COMPARISONS BETWEEN CONVENTIONAL AND SUSTAINABLE EGGPLANT

(Solanum melongena L.) PRODUCTION SYSTEMS

by

Kathryn Estelle Brunson

(Under the direction of SHARAD C. PHATAK)

ABSTRACT

The growing consumer and environmental concerns over the use of pesticides and nitrogen based fertilizers in agriculture has emphasized the need for more information concerning the reduction of these inputs on a commercial scale. Sustainable agriculture philosophy promotes using beneficial insects and legume cover crops as a means to do so. However, information is limited as to how sustainability can be conducted on a commercial crop such as eggplant, and still be economically feasible. Field trials were conducted during 1991-93 at four locations comparing sustainable and conventional eggplant production practices. The four sites differed by soil type and cropping histories. Overwintering cover crops of crimson and subterranean clovers were used to help maintain soil fertility and populations of beneficial insects in the sustainable production system. No pesticides were used throughout the study. Velvetbean (Mucuna deeringiana L.) was incorporated into the rotation following eggplant in 1992-93 to help suppress populations of southern root-knot nematode (Meloidogyne incognita Koford and White). The conventional production system differed in that cereal rye was the plow-down cover crop and recommended fertilizer and pesticide practices were followed. Highest marketable eggplant yields were in the conventional system for each location and year. Crimson clover generally had the better yields compared to the subterranean clover but there were differences between locations and year. Regression analysis showed conventionally grown eggplant fruited earlier but that crimson clover had the potential to "catch" up in later harvests. Pest and beneficial insects populations were assessed by visual and shake sampling methods to determine differences among production systems. Shake sampling of eggplant foliage resulted in more species being recovered than did visual inspection. Weed populations differed according to location. Each location appeared to have had its own distinctive weed species. Overall percent weed cover was less in the sustainable compared to the conventional where nutsedge was the predominant problem. Use of velvetbean in the rotation in 1993 seemed to have an effect on populations of southern root-knot nematode incurred in the sustainable production. Levels were generally reduced in most locations while levels either stayed the same or increased in the conventional system that had been treated with a nematicide. Root gall and root disease severity ratings of eggplant were not significantly different between systems. The economic comparisons seemed to indicate that production costs and net returns for the conventional system were higher than for the sustainable, but sustainable yields were lower.

INDEX WORDS: Eggplant, Solanum melongena L., Sustainable Production, Conventional Production, Beneficial Insects, Insect Pests, Vegetable Production, Weeds, Soil Borne Diseases, Plant Parasitic Nematodes, Risk Assessment, Agricultural Economics, Economic Feasibility COMPARISONS BETWEEN CONVENTIONAL AND SUSTAINABLE EGGPLANT (Solanum melongena L.) PRODUCTION SYSTEMS

by

KATHRYN ESTELLE BRUNSON

B.S.A. The University of Georgia 1982

M.S. The University of Georgia 1991

A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial

Fulfillment of the Requirements for the Degree

DOCTOR OF PHILOSOPHY

ATHENS, GEORGIA

2002 © 2002

Kathryn Estelle Brunson

All Rights Reserved COMPARISONS BETWEEN CONVENTIONAL AND SUSTAINABLE

EGGPLANT (Solanum melongena L.) PRODUCTION SYSTEMS

by

KATHRYN ESTELLE BRUNSON

Approved:

Major Professor: Sharad C. Phatak

Committee: Albert K. Culbreath Juan Carlos Diaz-Perez John R. Ruberson Michael E. Wetzstein

Electronic Version Approved:

Gordhan L. Patel Dean of the Graduate School The University of Georgia May 2002 DEDICATION

To All Who Helped Me Complete This Part of the Journey

iv ACKNOWLEDGMENTS The author wishes to express her sincere appreciation to her major professor, Dr. Sharad

C. Phatak, for his continual support, guidance and encouragement throughout this endeavor. His humor and enthusiasm in the face of adversity I will always remember. I also wish to express my deep appreciation to the members of my graduate committee, Dr. Albert K. Culbreath, Dr. Juan

Carlos Diaz-Perez, Dr. John R. Ruberson and Dr. Michael E. Wetzstein for their counsel and direction. Gratitude is also expressed to Dr. Phatak's supporting staff, especially Anthony Bateman and the late Jimmy Hornbuckle, for helping me progress through this work. I also wish to express deep gratitude to Dr. Bob Stark of the University of Arkansas-Monticello for his assistance in preparing the economic budgets. Lastly, I thank Kathy Mullinix, Kim Giddens and Richard Layton for their continued help and friendship throughout these past years.

Financial support for this work was provided through the Southern Region IPM Program of the Cooperative State Research Service, USDA, Grant # 89-34103-4257 and other funds allocated to the Coastal Plain Experiment Station, College of Agriculture and Environmental

Sciences, University of Georgia, Tifton, Georgia.

v TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ...... v

LIST OF TABLES ...... ix

LIST OF FIGURES ...... xii

CHAPTER

1 LITERATURE REVIEW ...... 1 Introduction ...... 2

Sustainable Production ...... 4

Conventional Production ...... 32 Economic Considerations of Sustainable and Conventional Production ...... 34

Literature Cited ...... 37

2 EFFECT OF LOCATION AND PRODUCTION SYSTEM ON

CONVENTIONAL AND SUSTAINABLE EGGPLANT YIELDS ...... 47

Abstract ...... 48

Introduction ...... 48 Materials and Methods ...... 49

Results ...... 54

Discussion ...... 60 Conclusion ...... 63

Literature Cited ...... 65

vi 3 INFLUENCE OF LOCATION AND PRODUCTION SYSTEM

ON SEASONAL INSECT POPULATIONS, WEEDS, NEMATODES,

ROOT DISEASE AND PLANT STAND IN CONVENTIONAL AND

SUSTAINABLE EGGPLANT ...... 87

Abstract ...... 88

Introduction ...... 89

Materials and Methods ...... 92 Results ...... 94

Discussion ...... 102

Conclusion ...... 110 Literature Cited ...... 113

4 ECONOMIC COMPARISONS OF ALTERNATIVE AND CONVENTIONAL

PRODUCTION TECHNOLOGIES FOR EGGPLANT IN SOUTHERN GEORGIA 132 Abstract ...... 133

Introduction ...... 133

Materials and Methods ...... 134 Results and Discussion ...... 138

Conclusion ...... 142

Literature Cited ...... 142

5 CONCLUSIONS ...... 156

vii LIST OF TABLES

TABLE Page

CHAPTER 2

2.1 Influence of location and production system on marketable eggplant

yields...... 66

2.2 Influence of location and production system on unmarketable

eggplant yields...... 67

2.3 Effect of location and production system on eggplant cull yields ...... 68

2.4 Eggplant rot yields influenced by location and production system ...... 69

2.5 Eggplant insect damage influenced by location and production system ...... 70

CHAPTER 3

3.1 Effect of location and production system on seasonal insect

populations of Geocoris, Lygus, Colorado Potato Beetle and

Coccinellids recovered from visual inspections 1992 ...... 117

viii 3.2 Effect of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and

Coccinellids recovered from visual inspections 1993 ...... 118

3.3 Influence of location and production system on seasonal insect

populations of Geocoris, Lygus, Colorado Potato Beetle and

Coccinellids recovered from 1992 shake sampling...... 119

3.4 Influence of location and production system effects on seasonal insect

populations of Aphids, Stinkbugs, Loopers, Thrips, and Other Hoppers recovered from 1992 shake sampling...... 120

3.5 Influence of sustainable and conventional production practices on weeds...... 121

3.6 Visual weed evaluations in sustainable and conventional eggplant production from the Horticulture Farm...... 122

3.7 Visual weed evaluations in sustainable and conventional eggplant production from the Little River Farm...... 123

3.8 Visual weed evaluations in sustainable and conventional eggplant production from the Hodnett Farm...... 124

ix 3.9 Visual weed evaluations in sustainable and conventional eggplant production from the Blackshank Farm...... 125

3.10 Effect of production system and velvetbean (Mucuna deeringiana L.) on seasonal populations of southern rootknot nematode

(Meloidogyne incognita Koford and White) in eggplant...... 126

3.11 Influence of location and production system on eggplant plant stand and

root disease ratings ...... 127

CHAPTER 4

4.1 Average per acre costs of selected inputs by production system...... 144

4.2 Preharvest variable input costs by system...... 145

4.3 Yield summary statistics for four locations, 1992 and 1993

production seasons...... 146

4.4 Net returns summary statistics for four locations, 1992 and 1993

production systems...... 147

x LIST OF FIGURES

FIGURE PAGE

CHAPTER 2

2.1 Daily temperature and rainfall - Coastal Plain Experiment Station 1992...... 72

2.2 Daily temperature and rainfall - Coastal Plain Experiment Station 1993...... 74

2.3 Comparing regression trends of marketable eggplant yields in 1992 from Horticulture Hill, Little River, Hodnett and Blackshank

Farms sustainable and conventional production systems...... 76

2.4 Comparing regression trends of marketable eggplant yields in 1993

from Horticulture Hill, Little River, Hodnett and Blackshank

Farms sustainable and conventional production systems...... 78

2.5 Comparison of regression trends of eggplant culls in 1992

from Horticulture Hill, Little River, Hodnett and Blackshank Farms sustainable and conventional production systems...... 80

2.6 Comparisons of regression trends of eggplant culls in 1993 from Horticulture Hill, Little River, Hodnett and Blackshank

Farms sustainable and conventional production systems...... 82

xi 2.7 Comparison of regression trends of eggplant rots in 1992

from Horticulture Hill, Little River, Hodnett and Blackshank

Farms sustainable and conventional production systems...... 84

2.8 Comparison of regression trends of eggplant rots in 1993

from Horticulture Hill, Little River, Hodnett and Blackshank Farms sustainable and conventional production systems...... 86

CHAPTER 4

4.1 Daily temperature and rainfall - Coastal Plain Experiment Station 1992...... 149

4.2 Daily temperature and rainfall - Coastal Plain Experiment Station 1993...... 151

4.3 Cumulative probability of marketable eggplant yields (cartons/acre) 1992-93. ....153

4.4 Cumulative probability of eggplant profits 1992-93 all locations...... 155

xii CHAPTER 1

LITERATURE REVIEW

1 Introduction In Georgia, Solanaceae is a botanical family that has several important vegetable crops.

Eggplant ranked nineteenth in total acreage in 2000. There was an estimated 1,259 acres of eggplant grown primarily in the southern part of the state. Approximately 823 acres of the 1,259 are plastic mulch culture and the remaining 436 acres are bare ground culture (Langston, 2000).

Sixty five percent of eggplant were produced from plastic mulch while thirty five percent came from bare ground. Most of the eggplant (59%) were grown in the spring, but forty one percent came from a fall crop and whether bare ground or plastic mulch, more than ninety percent of those were irrigated. These two production practices combined provided an estimated 1900 cartons per acre, resulting in more than $12,000,000 gross value to Georgia growers (Langston, 2000). Eggplant Origin: The eggplant belongs to the Solanaceae, or nightshade family and is known under the botanical name (Solanum melongena L.) (Thompson and Kelly, 1957). It is a semi-tropical plant having two centers of origin. Many botanists believe the larger fruited cultivars originated in the first center which was the Indo-Burma area of plant origins (Boswell, 1949; Khan,

1979; Nonnecke, 1989). Eggplant is known by several names in India but “brinjal” is the most common. De Candolle (1886) reported in the Origin of Cultivated Plants that the species S. melongena had been known in India from ancient Sanskrit writings. Khan (1979) suggested that these people were probably the first to cultivate it. The ancestral form was very likely a spiny plant with small bitter fruit. Selection over time for improved taste and for relative spinelessness resulted in a more acceptable type (Pierce, 1989; Yamaguchi, 1983). Eggplant appears to have been introduced into the Western World as recently as 1500 years ago. From the Indo-Burma region, the domesticated non-bitter fruited types spread eastward into China where small-fruited kinds developed that were distinctly different from those of Indian origin (Boswell, 1949; Nonnecke,

1989). The abundance of Arabic and North African names along with the lack of Greek and

Roman names seems to indicate that this species was probably not known to either ancient Greeks

2 or Romans. Arab traders carried eggplant into the Mediterranean region during the time of the

Dark Ages (Yamaguchi, 1983). Boswell (1949) mentioned that Melongena, a part of the scientific name, was a 16th century Arabic name for one kind of eggplant. He also states that some of the oldest records about eggplant are from 5th century Chinese writings and 9th, 10th, and 12th century

Arabic writings. From the Mediterranean region eggplant was carried to Spain by Moorish traders about 1200 B.C. and was reported in Northern Europe about 1500 B.C. (Nonnecke, 1989). The name eggplant comes from Gerard's 14th century description of small, white fruit resembling eggs

(Pierce, 1989). Writers in Europe during the 16th century were describing the colors of eggplant as ranging from purple to white or yellow to ash-colored, green, or brownish, with fruits being round, oblong, pear-shaped and long (Boswell, 1949; Nonnecke 1989). The larger purple fruits were most popular in North America while the smaller white or yellow varieties were most popular in Europe. As with many plant and vegetables introduced into Europe in the Middle Ages, eggplant was viewed suspiciously. The Spanish mala insana and Italian melazana names both translate into "mad apple". It was a common belief that ingesting eggplant could cause madness (Pierce,

1989). The eggplant was among the plants introduced early into America by the Spaniards.

Historical records indicate it was grown in Brazil before 1650 (Boswell, 1949). It was introduced into American gardens in 1806 where the purple and white varieties were primarily an ornamental curiosity until the early 1900's (Boswell, 1949; Pierce, 1989). While eggplant has never been a major crop in the United States, it is a particularly important vegetable in China and Japan where the smaller elongated fruits can be cooked or fried whole.

Eggplant Botany: Eggplant is grown as an annual in the northern hemisphere but in the tropics it is grown as a perennial. A shrubby or bushy plant is characteristic of eggplants but growth is indeterminate that produces new shoots in the leaf axils (Nonnecke, 1989). The result is a plant that gives the appearance of an erect or spreading growth habit. Plants grow to a height of 60-120 cm (2-4 ft.). The leaves are large, ovate, lobed and have spiny hairs on the underside.

3 They grow alternate on the stem. Flowers appear violet-colored, solitary, or in clusters of two or more 2.5 to 3 cm across (Thompson and Kelly, 1957; Nonnecke, 1989). They are similar to tomato but larger. The pendant fruit is a fleshy berry with seeds scattered throughout imbedded in a firm placenta (Pierce, 1989). Most eggplants are self-fertile but occasional crossing and parthenocarpic fruit set does occur.

Sustainable Production

History and Origin: American farms in the forty years after World War II were easily the envy of the world setting crop production records and becoming largely labor efficient. Farms had become highly mechanized and specialized relying heavily on cheap fossil fuels, borrowed capital and readily available chemical fertilizers and pesticides (Reganold et al., 1990). However, these same farms are now being associated with decreased soil productivity, degenerating environmental quality, diminishing profitability and hazards to human and animal health. This was evidenced in the last fifteen years by a growing segment of society that is questioning the environmental, economic and social impacts of conventional agriculture. Consequently, people began seeking alternative methods that would make agriculture more sustainable or “user friendly”.

The end result was a type of agriculture named sustainable. It has been faced with an "identity" crisis in recent years, because of confusing terminology. Opinions varied greatly in defining what sustainable is. Biological agriculture, conservation farming, ecological agriculture, environmentally sound agriculture, organic farming and agriculture, and alternative agriculture have all been used, sometimes without clear definition (Poincelot, 1986).

The USDA (1980) in their study, Report and Recommendations on Organic Farming, identified sustainable agriculture with organic farming, which is a system of production that largely avoids the use of chemical fertilizers, pesticides and plant growth regulators. This is because whenever feasible, sustainable agriculture relies upon crop rotations, crop residues, animal manures, off-farm organic wastes, mechanical cultivation, mineral bearing rocks, and aspects of biological

4 pest control to maintain the soil and its tillage, to supply plant nutrients, and to control insects and weeds (Oelhaf, 1978; USDA, 1980). The report concluded that because organic farming was highly energy efficient, environmentally sound, productive and stable it leaned toward sustainability.

Along these same lines, the Board on Agriculture of the National Research Council published their study Alternative Agriculture in 1989 which seemed to support further the idea that alternative

(sustainable) farms could be successful in using biological resources rather than chemical (National

Research Council, 1991). The conclusion was that alternative farms were more successful because they grew diverse crops with little or no chemicals and were well managed when compared to conventional farms.

Reganold et al. (1990) interpreted sustainable agriculture as embracing several variants of non-conventional agriculture that also are called organic along with alternative, regenerative, ecological or low-input. They went further in their definition however, by alluding to the fact that just because a farm is organic or alternative doesn't mean that it is sustainable. For a farm to be sustainable to them, it must produce adequate amounts of high-quality food, protect its resources and be both environmentally safe and profitable. A sustainable farm relies as much as possible on beneficial natural processes and renewable resources drawn from the farm itself, rather than purchased materials (Reganold et al., 1990). Poincelot (1986) felt the goal of sustainable agriculture was one of permanence that could be achieved from utilizing renewable resources and the conservation of energy, soil and water. MacRae et. al. (1989) defined sustainable agriculture as a philosophy and system of farming based on a set of values that involve benign designs and management procedures that work with natural processes to conserve all resources, minimize waste and environmental impact, prevent problems and promote agroecosystem resilience, self- regulation, evolution and sustained production for the nourishment and fulfillment of all. Lowrance et al. (1984) based sustainable agriculture on an application of an ecological model, while Odum

(1984), the "father of modern day ecology", stated that agroecosystems differ from natural

5 ecosystems in that they are partly powered by auxiliary energy sources (processed fuels, animal and human power). Such a description includes farming systems variously referred to as organic, biological, ecological, agroecological, biodynamic, regenerative, alternative, natural and permanent

(Odum, 1984). In all the effort at defining what sustainable is, it needs to be pointed out that sustainable agriculture is not advocating that growers return to pre-industrial revolution methods. Instead, traditional conservation-minded farming should be combined with modern technologies such as equipment, certified seed, productive use of the biological and genetic potential of plant and animal species and soil and water conservation practices. Emphasis is placed on rotating and diversifying crops, building up soil and controlling pests naturally. Diversity on the farm can provide a buffer against economic and biological risks. It results from mixing species and varieties of crops and from systematically integrating crops, trees and livestock. Biologically diverse farms are less susceptible to economic problems such as flooded markets or falling prices for a single crop

(Reganold et al., 1990). The move toward sustainable agriculture during in this new millennium continues slowly but still follows the same general principles put forth 30 years ago. The social ills of rural America have not gone away and must still be addressed. A completely sustainable agriculture system must also include a breeding program in which plant pest resistance is a part of crop production. The adverse production affects large machinery has on the soil and land needs to be recognized as well as replacing the current high input monoculture with a low input sustainable polyculture one that relies on nature’s system of checks and balances to control pests (Walker et al., 1999). This can be summed up by the great law of the Iroquois Confederacy that says, “In

Our Deliberation, We Must Consider The Impact of Our Decisions on The Next Seven

Generations” (Phatak, per comm.).

Green Manures, Cover Crops and Soil: To understand the rationale for sustainable agriculture, the critical concept of soil must be addressed. Soil is an irreplaceable natural resource.

6 It is not useful to think of soil just as another instrument for crop production, like fertilizers or pesticides or a John Deere™ tractor. Rather, soil needs to be thought of as a complex, living, delicate medium that must be nurtured and protected to ensure its stability and long-term productivity (Nash, 1990; Reganold et al, 1990). For soil to remain productive it must be well managed. Reduction in pesticide and commercial fertilizer inputs and still sustaining a crop, will depend greatly on how "well" the soils are. In order to build soil productivity, organic matter must be added. Regularly adding crop residues and other organic matter to the soil is a central feature of sustainable farming. Organic matter enhances soil structure, increases the water holding capacity, improves fertility and the physical condition of the soil or tilth. This is especially relevant for the sandy soils in south Georgia which contain <2% organic matter. One of the principles of cultivation is to keep soils in good tilth. Soils with good tilth are easier to work into beds because there is less draft on the plow, i.e., "it feels like a hot knife through butter", when the ground is worked (J.M. Hornbuckle, per. comm.). Organic matter also makes seedling emergence and downward root expansion easier, and furnishes a home and food for soil microorganisms.

Earthworms and soil microorganisms are essential to organic matter decomposition which makes mineral nutrients available to plants. Water can readily penetrate the surface which minimizes surface runoff and erosion.

A team of scientists headed by Dr. Sharad Phatak at the Coastal Plain Station-Tifton

Campus in Tifton, Georgia knows only too well how important this concept is. His research has been guided by the need to develop “healthy soil”. He saw first hand what a lack of such a critical element can be in the long run while on a visit to his family’s farm to Indore, India in 1985. For 62 years, the family farm had grown vegetables on 45 acres (Yancy 1994; 1996). During the first 30 years the farm could count on high yields and profits because his father did not use any off-farm inputs. By his visit in 1985, this had all changed. Yields and profits had suffered greatly since the mid 1950's, because farmers had begun relying on expensive fertilizers and pesticides. Many could

7 no longer afford such things and so the land had become unproductive. He saw that when farmers began depending on off-farm inputs instead of soil building practices of green manuring, composting, crop rotation and relay cropping, the land suffered. Phatak also realized that the same trends must bode true for U.S. agriculture which had been heavily influenced by the post WWII boom of “industrial agriculture”. It was cheaper to use synthetic fertilizers and pesticides than to compost. When Phatak came back to the United States, he began developing methods of whole- farm systems and soil productivity. His first attempts at growing crops without off-farm inputs resulted in reduced yields. Therefore he concluded that having healthy soil must be the key in growing profitable crops. With his team of scientists, he began experimenting with planting vegetables into strip-killed cover crops with minimal off-farm inputs. Over the next ten years they successfully showed how crops of cucumbers, cantaloupe, eggplant, zucchini, tomatoes, peppers and Southern peas could be grown using crimson and subterranean clovers. Their research was introduced to area growers and the Georgia Organic Growers Association. This work is showing how the concept of “healthy soil” benefits everyone.

1. Green manures : Organic matter can be added as composted material or animal manures or by growing and plowing under fast growing plants known as green manures. Green and animal manures are the principal sources of plant nutrients in sustainable farming. A green manure crop is usually a grass or a legume that is plowed into the soil or surface-mulched at the end of a growing season to enhance soil productivity and tilth (Pieters, 1927; Reganold et al.,

1990). Green manures protect against erosion, retain nutrients that otherwise might be leached from the soil, suppress the growth and germination of weeds, cycle nutrients from the lower to the upper layers of the soil, and if legumes are used, leave substantial nitrogen to the following crop.

In Georgia, velvetbean (Mucuna sp.) was grown as a green manure/soil building crop from the late

1930's to the 1950's. Eighty percent of the estimated 2.5 million acres of velvetbean were grown in Georgia, but today this legume is grown only to attract wildlife (Phatak and Brunson, 1993).

8 Green manures were extremely valuable to agriculture before the advent of modern day commercial fertilizers, yet their full potential remains unappreciated and unexplored (Coleman,

1989). In the past, many growers viewed green manures as an either/or scenario. Either a green manure or a cash crop was grown and most growers did not want to replace their cash crop resulting in a declining interest in green manures. This was especially true in the northern United

States with shorter growing seasons. It may not be possible to have both a cash crop and green manure crops within the same year. However, in more temperate areas of the country, green manures can be managed in four ways: 1) as overwintering crops, 2) main crops, 3) undersown or companion crops and 4) as catch crops (Coleman, 1989; Phatak and Brunson, 1993). Cool- season legumes were sown after crops of cantaloupe, cucumber, eggplant, pepper and tomato and occupied the ground until it was tilled in the spring (Brunson, 1991; Bugg et al., 1991; Phatak et al., 1990). Overwintering cover crops can be sown after the market crop has been harvested.

Green manures grown as the main crop can replace a cash crop that year. However, if extra land is available, a grower could grow a green manure crop and let his livestock graze it, thus serving a dual purpose. Companion crops are green manuring crops planted along with the cash crop, i.e., sweet clover and spring grain. This allows a grower to have the best of both worlds i.e., benefits of the green manure crop and the profit of the cash crop. Sustainable farming incorporates green manuring as a regular part of crop rotation since the long term goal is soil and crop productivity.

Catch crops are short duration crops that are worked in after the main crop has been harvested or between two main crops. In Georgia, cowpeas have been sown in the fall after corn. Presently velvetbean is being examined as a catch crop after spring vegetables.

2. Cover crops: Cover cropping is the practice of growing pure or mixed stands of annual or perennial herbaceous plants to cover the soil of croplands for part or all of the year. The plants may be incorporated into the soil by tillage, as in seasonal cover cropping, or they may be retained for one or more seasons. When plants are incorporated into the soil by tillage, the organic

9 matter added to the soil is called green manure (Altieri, 1987). Cover cropping, like green manures, can be an essential component in sustainable agriculture systems. Use of cover crops has the potential to increase yields because they increase soil organic matter, improve the long-term nitrogen status of the soil (if a legume), improve soil structure, conserve soil water, and reduce runoff and soil erosion. Cover crops can also control weed growth by establishing ground cover early in the growing season before weed emergence. However, these living mulches may compete with the companion crop for soil water and nutrients. Several growing tips proposed by Organic

Gardening Magazine can help eliminate potential problems until a balance in the growers’s fields is reached (Long, 2000). These six tips are for all areas of the country where cover crops can be grown and utilized. The first and most obvious is to match the crop to the season and the climate.

Cool-season annuals do best if planted in the fall and winter while hot-season annuals are planted during the summer months. To realize the benefits of “low maintenance”, a fall crop should be one that is winter killed thereby reducing off-farm inputs such as herbicides the following spring. The second tip is to plant legumes as cover crops. Legumes increase soil nitrogen levels which are essential to developing a healthy soil. Legumes may require being inoculated with beneficial bacteria that help fix atmospheric nitrogen. Grasses (Secale cereale L., Lolium multiflorum Lam) or buckwheat (Fagopyrum esculentum Moench) are recommended if the primary goal is to increase soil structure, prevent erosion or suppress weeds. Research in south Georgia revealed that a fast growing crimson clover (Trifolium incarnatum L.) cover crop worked the best in combination with subterranean clover (Trifolium subterraneum L.) in crops of cantaloupe

(Brunson, 1991). In that system, grasses proved to be unsatisfactory not only due to competition with the cantaloupe plants but they did not provide suitable habitats for beneficial overwintering insects.

Most research involving cover crops had been in corn, soybean and small grains. In the late 1980's work was begun in the southern United States investigating the use of winter cover

10 crops in vegetable production. This was due in part to weeds, diseases, nematodes, and insects that cause substantial quality and yield losses in vegetable production. Controlling weeds, insects and diseases cost vegetable growers a substantial amount. Weeds and weed control cost growers

$360 million (WSSA, 1992), diseases and control $55 million (Langston, 2000), and insects and control $72 million (Adams and Chalfant, 1992). Pesticides registered for use in vegetable production are limited, and registered pesticides are withdrawn from the market every year. Also, there is still consumer concern about pesticide residues in fresh produce as well as in the environment. Cover crops could be an essential component in the agricultural production system because they offer excellent potential in the integrated pest management (IPM) of weeds, insects, diseases and nematodes in vegetable production in the southeast. However, until recently, most cover crops were buried with a moldboard plow and hence all of the beneficial effects were not utilized. This management practice is being reexamined as research has shown that meeting crop

N needs by using legumes is economically feasible (Yancy, 1996). 2.1. Legumes as green manures and cover crops: The history of agriculture is filled with examples of how the nitrogen harvested from cropped soils was replenished, if at all, by leguminous nitrogen fixation. Whereas animal wastes, non-leguminous fixation and atmospheric deposition can be significant sources of N, a large fraction of the N can be traced to legume sources (i.e., alfalfa silage) and the latter two are generally insufficient for crop productivity (Smith et al., 1987). There is documented recognition of the value of green manures in the Mediterranean Civilizations from the writings of Xenophon (434-355 B.C.) (Wedderbuan and Collingwood, 1976). In a review of ancient agricultural practices, Semple (1928) showed several writers specifically discussed use of legumes for soil improvement. Theophrastus (373-287 B.C.) discussed how farmers of

Macedonia and Thessaly used bean crops as green manures. Cato (234-149 B.C.) and Columella

(-45 A.D.) compared various legumes for soil improvement. Lupine was the popular choice at that time. Pieters (1927) stated that Chinese writers recognized more than 2,000 years ago how

11 legumes increased production of the crops that followed. In the early 1900's there were many reports of yield enhancements of non-leguminous crops by incorporating a legume into the preceding growing season (Harrison, 1913; Pieters, 1927). It was a management practice of N replacement until the arrival of economical commercial fertilizers. Therefore, legume cover crops are not a "new" idea. The contribution of symbiotically fixed N by legumes in crop rotations and the possibilities of meeting crop N needs by this practice are being reexamined by researchers because of three main factors (Smith et al., 1987; Power, 1987). In the late 1970's and early

1980's there were large price increases in fossil fuels which resulted in related price increases for

N fertilizers. Although things have stabilized since then, there still is concern over the long term that these are likely to become more expensive or more limited in supply. The second factor was the concern about soil erosion and leaching of N into ground water supplies. The third factor was the rapid adoption of no-tillage and conservation tillage by crop producers in many parts of the United

States and throughout the world where it was seen that legume cover crops fit well into these systems. Pieters (1927) stated that many crops had been used for cover crops but the choice ultimately depended upon climatic conditions, the cropping system practiced and the availability of seed. Researchers in the southeast have found legumes such as crimson clover (Trifolium incarnatum), subterranean clover (Trifolium subterraneum) and hybrid vetch (Vicia sativa) add

90-135 kg fertilizer N ha-1 to the soil (Hargrove 1986). Utomo et al. (1985), and Frye and

Belvins, (1989) found that hairy vetch (Vicia villosa Roth) resulted in the greatest yields of corn grain because it produced more dry matter, thus more mulch, and had higher nitrogen content (135 kg ha-1) than other cover crops.

2.2 Using velvetbean (Mucuna deeringiana L.) in rotations as a cover crop: In the southern United States control of nematodes in many commercial vegetable crops relies mainly on the use of some restricted nonfumicant nematicide or on preplant applications of a limited number of fumigants (Johnson et al., 1992; Rodríguez-Kábana et al., 1992). However they may not be

12 available for producers in the future due to environmental concerns. This has prompted the search for alternative nematode control measures. Crop rotation has been an effective means of management of nematodes. Using crops that are nonhosts of Meloidogyne spp. such as corn (Zea mays), cotton (Gossypium hirsutum), and sorghum (Sorghum bicolor L.) can aid in the management of root-knot nematode problems in peanut (Arachis hypogaea) and soybean

(Glycine max)(Johnson, 1982; Rodríguez-Kábana and Ivey, 1986; Rodríguez-Kábana et al.,

1987; Rodríguez-Kábana and Touchton, 1984), especially if used preventively. Another promising crop to use in rotations is velvetbean (Mucuna deeringiana L.). Velvetbean is an African legume that has been used in the southern United States since the late 19th century as a forage and cover crop (McSorley and Gallaher, 1992; Phatak and Brunson, 1993; Weaver et al., 1993). It was originally used as an ornamental in Florida before agricultural production. When shorter season varieties such as “Alabama Velvetbean” were discovered, planted acreage rapidly expanded. Its value as a crop for managing several species of root-knot nematode had been known for a long time (Watson, 1922; Watson and Goff, 1937). The crop has been identified as a tool for management of the reniform nematode (Rotylenchulus reniformis) in cotton, which is spreading throughout the South (Taylor and Rodríguez-Kábana, 1998). It also provides for some suppression against Southern blight (Sclerotium rolfsii) in peanuts. These early researchers also recognized the soil building attributes of the crop, along with the demands for livestock feed and grazing. A standard practice was to interseed corn with velvetbean. After hand harvesting the corn, livestock were sent into the fields to graze on the velvetbean or the bean itself was harvested

(Taylor and Rodríguez-Kábana, 1998).

The effect velvetbean would have in vegetable production on reducing nematode infestations is currently under investigation in Georgia. It is being used in rotation with crops of eggplant, tomato and pepper. Rodríguez-Kábana et al. (1992) had shown velvetbean is not a host for M. incognita, M. arenaria, M. javanica or H. glycines and when used in crop rotation in

13 peanut, increased yields by 47% compared with peanut monocultures. Velvetbean produces alkaloids via the root system which exert a suppressive effect on the development of Meloidogyne populations (Vicente and Acosta, 1987). Kloepper et al. (1991) discovered that the rhizosphere bacterial microflora were significantly different from those of other legumes. Several bacterial species isolated from the velvetbean rhizosphere indicated that they might be antagonistic to phytonematodes (Johnson et al., 1992; Rodríguez-Kábana et al., 1992). Research conducted at

Auburn University in 1999 indicated that suppressiveness to plant parasitic nematodes following velvetbean is associated with the development of antagonistic microflora in the rhizosphere and soil

(Vargas-Ayala et al., 1998). Their conclusions indicated that using velvetbean in a cropping system alters the soil microflora resulting in nematode suppression. They surmised that the next step would be to research when and how the microflora shift occurs and if it is the direct result of velvetbean exudates. Then cropping methods could be devised to expand to practical agriculture.

There are several reasons why velvetbean should reemerge as a potential crop for Southern agriculture. Extensive experimenting has shown that velvetbean significantly reduces populations of harmful organisms and increases populations of beneficial organisms. Southern soils are notably deficient in nutrients and organic matter which the crop could greatly enhance. Changes in federal farm programs under the 1997 FAIR Act eliminated monoculture incentives for many traditional crops except peanut. Lastly, southern farms often lack sufficient feed and winter grazing for livestock. So it seems that once again, the velvetbean can offer considerable promise as a key ingredient of sustainable agriculture.

Cover Crops, Conservation Tillage and Crop Rotation: Sustainable agriculture usually employs some kind of conservation practice such as tillage or using overwintering cover crops in rotation with the main crop. In vegetable production, conservation tillage has not received the attention agronomic crops have but increasing concern about soil erosion from wind and water have prompted growers to seek an alternative to moldboard plowing. Concerns about the

14 environment and farm profitability have been previously addressed and several sustainable crop production systems with an emphasis on “Total System Approach” have been researched for a variety of vegetable and field crops (Brunson, 1991; Phatak, 1992, 1994, 1998). Conservation tillage and cover crops were key components in all these alternative technologies (Reed, 1999).

Two major hurdles preventing growers from completely adapting to the alternative systems have been decreased yields and specific pest problems. Yield reductions and specific pest problems made alternative technologies less attractive to growers. A prime crop example having specific pest problems was the boll weevil in cotton production in the southeastern United States. Positive results from conservation tillage and crop rotations was evidenced in Georgia by the Boll Weevil

Eradication Program (BWEP) started in 1987. By 1992, the weevil was essentially eradicated which resulted in a decrease in pesticide use and off-farm inputs. Encouraged by its success researchers and cotton producers could focus their interests on evaluating alternative technologies to further reduce off-farm pesticide and fertilizer use. Researchers had already been studying alternative technologies which reduced pesticide, fertilizer and tillage inputs (Bugg et al., 1991;

Phatak 1992, 1994; Phatak et al., 1991; Yancy, 1994, 1996). Information from on-going work with sustainable production of vegetable and field crops utilizing cover crops, reduced tillage, fertilizer and pesticides helped further develop these stratigies for use in cotton. Phatak (1993) and

Bugg (et al., 1991) had earlier proposed a “Relay Cropping System” to use in vegetables and cotton. These technologies were tested on small cotton acreages at grower farms successfully.

Cotton was grown with reduced fertilizer and pesticide inputs thus showing this system is economically feasible and environmentally friendly. At present research is being directed toward larger field operations in order to further understand the strengths and weaknesses of these technologies.

Some of this philosophy is being conducted with the Natural Resources Conservation

Service (NRCS) and Cooperative Extension personal in Coffee County, Georgia. In cooperation

15 with area growers, they were able to develop a conservation tillage program in 1995. Initially, only one 200-acre farm practiced conservation tillage in the 1980's. It has since expanded to include approximately 30,000 acres in cotton, peanut, soybean, corn, vegetables and tobacco (Reed,

1999). Some 8,000 to 10,000 acres of winter cover crops were planted annually into which summer crops are planted using no-till equipment purchased by a NRCS grant. By 1997, the

NRCS had determined that eight tons of topsoil per acre had been saved via these conservation methods, saving over 24,000 tons of soil. Growers using this system in Coffee County were able to reduce fertilizer and pesticide use, time, labor and fuel necessary to produce a crop because of less trips over the fields and experienced greater flexibility in planting and harvesting crops. They also realized a 15-20% decrease in production costs which converted to estimated savings of

$1,012,550 to $1,350,000. The success of conservation tillage in south Georgia has prompted continued research and educational efforts so other growers and supporting agencies can develop systems of their own. Reed (1999) proposed that this system is more biologically friendly and that it provides for greater profit margins while helping farmers meet government regulations to reduce soil erosion and protect water quality.

Vegetable growers traditionally have buried plant debris to reduce incidences of diseases.

Usually vegetables are not grown on marginal land as agronomic crops can be and a smooth even seed bed is preferred in order to obtain a uniform plant stand (Sumner, 1986b). A uniform plant stand is of more importance than in agronomic crops because of the high value per acre of most vegetable crops. The lack of interest by vegetable growers to conservation tillage can also be attributed to the fact that there is little research out there for them to turn to. Many vegetable researchers themselves are not interested doing any work in this area. It may be that there are too many crops to work on as over forty are produced in Georgia alone. As mentioned previously, it is difficult for growers to take risks with such high value crops like vegetables. The research that is currently out there points to yield reductions associated with conservation tillage. Yield

16 reductions mean money and to make any profit, growers have to be able to market their crops through narrow market windows. If one of them is missed due to a delayed harvest from weeds, diseases or insects caused by conservation tillage, the whole year’s profits could be at risk.

Converting from conventional tillage to conservation tillage saves only $30 to $50 per acre, which at present is not enough incentive to switch (Phatak and Reed, 1999). The usual benefits associated with conservation tillage can not be put on paper because they’re all intangible. That’s hard to sell. The only way to convince vegetable growers is a total system approach that includes cover crops with conservation tillage which will help them reduce tillage, fertilizer, and most pesticides. By reducing off-farm inputs they can reduce production costs. However, the conversion to conservation tillage can not be done haphazardly. It requires planning and having to implement those plans with precision. Many growers do not plan adequately enough which ends in a failure. It is important for them to be aware that no-till practices delay vegetable harvests by two to three weeks. Instead, they need to employ strip-tilling in order to harvest crops within the all important market windows.

Conservation tillage is defined as any tillage practice that leaves at least 30% of the soil surface covered with residues after planting (Hiemstra and Bauder, 1984; Rothrock, 1992).

Tillage has been instrumental in the past in reducing pest damage to crops. The USDA Statistical

Service estimated that over 100 million acres of farm land is now under conservation tillage (Phatak and Reed, 1999). There are many examples of where cover crops, particularly green manures plowed under, have been very effective in biologically controlling plant pathogens. Cover crops help prevent disease by reducing the splashing of soilborne disease spores (Long, 2000). A crop of green peas or dry sorghum plowed under effectively controlled Phymatotrichum root rot in cotton in the southwestern United States (Altieri, 1987). Legume cover crops can also control take-all in wheat as well as potato scab (Baker and Cook, 1974). Legume residues increase the amount of available nitrogen and carbon compounds as available vitamins that augments biological

17 activity as well as fungistatis and propagule lysis (Altieri, 1987). Cover crops have become important in conservation tillage practices because they control soil erosion and help increase soil tilth (Phatak and Reed, 1999; Phatak et al., 1999; Pieters, 1927). This is especially true in Georgia where the soils are of low fertility with little organic matter. Hargrove (1986) used crimson clover with no-till sorghum and soybeans and observed an increase in the amount of water and fertilizer that percolated through the upper soil layer. The clover acted as a mulch which increased organic matter that in turn increased the number of pore spaces in the soil. This resulted in an increase in water percolation that reduced erosion to non detectable levels. On a negative note, enhanced water percolation could actually speed up the passage of chemicals into the underlying water table

(Nash, 1990). An essential ingredient to almost all sustainable farming is the use of crop rotations which are planned successions of various crops grown on one field (Altieri, 1987). Reganold et al.

(1990) stated that yields are usually 10 to 15 percent higher using rotations than when using monocultures. In most cases a monoculture can only be successful by adding large amounts of fertilizers and pesticides. Several experiments conducted for over 100 years at the Agricultural

Experiment Station at Rothamted, England and the Morrow plots at the Illinois Agricultural

Experiment Station provided considerable data on the effects of crop rotations. Evidence indicates that rotations have an impact on plant production because they affect soil fertility and survival of plant pathogens, soil physical properties, soil erosion, soil microbiology, nematodes, insects, mites, weeds, earthworms and phytotoxins (Sumner, 1982). Rotating crops can suppress pest insects, weeds and diseases by effectively breaking the life cycles of pests. Bullen (1967) reported that a one-year break is sufficient to provide control with effectiveness increasing with length or frequency of breaks. However, this is dependent on environmental conditions and on the particular pathogens or insect species. Crop rotations have been known to produce soil microflora richer and more diversified than monocultures which could be useful in biological control of certain pathogens either

18 by reducing the population (inoculum) or reducing the inoculum potential (Williams and

Schmitthenner, 1962).

Crop rotations that use forage legumes greatly reduce soil loss. Stewart et al. (1976) showed that the dense vegetative cover and rooting of these crops resulted in a negligible soil loss.

The residual mulch improved infiltration and soil was not eroding for several years afterward.

Cover crops reduce soil loss by up to 50 percent when followed by crops with little residue cover such as corn silage, some grain legumes and most vegetable crops (Papendick and Elliot, 1984).

Most of the benefits of erosion control come from the residue left on the soil surface or mixed in the soil upper layers. Erosion is also influenced by conservation tillage practices that increase soil surface roughness. Improved infiltration and less run-off of water result from the above (Hargrove,

1985).

Cover Crops And Insects: In Georgia, crop losses from soil insects, aphids, and thrips totaled $72 million in 1992 (Adams and Chalfant, 1992). Of this, $15.4 million were spent on control costs and the remaining $57 million to loss from insect damage. It was unknown what the effect cropping sequences and cover crops had on beneficial and pest insects populations, until research by Bugg and Wilson (1989) found that generalist predators may be important in the biological control of insects that attack warm-season vegetable crops. They discovered that during periods when pests are scarce or absent, several important predators can subsist on nectar, pollen and alternative prey afforded by cover crops. Altieri and Letourneau (1982), Altieri and Schmidt

(1985) and Bugg and Ellis (1988) postulated that this could lead to enhanced biological control on the beneficiary crops. Bugg, Phatak and Dutcher (1990a) have shown that in south Georgia the insidious flower bug, (Orius insidiosus [Say]), bigeyed bugs, (Geocoris spp.) and various lady beetles (Coleoptera: Coccinellidae), can attain high densities in various vetches, clovers and certain

Cruciferae. These predators subsisted and reproduced on nectar, pollen, thrips and aphids, and thus were established before the arrival of key pests (Bugg et al., 1987, 1990a, 1991; Ehler and

19 Miller, 1978; Murdoch et al., 1985; Tamaki, 1981; Tedders, 1983). Bugg et al. (1990b; 1991) found that when summer vegetables were planted amid "dying mulches" of cool-season cover crops, some insects moved on to the vegetables. To optimize the consequences of such movement, work was begun in south Georgia on matching cover crops with the associated vegetable crop. Field trials consisting of 20 different types of cover crops were conducted and those that harbored high levels of beneficial insects were selected for further research in vegetable production. Cover crops not selected were those that sustained high levels of pest insects (Bugg and Dutcher, 1989; Bugg et al., 1990a). As a result of such work crops of cucumbers and cantaloupes grew without use of insecticides (Phatak et al.,1990; Brunson, 1991).

During the last ten years, studies conducted at the Coastal Plain Experiment Station indicated that cover crops significantly contributed to the effective management of insects in the spring planting of vegetables and agronomic crops (Phatak and Reed, 1999). No insecticides were used and losses from aphids, flea beetles, whiteflies and thrips were negligible. Earlier work by

Brunson (1991) and Bugg et al. (1991) showed that beneficial insects used cover crops as insectaries and many times were already in place at the time of planting. Phatak’s work further expanded this philosophy by developing a “cover crops-vegetable crop relay cropping system”.

It was already known that cover crops can provide the necessary habitats to enhance populations of predatory insects. These insects then move onto the vegetable or agronomic crop thereby maintaining insect pests below economic thresholds. However, it was shown that cool-season cover crops only provided effective habitats through May. Once the weather became warmer, the cover crops “died out” and the beneficial insects were not numerous on crops. Growers would only benefit from this in early Spring and it is not useful for subsequent vegetable or agronomic crops planted in late spring or early summer. The task for research now is to find appropriate habitats and trap crop to keep beneficial insects as a key management tool for late growing crops.

20 1. Cover Crops and Insect Management: In the natural world of a balanced ecosystem, there are checks and balances. Pest insects are controlled by their natural enemies—called beneficials in agricultural systems. These include predator and parasitoid insects and diseases. Phatak (1998) outlined how in conventional systems, synthetic chemical treatments that kill insect pests also kill the natural enemies present. Predators kill and eat other insects while parasitoids spend their larval stage within another insect, which then usually dies as the larva develops. This can be thought of as Aliens© on a microscopic scale. To include such processes on a large scale, Phatak and others have studied how to combine strategies that make each farm more hospitable to beneficials. First, is to reduce pesticide use, and, if use is essential try to select materials that are least harmful to the beneficials. The negative side effects of synthetic pesticides have long been known (e.g., environmental pollution, human health effects, pest resistance, secondary pest outbreaks, etc.). Case in point, over use of Sevin™ insecticide decimated natural populations of honey bees which are essential to pollination in many vegetable crops. Therefore growers have to bring in colonies of bees in order to ensure pollination and fruit set. Secondly, cultural practices that such as tilling and burning that kill beneficials and destroy their habitats should be avoided. Using conservation tillage is a better option because more of the cover crop residue is left on the surface of the soil. Cover crops left on the surface may be living, senesced, dying or dead. However their presence, they provide protection for the beneficials and habitats. In

Georgia, cotton and peanut farmers were able to reduce insecticide costs $50 to $100/A (Phatak,

1998). Growers substituted insect control materials such as Bacillus thuringiensis (Bt), pyrethroids and insect growth regulators that had less environmental impact. These materials do not persist in the field, are more targeted to specific pests and are less harmful to beneficials.

Cover crops were planted on field edges and in other non-crop areas which resulted in increased numbers of beneficials seen in field environments. Research has looked at how beneficials and crop plants interact. When attacked by pests, it has been shown that plants do not remain idle but

21 send signals to which other insects respond. Appropriate beneficials then move in to find their prey. Therefore, maximizing natural predator-pest interactions is the primary goal of Integrated

Pest Management (IPM) and cover crops can play a leading role.

Cover Crops, Soilborne Diseases And Nematodes: Of the 170,000 acres of vegetables grown in Georgia, diseases reduce yields about ten percent annually. This amounted to $40 million dollars in damage and $15 million for disease control, totaling $55 million dollars in 2000 (Langston 2000). One of the limiting factors to vegetable production in the southern United

States are soilborne pathogenic fungi (Sumner et al., 1983, 1986a, 1986b). Rhizoctonia solani,

Pythium myriotylum, P. aphanidermatum, and P. irregulare are the most virulent pathogenic fungi that cause pre- and post-emergence damping-off in vegetables (Sumner, 1985). Sclerotium rolfsii causes root, hypocotyl and stem rot in vegetables. The influence of different overwintering cover crops on the natural biological control of Rhizoctonia solani and subsequent root disease severity had not been investigated, although it had been known Rhizoctonia-like fungi antagonistic to Rhizoctonia solani were common in Georgia Coastal Plain soils (Sumner and Bell, 1982;

1988). Numerous studies on root disease severity and populations of soilborne pathogens have been conducted on vegetable and agronomic crops following legumes in Georgia (Parker et al.,1975; Sumner et al., 1981; Sumner et al., 1986a; Sumner and Bell, 1986; Sumner et al.,

1986b). Sumner (1982, 1984) had shown that R. solani and Pythium spp. are pathogens on roots of legumes and other crops but it was not known if this still would be the case using overwintering legume cover crops in the rotation with vegetables. Rhizoctonia solani and other related pathogens can survive in surface soil plant debris such as stems, roots, peanut shells and seeds (Sumner et al., 1981; Sumner and Bell, 1982; Bell and Sumner, 1984). R. solani does not survive well in subsoils below eight inches because of the low O2 and high CO2 (Rothrock, 1992;

Sumner, 1987; Sumner et al., 1986b). Tillage practices like conservation tillage that leave residue on the soil surface, can actually increase incidences of soilborne diseases. Plowing buries any

22 surface residue and R. solani propagules and in turn brings up soil to the surface with low R. solani populations. This is not the case with Pythium spp. pathogens which survive many months as free oospores within the plow layer and plowing only brings viable oospores back to the surface layer.

Therefore tillage would not have much effect on the incidence of Pythium spp. (Sumner, 1987).

Sumner et al. (1983) found debris brought up to the surface following peanut contributed to greater postemergence damping off caused by Pythium spp. Phytotoxins caused by decomposing peanut hulls and high soil temperatures may also have contributed to the increase in root disease. If crucifers were planted preceding crops of cucumbers there was less disease severity and damping off problems. Decomposing crucifers produce sulfur containing compounds that could be harmful to soilborne pathogens (Lewis and Papavizas, 1970). Rothrock and Hargrove (1988) showed legume cover crops significantly increased populations of Pythium spp. throughout the following crop compared to a rye cover crop or no cover crop. They did not attribute the buildup to strictly cover crop residue, because higher populations of Pythium spp. occurred when the legumes were desiccated. When the above ground residue was removed, populations of Pythium declined in the soil. Residue that was incorporated into the soil by tillage increased populations of Pythium more than an overwintering cover crop such as crimson clover. It was concluded from these experiments that cover crop treatments did not consistently influence soil populations of Fusarium spp., Rhizoctonia solani or Rhizoctonia-like binucleate fungi. They attributed differences in the effect the legume cover crops and residues had on Pythium spp. to be caused by narrow carbon- nitrogen (C:N) ratios that increased microbial activity in soil. Each legume has distinct (C:N) ratios that would result in differences in Pythium populations. Hoyt and Hargrove (1986) reported higher populations of Pythium following hairy vetch than crimson clover because it has a greater nitrogen content than hairy vetch. Organic matter had been previously associated with increases in soil Pythium populations. It acts as a pioneer colonizer of living, dying or dead substrates

(Stanghellini, 1974). Watson (1970) noticed that damage to lettuce seedlings by Pythium spp.

23 was proportional to the population counts in soil and that damage to plants was less in soils that had cover crops incorporated even though the actual Pythium counts were greater than the control soils.

The concern over soil erosion has prompted growers to look at tillage alternatives such as using overwintering cover crops with conservation tillage (Phatak, 1992). Previous research had indicated that winter legumes improve soil fertility, tilth and reduces erosion as well as increases water percolation (Hargrove, 1985). However, sustainable vegetable production could have potential disease problems that are associated with legume cover crops. While there was evidence that adding organic matter can reduce crop damage from soilborne pathogens, little information was available on the effect relay cropping would have on pathogens associated with spring and summer vegetables (Sumner and Bell, 1994; Watson, 1970). In field trials with 20 different winter cover crops using conservation tillage, Sumner et al. (1995) found higher incidences of Pythium spp. and

R. solani following the legumes than with the grasses. Fruit rot following the legumes was higher than following the grasses but overall yields of marketable fruit were greater following legumes than other cover crops. The legumes provided more nitrogen than did grasses but also populations of

Pythium spp. and R. solani increased. The crucifer cover crops did not reduce populations of

Pythium or R. solani or decrease root diseases in these experiments. Cucumber plant stand was affected by the amount of cover crop residue left on the soil surface as well as seedling diseases caused by R. solani and Pythium spp. Specifically designed planters that would cut through the heavy residue or slot planters that would keep seed away from residue could enhanced plant stand.

The root-knot nematode (Meloidogyne incognita) infects more than 2000 species of plants around the world (Sasser, 1977). Its pervasiveness along with other nematodes and the increasing costs of chemicals have focused attention on alternative methods of control.

Nematicides available for use in vegetable production are limited and may not be available in the future due to environmental and/or toxicological concerns. Some promising alternative management

24 strategies include crop rotation or cover crops and soil amendments. Crop rotation is one of the oldest and one of the most effective means of controlling plant parasitic nematodes. In 1911

Bessey investigated cropping sequences that would be effective in controlling root knot

(Meloidogyne spp.) on vegetables. He also investigated the role of potassium (K) in nematode host interactions and suggested that an increased supply of K could limit the damage caused on lima beans (Phaseolus lunatus). Before recommendations concerning crop rotations to control nematodes in vegetable production can be made, information concerning the diversity of production systems as well as the species, race and host range of the nematodes in question need to be addressed. Trivedi and Barker (1986) proposed that there are two primary principles involved in crop rotation. First is to reduce the initial pathogen population sufficiently enough to allow subsequent crops to complete early growth before being attacked and secondly preserve competitive, antagonistic and predaceous nematodes and other organisms at high enough levels to act as buffers against the pathogenic species. Some of these "buffers" could be grasses and legumes that are non-hosts of nematodes. Rodríguez-Kábana et al. (1992) cited examples of

American jointvetch (Aeschynomene americana), bahiagrass (Paspalum notatum), castorbean

(Ricinus comunis), corn (Zea mays), cotton (Gossypium hirsutum), hairy indigo (Indogofora hirsuta), sesame (Sesamum indicum), sorghum (Sorghum bicolor), and velvetbean (Mucuna deeringiana) as non-hosts or poor hosts for root-knot nematode (Meloidogyne spp.) and had been used in rotations with peanut (Arachis hypogaea), soybean (Glycine max) and vegetable crops. Successful crop rotation is ultimately dependent on the availability of resistant and tolerant plants. However, Meloidogyne spp. have such broad host ranges that even alternate crops may be attacked. Compounding this difficulty are frequent occurrences of crop or even host-cultivar- specific races of M. incognita as well as other taxa (Trivedi and Barker, 1986).

Adding organic matter amendments to reduce root galling is another control alternative.

It has been well documented. Various crop residues (Johnson, 1959, 1962; Linford et al., 1938;

25 Rodríguez-Kábana and Touchton, 1984; Trivedi and Barker, 1986), oil cakes (Goswami and

Swarup, 1971; Singh et al., 1980), sewage sludge (Habicht, 1975), and hardwood (Malek and

Gartner, 1975) and conifer barks (Cotter and Corgan, 1974; McGrady and Cotter, 1989) all exhibit nematicidal properties. Their use in vegetable production and more importantly by growers, is currently being investigated. Cost and availability would be key factors in their being accepted.

However, the design of cropping systems that can minimize nematode buildup and damage is receiving increasing interest in the southeastern United States, but in order for these systems to work knowledge about the potential for large nematode buildups on a wide range of crops is needed (McSorley and Gallaher, 1992). Where there are hot wet summers, the choice of crops adapted to such conditions may be limiting. Current research has indicated that alternative legumes such as velvetbean (Mucuna deeringiana) and sunn hemp (Crotalaria juncea) residues are effective in reducing root knot nematode populations (McSorley and Gallaher, 1992; Caswell et al.,1991; Rodríguez-Kábana et al, 1992) and can tolerate the summer conditions associated with south Georgia. Nematodes may be important in sustainable vegetable production when conservation tillage is used. They may be pathogens not only on the overwintering cover crop but also following the spring and summer vegetable crops. Rothrock and Hargrove (1988) determined that root knot nematodes (Meloidogyne spp.) could parasitize winter legume cover crops in the southeast. They suggested that since root knot nematodes have such a broad host range, they could easily parasitize and maintain high populations in winter legumes and then be in place to infect major summer crops. Actual losses to winter cover crops are uncertain except in warm sandy soils such as the coastal plain of Georgia. Generally nematodes are most active in warm weather

(Minton, 1986). The amount of damage caused is dependent upon the initial nematode population at planting and the subsequent life cycles that are developed on a plant. Root knot nematodes seem to be most damaging on winter legume cover crops in the warmer regions of the southeast.

Higher temperatures would allow for longer pathogenesis over a longer time during the winter, and

26 nematodes generally do more damage to crops grown in sandy soils (Rothrock and Hargrove,

1988). Winter legume cover crops that are resistant to Meloidogyne spp. are being worked on by plant breeders. Several cultivars already do exist and their future availability should enhance their usage as winter cover crops in conservation tillage or sustainable production systems. 1. Re-Thinking Disease Management: As per mentioned, growers have always been instructed to turn under plant debris with a moldboard plow to at least 6-8 inches. However, it is known now that such activities disrupt the entire soil profile, which eliminate any beneficial insect habitats or weed suppression effects. There are many barriers a pathogen has to cross before it can cause disease to roots, stems or leaves. Cover crops can be used to reinforce some of these barriers. When attacked by insects, plants send off signals that can be used by predators to find their prey. This also occurs with disease pathogens. In soils that harbor high levels of disease innoculum, it will take time to reduce populations of soil pathogens using just cover crops.

Research has indicated that it may take several years with different disease management strategies before the natural populations of microflora maintain optimal levels and can compete with disease pathogens. For example, dampening-off was found not to be a serious problem on Georgia farms and research plots that retained cover crops for two or three years. Increased soil organic matter levels were also found in these soils.

1.1 Plant cuticle layer: This is the first physical barrier to plant infection that pathogens face. It usually is waxy and composed of thousands of surface hairs. Many pathogens enter plant tissues via cracks on the leaf surface. Wounds and natural openings like stomates can also be sites of infection. Cultural practices such as cultivation, spraying, sand-blasting from wind erosion, and soil splashing from irrigation and raindrops can physically damage this protective layer. Using a well managed no-till or minimum-till crop system with cover crops may not need cultivation for weed control so spraying is minimized. Brunson (1991) and Phatak and Brunson (1993) and

27 Phatak et al.(1998) showed organic mulches from living, dying or killed covers held the soil and stopped soil splashing which in turn protected plant leaf cuticles from injury.

1.2 Plant surfaces and microflora: The leaf and stem surfaces of plants are home to many benign organisms. They compete with pathogens for the limited nutrient supply. Some of the organisms even produce natural antibiotics. Conventional usage of pesticides, surfactants, soaps and spreader-stickers can disrupt or kill the activities of these beneficial microflora that can weaken the plant’s defenses. Cover crops can maximize the natural protection process by reducing the need for synthetic protection. The plant surfaces of cover crops are often teeming with healthy populations of beneficial microflora, such as various yeasts that can migrate onto a cash crop after planting or transplanting (Phatak, 1998). 2. Re-Thinking Nematode Management: Management of nematode infestations in southern soils has gotten much more complex in recent years. Growers used to rely on soil fumigants like Methyl Bromide™ which will no longer be available after 2003 due to environmental concerns and federal legislation. Hence, growers and researchers have had to develop alternative management strategies. The incorporation of crop rotations, cover crops and velvetbean (Mucuna deeringiana) have already been discussed. Further information is presented here as a re-thinking of nematode management. It is interesting to note that nematodes act directly and indirectly on plants. Most nematodes are not parasitic but interact with the soil microflora which include fungi, bacteria and protozoa. Some species are root feeders while others use weakened plants as their food source and help introduce pathogens through feeding wounds. Damage to plants occurs when there is, 1) a break down of plant tissue, such as lesions or yellow foliage, 2) retarded growth of cells, i.e., stunted plants, 3) excessive growth evidenced by galls, swollen root tips or unnatural root branching (Phatak, 1998). In a balanced and undisturbed ecosystem, no one species of nematode dominates. However, in conventional agriculture, pest nematodes have abundant food and little environmental resistance. This can lead to rapid increases in parasitic nematodes, plant diseases

28 and yield losses. However, an increase of biological diversity within cropping systems over time, usually reduces nematode infestations. Scientists have pointed out that a dynamic soil ecosystem and improved healthy soil structures along with increased organic matter is the key to greater soil diversity. Soil diversity is for naught however, once a nematode species is established in a field.

It is then usually difficult to eliminate it. Research has shown some covers can actually enhance nematode populations if they are grown before or after another crop that hosts a plant-damaging nematode species (Brunson, 1991). A susceptible cover crop will not cause nematode problems as long as pest species are absent from the field. However, cultural practices such as sanitation with seed, transplants and machinery need to be observed.

A field’s nematode pest population can be gradually reduced or limited on cash crops by using specific cover crops. There are a few control tactics that have been outlined by Phatak

(1998). These include manipulating soil structure or soil humus, rotating with non-host crops and using crops with nematicidal effects, such as brassicas. Use of brassicas and many grasses as cover crops can help manage nematodes. It is important to match specific cover crops with the particular nematode species they suppress. Rather than bury cover crop residue, cotton growers in North Carolina left cereal rye either on the surface or incorporated it a few inches (Walker et.al.,

1999). They found that suppression of Columbia lance nematodes was more effective than when residue was plowed under. Another example of “re-thinking” nematode management occurred in sugar beets, where cover crops of malt barley, corn, radishes and mustard sometimes worked as well as nematicides in controlling sugar beet nematode (Phatak, 1998). Increased production more than offset the cover crop cost, and livestock grazing of the brassicas increased profit without diminishing nematode suppression. It needs to be noted that this success was conditional upon small initial nematode densities because the cover crop treatments were only effective if there were less than 10 eggs or juveniles per cubic centimeter of soil. Even so, a moderate sugar beet

29 nematode level was able to be reduced by 50-75 percent in about 11 weeks, and yields increased by nearly 4 tons per acre.

Cover Crops And Weeds: Losses caused by weeds in vegetable production are substantial. In Georgia alone vegetable crop losses from weeds exceeded $360 million annually

(WSSA, 1992). The ten most troublesome weeds in vegetable production in Georgia include nutsedge (Cyperus esculentus), crabgrass (Digitaria sp.), Texas panicum (Panicum texanum),

Florida pusley (Richardia scabra), Florida beggarweed (Desmodium tortuosum), cutleaf evening primrose (Oenothera luciniata), sicklepod (Cassia obtusifolia), cocklebur (Xanthium sp.), ragweed (Ambrosia sp.), and pigweed (Amaranthus sp.). Phatak (1987,1988) and Putnam

(1990a) proposed that with proper management, cover crops could suppress most of these weeds by smothering or allelopathy. Smother crops are a widely used cultural practice to reduce weed populations. Cereal grains, buckwheat and sorghum-sudan hybrids are examples of effective smother crops (Putnam, 1985; Weston et al., 1989). They quickly establish themselves and use up the resources that weeds would otherwise utilize. They are believed to suppress weeds through both competition and allelopathy (Overland, 1966). Cover crops that provide a smothering effect and whose residues also provide allelopathic effects on weeds are gaining approval by vegetable growers (Putnam, 1990a). One such crop used in the southeast is cereal rye. If residues of rye are left on the soil surface, then they release chemicals inhibitory to seedling growth of many annual dicotyledonous weeds (Barnes and Putnam, 1987). Rye is a major component in the killed organic mulches used in no-till vegetable transplanting systems. The response of grassy weeds is more variable. Additional benefits of rye residues are soil and water conservation, and protection of seedlings from wind damage. Putnam (1990b) obtained early weed control with rye residues in

30 cucumber and snapbeans. The rye was able to establish a canopy which effectively suppressed the later emerging weeds.

In Georgia and California, the concept of a "living mulch" was suggested to manage weeds in vegetable production (Andow et al., 1986, Bugg et al., 1991; Lanini et al., 1989). Living mulches are plants grown in place, which suppress weeds by blocking light. Unlike other conventional mulches, living mulches are rooted and do not blow away. Cover crops are left to grow between rows of the cash crop to suppress weeds by blocking out light and out-competing weeds for moisture and nutrients. They may also improve organic matter content. To avoid plant competition, living mulches are usually chemically or mechanically suppressed before crop planting.

Research in the southeast has shown cool-season living mulches gradually die out during crop growth and do not compete for water or nutrients (Brunson, 1991; Phatak et al. 1990). However, cover crops that regrow during spring and summer, ie, subterranean clover, white clover, and red clover, can compete strongly for moisture with spring planted crops unless the covers are adequately suppressed (Phatak, 1998). Killed cover crop mulches last longer if stalks are left standing, providing weed control well into the season for summer vegetables (Phatak, 1994).

Weeds are often suppressed early using cover crops. Cover crops then can prevent erosion or supply soil N later in the season. Phatak (1998) cited examples of shade tolerant legumes like red or sweet clover being planted along with spring grains. These clovers grow rapidly after the grain is harvested preventing weeds form dominating fields in late summer. Many growers in the southeast overseed annual ryegrass in soybeans when the soybean foliage begins to yellow. They not only get a weed-suppressing cover crop before frost, but also a light mulch that can suppress winter annuals as well. Some living mulches studied with vegetable production in the early 1990's were vetch, common lentil, subterranean clover, crimson clover, and mustard. Weeds were suppressed early due to competition by the covers for light, water and nutrients. Over wintering legume cover crops that were used in cantaloupe production provided good weed control early

31 in the growing season. Crimson clover and subterranean clover "smothered" or "shaded" out weeds until the cantaloupe plants began to vine (Brunson 1991). This research later evolved into what is now referred to “vegetable-cover crop/relay cropping”, using crimson clover and cereal

rye for weed suppression.

Conventional Production

Definitions: Conventional production or conventional agriculture is defined as the predominant farming practices, methods and systems used in a region. In Georgia, conventional

(commercial) eggplant production is concentrated mostly in the southern part of the state.

However, eggplant occurs throughout home gardens in Georgia. Conventional eggplant production differs from sustainable production in a number of ways. Differences occur in seedbed preparation, machinery usage, fertilizer and pesticide inputs, fuel and energy costs, labor and harvesting of the crop. Conservation tillage is replaced by conventional tillage and results in more trips over the field for disking, harrowing and spraying. Cover crops (rye) are usually buried in order to secure a smooth seedbed. Pesticides are relied upon to control insects and diseases. The use of black plastic mulch is gaining popularity among growers as a tool to control weeds and moisture in sandy soils, rather than "living mulch" cover crops. Most conventional vegetable production is highly mechanized whereas sustainable production may be more labor intensive. Conventional tillage is defined as plowing and harrowing with subsequent cultivation (Pierce, 1989; Thompson and

Kelley, 1957). Primary tillage (disking) provides the initial soil movement that gets rid of any surface vegetation and deepens the root zone. This is done in early spring before planting. A moldboard plow to a depth of 20-30 cm to bury old residues not gotten by disking and to loosen the soil (Pierce, 1989; Granberry, 2001; Thompson and Kelley, 1957). Soils should be plowed when relatively dry, adjusting the plow angle to offset compaction. Fall plowing is recommended where soils are poorly drained or high in silt or clay. The depth of plowing is related to the soil profile and how deep the crop roots are. Eggplant is a fairly deep rooted (20-25 cm) crop

32 especially in sandy soils. Secondary tillage (rotovator, disk or harrow) can follow after plowing to break up soil ridges created by plowing. A disk will cut through clods and sod to considerable depth (Thompson and Kelley, 1957). Occasionally after disking, a spike-tooth or spring tooth harrow or cultipacker is used to level, smooth and crush surface soil clods (Knott, 1988). Heavy soils break up into hard clods which will not be crushed by harrows. Using a heavy drag or roller behind the harrow crushes lumps easily. On light soils, a drag or roller is used to pack and smooth the soil (Knott, 1949). Well drained sandy loams are suited best for eggplant production. Poorly drained soils can impede plant growth and result in low yields. Early eggplant production requires site selection where there is a southern to southwestern exposure. This allows soil to receive more sunlight and warm up faster. Eggplant are "tender" plants and sensitive to any type of chilling. Plants are grown

60-75 cm apart in single rows (Knott, 1988). Fertilizer recommendations are based on soil tests.

The basic pH needs to be around 6.0-6.5. If magnesium levels are low dolomitic lime (contains magnesium) should be broadcast and incorporated into the soil 3 to 4 months before transplanting.

Eggplant requires a long growing season which calls for side dressings of nitrogen fertilizer at 2-3 week intervals. Twenty to thirty pounds of nitrogen are sidedressed when the fruit is the size of hen's eggs (Granberry, 2001). Eggplant requires high levels of phosphorous (P). Most of it is applied during or near transplanting. Pop-up fertilizer (10-34-0) is applied 5-8 cm from the side of the rows and below the roots for early growth. Potassium (K) is also applied in two bands (a to ½ recommended rates) 5-8 cm to the sides and below the roots before transplanting.

Weeds are controlled with plastic mulch, chemical herbicides and/or cultivation. Cultivation is important in early weed control. By eliminating the transpiring leaf surface of weeds, soil moisture is conserved and nutrients are retained for crop growth needs (Pierce, 1989). Cultivating equipment includes duckfoot (flared) shovels or sweeps, chisel tines, rotary hoe or rototillers

33 (Granberry, 2001). Most of these are effective for young weeds when disturbing the root system is most easily accomplished (Pierce, 1989).

Economic Considerations of Sustainable and Conventional Production Systems

Little information is available on economic comparisons between sustainable and conventional production systems. Stark et al. (1995) compared net returns in peanuts using conventional and No-till tillage systems. It was found that potential cost savings and increased net returns from No-till were feasible. While harvest costs remained the same in both systems, lower preharvest variable costs and fixed cost outlays gave the No-till system a cost advantage. This comparison would be further examined with more extensive price sensitivity and risk analysis of the data. Research programs, especially sustainable vegetable production, are limited. The studies that were conducted were on organic farming, of which sustainable production has been identified with recently. In reviewing this literature, it was found many organic techniques can be employed in sustainable vegetable production. Lockeretz et al. (1981), Pimental et al. (1983) and Oelhaf

(1978) had conducted one of the most comprehensive comparisons between conventional and organic (sustainable) systems. Still several points are noteworthy of presenting here because they could be applicable to current day sustainable and conventional systems. However, these were in agronomic crops in the Midwestern United States which is quite different from the vegetable growing regions of Georgia. Yields in corn and soybeans were 5-10 percent less than conventional farms. More favorable growing conditions resulted in higher conventional yields but under drier weather, sustainable (organic) did just as well or better. After several years when crop rotations had become established, the organic farm yields began to increase and eventually approached that of conventional farms (Altieri, 1987). Conventional farms consumed much more energy than sustainable (organic) farms, because they used more agrochemicals (there has been a decline in the use of pesticides even on conventional farms since this work was published in the late 70's, but it still can hold true today). Organic farms seemed more energy efficient. Lockeretz et al. (1981)

34 and Oelhaf (1978) found from selected organic corn production farms during 1974-1975, energy/input ratios (efficiency) to be 13 and 20 while conventional farms were 5 and 7. Sustainable

(organic) farmers use of more biologically fixed nitrogen and recycled wastes (animal and green manures) significantly reduced the energy inputs in production. However, it was also pointed out that part of the savings from reducing non-organic fertilizers on these farms may have been offset by the increased use of fuel and machinery to apply manure and cultivate (Altieri, 1987).

Lockeretz et al. (1981) found that between 1974-1978 the energy consumed to produce a dollars worth of crop on the organic farms was only about 40 percent greater than the conventional farms.

The yields were lower on the sustainable (organic) farms, but more importantly the operating costs were lower by about the same cash equivalent (Reganold et al., 1990). As a result, net incomes from production on the two types of farms were about the same every year (1974-1977) except one year (1978).

Pimental et al. (1983) compared the fossil energy, labor and extra land inputs from growing wheat, potatoes, apples and corn conventionally and organically. He suggested the energy efficiency is dependent upon the cropping system. Organic corn and wheat were 29-70 percent more energy efficient than conventional production. However, organic potatoes and apples were

10-90 percent less energy efficient than the conventional system. This was due in part to losses from insects and diseases when these crops were grown without pesticides (Altieri, 1987). Many of the sustainable (organic) farms were highly mechanized and used slightly more labor than conventional farms did. When this was based on the crop value, 11 percent more labor input was required on the sustainable (organic) farms because yields were lower (Lockeretz et al., 1981).

Oelhaf (1978) also found organic farms can require more labor such as weed pulling, etc. This would seem to be a major limitation as to the expansion of some sustainable (organic) farms and an important deterrent for conventional farmers who might consider sustainable or organic methods.

The fuel costs of conventional production is four times greater than those of sustainable production

35 because of the many trips of the farm machinery over the field (Pierce, 1989). If cover crops can be properly managed in vegetable production, the costs would be less because of lower fuel consumption from machinery and fewer pesticide and fertilizer applications. Even though conserving soil and farm productivity is important to growers, most select an agricultural system based upon its short-term profitability. Conventional systems have usually appeared to be more profitable in the short-term than sustainable systems only because the former have been promoted for over four decades as "the way to go" by research methods and USDA policies. Reganold et al. (1990) questioned the validity of such viewpoints because the environmental and health costs to society imposed by conventional agriculture will ultimately determine profitability. If these indirect costs were added into the cost of conventional versus sustainable production, then sustainable would be more profitable and would yield more benefit to society overall. When growers suddenly shift from conventional to sustainable without adequate preparation, difficult problems can arise but most are short-term. Yields can dramatically decrease when abrupt stoppage of pesticides and fertilizers on the whole farm is instigated. Radical changes such as these cause an explosive increase in weeds, insects and diminished soil fertility but Reganold et al. (1990) proposed that this would last only a few years. To help growers make it through this transition, the

Rodale Research Center suggested that growers approach any change with caution. Small decreases in yield can be brought about by even gradual changes while the soil reestablishes a new balance between chemical and biological forces (Reganold et al., 1990). S.C. Phatak (per. comm.), a noted horticulturalist familiar with sustainable practices, stated that “growers must learn to crawl before they can walk” and will not recommend new "sustainable" growers try any more than 1-5 acres at first until they figure out the system. Growers should only try one field at a time to avoid placing the whole farm at risk. Transition from conventional to sustainable practices is also easier if farmers regularly keep adding organic matter such as green or animal manures to the soil.

36 Literature Cited Adams, D.B. and R.B. Chalfant. 1992. Vegetable insects. pp.49-65. In:Summary of losses from insect damages and costs of control in Georgia 1991.R.M. McPherson and G.K. Douce(eds.). Georgia Cooperative Extension Service Special Publication Num. 81, Sept. 1992. Athens, Georgia.

Altieri, M.A. and D.K. Letourneau. 1982. Vegetation management and biological control in agroecosystems. Crop Protection 1:405-430.

Altieri, M.A. and L.L .Schmidt. 1985. Cover crop manipulation in northern California orchards and vineyards:Effects on arthropod communities. Biological Agricultural & Horticulture 3:1-24.

Altieri, M.A. 1987. Agroecology: The scientific base of alternative agriculture. Westview Press. Boulder, Colorado.

Andow, D.A., A.G. Nicholson, H.H. Wein and H.R. Wilson. 1986. Insect populations on cabbage grown with living mulches. Environ. Entomol. 15:293-299.

Baker, K.F. and R.J. Cook. 1974. Biological control of plant pathogens. W.H. Freeman. San Francisco.

Barnes, J.P. and A.R. Putnam. 1987. Role of benzoxazinones in alleopathy by rye (Secale cereale L.). J. Chem. Ecol. 13:889-906.

Bell, D.K. and D.R. Sumner. 1984. Unharvested peanut pods as a potential source o innoculum of soilborne plant pathogens. Plant Dis. 68:1039-1042.

Bertrand, P.F. 1994. 1993 Georgia plant disease loss estimates. Georgia Cooperative Extension Service Publ. Path. 94-007, Febr. 1994. Athens, Georgia.

Bessey, E.A. 1911. Root-knot and its control. U.S. Dept. of Agric. Bur. Plant Ind. Bull. 217. 89 p.

Boswell, V.R. 1949. Our vegetable travelers. National Geographic Magazine. Vol. 96, No.2. p.209.

Brunson, K.E. 1991. Winter cover crops in the integrated pest management of sustainable cantaloupe production. M.S. thesis. University of Georgia.

Bugg, R.L., L.E. Ehler, and L.T. Wilson. 1987. Effect of common knotweed (Polygonum aviculare) on abundance and efficiency of insect predators of crop pests. Hilgardia 55(7):1-52.

37 Bugg, R.L. and R.T. Ellis. 1988. Use of green manure crops to subsidize beneficial insects:a study in progress, pp.553-557. In: P. Allen & D. Van Dusen(eds.). Global perspectives on agroecology and sustainable agriculture systems. Proc. of the Sixth International Conference of the International Federation of Organic Agricultural Movements (1986), Vol. II, Agroecology Program, University of California, Santa Cruz.

Bugg, R.L. and J.D. Dutcher. 1989. Warm-season cover crops for pecan orchards:horticultural and entomological implications. Biological Agricultural & Horticulture 6:123-148.

Bugg, R.L. and L.T. Wilson. 1989. Ammi visnaga (L.) Lamarck (Apiaceae): Associated beneficial insects and implications for biological control with emphasis on the bell-pepper ecosystem. Biological Agricultural & Horticulture 6:241-268.

Bugg, R.L., S.C. Phatak, and J.D. Dutcher. 1990a. Insects associated with cool-season cover crops in southern Georgia: Implications for biological control in truck-farm and pecan agroecosystems. Biological Agricultural & Horticulture 7:17-45.

Bugg, R.L., F.L. Wäckers, K.E. Brunson, S.C. Phatak, and J.D. Dutcher. 1990b.Tarnished plant bug,(Hemiptera: Miridae), on selected cool-season leguminous cover crops. J. Entomol. Sci. 25(3):463-474.

Bugg, R.L., F.L. Wäckers, K.E. Brunson, J.D. Dutcher and S.C. Phatak. 1991. Cool-season cover crops relay intercropped with cantaloupe:influence on a generalist predator,Geocoris punctipes (Hemiptera:Lygaeidae). J. Econ. Entomol. 84(2):408-416.

Bullen, E.R. 1967. Break crops in cereal production. J. Royal Agric. England 128:77-85.

Caswell, E.P., J. DeFrank, W.J. Apt and C.S. Tang. 1991. Influence of nonhost plants on population decline of Rotylenchulus reniformis. J. of Nematol. 23(1):91-98.

Coleman, E. 1989. Fertilizer from the garden. MOTHER EARTH NEWS. No.119. Sept.-Oct. pp. 112-116.

Cotter, D.J. and J.N. Corgan. 1974. Media, varieties and cropping systems for greenhouse tomatoes. New Mexico Agr. Expt. Sta. Bul. 617.

De Candolle, A. 1886. Origin of cultivated plants.2nd ed.,reprinted 1959. New York.

Ehler, L.E. and J.C. Miller. 1978. Biological control in temporary agroecosystems. Entomophaga 23:207-212.

Frye, W.W. and R.L. Blevins. 1989. Economically sustainable crop production with legume cover crops and conservation tillage. J. Soil and Water Cons. Vol. 44:57-60.

Goswami, B.K. and G. Swarup. 1971. Effect of oilcake soil on the growth of tomato and rootknot nematode population. Indian J. Phytopathol. 24:419-494.

38 Granberry, D. 2001. Eggplant. Georgia Coop. Ext. Ser. Cir. No.812. Athens, Georgia.

Habicht, W.A., Jr. 1975. The nematicidal effects of varied rates of raw and composted sewage sludge as soil organic amendments on root-knot nematode. Plant Dis. Rptr. 59:631-633.

Hargrove, W.L. 1985. Legume cover crops in no-till soybeans. pp.24-28. In: W.L. Hargrove, F.C. Boswell, and G.W. Langsdale(eds.). Proceedings of 1985 Southern Region No-Till Conference. Georgia Agricultural Experiment Stations, Athens, GA.

Hargrove, W.L. 1986. Winter legumes as a nitrogen source for no-till grain sorghum. Agron J. 78:70-74.

Harrison, F. 1913. Roman farm management. MacMillian Co., New York.

Henis, Y.A, R. Ghaffer, R. Baker and S.L. Gillespie. 1978. A new pellet soil-sampler and its use for the study of population dynamics of Rhizoctonia solani in soil. Phytopathology 68:371-376.

Hiemstra, H.D. and J.W. Bauder. 1984. Conservation tillage: Strategies for the future. Proc. Conf. Conserv. Tillage. Conservation Tillage Information Center. Fort Wayne, Ind. 100 p.

Hoyt, G.D. and W.L. Hargrove. 1986. Legume cover crops for improving crop and soil management in the southern United States. HortSci. 21:397-402.

Johnson, A.W. 1982. Managing nematode populations in crop production. pp. 193-203. In: Nematology in the southern region of the United States. Southern Cooperative Series Bulletin 276. Arkansas Agricultural Experiment Station, Fayetteville.

Johnson, A.W., A.M. Golden, D.L. Auld and D.R. Sumner. 1992. Effects of rapeseed and vetch as green manure crops and fallow on nematodes and soil-borne pathogens. J. Nemotol. 24(1):117-126.

Johnson, L.F. 1959. Effect of the addition of organic amendments to soil on root-knot of tomatoes: 1. Preliminary report. Plant Dis. Rptr. 43:1059-1062.

Johnson, L.F. 1962. The effect of organic amendments to soil on root-knot of tomatoes: II. Relation of soil temperature, moisture, and pH. Phytopathology 52:410-418.

Khan, R. 1979. Solanum melongena and its ancestral forms. p. 629-636. In: J.G. Hawkes, R.N. Lester, and A.D. Skelding (eds.). The Biology and Taxonomy of the Solanaceae. Academic Press. London.

Kloepper, J.W., R. Rodríguez-Kábana, J.A. McInroy and D.J. Collins. 1991. Analysis of populations and physiological characterization of microorganisms in rhizospheres of plants with antagonistic properties to phytopathogenic nematodes. Plant and Soil. 136:95-102.

Knott, J.E. 1949. Vegetable Growing. Lea & Febiger. Philadelphia.

39 Knott, J.E. 1988. Knott's Handbook For Vegetable Growers-Third Edition. O.A. Lorenz and D.N. Maynard(eds.). John Wiley and Sons. New York.

Lanini, W.T., D.R. Pittenger, W.L. Graves, F. Munoz, and H.S. Agamalien. 1989. Subclovers as living mulches for managing weeds in vegetables. California Agriculture.43:25-27.

Langston, D.B.Jr. 2000. Vegetables. Pg. 16. In: 1999 Plant Disease Loss Estimates. J.L. Williams-Woodward (ed). University of Georgia Cooperative Extension Service Circular Path 99-002.

Lewis, J.A. and G.C. Papavizas. 1970. Evolution of volatile sulfur-containing compounds from decomposition of crucifers in soil. Soil Biol. Biochem. 2:239-246.

Linford, M.B., F.Yap and J.M. Oliveira. 1938. Reduction of soil population and root-knot nematodes during decopmposition of organic matter. Soil Sci. 45:127-140.

Lockeretz, W., G. Shearer and D.H. Kohl. Organic farming in the corn belt. Science Vol. 211, 6 February. pp.540-547.

Long, C. 2000. Build your soil with cover crops. ORGANIC GARDENING. pp. 56-59. November.-December 2000.

Lowrance, R., B. Stinner, and G. House. 1984. Introduction. pp. 1-4. In: R.Lowrance, B. Stinner and G. House(eds.). Agricultural ecosystems: Unifying concepts. John Wiley, New York.

MacRae, R.J., S.B. Hill, and G.R. Mehuys. 1989. Agricultural science and sustainable agriculture: A review of the existing scientific barriers to sustainable food production and potential solutions. Biological Agricultural & Horticulture 6:173-219.

Malek, R.B. and J.G. Gartner. 1975. Harwood bark as a soil amendment for suppression of plant parasitic nematodes on container grown plants. HortScience 10:33-35.

McGrady, J.J. and D.J. Cotter. 1989. Fresh conifer bark reduces root-knot nematode galling of greenhouse tomatoes. HortScience 24(6):973-975.

McSorley, R. and R.N. Gallaher. 1992. Comparison of nematode population densities on six summer crops at seven sites in North Florida. Supp. J. Nematology 24(4S):699-706.

Minton. N.A. 1986. Impact of conservation tillage on nematode populations. J. Nemtol. 18(2):135-140.

Mizelle, W.O., Jr. 1999a. Vegetable acreages estimates 1999. Georgia Cooperative Extension Service Agricultural Economics Publication 93-027. University of Georgia, Athens, Georgia.

40 Mizelle, W.O., Jr. 1999b. Vegetable economics: a planning guide for 1999. Georgia Cooperative Extension Service Agricultural Economics Publication 91-013. University of Georgia, Athens, Georgia.

Murdoch, W.W., J. Chesson, and P.L. Chesson. 1985. Biological control in theory and practice. Amer. Nat. 125:344-366.

Nash, J. M. 1990. It's ugly, but it works. TIME. pp.29-30. May 21, 1990.

National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. National Academy Press. Wash., D.C.

Nonnecke, I.L. 1989. Vegetable Production. VanNostrand Reinhold. New York.

Odum, E.P. 1984. Properties of agroecosystems. pp. 5-12. In: R. Lowrance, B. Stinner and G. House(eds.). Agricultural Ecosystems: unifying concepts. John Wiley, New York.

Oelhaf, R.C. 1978. Organic agriculture: Economic and ecological comparisons with conventional methods. Allanheld, Osmun and Co., New Jersey.

Overland, L. 1966. The role of allelopathic substances in the "smother crop" barley. Amer. J. Bot. 53:423-427.

Papendick, R.I. and L.F. Elliot. 1984. Tillage and cropping systems for erosion control and efficient nutrient utilization. pp.69-81. In: D.F Bezdicek and L.F. Elliot (eds.). Organic Farming . ASA Spec. Publ. No. 46.

Parker, M.B., N.A. Minton, O.L. Brooks and C.E. Perry. 1975. Soybean yields and lance nematode populations as affected by subsoiling, fertility, and nematicide treatments. Agron. J. 67:663-666.

Peirce, L. 1989. Vegetables: characteristics, production, marketing. John C. Wiley and Sons; Canada.

Phatak, S.C. 1987. Tillage and fertility management in vegetables. American Vegetable Grower 35(2):8-9.

Phatak, S.C. 1988. Integrating methods for cost effective weed control. pp. 24-25. In: Integrated Weed Management Symposium, Expert Committee on Weeds, Western Canada Sec. Mtg., Victoria, B.C..

Phatak, S.C., R.L. Bugg, D.R. Sumner, J.D. Gay, K.E. Brunson and R.B. Chalfant. 1990. Cover crops in IPM of weeds, diseases, and insects of vegetables. XXIII Intern'l. Hort. Cong. Aug 27-Sept. 1, 1990, Florence, Italy, Abstr. Paper No. 3239.

41 Phatak, S.C., R.L. Bugg, D.R. Sumner, J.D. Gay, K.E. Brunson and R.B. Chalfant. 1991. Cover crop effects on weeds, diseases, and insects of vegetables. pp. 153-154. In: W.L. Hargrove (ed.). Cover Crops for Clean Water. Proc. International Conf., West Tennessee Experiment Station, Jackson, Tennessee, April 9-11. Published by the Soil and Water Conservation Society.

Phatak, S.C. 1992. An integrated sustainable vegetable production system. HortSci. 27(7):738- 740.

Phatak, S.C. and K.E. Brunson. 1993. Green Manuring. pp. 2-5. Georgia Organic Growers Association Newsletter. November 1993.

Phatak, S.C. 1994. A no/low pesticide system for vegetables. pp. 75-76. Proc. 8th North Carolina Vegetable Expo. January 10-12, Raleigh, North Carolina.

Phatak, S.C. 1998. Managing pests with cover crops. pp. 25-33. In: Managing Cover Crops Profitably. 2nd Edition, Sustainable Agriculture Network, Handbook Series Book 3, Sustainable Agriculture Research and Education Program of CSREES, USDA, National Agricultural Library, Beltsville, MD 20705-2351.

Phatak, S.C. and R. Reed. 1999. Opportunities for conservation tillage in vegetable production. pp. 2-4. In: J.E. Hook (ed). Proceedings of the 22nd Annual Southern Conservation Tillage Conference for Sustainable Agriculture, Tifton, GA 6-8 July 1999. Georgia Agri. Expt. Station Spec. Pub. 95.

Phatak, S.C., R. Reed, W. Fussell, W.J. Lewis and G.H. Harris. 1999.Crimson clover-cotton relay cropping with conservation tillage. pp. 184-188. In: J.E. Hook (ed). Proceedings of the 22nd Annual Southern Conservation Tillage Conference for Sustainable Agriculture, Tifton, GA 6-8 July 1999. Georgia Agri. Expt. Station Spec. Pub. 95.

Pieters, A.J. 1927. Green manuring: principles and practices. John Wiley and Sons; London.

Pimental, D., G. Berardi and S. Fast. 1983. Energy efficiency of farming systems: organic and conventional agriculture. Agric. Ecosyst. Environ. 9:359-372.

Poincelot, R.P. 1986. Toward a more sustainable agriculture. AVI Publishing Comp.,Westport,Conn.

Power, J.F. 1987. Legumes: Their potential role in agricultural production. Amer. J. Alter. Ag. 2:69-73.

Putnam, A.R. 1985. Allelopathic research in agriculture: past highlights and potential, pp.1-8. In: The chemistry of allelopathy. American Chemical Society.

Putnam, A.R. 1990a. Vegetable weed control with minimal herbicide inputs. HortScience 25:155- 59.

42 Putnam, A.R. 1990b. Allelopathy: a viable weed control strategy. pp. 317-322. In: New directions in biological control: alternatives for suppressing agricultural pests and diseases. Alan R. Liss, Inc.

Reed, R. 1999. Adoption of conservation tillage in Coffee County. pp. 37-38. In: J.E. Hook (ed). Proceedings of the 22nd Annual Southern Conservation Tillage Conference for Sustainable Agriculture, Tifton, GA 6-8 July 1999. Georgia Agri. Expt. Station Spec. Pub. 95.

Reganold, J.P., R.I. Papendick, and J.F. Parr. 1990. Sustainable agriculture. Sci. Amer. pp. 112- 120. June 1990.

Rodríguez-Kábana, R. and J.R. Touchton. 1984. Corn and sorghum as rotational crops for management of Meloidogyne arenaria in peanut. Nematropica 14:26-36.

Rodríguez-Kábana, R. and H. Ivey. 1986. Crop rotation systems for the management of Meloidogyne arenaria in peanuts. Nematropica 16:53-53.

Rodríguez-Kábana, R., H. Ivey and P.A. Backman. 1987. Peanut-cotton rotations for the management of Meloidogyne arenaria. J. Nematology 19:484-486.

Rodríguez-Kábana, R., J.W. Kloepper, D.G. Robertson and L.W. Wells. 1992. Velvetbean for the management of root-knot and southern blight in peanut. Nematropica 22:75-80.

Rodríguez-Kábana, R., J. Pinochet, D.G. Robertson and L. Wells. 1992. Crop rotation studies with velvetbean (Mucuna deeringiana) for the management of Meloidogyne spp. Supp. J. Nematology 24(4S):662-668.

Rothrock, C.S. and W.L. Hargrove. 1988. Influence of legume cover crops and conservation tillage on soil populations of selected fungal genera. Can. J. Microbol. 34:201-206.

Rothrock, C.S. 1992. Tillage systems and plant disease. Soil Sci. 154(4):308-315.

Sasser, J.N. 1977. Worldwide dissemination and importance of the root-knot nematodes (Meloidogyne spp.). J. Nematol. 9:26-29.

Semple, E.C. 1928. Ancient Mediterranean Agriculture: Part II. Manuring and seed selection. Agric. Hist. 2:129-156.

Singh, S.P., M. Ahmad, A.M. Khan and S.K. Saxena. 1980. Effect of seed treatments with certain oilcakes or nematicides on the growth of tomato and on rhizosphere population of nematodes and fungi. Nematol. Mediter. 8:193-198.

Smith, M.S., W.W. Frye, and J.J. Varco. 1987. Legume winter cover crops. Adv. Soil Sci., 7:95- 139.

43 Stanghellini, M.E. 1974. Spore germination, growth and survival of Pythium in soil. Proc. Am. Phytopathol. Soc. 1:211-214.

Stark, C.R. Jr., S.C. Phatak, J.R. Ruberson, D. Waters, A.K. Culbreath and W.D. Branch. 1995. Comparisons of net returns and production costs by peanut variety under no-till and conventional tillage. Georgia Peanut Research - Extension Report.

Stewart, B.A., D.A. Woohiser, W.H. Wischmeier, J.H. Caro, and M.H. Frere. 1975. Control of water pollution from cropland. Vol.I. U.S. Dept. Agric. and Environ. Protection Agency.

Sumner, D.R., B. Doupik, Jr., and M.G. Boosalis. 1981. Effects of reduced tillage and multiple cropping on plant diseases. Annu. Rev. Phytopathol. 19:167-187.

Sumner, D.R. 1982. Crop rotation and plant productivity. In: Rechcigl, Jr., Miloslave [ed.] Handbook of Agricultural Productivity. Vol. 1. CRC Press, Boca Raton, Fla. pp. 273- 313.

Sumner, D.R. and D.K. Bell. 1982. Root diseases of corn inducted by Rhizoctonia solani and Rhizoctonia zeae. Phytopathology 72:86-91.

Sumner, D.R., C.C. Dowler, A.W. Johnson, N.C. Glaze, S.C. Phatak, R.B. Chalfant, and J.E. Epperson. 1983. Root diseases of cucumber in irrigated, multiple-cropping systems with pest management. Plant Dis. 67:1071-1075.

Sumner, D.R. 1984. Cropping practices and root diseases. In: C.A. Parker, A.D. Rovira, J.J. Moore, P.T.W.Wong and J.F. Kollmogen [eds.]. Ecology and management of soilborne plant pathogens. pp.267-270. Am. Phytopath. Soc. St.Paul, Minn.

Sumner, D.R. 1985. Virulence of anastomosis groups of Rhizoctonia solani and Rhizoctonia-like fungi on selected germ plasm of snap bean, lima bean, and cowpea. Plant Dis. 69:25-27.

Sumner, D.R., D.A. Smittle, E.D. Threadgill, A.W. Johnson, and R.B. Chalfant. 1986a. Interactions of tillage and soil fertility with root diseases in snap bean and lima bean in irrigated multiple-cropping systems. Plant Dis. 70:730-735.

Sumner, D.R., E.D. Threadgill, D.A. Smittle, S.C.Phatak, and A.W. Johnson. 1986b. Conservation tillage and vegetable diseases. Plant Dis. 70:906-911.

Sumner, D.R. and D.K. Bell. 1986. Influence of crop rotation on severity of crown and brace root rot caused in corn by Rhizoctonia solani. Phytopathology 76:248-252.

Sumner, D.R. 1987. Root diseases in crops following legumes in conservation tillage systems. In: J.F. Power [ed.]. The role of legumes in conservation tillage systems. Proc. of a Nat. Conf., Univ. GA, Athens. April 27-29, 1987. Soil Conservation Soc. of Amer.

44 Sumner, D.R. and D.K. Bell. 1988. Antagonism of binucleate Rhizoctonia-like fungi and other basidomycetes to Rhizoctonia solani AG-4 and AG-2 Type 2. Phytopathology 78:629 (Abstr.)

Sumner, D.R. and D.K. Bell. 1994. Survival of Rhizoctonia spp. and root diseases in a rotation of corn, snapbean, and peanut in microplots. Phytopathology 84, no. 2 (Feb 1994): p. 113-118.

Sumner, D.R., S.C. Phatak, J.D. Gay, R.B. Chalfant, K.E. Brunson and R.L. Bugg. 1995. Soilborne pathogens in a vegetable double-crop with conservation tillage following winter cover crops. Crop Protection 14:495-500.

Tamaki, G. 1981. Biological control of potato pests. pp. 178-192. In: J.H. Lashomb and R. Casagrande (eds.). Advances in potato pest management. Hutchinson Ross Publishing Co., Stroudsberg, PA.

Taylor, C.R. and Rodríguez-Kábana, R. 1998. History of the Alabama velvet bean and its potential for the future. Farming Systems Research Forum. February 1998.

Tedders, W.L. 1983. Insect management in deciduous orchard ecosystems: habitat manipulation. Envir. Mang. 7:29-34.

Thompson, H.C. and W.C. Kelly. 1957. Vegetable Crops. McGraw Hill. New York.

Trivedi, P.C. and K.R. Barker. 1986. Management of nematodes by cultural practices. Nematropica 16:213-236.

Utomo, M., W.W. Frye, and R.L. Blevins. 1985. Functions of legume cover crops in no-till and conventional till corn production. pp. 63-68. In: W.L. Hargrove, F.C. Boswell, and G.W. Langsdale(eds.). Proceedings of 1985 Southern Region No-Till Conference. Georgia Agricultural Experiment Stations. Athens, GA.

USDA, 1980. Report and recommendations on organic farming. Superintendent of Documents. Washington, D.C.

Vargas-Ayala, R., R. Rodríguez-Kábana, G. Morgan-Jones, J.A. McInroy and J.W. Kloepper. 2000. Shifts in soil microflora induced by velvetbean (Mucuna deeringiana) in cropping systems to control root-knot nematode. Biological Control 17:11-22.

Vicente, N.E. and N. Acosta. 1987. Effects of Mucuna deeringiana on Meloidogyne incognita. Nematropica 17:99-102.

Walker, A.L., S.C. Phatak and W.J. Lewis. 1999. In: J.E. Hook (ed.). Need for a systems approach to cotton production: A crop consultant’s perspective. Proceedings of the 22nd Annual Southern Conservation Tillage Conference for Sustainable Agriculture, Tifton, GA 6-8 July 1999. Georgia Agri. Expt. Station Spec. Pub. 95.

45 Watson, A.G. 1970. Phytopathology. 60:1537. Abstr.

Watson, J. R. 1922. Bunch velvet beans to control root-knot. Univ. Fla. Agric. Exp. Stn. Bull. 163:54-59.

Watson, J.R. and C.C. Goff. 1937. Control of Root-Knot in Florida. Univ. Fla. Agric. Exp. Stn. Bull. 311:1-22.

Weaver, D.B., R. Rodríguez-Kábana and E.L. Carden. 1993. Velvetbean in rotation with soybean for management of Heterodera glycines and Meloidogyne arenaria. Supp. J. Nematol. 25(4S):809-813.

Wedderbuan, C.H.M. and W.G. Collingwood. 1976. The Economist of Xenophon. Lenox Hill. New York.

Weston, L.A., R. Harmon, and S. Mueller. 1989. Allelopathic potential of sorghum-sudangrass hybrid (Sudex). J. Chem. Ecol. 15(6):1855-1865.

Williams, L.E. and A.F. Schmitthenner. 1962. Effect of crop rotations on soil fungus populations. Phytopathology 52:241-246.

WSSA, 1992. Crop losses due to weeds in Canada and the United States 1992. D. Bridges (ed.). Weed Science Society of America. Champaign, Ill.

Yamaguchi, M. 1983. World Vegetables. VanNostrand Reinhold. New York.

Yancy, C. Jr. 1994. Covers challenge cotton chemicals. THE NEW FARM. pp. 20-23. Feb. 1994 (Magazine of Regenerative Agriculture, Rodale Institute, Red Oak , IA. 51591- 0306).

Yancy, C. Jr.1996. Reduce costs with change to spare. THE PEANUT FARMER. pp. 10-12. June 1996. (Specialized Agricultural Publications, Inc., Raleigh, N.C. 27604).

46 CHAPTER 2

EFFECT OF LOCATION AND PRODUCTION SYSTEM ON CONVENTIONAL

AND SUSTAINABLE EGGPLANT YIELDS 1

1 Brunson, K.E. and S.C. Phatak. 2002. To be submitted to J. Alternative Agriculture.

47 ABSTRACT Marketable eggplant yields were significantly greater in the conventional production system than in the sustainable production throughout the two-year study. It was consistent within all locations, despite location or soil type. The locations with deep sand soils produced lower yields than the locations with loamy type soils. Generally more unmarketable eggplants were associated with the conventional system perhaps due to the general large amounts of eggplant being produced.

Rot and cull yields were also observed to be higher with conventional production. Regression trends of the marketable harvest data suggested that conventionally grown eggplant matured earlier than sustainably grown eggplant. The eggplant grown from the sustainable systems eventually caught up during later harvests. From a market and profit point of view, the conventionally grown eggplant appeared to have an advantage over no pesticide use sustainable eggplant.

INDEX WORDS: Eggplant, Solanum melongena L., Yields, Sustainable Production

Conventional Production.

INTRODUCTION

In Georgia, eggplant is gaining popularity as a commercial vegetable crop and is currently ranked 19th in the state in production, up 30 percent since 1992. Conventional (commercial) eggplant production is concentrated mostly in the southern part of the state. However, eggplant occurs throughout home gardens in Georgia. There is an estimated 1,259 acres of commercially grown eggplant. Approximately 823 acres are plastic mulch culture and the remaining 436 acres are bare ground culture (Langston, 2001). Most of the eggplant (59%) were grown in the spring but 41% came from a fall crop. These two production practices combined provide an estimated

$12,000,000 gross value to Georgia growers (Langston, 2001). Sustainable vegetable production has many possibilities as an alternative to high intensive commercial production. Pesticides registered for vegetable use are limited. Many are being taken off the market every year. The consumer concern over pesticides and residues in food are

48 prompting growers to look for alternatives. Using overwintering legume cover crops can reduce inputs of commercial fertilizer and lessen environmental concerns about water pollution. Soil productivity is maintained by sustainable systems as well as providing suitable habitats for beneficial insects. Increasing beneficial insect populations can reduce insecticide inputs. Several objectives were targeted from this research. First, we wanted to compare marketable yields from a sustainable production system with that of conventionally grown eggplant.

Second, because no pesticides were applied to the sustainable crop, we wanted to compare any differences in culls, rots and insect damaged eggplant from that of the conventional system. This information was needed to develop comparison economic budgets between the two production systems.

MATERIALS AND METHODS

A. Land Preparation 1992-93

Field trials were conducted during 1992-93 in south Georgia using four sites. Each differed by soil type and cropping histories. The Horticulture Farm was a 10 ha tract composed of Tifton loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudults), Little River Farm was 6 ha composed of Dothan loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudults), Hodnett

Farm was 12 ha composed of Bonifay sand (loamy, siliceous, thermic gross Arenic Plinthic

Kandiudults) and Blackshank Farm was 62 ha comprised of several soil types. The research plots were Tifton loamy sand 2-5 % slope, (fine-loamy, siliceous, thermic Plinthic Kandiudults).

Vegetables had been grown for many years at both the Horticulture and Little River Farms and both had what the Soil Conservation Service called highly productive soils. The cropping histories

49 of the Hodnett and Blackshank Farms were primarily row crops and the soils were less productive than the other farms.

Sustainable Production

Bed preparation at each location began 29 October 1991 and 19 October 1992, by turning soil 20-25 cm deep with a moldboard plow. Each plot was 12.2 m in length and comprised of 1.83 m wide raised beds (1.27 m exclusive of wheel tracks). Each location required different levels of fertilizer due to the varying soil types involved. In 1991 a complete fertilizer [(136.2 kg of 5-10-15 N-P-K (6.8 kg-13.6 kg-20.4 kg per hectare)] was broadcast onto the sustainable production plots at each location after bed preparation, using an electric powered Gandy™ spreader and incorporated 15 cm deep with a tractor-powered rototiller. In 1992 136.2 kg of 5-

10-15 was applied at the Horticulture Farm while 131 kg 5-10-15 was applied at the Little River,

Hodnett and Blackshank Farms. Fenamiphos [ethyl 3-methyl-4-(methylthio) phenyl (1- methylethyl) phosphoramidate] (6.7 kg a.i. ha-1) was applied 30 October 1991 to control nematodes. No fenamiphos was applied in 1992 as alternative nematode control measures using velvetbean (Mucuna deeringiana L.) were initiated. Permanent strips of cool-season cover crops of crimson clover (Trifolium incarnatum L.) and subterranean clover (Trifolium subterranum

L.) were planted at each location on 29 October in 1991 and 1992 at the seeding rates of 6.8 kg/ha and 13.6 kg/ha respectively. Beds were comprised of four rows planted 0.6 cm deep and spaced 30.5 cm apart using a tractor-drawn Stanhay™ seeder. The experiment at each location was Cool-season cover crops designated as the alternative or sustainable production system.

These alternative systems were chosen from earlier production systems research that had shown promise in vegetable production (Bugg et al., 1991; Phatak et al., 1990). The clovers at all farms were trimmed to 61 cm using a tractor-powered flail mower on 27

March, 6 April, 4 August 1992 and 8 and 22 March, 8 and 19 April, 6 August 1993. On 7 April

1992 and 25 March 1993, the two interior rows of cover crops in each plot (a 40 cm strip) were

50 sprayed with the herbicide glyphosate [ isopropylamine salt of N-(phosphono-methyl) glycine]

(1.68 kg a.i. ha-1). The two outside rows were shielded from the herbicide and left alive to help maintain populations of beneficial insects (Bugg et al., 1991). On 22 April 1992 and 31 March

1993 the treated strips were prepared for planting using minimum tillage methods. The soil was cultivated with a fluted disk 5-10 cm deep, subsoiled 20-25 cm deep and smoothed with a rolling cultivator. Eggplant, var. “Classic”, was transplanted 61 cm apart in single rows into the tilled strips at all locations on 23 April 1992 and 1 April 1993, using a tractor-drawn mechanical transplanter

(Model 800 2 6000 Two Row Pull-Type, Mechanical Transplanter Corp.).

Initial fertilizer to stimulate cover crop growth was made in two applications 7 January and

7 February 1992 at all locations using 31.8 kg/ha and 34.1kg/ha of ammonium nitrate (34-0-0), respectively. On 22 February 1993, one application was made of 68.1 kg/ha of ammonium nitrate

(34-0-0) at all locations. Broadcast applications of DAP (diammonium phosphate 18-46-0) were later applied to all locations except the Horticulture Farm at 45.4 kg/ha on 18 April 1992. On 1

May 1992, 34.1 kg/ha DAP was applied at all farms. On 4 May 45.4 kg/ha DAP was broadcast at all farms except Little River. In 1993, applications of DAP were put out on 6 January at rates of 50 kg/ha at all locations except the Horticulture Farm. On 4 February 1993 45.4 kg/ha of DAP was applied to the Horticulture Farm, 91 kg/ha to the Little River Farm and 59 kg/ha to the

Hodnett Farm. Two other applications of DAP were applied 8 and 20 of April 1993 at rates of

32 and 59 kg/ha at all locations. On 17 March 1992 68.1 kg/ha (10-10-10 N-P-K) was applied at the Horticulture Farm while the other locations received 90.8 kg/ha (10-10-10 N-P-K). Ten days later, on 27 March 1992 136.2 kg/ha (10-10-10 N-P-K) was put out at the Hodnett Farm.

On 14 May and 1 June 1992 90.8 and 68.1 kg/ha (10-10-10 N-P-K) were applied at all farms.

On 10 June 1992 68.1 kg/ha (10-10-10- N-P-K) was put out at the Horticulture Farm while all other locations received 90.8 kg/ha 10-10-10 (N-P-K). The last application of 10-10-10 (N-P-

K) in 1992 occurred on 26 August when 90.8 kg/ha was broadcast at all farms. In 1993,

51 applications of 10-10-10 (N-P-K) were on 4 and 27 May. On 4 May the Hodnett Farm received

136.2 kg/ha and 68.1 kg/ha were applied at the other three locations. On 27 May 68.1 kg/ha 10-

10-10 (N-P-K) was applied at all the farms. Supply of micronutrients were obtained by using

CAB (calcium, magnesium, boron) 2 June 1992 at 1.89 l/ha, and Sul-po-mag (sulfur, potassium, magnesium) 6 January 1993 at 45.4 kg/ha at all farms except the Horticulture Farm.

No insecticides were applied to the crop in 1992, but methamidophos (O,S-Dimethyl phosphoroamidethioate) was sprayed 6 June 1993 to combat spider mites brought on by dry weather. Sethoxydim (2[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3hydroxy-2-cyclohexen-

1-one) to control perennial grasses was applied 22 June 1992 and 2,4-DB (4-(2,4-

Dichlrophenoxy) butyric acid) was used 23 February 1993 to control cutleaf evening primrose

(Oenothera luciniata Hill).

Conventional Production

Bed preparation at each location was begun on the same dates as the sustainable systems using conventional tillage methods. Soil was turned 20-25 cm deep with a moldboard plow. Each plot was the same type of raised bed mentioned previously for the sustainable production system.

Initial fertilizer inputs of 136.2 kg/ha of 5-10-15 (6.8 kg/ha N-13.6 kg/ha P- 20.4 kg/ha K) were broadcast on 29 October 1991, 21 October 1992 and incorporated 15 cm deep with a tractor drawn rototiller. Cereal rye, 'Wrens Abruzzi' (Secale cereale), at the seeding rate of 40.9 kg/ha was drilled into the prepared beds 6 November 1991. Subsequent pesticide and fertilizer inputs were from the University of Georgia Cooperative

Extension Service recommendations for eggplant (Granberry, 2000). The rye was allowed to grow throughout the winter months and two 31.8 kg/ha applications of ammonium nitrate (34-0-0) applied 7 January and 4 February 1992 at all locations. On 16 March 1992 the beds were cultivated and on 17 March the rye was flail mowed using a tractor powered mower. The rye was deep turned to 25 cm using a moldboard plow on 6 April 1992 and 30 March 1993. On 17 April

52 and 30 March, 272.4 kg/ha 10-10-10 (N-P-K) was broadcast at each location. On 23 April

1992 and 30 March 1993, 3.78 l/ha fenamiphos [ethyl 3-methyl-4-(methylthio) phenyl (1- methylethyl) phosphoramidate] (6.7 kg a.i. ha-1) and .23 kg/ha trifluralin [%,%,% -Trifluoro-2,6- dinitro-N,N-dipropyl-p-toluidine] was sprayed and rototilled to 15 cm at all locations. Eggplant, var. “Classic”, was then transplanted at the same time and using the same methods as the sustainable system.

B. Eggplant Yields Three eggplant harvests were conducted in 1992 and four in 1993. Both production systems were evaluated for marketable, unmarketable, cull, rot and insect damaged yields. Total yields per each growing season were evaluated by General Linear Methods (SAS, 1989). Yields per harvest period were analyzed by regression analysis to determine trends associated with each production system. Eggplant in both production systems was harvested in 1992 on 7, 22, 30 July and 2, 8, 15, 23 July 1993 from random sections of five plants (3 m sections) per 22.67 m2 plot.

Fruit was separated into marketable, cull, rot and insect damaged categories and weighed in grams.

This data was converted into t/ha and cartons/acre. A standard carton was 1 1/9 bushel equivalent to 33 pounds (Mizelle, 1993b). The categories were based on size, shape and firmness of the eggplant. All harvest data was analyzed by general linear models (GLM) statistical procedures without prior transformation (SAS, 1989). To estimate total unmarketable yields, cull, rot and insect damaged yields were added together. Location and treatment effects were looked at for significant interactions. Means were separated by Duncan's Multiple Range Test (P=.05). Proc

Duncan procedures were then utilized to further separate means into location by treatment effects.

Linear and quadratic regressions were plotted using marketable, cull and rot yields per harvest by production system. To estimate percent of yield by production system, total weight of eggplant

53 was divided by marketable, unmarketable, cull, rot and insect-damaged categories and then multiplied by 100.

RESULTS

A. Eggplant Yields

Sustainable Production

Extremely dry weather conditions occurred during April-June of 1993. Compared to the prior 20 year period averages, temperatures from April 25 through June 29 in 1993 were some two degrees cooler than normal, but almost 2.5 degrees warmer than in 1992 (Coastal Plain

Experiment Station Meteorology Records). Precipitation during this period in 1993 was 3.45" or almost 5 inches below the 20-year average annual rainfall (8.37") for the period (Figs. 1&2).

Despite the use of irrigation, this period of weather stress in 1993 was thought to be a direct result of the poor overall yield results.

The crimson clover system tended to produce more marketable eggplant than did the subterranean clover for both growing seasons. Plant stands within the first two replications in the crimson clover at the Little River Farm were lost due to large populations of black cutworm

(Agrotis ipsilon [Hufnagel]) that eventually affected overall yields. However, no significant differences were observed in 1992 from any location (Table 1). Significant differences were detected in 1993 only from the Little River and Hodnett Farms. Subterranean clover was significantly different from crimson clover within year and location for unmarketable (culls, rots and insect damaged) eggplant (Table 2). Differences between years were observed when unmarketable yields were separated into respective cull, rot and insect damaged fruit per clover system. No significant differences for culls were observed in 1992 from either location. However in 1993, more culls were harvested from the crimson clover system at all locations except the

Horticulture Farm (Table 3). Differences in rots were observed from subterranean clover at the

Horticulture Farm in 1992 and from crimson clover at the Little River Farm in 1993 (Table 4).

54 Subterranean clover produced significantly more insect damaged fruit in 1992 at the Little River and Hodnett Farms (Table 5). In 1993, significant differences occurred in crimson clover at the

Little River Farm.

Regression analysis showing trends between production systems at each location was investigated. Numbers of marketable, cull and rot eggplant per harvest were compared. In 1992, a trend for the clover systems to initially produce small numbers (0-5 fruit) the first and second harvests was observed from the Horticulture Farm. By the second half of the season this was reversed. Later harvests showed a steady increase in marketable fruit for both production systems.

Subterranean clover had a greater increase in fruit per harvest than crimson clover (Fig. 3). At the end of the last harvest, 30 marketable fruit were picked from eggplant in the subterranean clover compared to 15 from the crimson clover. In 1993, essentially no trend could be detected between either clover system due to extremely low harvest numbers (Fig. 4). In 1992, a slow but steady trend increase in culls was observed in both clover systems. Few culls were observed the first and second harvests, but by later harvests (Fig. 5) more culls came from crimson clover than subterranean clover. In 1993 no significant differences in cull eggplant were seen (Fig. 6). The regression trend for eggplant rots in 1992 showed subterranean clover had slightly more rots than crimson clover but no significant differences were observed (Fig. 7). In 1993, a slightly higher trend toward rots came from crimson clover but the overall numbers were very low (Fig. 8).

Regression analysis of the 1992 marketable harvest data (Fig. 3) from the Little River Farm showed there was a slight but steady increase in marketable eggplant with crimson clover producing less than subterranean clover. The largest amount picked was never more than five for subterranean clover and three for crimson clover. Comparing the number of marketable eggplant over harvest periods showed no fruit until the second and later pickings. In 1993 yields were severely reduced due to dry conditions. No marketable eggplant were harvested from the subterranean clover plots and only 1 fruit/harvest came from crimson clover (Fig.4). There were

55 essentially no cull (Figs. 5&6) or rot (Figs. 7&8) eggplant fruits harvested from either crimson clover or subterranean clover during 1992-93. The regression trend showed only a slight rise indicating 1-2 cull or rot fruit from the last harvest.

Regression trends from the Hodnett Farm for the 1992 marketable eggplant data showed that the two clovers had no yields until after the second harvest, when both began a steady increase

(Fig. 3). Crimson clover had slightly higher numbers of fruit/harvest than did subterranean clover.

The trend for 1993 was similar for the crimson clover but virtually no marketable yields were observed from subterranean clover (Fig. 4). There was no trend for eggplant culls from crimson clover in 1992 as the line remained at zero for all harvests (Fig. 5). A slight upward trend was observed for culls in subterranean clover identical to the conventional production trend. Regression trends for culls in 1993 were reversed. No trend was indicated by the subterranean clover while a small increase in culls/harvest was indicated by the crimson clover regression trend (Fig. 6). A slight increase in rots was seen from both sustainable systems in 1992, but there was no difference in trends as the regression lines had identical slopes (Fig. 7). No trend was evidenced for rots in

1993, as few rots were harvested from the sustainable production systems (Fig. 8).

Regression trends from the Blackshank Farm for the marketable yields showed a large difference between years. In 1992 the crimson clover system produced very few eggplant until the last two harvest periods when a steep rise in yields was noted, while the subterranean clover system continued a trend of steadily increasing yields in all four harvests (Fig. 3). No distinguishable trend could be determined by the yields in 1993 for either sustainable system except for a slight rise observed from subterranean clover (Fig. 4) during the last harvest. Cull regression trends showed a tendency for both clover systems to produce more cull eggplant during the last two harvests in 1992 (Fig. 5). This trend was reversed in 1993 when the clovers yielded essentially no cull eggplant (Fig. 6). No distinguishable trends from the rot eggplant data occurred

56 in either year in the clover systems. Rot numbers (~1/harvest) increased slightly in the crimson clover system toward the latter part of season 1993 (Fig. 8).

Conventional Production

More marketable eggplant came from this system during 1992-93 than either sustainable system regardless of location. Yields from the Horticulture Farm averaged 632 and 564 cartons/acre equivalent to 23.2 and 21 t/ha (Table 1). There was an 12 percent decline in yield in 1993, probably because of dry weather, but it was not as severe as the 380 and 111 percent decrease seen with the clovers. At the Little River Farm, the 746 carton yield was well above the state average of 500 cartons. In 1993 yields had increased by 111 to 857 cartons which reflected a 672 percent gain (Table 1). However, at the Hodnett Farm, the differences in yields between the conventional and the best yielding sustainable production system (crimson clover) were not as great as at the previous two locations (Table 1). Increases in the number of cartons/acre were observed from both in 1993. The 1992 marketable yield data from the Blackshank Farm showed no significant differences among production systems. In 1993, a yield increase of 201 cartons to

460 cartons/acre or 129 percent, was 340 more cartons of marketable eggplant than the best sustainable yields from crimson clover (Table 1). Significant differences were also observed in unmarketable eggplant yields from the

Horticulture Farm when compared to the sustainable system. There was more unmarketable fruit harvested from the conventional than the crimson clover system in 1992-93. In 1993 there was a large increase of 189 cartons of unmarketable eggplant harvested from the conventional system.

This represented an increase of 420 percent compared to 116 and 227 percent increases in the sustainable clovers (Table 2). Unmarketable yields from the Little River Farm were not significantly different from the subterranean clover system in 1992 nor the crimson clover system in 1993 (Table

2). There were no significant differences in unmarketable yields between the conventional and sustainable systems in 1992 from the Hodnett Farm, but there were significantly more unmarketable

57 fruit in 1993 in the conventional system (Table 2). Unmarketable yields from the Blackshank Farm were only significantly different among systems in 1993, when the conventional system produced more fruit than the sustainable systems (Table 2).

The cull eggplant data observed from the Horticulture Farm seemed to follow the same trend as the unmarketable data. More culls came from the conventional system than the sustainable for both years, with a 230 percent increase seen in 1993 (Table 3). Significant differences in eggplant cull yields from the Little River Farm was observed between the conventional and sustainable systems for both 1992-1993 (Table 3). More culls were harvested in 1993 relative to 1992. At the Hodnett Farm when the cull eggplant data was evaluated for 1992, it followed the same trends as the total unmarketable data of that year. No significant differences in cull yields were observed between production systems. In 1993, no significant differences were observed between the conventional and crimson clover systems (Table 3). No significant differences were observed at the Blackshank Farm for eggplant culls, rots or insect damaged yields in 1992, but differences among them were seen in 1993. The conventional system produced more of culls and rots than either sustainable system.

There was no significant difference in eggplant rot yields for 1992 from the Horticulture

Farm between the conventional and crimson clover systems. In 1993, rots jumped to 121 cartons which was a 109 carton or a 908 percent increase (Table 4). At the Little River Farm there was no differences detected between systems for eggplant rots in 1992 (Table 4). In 1993, the conventional and crimson clover systems had significantly more rots than the subterranean clover system (Table 4). No significant differences were observed for eggplant rots in 1992 from the

Hodnett Farm in either production system. However, in 1993, there was a significant difference in the conventional system for rots (Table 4).

No insect damaged eggplant were harvested in 1992 from the Horticulture Farm. In 1993 no significant differences were observed between systems even though more insect damaged fruit

58 came from the conventional plots (Table 5). At the Little River Farm, no insect damaged eggplant came from the conventional plots in 1992 (Table 5), but 8 cartons were harvested in 1993. The trend of no insect damaged eggplant being harvested from the conventional production system in

1992 or 1993 was also observed at the Hodnett Farm (Table 5). Regression trends for marketable eggplant for both years at the Horticulture Farm was similar in that the numbers of fruit per harvest continued a steady increase until mid-season, then declined (Figs. 3&4). The trend for the cull eggplant suggested that in 1992 very few eggplant harvested were culls as the regression line started at .5 cull/harvest and remained that way throughout the season (Fig. 5). A few more culls were indicated in 1993 as the regression line showed a slight rise with each harvest period (Fig. 6). The regression for eggplant rots in 1992 shows the trend of greater numbers coming from the conventional system than either of the sustainable systems. Most were harvested in the middle of the season and then declined after then

(Fig. 7). More rots tended to come from the sustainable systems in 1992. The conventional regression line showed a very small rise until the second harvest and then the incidence of rots declined to zero the remainder of the season (Fig. 7).

Regression trends for marketable eggplant from the Little River Farm showed a steady rise in numbers/harvest in 1992. The number of marketable fruit increased by 5 each harvest, compared to the sustainable systems that increased by only one fruit (Fig. 3). In 1993 the trend showed a decrease in marketable yields each harvest period (Fig. 4). The regression trend for cull eggplant showed a steep rise from the second harvest period until the end of the season (Fig.

5). This indicated that the conventional system showed more of a trend to produce cull eggplant with each succeeding harvest than did either sustainable system. In 1993 the cull yields reflected the opposite trend. There were few cull eggplant harvested and the regression line remained horizontal throughout the season (Fig. 6). The data for the eggplant rots indicated a very slight trend for an increase of rots each harvest in 1992 (Fig. 7). In 1993, the regression line for rots

59 remained horizontal and no trend to increase was indicated (Fig. 8). At the Hodnett Farm, regression analysis of marketable eggplant yields for both years showed similar trends. There was a steady increase in numbers of fruit/harvest that continued the entire season each year (Figs. 3&4).

A slight trend of increasing culls/harvest was detected from the 1992 yield data. The regressions for the conventional and subterranean clover culls had similar slopes which were difficult to distinguish (Fig. 5). In 1993, the trend from crimson clover showed no culls were observed until after the second harvest period. After that, there was a steady rise until the end of the season (Fig.

6). There was a slight but steady rise in the regression trends for rots. The trend from the conventional system was the same as the crimson clover system in 1992 (Fig. 7). Slightly more rots/harvest was indicated from the conventional production system regression trend of the 1993 data (Fig. 8).

The Blackshank Farm regression trends of marketable yields in 1992 showed a steady rise in numbers/harvest (Fig. 3). In 1993, the trend indicated no yield increases/harvest (Fig. 4). The cull trends suggested a slight increase in culls/harvest in 1992, while in 1993 more of a steady rise in culls/harvest was indicated (Fig. 6). Very distinctive trends were evidenced from the eggplant rot yields. No trend was evident in 1992 while in 1993 the number of rotted fruit was higher at the first harvest and then decreased sharply for each harvest period (Fig. 8).

DISCUSSION

A. Eggplant Yields Eggplant yields seemed to reflect location and treatment effects throughout the study. The farms with the more productive soils (Horticulture and Little River) had higher marketable yields than either Hodnett or Blackshank. The Hodnett Farm had less productive soils and needed higher fertilizer inputs than the other locations, and that was reflected by lower yields both years. There were problems getting the clover cover crops established there and weeds were able to come in and crowd out the cover crop as well as compete with the eggplant transplants. Subterranean

60 clover was difficult to manage throughout the study at most of the sites. The growth habit caused it to produce a dense thick mat. Even though it was treated with glyphosate (Roundup®) at bed preparation, the clover grew back and was too competitive for the eggplant transplants. Much time was spent hand cutting holes into the clover to allow the eggplant to establish. The slower growth induced later fruit production compared to plants from crimson clover. Yield decreases in 1993 were thought to be the result of dry weather that supplemental irrigation did not ease. The increase in irrigation only succeeded in depleting any residual nitrogen that was available in these sandy soils by essentially washing it through the root zone. As a result plant growth slowed down in mid season and yields declined even with one fertilizer application of approximately 45.4 kg/ha (10-10-

10 N-P-K) to the clover systems. At each location during 1992-93 the conventional system with the higher production inputs had greater marketable yields than the sustainable systems. Crimson clover was the best yielding of the sustainable systems. Loss of plant stand in 1992 by black cutworm at two of the four sites contributed to poorer yield results. The clover apparently helped create a favorable habitat for these soil dwelling insects (Chalfant and Musick, 1979). Subterranean clover was the poorer yielding system due in part from the competition of the clover with the eggplant resulting in slower growth and lower yields. However, dry weather in 1993 was a major contributing factor in the yield declines observed from the clover systems offsetting the promising results of 1992.

Subterranean clover also tended to produce higher incidences of rots which may have indicated a build up of disease organisms. From previous research (Brunson, 1991; Sumner, 1987) it was observed that larger populations of rot causing organisms can inhabit soils in which legumes are grown. Once the fruit touches the soil surface, it can then be invaded by such organisms. Mature eggplants would bend the plant’s branches with the increasing weight and usually did come into contact with the soil surface.

The different soil types and cropping histories at the four locations also seemed to be a factor in the production of marketable yields. Locations with more productive soils produced

61 higher yields in both the sustainable and conventional systems. However, when the comparison of yields by system was evaluated a wide gap was detected between them. Conventional marketable yields from the Horticulture and Little River Farms were at least twice that of the best sustainable system, crimson clover. At the Hodnett and Blackshank Farms where the soils were less productive, the yield differences appeared to be smaller. It was interesting to see that crimson clover and the conventional system were about equal as far as the number of cartons produced.

The purposed advantages of higher input production modeled by the conventional system

(Granberry, 2000) didn't occur at those farms.

Percent marketable yield results showed that crimson clover and the conventional system had similar ratings in 1992 and displayed similar declines in 1993. This seemed to indicate that the quality of fruit was comparable between the two systems. While there was a greater amount of total overall yields associated with conventional production the percent that was unmarketable still remained similar to crimson clover. This was somewhat surprising because without the use of pesticides it might have been expected that crimson clover would have had many more unmarketable eggplant than the conventional system.

Regression trends between the production systems indicated regardless of location the conventional eggplant were harvested earlier and in greater numbers than the sustainable systems which was advantageous in securing higher prices at market. The trends also indicated that by mid season the crimson clover system had begun to catch up to the conventional but the subterranean clover never did. For the most part very few culls or rots came from the sustainable systems while trends indicated the number of culls/harvest increased proportionally to the number of marketable eggplant from the conventional system, which is what would have been expected from high input commercially grown eggplant (Granberry, 2000). The conclusion that can be drawn is that the conventionally grown eggplant with the higher fertilizer inputs, were growing faster than the sustainable plants with a the amount of fertilizer. It may be that supplemental fertilizer should have

62 been applied to the sustainable eggplant because the legume cover crops could not supply enough nitrogen on their own for consistent plant growth.

CONCLUSION

This study demonstrated several strengths and weaknesses prevalent to both production systems. The main strength concerning the sustainable system was it improved soil productivity and conservation by using overwintering legume cover crops. Soil is a non-renewable resource because once productivity is lost, it can’t be replaced. Sustainable production promotes conservation tillage and in so doing also promotes soil productivity. Conservation tillage is beneficial because it saves soil, fuel, time, labor, machinery, permits timely planting, maintains or slightly increases yields, is cost-effective, increases soil organic matter, soil moisture, irrigation efficiency, improves soil quality, water quality, wildlife habitats, reduces runoff and meets the 1990

Farm Bill requirements. Another strength of the sustainable clover systems was the environmental impact demonstrated by reductions or eliminations of pesticide and fertilizer applications. This has the potential to reduce pesticide residues in food crops as well as groundwater contamination by fertilizer runoff. Using overwinter legume cover crops as “insectories” helped maintain populations of beneficial insects that helped control pest insects. Even with small plot research where insects are subject to outside interference, we were still able to control pests.

There were weaknesses associated with the sustainable production system. The study was conducted with no pesticide use to determine what, if any, additional inputs would be needed. It was thought that careful monitoring of the clover systems would catch potential problems early enough so that remedial action could be taken. This was not always successful as major problems with weeds and fertility occurred. Weeds grew in the middle of the subsoiled beds along with the eggplant and became too competitive. However, this could be eliminated by adapting production practices to include crop rotations and banded applications of herbicide in the row. The sustainable crops tended to mature later than the conventional system which from a market point

63 of view was a disadvantage. This could be corrected by timeliness in fertilizer applications that would not greatly effect input costs. Other weaknesses were the potential for increases in soil diseases and nematodes from soils where legume cover crops were grown. In order to control soil diseases, crop and site rotation as well as occasional use of fungicides could be initiated. Deep turning every few years with a moldboard plow would bury old residue that harbor disease causing organisms. It was thought nematodes could be successfully controlled by incorporating non-host crops into the rotation. Velvetbean, sunn hemp, sesame, corn and sorghum have been cited as potential rotation crops and had been used with encouraging results.

Weaknesses and strengths also existed in the conventional production system. A key weaknesses was the high input of pesticides and fertilizers and their effect on the environment.

Consumers have continued to voice concerns over pesticide residues in food and contamination of groundwater resources. Use of insecticides eliminated the benefits of predatory insects and lack of cover (weed or cover crop) reduced favorable habitats. Even with pesticide usage, weeds

(nutsedge) and insect pests (Colorado Potato Beetle) continued to plague the conventional production system. Conservation tillage was usually not practiced and soil productivity can be more easily lost over time compared to sustainable production. Another weakness was that input costs were higher that would effect smaller growers with limited capital. Conventional production was not as energy efficient as sustainable production. Specialized machinery and more trips over the field increased machinery wear and fuel usage. Some strengths of conventional production was earlier crop maturity compared to the sustainable systems. This was a distinct advantage from a profit and market viewpoint. There was little competition from insects, diseases, nematodes or weeds early in the season allowing the eggplant transplants to establish faster than the sustainable systems. The eggplants had sufficient fertilizer to be able to produce a uniform crop throughout the season. There was no shade effect

64 from cover crops or weeds on the eggplants to retard growth or keep soils from warming up in the spring.

LITERATURE CITED

Brunson, K.E. 1991. Winter cover crops in the integrated pest management of sustainable cantaloupe production. M.S. thesis. University of Georgia.

Bugg, R.L., F.L. Wäckers, K.E. Brunson, J.D. Dutcher and S.C. Phatak. 1991. Cool-season cover crops relay intercropped with cantaloupe:influence on a generalist predator, Geocoris punctipes (Hemiptera:Lygaeidae). J. Econ. Entomol. 84(2):408-416.

Chalfant, R. B. and G. J. Musick. 1979. Influence of habitat modifications and multiple cropping on insect populations in vegetable and row crops in the eastern United States. (ed.) T. Kommedahl. In: Proceedings of Symposia IX International Congress of Plant Protection: Vol.1. August 5-11, Washington, D.C. p.57-60.

Coastal Plain Experiment Station. Local Weather Records, 1969-Present. Unpublished meteorological data maintained by Statistical and Computer Services support unit, The University of Georgia Agricultural Experiment Station, Tifton, Georgia, 1993.

Granberry, D. 2000. Eggplant. Georgia Coop. Ext. Ser. Cir. No. 812. Athens, Georgia.

Langston, D.B. Jr. 2001. Vegetables. Pg. 16. In: 1999 Plant Disease Loss Estimates. J.L. Williams-Woodward (ed). University of Georgia Cooperative Extension Service Circular Path 99-002.

Phatak, S.C., R.L. Bugg, D.R. Sumner, J.D. Gay, K.E. Brunson and R.B. Chalfant. 1990. Cover crops in IPM of weeds, diseases, and insects of vegetables. XXII Intern'l. Hort. Cong. Aug. 27-Sept. 1, 1990. Florence, Italy, Abstr. Paper No. 3239.

Sumner, D.R., 1987. Root diseases in crops following legumes in conservation tillage systems. In: J. F. Power [ed.]. The role of legumes in conservation tillage systems. Proc. of a Nat'l. Conf., Univ. GA, Athens. April 27-29, 1987. Soil Conservation Soc. Amer.

SAS Institute Inc. 1989. SAS/STAT User's Guide. Ver. 6. Fourth Ed., Vol.1. Cary, N.C., 943 pp.

United States Department of Agriculture-Soil Conservation Service. Soil Survey, Tift County Georgia. April 1983.

65 Table 2.1 Influence of location and production system on marketable eggplant yields. 1992† 1993‡ Location Production System T/Ha y % Mktable v Ctns /A y z T/Ha y % Mktable v Ctns /A y z Hort. Hill Crim. Clvr. 11.1 b 91 300 b 5.2 b 60 142 b Subclover 10.1 b 82 274 b 2.1 b 61 57 b Conv.(Rye) 23.2 a 93 632 a 21.0 a 71 564 a Little River Crim. Clvr. 1.6 b 74 43 b 14.1 b 69 384 b Subclover 4.6 b 69 126 b 1.2 c 68 33 c Conv.(Rye) 27.4 a 93 746 a 32.0 a 78 857 a Hodnett Crim. Clvr. 4.2 ab 87 117 ab 7.3 b 66 199 b Subclover 1.3 b 67 35 b 1.3 c 59 35 c Conv.(Rye) 8.8 a 88 212 a 14.3 a 68 388 a Blackshank Crim. Clvr. 8.9 a 92 242 a 4.4 b 66 120 b Subclover 3.7 a 83 99 a 2.6 b 70 71 b Conv.(Rye) 9.5 a 90 259 a 17.0 a 74 460 a † Based upon three harvests. ‡ Based upon four harvests. y Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. v Marketable harvest / total harvest (marketable + unmarketable) x 100. z Ctns /A, where a carton is equivalent to 1 1/9 bushel crate (33 lb.).

66 Table 2.2 Influence of location and production system on unmarketable eggplant yields. 1992† 1993† Location Production System T/Ha ‡ % Unmkt v Ctns/A‡ T/Ha ‡ % Unmkt v Ctns/A‡ y y

Hort. Hill Crim. Clvr. 1.1 b 9 30 b 3.6 b 41 98 b Subclover 2.3 a 18 62 a 1.4 b 39 134 b Conv.(Rye) 1.7 ab 7 45 ab 8.6 a 29 234 a Little River Crim. Clvr. .5 b 25 15 b 6.3 a 31 171 a Subclover 2.0 a 30 55 a .6 b 33 16 b Conv.(Rye) 2.1 a 7 57 a 9.0 a 22 246 a Hodnett Crim. Clvr. .7 a 13 18 a 3.8 b 34 103 b Subclover .6 a 33 18 a .9 c 41 24 c Conv.(Rye) 1.1 a 12 30 a 6.6 a 32 184 a Blackshank Crim. Clvr. .8 a 8 22 a 2.3 b 34 62 b Subclover .7 a 17 21 a 1.1 b 30 30 b Conv.(Rye) 1.1 a 10 30 a 6.0 a 26 163 a † Culls, rots and insect damaged fruit pooled. ‡ Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different. v Unmarketable / total harvest (marketable + unmarketable) x 100. y Ctns/A, where a carton is equivalent to 1 1/9 bushel crate (33 lb.).

67 Table 2.3 Effect of location and production system on eggplant cull yields. 1992† 1993‡ Location Production T/Ha y % Culls v Ctns/Az T/Ha y % Culls v Ctns/Az System Hort. Hill Crim. Clvr. .7 a 6 19 a 1.5 b 17 41 b Subclover .8 a 7 23 a .5 b 13 12 b Conv.(Rye) 1.2 a 5 33 a 4.0 a 14 109 a Little River Crim. Clvr. 0 b 2 1 b 3.3 b 16 91 b Subclover .2 b 3 5 b .5 c 26 13 c Conv.(Rye) 1.2 a 4 33 a 6.0 a 14 157 a Hodnett Crim. Clvr. .3 a 5 7 a 3.1 a 28 85 a Subclover .2 a 11 6 a .8 b 33 19 b Conv.(Rye) .6 a 7 17 a 4.0 a 19 107 a Blackshank Crim. Clvr. .8 a 8 22 a 2.0 ab 27 48 ab Subclover .5 a 12 15 a .5 b 14 14 b Conv.(Rye) .7 a 7 19 a 3.0 a 13 83 a † Based upon three harvests. ‡ Based upon four harvests. y Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different. v Culls / total harvest =(marketable + unmarketable [culls, rots, insect damaged fruit]) x 100. z Ctns/A, where a carton is equivalent to 1 1/9 bushel crate (33 lb.)

68 Table 2.4 Eggplant rot yields influenced by location and production system. 1992† 1993‡ Location Production System T/Ha y % Rots v Ctns/Az T/Ha y % Rots v Ctns/Az Hort. Hill Crim. Clvr. .4 b 3 11 b 2.0 b 24 57 a Subclover 1.4 a 12 39 a .9 b 26 24 b Conv.(Rye) .4 b 2 12 b 4.4 a 15 121 a Little River Crim. Clvr. .5 a 24 14 a 2.4 a 12 64 a Subclover 1.0 a 16 28 a .1 b 6 3 b Conv.(Rye) .9 a 3 24 a 3.0 a 7 81 a Hodnett Crim. Clvr. .4 a 8 11 a .6 b 5 16 b Subclover .2 a 11 6 a .2 b 8 5 b Conv.(Rye) .4 a 5 13 a .3 a 13 77 a Blackshank Crim. Clvr. 0.0 a 0 0 a .5 b 8 14 b Subclover .2 a 5 6 a .6 b 16 16 b Conv.(Rye) .4 a 4 11 a 3.0 a 12 77 a † Based upon three harvests ‡ Based upon four harvests y Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. v Rots / total harvest (marketable + unmarketable [culls, rots, insect damaged fruit]) x 100. z Ctns/A, where a carton is equivalent to 1 1/9 bushel crate (33 lb.).

69 Table 2. 5 Eggplant insect damage influenced by location and production system. 1992† 1993‡ Location Production System T/Ha y Ctns/Az T/Ha y Ctns/Az Hort. Hill Crim. Clvr. .00 a 0 a .00 a 0 a Subclover .00 a 0 a .00 a 0 a Conv.(Rye) .00 a 0 b .20 a 4 a Little River Crim. Clvr. .00 b 0 b .61 a 16 a Subclover .80 a 22 a .00 b 0 b Conv.(Rye) .00 b 0 b .30 ab 8 ab Hodnett Crim. Clvr. .00 b 0 b .09 a 2 a Subclover .20 a 6 a .00 a 0 a Conv.(Rye) .00 b 0 b .00 a 0 a Blackshank Crim. Clvr. .00 a 0 a .00 a 0 a Subclover .00 a 0 a .00 a 0 a Conv.(Rye) .00 a 0 a .10 a 3 a † Based upon three harvests ‡ Based upon four harvests y Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. z Ctns/A, where a carton is equivalent to 1 1/9 bushel crate (33 lb.).

70 Fig. 2.1 Daily Temperature and Rainfall - Coastal Plain Experiment Station 1992

71 72 Fig. 2.2 Daily Temperature and Rainfall - Coastal Plain Experiment Station 1993

73 74 Fig. 2.3 Comparing regression trends of marketable eggplant yields in 1992 from

Horticulture Hill, Little River, Hodnett and Blackshank Farms conventional and

sustainable production systems.

75 76 Fig. 2.4 Comparing regression trends of marketable eggplant yields in 1993 from

Horticulture Hill, Little River, Hodnett and Blackshank Farms conventional and

sustainable production systems.

77 78 Fig. 2.5 Comparison of regression trends of eggplant culls in 1992 from Horticulture

Hill, Little River, Hodnett and Blackshank Farms conventional and sustainable

production systems.

79 80 Fig. 2.6 Comparison of regression trends of eggplant culls in 1993 from Horticulture

Hill, Little River, Hodnett and Blackshank Farms conventional and sustainable

production systems.

81 82 Fig. 2.7 Comparison of regression trends of eggplant rots in 1992 from Horticulture

Hill, Little River, Hodnett and Blackshank Farms conventional and sustainable

production systems.

83 84 Fig. 2.8 Comparison of eggplant rots in 1993 from Horticulture Hill, Little River,

Hodnett and Blackshank Farms conventional and sustainable production systems.

85 86 CHAPTER 3

INFLUENCE OF LOCATION AND PRODUCTION SYSTEM ON SEASONAL

INSECT POPULATIONS, WEEDS, NEMATODES, ROOT DISEASE AND

PLANT STAND IN CONVENTIONAL AND SUSTAINABLE EGGPLANT 1

______

1 Brunson, K.E. and S.C. Phatak. 2002. To be submitted to J. Alternative Agri.

87 ABSTRACT Insect populations were monitored in both production systems by visual plant inspection and shake sampling methods. Very small numbers of pest and beneficial insects were observed although the shake sampling method did recover more species than the visual inspections.

Colorado potato beetle and tarnished plant bug caused more damage to plants in the conventional system due a lack of predatory insects, compared to the sustainable system which supported a greater diversity of insects resulting in minimal damage to plants or fruit. Weed species and populations were significantly different according to soil type-location and production system. Several herbicides were used in the conventional system to control weeds, while the sustainable system relied on the ground cover provided by the two legume cover crops.

These were not plowed under in contrast to the winter rye cover crop and provided good early season weed control. When the clovers began to senesce in early summer, one application of herbicide was used to help control perennial grasses. In contrast, serious problems occurred each year in the conventional plots with overwhelming amounts of nutsedge. At three of the four sites, it became thick enough to essentially retard further growth of the eggplant plants themselves.

Little root disease or root galling was observed on eggplant from sampling at any of the four locations. Root disease and root gall ratings differed between years and production system.

Subterranean clover had the greatest amount of root discoloration and galling. Crimson clover was never more than 2 = slight on a scale 1-5. The scale was based upon visual estimation of % root discoloration or root galling (Sumner and Bell, 1982). Loss of plant stand in the sustainable plots was attributed to black cutworm damage, evident during the 1992 season. Eggplant had to be replanted twice in the crimson clover plots at the Little River and Horticulture Farms. This was not the case in 1993 as minimal cutworm damage was observed. Velvetbean was incorporated into the rotation after the 1992 season to try to offset southern root-knot nematode infestations. Initial soil samples revealed populations at the three of the four locations were extremely high in the

88 sustainable clovers. However, root gall indices were insignificant. In 1993 soil samples from three of the four locations where velvetbean had been planted showed decreases in root-knot nematode from the sustainable clovers. The results comparing the soils samples from the two production systems seemed to indicate that velvetbean was just as effective as nematicides at suppressing root- knot nematode populations. Differences in plant stand establishment in the sustainable system was attributed to location, insect, weed and cover crop competition. In the conventional system where fungicides had been applied soilborne diseases affected plant stand. Higher root disease ratings from the clovers were consistent with previous data that suggested fungal pathogen populations increased in legume cover crops. However, overall only slight root disease and discoloration was observed.

INDEX WORDS: Eggplant, Solanum melongena L., Seasonal Insect Populations,

Weed Cover, Weed Species, Weed Diversity, Velvetbean, Root-Knot

Nematode, Root Discoloration, Soilborne Diseases.

INTRODUCTION

In Georgia, crop losses from soil insects, aphids and thrips totaled $72 million in 1992

(Adams and Chalfant, 1992). The majority ($57 million) went directly to loss from insect damage, while approximately $15.4 million were estimated control costs. Research was needed to investigate how these costs could be reduced without increasing pesticide usage. It was unknown what the effect cropping sequences and cover crops would have on beneficial and pest insect complexes until research by Bugg and Wilson (1989) and Bugg et al. (1990b) showed that cover crops afforded suitable habitats for generalist predators. These predators could subsist on alternate food sources such as pollen and nectar (Rodgers, 1985) afforded by the cover crops and thus be in “place” to control pest insects. By employing cover crops as insectories, crops of cucumbers, cantaloupes and peppers were grown without use of insecticides (Phatak et al, 1990; Brunson,

1991).

89 Losses in vegetable production from weeds can be substantial. It was estimated to be $36

million annually for control measures and actual losses to weeds (WSSA, 1992). Cover crops could be used to suppress weeds either by “smothering” or allelopathy (Phatak, 1987, 1988;

Putnam, 1990a). Living mulches were investigated by Bugg et al. (1991) and Brunson (1991) as a means of managing weeds in vegetable production in the southeast. Mulches such as subterranean and crimson clovers suppressed weeds by blocking light and provided good early season weed control. These living mulches gradually died out during the warmer months and little competition for nutrients or water was observed.

Soilborne pathogenic fungi are limiting factors in the production of vegetables in the southern United States (Sumner et al., 1983, 1986a, 1986b, 1988). Rhizoctonia solani, Pythium myriotylum, P. aphanidermatum, and P. irregulare are the most virulent pathogenic fungi that cause pre- and post-emergence damping-off in vegetables. Sclerotium rolfsii causes root, hypocotyl and stem rot. The influence of different winter cover crops on the natural biological control of Rhizoctonia solani and subsequent root disease severity has not been investigated, although it is known that Rhizoctonia-like fungi antagonistic to Rhizoctonia solani were common in Georgia Coastal Plain soils (Sumner and Bell, 1982). Southern root-knot (Meloidogyne incognita Kofoid and White) and other nematodes can cause severe yield losses in vegetables

(Johnson, 1982; Brunson, 1991). Infected plants that do not die may be stunted and unthrifty because of 1) lesions caused by fungi on primary or secondary roots, hypocotyls, stems or, 2) nematode galls on roots. Control of nematodes in commercial vegetable production hinges upon the use of preplant applications of a limited number of fumigants or restricted non-fumigant nematicides (Rodríguez-Kábana et al., 1992a; Johnson et al., 1992). However, these chemicals may not be available for future use because of concerns over pesticide use on food crops and pollution in the environment. Therefore growers have been prompted to look for alternative nematode control measures. One alternative is using crops that are non hosts of Meloidogyne spp.

90 in crop rotations. Corn, cotton and sorghum have been used in rotation with peanuts and soybeans to aid in the management of root-knot nematode problems (Johnson, 1982; Rodríguez-Kábana and Ivey, 1986; Rodríguez-Kábana et al., 1987; Rodríguez-Kábana and Touchton, 1984).

Velvetbean (Mucuna deeringiana L.) is another crop that had shown promise in suppressing root- knot nematode when incorporated into rotations with peanuts (Rodríguez-Kábana et al., 1992a;

Rodríguez-Kábana et al., 1992b). Velvetbean is not a host for M. incognita, M. arenaria, M. javanica or H. glycines and when used in crop rotations with peanuts, increased yields 47% compared to peanut monocultures (Rodríguez-Kábana et al., 1992a). Velvetbean had been used in the southern United States since the late 19th century as a forage and cover crop (McSorley and

Gallaher, 1992; Phatak and Brunson, 1993; Weaver et al., 1993). Its value as a crop for managing root-knot nematode has been known for a long time (Watson, 1922).

There were several objectives we wanted to explore based on this study. The first one was to see if there would be variations in pest complexes of insects, weeds, nematodes and root disease associated with the different production systems, as well as the four locations with differing soil types. This was a key point since the sustainable systems employed no pesticides on the vegetable crop. Secondly, we were interested in the effect velvetbean would have in vegetable management to reduce root-knot nematode. We wanted to incorporate velvetbean into the rotation associated with the sustainable production system and compare the nematode populations with the conventional production in which nematicides were employed as a management tool.

Thirdly, we wanted to evaluate incidences of root disease between the sustainable system where no fungicides were applied with the conventional system in which fungicides were applied.

91 MATERIALS AND METHODS

A. Land Preparation - Field trials were conducted following the same procedures previously mentioned.

Sustainable Production Insect control was obtained by using cool-season cover crops that provided habitats for beneficial insects. No pesticides were applied to the vegetable crop to control pests. Weed control was achieved by a combination of mulch and contact grass herbicides. The clovers had begun to naturally die back in early summer and thus provided a mulch which inhibited weed growth. An optional, late-season shielded application of the contact herbicide (sethoxidim; Poast®) was necessary on the clover strips if grassy weed infestations became serious. Nematode control in these eggplant systems has formerly been attained by fall applications of soil-incorporated nematicides. Non-chemical nematode control was initiated in the 1993 season by planting velvetbean as a fall green manure prior to clover seedlings.

Conventional Production

The rye system was typical of conventional eggplant production systems being utilized in the region. Rye was drilled as a cover crop in October of the previous year, deep-turn plowed as green manure in the spring, and eggplants are transplanted into the bare ground beds. Pest control

(disease, insect, nematode, and weed) was primarily achieved by applications of chemicals prior to transplanting and continuing throughout the production season. Weeds were controlled with mechanical cultivation. Subsequent pesticide and fertilizer inputs were from the University of

Georgia Cooperative Extension Service recommendations for eggplant (Granberry, 2000).

B. Insect Populations Seasonal insect populations were sampled following methods resulting from previous research (Brunson, 1991). Colonization, buildup and movement of beneficial predatory insects were assessed by whole plot visual inspection and shake sampling of the eggplant foliage.

92 Beginning on 25 April, visual inspections of the plants occurred weekly for 8 weeks at the Little

River and Hodnett Farms which were examples of high and low productivity situations. The procedure involved an observer walking the borders of the plots and enumerating insects seen within. Shake-sampling of eggplant foliage was also evaluated at the Little River and Hodnett

Farms. A 91.4 cm x 61 cm shake cloth was placed beneath the sample 5 plants (5.6 m2 area) and the foliage shaken. Any insect, pest or beneficial, that fell onto the cloth were identified, counted and returned to the plot. Adults and nymphs of tarnished plant bug (Lygus lineolaris [Palisot de

Beauvois]), bigeyed bug (Geocoris punctipes Say), stinkbug (Negara sp.), and adults, larvae and pupae of Coccinellidae (ladybeetles) were pooled for data analysis for both visual estimations and shake samples. Aphid numbers were transformed to a rating system for ease of analysis. Aphid populations were rated on a scale of 0 to 5, where 0 = <10, 1 = 11-30 individuals, 2 = 31-50 individuals, 3 = 51-70 individuals, 4 = 71-100 individuals, and 5>100 individuals (L. Chandler, per. comm.).

C. Weed Cover and Species Diversity

Weed populations were evaluated at each location and production system starting six weeks after planting (~May 25) and after the final harvest. Percent weed cover was estimated visually for each 22.67 m2 plot. At each location, weeds per plot were also identified by species after the final harvest. Percent weed cover/plot was analyzed by analysis of variance (ANOVA) and means separated by Duncan's Multiple Range Test (P=.05). Analysis was then used to separate ANOVA percent weed cover means into location times treatment effects.

D. Nematode Assays

Soil samples (30 cores, 15 cm deep, 2.5 in. diameter) were taken in April and August of each year from each plot at each location. Soil was composited, thoroughly mixed, subdivided and stored at 5-7o C for assays for nematodes and soilborne fungi. Soil for nematode assays was shipped to the University of Georgia Cooperative Extension Service Nematology Laboratory in

93 Athens and processed by the centrifugal-flotation method (Jenkins, 1984). All data was analyzed by analysis of variance (ANOVA) and ranked by Duncan's Multiple Range Test at .05 level. Proc

Duncan (SAS Inc., 1989) procedures were then used to analyze location times treatment

(production system) effects. After the final harvest, five random eggplant were dug from each plot in each production system and the roots rated for galls on a scale of 1 = no galls, 2 = 1-25%, 3

= 26-50%, 4 = 51-75% and 5 = 76-100% of the roots galled (Sumner and Bell, 1982).

E. Root Disease and Plant Stand Evaluations The same five plants dug at random to evaluate percent root galling were used to judge root discoloration and disease severity based on a 1-5 scale, where 1 = <2%, 2 = 2-10%, 3 = 11-

50%, 4 = >50% discoloration and decay and 5 = dead plant (Sumner and Bell, 1982). Stand counts were taken three weeks after planting and after the final harvest. All data was analyzed by analysis of variance (ANOVA) and ranked by Duncan's Multiple Range Test (P=.05). Means were further separated into location times treatment (production system) effects using Proc Duncan procedures (SAS Inc., 1989).

RESULTS

A. Insect Populations Pest and beneficial insect populations from both production systems were estimated by visual plant inspection and shake sampling of the eggplant foliage. Plant inspections occurred during both 1992-93, while shake sampling was conducted in 1992 only. Each sampling method was effective for specific kinds of insects based upon previous work by Bugg et al. (1991) and

Brunson (1991). The two farms sampled were examples of high and low productivity situations.

It was not known whether this would be a factor in determining differences among insect populations. Twelve different species of arthropods were observed from visual inspections in

1992-93. Of these, bigeyed bug (Geocoris punctipes [Say]), tarnished plant bug (Lygus lineolaris [Palisot de Beauvois]), colorado potato beetle (Leptinotarsa decemlineata [Say]),

94 coccinellids, aphids, and other plant hoppers (Homoptera: Cicadellidae [Oncometòpia sp. F.]

"Sharpshooters") were the most numerous.

Sustainable Production

The visual inspection data of 1992 from the Little River Farm did not reveal significant differences between the clovers for any insect, pest or beneficial. Extremely low numbers of geocoris, colorado potato beetle, lygus and coccinellids were observed (Table 1). No population trends between clover production systems was detected. In 1993 low numbers of Coccinellids

(ladybeetles) were observed from visual inspection. Observations of insects from visual inspections from the Hodnett Farm in 1992 showed no significant differences between clover systems. The

1993 data also showed a large increase in colorado potato beetle. No significant differences were detected among production systems for coccinellids or geocoris (Table 2).

Shake sampling from the Little River Farm recovered more species and in larger amounts than visual inspection. Higher numbers of geocoris, lygus and colorado potato beetle were collected relative to visual inspection (Table 3). Stinkbugs, loopers and thrips were observed where they had not previously been seen from visual inspection. Geocoris was the only insect that occurred in significantly greater numbers in the subterranean clover system. Coccinellids, lygus, colorado potato beetle, stinkbugs and loopers all occurred in significantly greater numbers in the crimson clover system (Tables 3&4). The results of shake sampling from the Hodnett Farm showed the same trend as at the Little River Farm in that subterranean clover continued to be significantly different from crimson clover for Geocoris in 1992 (Table 4). Crimson clover had more aphids, stinkbugs, thrips and sharpshooter hoppers but none were significantly different.

Conventional Production Visual inspections in 1992-3 from the Little River Farm showed colorado potato beetle to be highly significant within this production system (Tables 1&2), even with weekly use of insecticides. The trend seemed to be for this insect to make appearances earlier every year and

95 to stay later (S. Phatak, per. obs.). Coccinellids were not significantly different except in subclover but was the only other insect besides the colorado potato beetle seen in the conventional system in 1993. Colorado potato beetle was only observed in significant numbers from visual inspection in 1992-93 from the Hodnett Farm. It was first sampled in the conventional plots in 1992, (Table

1) but by 1993 it had spread to both production systems (Table 2). Coccinellids were seen in low numbers in 1992 (Table 1) and none were observed in 1993.

Shake sampling within this system resulted in low occurrences of insect populations at the

Little River Farm (Tables 3&4). Most of the sampling data showed very low numbers of insects and no population trend was established. Geocoris occurred in numbers less than those observed from the subclover but were greater than those of the crimson clover (Table 3). The shake sampling results from the Hodnett Farm showed that more different kinds of species were observed but overall numbers were very low with no significant differences.

B. Weed Cover and Species Diversity Percent weed cover was visually estimated by an observer and analyzed for treatment

(production system) and (location times treatment) effects. There were differences between location, production system and year. More weed cover was observed in crimson clover than in either the subterranean clover or the conventional plots (Table 5) in 1992. In 1993 the results were opposite 1992. Significantly more weed cover occurred in the conventional production system than in the clover systems. The average percent weed cover was not different between the crimson clover system and the conventional system, but both were significantly different from subterranean clover.

Sustainable Production Weed cover at the Horticulture Farm was greater in crimson clover than in subterranean clover in 1992 but there were no differences in 1993 (Table 6). At the Little River site, crimson clover had significantly greater weed cover than subterranean clover and the conventional system

96 in both years (Table 7). Crimson clover was not different from subterranean clover for percent weed cover in 1992 or 1993 at the Hodnett Farm, but there was a large decrease in the amount of weed cover in 1993 (Table 8). The crimson clover averaged significantly more weed cover than subterranean clover. The Blackshank Farm showed no significant differences between clover systems for percent weed cover within year (Table 9).

The sustainable systems appeared to have greater weed species diversity than the conventional system based upon the number of species observed from the Horticulture Farm. Two more weed species were sampled from the crimson clover plots than the subterranean clover plots in 1992. Red clover (Trifolium pratense L.) was seen only in crimson clover while large crabgrass (Digitaria sanguinalis L.) appeared in both clovers (Table 6). In 1993 three less weed species were observed from crimson clover but of the six, two species were new observations — sicklepod (Cassia obtusifolia L.) and prickly sida (Sida spinosa L.). Three weed species were observed in subterranean clover, a decline of six species from the 1992 data. Prickly sida had not been previously identified from the1992 observations.

Twelve weed species were identified from the clover systems at the Little River Farm during the two year study. Species diversity was higher in 1992 than 1993 (Table 7). Eight species were identified from crimson clover and seven from subterranean clover. Cuphea sp.,

Florida pusley (Richardia scabra L.), spotted spurge (Chamaesyce maculata L.) and Statice

(Limonium sp.) were species observed just from crimson clover in 1992. Cutleaf evening primrose, Oxalis sp. and volunteer canola (from previous trials) were endemic to subterranean clover. By 1993, only two species were observed from the sustainable systems. The volunteer

Cuphea had become the prominent weed in both, while crabgrass (Digitaria sp.) was specific to crimson clover.

The Hodnett site had displayed the most weed species diversity of all the locations in 1992 but by 1993 this was greatly reduced (Table 8). In 1992 seven species were identified from

97 crimson clover and ten were found in subterranean clover. Of these, crabgrass and cutleaf evening primrose were specific to crimson clover. Statice, Florida pusley, Florida beggarweed

(Desmodium tortuosum ), chickweed (Stellaria media L.), sicklepod, spotted spurge and large flower morningglory (Ipomoea purpurea L.) were specific to subterranean clover. In 1993 only four species were observed from crimson clover. Three of them, (Florida pusley, Florida beggarweed, volunteer millet) had not been seen previously. Subterranean clover was reduced from ten weed species to two, with crabgrass being a new observation. Subterranean clover had greater diversity in weed species than crimson clover at the

Blackshank Farm (Table 9). Eight total species were identified both years. Oxalis sp. was observed only from crimson clover while carpetweed and purslane were observed only from subterranean clover in 1992. Ivyleaf morningglory (Ipomoea hederacea L.), prickly sida and crowfootgrass (Dactyloctenium aegyptium L.) were observed only from subterranean clover in

1993. This location also had the only occurrence of two species of morning glory.

Conventional Production

This system from the Horticulture Farm had significantly greater percent weed cover than subterranean clover, but not crimson clover in 1992 (Table 6). There was a slight increase in percent weed cover in 1992 and it was significantly greater than either of the sustainable systems.

The average percent weed cover was significantly greater than either sustainable system.

No significant differences were observed between the conventional and subterranean clover systems from the Little River Farm for percent weed cover either year (Table 7). However the conventional data was much lower than the sustainable data even though a slightly higher percent weed cover was observed in 1993. Percent weed cover differed significantly between years at the Hodnett Farm. In 1992 there were fewer weeds present than in either sustainable system. The situation was reversed in

1993 when a large increase in the amount of weed cover was observed (Table 8), significantly

98 more than in the clover systems. The average percent weed cover was significantly greater than in the subterranean clover system, but not different from the crimson clover system. Weed cover at the Blackshank Farm increased from 1992 to 1993 within the conventional system, and in 1993 was significantly greater than the subterranean system (Table 9). There was little weed species diversity observed in the conventional system at the

Horticulture Farm compared to the sustainable systems (Table 8). The most troublesome weed seen both years was yellow nutsedge (Cyperus esculentus L.). It grew voraciously even with herbicide use and did appear to effect overall growth of the eggplants from mid-season to the final harvest (K. Brunson, per. obs.). Cutleaf eveningprimrose and prickly sida were the other two species observed. Weed species were also less diverse at the Little River Farm when compared to the sustainable systems. Seven species were identified from the conventional plots over the two years compared to twelve from the sustainable plots (Table 7). Cuphea and yellow nutsedge were identified from the conventional plots both years. Statice, volunteer canola and redroot pigweed

(Amaranthus retroflexus L.) were observed in 1992 but were replaced by volunteer peanuts and crabgrass in 1993. Higher weed species diversity was observed at the Hodnett Farm site than the previous two locations. Eleven weed species were identified in 1992. Cudweed (Gnaphalium sp.), annual sedge (Cyperus compressus L.) and carpetweed (Mollugo verticillata L.) were specific to the conventional system. A reduction was seen in 1993 as only four species were identified. Except for crabgrass the three remaining species were found only in the conventional system (Table 8).

At the Blackshank Farm weed species diversity differed between years. Six species were identified in 1992 and five in 1993. Yellow nutsedge and redroot pigweed were the only two weeds observed both years. Crabgrass, cutleaf eveningprimrose and Florida pusley were specific to 1992 while ivyleaf morningglory, prickly sida and crowfootgrass were specific to 1993.

99 C. Nematode Assays

Sustainable Production

Populations of nematodes were distinctively different between production systems from the four locations (Table 10). There were more nematodes in the sustainable clovers in 1992 at

Horticulture Hill, but there were no significant differences at the other locations. A comparison of nematode numbers by production system showed subterranean clover supported greater populations than crimson clover at all locations. In 1993 the results were significant in that major decreases in nematode populations were observed at two of the four locations. The largest change

(decrease) in population occurred at the Horticulture Farm while the greatest change (increase) appeared at the Hodnett Farm. No significant differences were detected between the sustainable clovers for nematode numbers in 1992 or 1993.

Root gall indices in 1992 indicated slight or no root galling within the sustainable systems but significant increases were detected from subterranean clover at the Horticulture and Little River

Farms (Table 10). No significant differences were observed at either the Hodnett or Blackshank

Farms. In 1993 subterranean clover increased galling at three of the four locations. Increases in root gall ratings were observed for subterranean clover at all locations, and differences were significant. The Hodnett Farm was the only location where root gall ratings approached a moderate level (10-25%). Five random plants evaluated for moderate or greater root galls were re-evaluated for per cent root gall (Table 10). There was very little injury in 1992 but in 1993 a greater percentage of the plants had moderate ratings, especially at the Little River and Hodnett

Farms. Subterranean clover had significantly more plants rated moderate at the Little Farm than crimson clover but the Hodnett Farm had the highest number of plants rated moderate.

Conventional Production

Significantly lower root-knot nematode populations levels were observed from this system compared to the sustainable systems at Hort Hill in 1992. In 1993 levels had increased at all farms

100 except the Blackshank Farm (Table 10). Root gall indices were indicative of a no to moderate (0-

25%) gall rating during both years of observations. Hodnett Farm had the highest percentage of plants whose root gall ratings were above 2.

D. Root Disease and Plant Stand Evaluations

Sustainable Production

Differences in eggplant plant stand within the clovers was evident during 1992. At the

Blackshank Farm subterranean clover (Table 11) had fewer plants than in crimson clover, while the reverse occurred at the Little River Farm. In 1993 crimson clover significantly increased stand compared with subterranean clover at the Little River Farm, but the reverse was true at the

Blackshank Farm. Root disease ratings were none to slight in 1992 with no significant differences being detected between the clovers (Table 11). By 1993, increases in root disease ratings were observed at all farms, and subterranean clover significantly increased ratings compared with crimson clover the Little River Farm.

Conventional Production

No significant differences were detected in stand in 1992 at any of the locations, but there were more dead plants in the conventional system than in the crimson clover system at the Little

River Farm (Table 11). In 1993, fewer plants were observed within the conventional system compared to one or the other sustainable clovers at three farms. No significant root disease ratings could be detected in 1992 between the conventional and sustainable systems because ratings were very low (Table 11). In 1993 slight increases were seen in crimson clover compared with the conventional system at the Hort Hill and Hodnett Farms.

101 DISCUSSION

A. Insect Populations

It was thought insect populations would be distinctive between production systems because of the differing philosophies concerning pesticide usage. Sustainable systems rely on beneficial insects to help control pests while conventional systems usually employ pesticides as management practices. Whole plot visual inspections can be useful in determining what initial populations might exist (Bugg et al., 1991; Brunson, 1991). However there are distinct disadvantages. Highly mobile insects, i.e. adult bigeyed bugs and tarnished plant bugs, are easily alarmed and take flight during visual inspection. They can be readily observed on cover crops such as rye and mustard where crop height improves the samplers ability to spot the insects. They cannot be easily observed in low growing, bushy crops such as subterranean clover. Bugg et al. (1990b) had shown from longitivity and fecundity studies that subterranean clover was not a preferred host of tarnished plant bug. Conversely, visual inspection can be useful with brightly colored insects such as coccinellids or colorado potato beetle. The lack of data from the two years of observations would seem to indicate the insects had taken flight or that there were not many to begin with. Very low numbers of insects except colorado potato beetle in the conventional system were observed in 1992. In

1993 colorado potato beetle had moved into the sustainable plots and was the only insect observed in significant numbers. There was little or no occurrence of the other insects that had been sampled from those plots in 1992. The dry weather was thought to be a contributing factor by reducing plant moisture that made leaf surfaces unattractive.

Of the two techniques employed, there were greater representations of insect populations in shake sampling. This sampling technique will pick up fast moving insects and those that can't be easily seen in low growing cover crops like subterranean clover. Bigeyed bugs and tarnished plant bugs can be more readily detected using shake sampling. Shake sampling can adequately account for nymphs and adults while whole plot visual estimates generally do not account for nymphs which

102 tend to be more difficult to see. Sampling of tall crops, such as rye and mustard can also present problems. Some insects tend to feed on flowers (Rodgers, 1985) and developing grain on the end of elongated stalks, while others prefer plant parts closer to the ground. On such large plants, shake sampling can not adequately enumerate insects. Another sampling method that is effective in determining absolute populations is vacuum sampling or “Dee-Vac” as it is commonly known.

The problem encountered within the sustainable plots was that this method actually damaged the young clover stands as well as crushing any insect unlucky enough to be on the leaves.

Identification of such was then not only time consuming but almost impossible. Also, the aim of the other methods was not to harm the insects but to release them (especially beneficials) back into their habitats. One should be aware of the biology and behavior of the target insect, as well as the growth patterns of the plants, and design sampling techniques to meet the need of the situation.

Shake sampling was discontinued in 1993 due to time constraints and that the method eventually damaged taller growing eggplants. No differences were evident in numbers of species between the two locations sampled. A more diverse pest and beneficial insect population was harbored by the sustainable systems. While the appearances of tarnished plant bug and colorado potato beetle may have indicated serious problems this was not the case in the sustainable systems.

Tarnished plant bug (Lygus lineolaris Palisot de Beauvois) is primarily a pest but it has been documented that it can also feed on soft bodied insects such as corn earworm or aphids

(Cleveland, 1987; Knight, 1941). It has also been shown that subterranean clover is not a preferred host of tarnished plant bug (Bugg et al., 1990b). Other predatory insects living in the cover crops were able to keep pests reduced and minimal insect damaged eggplant was harvested.

Actual predation of the colorado potato beetle larvae by two-spotted stinkbugs (Pentatomidae:

Perillus bioculatus F.) was seen (K. Brunson, per.obs.). However, colorado potato beetle continued to plague the conventional system resulting in plant damage even though insecticides were being applied weekly. No other insect except Colorado potato beetle was observed in the

103 conventional plots. This was an indication that: 1) everything, whether pest or beneficial, had been killed by insecticides; 2) lack of cover, whether it was weeds or clovers, resulted in a reduction of favorable habitats. The conventional plots did not have the benefit of living cover crops that predatory insects could hide in which would also help explain the lack of insect populations.

B. Weed Cover and Species Diversity

Visual observations for percent weed cover taken six weeks after planting showed significant differences between production systems. This is a critical time in seedling establishment because competition from weeds for space and nutrients can result in eventual yield decreases

(Granberry, 2000). It was thought the sustainable clovers would be able to suppress weeds by competition and/or produce a “smothering” effect in place of herbicides (Putnam, 1990a; Phatak,

1992).

The Hodnett Farm had the greatest amount of percent weed cover regardless of production system. The poorer soils and lower pH did not result in good clover establishment.

This allowed opportune weeds to move in and choke out what cover crop was left. Marginal land may need much higher inputs of lime and fertilizer than was originally thought. They may even surpass conventional inputs which might not be feasible for small farm operations with limited capital. The other locations followed a trend of higher percent weed cover observed in the sustainable systems than the conventional systems in 1992. Then in 1993 either by selection or the weed seed bank, the situation was reversed and the conventional had significantly greater weed cover than the clovers. The use of triflurilin (Treflan®) as a pre-plant herbicide in the conventional system was not effective at some of the more weedier locations. Subterranean clover showed the least amount of weed cover at either location when compared to crimson clover during the two year study. It was known for its "smothering competitive growth habit" and that was an advantage in early season weed control in previous research (Brunson, 1991; Phatak et al., 1990). More weed problems were observed in crimson clover than expected. It was thought the clover would

104 have provided more of a “smothering” effect but once it began to senesce, perennial grasses moved in. However in 1992, the increase in weeds was mainly due to loss of plant stand by cutworms.

More weeds were observed growing within the strip killed middle of the beds that had been prepared for planting than had been seen in the subterranean clover beds. The rationale for identifying weed species per location and production system was to be able to have an idea where potential problems might occur. Each location sampled seemed to harbor at least one weed that was specific to the area. Most of them were broadleaf plants. That complicated any herbicide use to the extent that eggplant was also a broadleaf and any herbicide sprayed to kill the weed would also kill the eggplant. Since regular herbicide use was not considered part of the sustainable management philosophy, fast growing cover crops were instead relied upon to "smother" weed competition (Putnam, 1990a). However, as seen by the data, this did not always occur. It was hoped regular inspection of the locations and plots would allow any weed problems to be caught early enough for remedial action. The Hodnett Farm was a prime example of how too many weeds could ultimately effect crop yields. Compared to the other farms, there were more species diversity and more weed problems. Land areas where vegetables had not been grown before had not experienced the selection pressures associated with such production. A greater emphasis on herbicides would probably be needed before an acceptable weed balance was achieved for vegetable production to be considered sustainable. Even when herbicides were used as in the conventional system, some weed species diversity existed. The main conclusion to be made concerning the conventional production system was it still had serious weed problems, sometimes to the extent that hand labor had to be employed in order to achieve optimum plant growth. Yellow nutsedge was not controlled by Treflan® and it ultimately began to overtake the plots. Cultivation and additional herbicide spray applications were no longer feasible once the eggplant were 33 cm tall. In essence very little could have been done to alleviate the weed. The

105 situation seemed to further point out the benefits of using "living mulch" cover crops in where the nutsedge may have been eliminated by competition or reduced to an acceptable level of infestation.

C. Nematode Assays

Sustainable Production The 1992 data reflects nematode populations prior to incorporating velvetbean into the rotation. Fenamiphos was applied in 1991 before seeding of the cover crops as part of the management practice. No fenamiphos was applied in 1992. Significant differences were only observed from the Horticulture Farm. This location had a long history of production of vegetables that were hosts of the root-knot nematode. The other locations had fewer nematodes present but highest populations still occurred within the sustainable systems. Root-knot nematode populations were low from crimson clover at the Little River Farm compared to the rest of the locations. A possible explanation was that the plant stand had been decimated in the first two replications by black cutworm thereby reducing susceptible hosts. Subterranean clover appeared to produce higher populations than crimson clover. This trend was observed before in previous research

(Brunson, 1991). Since root-knot nematode has a broad host range, Rothrock and Hargrove

(1988) stated that they could easily parasitize and maintain high populations in winter legumes and then be in place to infect major summer crops. Nematodes are most active in warm temperatures

(Minton, 1986) and Rothrock and Hargrove (1988) also documented how the warm sandy soils of the Coastal Plain were ideal for nematode development and pathogenesis. The idea that long cropping sequences of nematode susceptible crops will produce high populations is supported by comparing the Hodnett and Horticulture Farms. Very low nematode populations were observed at the Hodnett Farm because less susceptible crops, such as corn and sorghum, had been the cropping sequence.

Velvetbean was incorporated into the rotation after the last eggplant harvest in August

1992. Soil samples from 1993 showed significant decreases in population at the Horticulture Farm

106 that were thought to be a direct effect of velvetbean. Vicente and Acosta (1987) documented that velvetbean can produce alkaloids through root exudates that will exert a suppressive effect on

Meloidogyne sp. While no significant differences were detected at the other locations, decreases in populations were still observed from subterranean and crimson clover at the Little River and

Blackshank Farms. Hodnett Farm was the only location where velvetbean did not seem to have an effect. It appears that the data reflected the aftermath of a season of nematode attracting crops.

Successive seasons of velvetbean may have to be evaluated from this location in order to make any further conclusions as to whether it could be an effective tool. This holds true for the rest of the data that is presented. The results are inconclusive because they are based upon one season.

However, the changes in population were so dramatic that continued research is justified. With large nematode populations in 1992 it was expected that the root systems would have been severely damaged. However, the data showing the percentage of root galls on eggplant never got above a rating of 2 which was equivalent to no galling. Significant differences in root gall ratings were noted in subterranean clover from the Horticulture and Little River Farms, while at the

Hodnett and Blackshank Farms no significant differences were observed. These results may have been an effect of fenamiphos that was applied in 1991 before seeding of the cover crops as part of the management practice. No fenamiphos was applied in 1992 because velvetbean was introduced into the management scheme, yet there was more galling than in 1992. Significant differences occurred between subterranean and crimson clover at the Horticulture and Little River

Farms. Eggplant is normally a susceptible host and can be severely affected by root-knot nematode which was contradictory to the 1992 results. However, it has been shown that

Meloidogyne sp. have such broad host ranges that Trivedi and Barker (1986) proposed it would not be inconceivable to think host-specific or even crop-specific races could occur. That may have happened in 1993 when the overall gall ratings were approaching moderate levels at three of the four locations and several of the five random plants examined had moderate or greater galling.

107 Conventional Production Lower root-knot nematode populations were observed in the conventional system than the sustainable clovers in 1992, probably because of the effect of fenamiphos (Nemacur 4L).

Significant differences between this system and the sustainable clovers were only observed at the

Horticulture Farm. Fenamiphos was again used in 1993 to control root-knot nematode. No significant differences were observed at any of the locations. However, it was interesting to note population levels at three locations increased in spite of fenamiphos applications. The Blackshank

Farm had a decrease but it was approximately the same amount observed in crimson clover. More research comparing the two production systems needs to be done but from the data presented, velvetbean appeared to be as effective as fenamiphos in suppressing root-knot nematode. There was no galling at any of the locations in 1992, but galling was only reduced significantly compared with subterranean clover at the Horticulture and Little River Farms. As mentioned previously, winter legumes could be easily parasitized by root-knot nematode in the warmer temperatures of the Southeast and thus the nematodes could have been in place to attack summer crops. No significant differences occurred with crimson clover and surprisingly the root- gall indices were similar. In contrast, root gall ratings were significantly higher compared with crimson clover at the Little River Farm and lower compared with crimson clover at the Blackshank

Farm in 1993. When plants were individually evaluated for root galls, there appeared to be some that had moderate or greater ratings even though fenamiphos had been used. This was more evident at the Hodnett Farm that observed the most root galling of 1993.

D. Root Disease and Plant Stand Evaluations

Sustainable Production No pesticides were used to control possible soilborne diseases that would affect stand and ultimately yields either year. It was known from previous research (Brunson, 1991; Sumner et al.,

1994) that legumes tended to host higher populations of Rhizoctonia solani, Pythium

108 myriotylum, P. aphanidermatum, and P. irregulare that cause dampen-off diseases in vegetables. However, the problems resulting in loss of stand in 1992 did not seem to be disease related. The worst loss occurred in crimson clover at the Little River Farm because of infestations of black cutworm. The competitive nature of subterranean clover was the cause of poor stand establishment at Little River, Hodnett and Blackshank Farms in 1992. Plants had to be replanted at these locations. Cutworm damage was minimal in 1993 and good stand establishment was observed in crimson clover at three of the locations. Weed competition resulted in lower plant stand at the Blackshank Farm. No plants were replaced in 1993 at any location.

Plants were rated for root disease and discoloration in order to evaluate how lack of fungicides contrasted to conventional fungicide usage. The rating system was comparable to the one indicated for percent root galling. Since soil fungicides such as Terrachlor® (PCNB

[pentachloronitrobenzene]) were not applied, it was thought that Rhizoctonia solani, and

Sclerotium rolfsii would have caused major crop losses. Previous work (Rothrock and

Hargrove, 1987; Sumner, 1987; Brunson, 1991) had documented the tendency of legume cover crops to harbor high levels of soilborne pathogens. However, soil samples collected during this study were not examined for fungal populations due to time constraints so it was unknown whether this trend continued. Very little root disease was present in 1992 in either sustainable system. No significant differences were detected between location or clovers. Observations in 1993 showed higher root disease ratings that were found to be significantly different at three of the locations. The highest root disease ratings were at the Hodnett Farm and ratings were similar to the ratings for root gall. Why that location had the higher ratings is unknown because vegetables had not been grown there previously and the soils were the least productive. It does seem however, that the overall increase in root disease was a result of the build up of soilborne pathogens in legumes.

109 Conventional Production Soil fungicides were not used in this system but instead foliar applications of chlorothalonil

(Bravo®) were initiated. Plant stand was comparable to crimson clover during 1992 but greater than subterranean clover. Populations of yellow nutsedge (Cyperus esculentus L.) competed with the plants throughout the season at the Blackshank Farm. Weeds were also the cause of the decline in stand observed at the Little River Farm but instead of nutsedge Cuphea and Linmonium spp. were the problems. The 1993 stand counts indicated fewer plants than in the sustainable clovers survived because of diseases or weeds. Incidences of soilborne disease were noticed only in the conventional plots. Initial fungal populations were unknown. Southern blight (Sclerotium rolfsii) frequently attacked eggplant growing in the thick stands of yellow nutsedge (Brunson, per.obs.). Increased soil moisture and shade conditions at the soil surface were optimum for this pathogen. The amount of S. rolfsii was negligible initially but as the season progressed the pathogen was visible in most of the plots. It was assumed there would be little root disease associated with this system because of the use of fungicides, and root disease levels were low. Essentially no disease or discoloration was observed in 1992. In 1993 more significant differences were detected between the two production systems, but differences varied among locations. Slightly higher root disease ratings and root-knot galling were seen at the Little River and Hodnett Farms. Therefore it seems that the previous crop and not the production system may be primarily responsible for differences in levels of damage by root pathogens.

CONCLUSION

A. Insect Populations Seasonal insect populations were distinctive between production systems because of the differing philosophies concerning pesticide usage. Sustainable systems rely on beneficial insects to help control pests while conventional systems usually employ pesticides as management

110 practices. The use of insecticides in the conventional production system as well as the lack of suitable habitats for predatory insects resulted in more colorado potato beetle and tarnished plant bug damage to the conventionally grown eggplant than to the sustainable eggplant. There were more diverse insect populations observed from the sustainable systems and these predators helped to keep insect damage minimal. Comparisons between the two sampling methods showed shake sampling was more efficient at recovering greater numbers of insects than did visual whole plot inspection. Insects that would hide under leaves or were fast moving would be captured more easily. However, it was a time consuming technique that resulted in plant damage if the foliage was shaken too vigorously. The strength of visual inspection was it was less labor intensive as well as less time consuming. This might be important to small growers with limited labor resources and capital. However, the data this technique revealed was limited in that only certain types of insects could be sampled. Fast moving insects and those that hide under leaves would be missed.

B. Weed Cover and Species Diversity Comparisons of percent weed cover between the sustainable and conventional productions systems indicated that there was good early season weed control afforded by the legume cover crops. The cover crops reduced weed populations either by shading, i.e. crimson clover, or by

“smothering competition” evidenced from subterranean clover. Weed cover was also distinctive at each location. Crimson clover tended to have higher weed cover percentages than did subterranean clover, yet was similar to the conventional system where Treflan® herbicide had been applied. However, once the cover crops began to sense in early summer, perennial grasses presented serious enough competition that limited applications of Poast® herbicide were made.

This can be a weakness of sustainable production. However, banded applications of herbicide in the bed middles may be what is needed to help reduce late season weed competition. The conventional production system had more problems with populations of yellow nutsedge than did the sustainable system. While Treflan® was effective as a pre-plant herbicide, it did little against

111 nutsedge. The competition from this weed appeared to effect overall growth of the eggplant plants as the season progressed. Nutsedge would need to be controlled by herbicides other than Treflan.

Weed species diversity was greater within the sustainable production systems as more different kinds of species were observed. Even so, the amount of percent weed cover that was estimated did not increase. Each location also had specific weed species populations distinctive to the site and cropping histories. This would be useful information in planning future management strategies for sustainable production. Knowing what the weed seed bank or weed species were composed of would give growers an idea of potential problems, and thus be better prepared to control them either biologically or chemically.

C. Nematode Assays There appeared to be specific location effects because more root-knot nematode and root galling was observed at the Hodnett Farm. Marginal land such as this may be a higher risk regardless of production system. Incorporating velvetbean into the rotation did reduce nematode populations. The most dramatic change occurred at the Horticulture Farm where vegetables susceptible to nematode hosts, had been in production for many years. Root-knot populations did not decrease as much at the other locations, and there were even large population increases at some locations. It is premature to make conclusions based on one season's data, but it appears velvetbean was as effective a nematode suppressant as conventional chemicals. Root gall ratings were low in 1992 and the increases observed in 1993 were attributed to the tendency of winter legumes to support greater nematode populations. However, overall root gall indices were still low throughout the study. Further research with velvetbean will be needed especially at locations like the Hodnett Farm to determine if this type of root-knot management is feasible.

D. Root Disease and Plant Stand Evaluations

Problems with establishing a good plant stand appeared to be associated with the sustainable system initially and it too seemed to be location related. Stand establishment within

112 subterranean clover was less successful than crimson clover. This cover crop was very aggressive even with knock-down applications of glyphosate (Roundup®). It has excellent early season weed control potential, but from the results of this study it was concluded further management studies need to be conducted. Interestingly enough no severe disease outbreaks caused by soilborne pathogens was evident in the clovers. Diseases could have been a problem because soil fungicides were not used, but root disease ratings were minimal in 1992 with slight increases noted in 1993.

The 1992 results appeared to be as good as the conventional system in which fungicides were applied. It is known legumes are more susceptible to soilborne pathogenic fungi and root-knot nematodes than some other crops. Therefore, stringent monitoring of root-knot nematode by yearly soil samples is advised, and soil treatments with fungicides may be needed to keep fungal pathogens at manageable levels.

Root-knot nematode in the conventional production system was controlled by nematicides and diseases by fungicides. In many cases no differences were detected between the conventional or sustainable systems. This was especially evident at the Hodnett Farm where increases in nematodes and disease occurred regardless of production system. At marginal locations no advantage over the sustainable system could be seen. With available pesticides becoming more scarce it can be concluded growers will have to find alternatives that conventional production systems do not currently offer.

LITERATURE CITED Adams, D.B. and R.B. Chalfant. 1992. Vegetable insects. Pp.49-65. In: Summary of losses from insect damages and costs of control in Georgia 1991. R.M. McPherson and G.K. Douce (eds.). Georgia Cooperative Extension Service Special Publication Num. 81, Sept. 1992. Athens, GA.

Brunson, K.E. 1991. Winter cover crops in the integrated pest management of sustainable cantaloupe production. M.S. thesis. University of Georgia.

113 Bugg, R. L. and L.T. Wilson. 1989. Ammi visnaga (L.) Lamarck (Apiaceae): Associated beneficial insects and implications for biological control with emphasis on the bell-pepper ecosystem. Biol. Agric. & Hort. 6:241-268.

Bugg, R.L., F.L. Wäckers, K.E. Brunson, S.C. Phatak, and J.D. Dutcher. 1990b. Tarnished plant bug, (Hemiptera:Miridae), on selected cool-season leguminous cover crops. J. Entomol. Sci. 25(3):463-474.

Bugg, R.L., F.L. Wäckers, K.E. Brunson, J.D. Dutcher and S.C. Phatak. 1991. Cool-season cover crops relay intercropped with cantaloupe:influence on a generalist predator, Geocoris punctipes (Hemiptera:Lygaeidae). J. Econ. Entomol. 84(2):408-416.

Chalfant, R. B. and G. J. Musick. 1979. Influence of habitat modifications and multiple cropping on insect populations in vegetable and row crops in the eastern United States. (ed.) T. Kommedahl. In: Proceedings of Symposia IX International Congress of Plant Protection: Vol.1. August 5-11, Washington, D.C. p.57-60.

Cleveland, T.C. 1987. Predation by tarnished plant bugs (Heteroptera:Miridae) of Heliothis (Lepidoptera:Noctuidae) eggs and larvae. Environ. Entomol. 16:37-40.

Granberry, D. 2000. Eggplant. Georgia Coop. Ext. Ser. Cir. No. 812. Athens, Georgia.

Jenkins, W.R. 1984. A rapid centrifugal-flotation technique for separating nematodes from soil. Plant Disease Reporter 48:692.

Johnson, A.W. 1982. Managing nematode populations in crop production. In: Nematology in the southern region of the United States. Southern Cooperative Series Bulletin 276. pp. 193- 203. Arkansas Agricultural Experiment Station, Fayetteville.

Johnson, A.W., A.M. Golden, D.L. Auld and D.R. Sumner. 1992. Effects of rapeseed and vetch as green manure crops and fallow on nematodes and soilborne pathogens. J. Nematol. 24(1):117-126.

Knight, H.L. 1941. The plant bugs or Miridae of Illinois. Bull. Ill. Nat. His. Sur. No. 22.

McSorley, R. and R.N. Gallaher. 1992. Comparison of nematode population densities on six summer crops at seven sites in North Florida. Supp. J. Nematology 24(4S): 699-706.

Minton, N.A. 1986. Impact of conservation tillage on nematode populations. J. Nematol. 18(2):135-140.

114 Phatak, S.C. 1987. Tillage and fertility management in vegetables. American Vegetable Grower 35(2):8-9.

Phatak, S.C. 1988. Integrating methods for cost effective weed control. pp. 24-25. In: Integrated Weed Management Symposium, Expert Committee on Weeds, Western Canada Sec. Mtg., Victoria, B.C.

Phatak, S.C., R.L. Bugg, D.R. Sumner, J.D. Gay, K.E. Brunson and R.B. Chalfant. 1990. Cover crops in IPM of weeds, diseases and insects of vegetables. XXIII Intern'l. Hort. Cong. Aug. 27-Sept. 1, 1990, Florence, Italy, Abstr. Paper No. 3239.

Phatak, S.C. and K.E. Brunson. 1993. Green Manuring. pp. 2-5. Georgia Organic Growers Association Newsletter. November 1993.

Putnam, A.R. 1990a. Vegetable weed control with minimal herbicide inputs. HortScience 25:155- 59.

Rodgers, C.E. 1985. Extrafloral nectar:Entomological implications. Bull. Entomol. Soc. Amer. 31(3):15-20.

Rodríguez-Kábana, R. and J. R. Touchton. 1984. Corn and sorghum as rotational crops for management of Meloidogyne arenaria in peanut. Nematropica 14:26-36.

Rodríguez-Kábana, R. and H. Ivey. 1986. Crop rotation systems for the management of Meloidogyne arenaria in peanuts. Nematropica 16:53-56.

Rodríguez-Kábana, R., H. Ivey and P.A. Backman. 1987. Peanut-cotton rotations for the management of Meloidogyne arenaria. J. Nematology 19:484-486.

Rodríguez-Kábana, R., J.W. Kloepper, D.G. Robertson and L.W. Wells. 1992a. Velvetbean for the management of root-knot and southern blight in peanut. Nematropica 22:75-80.

Rodríguez-Kábana, R., J. Pinochet, D.G. Robertson and L.W. Wells. 1992b. Crop rotation studies with velvetbean (Mucuna deeringiana) for the control of Meloidogyne spp. Supp. J. Nematology 24(4S):662-668.

Rothrock, C.S. and W.L. Hargrove. 1988. Influence of legume cover crops and conservation tillage on soil populations of selected fungal genera. Can. J. Microbiol. 34:201-206.

SAS Inst. Inc., 1989. SAS/STAT User's Guide; Ver. 6. Fourth ed., Vol. 1. Cary, N.C. 943 pp.

115 Sumner, D.R. and D.K. Bell. 1982. Root diseases of corn induced by Rhizoctonia solani and Rhizoctonia zeae. Phytopathology 72:86-91.

Sumner, D.R. and D.K. Bell. 1988. Antagonism of binucleate Rhizoctonia-like fungi and other basidomycetes to Rhizoctonia solani AG-4 and AG-2 Type 2. Phytopathology 78:629 (Abstr.)

Sumner, D.R., C.C. Dowler, A.W. Johnson, N.C. Glaze, S.C. Phatak, R.B. Chalfant and J.E. Epperson. 1983. Root diseases of cucumber in irrigated, multiple-cropping systems with pest management. Plant Dis. 67:1071-1075.

Sumner, D.R., D.A. Smittle, E.D. Threadgill, A.W. Johnson and R.B. Chalfant. 1986a. Interactions of tillage and soil fertility with root diseases in snap bean and lima bean in irrigated multiple-cropping systems. Plant Dis. 70:730-735.

Sumner, D.R., E.D. Threadgill, D.A. Smittle, S.C. Phatak and A.W. Johnson. 1986b. Conservation tillage and vegetable diseases. Plant Dis. 70:906-911.

Sumner, D.R., 1987. Root diseases in crops following legumes in conservation tillage systems. In: J.F. Power [ed.]. The role of legumes in conservation tillage systems. Proc. of a Nat'l. Conf., Univ. GA, Athens. April 27-29, 1987. Soil Conservation Soc. Amer.

Sumner, D.R., S.C. Phatak, J.D. Gay, R.B. Chalfant, K.E. Brunson and R.L. Bugg. 1995. Soilborne pathogens in a vegetable double-crop with conservation tillage following winter cover crops. Crop Protection 14:495-500.

Trivedi, P.C. and K.R. Barker. 1986. Management of nematodes by cultural practices. Nematropica 16:213-236.

Vicente, N.E. and N. Acosta. 1987. Effects of Mucuna deeringiana on Meloidogyne incognita. Nematropica 17:99-102.

Watson, J.R. 1922. Bunch velvet beans to control root-knot. Univ. Fla. Agric. Exp. Stn. Bull. 163:54-59.

Weaver, D.B., R. Rodríguez-Kábana and E.L. Carden. 1993. Velvetbean in rotation with soybean for management of Heterodera glycines and Meloidogyne arenaria. Supp. J. Nematol. 25(4S):809-813.

United States Department of Agriculture-Soil Conservation Service. Soil Survey, Tift County Georgia. April 1983.

116 Table 3.1 Effect of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and Coccinellids observed from visual inspections 1992.

0 ± / Five Random Plants† Location Production Geocoris‡ x Lygus ‡x Colorado Coccinellids ‡x System Potato Beetle ‡x Little River Crim. Clvr. 0.00±.00 a 0.00±.00 a 0.00±0.00 b 0.00±.00 a Subclover 0.25±.25 a 0.00±.00 a 0.25±0.25 b 0.00±.00 a Conv.(Rye) 0.25±.25 a 0.00±.00 a 5.75±2.53 a 0.00±.00 a Hodnett Crim. Clvr. 0.50±.50 a 0.00±.00 a 0.00±0.00 b 0.00±.00 a Subclover 0.00±.00 a 0.00±.00 a 0.00±0.00 b 0.00±.00 a Conv.(Rye) 0.00±.00 a 0.00±.00 a 2.25±2.63 a 0.25±.50 a †Data from visual inspection over 8 week period. ‡Data analyzed by analysis of variance (ANOVA) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. xAdults, nymphs and larvae counts pooled.

117 Table 3.2 Effect of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and Coccinellids observed from visual inspections 1993.

0 ± / Five Random Plants† Location Production Geocoris‡ x Lygus ‡ x Colorado Coccinellids ‡x System Potato Beetle‡ x Little River Crim. Clvr. 0.00±.00 a 0.00±.00 a 0.00±0.00 a 0.25±.71 b Subclover 0.00±.00 a 0.00±.00 a 0.00±0.00 a 0.63±.92 a Conv.(Rye) 0.00±.00 a 0.00±.00 a 2.13±2.53 a 0.25±.46 b Hodnett Crim. Clvr. 0.08±.29 ab 0.08±.29 a 8.66±9.22 a 0.08±.29 a Subclover 0.25±.62 a 0.00±.00 a 3.83±11.45 a 0.08±.29 a Conv.(Rye) 0.00±.00 b 0.00±.00 a 6.75±5.71 a 0.00±.00 a † Data from visual inspection over 8 week period. ‡ Data analyzed by analysis of variance (ANOVA) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. x Adults, nymphs and larvae counts pooled.

118 Table 3.3 Influence of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and Coccinellids recovered from 1992 shake sampling.

0 ± / Five Plants† Location Production Geocoris‡x Lygus ‡x Colorado Potato Coccinellids ‡x System Beetle‡x Little Crimson 0.17±.17 b 0.67±.33 a 1.33±.67 a 0.67±.37 a River Clover Subclover 1.44±.47 a 0.00±.00 b 0.33±.24 b 0.11±.11 b Conv. (Rye) 0.33±.19 b 0.08±.08 b 0.00±.00 b 0.00±.00 b Hodnett Crimson 0.25±.16 b 0.00±.00 a 0.25±.16 a 0.00±.00 a Clover Subclover 2.13±.64 a 0.00±.00 a 0.38±.18 a 0.00±.00 a Conv. (Rye) 0.13±.13 b 0.00±.00 a 0.00±.00 a 0.25±.25 a † Sample means from random 5.6 m2 (= 5 plants) / 22.67 m2 beds. ‡ Data analyzed by general linear model (GLM) and ranked by DMRT (P= .05); means followed by same letter are not significantly different. x Adults, nymphs and larvae counts pooled.

119 Table 3.4 Influence of location and production system on seasonal insect populations of Aphids, Stinkbugs, Loopers, Thrips, and Other Hoppers recovered from 1992 shake sampling.

x6 ± / Five Plants† Location Production Aphids ‡x Stinkbugs‡x Loopers ‡ Thrips ‡ Other System Hoppers ‡ Little Crimson 0.56±.18 a 0.89±.35 a 0.67±.33 a 0.11±.11 a 0.22±.15 a River Clover Subclover 0.44±.29 a 0.11±.11 b 0.00±.00 b 0.22±.22 a 0.00±.00 a Conven. 0.00±.00 b 0.08±.08 b 0.08±.08 b 0.00±.00 a 0.17±.11 a (Rye) Hodnett Crimson 0.00±.00 a 0.13±.13 a 0.00±.00 a 0.75±.75 a 0.88±.48 a Clover Subclover 0.50±.19 a 0.00±.00 a 0.00±.00 a 0.00±.00 a 0.50±.27 a Conven. 0.13±.13 a 0.00±.00 a 0.00±.00 a 0.00±.00 a 0.25±.16 a (Rye) † Sample means from random 5.6 m2 (= 5 plants) / 22.67 m2 beds. ‡ Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. x Adults, nymphs and larvae counts pooled.

120 Table 3.5 Influence of Sustainable and Conventional Production Practices on Weeds.

% Weed Ground Cover † Production System 1992 1993 Averag ‡ ‡ e Crimson Clover 29.7 a 22.2 b 25.6 a Subclover 21.0 b 18.7 b 19.9 b Conv. (Rye) 21.0 b 27.7 a 24.4 a † Data from visual ratings taken six weeks after planting of eggplant. ‡ Data averaged from 22.67 m2 area; analyzed ANOVA and ranked by DMRT (P=.05); means followed by same letter are not significantly different.

121 Table 3.6 Visual weed evaluations in sustainable and conventional eggplant production from the Horticulture Farm.

Visual Weed Evaluations / 22.67 m2 area†

% Weed Cover‡z Weed Species Present‡y

Production System 1992 1993 Avg. 1992 1993

Crimson Clover 26.4 a 10.0 b 18.2 b 1, 2, 3, 4, 5, 6, 7, 9, 10 1, 4, 5, 6, 11, 12

Subterranean Clover 17.3 b 16.3 b 17.6 b 1, 2, 3, 4, 5, 6, 7, 8 3, 4, 12,

Conv. (Rye) 26.4 a 28.1 a 27.1 a 2, 4 4, 12

†Data from visual ratings taken six weeks after planting crop. ‡Data averages of four replications/treatment. z Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different. y Weed Species: 1 - Crabgrass 7 - Carpetweed 2 - Cutleaf Evening primrose 8 - Large Crabgrass 3 - Annual Sedge 9 - Oxalis 4 - Yellow Nutsedge 10 - Red Clover 5 - Cudweed 11 - Sicklepod 6 - Redroot Pigweed 12 - Prickly Sida

122 Table 3.7 Visual weed evaluations in sustainable and conventional eggplant production from the Little River Farm.

Visual Weed Evaluations / 22.67 m2 area†

% Weed Cover‡z Weed Species Present‡y

Production System 1992 1993 Avg. 1992 1993

Crimson Clover 32.2 a 30.7 a 31.0 a 1, 2, 3, 4, 5, 6, 7, 8 1, 14

Subterranean Clover 18.1 b 25.5 b 20.3 b 3, 5, 6, 7, 9, 10, 11 1

Conv. (Rye) 11.1 b 16.3 b 14.7 c 1, 3, 8, 11, 12 1, 3, 13, 14

†Data from visual ratings taken six weeks after planting crop. ‡Data averages of four replications/treatment. z Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different.

y Weed Species: 1 - Cuphea 8 - Statice 2 - Florida Pusley 9 - Cutleaf Evening primrose 3 - Yellow Nutsedge 10 - Oxalis 4 - Spotted Spurge 11 - Volunteer Canola 5 - Crowfoot Grass 12 - Redroot Pigweed 6 - Chickweed 13 - Volunteer Peanut 7 - Carpetweed 14 - Crabgrass

123 Table 3.8 Visual weed evaluations in sustainable and conventional eggplant production from the Hodnett Farm.

Visual Weed Evaluations / 22.67 m2 area†

% Weed Cover‡z Weed Species Present‡y

Production System 1992 1993 Avg. 1992 1993

Crimson Clover 30.7 a 23.5 b 26.1 a 1, 2, 4, 5, 10, 12, 13 4, 8, 9, 15

Subterranean Clover 22.3 ab 16.3 b 19.3 b 3, 4, 5, 8, 9, 10, 11, 12, 1, 4 13, 14

Conv. (Rye) 19.7 b 31.3 a 26.0 a 2, 4, 5, 6, 7, 8, 9, 10, 1, 3, 13, 14 13, 14

† Data from visual ratings taken six weeks after planting crop. ‡ Data averages of four replications/treatment. z Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different. y Weed Species: 1 - Crabgrass 8 - Florida Pusley 2 - Cutleaf Evening primrose 9 - Florida Beggarweed 3 - Statis 10 - Large Crabgrass 4 - Yellow Nutsedge 11 - Chickweed 5 - Cudweed 12 - Sicklepod 6 - Annual Sedge 13 - Spotted Spurge 7 - Carpetweed 14 - Large flower Morningglory 15 - Volunteer Millet

124 Table 3.9 Visual weed evaluations in sustainable and conventional eggplant production from the Blackshank Farm.

Visual Weed Evaluations / 22.67 m2 area†

% Weed Cover‡z Weed Species Present‡y

Production System 1992 1993 Avg. 1992 1993

Crimson Clover 27.6 a 25.3 ab 26.0 ab 1, 2, 3, 4, 6, 9, 1, 3, 4, 8

Subterranean Clover 26.1 a 20.7 b 23.1 b 1, 2, 3, 4, 5, 6, 7, 8 1, 3, 4, 6, 8, 11, 12, 13

Conv. (Rye) 27.4 a 32.5 a 30.9 a 1, 2, 3, 4, 6, 10 4, 6, 11, 12, 13

†Data from visual ratings taken six weeks after planting crop. ‡Data averages of four replications/treatment. z Data analyzed by general linear model (GLM) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different.

y Weed Species: 1 - Crabgrass 8 - Florida Purslane 2 - Cutleaf Evening primrose 9 - Oxalis 3 - Small flower Morningglory 10 - Florida Pusley 4 - Yellow Nutsedge 11- Ivyleaf Moringglory 5 - Large Crabgrass 12 - Prickly Sida 6 - Redroot Pigweed 13 - Crowfootgrass 7 - Carpetweed

125 Table 3.10 Effect of production system and velvetbean (Mucuna deeringiana L.) on seasonal populations of southern rootknot nematode (Meloidogyne incognita Kofoid and White) in "Classic" eggplant.

Mean No. Juveniles Mean Root Gall % Plants with / 100 cc soil † Rating y Moderate or Greater Root Gall (>50%) z

Location Production 1992‡ 1993‡ Change in 1992‡ 1993‡ 1992‡ 1993‡ System Population‡y

Hort Hill Crim. Clover 2632.50 a 157.00 a - 2475.50 a 1.35 b 1.35 b 0.00 a 0.00 a

Subclover 2778.00 a 542.50 a - 2235.50 a 1.90 a 2.00 a 0.00 a 0.00 a

Conven. (Rye) 328.50 b 500.00 a + 171.50 b 1.00 b 1.15 b 5.00 a 0.00 a

Little River Crim. Clover 91.00 a 341.50 a + 250.50 a 1.00 b 1.10 b 0.00 a 0.00 b

Subclover 895.00 a 642.50 a - 250.50 a 1.75 a 2.50 a 0.00 a 20.00 a

Conven. (Rye) 131.50 a 409.00 a + 277.50 a 1.00 b 1.50 a 0.00 a 0.00 a

Hodnett Crim. Clover 9.00 a 848.50 a + 839.50 a 1.15 a 2.90 a 0.00 a 45.00 a

Subclover 47.50 a 880.00 a + 832.50 a 1.20 a 2.60 a 0.00 a 40.00 a

Conven. (Rye) 3.00 a 411.50 a + 408.50 a 1.00 a 2.30 a 0.00 a 15.00 b

Blackshank Crim. Clover 554.00 a 354.00 a - 200.00 a 1.10 a 1.60 a 5.00 a 5.00 a

Subclover 626.50 a 635.00 a + 8.50 a 1.20 a 1.85 a 5.00 a 0.00 a

Conven. (Rye) 442.00 a 244.00 a - 198.00 a 1.05 a 1.10 b 5.00 a 0.00 a † Samples taken in August after final harvest of each year. ‡ Data analyzed by analysis of variance (ANOVA) and ranked by DMRT (P=.05); means followed by the same letter are not significantly different. y - indicates a reduction in population between years; + indicates an increase in population between years. z Average of 5 random plants / 22.27 m2 bed; rating 1=no galling (0-2%), 2=slight galling (2-10%) , 3=moderate galling (10-25%), 4=severe galling (26-50%), 5=>50% galling.

126 Table 3.11 Influence of location and production system on eggplant plant stand and root disease ratings.

Mean Plant Stand / 22.27 m2x

1992† 1993† Root Disease Ratings†y

Location Production Alive Dead Alive Dead 1992 1993 System

Hort Hill Crim. Clover 17.75 a 1.25 a 19.50 a 0.50 a 1.25 a 1.80 a

Subclover 18.00 a 1.50 a 19.75 a 0.00 a 1.05 a 1.60 ab

Conv. (Rye) 18.00 a 0.50 a 17.75 a 1.25 a 1.20 a 1.05 b

Little River Crim. Clover 2.75 b 11.50 a 19.50 a 0.00 a 1.00 a 1.10 b

Subclover 13.25 a 2.50 b 16.00 b 1.50 a 1.00 a 2.00 a

Conv. (Rye) 15.50 a 2.00 b 16.50 b 0.25 a 1.10 a 1.55 ab

Hodnett Crim. Clover 14.00 ab 3.75 a 18.50 a 0.75 a 1.00 a 2.55 a

Subclover 12.50 b 1.25 a 16.00 ab 1.25 a 1.40 a 2.20 ab

Conv. (Rye) 17.00 a 1.00 a 15.25 b 1.00 a 1.00 a 1.75 b

Blackshank Crim. Clover 17.00 a 1.25 a 16.25 b 2.75 a 1.20 a 1.25 a

Subclover 10.75 b 1.50 a 19.50 a 0.00 b 1.33 a 1.50 a

Conv. (Rye) 16.75 a 0.75 a 16.00 b 1.75 ab 1.15 a 1.15 a † Data analyzed by analysis of variance (ANOVA) and ranked by DMRT (P=.05); means followed by same letter are not significantly different. x Data from initial plant stand (3 weeks after planting) and after final harvest. y Ratings based on scale where 1=none-2%, 2=2-10%, 3=11-25%, 4=26-50%, 5=dead or dying.

127 Fig. 3.1 Daily Temperature and Rainfall - Coastal Plain Experiment Station 1992

128 129 Fig. 3.2 Daily Temperature and Rainfall - Coastal Plain Experiment Station 1993

130 131 CHAPTER 4

ECONOMIC COMPARISONS OF ALTERNATIVE AND CONVENTIONAL

PRODUCTION TECHNOLOGIES FOR EGGPLANT IN SOUTHERN

GEORGIA1

1 Brunson, K.E., C.R. Stark, Jr., M.E. Wetzstein and S.C. Phatak. Journal of Agribusiness, 13-2

(Fall 1995): 159-173.

132 ABSTRACT Environmental concerns about pesticide usage in traditional production systems are prompting vegetable producers to consider alternative systems. Research results from a multi-year study on eggplant in Southern Georgia compare two alternative production technologies to the conventional rye cover crop technology. Alternative technologies utilize beneficial insect principles as substitutes for conventional pesticide controls. Eggplant production budgets are developed, using field data, to generate net return estimates under each system. Yield and profitability results indicate that higher yields under rye are not offset by cost reductions in alternative technologies.

Cash input requirements for alternative systems suggest potential for limited resource producers.

INDEX WORDS: Alternative Systems, Budgets, Eggplant, Expected Value, Limited Resource, Stochastic Dominance

INTRODUCTION

Vegetable production in Georgia approached 225,000 acres in 1992 representing a 13% increase from the 1990 acreage level and a 30% increase over the 1987 level (Georgia

Cooperative Extension Service, Feb., 1993). The 1993 farm gate value of vegetable production was estimated to exceed $334 million (Stephens and Dunn, 1993), more than a 250% increase over the value in 1985 (Georgia Crop Reporting Service). Along with this acreage increase has come a similar increase in chemical and fertilizer expenses for Georgia agricultural production

(Georgia Crop Reporting Service). To achieve these gains, vegetable producers are now utilizing intensive production systems with chemical and fertilizer inputs averaging 15% of their total variable production costs (Georgia Cooperative Extension Service, July, 1993). These high-input systems can be financially infeasible for limited resource producers who comprise some 67% of Georgia's farm operations (Brown, 1989). Applications of these increased quantities of chemicals and fertilizers, especially in the sandy soils of South Georgia, also present environmental concerns for the ecology of the region and water quality concerns for the water supplies of both rural and urban

133 residents. Clarke and McConnell reported in 1986 that about one million people in the rural areas of South Georgia received their water supply from domestic wells and another 1.6 million state residents obtained their water from other groundwater sources. Potential contamination of these water sources has prompted small plot research into alternative production systems which utilize less toxic pesticide inputs and more desirable application schedules while remaining economically viable for both traditional and limited-resource producers.

The research reported in this paper was conducted to evaluate the economic viability of alternative eggplant production systems in Southern Georgia. Multi-year data was gathered from field trials conducted on four research farms of the Coastal Plain Experiment Station in Tifton,

Georgia. Stochastic dominance and expected value analyses were used to develop risk efficient rankings of the production systems.

MATERIALS AND METHODS

The field trials in this research were conducted over the 1992 and 1993 eggplant production seasons at the Horticulture, Little River, Black Shank, and Hodnett Farms of the

Coastal Plain Experiment Station. Trials consisted of strip beds of crimson clover, Trifolium incarnatum L. 'Dixie'; subterranean clover, Trifolium subterraneum L. 'Mt. Barker'; and rye,

Secale cereale L. 'Wrens Abruzzi' with each system having four replications at each farm. Trial procedures were adapted from previous system research efforts conducted in vegetable production

(Bugg et al., 1991; Phatak et al., 1990). The rye system is typical of conventional eggplant production systems being utilized in the region. Rye is drilled as a cover crop in October of the previous year, deep-turn plowed as green manure in the spring, and eggplants are transplanted into the bare ground beds. Pest control

(disease, insect, nematode, and weed) is primarily achieved by applications of chemicals prior to

134 transplanting and continuing throughout the production season. Weed control through mechanical cultivation is also practiced.

The clover systems selected for these research trials are alternative systems which have shown promise in earlier production systems research (Bugg, et al., 1991). These alternative systems utilize beneficial insect principles to reduce chemical applications during the production season. Clovers are drilled at the same time as the rye cover crop. In the spring, the central third of each clover bed is killed with a spray application of contact herbicide, glyphosate (Monsanto

Corporation, St. Louis) in this trial. The area is subsoiled and tilled for transplanting. Insect pest control during the growing season is maintained by beneficial predator insects which have been sustained in the clover strips alongside each vegetable row. Nematode control in these eggplant systems has formerly been attained by fall applications of soil-incorporated nematicides. Non- chemical nematode control was initiated in the 1993 season by planting velvetbean as a fall green manure prior to clover seedings. Weed control is achieved by a combination of mulch and contact grass herbicides. The clovers begin to naturally die back in early summer and thus provide a mulch which inhibits weed growth. An optional, late-season shielded application of contact herbicide may be necessary on the clover strips if grassy weed infestations become serious. Each replication was treated as a separate plot for economic analysis. Variations between the farm soils required different irrigation treatments and some minimal variation in inputs during the growing seasons. After basic production budgets were developed for each system, input variations were incorporated according to location and system. Yield data was obtained by harvest for each replication in each growing season (four harvests in 1993 and three in 1992). Combining this data, annual net return calculations for each replication in the research plan were generated.

CONCEPTUAL MODEL

The theoretical basis for this research centers on the stochastic economic state variable which we call "annual net returns per acre". This variable is notationally expressed as AAB where

135 A denotes the field plot designation and B represents the production system being employed. Full representation of the theoretical model is:

Annual Net Returns = Gross - Preharvest - Harvesting & - Fixed - Charges for Overhead

Per Acre Returns Variable Costs Marketing Costs Costs & Management In equation form, this model is: where:

A = field & farm Xj = quantity of input or rd = annual fixed cost per designation operation j implement d

B = production system rj = price per unit of input L = annual charges for t = harvest time period or operation j overhead & mgmt.

Yt = eggplant yield in I = biannual interest rate period t rk = cost per unit of harvest

Pt = eggplant market & mkt. activity k price in time period t Xd=number of implement

d's used in the system

Prices and Input Costs Eggplant market prices were developed from Atlanta Wholesale Market weekly quotations over the June-July marketing period (Georgia Cooperative Extension Service, November, 1993).

Produce harvested on each field plot was graded into marketable, cull, and rot classifications. The

136 marketable yield was adjusted to a per acre basis and recorded for each respective location and system. Gross return figures were then calculated for each location.

Charges for machinery and labor requirements in eggplant production were developed from

University of Georgia Cooperative Extension Service enterprise budgets (Georgia Cooperative

Extension Service, July, 1993). Input quantities and prices were recorded by production system and field test plot for each year of the research project. When input prices were not directly available due to use of materials on station inventory, local supplier prices were surveyed to determine the prevailing price. Average per acre costs, for selected inputs, are presented in Table

1 for each system. Total preharvest variable input costs associated with each system may be found in Table 2.

Risk Efficiency Criteria

Risk is a concept wherein producers know all possible outcomes and the probabilities that each outcome will occur. Although often improperly interchanged, risk differs fundamentally from uncertainty. In uncertainty, producers know that they are subject to various outcomes, but do not know the probabilities of given outcomes occurring. Risk efficient sets are composed of all outcomes which would be most desirable at some period of the time frame. Each set is determined on the basis of producer risk aversion. When producer aversion is not known with certainty, the efficient set is based on approximations of the probability distributions (Chyen et al., 1992). These distributions are approximated through an assumed preference relation and various approximations of decision probability distributions (Wetzstein et al., 1988). The efficiency criteria adopted by the researcher specifies the preference and probability distribution restrictions under which the analysis is made. For this paper, distributions of profit and yield are compared for each of the three production systems.

Two efficiency criteria widely used in risk studies are expected value analysis (EV) and stochastic dominance (SD). The more basic condition, expressed in all risk efficiency criteria and

137 necessary for one distribution to dominate another, is EV. This analysis involves taking the first moments of the decision density functions. Stochastic dominance analysis compares the areas below probability distributions of the respective production systems. A system, A, is said to express first degree stochastic dominance (FSD) over another system if its cumulative probability function remains below the probability function of an alternative system at all points. Second degree stochastic dominance (SSD) over another system is expressed if the area below system A's cumulative distribution is less than or equal to the area below the dominated distribution. SSD allows the formation of risk efficient sets composed of all systems whose probability functions comprise a portion of the efficient frontier.

RESULTS AND DISCUSSION Production budgets were estimated for crimson clover, subterranean clover, and conventional rye eggplant production systems by averaging input quantities and costs over the 1992 and 1993 production seasons at all locations. Comparisons by system for selected inputs are presented in Table 1 with system estimates of Total Average Preharvest Input Costs presented in

Table 2.

Eggplant summary statistics for yield and profit were aggregated for the 1992 and 1993 production seasons and are presented in Tables 3 and 4. Results in each table are presented, by production system, for each of the four locations in the small plot test. Aggregate results over all locations are also provided. Both profit and yield results were highly variable. This variance can be partially attributed to the small plot scale of the tests which required extrapolation of data to reach a "per acre" basis. An additional factor was the South Georgia weather during the 1993 growing season. Compared to the prior 20 year period averages, temperatures from April 25 through June 29 in 1993 were some two degrees cooler than normal, but almost 2.5 degrees warmer than in 1992 (Coastal Plain Experiment Station). Precipitation during this period in 1993 was 3.45" or almost 5 inches below the 20-year average annual rainfall (8.37") for the period (Figs.

138 1&2). Despite the use of irrigation, this period of weather stress reduced 1993 eggplant yields and likely contributed to the unusually large variances in the yield data results.

Input Costs

Examination of the distribution of expenditures on selected inputs and the total average preharvest input costs associated with each system can identify potential areas for producer savings. From Table 1, clover systems are shown to have lower fertilizer costs than conventional rye systems and substantially less input expenditures on insecticides, fungicides, and nematicides.

Further savings may be possible with less chemical applications if the velvetbean method of nematode control proves effective in continued tests. Total herbicide costs increase with the clover systems due to the pre-transplant strip-killing of clover to prepare the seedbed. But an approximate $90 per acre total savings is indicated for these selected inputs when a clover production system is adopted.

Total preharvest input costs for each system are estimated in Table 2. The conventional rye system was found to have approximately $50 per acre greater expenditures on preharvest inputs, including labor. Clover systems are essentially equal in cost with the difference representing the cost differential between crimson and subterranean clover seeding costs. The preharvest input costs are averages over all locations for each system and indicate the potential for input expenditure savings which clover systems offer. This savings is especially important to limited resource farmers whose operations generate between $2,500 and $40,000 of annual gross sales. A recent survey of limited resource and commercial farming operations in two South Georgia counties indicated that the limited resource operations were overutilizing fertilizer, labor, and machinery inputs in their present enterprises (Nelson et al., 1991). Adoption of clover production systems could shift these operations toward more efficient inputs while reducing the growing dependence on chemicals.

139 Yields Eggplant production yields, aggregated over all locations for the 1992 and 1993 marketing seasons, ranged from a low of zero marketable cartons per acre to a high of 1,067.24 cartons.

Standard eggplant marketing cartons are 1 1/9 bushel in size with a net weight of 33 pounds

(Georgia Cooperative Extension Service, Nov., 1993). The conventional rye system produced the highest average yield (514.94 cartons per acre) when aggregating over all locations. This yield level appears reasonable given the 1992 state average yield of 494 cartons per acre for irrigated bareground acreage (Georgia Cooperative Extension Service, Feb., 1993). Conventional rye systems also produced the highest average yields at each of the four locations. Crimson clover systems had the second highest yields with an average of 193.43 cartons per acre over all locations. Subterranean clover yields were a distant third, generally half or less of the crimson clover yields and ranging from 10 to 27% of the conventional rye yield. Average yields for the alternative systems over all locations, as a percentage of the conventional rye yield, were 17.7% for subterranean clover and 37.6% for crimson clover.

Location appeared to be influencing eggplant yield with the most likely factor being soil type and the associated productivity rating. According to USDA-SCS soil surveys of Tift County, the Little River and Horticulture Hill Farms both contain loamy sand soils which possess good productivity ratings. Blackshank Farm is predominantly Carnegie sandy loam, but does not have the production capacity of the loamy sand soils. Hodnett Farm is predominately a Bonifay deep sand soil with less than 1% organic matter. The productivity rating is fair. As would be expected, eggplant yields at Hodnett Farm trailed all other locations for each system.

Net Returns Calculations of net returns per acre were generated for each system replication plot at each location. These net returns are summarized in Table 4. Research technician logs of production inputs and operations at each farm were combined with market prices and input cost estimates to

140 produce net return figures. Average net return levels, by system and location, ranged from -$765 on Hodnett subterranean clover to $4,892 for Little River conventional rye. Considering location, subterranean clover was profitable at only the Horticulture Hill Farm. Crimson clover showed an average profit over each location with a maximum net return of $655 per acre and a minimum of

$49. Examining each of the 32 observations separately, each system was found to have at least one plot with negative net returns.

Net returns for these research results were calculated using marketable harvested produce yields. For some replications, these yields were extremely low and resulted in a large percentage loss of preharvest input investment while also incurring the harvesting and marketing costs on the low yield. Actual field operations would be expected to establish a minimum harvest yield level below which no harvesting and marketing activities would occur. When the minimum yield level was not reached, producers would lose only their preharvest investment and would not incur any harvesting or marketing costs. In this research, actual harvest yields were used to more fully illustrate the range of net return possibilities.

Expected Value Analysis

Analysis of the yield and net returns summary statistics in Tables 3 and 4 according to expected value criteria shows that the conventional rye system dominates the subterranean and crimson clover systems. This dominance exists when systems are compared over all locations and remains in place when the analysis is extended to an individual location basis. Crimson clover dominates subterranean clover in a similar manner for both yield and net returns.

Stochastic Dominance Analysis

Risk aversion of producers is introduced to the analysis by considering stochastic dominance criteria. When cumulative probability functions are generated for each production system in terms of yield (Fig. 3) and net returns (Fig. 4), the alternative production systems are shown to not enter the risk efficient set of systems when considered over all locations. The

141 conventional rye system is thus found to have First Degree Stochastic Dominance for both yield and net returns. This indicates that the clover systems, as designed in this research, are not preferable alternatives to the conventional rye system currently being used in eggplant production.

CONCLUSIONS Economic comparisons of eggplant production systems using expected value and stochastic dominance analysis indicate that the conventional rye system remains superior to alternative clover systems on the basis of both yield and net returns. The difference in yield between rye and clover systems continues to be the major determining factor. Differences in preharvest variable input costs are noted between systems with the clover systems being approximately 6-7% less. Potential savings are identified in the clover systems for selected production input items, especially insecticides and fungicides. Potential environmental benefits are also noted with the input adjustments in clover systems. And the potential savings on input expenditures are shown to have additional value to limited resource farmers, given their current efficiency level in utilizing the inputs.

Literature Cited

Brown, N.B.1989. Marketing Activity of Limited Resource Farmers in Georgia through the Use of Cooperatives. The University of Georgia College of Agriculture, T.833:110.

Bugg, R L., F.L.. Wäckers, K.E. Brunson, J.D. Dutcher, and S.C. Phatak.1991. Cool-Season Cover Crops Relay Intercropped with Cantaloupe: Influence on a Generalist Predator, Geocoris punctipes (Hemiptera: Lygaeidae). Journal of Economic Entomology 84:408- 416.

Chyen,D., M.E. Wetzstein, R.M.McPherson, and W.D.Givan.1992 An Economic Evaluation of Soybean Stink Bug Control Alternatives for the Southeastern United States. Southern Journal of Agricultural Economics 24: 83-94.

Clarke, J.S. and J.B. McConnell. 1986. Georgia Ground-Water Quality. U.S. Geological Survey Water-Supply Paper 2325.

Coastal Plain Experiment Station. Local Weather Records, 1969-Present. Unpublished meteorological data maintained by Statistical and Computer Services support unit, The University of Georgia Agricultural Experiment Station, Tifton, Georgia, 1993.

142 Georgia Cooperative Extension Service. VEGETABLE ACREAGE ESTIMATES, 1992. Publication Ag Econ 93-027. The University of Georgia, College of Agriculture and Environmental Sciences, Athens, Georgia, February, 1993.

Georgia Cooperative Extension Service. VEGETABLE ECONOMICS: A Planning Guide for 1994. Publication Ag Econ 91-013. The University of Georgia College of Agriculture and Environmental Sciences, Athens, Georgia, November, 1993.

Georgia Cooperative Extension Service. VEGETABLE PRODUCTION COSTS and "Risk Rated" Returns. Publication Ag Econ 91-016. The University of Georgia, College of Agriculture and Environmental Sciences, Athens, Georgia, July, 1993.

Georgia Crop Reporting Service. Georgia Agricultural Facts. 1992 edition.

Nelson, M.C., N.B. Brown, Jr., and L.F. Toomer.1991 Limited Resource Farmers' Productivity: Some Evidence from Georgia. American Journal of Agricultural Economics 73:1480- 1484.

Phatak, S.C., R.L. Bugg, D.R. Sumner, J.D. Gay, K.E. Brunson, and R.B. Chalfant. 1991. Cover Crop Effects on Weeds, Diseases, and Insects of Vegetables. In: Cover Crops for Clean Water, Proc. International Conf., W. L. Hargrove, ed.; West Tennessee Experiment Station, Jackson, Tenn., April 9-11, 1991; Published by Soil & Water Conservation Society.

Stephens, J. and D. Dunn. 1993 Georgia Farm Income Summary. Georgia Coop.Extension Service.

United States Department of Agriculture-Soil Conservation Service. Soil Survey, Tift County Georgia. Series 1946, No. 3, January, 1959.

Wetzstein, M.E., P.I. Szmedra, R.W. McClendon, and D.M. Edwards. 1988. Efficiency Criteria and Risk Aversion: An Empirical Evaluation. Southern Journal of Agricultural Economics 20: 171-178.

143 Table 4.1 Average Per Acre Costs of Selected Inputs By Production System. Fertilizers Herbicides Insecticides Nematicides Total Selected Input Fungicides System Costs System ------Dollars Per Acre------Crimson Clover 117.47 43.35 0.00 29.88 190.70 Subterranean 116.85 43.35 0.00 29.88 190.88 Clover Conventional 140.52 12.50 69.76 59.75 282.53 Rye

144 Table 4.2 Preharvest Variable Input Costs by System. Production System Average Total Preharvest Input Costs -----Dollars Per Acre---- Crimson Clover 689.45 Subterranean Clover 698.44 Conventional Rye 743.72

145 Table 4.3 Yield Summary Statistics for Four Research Locations, 1992 and 1993 Production Seasons.

System Number of Mean Variance Minimum Maximum Observations All Locations ------Cartons Per Acre------Crimson Clover 32 193.43 18,412.99 0.00 617.64

Subter. Clover 32 91.28 9,535.18 0.00 398.32

Conv. Rye 32 514.94 63,945.44 55.80 1,067.24

Horticulture Hill

Crimson Clover 8 221.60 15,620.96 95.36 398.80

Subter. Clover 8 165.71 23,323.73 0.00 398.32

Conv. Rye 8 598.13 12,097.71 438.08 797.64

Little River

Crimson Clover 8 213.46 44,997.25 0.00 617.64

Subter. Clover 8 79.15 6,292.81 0.00 222.88

Conv. Rye 8 801.61 36,639.56 448.44 1,067.24

Hodnett

Crimson Clover 8 158.03 10,952.61 49.36 360.04

Subter. Clover 8 34.91 618.59 7.08 85.32

Conv. Rye 8 300.29 34,479.53 55.80 636.04

Blackshank

Crimson Clover 8 180.63 6,987.40 85.32 298.40

Subter. Clover 8 85.34 1,821.58 22.20 156.56

Conv. Rye 8 359.72 17,947.90 161.16 531.88

146 Table 4.4 Net Returns Summary Statistics for Four Research Locations, 1992 and 1993 Production Seasons.

System Number of Mean Variance Minimum Maximum Observations All Locations ------Dollars Per Acre------Crimson Clover 32 346.85 846,786.51 -907.99 2,938.95

Subter. Clover 32 -398.52 405,432.20 -934.46 1,689.98

Conv. Rye 32 2,461.26 4,154,659.21 -853.78 7,161.34

Horticulture Hill

Crimson Clover 8 655.01 785,330.62 -216.24 2,018.04

Subter. Clover 8 61.93 1,022,548.36 -926.20 1,689.98

Conv. Rye 8 3,379.67 984,133.37 1,979.28 5,320.18

Little River

Crimson Clover 8 455.67 1,912,316.96 -907.99 2,938.95

Subter. Clover 8 -421.11 281,562.32 -934.46 541.61

Conv. Rye 8 4,891.98 2,051,720.87 2,401.99 7,161.34

Hodnett

Crimson Clover 8 49.24 548,342.29 -691.44 1,564.08

Subter. Clover 8 -764.94 19,346.62 -919.46 -498.92

Conv. Rye 8 731.91 808,511.58 -853.78 2,253.23

Blackshank

Crimson Clover 8 227.47 264,493.59 -453.19 969.85

Subter. Clover 8 -469.94 69,875.89 -833.84 19.50

Conv. Rye 8 841.51 422,151.03 -59.77 2,150.74

147 Fig. 4.1 Daily Temperature and Rainfall - Coastal Plain Experiment Station 1992

148 149 Fig. 4.2 Daily Temperature and Rainfall - Coastal Plain Experiment Station 1993

150 151 Fig. 4.3 Cumulative Probability Function of Marketable Eggplant 1992-93.

152 153 Fig. 4.4 Cumulative Probability Function of Eggplant Profits 1992-93.

154 155 CHAPTER 5

CONCLUSIONS

156 This study demonstrated several strengths and weaknesses prevalent to both production systems. The main strength concerning the sustainable system was it improved soil productivity and conservation by using overwintering legume cover crops. Soil is a non-renewable resource because once productivity is lost, it can’t be replaced. Sustainable production promotes conservation tillage and in so doing also promotes soil productivity. Conservation tillage is beneficial because it saves soil, fuel, time, labor, machinery, permits timely planting, maintains or slightly increases yields, is cost-effective, increases soil organic matter, soil moisture, irrigation efficiency, improves soil quality, water quality, wildlife habitats, reduces runoff and meets the 1990

Farm Bill requirements. Another strength of the sustainable clover systems was the environmental impact demonstrated by reductions or eliminations of pesticide and fertilizer applications. This has the potential to reduce pesticide residues in food crops as well as groundwater contamination by fertilizer runoff. Using overwinter legume cover crops as “insectories” helped maintain populations of beneficial insects that helped control pest insects. Even with small plot research where insects are subject to outside interference, we were still able to control pests.

There were weaknesses associated with the sustainable production system. The study was conducted with no pesticide use to determine what, if any, additional inputs would be needed. It was thought that careful monitoring of the clover systems would catch potential problems early enough so that remedial action could be taken. This was not always successful as major problems with weeds and fertility occurred. Weeds grew in the middle of the subsoiled beds along with the eggplant and became too competitive. However, this could be eliminated by adapting production practices to include crop rotations and banded applications of herbicide in the row. The sustainable crops tended to mature later than the conventional system which from a market point of view was a disadvantage. This could be corrected by timeliness in fertilizer applications that would not greatly effect input costs. Other weaknesses were the potential for increases in soil diseases and nematodes from soils where legume cover crops were grown. In order to control soil

157 diseases, crop and site rotation as well as occasional use of fungicides could be initiated. Deep turning every few years with a moldboard plow would bury old residue that harbor disease causing organisms. It was thought nematodes could be successfully controlled by incorporating non-host crops into the rotation. Velvetbean, sunn hemp, sesame, corn and sorghum have been cited as potential rotation crops and had been used with encouraging results.

Weaknesses and strengths also existed in the conventional production system. A key weaknesses was the high input of pesticides and fertilizers and their effect on the environment.

Consumers have continued to voice concerns over pesticide residues in food and contamination of groundwater resources. Use of insecticides eliminated the benefits of predatory insects and lack of cover (weed or cover crop) reduced favorable habitats. Even with pesticide usage, weeds

(nutsedge) and insect pests (Colorado Potato Beetle) continued to plague the conventional production system. Conservation tillage was usually not practiced and soil productivity can be more easily lost over time compared to sustainable production. Another weakness was that input costs were higher that would effect smaller growers with limited capital. Conventional production was not as energy efficient as sustainable production. Specialized machinery and more trips over the field increased machinery wear and fuel usage. Some strengths of conventional production was earlier crop maturity compared to the sustainable systems. This was a distinct advantage from a profit and market viewpoint. There was little competition from insects, diseases, nematodes or weeds early in the season allowing the eggplant transplants to establish faster than the sustainable systems. The eggplants had sufficient fertilizer to be able to produce a uniform crop throughout the season. There was no shade effect from cover crops or weeds on the eggplants to retard growth or keep soils from warming up in the spring.

Differences in preharvest variable input costs are noted between systems with the clover systems being approximately 6-7% less. Potential savings are identified in the clover systems for

158 selected production input items, especially insecticides and fungicides. Potential environmental benefits are also noted with the input adjustments in clover systems. And the potential savings on input expenditures are shown to have additional value to limited resource farmers, given their current efficiency level in utilizing the inputs.

159