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This is to certify that the
dissertation entitled

Corn (Zea mays L.) and Cover Crop Response to Corn
Density in an lnterseeding System and Subsequent Dry
Bean (Phaseolus vulgaris L.) Yield

presented by

Dieudonné Nkundizana Baributsa

has been accepted towards fulfillment
of the requirements for the

PhD. degree in CROP AND SOIL SCIENCE

 

 

f Major Professor’s Signature

/(2 - /</- Clé

 

Date

MSU is an Affirmative Action/Equal Opportunity Institution

 

LIBRARY
Mict. 4,. State
University

 

 

 

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PLACE IN RETURN BOX to remove this checkout from your record.
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2/05 p:lClRC/DateDue.indd-p1

 

 

CORN (Zea mays L.) AND COVER CROP RESPONSE TO CORN DENSITY IN
AN INTERSEEDING SYSTEM AND SUBSEQUENT DRY
BEAN (Phaseolus vulgaris L.) YIELD
By

Dieudonné Nkundizana Baributsa

A DISSERTATION
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
Department of Crop & Soil Science

2006

ABSTRACT
CORN (Zea mays L.) AND COVER CROP RESPONSE TO CORN DENSITY IN
AN INTERSEEDING SYSTEM AND SUBSEQUENT DRY
BEAN (Phaseolus vulgaris L.) YIELD
By

Dieudonné Nkundizana Baributsa

Reliable cropping strategies are needed to enhance legume cover crop
utilization as a nitrogen (N) source for corn (Zea mays L.) and dry edible beans
(Phaseolus vulgaris L.). Nitrogen can be applied as a fertilizer or provided by
leguminous cover crops. Planting corn with interseeded legume cover crops into
a killed leguminous stand and planting dry bean the subsequent year can reduce
N input costs for com and dry bean. It is important to know how leguminous
cover crops affect corn yield when used as the sole N source, the effect of
interseeding, and the maximum plant density at which this approach is feasible.
This study evaluated (1) the effect of four com densities (37 500 to 75 000 plants
ha") in an interseeding system on corn yield and on red clover (Trifolium
pretense L. ) or Chickling vetch (Lathyrus sativus var. AC Greenfix,) dry matter;
(2) the effect of mineral N fertilizer versus organic N provided by plowed red
clover on corn yield and N status at various corn densities; (3) the effect of corn
density and interseeding on N status in plant tissues of com and cover crops;
and (4) the effect of these management practices on soil mineral N (N03 and
NH‘..), subsequent dry bean yield, and N status of dry bean. Results suggest that

interseeded cover crops did not affect corn yield at any plant density.

Across years, yield of com planted into plowed red clover was similar to that of
corn fertilized with mineral N. During optimum growing conditions, corn fertilized
with mineral N outyielded com planted into plowed red clover, however the
reverse was seen in dry years. Interseeded cover crop biomass decreased as
com density increased. However the subsequent spring, red clover biomass was
similar regardless of previous corn density.

Across years, com grain N concentration decreased as corn density
increased and was highest in corn fertilized with mineral N. lnterseeding cover
crops did not reduce corn grain N concentration. Overall, grain N content of corn
planted into plowed red clover was lower compared with fertilized com. By fall,
interseeded cover crops accumulated more N at low com density compared with
higher plant densities. The subsequent spring, red clover accumulated significant
N ranging from 58 to 162.3 kg ha".

lnterseeding cover crops did not influence soil mineral N. During optimum
growing conditions, dry bean yield following com interseeded with red clover was
similar to yield of dry bean fertilized with 45 kg ha'1 of mineral N. Similar trends
were seen for bean seed N accumulation. Red clover can be interseeded at high
com densities (up to 75000 plants ha") and accumulate sufficient N the
subsequent spring to meet the N demand of the following dry bean crop. These
results are valuable to conventional, organic and low-input or low-resource
farmers as they seek to maximize production while reducing the cost of N

fertilizer.

Dedicated to my
daughter Jemima Baributsa,
son Dieubeni Baributsa,
wife Lydia Mun yantore, and

mother Elina Nyirabagenzi.

In memory of my
father Aaron Baributsa Muhire
and

brother-in-law Twenge Mun yantore

iv

ACKNOWLEDGEMENTS

I want to express many thanks and gratitude to Dr. Eunice Foster for
accepting me in her program, providing the funding, and for her unwavering
support and guidance during my education. Thanks to Dr. Kurt Thelen (Co-
advisor), Dr. Sasha Kravchenko, Dr. Mathieu Ngouajio and Dr. Dale Mutch,
members of my committee, for their guidance and their unmeasurable
contribution to my training.

I want to thank Dr. Karim Maredia for the opportunity of being involved in
international development and financial support through the lPM-CRSP. I want to
acknowledge Dr. Kirk and Marjorie Lawton, the Graduate School, the College of
Agriculture and Natural Resources, and the department of Crop and Soil Science
for their financial support. I thank the Great Lakes Hybrids Company for providing
the corn hybrid 4979. Thanks to Dr. Jim Kelly for providing dry bean seeds. Many
thanks for North Dakota Seed Frontier for providing the AC Greenfix seed.

Thanks to Greg Parker, Bill Widdicombe, Keith Dysinger, Todd Martin and
Jon Dahl for their help with my research. Special thanks to my friends and
members of the First Assembly of God-Greater Lansing for their encouragement
and support. Thanks to the 088 faculty and staff for the outstanding support
during my training. Finally, I want to thank my family for their sacrifice, my wife
Lydia, my daughter Jemima and my son Dieubeni, and my extended family and
relatives for their constant excitement for this achievement. Thanks to the

Allmighty God for his love, care and compassion.

TABLE OF CONTENTS

LIST OF TABLES ................................................................................................. ix
LIST OF FIGURES ............................................................................................. xiii
Literature Review ................................................................................................ 1
Introduction ........................................................................................................... 1
lnterseeding system .............................................................................................. 4
a. Spatial arrangement ..................................................................................... 5
b. Plant density ................................................................................................ 6
c. Maturity dates .............................................................................................. 6
d. Plant architecture ......................................................................................... 6
Cover crops ........................................................................................................... 8
a. Annual cover crops .................................................................................... 1 1
b. Biennial cover crops ................................................................................... 12
c. Perennial cover crops ................................................................................ 13
Red clover ........................................................................................................... 14
Chickling vetch .................................................................................................... 15
Cover crop adoption and management constraints ............................................. 18
Influence of legume cover crop on crop yield and N content ............................... 20
References .......................................................................................................... 22

Chapter One: Corn and Cover Crop Response to Corn Density In an

lnterseeding System .................................................................................... 30
Abstract ............................................................................................................... 30
Introduction ......................................................................................................... 31
Materials and Methods ........................................................................................ 37

Site description .............................................................................................. 37

Experimental design ...................................................................................... 38

Corn ............................................................................................................... 38

Soil sampling and agricultural inputs ............................................................. 39

Cover crop ..................................................................................................... 41

Soil moisture measurements ......................................................................... 42

Statistical analysis ......................................................................................... 42
Results and discussion ....................................................................................... 43

Weather patterns ........................................................................................... 43

Soil moisture in 2004 and 2005 ..................................................................... 44

lnterseeding system and N source effect on com yield .................................. 46

Com density effect on interseeded cover crops in fall ................................... 52

Pure or monoculture cover crops in 2004 and 2005 ...................................... 55

Red clover dry matter the subsequent spring ................................................ 56
Conclusion .......................................................................................................... 58
References .......................................................................................................... 60

Chapter Two: Effect of Com Density on Corn and Cover Crop Nitrogen in

an lnterseeding System ................................................................................... 78
Abstract ............................................................................................................... 78
Introduction ......................................................................................................... 80
Materials and Methods ........................................................................................ 85
Site description .............................................................................................. 85
Experimental design ...................................................................................... 86
Corn ............................................................................................................... 87
Chlorophyll content and ear leaf N ................................................................. 87
Com whole plant N ........................................................................................ 88
Cover crop N .................................................................................................. 88
Total Kjeldahl nitrogen and N calculation ....................................................... 89
Statistical analysis ......................................................................................... 90
Results and Discussion ....................................................................................... 91
Weather patterns ........................................................................................... 91
Corn grain N .................................................................................................. 92
Corn leaf N ..................................................................................................... 95
Corn stalk N ................................................................................................... 96
Chlorophyll content ........................................................................................ 96
Ear leaf N ..................................................................................................... 100
Effect of com density on interseeded cover crop N ..................................... 101
Monoculture cover crop N ............................................................................ 103
N of interseeded cover crop the subsequent spring ..................................... 104
Conclusion ........................................................................................................ 105
References ........................................................................................................ 106

Chapter Three: Effect of Interseeded Cover Crop on Soil Mineral N and

Subsequent Dry Bean Yield and N Status .............................................. 122
Abstract ............................................................................................................ 122
Introduction ....................................................................................................... 124
Materials and Methods ...................................................................................... 127

Site description ............................................................................................ 127

Experimental design .................................................................................... 127

Cover crops ................................................................................................. 128

Soil mineral N .............................................................................................. 128

Dry bean ...................................................................................................... 129

Statistical analysis ....................................................................................... 131
Results and Discussion ..................................................................................... 133

Weather conditions ...................................................................................... 133

N accumulation by interseeded red cover or AC Greenfix ........................... 133

Dry bean yield .............................................................................................. 134

Dry bean N concentration and content ........................................................ 135

Fall and subsequent spring soil mineral N ................................................... 137
Conclusion ........................................................................................................ 139

vii

References ........................................................................................................ 141
Summary and Conclusions ............. _ ............................................................... 152
Appendices ...................................................................................................... 1 55

Appendix A. Total monthly precipitation (mm) during the 2002, 2003, 2004 and
2005 growing seasons, compared with 30-year monthly precipitation average at
Kellogg Biological Station, Hickory Corners, Ml. ............................................... 156

Appendix B. Monthly average minimum and maximum temperatures (°C) during
the 2002, 2003, 2004 and 2005 growing seasons, compared with 30-year
average minimum and maximum temperatures at Kellogg Biological Station,
Hickory Comers, Ml. ......................................................................................... 157

Appendix C. Percent volumetric soil moisture at 0 to 18 and 18 to 36 cm depths
in management practices across corn density during the 2004 growing season at
Kellogg Biological Station, Hickory Comers, Ml. ............................................... 158

Appendix D. Percent volumetric soil moisture at 0 to 18 and 18 to 36 cm depths
in management practices across com density during the 2005 growing season at
Kellogg Biological Station, Hickory Comers, Ml. ............................................... 159

Appendix E. Percent volumetric soil moisture at 0 to 18 and 18 to 36 cm depths
at four corn densities across management practices during the 2004 growing
season at Kellogg Biological Station, Hickory Comers, Ml ................................ 160

Appendix F. Percent volumetric soil moisture at 0 to 18 and 18 to 36 cm depths

at four com densities across management practices during the 2005 growing
season at Kellogg Biological Station, Hickory Comers, Ml ................................ 161

viii

LIST OF TABLES

Chapter One

Table 1. Dry matter and N content of red clover (Trifolium pretense L.),
established the previous year in strips and sampled before planting com (Zea
mays L.), in spring of 2002, 2003, 2004 and 2005 at Kellogg Biological Station,
Hickory Comers, MI. ........................................................................................... 66

Table 2: Significance of the effect of plant density (PD) and management
practices (MP) across four years (Y) on corn (Zea mays L.) yield (CY), days to
flowering (DF), plant height (PH), ears per plant (EP), grain moisture (GM) and
test weight (TW), and on cover crop fall dry matter (FDM), fall cover crop density
(FCD), fall cover crop height (FCH) and spring red clover (Trifolium pretense L.)
dry matter (SRDM) at Kellogg Biological Station, Hickory Comers, Ml. .............. 66

Table 3. Mean corn (Zea mays L.) yield (Mg ha") of management practices
across com plant density during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Comers, Ml ................................ 67

Table 4. Mean corn (Zea mays L.) yield (Mg ha") of combined four-year data
across management practices and corn plant density at Kellogg Biological
Station, Hickory Comers, MI. .............................................................................. 68

Table 5. Mean corn (Zea mays L.) yield (Mg ha") in management practices
across plant density during the 2002, 2003, 2004, 2005 and four-year average at
Kellogg Biological Station, Hickory Comers, Ml. ................................................. 68

Table 6. Days to flowering, plant height, ears per plant, grain moisture and test
weight of corn (Zea mays L.) in management practices across plant density
during the 2002, 2003, 2004 and 2005 growing seasons at Kellogg Biological
Station, Hickory Comers, Ml. .............................................................................. 69

Table 7. Days to flowering, plant height, ears per plant, grain moisture and test
weight of corn (Zea mays L.) at four plant densities across management
practices during the 2002, 2003, 2004 and 2005 growing seasons at Kellogg
Biological Station, Hickory Comers, MI. .............................................................. 70

Table 8. Effect of monoculture and interseeding at four com (Zea mays L.)
densities on red clover (Trifolium pretense L.) or AC Greenfix (Lathyrus sativum
L.) DM (Mg ha"), density (plants m'2) and height (cm) in fall during the 2002,
2003, 2004 and 2005 growing seasons at Kellogg Biological Station, Hickory
Comers, Ml. ........................................................................................................ 71

Table 9. Mean interseeded red clover (Trifolium pretense L.) and AC Greenfix
(Lathyrus sativum L.) DM (Mg ha"), density (plant m‘z) and height (cm) at four
corn (Zea mays L.) plant densities in fall 2002, 2003 and 2004 at Kellogg
Biological Station, Hickory Comers, Ml. .............................................................. 72

Table 10. Effect of interseeding com (Zea mays L.), at four plant densities, on red
clover (Trifolium pretense L.) DM (Mg he“) the subsequent spring in 2003, 2004
and 2005 at Kellogg Biological Station, Hickory Comers, Ml. ............................. 72

Chapter Two

Table 1. Nitrogen concentration (9 kg“) in corn (Zea mays L.) grain across
management practices and corn plant density during the 2002, 2003, 2004 and
2005 growing seasons at Kellogg Biological Station, Hickory Comets, Ml. ...... 110

Table 2. Significance of the effect of plant density (PD) and management
practices (MP) across four years (Y) on nitrogen concentration of corn (Zea mays
L.) grain (G), leaf (L), stalk (S), ear leaf (EL), cover crop sampled in fall (FC) and
cover crop sampled in spring (SC); on N accumulation of com grain (G), ear leaf
(EL), cover crops sampled in fall (FC) and cover crop sampled in spring (SC);
and on SPAD-502 readings in 2004 and 2005 at Kellogg Biological Station,
Hickory Comers, Ml. ......................................................................................... 11 1

Table 3. Pearson correlation coefficients for chlorophyll content, plant density,
grain N concentration, ear leaf N concentration and yield of corn (Zea mays L.)
during the 2004 and 2005 growing seasons at the Kellogg Biological Station,
Hickory Comers, Ml. (n=64). ............................................................................. 1 12

Table 4. Corn (Zea mays L.) grain N content (kg ha") in four management
practices across corn plant density during the 2002, 2003, 2004 and 2005
growing seasons at Kellogg Biological Station, Hickory Comers, Ml. ............... 113

Table 5. Corn (Zea mays L.) leaf N concentration (9 kg") across management
practices and corn plant density during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Corners, Ml. ............................. 113

Table 6. Corn (Zea mays L.) stalk N concentration (9 kg") across management
practices and corn plant density during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Comers, Ml. ............................. 114

Table 7. Leaf chlorophyll content (SPAD-502 meter readings) across
management practices and com (Zea mays L.) plant density during the 2004
growing season at Kellogg Biological Station, Hickory Comers, Ml. ................. 115

Table 8. Leaf chlorophyll content (SPAD—502 meter readings) across
management practices and corn (Zea mays L.) plant density during the 2005
growing season at Kellogg Biological Station, Hickory Comers, MI. ................. 116

Table 9. Dry matter (9), N concentration (9 kg") and N content of 10 ear leaves
per plot of corn (Zea mays L.) across management practices and corn plant
density during the 2004 and 2005 growing seasons at Kellogg Biological Station,
Hickory Comers, Ml. ......................................................................................... 117

Table 10. Nitrogen concentration (9 kg") and accumulation (kg ha") of
interseeded and monoculture red clover (Trifolium pretense L.) or AC Greenfix
(Lathyrus sativum L.) at four com (Zea mays L.) plant densities in fall 2002, 2003,
2004 and 2005 at Kellogg Biological Station, Hickory Comers, MI. .................. 118

Table 11. Nitrogen concentration (9 kg") and accumulation (kg ha") of red clover
(Trifolium pretense L.) during the subsequent spring in 2003, 2004 and 2005 at
Kellogg Biological Station, Hickory Comers, Ml. ............................................... 119

Table 12. Comparison of N concentration of interseeded red clover (Trifolium
pretense L.) at the same corn (Zea mays L.) density from the first sampling in fall
(the year of establishment) to the second sampling in spring (the subsequent
spring) in 2002, 2003, 2004 and 2005 at Kellogg Biological Station, Hickory
Comers, Ml. ...................................................................................................... 1 19

Chapter Three

Table 1. Effect of com (Zea mays L.) density on N accumulation (kg ha") of
interseeded red clover (Trifolium pretense L.) or AC Greenfix (Lathyrus sativum
L.) in fall during 2002, 2003 and 2004 and the subsequent spring during the
2003, 2004 and 2005 at Kellogg Biological Station, Hickory Comers, MI. ........ 144

Table 2. Dry been (Phaseolus vulgaris L.) yield (kg ha") and seed N content (kg
ha") under various management practices during the 2003, 2004 and 2005
growing seasons at Kellogg Biological Station, Hickory Comers, MI. ............... 144

Table 3. Seed moisture mntent (g kg") and 100 seed weight (g) of dry bean
(Phaseolus vulgaris L.) in various management practices after harvest during the
2003, 2004 and 2005 growing seasons at Kellogg Biological Station, Hickory
Comers, Ml. ...................................................................................................... 145

Table 4. Effect of management practices on N concentration (9 kg") of seed,
leaves and stem of dry bean (Phaseolus vulgaris L.) a few days before harvest
during the 2003, 2004 and 2005 growing seasons at Kellogg Biological Station,
Hickory Comers, MI. ......................................................................................... 145

xi

Table 5. Effect of management practices on soil nitrate and ammonium after corn
(Zea mays L.) harvest in fall 2002, 2003, 2004 and 2005 and before planting dry
bean (Phaseolus vulgaris L.) during the subsequent spring of 2003, 2004 and
2005 growing seasons at Kellogg Biological Station, Hickory Comers, Ml. Each
year, planting occurred in a different field .......................................................... 146

Table 6. Comparison of soil NO’3-N concentration in fall [the year of corn (Zea
mays L.) establishment] to the second sampling under the subsequent spring
(before planting beans) in the same management practices in 2002, 2003, 2004
and 2005 at Kellogg Biological Station, Hickory Comers, MI. ........................... 147

Table 7. Comparison of soil NO'3-N and soil NHH-N concentration in fall and

subsequent spring under the same management practices in 2004 and 2005 at
Kellogg Biological Station, Hickory Comers, MI. ............................................... 147

xii

LIST OF FIGURES

Chapter One

Figure 1. Monthly average minimum and maximum temperature, and total
monthly precipitation during the 2002, 2003, 2004 and 2005 growing seasons
compared with the 30-year monthly average at Kellogg Biological Station,
Hickory Comers, MI. ........................................................................................... 73

Figure 2. Total daily Precipitation during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Corners, Ml. ............................... 74

Figure 3. Weekly percent volumetric soil moisture at 0 to 18 and 18 to 36 cm
depths in management practices across corn density during the 2004 (3a and b)
and 2005 (30 and d) growing seasons at Kellogg Biological Station, Hickory
Corners, Ml. Within week error bars are similar for all treatments ....................... 75

Figure 4. Weekly percent volumetric soil moisture at 0 to 18 and 18 to 36 cm
depths at four corn densities across management practices during the 2004 (4a
and b) and 2005 (4c and d) growing seasons at Kellogg Biological Station,
Hickory Comers, Ml. Within week error bars are similar for all treatments. ......... 76

Figure 5. Relationship between interseeded cover crop dry matter and com plant
density from 2002 to 2004. Data are averaged across years. Each point is the
mean of 10 samples. ........................................................................................... 77

Chapter Two
Figure 1. Monthly average minimum and maximum temperature, and total

monthly precipitation during the 2002, 2003, 2004 and 2005 growing seasons
compared with the 30-year monthly average at Kellogg Biological Station,

Hickory Comers, Ml. ......................................................................................... 120
Figure 2. Total daily precipitation during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Comers, Ml. ............................. 121
Chapter Three

Figure 1. Monthly average minimum and maximum temperature, and total
monthly precipitation during the 2002, 2003, 2004 and 2005 growing seasons
compared with the 30-year monthly average at Kellogg Biological Station,
Hickory Comers, MI. ......................................................................................... 148

xiii

Figure 2. Total daily precipitation during the 2003, 2004 and 2005 dry been
growing seasons at Kellogg Biological Station, Hickory Comers, Ml. ............... 149

Figure 3. Total daily precipitation and average temperature from 20 September to
25 November during the 2003, 2004 and 2005 growing seasons at Kellogg
Biological Station, Hickory Comers, Ml ............................................................. 150

Figure 4. Total daily precipitation and average temperature from 1 April to 31

May during the 2003, 2004 and 2005 growing seasons at Kellogg Biological
Station, Hickory comers, Ml. ............................................................................. 151

xiv

Literature Review

Introduction

There is a growing interest in cover crops and green manure in both
developing and developed nations due to cost and availability of agricultural
inputs, and concems about environmental pollution. Cover crops can provide
ground cover, increase soil organic matter and water infiltration, reduce soil
erosion, increase the population of soil microbes, suppress weeds, and reduce
insect pests and diseases (Sarrantonio, 1994; Dinesh et al., 1999; Peachy et al.,
1999; Ross et al., 2001; Smeltekop et al., 2002; Hendrickson, 2003). Cover crops
are classified as leguminous and non-leguminous. The major advantage of
legume cover crops compared to grass cover crops is the nitrogen (N)
contribution to the soil through symbiotic fixation. In contrast, some non-legume
cover crops are used to scavenge soil N that might be lost due to leaching and
are effective in increasing soil organic matter by supplying C through increased
biomass production (Sainju et al., 2000; Chambliss et al., 2003; Snapp et al.,
2005). Legume cover crops may convert up to 227 kg of atmospheric N ha" year'
1 and can provide all or part of the N needed by the subsequent crop (Cavigelli,
1998; Griffin et al., 2000; Diver et al., 2001 ). Legume cover crops can influence
carbon (C) and N mineralization, wet aggregate stability, and light fraction1 which

can be used to estimate soil organic matter (Biederbeck et al., 1998).

 

' Soil organic matter quality can be estimated by the characterization of a light fraction. The light
fraction is material that will float on the top of dense salt solution. The light fraction is generally
considered to be material rich in plant nutrients, relatively large in size compared to other soil
organic matter components and insoluble in water.

Studies have been conducted to assess the effect of monocnopping or
interseeding legume cover crops on subsequent corn (Zea mays L.) yield
(Jeranyama et al., 1998; Hively and Cox, 2001; Abdin et al., 1998). Research has
shown that yield of corn following a cover crop was higher compared with where
a cover crop had not been established (Vyn et al., 1999; Balkcom and Reeves,
2005). Most of these studies have looked at the effect of cover crop and/or
various rates of fertilizer on succeeding corn yield. However little or no research
has focused on the effect of cover crop versus N fertilizer on corn yield and
quality at various corn densities. Similarly, no research has looked at the effect of
interseeded red clover (Trifolium pretense L.) in various corn densities on
subsequent dry bean yield and quality.

Cover crops can be intercropped/interseeded or used in crop rotation as
the sole crop. Incorporating a cover crop through rotation is not economically
viable in many developing countries because of the loss of income from that field
for an entire growing season. In many developing countries of the tropics, land
constraint and economics are factors limiting the inclusion of cover crops into the
rotation system. lnterseeding is an alternative to rotating cover crops with cash
crops. lnterseeding presents the advantage of producing two or more crops on
the same land at the same time, while diversifying food supply. However, recent
interest in incorporating cover crops into cropping systems through interseeding
has revealed some production or management challenges. Among the
challenges are the choice of cover crops (some do not perform well because they

are not shade tolerant), growth habit (some are annual and cannot be used late

in the fall for biomass production), time of interseeding (when interseeded early,
cover crops can compete with the main crop; interseeded late, cover crops do
not perform well) and crop density in interseeding system (not knowing the right
crop density for intercropping). Some of these challenges have been studied
extensively and others have not. For example, it is well documented that red
clover is shade tolerant and could be used in an intercropping system with dense
canopy crops such as corn (Bowman et al., 1998; Sattell et al., 1998; Feet,
1995). Studies have been conducted on the time of cover crop establishment in
corn. Thompson and Wagner (2000) obtained satisfactory results when
interseeding red clover and nitro alfalfa (Medicago setiva) when they were
established after the second cultivation of the corn crop. Mutch and Martin (1998)
suggested that cover crops should be interseeded into corn between V4-V6
growth stages. However, other factors such as density of the main crop in an
interseeding system with a cover crop have not been addressed.

Planting corn in a plowed legume cover crop at various com densities can
help to understand how high corn density can be increased without using N
fertilizer in the production system. lnterseeding cover crops Into corn at various
corn densities can help assess cover crop growth, biomass and N content during
and after the growing season. Planting dry bean (Phaseolus vulgaris, L.) after

interseeded cover crops can help assess cover crop effect on dry been yield and

quality.

lnterseeding system

lnterseeding is a system of producing various crops in the same area at
the same time. The interseeding system has been used by low-input, small-scale
agricultural systems for many years (Andrews and Kassam, 1976; Foulds, 1987;
Vanderrneer, 1992). In many developing countries, the lack of agricultural inputs
such as mineral fertilizer and the reduction of farm size due to population growth
are among factors that have increased the use of intercropping. Further
advantages of interseeding are a diversified food supply and a more equal
distribution of the field work during the cropping season. lnterseeding helps to
better utilize farm labor, time, and equipment since plants have different
management requirements in term of planting and harvesting time. In the low
input agriculture of the tropics, food crops are mainly intercropped to reduce risk
in crop failure caused by unfavorable weather conditions as well as pests and
diseases (Trenbath, 1993; Carruthers et al., 1998; Sauerbom et al., 2000;
Maluleke et al., 2005). In developed countries, intercropping food crops has
received less attention from farmers and scientists due to difficulties of planting
and harvesting two different food crops (Hartwig and Ammon, 2002). However, in
recent decades the search for crop management practices that increase
sustainability of natural resources (reduce environmental pollution) is one of the
driving forces for the use of interseeding (Baumann et al., 2002).

Intercropping adds a spatial diversity to species across the field. In various
farming systems, intercropping has been used to optimize crop use of water,

nutrients and sunlight (Ghaffarzadeh, 1999; Sullivan, 2003a). In an intercropping

study, Zhang and Li (2003) showed that N uptake by intercropping of wheat
(Triticum eestivum) and corn was greater than in sole cropping under the same N
supply. Furthermore, com improved the uptake of iron by peanut (Arachis
hypogaea), and faba beans (Vicie faba) enhanced N and P uptake by
intercropped corn. Intercropping is more advantageous than monocropping due
to less competition for resources between plants within the same species
(Sullivan, 2003a). Plants with different architectures (plant height: tall vs. short,
rooting system: deep vs. shallow, canopy density: dense vs. light, and crop cycle:
long vs. short maturity) are used for their potential complementarity in sunlight
and water utilization to maximize crop production.

To achieve complementarity and reduce competition between intercrops,
four things need to be considered: spatial arrangement, plant density, maturity
dates, and plant architecture (Kantor, 1999; Akunda, 2001; Beueriein, 2001;
Sullivan, 2003a).

a. Spatial an'engement:

In intercropping systems, crops can be arranged in three different ways:

- Row intercropping: growing two or more crops at the same time with at least
one crop planted in rows.

- Sfiip intercropping: growing two or more crops together in strips wide enough to
permit separate crop production using machines, but close enough for the crops
to interact.

- Mixed intercropping: growing two or more crops together in no distinct row

arrangement.

b. Plant densmc' .

In intercropping systems, crop density is reduced from its full rate. Reducing the
plant density decreases competition and increases output of both crops when
compared to growing the same crops in monoculture on the same area of land.
In comparing sorghum (Sorghum bicolor) and soybean (Glycine max) yield in
sole and intercropping systems at various densities, Akunda (2001) found that
recommended crop density had the highest yield with intercropping, whereas
sole crops had highest yield at the highest crop density. The challenge comes in
knowing the optimum plant density for companion crops.

c. Mammy dates:

lntercrops with different maturity dates present the advantage of variations in
resource demands for nutrients, water, sunlight and labor. Competition is
lessened when one crop matures before its companion crop. Competition
between corn and legume cover crops is reduced when cover crops are
interseeded at corn Iaybay, approximately four weeks after planting corn
(Bowman et al., 1998; Jeranyama et al., 1998; Mutch and Martin, 1998).
Interseeded cover crops grow slowly under com and then rapidly as more light is
available when com dries down and after harvest.

d. Plant architecture:

Plant architecture between and among species has to be considered to reduce
competition for better use of nutrients, water and sunlight. For example using a
legume and cereal is the common practice to maximize the use of energy for

crop production, since both have different nutrient requirements. The goal is to

capitalize on the beneficial interactions between crops while avoiding negative
interactions. The Land Equivalent Ratio (LER) is used to measure the effect of
both positive and negative interactions between crops. The LER compares the
yield from growing two or more crops together with yield from growing the same
crops in monoculture. lntra and inter-species competition in the interseeding
system may affect yield and crop quality of companion crops (Baumann et al.,
2001; Blackshaw et al., 2001; Sullivan, 2003a).

The success of any intercropping system depends on the balance of
positive and negative interactions between crop components. lnterseeding can
provide a significant management challenge to both conventional and organic
growers due to different management practices and the economics related to .
each system. Incorporating cover crops in crop production might require a
change in the cropping system. For instance, planting a cover crop into an
established corn crop in June or late in fall, may delay the planting of the
succeeding crop in order to allow greater cover crop biomass accumulation in the
following spring. This may require planting a short season crop such as
vegetables instead of field crops. lnterseeding may also present the challenge of
cover crop establishment and weed control in conventional and organic farming.
Herbicide use in conventional systems may hinder the germination of the cover
crop. For example, it is not recommended to establish a clover stand in corn
treated with a preemergence broadleaf herbicide such as Atrazine (Knorek and
Staton, 2004). In organic production, mechanical weed control after the

establishment of the cover crop may be the most pertinent issue. Another

disadvantage is the timing of establishment. If established eariy, the cover crop
can compete with the main crop for nutrients and moisture, and if planted too
late, the main crop may limit the growth of the cover crop (Stute, 2000; Miles and

Nicholson, 2003).

Cover crops

Cover crops are grown to provide ground cover, whereas green manures
are grown for soil improvement purposes and incorporated while they are green
or soon after they flower. Cover crops should exhibit as many positive good
characteristics as possible, including fast germination and emergence,
competitiveness with weeds rather than the major crops, tolerance to adverse
climatic and soil conditions (drought), easy suppressibility, fertility benefits and
low cost of establishment (Roos, 2006). Weed reduction by cover crops can be
directly proportional to cover crop growth and canopy production, as shown by
Fisk et al. (2001), who suggested that the quantity of ground cover produced by
weeds was inversely proportional to that produced by the crops. Cover crops are
grown primarily to prevent or reduce soil erosion. In crop production, cover crops
may be selected to maximize benefits of biomass and N production.

Cover crops are used also for other purposes, either as catch crops or
smother crops. When used as catch crops, cover crops are established after
harvesting the main crop and are used to reduce nutrient leaching from the soil
profile, primarily nitrate (McLenaghen et al., 1996; Sullivan, 2002; Weinert et al.,

2002; Kristensen and Thorup-Kristensen, 2004). Legumes are not as effective as

non-legumes in sequestering and recycling soil inorganic N and should be grown
where little inorganic N is left in the soil (Sainju et al., 1998; lsse et al., 1999;
Sainju et al., 2000; Thorup-Kristensen et al., 2003). However, in a study on
sequestering residual N03 by cover crops, red clover was as effective as rye
(Secele cereale, L), oilseed radish (Raphunus sativus [L.] var oleiferus Metzg
[Stokes]) and cat (Avene setive L.), suggesting that N management in the com
cropping sequences could be improved by intercropping red clover (Vyn et al.,
2000). A catch crop is usually planted a few weeks before or just after the main
crops is harvested. Planting cereal rye following com harvest helps to scavenge
residual N, thus reducing the possibility of groundwater contamination (Brooks et
al., 2006). In this instance, the rye catch crop also functions as a winter cover
crop. When used as a smother crop, cover crops control weeds (Ross et al.,
2001; Miles and Nicholson, 2003). These cover crops are selected based on the
ability to compete with weeds, good seed germination and good plant vigor.
Cover crop ability to control weeds varies from one species to another (Ross et
al., 2001). Various studies have shown that cropping systems using annual cover
crops and red clover can significantly reduce weed dry weight and density
(Singer et al., 2000; Fisk et al., 2001; Ross et al., 2001). Fitting a cover crop into
a crop production system can be challenging. Important cover crop
characteristics are fast-growth, drought-tolerance, shade tolerance and minimal
management requirement. Species with the potential to reduce pest populations
are chosen, while those that harbor diseases or arthropod pests of the cash

crops are avoided. In a study conducted in the UK, red clover was successfully

used as a mean to reducing pest damage on winter wheat (Brooks et al., 2006).
In Canada, Studies have shown that the use of legume cover crops that are
resistant to grasshoppers could reduce the overall need for insecticides because
these crops will not likely become epicenters of grasshopper outbreaks (Olfert et
al., 1995).

A cover crop may be grown in a pure stand or mixed with other crops
during all or part of the year. It may be a fellow cover crop, winter cover crop,
summer green manure crop, living mulch, catch crop or a forage crop (Diver et
al., 2001). Specific terms have been used to refer to the incorporation of cover
crops into cropping systems (Agboola,1982;Davis, 1997; Nafziger, 2002).

- Double-cropping: also know as sequential cropping, refers to planting a second
crop after the first crop is harvested.

- Intercropping: also known as interseeding or underseeding is growing two or
more crops together on the same field at the same time.

- Monocropping, monoculture or sole cropping: is growing a cover crop as a
single crop in a field.

- Relay intercropping: refers to the planting of second crops when the standing
crop is at its reproductive stage.

- Living mulch: is a system where the cover crop is established prior to row crop
establishment and the row crop is established directly into all or a portion of the
suppressed or actively growing cover crop species. A living mulch is a cover crop

that is intercropped with an annual or perennial cash crop.

10

- Alley cropping: Alley cropping is the planting of trees or shrubs in two or more
sets of single or multiple rows with agronomic, horticultural, or forage crops.
Cover crops may be annual, biennial, or perennial herbaceous plants.
a. Annual cover crops:
They complete their life cycle in one growing season and are divided into
summer and winter annuals.
- Summer annual cover crops:
These cover crops are established during a portion of the summer growing
season and include oats, sorghum-sudan grass (Sorghum sudanense ), field
peas (Pisum sativum), sweet clover (Melilotus spp.), velvet bean (Mucuna
pruriens ) and buckwheat (Fagopyrum esculentum Moench). Summer annual
cover crops germinate and mature without a cold snap and usually tolerate warm
temperatures (Bowman et al., 1998; Creamer and Baldwin, 1999). Warm-season
cover crops can be used to fill a niche in crop rotations, to improve the conditions
of poor soils or to prepare land for a perennial crop (Sullivan, 2003b). Legume
cover crops such as cowpeas (Vigna unguiculata), annual sweet clover, or velvet
beans may be grown as summer green manure crops to add organic matter
along with N. Non-legumes such as sorghum-Sudan grass, Pearl Millet
(Pennisetum glaucum), or buckwheat are grown to provide biomass, smother
weeds, and improve soil tilth (Sullivan, 2003b). Since in the temperate climate
most of summer annual cover crops are killed by frost, no herbicide control is
needed the following spring except for buckwheat, which needs to be killed in a

timely manner to prevent it from shedding seed.

11

- Wrnter Annual cover crops:

Winter annual cover crops include cool-season legume such as some clovers,
vetches, medics (Medicago spp.), and field peas and non-legumes such as rye,
wheat, barley (Hordeum vulgare), and ryegrass (Lolium multiflorum). Winter
annual cover crops are more cold-tolerant and require cold temperature to set
seed (Bowman et al., 1998). These winter cover crops are selected for their
tolerance to cold and are planted in late summer or fall to provide soil cover
during the winter. Cereal cover crops such as winter rye and winter wheat are
used as cover crops to allow the production of biomass for ground cover and to
absorb excess nitrate from the soil (Sullivan, 2003b; De Bruin et al., 2005). Some
cereal cover crops can be incorporated, mowed or harvested for silage. If cover
crops are used as mulch, they will provide soil moisture conservation in case of
water stress during the growing season. If drought conditions occur directly
before crop establishment, there is a risk of crop water stress due to depletion of
soil moisture by the cover crops. The major benefits of a winter cover crop are
soil structure improvement, soil protection in the winter, reduced nitrate leaching
and the addition of organic matter and N in the case of legumes.

b. Biennial cover crops:

A biennial cover crop grows vegetatively during its first year and then sets seed
during its second year (Bowman et al., 1998). Biennial cover crops include
legumes such as sweetclover. Red clover is a perennial that acts like a biennial.
Annual ryegrass has a biennial tendency in cool regions because it will regrow

quickly and produce seed in late spring if it over-winters (Bowman et al., 1998).

12

c. Perennial cover crops:

Perennial cover crops are usually used in perennial crops such as orchards to
provide permanent covers (Hartwig and Ammon, 2002). They provide excellent
weed control and serve as a food source as well as refuge for beneficial insects.
There are various types of perennials, including short-lived perennials and long-
lived perennials. Red clover, which is a short-lived leguminous perennial, can be
established in summer, fall or frost-seeded late in the winter. Red clover can be
killed in the spring of the following year by tillage or herbicides. White clover
(Trifolium repens L.), a longer-lived leguminous perennial that grows more slowly
than red clover, is often used as living mulch in vegetable systems (Bowman et
al., 1998). Other leguminous perennial cover crops include perennial forages
such as Kura clover (Trifolium ambiguum L.) and alfalfa that are used in annual
crops to enhance the survival and improve the efficiency of natural enemies of
pests (Schmidt et al., 2004).

Biennial or perennial legumes can fit many different niches, sometimes
grown for a short period between cash crops. They can be interseeded into other
crops and left to grow after cash crop harvest and used as forage. In this case
they are functioning more as a rotation crop than a cover crop but are providing
many benefits, such as erosion and weed control, organic matter and N
production. They also can break weed, disease and insect cycles. Deep-rooted
biennial and perennial legume cover crops are not recommended for the most
severely drought-prone soils, as their excessive use of soil moisture will

negatively affect yield of the following crops (Biederbeck et al., 2000).

13

Red clover

Red clover has high cold tolerance, good N fixing capabilities, and good
shade tolerance (Bowman et al., 1998). Sattell et al. (1998) have grouped red
clover in two varieties/cultivars based on eariy flowering or late flowering types:
Mammoth red clover and Medium red clover. ‘Memmoth Red clover’ is one of the
most common late flowering, or single cut, varieties and is used at high
elevations or where the growing season is short. It is a winter-hardy perennial
that grows in a round clump without flowering stems the first year. 'Medium Red
clover' is an early flowering type or double cut (because it can be out several
times in a year for hay). It produces tall, erect flowering stems with leaves at the
nodes the spring after it is planted. Although they are perennials, early flowering
red clovers most often are treated as winter annuals (turned under or killed in
spring) when used as a cover crop. In Michigan, Knorek and Staton (2004)
classify red clover into three common cultivars: Michigan mammoth, Canadian
mammoth (also known as Altaswede clover) and medium red clover. Their
research suggests that Michigan mammoth performs better than the other red
clovers when frost-seeded into well-fertilized wheat. Canadian mammoth clover
does not tolerate the increased shading and competition from well-fertilized
wheat.

While red clover has low to moderate drought tolerance, it does not
tolerate flooded soil. Red clover can be planted in spring, summer and fall.
Generally, red clover is frost-seeded in small grains like wheat by the middle of

March. Red clover may also be sown in eariy summer, usually intercropped with

14

a cash crop. Red clover seedlings are very competitive with weeds. In fall, red
clover can be established before or after the harvest of the cash crop.
Traditionally, red clover is drilled at 9-14 kg ha" and overseeded at 11-20 kg ha"
(Bowman et al., 1998). In Michigan, the recommended red clover seeding rate is
11-13 kg ha" (Knorek and Staton, 2004), whereas Sattell et al. (1998) suggest
17- 28 Kg ha" for Oregon. Early seeding gives best stands, and if red clover is
allowed to go to seed, it will produce enough seed to re-establish itself.

For plow-down, red clover can be killed in the fall or the spring by tillage or
herbicide application. Timing is important when killing red clover in the spring.
Red clover should be allowed to grow as long as possible in the spring to add
additional nutrients to the soil and suppress weeds, but it can also use up soil
moisture and hurt the following cash crop if dry conditions exist. Red clover fixes
N and releases it slowly to the following crop. Research results have shown that
red clover can provide all or most of the N needed by a subsequent corn crop
(Vyn et al., 1999; Hively and Cox, 2001). Red clover can produce 2-3 tons of
biomass, can accumulate 79-168 kg ha" of N, and also can increase microbial
activity and accelerates the decomposition of surface crop residues (Doran et al.,

1987; Bowman et al., 1998; Drury et al., 1999).

Chickling vetch (Lathyrus sativum L.)
Chickling vetch (grass pea, guaya in Ethiopia, Keshari in India, garbanzo
in Venezuela, pois carré in France, etc.) is an annual legume crop grown in

different parts of the world (Campbell, 1997; IPBO, 2006; Small, 1999) as food

15

and sometimes as animal fodder or green manure. In North America, chickling
vetch is used primarily as a green manure alternative to summer fellow in small
grain production systems to reduce wind and water erosion and to improve soil
(Small, 1999). Chickling vetch seeds have a protein content of 25-28% (Bellido,
1994). In the past decades, chickling vetch has received more attention as a
multi-use crop in arid regions, because it is drought tolerant and adaptable to
marginal soils (Biederbeck et al., 1993;Biederbeck and Bouman, 1994;
Campbell, 1997).

Although chickling vetch is rich in protein and improves soil N, it contains
significant amounts of an anti-nutritional compound B-N-oxalylamino-L—alanine,
also known as B—N-oxalyl-L-a, B-diaminopropionic acid or ODAP (Chen et al.,
2000; Grela et al., 2001). There are three categories of ODAP concentration in
Lathyrus spp: low=0.06%, grass pea; medium=0.2 to 0.3%, chickling vetch; and
high=1.0%, Indian varieties (Klassen, 2002). The scientific community speculates
that ODAP probably confers resistance to pests or climatic extremes (Raloff,
2000). The ODAP is a neurotoxin amino acid known to cause muscular rigidity,
weakness, and paralysis of the leg muscles (Munro, 2003). Soaking and heating
before cooking are the two methods used to detoxify chickling vetch seeds in
order to help reduce the risk of the neurotoxin (Raloff, 2000). When used as
forage, the hay should be removed before it sets seed because it contains the
neurotoxin and may cause problems if fed in large quantities to cattle over an
extended period of time (DFS, 2003). Canadian plant breeders at the

lntemational Center for Agricultural Research in the Dry Areas (ICARDA) have

16

concentrated their efforts on developing low-ODAP cultivars. In recent years, a
low-ODAP variety of chickling vetch called ‘AC-Greenfix’ was developed and
released by the Semiarid Prairie Agricultural Research Centre (SPARC) in Swift
Current, Saskatchewan, Canada (DFS, 2003). Agriculture and Agri-food Canada,
which has been very active in developing low toxin varieties, has recommended
that low toxin type be referred to as grass peas while high toxin types be referred
to as chickling vetch (Klassen, 2002). AC Greenfix's low ODAP content, ability to
overcome the problems of soil moisture depletion and to fix high amounts of N
has led to its increased use and reduced the use of other more traditional green
manures (Krause and Krause, 2003). AC Greenfix can produce 2242 to 4483 kg
ha" of dry matter (DFS, 2003). Pauly (2004) reported that chickling vetch grown
in dry land areas produced enough N to meet the requirements of a subsequent
cereal crop.

Various management practices have been suggested for maximum benefit
from the cover crop (DFS, 2003) . AC Greenfix planted in spring yields best
results because it can tolerate temperatures as low as -6 to -3° C. Fall planting in
August when moisture is sufficient or with adequate watering can also yield
satisfactory results. AC Greenfix grows slowly for the first 30-40 days, with plants
in full bloom by about 60 days. For maximum N production, the plants should be
plowed under before pods begin filling, about 40-60 days after planting. The
seeding rate for AC Greenfix is 80 kg ha". AC Greenfix grows best and produces
greater dry matter when planted in N-depleted soil (DFS, 2003). It should be

clipped before seedpods begin to fill and will regrow if moisture is sufficient.

l7

Because AC Greenfix is such a short season crop, it could fit in various cropping

systems to provide N and organic matter.

Cover crop adoption and management constraints

Optimal success with cover crops depends on species selection, proper
management techniques, and a good understanding of the agro-ecosystem
(Roos, 2006). Cover crops present potential negative challenges related to cost
of establishment (seed cost, seeding and killing methods), depletion of soil
moisture, reduction of spring soil temperatures, allelopathy, and habitat for pests
and disease (Ewing et al., 1991; Roos, 2006). Farmers will increase adoption or
use of cover crops only if these negative aspects are minimized.

Seed cost, method of seeding, and method of killing the cover crop should
be considered. The benefits of cover crops need to be assessed in terms of cash
returns as it relates to a reduced need for inputs (mineral fertilizer, pesticides,
etc.) as well as the long-ten'n impact on soil improvement (soil structure, organic
matter, etc.). The benefit of the cover crop use has to consider cover crop seed
cost and establishment in comparison to N fertilizer cost reduction and crop yield
and quality. Soil moisture is another critical factor when considering cover crop
use. All cover crops require water for good growth; however, some cover crops
such as AC Greenfix use less water than others (Biederbeck et al., 1993;
Biederbeck and Bouman, 1994). Soil moisture use by cover crops is a concern
especially in areas with less precipitation in the spring before the establishment

of the main crop. Abdin et al. (1998) reported that crimson clover (Trifolium

18

incematum L.) competed with com when the moisture was limiting. Blackshaw et
al. (2001) showed soil water content reduction by sweetclover at the time of
seeding spring wheat compared to tilled fallow. The earlier the cover crop is
sown in the fall or the longer it is allowed to grow in the spring, the more water it
will use (lngels et al., 1996).

Additional management is required when cover crops are added to a
cropping system. Turning cover crops under or suppressing them requires
additional time and expense compared to having no cover crop at all. If a cover
crop is not winter-killed, other methods such as mechanical or chemical control
should be considered before the crop competes with the next cash crop. For
plow down, herbicide use is necessary where tillage does not provide full control
of the cover crop. Some cover crops need to be killed at a certain time in their life
cycle to ensure that they do not set seed and become a weed problem in future
years. For example, hairy vetch (Vicie villosa Roth) is not a good cover crop to
use when small grains are included in the rotation. If the vetch ever goes to seed,
it can become a terrible weed in a small grain crop (Sullivan, 2003b).

Some cover crops produce chemicals that can hinder weed germination
and/or crop growth (Ohno and Doolan, 2001; Dhima et al., 2006). Several
species of cover crops can affect the cash crop if the cash crop is planted too
soon after the cover crop is plowed down. Cover crops with allelopathic
properties can reduce the germination or establishment of the cash crop, and a
large amount of dry matter left by non-legume cover crops can tie up N needed

by the succeeding cash crop (Hamilton, 1998). To minimize yield reduction of

19

corn following winter-hardy cereal grain cover crops, it is recommended to
terminate the cover crop more than 14 days prior to com planting and use starter
fertilizer (Singer and Kaspar, 2006). Duiker and Curran (2005) found that with
adequate N, planting corn 7 to 10 days after killing rye does not reduce corn
yield. In a study conducted in the USA, Blacksburg, Virginia, Vaughan and
Evanylo (1998) found that com yields were reduced due to N immobilization
when rye biomass increased significantly. Cover crop residues can also lead to

cooler soils in the spring.

Influence of legume cover crop on crop yield and N content

When used in monocropping or interseeding, legume cover crops can
improve overall soil quality and contribute to yield improvement of the succeeding
crop (Jeranyama et al., 1998; Vyn et al., 2000; Hively and Cox, 2001; Balkcom
and Reeves, 2005). The use of cover crops such as annual medics can
significantly reduce weed density and dry weight and thereby its incidence on the
following crops (Fisk et al., 2001). Teasdale and Daughtry (1993) reported weed
density and biomass reduction by hairy vetch compared with a fellow treatment.
A leguminous cover crop interseeded with a row crop such as corn can supply N
for the subsequent crop. Bruulsema and Christie (1987) found that yield of com
following red clover and alfalfa was comparable to yield obtained by application
of 90 to 125 kg of N ha". Yield of a succeeding corn crop was increased
following intercropped legume cover crops compared to continuous corn.

Interseeded legume cover crops reduced fertilizer needs of the subsequent com

20

crop by 18 to 36 kg ha" (Jeranyama et al., 2000). Corn following interseeded
medium red clover and Dutch white clover produced greater yield compared to
corn following no cover crop or rye seeded after soybean [Glycine max (L.) Merr.]
harvest (Hively and Cox, 2001).

Few research studies currently exist on dry been, following a cover crop.
Some studies have been conducted to evaluate the effect of cover crops on a
subsequent snap bean crop. Yield of snap beans following a legume cover crop
was similar to yield of beans supplied with 90 kg ha" of N fertilizer (Skarphol et
al., 1987). Furthermore, research conducted in Maryland found that been
following cover crops required less N in some cases (Past, 1995). Beans
following hairy vetch, Austrian winter pea and crimson clover covers did not
respond to additional N, whereas bean succeeding wheat and wheat/legume
mixes needed additional N to achieve their highest yield. Bean yield in cropping
systems with cover crops were higher compared to those grown without cover
crops, particularly in the drier year of the experiment. However, in an
investigation of the effect of conventional system, rye and hairy vetch cover crops
on snap bean, Mwaja et al. (1996) found snap been yield was higher in the
conventional management. An investigation of the impact of interseeded cover
crops in various corn densities on dry beans yield is critical to assess their effects

on bean yield and quality.

21

References:

Abdin, 0., BE. Coulman, D. Cloutier, M.A. Faris, X. Zhou, and D.L. Smith. 1998.
Yield and yield components of corn interseeded with cover crops. Agron.
J. 90:63-68.

Agboola, AA. 1982. Crop mixtures in traditional systems, In L. H. MacDonald,
ed. Proc. of Workshop on Agro-forestry in the African Humid Tropics.
lbadan, Nigeria. 27 April - 1 May 1981. United Nations University Press,
Tokyo, Japan.

Akunda, E.M.W. 2001. Crop yields of sorghum and soybeans in an intercrop. J.
Food Technol. in Africa 622-4.

Andrews, D.J., and AH Kassam. 1976. The importance of multiple cropping in
increasing world food supplies p. 1-11, In Papendick, et al., eds. Multiple
cropping. ASA Special Publ. 27, Am. Soc. Agron., Madison, WI.

Balkcom, KS, and D.W. Reeves. 2005. Sunn-hemp utilized as a legume cover
crop for corn production. Agron. J. 97:26-31.

Baumann, D.T., L. Bastiaans, and M.J. Kropff. 2001. Competition and crop
performance in a leek-celery intercropping system. Crop Sci 41 :764-774.

Baumann, D.T., L. Bastiaans, J. Goudriaan, H.H. van Lear, and M.J. Kropff.
2002. Analysing crop yield and plant quality in an intercropping system
using an eco-physiological model for interplant competition. Agricultural
Systems 73:173.

Bellido, LL. 1994. Grain legumes for animal feed, p. 273-288, In J. E. Hernando
Bennejo and J. Leen, eds. Neglected crops: 1492 from a different
perspective. Plant Production and Protection Series N°. 26. FAQ, Rome,
Italy.

Beueriein, J. 2001. Relay cropping wheat and soybeans. Ohio State University
Extension Fact Sheet AGF-106-01.

Biederbeck, V.O., and CT Bouman. 1994. Water use by annual green manure
legumes in dryland cropping systems. Agron. J. 86:543—549.

Biederbeck, V.O., C.A. Campbell, V. Rasiah, R.P. Zentner, and G. Wen. 1998.

Soil quality attributes as influenced by annual legumes used as green
manure. Soil Biol. Biochem. 30:1177-1 185.

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Biederbeck, V.O., O.T. Bouman, J. Looman, A.E. Slinkard, L.D. Bailey, W.A.
Rice, and H.H. Janzen. 1993. Productivity of 4 annual legumes as green
manure in dryland cropping systems. Agron. J. 85:1035-1043.

Biederbeck, V.O., H.A. Bjorge, S.A. Brandt, J.L. Henry, G.E. Hultgreen, G.A.
Kielly, and AB. Slindard. 2000. Farm facts: Soil improvement with
legumes, including legumes in crop rotations, In B. J. Green and V. O.
Biederbeck, eds. Agriculture and Food. Canada-Saskatchewan
Agreement on Soil Conservation, Regina, SK.

Blackshaw, R.E., J.R. Moyer, R.C. Doram, A.L. Boswell, and E.G. Smith. 2001.
Suitability of undersown sweetclover as a fellow replacement in semiarid
cropping systems. Agron. J. 93:863-868.

Bowman, 6., C. Shirley, and C. Cramer. 1998. Managing cover crops
profitability. 2nd ed., Burlington, VT.

Brooks, AS, A. Wilcox, R.T. Cook, K.L. James, and M.J. Crook. 2006. The use
of an alternative food source (red clover) as a means of reducing slug pest
damage to winter wheat: towards field implementation. Pest Manag. Sci.
62:252-262.

Bruulsema, T.W., and B.R. Christie. 1987. Nitrogen contribution to succeeding
corn from alfalfa and red-clover. Agron. J. 79:96-100.

Campbell, 0.6. 1997. Grass pea. Lathyrus sativum L. Promoting the
conservation and use of underutilized and neglected crops.18. Institute of
Plant Genetics and Crops Plant Research, Gatersleben/lntemational Plant
Genetic Resources Institute, Rome, Italy.

Carruthers, K., O. Fe, D. Cloutier, and D.L. Smith. 1998. Intercropping corn with
soybean, lupin and forages: weed control by intercrops combined with
interrow cultivation. Eur. J. Agron. 8:225.

Cavigelli, MA. 1998. Nitrogen, p. 92, In M. A. Cavigelli, et al., eds. Michigan Field
Crop Ecology: Managing biological processes for productivity and
environmental quality, Vol. E-2646. Michigan State University Extension
Bulletin, East Lansing.

Chambliss, C.G., R.M. Muchovej, and J.J. Mullahey. 2003. Cover crops.
University of Florida Extension. SS-AGR-66.

Chen, X., F. Wang, Q. Chen, X.C. Gin, and Z. Li. 2000. Analysis of neurotoxin 3-

n-oxalyl-I-2,3-diaminopropionic acid and its -isomer in Lathyrus sativus by
high-perforrnance liquid chromatography with 6-Aminoquinolyl-N-

23

hydroxysuccinimidyl Carbamate (AQC) derivatization. J. Agric. Food
Chem. 48:3383-3386.

Creamer, N.G., and KR. Baldwin. 1999. Summer cover crops. North Carolina
Cooperative Extension Service HIL-37.

Davis, J.M. 1997. Organic sweet corn production. Horticulture Information
Leaflet, HIL-50.

De Bruin, J.L., P.M. Porter, and NR. Jordan. 2005. Use of a rye cover crop
following corn in rotation with soybean in the upper Midwest. Agron. J.
97:587-598.

DFS. 2003. Grow your own nitrogen. (Available online at
http://www.acgreenflx.com/).

Dhima, K.V., l.B. Vasilakoglou, l.G. Eleftherohorinos, and AS Lithourgidis. 2006.
Allelopathic potential of winter cereals and their cover crop mulch effect on
grass weed suppression and corn development. Crop Sci 46:345-352.

Dinesh, R., M.A. Suryanarayana, G. Shyam Prasad, A.K. Bandyopadhyay, A.K.
Nair, and T.V.R.S. Sharma. 1999. Influence of leguminous cover crops on
microbial and selected enzyme activities in soils of a plantation. J. Plant
Nutr. and Soil Sci. 162257-60.

Diver, S., G. Kuepper, and P. Sullivan. 2001. Organic sweet corn production.

(Available online at http://attra.ncat.org[attra-pub/PDF/sweetcom.mfl.

Doran, J.W., D.F. Fraser, M.N. Culik, and WC. Liebhardt. 1987. Influence of
alternative and conventional agricultural management on soil microbial
processes and nitrogen availability. Am. J. Altem. Agric. 2:99-106.

Drury, OF, C. Tan, T.W. Welacky, T.O. Oloya, A.S. Hamill, and SE. Weaver.
1999. Red clover and tillage influence on soil temperature, water content,
and com emergence. Agron. J. 91:101-108.

Duiker, S.W., and WS Curran. 2005. Rye cover crop management for corn
production in the Northern Mid-Atlantic Region. Agron. J. 97:141 3-1418.

Ewing, R.P., M.G. Wagger, and HP. Denton. 1991. Tillage and cover crop
management effects on soil-water and corn yield. Soil Sci. Soc. Am. J.
55:1081-1085.

Fisk, J.W., O.B. Hesterrnan, A. Shrestha, J.J. Kells, R.R. Harwood, J.M. Squire,

and CC Sheaffer. 2001. Weed suppression by annual legume cover
crops in no-tillage corn. Agron. J. 93:319-325.

24

Foulds, C. 1989. Interseedings in vegetable production. (Available online at

http://wwweap.mggill.ca/magrack/sf/Summer%2089°1020D.html.

Ghaffarzadeh, M. 1999. Strip intercropping. Iowa Cooperative Extension Service.
PM 1763.

Grela, E.R., T. Studzinski, and J. Matras. 2001. Antinutritional factors in seeds of
Lathyrus sativus cultivated in Poland. Lathyrus Lathyrism Newsletter
22101-104.

Griffin, T., M. Liebman, and J. Jemison, Jr. 2000. Cover crops for sweet corn
production in a short-season environment. Agron. J. 92:144-151.

Hamilton, M. 1998. Cover crops for use in North Carolina field crop production.
(Available online at

http://www.cropsci.ncsu.edu/organiggrains/production/covercrops.htm).

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

Hendrickson, J. 2003. Cover crops on the Intensive Market Farm. (Available

online at http://www.cias.wisc.edu/mf/cvrcrop.m1).

Hively, W.D., and W.J. Cox. 2001. lnterseeding cover crops into soybean and
subsequent corn yields. Agron. J. 93:308-313.

lngels, C.A., M. Van Horn, R.L. Bugs). and RR. Miller. 1996. Selecting the right
cover crop gives multiple benefits. California Agric. 48:43-48.

IPBO. 2006. IPBO Lathyrus research. Plant Biotechnology Institute for
Developing CountrieszAvailable online at

<httg/lwww.ipbo.rug.ac.be/activities/ourresearch/lathyrus.html>.

lsse, A.A., A.F. MacKenzie, K. Stewart, D.C. Cloutier, and D.L. Smith. 1999.
Cover crops and nutrient retention for subsequent sweet corn production.
Agron. J. 91 :934-939.

 

Jeranyama, P., O.B. Hesterrnan, and CC. Sheaffer. 1998. Medic planting date
effect on dry matter and nitrogen accumulation when clear-seeded or
intercropped with com. Agron. J. 90:616-622.

Jeranyama, P., O.B. Hestennan, S.R. Waddington, and RR. Harvvood. 2000.

Relay-intercropping of sunnhemp and cowpea into a smallholder maize
system in Zimbabwe. Agron. J. 92:239-244.

25

Kantor, S. 1999. Intercropping. Agriculture and Natural Resources Fact Sheet N°.
531.

Klassen, E. 2002. Faxed document from Eric Klassen to Ila Krause on 25/1/2002.

Knorek, J., and M. Staton. 2004. Red clover, In D. Mutch and T. Martin, eds.
Michigan Cover Crops Species. (Available online at

http://www.covercrops.msu.edu/CoverCrops/red clover.htm).

Krause, D., and I. Krause. 2003. New green manuring Lathyrus sativus variety
AC Greenfix available in USA, p. 13-14, In C. Hanbury, ed. Lathyrus
Lathyrism Newsletter, Vol. 3(1), CLIMA, Australia.

Kristensen, H.L., and K. Thorup-Kristensen. 2004. Root growth and nitrate
uptake of three different catch crops in deep soil layers. Soil Sci. Soc. Am.
J. 68:529-537.

Maluleke, M.H., A. Addo-Bediako, and K.K. Ayisi. 2005. Influence of maize/Iablab
intercropping on Iepidopterous stem borer infestation in maize. J. Econ.
Entomol. 98:384-388.

McLenaghen, R.D., K.C. Cameron, N.H. Lampkin, M.L. Daly, and B. Deo. 1996.
Nitrate leaching from ploughed pasture and the effectiveness of winter
catch crops in reducing leaching losses. New Zealand Journal Of
Agricultural Research 39:413-420.

Miles, C.A., and M. Nicholson. 2003. Can cover crops control weeds? Two-year
study tests efficacy in vegetable production systems. Agrichemical and
environmental news 203.

Munro, DB. 2003. Canadian poisonous plants information system. (Available

online at http://www.cbif.gc.calpls/pp/misonm x=px).

Mutch, D., and T. Martin. 1998. Cover crops, In M. A. Cavigelli, et al., eds.
Michigan Field Crop Ecology: Managing biological processes for
productivity and environmental quality. Michigan State University
Extension Bulletin. E-2646. 92pp.

Mwaja, V.N., J.B. Masiunas, and CE. Eastman. 1996. Rye (Secele cereale L)
and hairy vetch (Vicia villosa Roth) intercrop management in fresh-market
vegetables. J. Am. Soc. Hort. Sci. 121 2586-591.

Nafziger, ED. 2002. Cover crops and cropping systems, p. 54-58, In P.

Picklesimer, ed. Illinois Agronomy Handbook. University of Illinois Printing
Services-PYP.

26

Ohno, T., and KL Doolan. 2001. Effects of red clover decomposition on
phytotoxicity to wild mustard seedling growth. Appl. Soil Ecol. 16:187-192.

Olfert, 0., OF. Hinks, V.O. Biederbeck, A.E. Slinkard, and RM. Weiss. 1995.
Annual legume green manures and their acceptability to grasshoppers
(Orthoptera, Acrididae). Crop Prot. 14:349-353.

Pauly, D. 2004. Improving soil fertility with green manure legume crops.
(Available online at
httpzllwww1 .agric.gov.ab.ca/§department/deptdocs.nsf/alI/fad7979?opend

Quote—m)-

Peachy, E., J. Luna, R. Dick, and R. Sattell. 1999. Cover crop weed suppression
in annual rotations. Oregon State University Extension Service. EM 8725.

 

Peet, M. 1995. Sustainable practices for vegetable production in the South.
Focus Publishing, Newburyport MA 01950.

Raloff, J. 2000. Detoxifying desert's manna: Farmers need no longer fear the
sweet pea's dryl. Science News 158:74-76.

Roos, D. 2006. Cover crops: Benefits and challenges. (Available online at

http:/Iwww.ces.ncsu.eduIchatham/agISustAg/reading.html).

Ross, S.M., J.R. King, R.C. lzaurralde, and J.T. O'Donovan. 2001. Weed
suppression by seven clover species. Agron. J. 93:820-827.

Sainju, U.M., B.P. Singh, and W.F. Whitehead. 1998. Cover crop root distribution
and its effects on soil nitrogen cycling. Agron. J. 90:511-518.

Sainju, U.M., B.P. Singh, and W.F. Whitehead. 2000. Cover crops and nitrogen
fertilization effects on soil carbon and nitrogen and tomato yield. Can. J.
Soil Sci. 80:523-532.

Sarrantonio, M. 1994. Northeast cover crop handbook. Rodale Institute,
Emmaus, PA.

Sattell, R., R. Dick, D. Hemphill, and D. McGrath. 1998. Oregon cover crops: Red
clover (Trifolium pratense). Oregon State University Extension Service EM
8701.

Sauerbom, J., H. Sprich, and H. Mercer-Quarshie. 2000. Crop rotation to

improve agricultural production in sub-Saharan Africa. J. Agron. Crop Sci.
184:67-72.

27

Schmidt, N., M. Oneal, J.W. Singer, K.A. Kohler, J.R. Prasifka, and R.L.
Hellmich. 2004. The Effect of perennial cover crops on natural enemy

communities in corn and soybean. Entomological Soc. of Am. Annual
Meeting. Poster No. D0081.

Singer, J.W., and TC. Kaspar. 2006. Cover crop selection and management for
midwest farming systems. The Iowa Learning Farm. ILF 1. 1:3.

Singer, J.W., W.J. Cox, R.R. Hahn, and E.J. Shields. 2000. Cropping system
effects on weed emergence and densities in corn. Agron. J. 92:754-760.

Skarphol, B.J., K.A. Corey, and J.J. Meisinger. 1987. Response of snap beans to
tillage and cover crops. J. Am. Soc. Hort. Sci. 112:936-941.

Small, E. 1999. New crops for Canadian agriculture, p. 15-52., In J. Janick, ed.
Perspectives on new crops and new uses. ASHS Press, Alexandria, VA.

Smeltekop, H., D.E. Clay, and SA. Clay. 2002. The impact of intercropping
annual 'sava' snail medic on corn production. Agron. J. 94:917-924.

Snapp, 85., SM. Swinton, R. Labarta, D.,Mutch, J.R. Black, R. Leep, J.
Nyiraneza, and K. O'Neil. 2005. Evaluating cover crops for benefits, costs
and performance within cropping system niches. Agron. J. 97:322-332.

Stute, J. K. 2000. Proc. of the 2000 Wisconsin Fertlizer, Aglime, & Pest
Management, Madison, WI. University of Wisconsin Soil Science
Extension.

Sullivan, P. 2002. Rye as a cover crop. Attra Publication CT168.

Sullivan, P. 2003a. Intercropping principles and production practices. Agronomy
System Guide, ATTRA Publication IP135.

Sullivan, P. 2003b. Overview of cover crops and green manures. Fundamentals
of Sustainable Agriculture. ATTRA Publication IP024.

Teasdale, JR, and C.S.T. Daughtry. 1993. Weed suppression by live and
desiccated hairy vetch (Vicia ViIIosa). Weed Sci. 41:207-212.

Thompson, T., and N. Wagner. 2000. A low-cost mechanism for inter-seeding
cover crops in corn. GREENBOOK 2000. Energy and Sustainable
Agriculture Program.

Thorup-Kristensen, K., J. Magid, and LS. Jensen. 2003. Catch crops and green

manures as biological tools in nitrogen management in temperate zones.
Advances In Agronomy 79:227-302.

28

Trenbath, BR. 1993. Intercropping for the management of pests and diseases.
Field Crops Res. 34:381-405.

Vanderrneer, J.H. 1992. The Ecology of intercropping Cambridge University
Press, Cambridge.

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

Vyn, T.J., K.J. Janovicek, M.H. Miller, and E.G. Beauchamp. 1999. Soil nitrate
accumulation and corn response to preceding small-grain fertilization and
cover crops. Agron. J. 91 :17-24.

Vyn, T.J., J.G. Faber, K.J. Janovicek, and E.G. Beauchamp. 2000. Cover crop
effects on nitrogen availability to corn following wheat. Agron. J. 92:915-
924.

Weinert, T.L., W.L. Pan, M.R. Moneymaker, G.S. Santo, and R.G. Stevens.
2002. Nitrogen recycling by non-leguminous winter cover crops to reduce
leaching in potato rotations. Agron. J. 94:365-372.

Zhang, PS, and L. Li. 2003. Using competitive and facilitative interactions in

intercropping systems enhances crop productivity and nutrient-use
efficiency. Plant and Soil 248:305-312.

29

Chapter One

Corn and Cover Crop Response to Corn Density in an lnterseeding System

Abstract

Reliable cropping strategies are needed to enhance legume cover crops
utilization as a nitrogen (N) source for crop production. lnterseeding legume
cover crops into corn (Zea mays L.) can affect corn yield and cover crop dry
matter. This study evaluated (1) the effect of corn density (37 500 to 75 000
plants ha") on corn yield and cover crop dry matter when com was interseeded
with red clover (Trifolium pretense L.) or AC Greenfix (Lathyrus sativus L.) and
(2) the impact of N source [fertilizer vs. plowed red clover] on corn yield at
various com densities.

Four-year data suggest that interseeded cover crops did not affect corn
yield at any corn density. Overall, yield of corn planted into plowed red clover
was similar to corn yield supplied with N fertilizer. Interseeded cover crop dry
matter (DM) decreased as com density increased. However, red clover DM the
subsequent spring was similar regardless of com density. Interseeded cover
crops produced less DM compared with monoculture cover crops. Results show
that cover crops can be interseeded into corn densities up to 75 000 plants ha‘1
without com yield reduction and still produce substantial dry matter the

subsequent spring regardless of corn density.

30

Introduction

In recent decades, farmers in the temperate regions have increasingly
been interested in management practices that maintain soil productivity and
environmental quality and improve farm profitability (Baumann et al., 2001).
lnterseeding legume cover crops has been investigated as one way to achieve
these goals (Scott et al., 1987; Mutch and Martin, 1998; Smeltekop et al., 2002);
Brooks et al., 2006). Legume cover crops may be used in an interseeding system
to increase nutrient cycling, weed suppression, or enhance cropping-system
diversity (Sarrantonio, 1994; Diver et al., 2001; Oswald et al., 2002; Mutch et al.,
2003). lnterseeding a legume cover crop into wheat (Triticum aestivum L.) and
oats (Avena sativa L.) is common (Hesterrnan et al., 1992; Ross et al., 2005;
Singer et al., 2006). Similarly, cover crops have been interseeded into corn (Zea
mays L.), cassava (Manihot esculenta, L), sorghum (Sorghum bicolor) and
cabbage (Brassica oIeracea) (Some et al., 1992; Bellinder et al., 1996;
Jeranyama et al., 1998; Chikoye et al., 2001; Khan et al., 2002).

When cover crops are well established, interseeded cover crops can
reduce weed growth and density (Liebman and Dyck, 1993; Singer et al., 2000).
Mutch et al. (2003) suggested that the major advantage of frost—seeding legume
cover crops is ragweed (Ambrosia artemisiifolia) suppression, no reduction of
companion wheat yield, and the ability to supply nitrogen (N) to the subsequent
crop. Various studies have been conducted to assess the effect of monocropping
or interseeding legume cover crops on subsequent corn yield. Yield of com

following intercropped legume cover crops was higher compared to continuous

31

com (Jeranyama et al., 1998). Corn following interseeded medium red clover
(Trifolium pretense L.) and Dutch white clover (Trifolium repens L.) produced
greater yields compared with corn following no cover crop or rye (Secele cereale,
L) seeded after soybean [Glycine max (L.) Merr.] harvest (Hively and Cox, 2001).

In evaluating corn response to a preceding cover crop, Vyn et al. (1999)
found that com yield was consistently higher following red clover compared with
oilseed radish (Raphunus sativus [L.] var oleiferus Metzg [Stokes]), annual
ryegrass (Lolium multiflorum), and where a cover crop had not been established.
Balkcom and Reeves, (2005) observed that com yield following sunn-hemp
(Crate/aria juncea L.) with no additional N fertilizer was greater than corn yield
planted in fallow and supplied with 56 kg N ha". Planting mucuna [Mucuna
pruriens (L.) D.C.] and pigeon pea (Cajanus cajan L.) after com reduced N and P
fertilizer needs in the subsequent year and increased com grain yield by 37.5
and 32.1%, respectively (Sogbedji et al., 2006). In Michigan, com yield following
interseeded medics (Medicago polymorpha and M. scuteIIata L.) was higher
compared with corn yield without medic (Jeranyama et al., 1998). These studies
investigated the effect of cover crop and/or various rates of fertilizer on
succeeding corn yield. However, little or no research has examined the effect of
cover crop versus N fertilizer on com yield at various corn densities.

The success of any intercropping system depends on the balance of
positive and negative interactions between companion crops. Various factors

play a key role in the interseeding system, including companion crop species,

32

time of interseeding, crop density, and cover crop species. When grown together,
cash crops and cover crops compete for nutrients, water and light.

Scott et al. (1987) observed no reduction in corn yield when it was interseeded
with various cover crops. Kura clover (Trifolium ambiguum M. Bieb.), with
adequate suppression, can be managed as living mulch in corn with little or no
grain yield reduction (Zemenchik et al., 2000). Several studies have suggested
that competition in an interseeding system is determined by the time of
interseeding, while others suggest it is determined by the cover crop species that
is used. Research results have shown corn yield reduction when cover crops
were interseeded at com planting (Exner and Cruse, 1993; Jeranyama et al.,
1998). In West Africa, Sogbedji et al. (2006) found that relay intercropping
mucuna and pigeon pea into a maize crop does not cause maize grain yield loss
if established 50 to 60 days after corn planting. No reduction in com yield was
reported when cover crops were interseeded 28 days after corn planting or
between com growth stages V4 and V6 (Jeranyama et al., 1998; Mutch and
Martin, 1998). In contrast, Abdin et al. (1998) suggested that com yield was
affected by cover crop species and not by the time of interseeding. Increased
plant density in an interseeding system can increase competition of companion
crops (Ross et al., 2003). To increase output and reduce competition between
companion cash crops in an interseeding system, plant density may be reduced
(Akunda, 2001). However, when interseeding cash crops and small seeded cover
crops such as red clover, cover crop density may be increased (Bowman et al.,

1998). Since cover crop full growth in interseeding systems is after harvest of the

33

cash crop, it would be interesting to know the impact of increased plant density of
the cash crop on the growth of the cover crop. Another challenge is knowing the
optimum plant density for companion crops (Blaser et al., 2006).

Cover crop species and cultivars within species differ in their ease of
establishment in an interseeding system (Singer et al., 2006). In intercropping
seven legumes of Medicago spp, Alford et al. (2003) observed that only Black
medic (M. IupuIina L.) did not reduce corn yield. All the other cover crops
significantly reduced corn yield. Crimson clover (Trifolium incematum L.)
accumulated enough biomass to produce higher corn yield compared with other
legume cover crops due to its ability to tolerate shade (Freeman et al., 2000).
Cover crop growth, N accumulation and availability to a succeeding crop can be
affected by environmental factors such as precipitation, temperature, length of
growing season, and soil productivity (Hestennan et al., 1992; Dekker et al.,
1994 ; Stute and Posner, 1995; Singer et al., 2006). Red clover, a common cover
crop in Michigan, is used in several interseeding systems, because of its ease of
establishment and shade tolerance (Mutch and Martin, 1998; Bowman et al.,
1998). When interseeding various cover crops into corn, Thompson and Wagner
(2000) recommended mammoth red clover and nitro alfalfa (Medicago sativa)
because they were the easiest to establish and showed the most vigor. Rye and
hairy vetch (Vicia villosa Roth) did not perform as well. Singer et al. (2006)
observed greater dry matter with red clover diploid compared with tetraploid

cultivars.

34

Red clover is used in various cropping systems (Hesterrnan et al., 1992;
Mutch and Martin, 1998). When compared to alfalfa, black lentil (Lens culinaris
Medik. subsp. culinaris) and chickling vetch (Lathyrus sativus, L) in relay and
double cropping systems, red clover produced the most above ground dry matter
and had the fastest growth rate (Martens et al., 2001). lnterseeding a shade
tolerant cover crop like red clover can result in more rapid establishment of the
cover crop after the cash crop is harvested and extend the growing period for the
cover crop. When left in the field after corn harvest, red clover may provide
ground cover during the fall and spring, and supply N to the subsequent crop. A
greater understanding of cover crop growth and performance in various plant
densities is critical to assessing the potential for the use of cover crops in various
management systems.

Chickling vetch, an annual legume crop, is grown in different parts of the
worid as food and sometimes as animal fodder or green manure (Campbell,
1997; IPBO, 2006; Small, 1999). In past decades, chickling vetch has received
more attention as a multi-use crop in arid regions, because it is drought tolerant
and adaptable to marginal soils (Biederbeck et al., 1993; Biederbeck and
Bouman, 1994; Campbell, 1997). Chickling vetch seeds have a protein content of
25-28% (Bellido, 1994). AC Greenfix, a variety of chickling vetch, is used in North
America primarily as a green manure alternative to summer fallow in small grain
production systems to reduce wind and water erosion, and to improve soil (Small,
1999). AC Greenfix has a seeding rate of 80 kg ha'1 and the potential to produce
90-112 kg of N ha'1 in 8-10 weeks after planting (DFS, 2003). A Study of AC

35

Greenfix in several locations across southwest Saskatchewan, found AC
Greenfix forage yields averaged 2590 kg ha'1 with a crude protein content
averaging 19.63% (Biederbeck, 2005). Other studies by Rao et al. (2005) have
shown that at full bloom (75 days after planting), AC Greenfix produced an
average of 6415 kg ha‘1 of DM compared with only 2013 kg ha“1 for lentil (Lens
culinaris Med. cv. Indianhead). In evaluating cover crops in relay and double
cropping, AC Greenfix was ranked second to alfalfa when comparing the fertilizer
replacement value for cat following various cover crops (Martens et al., 2005).
Various management practices have to be considered for maximizing AC
Greenfix potential, including plowing it under before pods begin filling, about 40-
60 days after planting. Because AC Greenfix is such a short season crop it could
fit in various cropping systems to provide N and organic matter. Since cover crop
performance and dry matter production varies from one region to another,
between species and with crop management, research on AC Greenfix will help
to assess its performance, in comparison to red clover, in the interseeding
systems in Michigan.

As part of an on-going research effort in Michigan on incorporating cover
crops into corn production, studies have been conducted on cover crop
establishment in corn and wheat to investigate time of planting and performance
of various cover crop species and cultivars (Jeranyama et al., 1998; Mutch and
Martin, 1998). Interseeded cover crops appear to provide many benefits to crop
production systems, but a greater understanding of establishment and species

differences is needed in order to realize these potential benefits.

36

The objectives of this study were to assess the effect of (i) com density in
an interseeding system on corn yield and on red clover or AC Greenfix dry matter
and (ii) nitrogen fertilizer versus nitrogen provided by plowed red clover on corn

yield at various corn densities.
Materials and Methods

Site description

The research was conducted from 2002 to 2005 at the Kellogg Biological
Station (KBS) in Hickory Comets, Michigan. The soil types at KBS were the
Kalamazoo (fine-loamy, mixed, mesic Typic Hapludalfs) and Oshtemo (coarse-
loamy, mixed, mesic Typic Hapludalfs) series (Crum and Collins, 2004). The
experiment was conducted on a different field each year to permit planting on site
following red clover plow down. Every year after wheat harvest, red clover was
planted into wheat stubble in July-August except in 2001 when it was planted in
corn stubble harvested the previous year. Red clover was chisel-plowed the
subsequent spring before corn planting in order to serve as a N source for the
non-conventional plots. The period before and after the winter allowed red clover
to grow and produce relatively significant biomass for the following corn crop.
Each year, prior to the establishment of corn, red clover was sampled using a
0.45 by 0.45 m quadrat for estimating per hectare dry matter (DM) and N content.
Nitrogen concentration was determined using the Kjeldahl method. Nitrogen

content was obtained by multiplying the DM and the N concentration.

37

Experimental design

The field experiment was a split-plot in a completely randomized design
with four replications. The main plots were four corn densities: 37 500, 55 000,
65 000 and 75 000 plants ha". Subplots were four management practices:
(1) Conventional management, corn seeded into wheat stubble with N fertilizer
applied (CMNF); (2) Corn seeded into plowed red clover, no N fertilizer,
interseeded with AC Greenfix (PRIA); (3) Corn seeded into plowed red clover; no
N fertilizer, interseeded with red clover (PRIR) ; and (4) Com seeded into plowed
red clover, no N fertilizer, not interseeded with cover crop (PRNI). Individual
experimental units consisted of 6 rows of 4 by 4.5 m in 2002 and 2003 (due to

small field size in 2002) and of 5 by 4.5 m 2004 and 2005.

Corn

The hybrid Great Lakes 4979 (Great Lakes Hybrids), relative maturity 99
days, was planted on 29 May 2002 and 06 June 2003; and Pioneer Hybrid
38P05, relative maturity 93 days, was planted on 30 May 2004 and 27 May 2005.
The change in hybrid from Great Lakes 4979 to Pioneer Hybrid 38P05 was due
to a discontinuation of seed production by Great Lakes Hybrids. The trials were
planted at approximately 100,000 plants ha". Two weeks after emergence, each
plot was hand-thinned to target the appropriate plant density.

Corn was harvested from the four center rows of each plot on 17 October
2002, 29 October 2003, 10 November 2004 and 06 October 2005. Data collected

in the four center rows included grain yield, plant height, days to flowering,

38

number of ears harvested and the number of plants harvested. In 2002 and
2003, prior to harvest two whole plants were collected from four center rows of
each plot for total N analysis. In 2004 and 2005, ten plants were collected from
the four center rows. Corn was harvested using a combine. Corn grain yield, test
weight and moisture content were automatically measured by the GrainGageT”,
a HarvestData SystemTM mounted on a plot combine (Juniper Systems, Logan
UT). Dry weight was determined by the method detailed by (Lauer, 2002). Grain
yields were a summation of combine and hand harvested corn and were reported
at 155 g kg'1 moisture content. Corn height was measured from the soil surface
to the tip of the tassel on five randomly selected plants from the four middle rows
of each plot. Days to flowering were determined from planting to the day on
which 50% of the plants had extruded tassels. Prior to harvest, the number of

plants per plot and ears per plots were counted in all four center rows.

Soil sampling and agricultural inputs

Each year, eight soil cores were taken from every plot at a depth of 25 cm
at the end of April. Soil samples were air-dried and sent to the MSU Soil and
Plant Nutrient Laboratory for NPK and pH analysis, and fertilizer
recommendations. Soil pH was 6.1 in 2002, 6.4 in 2003, 6.8 in 2004 and 6.9 in
2005. Each year, based on soil test results, either P or K or both were applied to
the whole field a few days before planting. Nitrogen was applied only to CMNF
plots as a starter fertilizer after planting corn. In 2002 and 2003, Urea was

applied as a starter fertilizer a few days after planting at the rate of 23 kg ha'1

39

whereas in 2004 and 2005, ammonium nitrate was applied as starter fertilizer at
the rate of 28 kg ha". In 2002, P and K were applied at the rate of 57 kg ha‘1 and
108 kg ha"1 respectively, and lime at the rate of 1000 kg ha". In 2003, P and K
were applied a few days before planting at the rate of 50 kg ha'1 and 82 kg ha",
respectively. In 2004, P and K were applied at the rate of 23 kg ha'1 and 68 kg
ha", respectively. In 2005, only P was applied at the rate of 40 kg ha". In mid-
June of every year, soil samples were taken for nitrate analysis. Based on
Preside-dress Nitrate Test results, supplemental N fertilizer was applied in CMNF
up to a total of 140 kg ha'1 every year.

Herbicides were used to control weeds. Each year, herbicides were
broadcast in CMNF and applied in 25.4 cm bands in PRIR, PRIA and PRNI to
reduce herbicide interference with the germination of cover crops that were
interseeded later. In 2002, Acetochlor (1.79 kg ai ha") was used one week after
planting. The first application of herbicide did not totally control weeds. Three
weeks later, a second application of herbicides, Atrazine (1.12 kg ai ha") and
Bromoxynil (0.42 kg ai ha") was broadcast on CMNF plots, whereas PRIR, PRIA
and PRNI plots were cultivated. In 2003, the preemergence herbicide S-
metolachlor (1.42 kg ai ha“) and Flumetsulam (0.06 kg ai ha") were applied four
days after planting. In 2004, S—metolachlor (1 .42 kg ai ha") and Atrazine (0.56 kg
ai ha“) were applied three days after planting. In 2005, Lumax (S-metolachlor
1.42 kg ai ha"; Atrazine 0.47kg ai ha"; mesotrione 0.15 kg ai ha“) was applied

directly after planting com.

40

Cover crops

Red clover and AC Greenfix were interseeded on 11 July 2002, 14 July
2003, 06 July 2004 and 01 July 2005 when com plants were V5-V7 growth
stages. In 2004 and 2005, pure or monoculture cover crop plots were established
at the time of interseeding to compare biomass in pure stand with biomass of
interseeded cover crops. Red clover was broadcast with a hand-seeder at the
seeding rate of 20.4 kg ha'1 and AC Greenfix was hand-broadcast at the rate of
90 kg ha". Before planting, AC Greenfix was inoculated with Rhizobium
Ieguminosarum. Above ground biomass of red clover and AC Greenfix were
hand-clipped at full bloom of AC Greenfix on 27 September 2002, 02 October
2003, 23 August 2004 and 08 August 2005 by removing plants from a random
quadrat of 0.209 m2 in each plot.

To assess cover crop density, the number of red clover and AC Greenfix
plants was counted and reported on a plants rn'2 basis. Plant height was
determined by measuring five randomly selected plants in each quadrat. After
corn harvest, corn stalks were mowed to increase cover crop exposure to light.
Plots were left undisturbed until the following spring. The subsequent spring, only
red clover biomass was sampled on 02 June 2003, 02 June 2004 and 01 June
2005 because AC Greenfix did not survive the winter. After each sampling, cover
crop biomass was oven dried at 60° C for 48 h to determine DM. Total DM of the
cover crop was calculated by multiplying the yield per quadrat by the number of

quadrats ha".

41

Soil moisture measurements

Soil moisture was measured after interseeding the cover crops. The
percent volumetric soil moisture content was measured using a Time Domain
Reflectometer (TDR) (MESA Systems Co., Medfield, Massachusetts). Soil
moisture was measured on 13 July, 19 July, 26 July, 2 August, 9 August, 16
August, 30 August, 13 September, 27 September and 11 October in 2004, and
on 19 July, 26 July, 2 August, 9 August, 16 August, 31 August, 06 September
and 13 September in 2005. The % volumetric soil moisture was measured in
three directions (parallel, perpendicular and diagonal to com row) at two different
depths (0 to18 and 18 to 36 cm) in tubes placed within one of the two center
rows of the six-row corn plot. Soil moisture readings of the three directions were

averaged at each depth since no difference was detected among directions.

Statistical analysis

All data were analyzed using Proc Mixed in Statistical Software Package
SAS version 8.2 (SAS, 2001). Plant density and cropping system were
considered fixed effects. Two error terms were considered in the analysis of the
data, one associated with the whole plot (plant density) and the other associated
with the subplot (management practices) and the interaction (plant density x
management practices). When interaction effects were found to be significant,
means separation was conducted for respective cell means. When main effects
were significant while interactions were not, means separation was conducted for

marginal means. Effects were considered statistically significant at p= 0.05.

42

Results and discussion

Weather patterns

Daily precipitation and monthly average temperature (minimum and
maximum) were obtained from the Long-Terrn Ecological Research weather
station (LTER-Weather, 2006). In 2002, there was a drought period in June and
July, and the average rainfall in June was below the 30-year average (Figure 1a
and Appendix A). Precipitation in June and July during the 2003 growing season
were lower than the 30-year average (Figure 1a). Seasonal total precipitation in
2004 was the only year above the 30-year average (Appendix A) and was well
distributed throughout the growing season (Figure 2). Precipitation in April, May
and August during the 2005 growing season was lower than any other growing
season and than the 30-year average (Figure 1a). The low rainfall in spring of
2005 helps explain the low red clover DM before com establishment (Table 1,
Figures 1a and 2). Although total precipitation in the 2005 growing season was
lower than the 30-year average, rainfall occurred during critical corn growth
stages (Figure 1a). Monthly average minimum temperature for April 2003 was
lower compared to the 30-year average (Figure 1b and Appendix B). Monthly
average maximum temperatures during the 2005 growing season from June to
September were higher than the 30-year average (Figure 1b). A drought period
combined with high temperature in 2005 prevented the germination of

interseeded red clover.

43

Soil moisture In 2004 and 2005

Soil moisture varied across management practices and com density at
both 0 to 18 cm and 18 to 36 cm depths (Figures 3 and 4). No interaction was
observed among sampling dates and depth with either management practices or
corn plant densities. Comparisons among treatments were conducted at each
sampling date for each treatment for an individual depth.

In 2004, across corn density, no significant difference was observed
among management practices at 0 to 18 cm depth at each sampling date from
13 July to 30 August (Figure 3a, and Appendix C). On 13 and 27 September, soil
moisture in PRIA and PRIR was significantly higher than in CMNF but not in
PRNI. No difference was seen at the last sampling ( 11 October) among
management practices. In 2004 at 18 to 36 cm, soil moisture was significantly
higher in PRIA compared with CMNF and PRIR at all sampling dates (Figure 3b).
No difference was seen between PRIA and PRNI. AC Greenfix appeared to be
using less water compared to red clover. In 2005 at 0 to 18 cm during the first
sampling, soil moisture in PRIR was significantly higher than in PRNI (Figure 3c
and Appendix D). However, no significance difference was detected among
treatments on the other sampling dates. Soil moisture decreased with time from
the second sampling (26 July) up to the last sampling (13 September). In 2005 at
18 to 36 cm, no significant difference was observed among management
practices from the first to the last sampling and soil moisture decreased with time

(Figure 4d).

Across management practices, soil moisture at four com densities varied
with depth and weather conditions in 2004 and 2005 (Figure 4). In 2004 at 0 to
18 cm depth within the same date, soil moisture in plant density was not
significantly different from 13 July to 9 August (Figure 4a). From 16 August to 11
October 2004 at 0 to 18 cm depth, soil moisture at 75 000 plants ha'1 was
significantly higher than at 55 000 plants ha'1 but not different at 37 500 and 65
000 plants ha". From 13 July to 11 October 2004 at 18 to 36 cm depth, soil
moisture at 75 000 plants ha'1 was higher than at 65 000 plants ha‘1 except on 2
August (Figure 4b). In addition, soil moisture at 75 000 plants ha'1 was
significantly higher than at 37 500 plants ha‘1 from 16 August to 11 October. In
2005 within the same date at both 0 to 18 cm and 18 to 36 cm depths, soil
moisture in plant density was significantly higher at 55 000 plants ha'1 compared
at 37 5000 plants ha'1 from 19 July to 2 August (Figures 40 and d). From 9
August to 13 September within the same date at both 0 to 18 cm and 18 to 36 cm
depths, no significant difference was seen in soil moisture at any plant density. In
2005, soil moisture decreased in all management practices and at all plant
densities with time, as rainfall decreased (Figure 3c and d, and 4c and d).

Overall, adequate rainfall conditions in 2004 seemed to increase strong
differentiation between treatments at 18 to 36 cm compared with 0 to 18 cm. At
low or no rainfall no clear differentiation was observed at both 0 to18 and 18 to
36 cm depths. No differentiation among treatments in dry conditions may be
explained by com plants accessing the deeper soil moisture in dry conditions that

create less moisture near the surface (Zemenchik et al., 2000). Similariy,

45

Biederbeck and Bouman (1994) observed a substantial decrease in soil moisture

at deeper depth during dry conditions.

lnterseeding system and N source effect on corn yield

There was no interaction between management practice and corn density
on corn yield; however, there was a year and management practices or corn
density effect on corn yield (Table 2). Mean corn yield for management practices
across corn densities varied from year to year and within years (Table 3). In
2002, corn yield of PRIR was significantly higher than PRIA at 55000 plants ha“.
In 2002, corn yield of CMNF was lower at each plant density compared with
those of corn planted into plowed red clover (PRIR, PRIA and PRNI). The
differences in yield of CMNF compared with PRIR, PRIA and PRNI may be
attributed to the rainfall pattern (Figure 2). In June and July of 2002, we had a
period of drought. These dry conditions happened just after side-dressing N to
CMNF plots. The lack of moisture probably reduced N uptake in CMNF plots and
resulted in lower corn yields. In the same year at the nearby Long Term
Ecological Research (LTER) at KBS, yield of com following cover crops was
significantly higher than those fertilized with N (LTER—Yields, 2002). Previous
studies have shown similar observations of good crop performance following
cover crops compared with non-cover crop plots when soil moisture was
inadequate. In Maryland, during a dry year, beans planted after a cover crop had
higher yields compared to those grown without cover crops (Feet, 1995). In

2003, no significant difference was observed in com yield among all

46

management practices. Corn yield in 2003 was lower compared to 2002, 2004
and 2005. This was probably due to low rainfall below the 30-year average, for
June, July and August (Figure 1a), and delayed planting because of slow growth
of the cover crop due to a cold spring (Figure 1b). Planting occurred one week
later compared to other growing seasons in order to allow red clover (used as
source of N for PRIR, PRIA and PRNI) to grow during the spring. The delay in
cover crop plow down may have also increased soil moisture depletion and
hence adversely affected corn growth and yield. Corn yield of CMNF was
significantly higher than PRIR, PRIA PRNI at 65 000 and 75 000 plants ha'1 in
2004. In 2003 and 2004 no significant difference was observed between corn
yield of PRIR, PRIA and PRNI (Table 3). In 2005, corn yield in CMNF was higher
than in PRIA and PRIR at 55 000 plants ha“, PRNI at 65 000 plants ha", and
PRIA, PRIR and PRNI at 75 000 plants ha“.

Mean corn yield at four corn densities across management practices
varied with year (Table 3). In 2002 and 2003, no significant increase in com yield
was observed for CMNF with increased plant density. When comparing
treatments planted into plowed red clover, no yield increase was observed for
PRIR and PRNI with increased plant density in 2003 (Table 3). In 2003, only two
replications were usable for data collection and analysis due to poor corn stand
caused by wildlife damage. Corn grain yield tended to be greater at higher plant
density, but was significantly different at 75 000 plants ha'1 for PRIA in 2003 and
CMNF in 2004. No significant increase in corn grain yield was observed beyond

65 000 plants ha‘1 for PRIR, PRIA and PRNI in 2004. In 2005, corn grain yield

47

was numerically higher at 75 000 plants ha'1 in all management practices, but not
significantly different from 65 000 plants ha'1 in PRIA and PRNI and from 55 000
plants in CMNF.

The four-year average corn yield across plant densities suggest increased
corn yield with increased corn density in both corn planted into plowed red clover
and corn supplied with N fertilizer (Table 4). No corn yield increase is observed
beyond 55 000 plants ha'1 for PRIR and PRNI. PRIA and CMNF showed corn
grain yield increases up to 65 000 plants ha". The four-year average corn yield
suggests no com yield reduction with interseeding at any plant density and no
difference between PRIR, PRIA, PRNI and CMNF at any plant density (Table 4).
This is in agreement with Abdin et al. (1998) who reported no effect on corn
yields due to interseeding red clover and other cover crops 10 days after com
emergence. When intercropping medics into corn three weeks after emergence,
Jeranyama et al. (1998) did not observe any corn grain yield reduction.

Mean com yield in management practices across plant density varied
significantly from year to year (Table 5). However, the four-year average of corn
yield in the four management practices suggest no significant difference between
treatments receiving N from plowed red clover or from N fertilizer (Table 5).
There was an interaction between year and management practices on corn yield
due to dry conditions that occurred in 2002 and affected com yield in CMNF
(Table 2). Corn yield in CMNF was lower in 2002 and similar in 2003 when
compared with corn yields of PRIR, PRIA, and PRNI (Table 5). However, in 2004

and 2005, com yield in CMNF was significantly higher than com yield of PRIR,

48

PRIA, and PRNI (Table 5). This is due probably to the higher and well distributed
rainfall (Figures 1 and 2) that occurred in 2004; and rainfall that occurred when
com was at critical growth stages (Coffman, 1998) in 2005. This study suggests
that in dry years, yield of corn following plowed red clover could be higher than
those with non-cover crop plus N fertilizer, while the opposite will be seen when
soil moisture is not a constraint. Corn following cover crops produced similar or
higher yield than fertilized corn in various studies. Vyn et al. (2000) reported
similar com grain yield in corn planted into plowed red clover compared to corn
supplied with 150 kg ha". Griffin et al. (2000) showed that legume cover crops
did not respond to additional N and supplied all N required by sweet corn. Vyn et
al. (1999) also noted that red clover was the best cover crop with respect to N
availability to succeeding com when compared to other cover crops such as
oilseed radish. Balkcom and Reeves (2005) showed higher com yield following
sunn-hemp compared to corn with no cover crop plus 56 kg ha'1 of N fertilizer.
There was an interaction between year and management practices on
days to flowering (Table 2). This was due to climatic conditions that occurred in
2005. Days to flowering, plant height, ears per plant, grain moisture and test
weight of corn varied with management practice, com density and year (Tables 5
and 6). Corn plants in the CMNF treatment flowered approximately two days later
in 2002 and 2003, and one day later in 2004 than plants in the PRIR, PRIA and
PRNI treatments. However, no difference was noticed in 2005 (Table 6). No
difference was observed in days to flowering in relation to plant density in any

growing season (Table 7). In 2005, all plants regardless of treatment flowered at

49

the same time. In 2005, corn flowered approximately 54 days after planting
compared to 66 days on average for the 2002, 2003 and 2004 growing seasons.
This was probably due to high temperatures in June and July, which were higher
compared to the 30-year average (Figure 1b). Similar findings were obtained by
Sarrantonio and Molloy (2003) who observed that sweet corn tasseled three
weeks earlier when temperatures were high.

There was an interaction between year and management practices on
corn height (Table 2). Dry conditions that affected corn growth in 2002 may
account for this interaction and explain the difference among treatments (Table 6;
Figure 1). In 2002, com plants in CMNF were on average 17 cm shorter than
corn planted into plowed red clover (Table 6). However no significant difference
was observed among management practices during the 2003, 2004 and 2005
growing seasons (Table 6). Sarrantonio and Molloy (2003) observed greater
height (20 cm difference) of sweet com following red clover compared to non-
clover in dry conditions and no difference when rainfall was sufficient. Abdin et al.
(1998) observed no difference in corn height in some treatments when rainfall
was non-limiting to crop growth. No consistency was observed in com height,
taken after tasseling, in relation to plant density, as no difference was seen in
2002 and 2003. In 2004, plants in the 75 000 plants ha'1 treatment were
significantly higher in plant height (1.83 m) compared to the 37 500 and 55 000
plants ha'1 treatments, 1.73m and 1.72 m respectively (Table 7). In 2005, 55 000
plants ha"1 was significantly higher in plant height (2.04m) compared to 37 500

plants ha‘1 (1.94 m).

50

The number of ears per plant was similar in management practices in
2002 and 2003 (Table 6). However in the following years, the CMNF treatment
had a higher number of ears compared with PRIR in 2004 and with PRIR, PRIA
and PRNI in 2005. In all four years, no significant difference was observed in
ears per plant between interseeded (PRIR, PRIA) and no interseeded (PRNI)
corn (Table 6). Similarly, in a study of interseeding various cover crops into corn,
Abdin et al. (1998) found no consistent effects of interseeded cover crop
treatments on corn grain yield components such as ears per plant. The four com
plant densities differed in number of ears per plant except in 2002 (Table 7). The
number of ears per plant at 37 500 plants ha”1 was significantly higher than all the
other densities in 2003 (except at 55 000 plants ha“), 2004, and 2005. In 2005,
the number of ears per plant at 55 000 plants ha”1 was also significantly higher
than at 65 000 and 75 000 plants ha". There was an interaction between year
and plant density on the number of ears per plant and this was probably due to
climatic conditions (Table 2). A higher number of ears per plant was observed in
2004 and 2005 (data not shown), probably due to optimum conditions for corn
growth. This study suggests that com planted at a much lower density likely will
have two or more ears per plant. This can be attributable to reduced stress at low
corn density because plants can compensate for factors that influence resource
capture at low corn density (Tollenaar et al., 2006). In a com crowding study,
Hashemi et al. (2005) observed a decrease in ears per plant in all hybrids as

plant density intensified.

51

In two of the four years of this study, corn grain moisture in CMNF was
significantly different from grain moisture of com planted into plowed red clover
(PRIR, PRIA and PRNI) (Table 6). In 2003, CMNF had higher grain moisture
compared with com planted into plowed red clover, whereas in 2004 it was lower.
In 2005, CMNF grain moisture was significantly higher compared to PRIR and
PRNI and not different from PRIA. No difference was detected in grain moisture
among treatments in 2002. No significant difference was observed for grain
moisture among plant densities in any year (Table 7). Overall, grain moisture was
very high in 2003 and low in 2005. This is presumably due to weather which was
cool in 2003 and dry and hot in 2005.

Corn grain test weight of CMNF was significantly lower compared with
PRIR and PRIA in 2002 and with PRIR, PRIA and PRNI in 2003 (Table 6).
However in 2004, the test weight of CMNF was significantly higher compared
with PRIR, PRIA and PRNI. No difference was observed in 2005. This difference
may have been due to hybrid types and growing conditions. Widdicombe and
Thelen (2002) reported a significant variation in test weight among various

hybrids and locations.

Corn density effect on Interseeded cover crops In fall

Separate analysis was conducted for the first three years of cover crop
data and the fourth year of AC Greenfix data because no data was available for
red clover for the fourth year. No interaction was observed between corn density

and cover crop DM (Table 2).

52

Interseeded cover crop DM varied during the fall of 2002, 2003, 2004 and
2005 growing seasons (Table 8). In 2002, cover crop emergence was delayed by
a two-week period without rain after interseeding in July (Figure 1). Dry matter of
interseeded red clover and AC Greenfix was numerically higher at the 37 500
plants ha'1 except in 2003 for interseeded red clover. Dry matter of red clover
was the lowest in 2003, ranging from 0.070 to 0.175 Mg ha“, with 65 000 plants
ha'1 producing the highest DM (Table 8). The low DM for red clover in 2003 was
probably due to low germination (density) by the cover crop when compared with
other growing seasons (Table 8). This might have been due to insufficient rainfall
at the time of interseeding (Figure 1a). In 2005, hot and dry weather conditions
(Figures 1 and 2) prevented red clover germination after the first and the second
attempts to interseed in July and August, respectively. Shallow sowing combined
with lack of moisture may have prevented red clover germination. During this
growing season, AC Greenfix produced the lowest DM compared with 2002,
2003 and 2004 growing seasons (Table 8). The ability to survive in dry conditions
of only 125-150 mm of rainfall (Biederbeck et al., 1993; Biederbeck and Bouman,
1994;Campbell, 1997;DFS, 2003) helped AC Greenfix survive hot and dry
conditions in 2005. Results on clover DM are supported by Hively and Cox
(2001) who found an average of 0.2 Mg ha'1 DM in fall when red clover was
interseeded into soybeans.

The three-year average DM for red clover ranged from 0.184 to 0.370 Mg
ha'1 and 0.228 to 0.567 Mg ha'1 for AC Greenfix (Table 9). Red clover and AC

Greenfix differed in DM, with AC Greenfix producing more DM than red clover

53

(Table 9). Com density significantly affected cover crop growth and DM
production. Overall Interseeded cover crop DM decreased as corn density
increased but significant differences were only observed at 37 500 plants ha‘1
compared to higher com plant densities except for red clover at 55 000 plants ha‘
1 (Table 9). Ross et al. (2003) also observed a decline in berseem clover
(Trifolium alexandrinum) DM with increasing oat plant density. Cover crop DM
was negatively correlated to com plant density with a correlation coefficient of
r2=-0.55 (Table 9).

Cover crop (Red clover and AC Greenfix) DM was affected by other
factors such as poor germination and soil moisture, which varied from year to
year. There was an interaction between year and cover crop species on cover
crop density (plants m‘z) due to poor red clover germination in some of the
growing seasons (Tables 2 and 8). No correlation was observed between cover
crop DM and cover crop density. Singer et al. (2006) also reported no
relationship between red clover DM and its density when red clover density was
high.

No correlation was observed between cover crop height and cover crop
DM (Table 2). The three-year average red clover and AC Greenfix height ranged
from 9.1 to 13.0 cm and 91 to 102 cm, respectively. No significant difference was
observed in height within species except in 2004 where AC Greenfix at 75 000
com plants ha‘1 was significantly shorter in height than at lower corn plant
densities (Table 9). Similarly, no significant difference was noticed in AC Greenfix

density in all four growing seasons. However, in 2002 red clover density was

54

significantly lower at 75 000 plants ha‘1 compared with lower corn plant density.
In 2003, red clover density was significantly higher at 65 000 plants ha“1
compared with 55 000 and 75 000 plants ha", but not different from 37 500

plants ha".

Pure or monoculture cover crops in 2004 and 2005

Monoculture cover crop was planted at the time of interseeding and
produced significant greater DM during the fall-compared to interseeded cover
crops (Table 8). Fall sampled pure red clover and AC Greenfix DM were
respectively 1.4 and 2.2 Mg ha" in 2004, and 0.46 and 1.6 Mg ha" in 2005
(Table 8). Biomass production was highest in 2004 compared with 2005 for both
cover crops. These differences could be attributed to above normal precipitation
during the 2004 growing season (Figure 1a and 2). However, in 2005 hot and dry
conditions resulted in poor cover crop germination (density) and hence low cover
crop DM. In 2005, soil moisture content decreased with time, with little
differences among treatments (Figure 3). In 2005 red clover density (256 m'2
compared to 640 rn'2 in 2004) was very low, particularly for monoculture. The
ability of AC Greenfix to perform well in low rainfall conditions allowed it to
survive. No difference in cover crop density was observed between monoculture
and interseeding. In both years, no difference was detected in AC Greenfix plant
height between monoculture and interseeding. However, red clover plant height
in monoculture was only similar to clover planted at 37 500 plants ha". The

height of both cover crops was lower in 2005 than in 2004 (data not shown).

55

AC Greenfix DM was similar to that reported by DFS (2003) who
suggested that it produces DM of 2242 to 4483 kg ha'1 and Biederbeck and
Bouman (1994) who reported DM of 2130 to 4080 kg ha’1 during five growing
seasons. Monoculture red clover and AC Greenfix results are similar to those of
Jeranyama et al. (1998) who obtained greater DM with clear seeded medics (up
to 3.0 Mg ha") compared with interseeded medics. AC Greenfix and red clover
DM was significantly reduced in interseeding compared with the monoculture
system. In 2004, interseeded red clover DM was 19 to 33 % of monoculture red
clover DM, whereas interseeded AC Greenfix DM ranged from 12 to 26% of
monoculture AC Greenfix DM. In 2005, interseeded AC Greenfix DM ranged from
8 to15% of monoculture AC Greenfix DM. If moisture is not limiting, red clover
can perform well compared with AC Greenfix in an interseeding system. When
soil moisture was not limiting interseeded AC Greenfix performed well during a
growing season with low temperature such as the 2004 growing season (Table 8

and Figure 1a).

Red clover dry matter the subsequent spring

AC Greenfix was hand-clipped a few days after collecting interseeded
cover crop DM to prevent podfill. Regrowth was expected from AC Greenfix,
however none occurred. In 2004, only few AC Greenfix plants produced
regrowth, we think because of adequate rainfall. AC Greenfix is an annual cover
crop and did not survive the winter. Com stalks were mowed after corn harvest

and plots left undisturbed until the subsequent spring. There was a seasonal

56

effect on red clover DM in the subsequent spring. In subsequent spring red
clover accumulated DM ranging from 3.10 to 4.12 Mg ha‘1 in 2003, 2.34 to 3.38
Mg ha'1 in 2004 and 5.36 to 6.05 Mg ha'1 in 2005 (Table 10). In the subsequent
spring of every growing season, red clover DM was similar regardless of the com
density into which it was seeded in the previous fall (Table 10). High DM of
interseeded red clover in. the subsequent spring of 2005 was due to higher and
well-distributed rainfall during the fall of 2004 growing season. Dry matter
accumulation increased significantly from the first sampling in the fall to the
second in the spring regardless of com plant density. Red clover DM
accumulation was comparable to results of other studies. Blaser et al. (2006)
found that DM of red clover intercropped with winter wheat was not affected by
wheat seeding rates when harvested after cereal harvest, and that red clover
produced up to 3.68 Mg ha'1 of DM 80 days after wheat harvest. Blackshaw et al.
(2001) found that sweet clover undersown in field pea (Pisum sativum L.), flax
[Brassica juncea L.) produced biomass yields of 3110 to 5370 kg ha'1 in June of
the subsequent year depending on the year and companion crops. In New York,
red clover interseeded into soybean in fall produced 0.8 Mg he1 the subsequent
spring (Hively and Cox, 2001). Hively and Cox (2001) obtained low DM because
of the time of sampling (early may), as our samples were taken in the first week
of June. In comparing the growth and DM of various cover crops, Odhiambo and
Bomke (2001) found that late (May) sampling of cover crop during the spring
provided a significant cover crop DM increase compared to eariier (March)

sampling. Similar results to our findings were obtained by Scott et al. ( 1987) who

57

reported an average red clover DM of 2.9 Mg ha'1 (roots and above ground DM)
in the subsequent spring after interseeded red clover into corn, at Aurora in New
York. Also, Cogger et al. (2006) reported that mid-may red clover sampling had
the greatest DM, averaging 2.22 Mg ha'1 DM. Interseeded red clover in high corn
density does not affect red clover DM production the subsequent spring if
allowed to grow during the spring. Delayed cover crop cultivation, presents an
obstacle to some cropping systems where there might be a need to establish a
crop early in the spring. For maximizing DM from red clover, it is better to allow
the cover crop to grow as long as possible. However, there is a risk of soil

moisture depletion with delayed cover crop plow down.

Conclusion

Under the conditions of this study, available N from red clover established
in the summer after wheat harvest was sufficient to produce corn yield that
exceeded the com yield supplied with mineral N fertilizer in a dry year. When
precipitation was adequate, corn supplied with mineral N fertilizer produced
similar or higher yield than corn supplied with red clover derived-N. lnterseeding
red clover or AC Greenfix did not reduce corn yield at higher com density. Corn
density influenced red clover growth and DM in fall with a trend of higher corn
density producing lower red clover DM. However the subsequent spring, red
clover DM was similar regardless of plant density in the previous fall.

AC Greenfix had good establishment when interseeded, but produced less

biomass compared with monoculture AC Greenfix. Although there are many

58

management questions to be investigated, this study suggests that red clover
derived-N can produce corn yields comparable to those produced by N fertilizer.
This research also suggests that interseeding red clover into corn densities up to
75 000 plants ha'1 could produce enough DM to provide N to a subsequent crop.
This type of management practice could be used in low-input farming systems to
reduce N fertilizer costs, especially in developing countries and organic farming
systems. Additional research is needed to investigate companion crop yield
quality and N contribution to a subsequent crop. As new hybrids are developed
that could withstand increased plant density, it would be interesting to investigate
the effect of increased corn density up to 100 000 plants ha'1 on cover crop DM.
Since AC Greenfix did not perform well in the corn grain interseeding system
compared to monoculture cropping, we recommend that research be done on
early establishment in the spring before planting short cycle vegetables or relay

establishment after winter wheat harvest or before soybean harvest.

59

References:

Abdin, 0., BE. Coulman, D. Cloutier, M.A. Faris, X. Zhou, and D.L. Smith. 1998.
Yield and yield components of corn interseeded with cover crops. Agron.
J. 90:63-68.

Akunda, E.M.W. 2001. Crop yields of sorghum and soybeans in an intercrop. J.
Food Technol. in Africa 6:2-4.

Alford, C.M., J.M. Krall, and SD. Miller. 2003. Intercropping irrigated corn with
annual legumes for fall forage in the High Plains. Agron. J. 95:520-525.

Balkcom, KS, and D.W. Reeves. 2005. Sunn-hemp utilized as a legume cover
crop for corn production. Agron. J. 97:26-31.

Baumann, D.T., L. Bastiaans, and M.J. Kropff. 2001. Competition and crop
performance in a leek-celery intercropping system. Crop Sci 41:764-774.

Bellido, LL. 1994. Grain legumes for animal feed, p. 273-288, In J. E. Hernando
Bermejo and J. Leon, eds. Neglected crops: 1492 from a different
perspective. Plant Production and Protection Series N°. 26. FAO, Rome,
Italy.

Bellinder, RR, R. Rajalahti, and J.B. Colquhoun. 1996. Using cultivation and
interseeded cover crops to control weeds in transplanted cabbage. In

Proc. de Colloque lntemational Sur la Biologie des Mauvaise Herbesz343-
348.

Biederbeck, V.O. 2005. Annual forages. Soil fact sheets. Saskatchewan Soil
Conservation Association. (Available online at

httpzllssca.usask.caIagronomics/).

Biederbeck, V.O., and GT Bouman. 1994. Water use by annual green manure
legumes in dryland cropping systems. Agron. J. 86:543—549.

Biederbeck, V.O., O.T. Bouman, J. Looman, A.E. Slinkard, L.D. Bailey, W.A.
Rice, and H.H. Janzen. 1993. Productivity of 4 annual legumes as green
manure in dryland cropping systems. Agron. J. 85:1035-1043.

Blackshaw, R.E., J.R. Moyer, R.C. Doram, A.L. Boswall, and E.G. Smith. 2001.
Suitability of undersown sweetclover as a fallow replacement in semiarid
cropping systems. Agron. J. 93:863-868.

Blaser, B.C., L.R. Gibson, J.W. Singer, and J.-L. Jannink. 2006. Optimizing

seeding rates for winter cereal grains and frost-seeded red clover
intercrops. Agron. J. 98:1041-1049.

6O

Bowman, G., C. Shiriey, and C. Cramer. 1998. Managing cover crops
profitability. 2nd ed., Burlington, VT.

Brooks, AS, A. Wilcox, R.T. Cook, K.L. James, and M.J. Crook. 2006. The use
of an alternative food source (red clover) as a means of reducing slug pest
damage to winter wheat: towards field implementation. Pest Manag. Sci.
62:252-262.

Campbell, CG. 1997. Grass pea. Lathyrus sativum L. Promoting the
conservation and use of underutilized and neglected crops.18. Institute of
Plant Genetics and Crops Plant Research, Gatersleben/lntemational Plant
Genetic Resources Institute, Rome, Italy.

Chikoye, D., F. Ekeleme, and El. Udensi. 2001. Cogongrass suppression by
intercropping cover crops in com/cassava systems. Weed Sci. 49:658-
667.

Coffman, CG. 1998. Critical growth stages of com. (Available online at
httpzlllubbocktamu.edu/com/pdf/criticalgrth.mt).

Cogger, C., A. Bary, and E. Myhre. 2006. Cover crops in vegetable systems.
Washington State University Center for Sustaining Agriculture and Natural
Resources. (Available online at:

http:/Iwww.puyallupmsu.edu/soilmgmt/SusAg Sum CvrCrop.htm).

Crum, JR, and HP. Collins. 2004. Kellogg Biological Station soils. (Available
online at httpzlllter.kbs.msu.edu/Soil/characterizationl).

Dekker, A.M., A.J. Clark, J.J. Meisinger. F.R. Mulford, and MS. McIntosh. 1994.
Legume cover crop contributions to no-tillage com production. Agron. J.
86:126—135.

DFS. 2003. Grow your own nitrogen. (Available online at

httpzllwwwaggreenfixcoml).

Diver, S., G. Kuepper, and P. Sullivan. 2001. Organic sweet corn production.
(Available online at httpzllattra.ncat.o[g/attra-pub/PDF/sweetcom.pg!)

Exner, ON, and RM. Cruse. 1993. Interseeded forage legume potential as
winter ground cover, nitrogen-source, and competitor. J. Prod. Agric.
6:226-231.

Freeman, K.W., W.E. Thomason, D.A. Keahey, K.J. Wynn, R.W. Mullen, G.V.

Johnson, W.R. Raun, and MT. Humphreys. 2000. Improving fertilizer
nitrogen use efficiency using alternative legume interseeding in continuous

61

com. (Available online at
http://nue.okstate.edu/ngume lntegeedinghtml.

Griffin, T., M. Liebman, and J. Jemison, Jr. 2000. Cover crops for sweet corn
production in a short-season environment. Agron. J. 92:144-151.

Hashemi, A.M., S.J. Herbert, and DH. Putnam. 2005. Yield response of com to
crowding stress. Agron. J. 97:839-846.

Hesterrnan, O.B., T.S. Griffin, P.T. Williams, G.H. Harris, and DR. Christenson.
1992. Forage-legume small-grain intercrops-nitrogen production and
response of subsequent corn rotations. J. Prod. Agric. 5:340-348.

Hively, W.D., and W.J. Cox. 2001. lnterseeding cover crops into soybean and
subsequent corn yields. Agron. J. 93:308-313.

IPBO. 2006. IPBO Lathyrus research. Plant Biotechnology Institute for
Developing Countries: Available online at

<http://www.ipbo.rug.ac.be/activities/ourresearch/lathvrus.htmk.

Jeranyama, P., O.B. Hesterrnan, and CC. Sheaffer. 1998. Medic planting date
effect on dry matter and nitrogen accumulation when clear-seeded or
intercropped with com. Agron. J. 90:616-622.

Khan, Z.R., A. Hassanali, W. Overholt, T.M. Khamis, A.M. Hooper, J.A. Pickett,
L.J. Wadhams, and CM. Woodcock. 2002. Control of witchweed Shiga
hermonthica by intercropping with Desmodium spp., and the mechanism
defined as allelopathic. J. Chemical Ecol. 28:1871-1885.

Lauer, J.G. 2002. Methods for calculating corn yield. Agronomy advice: Field
Crops 28.47-33.

Liebman, M., and E. Dyck. 1993. Crop-rotation and intercropping strategies for
weed management. Ecol. Applications 3292-122.

LTER—Weather. 2006. Weather data during the 2002, 2003, 2004 and 2005
growing seasons. Available online
at:<http://Iter.kbs.msu.edu/Data/table.isp?Prodt_ict=KB8002-
001&limitBy=Year&ordeFdesc>. Kellogg Biological Station, Hickory
Comers, Ml.

 

LTER-Yields. 2002. Available online at:

<http://Iter.kbs.msu.edu/Data/table.isp?Product=KB8020-
001 &limith=Yea r&tools=show&order=de§c&from=2002&to=A)02>.

Kellogg Biological Station, Hickory Comers, MI.

62

 

Martens, J.R.T., J.W. Hoeppner, and M.H. Entz. 2001. Legume cover crops with
winter cereals in Southern Manitoba: establishment, productivity, and
microclimate effects. Agron. J. 93:1086—1096.

Martens, J.R.T., M.H. Entz, and J.W. Hoeppner. 2005. Legume cover crops with
winter cereals in Southern Manitoba: Fertilizer replacement values for cat.
Can. J. Plant Sci. 85:645-648.

Mutch, D., and T. Martin. 1998. Cover crops, In M. A. Cavigelli, et al., eds.
Michigan Field Crop Ecology: Managing biological processes for
productivity and environmental quality. Michigan State University
Extension Bulletin. E-2646. 92pp.

Mutch, D., T. Martin, and R. Kosola. 2003. Red clover (Trifolium pretense L.)
suppression of common ragweed (Ambrosia artemisiifolia) in winter wheat
(Triticum aestivum). Weed Technol. 1 7:181-185.

Odhiambo, J.J.O., and AA. Bomke. 2001. Grass and legume cover crop effects
on dry matter and nitrogen accumulation. Agron. J. 93:299-307.

Oswald, A., J.K. Ransom, J. Kroschel, and J. Sauerbom. 2002. Intercropping
controls Striga in maize based farming systems. Crop Prot. 21:367-374.

Peet, M. 1995. Sustainable practices for vegetable production in the South.
Focus Publishing, Newburyport MA 01950.

Rao, S.C., B.K. Northup, and HS. Mayeux. 2005. Candidate cool-season
legumes for filling forage deficit periods in the Southern Great Plains. Crop
Sci. 45:2068-2074.

Ross, S.M., J.R. King, J.T. O'Donovan. and RC. Izaurralde. 2003. Seeding rate
effects in cats and berseem clover intercrops. Can. J. Plant Sci. 83:769-
778.

Ross, S.M., J.R. King, J.T. O'Donovan. and D. Spaner. 2005. The productivity of
cats and berseem clover intercrops. I. Primary growth characteristics and
forage quality at four densities of cats. Grass and Forage Sc. 60:74—86.

Sarrantonio, M. 1994. Northeast cover crop handbook. Rodale Institute,
Emmaus, PA.

Sarrantonio, M., and T. Molloy. 2003. Response of sweet corn to red clover
under two tillage methods. J. Sustainable Agric. 23291-109.

SAS Institute. 2001. SAS user's guide: Statistics. Release 8th ed. SAS Institute.

63

Scott, T.W., J. Mt. Pleasant, R.F. Burt, and DJ. Otis. 1987. Contributions of
ground cover, dry matter, and nitrogen from intercrops and cover crops in
a corn polyculture system. Agron. J. 79:792-798.

Singer, J.W., M.D. Casler, and K.A. Kohler. 2006. Wheat effect on frost-seeded
red clover cultivar establishment and yield. Agron. J. 98:265-269.

Singer, J.W., W.J. Cox, R.R. Hahn, and E.J. Shields. 2000. Cropping system
effects on weed emergence and densities in corn. Agron. J. 92:754—760.

Small, E. 1999. New crops for Canadian agriculture, p. 15-52., In J. Janick, ed.
Perspectives on new crops and new uses. ASHS Press, Alexandria, VA.

Smeltekop, H., D.E. Clay, and SA. Clay. 2002. The impact of intercropping
annual 'sava' snail medic on corn production. Agron. J. 94:917-924.

Sogbedji, J.M., H.M. van Es, and KL. Agbeko. 2006. Cover cropping and nutrient
management strategies for maize production in Western Africa. Agron. J.
98:883-889.

Some, 8., W.L. Hargrove, and DE. Radcliffe. 1992. Effect of intercropping and
residue management on soil water depletion, plant biomass and grain
production, In M. D. Mullen and B. N. Duck, eds. Proc. of the 1992
Southern Conservation Tillage Conference, Jackson and Milan,
Tennessee, USA.

Stute, J.K., and J.L. Posner. 1995. Legume cover crops as a nitrogen source for
com in an oat—com rotation. J. Prod. Agric. 82385-390.

Thompson, T., and N. Wagner. 2000. A low-cost mechanism for inter-seeding
cover crops in com. GREENBOOK 2000. Energy and Sustainable
Agriculture Program.

Tollenaar, M., W. Deen, L. Echarte, and W. Liu. 2006. Effect of crowding stress
on dry matter accumulation and harvest index in maize. Agron. J. 98:930-
937.

Vyn, T.J., K.J. Janovicek, M.H. Miller, and E.G. Beauchamp. 1999. Soil nitrate
accumulation and corn response to preceding small-grain fertilization and
cover crops. Agron. J. 91:17-24.

Vyn, T.J., J.G. Faber, K.J. Janovicek, and E.G. Beauchamp. 2000. Cover crop
effects on nitrogen availability to corn following wheat. Agron. J. 92:915-
924.

64

Widdicombe, W.D., and KO. Thelen. 2002. Row width and plant density effect on
corn forage hybrids. Agron. J. 94:326-330.

Zemenchik, R.A., K.A. Albrecht, C.M. Boerboom, and J.G. Lauer. 2000. Corn
production with kura clover as a living mulch. Agron. J. 92:698-705.

65

Table 1. Dry matter and N content of red clover (Trifolium pretense L.), established the
previous year in strips and sampled before planting corn (Zea mays L.), in spring
of 2002, 2003, 2004 and 2005 at Kellogg Biological Station, Hickory Comers, Ml.

 

 

DM N content
Kg ha'1
2002 6531 221
2003 7780 264
2004 5520 161
2005 3444 132

 

 

Table 2: Significance of the effect of plant density (PD) and management practices (MP)
across four years (Y) on corn (Zea mays L.) yield (CY), days to flowering (DF),
plant height (PH), ears per plant (EP), grain moisture (GM) and test weight (TW),
and on cover crop fall dry matter (FDM), fall cover crop density(FCD), fall cover
crop height (FCH) and spring red clover (Trifolium pretense L.) dry matter
(SRDM) at Kellogg Biological Station, Hickory Comers, Ml.

 

 

 

 

Corn Cover cr0p
CY DF PH EP GM TW FDM FCD FCH SRDM
y? *** «um 4* we iii um NS * we a.“
PD *** ** NS *** NS NS *“ NS NS NS
Y x PD * NS NS *** NS NS NS NS NS NS
MP3 NS iii a * NS NS n en we __
Y X MP no m n NS *1» e t *tt mu ___
PD x MP NS NS NS NS NS NS NS NS NS --
Y x PD x MP NS NS NS NS NS NS NS NS NS ---

 

*Significant at the 0.05 level
“Significant at the 0.01 level
***Significant at the 0.001 level
*for SRDM is three years.

*for FDM, FPM and FCH, MP is cover crops species

66

Table 3. Mean corn (Zea mays L.) yield (Mg ha") of management practices across corn
plant density during the 2002, 2003, 2004 and 2005 growing seasons at Kellogg
Biological Station, Hickory Comers, Ml.

 

 

 

 

 

 

 

 

 

 

 

 

 

Management Corn density (plants he“)
practices 37 500 55 000 65 000 75 000
Mg ha"
2002

PRIR 7.858* C” 10.358 A 9.418 AB 9.058 B
PRIA 8.108 B 9.210 A 10.018 A 9.028 AB
PRNI 7.588 B 10.0580 A 9.608 A 9.348 A
CMNF 6.080 A 5.990 A 6.930 A 6.360 A
cv (%) 12

2003
PRIR 6.338 A 7.268 A 7.088 A 7.688 A
PRIA 6.368 B 6.868 B 5.888 B 7.988 A
PRNI 5.788 A 6.728 A 6.828 A 7.438 A
CMNF 6.438 A 7.268 A 6.918 A 7.638 A
CV (%) 12

2004
PRIR 7.588 B 8.378 AB 8.560 AB 9.010 A
PRIA 7.858 B 8.178 B 8.610 AB 9.530 A
PRNI 7.798 B 8.138 AB 8.840 AB 9.140 A
CMNF 7.668 C 8.878 B 9.968 B 11.248 A
cv (%) 10

2005
PRIR 9.118 B 9.820 AB 10.3080 A 9.70 AB
PRIA 8.538 C 9.720 B 10.7180 AB 10.980 A
PRNI 8.748 B 10.2480 A 9.640 AB 10.11bc A
CMNF 9.428 C 11.358 AB 11.048 B 12.328 A
CV (%) 8

 

*Means within columns in the same year followed by the same lower case
letter are not significantly different at P=0.05.
** Means within rows in the same year followed by the same upper case
letter are not significantly different at P=0.05.
PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: coefficient of variation.

67

Table 4. Mean corn (Zea mays L.) yield (Mg ha") of combined four-year data across
management practices and com plant density at Kellogg Biological Station,
Hickory Comers, Ml.

 

 

 

 

 

Management Corn density (plants ha'r)

practices 37 500 55 000 65 000 75 000
Mg ha'T

PRIR 7.728* B" 8.958 A 8.848 A 8.868 A

PRIA 7.718 C 8.498 B 8.808 AB 9.388 A

PRNI 7.478 B 8.788 A 8.738 A 9.008 A

CMNF 7.40a C 8.36a B 8.71a AB 9.39a A

CV (%) 10

 

* Means within columns followed by the same lower case letter are not
significantly different at P=0.05.

** Means within rows followed by the same upper case letter are not
significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: coefficient of variation

Table 5. Mean corn (Zea mays L.) yield (Mg ha“) in management practices across plant
density during the 2002, 2003, 2004, 2005 and four-year average at Kellogg
Biological Station, Hickory Comers, MI.

 

 

 

 

 

Corn yield
Management 2002 2003 2004 2005 Average
practices Mg ha1
PRIR 9.16a* 7.09a 8.38b 9.73b 8.59a
PRIA 9.09e 6.77e 8.54b 10.0b 8.59a
PRNI 9.14a 6.69a 8.47b 9.68b 8.50a
CMNF 6.34b 7.05a 9.43a 11.03a 8.46a
CV (%) 12 12 10 8 18

 

*Means within columns followed by the same letter are not significantly different
at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

68

Table 6. Days to flowering, plant height, ears per plant, grain moisture and test weight of
com (Zea mays L.) in management practices across plant density during the
2002, 2003, 2004 and 2005 growing seasons at Kellogg Biological Station,
Hickory Corners, MI.

 

 

 

 

 

 

 

 

 

 

 

Management Days to Height Ears Grain Test
practices flowering (m) plant‘1 Moisture weight
(913:)

2002
PRIR 66.503" 1.81a 1.023 253.63 52.56a
PRIA 66.633 1 .803 1 .023 246.83 52.53a
PRNI 66.563 1.793 1.023 249.93 50.81 ab
CMNF 68.94b 1.63b 1.003 243.53 47.22b
CV (%) 1 7 2 16 1 1

2003
PRIR 66.003 1 .97a 1 .02a 294.9b 48.58a
PRIA 66.003 1.943 1 .033 301 .8b 48.533
PRNI 66.003 1 .943 1 .023 300% 48.503
CMNF 68.63b 1 .933 1 .053 328.83 47.38b
CV (%) 1 4 3 5 1

2004
PRIR 66.133 1.753 1.10b 209.13 55.15b
PRIA 66.193 1.763 1.11ab 211.43 55.19b
PRNI 66.003 1.783 1.113b 210.83 55.20b
CMNF 67.06b 1.743 1.153 199.9b 55.563
CV (%) 1 7 6 5 1

2005
PRIR 543 2.003 1 .24b 179.8b 57.763
PRIA 543 2.003 1 .23b 180.8ab 57.703
PRNI 543 2.003 1.21b 180.1b 57.703
CMNF 543 1.973 1.493 186.03 57.753
CV (2g -- 7 34 7 1

 

* Means within columns in the same year followed by the same letter are
not significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: coefficient of variation.

69

Table 7. Days to flowering, plant height, ears per plant, grain moisture and test weight of
corn (Zea mays L.) at four plant densities across management practices during
the 2002, 2003, 2004 and 2005 growing seasons at Kellogg Biological Station,
Hickory Comers, MI.

 

 

 

 

 

Corn density Days to Height Ears Grain Test
(plants ha") flowering (m) plant'1 moisture weight
(M11

2002
37 500 66.758" 1.758 1.048 233.88 51.198
55 000 66.818 1.798 1.008 262.78 49.438
65 000 67.500 1.758 1.018 248.18 51.978
75 000 67.560 1.758 1.008 249.18 50.538
cv (%) 1 7 2 16 11

2003
37 500 66.638 1.948 1.088 303.88 48.478
55 000 66.638 1.938 1.0280 303.18 48.288
65 000 66.638 1.958 1.010 305.58 47.860
75 000 66.758 1.968 1.010 313.98 48.388
CV (%) 1 4 3 5 1

2004
37 500 66.008 1.730 1.298 204.18 55.548
55 000 66.258 1.720 1.070 208.78 55.000
65 000 66.508 1.7680 1.050 207.98 55.2780
75 000 66.638 1.838 1.070 210.68 55.2780
CV (%) 1 7 6 5 1

2005
37 500 548 1.940 1.638 179.28 57.758
55 000 548 2.048 1.170 188.58 57.858
65 000 548 2.0180 1.100 179.68 57.768
75 000 548 1.9980 1.070 179.48 57.568
CV (%) -- 7 34 7 1

 

 

 

 

 

 

 

* Means within columns in the same year followed by the same letter

are not significantly different at P=0.05.
CV: coefficient of variation

70

Table 8. Effect of monoculture and interseeding at four corn (Zea mays L.) densities on
red clover (Trifolium pretense L.) or AC Greenfix (Lathyrus sativum L.) DM
(Mg ha“), density (plants m‘z) and height (cm) in fall during the 2002, 2003, 2004
and 2005 growing seasons at Kellogg Biological Station, Hickory Comers, Ml.

 

 

 

 

 

 

 

 

 

 

 

Plant Red clover AC Greenfix
density DM Density Height DM Densiy Height
Plants ha" Mg ha'1 plants rn‘2 cm Mg ha3 plants rn'2 cm
2002
37 500 0.4808* 8393 12.38 0.4558 868 71.08
55 000 0.3080 6368 9.28 0.36080 798 74.28
65 000 0.2630 6898 13.18 0.37080 1013 79.38
75 000 0.1830 5710 8.18 0.2030 713 78.58
CV (%) 36 39 28 36 39 28
2003
37 500 0.1 558 34580 9.78 0.6858 1273 67.38
55 000 0.1008 3070 8.58 0.2150 1173 60.78
65 000 0.1758 5128 7.98 0.2550 1133 60.68
75 000 0.0708 2490 6.78 0.2200 1378 55.68
CV (%) 33 31 22 33 31 22
2004
0" 1.4403 640a 24.93 2.1953 943 94.63
37 500 0.4750 7378 1 7.080 0.5630 938 103.98
55 000 0.37500 6298 14.20 0.3400 773 103.68
65 000 0.2730 6468 13.20 0.3830 908 98.58
75 000 0.3000 7538 12.40 0.2630 798 87.80
cv (%) 35 37 13 35 37 13
2005
0 0.456 258 12.9 1 .5998 808 60.68
37 500 ---- --—- --- 0.2420 768 58.58
55 000 ----- ----- --—--- 0.18800 868 61.38
65 000 ----- ---------- 0.2160 908 63.58
75 000 ----- ------ ----- 0.1270 728 63.38
Cfl%) 27 23 1 8

 

*Means within columns in the same year followed by the same letter are not

significantly different at P=0.05.

Monoculture cover crops.
CV: coefficient of variation.

71

Table 9. Mean interseeded red clover (Trifolium pretense L.) and AC Greenfix (Lathyrus
sativum L.) DM (Mg ha"), density (plant m'2)and height (cm) at four corn
(Zea mays L.) plant densities in fall 2002, 2003 and 2004 at Kellogg Biological
Station, Hickory Comers, MI.

 

 

 

 

 

 

 

Red clover AC Greenfix

Plant density DM Density Heght DM Density Height
Plants ha'1 Mgha'1 plants m'2 cm _Mg ha’1 plants rn'2 cm
37 500 0.3708* 6408 13.08 0.5678 1028 80.78
55 000 0.26080 5248 10.68 0.3050 918 79.58
65 000 0.2370 6168 11.48 0.3360 1013 79.58
75 000 0.1840 5248 9.13 0.2280 958 74.08
CV (%) 38 39 21 38 39 21

 

Correlation coefficient between cover crop DM and corn plant density =-0.55 (p < 0.0001)
*Means within columns followed by the same letter are not significantly different at

=0.05.
CV: coefficient of variation.

Table 10. Effect of interseeding com (Zea mays L.), at four plant densities, on red clover
(Trifolium pretense L.) DM (Mg he") the subsequent spring in 2003, 2004 and
2005 at Kellogg Biological Station, Hickory Comers, MI.

 

 

 

 

 

 

Red clover DM
Plant density 2003 2004 2005 Average_
( Plants ha") Mg ha"
0* ---- 8.173 ----
37 500 3.923“ 2.783 6.05b 4.253
55 000 3.623 3.383 5.48b 4.163
65 000 4.123 2.873 5.88b 4.293
75 000 3.103 2.343 5.36b 3.603
CV (%) 20 32 14 19

 

'Monoculture cover crops.

“Means within column followed by the same letter are not
significantly different at P=0.05.

CV: coefficient of variation

72

 

       
   
  

        

       

    

 

 

 

 

   

 

 

 

 

 

 

 

 

 

   
  

 
     
   
 

 

 

 

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Figure 1. Monthly average minimum and maximum temperature, and total monthly
precipitation during the 2002, 2003, 2004 and 2005 growing seasons
compared with the 30-year monthly average at Kellogg Biological Station,
Hickory Comers, MI.

73

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Corn density (plants ha'1)

Figure 5. Relationship between interseeded cover crop dry matter and
corn plant density from 2002 to 2004. Data are averaged across
years. Each point is the mean of 10 samples.

77

Chapter two

Effect of Com Density on Corn and Cover Crop Nitrogen in an

lnterseeding System

Abstract

Little is known about the effect of an interseeding system at various corn
(Zea mays L.) densities on nitrogen (N) concentration and content of com or
cover crops. Field assessment and laboratory analysis of plant tissues can help
to evaluate the effect of crop management on crop N. A study was conducted to
evaluate (1) the effect of corn density (37 500 to 75 000 plants ha") and plowed
red clover (Trifolium pretense L.) versus mineral N fertilizer on corn N
concentration and content during and at the end of the growing season; and (2)
the impact of corn density on N concentration and accumulation of interseeded
red clover or AC Greenfix (Lathyrus sativus L.). Both chlorophyll content and ear
leaf N concentration were used to assess com N status during the growing
season. At the end of the growing season, N was measured in corn grain, leaves
and stalks. Interseeded cover crop N was measured in fall of the growing season
and the subsequent spring. Grain N concentration was higher at low corn
density, with a decreasing trend as corn plant density increased. Grain N
concentration was the highest in corn supplied with mineral N fertilizer. In three of
the four years when rainfall was optimal, grain N content of corn supplied with

mineral N fertilizer was the highest and accumulated up to 140 kg ha".

78

Chlorophyll content and ear leaf N concentration were the highest in the lowest
com density and in com supplied with N fertilizer. Chlorophyll content and ear
leaf N at silking were good indicators of corn grain N concentration at the end of
the growing season.

In the fall, N concentration of interseeded red clover and AC Greenfix was
not affected by com plant density. Nitrogen concentration of monoculture cover
crops was similar to N concentration of interseeded cover crops, except for AC
Greenfix in 2005. In the fall, N accumulation of interseeded cover crops at low
com density was significantly higher compared to higher plant densities, ranging
from 2.18 to 15.58 and 5.0 to 20.25 kg ha'1 for red clover and AC Greenfix,
respectively. Monoculture red clover (20.62 to 48.15 kg ha“) and AC Greenfix
(75.41 to 81.80 kg ha") accumulated more N then interseeded red clover and AC
Greenfix respectively.

There was a seasonal effect on cover crop dry matter in the subsequent
spring. The subsequent spring, in two of the three years, interseeded red clover
N concentration was highest at 37 500 plants ha". Monoculture red clover
accumulated more N (234.41 kg he") by the subsequent spring compared with
interseeded red clover (58 to 162.3 kg ha'1). Red clover can be interseeded at
high com plant densities and accumulate significant N the subsequent spring,

sufficient to meet N demand of the following crop.

79

Introduction

Crop production and quality can be influenced by management practices.
The use of management practices such as cover crops, nitrogen (N) fertilizer and
interseeding can affect crop N concentration and uptake (Jeranyama et al., 1998;
Eghball and Power, 1999; Sainju and Singh, 2001; Sweeney and Moyer, 2004).
Legume cover crops provide 3 potential to meet the N demand of crops and to
reduce the reliance on N fertilizer in agricultural production. Nitrogen source,
such as the use of mineral or organic N can also affect crop yield and other
quality attributes such as taste of tomatoes (Lycopersicon esculentum L.) (Heeb
et al., 2005). Several studies evaluated the effect of N source on N concentration
and content of various crops. Total N uptake of corn (Zea mays L.) fertilized with
synthetic N was greater than in corn supplied with manure and compost (Eghball
and Power, 1999; Eghball et al., 2004). Corn grain N concentration and uptake
were influenced by varying N rates (Katsvairo et al., 2003). Merino et al. (2004)
showed that N concentration and uptake of forage increased with increased N
fertilizer rates. Similarly, Sweeney and Moyer (2004) found that N uptake by
sorghum (Sorghum bicolor L.) increased with N fertilizer rates. In addition to
increased N concentration with increased N fertilizer rates, Fan et al. (2004)
observed a significant variation in N concentration of wheat (Triticum aestivum) In
relation to N fertilizer source (Urea versus coated urea). Grain N uptake of wheat
was higher with coated urea compared with common urea. Cover crop use can
affect N concentration and uptake of crops. In comparing crop N uptake in

various management systems, Sweeney and Meyer (2004) found that sorghum

80

following red clover (Trifolium pretense) accumulated more N then continuous
sorghum with no previous cover crop. Balkcom and Reeves (2005) observed that
com grain N content was higher following sunn- hemp (Crate/aria juncea L.) than
when com followed fallow. Similarly, Jeranyama et al. (1998) found that N
content of com following interseeded medics (Medicago polymorpha and M.
scutellata L.) was higher then In com without medic. Vyn et al. (1999) found that
whole plant N content of corn at enthesis was strongly affected by cover crop
species, with corn following annual ryegrass (Lolium multiflorum) averaging one-
half of the total N content of that observed after red clover. Monoculture or
interseeding systems can also affect N concentration and content/accumulation
of companion crops. Some studies have suggested that N accumulation of crops
can increase with interseeding, whereas others have suggested no increase in
total N yield (Carr et al., 1998; Hauggaard-Nielsen et al., 2001; Viller-Mir et al.,
2002). Crude protein yield of berseem clover was lower in monoculture
compared with interseeded berseem clover into oat (Avene sative L.) (Ross et
al., 2005). Yield and N content of com and cowpea (Vigna unguiculata) were
reduced when intercropped compared with monocropping, however N
concentration was not affected (Ofori and Stern, 1986). When grown in
monoculture or intercropped, barley (Hordeum vulgare L.) accumulated similar
amount of aboveground N, however total N accumulation by field pea (Pisum
sativum L.) was less when intercropped than as a monoculture crop (Hauggaard-
Nielsen et al., 2001). In contrast, Szumigalski and Van Acker (2006) suggested

that greater N concentrations were seen in wheat and canola when intercropped

81

with field pea. In comparing two cover crops in an interseeding system, Abdin et
el. (1998) observed a lower concentration of grain protein when com was
interseeded with hairy vetch (Vicie villosa Roth) in comparison with subterranean
clover (Trifolium subterraneum), red clover-rye mixture or a control. Increased
plant density of intercrops can also affect N concentration and uptake of
companion crops. Ross et al. (2005) showed that when cat was interseeded with
berseem clover, crude protein was reduced with increased oat density compared
with monoculture crops. Similar findings were obtained by Carr et al. (1998) who
suggested that forage crude protein decreased as barley (Hordeum vulgare)
density increased. Thorsted et al. (2006) found that increased wheat density
reduced grain N concentration. Corn forage crude protein decreased with
increased corn density (Cusicanqui and Lauer, 1999; Widdicombe and Thelen,
2002). Little is known about the effect of an interseeding system at various com
densities on N concentration and content of corn or cover crops.

These studies investigated the effect of monoculture or interseeded cover
crop and/or various rates of fertilizer on com N concentration and content/uptake.
No study has looked at the effect of combination of N source versus com density
and interseeding versus corn density on N concentration and content of com and
cover crops. A study and comparison of red clover derived-N versus N fertilizer at
various corn densities is needed to assess N concentration and content of corn.
In addition, there is a need for an evaluation of the effect of interseeding system
at various corn densities on N concentration and content of corn when

interseeded with red clover or AC Greenfix.

82

Cover crop N accumulation and availability to a succeeding crop depend
on cover crop species, environmental conditions, and management (Hestennan
et al., 1992; Dekker et al., 1994; Stute end Posner, 1995). AC Greenfix (Lathyrus
sativum L.), a variety of chickling vetch, has the potential to produce 90-112 kg
ha‘1 of N in 8-10 weeks after planting (DFS, 2003). Rao et al. (2005) showed that
at full bloom, AC Greenfix N concentration was 26.2 g kg“1 and produced 168 kg
ha’1 of total N. Conversely, lentil contained 26.3 g kg“1 N and accumulated only
53 kg ha'1 of N. Red clover has the potential of accumulating 79-168 kg ha‘1 of N
in a growing season (Bowman et al., 1998). Shrestha et al. (1998) showed a
variation in crude protein concentration of annual medics (Medicago spp.),
berseem clover (Trifolium alexandrinum L.), and alfalfa (Medicago sativa L. ).
Similariy, Alford et al. (2003) observed differences in crude protein of forages
including alfalfa, sweet clover (Melitotus officinalis Lam) and various cultivars of
medics. Sampling time can also affect N concentration in companion crops.
Sainju and Singh (2001) found that biomass, N concentration and N
accumulation of hairy vetch increased with late sampling compared to early
sampling. In contrast, Merino et al. (2004) showed that annual grass N
concentration decreased with time. Alford et al. (2003) observed a decrease in
crude protein from 45 to 40 % of annual legumes from a July to November
sampling time. There is a need to assess whether interseeded cover crops can
perform similarly to monoculture cover crops and accumulate sufficient N to meet
the needs of a subsequent crop. Supplying N through interseeded cover crops is

an alternative to monoculture cover crops and provides the advantage of

83

producing a cash crop. An assessment of cover crop N accumulation, when in
monoculture or interseeded into various plant densities, in the fall and the
subsequent spring can help estimate its potential for N contribution to a

subsequent crop.

Measurements of N status in corn

Various methods are used to evaluate corn N status in situ and at the end
of the growing season. Methods include use of chlorophyll meter [(Minolta SPAD-
502 meter), Spectrum Technologies, Inc. Plainfield, Illinois] and ear leaf analysis.
These methods can help to assess whether N availability may have contributed
to observed differences in grain N uptake or yield. The chlorophyll meter
assesses the degree of greenness, which is an indication of chlorophyll content
and leaf N concentration during the growing season (Varvel et al., 1997). A
correlation of R=0.78 (p=0.001) has been reported between measured SPAD-
502 meter values and leaf N concentration in corn (Bullock and Anderson, 1998).
Chlorophyll content also can be used as an indicator of N uptake and corn yield
(Eghball and Power, 1999). Chlorophyll content can be affected by N
management and weather conditions such as wet or dry growing conditions
(Hussein et al., 2000). Scharf et al. (2002) showed that relatively wet conditions
during the growing season led to greater apparent N stress and lower chlorophyll
readings. Ear leaf N has been used as a tool to assess in-season com N status.
Scott et al. (1987) found no significant differences in ear leaf N concentration of

corn following legume cover crops compared with com supplied with N fertilizer.

84

The above tools have been used in comparing various rates of fertilizer or cover
crops on N content of corn. No study has looked at the use of these tools in
assessing N status of corn in an interseeding system at various corn densities.
There is a need to evaluate the effect of N source, interseeding and corn density
on corn N status using a chlorophyll meter and ear leaf N analysis.

Research in Michigan has investigated the effect of interseeding cover
crop on yield and N content of companion crops (Hesterrnan et al., 1992;
Jeranyama et al., 1998). However, no study has looked at the impact of corn
density on N concentration and content of corn and cover crops in an
interseeding system. The objectives of this study were to: (1) compare the effect
of mineral N fertilizer and monoculture red clover derived-N on com N at various
corn densities; (2) assess the effect of com density in an interseeding system on
red clover-N and AC Greenfix-N in fall and the subsequent spring; (3) assess the
effect of interseeding and corn density on com-N using the in- season test (ear

leaf and chlorophyll content) versus end-season N test (plant analysis).

Materials and Methods

Site description

Field studies were conducted from 2002 to 2005 at the Kellogg Biological
Station (KBS) in Hickory Comers, Michigan. The soil types at KBS were the
Kalamazoo (fine-loamy, mixed, mesic Typic Hapludalfs) and Oshtemo (coarse-

Ioamy, mixed, mesic Typic Hapludalfs) series (Crum and Collins, 2004).

85

The research was conducted on a different field each year to permit planting on
site following red clover plow down. Corn research plots were established in
2002 (Field 1), 2003 (Field 2), 2004 (Field 3) and 2005 (Field 4). In the year prior
to corn establishment, red clover was planted in each field into wheat stubble in
July-August except in 2001, when red clover was established in com stubble.
Red clover was chisel-plowed the subsequent spring before com planting in

order to serve as a N source for the non-conventional treatments.

Experimental design

Each year the experiment was replicated four times except in 2003 where
only two replications were used due to poor corn stand caused by wildlife
damage. The experimental design was a split-plot with four corn densities and
four management practices. The main-plots were four com densities (37 500, 55
000, 65 000 and 75 000 plants he"). Sub-plots were four management practices:
(1) Conventional management, com seeded into wheat stubble with N fertilizer
applied (CMNF); (2) Corn seeded into plowed red clover, no N fertilizer,
interseeded with AC Greenfix (PRIA); (3) Corn seeded into plowed red clover, no
N fertilizer, interseeded with red clover (PRIR) ; (4) Corn seeded into plowed red
clover, no N fertilizer, not interseeded with cover crop (PRNI). Based on the
Preside-dress Nitrate Test (PSNT) results, N fertilizer was applied to the CMNF

treatment up to a total of 140 kg ha'1 every year.

86

Corn

The hybrid Great Lakes 4979 (Great Lakes Hybrids), relative maturity 99
days, was planted into 6-row plots of 4 by 4.5 m on 29 May 2002 and 06 June
2003. In 2004 and 2005, Pioneer Hybrid 38P05, relative maturity 93 days, was
planted on 30 May and 27 May respectively, into 6-row plots of 5 by 4.5 m. The
trials were planted at approximately 100,000 plants he". Two weeks after
emergence, each plot was hand-thinned to the appropriate com density. In
season corn N status was measured only during the 2004 and 2005 growing
seasons using chlorophyll meter and ear leaf N. Whole plant (grain, leaf and

stalk) com N was assessed at the end of the growing season from 2002 to 2005.

Chlorophyll content and ear leaf N

A chlorophyll meter (Minolta SPAD-502), was used to measure leaf
chlorophyll content of corn during the 2004 and 2005 growing seasons. The
procedure described by Piekielek et al. (1995) was used in collecting SPAD-502
meter readings. SPAD meter readings were taken at 1 to 2 cm from the edge of
the leaf and two-thirds to three-quarters of the leaf length from the base.
Damaged and diseased leaves were avoided.

Chlorophyll meter readings were taken six and five times in 2004 and
2005, respectively. In 2004, chlorophyll readings were taken on 10 July, 16 July,
23 July, 1 August, 6 August and 15 August. In 2005, chlorophyll readings were
taken on 7 July, 15 July, 21 July, 29 July and 5 August. The average of ten

chlorophyll meter readings (10 randomly selected plants per plot) was measured

87

starting at the V8-V9 growth stage. Measurements were taken on the uppermost
top fully expanded leaf. Once corn reached the VT stage, measurements were
taken on the ear leaf (leaf at the base of the primary ear).

The ear leaf was collected at corn silking stage for N analysis. Ten leaves
were randomly collected from ten plants from each plot in the four center rows on
15 August 2004 and 05 August 2005. Ear leaf samples were dried in an oven at
60° C for 2 days, and then weighed to determine the dry matter (DM). Ear leaf N
concentration was determined using Total Kjeldahl Nitrogen (TKN) analysis,

described later.

Corn whole plant N

Com was harvested from the four center rows of each plot using a
combine on 17 October 2002, 29 October 2003, 10 November 2004 and 06
October 2005. Corn plants for N analysis were sampled 1-4 days prior to harvest,
and separated into grain, leaves and stalks. In 2002 and 2003, two plants were
collected from each plot. In 2004 and 2005 however, ten plants were collected
from each plot. Grain yield was a summation of combine and hand harvested
corn. Yield was adjusted to 155 g kg'1 moisture content. The TKN procedure was

used to measure grain, leaf and stalk N concentration.
Cover crop N

Red clover and AC Greenfix were interseeded when com plants were

between V5-V7 corn growth stages, the first two weeks of July each year.

88

In 2004 and 2005, monoculture red clover and AC Greenfix treatments were
established at the time of interseeding to compare biomass production with
interseeded cover crops. Red clover was broadcast with e hand-seeder at the
seeding rate of 20.4 kg ha'1 and AC Greenfix was hand-broadcast at the rate of
90 kg ha". Red clover and AC Greenfix aboveground biomass (leaves and stem)
were hand-clipped when AC Greenfix was at full bloom by removing plants from
a random quadrat of 0.209 m2 in each plot. Cover crop samples were dried in an
oven at 60° C for 2 days, and then weighed to determine the DM. Dry matter of
interseeded cover crops was determined in the fall during the year of
establishment on 27 September 2002, 02 October 2003 and 23 August 2004. In
2005, only interseeded AC Greenfix was sampled on 08 August because
Interseeded red clover did not germinate due to dry, hot weather conditions.
Monoculture cover crops were sampled on 23 August 2004 and 08 August 2005.
The subsequent spring red clover was sampled on 02 June 2003, 02 June 2004
and 01 June 2005. The TKN was used to assess N concentration of red clover

and AC Greenfix.

Total Kjeldahl nitrogen and N calculation

All corn (ear leaf, grain, leaf and stalk) and cover crop (aboveground
biomass) tissue samples were ground in a Wiley mill to pass through 1-mm
screen. All samples were digested using a 40-tube Tecator Model 1016 Digester
(Tecator, Hcganéis, Sweden). Cover crop and corn tissue samples of 0.1 g were

digested in 4 ml of 18 M H2804 with 1.5 g K280; and 0.015 g Se catalyst in 100

89

mI-constricted tubes. All samples were digested at 350° C for 4 hours. The tissue
extracts were analyzed using a Lachat Flow Injection Analyzer (Hachat Co.,
Loveland, Colorado). Total N content or accumulation of com grain or cover crop

was calculated as the product of DM yield and N concentration.

Statistical analysis

All data were analyzed using Proc Mixed in Statistical Software Package
SAS version 8.2 (SAS, 2001). Plant density and cropping system were
considered fixed effects. Two error terms were considered in the analysis of the
data, one associated with the whole plot (plant density) and the other associated
with the subplot (management practices) and the interaction (plant density x
management practices). When interaction effects were found to be statistically
significant, means separation was conducted for respective cell means. When
main effects were significant while interactions were not, means separation was
conducted for marginal means. Effects were considered statistically significant at
p= 0.05. Data of weekly chlorophyll content of corn leaves was analyzed as

repeated measurements.

90

 

 

Results and Discussion

Weather patterns

Total monthly Precipitation and monthly average temperature (minimum
and maximum) data from the 2002 to 2005 growing seasons were obtained from
the Long-Tenn Ecological Research weather station (LTER-Weather, 2006). In
2002, there was a drought period in June and July, and the average rainfall in
June was below the 30-year average (Figure 13). Precipitation in June and July
during the 2003 growing season was lower than the 30-year average (Figure 13).
Seasonal total precipitation in 2004 was above the 30-year average (Appendix A)
and well distributed throughout the growing season (Figures 2). Precipitation in
April, May and August during the 2005 growing season was lower than any other
growing season and lower than the 30-yeer average (Figure 13). Although total
precipitation in the 2005 growing season was lower than the 30-year average,
rainfall occurred at critical corn growth stages in June and July. The monthly
average minimum temperature for April 2003 was lower than to the 30-year
average (Figure 1b). Monthly average maximum temperatures during the 2005

growing season from June to September were higher than the 30-year average.

91

Corn grain N
Effect of corn density on corn grain N concentration

Plant density influenced N concentration in corn grain (Table 1). In 2002
and 2004, the lowest plant density, 37 500 plants he", had a significantly higher
grain N concentration than all other plant densities. In 2003, grain N
concentration at 37 500 plants ha‘1 was significantly higher than 65 000 and 75
000 plants he". In 2005, grain N concentration at 37 500 plants he1 was
significantly higher than other com densities, and 55 000 plants he1 was only
significantly higher than 75 000 plants he“. There was an interaction between
plant density and year on com grain N concentration (Table 2). This may have
been due to climatic conditions. There was no corn yield increase at high plant
density when moisture was limiting, suggesting a nutrient competition or low N
uptake.

The four-year average showed that increased plant density decreased N
concentration in grain with no significant differences between 65 000 and 75 000
plants ha'1 (Table 1). These results corroborate the results by Thorsted et al.
(2006) who also observed a decline in grain N concentration as wheat plant
density increased. Similarly, Widdicombe and Thelen (2002), observed a
decrease in onlde protein of forage com as corn density increased. In contrast,
Shapiro and Wortmann (2006) observed no effect of com plant density on grain
N concentration. Grain N concentration was negatively, but significantly
correlatedto corn density with very low correlation coefficients of -0.37

(p=0.0027), -0.63 (p<0.0001), -0.34 (p=0.0057) and -0.41 (p=0.0008) for the

92

2002, 2003, 2004 and 2005 growing seasons respectively (Table 3). Across
years, there was a significant negative correlation of -0.32 (p<0.0001) (data not
shown).

Effect of management practices on corn grain N concentration

Corn grain N concentration was influenced by management practices
(Table 1). In 2002, 2004 and 2005 grain N concentration in CMNF was
significantly higher than in other treatments. In 2003, grain N concentration
differed only between CMNF and PRIA.

Corn grain N concentration ranged from 10.9 to 14.8 g kg". These values
are similar to those obtained by Brouder et al. (2000) who observed corn grain
concentration ranging from 10.6 to 16.5 g kg". Corn grain N concentration in
2002 and 2003 seemed to be higher than corn grain N concentration in 2004 and
2005. This may be related to the hybrid used during these two sets of years.
Great Lakes Hybrid discontinued GL 4973 in 2003, so we switched to Pioneer
38P05 for the 2004 and 2005 growing seasons. Widdicombe and Thelen (2002)
observed a variation in crude protein of forage by hybrid type, with duel-purpose
hybrids containing higher crude protein than the full-season leafy hybrid. When
averaged across four years, the data showed that com supplied with N fertilizer
had a significantly higher grain N concentration than corn planted into plowed red
clover (Table 1).

Effect of management practices on corn grain N content
There was a seasonal (year) effect on corn grain N content (Table 4).

There was an interaction between year and management practices on corn grain

93

N content (Table 2). This was due to dry weather conditions after N side dressing
the CMNF treatment in 2002, resulting in reduced com grain yield and hence
reduced N content. In 2002, grain N content was lower in CMNF compared with
PRIA, PRIR and PRNI (Table 4). In 2003, N content was higher in CMNF
compared with PRIA. In 2004 and 2005, com grain N content was higher in
CMNF compared with PRIA, PRIR and PRNI. When rainfall was optimal, corn
grain N content was the highest in corn supplied with N fertilizer compared with
com planted into plowed red clover (Table 4 and Figure 2). When averaged
across four years, the data showed that com supplied with N fertilizer had a
significantly higher grain N content compared with corn planted into plowed red
clover (Table 4). These findings are in accordance with results of Jeranyama et
al. (1998) who showed low N content in com grain obtaining N from cover crops
rather than mineral N fertilizer.

Effect of interseeding system on grain N concentration and content

No significant difference was observed in grain N concentration and

content when com was grown in monoculture (PRNI) compared to com
interseeded with red clover (PRIR) or AC Greenfix (PRIA) (Tables 1 and 2). In
contrast to our results, Sangakkare et al. (2003) found that the use of a green
manure as an intercrop reduced corn grain N content. Similarly, Ofori and Stern
(1986) found that com grain N content was reduced by intercropping. However

they found that com grain N concentration was not reduced by intercropping.

94

Com Leaf N

Both management practices and corn density had an interaction on N
concentration in corn leaf (Table 2). This interaction may have been due to
differences in climatic conditions during various growing seasons. In 2002 for
instance, dry conditions resulted in no difference among treatments due to low N
uptake by com planted in CMNF.

Corn density affected N concentration in com leaf at the end of the
growing season (Table 5). In 2002, corn density at 75 000 plants he" had a
significantly lower leaf N concentration than all other densities. No difference was
observed in leaf N concentration in com density during the 2003 growing season.
In 2004, leaf N concentration was higher at 37 500 plants ha" but was
significantly different only from 65 000 plants ha". In 2005, only leaf N
concentration at 37 5 000 plants he" was significantly higher than 65 000 plants
he". The four-year average shows that plant density at 37 500 plants he" was
only significantly higher than 65 000 and 75 000 plants he".

Leaf N concentration varied from year to year in management practices
(Table 5). In 2002, leaf N concentration was the same under all management
practices. In 2003, across corn density, leaf N concentration was higher in CMNF
and PRIR compared with PRIA and PRNI. In 2004, leaf N concentration was
higher in CMNF but only significantly different from PRIR and PRNI. In 2005, leaf
N concentration was significantly higher in CMNF compared with corn planted
into plowed red clover. The four-year average for leaf N concentration was higher

in CMNF compared with corn planted into plowed red clover. The four-year ‘

95

average suggests that leaf N concentration was significantly higher in PRIR than
in PRIA or PRNI. No clear pattern was observed in leaf N concentration in

interseeding compared to no interseeding system.

Corn stalk N

There was a seasonal effect on stalk N concentration (Table 2). In 2002,
2004 and 2005 there was no significant difference in stalk N concentration
among corn densities. In 2003, stalk N concentration at 65 000 plants he" had a
lower N concentration compared to other plant densities (Table 6). The four-year
average showed no difference in stalk N concentration among various corn
densities. In 2002, stalk N concentration was significantly different in PRNI
compared with CMNF (Table 6). In 2003 and 2004, no difference was detected in
management practices with regard to stalk N concentration. In 2005, stalk N
concentration was significantly higher in CMNF and PRIA treatments compared
to PRNI (Table 6). The four-year average for stalk N concentration showed no

significant differences within management practices.

Chlorophyll content
Effect of corn density on chlorophyll content
In 2004, there was a weekly variation in chlorophyll content of corn leaves
in plant density (Table 7). Across management practices, chlorophyll content on
10 July was similar at all plant densities. On 16 July, the only difference was

observed between 37 500 and 55 000 plants ha". However, from the 23 July up

96

to 15 August, chlorophyll content was consistently higher in the lowest corn
density (37500 plants he") compared with higher plant densities.

In 2005 similarly to 2004, 37 500 plants he" had the highest chlorophyll
content compared to higher com densities, except on 29 July where the three
lowest plant densities were significantly higher than 75 000 plants ha" (Table 8).
On 7 July, 55 000 and 65 000 plants he" were higher than 75 000 plants ha". On
15 July chlorophyll content decreased as plant density increased with significant
difference at all four corn densities. On 21 and 29 July, and 5 August, chlorophyll
content continued to be lower at higher corn densities with no significant
difference between 65 000 and 75 000 plants he" on 21 July and 5 August.

Overall, chlorophyll content of ear leaf in 2005 was higher than in 2004
with a decreasing trend as corn plant density increased. There was also an
interaction between corn density and sampling time on chlorophyll content in
2004. This may have been due to differences in plant stand as we did not
achieve the targeted highest plant density in all plots in 2004. Chlorophyll content
was negatively correlated to corn plant density in both years. In 2004, we
observed low correlation coefficient values of -0.34 (p<0.0062), -0.50 (p<0.0001),
-0.38 (p=0.0021), -0.35 (p=0.0047) for 23 July and 1, 6 and 15 August,
respectively (Table 3). In 2005, we observed high correlation coefficient between
chlorophyll content and plant density of -0.62 (p<0.0001), -0.83 (p<0.0001), -0.79
(p<0.0001), -0.64 (p=<0.0001) and -0.57 (p<0.0001) for 7, 15, 21 and 29 July,

and 5 August, respectively (Table 3).

97

Effect of management practices on chlorophyll content

In 2004, weekly chlorophyll content of corn leaves varied with
management practices (Table 7). On 10 July, no clear pattern was observed
between com planted into plowed red clover and corn supplied with N fertilizer,
whereas on 16 July, no significant difference was observed among treatments.
On 23 July, chlorophyll content in CMNF was higher than com planted into
plowed red clover, except with PRIR. From the fourth sampling up to the last
sampling, chlorophyll content of com supplied with N fertilizer (CMNF) was
consistently higher than chlorophyll content of corn planted into plowed red
clover (PRIR, PRIA and PRNI) (Table5). This differentiation among treatments
may be due to increased N uptake overtime in CMNF.

In 2005, we had fewer sampling dates than in 2004 due to fast corn
growth as monthly average temperatures were above the 30-year average during
the months of June and July (Table 8 and Figure 10). At the first sampling
chlorophyll meter readings in PRIR, PRIA and PRNI were significantly higher
than CMNF, but no clear pattern was observed between the interseeding and no
interseeding systems, although PRNI was significantly higher than PRIR. On 15
and 21 July, chlorophyll content was not significantly different among treatments.
On 29 July and 5 August, chlorophyll content in CMNF was significantly higher
than all treatments planted into plowed red clover (Table 8).

There was an interaction between management practices and sampling
time on chlorophyll content in both years. There were very high chlorophyll

readings on 21 and 29 July and 05 August in 2005. This may be due to dry, high

98

temperatures that occurred in 2005 compared to wet and cool conditions in 2004.
These results parallel the higher N concentration and content in the grain, and
the higher leaf N concentration in the CMNF treatment. These findings
corroborate results by Scharf et al. (2002), who observed higher chlorophyll
meter readings on corn in dry years compared to wet growing seasons.

Similarly to corn grain N concentration, CMNF and 37 500 plants he" had
higher chlorophyll content for ear leaf compared to corn planted into plowed red
clover and higher plant densities. Chlorophyll content of ear leaf was a good
indicator of com grain N concentration with a positive correlation coefficient
(Table 3). In 2004, correlation coefficients between chlorophyll content of ear leaf
and corn grain N concentration were 0.66 (p<0.0001) and 0.62 (p<0.0001) for 6
and 15 August, respectively. In 2005, correlation coefficients between chlorophyll
content of ear leaf and corn grain N concentration were 0.43 (p=0.0004) and 0.44
(p=0.0003) on 21 and 29 July, respectively (Table 3). When combined, the Mo-
year data suggested that the two last samplings of chlorophyll content of ear leaf
were good indicators of corn grain N content with positive correlation coefficients
of 0.54 (p<0.0001) and 0.55 (p<0.0001) (data not shown). These findings are
similar to those obtained by Eghball and Power (1999) who found that chlorophyll
meter readings did provide a good indication of N uptake in a wet not in a dry
growing season. In contrast to Eghball and Power (1999) our results showed that

both wet and dry years provided a good indication of com grain N concentration.

99

Ear leaf N

In both years as expected, ear leaf DM at 37 500 plants he" was higher
than that at higher plant densities. In 2005, ear leaf DM at 55 000 and 65 000
plants he", were significantly higher than that at 75 000 plants he". Ear leaf DM
at silking showed no significant difference due to management practices in 2004,
but in 2005 DM in CMNF was significantly lower than PRIR and PRIA but not in
PRNI (Table 9).

Ear leaf N concentration, in both years, was significantly higher in corn
supplied with N fertilizer than in corn planted into plowed red clover. Conversely,
Scott et al. (1987) found that ear leaf N concentration of corn following various
legume cover crops was not different from controls that received between 56 and
112 kg ha" of N fertilizer. In both years, ear leaf N concentration was the highest
in plants grown at 37 500 plants he". In 2005, ear leaf N concentration was also
higher in plants grown at 55 000 plants he" then in plants grown at 65 000 plants
he".

Ear leaf N content varied with com density and management practices
(Table 9). There was an interaction between plant density and year on ear leaf N
content (Table 2). This may have been due to differences in plant stand as we
achieved the targeted high plant density in all plots in 2005 but not in 2004. In
2004, N content of com supplied with N fertilizer was higher compared with corn
planted into plowed red clover; however in 2005 significant differences were only
detected between CMNF and PRNI. N content of corn at 37 500 plants ha‘1 in

2004 and 2005 was higher compared with N content at greater plant densities;

100

however in 2005 N content of corn grown at 55 000 plants he" was significantly
higher than in plants grown at 65 000 and 75 000 plants he". There was a
positive correlation coefficient of 0.51 (<0.0001) in both years between corn ear

leaf and corn grain N concentration.

Effect of corn density on Interseeded cover crop N

Nitrogen concentration and accumulation in interseeded cover crops
varied between cover crops species (Table 10). We observed an interaction
between cover crop species and year on fall N concentration and accumulation.
This may be explained by variation in climatic conditions that occumed in 2005.

In 2002, N concentration ranged from 32.7 to 34.6 g kg" for red clover and
31.5 to 33.9 g kg" for AC Greenfix but differences were not significant in either
cover crop (Table 10). In 2003, N concentration was similar at all plant densities
within species ranging from 30.4 to 31.5 and from 29.0 to 34.3 g kg" for
interseeded red clover and AC Greenfix, respectively. In 2004, N concentration of
interseeded red clover and AC Greenfix was similar within species at all plant
densities. In 2005, interseeded red clover did not germinate due to dry, hot
weather conditions. In 2005, no difference was observed in N concentration of
interseeded AC Greenfix at any plant density. There was a trend of higher N
concentration for interseeded AC Greenfix in 2004 and 2005 when compared to
2002 and 2003. However, interseeded red clover N concentration values seem to

be similar across years.

101

There was a seasonal effect on cover crop N accumulation (Table 2). In
2002, N accumulation of interseeded red clover was highest at 37 500 plants ha"
but was only significantly different from N accumulation at 65 000 and 75 000
plants ha'1 (Table 10). Similarly, N accumulation of interseeded AC Greenfix was
highest at 37 500 plants ha" but was only significantly different from N
accumulation at 75 000 plants ha". In 2003, N accumulation of interseeded red
clover was lowest when compared to other growing seasons and no significant
differences were noticed among plant densities (Table 10). However, N
accumulation of interseeded AC Greenfix was significantly higher at 37 5000
plants he" compared to other plant densities. The low N accumulation of
interseeded red clover in 2003 was due to poor germination and growth of red
clover compared to other growing seasons. In 2004, N accumulation of
interseeded red clover at 37 500 plants he" was higher than other com plant
densities, except at 55 000 plants he". In 2004, Interseeded AC Greenfix N
accumulation was higher at 37 500 plants ha" compared with other plant
densities. In 2005, N accumulation of interseeded AC Greenfix was only
significantly different between 37 500 plants he" and 75 000 plants he".
Differences observed in N accumulation were mainly related to DM matter
production. Results similar to our findings were obtained by Hively and Cox
(2001) who observed low N accumulation of interseeded cover crops of 2 to 6 kg
ha". Interseeded red clover and AC Greenfix N accumulation are in the range of
those obtained in corn interseeded with medics (2.1 to 32 kg ha"; Jeranyama et

al., 1998), red clover and hairy vetch (8 to 29 kg ha"; Scott et al., 1987), and

102

similar to oat interseeded with Nitro alfalfa and mammoth red clover (10 to 14 kg

ha"; Hesterman et al., 1992).

Monoculture cover crop N

In 2004 and 2005, monoculture cover crops were included in our
experiment for comparing N concentration and accumulation of monoculture with
interseeded cover crops (Table 10). In 2004, N concentration of monoculture red
clover was only higher than interseeded red clover at 55 000 and 75 000 plants
ha". In 2004, N concentrations of monoculture and interseeded AC Greenfix
were similar whereas in 2005, N concentration of monoculture AC Greenfix was
higher than interseeded AC Greenfix at all plant densities. Nitrogen concentration
of monoculture red clover was significantly lower in 2004 than in 2005. Similarly,
N concentration of AC Greenfix was significantly lower in 2004 than in 2005. This
may be related to dry, hot conditions that occurred in 2005.

In 2004 and 2005, monoculture cover crops accumulated more N then
interseeded cover crops (Table 10). Our findings are similar to results obtained
by Jeranyama et al. (1998) who obtained N accumulation of up to 75 kg ha" for
clear-seeded medics. Although higher N concentrations were observed in 2005
than in 2004, N accumulation for both cover crops was the highest in 2004
compared with 2005. This was due to high DM of both cover crops resulting from

good and well distributed rainfall that occurred in 2004 (Figure 2).

103

N of Interseeded cover crop the subsequent spring

Nitrogen concentration of interseeded red clover in the subsequent spring
varied from year to year (Table 11). In spring 2003, N concentration of red clover
previously interseeded at 37 500 plants he" was only significantly different
compared with plants at 75 000 plants ha", whereas in spring 2004 it was only
significant from plants at 65 000 plants he". In 2005, no differences were
observed, even with monoculture red clover. N concentration of interseeded red
clover in the fall (year of establishment) was higher than N concentration of
interseeded red clover the subsequent spring (Table 12). These results
conoborate findings of Merino et al. (2004) and Alford et al. (2003) who observed
a decrease in N concentration of cover crops with sampling time.

Interseeded red clover accumulated more N in the subsequent spring
compared to the fall sampling. There was a seasonal effect on N accumulation of
interseeded cover crop in the subsequent spring (Table 2). In spring 2003, N
accumulation of red clover was only significantly different between 37 500 and 75
000 plants ha". However in spring of 2004 and 2005, no significant differences
were observed in interseeded red clover N accumulation. Red clover N
accumulation was the highest in 2005 followed by 2003 and 2004. Spring red
clover N accumulation increased in the range of 7-28 times of fall N accumulation
(Tables 10 and 11). In the spring of 2005, N accumulation of monoculture red

clover was significantly higher than previously interseeded red clover.

104

Conclusion

Corn density affected grain N concentration with high grain N
concentration at low corn density. Interseeded cover crops did not affect corn
grain N concentration and accumulation. Grain N concentration was higher in
corn supplied with N fertilizer than in corn planted into plowed red clover.
Chlorophyll content of ear leaf and ear leaf TKN were good indicators of corn
grain N concentration. Interseeded cover crop accumulated more N at low corn
density than at higher plant densities, but less than monoculture cover crops.
Red clover biomass increased significantly up to 28 fold from fall to spring,
however N concentration significantly decreased, suggesting N dilution by
biomass production. Biederbeck et al. (1996) observed a low N concentration for
less productive green manure when compared with highly productive cover
crops. In the subsequent spring, interseeded and monoculture red clover
accumulated up to 162.3 kg ha" and 234.4 kg ha" of N, respectively. When
interseeded at high corn plant densities, red clover can accumulate significant N

the subsequent spring to use in meeting the N demand of the following crop.

105

References:

Abdin, 0., BE. Coulman, D. Cloutier, M.A. Faris, X. Zhou, and D.L. Smith. 1998.
Yield and yield components of corn interseeded with cover crops. Agron.
J. 90263-68.

Alford, C.M., J.M. Krall, and SD. Miller. 2003. Intercropping irrigated corn with
annual legumes for fall forage in the High Plains. Agron. J. 95:520-525.

Balkcom, KS, and D.W. Reeves. 2005. Sunn-hemp utilized as a legume cover
crop for corn production. Agron. J. 97226-31.

Biederbeck, V.O., O.T. Bouman, C.A. Campbell, L.D. Bailey, and GE.
Winkleman. 1996. Nitrogen benefits from four green-manure legumes in
dryland cropping systems. Can. J. Plant Sci. 76:307-315.

Bowman, G., C. Shirley, and C. Cramer. 1998. Managing cover crops
profitability. 2nd ed., Burlington, VT.

Bullock, D.G., and D.S. Anderson. 1998. Evaluation of the Minolta SPAD-502
chlorophyll meter for nitrogen management in corn. J. Plant Nutr. 21 :741-
755.

Brouder, S.M., D.B. Mengel, and BS. Hofmann. 2000. Diagnostic efficiency of
the blacklayer stalk nitrate and grain nitrogen tests for corn. Agron. J.
92:1236-1247.

Carr, P.M., G.B. Martin, J.S. Caton, and WW. Poland. 1998. Forage and
nitrogen yield of barley-pea and oat-pea intercrops. Agron. J. 90:79-84.

Crum, JR, and HP. Collins. 2004. Kellogg Biological Station soils. (Available
online at http://Iter.kbs.msu.edu/SoiI/characterizationl).

Cusicanqui, J.A., and J.G. Lauer. 1999. Plant density and hybrid influence on
corn forage yield and quality. Agron. J. 91:911-915.

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

DFS. 2003. Grow your own nitrogen. (Available online at

http:/Iwww.aggreenfix.coml).

Eghball, B., and J.F. Power. 1999. Composted and noncomposted manure
application to conventional and no-tillage systems: corn yield and nitrogen
uptake. Agron. J. 91:819-825.

106

Eghball, B., D. Ginting, and J.E. Gilley. 2004. Residual effects of manure and
compost applications on corn production and soil properties. Agron. J.
96:442-447.

Fan, X., F. Li, F. Liu, and D. Kumar. 2004. Fertilization with a new type of coated
urea: Evaluation for nitrogen efficiency and yield in winter wheat. J. Plant
Nutr. 27:853.

Hauggaard-Nielsen, H., P. Ambus, and ES. Jensen. 2001. Interspecific
competition, N use and interference with weeds in pea-barley
intercropping. Field Crops Res. 70:101.

Heeb, A., B. Lundegardh, T. Ericsson, and GP. Savage. 2005. Nitrogen form
affects yield and taste of tomatoes. J. Sci. Food and Agric. 85:1405-1414.

Hesterman, O.B., T.S. Griffin, P.T. Williams, G.H. Harris, and DR. Christenson.
1992. Forage-legume small-grain intercrops-nitrogen production and
response of subsequent corn rotations. J. Prod. Agric. 5:340-348.

Hively, W.D., and W.J. Cox. 2001. lnterseeding cover crops into soybean and
subsequent corn yields. Agron. J. 93:308-313.

Hussein, F., K.F. Bronson, S. Yadvinder, S. Bijay, and S. Peng. 2000. Use of
chlorophyll meter sufficiency indices for nitrogen management of irrigated
rice in Asia. Agron. J. 92:875-879.

Jeranyama, P., O.B. Hesterman, and CC. Sheaffer. 1998. Medic planting date
effect on dry matter and nitrogen accumulation when clear-seeded or
intercropped with corn. Agron. J. 901616-622.

Katsvairo, T.W., W.J. Cox, HM. Van Es, and M. Glos. 2003. Spatial yield
response of two corn hybrids at two nitrogen levels. Agron. J. 95:1012-
1022.

LTER-Weather. 2006. Weather data during the 2002, 2003, 2004 and 2005
growing seasons, pp. Available online

at:<http:/Ilter.kbs.msu.edu/Data/table.jsp?Product=KB8002-
001&limitBy=Year&order=desc>. Kellogg Biological Station, Hickory

Comers, Ml.
Merino, MA, A. Mazzanti, S.G. Assuero, F. Gastal, H.E. Echeverria, and F.

Andrede. 2004. Nitrogen dilution curves and nitrogen use efficiency during
winter-spring growth of annual ryegrass. Agron. J. 96:601-607.

107

Ofori, F., and W.R. Stern. 1986. Maize cowpea intercrop system - effect of
nitrogen-fertilizer on productivity and efficiency. Field Crops Res. 14:247-
261.

Piekielek, W.P., R.H. Fox, J.D. Toth, and K.E. Macneal. 1995. Use of a
chlorophyll meter at the early dent stage of corn to evaluate nitrogen
sufficiency. Agron. J. 87:403-408.

Rao, S.C., B.K. Northup, and HS. Mayeux. 2005. Candidate cool-season
legumes for filling forage deficit periods in the Southern Great Plains. Crop
Sci. 45:2068-2074.

Ross, S.M., J.R. King, J.T. O'Donovan, and D. Spaner. 2005. The productivity of
cats and berseem clover intercrops. I. Primary growth characten'stics and
forage quality at four densities of cats. Grass and Forage Sc. 60:74-86.

Sainju, U.M., and BF. Singh. 2001. Tillage, cover crop, and kill-planting date
effects on corn yield and soil nitrogen. Agron. J. 93:878-886.

Sangakkara, U.R., W. Richner, F. Steinebrunner, and P. Stamp. 2003. Impact of
the cropping systems of a minor dry season on the growth, yields and
nitrogen uptake of maize (Zea mays L.) grown in the humid tropics during
the major rainy season. J. Agron. Crop Sci. 189:361-366.

SAS Institute. 2001. SAS user’s guide: Statistics. Release 8th ed. SAS Institute.

Scharf, P.C., W.J. Wiebold, and J.A. Lory. 2002. Corn yield response to nitrogen
fertilizer timing and deficiency level. Agron. J. 94:435-441.

Scott, T.W., J. Mt. Pleasant, R.F. Burt, and DJ. Otis. 1987. Contributions of
ground cover, dry matter, and nitrogen from intercrops and cover crops in
a corn polyculture system. Agron. J. 79:792-798.

Shapiro, C.A., and CS. Wortmann. 2006. Corn response to nitrogen rate, row
spacing, and plant density in Eastern Nebraska. Agron. J. 98:529-535.

Shrestha, A., O.B. Hesterman, J.M. Squire, J.W. Fisk, and CC. Sheaffer. 1998.
Annual medics and berseem clover as emergency forages. Agron. J.
90:197-201.

Stute, J.K., and J.L. Posner. 1995. Legume cover crops as a nitrogen source for
com in an oat-com rotation. J. Prod. Agric. 82385—390.

Sweeney, D.W., and J.L. Moyer. 2004. ln-season nitrogen uptake by grain

sorghum following legume green manures in conservation tillage systems.
Agron. J. 96:510-515.

108

Szumigalski, AR, and RC. Van Acker. 2006. Nitrogen yield and land use
efficiency in annual sole crops and intercrops. Agron. J. 98:1030-1040.

Thorsted, M.D., J.E. Olesen, and J. Weiner. 2006. Width of clover strips and
wheat rows influence grain yield in winter wheat/white clover
intercropping. Field Crops Res. 95:280.

Varvel, G.E., J.S. Schepers, and DD. Francis. 1997. Chlorophyll meter and stalk
nitrate techniques as complementary indices for residual nitrogen. J. Prod.
Agric. 10:147-151.

Villar-Mir, J.M., P. Villar-Mir, C.O. Stockle, F. Ferrer, and M. Aran. 2002. On-fann
monitoring of soil nitrate-nitrogen in irrigated corn fields in the Ebro Valley
(Northeast Spain). Agron. J. 94:373-380.

Vyn, T.J., K.J. Janovicek, M.H. Miller, and E.G. Beauchamp. 1999. Soil nitrate
accumulation and corn response to preceding small-grain fertilization and
cover crops. Agron. J. 91 :17-24.

Widdicombe, W.D., and K.D. Thelen. 2002. Row width and plant density effect on
corn forage hybrids. Agron. J. 94:326-330.

109

Table 1. Nitrogen concentration (9 kg") in com (Zea mays L.) grain across management
practices and corn plant density during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Comers, Ml.

 

Grain N concentration

 

 

 

 

Management 2002 2003 2004 2005 Average
practices 9 kg"

PRIR 13.2b* 12.6ab 11.1b 11.40 12.10
PRIA 13.0b 12.0b 11.00 11.40 11.8b
PRNI 13.1b 13.030 11.3b 10.9b 12.1b
CMNF 14.23 13.63 13.13 12.73 13.43
CV (%) 9 11 7 8 9
Corn density

(plants ha")

37 500 14.33 14.83 12.43 12.33 13.43
55 000 13.2b 13.1ab 11.5b 11.78b 12.4b
65 000 12% 11.3b 11.2b 11.5bc 11.7c
75 000 13.1b 12.0b 11.2b 10.8c 11.8c
CV (%) 9 11 7 8 9

 

*Means within columns in the same treatment followed by the same letter
are not significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

110

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111

Table 3. Pearson correlation coefficients for chlorophyll content, plant density, grain N
concentration, ear leaf N concentration and yield of corn (Zea mays L.) during the

2004 and 2005 growing seasons at the Kellogg Biological Station, Hickory
Corners, Ml. (n=64).

 

 

Density Grain N conc. Ear Leaf N
R2 p-value R7 p-value R2 p-value

2002
Grain N-TKN" -0.37 0.0027 ---- ----
Corn yield 0.26 0.0391 -0.34 0.0054

2003
Grain N-TKN -0.63 <0.0001 ----
Com yield 0.53 0.0017 -0.23 0.21

2004
CC**-10 July -0.02 0.86 -0.17 0.19 -0.15 0.44
CC-16 July -0.18 0.15 0.11 0.36 0.18 0.15
CC-23 July -0.34 0.0062 0.48 <0.0001 0.29 0.0215
CC-1 August -0.50 <0.0001 0.59 <0.0001 0.59 <0.0001
CC-6 August‘I -0.38 0.0021 0.66 <0.0001 0.56 <0.0001
CC-15 August‘ -0.35 0.0047 0.62 <0.0001 0.61 <0.0001
Grain N-TKN -0.34 0.0057 ---- 0.51 <0.0001
Ear Leaf N-TKN -0.27 0.0315 0.51 <0.0001
Corn yield 0.62 <0.0001 0.09 0.51 0.15 0.2462

2005
CC-7 July -0.62 <0.0001 0.05 0.68 0.21 0.09
CC-15 July -0.83 <0.0001 0.43 0.0003 0.57 <0.0001
CC-21 July -0.79 <0.0001 0.52 <0.0001 0.61 <0.0001
0029 July‘ -0.64 <0.0001 0.43 0.0004 0.58 <0.0001
CC-5 August‘ -0.57 <0.0001 0.44 0.0003 0.58 <0.0001
Grain N-TKN ~0.41 0.0008 --—-- 0.51 <0.0001
Ear Leaf N-TKN -0.55 <0.0001 0.51 <0.0001
Corn yield 0.55 <0.0001 -0.06 0.6561 -0.16 0.2042

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

*TKN: Total Kjeldahl Nitrogen analysis
“CC: Chlorophyll content

‘: Chlorophyll content measured on ear leaf

112

Table 4. Corn (Zea mays L.) grain N content (kg ha") in four management practices
across corn plant density during the 2002, 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Corners, MI.

 

Grain N content

 

 

 

 

Management 2002 2003 2004 2005 Average—
practices kg ha‘1

PRIR 121.0a* 89.1 ab 92.6b 110.9b 103.4b
PRIA 117.5a 81 .0b 93.5b 112.9b 101.2b
PRNI 118.8a 86.4ab 95.5b 105.6b 101.6b
CMNF 90.4b 95.3a 122.3a 140.1a 112a

CV (%) 16 16 13 10 13

 

*Means within columns followed by the same letter are not significantly different
at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

Table 5. Corn (Zea mays L.) leaf N concentration (9 kg") across management practices
and corn plant density during the 2002, 2003, 2004 and 2005 growing seasons at
Kellogg Biological Station, Hickory Comers, Ml.

 

Leaf N concentration

 

 

 

 

Management 2002 2003 2004 2005 Average_
practices g kg"

PRIR 11.1a* 11.9a 10.2b 7.0b 10.1b
PRIA 10.5a 8.0b 10.7ab 6.9b 9.00
PRNI 10.6a 9.4b 10.2b 6.9b 9.3c
CMNF 10.2a 12.2a 11.6a 9.1a 10.8a
CV (%) 24 22 17 14 21
Corn density

(plants ha")

37 500 11.7a 11.7a 11.5a 8.7a 11.0a
55 000 10.8a 11.0a 10.9ab 7.6ab 10.0ab
65 000 11.4a 9.6a 9.6b 6.8b 9.3bc
75 000 8.6b 9.2a 10.6ab 7.0ab 8.8c
CV (%) 24 22 17 14 21

 

*Means within columns in the same treatment followed by the same letter
are not significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

113

Table 6. Corn (Zea mays L.) stalk N concentration (9 kg") across management practices
and corn plant density during the 2002, 2003, 2004 and 2005 growing seasons at
Kellogg Biological Station, Hickory Corners, Ml.

 

Stalk N concentration

 

 

 

 

Management 2002 2003 2004 2005 Average_
practices 9 kg"

PRIR 5.0ab* 4.7a 2.7a 6.4ab 4.8a
PRIA 4.9ab 4.1a 3.3a 7.0a 4.8a
PRNI 4.8a 4.5a 3.1a 5.8b 4.5a
CMNF 5.7b 4.0a 3.6a 7.0a 5.1a
CV (%) 24 28 12 31 28
Corn density

(plants ha")

37 500 5.0a 4.8a 3.4a 6.6a 5.0a
55 000 5.2a 4.4a 3.5a 6.4a 4.9a
65 000 5.2a 3.6b 3.1a 6.8a 4.7a
75 000 5.0a 4.5a 3.0a 6.3a 4.7a
CV (%) 24 28 12 31 28

 

*Means within columns in the same treatment followed by the same
letter are not significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

114

Table 7. Leaf chlorophyll content (SPAD-502 meter readings) across management
practices and corn (Zea mays L.) plant density during the 2004 growing season
at Kellogg Biological Station, Hickory Comers, Ml.

 

Chlorophyll meter readings in 2004

 

 

 

 

Management Top leaf Ear leaf
practices 10-Jul 16-Jul 23-Jul 1-Aug 6-Aug 15-Aug_
PRIR 54.3b* 57.7a 54.1ab 52.1b 54.2b 52.8b
PRIA 53.5ab 56.9a 53.2b 51 .8b 54.3b 52.3b
PRNI 54.4a 57.3a 53.9b 52.4b 54.7b 52.5b
CMNF 52.8b 57.6a 55.3a 55.4a 58.1a 58.4a
CV (%) 5 3 3 3 3 3
Corn density

(plants ha")

37 500 53.5a 58.2a 55.8a 55.5a 57.1a 56.4a
55 000 54.3a 56.6b 53.2b 51 .8b 54.7b 53.1b
65 000 54.0a 57.6ab 53.8b 52.5b 54.5b 53.2b
75 000 53.2a 57.1ab 53.8b 51 .8b 55.0b 53.2b
CV (%) 5 3 3 3 2 3

 

*Means within columns in the same treatment followed by the same letter are not
significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenflx;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

115

Table 8. Leaf chlorophyll content (SPAD-502 meter readings) across management
practices and corn (Zea mays L.) plant density during the 2005 growing season
at Kellogg Biological Station, Hickory Corners, Ml.

 

Chlorophyll meter readings in 2005

 

 

Management Top leaf Ear leaf
practices 7-Jul 15-Jul 21-Jul 29-Jul 5-AuL
PRIR 55.3b* 53.4a 60.5a 63.0b 63.7b
PRIA 56.83b 53.7a 60.5a 63.1 b 63.8b
PRNI 57.4a 53.5a 60.6a 63.0b 63.9b
CMNF 53.00 54.0a 62.1 a 65.3a 65.9a
CV (%) 3 3 3 4 3

Corn density

(plants ha")

37 500 58.4a 57.1a 64.1a 66.1a 66.6a
55 000 55.5b 54.7b 61 .4b 64.7a 64.6b
65 000 55.2b 52.40 60.1 bc 62.8b 63.5bc
75 000 53.20 50.4d 58.20 60.70 62.60
CV (%) 3 3 3 4 ‘ 3

 

*Means within columns in the same treatment followed by the same
letter are not significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

116

Table 9. Dry matter (9), N concentration (g kg") and N content of 10 ear leaves per plot
of corn (Zea mays L.) across management practices and corn plant density
during the 2004 and 2005 growing seasons at Kellogg Biological Station, Hickory

 

 

 

 

Corners, Ml.
DM N concentration N content

Management 2004 2005 2004 2005 2004 2005
practices -—-g /leaf--- -—g kg"--- -—--g/Ieaf
PRIR 4.6a* 5.11a 20.3b 23.6b 0.094b 0.122ab
PRIA 4.6a 5.12a 21 .6b 24.8b 0.099b 0.128ab
PRNI 4.7a 5.05ab 19.7b 23.5b 0.093b 0.120b
CMNF 4.7a 4.86b 25.2a 27.0a 0.119a 0.132a
CV (%) 7 6 14 10 15 14
Corn density
(plants ha")
37 500 5.1a 5.8a 24.0a 27.7a 0.121a 0.160a
55 000 4.5b 5.0b 20.7b 25.3b 0.094b 0.126b
65 000 4.6b 4.9b 20.5b 22.70 0.093b 0.1110
75 000 4.5b 4.50 21 .6b 23.3bc 0.097b 0.1060
CV (%) 7 6 14 10 15 14

 

*Means within columns in the same treatment followed by the same letter are
not significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;

PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of Variation.

117

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00.0%. .0 00.0.0.0 200000.000 .00 0.0 .000. 00.00 00. >0 0032.2 00.00.00 0.5.3 0000.2.
00.0 .0>00 0.2300005...

 

 

 

 

118

 

 

 

 

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Table 11. Nitrogen concentration (9 kg") and accumulation (kg ha") of red clover

(Trifolium pratense L.) during the subsequent spring in 2003, 2004 and 2005 at
Kellogg Biological Station, Hickory Corners, Ml.

 

 

 

Com density N concentration N accumulation
(plants ha") 2003 2004 2005 2003 2004 2005

————-—g kg"-----— -—----kg ha"-—-——--—--
oT ---- ---- 28.6a —-—— -—-- 234.4a
37 500 27.9a“ 26.2a 25.8a 108.6a 68.7a 157.1 b
55 000 26.2ab 24.7ab 27.9a 94.5ab 83.3a 152.3b
65 000 25.7ab 21 .4b 27.7a 105.2ab 63.6a 162.3b
75 000 24.4b 25.1ab 26.8a 75.5b 58.3a 143.5b
CV (%) 7 1 7 8 18 29 17

 

1‘Monoculture cover crop

*Means within columns followed by the same letter are not significantly
different at P=0.05.

CV: Coefficient of Variation.

Table 12. Comparison of N concentration of interseeded red clover (Trifolium
pratense L.) at the same com (Zea mays L.) density from the first sampling in fall
(the year of establishment) to the second sampling in spring (the subsequent
spring) in 2002, 2003, 2004 and 2005 at Kellogg Biological Station. Hickory

 

 

 

 

Corners, Ml.
Com density (plants ha")
37 500 55 000 65 000 75 000
Pr > F
Fall 2002 x Spring 2003 0.012* 0.004 <0.0001 <0.0001
Fall 2003 x Spring 2004 0.049 0.019 0.001 0.022
Fall 2004 x Spring 2005 0.014 0.753 0.029 0.259
Across years Fall x Spring 0.004 0.002 <0.0001 <0.0001

 

*No significant difference if p value=0.05

119

 

300
(a) Precipitation

  

E53 2003

E I‘ m 2004
E 200 1 3 am: 2005 FT21,0
E E: 30-yr—Av.
g 150 - :3
a t
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—B— 2004-Max.
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9
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E
a)
.—
10 — —O-- 2003-Min.
+ 2004-Min.
+ 2005-Min.
0 v , 30—yrs-Av. Min

 

April May June July August Sept.
Month

Figure 1. Monthly average minimum and maximum temperature, and total monthly
precipitation during the 2002, 2003, 2004 and 2005 growing seasons
compared with the 30-year monthly average at Kellogg Biological Station,
Hickory Corners, MI.

120

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121

Chapter three
Effect of Interseeded Cover Crop on Soil Mineral N and Subsequent Dry

Bean Yield and N Status

Abstract

Reliable cropping strategies are needed to enhance N contribution from legume
cover crops to subsequent crops. Field studies were conducted at the Kellogg
Biological Station, Hickory Corners, Mi, to assess the effect of interseeded red
clover (Trifolium pretense L.) or AC Greenfix (Lathyrus sativum L.) on soil mineral
N (NO‘3-N and NHH—N) and on subsequent dry bean (Phaseolus vulgaris L.)
yield and N status. In 2003, 2004 and 2005, dry bean was planted at 232,500
plants ha'1 into previous corn (Zea mays L.) treatments that consisted of four
corn densities ranging from 37 500 to 75 000 plants ha'1 and four management
practices: conventional (no cover crop, N fertilizer applied) and three non-N
fertilized treatments planted into plowed red clover (interseeded with AC Greenflx
or red clover, and no interseeding). Bean planted into conventional treatments
received 45 kg ha'1 of N. There was a seasonal effect on dry bean yield, N
concentration and content, and soil mineral N. In 2003, no yield difference was
observed between fertilized bean and bean following interseeded red clover or
AC Greenfix plots. in 2004, dry bean yield from the conventional treatment was
significantly higher than yield of been following interseeded AC Greenfix and no
interseeding, but similar to been planted into plowed interseeded red clover. in

2005 however, bean yield supplied with N fertilizer was lower than bean yield

122

following interseeded red clover or AC Greenfix and no interseeding. In two of
the three years, bean seed N concentration and content was the highest in beans
supplied with N fertilizer. No effect of interseeded cover crops was seen on soil
mineral N either in the fall or the subsequent spring. During optimal growing
conditions, interseeded red clover contributed sufficient N and was able to
produce dry bean yields comparable to bean supplied with 45 kg ha“1 of N
fertilizer. This system has the potential to help farmers reduce or eliminate N
application in dry beans, resulting in positive environmental and economic

impacts.

123

Introduction

In 2004, the state of Michigan was ranked second after North Dakota in
dry bean (Phaseolus vulgaris L.) production in the US (USDA-NASS, 2005). Dry
bean requires 45 kg ha'1 of supplemental nitrogen (N) fertilizer to maintain
optimum growth and yield. Alternative management practices for dry bean
production are needed to help address issues related to increased environmental
pollution and to reduce the cost of agricultural inputs. The ability to supply all or
part of the plant N needs via cover crops is a potential aitemative to conventional
practices. Monoculture or interseeded cover crops have been used to reduce N
fertilizer application (Hesterman et al., 1992; Jeranyama et al., 1998). Vyn et al.
(1999) showed that com (Zea mays L.) yield following red clover (Trifolium
pretense, L.) was consistently higher compared with corn following oilseed radish
(Raphunus sativus [L.] var oleiferus Metzg [Stokes]) or annual ryegrass (Lolium
multiflorum). Also, Sogbedji et al. (2006) observed that planting mucuna [Mucuna
pruriens (L.) D.C.] and pigeon pea (Cajanus cajan L.) after corn reduced N
fertilizer needs of the subsequent corn crop. Similarly, Balkcom and Reeves
(2005) observed that com yield following sunn-hemp (Crotalaria juncea L.) with
no additional N fertilizer was greater than corn yield supplied with 56 kg N ha".

Nitrogen fertilization is important in dry bean production because excess N
can delay leaf canopy growth which can result in disease incidence (Moraghan
and Franzen, 1995). Legume cover crops can provide adequate N to meet the
demand of a subsequent dry bean crop. Liebman and Gallandt (2002) found that

dry bean yield following red clover was similar to dry bean yield supplied with 84

124

kg ha'1 of ammonium nitrate fertilizer. Plots planted to snap bean following cover
crops yielded higher than those without cover crop, particularly in dry seasons
(Feet, 1995). Studies have been conducted to evaluate the effect of
management practices such as plant density, row spacing, different tillage
methods and herbicides on weed density and dry bean yield (Aleman, 2001;
Amador—Ramirez et al., 2001; Amador—Ramirez et al., 2002; Blackshaw et al.,
2000; Soltani et al., 2006; Wilson, 2005; Xu and Pierce, 1998 ). Liebman et al.
(1995) recommended an investigation of the use of legume green manure as a N
source in the temperate bean production systems after they observed growth, N
status, and yield reduction of bean in a no-tillage-rye mulch system. lnterseeding
a legume cover crop into corn has the potential to provide N to a subsequent
crop. Studies have assessed the effect of cover crops in a monoculture system
on various crops including dry beans. Other studies have investigated the effect
of an interseeded cover crop on subsequent corn crop. However, little or no
research has examined the effect of interseeded cover crops on subsequent dry
bean yield and quality.

Soil chemical properties are essential in assessing the soils ability to
supply nutrients (Campbell et al., 1991; Mikha et al., 2006). Researchers have
attempted to develop yield response functions by regressing crop yield against
late-spring NO'3-N concentration (Katsvairo et al., 2003) and soil organic matter
(Schmidt et al., 2002). Studies have shown that cover crops can influence soil
NO‘a-N and that com yield is correlated with soil NO'3-N (Shahandeh et al., 2005;

Vyn et al., 1999). However, Villar-Mir et al. (2002) showed that plant N uptake

125

and grain yield were not related to soil N availability. Management practices such
as the use of monoculture and interseeded cover crops can also influence soil
mineral N. Vaughan and Evanylo (1998) found that soil nitrate was higher
following hairy vetch compared with rye. Hairy vetch leached more NO'3-N
compared with a rye cover crop (McCracken et al., 1994). Ditsch and Alley
(1991) found no significant difference in soil NO'3-N in spring at plowdown of
various cover crops.

N fertilizer can also influence soil mineral N. Vyn et al. (1999) found that
applying more fertilizer N to the previous year’s small-grain crop rarely increased
spring soil NO‘3-N concentrations or com yields. However, MacKown et al. (1999)
showed that soil mineral N was related to the quantity of broadcast-applied N
fertilizer. Doran et al. (1987) observed an increase in soil nitrate due to fertilizer
application, red clover and hairy vetch (Vicia villosa Roth). Little is known about
the effect of management practices such as the use of red clover as a N source
combined with interseeding on soil mineral N. The objectives of this study were
(1 ) to assess the effect of plowed red clover and interseeded red clover or AC
Greenfix on soil mineral N in fall and the subsequent spring before dry bean
establishment and (2) to assess the effect of interseeding red clover or AC

Greenflx on subsequent dry bean yield and N status.

126

Materials and Methods

Site description

The research was conducted from 2002 to 2005 at the Kellogg Biological
Station (KBS) in Hickory Corners, Michigan. The soil types at KBS were the
Kalamazoo (fine-loamy, mixed, mesic Typic Hapludalfs) and Oshtemo (coarse-
loamy, mixed, mesic Typic Hapludalfs) series (Crum and Collins, 2004). The
experiment was conducted on a different field each year to permit planting on site
following red clover plow down. Corn research plots were established in 2002
(Field 1), 2003 (Field 2), 2004 (Field 3) and 2005 (Field 4). In the year prior to
corn establishment, red clover was planted in each field into wheat stubble in
July-August except in 2001 when it was planted into corn stubble. Red clover
was chisel-plowed the following spring before com planting to serve as a N

source for the non-conventional plots.

Experimental design

Each year the experiment was replicated four times except in 2003 where
only two replications were used due to animal damage. The experiment was a
split-plot in a completely randomized design. The main-plots were four corn
densities (37 500, 55 000, 65 000 and 75 000 plants ha"). Subplots were four
management practices: (1) Conventional management, com seeded into wheat
stubble with N fertilizer applied (CMNF); (2) Com seeded into plowed red clover,

no N fertilizer, interseeded with AC Greenfix (PRIA); (3) Corn seeded into plowed

127

red clover; no N fertilizer, interseeded with red clover (PRIR) ;(4) Corn seeded
into plowed red clover, no N fertilizer, not interseeded with cover crop (PRNI).
Based on Preside-dress Nitrate Test (PSNT) results, N fertilizer was applied to
the conventional corn plots, up to a total of 140 kg ha‘1 every year. Corn was
planted into 6-row plots of 4 by 4.5 m in 2002 and 2003 and of 5 by 4.5 m in 2004

and 2005.

Cover crops

Red clover and AC Greenfix were interseeded in the first two weeks of
July when com plants were between V5-V7 growth stages. Red clover was
seeded at the rate of 20.4 kg ha'1 and AC Greenfix at the rate of 90 kg ha".
Above ground biomass of red clover and AC Greenfix were hand-clipped at full
bloom of AC Greenfix by removing plants from a random quadrat of 0.209 m2 in
each plot. AC Greenfix was cut to allow regrowth, but was winter-killed and could
not be sampled the subsequent spring. After corn harvest, corn stalks were
mowed and plots were left undisturbed until the following spring. Before bean
establishment, the subsequent spring, red clover was again sampled to assess

its biomass and N accumulation.

Soil mineral N
Soil samples were collected in each field (Field 1, 2, 3 and 4) after com
harvest from fall 2002 to fall 2005 and the subsequent spring of 2003 to 2005 to

assess the effect of the four different management practices (PRIR, PRIA, PRNI

128

and CMNF) on soil mineral-N (NO'3-N and NHH-N). Soil nitrate was assessed
from 2002 to 2005 whereas soil ammonium was measured only in spring and fall
of 2004 and 2005. Depending on the weather, soil samples were collected a few
weeks after corn harvest in the fall and a few weeks before bean establishment
in the following spring. Soil samples were taken in the fall on 01 November 2002,
18 November 2003, 22 November 2004 and 05 November 2005; and the ‘
subsequent spring on 03 May 2003, 02 May 2004 and 23 May 2005. Eight 2-cm-
diameter soil cores were randomly taken at the depth of 25 cm in the four center
rows from each subplot, air-dried for 2 days and mixed thoroughly to obtain a
composite sample. Soil NO'3-N and NHH-N were measured using Cadmium

reduction and Salicylate method, respectively.

Dry bean
Planting

Three 2-year crop rotations were used in this study to assess the effect of
interseeded cover crops on subsequent dry bean. Dry bean was established in
2003 (Field 1), 2004 (Field 2) and 2005 (Field 3). Dry bean planted into the
conventional plots (CMNF) was supplied with N fertilizer and no N was applied to
bean planted into plowed interseeded red clover or AC Greenfix and no
interseeding (PRIR, PRIA and PRNI). Nitrogen fertilizer was applied at the rate of
45 kg ha'1 as urea in 2003 and 2004 and as liquid N fertilizer in 2005. Nitrogen
was applied a few days after planting except in 2005 where the application was

delayed due to dry conditions and high temperature. Phosphorus and K were

129

applied a few days before planting based on the soil test recommendation of the
MSU Soil and Plant Nutrient Laboratory. Navy bean (cultivar Seahawk,) was
planted at a seeding rate of 232,500 plants ha“1 on 06 June in 2003, 24 June in
2004 and 16 June in 2005. Dry bean seed was inoculated with a Rhizobial
inoculant (Bacillus subtilis, MBl 600).
Pest control

Herbicides were used on the whole field to control weeds, and cultivation
was utilized when necessary. In 2003, both insecticides and herbicides were
used. On 18 July 2003, Esfenvalerate was applied at the rate of 0.056 kg ai ha'1
to control Ieafhoppers. On July 22, Fomesafen was applied at the rate of 0.28 kg
ai ha'1 for weed control. On 11 August, beans were cultivated because the
herbicide did not provide good weed control. An additional hand pulling was done
to remove weeds missed by cultivation. In 2004, herbicides were applied two
times. On 27 June, lmazethapyr (0.035 kg ai ha") and S-metolachlor (1.07 kg ai
ha") were broadcast on the entire field. On 21 July, Bentazon (1.121 kg ai ha“)
and Quizalofop (0.049 kg ai ha") were applied to the whole field. The same day,
Esfenvalerate (0.056 kg ai ha") was sprayed to control Ieafhoppers. In 2005 after
bean planting hot, dry conditions followed which delayed herbicide application.
To control weeds, on 6 July Quizalofop (0.049 kg ai ha") and on 8 July
lmazamox (0.036 kg ai ha") and Bentazon (0.52 kg ai ha“) were broadcast on
the entire field. On 29 July a second herbicide application was made using
Bentazon and Clethodim at the rate of 1.121 kg ai ha‘1 and 0.140 kg ai ha",

respectively. Since herbicides did not provide very good weed control after the

130

second application, beans were cultivated on 5 August 2005. In 2005, beans
were burned by the application of herbicide due to hot, dry conditions.
Harvest and N analysis

Only the four center-row of the six row-plots dry bean were harvested on
25 September 2003, 01 October 2004 and 06 October in 2005. After harvest,
beans were dried at air temperature and threshed using a thresher (ALMACO,
Nevada, Iowa). in 2003, a sub-sample of approximately half a kilogram of
threshed bean seed was taken for estimating N concentration. The two following
years, five plants were collected from each plot a few weeks before harvest to
assess N concentration. At each sampling, leaf, stem and seed were separated
and dried for two days at 60°C. Samples were digested using a 40-tube Tecator
Model 1016 Digester (Tecator, Hoganas, Sweden). Bean tissue samples of 0.1 g
were digested in 4 ml of 18 M H2804 with 1.5 g K2804 and 0.015 9 Se catalyst in
100 ml-constricted tubes. All samples were digested at 350° C for 4 hours. To
determine N concentration, tissues extract were analyzed using a Lachat Flow

Injection Analyzer (Hachat Co., Loveland, Colorado).

Statistical analysis

All data were analyzed using Proc Mixed in SAS Statistical Software
Package version 8.2 (SAS, 2001). Plant density and management practices were
considered fixed effects. Two error terms were considered in the analysis of the
data, one associated with the whole plot (plant density) and the other associated

with the subplot (management practices) and the interaction (plant density x

131

management practices). When interaction effects were found to be statistically
significant, means separation was conducted for respective cell means. When
main effects were significant while interactions were not, means separation was
conducted for marginal means. Effects were considered statistically significant at

p= 0.05.

132

Results and Discussion

Weather conditions

Total monthly precipitation and monthly average temperature (minimum
and maximum) data from the 2002 to 2005 growing seasons was obtained from
the Long-Tenn Ecological Research weather station (LTER-Weather, 2006).
Weather conditions during the 2003, 2004 and 2005 dry been growing seasons
from June to September were variable and affected treatments (Figures 1 and 2).
Likewise, climatic conditions were variable from 2002 to 2005 during the
assessment of soil mineral N (Figures 3 and 4). Total monthly precipitation in
June and July during the 2003 growing season were lower than the 30-year
average (Figure 1a). Monthly average maximum temperatures during the 2005
growing season from June to September were higher than the 30-year average
(Figure 1b). Precipitation in August 2005 was lower than in any other growing
season and than the 30-year average (Figure 1a). Rainfall during the 2004

growing season was well distributed in compared with 2003 and 2005 (Figure 2).

N accumulation by interseeded red clever or AC Greenflx

N accumulation by interseeded cover crops during the year of
establishment (fall) was variable and very low compared with N accumulation the
subsequent spring (Table 1). AC Greenfix was hand-clipped a few days after
sampling cover crop DM to prevent podflll. Regrowth was expected from AC

Greenfix, however none occurred. The subsequent spring, prior to dry bean

133

establishment, interseeded red clover accumulated substantial N (Table 1). in
spring 2004 and 2005 red clover N accumulation was similar regardless of corn
density, but differed in 2003. Spring red clover N accumulation was significantly

higher in 2005, followed by 2003 and then 2004.

Dry bean yield

Dry bean yield varied across years and among treatments (Table 2). No
interaction was observed between year and treatments (data not shown). Dry
bean yield was comparable to results of Xu and Pierce (1998) who obtained dry
bean yield ranging from 2.3 to 3.4 Mg ha". In 2003, bean planted in CMNF had
similar yield to bean planted after interseeded red clover or AC Greenfix (Table
2). Bean planted in CMNF and PRIR yielded more than been following PRNI but
were not significant different from PRIA. In 2004, dry bean yield in CMNF was
significantly higher than PRIA, but similar to PRIR (Table 2). In both years, dry
bean following interseeded red clover treatments produced yields comparable to
bean supplied with 45 kg ha'1 of N. Results support work of Skarphol et al. (1987)
who found that bean yield following legume cover crops was similar to yield
obtained with N fertilizer without a legume cover crop. Similarly, Liebman and
Gallandt (2002) found comparable yield of dry bean following red clover and
bean supplied with 84 kg ha'1 N fertilizer. in 2003 and 2004, dry bean following
interseeded red clover treatments produced greater yields than the no
interseeding system. Peet (1995) found that planting snap bean following cover

crops yielded higher than snap bean without cover crop. In 2005, however, been

134

supplied with N fertilizer yielded lower than any other treatment. The difference
among treatments may be due to the dry, hot conditions that occurred in 2005.
These conditions may have reduced N fertilizer uptake by bean planted in
CMNF. Poor weed control by herbicides may be an additional factor in explaining
lower yields in 2005 compared with other growing seasons. In 2005, been yield
following no interseeding were comparable to yield of beans following
interseeded red clover or AC Greenfix.

There was a seasonal effect on dry bean yield. Across years, dry bean
yield was higher in 2004, followed by 2003 and then by 2005 (data not shown).
The high yield in 2004 was due in part to well-distributed rainfall that occurred
throughout the growing season (Figure 2). Poor herbicide efficacy due to low
rainfall helps explain low yield in 2003 compared with 2004 (Table 2). These
differences in yield during drought versus wet conditions may be explained by
findings from Lodeiro et al. (2000) who concluded that common bean grown
under conditions of N fixation were more drought tolerant than those provided
with sufficient levels of N fertilizer. The 100 seed weight varied with treatments

and year and no clear pattern was observed (Table 3).

Dry bean N concentration and content

Nitrogen concentration varied with management practices and among
growing seasons (Table 4). In 2003, seed N concentration of bean planted in
CMNF was significantly higher than bean seed N concentration in PRIA and

PRNI. No significant difference was observed in seed N concentration of bean

135

following interseeded red clover and bean supplied with N fertilizer. In 2004, seed
N concentration was higher in CMNF and significantly different from PRIR and
PRNI, but not significant different from PRIA. The low N concentration in dry
bean seed may be related to low N contribution by interseeded red clover in the
subsequent spring of 2004, before dry bean establishment. This is supported by
a positive correlation coefficient of 0.61 (<0.0001) between dry bean seed N
concentration and red clover N accumulation before planting dry bean (data not
shown). in 2005 however, no significant difference was observed in bean seed N
concentration among management practices. Across years, N concentration of
bean seed was significantly higher in 2005, followed by 2003 and then by 2004
(data not shown). There was a negative correlation coefficient of -0.28 (0.0003)
between dry bean yield and seed N concentration (data not shown).

N concentration in beans stem and leaf showed no significant difference
among treatments in either 2004 or 2005 (Table 4). Nitrogen concentration of
bean leaves and stems were significantly higher in 2005 compared with 2004
(data not shown). This was probably due to hot, dry weather conditions that
occurred in 2005.

Dry bean seed N content followed the yield trend (Table 2). in 2003, bean
planted in both CMNF and PRIR accumulated more seed N than PRNI. In 2004
only been planted in CMNF had a higher seed N content than PRNI. However in
2005, bean planted in CMNF accumulated less N than all other treatments (Table
2). Across years, there was a very high positive correlation coefficient of

0.91(p<0.0001) between dry bean yield and seed N content. Results of this study

136

are similar to findings of Lopez-Bellido et al. (2003) who observed faba bean

seed N content ranging from 50 to 127 kg N ha".

Fall and subsequent spring soil mineral N
Soil mineral N was variable within sampling period (fall or spring) and from
fall to the subsequent spring, due probably to weather conditions and time of
sampling (Table 5, 6 and 7, and Figures 3 and 4).
Soil Nitrate and Ammonium in fall
In fall 2002, soil nitrate was the lowest in the treatment supplied with N
fertilizer, but only significantly different from PRNI (Table 5). No difference was
observed between interseeded cover crop and no interseeding. In fall 2003, no
significant difference was observed among treatments; however soil nitrate was
lower in all management practices. Low values in fall 2003 may be explained by
leaching due to increased rainfall before soil sampling (Figure 3). In fall 2004, soil
nitrate in CMNF was significantly higher than in PRIR, but not different from PRIA
and PRNI. In fall 2005, soil nitrate in CMNF was significantly higher compared to
PRIR, PRIA and PRNI. In fall 2004 and 2005, no significant difference was
observed in soil ammonium among management practices. In fall 2004 and
2005, soil ammonium was significantly higher than nitrate in all management
practices except in CMNF in 2004 (Table 7).
Soil Nitrate and Ammonium in the subsequent spring
In spring 2003, nitrate decreased significantly, no difference was observed

among management practices (Table 5). Low values in spring 2003 may be due

137

to leaching as heavy rain occurred in spring before soil samples were collected
(Figure 4). In spring 2004, soil NO'3-N was significantly higher in PRNI compared
with CMNF, but not different from PRIA and PRIR. In spring 2005, soil nitrate in
PRNI and PRIA were significantly higher than PRIR but not different from CMNF.
In spring 2004 and 2005, no significant difference was observed in soil NH”4-N
among management practices (Table 5). No significant difference was observed
between soil nitrate and ammonium in spring 2004 and 2005 (Table 7).

Soil NO'3-N varied significantly in all management practices from fall 2002
to spring 2003 (Table 6). However, no variation in soil NO'3-N occurred among
management practices from fall 2003 to spring 2004 (Table 6). From fall 2004 to
spring 2005, no difference was observed in soil NO'3-N among management
practices, except in PRNI where soil NO'3-N in fall 2004 was significantly lower
than the subsequent spring in 2005 (Table 6). From fall 2004 to spring 2005,
there was a trend of increase in soil nitrate that was probably due to temperature
and rainfall that may have contributed to more soil N mineralization. No
significant difference was observed in soil NHH—N from fall 2004 to the
subsequent spring in 2005 (data not shown).

Fall comparison across years showed that soil nitrate was significantly
higher in 2002 compared with 2005, which was also significantly higher than
2003 and 2004 (data not shown). This may be explained by good cover crop
stand in spring 2002 combined with high temperature and moderate rainfall early
in the season and low rainfall toward the end of the growing season (Figure 3).

The correlation coefficient between dry bean yield and soil mineral N was very

138

small and no significant difference was detected (data not shown). Overall,
interseeded cover crops did not influence soil nitrate and ammonium. Soil
mineral N was influenced by the time of sampling as also observed in a study

conducted by lsse et al. (1999).

Conclusion

In two of the three years, dry bean yield following corn interseeded with
red clover was similar to dry bean yield following corn and supplied with mineral
N fertilizer. Dry bean yield following interseeded red clover could be better
explained by N accumulation from interseeded cover crop than soil mineral N
before bean establishment. There was a positive correlation between N
accumulation of interseeded red clover the subsequent spring (before bean
establishment) and dry bean yield. Dry bean seed N concentration was variable
within management practices and years. Dry bean N concentration in seed, leaf
and stem tended to be high during hot and dry conditions. In two of the three
years, bean seed N content was the highest in beans supplied with N fertilizer
and the lowest during dry conditions. Across years, there was a strong
correlation between interseeded red clover N accumulation before bean
establishment and dry bean seed N concentration. Soil nitrate and ammonium in
the fall and the subsequent spring were not influenced by interseeded cover
crops but rather by climatic conditions. No correlation was found between early
spring soil mineral N with dry bean yield. The data suggest that interseeding red

clover into corn can result in sufficient N accumulation to meet the demand of a

139

subsequent dry bean crop. This system appears to have the potential to help
reduce N fertilizer use and hence could reduce the cost of inputs and
environmental pollution. It could also be useful system for organic farmers and

for low-resource farmers in developing nations.

140

References:

Aleman, F. 2001. Common bean response to tillage intensity and weed control
strategies. Weed Sci. 93:556-563.

Amador—Ramirez, M.D., R.G. Wilson, and AR. Martin. 2001. Weed control and
dry bean (Phaseolus vulgaris) response to in-row cultivation, rotary
hoeing, and herbicides. Weed Sci. 15:429-436.

Amador-Ramirez, M.D., R.G. Wilson, and AR. Martin. 2002. Effect of in-row
cultivation, herbicides, and dry bean canopy on weed seedling
emergence. Weed Sci. 50:370-377.

Balkcom, KS, and D.W. Reeves. 2005. Sunn-hemp utilized as a legume cover
crop for corn production. Agron. J. 97226-31.

Blackshaw, R.E., L.J. Molnar, H.H. Muendel, G. Saindon, and X. Li. 2000.
Integration of cropping practices and herbicides improves weed
management in dry bean (Phaseolus vulgaris). Weed Sci. 14:327-336.

Campbell, C.A., V.O. Biederbeck, R.P. Zentner, and GP. Lafond. 1991. Effect of
crop rotations and cultural practices on soil organic matter, microbial

biomass and respiration in a thin Black Chemozem. Can. J. Soil Sci.
71:363-376.

Crum, JR, and HP. Collins. 2004. Kellogg Biological Station soils. (Available
online at httpzlllter.kbs.msu.edu/Soil/characterizationl).

Ditsch, D.G., and MM. Alley. 1991. Nonleguminous cover crop management for
residual N recovery and subsequent crop yields. J. Fertilizer 8:6-13.

Doran, J.W., D.F. Fraser, M.N. Culik, and WC Liebhardt. 1987. Influence of
aitemative and conventional agricultural management on soil microbial
processes and nitrogen availability. Am. J. Altem. Agric. 2:99-106.

Hesterman, 0.8., TS. Griffin, P.T. Williams, G.H. Harris, and DR. Christenson.
1992. Forage-legume small-grain intercrops-nitrogen production and
response of subsequent corn rotations. J. Prod. Agric. 5:340-348.

lsse, A.A., A.F. MacKenzie, K. Stewart, D.C. Cloutier, and D.L. Smith. 1999.
Cover crops and nutrient retention for subsequent sweet corn production.
Agron. J. 91:934—939.

Jeranyama, P., 0.3. Hesterman, and CC. Sheaffer. 1998. Medic planting date

effect on dry matter and nitrogen accumulation when clear-seeded or
intercropped with corn. Agron. J. 90:616-622.

141

Katsvairo, T.W., W.J. Cox, HM. Van Es, and M. Glos. 2003. Spatial yield
response of two corn hybrids at two nitrogen levels. Agron. J. 95:1012-
1022.

Liebman, M., and ER. Gallandt. 2002. Differential responses to red clover
residue and ammonium nitrate by common bean and wild mustard. Weed
Sci. 50:521-529.

Liebman, M., S. Corson, R.J. Rowe, and WA. Halteman. 1995. Dry bean
responses to nitrogen-fertilizer in 2 tillage and residue management-
systems. Agron. J. 87:538-546.

Lodeiro, A.R., P. Gonzalez, A. Hernandez, L.J. Balague, and G. Favelukes.
2000. Comparison of drought tolerance in nitrogen-fixing and inorganic
nitrogen-grown common beans. Plant Sci. 154:31.

Lopez-Bellido, R.J., L. Lopez-Bellido, F.J. Lopez-Bellido, and J.E. Castillo. 2003.
Faba bean (Vicia faba L.) response to tillage and soil residual nitrogen in a
continuous rotation with wheat (Triticum aestivum L.) under rainfed
Mediterranean conditions. Agron. J. 95:1253—1 261.

LTER. 2006. Weather data during the 2002, 2003, 2004 and 2005 growing
seasons, pp. Available online
at:<http://lter.kbs.msu.edu/Data/table.isp?Prod_t_Jct=KBS002-
001&limitBE—Year&order=desc>. Kellogg Biological Station, Hickory
Comers, Ml.

MacKown, C.T., S.J. Crafts-Brandner, and T.G. Sutton. 1999. Relationships
among soil nitrate, leaf nitrate, and leaf yield of burley tobacco: Effects of
nitrogen management. Agron. J. 91 :613-621.

McCracken, D.V., MS. Smith, J.H. Grove, C.T. Mackown, and R.L. Blevins.
1994. Nitrate leaching as influenced by cover cropping and nitrogen-
source. Soil Sci. Soc. Am. J. 58:1476—1483.

Mikha, M.M., M.F. Vigil, M.A. Liebig, R.A. Bowman, B. Mcconkey, E. Delbert, and
J.L. Pikul Jr. 2006. Cropping system influences on soil chemical properties
and soil quality in the Great Plains. Renewable Agriculture and Food
System 21 :26-35.

Moraghan, J., and D.W. Franzen. 1995. Fertilizing Pinto, Navy, and other dry

edible bean. NDSU Extension Service. North Dakota State University,
Fargo, ND 58105.

142

Peet, M. 1995. Sustainable practices for vegetable production in the South.
Focus Publishing, Newburyport MA 01950. (Available online at

httpzllwww.ncsu.edulsustainable/index.html).
SAS Institute. 2001. SAS user's guide: Statistics. Release 8th ed. SAS Institute.

Schmidt, J.P., A.J. DeJoia, R.B. Ferguson, R.K. Taylor, R.K. Young, and J.L.
Havlin. 2002. Corn yield response to nitrogen at multiple in-field locations.
Agron. J. 94:798-806.

Shahandeh, H., A.L. Wright, F.M. Hons, and R.J. Lascano. 2005. Spatial and
temporal variation of soil nitrogen parameters related to soil texture and
corn yield. Agron. J. 97:772-782.

Skarphol, B.J., K.A. Corey, and J.J. Meisinger. 1987. Response of snap beans to
tillage and cover crops. J. Am. Soc. Hort. Sci. 112:936-941.

Sogbedji, J.M., H.M. van Es, and KL. Agbeko. 2006. Cover cropping and nutrient
management strategies for maize production in Western Africa. Agron. J.
98:883-889.

Soltani, N., C. Shropshire, and RH. Sikkema. 2006. Responses of various
market classes of dry beans (Phaseolus vulgaris L.) to Iinuron. Weed
Technol. 20:118-122.

USDA-NASS. 2005. Michigan Department of Agriculture 2004 Annual Report.
Michigan Department of Agriculture and United State-National Agricultural
Statistics Service, East Lansing, Michigan.

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

Villar-Mir, J.M., P. Villar-Mir, C.O. Stockle, F. Ferrer, and M. Aran. 2002. On-farrn
monitoring of soil nitrate-nitrogen in irrigated comfields in the Ebro Valley
(Northeast Spain). Agron. J. 94:373-380.

Vyn, T.J., K.J. Janovicek, M.H. Miller, and E.G. Beauchamp. 1999. Soil nitrate
accumulation and corn response to preceding small-grain fertilization and
cover crops. Agron. J. 91:17-24.

Wilson, R.G. 2005. Response of dry bean and weeds to fomesafen and
fomesafen tank mixtures. Weed Sci. 19:201-206.

Xu, 0., and F.J. Pierce. 1998. Dry bean and soil response to tillage and row
spacing. Agron. J. 90:393-399.

143

Table 1. Effect of corn (Zea mays L.) density on N accumulation (kg ha") of interseeded
red clover (Trifolium pretense L.) or AC Greenfix (Lathyrus sativum L.) in fall
during 2002, 2003 and 2004 and the subsequent spring during the 2003, 2004
and 2005 at Kellogg Biological Station, Hickory Comers, Ml.

 

N accumulation

 

 

 

 

 

 

 

 

 

 

 

Red clover AC Greenflx
quha'1
Corn density Fall (gar of establishment)
(plants he") 2002 2003 2004 2002 2003 2004
37 500 15.6a* 4.8a 14.5a 14.6a 20.a 20.3a
55 000 10.3ab 3.0a 10.6ab 11.4ab 70.b 13.1 b
65 000 9.2b 5.4a 8.7b 11.7ab 7.9b 13.5b
75 000 5.9b 2.2a 8.5b 6.8b 7.6b 10.0b
CV (%) 37 52 29 37 52 29
Subsequent spring
2003 2004 2005
37 500 1 09a 69a 1 57a ---- ----- ----
55 000 95ab 83a 152a ----- ----- -----
65 000 105eb 64a 162a ----- ---- -----
75 000 76b 58a 144a ---- ---- ----
CV (%) 18 29 17 ---- -----

 

*Means within columns, cover crop and season followed by the same letter are not
significantly different at P=0.05.
CV: Coefficient of variation

Table 2. Dry been (Phaseolus vulgaris L.) yield (kg ha") and seed N content (kg ha")
under various management practices during the 2003, 2004 and 2005 growing
seasons at Kellogg Biological Station, Hickory Comers, MI.

 

 

 

 

 

 

Yield Seed N content
2003 2004 2005 2003 2004 2005
kg ha"

PRIR 3424a* 3737ab 2964a 109.8a 102.6ab 103.3a
PRIA 3220ab 3453bc 2873a 100.3ab 99.0ab 99.7e
PRNI 3057b 3384c 2810a 95.0b 93.0b 92.6a
CMNF 3430a 3863a 2244b 1 12.7a 1 15.2a 77.8b
CV (%) 1 7 9 33 1 9 8 35

 

*Means within columns followed by the same letter are not
significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.
CV: Coefficient of variation

144

Table 3. Seed moisture content (9 kg") and 100 seed weight (g) of dry bean

(Phaseolus vulgaris L.) in various management practices after harvest during the

2003, 2004 and 2005 growing seasons at Kellogg Biological Station, Hickory

 

 

 

 

 

Corners, MI.
100 seeds weight Seed moisture
2003 2004 2005 2003 2004 2005
9 “-9 k9'1m

PRIR 18.83“ 19.8a 22.6a 118.9a 116.9a 108.3a
PRIA 17.9b 19.5ab 21 .8a 118.6e 113.8a 110.3a
PRNI 18.2b 19.4b 21 .9a 118.6e 117.9a 109.8a
CMNF 18.0b 19.9a 21 .5a 118.5a 115.5a 109.4a
CV (%) 7 4 10 3 9 3

 

*Means within columns followed by the same letter are not

significantly different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;
PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

CV: Coefficient of variation

Table 4. Effect of management practices on N concentration(g kg“) of seed, leaves and

stem of dry been (Phaseolus vulgaris L.) a few days before harvest during the
2003, 2004 and 2005 growing seasons at Kellogg Biological Station, Hickory

 

 

 

 

 

 

 

Corners, Ml.
Seed N concentration Leaves N Stern N
concentration concentration

Management 2003 2004 2005 2004 2005 2004 2005
practices 9 kg"I
PRIR 3Zab* 27.5b 35.1a 20.9a 25.5a 6.2a 13.4a
PRIA 31 .1bc 28.7ab 34.9a 22.4e 25.03 6.3a 12.9a
PRNI 30.3c 27.8b 33.3a 21 .3a 25.3a 6.7a 14.03
CMNF 32.7a 29.8a 34.3a 20.5a 25.1a 6.3a 12.2a
CV (%) 7 7 10 12 20 9 27

 

*Means within columns followed by the same letter are not significantly

different at P=0.05.

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.
CV: Coefficient of variation

145

Table 5. Effect of management practices on soil nitrate and ammonium after corn
(Zea mays L.) harvest in fall 2002, 2003, 2004 and 2005 and before planting

dry bean (Phaseolus vulgaris L.) during the subsequent spring of 2003, 2004 and

2005 growing seasons at Kellogg Biological Station, Hickory Comers, MI. Each

year, planting occurred in a different field.

 

 

 

 

 

 

 

 

 

 

 

 

 

N03‘ N03’ NH.+ NO3’ NH4" N03‘ NH4+
are"
Fall
2002 2003 2004 2005
PRIR 12.5ab* 2.2a ---- 1.3b 2.6a 6.1b 4.4a
PRIA 15.4ab 2.3a -——- 1.7ab 2.7a 5.8b 4.2a
PRNI 16.1a 2.5a ----- 1.6ab 2.9a 5.8b 3.7a
CMNF 11.6b 1.3a ---- 2.2a 2.8a 7.6a 3.7a
CV (%) 41 62 ---- 54 26 23 39
Subsequent spring
2003 2004 2005
PRIR 1.7a 3.8ab 3.6a 2.4b 3.2a
PRIA 2.0a 4.0ab 3.3a 3.4a 2.7a
PRNI 1.5a 4.4a 3.5a 3.7a 3.1 a
CMNF 2.0a 2.7b 3.5a 3.0eb 2.7a
CV (%) 68 33 22 36 26

 

 

*Means within columns and season followed by the same letter are not
significantly different at P=0.05.
PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;
CMNF: Conventional management, supplied with N fertilizer.
CV: Coefficient of variation

146

Table 6. Comparison of soil NO'3-N concentration in fall [the year of corn (Zea mays L.)
establishment] to the second sampling under the subsequent spring (before
planting beans) in the same management practices in 2002, 2003,2004 and
2005 at Kellogg Biological Station, Hickory Comers, Ml.

 

Management practices

 

 

 

PRIR PRIA PRNI CMNF
Pr > F
Fall 2002 x Spring 2003 <0.0001* <0.0001 <0.0001 <0.0001
Fall 2003 x Spring 2004 0.256 0.214 0.177 0.325
Fall 2004 x Sjflg 2005 0.259 0.083 0.036 0.409

 

*No iicmificent difference if p value=0.05

PRIR: Plowed red clover interseeded with red clover;

PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;

CMNF: Conventional management, supplied with N fertilizer.

 

Table 7. Comparison of soil NO'a-N and soil NH*4-N concentration in fall and subsequent
spring under the same management practices in 2004 and 2005 at Kellogg
Biological Station, Hickory Corners, Ml.

 

Management practices
PRIR PRIA PRNI CMNF
Pr > F

Spring 2004( NO'3-N x NH‘4-N) 0.7670" 0.2151 0.1118 0.2023
Fall 2004( NO'3-N x NHH-N) 0.002 0.0159 0.0040 0.1271
Spring 2005( NO'3-N x NH*4-N) 0.0694 0.1015 0.1341 0.5146
Fall 2005 ( NO’3-N x NH*4-N) <0.0001 0.0002 <0.0001 <0.0001
*No significant difference if p value=0.05
PRIR: Plowed red clover interseeded with red clover;
PRIA: Plowed red clover interseeded with AC Greenfix;
PRNI: Plowed red clover no interseeding;
CMNF: Conventional management, supplied with N fertilizer.

 

 

 

 

 

147

300

 

 

 

 

 

 

 
   
  

     
   
 

 

 

(a) Precipitation
250 - L. '. . 2002
Lift: 2003
E rxxxa 2004
E 200 ' m 2005 FT21,0
E 30-yr-Av.
'3}: 150 - ‘_
I§ ‘
8
Dh. 100 ‘
50 i
o J l
40
-- 2002-Max.
-.-— 2003-Max.
—B— 2004-Max.
30 --— 2005-Max.
5" ~ * 30-yr-Av.Max
8
2
*3 2o -
d.)
O.
E
ID
'— 10 _ 4— 2002-Min.
+ 2003-Min.
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+ 2005-Min.
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April May June July August Sept.
Month

Figure 1. Monthly average minimum and maximum temperature, and total monthly
precipitation during the 2002, 2003, 2004 and 2005 growing seasons
compared with the 30-year monthly average at Kellogg Biological Station,
Hickory Comers, MI.

148

 

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30-

20‘

10‘
0 -../\Ai WMA,,

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Date

Figure 2. Total daily precipitation during the 2003, 2004 and 2005 dry been
growing seasons at Kellogg Biological Station, Hickory Comers, MI.

 

 

 

 

 

 

 

 

 

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Precipitation Spring 2003

— — Average temperature

 

 

 

 

 

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60—
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Spring 2004

 

 

 

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70
60 '
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04-Apr 18-Apr 02-May 16-May 30-May

Date

Figure 4. Total daily precipitation and average temperature from 1 April to
31 May during the 2003, 2004 and 2005 growing seasons at
Kellogg Biological Station, Hickory corners, MI.

151

Summary and Conclusions

The objectives of this study were to evaluate (1) the effect of corn density
(37 500, 55 000, 65 000 and 75 000 plants ha“) and cover crops in an
interseeding system on com yield and on red clover or AC Greenfix dry matter;
(2) the effect of nitrogen fertilizer versus nitrogen provided by plowed red clover
on corn yield and N status at various corn densities; (3) the effect of corn density
and interseeding on nitrogen status in corn and cover crop; and (4) the effect of
interseeded cover crops on soil mineral N (NO'3 and NH“.;), and subsequent dry
been yield and N status.

Corn yield was not affected by interseeded cover crops at any plant
density, suggesting that interseeding cover crops at corn densities up to 75 000
plants ha'1 does not reduce corn yield. Red clover and AC Greenfix responded
similarly to corn density with a decrease in DM as corn density increased. AC
Greenfix established well in the interseeding system but produced on average
only 10 to 20 % of its expected biomass in a monoculture system. AC Greenfix
performed best during cool, wet seasons such as in 2004 where it produced
considerable biomass in only 48 days. Red clover biomass increased
significantly from fall to the subsequent spring as did N accumulation. However N
concentration significantly decreased, suggesting a dilution factor with increased
biomass production.

Corn density influenced corn grain and ear leaf N concentration, and

chlorophyll content with significantly higher values at the lowest corn density,

152

suggesting competition for N as com density increased. Corn grain and ear leaf
N concentration, and chlorophyll content were significantly higher in com
supplied with N fertilizer regardless of dry or wet growing seasons. Ear leaf N
concentration and chlorophyll content can be used as a good indicator of N
concentration in corn grain. Corn grain N concentration was reduced by using
cover crops as a N source and by increasing corn density regardless of N
source. There was a trend for increased N concentration in corn ear leaf and
chlorophyll content, and in dry bean grain, leaf and stem during dry conditions.
Corn density did not influence N concentration of red clover and AC Greenfix. N
accumulation for corn grain, red clover, AC Greenfix and dry been paralleled dry
matter production in every growing season. Across years, the correlation
coefficient between DM and N content were R2=0.97 (p<0.0001) for cover crops,
R2=0.98 (p<0.0001) for corn grain and R2=91 (p<0.0001) for dry been (data not
shown).

Yield of dry been planted following red clover interseeded into corn was
associated with the amount of N accumulated by red clover before been
establishment and with climatic conditions. In dry conditions, yield of dry been
supplied with N fertilizer was lower than been planted after interseeded red
clover, whereas comparable yields were observed during a wet growing season.
Red clover consistently achieved the objective of supplying sufficient N to
produce dry bean yield similar to been supplied with N fertilizer. Soil mineral N
(NH*4 and N03) was not influenced by interseeding cover crops and varied with

sampling time and growing season.

153

Under the conditions of this study, interseeded AC Greenfix did not
accumulate significant amount of N in the fall to maintain subsequent dry bean
yield. Similarly, AC Greenfix was not suitable for interseeding due to its low
biomass production when compared with growth in monoculture. Alternative
management practices should be explored such as planting after wheat harvest
in July or August since the cover crop does well in cool temperature. Another
aitemative to consider is early establishment of AC Greenfix in April before a
short cycle crop, since AC Greenfix can tolerate very low temperatures and can
produce significant biomass in only 60 days. Although red clover did have slow
growth in fall, it accumulated significant N in the subsequent spring. To obtain
adequate N accumulation by red clover, it should be plowed under at the end of
May or early June. To allow this, there should be a plan to plant a short cycle
crop such as been or vegetable crops which do not require a full growing season.

Results of this study are valuable to conventional, organic, low-input, and
low-resource farmers. For conventional farmers, interseeding at corn densities up
to 75 000 plants ha'1 will allow maximization of com yield, the benefit of cover
crops during the winter (reduction of soil erosion) and reduce or eliminate
fertilizer need for the subsequent crop. Organic farming systems and low-input
farming systems of developing countries may use this system to serve as N
source and to reduce soil erosion. In conclusion, this type of production system
can be utilized to reduce costs in conventional, organic, and low-input farming

systems, while maintaining crop yield.

154

Appendices

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