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dissertation entitled

ENHANCING YIELD, PROFITABILI‘I’Y, AND
NITROGEN MINERALIZATION IN CORN BASED
INTEGRATED CROPPING SYSTEMS

presented by

Marcus Jones

has been accepted towards fulfillment
of the requirements for

 

Ph.D. degreein grog and Soil Science

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MSU Is An Affirmative ActiorVEqual Opportunity Institution

ENHANCING YIELD, PROFITABILITY AND NITROGEN MINERALIZATION
IN CORN-BASED INTEGRATED CROPPING SYSTEMS

By

Marcus Jones

A DISSERTATION

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

DOCTOR OF PHILOSOPHY
Department of Crop and Soil Sciences

l 996

ABSTRACT
ENHANCING YIELD, PROFITABILITY AND NITROGEN MINERALIZATION
IN CORN-BASED INTEGRATED CROPPING SYSTEMS
13?

Marcus E. Jones

Cropping systems that emphasize high productivity while causing minimal
environmental degradation are currently being developed. Integrated cropping systems
focus on biological interactions within combinations of crop species, in contrast to
continuous cropping of a single species. Crop diversity is achieved through the use of
crop rotations, and with cover crops. To ensure farmer adoption of these systems, more
information is needed on their economic productivity.

In corn (Zea mays L.) -based cropping systems in Michigan, an adequate level of
mineralized soil N is essential early in the growing season in order to obtain optimum
growth and productivity. This study evaluated the changes in com productivity through
the combination of rotation and cover crops using commercial fertilizer or dairy manure
compost as a fertility source. Net economic returns at alternate price ratios for the first
three years of a cropping system were also studied.

In consecutive years of transition from alfalfa to corn in rotation, first-year corn
following wheat (Triticum aestivum L.). produced the highest yield and net economic
return. This effect occurred under both fertilizer and compost management systems. In
the second year of transition, the advantage of corn following wheat was enhanced by
overseeded red clover (T rifolium pratense L.) in wheat, especially under compost
management. When net returns for continuous corn and for a com-corn-soybean-wheat
rotation were averaged over the three years, the rotation produced the best economic

returns when the price of corn was low relative to soybean and wheat.

Mineralized N available to a corn crop was greatly afl‘ected by the previous crop
sequence. Soil nitrate levels in June were highest following wheat in year two, and
following a soybean wheat sequence in year three. This resulted in higher corn grain plus
stover biomass N. In an ancillary N fertilizer rate study conducted for two growing
seasons, annual ryegrass (Lolium multrflorum Lam.) overseeded into corn did not reduce
uptake by com of available N, but reduced fall soil N03 levels. Integrated cropping
systems that incorporate rotation and cover in crop production are economically beneficial

and reduce environmental impact.

ACKNOWLEDGMENTS

I thank my graduate committee advisor, Dr. Richard Harwood for his patient
guidance and oversight of my program. I also thank my committee members; Dr.
Maury Vitosh, Dr. Gerald Schwab, and Dr. Bernard Knezek for their input and
direction. I am grateful to the taxpayers of Michigan for their support. I thank Dr. James
Jay for his initial efforts to invite me to Michigan State University, and for his continued
support and encouragement. I greatly appreciate the technical help provided by Tim
Pruden, Elaine Parker, Jeff Smeenk, and Gary Zehr. I thank Greg Parker and the Farming
Systems Research Center staff for all their help in establishing and carefitlly maintaining
research plots. Thanks also to Brian Graff, Tom Galeka, Dallas Hyde, Cal Bricker, Lee
Siler, and the staff of Crop and Soil Sciences Farm for so greatly helping a newly arrived
“rookie”. I thank my friend fellow graduate student, Tom Willson for all the helpful
suggestions and good advice A special thanks to Neva Dehne, for the very long hours
taking and processing samples Thanks to Mario Mandujano, for the timely assistance.
Thanks to Anne Conwell for pomting me in the right direction so many times. Above all I
thank my wife Marquita, my son Jared, and my daughter Michal for their long-suffering
and forbearance. I thank my mother for her guidance and for long ago encouraging me to

study agriculture

iv

PREFACE

Chapter 1 written in publication format for Journal of Production Agriculture

Chapter 2 written in publication format for Agronomy Journal

TABLE OF CONTENTS

LIST OF TABLES ................................................... vii
LIST OF FIGURES ........................................................................................................ x
CHAPTER I -

CROP YIELD AND NET ECONOMIC RETURN OF CORN, SOYBEAN
AND WHEAT AS AFFECTED BY POSITION IN ROTATION,

FERTILITY SOURCE, AND COVER CROP ................................................................ 1
ABSTRACT ....................................................................................................... 1
INTRODUCTION .............................................................................................. 3
MATERIALS AND METHODS ........................................................................ 5
RESULTS AND DISCUSSION .......................................................................... 9
SUMMARY ....................................................................................................... 13
REFERENCES ................................................................................................. 15

CHAPTER 2 ‘

EARLY AND LATE SEASON SOIL NITRATE LEVELS IN CORN AS
AFFECTED BY POSITION IN ROTATION, FERTILITY SOURCE,

AND COVER CROP .................................................................................................... 37
ABSTRACT ..................................................................................................... 37
INTRODUCTION ............................ 38
MATERIALS AND METHODS ....................................................................... 40
RESULTS AND DISCUSSION ........................................................................ 44
SUMMARY ...................................................................................................... 48
REFERENCES ................................................................................................. so

LIST OF TABLES

CHAPTER 1
Table 1. Compost analysis ........................................................................................... 20
Table 2. Input values for calculation of variable costs used in

PLANETOR analysis .................................................................................... 21
Table 3. Soybean yield means within each year by fertility

management type, and cover ........................................................................ 22
Table 4. Analysis of variance for soybean grain yield ................................................... 22
Table 5. Wheat yield means within each year by fertility

management type, and cover ......................................................................... 23
Table 6. Analysis of variance for wheat grain yield ..................................................... 23
Table 7. Corn yield means for each year by fertility

management type, entry point, and cover ..................................................... 24

Table 8. Analysis of variance for corn grain yield, 1993-1995 ..................................... 25

Table 9. Product income, variable costs. and net economic return .
for all crops under integrated compost management, 1993-1995 ................... 26

Table 10. Product income, variable costs, and net economic return
for all crops under integrated fertilizer management, 1993-1995 .................. 27

Table 11. Net economic return for each entry point in the
third year of the rotation (1995) ............................................................. 28

Table 12a. 1993-1995 average net economic return of continuous corn
and corn in rotation ....................................................................... 29

Table 12b. 1993-1995 average net economic return of continuous corn
and corn in rotation if com becomes 10% more valuable
relative to soybean and wheat .................................................................. 29

Table 12c. 1993-1995 average net economic return of continuous corn
and corn in rotation if corn becomes 10% less Valuable
relative to soybean and wheat .................................................................... 29

vii

Table 13a. 1993-1995 average net economic return of continuous corn
and corn in rotation ................................................................................... 30

Table 13b. 1993-1995 average net economic return of continuous corn
and corn in rotation if corn becomes 10% more valuable
relative to soybean and wheat .................................................................... 30

Table 13c. 1993-1995 average net economic return of continuous corn
and corn in rotation if corn becomes 10% less valuable
relative to soybean and wheat .................................................................... 30

Table 14a. Net economic return of continuous corn and equal acreage of
com-corn-soybean-wheat in rotation in 1995 .............................................. 31

Table 14b. Net economic return of continuous corn and equal acreage of
corn-corn-soybean-wheat in rotation if corn becomes 10% more
valuable relative to soybean and wheat ....... 31

Table 14c. Net economic return of continuous corn and equal acreage of
com-com-soybean-wheat in rotation if corn becomes 10% less

valuable relative to soybean and wheat ....................................................... 31

CHAPTER TWO
Table 1. Compost analysis .......................................................................................... 52
Table 2. Pre-sidedress nitrate test means by fertility management type,

entry point, and cover, 1993-1995 ................................................................. 53
Table 3. Analysis of variance for presidedress nitrate test, 1994 and 1995 .................... 54
Table 4. Fall 0-90 cm N03 sample means, November 8, 1994 .................................... 55
Table 5. Fall 0-90 cm N03 sample means, November 13, 1995 .................................. 56
Table 6. Analysis of variance for fall 0-90 cm N03 sample means

November 8, 1994 ........................................................................................ 57
Table 7. Analysis of variance for fall 0-90 cm N03 sample means

November 13, 1995 ...................................................................................... 57
Table 8. Corn grain+stover biomass N means for each year by

fertility management type, entry point, and cover .......................................... 58
Table 9. Analysis of variance for corn grain and stover biomass N, 1993-1995 ........... 59

viii

Table 10.

Table 11.

Table 12.

Table 13.

Table 14.

Table 15.

Table 16.

Table 17.

Table 18.

Table 19.

Table 20.

Overall corn yield means for each year by,

fertility management type, entry point, and cover .......................................... 60
Analysis of variance for cover crop biomass N, 1993-1995 .......................... 61
Cover crop biomass N means for each year.... .............................................. 61
Corn grain and stover biomass N and %N efficiency at three fertilizer

rates, with and without annual ryegrass cover in 1994 and 1995 .................. 62 _
Analysis of variance for corn grain and stover biomass N and N

efliciency at three fertilizer rates, with and without annual ryegrass

cover in 1994 and 1995 ............................................................................... 63

Analysis of variance for annual ryegrass biomass N at three N rates
in 1994 and 1995 ......................................................................................... 64

Annual ryegrass biomass N means and % N efficiency
at three N rates in 1994 and 1995 ................................................................ 64

Analysis of variance for the fall 0-90 cm soil N03 samples at three

N rates, with and without annual ryegrass cover October 26, 1994 .............. 65
Fall 0-90 cm soil N03 samples at three fertilizer N rates, with and
without annual ryegrass, after corn grain harvest, October 26, 1994 ............ 65

Analysis of variance for the fall 0-90 cm soil N03 samples at three
N rates, with and without annual ryegrass cover, November 13, 1995 ......... 66

Fall 0-90 cm soil N03 samples at three fertilizer N rates, with and
without annual ryegrass, after corn grain harvest, November 13, 1995 ....... 66

ix

LIST OF FIGURES
Figure 1. Living Field Laboratory plot design ........................................................... 19

Figure 2. Corn grain yield within each of three years under integrated
compost or fertilizer management .............................................................. 32

Figure 3. Efl‘ect of corn entry point within each year on corn grain yield,
1993-1995 ................................................................................................. 33

Figure 4. Effect of corn rotation and cover on grain yield in the second
year of the rotation (1994) ........................................................................ 34

Figure 5. Effect of corn entry point and cover on grain yield in the third year
of the rotation ............................................................................................ 35

Figure 6. Effect of corn entry point on grain yield under integrated
compost or integrated fertilizer management in the second -
year of the rotation ................................................................................ 36

CHAPTER 1
CROP YIELD AND NET ECONOMIC RETURN OF CORN, SOYBEAN AND
WHEAT AS AFFECTED BY POSITION IN ROTATION,
FERTILITY SOURCE, AND COVER CROP
ABSTRACT

Corn (Zea mays L.) is the most commonly grown cash grain crop in Michigan.
Although most com is grown in rotation with another crop, little published data is
available on corn grown in rotation with soybean [Glycine max (L.) Merr.] and wheat
(T riticum aestivum L.). Cover crops have been used as a N source and to tie up residual
N afier crop harvest. A long-term experiment was established in 1993 on a
Kalamazoo/Oshtemo sandy loam in southwestern Michigan to compare grain yields and
net economic return of a corn-corn-soybean-wheat rotation with those of continuous corn.
Each of the four rotation crops was started in 1993, to have each crop grown each year.
Corn, soybean, and wheat were grown with or without annual ryegrass (Lolium
multiflorum Lam.) and/or hairy vetch ( I 'icia villosa Roth), or Michigan mammoth red
clover (T rifolimn pralense L 1 Crop and cover combinations were grown under two
fertility management systems. one using commercial fertilizer, the other using composted
dairy manure as the only nutrient source First-year corn following wheat produced yields
32% higher than corn following corn in 1994, and 17% higher in 1995. Corn following
wheat overseeded with red clover increased this effect in 1995 to 35% under integrated
compost management. The effect of cover was less under fertilizer management. Under
both fertility management systems. and in both years of transition, first-year corn produced
higher net returns than corn following corn. 1n the integrated compost system in 1994,
first-year com net returns were $143.00/acre higher than net returns from corn following
corn. In 1995, the margin between returns for first-year corn and corn following corn was

less if cover was in the system. When crop rotation was compared with continuous corn

over the three years of the experiment, net returns fluctuated with corn to soybean and
wheat price ratios. Crop rotation produced higher net returns when the price of corn was

low relative to soybean and wheat. Continuous corn produced higher net returns when

the price of corn was high relative to soybean and wheat.

INTRODUCTION

The need for highly productive cropping systems that reduce undesirable
environmental impact has been underscored in several publications (Hatfield and Karlen,
1993, Francis et. al., 1990, Liebhardt et a1, 1989). A common theme throughout the
literature is the importance of increased diversity in a cropping system because of its
influence on soil microbial activity which in turn affects nutrient cycling and crop uptake
(Doran and Linn, 1994). This diversity can be achieved with the use of crop rotations and
cover crops. Several crOpping systems currently being utilized incorporate the benefits of
crop rotation, cover crops and other management practices that allow for more eflicient
use of inputs. Reported benefits of crop rotation include improved soil structure
(Raimbault and Vyn, 1991), potential increased water use efficiency (Pierce and Rice,
1988), increased soil nutrient uptake (Stecker et al., 1995, Copeland and Crookston,
1992) and lower incidence of insect pests (Benson, 1985) and diseases (Edwards et al.,
1988). Cover crops, heavily relied upon as a legume N source before the advent of
commercial fertilizers in monocropped systems, have been used to reduce soil erosion
(Langdale, et al 1985); as both a N source (Power, 1987, Stute and Posner, 1993), and
to tie up residual soil N after grain harvest (Ditsch et al., 1993, Brinsford and Staver,
1991). Other advantages attributed to cover crops include improved soil structure and
increased organic matter content (Bruce et al, 1990), increased water penetration (Benoit
et al, 1962), weed suppression (Worsham. 1991) and increases in beneficial insect
populations (Roberts and Cartwright, 1991) In livestock systems, forage cover crops can
also be recycled as nutrient sources through manure (Hoveland, et al, 1988). .

Much of the research on crop rotations in the upper midwest involves the com-
soybean rotation (Crookston, 1984), and focuses on the effects of tillage or N rates
(Meese, et al. 1991, Peterson and Varvel, 1989). While some research has been reported
on com-soybean and wheat in rotation (Lund and Oplinger, 1993, Peterson et al., 1991),

few studies include the effects of cover crops in this cropping pattern. In Wisconsin,

Mallory and Posner (1994) found that overseeding red clover into wheat increased yields
of corn grown the following year. Similar findings were reported in Ontario by Raimbault
and Vyn (1991). In the cash-grain crop regions of Michigan, more information is needed
on the potential for cropping systems that include com, soybean and wheat with
overseeded cover crops. Although corn is the cash grain crop grown on the most acreage
in Michigan, it is often rotated with another crop (Landis and Swinton, 1994). Acreage
for both soybean and wheat have increased since 21993 (Ferris, 1995) and 1995 yields for
both crops were at record highs (Mchigan Agricultural Statistics, 1996).

To ensure farmer interest in these cropping systems, it must be demonstrated that
these systems are profitable as well as environmentally beneficial. Reluctance to
implement a system that integrates cover crops into a rotation, for instance, has been
associated with the risk that the cover will compete for moisture, and that the cost of
seeding the cover will not be recovered in net return (Robertson et al, 1991). In the case
of legume covers in corn-based systems of the Coastal Plain, Kentucky, and the
Appalachian region, the economic concerns have been addressed (Hanson, et al, 1993, Ott
and Hargrove, 1989, Frye, et al, 1985). In Michigan, Roberts and Swinton (1995) report
on-farm results which conclude that cover crops in corn-soybean-wheat rotations reduced
environmental contamination while maintaining farm profitability.

The purpose of this study was to quantify the incremental changes in corn
productivity brought about by the combination of rotation and cover crops under a fertility
management utilizing (i)commercial fertilizer, or (ii) dairy manure compost. This paper
presents crop yield and net economic returns over the first three years of transition to
cropping systems that increase in crop diversity and complexity. The overall goal is to
demonstrate short-term net economic return from these cropping systems, while the
longer-term effects (soil enhancing factors such as soil organic matter, aggregate stability,

microbial activity, etc.) of crop diversity are established over time.

MATERIALS AND METHODS

This research is part of the Living Field Laboratory (LFL), a long-term crop
rotation experiment established in 1992 at the Kellogg Biological Station in Hickory
Corners, MI. The LFL is designed to test varying combinations of rotation and cover
crops under several agronomic management regimes. The site soil type is a
Kalamazoo/Oshtemo sandy loam (coarse-loamy, mixed, mesic Typic Hapludalf), and had
been in mixed alfalfa grass-hay for six years. The design is a split-split plot with four
replications, ( Figure 1). The main plots that comprise the portion of the LFL reported
here are two levels of agronomic management:

(i) integrated compost management: minimal pesticides; banded herbicide plus
cultivation for weed control; dairy manure/straw or sand compost as a fertility
source

(ii) integrated fertilizer management: minimal pesticides; banded herbicide plus
cultivation for weed control; commercial fertilizer as a fertility source

Sub-plots are the entry points of a corn-corn-soybean-wheat rotation, plus continuous
corn; each crop in the rotation is grown every year. The second year corn entry point is
ineluded for research purposes to document an anticipated decreasing yield phenomenon
(Crookston et al., 1991,Benson, 1985, ). Prior to enactment of the Fedaeral Improvement
and Reform Bill of 1986, Michigan corn growers ofien included second year corn to
maintain base acres in government commodity programs (Landis and Swinton, 1994). All
crops in the rotation are grown with and without an overseeded cover crop except
soybean, which are not grown with a cover crop. The cover crop sequence for the entry
points is as follows:

(i) first-year corn: legume (hairy vetch in 1993, red clover thereafter + annual

ryegrass

(ii) second-year corn: annual ryegrass

(iii) continuous corn: legume (hairy vetch in 1993, red clover thereafter) + annual

ryegrass

(iv) wheat: red clover fiost seeded in March

Primary tillage is chisel-plowing followed by a disk and field-cultivator. Plots are
50 by 15 ft with corn and soybean planted in 30 in. rows and wheat planted in 7 in. rows.
Corn hybrid 'Pioneer 3751' was planted each year at about 27,000 seeds/acre. Soybean
variety 'BSR 101' was planted each year at 1 bu/a. The spring wheat variety 'Butte 86'
was planted in late April 1993 because it was too late to establish winter wheat. The
winter wheat variety 'Augusta' was planted in subsequent years at 130 lbs/acre. Cover
crops in corn were sown at second cultivation with a hand seeder in 1993, or with a pto
driven Orbit-air seeder in subsequent years. Red clover was seeded at 121bs/acre, and
annual ryegrass at 25 lbs/acre. 1n the cover sub-plots of wheat, red clover was seeded
with an Orbit-air seeder in early March at 15 lbs/acre. After seeding the main crop,
herbicides were banded pre-emergence at the recommended rates.

Nitrogen was applied to corn plots based on a 130 bulacre yield goal and pre-
sidedress-nitrate-test (PSNT) levels (Magdoff, 1991). In 1995, a 60 lb N credit was
given to first-year corn following w heat that had been frost-seeded with red clover.
Phosphorus and potassium for all fertilized plots were applied based on soil test
recommendations (Vitosh et al , 1995) in wheat plots, N was sidedressed at 50-60 lbs
in early April. Soybean plots received no fertilizer N. Each year, composted dairy manure
from a companion research project was applied on a dry weight basis to the integrated
compost management plots in April (corn) and October (wheat) with a manure spreader.
An attempt was made to supply N from the compost to meet corn yield goals, assuming
15% N available in the first year of application. Because of the low N availability, and a
sand content in the bedding greater than 50%, the decision was made to apply a larger
amount of compost than the 5-10 tons/a commonly used in manure applications. This

resulted in an application rate in corn of 25 tons/acre in 1993, 47 tons/acre in 1994

followed by a reduction down to two tons/acre in 1995. The plots in wheat and soybean
in 1993 received the higher compost amount in a subsequent corn crop. No compost was
applied in any year immediately preceding soybean. Compost application rate and analysis
is shown in Table 1.

Corn grain yield was calculated from a 20 ft. section of two rows in each plot.
Final grain yield was adjusted to 15.5% moisture. After harvest, the remaining rows were
combined and stalks chopped. Soybean and wheat plots were machine harvested, and
grain yield adjusted to 13 and 13.5% moisture content, respectively. Analysis of variance
was performed on yield data for each of the three data years.

Product income, which is the price paid per bushel times the grain yield, and net
economic return were determined for each crop and rotation on a per acre basis using the
PLANETOR economic planning program, version 2.0 (Center for Farm Financial
Management, 1995). Net economic return represents the return to fixed costs such as
land, capital and labor, and is defined as the product income minus the variable costs,
which include the purchased inputs such as seed, fertilizer and herbicide. The input values
used in PLANETOR to calculate variable costs for each crop were actual prices paid each
year and are listed in Table 2. There was no charge for making the dairy manure compost
itself. Only the cost of spreading was included. Machinery, fuel, and implement costs per
acre were calculated by PLANETOR. Cover crop seed costs were charged within the
year they were overseeded into the main crop except in the case of wheat, which was
charged to the following corn crop. Grain prices are approximate average prices obtained
by Michigan farmers from 1992-1995 (Ferris, 1995). In addition to the average prices of
$2.50 for corn, $6.25 for soybean, and $4.00 for wheat, alternative price ratios were used
to analyze the three-year comparison between continuous corn, and corn in rotation. The
alternatives were: a) com 10% more valuable relative to soybean and wheat, 2) corn 10%

less valuable relative to soybean and wheat.

In order to compare the crop rotation with continuous corn over the three years of
the experiment, two net economic return scenarios were analyzed under each fertility
management. In the first scenario, continuous corn is compared to the rotation that began
with corn in 1993, followed by soybean in 1994, and wheat in 1995. In the second
scenario, continuous corn is compared to the rotation that began with soybean in 1993,
followed by wheat in 1994, and corn in 1995. This analysis was conducted to determine if
there was an advantage in starting the rotation with corn as opposed to starting with
soybean, based on net returns averaged over 1993-1995.

Net economic return data for 1995 was also summarized with the assumption that
all crops in a com-com-soybean-wheat rotation were grown in equal acreage within the
same year. The average net return for this rotation is compared with continuous corn.
Data from 1995 are used because continuous corn is in the third year, and can be truly

compared to second-year corn.

RESULTS AND DISCUSSION
Crop Yield
Mean grain yields and analysis of variance for each year are presented in

Tables 3 and 4 for soybean, Tables 5 and 6 for wheat, and in Tables 7 and 8 for corn,
respectively. In 1993, soybean under integrated compost management yielded higher than
soybean under integrated fertilizer management (Table 3). In wheat, there were no
significant differences in 1993 or 1994. In 1995, wheat under integrated fertilizer
management yielded higher than wheat under integrated compost management (Table 5).
Also in 1995, the no cover wheat plots yielded higher than wheat with cover (Table 5).

In corn, no differences in the three rotation entry points were detected in 1993.
No differences were expected, as 1993 was the rotation establishment year, with all crops
being planted into alfalfa/fallow soil. There was a significant management difference,
however, with integrated fertilizer management yielding 21% higher than integrated
compost management . This was thought to be due to low N availability from the spring
1993 compost application, which was 2.5 tons. An additional 25 tons was applied in the
fall of 1993. The integrated fertilizer management plots still yielded 16% higher than the
integrated compost management plots in 1994 (Figure 2). There was no significant
management difference in 1995

The position in the rotation. or entry point, had a significant effect on corn yield in
1994 and 1995 (Table 7). In 1994. first-year corn yield following wheat was 187 bulacre,
at least 32% higher than bath entry points of corn following corn (Fig. 3). In 1995, first-
year corn yield was 155 bulacre. 17% higher than continuous (third year) corn (Fig. 3).

There was a significant entry point it cover interaction in 1994 and 1995 (Table 7).
In 1994, first-year corn with or without overseeded red clover yielded over 185 bulacre.
The next closest yield was second year corn with no cover, at 155 bulacre (Fig. 4). The
effect of annual ryegrass in 1994 is also shown in Figure 4, as second-year corn with no
cover yielded significantly higher than second-year corn overseeded with the annual

10

ryegrass. Second-year corn with no cover also yielded higher than the continuous corn
rotation with or without overseeded red clover/annual ryegrass cover (Fig. 4).
(Continuous and second-year corn in 1994 are both actually second-year com, difi‘ering
only in the types of cover crops overseeded). In 1995, first-year corn yield following
wheat overseeded with red clover was 163 bulacre, compared with 146 bulacre for first-
year corn without cover, and at least 21% higher than second-year or continuous com
with or without cover (Fig. 5).

There was a significant entry point x management difference in 1994 only, with
integrated compost causing a yield depression in both second-year continuous corn crops.
First-year corn yields were about 187 bu/acre for both fertility management types, second-
year corn yields under the integrated fertilizer management were not significantly different
from first-year corn (Fig. 6). However, second-year corn under integrated compost
management yielded only 118 bu/acre (Fig. 6).

Net Economic Return

For both fertility management systems, product income, variable costs, and net
economic return data for each year are summarized in Table 9 and 10. Net returns in
1995 represent the effect of the previous two years of the rotation on each entry point
(Table 11).

Under both fertility management systems, and in both years of transition from
long-term alfalfa, first-year corn produced higher net returns than corn following corn. In
the integrated compost system in 1994, first-year com net returns were $143.00/acre
higher than net returns from corn following corn (Table 9). This ratio was consistent
whether or not cover was present, even though cover crops add as much as $30.00/acre in
variable cost. In 1994, the integrated fertilizer system net returns were higher for first-
year corn than for corn following corn; but this difference was greater between the cover
plots than between the no-cover plots (Table 10). Net returns in first-year corn with cover

were $61.00/acre higher than net returns from corn following corn with cover, but net

11

returns in the same comparison in the no cover plots reveal only a $15.00/acre advantage
to first-year corn (Table 10).

In the integrated compost system with cover plots in 1995, first-year corn
produced net returns $84.00/acre higher than second year corn; and $99.00/acre higher
than continuous (third year corn, Table 11). In the no-cover compost plots, first-year
corn produced net returns $25.00/acre higher than second year corn; and $51.00/acre
higher than continuous corn. In 1995 in the integrated fertilizer plots with cover, first-
year corn produced net returns $49.00 and $59.00 lacre higher than second-year or
continuous corn, respectively. Net returns in the no-cover plots of first-year corn were
$30.00 and $45.00/acre higher than second-year and continuous com, respectively.

Data for the crop rotation net economic return scenarios under each fertility
management is presented in Tables 12a-c and 13a-c. In the scenario comparing
continuous corn with the com-soybean-wheat rotation under average prices from 1993-
1995, continuous corn with cover produced net returns higher than the rotation with cover
(Table 12a). Continuous corn integrated compost with cover net returns were 13% higher
than corn in rotation integrated compost with cover net returns. In both fertility
management types, there was little difference in the net returns of continuous corn with no
cover and the rotation with no cover. When corn was 10% more valuable relative to
soybean and wheat, continuous corn with cover net returns were fiIrther enhanced.
Continuous corn integrated compost with cover net returns were 22% higher than the
rotation integrated compost with cover net returns (Table 12b.) However, when com was
10% less valuable relative to soybean and wheat, the rotation with no cover produced net
returns slightly higher than continuous corn without cover, regardless of fertility
management type (Table 12c). There was little difference in the net returns of continuous

corn with cover and the rotation with cover.

12

The second rotation scenario compared continuous corn with the soybean-wheat-
com rotation. Under average prices from 1993-1995, integrated fertilizer continuous corn
with no cover produced net returns 16% higher than integrated fertilizer rotation with no
cover (Table 13a). As was the case in the com-soybean-wheat scenario, when com was
10% more valuable relative to soybean and wheat, continuous com net returns were
fiIrther enhanced (Table 13 b). When corn was 10% less valuable relative to soybean and
wheat, the advantage of the rotation over continuous corn was evident only under
integrated compost management (Table 13c).

For the scenario that assumes all crops in a com-corn-soybean-wheat rotation
were grown in equal acreage within the same year, data is presented in Table 13a-c.
Under average prices from 1993-1995, net returns between continuous corn and the
rotation are similar for each management type (Table 14a). When corn was 10% more
valuable relative to soybean and wheat, continuous com net returns were slightly higher
than the rotation net returns (Table 14b). When corn was 10% less valuable relative to
soybean and wheat, rotation net returns were 17% higher than continuous corn, but only

under integrated fertilizer management with no cover (Table 14c). »

SUMMARY

In consecutive years of transition fi'om long-term alfalfa, first-year corn following
wheat produced the highest yield. This effect occurred under both compost and fertilizer
management. In the second year of transition, the advantage of corn following wheat was
enhanced by overseeded red clover in wheat, especially under compost management. The
presence of overseeded cover crops in second-year corn drastically reduced yield and net
returns in 1994. Cover in third-year corn reduced net returns in 1995. '

When considering yield and net return data within each year, the benefits of
rotation, especially corn following wheat overseeded with red clover are very clear.
However, when considering net returns for the rotation over three years, the benefit of
first-year corn is masked by lower soybean and wheat net returns in the other rotation
years. The advantage of rotation is evident when the price of corn is low compared to
wheat and soybean. This finding has also been reported elsewhere (Peterson et. al., 1991).
The presence of overseeded cover in corn reduced net returns under both continuous corn
and in the rotation, especially under compost management. Under the scenarios where
the rotation produced lower net returns than continuous corn, leaving only the red clover
overseeded into wheat as the only cover crop in the rotation may have increased the short-
tenn benefits of rotation. The net return of first-year corn would increase by removing the
cost of overseeding Other factors adding to the net returns of rotation were not
considered in this experiment. such as the profit from a hay crop taken from the clover in
the fall after wheat harvest.

Under most scenarios discussed here. integrated compost management produced
higher returns than integrated fertilizer management. Taken into consideration is the fact
that the price of compost is a major determinant. In a cropping system where manure is
available, or is a by-product of a livestock operation, the integrated compost system that
utilizes first-year corn following wheat/red clover may prove to be advantageous. Roberts

and Swinton (1995) found similar results in looking at on-fann data where the

13

14

combination of manure and cover were used. In their study, manure enhanced the
beneficial effect of multiple crops in rotation .

The rationale for crop rotation as opposed to monocropping is well defined. The
current generation of questions have to do with selecting a particular rotation under the
specific growing conditions. The potential for corn-soybean-wheat was analyzed in this
experiment, and will be expanded to areas in Michigan where it may be an ideal mix As
mentioned previously, acreage for both soybean and wheat is increasing in Michigan, and
there is impetus for obtaining higher yields as these crops become more prominent. Soils
at the experimental site are coarse-textured and low in organic matter. We suggest that
adding crop diversity on these soils via rotation and cover will increase crop yield and net
returns over time. With this kind of rotation, poor returns in one year can be overcome
with the next crop, as was the case in this experiment with wheat in 1993. A net return of
$3.32/acre in 1993 integrated fertilizer wheat was followed by the highest net return of
any crop in any of the three years, at $338.74/acre in 1994 first-year corn (no cover).

When growing crops in rotation with cover crops, several factors must be taken
into consideration, such as the extra planting and harvesting equipment needed for
different mom, and extra management decisions with respect to planting of cover crops.
For example, the grower must consider what equipment is needed to plant the cover
crops, and what method is to be used to kill the cover crop in the spring. Nutrient needs
must be monitored when rotating from one crop to the next. The additional crops create
more opportunities for fluctuation in profits and this is fiirther affected by crop price
ratios. Economic and agronomic evaluation of these scenarios will continue in this

experiment.

REFERENCES

Benoit, RE, N.A. Willits, and W.J. Hanna. 1962. Effect of winter rye cover crop on soil
structure. Agron. J. 54:419-429.

Benson, 6.0. 1985. Why the reduced yields when com follows corn and possible
management responses. P. 161-174. In D. Wilkinson (ed.) Proc. Corn and Sorghum
Res. Conf., Chicago, IL. 11-12 Dec. 1985. Am. Seed Trade Assoc, Washington,
DC.

Brinsford, RB, and K.W. Staver. 1991. Use of cereal grain crops for reducing
groundwater nitrate contamination in the Chesapeake Bay region. p. 79-82. In W.L.
Hargrove (ed.) Cover Crops for Clean Water. Soil and Water Conservation Society,
Akeny, IA.

Bruce, RR, G.W. Langdale, and LT. West. 1990. Modification of soil characteristics of
degraded soil surfaces by biomass and tillage affecting soil water regimes. Int. Congr.
Soil Sci. Trans. 14:VI:4-9.

Copeland, P.J., and RR. Crookston, 1992. Crop sequence affects nutrient composition
of corn and soybean grown under high fertility. Agron. I. 84:503-509.

Crookston, R.K., J.E. Kurle, P.J. Capeland, J.H. Ford, and WE. Lueschen. 1991.
Rotational cropping sequence affects yield of corn and soybean. Agron. J. 83:108-113.

Crookston, RR. 1984. The rotation efi‘ect: what causes it to boost yields? Crops and
Soils. March p. 12-14. .

Ditsch, D.C., M M Alley, K R Kelly. and Y2. Lei. 1993. Effectiveness of winter rye
for accumulating residual fertilizer N following corn. J. Soil Water Cons. 48(2): 125-
132.

Doran, J.W., and DM. Linn Microbial ecology of conservation management. p. 1-20.
In Hatfield IL, and BA Stewart (eds ) Soil Biology: Effects on Soil Quality.
Advances in Soil Science C RC Press. Boca Raton, FL.

Edwards, J.I-I., D.L. Thurlow. and IT. Eason. 1988. Influence of tillage and crop
rotation on yields of corn. soybean. and wheat. Agron. J. 80:76-80.

Ferris, J. 1995. Using seasonal cash price patterns for selling decisions on corn, soybean,
and wheat. NCR Extension Publication No. 217. Michigan State University.

Francis, C.A., C.B. Flora, and L.D. King (eds) 1990. Sustainable Agriculture in
Temparate Zones. John Wiley and Sons, New York, NY 487pp.

15

l6

Frye, W.W., W.G. Smith, and R.J. Williams. 1985. Economics of winter cover crops as a
source of nitrogen for no-till com. J. Soil Water Cons. 40:246-249.

Hanson, J.C., E. Lichtenberg, AM. Decker, and AI. Clark. 1993. Profitability of no-
tillage corn following a hairy vetch crop. J. Prod. Agric. 62437-444.

Hatfield, J .L., and BL. Karlen (eds) 1994. Sustainable Agriculture Systems. CRC
Press, Boca Raton, FL. 316 pp.

Hoveland, C.S., N.S. Hill, RS. Lowrey Jr., S.L. Fales, M.E. McCormick, and AE. Smith,
Jr. 1988. Steer performance on birdsfoot trefoil and alfalfa pasture in central Georgia
I. Prod. Agric. 1:343-346.

Langdale, G.W., RA. Leonard, and AW. Thomas. 1985. Conservation practice effects
on phosphorus losses from southern Piedmont watersheds. J. Soil Water Cons.
40:157-160.

Landis, D., and S. Swinton. 1994. Corn insect management in Michigan: results of a
1992 corn grower survey. Research Report 537. Mich. Agri. Exp. Sta. Michigan
State University.

Liebhardt, W.C., RW. Andrews, MN. Culik, RR. Harwood, RR. Janke, J .K. Radke,
and S.L. Rieger-Schwartz. 1989. Crop production during conversion fiom
conventional to low-input methods. Agron. J. 81: 150-159.

Lund, M.G., P.R. Carter, and ES. Oplinger. 1993. Tillage and crop rotation affect corn,
soybean, and winter wheat yields. J. Prod. Agric. 62207-213. ,

Magdoff, F. 1991. Understanding the Magdotf pre-sidedress nitrate test for corn. J.
Prod. Agric. 4:297-305.

Mallory, EM, and J. Posner. 1994. Performance, economics, and adoption of cover
crops in Wisconsin cash grain rotations: On farm trials. p. 68-77. In: The Wisconsin
Integrated Cropping Systems Trial, Forth Report. Lakeland Agricultural Complex,
Arlington Agricultural Research Station.

Meese, B.G., P.R. Carter, E.S. Oplinger, and J.W. Pendleton. 1991. Com-soybean
rotation effect as influenced by tillage, nitrogen, and hybrid/cultivar. J. Prod. Agric.
4:74-80.

Michigan Agricultural Staistics 1996. Michigan Dept. Agric. Lansing.

Ott, S.L., and W.L. Hargrove. 1989. Profits and risks of using crimson clover and hairy
vetch cover crops in no-till corn production. Am. J. Altem. Agric. 4(2):65-70.

l7

Peterson, TA, and GE. Varvel. 1989. Crop yield as afl‘ected by rotation and nitrogen
rate. I. Soybean. Agron. J. 81:727-731.

Peterson, WR, D.T. Walters, R.J. Supalla, and RA. Olson. 1991. Yield and economic
aspects of irrigated cropping systems in eastern Nebraska. J. Prod. Agric. 4:3 53-
360.

Pierce, P.J., and CW. Rice. 1988. Crop rotation and its impact on efiiciency of water
and nitrogen use. In Cropping Strategies for Eflicient Use of Water and Nitrogen.
ASA Special Publication No. 51.

PLANETOR. 1995. A farm economic planning program developed by the Center for
Farm Financial Management, Dept. Of Agric. And Appl. Econ. University of
Minnesota.

Power, J.F. 1987. The Role of Legumes in Conservation Tillage Systems. Soil and
Water Conservation Society, Akeny, IA.

Raimbault, BA, and TI Vyn. 1991. Crop rotation and tillage effects on corn growth
and soil structural stability. Agron. J. 83:979-985.

Roberts, B.W., and B. Cartwright. 1991. Cover crop, nitrogen, and insect interactions.
p. 164-167. In W.L. Hargrove (ed.) Cover Crops for Clean Water. Soil and Water
Conservation Society, Akeny, IA.

Roberts, W.S., and SM. Swinton. 1995. Increased cropping diversity to reduce leaching
and runoff: economic and environmental analysis. Staff Paper No. 95-70. Dept. Agric.
Econ. Michigan State University. East Lansing, MI.

Robertson, T., V. Benson, JR. Williams, CH. Lander, and D.L. Schertz. Long-run
impacts of cover crops on yield, farm income, and nitrogen recycling. p. 117-120. In
W.L. Hargrove (ed.) Cover Crops for Clean Water. Soil and Water Conservation
Society, Akeny, IA.

Stecker, J.A., DD. Buchholz, R.G. Hanson, N.C. Wollenhaupt, and K.A. McVay. 1995.
Tillage and rotation effects on corn yield response to fertilizer nitrogen on Aqualf
soils. Agron. J. 87:409-415.

Stute, J.K., and J .L. Posner. 1993. Legume cover crop options for grain rotations in
Wisconsin. Agron. J. 85: 1 128-1 132.

Vitosh, M.L., J.W. Johnson, and DB. Mengel, 1995. Tri-state fertilizer
recommendations for corn, soybeans, wheat, and alfalfa. Michigan State University,
The Ohio State University, Purdue University. Extension Bulletin E-2567. East
Lansing, MI.

18

Worsham, AD. 1991. Role of cover crops in weed management and water quality. p.
141-145. In W.L. Hargrove (ed.) Cover Crops for Clean Water. Soil and'Water
Conservation Society, Akeny, IA.

19

Management Types

 

 

 

 

 

 

 

 

 

Integrated Compost Management
I l l I
m at ” al'
I | ‘ | l
I I“ l 1" l I
I l l l
' Cont. Soy lat Yr 2nd Yr
Wheat Com Beans Com Com
| l | ‘l
| l | l
I | I |
l l | I
Integrated Fertilizer Management
,, I ,c I ,, l ,, l
m l I l m I
| l l l
l I l l
lst Yr Soy ' 2nd Yr Cont.
Corn Beans Wheat Corn

_—_—

 

 

l
|
l
l
I

 

 

-————§

 

 

 

ar = annual ryegrass
rc = red clover

 

Figure 1. Living Field Laboratory plot design

 

 

20

Table 1. Compost analysis.

 

APPLICATION DATE

4/22/93 10/18/93 4/21/94 10/4/94 4/28/95 10/22/95

Compost applied (dry lbs/a 3200 45500' 39900 56800‘ 40001 4000‘
Nitrogen supplied (lbs/a) 40 190 600 440 250 250

 

 

 

Estimated available lbsN/a’ <10 30 90 ' 70 4o 40
Nitrogen (%) 1.2 0.4 1.5 0.8 0.6 0.6
Carbon (%) 14.1 6.2 20.2 10.2 11.5 11.5
C:N ratio 12 15 13 13 19 19
Nitrate-Nitrogen (ug/ml) - - 4 13 28 28
Ol.
Phosphorus 0.5 0.2 0.4 0.2 0.2 0.2
Potassium 0.3 0.5 1.7 0.8 0.7 0.7
Calcium 1.0 , 2.2 2.3 14.0 2.4 2.4
Magnesium 0.4 0.6 0.5 1.8 0.6 0.6
PP!“-
Boron 10 20 50 40 14.4 14.4
Zinc 220 50 68.2 68.2
Manganese 2 10 100 190 420 191 191
Copper 130 20 - - 29 29
pH - - 8.4 9.2 9.1 9.1
Electrical conductivity (mmhos/cm) 5.5 11.6 . 6.3 6.3
Moisture (%) 60 30 50 20 40 40

 

lcompost applied on these dates had been made with dairy manure where sand had been
used for bedding. Sand content was estimated to be 60%, by water sedimentation.

2assumes 15% estimated release in first year after application. Mineralization in
subsequent years was not estimated.

Table 2. Input values for calculation of variable costs used in PLANETOR

21

 

 

Inputs Units Price
Compost application Slacre 15.00
Fuel S/gal 0.90
Seed ~
Corn Slacre 24.00
Soybean $lacre 12.00
Wheat $/acre 20.00
Ann. ryegrass $/acre 7.50
Red clover $/acre 12.00
Fertilizer
NHaNO3 Mb 0.18
P205 W“) 0.10
K20 Mb 0.10
Herbicide
Corn S/acre 8.52
Soybean S/acre 5.42
Insecticide
Corn S/acre 13.00
Operating interest S/acre 10.00

 

22

Table 3. Soybean yield means within each year by fertility management type,

 

 

and cover.
1993 1994 1995
no cover no cover cover no cover cover
. tallest:
Integrated compost 50 50 43 37 39
Integrated fertilizer 45 40 38 ‘ 32 34

 

Table 4. Analysis of variance for soybean grain yield, 1993-1995.

 

1993 1994 1995
Source of variation PR>F PR>F PR>F
Replication 0.021 0.830 0.697
Management 0.028 0.43 1 0.413
Cover 0.019 0.27 0.295
Management x cover 0.986 0.533 0.875

 

23

Table 5. Wheat yield means within each year by fertility management type, and cover.

 

 

 

1993* 1994 1995 ,
no cover no cover cover Mean no cover cover Mean
bulacre-mm-
Integrated compost 23 48 46 47 58 48 53a“
Integrated fertilizer 18 47 47 47 66 57 62b
Mean 21 48 47 47 62a 52b

 

‘1993 wheat was spring wheat

"Numbers not followed by the same letter are significantly difl‘erent at p= 0.05

Table 6. Analysis of variance for wheat grain yield in 1995.

 

Source of variation
Replication
Management

Cover

Management x cover

PR>F
0.45
0.055
0.019
0.986

 

24

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25

Table 8. Analysis of variance for corn grain yield, 1993-1995.

 

 

1993 1994 1995

Source of variation Pr. >F Pr. >F Pr. >F
Replication 0.748 0.573 0.528
Main efl‘ects

Management 0.045 0.03 0.20

Entry point 0.665 0.0001 0.002

Cover 0.882 0.276 0. 123
Interaction efi‘ects

Management x entry point 0.839 0.038 0.556

Management x cover 0.309 0.97 0.136

Entry point x cover 0.781 0.006 0.026

Manage_ment x entry point x cover 0.637 0.828 0.346

 

26

 

 

 

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28

Table 11. Net economic return for each entry point in the third year

 

 

the rotation (1995).
Integrated compost htefled fertilizer.
Cover No cover Cover No cover
”Shore--
First yr. corn 315.30 274.30 251.17 256.87
Second yr. corn , 231.80 249.30 201.87 226.87
Continuous corn 216.80 223.80 191.87 211.37
Wheat 137.28 177.28 168.20 204.20

Soybean 193.04 180.54 176.79 164.29

29

Table 12a. 1993-1995 average net economic return of continuous corn and

 

 

corn in rotation.
Continuous corn Com-soybean-wheat rotation
Management cover no cover cover no cover
--$/acre--- "'
Integrated compost 220.28 225.78 195.40 225.81
Integrated fertilizer 220.18 239.02 204.96 230.46

 

* ba'sod on following prices: Com@ $2.50/bu, soybean@ $6.25/bu
and wheat@ $4.00/bu

Table 12b. 1993-1995 average net economic return of continuous corn and corn in
rotation if corn becomes 10% more valuble relative to soybean and wheat

Continuous corn Com-soybean-wheat rotation

 

 

Management cover no cover cover no cover
--$/acre-- “
Integrated compost 220.28 225.78 180.04 207.62
‘ Integrated fertilizer 220.18 239.02 189.45 230.46

 

"' based on following prices: Com@ $2.50/bu, soybean@ $5.63/bu
and wheat@ $3.60/bu

Table 12c. 1993-1995 average net economic return of continuous Corn and corn in
rotation if corn becomes 10% less valuble relative to soybean and wheat.

 

 

Continuous corn Corn-soybean-wheat rotation
Management cover no cover cover no cover
----$/acre--- "'
Integrated compost 220.28 225.78 210.75 243.46
Integrated fertilizer 220.18 239.02 220.48 247.60

 

" based on following prices: Com@ $2.50/bu, soybean@ $6.88/bu
and wheat@ $4.40/bu

30

Table 13a. 1993-1995 average net economic return of continuous corn and
corn in rotation.

 

 

Continuous corn Soybean-wheat-corn rotation
Management cover no cover cover no cover
_ "Share-- *
Integrated compost 220.28 225.78 234.94 223.94
Integrated fertilizer 220.18 239.02 203.89 205.79

 

" based on following prices: Com@ $2.50/bu, soybean@ $6.25/bu
and wheat@ $4.00/bu

Table 13b. 1993-1995 average net economic return of continuous corn and corn in
rotation if corn becomes 10% more valuble relative to soybean and wheat. ‘

 

 

Continuous corn Soybean-wheat-corn rotation
Management cover no cover cover no cover
m-Slacrem- “
Integrated compost 220.28 225.78 218.39 207.13
Integrated fertilizer 220.18 239.02 188.25 190.15

 

* based on following prices C orn@ $2.50/bu, soybean@ $5.63/bu
and wheat@ $3.60/bu

Table 13c. 1993-1995 average net economic return of continuous corn and corn in
rotation if corn becomes 10% less valuble relative to soybean and wheat.

 

 

 

 

p Continuous corn Soybean-wheat-com rotation
Management cover _ _no cover cover no cover
----$/acre--- "'
Integrated compost 220 28 225 78 251.49 239.76
Integrated fertilizer 220 18 239 02 219.53 221.43

 

 

“ based on following prices Corn—‘5’; $2 SO/bu. soybean@ $6.88/bu
and wheat@ 54 40/bu

31

Table 14a. Net economic return of continuous corn and equal acreage of
corn-com-soybean-wheat in rotation in 1995.

 

 

Equal acreage of
Continuous corn Com-soybean-wheat rotation
Management cover no cover cover no cover
u-S/acre-m "‘-
Integrated compost 216.80 223.80 219.35 220.35
Integrated fertilizer 191.87 211.37 199.50 213.05

 

*E’sod on following prices: Com@ $2.50/bu, soybean@ $6.25/bu
and wheat@ $4.00/bu

Table 14b. Net economic return of continuous corn and equal acreage of
corn-com-soybean-wheat in rotation in 1995 if corn becomes
10% more valuable relative to soybean and wheat.

 

 

 

Equal. acreage of
Continuous corn Com-soybean-wheat rotation
Management cover no cover cover no cover
----$/acre---- "‘
Integrated compost 216.80 223.80 208.46 208.79
Integrated fertilizer 191.87 21 1.37 188.49 201.45

 

 

" based on following prices: C omit? $2.50/bu, soybean@ $5.63/bu
and wheat@ $3.60/bu

Table 14c. Net economic return of continuous corn and equal acreage of
corn-corn-soybean-u heat in rotation in 1995 if corn becomes
10% less valuable relative to soybean and wheat.

 

 

 

 

Equal acreage of
Continuous corn _ -- Corn-soybean-wheat rotation
Management cover no cover cover no cover
m-S/acrem- "
Integrated compost 216.80 223 80 230.25 231.93
Integrated fertilizer 191.87 211 37 215.52 224.65

 

 

"' based on following prices: C orn@ $2.50/bu, soybean@ $6.88/bu
and wheat@ $4.40/bu

Mean Yield, 311191

32

 

170

- integ. comp
- integ. fat

 

 

 

1993 1994 1995

*Letters different from each other are significamly difi‘erent at p _<. 0.05.

Figure2. Comgrainyieldwithineachoftlueeyearstmderintegrated
compostorintegratedferfilizermanagemmt.

33

 

hflbemnYfiekLIBuflA

 

 

 

1993 1994 1995

*Letters different from each other are significantly different at p S 0.05.

Figure 3. Effect of com entry pomt withm each year on corn grain yield (1993-1995).

34

 

200

Mean Yield, Bulls

- inns mp

.inwsfat

 

 

 

lstyrcom 2ndyrcorn ccntccrn

‘Letters different from each other are significantly different at p S 0.05.

Figure 4 . Effect of com entry point on grain yield under integrated compost and
integrated fertilizer managementintln secondyearofthe rotation
(1994).

Nlean Yield, BuIA

35

 

8*

160I

1501

140‘

130l

.nocover
-cover

 

 

 

lstyrcom 2ndyrcom contcom

*Letters different from each other are significantly different at p S 0.05.

Figure 5. Effect ofcorn entry point and coveron comgrainyield inthe
third year of the rotation (1995).

36

 

Nlean Yield BulA

 

 

 

lstyrcom anyrcom contcom

*Letters different from each other are significantly different at p S 0.05.

Figure6. Efi‘ectofcomentrypointongrainyieldtmderintegated
compost and integrated fertilizer management in the second
year of the rotation (1994).

CHAPTER 2
EARLY AND LATE SEASON SOIL NITRATE LEVELS IN CORN
AS AFFECTED BY ROTATION, FERTILITY SOURCE, AND COVER CROP
ABSTRACT p

Crop rotation and cover crops have a direct efi‘ect on uptake and release of
available soil N. In Michigan, soil N sufficiency in corn (Zea mays L.) is often determined
using the presidedress nitrate test (PSNT) at stage V-6 of corn growth. In order to
evaluate the dynamics of soil N mineralization and related factors, a long-term crop
rotation experiment, Living Field Laboratory (LFL), was established in 1993 at Hickory
Comers, MI. The design is a split-block within a split-plot. Main plots are commercial
fertilizer vs. dairy compost as a nutrient source. Sub-plots are the entry points in a com-
corn-soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) rotation, and
continuous corn. These are further split so that each entry point is grown with or without
a cover crop. By I994, the second year of rotation, the first-year corn treatment
following wheat produced PSNT levels up to 62% higher than the corn following corn
treatment. In 1995. rotation and cover crop showed similar effects. Red clover
(Trifolium pron-me L ) residue following wheat provided both the earliest and highest
amount of mineralization. In both years. first-year corn biomass N levels were at least
33% higher than biomass N lex els in corn following corn. These effects occurred under
both compost and commercial fertilizer management systems. Early season soil N
mineralization appears to be linked to several factors which influence corn productivity.

An ancillary experiment was established at a site adjacent to the LFL in 1994 to
measure the effects of overseeded cover in corn. At three rates of N fertilizer, the
presence of annual ryegrass (1.0/mm mulriflomm Lam.) cover did not reduce biomass N
accumulation in corn. However, in 1995, annual ryegrass reduced late-season soil NO;-

available for leaching.

37

INTRODUCTION

In order to obtain maximum corn grain production, an adequate supply of available
N is needed early in the growing season. Ideally, this supply of N should be available just
prior to the period of greatest N uptake, and can be measured using the PSNT (Magdofl‘,
1991). Soil samples are taken at 20-30 cm depths between growth stage V-5 and V-6 of
corn growth. The rate of N to be applied is then calculated based on the amount of N03
present in the PSNT. Use of the PSNT enables producers to synchronize N demand with
crop uptake, while avoiding heavy losses of leached N03 -N afier crop harvest (Magdofl‘,
1991)

Various other strategies have been employed to manage early and late-season N
levels. Cover crops have been used as both a legume N source (Power, 1987; Stute and
Posner, 1993) and to tie up residual soil N afier grain harvest (Ditsch et al., 1993,
Brinsford and Staver, 1991). Few studies have looked at early and late-season N levels in
a cropping system that includes corn grown in rotation with or without cover crops.

There are opportunities to manage N levels in crops that precede corn, by the use of
overseeded legume cover crops. Dou et al. (1995) reported that mineralized N
concentrations from red clover that had been seeded into wheat peaked about four weeks
afler planting of a following corn crop, and that grain yields in corn were similar to those
obtained where fertilizer N was applied without legume N. After removal of the corn
crop, residual soil N levels were similar in both systems. Brown et al (1993) found that
hairy vetch overseeded into continuous corn significantly increased soil N03 -N levels in
the following crop 50 days after planting, but there was no difference in fall residual N03-
N. These studies show that early-season N availability can be altered through use of cover
crops and rotation. The goal is to obtain optimum grain yields while keeping residual fall

soil N03 -N at low levels to avoid NO3 leaching to ground-water.

38

39

Corn is the most commonly grown cash grain crop in Michigan, with most of it
grown in rotation with other crops (Landis and Swinton, 1994). Cropping systems that
incorporate the benefits of rotation and cover crops must be designed so that soil N levels
coincide with crop uptake patterns while leaving little residual soil N03 -N after crop
harvest.

More information is also needed regarding the amount of N recovered in the
various components of a cropping system. Harris et. al (1994), in a crop rotation
experiment using labeled N, found higher losses of fertilizer N than legume N. Varvel and
Peterson (1990), using isotopic methods, found that N recovery for corn in rotation was
significantly higher than N recovery in continuous corn.

Two experiments were conducted over a three year period to determine the
potential for managing seasonal levels of soil NO3 through rotation, cover crops and
nitrogen source. The first experiment determined the influence of previous crop and input
history on soil N and corn biomass N. The second experiment isolated the nitrogen

partitioning effects of a cover crop overseeded into corn.

MATERIALS AND METHODS

This research is part of the Living Field Laboratory (LFL), a long-term crop
rotation experiment established in 1993 at the Kellogg Biological Station in Hickory
Corners, MI. The LFL is designed to test varying combinations of rotation and cover
crops under several agronomic management regimes. The site soil type is a
Kalamazoo/Oshtemo sandy loam (coarse-loamy, mixed, mesic Typic Hapludalt). Six
years prior to the establishment of the experiment, the site was in a mixed stand of alfalfa
and grass hay. The design is a split-block within a split plot with four replications. For
this paper, the main plots that comprise this experiment are two levels of fertility
management:

(i) integrated compost management: minimal pesticides; banded herbicide plus
cultivation for weed control; dairy manure/straw or sand compost as a fertility
source

(ii) integrated fertilizer management: minimal pesticides; banded herbicide plus
cultivation for weed control; commercial fertilizer as a fertility source

Sub-plots are the entry points of a com-com-soybean-wheat rotation, plus continuous
corn. Each crop in the rotation was started in 1993, with the appropriate crop sequence
grown in each plot in subsequent years. In 1994, "continuous" corn was also second
year corn, differing from the other second year corn rotation only in cover crop mix.. All
crops in the rotation except soybeans were grown with and without an overseeded cover
crop. The cover crop sequence for the rotation is as follows;

first year corn: overseeded red clover + annual ryegrass (ann. rye/re)

second year corn: overseeded annual ryegrass (ann. rye)

continuous corn: overseeded (arm. rye/re)

wheat: red clover fi'ost seeded in March into overwintered wheat

40

41

A chisel-plow was used for primary tillage, followed by a disk and field-cultivator. Plots
were 15.2 by 4.56 m with corn and soybeans planted in .76 m rows and wheat planted in
18 cm rows. Cover craps in corn were sown at second cultivation with a hand seeder in
1993, and with a pto driven Orbit-air seeder in subsequent years. Red clover was seeded
at 13.4 kg ha-l, and annual ryegrass at 28 kg ha-l. In the cover sub-plots of wheat, red
clover was seeded with an Orbit-air seeder in early March at 13.4 kg ha-l.

In the fertilizer treatment, N was applied as NH4NO3 to corn plots based on 8.15
Mg ha-l yield goal and measured PSNT levels (Magdoff, 1991). In 1995, a 67 kg ha-l N
credit was given to first-year corn following wheat that had been fi‘ost-seeded with red
clover, as the rotation effects became established. Application of P & K for all fertilized
plots was based on soil test recommendations (Vitosh et. al., 1995). In wheat plots, N
was broadcast as urea at 56-67 kg ha’1 in early April. Soybean plots received no fertilizer
N. In the compost treatment, composted dairy manure from a companion research project
was applied on a dry weight basis in April (corn and soybeans) and October (wheat) with a
manure spreader. The goal was to supply N from the compost to meet corn yield goals,
assuming 15% N available in the first year of application. Because of the low N
availability in the early years of the rotation, and 60% sand content, a larger amount of
compost was applied than the 1 1-22 Mg ha-l rate commonly used by farmers in manure
application . This resulted in an application rate in corn plots of 56 Mg ha"1 in 1993, 105
Mg ha'1 in 1994 followed by a reduction down to 4.5 Mg ha'1 in 1995. Compost
application rate and analysis is presented in Table 1.

Soil samples at a 30 cm depth were taken periodically each year with a 1.9 cm dia.
soil probe to coincide with early spring mineralization and fall residual soil N levels. Five
cores per plot were taken from between rows and composited. Afier harvest in 1994 and
1995, samples were also taken to a depth of 90 cm with a Giddings 5 cm dia. hydraulic
soil probe, and divided into 30 cm increments. Three cores per plot were takenand

composited by depth. The samwes were dried at 40 0C for 72-96 h, crushed and sieved

42

through 10 mesh screen, extracted with 1N KCl and analyzed for NO3-N by a Lath

autoanalyzer (Lachat Instruments.)

Corn grain + stover biomass samples were taken each year at physiological maturity. Ten

plants per 15.2 m row were weighed wet, fieldochopped in a silage ch0pper, dried at 40

0C for at least 96 11, weighed dry, and ground for mass spectrometer analysis (Harris and

Paul, 1989) for total N. Cover crop samples were taken in late fall, alter main crop
harvest. Two 77.4 sq cm areas were cut from each plot at a 2.5 cm height. The samples

' were weighed, dried and ground for mass spectrometer analysis for total N.

The second experiment, designed to measure the nitrogen effect of annual ryegrass
overseeded into corn, was conducted during 1994-1995 and 1995-1996 seasons in an
adjacent field that had been planted to soybeans. The soil type was similar to the LFL soil
type. The experimental design was a split-plot with four replications. A 34 kg N ha’1
credit was given to corn in both years (Crookston, 1984). Main plots are three N rates. In
1994, the rates were 0, 67 kg N ha‘l, and 134 kg N ha’l. In 1995, the rates were 0, 67
kg N ha-l, and 179 kg N ha" The 179 kg N ha-1 rate was used in 1995 to increase N
uptake by both the corn and cover crop In both years, the 0 N rate was used as a check
plot, and the 67 k g ha‘I rate was used as a rate close to that applied to corn in the rotation
experiment in the LFL plots (after the N credit from soybeans was added ). Main plot size
was the same as the LFL plots Sub-plots were annual ryegrass overseeded at the same
time and rate as in the LFL plots. and a no-cover check. Enriched 15N (5 atom %)
NH4NO3 was applied in 1.52 by 1 52 m microplots contained within the main plots. The
labeled material was dissolved in one L of water and applied with a C02 backpack sprayer
pressurized to 40 psi. The sprayer boom straddled the three microplot rows, and was held
at constant height to distribute the solution in an even spray pattern. The corn biomass .
sampling row for the microplot was the middle row of three rows. Microplots were
seeded such that there were eight equally spaced plants in 1.52 m of row. The four

innermost plants inthe eight plant middle row were sampled for stover and grain biomass

43

N and atom % 15N. Percent N derived fi'om fertilizer (NDFF) was determined. The
annual ryegrass was sampled in the same way as in the LFL plots, and analyzed for NDFF.
After crop harvest, corn biomass was returned to the microplots, which were then covered
with wire mesh to minimize labeled material movement from the microplots. In both years
that the experiment was conducted, the annual ryegrass was sampled in the following

spring to determine uptake of remaining N from the initial labeled N application .

RESULTS
Effect of rotation on soil NO3-N in the LFL

Means for PSNT from 1993-1995 are shown in Table 2, the analysis of variance is
shown in Table 3. Means for fall soil samples in 1994 and 1995 are shown in Tables 4 and
5, respectively. The analysis of variance for the fall samples in 1994 and 1995 is shown in
Tables 6 and 7, respectively. In 1993, there were no treatment difl‘erences in the rotation
experiment for soil NO3-N in samples taken at stage V-6, the PSNT sampling (Table 2).
No differences were expected at this stage, as the experiment had just been established and
there was no treatment legacy.

In 1994, at the PSNT (June 10) sampling, first year corn following wheat had a
NO3-N level of 9.4 mg kg'l, 58% higher than both rotations of corn following corn,
indicating earlier N mineralization (Table 2). In the 1994 fall soil sampling, treatment
differences varied with depth. In the 0-30cm depth, NO3-N was significantly higher in the
fertilizer plots (4.2 mg kg ‘1) than in the compost plots (3.0 mg kg '1), Table 4. There was
also a significant cover by management interaction; the fertilizer with no cover plots had a
NO3-N level of 4.8 mg kg '1, higher than the fertilizer with cover .or the compost with or
without cover plots (Table 4). In the 30-60 and 60-90 cm depths, the only significant
treatment difference was due to cover. No-cover plots had higher NO3-N than the cover
plots at both of these depths (Table 4).

In 1995, NO3-N levels at the PSNT (June 8) sampling were significantly higher in
the cover plots (10.6 mg kg ‘1) than in the no-cover plots (7.6 mg kg '1), shown in Table
2. Also, first-year corn had NO3-N levels of 12.0 mg kg '1, 64% and 48% higher than
continuous corn and second-year com, respectively (Table 2). There was also a rotation
by cover interaction in 1995. First-year corn with cover had NO3-N levels of 15.2 mg kg
'1, higher than first-year, second-year or continuous corn with or without cover (Table 2).
In the fall 1995 sampling, there was a significant rotation by cover by management
interaction at all three sample depths (Table 5). At all three depths, NO3-N in first-year

44

 

45

com with cover in the compost plots is found at the highest levels, significantly higher
than in first-year corn with cover in the fertilizer plots. This indicates a potential for high
residual fall N levels when compost and clover residue fi'om the previous wheat crop are
combined. These plots received 213 kg ha’1 in 1993, none in 1994, and 280 kg ha"1 in
1995. With an estimated 15% per year mineralization rate, N from compost was expected
to be available in modest amounts.

Grain + Stover Biomass N

Means for grain+stover biomass N are shown in Table 8, analysis of variance is
shown in Table 9. In 1993-1995, grain+stover biomass N was significantly higher in the
fertilizer plots than in the compost plots (Table 8). This was probably due to low N
availability in the compost plots, even though the amount of compost applied to corn in
1993 was nearly doubled in 1994.

In 1994, first-year corn produced biomass N levels of 236 kg N ha'l, 33% higher
than either second-year corn rotation (Table 8). There was a significant rotation by
management interaction in 1994 F irst-year corn under either fertilizer or compost
management, and also second-year corn under fertilizer management produced higher
biomass N than second year corn under compost management (Table 8). Compost
without the addition of a clover cover crop did not supply sufficient N for second-year
com. This effect is seen in 100-: corn grain yields, which are presented with overall corn
yields for the rotation experiment in Table 10 A complete discussion on corn grain yield
is given in another paper.

In 1995, first year corn produced biomass N levels of 227 kg N ha‘l, 33% higher
than either second or third-year corn (Table 8). There was a significant cover by
management interaction; the no-cover fertilizer plots produced biomass N levels of 219
kg N ha'l, higher than the fertilizer plots with cover and the compost plots with or

without cover (Table 8).

46

In 1995, after corn grain harvest, biomass N levels were also determined for each
of the cover crop(s) overseeded in the corn at stage V-6. Analysis of variance for
overseeded covers is shown in Table 11, means are shown in Table 11. There was a
significant rotation effect for cover crop biomass N. The arm. rye/re mix overseeded into
first-year corn produced higher biomass N than either ann. rye overseeded seeded into
second year corn or the ann.rye/rc mix overseeded into continuous corn (Table 11).
There was also a cover crop by management interaction. The ann.rye/rc mix overseeded
into first-year corn under fertilizer management produced higher biomass N than ann. rye
overseeded into second year corn under fertilizer or compost management (Table 11). In
the arm. rye/re mix overseeded into continuous corn, biomass N was significantly higher
in the compost plots than in the fertilizer plots. Compost may provide a beneficial

environment for cover establishment in continuous corn.

Fertilizer N uptake by com with overseeded annual
ryegrass in the two-year labeled N experiment

N derived from fertilizer (NDFF) was determined in the 5 ug plant samples as

follows:

(NDFF) = atom % excess (plant) - .3667 (atom °/g 15N in ggfeniljgeg plants)

atom % labeled fertilizer (5%) - .3667 (atom % 15N in unfertilized plants)

From NDFF, % N fertilizer efiiciency (NFE)was determined from:
Total kg N ha-l (grain or stover) X NDFF = kg N ha-l fi'om fertilizer

Then: kg N ha-l fi’om fertilizer X 100 = %NFE
the kg N ha-l application rate

Grain and stover biomass N and %NFE data for 1994-1995 are presented in Table 12,
analysis of variance is shown in Table 13. Analysis of variance for annual ryegrass cover
biomass N is shown in Table 14, means and %NFE data are presented in Table 16. The
significant difference in grain and stover biomass N between the three application N rates

47

was expected (Table 12). The presence of overseeded ryegrass did not affect N (as
measured by %NFE) uptake in corn grain or stover in either year, even though grain
biomass N was less in 1995 than in 1994, and stover biomass N was greater in 1995 than
in 1994 (Table 12). At all four sampling periods that annual ryegrass cover biomass was
taken, N uptake was significantly different only at the highest N application rate (Table
15).

Fall 0-90cm soil N03 analysis of variance and corresponding means are shown for
1994 in Tables 17 and 18, and for 199s in Tables 19 and 20. In both years, at all three
sampling depths, differences in soil N03 for N rate occurs only at the highest rate. The 0 N
rate is not different fiom the middle rate. In 1995, there was a reduction in soil N03 due
to cover (Table 20). There was also a difference in soil N03 due to cover by N rate
(Table 20). Soil N03 levels in the no-cover plots at the 179 kg N ha-l N application rate

were twice as high as in the cover plots.

SUMMARY

Across fertilizer and compost fertility management, early season N available to a
corn crop was greatly affected by the previous crop in rotation. Corn following wheat
provided the highest NO3-N levels at PSNT sampling for two consecutive years, and
resulted in higher grain + stover biomass N. This effect on PSNT levels was enhanced by
red clover residue overseeded into the preceding wheat crop. The efl‘ect was consistent
as well in overseeded cover crops when their biomass was measured after corn grain
harvest, suggesting that a sufficient level of N early in the growing season can adequately
supply the main crop and the cover crop. Farmers are reluctant to use cover crops
because of potential competition for nutrients. In the ancillary study using labeled N,
neither biomass N in corn, or N efficiency were affected by the overseeded annual
ryegrass. However this does not rule out the potential for cover crop competition when
water, not N, is the limiting resource. Annual ryegrass caused a 50% reduction in soil
.NO3 levels in the fall at the highest N application rate while only taking up less than 6% of
the N available to com. This suggests that at high levels of N application in corn, as
occurs in the seed corn industry overseeding annual ryegrass reduces the potential for
N03 leaching. This is especially important when considering the coarse-textured soils in
the region this experiment was conducted

Cover crops reduced residual soil N afier harvest, in the fertilizer plots and in
compost plots without red clover Compost plots with red clover residue resulted in
higher residual soil N after harvest in one of the two experiment years. All other compost
and cover combinations except red clover resulted in the lowest after harvest N levels, at
all three sampling depths. Perhaps overseeding an alternative cover into corn following
wheat would alter this effect of compost/red clover. Such scenarios are being considered

in the LFL experiment.

48

49

 

The ideal combination of crop rotation and cover crops will result in higher early
season N levels for uptake in synchrony with corn crop needs while reducing residual N
after crop harvest.

REFERENCES

Brinsford, RB, and KW. Staver. 1991. Use of cereal grain crops for reducing
groundwater nitrate contamination in the Chesapeake Bay region. p. 79-82. In W.L.
Hargrove (ed.) Cover Crops for Clean Water. Soil and Water Conservation Society,
Ankeny, IA

Brown, as, G.E.Varvel, and CA Shapiro. 1993. Residual efects of interseeded hairy
vetch on soil nitrate-nitrogen levels. Soil Sci. Soc. Am I. 57:121-124

Crookston, R.K. 1984. The rotation effect: what causes it to boost yields? Crops and
. Soils. March: p. 12-14.

Ditsch, D.C., M.M. Alley, KR. Kelly, and Y2. Lei. Efi‘ectiveness of winter rye for
accumulating residual fertilizer N following com. 1993. J. Soil and Water Cons.
48(2): 125-132

Dou, 2., RH. Fox, and JD. Toth. 1995. Seasonal soil nitrate dynamics in corn as
affected by tillage and nitrogen source. Soil Sci. Soc. Am I. 59:858-864.

Harris, D., and EA. Paul. 1989. Automated analysis of 15N and 14C in biological
samples. Commun. In Soil Sci. Plant Anal. 20:935-947

Harris, G.H., O.B. Hesterman, E.A. Paul, S.E. Peters, and RR. Janke. 1994. Fate of
legume and fertilizer N-l 5 in a long-term cropping systems experiment. Agron. J.
86:910-915.

Landis, D., and S. Swinton. 1994. Corn insect management in Michigan: results of a
1992 com grower survey. Research Report 537. Mich. Agri. Exp. Sta. Michigan
State University.

Magdoff, F. 1991. Managing nitrogen for sustainable corn systems: Problems and
possibilities. Am. J. Alternative Agr. 623-8.

Power, J.F. 1987. The Role of Legumes in Conservation Tillage Systems. Soil and
Water Conservation Society, Ankeny, IA. 153pp.

Stute, J.K., and J.L. Posner. 1993. Legume cover crop options for grain rotations in
Wisconsin. Agron. J. 85:1128-1132.

Varvel, GE, and TA. Peterson. 1990. Nitrogen fertilizer recovery in monoculture and
rotation systems. Agron. .1. 82:935-988.

50

51

Vitosh, M.L., J.W. Johnson, and DB. Mengel, 1995. Tri-state fertilizer
recommendations for corn, soybeans, wheat, and alfalfa. Michigan State University,
The Ohio State University, Purdue University. Extension Bulletin E-2567. East
Lansing, MI.

Table l. Compost analysis.

APPLICATION DATE

 

Compost applied (Mg ha-l)
Nitrogen supplied (Mg ha-l)

Estimated available (Mg ha-l)2

Nitrogen (%)

Carbon (%)

C:N ratio
Nitrate-Nitrogen (ug/ml)

Phosphorus
Potassium
Calcium
Magnesium

Boron
Zinc
Manganese
Copper

pH

Electrical conductivity (mmhos

Moisture (%)

4/22/93 10/18/93 4/21/94 10/4/94 4/28/95 10/22/95

3200 45500' 39900 56800‘ 4000l
40 190 600 440 250
<10 30 '90 70 40
1.2 0.4 1.5 0.8 0.6
14.1 6.2 20.2 10.2 11.5
12 15 13 13 19
- - 4 13 28
9’;
0.5 0.2 0.4 0.2 0.2
0.3 0.5 1.7 0.8 0.7
1 2.2 2.3 14 2.4
0.4 0.6 0.5 1.8 0.6
ppm
10 20 50 40 14.4
220 50 68.2
210 100 190 420 191
130 20 - - 29
- - 8.4 9.2 9.1
- - 5.5 11.6 6.3
60 30 50 20 40

 

 

 

4000‘

250
40

0.6
11.5
19
28

0.2
0.7
2.4
0.6

14.4
68.2
191
29

9.1
6.3
40

 

Icompost applied on these dates had been made with dairy manure where sand had been
used for bedding. Sand content was estimated to be 60%, by water sedimentation.

2assumes 15% estimated release in first year afier application. Mineralization in

subsequent years was not estimated.

53

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54

Table 3. Analysis of variance for pre-sidedress nitrate test, 1994 and 1995.

 

 

June 10 1994 June 8 1995

Source of variation Pr. >F Pr. >F
Replication 0.30 0.93
Main effects

Management 0.23 0.698

Entry point 0.0001 0.0001

Cover 0.717 0.0001
Interaction efi‘ects

Management x entry point 0.855 0.653

Management x cover 0.245 0.45

Entry point x cover 0.816 0.01

Management x entry point x cover 0.653 0.438

55

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57

Table 6. Analysis of variance for N03 samples at three incremental

depths, November 8, 1994.

 

 

 

 

 

0-30cm 30-60cm 60-90cm

Source of variation Pr. >F Pr. >F Pr. >F
Replication 0.044 0.359 0.484
Main effects

Management 0.005 0.085 0.638

Entry point 0.911 0.861 0.543

Cover 0.810 0.021 0.031
Interaction effects

Management x entry point 0.479 0.277 0.484

Management x cover 0.037 0.292 0.074

Entry point x cover 0.019 0.699 0.866

Management x entry point x cover 0.383 0.976 0.522
Table 7. Analysis of variance for fall N03 samples at three incremental

depths, November 13, 1995.
0-3 0cm 30-60cm 60-90cm

Source of variation Pr. >F Pr. >F Pr. >F
Replication 0.868 0.514 0.179
Main effects

Management 0.793 0.061 0.395

Entry point 0.919 0.004 0.036

Cover 0.260 0.807 0.445
Interaction efiects

Management x entry pm!“ 0120 0.165 0.100

Management x cover 0.097 0.006 0.879

Entry point x cover 0.079 0.441 0.221

Management x entry pOInl it cover 7 0.006 0.027 0.008

 

 

58

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59

Table 9. Analysis of variance for com grain+stover biomass N, 1993-1995.

 

1993 1994 1995

 

Source of variation Pr. >F Pr. >F Pr. >F
Replication 0.307 0.416 0.58
Main efl‘ects
Management 0.03 0.043 0.036
Entry point 0.144 0.0001 0.007
Cover 0. 132 0.238 0.807
Interaction efi‘ects
Management x entry point 0.041 0.04 0.261
Management xrcover 0.127 0.473 0.009
Entry point x cover 0.591 0.30 0.099

Management x entry point x cover 0.339 0.976 0.749

60

Table 10. Overall corn yield means for each year by fertility management type,
entry point, and cover.

 

 

1993 1994 1995
no cover cover no cover cover no cover cover
yield Mg ha-1
Compost
lstyrcom 8.4 8.2 11.7 11.7 8.8 10.6
2nd yr corn 8.0 8.3 8.0 6.8 8.2 7.9
cont corn 7.5 8.3 7.4 7.8 7.8 8.2
Fertilizer
1st yr corn 9.8 9.8 11.6 12.0 9.5 9.9
2nd yr corn 10.4 9.6 11.2 9.8 8.8 8.3

cont corn 9.9 9.6 8.6 8.8 8.7 8.7

 

61

Table 11. Analysis of variance for cover crop biomass N, 1993-1995.

 

 

 

 

 

1993 1994 1995
Source of variation Pr. >F Pr. >F Pr. >F
Replication 0.522 0.065 0.888
Main efi‘ects
Management 0.1 15 0.242 0.895
Cover crop 0.287 0.105 0.025
Interaction effects
Management x cover 0.613 0.245 0.058
Table 12. Cover crop biomass N means for each year.
1993 1994 1995
Overall means
Management ----- kg N ha"----
Integrated compost
ar/rc“ inlst yr corn 3.8 23.0 10.6abc“
ar in 2nd yr corn 5.0 13.2 6.5bc
ar/rc in com com 5.6 26.1 11. lab
Integrated fertilizer
who in lst yr corn 6.6 18.5 14.2a
ar in 2nd yr corn 10.2 22.8 . 7.5bc
ar/rc in cont corn 8.1 31.2 5.4c
Cover crop
ar/rc in lst yr com 52 20.8 13.9a
ar in 2nd yr corn 7 6 18.0 7.8b
ar/rc in cont corn 6 9 28.7 9.2b
Management
Integrated compost 4 8 20.5 9.4
Integrated fertilizer - 8.3 23.7 9.0

 

 

‘ar/rc= annual ryegrass/red clover. ar= annual ryegrass
"Numbers not followed by same letter are significantly different according to

Duncan's Multiple Range Test (p= 0.05).

62

Table 13. Corn grain and stover biomass N and % N efiiciency at three fertilizer
N rates, with and without annual ryegrass cover in 1994 and 1995.

 

 

1994

Grain No cover Cover Mean No cover Cover
-—-Biomass kg N ha 4... ‘ %NFE

0 rate 87 91 89 - — —
67 kg N ha“ 138 132 135 56% 57%
134ng ha" 146 159 153 47% 49%
5191::
0 rate 30 32 31 — -—
67 kg N ha" 45 41 43 19% 19%
134kg N ha" 60 67 64 20% 21%
Cgainfitgver
0 Rate 117 123 1206*
67 kg N ha" 183 173 178b
134kg N ha" 206 225 216a

 

*Numbers not followed by same letter are significantly different according to
Duncan's Multiple Range Test (p= 0.05).

 

 

1995

Grain No cover Cover Mean No cover Cover
---Biomass kg N ha "--- ’ %NFE
0 rate 39 44 42 — ——
67 kg N ha" 91 98 95 52% 59%
179 kg N ha" 130 120 125 52% 45%
$1911.64"
0 rate 37 36 37 — —
67 kg N ha" 63 6o 62 36% 39%
179 kg N ha" 104 93 99 38% 32%
in+ v r

0 Rate 76 80 78c"
67 kg N ha" 154 158 156b
179 kg N ha" 234 213 2248

 

*Numbers not followed by same letter are significantly difl‘erent according to
Duncan's Multiple Range Test (p= 0.05).

63

Table 14. Analysis of variance for corn grain and stover biomass N and °/o N
efliciency at three fertilizer N rates, with and without annual ryegrass

cover in 1994 and 1995.

 

 

1994 1995
Source of variation Pr. >1? pr, >1?
Replication 0.197 0.725
N Rate 0.001 0.0001
Cover 0.591 0.706

N Rate it cover 0.477 0.574

64

Table 15. Analysis of variance for annual ryegrass biomass N at
three N rates, 1994 and 1995.

 

Fall 1994 Spring 1995 Fall 1995 Spring 1996

Source of variation Pr. >F Pr. >17
Replication 0. 159 0.753 0.484 0.725
N Rate 0.004 0.696 - 0.006 0.011

 

Table 16. Annual ryegrass biomass N means and %N eficiency at three N rates
in 1994 and 1995.

 

Biomass kg N ha " 20m
an 1994
0 rate 5.5b“ —
67 kg N ha" 2.8b 0.50
134kg N ha" 13.8a 2.5
Spring 1995
0 rate 6.0 ~—
67 kg N ha" 4.6 0.35
134kg N ha“ 6.3 0.65
Fall 1995
0 rate l.3b —
67 kg N ha" 321: 1.5
179kg N ha" 9.3a 2.4
Spring 1996
0 rate 1.4b —
67 kg N ha" 2.2b 0.23
179kg N ha" 4.9a 0.48

 

‘Numbers not followed by same letter are significantly different according to
Duncan's Multiple Range Test (p= 0.05).

Table 17. Analysis of variance for the fall 0-90 cm soil N0; samples at
three N rates, with and without annual ryegrass cover, October 26,1994.

65

 

0.30cm 30-60cm 60-90cm
Source of variation Pr. >F Pr. >F Pr. >F
Replication 0.572 0.482 0.529
N Rate 0.009 0.018 ' 0.066
Cover 0.3 17 0.832 0.639
N Rate x cover 0.287 0.937 0.176

 

Table 18. Fall 0-90 cm soil N03 levels at three fertilizer N rates, with and without
annual ryegrass after corn grain harvest, October 26, 1994.

 

MW

0 rate

67 kg N ha"
134 kg N ha"

30-60m dgpth

0 rate

67 kg N ha"
134 kg N ha"

60-90cm depth

0 Rate

67 kg N ha"
134 kg N ha"

no cover
—— mg kg'1 N03!—

1.2
1.5

4.3
2.3

1.0
1.0

2.7
1.6

0.8
0.9

1.9
1.2

mm

1.4
1.2

3.2
1.9

1.2
0.9

2.8
1.6

0.8
1.2

1.4
1.1

M9411

1.3b
1.4b
3.6a

1.1b
1.0b
2.8a

0.8
1.1
1.7

 

I"Numbers not followed by same letter are significantly difi‘erent according to

Duncan's Multiple Range Test (p= 0.05).

66

Table 19. Analysis of variance for the fall 0-90 cm soil N03 samples at three
N rates, with and without annual ryegrass cover, November 13, 1995.

 

Source of variation
Replication

N Rate

Cover

N Rate x cover

0-3 0cm

Pr. >F
0.647
0.162
0.378
0.747

30-60cm

Pr. >F
0.515
0.016
0.606
0.836

60-90cm
Pr. >F
0.237
0.0001
0.028
0.054

Table 20. Fall 0-90 cm soil NO; levels at three fertilizer N rates, with or without
annual ryegrass cover, November 13, 1995.

 

0-300m e th
0 rate
67 kg N ha"

179 kg N ha"

Mean
30-60cm depth
0 rate

67 kg N ha’l

179 kg N ha'l

Mean
60-90cm depth
0 Rate

67 kg N ha"

179 kg N ha"
Mean

no cover
--- mg kg’1 N03*——

1.4
1.3

4.9
2 S

12
12
65
30

08b
llb
2%
168

 

C_0_V_el'

1.3
3.4

6.2
3.6

08
12
47
22

08
10b

Mb
1115

Mean

1.4
2.4
5.6

1.0b
1.2b
5.6a

0.8b
1.05b
2.15a

 

*Numbers not—followed by same letter; aredsignifrcantly different according to
Duncan's Multiple Range Test (p= 0.05).

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