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AGRONOMIC AND ECONOMIC ASPECTS OF
INTEGRATING A WINTER ANNUAL CEREAL INTO A CORN-
SOYBEAN ROTATION IN MICHIGAN CROPPING SYSTEMS

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MICHAEL R. JEWE'l'l'

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Master of degree in Department of Crop and Soil
Science Sciences

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AGRONOMIC AND ECONOMIC ASPECTS OF INTEGRATING A WINTER
ANNUAL CEREAL INTO A CORN - SOYBEAN ROTATION IN MICHIGAN
CROPPING SYSTEMS
By

Michael R. Jewett

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE

Department of Crop and Soil Sciences

2004

ABSTRACT
AGRONOMIC AND ECONOMIC ASPECTS OF INTEGRATING A WINTER

ANNUAL CEREAL INTO A CORN - SOYBEAN ROTATION IN MICHIGAN
CROPPING SYSTEMS

BY

MICHAEL R. J EWETT

The addition of a winter annual cereal into a Michigan com-soybean rotation had direct
impacts on many agronomic and economic aspects of the cropping system. Winter wheat
(T riticum aestivum L.) and rye (Secale cereale L.) scavenged nitrogen over the fall and
winter compared with having no cover crop present. With a late April glyphosate burn
down of wheat or rye cover crops, the killed plants began to release nitrogen to the soil
by the first week of June. Winter annual cereals were able to provide a second profitable
crop to the system when harvested as forage. Insect pressure on rotational crops
following winter annual cereals varied by the crop and insect, but often were dependant
on rotational crop planting date. Soybean [Gycine max (L.) Merr.] yield following a
wheat or rye cover crop may be increased over no cover crop, while corn grain (Zea mays
L.) and corn silage yield tended to follow a pattern of higher yield with earlier corn
planting date, which ultimately depended on whether the winter annual cereal was used
for a cover crop, forage, or grain. Depending on the planting date of the corn or soybean
rotational crop following harvest of a winter annual cereal, the economic benefit of the

additional crop may increase or decrease the net profit to the system.

ACKNOWLEDGEMENTS

I would like to express my sincere thanks to the members of my graduate committee for
help and guidance in the pursuit of the research and processes involved in this study.
Especially Dr. Chris DiFonzo for not only helping with the entomology aspects of the
study, but also for graciously allowing me time from work to pursue this degree. The
other members of my committee included my major advisor Dr. Kurt Thelen, who
provided leadership and direction through out the research, Dr. Darryl Warncke, who
advised me on many aspects of the soil and nutrient dynamics and Dr. Richard Leep, who
advised me on the forage aspects of the study. I am grateful for the help of Dr. Sasha

Kravchenko with the complicated statistics involved in this study.

I would also like to thank the Department of Crop and Soil Science farm manager, Brian
Graff, who helped keep the soil probe truck operational, as well as the technicians Keith
Dysinger and Bill Widdicombe who were invaluable for setting up the trial, timely
planting and herbicide applications, as well as excellent record keeping with an immense

quantity of data.

The research was able to take place due to funding by the Michigan Soybean Promotion

Committee and the Corn Marketing Program of Michigan.

I was very fortunate to have the help and support of my friends and family, especially

Marella Briones who provided much love, patience, and encouragement in this pursuit.

iii

TABLE OF CONTENTS

LIST OF TABLES ............................................................................................................. vi
LIST OF FIGURES .......................................................................................................... vii
CHAPTER 1
SOIL NITRATE LEVELS .................................................................................................. 1
Abstract ................................................................................................................... 1
Introduction ............................................................................................................. 2
Materials and Methods ............................................................................................. 4
Results and Discussion ............................................................................................ 8
Conclusions ............................................................................................................ 56
References ............................................................................................................. 58
CHAPTER 2
AGRONOMIC AND ECONOMICS ................................................................................. 60
Abstract ................................................................................................................. 60
Introduction ........................................................................................................... 61
Materials and Methods .......................................................................................... 64
Results and Discussion ......................................................................................... 69
Ground Cover ............................................................................................ 69
Insect Damage ............................................................................................ 74
Winter Annual Cereal Yields .................................................................... 83
Rotational Crop Yields .............................................................................. 83
Economics .................................................................................................. 92
Conclusions ............................................................................................................ 92
References .............................................................................................................. 95

iv

LIST OF TABLES

CHAPTER 1
Table 1.1: Calendar dates of burn down or harvest of winter annual cereals and

planting dates of rotational crops ........................................................................ 7
Table 1.2: Monthly Precipitation ....................................................................................... 10
Table 1.3: Significance Table ............................................................................................ 11
Table 1.4: BS1 soil nitrate levels ....................................................................................... 13
Table 1.5: CSl soil nitrate levels ....................................................................................... 15
Table 1.6: BS2 soil nitrate levels ....................................................................................... 18
Table 1.7: C82 soil nitrate levels ....................................................................................... 20
Table 1.8: BF2 soil nitrate levels ....................................................................................... 26
Table 1.9: Soybean yields .................................................................................................. 29
Table 1.10: Corn grain yields ............................................................................................. 29
Table 1.11: Corn silage yields ........................................................................................... 30
Table 1.12: BF2 rotational crop soil nitrate levels ............................................................. 32
Table 1.13: BF2 wac * rotational crop nitrate levels ......................................................... 34
Table 1.14: CF 1 soil nitrate levels ..................................................................................... 37
Table 1.15: CF 1 rotational crop soil nitrate levels ............................................................. 39
Table 1.16: CF 2 winter annual cereal soil nitrate levels .................................................... 42
Table 1.17: CF 2 rotational *depth soil nitrate levels ......................................................... 45
Table 1.18: B1 soil nitrate levels ....................................................................................... 47
Table 1.19: B2 soil nitrate levels ....................................................................................... 49
Table 1.20: CI soil nitrate levels ....................................................................................... 52
Table 1.21: C2 soil nitrate levels ....................................................................................... 54
CHAPTER 2
Table 2.1: Calendar dates of burn down or harvest of winter annual cereals and

planting dates of rotational crops ...................................................................... 66
Table 2.2: Significance tables for forage yield .................................................................. 84
Table 2.3: Forage yields ..................................................................................................... 84
Table 2.4: Significance table for wheat grain yields .......................................................... 85
Table 2.5 Wheat grain yields ............................................................................................. 85
Table 2.6: Wheat grain yields ............................................................................................ 85
Table 2.7: Soybean yields .................................................................................................. 86
Table 2.8: Corn grain yields ............................................................................................... 88
Table 2.9: Corn silage yields ............................................................................................. 90
Table 2.10: Monthly Precipitation ..................................................................................... 91
Table 2.11: Economics ....................................................................................................... 93

LIST OF FIGURES

CHAPTER 1

Figure 1.1:
Figure 1.2:
Figure 1.3:
Figure 1.4:
Figure 1.5:
Figure 1.6:
Figure 1.7:
Figure 1.8:

BS1 soil nitrate levels ...................................................................................... 14
CS1 soil nitrate levels ...................................................................................... 16
BS2 soil nitrate levels ...................................................................................... 19
C82 soil nitrate levels ...................................................................................... 21
BF 2 soil nitrate levels ...................................................................................... 27
BF2 rotational crop soil nitrate levels ............................................................. 33
BF 2 wac "' rotational crop nitrate levels .......................................................... 35
CFl soil nitrate levels ...................................................................................... 38

Figure 1.9: CFl rotational crop soil nitrate levels ............................................................. 40
Figure 1.10: CF2 winter annual cereal soil nitrate levels .................................................. 43
Figure 1.11: CF2 rotational *depth soil nitrate levels ........................................................ 46
Figure 1.12: Bl soil nitrate levels ...................................................................................... 48
Figure 1.13: B2 soil nitrate levels ...................................................................................... 50
Figure 1.14: C1 soil nitrate levels ...................................................................................... 53
Figure 1.15: C2 soil nitrate levels ...................................................................................... 55
CHAPTER 2

Figure 2.1: Percent ground cover 2000 .............................................................................. 70
Figure 2.2: Percent ground cover corn silage residue field 2001 ...................................... 71
Figure 2.3: Percent ground cover soybean rotational crops 2001 ...................................... 72
Figure 2.4: Percent ground cover corn rotational crops 2001 ............................................ 73
Figure 2.5: Armyworm damage soybean residue .............................................................. 75
Figure 2.6: Armyworm damage corn silage residue .......................................................... 76
Figure 2.7: ECB larvae number ......................................................................................... 77
Figure 2.8: ECB tunnels per stalk... .................................................................................. 78
Figure 2.9: ECB tunnel length ........................................................................................... 79
Figure 2.10: BLB damage .................................................................................................. 81
Figure 2.11: Soybean aphid rating ..................................................................................... 82

vi

CHAPTER 1
THE EFFECT OF WINTER ANNUAL CEREALS ON RESIDUAL SOIL
NITRATE LEVELS IN ROTATIONAL CORN AND SOYBEANS

Abstract

The addition of winter annual cereals into Michigan com-soybean rotations had direct
impacts on the nitrogen cycle in several cropping systems. Wheat and rye winter annual
cereals scavenged nitrogen over the fall and winter compared with having no cover
present. With a late April glyphosate burn down of wheat or rye cover crops, the killed
plants already began to return nitrogen to the soil by the first week of June. Afier wheat
or rye was harvested for forage or grain, although there was a removal of N from the
system, the decaying plant and root matter returned some N. After harvest of the
rotational crops in the fall, there were still apparent differences in soil nitrate levels
depending on what winter annual cereal was present before the planting of rotational

crops.

Introduction

Diverse ecological systems are often more productive with regards to the cycling
of nutrients than rotational crops. Although a two-year corn soybean rotation has been a
traditional cropping system in Michigan agriculture, introducing a winter annual cereal
crop to the rotation may increase production efficiency. Nitrogen use efficiency is
becoming increasingly important both from an environmental and economic aspect.
Higher nitrate concentrations in groundwater are associated with increased fertilizer use.
Winter annual crops may be used to scavenge nitrogen over the fall and winter thereby
reducing the need for fertilizer inputs. Owens et al. (1995) using lysirneters in Ohio,
found that the highest movement of nitrate occurred between February through April.
Without a winter cover crop, nitrate may travel deeper into the soil profile and even leach
into the ground water (Owens et al., 1995).

The extent of nitrate leaching is dependent on weather conditions. Mineralization
of N is temperature dependant and cold wet springs have less mineralization and greater
nitrate percolation (Bemer et al., 1995). In general, diverse cropping systems leach less
and have less subsoil nitrate concentration than annual rotations. (Entz et al., 2001).
Ditsch et al. (1993) found that the combined nitrogen fi'om the top ninety centimeters of
soil and the nitrogen the corn plant took up accounted for only seventy six and fifty seven
percent of the fertilizer nitrogen (FN) applied for each year, indicating a loss of FN with
no cover crop. Ditsch et a1. (1993) also found that a rye cover crop recovered between 2
to 36 kg N ha'1 of the fertilizer N. Rye is an excellent crop at recovering residual soil
nitrogen (RSN) as Ditsch et al. (1993) found that regardless of fertilizer rates applied, the

soil nitrate concentration afier rye was reduced to that with no fertilizer N applied, down

to a depth of ninety centimeters. Brandi-Dohm et al. (1997) found that wheat and rye
reduced nitrate leaching by 32-42 percent over three years in a vegetable cropping
system. Wyland and Jackson (1996) also found that winter cover crops incorporated in a
vegetable cropping system reduced nitrate leaching. The soil incorporation of the rye
cover crop increased net minerizable N over six weeks and 3 led to a corresponding
decline in inorganic N from immobilization by microbes. After six weeks there was a net
mineralization and some denitrification due to the fast decomposition of incorporating the
cover crop. Kessalvou and Walters (1999) said “some N-credit (~40 Kg N/ ton rye dry
matter) should be given to winter rye cover crops in formulating corn N
recommendations.” This credit may lower RSN accumulation and increase efficiency of
fertilizer use while reducing nitrate leaching.

Another factor that effects nitrate leaching is tillage. Conservation tillage may
also help conserve water (Entz et al., 2001). Meek et al. (1995) found that no till reduced
nitrate leaching compared to conventional till. There are several methods of measuring
soil nitrate including soil sampling and lysimeters. Logsdon et al. (2002) used lysimeters
and discovered rye cover crops in a com-soybean rotation will reduce nitrate leaching
and suggested that this same trend will happen in the field. Meek et al. (1995) stated that
ceramic soil solution samplers might not estimate the entire nitrate in soil solution in no-
till, compared to soil sampling. The larger pores in no till may allow water to by—pass the
nitrate thereby not providing an accurate reading of nitrate in the soil profile. Thurman et
al. (1998) discussed an evaluation of field studies versus lysimeters that found soil
monoliths have unrealistic boundaries compared with the field. Lysimeters may change

the natural water flow in the soil due to the lysimeter wall and the disruption of the lower

boundary of the soil in the lysimeter. Also, field studies allow periodic soil sampling to
verify N cycling whereas soil monoliths do not.

Winter annual cereal cover crops also add benefits by increasing residue cover
and decreasing weed populations. Guy and Gareau ( 1998) found that weed populations
decreased when the surface residue increased. In Iowa, a rye cover crop increased
infiltration and reduced erosion and runoff in two of three years (Kaspar et al., 2001). The
rye also improved soil structure by protecting the soil surface from raindrops, holding
residue in place, and protecting the soil from freezing, thawing, and compression by ice
and snow. Kessavalou and Walters (1997) found that rye afier soybeans helped protect
the soil from erosion. The rye provided thirty percent extra surface residue, which was
equivalent to the residue left by corn in conservation tillage. These benefits of winter

annual cereals may create a viable reason to plant winter c0ver crops in Michigan.

Objectives
1) Examine the ability of several winter annual cereal crops to scavenge subsoil

nitrate over the fall and winter by measuring soil nitrate in the spring.
2) Determine winter annual cereals and rotational crops effects on residual soil

nitrates levels.

Materials and Methods

On 28 September 1999 and 13 October 2000, winter annual cereal crops were
planted into a Capac loam soil (fine-loamy, mixed, mesic Aeric Ochra-qualf) at the
Michigan State University Research farm in East Lansing, MI. In both years of the study,

the winter annual cereals were no-till planted in two fields on the farm, one following

soybean, and the other following silage corn. The planting was done in a randomized
complete block split-split plot design replicated four times. Main plots consisted of the
previous corn silage (corn silage residue) or previous soybean fields (soybean residue),
sub plots consisted of the winter annual cereals, and sub-sub plots consisted of rotational
crops of corn grain, corn silage, and soybean. The winter annual cereal treatments
consisted of wheat cover crop (WCC) and rye cover crop (RCC) burned down with
glyphosate; rye harvested for forage (RF); wheat harvested for forage early out (WEF)
and late cut (WLF); an early maturing variety of wheat harvested for grain (WEG) and a
late maturing variety of wheat harvested for grain (WLG); and a no cover crop (NC).
The wheat variety was “Harus” an early maturing awnless sofi white winter wheat
developed at the Agriculture Canada Research Station in Harrow. The WLG variety used
was “Patterson” a soft red winter wheat developed at Purdue University. The rye variety
used was “Wheeler” which was released by the Michigan Agricultural Experiment
Station. The wheat was planted at 134 kg ha'1 and the rye at 125 kg ha]. The grain and
forage crops received 52 kg ha'1 of elemental N applied as granular urea (46-0-0) at
green-up the following spring. The no cover and the wheat and rye cover crops did not
receive supplemental nitrogen.

The following spring, the winter annual cereals were removed at different times.
WCC and RCC were burned down with glyphosate on 14 April and 26 April for 2000
and 2001, respectively. The rye forage was harvested in the early boot stage on 26 April
2000 and 7 May 2001. The early out wheat was harvested for forage when the wheat was
in the boot stage (Feeke’s scale 10.0) on 11 May 2000 and 19 May 2001; the late cut

wheat was harvested when the wheat was in the early head stage (F eeke’s scale 10.1) on

22 May 2000 and 24 May 2001. The early and late wheat grain was harvested 5 July and
13 July in 2000 and 9 July and 12 July in 2001.

Rotational crops consisting of corn grain (CG), corn silage (CS), and soybean (B)
were planted following burn down or harvest of the winter annual cereals. The plots were
3.0 m x 12.2 m. The calendar dates for burn down or harvest of winter annual cereals and
the following planting dates of rotational crops are shown in Table 1.1.

Glyphosate applications were made to the rotational plots as needed after the burn
down or harvest of the winter annual cereals. On 7 March, 2000 and 2 March, 2001 the
forage and grain plots received 52 kg ha'1 of elemental N applied as granular urea (46-0-
0), as mentioned previously. On 22 June, 2000 and 5 June, 2001, all the corn plots except
the WEG and WLG were side dressed with 468 Liters ha'1 of 28% N, which equals 168
kg ha'1 N. On 31 July, 00, the corn grain and silage, WEG and WLG plots received 468
Liters ha“1 of 28 % N. However, in 2001, corn following WEG and WLG was not side
dressed based on results from 2000, which showed no yield benefit.

The spring soil samples were taken between June 6th- 20th in 2000 and June 11th —
15th in 2001 to allow the forages to be harvested prior to soil sampling and see if the
cover crops burned down with glyphosate were releasing N back into the soil by this
time. Fall soil samples were taken between December 5th 8" in 2000 and November 6th -
8th in 2001. Two samples were taken per plot down to a depth of 90 cm, using a hydraulic
soil probe truck. The samples were divided into 30 cm increments and dried in an oven
at 38° C. The samples were processed using a 1N KCl solution in a 1:5 soil to solution
ratio, to extract the nitrate and the nitrate reduction method was used, through the LaChat

rapid flow injection unit, to measure the nitrate content (LaChat 1988). The sample was

Table 1.1: Calendar dates of burn down or harvest of winter annual cereals and the
following planting dates of corn and soybean rotational crops in 2000 and 2001.

 

 

 

 

 

 

 

 

 

Winter 2000 2001
Annual Bum Corn Soybean Burn Corn Soybean
Cereal Down or Rotational Rotational Down or Rotational Rotational
Treatment Harvest Planting Planting Harvest Planting Planting
Date Date Date Date Date Date
NC - 29 April 11 May - 5 May 5 May
WCC 14 April 29 April 11 May 26 April 5 May 5 May
RCC 14 April 29 April 11 May 26 April 5 May 5 May
RF 26 April 11 May 11 May 7 May 14 May 14 May
WEF 11 May 15 May 11 May 19 May 22 May 22 May
WLF 22 May 22 May 22 May 24 May 26 May 26 May
WEG 5 July 6 July 6 July 9 July 10 July 10 July
WLG 13 July 14 July 14 July 12 July 13 July 13 July

 

NC- no cover, WCC - wheat cover crop, RCC - rye cover crop, RF - rye forage, WEF -
wheat early harvested forage, WLF - wheat late harvested forage, WEG - wheat early

maturing variety grain, WLG - wheat late maturing variety grain.

analyzed with a LaChat spectrophotometer at 520 nm. The data was then analyzed with
SAS software using a proc-mixed model with Tukey’s HSD and lsd’s P (p<0.05) (SAS
Inst, 1999). A log transformation of the data was made so that it would be normally
distributed. The rotational crops had no effect on spring soil nitrates, so in effect this
allowed for twelve replications in the analysis of the winter annual cereals. The fall soil
analysis included the effects of rotational and winter annual crops. The following
abbreviations will be used to clarify the fields being referred to in this study, with the
previous crop, season and year of the fields reported respectively: corn silage residue
spring sampling year 1 (CS1), corn silage residue field spring sampling year 2 (C82),
soybean residue field spring sampling year 1(BS1), soybean residue field spring sampling
year 2 (BSZ), corn silage residue field fall sampling year 1 (CFl), corn silage residue
field fall sampling year 2 (CF2), soybean residue field fall sampling year 1(BF1) and
soybean residue field fall sampling year 2 (BF2) will be used from here on. The data
from BFl was eliminated from the study due to extensive ground hog damage in the field

plots.

Results and Discussion

The soil nitrate-N level as affected by the cover crop for the spring soil sampling
was significantly different at the 0.001 probability level in both fields, both years. The
interaction of cover and soil depth for nitrate content was significant in BS2, CSI and
C82 for the spring to the 0.001 probability level. The reason the nitrate-N content with
depth was not significant for B81 is probably due to the extremely low nitrate levels

throughout, averaging less than 2 mg/kg, although the trend remains similar in BS1 to the

other fields. These low N levels may be due to the high precipitation early on in the
spring, including, the April rainfall of which over 5 cm occurred on one day (Table 1.2).
In the fall, the analysis included the winter annual cereals and rotational crops to
determine if there were differences in rotational crops effects on soil nitrate by the fall
sampling. The soil nitrate variability with rotational crop was only significant in BF 2,
while soil nitrate with depth was significant at the 0.001 probability level in BF2, CF 1
and CF2. The interaction of rotation"‘depth was also significant at the 0.001 probability
level in BF2, CFl, and CF2. The nitrate level with cover crop was significant in BF2 to
the 0.001 probability level and CF] to the 0.05 probability level, although the interaction
of rotational*cover was only significant in BF2. The interaction of cover*depth was
significant in BF2, CFl and CF2 to the 0.05 probability level. The interaction of
cover*season was significant for BF2, CFl and CF2 (Table 1.3).
The soil nitrate levels in the spring following winter annual cereals followed a distinct
trend with significant differences in both fields for 2000 and 2001. When looking at the
general pattern of soil nitrate levels across all three depths in both fields (previously in
corn silage and corn grain) the no cover had significantly or tended to have higher soil
nitrate levels then all treatments at all depths, especially depth two (30-60cm) and three
(60-90cm). The no cover tended to have higher soil nitrate levels while going deeper into
the soil profile, indicating nitrate leaching. The lower quantity of soil nitrate following
the winter annual cereals was due to the winter annual cereals scavenging soil nitrate over
the fall and winter. WCC and RCC had significantly or tended to have more soil nitrate at
depths one (0-30cm) and two (30-60cm) than other winter annual cereals. The higher

soil nitrate levels following the cover crops indicate the release of N from desiccation of

Table 1.2 Monthly precipitation and growing degree unit (GDU) accumulation for the
1999 through 2001 winter annual and rotational crop growing seasons at the experimental
location. Thirty-year means have been included for comparison (1971-2000).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PRECIPITATION GROWING DEGREE UNITS
Month 1999 l 2000 ] 2001 | 30yr 1999 l 2000 J 2001J 30yr

---- Millirneters ---- ---- Degrees Centigrade ----
April - 74.4 72.1 - - - - -
May - 134.6 144.8 68.6 - 193 191 128
June - 78.7 83.8 78.7 - 294 281 263
July - 94.0 22.9 76.2 - 288 333 337
August - 86.4 40.6 86.4 - 314 338 308
September 40.6 111.8 101.6 86.4 213 208 174 173
October 20.3 53.3 137.2 61.0 75 131 51 43
Seasonal 61.0 558.8 393.7 457.2 306 1517 1457 1341
total

 

GDU calculated for corn at a base 100C, with 100C and 300C minimum and maximum
temperatures.

Data recorded at the Horticultural Research Station, East Lansing, MI.

10

 

Table 1.3: Significant differences in residual soil nitrate levels in the spring, after prior
fall planting of winter annual cereals (wac), no-till planted into soybean residue or corn
silage residue; and significant differences in residual soil nitrate levels in the fall, after

rotational crops of corn or soybean were harvested.

 

 

 

 

 

 

 

 

 

 

 

 

Spring Soil Nitrate Soybean Soybean Corn Silage Corn Silage Degrees
Significant Residue Residue Residue Residue of
Differences Yr 1 Yr 2 Yr 1 Yr 2 Freedom
Wac *1”: mini: aunt: an” 7
Depth NS at: an: Hut 2
Wac * Depth NS *3”! aural: uni: 14
Rotational Crop - * NS NS 2
Fall Depth _ sun tan: *1”! 2
Rotational *Depth - *** *** *** 4
Wac _ mint :1: NS 7
Rotational * Wac - ** NS NS 14
Wac*Depth - * * * 1 4
Rot * Wac *Depth - NS NS 28

 

 

 

 

 

 

 

*, **, *** Significant at the 0.05, 0.01, and 0.001 probability levels respectively.

11

 

plant material in the upper soil profile. The lower soil nitrate content following winter
annual cereals over no cover, at all depths, shows that the winter annual cereals picked up
nitrate over the fall and winter, while the greater soil nitrate concentration at the surface
of WCC and RCC indicates release back into soil (Tables 1.4-1.7, Figures 1.1-1.4). The
WEG and WLG treatments had significantly less or tended to have less soil nitrate in the
upper soil profile, probably due to the corn grain and corn silage not being side dressed in
these plots prior to spring soil sampling. The following provides a more in depth account
of how the soil nitrate levels varied with treatment. The soil nitrate content in the no
cover treatment was significantly higher than any of the winter annual cereal treatments
at depth three (60-900m) in both fields for both years except in BSl where they tended to
be higher than all but the rye forage soil nitrate levels. This indicates winter annual
cereals were able to scavenge nitrate-N over the fall and winter, rather than losing it
deeper into the soil profile through nutrient leaching. Soil nitrate tends to increase with
depth and amount of FN (fertilizer nitrogen) applied in fallow plots compared to cover
crop (Ditsch et al., 1993).

When comparing the soil nitrate content in the winter annual cereal plots of the
two fields in the spring over both years at the 60-90 cm depth, the trend did not stay
consistent for each field, other than NC; rather each field had unique differences. In BS1
there were no significant differences due to low soil nitrate levels throughout the field
(Table 1.4, Figure 1.1). In CS1 the rye forage and wheat late forage at depth three (60-90
cm) had significantly less soil nitrate than WEF, WCC, and WEG. The WLG had less
soil nitrate than WCC (Table 1.5, Figure 1.2). This was probably due to field variability

since the forages only had different harvest dates and neither RCC nor WCC had

12

Table 1.4: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
depth in field with soybean residue, spring 2000 (BS1).

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0-30 cm) Depth (30-60 cm) Depth (60—90 cm)
Cereal

No Cover 1.4 1.6 1.5

Wheat Cover Crop 1.1 0.9 0.6

Rye Cover Crop 1.1 0.8 0.7

Rye Forage 0.9 0.8 1.0

Wheat Early Forage 0.8 0.9 0.5

Wheat Late Forage 0.6 0.6 0.7

Wheat Early Grain 0.8 0.7 0.8

Wheat Late Grain 1.1 0.7 0.8

 

 

 

 

 

 

No significant differences.

13

Figure 1.1: Soil nitrate-N levels for the interaction of winter annual cereal * depth in
field with soybean residue, spring 2000 (BS1).

BSl Soybean Residue Field, Spring 2000
Winter Annual Cereal * Depth

 

 

0.8 , A

ND; -N mg/kg

0.6 *

 

0.47 7 77777777

0.2 e 77

 

 

 

0.0

 

0-30 30-60 60-90 1
I Depth (cm) I

 

No significant differences.

l4

Table 1.5: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
depth in field with corn silage residue, spring 2000 (CS1).

 

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0-30 cm) Depth (30-60 cm) Depth (60—90 cm)
Cereal

No Cover 6.1 b 5.7 a 7.8 a
Wheat Cover Crop 6.4 ab 5.3 a 4.1 b

Rye Cover Crop 6.5 ab 4.4 ab 2.8 bcd
Rye Forage 9.1 a 3.2 be 1.9 d
Wheat Early Forage 6.7 ab 3.3 bc 3.4 bc
Wheat Late Forage 5.7 b 2.3 cd 2.2 (1
Wheat Early Grain 5.0 b 2.5 cd 3.2 bc
Wheat Late Grain 4.6 b 1.8 d 2.5 cd

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

15

 

Figure 1.2: Soil nitrate-N levels for the interaction of winter annual cereal * depth in
field with corn silage residue, spring 2000 (CSI).

I
l CSI ComSilageResidueFIeld, Spring2001
; WaterAunuaICemImepth

 

10.0

N03' -N mg/kg

 

 

 

 

0-30 30-60 60-90 1

 

supplemental N applied. Kessalvou and Walters (1999) suggest that differences in the
field beforehand make it hard to be sure all interactions are true treatment effects.
Therefore, fall sampling was done in this study, to show if the soil nitrate in each cover
crop met expectations in going from spring to fall. In BS2 and CS2 (both fields the
second year of the study), there were no significant differences between any of the winter
annuals except the NC at the 60-90 cm depth, which had significantly more soil nitrate
than any of the winter annual cereal treatments (Tables 1.6-1.7: Figures 1.3-1.4).

At depth two (30-60cm) in BS1, BS2, CS1 and CS2, the no cover had
significantly more or tended to have more soil nitrate than any of the other winter annual
cereals, again showing the ability of winter annuals to scavenge soil nitrate. Small grain
cover crops will adsorb residual nitrogen (Ditsch et. a1 1993). With CSI, the NC at depth
two tended to have more soil nitrate than any of the other winter annuals at this depth, but
statistically only had more nitrate than WLF, WEF, WEG, WLG, and RF. The only two
treatments the NC was not statistically higher than were WCC and RCC, which had no
supplemental N applied. The higher soil nitrate content for WCC and RCC was probably
due to the release of nitrogen after decomposition. The WCC and RCC were killed in
April. Decker, et al. (1994) found that decomposition and N release into the nitrate form
was more rapid in early killed rye. Kessavalou and Walters (1999) found that cover crops
release N as they decay in the spring or summer.

When comparing the winter annual cereals amongst each other at depth two (30-
60cm) there were also interesting trends. In BS2, CSI and CS2 the highest soil nitrate

was in NC followed by WCC, then RCC, then and RF. The higher soil nitrate following

17

Table 1.6: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
depth in field with soybean residue, spring 2001 (BS2).

 

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0-30 cm) Depth (30-60 cm) Depth (60—90 cm)
Cereal

No Cover 2.8 a 3.4 a 2.7 a
Wheat Cover Crop 2.7 a 2.4 b 1.9 b

Rye Cover Crop 2.2 a 2.0 be 1.9 b

Rye Forage 2.3 a 1.7 c 1.8 b
Wheat Early Forage 1.5 b 1.3 d 1.7 b
Wheat Late Forage 1.5 b 1.3 d 1.6 b
Wheat Early Grain 1.3 b 1.2 d 1.6 b
Wheat Late Grain 1.3 b 1.2 d 1.6 b

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

18

 

Figure 1.3: Soil nitrate-N levels for the interaction of winter annual cereal * depth in
field with soybean residue, spring 2001 (B82).

4.0

 

 

B82 SoyTIean Residue Field, Spring 2001
Winter Annual Cereal * Depth

 

3.5

3.0

2.5

1.5 - ~

1.0 ~

0.5 .

 

0.0

 

 

 

 

 

 

 

 

 

0-30 60-90

 

l9

 

IW‘TI

I—x— WCC I
I—+— RCC I

I-+-RF I

I—O—WEF Il
I—e—WLF I

_i-'-- WEGII

I
, , ._ Q

Table 1.7: Soil nitrate-N levels in mg kg’1 for the interaction of winter annual cereal *
depth in field with corn silage residue, spring 2001 (C82).

 

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0-30 cm) Depth (30-60 cm) Depth (60-90 cm)
Cereal

No Cover 2.9 a 3.8 a 3.1 a
Wheat Cover Crop 2.9 a 2.3 b 1.7 b

Rye Cover Crop 2.5 ab 1.9 bc 1.8 b

Rye Forage 2.9 a 1.5 cd 1.5 b
Wheat Early Forage 1.5 c 1.3 d 1.6 b
Wheat Late Forage 1.8 be 1.4 cd 1.9 b
Wheat Early Grain 1.5 c 1.5 cd 1.6 b
Wheat Late Grain 1.3 c 1.2 d 1.5 b

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

20

 

Figure 1.4: Soil nitrate-N levels for the interaction of winter annual cereal * depth in
field with corn silage residue, spring 2001 (C82).

 

C82 Corn Silage Residue Field, Spring 2001
Winter Annual Cereal * Depth

 

4.0

 

L--- /\ __fi-___
/ I

3.0 I __ ~ ~ - I
a. _ _I
' \ -. 7 - _ —"'NC .

2.5 —m—+:—‘4.—

 

 

 

 

 

 

 

 

 

 

 

 

 

l

l

I I
I l
I 1.» .. wuw_c~-- I
I I
I l
I 0.5 ___ we.
I I
l l
I 0.0 . I
030 30-60 60-90 I

I Depth (cm) I

 

21

the cover crops was probably due to WCC and RCC releasing N after burn down, since
neither had supplemental N applied. Kessavalou and Walters (1999) found that nitrogen
is quickly mineralized from rye residues afier desiccation and that net mineralization of
soybean residue will increase if rye residue is also present. The 381 winter annual
cereals were not significantly different from each other, but they all averaged less than
2mg NO3' N kg".

In BSZ depth 2 (30-60cm) the WCC, RF, RCC, and NC had significantly more
soil nitrate than WLF, WEF, WEG and WLG, again showing nitrate moving down in the
soil profile after NC, while WCC and RCC release N afier burn down (Table 1.5, Figure
1.2). The RF also had significantly less soil nitrate than the WCC at depth two and
tended to have less then RCC, but not significantly. Kuo and J ellum 2002 found that soil
nitrogen had the greatest effect on corn yield regardless of cover crop residue. Although,
if a forage is needed for livestock feed it may be worthwhile to harvest the forage for an
extra crop.

In C81 depth two (30-60cm) the WCC had significantly more soil nitrate than all
the other winter annual cereals except for RCC. The RCC had significantly more soil
nitrate than WLF, WEG, and WLG and tended to have more than the other winter annual
cereals, but not significantly. The RF and WEF had significantly more soil nitrate than
WLG. RF and WEF tended to have more soil nitrate than WLF, WEG, and WLG, but
not significantly, likely due to RF and WEF being harvested prior to the WLF, WEG and
WLG, and therefore not drawing nitrogen from the soil as long (Table 1.6, Figure 1.3).

Although, the crude protein content of the forages was measured from which the N value

22

could be estimated, the protein content of the grain was not measured for comparison. In
2001 the WEF only tended to have more soil nitrate than WLG.

In C82 at depth two (30-60cm) the WCC again had significantly more soil nitrate
than all the other winter annual cereals except RCC. The RCC had significantly more soil
nitrate than WLG and WEF and tended to have more than the other winter annual cereals,
but not significantly. This again shows the ability of the WCC and RCC to relinquish N
after burn down.

When looking at the nitrate variability with depth 1 (0-30 cm) in the spring, B81,
B82, and C82 tended to have the highest soil nitrate in the NC treatment followed by
RCC and WCC, although the differences were not significantly higher than the other
winter annual cereals. In CSl there was also a tendency for NC, WCC, and RCC to have
a higher soil nitrate at depth 1 (0-30 cm) except for RF, which tended to have the highest
soil nitrate. Wager (1989) found that decomposition and nitrogen release occurred more
rapidly with an early burn down of the winter armual cereal. This was probably due to
other winter annuals taking up nitrate N in the first thirty centimeters. With B81, the NC
soil nitrate was not significantly higher than RF, RCC, WCC or WEF, although the NC
did tend to have the highest soil nitrate concentration.

In 881, depth 1 (0-30 cm), WCC, RCC, and WLG have significantly more
soil nitrate than WLF. NC tended to have the highest soil nitrate, although significantly
was only higher than WLF, WEF and WEG. With C81, RF tended to have the highest
soil nitrate, but significantly RF was only higher than WLF, WEG, WLG and NC. The

other winter annual cereals were not significantly different, although RCC and WCC

23

tended to have more soil nitrate, supporting the idea they were releasing N into the soil
profile afier burn down (Table 1.4, Figure 1.1).

In B82 depth one (0—30 cm) NC, WCC, RCC and RF had significantly more soil
nitrate than the other winter annual cereals. Again, the WCC and RCC were probably
releasing N after burn down while the NC had no crop present to scavenge N over the fall
and winter (Table 1.5, Figure 1.2).

In C81, depth 1 (0-30 cm), the RF, WEF, RCC, WCC and NC tended to have
more soil nitrate than the other winter annual cereals, although only the RF had
significantly more soil nitrate than the wheat grains and WLF (Table 1.6, Figure 1.3).

In C82, depth 1 (0-30 cm), the NC, RF, and WCC had significantly more nitrate
than all other winter annuals except RCC. The RCC had significantly more nitrate than
WEF, WEG and WLG (Table 1.7, Figure 1.4). This also supports that wheat and rye
burned down with glyphosate released nitrate by early June, when spring soil sampling
was done. The tendency for higher soil nitrate following WCC and RCC in the upper soil
profile suggests that the addition of a cover crop should be accompanied by a PSNT to
determine available nitrate levels prior to side dressing corn.

The fall analysis portrayed unique differences in nitrate variability with treatment
as shown in tables 1.8-1.15 and figures 1.5-1.12. For CFl, BF2 and CF2 there were
differences among winter annual cereals with depth at p< 0.05. There was also a
significant interaction in soil nitrate for rotational crop * depth at p< 0.001 in BF2, CF 1
and CF 2. There was a significant interaction of soybean and corn rotational crops *

winter annual cereals for BF2 (Table 1.3).

24

In BF2 there was a significant interaction of winter annual cereal with depth. At
depth one (0-30 cm), wheat late grain had significantly less soil nitrate than any of the
other winter annuals including NC. WEG had significantly less soil nitrate than RF and
NC. The lower soil nitrate for the wheat grain crops was most likely due to the corn in
these plots not having been side dressed with nitrogen in 2001. RF had the most soil
nitrate at depth one, having significantly more than WCC, WEG, WLG and RCC. NC
only had significantly more soil nitrate than WEG and WLG, although it tended to have
more than all but RF (Table 1.8, Figure 1.5). The wheat and rye cover crops had already
released their nitrogen back into the soil and had likely been absorbed by the rotational
crops. Kuo and J ellum (2002) stated that soil N may still be increased with root
degradation even if the top growth is removed. Decker et al. (1994) found that fertilizer
nitrogen (FN) requirements increased after wheat compared to no cover.

In BF2 depth two (30-60 cm), the pattern was similar to the above although the
significance was slightly different (Table 1.8, Figure 1.5). WLG had significantly less
soil nitrate than all the winter annual cereals including NC, except for WEG. WEG had
significantly less soil nitrate than all except WLG, WLF, WEF and RCC. NC and RF
had significantly more soil nitrate than all treatments except for WCC. WCC had
significantly more soil nitrate throughout than WEG and WLG. The lower soil nitrate for
the plots with wheat grain was again probably due to the lack of side dressing, which was
still apparent at this depth. The no cover also had a higher soil nitrate at this depth,
perhaps due to the dry summer, where the rotational crops were not taking up as much

nitrogen.

25

Table 1.8: Soil nitrate-N levels in mg kg"1 for the interaction of winter annual cereal *
depth in field with soybean residue, fall 2001 (BF2).

 

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0-30 cm) Depth (30-60 cm) Depth (60-90 cm)
Cereal

No Cover 3.8 ab 4.5 a 2.4 ab
Wheat Cover Crop 3.5 be 3.7 ab 2.3 ab

Rye Cover Crop 3.4 be 3.3 bc 2.4 ab
Rye Forage 4.7 a 4.7 a 2.8 3
Wheat Early Forge 3.7 abc 3.2 be 2.1 bc
Wheat Late Forage 3.6 abc 2.9 bc 2.1 bc
Wheat Early Grain 2.8 c 2.6 cd 1.7 c
Wheat Late Grain 1.8 d 2.2 d 1.7 c

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

26

 

Figure 1.5: Soil nitrate-N levels for the interaction of winter annual cereal * depth in

field with soybean residue, fall 2001 (BF 2).

BF2 Soybean Residue Field, Fall 2001
Winter Annual Cereal * Depth

 

5.0

4.5

 

3.0

NO3' -N mg/kg

2.0

1.5 «E

1.0 *

 

0.5 k ,

Anmflmflmemumn-A

 

  

 

 

0.0

0-30 30-60 60-90
Depth (cm)

 

27

In 2001, the soybean yields following RCC and RF were significantly higher than
NC and soybean yield following WCC tended to be higher. The higher soybean yield
following RCC, RF and WCC may be due to factors such as improved soil physical
properties, since the soil nitrate differences were probably not large enough to cause
significant yield differences (Table 1.9). In 2000, the corn grain yields tended to be
higher with an earlier corn planting date. In 2001, the corn grain yields in both fields
tended to be highest with earliest corn planting date with corn following NC and RCC
being significantly higher than all but WCC (Table 1.10). The corn silage yields in 2000
were not significantly different, although there was a tendency for a higher yield with an
earlier com planting date, with corn silage following the cover crops somewhat higher
than following the NC (Table 1.11). The corn silage yields followed a similar pattern in
2001, with corn silage planted the earliest having the highest yields. Corn silage yield
following NC was significantly higher than following all winter annual cereals except
WCC.

In BF 2 depth three (60-90 cm) the trend in soil nitrate levels was similar to depth
1 and 2 (0-30 and 30-60 cm), although there was less variation than with the first two
depths. WLG had significantly less soil nitrate than WCC, RF, RCC and NC. WEG had
significantly less soil nitrate than RF, RCC and NC. RF had the most soil nitrate,
significantly more than WLG, WEG, WEF and WLF. The lack of side dressing the wheat
grain crops was still apparent in the fall. All of the plots tended to have less soil nitrate at
this depth due to the rotational crops taking up nitrogen during the growing season.

There was an interaction of rotational crop with depth one and two, from 0-30 and

30-60 cm for BF2. The corn grain and silage had significantly more soil nitrate than

28

Table 1.9: Soybean yields following winter annual cereals no-till planted into corn silage
or soybean residue fields.

 

 

 

 

Winter Annual Yield
Cereal Corn Silage Residue Field Soybean and Corn Silage
Previous 2000 Residue Fields 2001

Mg ha'1 Mg ha'1

No Cover 3.6 2.8 b

Wheat Cover Crop 3.6 3.0 ab

Rye Cover Crop 3.2 3.1 a

Rye Forage 3.4 3.1 a

Wheat Early Forage 3.5 2.8b

Wheat Late Forage 3.5 2.64c

Wheat Early Grain - -

Wheat Late Grain - -

 

 

 

Treatment yields followed by the same letters were not significantly different at P < 0.05.

Table 1.10: Corn grain yields following winter annual cereals no-till planted into corn
silage or soybean residue fields.

 

 

 

 

Winter Annual Yield
Cereal Corn Silage Residue Field Soybean and Corn Silage
2000 Residue Fields 2001

Mg ha’1 Mg ha'1

No Cover 12.1 8.6a

Wheat Cover Crop 12.0 7.4abc

Rye Cover Crop 11.7 8.43

Rye Forage 11.5 6.9bc

Wheat Early Forage 10.2 5.7d

Wheat Late Forage 8.0 6.9bc

Wheat Early Grain - -

Wheat Late Grain - -

 

 

 

Treatment yields followed by the same letters were not significantly different at P < 0.05.

29

Table 1.11: Corn silage yields following winter annual cereals no-till planted into corn
silage or soybean residue fields.

 

 

 

 

Winter Annual Yield
Cereal Corn Silage Residue Field Soybean and Corn Silage
2000 Residue Fields 200]

Mg ha'1 (DhQ Mgha'l (DM)

No Cover 17.9 11.6 a

Wheat Cover Crop 18.6 11.2 ab

Rye Cover Crop 19.7 10.1 bc

Rye Forage 16.1 8.7 cd

Wheat Early Forage 16.4 8.5 (1

Wheat Late Forage 14.3 9.2 cd

Wheat Early Grain 5.8 5.4 e

Wheat Late Grain 4.5 3.1 f

 

 

 

Treatment yields followed by the same letters were not significantly different at P < 0.05.

30

soybean plots at depths one (0-30 cm) and two (30-60 cm), however for depth three (60-
90 cm) the soil nitrate content dropped off suddenly for corn grain and silage, so there
were no significant differences with rotational crop (Table 1.12, Figure 1.6). There are a
couple of possibilities for the higher soil nitrate following the corn crops. The extra
nitrogen fi'om the corn may be due to fertilizer N, especially with the dry summer, the
corn may not have picked up all the nitrogen from the soil. The soybean plant and root
residue also may not have decomposed enough by the fall sampling in order to release N
back into the system.

In BF2, when evaluating the interaction of rotational crop with winter annual
cereal, there were interesting trends (Table 1.13, Figure 1.7). The soybean rotational crop
had little variation in soil nitrate, although WLG had significantly less soil nitrate than
WLF, otherwise there were no significant differences.

In the plots with corn silage there was more variation in soil nitrate among winter
annual cereals. WLG had significantly less soil nitrate than all but WLF and WEG.
WLF and WEG had significantly less soil nitrate than WCC, RF, RCC, and NC. WEF
had significantly less soil nitrate than WCC and RF. NC, WCC, RCC and RF had
significantly more soil nitrate than all, but WEF.

In the plots with corn grain, the WLG and WCC had significantly less soil nitrate
than WLF and RF. The RCC and WEG had significantly less soil nitrate than the RF.
Therefore, the RF had significantly more soil nitrate than WCC, WEG, WLG, and RCC.
The higher soil nitrate following corn silage compared to corn grain may be due to the
earlier harvest date for the silage, allowing for a quicker start toward root and plant

residue decomposition and release of nitrogen back to the soil. The corn grain may also

31

Table 1.12: Soil nitrate-N levels in mg kg'1 for the interaction of rotational crop * depth

in field with soybean residue, fall 2001 (BF2).

 

 

 

 

 

Rotational Crop Depth (0-30 cm) Depth @60 cm) Depth (60-90 cm)
Soybean 2.6 b 2.4 b 2.0 3
Corn Silage 3.8 a 4.0 a 2.3 a
Corn Grain 3.6 a 3.7 a 2.1 a

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

32

 

Figure 1.6: Soil nitrate-N levels for the interaction of rotational crop * depth in field with
soybean residue, fall 2001 (BF 2).

 

BF2 Soybean Residue Field, Fall 2001 I
Rotational crop*Depth I

I

I

I

4.5

 

 

 

 

" ‘——1

 

I—Soybean
I —l— Corn Silage
I ........... Corn Grain I'

 

 

 

 

 

 

 

 

 

0-30 30-60 60-90

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I Depth (cm)
I

 

33

Table 1.13: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
rotational crop in field with soybean residue, fall 2001 (BF2).

 

 

 

 

 

 

 

 

 

 

 

 

 

Winter Annual Soybean Corn Silage Corn Grain
Cereal

No Cover 2.5 ab 4.8 ab 3.3 abc
Wheat Cover Crop 2.5 ab 4.8 ab 2.4 c
Rye Cover Crop 2.7 ab 4.0 ab 2.5 bc
Rye Forage 2.5 ab 5.4 a 4.5 a
Wheat Early Forage 2.7 ab 3.2 be 3.3 abc
Wheat Late Forage 2.7 a 2.2 cd 3.7 ab
Wheat Early Grain 1.9 ab 2.3 cd 2.9 bc
Wheat Late Grain 1.7 b 1.7 d 2.3 c

 

Treatments followed by the same letters were not significantly different at P < 0.05.

34

 

Figure 1.7: Soil nitrate-N levels for the interaction of winter annual cereal * rotational
crop in field with soybean residue, fall 2001 (BF2)

N03- 'N mg/kg

 

BF2 Soybean Residue Field, Fall 2001
Winter Annual Cereal * Rotational Crop

 

6.0 ,

 

 

 

 

 

 

 

 

 

 

 

 

 

, , x
2.0 ‘—— ‘7’"? ‘ f‘ —— w—
— II -— " /
1.0 -. --
0.0 I I
Soybean Corn Silage Corn Grain
Rotational Crop

 

 

 

—+—RCC II
-A--RI= I
—o—WEFI
—<~>—WLF I
---- WEGI
:-"_' WEE-II

 

 

 

 

 

 

 

35

have continued to take up soil nitrogen after the harvest of silage. The reason the soil
nitrate differences between grain and silage only show up in the NC, WCC, RCC and RF
plots may be due to these plots being planted to corn earlier and therefore the corn was
able to obtain more biomass, with more plant and root residue available to release N back
into the soil. The corn in these plots was also side dressed the earliest allowing for the
uptake of the fertilizer and soil nitrogen, sooner then following the other winter annual
cereals. This effect may be compounded by the dry summer, where the corn in the other
plots was not growing as rapidly and therefore taking up less nitrogen. Rotational crop
yields for BF 2 can be seen in (Tables 1.9-1.11) and are described for BF 2 previously.

In CFl with the interaction of winter annual cereal * depth (Table 1.14, Figure
1.8), WEG had significantly more soil nitrate than all but WLG at depth one (0-30 cm).
WLG had significantly more soil nitrate than WLF, WEF, and NC. At depth 2 (30-60
cm), RF had significantly more soil nitrate than WLF, WEF and RCC. WLG had
significantly more soil nitrate than WEF. At depth 3 (60-90 cm), WLF had significantly
less soil nitrate than WCC, WEG and RF, otherwise there were no significant differences.
The greater soil nitrate from 0-30 cm for the grain plots may be due to the late nitrogen
side dress application to these plots. The wheat grain plots were side dressed this year on
31 July and the effects of this late nitrogen application was probably still apparent during
the fall sampling. The effect of side dressing the wheat grain plots was also still apparent
from 30-60 cm.

In CFl there was an interaction of rotational crop and depth with a tendency
toward less soil nitrate in the soybeans then the corn grain or silage, but not significantly

(Table 1.15, Figure 1.9). This may be an apparent effect of the late side dress application

36

Table 1.14: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
depth in field with corn silage residue, fall 2000 (CF 1).

 

 

 

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0—30 cm) Depth (30-60 cm) Depth (60—90 cm)
Cereal

No Cover 3.8 c 3.8 abc 3.7 ab
Wheat Cover Crop 5.1 be 4.3 ab 4.2 a

Rye Cover Crop 4.8 bc 3.4 be 3.2 ab

Rye Forage 4.6 bc 4.7 a 4.2 a
Wheat Early Forage 4.3 c 3.1 c 3.4 ab
Wheat Late Foge 4.1 c 3.4 be 2.9 b
Wheat Bag Grain 6.9 a 4.2 abc 4.1 a
Wheat Late Grain 5.9 ab 4.4 ab 3.5 ab

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

37

 

Figure 1.8: Soil nitrate-N levels for the interaction of winter annual cereal * depth in
field with corn silage residue, fall 2001 (CFl).

l

 

Corn Silage Previous, Fall 2000
Winter Annual Cereal * Depth

 

8.0

7 0 ,________ t» H BEL -"_

 

 

 

 

 

 

 

 

 

 

 

 

 

2.0 —I -- -, ~ 1 r~-~ - I
I

1.0 ————~- - ~ MW—Mm— I
I

0.0 I
080 30-60 60-90 I

Depth (cm) I

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

 

38

Table 1.15: Soil nitrate-N levels in mg kg'1 for the interaction of rotational crop * depth
in field with corn silage residue, fall 2000 (CF 1).

 

 

 

 

 

 

Rotational Crop Depth (0-30 cmL Depth (30-60 cm) Depth (60-90 cm)
Sfllbean 4.8 a 2.9 a 2.7 a
Corn Silage 4.7 a 4.3 a 4.2 a
Corn Grain 5.0 a 4.6 a 4.2 a

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

39

 

Figure 1.9: Soil nitrate-N levels for the interaction of rotational crop * depth in field with
corn silage residue, fall 2000 (CFl).

 

I

I CFl Corn Silage Residue Field, Fall 2000
I Rotational Crop * Depth

I

6.00

 

5.00 ———-—,,—- —-——-——.——* Hfl ,,_ ,fl ‘, _ -

 

 

 

-._...,

 

 

 

 

 

 

 

 

 

 

 

I

‘

I

I

I

I

I

I

I on

I r -

I E) —Soybean I
I z 3.00 ____I , : Corn SilageI
I I'm \ IMCOmGrainI
I 0 ________+
I Z

I 2.00 F #—

I

I

I 1.00

I

I

I 0.00 - . .

I 0-30 30-60 60-90 I
I I
I I

Depth (cm)

 

 

40

to the corn following the wheat grain plots, allowing the over all average for the corn
grain and silage soil nitrate to be higher than the soybean plots. Also, the soybeans had
significantly higher nitrate content in the upper thirty cm of the soil profile, then at depth
two (30-60 cm) and three (60-90 cm). The soybean roots and residue may have decayed
and released nitrogen back into the soil. The rotational crop yields are shown in Tables
1.9-1.11. The soybean, corn grain and corn silage yields followed a pattern of greater
yield with earlier rotational crop planting date. The rotational crops following NC, WCC
and RCC had the highest yield. The rotational crop yield differences in CFl are more
likely due to improved soil physical properties such as increased soil aeration and
increased water permeability, rather than due to N differences.

In CF2, there was a significant interaction of winter annual cereal * depth (Table
1.16, Figure 1.10). At depth one (0-30 cm) WLG had significantly less soil nitrate than
WCC, otherwise there were no significant differences. WLG and WEG had significantly
less soil nitrate than WCC and NC at depth two (30-60 cm). At depth three (60-90 cm),
there were no significant differences in soil nitrate. The significantdifferences in soil
nitrate levels would probably not be of practical importance. The wheat early and late
grain plots tended to have less soil nitrate then any of the other treatments, probably due
to a lack of side dress application on the late planted corn for these plots.

In CF2 the soybean yields following RCC and RF were significantly higher than
NC, WEF and WLF (Table 1.9). The soybean yields following WCC tend to be higher
than following NC, but not significantly. The higher yields following WCC, RCC and

RF are more likely due to soil physical benefits than due to soil nitrate differences. The

41

Table 1.16: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
depth in field with corn silage residue, fall 2001 (CF2).

 

 

 

 

 

 

 

 

 

 

Winter Annual Depth (0-30 cm) Depth (30-60 cm) Depth (60-90 cm)
Cereal

No Cover 2.5 ab 2.9 a 1.8 a
Wheat Cover Crop 2.9 a 2.9 a 1.8 a

Rye Cover Crop 2.6 ab 2.3 ab 2.0 a

Rye Forag 2.3 ab 2.2 ab 1.8 a
Wheat Early Forage 2.8 ab 2.1 ab 1.5 a
Wheat Late Forage 2.7 ab 2.4 ab 1.7 a
Wheat Early Grain 2.2 ab 2.0 b 1.5 a
Wheat Late Grain 2.0 b 1.8 b 1.9 a

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

42

 

Figure 1.10: Soil nitrate-N levels for the interaction of winter annual cereal * depth in
field with corn silage residue, fall 2001 (CF2).

N03" -N mg/kg

3.50

3.00 -

2.50 ,

2.00

1.50

1.00

0.50 7

0.00

CF2 Corn Silage Residue Field, Fall 2001

Winter Annual Cereal * Depth

 

 

 

 

 

0-30 30-60
Depth (cm)

43

60-90

 

I «mwAwmv RF
I —©— WEF I I

corn grain and corn silage yields follow a pattern of increased yield with earliest planting
date with NC tending to have the highest yield (Tables 1.10-1.11).

For CF2, there was a significant interaction of rotational crop * depth (Table 1.17,
Figure 1.11). At depth one (0-30 cm), soybeans and corn silage had significantly less soil
nitrate than corn grain and at depth two (30-60 cm) soybeans had significantly less soil
nitrate than corn silage. At depth three (60-90 cm) there were no significant differences.
This may be due to the shallow root system of soybeans, or as in BF2 the extra nitrogen
in the soil that had corn planted may be due to fertilizer N.

There was a significant interaction of winter annual cereal * season for both fields
(corn silage residue and soybean residue) in 2000 and 2001 (Tables 1.18-1.21 and
Figures 1.12-l.15). In B1 (Table 1.18 and Figure 1.12) the NC had significantly more soil
nitrate in the spring than the other winter annual cereals, although from a practical value
the difference was negligible. In the fall, there were no significant differences in soil
nitrate following winter annual cereal treatments. This figure stands out because of the
higher soil nitrate levels after fall sampling compared with spring sampling. The higher
soil nitrate levels in the fall may reflect the release of nitrogen back into the soil from
plant or root decay following rotational crop harvest.

In B2, the NC also had significantly more soil nitrate compared with winter
annual cereals in the spring and tended to in the fall (Table 1.19 and Figure 1.13). Again,
all of the winter annual cereal treatments tended to have more soil nitrate in the fall than
the spring. This difference between spring and fall for the winter annual cereals is

probably due to the winter annual cereals holding on to soil nitrate in the spring which

44

Table 1.17 : Soil nitrate-N levels in mg kg'1 for the interaction of rotational crop * depth
in field with corn silage residue, fall 2001 (CF2).

 

 

 

 

 

Rotational Crop Depth (0-30 cm) Depth (30-60 cm) Depth (60-90 cm)
Soybean 2.1 b 2.0 b 1.7 a
Corn Silage 2.4 b 2.7 a 1.8 a
Corn Grain 3.0 a 2.3 ab 1.7 a

 

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

45

 

Figure 1.11: Soil nitrate-N levels for the interaction of rotational crop * depth in field
with corn silage residue, fall 2001 (CF2).

CF2 Corn Silage Residue Field, Fall 2001
Rotational Crop * Depth

3.50 -

 

3.00 *

2.50 -*

 

 

 

 

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

 

 

I'm”- Corn Grain I
1.50 ~~ *—

s x
200 ——~ —~ . j
E \+ I—Soybean I
Z' I I—l—Com SilageI!
6"
Z

 

 

 

 

 

 

1.00 -i._._ m__‘
I
0.50 ——-— - -nf -—— #m
I
0.00 , I I
030 30-60 60-90 I

Depth (cm)

 

46

Table 1.18: Soil nitrate-N levels in mg kg'1 for the interaction or winter annual cereal *
season in field with soybean residue, 2001 (B1).

 

 

 

 

 

 

 

 

 

 

 

 

 

Winter Annual Spring Fall
Cereal

No Cover 1.5 a 3.0 a
Wheat Cover Crop 0.9 bc 3.5 a
Rye Cover Crop 0.9 be 3.2 a
Rye Forage 0.9 bc 3.7 a
Wheat Early Forage 0.7 c 3.5 a
Wheat Late Forage 0.7 c 3.8 a
Wheat Early Grain 0.8 be 3.4 a
Wheat Late Grain 0.8 bc 3.5 a

 

Treatments followed by the same letters were not significantly different at P < 0.05.

47

Figure 1.12: Soil nitrate-N levels for the interaction of winter annual cereal * season in
field with soybean residue, 2000 (B1).

 

ry‘ — -— _____ — .— .— —- —— -——*——*- V“ ‘d’ v ,fi

B1 Soybean Residue Field, 2000
Winter Annual Cereal * Season

 

4.5

40 _ __ _ __ _______r___d________. _._~. __,
4»

3 5 _—__ __ W.” W :5. _—

 

 

NO3' -N mg/kg

 

 

 

 

 

 

 

 

 

 

 

 

I
I
I
f I
1 O ‘ j — m w-fi —— I
. I
‘
0.5 ——— — - — ’—
Spring Fall I
I

Season

48

Table 1.19: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
season in field with soybean residue, 2002 (B2).

 

 

 

 

 

 

 

 

 

 

 

 

 

Winter Annual Spring Fall.
Cereal

No Cover 3.0 a 3.4 ab
Wheat Cover Crop 2.3 b 3.1 bc
Rye Cover Crop 2.1 b 3.0 bc
Rye Forage 1.9 b 3.9 a
Wheat Early Forage 1.5 cd 2.9 bcd
Wheat Late Forage 1.5 cd 2.8 cd
Wheat Early Grain 1.3 d 2.3 de
Wheat Late Grain 1.3 d 1.9 e

 

Treatments followed by the same letters were not significantly different at P < 0.05.

49

Figure 1.13: Soil nitrate-N levels for the interaction of winter annual cereal * season in
field with soybean residue, 2001 (B2).

 

Im— ’__ #— B2 Soybean Residue Field, 2001 W W i
Winter Annual Cereal * Season

 

4.5

 

 

 

 

 

 

 

 

NO3' -N mg/kg

 

 

 

 

 

 

 

 

 

 

1.0 - +++++

 

 

 

 

 

 

0.5

 

 

0.0
I Spring Fall

 

 

I Season

 

 

 

 

50

was scavenged over the previous fall and winter, then released back into the soil either
from plant or root decay, after harvest or burn down. Kessavalou and Walters (1999)
showed that rye reduced RSN afier soybeans.

In C1, there was a significant interaction of winter annual cereal * season (Table
1.20, Figure 1.14). The NC had significantly higher soil nitrate in the spring than all
winter annual cereals except for WCC, where there was still a tendency for NC to have a
higher soil nitrate level. The NC soil nitrate had the most dramatic drop by the fall
compared to the winter annual cereals, while the WEG and WLG soil nitrate levels rose
in the fall. The increase of the WEG and WLG soil nitrate levels by the fall may be due to
the late side dress application necessary for the late corn planting dates following the
wheat grain harvest. The decline of the no cover soil nitrate from spring to fall was
mainly due to initially higher spring soil nitrate levels in the no cover compared to the
winter annual cereals, which was taken up by the com grain and corn silage during the
growing season. In the fall the differences in soil nitrate were probably not of practical
importance. (Kessavalou and Walters 1999) showed that fall planted rye following
soybeans, but before corn planting, reduced RSN by 18-33%, although the RSN
increased after com the following spring. Johnson and Raun (1995) found that nitrogen
immobilized into organic N by microbes might be released later in the season, especially
with higher fertilizer N rates.

When looking at what happens to soil nitrate from spring to fall, in C2 (Table
1.21, Figure 1.15) there was also an interaction of winter annual cereal * season, similar
to that of C1. The NC soil nitrate was significantly higher in the spring than the winter

annual cereals, while in the fall NC had similar soil N03' levels to the winter annual

51

Table 1.20: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
season in field with corn silage residue, 2000 (C1).

 

 

 

 

 

 

 

 

 

 

 

Winter Annual Spring Fall
Cereal

No Cover 6.5 a 3.7 ab
Wheat Cover Crop 5.2 ab 4.5 ab
Rye Cover Crop 4.3 bc 3.7 ab
Rye Forage 3.9 cd 4.5 ab
Wheat Early Forage 4.2 bc 3.6 b
Wheat Late Forage 3.1 de 3.5 b
Wheat Early Grain 3.4 cc 4.9 a
Wheat Late Grain 2.8 e 4.5 ab

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

52

 

Figure 1.14: Soil nitrate-N levels for the interaction of winter annual cereal * season in
field with corn silage residue, 2000 (C1).

 

.— _____.___.__. .__,_._,,_.__ .~—__——_...—..—.__._ _.—__ -_1

C1 Corn Silage Residue Field, 2000
Winter Annual Cereal * Season

 

7.00

 

6.00 ~

5.00 —

 

 

4.00 a

 

 

 

3.00 *

 

NO3' -N mg/kg

 

 

2.00 - ~ — ~

 

1.00 *

 

 

 

 

 

0.00

 

Spring Fall

 

Season I

 

 

 

 

 

 

 

53

Table 1.21: Soil nitrate-N levels in mg kg'1 for the interaction of winter annual cereal *
season in field with corn silage residue, 2001 (C2).

 

 

 

 

 

 

 

 

 

 

 

 

 

Winter Annual Spring Fall
Cereal

No Cover 3.3 a 2.3 ab
Wheat Cover Crop 2.2 b 2.5 3
Rye Cover Crop 2.0 bc 2.3 ab
Rye Forage 1.9 bcd 2.1 ab
Wheat BarbI Forage 1.5 de 2.1 ab
Wheat Late Forage 1.7 cde 2.2 ab
Wheat Early Grain 1.6 de 1.9 b
Wheat Late Grain 1.3 e 1.9 ab

 

Treatments followed by the same letters were not significantly different at P < 0.05.

54

Figure 1.15: Soil nitrate-N levels for the interaction of winter annual cereal * season in
field with corn silage residue, 2001(C2).

 

,_r___- - _.___.__iAL_.ALT

C2 Corn Silage Residue Field, 2001
Winter Annual Cereal * Season

 

3.5

 

 

 

 

 

 

 

 

 

 

0.5 »

 

 

 

 

 

Spring Fall

Season

 

 

55

cereals. As in 2000, NC soil nitrate tended to drop dramatically by the fall while the
winter annual cereal plots tended to have an increase in soil nitrate. This was also likely
due to the high initial spring levels of soil nitrate in the no cover plots during the spring
soil sampling compared to winter annual cereals. The higher soil nitrate following NC
was probably picked up by the corn grain and silage during the growing season. Also, the
tendency for higher fall soil nitrate levels following winter annual cereals may reflect the
decomposition of plant and root residue releasing N back into the soil after the harvest of
rotational crops. Kessavalou and Walters (1999) showed that mineralization from rye
residue may build soil N and cause leaching later in the season. All the winter annual
cereals tended to have higher soil nitrate in the fall, but only the ones mentioned above
were significantly higher. Ditsch et al. (1993) stated that rye N uptake varies with

previous crop, its influence on soil moisture and subsequent residual N levels.

Conclusions

Use of a winter annual cereal to scavenge nitrogen over the fall and winter has
potential to reduce fertilizer use and make more efficient use of nitrogen already in the
system. In both years of the study with either soybeans or corn as the previous crop,
winter annual cereals had a significantly reduced soil nitrate level in the spring compared
to having no cover. Excluding the no cover treatment, discovering trends in nitrate
content with depth between different winter annual cereals, across different fields and
years is difficult. The greater amount of rainfall the first year may have been a big factor
in creating these differences, although soil variability between fields and landscape

features may also make a difference in the extent that a winter annual cereal may help

56

reduce nitrogen loss. Johnson and Raun (1995) showed that wheat would continue to take
up N with increased fertilizer use even after the maximum yield was reached. Perhaps
this buffer zone is where the plant is increasing its protein content, although they also
found that plant N loss through ammonia volatilization continued to increase with
increased fertilizer N applied even after maximum yields were reached. Bauder et al.
(1979) found that under optimum irrigation in greenhouses, split urea applications may
reduce nitrate leaching. Perhaps cover crops also play a role by changing the time soil
nitrate is available for the rotational crop. Kuo and J ellum (2002) found that cover crops
and residue management affected corn yield and N-uptake by their influence on nitrogen.
Garwood et al. (1999) did a study in England where winter cover crops created a positive
N balance, which may be held as immobilized organic N that is available for years. In the
future a new method of burn down may be available for cover crops. Stanislaus and
Cheng (2002) are working on genetically engineered tobacco plants that will self-destruct
under heat induction according to the photoperiod. Perhaps this technology will be

perfected for wheat and rye as well.

57

References Cited

Bauder, J. W., and R. P. Schneider. 1979. Nitrate-nitrogen leaching following urea
fertilization and leaching. Soil Sci. Soc. Am. J. 43:348-352.

Bemer, A., D. Scherrer, and U. Niggli. 1995. Effect of different organic manures and
garden waste compost on the nitrate dynamics in soil, N uptake and yield of winter
wheat. Biol. Agric. Hortic. 11:289-300.

Brandi-Dohm, F. M., R. P. Dick, M. Hess, S. M. Kauffman, D. D. Hemphill, Jr., and J. S.
Selker. 1997. Nitrate leaching under a cereal rye cover crop. J. Environ. Qual. 26: 181-
1 88.

Decker, A. M., A. J. Clark, J. J. Meisinger, F. R. Mulford, and M. S. McIntosh. 1994.
Legume cover crop contributions to no-tillage corn production. Agron. J. 86: 126-135.

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

Entz, M.H., V.S. Baron, D.W. Meyer, S.R.Jr. Smith, and WP. McCaughey.2002.
Potential of forages to diversify cropping systems in the northern Great Plains. Agron. J.
94(2):240-250.

Garwood, T. W. D., D. B. Davies, and A. R. Hartley. 1999. The effect of winter cover
crops on yield of the following spring crops and nitrogen balance in a calcareous loam. J.
Agric. Sci. 132:1-11.

Guy, S. 0., and R. M. Gareau. 1998. Crop rotation, residue durability, and nitrogen
fertilizer effects on winter wheat production. J. Prod. Agric. 11:457-461.

Johnson, G. V., and W. R. Raun. 1995. Nitrate leaching in continuous winter wheat: Use
of a soil-plant buffering concept to account for fertilizer nitrogen. J. Prod. Agric. 8:486-
491.

Kaspar, T.C., J .K. Radke, and J .M. Laflen. 2001.Small grain cover crops and wheel
traffic effects on infiltration, runoff, and erosion. J. Soil Water Conserv. 56:160-164.

Kessavalou, A., and D.T. Walters. 1999. Winter rye cover crop following soybean under
conservation tillage residual soil nitrate. Agron. J. 91:643-649.

Kessavalou, A., and D. T. Walters. 1997. Winter rye cover crop following soybean under
conservation tillage. Agron. J. 89:68-74.

Kuo, S. and E]. J ellum. 2002. Influence of Winter Cover Crop and Residue Management
on Soil Nitrogen Availability and Corn. Agron. J. 94:501-508.

58

Lachat Instruments (1988)
Logsdon, S.D., T.C. Kaspar, D.W. Meek, and J .H. Prueger. 2002. Nitrate Leaching as
Influenced by Cover Crops in Large Soil Monoliths. Agron. J. 94:807-814.

Meek, B. D., D. L. Carter, D. T. Westermann, J. L. Wright, and R. E Peckenpaugh. 1995.
Nitrate leaching under furrow irrigation as affected by crop sequence and tillage. Soil Sci.
Soc. Am. J. 59:204-210.

Owens, L. B., W. M. Edwards, and M. J. Shipitalo. 1995. Nitrate leaching through
lysimeters in a com-soybean rotation. Soil Sci. Soc. Am. J. 59:902-907.

SAS Institute. 1999. SAS online help. SAS Inst., Cary,NC.

Stanislaus,M.A. and CL. Cheng. 2002. Genetically engineered self-destruction: an
alternative to herbicides for cover crop systems. Weed Science. 50:794-801.

Thurman, N.C., J. K. Wolf, J. A. Hetrick, L. L. Parsons, M. R. Barrett, L. Liu, W. R.
Effland, and E. Behl. 1998. Evaluating pesticide fate and transport: 1. The use of
lysimeter, field, and groundwater monitoring studies. In F. F uhr et al. (ed.) The lysimeter
concept environmental behavior of pesticides. Proc. Symp. Natl. Meeting of the Am.
Chem. Soc., 213th, San Francisco. 13-17 Apr. 1997. Am. Chem. Soc., Washington, DC.

Wagger, MG. 1989. Time of desiccation effects on plant composition and subsequent
nitrogen mineralization from several winter annual cover crops. Agron. J. 81 :236-241.

Wyland, L. J ., L. E. Jackson, W. E. Chaney, K. Klonsky, S. T. Koike, and B. Kimple.
1996. Winter cover crops in a vegetable cropping system: Impacts on nitrate leaching,
soil water, crop yield, pests and management costs. Agric. Ecosyst. Environ. 59:1-17.

59

CHAPTER 2

AGRONOMIC AND ECONOMIC ASPECTS OF INTEGRATING A
WINTER ANNUAL CEREAL INTO A CORN OR SOYBEAN
ROTATION IN MICHIGAN

Abstract

The addition of winter annual cereals into a com-soybean rotation impacts many
agronomic and economic aspects of cropping systems. Ground cover and residue may be
increased by the presence of a winter annual cereal. A winter annual cereal may also
provide a second profitable crop to the system. Insect pressures on rotational crops
following winter annual cereals vary by the crop and insect, but often are dependant on
rotational crop planting date. Armyworm (Pseudaletia unipacta) infestations ofien occur
in winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) and if the cereal grains
are burned down with glyphosate, the armyworms may move to corn (Zea mays L.) in
adjacent fields or plots. European corn borer (ECB) (Ostrinia nubilalis) stalk tunneling
tends to be higher in corn at an ideal maturity during peak moth flight times. Bean Leaf
Beetle (BLB) (Cerotoma trzfurcate) damage tends to be higher in earlier planted
soybeans [Gycine max (L.) Merr.], and soybean aphid (Aphis glycines) numbers tend to
be higher in later planted soybeans. The winter annual cereals provide an extra crop
when harvested for forage or grain. Later harvest dates of forages provide an increased
yield, but lower quality. Soybean yields following a wheat or rye cover crop may be
increased over no cover crop, while corn grain and corn silage yields tend to follow a
pattern of higher yield with earlier corn planting date, which ultimately depends on

whether the winter annual cereal is used for a cover crop, a forage, or a grain. Depending

6O

on the planting date of a corn or soybean rotational crop following harvest of a winter
annual cereal, the economic benefit of the additional crop may increase the net profit to

the system.

Introduction

There are many prospects for integrating a winter annual cereal into a corn -
soybean rotation in Michigan. The possibilities range from harvesting the winter annual
cereal as a small grain or early spring forage, to simply utilizing it as a cover crop. Entz
(1994) found rotating a forage with an annual grain crop increased annual grain crop
yields in years with adequate moisture, but reduced yields in dry years.

The benefits of integrating a winter annual cereal into a traditional corn-soybean
rotation exist at the soil and agronomic level. When making management decisions on
what cropping system to plant, it is important to take into account all agronomic factors
including soil water, nutrients and microbes, as well as above ground aspects such as
insects and yields.

Soil benefits of using winter annual cereals include scavenging residual nitrogen
over the fall, winter, and early spring, improving soil quality, reducing soil erosion,
increased soil aeration and water infiltration. Kessavalau (1997) found that rye planted
after soybean increased residue 16%, providing erosion control equivalent to that of corn.
Eckert (1988) found rye provided 60% greater ground cover than other covers, due to
rye’s winter hardiness. Kaspar (2001) showed rye increased soil water infiltration and
reduced erosion and runoff. The infiltration improved soil structure and protected the soil

from rain pounding, while the roots held the residue together. The rye also protected soil

61

from freezing, thawing and compression. While no-till planting also conserved soil water
(Entz 1994), no-till combined with a cover crop, reduced runoff and erosion Hartwig
(2002). Cover crops add organic matter to the soil, increasing soil tilth and productivity
(Hartwig 2002). The high root production of rye increases soil microbe biomass. Soil
microbes break down plant residues producing “gums” that hold larger soil particles
together in “peds”, allowing for greater soil permeability and aeration (Hartwig 2002).
Earthworrns increase in soil with a green cover crop, up to seven times in no-till,
providing increased soil quality and aeration (Hartwig 2002).

The effects of winter annual cereals on soil moisture and corn yield depend on the
quantity and distribution of rain, soil type, cover species and kill date. These
environmental conditions and kill date allow for a large variation in spring water
depletion and summer water conservation in different years and field locations (Clark
1997). The residue fiom winter annual cereals conserves soil moisture, creating increased
yields in corn following a cover crop (Eckert 1988, Moschelr 1967). Clark (1997)
showed residues reduce evaporation. Vaughan (1998) reported rye was better for soil
moisture conservation than in combination with hairy vetch.

However, the kill date of cover crops is important in determining the benefits of
cover crop soil water conservation. Clark (1997) reported late April or early May kill
dates in Maryland, increased corn yields over earlier kill dates due to increased soil
moisture conservation and differences in soil-N availability. The later kill dates provided
an increase in cover biomass and N release. Clark (1997) showed summer moisture

conserved by killed covers was more important then spring moisture conservation to com

62

yield. Actively growing covers did not deplete spring soil moisture. Moisture deficits in
corn are most detrimental to yield during silking, around mid to late July (Clark 1997).

Delaying corn planting for several weeks after cover crop kill provides better
synchronization between N release and corn N uptake (Vaughan 1998). Rye may have
allelopathic effects, which reduce subsequent corn yields (Kessavalou 1997) or decrease
corn yield due to poor stand at planting (Eckert 1988). However, delayed spring planting
after rye may reduce any allelopathic affects (Garwood 1999). N availability may be
more important for increasing corn yields than soil moisture. An early desiccation (late
April) provided greater corn yields than a mid May desiccation (Vaughan 1998). The
main effect on corn yield was due to N availability, rather than cover crop management
(Kuo 2002). In fields with excess nitrogen the cover crops may scavenge the nitrogen and
make it available the next season (Hartwig 2002). Living corn roots are able to increase
inorganic N by mineralization in conditioned soil by over 50% (Sanchez 2002).

Soybean may have a higher yield following a grass crop than in continuous
monoculture. There was greater N immobilization following grain sorghum, which may
have become available during pod fill. Also, soybean yield increased following grain
sorghum with the addition of fertilizer N, but not following corn (Peterson 1989 1).

Objectives:

1) Compare the percent ground cover from winter annual cereal and no-till

residue.

2) Compare insect pressure in corn and soybean following several winter annual

cereal treatments.

3) Evaluate early and late harvested winter annual cereal forage yield.

63

4) Evaluate wheat (early and late maturing variety) grain yield, following no-till
planting into soybean and corn silage fields.

5) Compare the yields of rotational crops (soybeans, com grain and corn silage)
following several winter annual cereal treatments.

6) Compare the commodity returns of several cropping systems to determine the

economic values of different management strategies in Michigan.

Materials and Methods

On 28 September, 1999 and 13 October, 2000, winter annual cereal crops were
no-till planted into a Capac loam soil (fine-loamy, mixed, mesic Aeric Ochra-qualf) at the
Michigan State University Research farm in East Lansing, MI. In both years of the study,
the winter annual cereals were planted in two fields on the farm, one following soybean,
and the other following silage corn. The planting was done in a randomized complete
block split-split plot design replicated four times. Main plots consisted of the fields
previously in corn silage (corn silage residue) or soybeans (scybean residue), sub plots
consisted of the winter annual cereals, and sub-sub plots consisted of rotational crops of
corn grain, corn silage, and soybean. The winter annual cereal treatments consisted of the
following: wheat cover crop (WCC) and rye cover crop (RCC) burned down with
glyphosate; rye harvested for forage (RF); wheat harvested for forage early (WEF) and
late (WLF); an early maturing variety of wheat harvested for grain (WEG) and a late
maturing variety of wheat harvested for grain (WLG); and an untreated check with no
winter cereal (NC). The wheat variety was “Harus” an early maturing awnless soft white

winter wheat developed at the Agriculture Canada Research Station in Harrow. The

64

WLG variety used was “Patterson” a soft red winter wheat developed at Purdue
University. The rye variety used was “Wheeler” which was released by the Michigan
Agricultural Experiment Station. The wheat was planted at 134 kg ha'1 and the rye at 125
kg ha]. The grain and forage crops received 52 kg ha’1 of elemental N applied as granular
urea (46-0-0) at green-up the following spring. The no cover and the wheat and rye cover
crops did not receive any supplemental nitrogen.

The following spring, the winter annual cereals were removed at different times.
WCC and RCC were burned down with glyphosate on 14 April and 26 April for 2000
and 2001, respectively. The RF was harvested in the early boot stage on 26 April, 2000
and 7 May, 2001. The WEF was harvested when the wheat was in the boot stage (F eeke’s
scale 10.0) on 11 May, 2000 and 19 May, 2001; the WLF was harvested when the wheat
was in the early head stage (F eeke’s scale 10.1) on 22 May, 2000 and 24 May, 2001. A
Carter flail harvester (Carter Manufacturing Co. Inc., Brookston, IN) was used to harvest
the forage plots. The WEG and WLG plots were harvested on 5 and 13 July respectively
in 2000, and 9 and 12 July respectively in 2001 using a small plot combine with a five
foot head to harvest the center five feet of each plot. Wheat grain moisture content and
field weights were automatically measured by a GrainGageTM, HarvestData SystemTM
mounted on the plot combine. The wheat grain yields were corrected to 13.5% moisture.

Rotational crops of corn grain (CG), corn silage (CS), or soybean (B) were
planted following burn down or harvest of the winter annual cereals. The plots were 3.0
m x 12.2 m (Table 2.1).

Glyphosate applications at one quart per acre were made to the rotational plots as

needed after the burn down or harvest of the winter annual cereals. On 22, June 00 and 5

65

Table 2.1: Dates of burn down or harvest of winter annual cereals and following planting
dates of corn and soybean rotational crops.

 

 

 

 

 

 

 

 

 

Winter 2000 2001
Annual Burn Corn Soybean Burn Corn Soybean
Cereal down or Rotational Rotational down or Rotational Rotational
Treatment Harvest Planting Planting Harvest Planting Planting
Date Date Date Date Date Date
NC - 29 April 11 May - 5 May 5 May
WCC 14 April 29 April 11 May 26 April 5 May 5 May
RCC 14 April 29 April 11 May 26 April 5 May 5 May
RF 26 April 11 May 11 May 7 May 14 May 14 May
WEF 11 May 15 May 1 1 May 19 May 22 May 22 May
WLF 22 May 22 May 22 May 24 May 26 May 26 May
WEG 5 July 6 July 6 July 9 July 10 July 10 July
WLG 13 July 14 July 14 July 12 July 13 July 13 July

 

NC- no cover, WCC - wheat cover crop, RCC - rye cover crop, RF - rye forage, WEF -
wheat early harvested forage, WLF - wheat late harvested forage, WEG - wheat early

maturing variety grain, WLG - wheat late maturing variety grain.

66

June, 01, all the corn plots except the WEG and WLG were side dressed with 468 Liters
ha’1 of 28% N, which equals 168 kg ha'1 N. On 31 July, 2000, the corn grain and silage,
WEG and WLG plots received 468 Liters ha'1 of 28% N, which equals 168 kg ha'1 N.
However, in 2001, corn following WEG and WLG was not side dressed based on results
from 2000, which showed no yield benefit. The corn silage was harvested when the grain
was approximately at the 2/3 milk line (Wiersma et al. 1993). The soybeans were
harvested after maturity and leaf drop. Soybean and corn grain moisture content and field
weights were automatically measured by a GrainGageTM, HarvestData SystemTM
mounted on a plot combine. Soybeans yields are reported at 13% moisture and corn grain
yields are reported at 15.5% moisture. Corn grain, corn silage and soybean rotational crop
yield data was eliminated from the soybean previous field in 2000, due to extensive
ground hog damage.

Ground cover and residue measurements were made on 23 June, 2000 and 29
June, 2001 using a rope with a knot every 15.2 cm (6 inches) strung diagonally across the
length of a plot from corner to corner. The knots above ground cover or residue were
counted and the percentage of knots was used as an estimate of percent ground cover and
residue for each plot. The method was repeated diagonally the other way across the plot
and results were averaged, similarly to (Sloneker 1977). The WEG and WLG was not yet
harvested at the time of ground cover measurement, and therefore had a full stand of
wheat, so ground cover was considered to be 100% in these plots.

Measurements of numbers or damage were taken for insect pests noted in the
experiment. Armyworm damage in corn plots was evaluated on 12 June, 2001 (due to a

large outbreak in the study) by examining 20 consecutive plants in a center row of each

67

plot. The percentage of plants with feeding damage was calculated and averaged across
treatments. After sampling, all plots in the study were sprayed with esfenvalerate (Asana
XL. DuPont) at 83.6 ml ha'1 on 6 June, 2001. In the fall of 2001, European corn borer was
sampled by splitting 5 randomly chosen plants per corn grain plot. The number of larvae,
number of tunnels, and centimeters of tunneling was recorded for each plant, and
averages were calculated per plot.

In soybean, bean leaf beetle damage was rated on 12 June, 2001 by determining
the percentage of 20 consecutive plants with BLB feeding in each soybean plot. Soybean
aphid numbers were assessed on 8 August, 2001 by rating 30 leaflets per soybean plot
using the following scale: 0 (no aphids), 1 (<10 aphids), 2 (10-24 aphids), 3(25-
99aphids), and 4(>100 aphids) per trifoliate leaf (DiFonzo and Hines 2002). All ground
cover, insect and yield data was analyzed with SAS software using a proc-mixed model
with Tukey’s HSD and lsd’s P(p< 0.05) (SAS Inst.,1999).

For the economic analysis the input costs used were the actual costs accrued for
fertilizer, seed, equipment, labor for planting, harvesting, and herbicide applications.
These costs reflect 2000 prices as reported in Schwab (2001). The insecticide application
cost was not included because all plots were sprayed for armyworm to prevent movement
from one plot to another and therefore didn’t represent a realistic need for insecticide
application in an isolated cropping system. The cash receipts reflect the most recent five-
year average commodity price as reported by the Michigan Agricultural Statistics

Service.

68

Results and Discussion

Ground Cover: The percentage ground cover following winter annual cereal was
significantly different in both fields for both years. The WEG and WLG had
significantly more ground cover and residue than any of the other winter annual cereals
including the no cover plots. This was due to the grain crops remaining on the field at the
time of residue measurement, contributing to 100% ground cover. In 2000, the soybean
previous field was eliminated due to ground hog damage. In 2000, the corn silage
previous field showed significant differences in percent ground cover with winter annual
cereal at p< 0.0001 (Figure 2.1). The significant differences in 2000 were mainly because
the wheat grain plots were not yet harvested and contained 100% cover at the time of
measurement. In 2001, there was a significant difference in ground cover between the
fields planted into a previous corn silage field (corn silage residue) and a previous
soybean field (soybean residue), winter annual cereal * previous crop was significant at
p< 0.0001. The field with corn silage residue showed no significant differences in
ground cover and residue between the rotational crops (soybean, corn grain and corn
silage) so the results were pooled for the analysis. The corn silage residue field in 2001
showed significant differences in percent ground cover and residue between winter
annual cereal treatments at p< 0.0001 (Figure 2.2). Although, in 2001 the soybean residue
field showed significant differences in percent ground cover and residue in the soybean
and corn rotational crops at p< 0.05 (Figures 2.3 and 2.4 respectively). The soybean
residue field tended to have greater cover than the corn silage residue field, but only

significantly higher in the wheat cover crop treatment. The greater ground cover in the

69

Figure 2.1: Percent ground cover and residue averaged between soybean and com
rotational crops planted after winter annual cereal harvest in 2000. The field was
previously in corn silage.

 

Percent Ground Cover and Residue in Soybean and
Corn Rotational Plots Following Winter Annual
Cereal Planted into a Field with Corn Silage
Residue
(26 June, 2000)

 

 

 

 

 

Percent Ground Cover and Residue

 

 

 

NC WCC RCC RF WEF WLF WEG WLG

Winter Annual Cereal

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

70

Figure 2.2: Percent ground cover and residue averaged between soybean and corn
rotational crops planted afier winter annual cereal harvest in 2001. The field was
previously in corn silage.

 

 

 

 

 

 

 

 

Percent Ground Cover and Residue in Corn and
Soybean Rotational Plots Following Winter Annual
Cereal Planted into a Field with Corn Silage Residue
(29 June, 2001)
c c
100
90
“5 80 -
352
§ 70
7c
E 60 -
D
>
8 50 ~
7:3
E
o 40 7
:5
a: 30
§
5‘: 20 ~
10 7
0 i I .
NC WCC RCC RF WEF WLF WEG WLG
Winter Annual Cereal

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

71

Figure 2.3: Percent ground cover in soybean rotational crops planted following winter
annual cereal harvest.

 

Percent Ground Cover and Residue Following
Winter Annual Cereal and Soybean Rotational
Crop Planted into a Field with Soybean Residue

(29 June, 2001)

 

 

Percent Ground Cover and Residue

 

 

 

NC WCC RCC RF WEF WLF WEG WLG
Winter Annual Cereal

 

 

 

Treatments followed by the same letters were not significantly different at P < 0.05.

72

Figure 2.4: Percent ground cover in corn grain and corn silage rotational crops planted
following winter annual cereal harvest.

 

Percent Ground Cover and Residue Following
Winter Annual Cereal and Corn Grain and Corn
Silage Rotational Crops Planted into a Field with

Soybean Residue
(29 June, 2001)

 

 

Percent Ground Cover and Residue

 

 

 

NC WCC RCC RF WEF WLF WEG WLG
Winter Annual Cereal

 

 

L

Treatments followed by the same letters were not significantly different at P < 0.05.

73

soybean residue field was most likely due to the soybean plants originally having a higher
plant population (more plant residue cover per square meter) than the corn and therefore
leaving more cover in the plots. Another possibility is the greater amount of biomass
being removed via corn silage and therefore less residue. In 2001, in the corn silage
residue field, the later harvested winter annual cereals tended to have more ground cover
than earlier harvested winter annual cereals. The later harvested winter annual cereals
may not have broken down and decayed as much by the time of sampling as the earlier
harvested winter annual cereals.

Insect Damage: There were differences in insect pressure in corn and soybean
rotational crops following winter annual cereal treatments. The armyworm damage in the
soybean and corn silage residue fields was analyzed separately due to field layout design
of being (four or six) plots distant from rye cover crop or rye forage in the (soybean and
corn silage) residue fields respectively. Armyworm damage was significantly greater in
corn following RF and RCC and in plots within close proximity to the rye winter annual
cereals at p< 0.0001 (Figs 2.5-2.6). If a herbicide is used on a small grain or the small
grain matures before armyworm larvae finish development they may move to corn
(Steffey 1999). Corn no-till planted into a small grain cover crop is most likely to suffer
armyworm injury (O’Day 1998).

European corn borer (ECB) larvae numbers, number of tunnels and length of
tunnels in corn stalks following winter annual cereal treatments was significant at p<
0.05. The number of larvae, number of tunnels and length of tunnels were all
significantly lower in the wheat early and late grain plots. This was probably related to

the corn not reaching maturity, due to the later corn planting date associated with the

74

Figure 2.5: Percent of com plants damaged by armyworm in the soybean residue field
on 12 June, 2001. The treatment differences were based on the plots proximity to rye,
rather than the particular winter annual cereal; rye cover crop and rye forage plots were
considered to be point 0.

Percent of Corn Plants Infested by Armyworm (No-
Till Planted into Soybean Residue Field)
(2001)

 

 

 

I
100 I
I
I
I
I
I

 

 

 

 

Percent Infested Plants

 

 

 

 

 

 

 

I
I
I
Plot Proximity to Rye Cover Crop or Rye Forage

 

Armyworm damage based on proximity to rye was not significantly different when
followed by the same letters at P < 0.05.

75

Figure 2.6: Percent of corn plants damaged by armyworm in the corn silage residue field
on 12 June, 2001. The treatment differences were based on the plots proximity to rye,
rather than the particular winter annual cereal; rye cover crop and rye forage plots were
considered to be point 0.

Percent of Corn Plants Infested by Armyworm (No- I
Till Planted into Corn Silage Residue Field)

 

 

 

 

 

 

 

 

I

(2001) I

I

100 I

I

I 90 -- 7 7 77.- -777774774———-——- I

I

I 80 - ”r”,i iriiir#;rl—I I

I . I

I g I

I °~ I
-e

a I

I 7% I

I
O

s I

°‘ I

‘ I

I

I

I I

I I

, ., I I

0 1 2 3 4 5 6 I

L Plot Proximity to Rye Cover Crop or Rye Forage I

 

Armyworm damage based on proximity to rye was not significantly different when
followed by the same letters at P < 0.05.

76

Figure 2.7: Average number of European corn borer larvae per corn stalk in relation to

the preceding winter annual cereal in corn grain rotational plots, planted following
harvest of winter annual cereals. Sampling done on 18 October, 2001.

 

0.8

Average Number of ECB Larvae per Stalk (2001)

 

 

0.7

0.6 v

0.5 A

0.4 —

0.3

Average Number Larvae per Stalk

0.2 —

0.1 7

 

   

 

L

NC WCC RCC RF WEF WLF WEG WLG

 

 

 

Winter Annual Cereal

Winter annual cereal treatments followed by the same letter were not significantly

different at P < 0.05.

77

 

Figure 2.8: Average number of European corn borer larvae per corn stalk in relation to
the preceding winter annual cereal in corn grain rotational plots, planted following
harvest of winter annual cereals. Sampling done on 18 October, 2001.

 

FF“ I
Average Number of ECB Tunnels per Stalk (2001)

1.6

 

 

 

Number of Tunnels per Stalk

 

 

 

NC WCC RCC RF WEF WLF WEG WLG

 

Winter Annual Cereal

 

Winter annual cereal treatments followed by the same letter were not significantly
different at P < 0.05.

78

Figure 2.9: Average European corn borer tunnel length per corn stalk in relation to the
preceding winter annual cereal in corn grain rotational plots, planted following harvest of
winter annual cereals. Sampling done on 18 October, 2001.

 

Average ECB Tunnel Length per Stalk (2001)

 

 

 

 

Average Tunnel Length (cm)

 

 

 

NC WCC RCC RF WEF WLF WEG WLG
Winter Annual Cereal

 

 

 

Winter annual cereal treatments followed by the same letter were not significantly
different at P < 0.05.

79

wheat grain treatments. The stalks remained small and wet at the time of ECB second-
generation moth flight (Figures 2.7-2.9). Only the corn grain rotational plots in the corn
silage residue field were sampled, as a representation of ECB in corn following a winter
annual cereal.

The winter annual cereal treatment was significant at p< 0.01 for bean leaf beetle
(BLB) damage in soybeans. The BLB feeding was significantly higher in the earlier
planted soybeans, (planting date dependant on winter annual cereal harvest date). This
was probably due to the soybean plants being in an early developmental stage at the time
of bean leaf beetle feeding (Figure 2.10). Bean leaf beetle feeding tends to be more
prevalent in early season (Higley 1994).

The soybean aphid numbers showed no significant differences between soybean
and corn silage residue fields, so data was pooled for analysis. Winter annual cereal
treatments were significant for soybean aphid numbers at p< 0.001. The soybean aphid
numbers were significantly higher or tended to be higher in the late planted soybeans
especially following wheat early grain (Figure 2.11). One possibility is the late-planted
soybeans were in an early vegetative stage at the time of sampling due to late emergence.
The later planted soybeans may not have been colonized by aphids as soon as earlier
planted soybeans. Therefore, the later planted soybeans were more likely colonized by
aphids fi'om surrounding soybeans that already were infested by aphids. This “new”
colonization may have contributed to an increased reproductive efficiency of the aphids
on these plants. The soybean plants in the wheat late grain treatments had not emerged in

most of the plots at the time of aphid sampling.

80

Figure 2.10: Bean leaf beetle damage in soybeans planted following winter annual cereal
harvest (12 June 01)

BLB Damage in Soybeans, Averaged Between Corn I
Silage and Soybean Residue Fields I

(2001) I

I

100

 

90 - W,” — L_7.,7,i_,_f_

80- , ~

70 _

 

«so—VJV

 

 

 

 

 

Percent Plants Damaged

 

 

 

 

 

Winter Annual Cereal

 

 

 

Winter annual cereal treatments followed by the same letter were not significantly
different at P < 0.05.

81

Figure 2.11: Soybean aphid rating on 8 August, 2001 in soybeans following winter
annual cereals. Soybean aphid rating consisted of a 0-4 scale; 0 (no aphids), l (<10
aphids), 2 (10-24 aphids), 3(25-99aphids), and 4(>100 aphids) per trifoliate leaf.

 

 

 

 

 

 

 

 

r? _7
Soybean Aphid Rating Following Winter Annual
Cereals No-Till Planted into Either Corn Silage or
Soybean Fields
2001
4
3.5
3
00 c
.S
L3
'1:
LE
:2.
<2
5
.8
>5
0
U)
Winter Annual Cereal
L

 

 

 

Winter annual cereal treatments followed by the same letter were not significantly
different at P < 0.05.

82

Winter Annual Cereal Yields: There were significant differences in forage
yields among winter annual cereals. The winter annual cereal forage yields showed no
significant differences in year or previous crop, however there was a three way
interaction of winter annual cereal * rotational crop * year in the forage yields. Later
harvest dates contributed to significantly greater yields in both years of the study except
for wheat early forage, which was significantly greater than the wheat late forage, in the
corn silage residue field in 2001 (Tables 2.2-2.3). The rye forage had significantly greater
yields in the corn silage residue field the first year, probably due to groundhog damage in
the field where soybean was the previous crop. The yield differences by year, although
significant, varied with previous crop and winter annual cereal and therefore were
probably due to standard yield variances. The forage quality was reported in a previous
paper (Thelen and Leep 2002).

Wheat grain yields showed significant differences with wheat variety at p < 0.01,
with year at p < 0.0001, with previous crop at p < 0.001, and had a significant interaction
of wheat variety * year at 0.01 (Table 2.4). The wheat grain yields were significantly
higher when planted into the soybean residue field compared to the corn silage residue
field in both years of the study (Table 2.5). This may be due to soybean plants
contributing nitrogen to the grain in the spring. The WEG and WLG plots showed no
significant difference in yield in 2000, however in 2001 the wheat late grain had a
significantly greater yield (Table 2.6). The lower yield in the wheat early grain plots may
be due to varietal differences.

Rotational Crop Yields: In 2000 there were no significant differences in

soybean yields following winter annual cereal in the corn silage residue field (Table 2.7).

83

Table 2.2: The significance of factors and interactions affecting wheat (early and late
harvested) forage yields, planted after corn or soybeans (two year average).

 

Factors and Interactions

Significance Level

 

 

 

 

 

 

 

 

Winter Annual Cereal 0.0001
Year Not Significant
Winter Annual Cereal*year 0.0001
Previous crop Not Significant
Winter Annual Cereal * Previous Crop 0.05

Year * Previous Crop Not Significant
Winter Annual Cereal * Year * Previous Crop 0.05

 

Table 2.3: Yields of winter annual cereal forages no-till planted into corn silage or
soybean residue fields, over two years. The first, second and third letters following the
yield represent significant differences between winter annual cereal, previous crop and

 

 

 

 

 

 

 

year respectively.
Winter Annual Yield
Cereal 2000 2001
Corn Silage Soybean Corn Silage Soybean
Residue Field Residue Field Residue Field Residue Field
Mg ha'1 Mg ha'1 Mg ha'1 Mg ha"1
Rye forage 4.48 Aay 2.91 Aby 3.36 Aaz 3.81 Aaz
Wheat early forage 4.93 Aay 4.26 Bay 6.72 Caz 6.5 Baz
Wheat late forage 6.5 Bay 6.94 Cay 5.6 Baz 6.05 Baz

 

 

 

Treatment yields followed by the same letters were not significantly different at P < 0.05.

84

Table 2.4: The significance of factors and interactions for the following tables 2.6-2.7,
showing yields for wheat (early and late maturing) grains harvested after no-till planting
into soybean residue or corn silage residue fields over two years.

 

 

 

 

 

 

 

 

 

Factors and Interactions Significance Level

Winter Annual Cereal 0.01

Year 0.0001
Wheat Variety * Year 0.01
Previous Crop 0.001

Wheat Variety * Previous Crop Not SLgnificant
Year * Previous Crop Not Significant
Wheat Variety * Year * Previous Crop Not Significant

 

Table 2.5: The interaction of year * previous crop in wheat grain yields following corn
silage or soybean previous fields, over two years.

 

 

 

 

 

 

Previous Crop Yield
2000 200]
Mg ha'1 Mg ha'1
Corn Silage Residue 79.5a 65.7a
Soybean Residue 95.2b 72.5b

 

Treatment yields followed by the same letters were not significantly different at P < 0.05.

Table 2.6: The interaction of wheat variety * year in wheat grain yields (early and late
maturing variety), following corn silage and soybeans over two years.

 

 

 

 

Previous Crop Yield
2000 2001
Mg ha'1 Mg ha'1
Wheat Early Grain 87.9a 63.9a
Wheat Late Grain 86.8a 74.3b

 

 

 

Treatment yields followed by the same letters were not significantly different at P < 0.05.

85

Table 2.7: Soybean yields following winter annual cereals no-till planted into corn silage
or soybean residue fields.

 

 

 

 

Winter Annual Yield
Cereal Corn Silage Residue Field Soybean and Corn Silage
Previous 2000 Residue Fields 2001

Mg ha'1 Mg ha'1

No Cover 3.6 2.8 b

Wheat Cover Crop 3.6 3.0 ab

Rye Cover Crop 3.2 3.1 a

Rye Forage 3.4 3.1 a

Wheat Early Forage 3.5 2.8b

Wheat Late Forage 3.5 2.64c

Wheat Early Grain - -

Wheat Late Grain - -

 

 

 

Treatment yields followed by the same letters were not significantly different.

86

However, soybean yields following NC and WCC tended to be greater, probably due to
an earlier planting date. In 2001, there were no statistical differences in yields based on
previous crop and no significant interaction of winter annual cereal "‘ previous crop, so
the yield data from plots in the soybean and corn silage residue fields was pooled for
analysis. In 2001, soybean yield following winter annual cereal treatment was significant
at p< 0.001 with RCC and RF having significantly higher soybean yield than NC, while
soybean yield following the wheat cover crop tended to be greater than no cover (Table
2.7). This may be due to the winter annual cereals improving soil physical properties,
such as increased soil aeration and water infiltration or the cover crops releasing N after
burn down and rye forage roots releasing N from decomposition. Peterson and Varvel
(1989 a) found soybean yields following sorghum but not com, may be increased with
fertilizer N additions. The soybeans following wheat grain were planted too late to reach
maturity and were not harvested.

In 2000, the corn grain yields showed a significant difference following winter
annual cereal treatment at p< 0.01. The corn grain yields were significantly higher or
tended to be higher with earliest planting date, following NC being the highest (Table
2.8). Corn grain following wheat late forage yielded significantly less than corn
following other winter annual cereals due to the late planting date. In 2001, there were no
statistical differences in yields based on previous crop so the yield data from plots in the
soybean and corn silage residue fields was pooled for analysis. The winter annual cereal
treatment was significant for corn grain yield at p< 0.001, while previous crop and winter
annual cereal * previous crop were not significant. The corn grain yields following NC,

WCC and RCC were significantly greater than corn grain following other cover crops,

87

Table 2.8: Corn grain yields following winter annual cereals no-till planted into corn
silage or soybean residue fields.

 

 

 

 

Winter Annual Yield
Cereal Corn Silage Residue 2000 Soybean and Corn Silage
Residue Fields 2001

Mg ha'1 Mg ha’1

No Cover 12.1 8.63

Wheat Cover Crop 12.0 7.4abc

Rye Cover Crop 11.7 8.4a

Rye Forage 11.5 6.9bc

Wheat Early Forage 10.2 5.7d

Wheat Late Forage 8.0 6.9bc

Wheat Early Grain - -

Wheat Late Grain - -

 

 

 

Treatment yields followed by the same letters were not significantly different.

88

again mainly due to an earlier planting date facilitated by the earlier removal of the
winter annual cereal in these treatments. The armyworm infestation may have also
contributed to a lower corn grain yield following the winter annual cereals. As in 2000,
the corn grain following wheat grain in 2001 never reached maturity due to the late corn
planting date and was not harvested.

In 2000, the corn silage yield was significant for winter annual cereal at p<
0.0001. The corn silage yield was significantly higher or tended to be higher with earlier
planting date following winter annual cereal (Table 2.9). Corn silage yield following the
wheat and rye cover crop tended to be greater, possibly due to N release following burn
down or improved soil physical properties. Peterson and Varvel (1989 b) reported greater
yields in corn following legumes. The rainfall was above the 30-year average in July
2000 (Table 2.10). This precipitation may have contributed rain at a key time for corn
silage taking up soil N afier cover crop release. Corn moisture stress around silking is the
most detrimental time for yields (Clark et al. 1997). Corn may benefit from later
plantings when silking occurs during timely July and August rains (Clark et al. 1997). In
2001, there were no significant differences between previous crop, so the yields were
averaged between corn silage residue and soybean residue fields, however corn silage
following winter annual cereal treatment was significant at p< 0.0001. Corn silage yields
were significantly lower or tended to be lower with later planted corn, similar to 2000
(Table 2.10). The rainfall was below the thirty-year average in July 2001 (Table 2.2).
Peterson and Varvel (1989 b) showed lack of rain during pollination (July) may reduce

corn yields.

89

Table 2.9: Corn silage yields following winter annual cereals no-till planted into corn
silage or soybean residue fields.

 

 

 

 

 

 

Winter Annual Yield
Cereal Corn Silage Residue Soybean and Corn Silage

2000 Residue

2001
Mg ha'1 (DM) Mg ha'1 (DM)

No Cover 17.9 11.6 a
Wheat Cover Crop 18.6 1 1.2 ab
Rye Cover Crop 19.7 10.1 bc
Rye Forage 16.1 8.7 cd
Wheat Early Forage 16.4 8.5 (1
Wheat Late Forage 14.3 9.2 cd
Wheat Early Grain 5.8 5.4 e
Wheat Late Grain 4.5 3.1 f

 

Treatment yields followed by the same letters were not significantly different.

90

Table 2.10: Monthly precipitation and growing degree unit (GDU) accumulation for the
1999 through 2001 winter annual and rotational crop growing seasons at the experimental
location. Thirty-year means have been included for comparison (1971-2000).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Month Precipitation Growing Degree Units
1999 I 2000 I 2001 I 30 yr 1999 I 2000 I 2001 I 30 yr
---- Millirneters ---- -—-- Degrees Centigrade ----
May - 134.6 144.8 68.6 — 193 191 128
June - 78.7 83.8 78.7 - 294 281 263
July - 94.0 22.9 76.2 - 288 333 337
August - 86.4 40.6 86.4 - 314 338 308
September 40.6 111.8 101.6 86.4 213 208 174 173
October 20.3 53.3 137.2 61.0 75 131 51 43
Seasonal 61.0 558.8 393.7 457.2 306 1517 1457 1341
Total

 

GDU calculated for com at a base 100C, with 100C and 300C minimum and maximum

temperatures.

Data recorded at the Horticultural Research Station, East Lansing, MI.

91

 

Economics: The economics showed the greatest profit when incorporating a
winter annual forage into the cropping system, whether followed by soybeans, corn grain,
or corn silage (Table 2.11). This was due to the added value of a forage crop in all
systems and the higher yield of soybeans following rye forage. Cropping systems
including wheat and rye cover crops still made a profit, although reduced from no cover.
However, the economic analysis did not consider the long-term environmental and soil
quality aspects associated with cover crops. The cropping systems with wheat grains
showed little profit when followed by corn silage and loss when followed by soybean or
corn grain. The wheat grain cropping systems had rotational crops planted too late for
adequate maturation time, demonstrating that a wheat grain-double crop system is usually

not feasible at the Northern latitude associated with the East Lansing study site.

Conclusions:

Integrating a winter annual cereal into a com-soybean rotation will increase the
ground cover and residue present, which may improve the soil physical properties. The
presence or damage by insect pests mainly depends on the timing of rotational crop
planting, which is based on whether the winter annual cereal is burned down, harvested
for forage or harvested for grain. Although, wheat and rye winter annual cereals increase
the likelihood of an armyworm infestation. If the wheat or rye is burned down with
glyphosate, there is an increased chance of the armyworms moving to adjacent fields or
plots of corn to find a source of food. ECB moth flight does not coincide with very late-
planted corn, such as that planted following harvest of a wheat grain crop, therefore

tunneling will not take place in this corn. BLB damage is ofien higher in soybeans with

92

Table 2.11: Economic net return of following a winter annual cover crop, forage or grain
by soybeans, corn grain or corn silage.

 

Net Return in S/Hectare

 

 

 

 

 

 

 

 

 

Wheat Rotational Cropping
Winter Annual Cereal Rotation Forage Grain Crop System
N0 Cover Soybean — - 55.39 337.33 c
Wheat Cover Soybean - - 41.54 252.81 d
Rye Cover Soybean - - 39.49 251.70 d
Rye Forage Soybean 3.71 - 57.75 379.86 c
Wheat Early Forage Soybean 28.84 - 54.46 463.00 b
Wheat Late Forage Soybean 32.01 - 56.97 583.35 a
Wheat Early Grain Soybean - 41.74 ~55.45 -59.54 e
Wheat Late Grain Soybean - 49.84 -60.07 -71.28 e
No Cover c, Silage - — 92.63 560.79 ab
Wheat Cover C. Silage - - 78.38 469.90 bc
Rye Cover C. Silage - - 80.89 485.92 bc
Rye Forage C. Silage 3.71 - 63.15 423.64 0
Wheat Early Forage C. Silage 28.84 - 69.04 607.25 a
Wheat Late Forage C. Silage 32.01 - 60.36 520.27 abc
Wheat Early Grain C. Silage - 41.74 -11.32 211.56 d
Wheat Late Grain C. Silage - 49.84 -34.44 96.86 d
N0 Cover C. grain - - 62.90 383.33 ab
Wheat Cover C. grain — - 42.82 260.93 0
Rye Cover C. grain — - 45.79 279.12 0
Rye Forage C. grain 3.71 - 48.17 324.73 bc
Wheat Early Forage C. grain 28.84 — 36.86 438.60 a
Wheat Late Forage C. grain 32.01 - 35.61 421.47 a
Wheat Early Grain C. grain - 41 .74 -83.63 -231.63 d
Wheat Late Grain C. grain - 49.84 -83.63 -82.84 d

 

Economic values followed by the same letters within a rotational cropping system were

not significantly different at P < 0.05.

93

an earlier planting date such as those planted following burn down of wheat and rye
rather than following wheat or rye harvested as forage or grain. Soybean aphid numbers
tend to be higher in later planted soybeans such as those following a wheat grain crop,
probably due to colonization by generations of aphids fi'om neighboring soybean plots
that were previously colonized. Planting wheat and rye for a forage will add a second
profitable crop to the system. The later harvested forages have a higher yield than the
earlier harvested forages, but a lower plant quality. Double cropping with wheat for grain
will provide a small grain profit, but the late planting of soybeans or corn following
wheat grain harvest is not profitable in the northern climates such as Michigan.
Rotational crop yields following winter annual cereals tend to be higher with an earlier
rotational crop planting date for both soybeans and corn. The rotational crop planting
date occurs after the burn down or harvest of the winter annual cereal and therefore is
dependent on whether the winter annual cereal is used for a cover crop, a forage or a
grain. The only exception to this is soybeans following a cover crop have a greater yield
over no cover crop. The overall economics of the system depend on whether the winter
annual cereal is burned down, harvested for a forage or for a grain. Integrating a wheat or
rye forage into the system will increase the net profit to the system over no cover,
especially when followed by soybeans, although also when followed by corn silage or
corn grain. Although the wheat and rye cover crops burned down with glyphosate do not
show a short-term economic benefit, the long-term environmental benefits of improving

soil physical properties and nutrient dynamics was not measured by this study.

94

References Cited

Clark, A. J ., A. M. Decker, J. J. Meisinger, and M. S. McIntosh. 1997. Kill date of vetch,
rye, and a vetch-rye mixture: H. Soil moisture and corn yield. Agron. J. 89:434-441.

DiFonzo, C. and B. Hines. 2001. Soybean Aphid in Michigan. Extension Bulletin E-
2748. Michigan State University, E. Lansing, MI.

Eckert, DJ. 1988. Rye cover crops for no-till corn and soybean production. J. Prod. Agic.
1:207-210.

Entz, M.H., V.S. Baron, D.W. Meyer, S.R.Jr. Smith, and WP. McCaughey.2002.
Potential of forages to diversify cropping systems in the northern Great Plains. Agron. J.
94(2):240-250.

Garwood, T. W. D., D. B. Davies, and A. R. Hartley. 1999. The effect of winter cover
crops on yield of the following spring crops and nitrogen balance in a calcareous loam. J.
Agric. Sci. 13211-11.

Hartwig, N.L., and H.U. Ammon. 2002. 50th Anniversary-Invited Article. Cover crops
and living mulches. Weed Science. 50:688-699.

Kaspar, T.C., J .K. Radke, and J .M. Laflen. 2001.Sma11 grain cover crops and wheel
traffic effects on infiltration, runoff, and erosion. J. Soil Water Conserv. 56:160-164.

Kessavalou, A., and D. T. Walters. 1997. Winter rye cover crop following soybean under
conservation tillage. Agron. J. 89:68-74

Kuo, S. and E]. J ellum. 2002. Influence of Winter Cover Crop and Residue Management
on Soil Nitrogen Availability and Corn. Agron. J. 94:501-508.

Moschler, W.W., G.M. Shear, D. L. Hallock, R. D. Sears, and GD. Jones. 1967. Winter
cover crops for sod-planted corn: Their selection and management. Agron. J. 59: 547-
55 1.

O'Day, M., A. Becker, A. Keaster, L. Kabrick, and K. Steffey. 1998. Corn Insect Pests. A
Diagnostic Guide. MU Extension, University of Missouri-Columbia. p. 24-25.

Peterson, T. A., and G. E. Varvel. 1989. Crop yield as affected by rotation and nitrogen
rate. I. Soybean. Agron. J. 81:727-731.

Peterson, T. A., and G. E. Varvel. 1989. Crop yield as affected by rotation and nitrogen
rate. HI. Corn. Agron. J. 81:735-738.

95

Sanchez, J. E., R.R. Harwood, E.A. Paul, T.C. Wilson, and J. Smeenk. 2002. Corn root
effects on the nitrogen-supplying capacity of a conditioned soil. Agron. J. 94: 391-396.
SAS Institute. 1999. SAS online help. SAS Inst., Cary,NC.

Sloneker, L. L. and W. C. Moldenhauer. 1977. Measuring the amounts of crop residue
remaining after tillage. J. Soil and Water Cons. 231-236.

Steffey, K.L., M.E. Rice, J. All, D.A. Andow, M.E. Gray, and J .W.V. Duyn. 1999.
Handbook of Com Insects. Entomological Society of America, Lanham, MD. p.50-51.

Thelen, K.D. and RH. Leep. 2002. Integrating a double-cropped winter annual forage

into a com-soybean rotation. Crop Management. Electronic journal available at URL:
http://www.plantmflagemenmetwork.or ub/cm/research/winter

Vaughan, J. D., and G. E. Evanylo. 1998. Corn response to cover crop species, spring
desiccation time, and residue management. Agron. J. 90:536-544.

Wiersma, D.W., P.R. Carter, K.A. Albrecht, and J .G. Coors. 1993. Kernel milkline stage
and corn forage yield, quality, and dry matter content. J. Prod. Agric. 6(1): 94-99.

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