mulch = Direct seeding in clover with in-row subsoil no-tillage
planter. Fallow = No winter cover crop, area kept clean tilled as
a control treatment. Values in rows within each management
treatment not followed by the same letter (a,b,c,d,e) are
significantly different at the 0.05 level of probability according
to LSD. Values in columns not followed by the same letter
(v,w,x,y,z) are significantly different according to Duncan's
multiple range test.


Corn ear leaf weight from tillage-
clover management and N fertilizer


0 50 100 150 200 250 300
Nitrogen Applied in kg/ha
- CT Forage -- CT Green Manure NT Muloh
- NT Forage Fallow


Figure 2










Table 4. Corn ear leaf N affected by clover-tillage management
and N fertilizer. (Average of five ear leaves)
Nitrogen level (kg/ha)
Management 0 67 134 201 268 Average
-------------- Percent ---------------
CT-forage 1.86 2.53 2.62 2.95 3.10 2.61 w

CT-Green manure 2.53 2.62 2.77 2.99 3.23 2.83 v

NT-Mulch 1.87 2.82 2.74 2.91 2.99 2.67 vw

NT-Forage 1.64 2.52 2.53 2.73 3.22 2.53 w

Fallow 1.71 2.39 2.75 3.10 3.16 2.62 w

LSD=.20
Average 1.92 d 2.58 c 2.68 c 2.94 b 3.14 a
CV=7.96%
CT-forage = Clover harvested for forage followed by conventional
tillage soil preparation. CT-Green manure = Clover turned under
with conventional tillage. NT-Forage = Clover harvested for forage
followed by direct seeding with in-row subsoil no-tillage planter.
NT-Mulch = Direct seeding in clover with in-row subsoil no-tillage
planter. Fallow = No winter cover crop, area kept clean tilled as
a control treatment. Values in rows within each management
treatment not followed by the same letter (a,b,c,d,e) are
significantly different at the 0.05 level of probability according
to LSD. Values in columns not followed by the same letter
(v,w,x,y,z) are significantly different according to Duncan's
multiple range test.


Corn ear leaf N affected by tillage
clover management and N fertilizer


0 50 100 160 200 250
Kg/ha Nitrogen
- CT Forage -- CT Green Manure -- NT Muloh
- NT Forage -- Fllow


300


Figure 3











Table 5. Corn ear leaf area affected by rye-tillage management
and N fertilizer. (Average of five ear leaves)
Nitrogen level (kg/ha)
Management 0 67 134 201 268 Average
----- Square centimeter/5 leaves ------
CT-forage 2102 2864 3101 3208 3085 2872 v

CT-Green manure 1952 2802 2952 2974 3095 2755 v

NT-Mulch 2201 2691 2782 3047 3161 2776 v

NT-Forage 2047 2589 2609 2874 2777 2579 v

Fallow 1607 2750 2858 2926 3111 2658 v

LSD=135
Average 1982 c 2739 b 2860 b 3013 a 3046 a
CV=7.96%


CT-forage = Rye harvested for forage followed by conventional
tillage soil preparation. CT-Green manure = Rye turned under with
conventional tillage. NT-Forage = Rye harvested for forage
followed by direct seeding with in-row subsoil no-tillage planter.
NT-Mulch = Direct seeding in rye with in-row subsoil no-tillage
planter. Fallow = No winter cover crop, area kept clean tilled as
a control treatment. Values in rows within each management
treatment not followed by the same letter (a,b,c,d,e) are
significantly different at the 0.05 level of probability according
to LSD. Values in columns not followed by the same letter
(v,w,x,y,z) are significantly different according to Duncan's
multiple range test.


Corn ear leaf area affected by tillage
rye management and N fertilizer

8.4
8.2-
2.4 -- -......
2.6 .

2

1.8 I -----


60 100 160
Kg/ha Nitroge


200 260 300


- CT Forage CT Green Manure -- NT Mulch
-- NT Forage Fallow


Flgwu 4









Table 6. Corn ear leaf weight affected by rye-tillage management
and N fertilizer. (Average of five ear leaves)
Nitrogen level (kg/ha)
Management 0 67 134 201 268 Average
----------- Grams/5 leaves -----------
CT-forage 11.50 17.86 20.64 22.41 20.70 18.62 v

CT-Green manure 10.68 17.99 18.78 19.73 20.06 17.45 v

NT-Mulch 12.60 16.82 16.45 19.51 20.83 17.24 v

NT-Forage 10.82 15.73 16.42 19.35 19.12 16.29 v

Fallow 8.11 16.93 18.22 18.98 20.70 16.59 v

LSD=1.17
Average 10.74 c 17.07 b 18.10 b 20.00 a 20.28 a
CV=7.96%
CT-forage = Rye harvested for forage followed by conventional
tillage soil preparation. CT-Green manure = Rye turned under with
conventional tillage. NT-Forage = Rye harvested for forage
followed by direct seeding with in-row subsoil no-tillage planter.
NT-Mulch = Direct seeding in rye with in-row subsoil no-tillage
planter. Fallow = No winter cover crop, area kept clean tilled as
a control treatment. Values in rows within each management
treatment not followed by the same letter (a,b,c,d,e) are
significantly different at the 0.05 level of probability according
to LSD. Values in columns not followed by the same letter
(v,w,x,y,z) are significantly different according to Duncan's
multiple range test.


Corn ear leaf weight from tillage
rye management and N fertilizer


0 60 100 160 200 250
Kg/ha Nitrogen
- CT Forage CT Green Manure NT Muloh
-- NT Forage -*- Fellow


800


Figure B











Table 7. Corn ear leaf N affected by rye-tillage management
and N fertilizer. (Average of five ear leaves)
Nitrogen level (kg/ha)
Management 0 67 134 201 268 Average
------------- Percent ---------------
CT-forage 2.38 2.05 2.64 2.86 3.16 2.62 v

CT-Green manure 2.19 2.01 2.56 3.01 3.07 2.57 v

NT-Mulch 2.48 2.39 2.37 2.91 3.18 2.67 v

NT-Forage 2.25 1.86 2.22 2.42 2.96 2.34 v

Fallow 1.77 1.88 2.14 2.74 3.01 2.31 v

LSD=0.17
Average 2.21 d 2.04 e 2.38 c 2.74 b 3.08 a
CV=7.96%
CT-forage = Rye harvested for forage followed by conventional
tillage soil preparation. CT-Green manure = Rye turned under with
conventional tillage. NT-Forage = Rye harvested for forage
followed by direct seeding with in-row subsoil no-tillage planter.
NT-Mulch = Direct seeding in rye with in-row subsoil no-tillage
planter. Fallow = No winter cover crop, area kept clean tilled as
a control treatment. Values in rows within each management
treatment not followed by the same letter (a,b,c,d,e) are
significantly different at the 0.05 level of probability according
to LSD. Values in columns not followed by the same letter
(v,w,x,y,z) are significantly different according to Duncan's
multiple range test.


Corn ear leaf N affected by tillage
rye management and N fertilizer


p 3.1
e
r
o 20
n
t
N 2.1


0 60 100 160 200 250 300
Kg/ha Nitrogen
- CT Forage CT Gren Manure -- NT Mulch
SNT Forage -"- Fallow


Figure 6




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