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THESIS

 

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2009 LS . BABY
ichigan State
University

 

 

 

This is to certify that the
thesis entitled

SPRING INTERSEEDED WINTER ANNUAL RYE IN DRY
BEAN CROPPING SYSTEMS: WEED CONTROL AND STEM
ELONGATION

presented by

STEVEN A. WAGSTAFF

has been accepted towards fulfillment
of the requirements for the

degree In Crop and Soil Sciences

 

 

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Date

 

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5/08 K./Prolecc&Pres/CIRC/DateDue indd

 

SPRING INTERSEEDED WINTER ANNUAL RYE IN DRY BEAN
CROPPING SYSTEMS: WEED CONTROL AND STEM
ELONGATION

By

Steven A. Wagstaff

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirments
for the degree of

MASTERS OF SCIENCE
Crop and Soil Sciences

2009

ABSTRACT

SPRING INTERSEEDED WINTER ANNUAL RYE IN DRY BEAN
CROPPING SYSTEMS: WEED CONTROL AND AGRONOMIC
TRAITS.

By
Steven A. Wagstaff

Public concern over herbicide contamination of water, surfactant effects on
amphibians, and herbicide resistant weeds has led to increased interest in alternative
weed control systems. In addition, direct-cut harvest-associated yield losses of dry bean
(Phaseolus vulgaris L.) are of concern to some growers. Often, there is difficulty
operating combine mechanisms near soil surfaces, in order to reach the lowermost bean
pods. The objectives of this study were to evaluate the utility of an interseeded spring-
planted rye (Secale cereale L.) cover for: (a) weed suppression, and (b) elongation of
dry bean stems for potential reduction in harvest-associated yield losses. We
hypothesized that a rye cover would shade dry bean plants, resulting in a stem

elongation response.

Overall, interseeded rye cover reduced dry bean yields, above-ground biomass,
and plant heights. Rye cover also suppressed above-ground weed biomass in several
instances. However, despite overall reductions in dry bean plant vigor, treatments
including rye cover resulted in significantly greater heights of lowermost dry bean pod

attachment, indicating the presence of a stem elongation effect.

ACKNOWLEDGEMENTS

I would like to thank the members of my graduate committee, Dr. James Kelly,
Dr. Dale Mutch, Mathieu Ngouajio, and Dr. Kurt Thelen. A special thanks is due to Dr.
Kurt Thelen, as my graduate adviser, who has provided much support and advise during
my studies.

I would also like to recognise Mr. Jerry Grigar, who was enthusiastic about
hosting this research on his Gratiot County farm. Jerry was a pleasure to work with and I
could not have hoped for a more friendly and hospitable grower-cooperator.

I would also like to recognise the efforts of many other faculty, staff, students,
and seasonal employees, without whom, this work would have been impossible: Bill
Widdicombe, Keith Dysinger, Todd Martin, Nora Bello, Chrisy Sprague, Gary Zehr,
TimDietz, Tom Galecka, Brian Graff, Norm Blakely, Brian Long, Gary Powell, and Lee
Siler, Terry Shultz, Stephanie Smith, Megan Black, Nathan Blosser, Megan Pickler, and
Evan Wright.

A very special thanks is due to my family for the love, support, and ecouragment
they have provided. My wife, Emily, whose efforts included last-minute and late-night,

proofreading marathons, was especially integral to this work.

iii

TABLE OF CONTENTS

 

List of Tables ........................................................................................ vi
List of Figures ...................................................................................... vii
CHAPTER 1: LITERATURE REVIEW - - - - 1
Introduction ......................................................................................................................... 1
Dry Bean Agronomy ........................................................................................................... 3
Harvest Methodology ......................................................................................................... 5
Weed Suppression ............................................................................................................... 8
Cover Crops ........................................................................................................................ 9
Living Mulch ............................................................................................................. 10
Green Manure ........................................................................................................... 10
Catch Crop ................................................................................................................ 11
Smother Crop ............................................................................................................ 11
Trap Crop .................................................................................................................. 12
Spring-Seeded Cover Crop ....................................................................................... 12
F rost-Seeded Cover Crop ......................................................................................... 12
Winter Cover Crops .................................................................................................. 13
Summer Cover Crops ................................................................................................ 13
Interseedea', Overseeded, Underseeded Cover Crops .............................................. 13
Weed Control with Living Mulch ..................................................................................... 14
Literature Cited ................................................................................................................. 18

CHAPTER 2: UTILITY OF INTERSEEDED WINTER-ANNUAL RYE IN DRY

 

BEAN CROPPING SYSTEMS 22
Introduction ....................................................................................................................... 22
Materials and Methods ...................................................................................................... 23
Results and Discussion (Ingham) ...................................................................................... 26
Dry bean biomass ..................................................................................................... 26
Rye biomass .............................................................................................................. 27
Grass weed biomass .................................................................................................. 27
Broad-leaf weed biomass .......................................................................................... 2 7
Dry Bean Plant Height ............................................................................................. 28
Uppermost Pod Height ............................................................................................. 29
Lowermost Pod Height ............................................................................................. 29
Yield .......................................................................................................................... 30
Conclusions ....................................................................................................................... 30
Literature Cited ................................................................................................................. 42

CHAPTER 3: UTILITY OF INTERSEEDED WINTER-ANNUAL RYE IN

iv

ORGANIC DRY BEAN CROPPING SYSTEMS -- 43

 

Introduction ....................................................................................................................... 43
Materials and Methods ...................................................................................................... 44
Results and Discussion ..................................................................................................... 46
Bean Biomass ............................................................................................................ 46
Grass Weed Biomass ................................................................................................ 4 7
Broadleaf Weed Biomass .......................................................................................... 4 7
Height of Uppermost Dry Bean ................................................................................ 48
Height to Lowermost Dry Bean Pod ......................................................................... 48
Yield .......................................................................................................................... 49
Conclusions ....................................................................................................................... 49
Literature Cited ................................................................................................................. 57

LIST OF TABLES

Table 2.1 List of treatments design at Ingham and Gratiot. 2006 and 2007. ................... 32

Table 2.2 Effects of rye cover crop and herbicide regime on bean biomass, rye
biomass, weed biomass and dry bean yield at Ingham and Gratiot. 2006

and 2007. .......................................................................................................... 33
Table 2.3 Effect of year on average bean dry-weight at Ingham and Gratiot. 2006

and 2007. .......................................................................................................... 34
Table 2.4 Monthly precipitation at Ingham and Gratiot (mm). 2006 and 2007 ............... 35
Table 2.5 Effect of year on dicot weed biomass at Ingham. 2006 and 2007. .................. 36
Table 2.6 Effect of herbicide, and row space on dicot weed biomass when no rye

cover is present at Ingham. 2006 and 2007. ..................................................... 37
Table 2. 7. Effect of herbicide, and row space on dicot weed biomass when no rye

cover is present at Ingham. 2006 and 2007. ..................................................... 38
Table 2.8 Effect of rye cover and herbicide on dicot weed biomass in 76 cm row

space configurations at Ingham. 2006 and 2007. ............................................. 39
Table 2.9 Effects of rye cover crop and herbicide regime on bean archetecture

and dicot weed biomass at Ingham and Gratiot. 2006 and 2007. .................... 40
Table 2.10 Effects of rye cover crop and herbicide regime on bean archetecture

and yield at Ingham and Gratiot. 2006 and 2007. ............................................ 41
Table 3.1 List of treatment design at Kalamazoo. 2006 and 2007. ................................ 51
Table 3.2 Effect of year and rye cover crop on dry bean and dicot weed biomass

at Kalamazoo, conditional on no cultivation. 2006 and 2007. ......................... 52
Table 3.3 Monthly precipitation at Kalamazoo (mm). 2006 and 2007 ............................ 53

Table 3.4 Effect of cultivation on dry bean biomass, plant height, and pod height
at Kalamazoo. Conditional on no cover and no drilled row-spacing.
2006 and 2007. ................................................................................................. 54

Table 3.5 Effect of year and cover crop on dry bean plant, top, and bottom pod
height at Kalamazoo, conditional on no cultivation. 2006 and 2007. .............. 55

Table 3.6 Effect of year and cover crop on dry bean yield at Kalamazoo,

vi

conditional on no cultivation. 2006 and 2007. ................................................. 56

vii

LIST OF FIGURES

Figure 1.] Architectural differences between growth habits within P. vulgaris ............. 17

viii

CHAPTER 1: Literature Review

Introduction

Common bean (Phaseolus vulgaris L.) is an annual, herbacious plant grown for
its edible bean from temperate to tropical climates worldwide. Common beans are
primarily eaten fresh, e.g., green beans, or grown to physiological maturity and dried, as
dry beans, for storage. Production and consumption of dry beans is far greater than that
of green beans. In additon to the beans being eaten, the flowers and leaves may be
harvested for consumption in some parts of Latin America as well as Central and Eastern
Africa. Also, special heirloom “popping” cultivars are cultivated in Bolivia and Peru.
These cultivars are believed to have been roasted on open fires for consumption, prior to
the invention of pottery (and thus, boiling), by the natives of the Andean highlands
(Singh 1999).

The common bean was originally domesticated, independently, in both ancient
regions of Mesoamerica and the Andes sometime between 5000 and 7000 BC. from
morphologically and biochemically distinct populations (Chacon et al. 2005). Around
700 years ago, common beans were used extensively with squash and corn as part of the
native American "Three Sisters" polyculture farming systems. Although there is
uncertainty, it has been theorised that Spanish-Potugese sailors obtained and introduced

common bean germplasm to Spain and other parts of Europe in late 1400 (Zeven 1997).

Today, as a major source of protein and starch for many developing nations, dry

beans are an extremely important legume crop worldwide, and, in-fact, they are the most

widely consumed grain legume in the world (Acosta-Gallegos et al. 2007). It has been
documented that some per-capita consumptions in easterm Africa are over 60 kg per year
(Gepts 2001; Miklas and Singh 2007). The protein present in dry bean accounts for 20-
25% of seed weight (Ma and Bliss 1978). Addtionally, dry beans are an important source
of mineral micronutrients (Calcium, Copper, Iron, Magnesium, Manganese, Phosphorous,
and Zinc) as well as the vitamin, folate(We1ch et al. 2000).

In addition to the nutritional importance of dry beans in developing nations,
recent research points to the potential additional health benefits of dry bean consumption
in developed nations. Many health-conscious countries are increasing dry bean
consumption (Acosta-Gallegos et al. 2007), although consumer preference for market
class may vary widely. Bean consumption has been linked to reduction in both total and
low-density lipoprotein (LDL), or “bad”, cholesterol levels (Anderson et al. 1984;
Anderson 1987). In a recent study, Winham et al. (2007), concluded that eating pinto
beans for eight weeks significantly lowered total and LDL cholesterol and thus, the risk
of heart disease. In a separate study, Hangen and Bennink (2003) showed that
consumption of black and navy beans reduced the incidence of colon cancer in rats.

In 2005, the United States ranked sixth in the world for production of dry edible
beans, behind Brazil, India, China, Burma (Myanmar), and Mexico. The Americas
collectively produced 6.5 million metric tons (MMT) with the majority of the production
concentrated in the top three nations: Brazil (3 MMT), the United States (1.3 MMT), and
Mexico (1.2 MMT) (Anonymous 2007).

Although many regions of the United States produce of dry beans, the majority of

production is concentrated in the lower peninsula of Michigan and North Dakota. In

2006, Michigan ranked second in the United States for edible dry bean production, with
an estimated wholesale value of $127,000,000 (Anonymous 2006). F orty-one percent of
Michigan’s 191,000 total dry bean acres were planted in black beans, making Michigan
the top producer of black beans in 2006 (Anonymous 2006).

The wholesale value of the US. dry bean crop for 2007 was approximately
$677,000,000 with an estimated 1.15 MMT harvested from 598,429 hectares planted.
Although there was a 6.3% decrease in area planted from 2006 to 2007, there was a 22%
increase in total wholesale value. In Michigan, wholesale value of the 2007 dry bean
crop was $88,000,000, with 141,500 metric tons harvested from 78,917 hectares planted.

(Anonymous 2008).

Dry Bean Agronomy

Dry beans are adapted to a wide range of temperatures, but as a short day crop,
the optimum temperature range is between 18 and 24 °C. Cooler temperatures are
undesirable and frost is not tolerated well. Dry beans are also adapted for a wide range of
soil types, but are intolerant of saline or poorly drained soils (Anonymous 1997).

In Michigan, the crop is typically planted during the first week of June. A normal
growing season will range from 100 to 130 days to maturity (Singh 1999). Desired plant
populations range from 296,000 plants per hectare (ha) in drilled (19 cm) spacings to
148,000 plants per ha in wide row (76 cm) spacings. When planted in 62 cm rows, the
plants may take several weeks to close their canopies across rows, although this may
never occur in some fields. The seed should be planted between 2.5 and 5 cm deep.
Growers are encouraged to plant certified seed to control seed-bome diseases such as

baterial blight and anthracnose as well as to ensure genetic purity (Anonymous 1997).

3

Although dry beans are a legume, their fixation of nitrogen is considered to be
highly variable due to environmental conditions and variablitity between varieties
(Wamcke et al. 2004). Michigan State University recommends applying 45 to 67 kg
nitrogen per ha (N/ha) to dry bean crops. Growers utilizing narrow rows, irrigation, and
other intense managment systems are encouraged to use a rate near 67 kg N/ha, while
gorwers practicing less intense managment should utilize a rate closer to 45 kg N/ha.
Phosphorus availablity should be at least 40 parts per million (ppm). Potassium
recommendations are based on soil CEC (cation exchange capacity) and yield targets.
The recommended soil test level is 135 ppm for a soil with a CEC of 4, regardless of
yield goal. Additionally, growers should not apply fertilizer with seed, but should instead
broadcast and incorporate fertilizer prior to planting or band between rows. Zinc
deficiency, although uncommon, may be experienced in high pH soils (> pH 7.8) or
following a sugarbeet crop due to lack of mycorrhizal-assisted nutrient mining of zinc
(Wamcke et al. 2004).

There are several different dry bean market classes, including: kidney, navy,
pinto, and black beans. Although the beans within these various classes differ in size and
shape, they are all recognized as the same species, P. vulgaris. There are three basic
growth habits of dry bean varieties grown in the US (Figure 1.1). Type 1, ‘bush’
varieties, are determinate, while Types II and III are indeterminate. Type II, ‘upright’
varieties exhibit an upright architecture, having most of their pods held above the ground.
Type III, ‘vine’ varieties exhibit varying degrees of prostrate architecture, with the
potential for many pods to touch the ground (Figure 1.1). In addition, there is a climbing

type growth habit (type IV). Upright varieties grow up to 71 cm tall while vine varieties

may obtain vine lengths of up to 3 m (Anonymous 1997).

Harvest Methodology

Most dry bean growers practice one of two types of harvest procedures, the
pulling-windrow method or the direct combine method. Prior to modern breeding efforts,
the predominantly prostrate architecture of available bean germplasm necessitated pulling
and windrowing, requiring multiple pieces of equipment. Even with modern breeding
efforts, the windrow method is still the most common harvest procedure. First, a bean
puller is run through the field, cutting and pulling the beans as low on the stem as
possible and laying them on the soil surface. Secondly, the plants are mechanically raked
into long rows, or windrows. In Michigan, this procedure is done early in the morning,
while dew is present, in order to minimize yield loss associated with pod shatter. The
bean plants are allowed to sit in the windrows for several hours until the beans are dry
before finally being threshed. In regions with drier fall climates than Michigan, such as
parts of North Dakota, Idaho, and Washington, beans are cut and windrowed while green
and immature and allowed to cure in the windrows for up to two weeks prior to threshing.
The thresher separates the grain from the bean plant while leaving the remainder of the
plant in the field, adding vital organic matter back into the system. Often, further
cleaning with a winnower is required after this step.

Despite its common use, the pulling-windrow harvest method does pose serious
risks and can have considerable drawbacks to growers in the Upper Midwest. While the
beans are in windrow they are vulnerable to precipitation events. If beans in a windrow
are rained on, there is a major possibility for grain quality degredation, disease-associated
yield loss, sprouting seed, mold, and other quality reductions. In addition, due to

5

multiple field passes with equipment, the process can be fuel-intensive and exacerbate
soil compaction problems. Equipment, labor, and maintenance costs may be high. Also,
due to the technical complexity of harvest, it can be difficult to time each phase correctly,
especially under adverse environmental conditions (Nuland et al. 1983).

Another type of harvest procedure, which growers are increasingly adopting in
Michigan, is the direct combine method. Direct harvest utilizes a combine, a piece of
equipment that many growers already own, to cut and harvest beans. A rotary combine,
often equipped with a floating-head, such as is used in soybean production, cuts and
threshes the beans in one pass. Little modification of most combines is needed to execute
this method. Modern upright bean varieties have made direct combine harvest feasible.
Upright varieties, with most of their pods above the soil surface, make it much easier for
a combine to cut plants and pull them into a threshing mechanism without cutting pods
that touch the ground. The direct combine method simplifies the harvest procedure
compared to windrowing and offers savings on fuel, labor, and equipment costs. Often,
growers that utilize the direct combine method must roll their ground with a tractor-
driven implement prior to planting because a uniformly flat and rock-free bed of soil is
required for ease of combine operation and minimization of post-harvest losses. This
method is desirable to some farmers in the Midwest due to weather related risks, shorter
harvest windows, and high fuel costs (Kelly 2008).

While upright varieties have made direct harvest possible, harvest-associated
yield losses are still of major concern. Regardless of the degree of upright architecture
exhibited by any given variety, yield loss is possible. Even in the most upright of

varieties, the lowest pods on the plant may still be below the cutter bar of the combine.

When compared to soybean, dry bean pods often have longer pods with more seeds, with
the potential for pods to hang lower and loss from pod shatter to be greater. One study
has shown that direct combine losses can range from 8% to 13.5%, while the windrow
method typically results in losses of 3% to 12% (Harrigan and Poindexter 1999). Simply
lowering the cutter bar to the level of the soil is not possible due to the potential of hitting
the soil with the cutter-bar of a combine, or earth tag, which can damage equipment, slow
harvest times, and reduce quality of the harvest. Therefore, combine operators are
required to operate combine cutter-bars as low as possible while avoiding earth tag, a
daunting task in fields with uneven topography.

Despite the potential benefits of direct harvest, most Michigan growers utilize the
pulling-windrow method, although adoption of the direct harvest method is growing
(Kelly 2008). Grower concern for yield losses as well as prior investments in windrow
equipment may contribute to this lack of adoption. Also, when compared to the direct
harvest, pulling-windrowing may result in less bean splitting due to increased seed
cushioning from excess plant material (i.e. roots and lower stems) being processed within
threshing mechanisms. Additionally, costs associated with purchasing new combine
equipment may also be prohibitive.

Once the crop is harvested by either method, the grain will often undergo fiirther
cleaning procedures. Beans will also be polished to enhance their cosmetic appeal and
ensure cleanliness. For long-term storage, the beans will be kept below 18% moisture by
weight. If beans are stored at a higher moisture content, mold may significantly reduce
quality. Although, if held for less than 6 months, a moisture content of 18% may be

acceptable (Anonymous 1997). Likewise, too low of a moisture content can be

problematic, resulting in increased seed damage during handling. Also, as moisture is

reduced, cooking times increase and quality is diminished.

Weed Suppression

In addition to harvest methodology, weed suppression is another area of intense
concern within dry bean production. In dry bean cropping systems, a considerable
amount of time, energy, and money is invested in weed management. Vigorous control
of early season weeds is imperative. Dry beans are quite susceptible to weed pressure,
especially in early to mid-season while the canopies are still open (Urwin et al. 1996;
Webber & Shrefier 2003). The critical weed-free period for dry bean may vary by
location and environment. Based on an experiment in Ontario, Canada, Woolley et al.
(1993) reported that the critical weed-free period was between the second trifoliate and
first-flower stages. Woolley et al. also noted that variation was probable at other
locations and in other years due to non-static environmental factors and weed densities.
N gouajio et al. (1997) found that, in Cameroon, the critical period occurred between
emergence and second trifoliate leaf at two locations and between first trifoliate leaf and
pod filling stages of bean growth in other locations. Yield losses attributable to weed
pressure of up to 75% have been reported (Vangessel and Westra 1997).

Depending on specific farm management styles, a combination of chemical,
mechanical, and cultural methods may be utilized to reduce weed competition. Examples
of these methods include: herbicide application, tillage, rotary hoeing, hand hoeing, in-
row cultivation, cover crop usage, narrow row spacing, and increased planting
populations. Transgenic varieties of dry beans which are resistant to the herbicide

glufosinate have been devoloped in Brazil, but have not been registered for use in

8

commerical production (Aragao et al. 2002) due to percieved consumer adversity to

purchasing genetically modified dry beans.

Cover Crops

Cover crops are vegetation grown for their abilities to protect and improve soil
quality rather than for direct economic gain through harvest (Lal et al. 1991). Cover
crops are an important agricultural tool and offer many potential benefits to the grower
even beyond the defintion provided by Lal et al. (1991). In addition to improving soil
quality, cover crops can also prevent nutrient leaching (Parkin et al. 1997; Shipley et al.
1992), reduce pathogenic and insect pests (Ingham 1993 ), sequester and add carbon into
agricultural systems, reduce erosion (Edwards et al. 1993), provide nitrogen to
succeeding crops, and suppress weed growth through competition and allelopathy
(Teasdale et al. 1991).

However, despite the many potential benefits of cover crop usage, several
negative impacts have been documented. Cover crops immobilize nutrients, increase
labor and other costs, and increase the risk of certain pests (Luna 1993). Planting times
may be delayed due to a slowed soil warming effect in the spring and also by heightened
soil moisture due to increased infiltration (Teasdale 1998; Luna 1993).

There is a great variey of terminology used to describe cover cropping systems.
Some of these terms describe the function of the crops, while others describe the method
or timing of crop establishment. Much of the terminology can be combined and/or used
interchangeably. The following portion of this review briefly explains a number of terms
and some literature associated with cover cropping systems, but will ultimately focus on
weed control through the use of living mulch cover crop systems.

9

Living Mulch

A living mulch is a cover crop that is grown along with a primary crop in the
field, for all or part of the growing season. Competition is a major concern with living
mulch systems because the mulch and the primary crop are forces to share resources. A
living mulch is typically established, and occasionally suppressed, prior to primary crop
establishment. Although, suppression may not be necessary if the living mulch is
expected to senesce early in the developmental stages of the primary crop, thus
significantly reducing or even eliminating inter-crop competition. Research into living
mulch systems has tended to focus on weed control and managment of the mulches, and
has showed mixed results (Ateh and Doll 1996; Eadie et al. 1992; Enache and Ilnicki

I992; Thelen et al. 2004).

Green Manure

Green manures have historically been used to add both nutrient and organic
matter back into the soil and have been a subject of study for over 150 years. In 1843,
the Rothamsted Experimental Station was established in England. In the US, the Morrow
Plots research began at the University of Illinois in 1876. These research stations laid the
foundation for our understanding of soil fertility and quality improvements with the use
of cover crops. Unlike a living mulch, green manure is typically established and grown
separately from the primary crop. Subsquently, the cover crop is plowed under or
otherwise incorperated into the soil before planting the primary crop. These crops often
include biennials, perennials, or mixtures of the two, and may be grown for two years or
more before being incorporated. Various crops may be used depending on the goal of the

grower. For instance, a legume manure may be used if the goal is to provide nitrogen for

10

a succeeding crop, while winter rye may be used for its rapid accumulation of biomass if

the grower seeks to add organic matter to the soil (Bowman et al. 1998).

Catch Crop

The primary fimction of a catch crop is to immobilize excess water soluable
nutrients. Typically, the primary nutrient of concern is nitrate, which is often provided in
excess of crop demands in the form of nitrogen fertilizers or manure. Nitrate leaching
has been cited for contamination of groundwater, a potentially dangerous situation if
consumed by humans, particularly infants (Spalding and Exener 1993). In particular,
grass cover crops have been noted to sequester more nitrogen than legumes (Shipley et al.
1992). Aronsson and Torteson (1998) showed that an Italian Ryegrass (Lolium perenne)
catch crop could potentially reduce total nitrogen leaching by 40 to 50% when properly
established with spring cereal cash crops. In addition to potentially ameliorating the
effects of water contamination, catch crops may also release nitrogen to successive crops

if they are left to decompose in the field or turned under as a green manure (Jensen 1992).

Smother Crop

Smother crops are high biomass producing crops used primarily for weed control
purposes. A smother crop is very similar to a living mulch in that it may be established
and supressed before, simultaneously with, or subsequent to the seeding of a primary
crop. Smother crops can suppress weeds through allelopathy and competition for
moisture, light, and nutrients. Smother crops, as defined by Teasdale (1998) are

analagous to living mulch.

ll

Trap Crop

Trap crops are crops that are planted with the intention of luring insects and
other pests away from cash crops. An important requirment for these crops is that they
must be more attractive to the targets pest. Trap crops may be planted around the
perimeter of the cash crop or intercropped within the cash crop. An early or late planting
of the same species as the cash crop or a completely different species altogether may be
used to suit different pest species. A trap crop may be a cash crop itself, or it’s sole
purpose may be to fuction as a trap crop. For example, alfalfa may be used as a trap crop
for lygus bug in cotton production, while also being harvested for forage. Alfalfa is
intercropped in strips within cotton plantings, and is only partially harvested while the

threat of lygus bug (Lygus spp.) damage remains high (Stem I969).

Spring-Seeded Cover Crop

Spring-seeded cover crops are established prior to the planting of a spring or
summer crop and, for research purposes, are often considered a type of living mulch or
smother crop. Field conditions, such as waterlogged soils, can make planting a difficult
or even impossible task in some years. In addition, a spring cover may delay radiative

soil warming (Teasdale 1998).

F rost-Seeded Cover Crop

Frost-seeding is a practice where a cover crop is broadcast seeded while the
ground is still frozen, in late winter to early spring. The fi'eeze and thaw cycles create
surface cracks within the soil, which the seed is then drawn into, creating good seed-to-

soil contact and enhancing germination and establishment (Bamhart 2002). A common

12

practice is to frost-seed red clover into winter cereal grains (Mutch and Snapp 2003).
Mutch et al. (2003) demonstrated successfiil suppression of ragweed by frost-seeding red

clover into established winter wheat stands.

Winter Cover Crops

Winter cover crops are often established after a fall harvest to control soil erosion.
In cooler climates, however, it may be advantageous to overseed before harvest of a
primary crop. Often, the goal of the grower is to accumulate as much biomass as possible
before winter, when the crop will be dormant or possibly winter-killed. In many regions,
growers should plant these covers six weeks before a hard frost. (Bowman et al. 1998).
Due to its winter hardiness, cereal rye is a popular winter cover in the North Central
region of the United States (Bollero and Bullock 1994). Ruffo et al. (2004) investigated
the effect of a winter rye crop, killed with herbicide approximately two weeks prior to no-
till soybean planting. Not only did the rye not effect soybean yield it also “provided an
environmental service” by immobilizing pre-season nitrate (Ruffo et al. 2004).
Summer Cover Crops

Summer cover crops are established and grown for a portion of the summer
growing season. A warm season cover is often selected to fill a niche between the
harvest of spring crops and before the planting of fall vegetable or grains. Summer cover

crops are often grown for the purpose of suppressing weed grth or as a green manure.

Interseeded, Overseeded, Underseeded Cover Crops

Interseeded cover crops, also called either overseeded or underseeded cover crops,

are seeded directly into a primary crop at any point from the time of establishment until

13

the time of harvest. Competition is an important concern with interseeded systems as the
cover and the primary crop must coexist. Many studies have documented cover crop
competition within interseeded systems (Ateh and Doll 1996; Exner and Cruse 1993;
Knake andf Slife 1965; Knake and Slife 1969; Kurtz et al. 1952; Thelen et al. 2004;

Schmenk 1994).

Weed Control with Living Mulch

A specific type of cover crop, living mulch, has recently shown potential for
integration with soybean (Ateh and Doll 1996; Thelen et al. 2004). Living mulch is a
cover crop that is planted prior to, or simultaneously with, a primary crop, where-by the
cover crop and primary crop grow together in the field for all or part of the growing
season. Living mulch can suppress weeds through competition for resources such as
sunlight, moisture, physical space, and nutrients as well as through allelopathy. However,
living mulches must often be either suppressed or killed by application of herbicides or
by mechanical methods to reduce competition with the primary crop (Ateh and Doll
1996; Hartwig and Ammon 2002).

Living mulches have been evaluated for use along with several crops other than
common beans, with mixed success. Enache and Ilnicki (1990) found that the use of
subterranean clover as a living mulch in a no-till system significantly reduced weed
biomass and resulted in corn grain and silage yields comparable to conventionally tilled,
no-mulch systems. Enache and Ilnicki (1992), in a later, expanded experiment,
concluded that subterranean clover used as a living mulch significantly reduced weed
biomass and did not adversely affect yield in several cropping systems: corn, sweet corn,
cabbage, snap beans and tomato. In contrast, Echtenkamp and Moomaw (1989) reported

14

that winter cereal rye used as a living mulch adversely affected corn grain yields due to
its competition for both moisture and nutrients. Also, Sheaffer et al. (2002) explored the
utility of annual medicago as a living mulch in soybean systems. Although annual
medicago did suppress weeds, they reported that soybean yield was negatively impacted
by the cover (Sheaffer et al. 2002). Despite the decreased soybean yield, Sheaffer et al.
(2002) noted that “decreased purchase of herbicides and N fertilizers should reduce
production costs and provide some compensation for the decreased grain yields and seed
costs.” Hartwig and Ammon (2002) reviewed several successful adaptations of living
mulches in a variety of systems including both perrenial (vineyards and orchards) and
common annual agronomic crops (corn, small grains and forages). Although living
mulches were often successful, some form of suppression was often needed in order to
minimize competition with primary crops (Hartwig and Ammom 2002). Competition for
moisture, however, may potentially be overcome in select perrenial and annual croppings
systems, such as vineyards and corn, due to their ability to tap subsoil moisture (Hartwig
and Ammon 2002).

A spring-planted rye as a living mulch cover crop has the potential to address two
previously discussed problems with dry bean production systems, direct cut harvest
losses and weed control. Spring-planted rye does not undergo a period of vemalization,
and thus, remains in a relatively prostrate vegetative state, minimizing competition with
the crop. The less aggressive growth habit has been noted as a desirable trait for a living
mulch as compared to fall-planted rye (Thelen et al. 2004). Despite the somewhat
prostrate morphology of spring-planted rye, it has demonstrated the ability to reduce

weed biomass by 93% as compared to no rye plots (Barnes and Putnam 1983).

15

This research focuses on the use of spring-planted cereal rye mulches to reduce
weed infestation in dry bean cropping systems. In addition, the potential for reducing
yield losses associated with direct combine harvest will be explored. It was hypothesized
that a rye cover would shade developing bean plants and would result in more elongated
dry bean architecture. Also, an elongated dry bean architecture may result in lower direct
combine yield losses. It was further hypothesized that spring-planted cereal rye as a
living mulch would provide weed control benefits through direct competition with weed
species as well as through a mulch effect. This system may also be of particular interest

to organic farmers who cannot use synthetic herbicides.

l6

1.1). Kelly

 

 

Type 1 Type II Type III
Determinate Indeterminate Indeterminate

 

 

 

 

 

 

 

Figure 1.] Architectural difirerences between growth habits within P. vulgaris.

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20

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21

Chapter 2: Utility of Interseeded Winter-Annual Rye in Dry Bean Cropping

Systems

Introduction

Public concern over herbicide contamination of water, surfactant effects on
amphibians, and herbicide resistant weeds has led to increased interest in alternative
weed control systems for crop production. Living mulches may prove to be an important
tool for control of weeds and could reduce grower reliance upon chemical herbicides.
Various applications of living mulches have been evaluated (Ateh and Doll, 1996; Eadie
et al., 1992; Enache and Ilnicki, 1992; Thelen et al., 2004) with mixed results.

Cereal rye (Secale cereale L.) is a popular cover crop in the northern United
States due to its cold hardiness. Rye, like other cover crops, may prevent nutrient
leaching (Kaspar et al. 2007; Shipley et al., 1992), reduce pathogenic and insect pests,
sequester and add carbon to agricultural systems, reduce erosion (Edwards et al., 1992),
provide nitrogen to succeeding crops, and suppress weed growth. Rye suppresses weed
growth through several mechanisms, including competition for water and nutrients,

allelopathy, and physical competition (Teasdale, 1991).

While spring-planted cereal rye has shown potential for integration in soybean
cropping systems as a living mulch (Ateh and Doll, 1996; Thelen et al., 2004), it has not
yet been evaluated within dry bean (Phaseolus vulgaris L.) cropping systems. Spring-
planted rye does not undergo a period of vemalization, and thus, remains in a less
vigorous, vegetative state, minimizing competition with the crop. The less aggressive

growth habit has been noted as a desirable trait for a living mulch as compared to fall-

22

planted rye (Thelen et al., 2004).

Dry bean growers commonly utilize the windrowing-pulling method of harvest,
which requires multiple passes with different pieces of equipment. A new method, direct
combining, is gaining popularity in regions that experience significant rainfall during
harvest time. These growers are concerned about quality losses, due to seed sprouting,
and mold associated with precipitation events while bean plants are in windrows. Direct
combine harvest is seen as a way to reduce fuel and labor costs as well as weather related

risks because beans are not left exposed.

It was hypothesized that a spring-planted rye cover would shade bean plants and
would result in an elongated dry bean architecture, commonly referred to as the “near-
neighbor effect”. Shading reduces energy for photosynthesis and lowers the ratio of
redzfar red light, which can trigger stem elongation in herbaceous plants (Smith, 1982).
An elongated dry bean architecture could result in reduced direct combine yield losses
due to bean pods being held higher off the soil surface, and thus more readily entering the

combine mechanism.

The objectives of this study were to assess the utility of spring-interseeded rye for
weed suppression and for potential reduction of direct-cut harvest-associated yield loss

through elongation of the dry bean plant.

Materials and Methods

Field research was conducted at the Michigan State University Experiment Farm
in Ingham County and at a farmer-cooperator farm in Gratiot County, Michigan for the

two-year period, 2006 and 2007. The predominant soils at the Ingham county site were

23

Riddles-Hillsdale Sandy Loams in 2006 (fine loamy, mixed mesic Typic Hapludalf-
coarse-loamy, mixed mesic Typic Hapludalf) and Capac Loam (fine-loamy, mixed, mesic
Aeric Ochraqualfs) in 2007. The predominant soil at the Gratiot County site was Capac
Loam in both years. The previous crops were soybean and corn in 2006 and 2007,
respectively. The soil pH was 5.3 and 6.2 at Ingham and 6.5 and 6.4 at Gratiot for 2006
and 2007, respectively. The variety of dry bean was “Jaguar” black bean (Kelly et al.,
2001) and the variety of rye was “Wheeler” (‘Wheeler’, Michigan Agric. Exp. Stn., East
Lansing, MI). Dry bean was planted in 19 cm rows at the Gratiot site and both 19 cm and
76 cm at the Ingham site. Target planting populations were 433,000 plants/ha in 19 cm
rows and 194,000 in 76 cm rows. Planting dates were 6 June, 2006 and 4 June 2007 at
both sites. Plot sizes were 3 m by 12.2 m. An inoculant containing Rhizobium sp. was
applied at the recommended rate to all seed prior to planting (N itrastik-D, LiphaTech

Inc., Milwaukee, WI). In applicable treatments, rye was planted at 126 kg/ha.

The experimental design was a randomized complete block design with four
replications at both sites with Ingham in a split-split plot configuration (Table 2.1) and
Gratiot in a split plot configuration (Table 2). The main plots were cover crops: (a) rye
planted on the same day as dry bean, and (b) no rye planted. The subplots were: (a) broad
spectrum herbicide application, (b) broadleaf herbicide application, and (c) no herbicide
application. The sub-sub plots (present only at Ingham) were: (a) 19 cm row spacing and

(b) 76 cm row spacing. The Gratiot county site was only planted in 19 cm rows.

The Gratiot site was treated with glyphosate one month prior to planting in 2006
and two weeks prior to planting in 2007. Ingham site was disked three days prior to

planting in 2006 and two days prior to planting in 2007. Broadleaf herbicide treatments

24

consisted of Basagran (benzatone) at 0.28 kg a.i./ha + Raptor (imazamox) at 0.038 kg a.i
fha + 1% crop oil concentrate (COC) + spray-grade ammonia sulfate at 6.8 kg per 379
liters. Broad-spectrum treatment applications were identical to broadleaf treatments
except Select (clethodim) was added at 0.11 kg a.i.fha. Herbicide applications were made
on 26 June and 14 July in 2006 and 22 June and 16 July in 2007 at Gratiot. At Ingham,
herbicide applications were made 1 July and 25 July in 2006 and 22 June and 16 July in
2007. One additional application was made at Ingham on 11 July in 2006 to suppress rye
re-growth in treatments that received broad-spectrum applications. This additional

application consisted of 0.11 kg a.i./ha Select (clethodim) + 1% COC.

Early (data not presented) and late season biomass readings were taken in both
years of the study by hand-clipping plants at ground level from two randomly placed 0.5
m2 quadrats per plot. Plants were hand sorted. Rye, bean, and weed biomass ratings were
recorded, with weed biomass being classified by species. Early season biomass
measurements were taken 19 June and 21 June in 2006 and 19 June and 21 June in 2007
at Ingham and Gratiot, respectively. Late season biomass measurements were taken 19
September and 21 September in 2006 and 18 September and 21 September in 2007 at
Ingham and Gratiot, respectively. Plants were separated, and placed in a forced-air dryer
until a constant weight was observed. The dry plant material was then weighed to obtain

total dry matter.

Several plant measurements were taken on 17 Sept and 16 Sept in 2006 and 19
Sept and 18 Sept in 2007 at Ingham and Gratiot, respectively. These measurements
included: height to the attachment point of the lowest and highest mature pods, total

height of the plant, total mature pods per plant, and total mature seeds per plant.
25

Dry bean was harvested with a plot combine (Massey Ferguson, Duluth, Georgia)
from the center 1.5 m transect of each plot, and yield was adjusted to 18% moisture. Post-
harvest yield losses were assessed following harvest by counting the number of beans
within two 0.5 m2 quadrats that were randomly placed within the harvested 1.5 m
transect. Unfortunately, these data were made unusable, possibly because of seed
additions in the sampling area from the combine threshing mechanism or due to a small
sampling area. Statistical analyses were performed using the statistical analysis software
(SAS, version 9.1, SAS Institute Inc., Cary, NC). The MIXED procedure of SAS was
used to develop a mixed linear model to fit the split-split plot design of the data at
Ingham and the split plot design at Gratiot. Multiple comparisons between factor level
combinations were performed using Bonferroni adjustments. Results are presented as

estimated least squares means.

Results and Discussion (Ingham)

Dry bean biomass

Main effects of herbicide and year significantly impacted dry bean biomass at
both Ingham and Gratiot sites. In addition, significant main effects of rye and rowspace
were present at Ingham. Treatments with no rye cover resulted in significantly greater dry
bean biomass when compared to plots with rye cover in 2006 and 2007 at Ingham (Table
2.2). These results are similar to those presented by Ateh and Doll (1996) and Thelen et
al. (2004), who noted that interseeded rye reduced soybean vigor. Ateh and Doll (1996)
noted significant reductions in soybean vigor in living mulch treatments in 2 of 3 years,

with reductions ranging between 30-40% when rye was planted at 112 kg/ha.

26

Plots without herbicide treatment resulted in significantly lower dry bean biomass
when compared to broad leaf and broad-spectrum herbicide treatments in all site-years
(Table 2.2). Dry bean biomass was greater in 2006 than in 2007, which was likely due to
drought stress in July of 2007 at both sites, resulting in reduction of dry bean vigor (Table

2.3).

Rye biomass

A significant main effect of herbicide was present within treatments containing
rye cover (Table 2.2). Broad-spectrum herbicide treatments resulted in significantly less
rye biomass when compared to no-herbicide and broad-leaf herbicide treatments in all
site-years. Rye was suppressed but not killed by the broad-spectrum herbicide regime,
which may have been due to reduced grass herbicide efficacy from tank mixing of

chemicals within the treatment (ie: antagonism).

Grass weed biomass

Herbicide and rye-cover factors had a significant impact on grass weed biomass at
both sites (Table 2.4). Broad-spectrum herbicide treatments resulted in significantly
lower grass weed biomass than in broad-leaf and no-herbicide treatments in all site years.
Treatments without rye cover resulted in significantly greater grass weed biomass than in

treatments with rye cover in all site-years.

Broad-leaf weed biomass

A significant effect of year and a significant three-way interaction effect of rye,
herbicide, and row-space factors was present at Ingham. In addition, a significant main

effect of herbicide was present at Gratiot. In 2006, broad-leaf weed biomass was greater

27

than in 2007 at Ingham (Table 2.5) which was likely due to drought related plant stress in
July of 2007 (Table 2.4)

In treatments containing no rye cover and 19 cm row-space configurations,
treatments with no herbicide application resulted in significantly greater biomass than in
treatments containing broadleaf or broad-spectrum herbicide regimes at Ingham (Table
2.6). In treatments containing no rye cover and 76 cm row-space configurations,
treatments with no herbicide application resulted in significantly greater biomass then in
treatments containing broad-leaf or broad-spectrum herbicide regimes at Ingham (Table
2.7). In treatments planted in a 76 cm row-space configuration and with no herbicide
application, rye cover resulted in significantly less biomass than in treatments with no rye
cover at Ingham (Table 2.8). No-herbicide treatments resulted in significantly greater
broad-leaf weed biomass than broad-leaf and broad-spectrum herbicide treatments at

Gratiot (Table 2.9).

Dry Bean Plant Height

Significant main effects of rye, year, and herbicide were present at both sites.
Plots with rye cover resulted in significantly lower plant heights than in plots with no rye
cover in all site-years (Table 2.9), which is similar to dry bean biomass reductions
associated with rye treatments. Plant height was greater in 2006 when compared to 2007
at both sites, which is supported by reductions in dry bean biomass in 2007. These
reductions were likely associated with drought conditions at both sites in July of 2007.
Dry bean plant height was significantly greater in broad-spectrum herbicide treatments
than broad-leaf and no-herbicide treatments in all sites years (Table 2.9), indicating at
least partial suppression of rye cover and weed species, and reduction of competition with

28

dry bean.

Uppermost Pod Height

Significant main effects of rye cover and herbicide were present at both sites. An
additional main effect of year was present at Gratiot. Plots with no rye cover resulted in
significantly greater uppermost pod attachment height than in plots with rye cover in all
site-years (Table 2.9), which may be attributable to the overall increase in plant height ,
and biomass associated with no-rye treatments. Broad-spectrum herbicide treatments
resulted in significantly greater attachment heights than both no-herbicide and broad-leaf
regimes in all site-years. At Gratiot, pod heights were greater in 2006 when compared to
2007, possibly due to drought in 2007 (Table 1.10). This effect of year is supported by
reductions in dry bean biomass and overall height at Gratiot in 2007, as is likely due to

drought conditions in 2007.

Lowermost Pod Height

Significant main effects of rye cover and herbicide were present. Treatments with
no rye cover had significantly greater lowermost pod heights than in treatments
containing rye cover in all site-years (Table 2.10), indicating a positive elongation effect.
These increases amounted to a 1.9 cm increase in pod attachment height when averaged
across all levels of year and herbicide factors. Lowermost pod attachment heights were
also significantly greater in no-herbicide treatments when compared to broad-leaf
herbicide treatments treatments at Ingham and broad-spectrum treatments at Gratiot

(Table 2.10).

29

Yield

Herbicide regime and rye cover factors both had a significant effect on dry bean
yield at both sites. In addition, a significant main effect of year was present at Gratiot.
The broad-spectrum herbicide regime resulted in significantly greater yield than both
broad-leaf and no-herbicide regimes at Ingham. (Table 2.2) Broad-leaf herbicide
treatments resulted in significantly greater yields than no-herbicide treatments at Gratiot.
The increased dry bean yield associated with these herbicides may be attributable to
reduced competition from rye and weed species. Inter-seeded rye cover significantly
reduced yield as compared to plots with no rye at both sites. These results are similar to
those presented by Ateh and Doll (1996) and Thelen et al. (2004), who noted potential
competition between soybean and interseeded rye. Dry bean yield was greater in 2006
than in 2007 at Gratiot (Table 2.10), which was likely due to drought conditions in 2007,
and is supported by data confirming reduced dry bean plant height, biomass, and

uppermost pod height in 2007.

Conclusions

Interseeded rye cover significantly reduced dry bean yields at both Ingham and
Gratiot locations. Rye cover also significantly reduced dry bean plant and uppermost pod
attachment heights, which may be attributable to overall reductions in bean height and

biomass.

However, rye cover significantly increased lowermost pod attachment heights,
indicating the presence of stem elongation, despite overall reductions in dry bean growth

and vigor. Rye also significantly reduced broadleaf weed biomass at Ingham and grassy

30

weed biomass at Gratiot, reinforcing the potential of rye as a weed suppression tool.

Although rye cover was suppressed by broad-spectrum herbicide treatments, yield was
still significantly less in those treatments than in broad-spectrum herbicide with no-rye
cover treatments. These yield losses reflect incomplete suppression or rye and probable

competition between the species.

Broad-spectrum herbicide treatments resulted in greater bean yield at both
locations, which was likely attributable to suppression of rye and weed species, and the
resulting reduction in competition. Broad-leaf herbicide treatments had no significant
effect on yield when compared to no-herbicide treatments, which may be due to
competition from rye and grass weed species. No-herbicide treatments significantly
reduced dry bean biomass when compared to broad-spectrum and broad-leaf herbicide
treatments at both locations, which is also likely attributable to competition from both

grass and broadleaf weed species.

Overall, spring interseeded rye successfully suppressed weed biomass in some
cases and increased the height of the lowest dry bean pod attachment point, however,
these results are overshadowed by the lower dry bean yield, reduced height, and biomass

associated with interseeded rye treatments.

If competition from rye cover were minimized, stem elongation could possibly
occur without the associated yield losses noted within this study. This elongation effect
could possibly be more pronounced if rye were suppressed more effectively and if dry
bean vigor was improved. Future research should focus on reducing or eliminating this

competition.

31

Table 2.1 List of treatments design at Ingham and Gratiot. 2006 and 2007.

 

 

 

 

 

 

 

 

 

 

Cover crop Row spacing (cm) Herbicide regime . .
Ingham srte Gratiot srte
None None
19 Broad Leaf Broad Leaf
None Broad-Spectrum Broad-Spectrum
None -
76 Broad Leaf -
Broad-Spectrum -
None None
19 Broad Leaf Broad Leaf
R Broad-Spectrum Broad-Spectrum
ye
None -
76 Broad Leaf -
Broad-Spectrum -

 

32

 

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33

Table 2.3 Effect of year on average bean dry-weight at Ingham and
Gratiot. 2006 and 2007.

Year Weight at Ingham (g/plant) Weight at Gratiot (g/plant)

2006 88.2a* l 17.93

2007 67.5b 78.3b
*Numbers followed by the same letter within columns are not
significantly different. (a=0.05)

34

Table 2.4 Monthly precipitation at Ingham and
Gratiot (mm). 2006 and 2007.

 

 

 

 

 

 

 

 

 

 

 

 

Ingham Gratiot
2006 2007 2006 2007
April 59 47 5 1 79
May 142 106 161 5 8
June 74 141 1 00 41
July 93 13 129 67
August 143 l 32 5 7 99
September 75 53 85 49
Total 586 492 583 393

 

 

 

35

 

Table 2.5 Effect of year on dicot weed biomass at
Ingham. 2006 and 2007.

 

 

Year Weight (kg/hag
2006 192.5a*
2007 68.8b

 

*Numbers followed by the same letter within columns
are not significantly different. (a=0.05)

36

Table 2. 6 Effect of herbicide, and row space on dicot weed biomass when no rye cover is
present at Ingham. 2006 and 2007.

 

 

 

Type of cover Row space Herbicide Weighgkyha)
None 19 cm Broadleaf 87.4b*
Broad spectrum 28.7b
None 446.0a
*Numbers followed by the same letter within columns are not significantly different.
(u=0.05)

37

Table 2. 7 Effect of herbicide, and row space on dicot weed biomass when no rye cover is
present at Ingham. 2006 and 2007.

 

 

Type of cover Row space Herbicide Weight (kg/ha)
None 76 cm Broadleaf 25.3a*
Broad spectrum 72.8a
None 987.4b

 

*Numbers followed by the same letter within columns are not significantly different.
(a=0.05)

38

Table 2.8 Effect of rye cover and herbicide on dicot weed biomass in 76 cm row space
configurations at Ingham. 2006 and 2007.

 

 

Row Space Herbicide Type of cover Weight (kg/hag
76 cm None None 987.2a*
Rye 24.3b

 

*Numbers followed by the same letter within columns are not significantly different.
(a=0.05)

39

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41

Literature Cited

Ateh CM. and J .D. Doll. 1996. Spring-planted winter rye (Secale cereale) as a living
mulch to control weeds in soybean (Glycine max). Weed Technol. 10:347-353.

Eadie, A. G., C. J. Swanton, J. E. Shaw, and G. W. Anderson. 1992. Integration of cereal
crops in ridge-tillage corn (Zea mays) production. Weed Technol. 6:553-560.

Edwards, J .H., C.W. Wood, D.L. Thurlow, and M.E. Ruf. 1992. Tillage and crop rotation
effects on fertility status of a Hapludult soil. Soil Science Soc. Amer. J. 56:1577-1582.

Enache A.J. and RD. Ilnicki. 1992. Subterranean clover living mulch: an alternative
method of weed control. Agriculture, Ecosystems & Environment. 40: 249-264

Kaspar, T.C., D.B. Jaynes, T.B. Parkin, and TB. Moorman. 2007. Rye cover crop and
gamagrass stn'p effects on N03 concentration and load in tile drainage. J. Environ. Qual.
36:1503—1511.

Kelly, J .D., G.L. Hosfield, G.V. Vamer, M.A. Uebersax, and J. Taylor. 2001.
Registration of 'Jaguar' black bean. Crop Sci. 41:1647.

Shipley, P.R., J .J . Meisinger, and A.M. Decker. 1992. Conserving residual corn fertilizer
nitrogen with winter cover crops. Agron J. 842869-876.

Smith, H. 1982. Light quality, photoperception, and plant strategy. Ann. Rev. Plant
Physiol. 33:481-518.

Teasdale, J .R., C.E. Beste, and WE. Potts. 1991. Response of weeds to tillage and cover
crop residue. Weed Sci. 39:195-199.

Thelen, K.D., D.R. Mutch, and TE. Martin. 2004. Utility of interseeded winter cereal rye
in organic soybean production systems. Agron. J. 96:281-284.

42

Chapter 3: Utility of Interseeded Winter-Annual Rye in Organic Dry Bean

Cropping Systems

Introduction

Organic growers do not use synthetic herbicides and instead typically rely on a
combination of physical and cultural control of weeds. Many forms of physical control
that are utilized in organic systems are more fuel intensive and less flexible than synthetic
herbicide application. In addition, various forms of tillage have been shown to negatively
impact soil structure (Arshad, 1999) and contribute to soil erosion (Oost et al. 2006).

Other types of physical control have also been adapted to organic systems
including: flame weeding, mowing, and mulching. Organic growers may also utilize
various forms of cultural weed control such as: cover crops, crop rotation, reduced tillage,
and competitive crop agronomic trait selection (Bond and Grundy, 2001). Despite the
seemingly many options for organic weed control there are serious shortcomings with
many of these methods.

A type of cover crop, living mulches, may be a viable method of cultural weed
control for organic growers. Various applications of living mulches have been evaluated
with mixed crop yield results, yet all showed significant reductions of weed biomass
(Ateh and Doll 1996; Eadie et al. 1992; Enache and Ilnicki 1992; Thelen et al. 2004).

While spring-planted rye has shown potential for integration in both organic and
conventional soybean cropping systems as a living mulch (Ateh and Doll, 1996; Thelen
et al., 2003), it has not yet been evaluated within dry bean (Phaseolus vulgaris L.)

cropping systems. Spring-planted rye does not undergo a period of vemalization, and

43

thus, remains in a less vigorous, vegetative state, minimizing competition with the crop.
The less agressive growth habit has been noted as a desirable trait for a living mulch as
compared to fall-planted rye (Thelen et al., 2004). Despite this less aggressive grth
habit, Barnes and Putnam (1983) demonstrated that spring-planted rye reduced weed
biomass by 93% when compared to no rye plots.

The objectives of this study were to assess the utility of spring-interseeded rye for
weed suppression in organic dry bean cropping systems and for potential reduction of

harvest-associated yield losses through elongation of the dry bean plant.

Materials and Methods

Field research was conducted at the Kellogg Biological Station in Kalamazoo
County for the two-year period, 2006 and 2007. The crops were managed according to
organic standards and the land certified organic by the Organic Crop Improvement
Association. The previous crops were com in 2006 and 2007. The soil was a Kalamazoo
loam (fine-loamy, mixed, mesic Typic Hapludalfs) with pH was 6.8 and 6.9 for 2006 and
2007, respectively. The variety of dry bean was “Jaguar” black bean (Kelly, 2001) and
the variety of rye planted was “Wheeler” (‘Wheeler’, Michigan Agric. Exp. Stn., East
Lansing, MI). Dry bean was planted in 19 cm, 38 cm, and 76 cm rows. Target planting
populations were 433,000 plants/ha in 19 cm rows, 301,000 plants/ha in 38 cm rows, and
194,000 plants/ha in 76 cm rows. Planting dates were 9 June 2006 and 31 May 2007.
Plot sizes were 3 m by 12 m. An innoculant containing Rhizobium sp. was applied at the
recommended rate to all seed prior to planting (N itrastik-D, LiphaTech Inc., Milwaukee,
WI). In applicable treatments, rye was planted at 126 kg/ha. The experimental design

was a randomized complete block design with four replications (Table 3.1).

44

All plots were chiseled and disked prior to planting. All plots were also rotary
hoed on 14 June, 22 June, and 30 June in 2006 and on 7 June and 13 June 2007.
Applicable treatments were cultivated on 19 and 29 June in 2006 and 21 June in 2007.
Due to drought, overhead irrigation was applied in the amount of 13 mm and 18 mm on
23 July and 27 July 2007, respectively. Pyganic insecticide (pyrethrum) was applied as

needed for control of potato leafhopper (Empoascafabae L.).

Early (data not presented) and late season biomass readings were taken in both
years of the study by hand-clipping plants at ground level from two randomly placed 0.5
m2 quadrants per plot. Rye, bean, and weed biomass ratings were recorded, with weed
biomass being classified by species. Late season biomass measurements were taken on 5
September in 2006 and 28 August in 2007. Plants were separated, and placed in a forced-
air dryer until a constant weight was observed. The dry plant material was then weighed

to obtain total dry matter.

Several plant measurements were taken on 15 Sept in 2006 and 28 August in
2007. These measurements included: height to the attachment point of the lowermost and

uppermost mature pods, and total height of the plant. Four plants were measured per plot.

Dry bean was harvested with a plot combine (Wintersteiger, Ried/l., Austria) from the
center 1.5 m transect of each plot, and yield was adjusted to 18% moisture. Post-harvest
yield losses were assessed following harvest by counting the number of beans within two
0.5 m2 quadrats which were randomly placed within the harvested 1.5 m transect but the
data were unusable, possibly due to seed additions in the sampling area from the combine
threshing mechanism or too small of a sampling area. Statistical analyses were performed

using the statistical analysis software (SAS, version 9.1, SAS Institute Inc., Cary, NC).
45

The MIXED procedure of SAS was used to develop a mixed linear model to fit the
design of the data. The lack of observations for the rye cover by row space by cultivation
combinations prevented 3-way factorial analyses of the data (Table 1). The analyses were
divided into two parts, as follows: (a) effect of rye cover and planting row space on
response variables, conditional on no cultivation and, (b) effect of cultivation on response
variables, considering only treatments with no rye cover and planted with a row spacing

of 19 or 76 cm. Results are presented as estimated least squares means.

Results and Discussion

Bean Biomass

Significant main effects of year and rye cover were present. Biomass was
significantly greater in 2006 than in 2007 (Table 3.2), which may be attributable to lack
of precipitation in July 2007 (Table 3.3), and possible resulting growth suppression.
Treatments containing rye cover resulted in significantly less biomass than in treatments
with no rye cover indicating the presence of competition between rye and dry bean (Table
3.2). It is unclear if allelopathy was an important mechanism of competition between rye
and dry bean, but competition for moisture and nutrients, although not tested, likely
played a role. Ateh and Doll (1996) noted that spring—interseeded rye resulted in moisture
reductions of up to 29% when compared to weed-free check plots.

Cultivated treatments resulted in significantly greater dry bean biomass than in
treatments with no cultivation (Table 3.4), indicating a likely reduction in competition

between dry bean and weed species.

46

Grass Weed Biomass

There were no significant effect on grass weed biomass. This is likely attributable
to the low amounts of grassy weeds present at this location. Monocot weed species
biomass amounted to 124 kg/ha in treatments with no rye cover, which is 83% less than

the weight of dicot species within treatments with no rye cover, which averaged 735

kg/ha.

Broadleaf Weed Biomass

Significant main effects of rye cover and year were present. Treatments
containing rye cover resulted in significantly less broadleaf weed biomass than in
treatments without rye cover (Table 3.2) which may indicate competition between rye
and weed species for water and nutrient resources, in addition to a possible allelopathic
effect. Ateh and Doll ( 1996) documented overall weed bio-mass reductions of between
60-90% when comparing interseed rye plots with weed fi'ee check plots. Broad-leaf weed
biomass was greater in 2006 than in 2007, which is likely attributable to dought
conditions in 2007, and corresponds with reductions in dry bean and rye biomass in 2007
(3.2).

There was no significant effect of cultivation on broad-leaf weed biomass.
Cultivation of in-row weeds proved to be difficult and many large broadleaf weeds were
visually apparent in cultivated treatments.

Dry Bean Plant Height

Significant main effects of year and rye cover were present. There was

significantly greater plant heights in 2006 than in 2007 which was likely due to low

amounts of precipitation in 2007 as compared to 2006 (Table 3.5). Plant heights were

47

significantly lower in treatments containing rye cover than in treatments without rye
cover (Table 3.5). Ateh and Doll (1996) noted significant reductions in soybean vigor in
living mulch treatments in 2 of 3 years, with reductions ranging between 30-40% when
rye was planted at 112 kg/ha.

Cultivated treatments likely reduced competition from weed species and resulted
in significantly greater plant heights when compared to treatments without cultivation

(Table 3.4).

Height of Uppermost Dry Bean

Significant main effects of year and rye cover were present. There was
significantly greater pod attachment heights in 2006 than in 2007 (Table 3.5). Heights
were significantly lower in treatments containing rye cover than in treatments without rye
cover (Table 3.5).

Treatments with cultivation resulted in significantly greater heights when
compared to treatments without cultivation (Table 3.4), which could be attributed to

competition for resources between the interseeded rye and dry bean plants.

Height to Lowermost Dry Bean Pod

A significant main effect of rye cover was present. Treatments containing rye
cover resulted in significantly greater pod heights when compared to treatments without
rye cover (Table 3.5), which could be attributed to competition for resources between the
interseeded rye and dry bean plants. When compared to plots with no cover, rye cover
resulted in an average pod attachment height increase of 1.3 cm when when averaged

across year and row space.

48

Cultivated treatments resulted in significantly lower pod heights when compared
to treatments without cultivation (Table 3.4), which could be attribuable to less shading
from weed species, exhibiting a similar response to effect of rye cover on lowermost pod

heights.

Yield

Significant main effects of year and rye cover were present. Yield was
significantly greater in 2006 than in 2007, which is likely due to lack of precipitation in
July 2007 (Table 3.6). Stunted plant grth was visually noted prior to irrigation in 2007.
Within rye cover treatments dry bean yielded significantly less than in treatments with no
rye (Table 3.6), which is similar to results presented by Ateh and Doll (1996) and Thelen
et al. (2004), who noted reduced soybean yields in treatments with interseeded spring rye

COVCI‘.

Conclusions

Interseeded spring rye cover competed heavily with dry bean, reducing it’s overall
vigor. Treatments containing rye significantly reduced dry bean yield, biomass, plant
height, and height of uppermost dry bean pods. However, interseeded rye cover increased
the height of the lowermost dry bean pod attachment point, despite overall suppression of
growth. This elongation effect could possibly be more pronounced if rye were suppressed
more effectively, leading to increased dry bean vigor. Rye also significantly suppressed
weed growth. Plots containing rye had 66% less broadleaf weed biomass when compared
to plots with no rye.

If this system could be adapted with a more complete method of rye suppression,

49

it’s viability would be improved. Such a system could potentially reduce harvest-
associated yield losses, especially if a stem elongation response were more pronounced
due to the probable resulting improvement in dry bean vigor. In addition, such a system
could provide a less fuel and labor intensive method of weed control with environmental
benefits. Future research should focus on methods of completely killing cover crops
while also maintaining large quanitities of biomass above the soil surface throughout the

growing season.

50

Table 3.1 List of treatment design at Kalamazoo.

 

 

 

 

 

 

 

 

2006 and 2007.

Row Space Cultivation Cover

19 cm No None

Rye

None

38 cm NO Rye

Yes None

Yes None

76 cm No Rye

 

 

 

 

51

 

Table 3.2 Effect of year and rye cover crop on dry bean and dicot weed biomass at
Kalamazoo, conditional on no cultivation. 2006 and 2007.

 

 

Factor Treatment Bean dry biomass Dicot weed dry biomass
------------ (g/plant) ----------- -------------(kg/ha)------------
Year 2006 83.0a* 966.3a*
2007 35% 404%
Cover crop No cover 106.4a* 735.4a*
Rye 12.5b 324.2b

 

*Within columns and factors (year or cover crop) numbers followed by the same letter are
not significantly different. (a=0.05)

52

Table 3.3 Monthly precipitation at
Kalamazoo (mm). 2006 and 2007.

 

 

 

 

 

 

 

 

2006 2007
April 58 84
May 15 7 48
June 43 43
July 107 20
August 1 57 163
September 89 58
Total 61 1 4 1 6

 

 

 

 

 

53

Table 3.4 Effect of cultivation on dry bean biomass, plant height, and pod height
at Kalamazoo. Conditional on no cover and no drilled row-spacing. 2006 and
2007.

 

 

 

Bean dry Bean plant Lowermost pod
Treatment biomass height Top pod heiglit height
"(g/Plant)" (cm)
No cultivation 43.3b* 25.5b 20.3b 11.9a
Cultivation 1 18.4a 37.03 28.4a 10.6b

 

*Numbers followed by the same letter within columns are not significantly
different. (a=0.05)

54

Table 3.5 Effect of year and cover crop on dry bean plant, top, and bottom pod height at
Kalamazoo, conditional on no cultivation. 2006 and 2007.

Factor Treatment Plant height Uppermost pod height Lowermost pod height

 

 

 

(0m)
Year 2006 34.0a* 28.2a* -
2007 22.1b 16.2b -
Cover cropNone 36.0a* 2553* l 1.1b
Rye 22.1b 18.9b 12.2a*

 

*Within columns and factors (year or cover crop) numbers followed by the same letter are
not significantly different. (a=0.05)

55

Table 3.6 Effect of year and cover crop on dry bean yield at
Kalamazoo, conditional on no cultivation. 2006 and 2007.

 

 

Factor Treatment Yield (kg/ha)

Year 2006 581. la*
2007 324.4b

Cover crop No cover 1218.6a*
Rye 208.7b

 

*Within columns and factors (year or cover crop) numbers
followed by the same letter are not significantly different.
(a=0.05)

56

Literature Cited

Arshad MA. 1999. Tillage and soil quality. Tillage practices for sustainable agriculture
and environmental quality in different agroecosystems (editorial). Soil Till. Res. 53:1—2.

Ateh C .M. and J .D. Doll. 1996. Spring-planted winter rye (Secale cereale) as a living
mulch to control weeds in soybean (Glycine max). Weed Technol. 10:347-353.

Barnes, J. P. and A. R. Putnam. 1987. Role of benzoxazinones in allelopathy by rye
(Secale cereale L.). J. Chem. Ecol. 13:889-905.

Eadie, A. G., C. J. Swanton, J. E. Shaw, and G. W. Anderson. 1992. Integration of cereal
crops in ridge-tillage corn (Zea mays) production. Weed Technol. 62553-560.

Enache A.J. and RD. Ilnicki. 1992. Subterranean clover living mulch: an alternative
method of weed control. Agriculture, Ecosystems & Environment. 40:249-264.

Kelly J.D., G.L. Hosfield, G.V. Vamer, M.A. Uebersax, and J. Taylor. 2001. Registration
of 'Jaguar' black bean. Crop Sci. 41 : 1647.

Oost K.V., G. Govers, S. De Alba, and TA. Quine. 2006. Tillage erosion: a review of
controlling factors and implications for soil quality. Progress is Physical Geography.
30:443-466.

Thelen, K.D. D.R., Mutch, and TE, Martin. 2004. Utility of interseeded winter cereal
rye in organic soybean production systems. Agron. J. 96:281-284.

57

 

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