Pollution prevention in agricultural crop production / Thomas T. Adams and Lawrence Mark Risse

POLLUTION PREVENTION IN AGRICULTURAL CROP PRODUCTION
Technical Assistance and Applied Research Program for Pollution Prevention in Agriculture: Cooperative Extension Service,
Biological and Agricultural Engineering Department The University of Georgia in association with
Georgia Department ofNatural Resources, Pollution Prevention Assistance Division
1996

POLLUTION PREVENTION IN AGRICULTURAL CROP PRODUCTION
Thomas T. Adams, M.S., P.E. Research Assistant
Biological and Agricultural Engineering Department The University of Georgia and Dr. Lawrence Mark Risse
Agricultural Pollution Prevention Specialist The University of Georgia Cooperative Extension Service
Funded by: The Pollution Prevention Assistance Division of the
Georgia Department of Natural Resources

TABLE OF CONTENTS

LIST OF TABLES iii

L I S T O F FIGURES . . . . . iii 0 " II 0 " 0

EXECUTIVE SUMMARY

III II "

1

INTRODUCTION

.

.3

Crop Production in Georgia It

4 0

Regulations

"

5 GI 0 0 0 0 " 0

Pollution Prevention in Crop Production .................................. 7

WASTE STREAMS .. "

9 0 0 0 0

Erosion . 9 e eo.ooCl

Crop Fertilization

11

Pesticides

.

16

Fuel Storage and Handling

.

.24

Crop Residue, and Harvest Losses .25 00.

POLLUTION PREVENTION OPPORTUNITIES .27 G 0

Best Management Practices

. 0

27 0

Controlling Runoff and Soil Erosion

. 28

Conservation Tillage

3 0 0 CI 0 ., e

Increase Organic Matter ......................................... .32

Cropping Practices

.,

33 0

Forage and Pasture Management ............................. 35

Natural Vegetative Systems

.,

0 " "

36 .,

Crop Fertilization

e

"

e

3 7 e ., 0 0 " 0

1

Organic Fertilizers

39 0

Nutrient Management Planning

42

Application Technologies

45

Precision Farming

4 6 0

Pesticides

48

Integrated Pest Management (IPM)

48

Natural Predators

51

Pesticide Selectivity

52

Crop BMPs

54 0

Application timing and methods

56

Pesticide mixing and loading

58

Biotechnology

59

Composting and Biomass Additions

62

Petroleum Storage and Handling

65

Protection of Water Supplies

68

Wellhead Protection

68

Water Conservation

69

Computers and Models

72

Other Opportunities and Impediments

73

Risk reduction

73

Social and Economic Factors

75

Agricultural Policy

76

RESEARCH NEEDS

78

CONCLUSIONS AND RECOMMENDATIONS

82

REFERENCES

84

APPENDIX: AN OVERVIEW OF GEORGIA'S PRIMARY CROPS
11

LIST OF TABLES

Table 1 Georgia Pesticide Use in 1992 by Active Ingredient. . ..................... 18

Table 2 Georgia Pesticide use in 1992 by crop type. . ....................... 19

Table 3 Best Management Practice Summary Guide. .

29

Table 4 Expected 1996 Yields, Production Costs and Profits of Selected Georgia Crops with

Varying Frequency of Planting

35

Table 5 Commercial fertilizer consumption in Georgia in 1995.

38

Table 6 An example of the insecticide ratings chart

53

Table 7 Example of potential pesticide loss to surface runoff matrix

53

Table 8 Effect of peanut and cotton rotations on nematode pressure and yield. .

55

LIST OF FIGURES

Figure 1 Georgia 1995 crop values as a percent of total crop value ($2.08 billion). .

4

Figure 2 Insecticide/herbicide use in Georgia. .

17

Figure 3 Georgia corn production by county ........................... Appendix A

Figure 4 Georgia cotton production by county . . . . . . . . . . . . . . . . . . . . . . . . .. Appendix A

Figure 5 Peanut production by county

Appendix A

111

EXECUTIVE SUMMARY
There is increasing public awareness and concern regarding environmental pollution. Agriculture is one of several industries that face criticism today because of their impact on the environment. Pollution prevention technologies can go a long way toward addressing these concerns. They could also be beneficial to producers as they represent a move toward efficiency. Anytime waste is reduced, there is opportunity for an increase in efficiency and usually profitability. This paper describes common agricultural crop production processes and identifies potential pollution prevention measures. The most common environmental pollutants from crop production are sediment, nutrients, and production chemicals including herbicides and pesticides. This paper identifies pollution prevention opportunities that are economically viable to the farmer and minimize the impacts of these contaminants. It also lists impediments that limit the adaptation of these practices. Finally, it identifies areas where further research is needed to develop pollution prevention techniques that would be economically viable, technically sound and environmentally sustainable.
The overriding issue concerning pollution prevention in crop production is economics. If economic benefit cannot be derived by the producer, the long-term result will be that pollution prevention technology will be ignored or resisted. Despite the benefits of improved water quality, protecting the diversity of species, and the global environment, producers will give priority to economic survival. Pollution prevention practices that increase the efficiency of resource utilization and land productivity are the practices that will succeed. Specifically, methods of decreasing chemical use for crop fertilization or pest control, best management practices that preserve soil and water quality, and practices that reduce equipment fuel consumption while maintaining or increasing net returns per acre are methods that will benefit both the producer and the ecology of the crop production industry.
Conventional practices of crop production have relied on ever-increasing amounts of chemicals and energy inputs. Chemicals are used to replenish resources used by the crops, to control losses attributable to plant competitors, and to prevent damage from insects and disease. The soil has all too often become a sterile environment. Producers attempt to create the correct chemical environment for the crop to grow without the aid of the natural soil ecology. An opportunity exists to utilize the soil and its natural ecology as a resource. Sustainable agricultural practices including nutrient cycling, natural predation of pests, water use efficiency, and biochemical degradation of toxic chemicals can be increased to restore the soil to its natural state of high biological activity resulting in greater yields with less cost. This opportunity is particularly exciting since the National sustainable agriculture movement is already in place.
Educational programs need to focus on proven methods of pollution prevention and educators need to give full support and backing to these programs. New techniques need to be proven and demonstrated. Best management practices should be supported and implemented. Surface waters need to be protected from surface runoffby appropriate vegetated buffer zones. Several federal and state government agencies offer technical and financial assistance to land users to develop and implement conservation, water quality, and waste management plans. These
1

programs have been very successful; however, there is a continuing need for further education and financial assistance. Since resources are often limited, a statewide system using geographical information system (GIS) modeling is recommended for monitoring, planning, and targeting sensitive crop production areas.
2

INTRODUCTION
The Pollution Prevention Assistance Division (P2AD), created by the 1993 Senate Bill 200, serves as a source of technical and financial assistance for pollution prevention programs in Georgia. Pollution prevention is the elimination or reduction of wastes at the source of generation rather than control of emissions at the outlet. This can be accomplished through a reduction in inputs, modification ofproduction processes, reuse or recycling ofprocess outputs, or, as a last resort, development of alternative uses for by-products of production. Pollution prevention can increase the profitability of a process while decreasing the stresses that the process exerts on the environment. The driving forces behind the move toward pollution prevention can be broken into two categories, economic and environmental. The environmental concerns include a response to regulation and the more common notion of being good stewards of our environment. The economic concerns are based on the fact that crop production is the same as any other industry in Georgia. The more efficient producer will usually survive the longest.
As one of the largest industries in Georgia, agriculture is a significant contributor of pollution. The diversity of agricultural industries presents many obstacles to the adoption of pollution prevention technologies. p 2AD recognized these facts and allocated a budget to establish an agricultural pollution prevention program in cooperation with The University of Georgia Cooperative Extension Service. The primary emphasis of this program is to provide education and technical assistance on pollution prevention to the agricultural community.
This paper and its companion paper on pollution prevention in animal production were created to provide guidance to the agricultural pollution prevention efforts. The purpose of this paper is to describe common agricultural crop production processes and to identify potential pollution prevention measures. It results from an in-depth analysis and review of the literature associated with pollution prevention and crop production practices. Information was also gathered from discussions with academicians, extension specialists, and producers to determine current practices and potential waste reduction techniques. By analyzing existing production practices and the concepts behind pollution prevention technologies, many opportunities, impediments, and research needs have been identified. These needs, and the potential for new pollution prevention techniques are presented and discussed. The incorporation of pollution prevention principles into crop production has the potential to reduce environmental degradation and increase the economic return to the producer. Hopefully, this paper can serve as a catalyst for converting this potential to reality.
To discuss pollution prevention opportunities in crop production adequately, we must first understand the waste streams associated with crop production. Therefore, following a brief introduction, waste streams common to all cropping systems will be discussed and characterized. Conventional cropping procedures and specific pollution prevention concerns for the major crops of Georgia are included as an appendix. General pollution prevention opportunities that are available or can be implemented are then presented. Specific economic methods of pollution prevention are identified. This is followed by a discussion of needed research and impediments
3

to pollution prevention. Conclusions and recommendations are then made based on both the opportunities and impediments. Crop Production in Georgia
Total gross farm income in Georgia in 1994 was $5.65 billion (Georgia Agricultural Statistics Service, 1995). Crop production, including row crops, small grains, turf, hay, commercial vegetable production, orchards, and vineyards accounted for $2.05 billion or 40.9% ofthis total. During 1994, there were more than 43,000 farms larger than ten acres producing income in Georgia. Land producing crops totaled 4,497,000 acres excluding orchards and vineyards or approximately 12% of total land area. This accounted for 45% of total farmland. Georgia leads the nation in the production of peanuts, pecans, and rye. The state ranks third in the production of peaches, fifth in tomatoes, sixth in tobacco, and seventh in cotton and sweet potatoes. Figure 1 shows the distribution of crop production in Georgia. In 1995, the production of cotton, peanuts, and vegetables accounted for 71.7% of Georgia's total crop value. Figure 1 Georgia 1995 crop values as a percent oftotal crop value ($2.08 billion). From Georgia Agricultural Statistics Service, 1996.
For the first time since 1965, cotton was the number one crop in Georgia in terms of value and acreage. A total planted acreage of 885,000 acres produced more than $540 million in lint and an additional $35 million in cottonseed. Peanuts followed cotton with a total of 642,000 acres and $533 million in annual cash receipts. These two major crops were followed by com (600,000 acres and $140 million), tobacco (37,000 acres and $133 million), soybeans (520,000 acres and $82.9 million), small grains including wheat oats, and rye (860,000 acres and $72.1 million) and sorghum (65,000 acres and $5 million). In addition, hay production on 650,000 acres produced $118 million and nursery, greenhouse, and turf produced $168 million. Truck crops including pecans, peaches, apples, grapes, blueberries, and vegetables accounted for an additional $365 million in production. Commercial vegetable production represented one of the
4

fastest growing segments oftruck crop production exceeding 100,000 acres in 1994 for the first time ever.
While this income alone suggests that crop production is big business, farm expenses also have a large impact on the State's economy. Total farm production expenditures amounted to more than $3.6 billion. To achieve production, farmers applied 1,415,047 tons of chemical fertilizers and lime ($260 million) and 105,762 tons of organic fertilizers to their soils in 1994. Farmers paid an estimated $171 million for fungicides, herbicides and insecticides to achieve crop production levels in the same year (Crop Enterprise Cost Analysis, 1994). Other major expenses included interest ($237 million), labor ($234 million), repairs and maintenance materials ($168 million), rent ($126 million), fuel and oil ($103 million), and taxes ($102.5 million).
Regulations The key issues and challenges to be addressed concerning pollution include (1) the
control of toxic substances, (2) the reduction of nonpoint source pollution, and (3) the need to increase public involvement in air and water quality improvements (Water Quality in Georgia, 1993). The pollution impact on Georgia's environmental resources has radically shifted over the last two decades. Streams are no longer dominated by untreated or partially treated sewage discharges that result in little or no oxygen and little or no aquatic life. Sewage is now treated, oxygen levels have returned, and fish have followed. However, another source of pollution is now emerging as the primary pollutant of Georgia's water resources. That source is referred to as nonpoint and consists of mud, litter, bacteria, pesticides, fertilizers, metals, oils and fuel, and a variety of other pollutants being washed into rivers and lakes by storm water or leached into groundwater. This form ofpollution, although less dramatic than raw sewage, should be reduced and controlled to protect Georgia's environmental resources. As with toxic control, nonstructural techniques such as pollution prevention and best management practices must be significantly expanded. These include both watershed protection through planning, zoning, and buffer zones, as well as fine-tuning pesticide and fertilizer usage and refining agricultural techniques. The consensus is that most nonpoint source pollution (NPS) problems occur close to the source and that sound management decisions on usage of agricultural chemicals, nutrients, and animal waste, along with the application of effective conservation practices, can reduce pollutant transport.
For the most part, Georgia crop producers face very little environmental regulation. While voluntary application ofpollution prevention technology is preferred, having an understanding of
(
the existing regulations that influence crop production is necessary. Regulations can be a driving force behind producers seeking technical assistance to reduce emissions while pollution prevention provides an alternative for producers facing regulatory action. In this section, an overview of the key regulations that impact agricultural crop production is presented
The Clean Water Act (CWA), initially enacted in 1972, is the principal federal statute governing water pollution. The goals of the CWA are to eliminate the discharge of pollutants, achieve water quality that protects aquatic life and recreation, and prohibit the discharge of toxic pollutants in toxic amounts. CWA standards are enforced using National Pollution Discharge Elimination System (NPDES) permits. Effluent standards have been set for specific industries.
5

To protect publicly owned treatment works (municipal treatment systems), EPA established pretreatment standards that must be met before contaminated wastewater can be discharged. Since most pollutants from crop production are nonpoint source in nature, this part of the act has little impact on most producers except for those that store large quantities of fuel (more than 1,100 gallons) or pesticides. For producers that do store large quantities of oil or hazardous substances, the CWA requires that discharges must be reported. Owners and operators who meet size criteria must prepare a Spill Prevention Control and Countermeasure (SPCC) plan for the accidental discharges of oil.
Other subjects covered by the CWA are groundwater quality, nonpoint source pollution, erosion, sedimentation and wetlands. The Federal Clean Water Act of 1987, an extension of the 1972 act, established as a national policy "that programs for the control of nonpoint sources of pollution be developed and implemented by each state in an expeditious manner so as to enable the goals of the Act to be met through the control of both point and nonpoint sources of pollution." Section 319 of the Clean Water Act focuses on nonpoint sources of water pollution. Nonpoint source pollution can be described as any pollution whose specific point of generation and whose exact point of entry into a water course cannot be defined. Origins of these contaminants include percolation, seepage, and surface runoff from agricultural and silviculturallands and from construction, mining, and urban areas.
In Georgia, the Environmental Protection Division (EPD) of the Department of Natural Resources is authorized to carry out the Clean Water Acts. Section 319 of the CWA requires each state to: 1) identify impaired bodies of water, 2) identify nonpoint sources that add significant amounts of pollutants to these waters and 3) develop NPS management plans to control and reduce NPS pollution. While Congress allocates significant amounts of money to this program, each state is responsible for administering the program as they see fit. This has resulted in mainly educational and technical assistance type programs that promote the voluntary implementation of best management practices (BMPs).
Another federal program with provisions to address NPS pollution is the Food, Agriculture, Conservation and Trade Act of 1990 in the 1990 Farm Bill. The Agricultural Water Quality Protection Program in the Farm Bill, was designed to give producers the financial and technical assistance necessary to develop and implement a comprehensive water quality protection plan. The Integrated Management Systems Program included in the 1990 Farm Bill encourages producers to adopt an integrated crop and livestock management practices that minimize agricultural impact. The Conservation Reserve Program and the Agricultural Conservation Program were designed to reduce soil erosion. These programs with the Wetlands Reserve Program will help reduce NPS contamination by reducing runoff and increasing sedimentation and biofiltration. These efforts attempt to "polish" water before entry into streams and lakes.
Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) sets forth procedures and criteria for the registration and reregistration of pesticide products. Requirements are listed for agricultural pesticide worker protection, pesticide tolerances in or on raw agricultural commodities, restricted use pesticide applicator certification, and reporting and labeling. Recommended procedures for storage and disposal of pesticides and pesticide containers are described. EPA also has
6

procedures for special review and cancellation of pesticides believed to be dangerous. Since education and training are key provisions in this act, it is important to pollution prevention as it provides an opportunity for educational programs to be implemented as part of the recertification process.
Passed in 1963 and amended most recently in 1990, the Clean Air Act has been the basis for regulating emissions of air pollutants to protect human health and the environment. Both stationary and mobile sources are regulated. A basic objective of the CAA is to prevent deterioration of and to improve present air quality. Under clean air regulations promulgated by EPA, that agency sets National Ambient Air Quality Standards (NAAQS) and the states regulate air emissions from existing stationary sources according to their State Implementation Plans. New and modified stationary industrial sources must comply with federal New Source Performance Standards. The 1990 amendments to the CAA increased from 7 to 189 the number of toxic chemicals that are subject to Maximum Achievable Control Technologies. Stiff penalties can be imposed under the new law, including civil penalties of up to $5,000 per day and administrative penalties as high as $25,000 per day. Recently, agricultural processing facilities such as cotton gins have been mandated to meet many requirements set forth in this act.
Commonly known as Superfund, the Comprehensive Environmental Response, Compensation and Liability Act CERCLA became law in 1980. It focuses on closed waste sites, spill response, and issues ofliability and funding cleanup. The law established a program to identify sites from which releases of hazardous substances into the environment have occurred or might occur, to ensure that they are cleaned up by responsible parties or the government, to evaluate damages to natural resources, and to create a claims procedure for parties who have cleaned sites or spent money to restore natural resources. A tax was levied on certain manufactured chemicals and petroleum to provide money for the fund. Chemicals used for fertilizers are exempt from the tax, however, many agricultural chemicals in pesticides and petroleum are subject ofthis tax.
Over the last decade, the Environmental Protection Agency and other regulatory agencies have shifted their emphasis away from pollution control and toward pollution prevention. This has coincided with a shift toward greater consideration ofnon-point sources of pollution that may be attributable to agriculture. The Pollution Prevention Act of 1990 states "that pollution should be prevented or reduced at the source whenever feasible." In Georgia, Senate Bill 200 created the Pollution Prevention Assistance Division (P2AD) within the Department of Natural Resources and authorized it to develop programs of technical and financial support to industries and agricultural producers. Hopefully, through the development and acceptance of pollution prevention technologies that are economically and environmentally sound, the need for future regulation in agriculture industries can be minimized.
Pollution Prevention in Crop Production Regulations do an adequate job of protecting the environment from the most hazardous
contaminants. However, with the exception of pesticides, they do not really address the most common pollutants in crop production. These include sediment, nutrients and other nonhazardous chemicals. Most ofthese pollutants originate from nonpoint sources that are difficult to locate and regulate. The existence of nonpoint source pollution may be an indication
7

of inefficient use of resources or a production technique that has not been thoroughly analyzed. Usually where there exists an excess or loss of resources there is an opportunity for greater efficiency to increase profits. Resource management techniques will be the central themes for methods of pollution prevention contributing to sustainable crop production for Georgia's future. Pollution prevention also encompasses atmospheric considerations. The condition of the air within plant canopies, precipitation pH, and the loss of carbon, nitrogen, and pesticides to the atmosphere can all significantly affect the bottom line. Agriculture is conducted on such a large scale that the practices of farmers collectively can impact in a large way the total amounts of carbon and nitrogen compounds that transfer from biomass and agrichemicals to the atmosphere. In the future, agriculture may need to pay greater attention to sequestering carbon and nitrogen compounds (degradation products from plants and animal manures) in the soil and in plants.
8

WASTE STREAMS
Most cropping systems produce similar waste streams regardless of the type of crop being produced. The waste streams occur from common production and cultivation practices. For example, soil loss occurs because of erosion from wind and water, applied chemicals including fertilizers and pesticides are lost via vaporization, bioconversion, and the erosion of soil and crop residues, and organic matter is lost via bioconversion, tillage, and harvesting. While common principles result in resources being lost, each crop is also unique. The amounts and type of chemicals used, the cultivation technique used, and the tolerance of a plant to stress may be specific to the crop or the location. Since a detailed evaluation of each crop and condition is beyond the scope of this text, this section will review the common waste streams that are consistent among most crops. A more detailed description of practices and process specific to individual crops common to Georgia can be found in the appendix.
Erosion Erosion occurring on the State's 8.9 million acres ofland produces about 7.6 million tons
of sediment each year (USDA et aI., 1993). The process of erosion is important because eroded sediment is not only the greatest potential pollutant by volume and weight but also poses a double threat in that it often carries adsorbed nutrients and chemicals. While soil erosion is a natural process, it is accelerated by any activity that disturbs the soil surface. Severe soil loss from wind erosion and runoff can begin in spring if fields are turned over prior to planting. Soil loss continues an event basis as precipitation occurs and as the crops are cultivated. Erosion also occurs after crops are harvested, especially if crop residues are not sufficient to provide cover or are plowed under prior to establishment of crop cover.
Soil erosion is not only detrimental to crop production, but also causes considerable off-farm damage. Erosion by wind and water causes yield reductions through loss of crop stands, damage and stress to seedlings and young plants, and a deterioration in soil quantity. Soil quality is affected by the separation and gradual removal of organic matter, silt, and clay from the soil surface. In fact, cotton yields from eroded soils in Georgia can be as much as 50% less than yields from non-eroded fields. This problem is compounded by the fact that eroded soils will often require increased inputs to sustain comparable yields. The EPA has also identified soil erosion as the leading source of impairment to rivers and lakes. Eroded sediments and associated nutrients and pesticides from cropland fill roadside ditches and reservoirs, block navigational channels, adversely affect aquatic plant and animal life, reduce recreational opportunities, and can indanger human health.
The universal soil loss equation (USLE) is the most popular erosion prediction tool. It was developed using more than 20,000 plot-years of natural runoff plot data and has proven reliability (Risse et aI., 1993). The USLE relates soil erosion to five empirically derived factors, the rainfall factor, the soil erodibility factor, the slope length and steepness factors, the cropping and management factor, and a support practice factor.
9

The rainfall and soil factors are primarily functions of climate and geography and are independent of agricultural production practices. Man can do very little to substantially change the rainfall energy a location receives and has little effect on the natural soil erodibility. However, some indirect soil properties can be managed to reduce the impact of these factors. For example, increasing infiltration is an indirect means of reducing erosion as a certain rainfall will produce less runoff and corresponding erosion. Knowledge of rainfall patterns will also allow farmers to insure that cover crops are planted during the periods of the year when they receive the largest amounts of rainfall energy. The organic matter of a given soil can also be manipulated over time to produce a soil with more organic matter and a lower erodibility. While these changes usually require a long term management commitment, the results will have production benefits with erosion reductions.
Slope steepness and slope length factors depend on topography and have historically been the primary means of erosion control. Since the dawn of agriculture, man has known that longer and steeper slopes produce more soil erosion and has used methods such as the construction of levies and terraces to reduce slope length and steepness. More recently, practices such as strip cropping and vegetated waterway construction.have been used to reduce runoff velocities and effective slope length. Perhaps the most substantial contribution of these factors has come in the development of conservation reserve programs. Most of the land enrolled in these programs is classified as highly erodible land, based primarily on the slope steepness, and therefore has been removed from production.
The cropping and management factor estimates the combined effect of all interactions between cover and management factors. The cropping and management factor is defined as the ratio of soil loss from land cropped under specified conditions to the corresponding loss from tilled continuous fallow land (Wischmeier and Smith, 1978). Crop canopy and surface cover or residue acts as a buffer between the soil surface and the raindrops, absorbing much ofthe rainfall energy and ultimately reducing soil loss. Therefore, crops that produce more vegetative cover, have longer growing seasons, or produce a persistent residue will have lower C factors and less soil erosion. Management is also an important part of this factor as tillage can drastically reduce the amount of surface cover and residue. The arrival of modern no-till and conservation tillage systems was primarily in response to the effectiveness that these systems have on maintaining surface cover and reducing soil erosion. Any cropping system with less tillage or greater amounts of biomass production, such as perennial systems, will result is less sediment leaving the field.
The support practice factor of the USLE relates to the effect of management practices on soil erosion. It is designed to account for reductions in soil loss due to cultural practices such as contouring, strip cropping, and the construction ofterraces. As runoff and accompanying sediment leave fields they constantly move through differing environments where the rate and volume of movement are affected. Any deceleration in movement causes sediment to be dropped out of suspension along the water course. Heavy vegetation, flatter slopes, depressions, swamps, wetlands, ponds, and sediment retention structures can all cause sediment deposition and prevent water quality degradation.
10

While the USLE is the most popular soil erosion model, the USDA has recently developed its replacement through the Water Erosion Prediction Project (WEPP). WEPP is a physically based, process oriented model that offers many advantages over the USLE. Not only can it estimate spatial and temporal variations in soil loss, but it can also handle processes such as snow melt, rilling and gully erosion, and non-uniform slopes that have traditionally been stumbling blocks for the USLE. As better user interfaces are developed for this model, it will become a tool that farm managers can use to explore erosion reduction strategies on their farms.
Though not as important in Georgia as some other states, wind erosion can still cause substantial losses in terms of topsoil and productivity for Georgia producers. In practice, any technique that increases soil moisture content or water holding capacity, or decreases wind velocity will effectively reduce wind erosion. Practices used to control water erosion, such as residue maintenance and reduced tillage, in combination with windbreaks, are the most effective tools for combating wind erosion.
Crop Fertilization In 1995, more than 1,661,885 tons of commercial fertilizers were sold in Georgia. This
included more than 985,000 tons of mixed fertilizer, 418,000 tons of nitrogen materials, 68,000 tons of phosphate materials, 44,000 tons of potash materials, and 145,000 tons of secondary and micronutrients (Georgia Agricultural Statistics Service, 1995). Beyond this, an estimated 84,000 tons of nitrogen and 33,000 tons of phosphorus were generated from animal waste and used in crop production. Nationally, the use of fertilizers continues to increase. However, this increase corresponds to increases in the amount of nutrients harvested in increased crop yields. Ifthe efficiency of fertilizer use is increasing, resulting in increased yields and harvested nutrients per unit input, productivity can improve and environmental integrity will be maintained. The problem that can stem from the use of fertilizer inputs results from decreased fertilizer use efficiency and losses to the environment. This can lead to many water quality and environmental problems.
Crop fertilization is required on most Georgia farms because the natural soil fertility is not high enough to sustain crop productivity at the desired yields. Crops are fertilized by application of organic and inorganic chemicals to the soil or by foliar application. Fertilizers may be solids, liquids, or gases. They may be applied to the soil surface, incorporated into the soil, injected below the soil surface, applied to the plant leaves, or released as a gas, vapor, or liquid spray into the plant canopy. Critical considerations are the quantity and rate of fertilizer applied. Soil pH,
~..
cation exchange capacity, anticipated plant requirements, and plant uptake generally are the factors used to calculate the quantity and rate of fertilizer application.
Crops require considerable amounts of macronutrients and lesser amounts of micronutrients. The primary, or macronutrients, include carbon, oxygen, hydrogen, nitrogen, phosphorus, and potassium. Calcium, magnesium, and sulfur are secondary macronutrients. Micro nutrients include zinc, iron, copper, manganese, molybdenum, boron, and chlorine.
11

Carbon: Crops obtain carbon from carbon dioxide in the air above the.canopy and from carbon dioxide emitted to the air from respiration below the canopy (Tisdale et aI., 1985). More than 95% of the carbon in the crop is obtained from gas phase carbon dioxide transferred through the leaf stomata. The carbon represents more than 85% of plant tissue dry weight.
Organic matter on and within the soil is an important source for carbon dioxide within the canopy. Microorganisms utilize organic matter as a carbon and energy source. Carbon dioxide is released to the canopy air space as the microorganisms respire. Organic matter has many beneficial effects on soil properties. It directly affects the cation exchange capacity of the soil and as a result can either increase or decrease the mobility of ions in the soil. Organic matter is applied as a solid via in field equipment such as a manure spreader, as a slurry by spraying onto fields, or obtained from crop residues. The carbon to nitrogen ratio must be examined when organic matter is applied to a pasture or a field crop. Many short chain organic compounds such as volatile fatty acids react quite fast and produce explosive microorganism growth that can rob the soil of nitrogen (nitrogen immobilization) and other nutrients. This phenomenon produces the "burn" or yellowing and necrosis of plant leaves that can occur when nitrogen is immobilized or sequestered within the microbial biomass as a result of application of a "strong" organic material.
Carbon from the soil is lost to the atmosphere when carbon dioxide is emitted by microorganisms and by vaporization of volatile organic compounds. The carbon becomes a water pollutant when it is lost via erosion and surface runoff. If not captured before entering a stream, carbon compounds will exert a biochemical oxygen demand (BOD) in the receiving stream that will deplete dissolved oxygen. Organic matter can also increase the total and dissolved solids in a stream adding to its turbidity and increasing bacterial and algal growth in the stream. Microorganisms originating from manure and sludges can pollute surface water.
Percolation to ground water is usually not a problem. In fact, organic carbon in subsoil is usually desirable. However, if soils become saturated due to a high water table and an over application of organic matter, or if short circuiting occurs through geological faults, then contamination of springs and wells can occur. Usually the contamination is measured as a count of a particular organism such as fecal coliform or streptococci.
Nitrogen (N): Crop production requires more nitrogen than any other nutrient and therefore, more nitrogen is sold to supplement crop nutrient requirements than any other fertilizer element. The chief problem with nitrogen is the formation of nitrates and nitrites. Nitrates move more rapidly in soils than most ions. The drinking water standard for nitrate is 10 ppm. At 40 ppm nitrates in water fed to infants can result in methemoglobinemia (nitrate cyanosis), which can cause blindness and can be lethal. In Georgia, 3.8% of3,419 shallow wells (having depths less than 100 feet) tested between 1989 and 1993 had nitrate concentrations exceeding 10 ppm. Of the deep wells, 0.9% had concentrations exceeding 10 ppm (Tyson et aI., 1995).
Nitrogen, usually as ammonium, nitrate, or nitrite ion is brought to crop roots by mass flow in aqueous solution (Foth and Ellis, 1988). The amount taken up by the roots is dependent on the concentration of nitrogen in solution. Nitrogen is very active in the biosphere and life depends
12

on it. In crops it constitutes from 2.5 to 5.5% of plant tissue. In leaves, nitrogen affects the chlorophyll present. It stimulates growth and delays senescence. Sometimes foliar application of nitrogen is practiced. Nitrogen sources include commercial sales (64% of total N use), legumes and crop residues (21 %), and animal manures (12%). All N sources, when applied to the soil, are gradually transformed by soil organisms to inorganic ammonium and nitrate that can be used by the plant.
Soils naturally obtain N through several mechanisms. Nitrogen is obtained from the atmosphere by legume crops through a symbiotic relationship between the host plant and microorganisms on the roots. This symbiotic relationship can fix 60 to 160 lbs. N/acre/year. Lightning also fixes nitrogen from the atmosphere by oxidizing nitrogen molecules to form ammonia. Lightning adds 10 to 12 lbs. N/acre/year to most Georgia soils. Nitrogen is also obtained through mineralization (biochemical catabolic activity) of organic matter. Microbes and soil fungi use biochemical pathways to break down proteins and enzymes catalyze the conversion of more complex nitrogen containing compounds to ultimately form ammonia. Nitrogen obtained from organic matter may be calculated by examining the organic content of the soil through a soil test. Applications of organic matter to a field are often based on the nitrogen content of the material and the needs of the crop to be planted.
Most N used in crop fertilization is applied as a chemical fertilizer. It is available commercially in varying forms and concentrations. The most popular forms are aqueous ammonia injected into the soil and granular urea or ammonium nitrate, which are applied to the soil surface and tilled in or irrigated. The basis for nitrogen fertilizer recommendations is an equation that relates a yield goal to a nitrogen mass balance:
Nf = [(Dmx N ) - (Em X Nm) - (Er X Nr)]/Ef where Nf is the recommended nitrogen application rate (lbs.), Dmis the desired dry matter yield, N is the nitrogen concentration in the dry matter, Em is the efficiency of nitrogen uptake from soil organic matter, Nmis the concentration of nitrogen in soil organic matter, Er is the efficiency of uptake of residual nitrogen in the soil, Nr is the concentration of the residual nitrogen, and Ef is the efficiency of plant uptake. The limitation of this mass balance is the estimate of the amount of mineralized nitrogen in the soil. Nitrate nitrogen is highly mobile in the soil, especially in wet, warm, acid soil conditions and weathered clays and sands that exist over much of Georgia. Thus, it is difficult to estimate values for Em and Er accurately.
Volatilization is one way that nitrogen is lost to the environment. Ammonia is volatilized when fertilizers are surface-applied to soils under high pH conditions (pH greater than 6.5). Volatilization can be reduced by increasing the buffering capacity of the soil and by increasing the soil's cation exchange capacity. This may be achieved by increasing the soil's organic matter content. This method also improves soil friability and allows the soil to close over ammonia injection knives more readily. Granular fertilizers are usually tilled in or irrigated after application to reduce ammonia volatilization. Other methods to reduce volatilization include application during cool weather to slow down hydrolysis, use of a urease enzyme inhibitor such as potassium chloride, application of gypsum, or use of a time release fertilizer with a coating. All these methods of decreasing the volatilization of ammonia can improve efficiency and prevent possible groundwater contamination.
13

Bacteria in the soil convert ammonia to nitrates and nitrites in a process called nitrification. The conversion releases hydrogen ions causing the soil to become more acidic. Nitrification is affected by the carbon to nitrogen ratio in the soil, soil pH (6.6 to 8.0 is optimum), soil water content (50 to 67% is optimum), and soil temperature (5 to 40 C). By understanding the processes that drive these reactions and applying nitrogen at appropriate times, producers can often decrease nitrogen lost to the environment.
Nitrogen compounds are pollutants in water and will exert an oxygen demand, thus reducing the dissolved oxygen content and inducing bacterial and algal growth. Much of the applied nitrogen is lost by lithotrophic (denitrifying) bacteria that convert nitrate to dinitrogen and nitrous oxide gas that is released to the atmosphere. Nitrous oxide is thought to contribute to ozone depletion, however, the amounts lost to the environment are variable and difficult to quantify
The percolation ofnitrates is a special problem. Once nitrates migrate below the plant root zone there is little chance of plant uptake or biological conversion under normal field situations. An anion such as nitrate, in most Georgia soils, is prone to ion exclusion in its transport through the soil. This means little if any nitrate is retained by adsorption in the subsoil. Severe nitrogen migration to the subsoil can occur in cropping situations where irrigation is used. However, water moves very slowly through the soil so it may take many years for nitrates to reach ground water. Therefore, infiltration that may have taken place thirty years ago may only now be arriving in a well used for drinking water. This makes this form of pollution highly difficult to identify and control.
Phosphorus (P): Most crops have a difficult time getting enough phosphorus under normal circumstances. Phosphorus readily combines with other minerals in the soil preventing movement to plant roots. Phosphorus movement is usually limited to one to two inches in depth even in sandy soils. Crop roots obtain phosphorus from the soil by diffusion. Surface runoff can erode soil particles containing phosphorus and is the primary mechanism by which phosphorous becomes a surface water pollutant. Erosion and crop removal are the most significant ways soil loses phosphorus. The adsorption capacity of the soil can, over time, become depleted if manures are repeatedly applied to the same area. As phosphorus migrates to lower, less weathered soils, it becomes more mobile. Thus, phosphorus can become a groundwater contaminant; however, it is of much greater concern in surface waters.
Phosphorus is very reactive. It exists in the soil in solution, as insoluble precipitates, or adsorbed onto mineral and organic substrates. Organic phosphorus exists as orthophosphate and is available to plants. Humic phosphorus is unavailable or resistant. Inorganic fertilizers contain phosphorus as orthophosphate since they are designed to be available for plant uptake.
Phosphorus that is precipitated or becomes insoluble and unavailable for plant uptake is dependent upon soil type and pH. In clay soils under mildly acidic conditions iron and aluminum phosphates are formed. Under strongly acidic conditions phosphorus is occluded in amorphous iron and aluminum oxides and hydroxides. Amorphous phosphorus over time crystallizes. The amount of phosphorus retained by soils (bound and thus lost in an insoluble form, not available to plants) depends on:
14

1. Soil type (l: 1 expanding clays and hydrous oxides adsorb large amounts of P) 2. Amount of clay in the soil, 3. Presence of amorphous colloids, 4. pH (maximum phosphorus available at pH 6.0 to 6.5), 5. Cation effects (higher valence gives more adsorption), 6. Organic matter (decreases adsorption, more available), The basis for phosphorus application to a crop is a soil test correlated with a history of the field (a soil fertility study). Eventually exchange sites in the soil, even a clay soil, can be filled. Thus, over time a field will require a lower rate of phosphorus application.
Phosphorus can be highly destructive as a water pollutant as it is often the limiting nutrient for algal growth. In small concentrations (even as low as 10 parts per billion) phosphorus can cause algal blooms in surface water. Algae can grow so fast when phosphorus is available that severe oxygen deprivation can occur when the algae die and decays, causing death to aquatic life. Ground water is usually not contaminated by phosphorus. However, repeated applications can fill soil exchange sites and contaminate ground water, especially in shallow aquifers.
Potassium: Potassium is usually not a problem environmentally. If applied in excess, potassium can adversely affect the uptake of other cations such as ammonium, magnesium, and calcium. Like phosphorus, potassium tends to stay in place. Leaching can occur in deep sands.
Secondary nutrients: Problems occur only when there is a deficiency of the secondary nutrients. A deficiency of magnesium in grasses can produce grass tetany in cattle. Magnesium is the central atom in chlorophyll. Calcium has multiple benefits for ensuring the production of healthy plants. Since calcium and magnesium leach readily, it is important to minimize their leaching for the benefit of the crop. Sulfur in the soil exists as the sulfate anion. Sulfur leaches faster than calcium or magnesium. Sulfur is usually not applied in sufficient quantity for it to become an environmental hazard.
Micronutrients: cronutrients are strongly held by soils and are not leached under optimal cropping conditions. Acidic soil conditions increase the availability and toxicity of these nutrients to crops. The micronutrients occur in small concentrations and are not considered a hazard to the environment.
Crop Fertilization: The economical use of fertilizers requires the consideration of a number interdependent factors. These factors include:
1. Soil test, 2. Yield goal of the selected crop, 3. Soil organic matter content, 4. Friability of the soil, 5. Weather and soil moisture conditions at time of application, 6. Application method. These factors require careful analysis. Farmers are turning to computer programs to calculate optimum application rates, however, the scientific community needs an understanding of nutrient
15

transport and use to refine these models. Typical or "rule of thumb" rates of fertilizer application are not recommended. Instead, the entire soil profile and soil history needs to be examined to develop recommendations that will sustain productivity and enhance soil quality. There is tremendous opportunity to look for non-traditional sources of nutrients. Municipal biosolids, many ashes and sludges, and other material that has been landfilled in the past could provide the crop production industry with economical nutrient sources.

Pesticides

While the most prevalent image of an agricultural pest is the insect, damaging pests can

also include weed, nematodes, plant and animal disease agents, and rodents. Plants, animals, and

microbes become pests when they cause economic, health, or aesthetic problems for humans. A

."

pesticide is defined by FIFRA as " ... any substance or mixture of substances intended for

preventing, destroying, repelling, or mitigating any insects, rodents, nematodes, fungi, or weeds,

or any other forms of life declared to be pests; and any substance or mixture intended for use as a

plant regulator, defoliant, or desiccant." Pesticides can be either natural or synthetic. Since the

1950's, most growers in the United States have preferred to use synthetic chemical pesticides to

control crop pests. The reasons for this include the immediate and dramatic effects on pests, the

ease with which they can be obtained and used, the ability to produce more consistent and higher

quality products with synthetic pesticides, and the fact that they require less management and

labor than alternative control methods. Since the 1970s, synthetic pesticide use has begun to

level off and even decline in some areas (PPRC, 1995). These usage trends have mainly been

affected by the development of pest resistance and regulatory and legislative action resulting

from environmental concerns.

Although detailed records on pesticide inventories in Georgia are not kept, in 1994, growers purchased more than $156 million worth ofpesticide products (Georgia Agricultural Statistics Service, 1995). Figure 2 shows the distribution ofpesticide applications throughout the State. As expected, most of the pesticide applications are throughout mid to south Georgia where crop production is dominant. Tables 1 and 2 show pesticide use by active ingredient and crop type in 1992. From these tables a variety of chemicals are obviously used in varying amounts depending on the crops being grown. Concerning active ingredients, Georgia farmers used more fungicides than herbicides and pesticides. This is mainly because it takes larger amounts of fungicide to cover a given area. Insecticides were the least common form of pesticide in terms of active ingredient used, however, very little active ingredient is required for pesticides to be effective. The category of other chemicals was also quite large. These chemicals primarily consist of nematicide, defoliants, and harvest aids. It is also interesting that the fumigant methyl bromide, the second most popular chemical in terms of active ingredient used, is in the process of being banned due to atmospheric environmental concerns. Much research emphasis is currently being placed on developing alternatives to methyl bromide, but few projects have yielded promising results.

16

Figure 2 Insecticide/Herbicide Use in Georgia. (Georgia Department of Natural Resources, 1993)

rt Mil,

o

Insec1Iclde/Helblcldce \J$91eSS than 50.000 Application-Acres

~t t " :.
~\~~~!

Insec1i=Ide/HertJidde use between 50..000 and 100.QOO Appllcotlon-Ac:res
lnSElctlclde/Herbicide use geoter tt.on 1OO.COO Application-Acres

N01&: An oppllcaltc:n--ocrete~ts one oPJ)llcollcn of i'lSeCtIclde-herblclde 10 one
Oct8 of land. Some crops trra>{ '9CfJlre ffiU-
tip/a applications.

"
17

Table 1 Georgia Pesticide Use in 1992 by Active Ingredient. (Gianessi and Anderson, 1995)

Active Ingredient (AI)

Trade Name

Fungicides

Chlorothalonil

Bravo

Sulfur

Thiolux

Maneb

Manex

PCNB

Terrac10r

Moncozeb

Dithane

"),
Total Fungicides*

Herbicides

lbs AI used/yr
3,982,500 2,646,200
325,300 322,500 311,800 8,065,300

MSMA Atrazine Pendimethalin Metolachlor 2,4-D Total Herbicides* Insecticides

Bueno Aatrex Prowl Dual 2,4-D

855,100 806,900 719,100 636,000 495,900 7,651,400

Aldicarb Chlorpyrifos Carbaryl Methomyl Carbofuran Total Insecticides* Other Chemicals 1,3-D Methyl Bromide Ethephon TotalOther*

Temik Lorsban Sevin Lannate Furadan
Telone Methyl Bromide Ethrel

1,125,300 976,600 308,000 253,400 240,800
5,269,900
4,633,900 4,076,100
410,400 10,138,000

*Total does not represent the sum as only the most common products are listed for each category

18

Table 2 Georgia Pesticide use in 1992 by crop type. (Data from Gianessi and Anderson, 1995)

Crop

Total AI used in 1992 (lbs)

Avg App Rate Most common AI by (lbs AIlacre)* weight

Alfalfa

12,000

0.4 Carbofuran

Apples

143,000

52.8 Mancozeb

Blueberries

45,000

12.9 Oil

Corn

2,274,000

3.1 Atrazine

Cotton

7,278,000

1l.5 MSMA

Oats, Rye, and Wheat

212,000

0.3 2,4-D

Onions

148,000

18.0 Chlorothalonil

Hay and Pasture

464,000

0.1 2,4-D

Peaches

1,140,000

54.2 Sulfur

Peanuts

10,581,000

15.7 Chlorothalonil

Pecans

1,614,000

13.3 Sulfur

Sod

18,000

3.0 2,4-D

Sorghum

113,000

2.1 Atrazine

Soybeans

859,000

1.3 Pendimethalin

Tobacco

892,000

20.3 Methyl Bromide

Vegetables

5,334,000

44.0 Methyl Bromide

'("
* Average Application rate is calculated by taking the sum of all chemicals applied to the crop and dividing by the total acreage. Therefore, this number represents a cumulative total application of many different chemicals.

19

The primary target of most synthetic insecticides is the insect's nervous system. Nerve poisons characteristically induce the appearance of symptoms in four stages: excitation, convulsion, paralysis, and death. Chlorinated hydrocarbon pesticides are neurotoxins as are the organophosphorus and carbamate insecticides. In addition the organophosphorus compounds have been used as ovicide to control insects in the egg stage. Other insecticides inhibit chitin formation or cause a breakdown of chitin and are considered more selective since mammals do not have chitin. However, chitin inhibitors are considered less effective than other insecticides (Tanada and Kaya, 1993).
Recently, products have been developed and marketed that use naturally occurring insecticides produced by bacteria. Certain bacteria (primarily Bacillus thuringiensis and its subspecies) produce protein crystals called endotoxins. When ingested by the larvae of some insects, the toxin, a crystalline protein, inflicts mortality. Bacterial insecticides are attractive since they are generally nontoxic to any life forms other than their specific target. Additionally, the toxin is readily biodegradable. These Bt toxins represent an exciting advance in pesticide development and will have a significant impact on future chemical use in the crop production industry.
Handlers and users of pesticides and other agrichemicals must recognize that these chemicals can contaminate groundwater. They can enter groundwater by direct routes (i.e. point sources) or by sustained doses of low concentrations. Point sources include spills, back siphoning, substandard well construction, improperly maintained equipment, and improper disposal of rinse water and chemical containers. Chemicals also can reach groundwater from nonpoint sources, including runoff and leaching from fields. Concern about the contamination of ground water by pesticides is increasing. Very small amounts ofpesticide can create concentrations in water in excess of health standards. Seepage of pesticides into groundwater is a particular concern to farm families since their own well may be affected. Well contamination can make the water unusable for years and the cost of cleaning contaminated wells is extremely high. Nationally, more than 74 different pesticides have been detected in groundwater in 38 different states. Of these 74 detections, 46 were attributed to normal use and 32 were attributed to point sources or misuse (Ritter, 1990). The USEPA has estimated that 4.2% of rural domestic wells nationwide contain at least one pesticide at detectable levels, and that in cropped vulnerable areas 5.5% of the wells may be contaminated (Clay et aI., 1995). In Minnesota, 36% of 504 wells tested in susceptible areas were contaminated with low concentrations of pesticides. Of the contaminated wells, 92% contained atrazine and 13.5% contained alachlor (herbicides).
Groundwater contamination in Georgia due to pesticides has not been a consistently significant problem (Georgia Dept. of Natural Resources, 1993). Only a few pesticides, mostly herbicides, have been found in groundwater. The state has found no particular pattern to these occurrences and several detections have been transient. That is, the chemical is no longer present when the well is resampled. Prudent agricultural use of pesticides, therefore, does not appear to represent a significant threat to drinking water aquifers in Georgia. It appears that localized over application of chemical pesticides, misuse, and improper handling are the major threats to water resources. Farm workers can also be directly affected by handling and application to crops, however, worker protection standards have been established to protect these workers.
20

Pesticides can also contaminate surface water. Typically, annual herbicide losses with water and sediment in runoff from a herbicide treated field are less than 5% of the amount applied (Baker et aI., 1995). These losses can result in temporarily high concentrations, in the part-per-million range, in nearby receiving waters. Losses with subsurface flow are lower, usually less than 1%, and often less than 0.1 %. These losses are low from an economic perspective but can result in part-per-billion concentrations of herbicides in groundwater or surface water.
Pesticide loss can occur through microbial degradation, volatilization, leaching, erosion and runoff, absorption by plants, or spontaneous chemical breakdown (Brock et aI., 1994). The persistence of a pesticide is a measure of its ability to remain in the environment. While the most persistent pesticides are often effective for longer durations, they also pose more of a risk for both transport to water or off-site areas and accumulations to excessive levels. Persistence rates of pesticides vary widely and are influenced by a wide variety of environmental factors such as temperature, pH, aeration, and organic matter content ofthe soil. Some chlorinated insecticides are so indestructible that they have persisted for more than 10 years, but most pesticides degrade rapidly enough to prevent buildup in soils. The most widely used herbicide, 2,4-D (chlorinated phenoxy acetic acid), persists in soils for only two to four weeks. Organophosphate insecticides may last only a few days in soils. However, organophosphates can be toxic to humans so this low persistence is essential. The carbamates are readily biodegradable and have relatively low mammal toxicity. However, some carbamates used as nematicide are quite soluble in water, are not adsorbed by the soil, and consequently leach downward and into the ground water. Herbicides are generally biodegradable, and most of them are relatively low in mammal toxicity. However, some are quite toxic to fish and to other wildlife.
Biochemical degradation by soil organisms is the single most important method by which synthetic pesticides are lost from soils (Brady, 1990). Certain polar groups on the pesticide molecules provide points of attack for the organisms. Organophosphate insecticides, herbicides such as 2,4-D, the phenylureas, the aliphatic acids, and the carbamates are readily attacked by a host of organisms. The exceptions are the triazines, such as atrazine, and the chlorinated hydrocarbons such as aldrin, dieldrin, and heptachlor that are broken down very slowly or are broken down by chemical action. Most organic fungicides are subject to microbial decomposition, although the rate of the breakdown of some is slow and can cause residue problems. A biological breakdown is the desired mechanism when one wishes to avoid potential long-term hazards associated with the parent pesticide and its derivatives (Brady, 1967).
The overall levels of bacteria in the soil are generally not seriously affected by pesticides. Bacteria are important as they catalyze the degradation of pesticides. Therefore, measures that increase soil bacteria levels have a positive affect on pesticide breakdown. Problems can occur in conventional tillage crop production with soils that have low organic matter contents. Less organic matter usually results in low microorganism concentrations except near roots. Thus, it may be that there will not be an adequate environment and microbial population for the timely biodegradation of residual pesticides in the soil.
The organisms responsible for nitrification and nitrogen fixation are sometimes adversely affected by pesticides. Insecticides and fungicides affect both processes more than do most
21

herbicides, although some of the latter can reduce the numbers of organisms carrying out these two reactions. Recent evidence suggests that some pesticides can enhance biological nitrogen fixation by reducing the activity of protozoa and other organisms that are competitors or predators of the nitrogen fixing bacteria. The process of ammonification is often benefited by pesticide use. The negative effects of most pesticides on soil microorganisms are temporary, and after a few days or a few weeks, organism numbers generally recover.
Some pesticides undergo chemical modification independent of soil organisms. Diaquat and the triazines are subject to slow photodecomposition activated by solar radiation. The triazine herbicides and organophosphate insecticides are subject to hydrolysis and subsequent degradation in the soil.
Pesticides are commonly absorbed by higher plants, a necessary process for the effectiveness of most herbicides and of some insecticides. The absorbed chemicals may remain intact inside the plant or they may be degraded. Some degradation products are quite harmless to humans and other creatures, but others are toxic, in some cases even more toxic than the original pesticide. Pesticide residues, especially those found in the edible portion of plants are of critical concern and levels are strictly regulated by law.
Pesticides vary greatly in their volatility and subsequent susceptibility to atmospheric loss. Some soil fumigants, such as methyl bromide, are selected because of their very high vapor pressure, which permits them to penetrate soil pores to contact the target organisms. This characteristic encourages rapid loss to the atmosphere after treatment unless soil is covered or sealed. A few herbicides and fungicides are sufficiently volatile to make vaporization a primary means of their loss from soil. Early assumptions that disappearance of pesticides from soils was evidence of their breakdown are now questionable. It appears that some apparent pesticide loss returns to the soil in precipitation. Currently there is little work being conducted to quantify pesticide losses to the atmosphere. Except for drift from aerial applications and windy conditions, there is little evidence that significant amounts of pesticides are transported through the atmosphere.
Tillage also affects pesticide losses. Restricting tillage reduces weed control options and increases reliance on herbicides. The net result is that in conservation tillage systems, more diverse and intense weed populations often need to be managed with fewer control tools. However, crop residue tends to promote pesticide adsorption and definitely reduces runoff and erosion. Meeting the combined goals of crop residue management and herbicide use reduction, while maintaining effective weed management, is a major challenge. The effects of conservation tillage on chemical use and potential pollution are highly variable and dependent on site specific conditions. More research is needed to document the impacts of conservation tillage on pesticide use and mobility.
While the Clean Water Act does not provide for regulatory actions unless spills occur, morally it is responsibility of individual pesticide users and handlers to provide a~surance that these chemicals do not become point or nonpoint sources of contamination. FIFRA does require that most pesticide handlers obtain certification and establish procedures to insure that pesticides do not present health hazards to agricultural employees, however, since only one certified applicator
22

is required, most employees receive little training on proper storage and handling techniques. Five major factors determine whether pesticides will reach groundwater:
1. Practices of the chemical applicator, 2. Presence of surface water, 3. Characteristics of the chemical, 4. Texture ofthe soil, 5. Proximity of groundwater and type of overlying geological formations.
In addition, several other factors affect the likelihood of agricultural chemicals moving into groundwater. The soil itself also greatly influences the fate of the chemical after application. Three major soil characteristics affect soil adsorption and corresponding chemical movement. They are soil texture, permeability, and organic matter content. The relative amounts of sand, silt and clay determine soil texture. Because there is more surface area for adsorption to occur, less leaching occurs in soils high in clay; while more occurs in coarse, sandy soils. Permeability is the measure of the extent to which water moves through the soil. In soils with low permeability, water tends to collect, causing runoff and possibly surface water contamination. Highly permeable soils must be managed carefully since chemicals not adsorbed tightly will move downward fairly rapidly, perhaps to groundwater. Rainfall and irrigation also directly influence pesticide migration as greater amounts increase the likelihood of pesticide migration (Jury et aI., 1991). Organic matter increases the soil's water-holding capacity. Also, some chemicals are adsorbed onto soil organic matter, preventing leaching to groundwater and holding the chemical in place. Increasing the soil's organic matter content is the only economical way the soil can be manipulated to decrease the pollution potential. In general, soils with high organic carbon and a low annual drainage rate have a low potential for migration due to leaching. Soils with low organic carbon and high annual drainage rate (as in south Georgia) have a high potential for migration due to pesticide leaching.
The tendency of pesticides to leach from soils is also closely related to chemical properties including their solubility, persistence, and their potential for adsorption. Solubility is a measure of the pesticide's ability to be absorbed in water. Pesticides that have high solubilities are much more likely to move with the water. In general, herbicides seem to be more mobile than either fungicides or insecticides (Brady, 1990). Chemical persistence, or the length of time required for the chemical to break down into nontoxic materials, also has a tremendous impact on pollution potential. By selecting chemicals with less persistence, the potential for chemical waste and groundwater contamination can be reduced. Likewise, conditions that encourage adsorption will discourage leaching as strongly adsorbed molecules are not likely to move down the soil profile. The adsorption of pesticides by soil can be determined by the chemical characteristics of the pesticide. The presence of polar functional groups on the pesticide encourages adsorption, especially on the soil humus. Hydrogen bonding and protonation promote adsorption. Some pesticides with positively charged groups, such as the herbicides diaquat and paraquat, are also adsorbed by silicate clays. Adsorption by clays of some pesticides tends to be pH dependent with maximum adsorption occurring at low pH levels where protonation occurs.
23

Groundwater proximity should also be considered when using chemicals. Chemicals are much more likely to reach groundwater that is only a few feet beneath the surface, especially if the soil is sandy, than when the groundwater is deeper. Permeability of geological layers between the surface and the groundwater zone also determines the vulnerability to contamination from the surface. Sinkholes, sinking streams, karst limestone areas with shallow top soils, and areas with high watertables are integral parts ofthe subsurface drainage system in some areas. Such features provide direct avenues for potential contamination of groundwater. Improperly sealed wells also can provide a direct pathway for surface water to enter the groundwater. Chemicals should never be mixed in the vicinity of these sites. If chemicals are to be applied near these areas or areas draining directly into streams, an untreated grassy barrier around the sinkhole or the stream should be left free from chemicals.
The risks of groundwater contamination from agrichemicals can be reduced by following general guidelines (Agricultural Pesticide Application Equipment, 1989 and Parker, 1992):
1. Follow label directions, 2. Handle chemicals safely, 3. Mix and calibrate accurately, 4. Protect wellheads, 5. Prevent back-siphoning, 6. Use field maps to plan application rates in advance. 7. Follow best management practice guidelines and Extension recommendations.
Fuel Storage and Handling Although it may not be considered a waste stream, Georgia farmers purchased more than
$103 million worth of fuel and oil in 1994. While most of this is converted to power for crop production, if not properly managed, petroleum and oil can cause environmental degradation. In fact, Farm*A*Syst environmental self assessments identify petroleum storage and handling as a high pollution risk on farmsteads more often than any other factor. Contamination from tanks occurs from spills during filling and transfer, piping failures, installation mistakes, corrosion of tank walls, and ineffective leak monitoring practices. Many petroleum products contain benzene and xylene that are known human carcinogens and are dangerous at very low levels. One gallon of gasoline can contaminate two to ten million gallons of water. Furthermore, since most farms are dependent on groundwater for drinking purposes, fuel spills can directly affect their families' health.
Petroleum is stored in underground tanks or aboveground tanks. Petroleum refers primarily to gasoline and diesel fuel, liquid propane, and heating oil. Most farm petroleum tanks hold less than 1,100 gallons and are exempt from federal tank regulations, however, tank owners are still legally responsible for cleaning up any petroleum tank leaks. Bare steel tanks have a life of 15 to 25 years underground. Buried tanks can hold up property sales or loans. Most insurance companies no longer insure for ground water contaminated by gasoline as cleanup costs can easily exceed the value of property.
Pollution prevention can playa vital role in a farmer's ability to manage petroleum resources. Most farms have shops that can benefit from following pollution prevention practices established
24

for commercial garages. Since fuel is a costly input, substantial efforts have already been made to minimize consumption. Therefore, pollution prevention efforts should probably focus on improved storage and handling. It is usually considered essential that petroleum storage tanks be placed a minimum of 100 ft. from drinking water wells. Tanks should be located at a lower elevation than wells. Tanks should be at least 50 ft. from any building to protect against explosion or fire. Pressure relief valves and vents should be used to protect the tank integrity and extend tank life. Although not required by law, secondary containment could easily be economically justified on many large farms. It is essential that crop producers realize the pollution potential of on-farm petroleum storage and devise pollution prevention plans to protect themselves and the environment.
Crop Residue, and Harvest Losses Two classes of waste are associated with field crop production. Crop residue is left in the
field after harvest of the economically valuable portion of the crop. The second kind of waste includes pesticide and fertilizer containers, excess pesticides, and other inputs such as plastic for vegetable production or packaging materials. It will be discussed in future sections. While neither of these waste streams pose significant environmental problems, both present opportunities for economic gain through pollution prevention activities.
The amount of aboveground residue remaining on the field after crop harvest depends on both the crop type and management practices. Often these amounts can be substantial, ranging from 7,200 lb/ac for conventional tilled corn to less than 1,000 lb/ac for cotton. No till or conservation till practices can result in more residue and less energy input, but can create the need for additional pesticide inputs. The Harvest Index (HI), defined as the mass of harvested or useable plant product as a fraction of the total plant biomass output per unit area, is a measure of the crop residue. Crop residues help to recycle nutrients back to the soil, thereby diminishing the need for applied nutrients. For example, the 3,900 lb/ac of soybean residue remaining after harvest has an approximate fertilizer value of$12.19 (CAST, 1995). Retention of crop residues on the land where grown is usually the most practical and sound waste management practice. Of the nutrients in crop residues, N presents the greatest environmental concern due to its leaching potential. However, the recycling ofN in a purely crop oriented system retains N in the soil surface and residue as long as fertilizer N is not applied in excess. Some crop residues are burned. Burning residues creates an air pollution concern and has little impact on the productivity of most systems, so it should be avoided under most conditions. Residues can be used for many other things including animal feeds, energy generation, off-site fertilization or erosion control, and heating. However, as a pollution prevention practice, leaving it in the field is probably the best alternative.
Much of the material harvested in crop production does not reach the consumer. Post harvest losses can range from 10% to 80% depending on the crop. While losses in the field are usually dispersed or applied to the land, ultimate disposal from packing houses, transport, processing plants, and at the market is usually in landfills or mixed with sewage. Generally, food processed for human consumption produces more waste than that sold in the fresh market. Cull produce from the field is a problem only when large quantities are placed near bodies of water or human habitation. Problems associated with this activity are usually nuisance type problems, with odors
25

and flying insects causing the bulk of complaints. Waste organic material is usually applied to the field, or land-filled. Care must be taken in assessing the carbon to nitrogen ratios of applied organic waste as material with high carbon content in the form of short chain fatty acids can rob the soil of nitrogen and water and raise soil temperatures. Composting waste materials may be required to correct this situation, especially if planting is planned in the applied area within a month of waste application to the soil (Foth and Ellis, 1988). Opportunities to return these wastes to the fields, develop new products from the wastes, and define new uses for the wastes need to be considered. When implemented at the field level, these are activities that would reduce post harvest losses at the source.
26

POLLUTION PREVENTION OPPORTUNITIES
Along the way to developing modem agricultural practices, the old knowledge of how to live with the land and with nature has sometimes been neglected. Today, farmers are increasingly turning to chemicals when they need to fertilize or kill pests. This does not have to be the case. Utilizing principles of sustainable agriculture, farmers are learning to apply chemicals in ways that have little if any effect on people and wildlife while increasing the profitability of their operations. As an example, researchers in Tifton, Georgia have reduced the pesticide used to grow peanuts by 93% while maintaining above average yields with no synthetic fertilizers. Today's sustainable agricultural practices combine the innovations of biotechnology, chemistry, and agricultural technology with the old knowledge of living in harmony with nature. The combination is powerful and offers hope for increasing the fertility of the land, building topsoil, more effectively controlling pests, and increasing the competitiveness of American agriculture and well-being of the Georgia farmer.
The goals of sustainable agriculture are often similar to those of pollution prevention. Both focus on reducing inputs to protect the environment and increase economic gain. In fact, pollution prevention may be view as the immediate tool for achieving long-term sustainability. In this section, the pollution prevention technologies with the most promise for application to crop production are reviewed. For each technology, both the opportunities and impediments are presented and, if possible, strategies for implementation are presented.
Best Management Practices Best Management Practices (BMPs) refers to a combination of practices determined to be
effective economical approaches to preventing or reducing pollution generated by nonpoint sources. BMPs can be structural (ie. terraces, dams, pesticide mixing facilities, and fencing) or they can be managerial (ie. Crop rotation, nutrient management, and conservation tillage). Both types ofBMPs require good management to be effective in reducing the generation or delivery of pollutants from agricultural activities. Preventive practices such as these are the most practical approaches to reducing nonpoint source pollution. If the farming community does not participate in voluntary programs using BMPs, then it can be expected that there will be additional calls for mandatory programs to implement BMPs.
Presently, several Rural Clean Water Programs (RCWP), Agricultural Conservation Programs, and Special Water Quality Projects across the United States are designed to demonstrate the effectiveness of various BMPs for the abatement of agricultural pollution. These programs not only promote the use ofBMPs to the agricultural community, but also serve as learning tools. A review of21 different RCWP projects recently summarized many findings nationwide (Osmond et aI., 1995). For voluntary BMPs to be effective, they must be implemented as systems rather than individual practices because systems reduce the impact ofthe pollutant at several points: the source, the transport process, and the delivery. Properly designed BMP systems must also be site specific and placed in the correct locations. Finally, since financial resources are generally limited, BMP implementation should be prioritized and cost-share money should only be used in those locations that will have the most impact. This report also stressed the fact that successful
27

adaptation of on-farm BMPs is highly dependent on education. Producers must understand the impact their practices have on the environment and the mechanism that the BMP uses to reduce this impact.
As part of an effort to promote voluntary adoption ofBMPs, the Georgia State Soil and Water Conservation Commission has published a booklet called Agricultural Best Management Practices for Protecting Water Quality in Georgia. This publication is intended to serve as a basic guide for anyone implementing agricultural BMPs. In addition, the Conservation Commission is designated as the lead agency for protecting water quality from agricultural nonpoint source pollution. They provide education and technical assistance to insure that stewardship principles incorporated in agricultural BMPs are understood and employed for maximum benefit to Georgia's land and people. In doing so, they work closely with the Cooperative Extension Service, the NRCS, and the DNR. Since this publication adequately covers most BMPs that would be effective in Georgia, it should serve as the reference for BMPs to be used in the agricultural pollution prevention program.
BMPs are used to reduce the effects of all forms of pollutants. They use a variety of mechanisms that result in degrees of effectiveness. Table 3 presents a review ofBMPs that are particularly applicable to Georgia Crop Production. Some of these BMPs that are particularly relevant will be discussed in more detail in future sections. All of them are proven techniques that prevent pollution. Most are practiced to varying degrees in Georgia. The main impediments to more widespread use are a lack of capital for implementation, a lack of knowledge concerning the benefits, a lack of willingness to accept responsibility, and a lack of incentives. Often, BMPs do make economical sense, however, the payback periods are long term and less apparent than an immediate yield increase.
Controlling Runoff and Soil Erosion Control of soil erosion is probably the primary opportunity for preventing pollution as
sediment is not only a pollutant itself, but also carries nutrients and pesticides with it. In addition, farmers are tuned into the effects of soil erosion and its impacts on soil quality and productivity. Since the dust bowl years of the 1920s and 1930s, both Federal and State efforts have concentrated on reducing or controlling soil erosion. Farmers have responded and do a better job of controlling soil erosion than anytime in the past. According to the National Resources Inventory, farmers have reduced erosion from an average of 4.5 tons/acre/year in 1982 to less than 3.5 tons/acre/year in 1992. Much ofthis improvement has been attributed to the move toward conservation tillage systems, the removal of highly erodible land from production, and an increase in awareness ofBMPs. Weather is the dominant uncontrollable factor in reducing runoff and soil erosion. The cost of completely preventing rainfall erosion on cropland would be well in excess of 143 trillion dollars (Porterfield et aI., 1995). This is something neither the farmers or the public could afford. However, through the voluntary implementation ofBMPs and pollution prevention techniques, soil erosion and its environmental impact can be substantially reduced.
28

Table 3 Best Management Practice Summary Guide

Surface Water

Ground Water

BMP

Sediment Soluble Adsorbed NLoss Pesticide

Pollutants Pollutants

Loss

Soil testing/Plant analysis

0

++

+

++ 0

Setting realistic yield goal

0

++

++

++ +

Site specific management

0

+

+

+

+

Equipment Maintenance & Calibration 0

+

+

+

+

Application methods and timing

0

++

++

+

+

Water Control Structures

++

+

++

-

-

Subsurface drainage

?

-

?

++ ++

IPM

0

++

++

0

++

Pesticide selection and rotation

0

++

++

0

++

Conservation Tillage

++

?

++

?

?

Contours and Terraces

++

+

++

-

-

Stripcropping

+

+

+

0

0

Cover Crop

+

+

+

+

0

Crop Rotation

++

+

++

0

+

Irrigation Management

+

++

+

++ +

Pasture Management

+

0

+

0

0

Waterbody Protection

++

+

++

0

?

Grassed Waterways

+

0

+

0

0

Critical Area Planting

++

+

+

0

0

Stream Buffers

++

+

++

+

?

KEY: ++ Medium to high effectiveness

oAlmost no effect

+ Low to Medium effectiveness

- Could have detrimental effect

? Further research is required

Note: BMPs are site specific in nature. These generalizations are not necessarily true under all

conditions. Practices in bold represent source reduction opportunities.

29

Essentially, any measure that increases the infiltration rate or water holding capacity of the soil, limits flow velocity, or increases the time that water remains on the soil surface will decrease runoff and corresponding soil loss. Traditional methods used in crop production include conservation tillage, contour farming, and strip cropping. In this section, some of these traditional practices are reviewed and a few less frequently used options are presented. Since many practices that reduce runoff and soil erosion also prevent nutrient and pesticide losses, the discussion will not be limited to soil erosion.
Conservation Tillage While BMPs such as contouring, terraces, vegetated waterways, and filter strips are all
effective at trapping sediment and preventing their movement to offsite areas, they do little or nothing to curtail the real man-induced causes of soil erosion, namely soil disturbance and compaction. Soil disturbance or tillage is the primary reason that agricultural fields produce more erosion than most other land uses. It exposes the soil surface to rainfall impact that detaches soil particles, increases the amount of soil crusting that occurs causing greater amounts of runoff, and decreases vegetation at the soil surface which holds the soil in place. In addition, soil compaction causes substantial reductions in productivity. Wheel track compaction produces disproportionately larger amounts of runoff and sediment than non wheel tracked areas. The effects of compaction alone have reduced alfalfa yields 40% and com yields up to 25% (porterfield et aI., 1995).
Many Georgia row crops can be produced using conservation tillage which is generally considered the most effective single practice for controlling erosion and sediment transport (Georgia Soil and Water Conservation Service, 1994). Conservation tillage is a means of planting and culturing crops with a minimum disturbance of soil. It can include no-till, ridge till, mulch till, and chisel till systems. In conservation tillage at least 30 percent of the soil surface is left covered with a cover crop or crop residue immediately after planting. Crop residues, including old plant stalks and leaves, can dissipate rainfall energy and protect the soil surface from wind erosion. It also creates a rougher soil surface that reduces flow velocities and increases surface storage and infiltration The actual amount of tillage needed with conservation tillage varies with soil type and crop. The key in conservation till systems is obtaining a suitable growing environment, weed free and non-compacted, without burying large amounts of residue beneath the soil surface. New equipment for both the actual tillage and planting have been extremely helpful in accomplishing this. In-row subsoilers have been especially valuable for summer crops like soybeans, cotton, and com in Georgia.
The most common approach to conservation tillage in Georgia is to grow a winter small grain, harvest it, spread the residue, then use special conservation tillage planters to plant directly into the small grain residue. Conservation tillage has been shown to reduce surface soil temperature by as much as 30 degrees F and soil water runoff/erosion by as much as 95% over that of conventional tillage. Conservation tillage reduces soil loss by 50 to 95%. The actual amounts or often directly related to the amount of residue left on the soil surface. By reducing soil movement, the pollution of streams and lakes from sediment, nutrients, and pesticides is reduced. The reduction in pollution is proportional to the amount of soil saved. Over time, organic matter begins to accumulate which has multiple beneficial effects.
30

Conservation tillage systems depend on pesticides more than conventional tillage systems. They depend on herbicides to manage weed growth and insecticide to handle increased pest populations (although research suggests that insect populations return to normal levels after a couple of years). While these inputs may increase slightly, research has shown that pesticide losses in surface runoff tend to be less than those under conventional tillage. Three studies on highly erodible land showed that average runoff and soil loss rates from no till systems were 31 % and 7% of that from conventional tilled systems (CTIC, 1992). Average herbicide runoff under these no-till systems was 30% of the conventional tilled runoff. Similarly, a review by Fawcett et aI., 1994 showed that herbicide runoff from no-till, chisel plow, and ridge till systems was 30%,31%, and 58% of that from conventional tilled systems. They attribute this reduction to increases in infiltration. This increases the likelihood of ground water contamination, however, most herbicides will degrade before they reach groundwater.
Georgia has many impediments to conservation tillage that are not evident in other parts of the country. Nationally, conservation tillage has become the norm with an estimated 60% of the crop acreage in some form of conservation tillage. In Georgia, however, adoption rates are significantly lower. Part ofthis is due to the crops produced. Peanuts, for example, require some sort of plowing to insure that the subsoil is loose and non-compacted. Soil types also influence the farmer's selection. Although research results have shown that conservation tillage in Georgia can increase yields, most farmers feel that the compacted clay layers beneath their fields must be broken by some sort of plowing. This, in fact, may be true as yields can decline in the first year or two, however, after this period natural processes such as insect, animal, and worm activity and the accumulation of organic matter will begin to negate the effects of compacted clay layers. The cost of effective conservation tillage machinery and its availability also have a profound effect on the adoption of conservation tillage in Georgia.
Conservation tillage, beyond controlling erosion, provides savings oftime, fuel, labor, and soil moisture. It also requires more timely and intensive management than conventional tillage. Usually the savings in fuel and labor can more than offset the cost of additional equipment on an annual basis, however, purchasing the equipment is a large investment. The equipment must be more readily available if conservation tillage is to be successful in Georgia. Educational programs also need to be developed to give the farmers the detailed management procedures that will be required in Georgia.
Many actions are already underway to increase conservation tillage in Georgia. The Conservation Technology Information Center (CTIC) is a national organization affiliated with the EPA that promotes reduced tillage practices. They are quite active in Georgia and exhibit at many trade shows. They also have established programs in some areas of Georgia to rent no till planters to farmers wishing to use them that cannot afford to purchase the machinery. This program is highly effective and needs to be expanded as the demand for these machines is seasonally quite high. In addition, the University of Georgia Cooperative Extension Service and Experiment Station have established demonstration plots and outreach programs to show the producers that conservation tillage can be effective in Georgia.
31

Increase Organic Matter: Many crops in Georgia need to be cultivated for weed control and to improve soil
moisture infiltration. These practices are particularly applicable to the soils of the coastal plain region in the southern half of the state. A primary problem with conventional tillage is that it buries the organic matter in the surface residue where it is oxidized much faster. This organic matter is essential to soil quality and is an additional reason for the improved productivity of conservation tillage systems. For example, moldboard plowing wheat stubble after harvest causes a loss of over 3,600 pounds of organic matter per acre in just 19 days (Porterfield et aI., 1995). Using conservation tillage, most ofthis organic matter could have been preserved at the soil surface to protect it from erosion and improve soil quality.

Soil quality is a key factor in determining how much soil erosion occurs, and how much of the

applied nutrients and pesticides escape from the soil. When asked what was the number one

descriptive term for recognizing a healthy soil, farmers in Wisconsin overwhelmingly answered

that organic matter was the best term. Organic matter is the "glue" that holds soil aggregates

together and allows them to resist erosive and compactive forces. Tisdale et aI., 1985, list the

following benefits associated with increased soil organic matter:

~

It increases the cation exchange capacity allowing the soil to act as a storehouse for

nutrients,

~

It provides energy for microorganism activity, releases carbon dioxide, and restores a

sterile soil to a natural state of high biological activity,

~

It increases soil water-holding capacity, stabilizes structure, and improves tilth,

~

It provides surface protection and thus reduces crusting and increases infiltration,

~

It buffers the soil against rapid changes in acidity, alkalinity and salinity,

~

It provides a carbon source for denitrifying bacteria that reduce nitrates that would

otherwise be lost to subsoil drainage and groundwater contamination.

Most of these functions depend on organic matter decomposition. Organic matter is difficult to

maintain using crop residues alone. Green manure or cover crops, proper crop rotations, and

organic matter amendments are usually required to maintain high levels of soil organic matter.

Winter cover crops are generally thought to be good protection against soil erosion. Cover crops are crops of close growing grasses, legumes, or small grains grown mainly to protect or improve soil. When these residues are left on the soil, they add organic matter and possibly nutrients if a legume was used. Cover crops control erosion during periods ofthe year when the major crop would not provide adequate cover. They can reduce erosion by 40-60 percent when compared with bare soil conditions. Critical studies suggest that the effect of cover crops on soil loss is generally diminished when winter cover crops are turned under in the usual manner in early spring. Georgia weather patterns are usually dominated by high rainfall amounts in late winter and early spring. Freshly prepared land is quite susceptible to erosion, so it is important that the cover crop provide enough protection to have the desired effect at this time. Mulch treatments, such as residues left on the surface, have been more effective than incorporation. Methods of handling residues in the fall also have a marked effect on soil loss. Shredding cornstalks reduced soil losses to about half that obtained from cornstalks left by com harvesters (Mannering, 1979). Cotton residue provides substantially more cover and erosion protection if it is shredded after harvest. Many residues, such as peanut vines, are removed from fields. An effective pollution

32

prevention practice is to retain these residues in the field for both improved soil quality and environmental protection.
Organic matter can also be added to the soil in the form of amendments. Land applying animal manures, yard wastes, compost, and other organic biomass for crop production is an attractive disposal method that could relieve landfills in some areas. There is considerable data in the literature that proves that land applied organic matter significantly decreases runoff and soil erosion (Abu-Zreig et aI., 1994). Surface application of organic matter has been reported to be more effective in reducing soil loss than incorporating under field conditions (Free, 1949; Deizman, 1989). Sludge when applied at the rate of 105 kg N/ha, reduced soil loss by 95%, and water runoff by 29%. Also the stabilization effects of organic wastes, manures, crop residues, etc. on soil seems to be highly dependent on time. The soil chemical and physical properties are enhanced as decomposition proceeds. Application of organic matter has also been seen to reduce wind erosion greatly (Woodruff, 1974).
Impediments to organic matter additions in Georgia include high decomposition rates, increased labor and management, and a lack of economical sources. In South Georgia, where most crop production occurs, high temperatures and moisture conditions rapidly decompose most types of organic material. This is why natural soil levels of organic carbon are very low compared to soils of most other agricultural regions. Soil organic matter levels range from 0.1 to 1.0% in most of the Coastal Plain while organic matter levels of 3 to 5 % are not uncommon in the Midwest. Unless very large organic matter additions are made or cropping practices are changed for extended periods, the soil will quickly return to its natural state. In addition, obtaining biomass resource in most of Georgia crop production regions is often difficult. This may be changing as the poultry industry expands into this area and more attention is focused on diverting organic materials from landfills.
The Farm Bureau proposed an innovative program that could be used to improve levels of soil organic matter. They lobbied to have a graduated incentive program for increasing soil organic matter in the 1996 Farm Bill. This program called for a set, per acre incentive, for each incremental increase in organic matter that could be documented with soil tests. Once the top level of improvement was reached the plan called for a federal income tax credit so that the farmer would be encouraged to maintain these improvements over a long term. While this plan would have been costly and difficult to implement, it shows that there is a grassroots realization ofthe importance of maintaining soil organic matter. Programs should be developed to encourage farmers to maintain soil quality as it is an effective pollution prevention tool that increases productivity and protects the environment.
Cropping Practices: Cropping Practices and the selection of crop rotations also have a dramatic effect on soil
quality, runoff and erosion~ and the loss of nutrients and pesticides. By simply changing practices or the sequence of crops he grows, a farmer can substantially reduce erosion and improve productivity. Both rotations and practices can increase organic matter and improve soil quality, however, each also have additional benefits that cannot be obtained through organic matter additions or changes in tillage.
33

Crop rotations involve a planned sequence of changing crops grown on a particular field. A typical rotation often involves a year or two of a high value crop such as peanuts, com, or cotton followed by a grass or legume such as soybeans, small grains, or hay. Not only do crop rotation reduce erosion through organic matter additions, but they also provide increase cover during certain points in the sequence to lower the overall average erosion rate. In addition, rotations can be used to reduce or control nematodes, insects, and diseases by including a non-host crop in the rotation and they prevent the buildup of certain weeds associated with the continuous production of one crop. This usually results in less pesticide consumption when rotations are used. Finally, when legumes are used in rotation, the nitrogen formed by fixation can reduce the nitrogen supplement required for the subsequent crop.

The keys to establishing proper rotations include alternating crops that are profitable and adapted

'')"

to site specific conditions, insuring that host crops are not followed by crops that are susceptible

to the hosts, and establishing rotations that are longer than one year. Crop rotations should be

longer than a year to maintain the effectiveness of pesticide inputs. Different crops require the

use of different insecticides and herbicides. By alternating crops, rotations often require that

chemical inputs rotate as well. This reduces the need for pesticide inputs and increases their

effectiveness by not allowing the pest, be it weeds or insects, to develop resistance to any

individual chemical.

While most farmers realize that crop rotation can increase yields, few take advantage of this fact because they want to get the maximum return every year. Table 4 shows expected 1996 crop yields for various crop rotations as forecast by the Extension service. When using this table many farmers get caught up in the fact that peanuts can return $145 per acre and this is the best return. In almost every case though, crop yields increase with rotations. For example, a twoyear rotation of peanuts and com will return $308 per acre over two years while continuous peanuts will only provide $290. To prevent pollution through crop rotation, we need to do a better job of distributing this information and changing the attitude of farmers from making annual decisions to looking at the long term impacts of his decisions.

Runoff and soil loss are directly correlated to crop cover conditions and leaf area indexes. Studies have shown that losses are greatly reduced by closed canopies. In one study on peanuts at a full canopy, two and four-row peanut plots had at least 74% less soil loss than continuous fallow and bare-bedded plots. Four-row peanut plots had up to 64% less soil loss than two-row peanut plots (Truman and Williams, 1994). The two and four-row plots had at least 24% less runoff than continuous fallow and bare-bedded plots. By conserving soil and water, cropping practices can increase profits by providing more efficient use of nutrients and decreasing management requirements and risk. While cropping practices are inherently tied to machinery constraints and continuously evolve over time, farmers need to be aware of the effects of various practices on both yield and the environment.

34

Table 4 Expected 1996 Yields, Production Costs and Profits of Selected Georgia Crops with
V,aryI.ng Frequency 0 fPIantI' ng"*

Crop

Frequency of Planting

Expected Yield Projected (bu orlb/A) P. Costs ($/A)

Projected Profit ($/A)

Cotton

every year every 2nd year* every 3rd year*

86% 98% 100% (700 lb)

105-115% 100% 100%

@78/lb

$ 38.36 $143.00 $154.00

Peanut

every year every 2nd year* every 3rd year*

80% 90% 100% (300 lb)

106-108% 100% 100%

@$610/T $145.00 $274.00 $366.00

Soybeans

every year every 2nd year* every 3rd year*

85% 95% 100% (32 bu)

106-112% 100% 100%

@$6.75/bu $-21.32 $ 17.20 $ 28.00

Com

every year every 2nd year** every 3rd year **

90% 100% 100% (90 bu)

105% 100% 100%

@$3.00/bu $-4.00 $34.00 $34.00

Wheat

every year every 2nd year** every 3rd year**

75% 95% 100% (75 bu)

110% 100% 100%

@$4.00/bu $-23.60 $ 59.00 $ 74.00

*Rotated with com **Rotated with non grass crops

Forage and Pasture Management
Although areas used for pasture and forage production have a low potential for pollution due to an abundance of soil cover and relatively low amounts of chemical and nutrient input, if improperly managed they can contribute significant amounts of nonpoint source contamination. Grasslands or pastures are essential to almost any livestock operation. They provide nutrition for cattle or other livestock and food and cover for wildlife. Well-managed grasslands protect valuable soil resources and improve water quality. The fibrous root systems of healthy grasses hold the soil in place so that surface water supplies are not contaminated with sediment. They also provide a nutrient sink for many elements in animal manures. Yet, pastures and hay fields represent a very large portion of total farm acreage and are the second largest land use in Georgia, so even minor pollutant concentrations could have a cumulative effect. Therefore, pollution prevention, especially runoff and erosion prevention measures, needs to be incorporated into forage production as well.

35

There are several keys to maintaining adequate and sustainable pastures. Plant selection is critical as the plant must be adapted to both the soil and climate to insure adequate cover throughout the year. Determining proper stocking rates that will not damage the vegetative cover and result in increased soil erosion is also essential. Controlling animal traffic can help to prevent bare spots that could lead to the formation of rills and gullies. Weeds may be a problem in some pastures, however, proper grazing management and fertilization should reduce weed problems. When herbicides are necessary, use only labeled products at recommended rates. When pasture renovation becomes necessary, no-till or other conservation tillage practices that minimize erosion should be used. Properly designed rotational grazing systems can reduce many water quality problems associated with pastures and often increase productivity. Animal access to surface waters and adjacent areas also represent possible sources of water contamination. Not only does the manure deposited directly in or adjacent to streams pollute the water, but the livestock also reduce stream-side vegetation by foraging or trampling. This increases erosion and decreases the buffering capacity of the stream-side vegetation.
In Georgia, the most significant opportunity provided by pastures and forage production is that they serve as nutrient sinks for the large amounts of animal waste produced within the state. While many growers use poultry litter or other forms of manure ontheir forage systems, improved and more economical waste storage, distribution, and transport systems could provide for more effective waste utilization and cut down on the use of commercial nutrient inputs on pastures and hayfields. As with most BMPs, the impediments to improved pasture management are often a lack of economic incentive, knowledge of improved practices, and awareness or acceptance of environmental issues. Most of these impediments can be overcome with improved educational programs and additional focus on the economic aspects of the particular practices.
Natural Vegetative Systems Most sediment can be effectively removed from runoff before it reaches areas where it
becomes a pollutant. Filter strips or buffer strips are strips of grass, shrubs, or other close growing vegetation intended to remove sediment or pollutants from runoff They are normally planted in an area where water will pass over them as sheet flow. The vegetation slows the water, allowing solids to settle out and become trapped in the vegetation. The filtered nutrients and organic matter are biologically decomposed by plants and microorganisms. Filter strips have been found to reduce nitrogen, phosphorus, fecal coliform, and COD in animal waste runoffby 77,94,95, and 96%, respectively (Johnson et al., 1982 and Larson, 1994). Natural or constructed wetland systems also act as a biological filter. Oxygenation and microbial degradation by plants and bacteria remove organics while sedimentation and filtering removes suspended solids and adsorbed compounds. As a result, wetland sediments act as a net sink for these constituents. While these systems are not used for primary treatment of waste, they are nevertheless an opportunity to prevent pollution in crop production. They could be used around highly erodible land, natural waterways, and land application areas to treat any runoff that may occur and hopefully prevent nutrients from leaving the site.
All streams, rivers, lakes, ponds, and other water bodies in Georgia are classified according to their use. Since pollutants that enter these water bodies can often travel quickly to other areas or have an increased likelihood of being consumed, these areas are more sensitive to environmental
36

pollutants. By managing the area aJ:"0und these water bodies more intensively, many conditions that may lead to surface or groundwater contamination can be prevented. All potential agricultural pollutants, including pesticides, herbicides, fertilizers, manures, petroleum products, and sediment should be handled with extreme care around any water body. Stream channels and banks should be protected to prevent erosion. Often this can be accomplished using vegetation, however, at times structural measures such as rock riprap may need to be used. Generally, livestock should never have unlimited access to any body of water, but when they do it should be in areas with dense vegetation, smooth stable slopes, and firm surfaces. Stream side forest buffers or riparian zones are areas of trees, woody shrubs and other vegetation, located adjacent to and up gradient from streams or other water bodies. They usually consist of natural vegetation that provides a filter for sediment and organic material that carries many pollutants. They also provide an area where nutrients may be utilized by vegetation and where chemical decomposition can take place. Riparian zones are not intended to serve as the only water quality practice or to replace erosion control but they do provide a final opportunity to improve water quality before it enters a stream.
Research has indicated that riparian zones and filter strips are so effective that the federal government recently considered altering the most effective erosion control program in history. The Conservation Reserve Program (CRP), first enacted in 1985, was designed to address problems on highly erodible land. Under the CRP, the USDA entered 10 to 15 year voluntary contracts with farmers to remove highly erodible cropland from production and establish a cover crop on it in return for annual federal rental payments. From 1986 to 1992, 10% of the nation's cropland (5% in the southeast) was removed from production at a nationwide cost of$19.5 billion through 2002. The National Resources Inventory cited this program, along with the move to conservation tillage, as the primary reason that the National average cropland soil loss values dropped from 7.4 tons/acre/year to 5.6 tons/acre/year from 1982 to 1992. In an effort to better manage the cost and benefits of this program, the Government Accounting Office (GAO) has recommended that the use of buffer zones and filter strips be used in place of set aside acreage to protect streams and wildlife. The recommended buffer zones would be 100-foot wide grass or tree "filter strips" adjacent to surface water or wetlands that reduce sediment and chemicals in agricultural runoff. The GAO estimates that only six million acres would be required nationwide to achieve objectives using buffer zones compared with the 36.4 million acres currently under contract in CRP (GAO, 1995). There is also much discussion that proposed legislation could shift CRP from a renting program to land purchase.
'~..
Crop Fertilization Since the arrival of chemical fertilizers in the late 1940's and 1950's, progressive farmers
have embraced the use of fertilizers as a way to reduce labor costs and increase yields. While the benefits are apparent in the fact that average crop yields continue to grow, when use first began, next to nothing was known about potentially harmful effects of these products on the environment, human health, and wildlife populations. As long as the costs were not prohibitive, farmers sometimes used higher rates of chemicals than were absolutely essential, often as insurance against low yields or a potential weed or insect infestation. Few applicators thought of the danger that might be posed by spraying close to wildlife habitat, water bodies, or applying
37

high rates of nitrogen on sandy soil. Today, this attitude is changing. Farmers now realize that fertilizer inputs cost money are aggressively pursuing alternative nutrient sources. They are also getting by with less environmental degradation by using improve application technologies, better management and planning, and by implementing structural BMPs to prevent off-site transfer of farm nutrients.
Crop production requires more nitrogen than any other nutrient. Nitrogen is essential to plant growth and there is no substitute. Production of every pound of food, feed, and fiber requires a near constant amount of nitrogen (PPJ, 1992). Therefore, if crop production is to expand or yields are to increase, then N use must increase proportionally. Commercial fertilizer, forage legumes, crop residues, and animal manure are the major sources of nitrogen. In 1992, commercial sources of nitrogen supplied about 64% of 17 million tons of nitrogen applied annually in the United States. Table 5 shows commercial consumption of fertilizers in Georgia.

Table 5 Commercial fertilizer consumption in Georgia in 1995. (Georgia Department of Agriculture, 1995)

Kind

Sales in Tons

Mixtures*

985,153

Nitrogen Materials

Anhydrous Ammonia Ammonium Nitrate Nitrogen Solution Urea Other Total Nitrogen Phosphate Materials

7,918 76,750 288,010 15,874 30,207 418,759

Ammonium Phosphate Triple Super Phosphates Other Total Phosphates Potash Materials Potassium Chloride (Muriate ofPotash) Potassium Sulfate (Sulfate ofPotash) Other Total Potash

37,992 4,622 25,576 68,190
27,129 7,285 9,956
44,370

38

Kind Secondary and Micronutrients Total of All Fertilizers

Sales in Tons 145,413
1,661,885

Commercial nitrogen sources include anhydrous ammonia, urea, urea-ammonium nitrate solution, and ammonium sulfate. All are excellent N sources and the use of any particular product is governed by economics, timing, and handling preferences. Urea contains 46% N. It is rapidly converted in the soil to ammonium, which is then available for uptake or conversion to nitrate before adsorption by plants. Under certain environmental conditions, significant volatilization losses ofN can occur if urea is not incorporated after application. Urea is widely used in N-P-K blends and also for topdressing crops that receive split applications of fertilizer. Other dry granular sources ofN include ammonium nitrate and ammonium sulfate. These sources are less prone to volatilization than urea. Urea-ammonium nitrate is the most common nitrogen solution in Georgia. Solutions vary in N content between 30% and 32% and offer the convenience of being able to mix fertilizer and pesticide applications in a single pass. Anhydrous ammonia must be placed under the soil surface to avoid vapor losses and consequently is most widely used in preplant N application programs. This material contains 82% N and generally cost less per pound than any other fertilizer sources. Although it is extensively used in the Midwest, it is rather uncommon in Georgia. This is because it requires specialized handling and application equipment, significant safety training for users, and concentrated crop production regions to make the distribution systems economical. From the pollution prevention point of view, this is probably a blessing as losses to the atmosphere can be substantial.

Major phosphorus sources in Georgia include diammonium phosphate, triple phosphates, and the

liquids 10-34-0 and phosphoric acid. All are about equal in performance and subject to

equivalent losses with wind and water erosion. The predominate potassium source is potassium

chloride. This material contains about 60% ~O, is water soluble, and can be applied as a dry

granular material, or used in blends and preparations. All these commercial fertilizers are

excellent sources of plant nutrients. Maximum production efficiency and environmental

stewardship will occur when growers understand the characteristics of each fertilizer material,

and select the material best suited for their environment and production system.

<..

Organic Fertilizers While most chemical fertilizers are no more toxic to the environment than natural or
organic sources of nutrients, greater use of these alternative sources can often cut farm input costs and provide a feasible solution to disposal problems. To maintain soil health and fertility, animal and green manures and compost may be used as soil amendme~ts. These organic amendments stimulate soil organisms to fix nitrogen, mineralize soil nutrients, decompose organic matter, and reduce pest outbreaks. Microbial activity also aggregates the soil to improve aeration, water infiltration and retention, and reduces erosion potential, all of which helps with

39

healthy root development. A primary advantage that organic fertilizers have over most manufactured fertilizers is the release mechanism. Organic fertilizers slowly release minerals into the soil. On warmer days, the soil microbes are more active so more minerals become available in the soil. On warmer days plants are growing faster and require more nutrients complementing the action of the microbes (Chan-Muehlbauer and Gunnink, 1994). In contrast, commercial fertilizers are soluble and tend to leach out of the crop root zone. To compensate, these fertilizers must either be applied at higher rates or be reapplied during crop growth. Timing is less critical when using natural fertilizers. Using natural fertilizers helps to reduce overall production costs resulting in a higher net return per acre.

Animal manure is the most widely used organic fertilizer in Georgia. Manure is an effective

'.,

source of nutrients for most crops, especially those with relatively high nitrogen requirements. Crops such as corn, sorghum, small grains, and grasses respond well to manure as do vegetable

and ornamental crops. Manure is able to moderate soil acidification resulting from repeated

applications of synthetic fertilizer. Manure has often been found superior to commercial

fertilizers when comparing yields (Tisdale et aI., 1985). All the reasons for the favorable action

of manure are unclear, but they probably include one or more of the following:

1. An additional supply ofNH4-N. 2. Greater movement and availability of phosphorus and micronutrients due to

complexation.

3. Increased moisture retention.

4. Improved soil structure with corresponding increases in infiltration rates and decreases in

soil bulk density.

5. Higher levels of carbon dioxide in the plant canopy, particularly in dense stands with

restricted air circulation.

6. Increased buffering capacity against drastic changes in pH.

7. Complexation of AI+3 thereby reducing its toxicity.

The water-holding capacities of very sandy soils are increased with heavy manure applications, as are structural stability and tilth of heavy-textured plastic clays. In both cases, the physical effects of manure justify its use, especially on the soils prevalent throughout Georgia. Only a fifth to half the nutrients supplied by animal manure are recovered by the first crop following the application. Much of the remainder is held in humus-like compounds subject to very slow decomposition. In these forms, the elements are released only very slowly, with rates of two to 4 percent per year being common. Thus, the humus-like compounds in manure will have continuing effects on soils years after their application (Brady, 1990).
Besides manure, there are many other "natural" sources of fertilizer. These include green manure crops such as legumes, crop residues, food processing and industrial by-products, organic material derived from pulp and paper mills, urban yard waste and sewage sludge, and other forms of compostable biomass products. While many of these products can serve as excellent soil amendments, most do not approach the fertility levels of commercial nutrient sources or manures. These amendments, however, can be used to improve soil quality and will be discussed in more detail in a future section.
40

Although land application is the most common manure disposal method, as it relates to crop production is not used to its potential. There are many reasons why it is not used to its potential. These include: 1) substantial energy and labor costs associated with handling and storage of waste; 2) lack of information on the value of manure as a fertilizer; 3) lack of recognition of its economic value; 4) regional availability and high transportation costs limiting the potential to transport to off farm areas; and 5) wide variability in nutrient content and determination of application rates that give the crop sufficient nutrients without having adverse environmental effects. The energy resources required for the production of commercial nitrogen fertilizers are estimated to be about six times higher than the energy requirements for truck and tractor operations for manure application (Smith and Kemper, 1992). Since energy prices are currently low, commercial sources of nitrogen are commonly used. However, with increasing energy prices the potential for greater use of animal waste will increase dramatically. Land application is also hindered in areas of urban and suburban populations by concerns for odors and flies. Public perception must be improved for land application to realize its potential.
The preference of commercial fertilizers instead of animal manure relates to the ease of application and known concentration of nutrient content. Studies have shown that the best method of avoiding groundwater and surface water contamination and possible crop damage is to limit applied manure to the amount required by the crop. This means that the total crop requirement, the nutrient pool in the soil, and the nutrient content of the manure must all be considered. Crop nutrient requirements are generally well known and can be obtained from a variety of sources. To apply the correct amount of manure to meet the nutritional requirements of the crop without applying excessive amounts that could be lost to the environment, producers must test both the soil and the manure. The wide variability of nitrogen in manure requires soil and manure analysis to apply optimum concentrations, whereas commercial fertilizer's nitrogen content is regulated by the state. Nutrients applied from waste should match the needs of the crop, but the ratios ofN, P, potassium, and the various micronutrients excreted by animals are generally different from those required by crops. Not only does this present problems for the development of application rate recommendations, but it can also produce nutrient imbalances in the soils and crops that receive land applications of animal waste. Animal wastes can improve soil fertility through the addition of potassium, calcium, magnesium, iron, zinc, and other micronutrients. However, excessive accumulations can result in increased salinity and reduced fertility (Overcash and Jumenik, 1976). Ideally, the value of animal manure could be maximized if each individual nutrient could be separated and removed from the waste mixture and crop and soil specific fertilizer mixtures could then be reformulated. Since this solution will not be economical in the future, soil testing and record keeping should be used to prevent nutrient imbalances from occurring.
Another hindrance to more efficient manure usage is the fact that livestock and poultry production are not distributed uniformly throughout Georgia. Where animal production is concentrated, the land base available for application is usually limited. This limitation mainly arises from restrictions imposed by the economics of manure transport. Freeze and Sommerfeldt, 1985, found that manure from large feedlots that haul manure in single axle trucks or pull type manure spreaders could only be economically hauled up to 15 km. Often, there is insufficient cropland or pasture within these short distances for environmentally sound land application of all
41

of the manure from large operations. Little research emphasis is being placed on the concepts of materials handling and metering for animal manure, yet the economics of transporting the material to the point of use is often the greatest concern limiting the livestock producers from maximizing the use of this biomass resource. Bosch and Napit, 1992, found that the export of poultry litter from surplus to deficit areas for use as a fertilizer in Virginia is often economically viable at larger scales, but large scale transfers of poultry litter were not occurring. They suggested that the use of government subsidies to crop producers who purchase litter for use as a fertilizer would encourage more research in transport and increase the incentives for commercial firms to provide litter transfer services. Many European governments do provide subsidized transport cost for manure and these programs have generally resulted in greater use of animal waste. Better integration of farms that produce the crops and livestock and educational programs aimed at showing farmers the economic value of manure as a fertilizer are other methods of reducing the transport costs. Separation, screening, condensing, and dewatering technologies could also be used to produce more transportable products; however, little research is being conducted in these areas.
There is little scientific evidence to recommend that farmer switch from one source of nutrient to another. All sources can provide an excess of nutrients unless they are properly managed. In fact, research has suggested that farmers who depend on animal manure often produce higher soil nitrate levels than those who depend on commercial fertilizers (PPI, 1992). This is probably due to the fact that farmers perceive the economic cost ofpurchasing fertilizer as greater than using animal waste and therefore do a better job of managing nutrient applications. Nevertheless, animal waste will continue to produce an abundance of plant nutrients that crop production can ultimately utilize. Experts at the U.S. Department of Agriculture have calculated that the available animal manure and sustainable biomass resources in the U.S. would only provide about one-third of the nutrients needed to support current crop production (Avery, 1995). Therefore, despite efforts to promote more efficient use of animal waste, manufactured nutrient sources will continue to dominate crop production.
Nutrient Management Planning Managing the amount, source, form, placement, and timing of nutrient applications are
activities that will accomplish both crop production and water quality goals (Georgia Soil and Water Conservation Service, 1994). This holds true for all nutrient sources including manure, organic wastes, chemical fertilizers, and crop residues. Nutrient management plans are essential to apply the right amount of nutrients, in the right place, and at the right time to maximize crop yield and environmental protection. Plans can be formulated by the landowner or farmer, by Extension or other service personnel, or done using computer nutrient models. Whatever the approach, the important concept is that nutrient management, plans examine all nutrients to minimize loss of nutrients to surface runoff and leaching, to maintain soil quality, and to insure adequate soil fertility to meet the intended crop yield goals.
Establishing a realistic, yet optimistic, yield estimate is essential to nutrient management planning. Matching the nutrient application rates to yield potentials will help reduce the potential for excessive availability of plant nutrients. Overly optimistic yield goals result in less profit and have a greater probability of environmental losses since they result in the application
42

of excessive nutrient rates. Under estimated yield potentials can also have a negative impact as plant available nutrients may limit production. Yield estimates work best when they are optimistic, yet realistic. Producers should use actual yield records for the given crop on the specific field, and adjust for the most current yield increase estimations. If these records are not available, a general rule of thumb is to either use 10% more than the five-year average annual yield for the given county or simply use the average of the three best yields from the preceding five years. County wide yield averages are readily available through the Extension Service and theNRCS.
The next step in nutrient management planning is to test the soil. Soil analyses are chemical tests that provide a measure of available nutrients. These tests must be correlated with plant responses in the field to set nutrient application rates. Although soil testing is not an absolute science, when the interpretation is based upon scientific research of crop responses to applied nutrients, soil testing allows producers to manage nutrients for maximum economic return with minimal environmental impact. Soil tests for nitrogen should be conducted annually while tests for other nutrients can be conducted every three years. A soil test is accomplished according to procedures set out in the current "Soil Test Handbook for Georgia" (Georgia Extension Service, periodic updates). The steps in soil testing include: sample collection, chemical analysis, interpolation, and recommendations. Usually the weak link in a soil test is sample collection. Thus, exact procedures must be carried out carefully. Soil sample bags, documentation forms, and the tests may be obtained through the Extension Service or at private laboratories. All soil test results should be recorded and kept for future use. By observing long-term fertility, changes in soil composition can be noted.
Utilizing the yield goal and soil test data, recommended application rates can be determined. These recommendations are usually supplied with the soil test results but can also be made based on other Extension Service publications. A computer software package called UGFERTEX is used for Extension Service recommendations. UGFERTEX also recommends lime requirements for neutralization of acidity resulting from nitrogen application and secondary and micronutrient application rates.
Another phase of the nutrient management planning is plant tissue analysis (Plank, 1988). Plant analysis is a measure ofthe nutrient concentrations in plant parts or plant sap. It can confirm a suspected nutrient element deficiency when visual symptoms are present, monitor the plant nutrient element status to detect whether each tested nutrient is in sufficient concentration for an optimum yield, and serve as the basis along with a soil test for making fertilizer recommendations for crops including fruit and nut crops. The monitoring role of a plant analysis offers the opportunity to maintain high quality production with a minimum of nutrient deficiency problems and preventing wasteful over application of nutrients. Plant analysis can also be obtained through the Extension Service and most private soil testing laboratories.
Computer models to assist farmers in managing nutrients are becoming more common as technology and science advance. These user friendly models use the soil test results and yield goals as well as farm specific land and management information to provide not only detailed fertility recommendations but also environmental evaluations of various alternatives. The Nitrate
43

Leaching and Economic Analysis Package (NLEAP) model for irrigated and non irrigated conditions for a wide range ofN-treatments can provide valuable insights concerning relationships among climates, N leaching, and irrigation management. For shallow water table conditions, DRAINMOD-N and VS2DT simulation models can be used to predict nitrate leaching using water table management techniques (Chescheir et aI., 1995). Many other models are currently being developed and tested. These models will serve as pollution prevention tools by allowing for a rapid analysis of many different management scenarios to determine the optimal management strategies for the given location, condition and crop.
Nutrient management planning has been adopted by most farmers in Georgia. The Soil and Plant analysis lab at the University of Georgia ran more than 80,000 soil samples and 3,500 plant samples in 1995. Private labs throughout the State are estimated to run at least that many as well (plank, Personal Communication, 1996). The farmers that do not use nutrient management planning are either unaware of the benefits or skeptical of the procedures. This is most often the case for livestock producers who are dealing with land application of manure rather than producers that are using manufactured fertilizers. Costs are usually not an issue since the Extension Service and many fertilizer dealers provide free testing to commercial growers. One impediment that does create some disillusion with producers is the fact that fertilizer recommendations can vary between labs. This is primarily due to the fact that most private labs prosper with greater fertilizer sales so their recommendations are not quite as conservative as recommendations obtained through the Extension Service.
Another impediment to nutrient management planning is that it is not an exact science. This is especially a problem when using organic sources of fertilizer. With manufactured fertilizers, blends can be formulated to match the nutrient requirements of the crop, however, the nutrient content ofthe organic wastes does not match the nutrient requirements of the crop. With most manures, in order to apply adequate amounts of nitrogen, phosphorus or other nutrients are over applied. One solution is to apply the correct amount according the maximum phosphorus and side dress with nitrogen. Some farmers use organic substances for a few years to allow phosphorus, potassium and micronutrients to build up in the soil profile and then switch to strictly nitrogen sources for a year or two. In general, the yield on plots receiving various types of animal manures at application rates based on the crop phosphorus needs plus supplemental N fertilizations are superior to yields on plots receiving only fertilizer (Francis et aI., 1995).
In summary, general nutrient management planning practices (Lamb et aI., 1995) should include the following:
1. Develop realistic yield goals. 2. Develop and use a record keeping system. 3. Adjust N rate according to soil organic matter, previous crop, and manure application. 4. Use a soil nitrate test when appropriate. 5. Use prudent manure management. 6. Credit second-year N contributions from alfalfa and manure. 7. Do not apply N above recommended rates. 8. Plan N application timing to achieve high N use efficiency. 9. Do not apply commercial N on frozen soils.
44

10. Check the calibration of application equipment. 11. Incorporate soil-applied urea-based fertilizers.
Application Technologies Although the nutrient management plan addresses many issues, its primary purpose is to
determine the amount of nutrients required to maximize crop yield and environmental protection. Proper and timely application of fertilizers and animal wastes is important in reducing nutrient losses and pollution potential. Time and method of application depend on climate, cropping system, management system, source and form of fertilizer, and equipment and labor availability. Each of these factors can affect the efficiency of fertilizer application.
Proper timing of fertilizer application is essential. In most crops, some of the required nutrients can be applied before planting, however, the majority should be applied later when the plant nutrient needs are greatest. Ideally, plant nutrients would be applied in small doses on a frequent basis, however, each pass over the field has an economic consequence and therefore applications are usually kept to a minimum. Where soils have a high nutrient holding capacity, there is probably little loss in yield when single applications are used, while soils with lower nutrient holding capacities could be dramatically affected. More farmers are fertilizing in several small applications rather than one heavy one, to increase effectiveness and reduce losses. Applications during the winter or off-season should also be avoided. During periods of little or no plant growth, nutrients are more likely to leach to groundwater or be carried offwith eroded soil particles. While this is rarely a problem with commercial fertilizers, farmers without adequate animal waste storage facilities must often land apply nutrients during the off-season. Animal waste should only be applied at periods when the nutrients can be used. For crops the best time is immediately prior to planting, while immediately following each hay harvest or grazing cycle usually results in optimal use in forage systems.
Nutrient applications should be made with the proper equipment. Crop nutrients should be applied in a manner that insures that the nutrients are available and utilized by the crop and that is economically and environmentally sound. Full width or boom sprayers (including gravity flow boxes, auger booms, drag chain booms, and pneumatic booms) are generally superior. All fertilizer spreaders should be calibrated for proper application rate and distribution pattern. Certain placement methods, such as subsurface banding and dual placement ofN and P below the surface mixing zone, allow reduced rates of nutrients by improving efficiency while reducing the potential for transport to surface water. Incorporation of surface preplant applications will almost always result in higher efficiencies for N applications, however, P availability may be reduced through soil fixation under certain conditions. Injection systems reduce losses and may be the most efficient application method; however, they are not used extensively because of the difficulty in injecting solid materials. Recent advances in injection technologies are allowing more farmers to "knife" fertilizer into the soil rather than having to incorporate on a second pass. These technologies will continue to improve application efficiency as the machinery costs continue to decline. In general, to maximize pollution prevention potential, farmers must be aware of all of the available application technologies and decide which makes the greatest economic and environmental sense.
45

Fertigation refers to the application of fertilizers in irrigation water. It increases N utilization by applying incremental amounts ofN during plant growth. Therefore, nutrient availability for environmental loss at any given time is reduced. If using this method, proper management is essential to insure that nutrient transport is reduced by controlling water applied. Fertigation often eliminates one or more field operations, allows for late season applications without crop damage, and can improve crop yield and quality. The major impediments to fertigation are the high costs of irrigation systems and the high level of management required.
Water table management means using an artificial drainage system in soils with shallow water tables to remove excess wetness early in the growing season and then applying water back through the drainage system later by subirrigation to avoid drought stress. Water table management results in more predictable yields, allowing more efficient use of applied agrichemicals, and less opportunity for water quality problems to develop. The potential for groundwater contamination by nitrates and pesticides is reduced 20 to 60%(Fausey and Cooper, 1995, Willis et aI., 1995, Chescheir et aI., 1995). The higher profit from subirrigation due to higher and more consistent crop yield and the ability to farm poorly drained land provide growers with an incentive to use this technology.
Fertilizers can also be manufactured to reduce environmental losses. Nitrification inhibitors are products that control or restrict the conversion of ammonium to nitrate. By keeping N in the ammonium form longer, N losses via leaching and erosion are reduced while the nutrient availability is extended for longer durations that better match the plant needs. Chemical nitrification inhibitors reduce populations of nitrifying bacteria rate decreasing their rate of reproduction. This reduces the amount of ammonium converted to nitrate. Slow release fertilizers reduce N losses by resisting biological or chemical breakdown. Some slow release fertilizers have protective coatings that delay N release. Both slow release fertilizers and nitrification inhibitors work best when incorporated and applied preplant with N. They are also most cost effective when leaching or denitrification causes yield reductions. Many companies market their fertilizer products using nitrification inhibitors or slow release formulations, however, the price is often higher. To promote more widespread use of these products, educational efforts need to focus on cost-effectiveness and the potential for yield increases by using these products.
Precision Farming Recently, a considerable amount of research has been accomplished on systems to
precisely target inputs such as fertilizers and chemicals according to the localized requirement within the field (Landers and Gore, 1994). The systems, described as spatially variable field operations, site specific agriculture, precision agriculture, and custom-prescribed operations, take into account variations in soil quality, nutrient levels, and pests that occur on most arable fields. In these systems the application rates of nutrients, pesticides, and other agronomic inputs are not predetermined and constant, but vary continuously based on specific soil and microclimate variations. The purpose is to precisely match the inputs and management to unique crop, land, and climate attributes rather than averaging across a field. The concept is based around the production of field maps where soil and plant characteristics are digitally mapped for arable crops. Some forms of the technology are already well established. For example, yield mapping
46

is frequently used on larger farms and many new combines and harvesters are sold with yield mapping capabilities.

Mapping is an essential aspect of precision agriculture. Soil maps are developed around a grid for digitally locating any point in a field. Each grid is a cell two to five acres in area. Soil tests are accomplished within each grid identifying soil type, quantifying organic matter and specific ions, nutrient status, soil water, and microclimate. Weed pressure, insect populations, and known crop disease history may also be identified and quantified on the grid. A primary impediment to adoption of this technology is the cost of these maps. However, technology should develop alternatives to detailed laboratory testing and mapping. For example, as an alternative to soil testing that can become expensive, electromagnetic induction can be used. Electromagnetic induction has been used to measure soil salinity, soil water content, soil clay content, and soil cation exchange capacity and exchangeable calcium and magnesium. Also, electromagnetic induction may be used to determine field scale leaching rates of solutes. Once calibrated this method may be used to delineate soils across a field in one pass of a tractor mounted computer (Jaynes, 1995).

Another aspect of precision agriculture is the production of maps correlating harvesting position

with yields. This has been accomplished primarily by using the global positioning system

(G.P.S.) satellite program initiated in the 1970's by the Department of Defense. Using these

satellites, positioning accuracy ranging from several meters to within several centimeters is

available depending on the level of sophistication of the receiver purchased by the

farmer(University of Minnesota, 1992). Yield and location data can be stored on a "smart card"

that is downloaded onto the farm office computer to produce yield maps. Spatial variations in

crop yields can then be analyzed using computer-based models, expert systems and neural

networks (Comstock and Broner, 1994). When compared to soil test data, crop residues, crop

rotation history, irrigation data, weed and insect infestation histories, and input maps, the need

for changes may then be deduced resulting in production of site specific requirements. The

ultimate goal of precision agriculture is to produce application maps. With G.P.S. receivers

fitted to planting equipment, sprayers, and fertilizer spreader inputs can then be varied on the

move, reducing the need to manage on a whole field basis. Equipment with precision farming

capabilities is now on the market. These include designs to evaluate yields and to deliver a site

specific water, chemical, and nutrient management. Developments have progressed rapidly to

the point where precision agriculture is now a reality in the field. The economics of this

technology should prove lucrative for the farmer (University of Minnesota, 1992). Getting

started in precision farming using a Global Positioning system will cost between $5,000 and

<..

$10,000 (Keller, 1995). Large farms will benefit from this approach since field sizes and

availability of machinery are key to the success of this approach. Small farmers could probably

benefit from this technology if a cooperative system is used.

Precision agriculture will result in more appropriate use of pesticides and fertilizers with an overall reduction in application rates. It reduces the potential for excessive availability of nutrients or pesticides by optimizing their quantity and placement. A computer aided pesticide application is part of an integrated farming system and will provide for a reduced cost of production. Precision farming techniques can allow farmers to reduce agrichemical rates

47

significantly without triggering a yield reduction and can result in yield increases. Knowledge of water and chemical movement in different soil types is influencing procedures for how, where, and when pesticides and fertilizer can be used. However, the more fanners reduce rates, the greater the risk of costly errors and the greater the management necessary to avoid them. Precision fanning will reduce the risk of rate cutting.
Pesticides The incidence of pests, including weeds, insects, disease causing organisms, and
nematodes is high in subtropical climates such as Georgia. This makes efficient pest management a paramount concern in these regions as pest management costs comprise a larger portion of the variable production cost. Plant diseases, nematodes, weeds, insects, and vertebrate pests cause substantial losses each year by reducing yields and quality as well as the cost of control. Insects alone cost Georgians more than $500 million in crop loss each year from 1985 to 1987. In 1988, insect pests cost Georgians $720 million and in 1989, another $753 million.
Reliance upon chemical solutions to pest problems has been the chief method to exert control. With the awareness of health risks to fanners, increasing chemical costs, concerns over drinking water supplies, waste disposal problems, and persistence and toxicity of chemicals in ecosystems, new and innovative approaches to pest management have been developed. These technologies are already reducing pesticide use nationally. From 1982 to 1992, overall pesticide use declined 6% in the United States while production increased almost 20% (Porterfield et aI., 1995). While some of this reduction can be attributed to chemical companies moving toward pesticides that require less active ingredient per acre, the bulk of the reduction is from the application of pollution prevention technologies. Reductions will continue to occur as new technology is developed and existing pollution prevention practices are adopted, however, synthetic pesticides will continue to be an integral part of crop production. Current research suggests that U.S. field crop yields would decline drastically ifwe substituted currently available organic pest controls for synthetic pesticides. Soybean yields would drop 37%, wheat by 38%, cotton by 62%, peanuts by 78%, and com by 53% (Avery, 1995). Since yield reductions such as these cannot be tolerated by society or individual growers, efforts should focus on developing pest management strategies dependent on both organic and synthetic pest control mechanisms.
Ritter (1990) reviews many alternatives available for pesticide pollution control. He supplied the following four categories: 1) Integrated Pest Management Systems to minimize the amounts of pesticides needed; 2) Substitution ofless biotoxic and less persistent pesticides; 3) Increasing the efficacy ofpesticide application technology; and 4) Soil and water conservation practices. While this text focuses on prevention rather than control, the same general categories apply.
Integrated Pest Management (IPM) IPM is defined as an interdisciplinary approach to pest control incorporating the judicious
application of ecological principles, management techniques, and biological and chemical methods to maintain pest populations at tolerable levels (EPA, 1980). It is a system that anticipates pest population increases and prevents pests from reaching damaging levels by using natural enemies, pest resistant plants, cultural management, pesticides, and other techniques. IPM systems minimize the use ofpesticides through careful planning of the crop system,
48

optimization of natural biological factors that disfavor pests, and the use of guidelines to help growers decide when pesticides are necessary. For over 20 years, IPM has maintained the goal of minimizing inputs using the economic threshold concept; pesticides are not applied unless pest levels are high enough to potentially reduce profits. In fact, nationally IPM reduced insecticide use on cotton by 74% from 1976 to 1982 as yields increased by 27% (Porterfield et aI., 1995).

IPM encompasses all methods of controlling pests. Scouting and surveillance are probably the most important aspects of an IPM system. Accurate records of pest locations and densities in the field are key factors used to formulate strategies for pest control in IPM. Crop rotation, cover crops, nutrient management, maintenance of soil biology, supplementation with commercial parasites, and adjusting planting and harvest times are also essential components of integrated pest management plans. These methods and others, such as the use of naturally occurring insects and toxins are used to formulate customized pest management plans to allow the most economical management of pests in a particular crop. Other methods of pest control that are used include the use of pest resistant crop varieties and genetically engineered plant varieties that produce natural insecticides (Lan et aI., 1994). IPM does not seek to eliminate the use of pesticides. It merely regulates the role of pesticides to one of a safety net to prevent economic losses. IPM is based on determining when a pest population is approaching the level at which control is necessary to prevent a decline in net returns, thus decreasing the total amount of control required.

By using a combination of rotation, delayed planting, precision farming, and mechanical tillage, herbicide usage can be greatly reduced using IPM. Harrowing after planting is an important tool for controlling weeds. Crop rotation can break weed, insect, and disease cycles. Herbicides constitute about 85% of all pesticides used. While IPM is the primary method of reducing required pesticide volume, new technologies are being developed based on weed physiology and soil parameters and by modeling techniques to predict the time of weed emergence. Herbicide use in conservation tillage systems may be reduced by integrating available control strategies, reducing herbicide rates and frequency of use through timely application, increased scouting of weed populations to better match treatments to weed populations, and improving cultural practices to maintain low weed densities (Buhler, 1995).

For the most part, existing Extension programs, at the State and National Level, have been

developed to educate growers on the principle ofIPM. In 1994, IPM programs involved more

than 7,700 Georgia growers producing on more than 1.5 million acres. In 1993, 88 percent of the

cotton and 48 percent of the peanuts in Georgia were grown under IPM management. In recent

( ..

years more than 1,000 people have attended annual Extension Scout schools and more than 2,000

people attended 10 cotton scouting schools in 1995 alone. Extensive IPM evaluation in the early

to mid-1980s revealed significant increased net profits to growers who used high levels ofIPM,

as opposed to non- or low-users. One peanut study showed a $32.32 per acre higher net return,

while cotton growers cut costs by $19.32 per acre with yields that were $37.04 per acre higher

(University of Georgia, 1995). With these kinds of results, selling farmers on the benefits of

IPM is easy.

49

While many growers will buy into the fact that IPM can improve their operations, few practice all aspects of a complete IPM program. The development of a knowledge base for specific crop requirements is key to the success of an IPM program. Non adoption ofIPM may be attributed to the complexity of its procedures that require skills that farmers may not have. The tendency to overreact to visible pests or damage symptoms is great (Escalada and Heong, 1993). Few growers can tolerate pest populations, even when the cost of eliminating them is greater than the economic damage that the pests can be expected to produce. This reluctance to take a chance on economic thresholds is based in history. Most growers have been programed to follow predetermined application schedules and are skeptical of changes. The goals of IPM are also often at odds with the commercial development and the advertising of pesticide manufacturers. This often leads to conflicting recommendations that leave the grower confused about what actions to take and can nullify both recommendations. Integrated crop ecosystem management models offer some promise in facilitating decision making processes (Lan et aI., 1994). Models being developed are an integration ofa series of mathematical equations derived from basic research data describing physical, biological, or economic processes for soils, plants, and insects. If growers can learn to depend on models and the theories behind them, many management decisions can be taken out oftheir hands.
Typically, farmers respond slowly to changes in production practices, especially when current practices are profitable. For more widespread adoption of systems such as IPM, a vigorous demonstration system must be established to show growers what IPM practices are, how they can be implemented, and what impact they have on farm economics. Farmer participation and experiential learning have emerged as essential features of extension and training programs. These programs should also extend to consumers who now expect that their food be 100% free of pests or visible pest damage. Under IPM, pest damage can occur and consumer's need to learn to accept this fact. Many other impediments exist. A recent National Forum on IPM identified the following constraints to widespread adoption ofIPM and some solutions for overcoming these constraints (Pollution Prevention Research Center, 1995):
Constraints: 1. Grower's economics. 2. Antagonism between growers consumers, public interest groups, and the media. 3. Lack of consumer education about potential quality loss with IPM. 4. Confusion related to the definition, goals, and objectives ofIPM. 5. Lack of holistic approach. 6. Lack of "level playing field" for imports. 7. Insufficient research/extension funding for demonstration. 8. Lack of incentives 9. Loss of safer chemicals due to high cost of registration. 1O. Few proven pesticide substitutes 11. Lack of government support for IPM growers.
Solutions: 1. Incentives for manufacturers to bring new materials to market for minor crops.
(Pesticides specific to minor crops)
50

2. Develop standards for pesticide use on imports. 3. Educate regulators about current practices to provide a sound framework for policy
development. 4. Crop Insurance program for expanding/testing IPM programs to cover unanticipated
losses. 5. Educate media about IPM practices and hold them accountable for accuracy. 6. Incorporate more feasibility and profitability analysis in IPM. 7. Rave growers take proactive stance about trying alternatives to pesticides. 8. Develop a dedicated national IPM extension system for growers, processors, and
consumers. Make research projects more holistic and inclusive. 9. Increased public IPM education 10. Label IPM grown crops so they can demand a premium price. 11. Seek funding from special interest groups to help finance IPM.

Many of these ideas have been addressed through recent changes in extension programing, however, more changes need to be made. In a 1987 national survey, growers reported that they adopted IPM programs primarily to protect the environment, improve pest control, and protect personal and public health and safety (Rajotte, 1987). These reasons were cited as being more important to the growers than improved crop yields and increased profit. Thus growers clearly perceive IPM programs as environmentally sound production systems and may not be fully aware of the economic benefits ofIPM.

Natural Predators

One of the weapons available for farmers using IPM to control pests is the use of natural

predators. In most settings, encouraging or conserving naturally occurring populations of

beneficial insects and mites is possible. More than 90% of insects spend part of their life cycle

in the soil (Tanada and Kaya, 1993). Conservation may be aided greatly by the development and

use of more selective, rapidly degrading insecticides and by using insecticides more selectively,

since most insecticides kill predators and parasitoids along with pests. Soil fungi control

nematodes naturally. Nematodes would not usually be a problem if the natural soil ecology were

in place to provide for their natural predators (mites and fungi). The soil needs organic matter

and moisture to foster beneficial organisms. Soils where high levels of organic matter have been

conserved maintain high levels of biological activity. This biological activity provides for an

increased level of natural occurring parasites that control insect populations. The greatest

promise for biological control may be a result of conservation tillage efforts and practices that

increase soil organic matter (Renn and Weinzieri, 1990).

(.

Sometimes, growers may enhance natural predation. They can create habitats to increase the population of known predatory insects in border, buffer, and grass way areas. Crops with cross predators can be grown side-by-side. Trees that are home for predators of low canopy insects can be planted adjacent to fields. In some cases, introduction of predators may be practical. The Georgia Extension Service is actively promoting the use ofthe musk thistle weevil for control of musk thistles. They estimate that the musk thistle is costing Georgians $20 million annually from lost forage and control costs. Tests to date are showing that a statewide weevil capture and

51

release program coupled with physical-chemical control may aid in solving the thistle problem at a reduced cost for the farmer.
While the use of naturally occurring beneficial insects or introduced species can be cost effective, they do not offer the benefit of immediate control and therefore can only be used as a supplement in a complete pest control program. Nevertheless, educational programs should emphasize the fact that these technologies can be used to decrease overall dependence on chemical pest control.
Pesticide Selectivity Besides selecting pesticides that do not target beneficials, the chemical characteristics of
pesticides, especially leachability, persistence, and toxicity, are important considerations when selecting pesticides. These characteristics in conjunction with soil type determine the amount of chemicals lost and their potential for ground water contamination. Sandy soils, high water tables, or shallow aquifers make ground water contamination more likely. In these areas, the user should be aware ofthe chemical properties ofpesticides. Leaching characteristics are especially important if groundwater is at risk. Other properties such as persistence, solubility, adsorptive capacity, and toxicity are also important and need to be considered in the pesticide selection process. In the mid-1980's the major pollution prevention advances came with the introduction of the imidazolinones and sulfonylureas, two low dosage herbicides that allowed farmers to obtain equivalent weed control using ounces per acre rates rather than the traditional pounds per acre. However, if these ounces were more toxic than pounds of another product, should it really be used? For users to make informed decisions, they need a through understanding of each ofthese chemical properties and a process or tool to analyze the properties as they relate to their specific soil and environmental conditions.
Pesticide users need a method of compiling information on pesticide characteristics and their potential impact on runoff and soil loss. The NRCS soil pesticide interaction screening procedure is one method of delivering this type of information to the applicators. This procedure breaks the potential for contamination down into one of three levels. At potential 1, the soilpesticide combination has a high probability of being lost to surface runoff or leaching and should be avoided unless the pesticide toxicity is very low. At potential 2, the risk is lower but the pesticide should not be used around sensitive areas, and at potential 3 there is little or no risk. To determine the potential, the farmer or pesticide applicator needs to know both the soil type and chemical name. Using the soil type, he can consult a series of tables that rank each soil as high, intermediate, or nominal for runoff or leaching potential. Likewise, he would consult a series of tables similar to Table 6 to find the pesticide leaching or runoff potential. Using each of these potentials, he could then use a matrix similar to Table 7 to figure out his overall potential for runoff or leaching. While national databases exist that can currently supply this type of information, by limiting the pesticides and soils to those commonly found in Georgia, a more effective pollution prevention tool could be developed to enhance the farmers understanding of these principles. These tools should be developed in fact sheet form for distribution by dealers and also in the Extension Services' Pest Control Handbook.
52

Table 6 An example of the insecticide ratings chart. Note: Original charts include many more chemicals as well as other pesticide information including toxicity, solubility, half life, etc. Similar tables exist for herbicides, fungicides, and growth regulators.

Trade/Common Name

Leaching Potential

Runoff Potential

Adsorption

Solution

Abate

Small

Medium

Small

Ambush

Small

Medium

Small

Diazinon

Small

Medium

Large

Furadan

Large

Medium

Large

Lannate

Large

Small

Medium

Lorsban

Small

Medium

Small

Sevin

Small

Small

Medium

Temik

Large

Small

Medium

Table 7 Example of potential pesticide loss to surface runoff matrix. Note: A similar matrix is available for leaching potential

Soil Surface Loss Potential

Pesticide Surface Loss Potential

Large

Medium

Small

High

Potential 1

Potential 1

Potential 2

Intermediate

Potential 1

Potential 2

Potential 3

Nominal

Potential 2

Potential 3

Potential 3

When selecting pesticides and pest management practices looking at the economics of various selections is also important. Bridges et aI., 1994 conducted one of the most thorough analyses of the use and benefits of pesticides presented in the literature. Unfortunately, they concentrated their efforts primarily on chemical control methods and only on peanuts, but the results were nonetheless useful. For example, their analysis provided a detailed cost benefit analysis for each specific pesticide; for example, the cost to benefit ratios for insecticides used on over 10% of Southeastern peanuts ranged from 0.6 to 5.7. On the average, herbicides had the highest cost to benefit ratios at 19.6:1, followed by nematicide (6.3:1), fungicides (4.6:1), and insecticides (2.4: 1). If studies like this could be extended to include cultural and management practices such
53

as tillage, crop rotation, and scouting, and add in the environmental costs associated with each chemical they would be much more useful as pollution prevention tools.
Producers need to rotate the chemicals that they depend on to prevent the development of pest resistance. Proper chemical rotation can reduce pesticide application rates by reducing 1) the possibility of applying ineffective pesticides; 2) the need to use higher rates to get equivalent control; and 3) the need for additional applications. Most pests, be it insects or weeds, can be controlled by more than one product. Often these products have different modes of action. If possible, growers should rotate the pesticides they use annually, based on the mode of action, to prevent the development of pest resistance. Several agencies offer detailed information on the modes of action for various pesticides as well as suggested rotation schedules.
CropBMPs BMPs not only prevent soil erosion and runoff, but can also be highly effective in
preventing loss of pesticides. By increasing infiltration and controlling soil erosion, most BMPs also decrease the availability and likelihood of having either soluble or absorbed pesticides carried off the site on soil particles or in the water. A quick review of Table 3 shows that most of the BMPs recommended for erosion control are also effective at controlling pesticide losses. While many of these BMPs are effective, some operate through mechanisms other than a reduction in pesticide availability for transport. Others may decrease the potential for surface water contamination at the cost of increased potential for groundwater contamination.
Among the suggested practices that reduce pesticide levels in soils is the addition of easily decomposed organic matter. Recycling animal manures and other biological wastes have already been touted in this text as effective methods of building soil organic matter and in turn improving soil fertility, increasing infiltration, and controlling soil erosion. Organic matter can also prevent pesticide losses. Soils with added organic matter have a higher exchange capacity that decreases leaching of most pesticides. The higher exchange capacity also enables more microorganisms to be held in the soil and subsequentially a more rapid breakdown ofmany pesticides. The growth of high-nitrogen cover crops and the additions of animal manures aid in the biodegradation of even the most resistant pesticides by creating conditions favoring overall microbial action.
Poor crop rotation patterns are probably the single largest contributor to the need for continued pesticide use. Monocultures such as cropland provide a specific habitat that favors the abundance of individual pest species rather than allowing many species to live in balance. This not only causes increased inputs due to a lack of beneficial populations, but also allows for the development of high levels of pest resistance. Table 8 shows the effects of crop rotation on nematode populations in peanuts. By simply rotating the peanut crop with a non-legume such as cotton, yields were increased while nematode populations decreased without the use of any nematicides. Crop rotation and the use of cover crops have the potential for reducing insecticide and herbicide use by reducing water percolating through the soil profile. Since more plant growth and less fallow soil use more water, less is available to leach the pesticides to the groundwater.
54

Table 8 Effect of peanut and cotton rotations on nematode pressure and yield. Data based on six year study in Georgia and Alabama. (John Woodruff, Personal Communication)

Nematode Population Juveniles/1 00 cm3 Soil

Yield Lbs.lacre

Crop Rotation

Peanuts

Cotton

Peanuts

Cotton

Continuous Peanuts

222

1931

2 yr Peanut-Cotton

62

3

2173

1749

3 yr Peanut-Cotton-Cotton

56

11

2176

1614

Under many circumstances there is no conflict between protecting surface waters and protecting ground waters but some practices that control surface runoff may increase the potential for ground water contamination by increasing infiltration. Conservation tillage, for example, prevents surface water contamination but may increase leaching potential since more herbicides are used and more infiltration may occur. In general, more research will be required to document the impact that conservation tillage has on leaching potential as the results from many studies are contradictory. In all probability, the impact of specific practices that increase infiltration on pesticide leaching will be highly dependent on both the soil and pesticide characteristics. The following general points can help reduce herbicide requirements in conservation tillage systems: 1. Anticipate changes in weed population dynamics and control options. 2. Be able to identify new weed species; the key to control is often timely and accurate
identification. 3. Proper sprayer calibration and operation will ensure maximum herbicide effectiveness. 4. Control emerged weeds at or before planting. Weeds that are emerged at the time of crop
planting have a head start on the crop, are very competitive, and rapidly become difficult to control. 5. Proper planter operation will protect seed from herbicide contact and potential injury, speed crop germination and establishment, and maximize crop competition with weeds. 6. Scout fields closely to determine the need for follow-up control and to identify developing weed problems. 7. Occasional tillage may aid weed control. This includes interrow cultivation and integration of tillage rotation into cropping systems.
In recent years several models for the transport and persistence ofpesticides in the subsurface soil environment have been developed. Two of these tested in Georgia include the Pesticide Root Zone Model (PRZM) and the Ground Water Loading Effects of Agricultural Management Systems (GLEAMS) model. These models can be used by both scientists or producers to simulate the effects of various management practices on both surface and ground water. These
55

simulations can serve as pollution prevention tools to evaluate existing practices and to test the effects of proposed changes before they are actually implemented.
Application timing and methods Application of pesticides involves determining the proper rate to apply, calibrating
equipment, determining the most effective timing and frequency of application, and selecting the method of application and the appropriate formulation. To prevent pollution effectively, only the amount of pesticide needed should be applied. Either over or under application can result in environmental contamination or waste. Application should be carefully timed to avoid heavy rains or the need for additional irrigation as this could also decrease the effectiveness of the pesticide and lead to increased costs. Application equipment should regularly be checked for leaks, malfunctions, and calibration (Parker, 1992). Finally, the most appropriate pesticide formulation and application technology should be used to insure that the product is being placed where it needs to be.
Calibration is essential to insure uniform application and that the intended rate is being applied. Guidelines established by the U.S. Department of Agriculture and the EPA indicate that the difference between a sprayer's actual and intended application rate should be no more than 5% of the intended rate. However, surveys conducted primarily in the Midwest suggest that less than one in four sprayers are applying chemical within 5% ofthe intended rate. Proper nozzle sizing and placement reduce the amount of pesticide drift and assure that more of the pesticide reaches its intended target. If equipment is properly sized and adjusted, more pesticide is assured of reaching its intended target. The extension service conducts statewide clinics on calibrating pesticide spraying equipment and has several publications available to assist growers in this process.
Adjuvants are products that can be mixed with pesticides to increase their effectiveness. The 1996 Farm Chemical Handbook (Meister and Sine, 1996) breaks over 250 different adjuvants down into the categories based on effect including acidifyinglbuffering agents, activators, antifoam/defoaming agents, compatibility agents, crop oil cocentrates/surfactants, deposition agents, dispersants, drift control agents, encapsulation agents, harvest aids, herbicide safeners, leaching aids, spreaders/penetrants/wetting agents, and stickers/adhesive agents. Many ofthese products can be used to improve the efficiency of pesticide application, however, the performance is often highly dependent on both the pesticide involved and the application technology. For example, a surfactant could significantly reduce the application of a certain herbicide by reducing the surface tension to obtain a more uniform application, however, if the pesticide already has a relatively low surface tension then the adjuvant would not make economical sense. Likewise, the addition of a drift control agent could be very important to an aerial applicator or on a windy day, but unimportant on a calm day. Additionally, starch encapsulation can reduce losses due to volatilization and leaching for most pesticides (Gish et aI., 1995, Hickman and Vail, 1995). Since most producers cannot maintain a working knowledge of all of the available products, adjuvant purchases are often based on pesticide dealer recommendations. There is considerable opportunity to provide educational"materials that outline specific conditions under which the utilization of adjuvants is worthwhile.
56

Controlling or reducing drift in pesticide application is also essential. Besides representing a loss of product, pesticide drift can cause environmental problems and yield losses to adjoining fields or neighboring farms. At times, it can even have legal ramifications. Airborne drift is the physical movement of spray droplets away from the target site at the time of application. It mainly results from factors associated with the application methods, timing, and equipment. Vapor drift, where volatilized pesticides move offsite as a vapor, is less controllable but can be dealt with through selection of alternative pesticides. Drift is influenced by many factors. Spray droplet size is by far the most important and primarily depends on nozzle type and size, nozzle orientation, spray height, spray pressure, and chemical formulation (Ozkan, 1995). Weather factors such as wind velocity and direction, humidity, temperature, and atmospheric stability are also critical considerations in minimizing drift. Equipment can also be modified to reduce drift. Some new developments for increasing deposition efficiency of small droplets include partially or completely covered booms, air assisted spraying, and electrostatic spraying. Under most conditions, drift can be reduced or avoided by recognizing the critical factors involved and taking precautions or making modifications. Therefore, educational programs, incorporated in pesticide applicator training programs, would probably be the most effective method ofreducing the losses associated with pesticide drift.
Technological advancements in pesticide application equipment will improve application efficiency and reduce pesticide waste. For example, sprayers with in-line pesticide injection systems eliminate leftover tank mixtures by using a small metering pump to feed the pesticide from a separate tank into the spray line. Many new sprayers are also equipped with small water tanks that allow applicators to instantly begin rinsing their equipment while they are in the field. Not only does this prevent the need to dispose of excess rinsate, but it applies residual products in the field where it may have some benefit. Research is also underway to develop systems that can automatically adjust pesticide rates according to organic matter in the soil. This system operates on the principle that lighter soils, which are low in organic matter, require less pesticide than darker soils. Banding pesticides in a narrow width along the row allows the total amount of product applied to the field to be reduced. Spot treatment also allows for significant reductions and may be highly effective. Intermittent spot-sprayers controlled by optical sensors to detect weeds may become a part of precision farming techniques that can drastically cut herbicide use (Von Bargen et aI., 1995).
Some studies indicate that ultra-low volume pesticide applications using electrostatic spray nozzles can provide satisfactory insect control at half the rate recommended for conventional spraying (Ozkan and Wilson, 1994). Air-assisted electrostatic sprayers produce electrically charged spray droplets that are carried to the plant with a high speed air stream. Because the droplets are charged, they will attract to plant surfaces instead of drifting away or falling to the ground. The pesticide droplets also adhere to the plant to apply a more uniform coverage since the charged droplets are not attracted. In fact, some studies show that underleaf coverage is increased by more than 70-fold over conventional sprayers (ESS, 1992). Besides being able to offer the equivalent control using one-half to one third the active ingredjent, the electrostatic sprayers have the added advantage of using 10 to 25 times less water carrier than standard hydraulic sprayers. This means that the time spent mixing and loading the pesticide sprayer is also tremendously reduced.
57

Electrostatic sprayers are commercially available for row crop production and will probably be the application technology of choice in the future. In the greenhouse industry, hand-held electrostatic sprayers are now common. The largest impediment to more widespread use in crop production is probably cost as the sprayers often list for prices that are three to four times higher than conventional sprayers. While only about eight electrostatic sprayers are currently in use in Georgia (Cooper, 1996), case studies indicate that the payback time on these sprayers is often less than a year. This is highly dependent on farm size and crop value, but in general the benefits that growers most often site include an overall net chemical savings of greater than 50%, labor savings between 30 and 50%, longer intervals between sprayings, ability to use less toxic chemicals with good results, and less visible waste on crop residues and soil surfaces.
Pesticide mixing and loading Research has shown that a very high proportion of environmental contamination
attributed to pesticide spraying has come from careless mixing and rinsing of application equipment and accidental spills. Industry research has also shown that 85% of all applicator pesticide exposure occurs during mixing and loading (Avery, 1995). Chemical handling is becoming safer and more effective by shifting to dry chemical formulations wherever practical. Formulations that can't be manufactured and shipped as dry powders are increasingly delivered in pre-measured water soluble pouches that can be simply dropped into a spray tank. In other cases, companies are moving toward shipping in larger, reusable containers that can lock into place on the pesticide application .equipment without ever exposing the farmer or permitting spillage. While these changes are all being implemented in the name of safety, they also serve as effective pollution prevention strategies as they are preventing the chance of accidental spills that could lead to losses.
Ground water contamination can result from spills at pesticide mixing and loading locations. Properly designed areas will have containment areas and drains where inadvertent spills may be contained and the spilled chemicals may be recaptured and used. Concrete areas should have an impervious sealer applied to prevent the infiltration ofthe pesticides into the concrete matrix. Pesticides can saturate concrete over time. The saturated concrete is then considered a hazardous waste necessitating an ultimate disposal plan that can be very costly. If a concrete mixing and loading pad is not an option then these operations should be conducted in the field, changing locations frequently and avoiding surface water.
Pesticide containers need to be disposed in a proper manner. Concentrated pesticide residues leaking from unrinsed, discarded containers can cause environmental contamination and economic loss. Up to 3 ounces of pesticide may be left inside a five-gallon container. Containers should be rinsed immediately after they are emptied as this is when the rinsate can be used and dried residues can be difficult to remove. Containers should be triple rinsed, punctured and rinse solutions deposited into the sprayer tank. This will insure that more than 99% of the pesticide that is purchased will reach the field. Cleaned containers need to be taken to a licensed sanitary landfill. Certain counties have started recycling pilot programs for the high density polyethylene pesticide containers. Only containers that have been properly rinsed are accepted. The Georgia Department of Agriculture and the Cooperative Extension Service are assisting
58

local initiatives. In 1995, the equivalent of 171,3002.5 gallon pesticide containers were recycled in Georgia alone (Tolar, 1996).
Pesticide safety issues are not limited to environmental concerns. Protection of the humans storing, selling, transporting, mixing, and applying pesticides is regulated under the EPA's Worker Protection Standards. These standards are quite lengthy and beyond the scope of this text, but they do present several pollution prevention opportunities. Mainly, they require that certain individuals that apply pesticides receive certification and annual training. These trainings programs are often conducted by the Extension and provide an opportunity for targeting sessions on pesticide pollution prevention. The standards and training material also provide suggestions on all aspects of pesticide safety including storage, transport, mixing and loading, applying, disposal, and methods of dealing with spills. Many methods that are "safe" also significantly reduce pollution and could be considered pollution prevention technologies. Opportunities for incorporating more pollution prevention principles into these trainings and documents such as those on safety (Delaplane, 1994) and the Georgia Extension Service's annual publication: "Georgia Pest Control Handbook." should be explored.
Agricultural retailers also playa vital role promoting pollution prevention both directly and indirectly. They can implement technologies and improved management practices onsite. They can provide services, counsel, and instruction about the safe use and handling of pesticides and fertilizers to farmers and other users. The TVA (Tennessee Valley Authority) has designed a pollution prevention program specifically for agricultural retailers. The general objective of the program is to provide research, development, and application of pollution prevention technologies and strategies for industries that market or use agrichemicals or fertilizers (Rylant, 1996). One of this program's achievements has been the establishment of69 ResearchDemostration sites at retail facilities in 27 states. These include both "model sites" that demonstrate good environmental stewardship throughout the operation and "individual technology demonstration sites" that focus on one or more specific technologies. Typical examples of technologies, applications, and recommendations include: (1) facility design for environmental efficiency; (2) improved environmental management practices; (3) methods of containment; (4) materials of construction and recommended coatings; (5) monitoring techniques and inventory reconciliation; (6) stormwater control; (7) large tank containment strategies; and (8) rinsate recycling procedures. This program serves as a great model for development of demonstration facilities in Georgia; however, successful demonstration programs are highly dependent on commitment from the agri-industry involved and funding. Georgia has one such demonstration facility located at the Sunbelt Expo, however, the facility is poorly maintained and rarely used. The opportunity to establish improved demonstration facilities, either independently or with TVA, should definitely be pursued.
Biotechnology The Green Revolution and modem agriculture have gotten their primary stimulus from
genetics. Until the early 1900's, agriculture had really advanced very little over time. With industrialization and the advent of power machinery, new farming systems, fertilization technology, and pest control chemistry, agriculture made its first major advance. Since the 1950's, with further developments in these other technologies, genetics has been the driving force
59

in improved agricultural crop yields (Avery, 1995). Genetics has produced more productive strains in virtually every crop and region of the world. Higher yielding, shorter strawed, pest resistant, cold tolerant, higher protein seeds have come from numerous plant breeding programs worldwide. These advances will proceed, and as they do, pollution prevention will continue as more product will be produced on each given acre. In fact, genetic improvement is probably the most significant method of source reduction as it is the only technology that successfully reduces all of the inputs at once.
Biotechnology is dependent on genetics and the enormous amount of information stored in genes. Techniques for managing genes have gradually become more complex. In the last 20 years, it has become possible to directly modify genes to help improve the health and productivity of agricultural plants and animals. With biotechnology research will move faster. Instead of crossing two organisms and waiting for an outcome, biotechnology allows us to take a particular gene from a particular place in one organism and insert it into the target organism for a desired result. In addition, biotechnology allows us to draw genes from a much wider pool as it is not confined by species limitations. Biotechnology's greatest contribution will be higher yields that can be obtained through environment friendly technology
Biotechnology is a modem tool in the old science ofplant and animal genetic improvement. It involves applying gene splicing methods to improve crops or to produce different products from living organisms. However, it also integrates advanced disciplines such as biology, genetics, molecular physics, biochemistry, chemical engineering, and computer science and applies them to alter or add information to a genetic blueprint within plant or animal cells. Some examples include: micropropagation, a technique used to clone identical plants, diagnostics, which help detect plant diseases, and biofertilizers and biopesticides which use natural agents such as bacteria to fertilize or protect crops.
While biotechnology rarely replaces traditional methods ofplant breeding, it often speeds up the process and allows for more precise control. Transgenic plants, those developed with transferred genes, are often more productive than traditional varieties. Increased productivity can depend on several factors including drought tolerance, resistance to disease or pests, and the ability to compete with weeds. From 1990 to 1995 the number of field tests on trangenic plants underway in Canada increased from 71 to 745 indicating the dramatic growth in biotechnology (Ag West Biotech, 1996). Most of the initial transgenic crops are aimed at reducing the need for chemical pesticides, making crops resistant to popular chemical weed killers, and making them impervious to viruses and fungal diseases. While expecting biotechnology to double or triple yields is unrealistic, continued incremental increases are very likely.
Using biofertilizers, scientists have found methods to improve the way plants use nutrients in the soil. For many years, farmers have applied the microbe rhizobium to plant seeds to help them capture nitrogen from the air and convert it to a usable form. Biotechnology is now producing more effective strains of rhizobium. A team ofplant molecular biologist at the Noble Foundation in Oklahoma have recently have recently isolated a particular gene in a fungus known to help plants ingest phosphates. Research work is currently focused on transferring the isolated gene to agricultural crop plant varieties so that plants will more effectively use soil
60

phosphorus and less fertilizer additions will be required. Although no one really knows how the mycorrhizal fungi works, it is known to infect plants' roots while enhancing the transpiration of phosphates. Besides the obvious impact this fungi could have on crop production, researchers are also looking at using a similar fungus to reduce soil P levels from long term manure additions. Scientists are also working with the genes that control nitrogen fixation in legumes. If successful, development of grasses or other crops that fix nitrogen could almost eliminate the need for nitrogen additions in agriculture.
Biopesticide products use genetically engineered organisms to control agricultural pests. While biopesticide products have been around for a long time, the technology to make them cost effective is just emerging. Many biopesticides are based on insect specific viruses called baculoviruses that can only replicate themselves in insects and cannot live in humans, plants, or animals. These viruses are delivered through a potent, naturally occurring, protein pesticide that has been genetically engineered into the virus. The protein will be replicated only in the target host and will cause rapid death to the target insects. The EPA has recently established a biopesticides division to facilitate the registration of nontoxic biological pesticides. In 1995 alone, more than 20 biological pesticides and three genetically engineered, pest resistant plants were approved for the marketplace (Goldman, 1996). Such measures, which promise to increase in the future, will likely curb agriculture's reliance on chemical-based pesticides.
Naturally occurring insecticides, such as Bacillus thuringiensis (Bt) products, are available for broad spectrum use and for specific insect pests. These products, produced through fermentations using species of Bacillus bacteria, have been found to be effective in the control of insects that go through a larval stage. The plasmids from the bacteria have been inserted into the genome of crop varieties to produce the Bt toxin within the plant. Insects found to be especially vulnerable include cutworms, various caterpillars, some web worms, Japanese beetles, soybean and com loopers, gypsy moths, homworms, tomato fruitworms, budworms, armyworms, com earworms, sod webworms, mosquitoes, black flies, and miscellaneous leaf feeders. Bt insecticides are desirable since they are nontoxic to mammals, reptiles, amphibians, or fish. They are specific to targeted pests so that beneficial insects are not affected, and they are readily biodegradable. As a result, they are not persistent in the environment. There or more than 40,000 strains ofBt bacteria, and each will only kill specific insects Bt products are the most effective bioinsecticides currently on the market. However, other methods ofbiocontrol are being developed. Viral insecticides are being used in Brazil with soybeans. There are several virus based products under development in the U.S. (Deterling, 1995). Other research is being conducted with entomopathogenic fungi and nematodes (Olcott-Reid, 1991).
Some plants release chemicals from their roots that retard the growth of other plant growing near them. This process is called alleopathy and it is being investigated as a form of weed control. Other products include developments concerning post harvest technologies that lengthen the time that fruits and vegetables can be stored without losing quality. Approaches such as these also show promise for eliminating the need for many chemical ripening agents that are currently being used.
While these advances all seem great, advances in pesticide technology do not come easily or inexpensively. For new agricultural products, the time from first discovery to
61

commercialization is often eight to ten years. To justify such an investment oftime and the $35

to $50 million needed in development costs, companies must be convinced of a potential

product's chance of success. Product registration and regulations are also major forces that

impede the development of new and improved biotechnologies. Development of resistance is

also an impediment. Some scientists speculate that, when faced with large monocultures of

genetically engineered crops, pests will rapidly develop resistance to the built in toxins. This, in

fact, is true as insects in the lab have been shown to develop resistance to Bt bacterial proteins.

In using these new products, educational efforts should focus on methods ofpreventing

resistance development. Finally, pollution prevention efforts need to focus on public perception.

Many people view biotechnology and genetic engineering as an evil that is no better than the use

of toxic chemicals. Since biotechnology does have the potential to alter the environment,

'),

development should be controlled and regulated but not impeded. By educating the public of the

benefits that genetic engineering and biotechnology have provided and can continue to provide,

many potential problems can be avoided and sustainable development can prosper.

Composting and Biomass Additions Each of the three preceding sections has suggested that organic matter additions to our
soils will aid in preventing pollution. Organic matter improves many soil physical properties and can reduce runoff and soil erosion. In doing so, it also reduces the off-site impacts of crop fertilizers and pesticides. Furthermore, organic matter can often reduce the need for both fertilizers and pesticides by supplying nutrients, by improving nutrient or pesticide availability, or by sustaining the microbes and organisms in a healthy soil. Biomass, from either plant or animal sources, can play an important role in sustainable agriculture and pollution prevention. Millions of tons of biomass from urban and rural yards, the forest industry, agricultural food processing, animal wastes, and crop residues that are currently being land filled could be put to good use on the farm. With increasing pressure being placed on landfills and with the arrival of requirements for the diversion of yard wastes, biomass availability should increase in the future. The agricultural sector should be posed to take advantage of this increase in availability as biomass should be viewed as a resource that is necessary for sustainable production.

Accomplished since ancient times, composting has obtained much popularity recently. Its popularity is derived mainly from the fact that biomass is greatly reduced in volume, weight, odor and moisture content. Therefore it can be transported and marketed more economically (Hansen et aI., 1991). Composting is a general term given to processes that use naturally occurring aerobic microorganisms living in biomass materials to produce organically stable soil amendments. Microorganisms utilize carbon and nitrogen compounds in the biomass for energy and metabolites to grow cell mass. In so doing, the microorganisms render the biomass a biologically stable and inactive material. As the microorganisms digest the biomass, they respire carbon dioxide emitting it to the atmosphere. The respired carbon dioxide accounts for all but a small part of the mass and volume reduction ofthe biomass. Additionally, nitrogen is excreted as urea by the microorganisms (Richards, 1987). Most ofthe nitrogen is used by other microorganisms as ammonia but a portion is lost to the atmosphere as nitrous oxide and additional nitrogen can be lost as nitrate in drainage (Agbim et aI., 1977, USDA Soil Conservation Service, 1990).

62

Composted material offers several advantages over raw waste material. Composting converts the nutrients in manure into more stable organic forms that release slowly and are less susceptible to leaching. It also has better handling properties that make it easier to apply, transport, or bag for sale. These improved handling capabilities and the reduced odor offer many opportunities to move large quantities of manure 'into nontraditional market places. Many argue that composting is not cost-effective with respect to agricultural manure, since it is time consuming, costly, and results in a product that is not any higher in nutrients. However, compost provides non-nutritive agronomic benefits such as improvements in soil structure and other physical properties. It also offers advantages in terms of organic matter buildup in the soil, and some plant disease suppression characteristics that are not completely understood (Riggle, 1994). Land application of organic composts also shows potential for mitigating the effects of some weeds and thus reducing herbicide needed in crop production (Edwards et aI., 1994). Maynard, 1994, found that yearly applications of spent mushroom compost and poultry manure compost increased the yields of eight varieties of vegetables when compared to control plots fertilized with equivalent rates ofN, P, and K. Part of the advantage that compost offers may lie in the fact that it contains a variety of microbial and biological stimulants. Not only is the humus beneficial, but the microbial nature of the product will actually inoculate the soils to improve soil structure further.
The typical operation composts material for approximately six months to a year. During this period the material is turned or mixed five to seven times then left to cure for a month or longer. Nitrogen loss during the composting process is dependent on the material as well as the process control. Considerable research opportunities for determining processes, amendments, or additives that reduce nitrogen loss exist. Higher quality compost may be produced by closely managing the composting process, maximizing aerobic conditions and controlling the internal temperature of the pile. The management time and labor invested in any compost operation relates to the quality of the product. Reduced mixing and/or abbreviated composting period reduces labor as well as the quality of compost. Better equipment for processing and handling composted materials and improved "recipes" are needed to reduce the time and labor associated with composting operations. To optimize this naturally occurring process, process equipment has been designed to facilitate the aeration and mixing of the composting biomass. Conventional large-scale composting is an equipment intensive, expensive operation. It is usually accomplished on an impervious surface where drainage and surface runoff can be collected and treated. Aeration is accomplished using electrically driven blowers (aerated static piles) or the biomass is turned by mechanical mixers in windrows or static piles.
The cost savings from using biomass in agriculture can be significant. By improving soil profiles and improving pest control, yields could be increased while costs are cut. Correctly designed aboveground conventional composting systems are expensive to construct and operate. Incorporating biomass into the soil or depositing it on top of the soil after harvest is more economical. However, before crops may be planted, soils containing some types of biomass need a significant amount of time at warm temperatures to complete microbial cycles. The time needed depends on temperature, the biomass applied, and the nitrogen and water available for the microorganisms.
63

Another reason that direct land application ofbiomass may be more appropriate than composting

it that it is now generally accepted in the scientific community that increasing levels of carbon

dioxide, methane, nitrous oxide and other gases in the atmosphere are creating change in global

atmospheric conditions (Acock and Allen, 1985). Since the handling of biomass materials in

crop production is conducted on such a vast scale, the collective emissions occurring from these

materials can be significant. The application of biomass to soils is a high priority management

strategy for restoring carbon pools in soils (CAST, 1992). It has been estimated that plant decay

accounts for 50 to 60 gigatons of carbon per year emitted to the atmosphere or half the total

carbon used in photosynthesis (Post et aI., 1990, Sundquist, 1993). Sequestering carbon and

nitrogen compounds in the soil offers one of the most promising, economic solutions to global

atmospheric degradation (Lal et aI., 1995). The United Nations has been called upon to

'"

coordinate a world soil policy for using the soil as a sink for atmospheric carbon (ISRIC, 1992, Lal, 1995). Since organic carbon is valuable in the soil and detrimental when emitted to the

atmosphere, more research should focus on comparing the emissions of carbon dioxide and other

gases as a result of composting to land application of biomass. It may be preferable from an

economic and environmental basis that biomass be placed on or incorporated into the soil in its

raw form.

Many downstream industries processing agricultural products have biomass waste products. One such waste occurs from ginning cotton. During the cotton ginning process, small particles of lint, dust, leaves and other trash may be emitted into the air. Since some particles are less than six microns in diameter, they are respirable and thus hazardous. The amount of emission depends on the condition of the seed cotton being ginned and the gin equipment. Machinepicked cotton usually contains about 100 pounds of foreign matter per bale. The potential air pollution problem is intensified because materials are handled almost exclusively by air. All of the air streams discharge outside the gin building. The collection and disposal of residues in these air streams are a problem. Usually trash storage facilities are present at the gin. Trash is separated from the air conveyance stream using a cyclone separator. The separated trash falls into the storage area.

At one time, most cotton gin trash was incinerated. Since the advent of emission standards for particulate matter occurring from stacks, the use of incineration as an ultimate disposal technique has greatly declined. Currently, gin trash is spread on land, fed to cattle, or dumped in landfills. At some gins, "motes" are recovered and sold for low quality batting. The motes are the fibers attached to immature seeds expelled at the gin stand and lint cleaners. There has been some research accomplished investigating the use of cotton gin waste as an energy source (Craig, 1994). Cratech, Inc. has developed a one ton per hour biomass-fueled integrated-gasifier gas turbine power plant. The unit could conceivably produce 2400 kg/hr steam and 750 kW electricity.

Gin trash contains significant amounts of chemicals (one to ten ppm) which remain from use of herbicides, insecticides, and harvest aid chemicals. Residues are quite stable, diminishing approximately 25% over a five-month period of open storage (Seiber et aI., 1979). The presence of chemicals reduces the appeal of gin refuse as an animal feed, but can increase its value as a soil amendment. When two to eight tons per acre were applied to cotton fields, a yield increases

64

of more than 20% resulted for seed cotton. Lint production increased an average 28 lbs. per acre (Harper, 1950; Box and Walker, 1959). Dry-land cotton yields increased between 16 and 36% by adding five tons per acre (Fryrear and Koshi, 1974). In long term tests, yields doubled in the fourth and fifth years of application of 4.4 tons per acre in Big Spring, Texas (Fryrear, 1979). Disease, insect problems, and weed seed problems have not resulted from applying cotton gin wastes to fields (Box and Walker, 1968; Thomassen, 1990).
Composting gin trash can reduce volume by 60% and weight by 50%. This makes the transport and application of gin trash more economical, but the long term benefits for the soil are not as great. In Georgia, cotton is primarily grown in the southern half of the state where additional organic matter in the sandy soils is especially helpful. Composting reduces some benefits that can be derived from raw cotton gin waste applied to soil since the nutrient and organic matter content is reduced during the composting process. Raw cotton gin trash is more valuable than compost for soil enhancement since it provides more total carbon and nitrogen. The carbon that would normally escape to the atmosphere in the composting process is sequestered in the soil and used for crop production when raw cotton gin trash is spread on and/or incorporated into field soil. Composting also concentrates chemical residues that can become a problem at high levels.
While this section has detailed the biomass resources available from the downstream processing of cotton, most other crops display similar waste issues. Composting is an efficient way of managing many non-manure solid wastes from both agricultural and non-agricultural settings. Spoiled feed, soiled bedding, and dead animals can be subjected to composting and result in stable, non-offensive products. In addition, many states have recently banned yard wastes and other organic material from entering landfills. Many farmers who need additional carbon sources and who usually have the space and equipment to develop composting operations, will be interested in obtaining these resources. Here, composting may give off-farm interests a waste disposal option and provide additional revenue sources through "tipping" fees to on-farm composters. Municipalities, food processors, and paper industries are examples of off-farm clients that have paid farmers to compost their usable waste resources (Riggle, 1994, Edwards et aI., 1994). More research associated with the waste streams of both agricultural and nonagricultural industries could result in increased use of off-farm amendments in composting operations. Educational programs should be used to allow the agricultural community to take full advantage of the economic and environmental advantages that on-farm composting can offer. To achieve effective pollution prevention, efforts must be intensified so that biomass from all sources may be efficiently utilized in crop production.
Petroleum Storage and Handling A small gasoline leak of one drop per second can often go unnoticed, yet, it could result
in the release of about 400 gallons of gasoline in one year. Not only does this result in economic loss, but also results in both environmental and health problems. Released gasoline may enter both ground and surface water where only small amounts can contaminate large quantities of water and create health risks for anyone wishing to use this water. According to the U.S. Environmental Protection Agency, nearly one in four underground storage tanks in the United States may now be leaking. Petroleum fuels contain many potentially toxic compounds including common solvents such as benzene, toluene, and xylene, and additives such as ethylene
65

dibromide and organic lead compounds. When mixed with water in low concentrations, these contaminants cannot be detected by smell or taste but can cause serious health problems. For example, benzene, considered a human carcinogen, has a drinking water standard of less than five parts per billion. These health hazards are compounded by the fact that products such as gasoline, diesel fuel, and fuel oil can rapidly move through soil surface layers and into groundwater. Here, they present hazards to both the people and animals that depend on groundwater for drinking purposes. In addition, owners of tanks that leak are responsible for clean up costs that typically range from $10,000 to $100,000.
Several publications outline opportunities for pollution prevention in petroleum product and farm chemical storage and handling (Hygnstrom et aI., 1995 and others). These publications show a variety of techniques including proper siting and design of storage and mixing facilities, methods for mixing chemicals that minimize spills and allow for recovery, and proper tracking and labeling of containers and rinsates. These techniques not only can protect human health and the environment, but also save the farmer money. Most production farms also maintain many farm vehicles and machines. The maintenance facilities could probably benefit from many of the same pollution prevention strategies employed in many commercial garages and service stations. This section outlines many major pollution prevention practices and opportunities that may be particularly important in on-farm petroleum storage.
One of the most important aspects of your liquid petroleum storage tank is location. Tanks should not be close to any wells, springs, rivers, lakes or other water resources. Generally, storage tanks should be located at least 250 feet from any well to provide adequate assurance that subsurface flow or seepage of contaminated water will not reach your water. Every site has unique geologic, soil, and hydrologic conditions that can affect groundwater movement. Regulations for siting above ground tanks are concerned more with the explosion potential of tanks than the groundwater protection potential. Along with maintaining adequate distance from your drinking water well and water resources, tank location should also be based on soil stability, current and previous land use, traffic, depth to groundwater and soil characteristics.
Tank design and installation procedures can also have a dramatic impact on the effectiveness of a system. The manufacturer's recommended practices for installation should be carefully followed whenever a fuel storage tank is installed. Proper installation is one sure way to reduce the leaking potential of the tank or the piping connected to it. All new underground petroleum storage tanks and related piping must be constructed of nonmetallic materials such as fiberglass, or have corrosion protection. Methods of corrosion protection include interior liners and "sacrificial anodes." Another form of corrosion protection is to paint the tank or coat it with asphalt. Not only is it unsafe, but also illegal to reuse an underground tank above ground without having it recertified. Above ground tanks offer several advantages over under ground tanks. They are easier to maintain and monitor, leaks are easier to discover and clean up, and installation and removal is often less expensive. The drawbacks to storing fuel above the ground include a higher risk for accidents and damage to the tank, increased risk of fires or explosions, and increased evaporation losses. State regulations for aboveground tank installation seek to reduce the potential for both pollution and fire. Requirements include 1) locating the tank at least 40 feet from any building; 2) supporting the tank at least six inches above the ground with concrete
66

blocks; and 3) maintaining the storage area by keeping it free of weeds and other combustible materials.
Although the regulations exempt tanks less than 1,100 gallons from requiring secondary containment, to decrease pollution potential, all farm tanks should be placed within a secondary containment structure. These structures can consist of a double walled tanks, a concrete pad with curbs, or a hard impermeable surface with diking. Secondary containment should be able to hold at least 110 percent of the tank volume. Above ground piping should be made of steel and coated to prohibit corrosion. All piping should be within the secondary containment system, if possible. Secondary containment systems should include a drain or sump that allows removal of water or fuel without uncontrolled drainage from the tank area.
Spill and overfill protection is also important for both above and under ground tanks. Spill protection typically consists of a catch basin for collecting spills when the tank is filled. Overfill protection is a warning or prevention of an overfill such as an automatic shutoff or buzzer. Spill and overfill protection are important because they can prevent many small releases over a long period from polluting the groundwater.
Monitoring fuel consumption and leak detection are also integral parts of pollution prevention planning in petroleum storage. Leak detection refers to two different things. First, it refers to test that can be done on your tank using specialized equipment to make sure that it is sealed tight and not leaking fuel. This process is called tank tightness testing and should be done every couple of years. Methods to test the tightness of the tank include precision testing, tightness testing, and volumetric analysis. The second method of leak detection is through inventory control practices. This is something that can be done by simply keeping a close eye on the amount of fuel that is in the tank. Measuring tank inventories, or gauging, is an inexpensive and easy way to help detect leaks. This procedure consists of taking two consecutive measurement of the tank's product level at the beginning and end of a 36-hour period using a gauging stick scaled to one-eighth inch increments. Leakage is apparent when there is any decrease in level \yithout any withdrawal of fuel. At the very minimum, tank owner should measure the amount of product in the tank monthly and compare against the amount of product delivered and dispensed. Consistent discrepancies may indicate a leak. While inventory measurement will not detect very small leaks, it will at least provide a warning that further investigation may be necessary. Besides protecting groundwater and health, leak detection can save money by preventing unnecessary fuel losses.
<..
When tanks are abandoned, they should be pulled by a certified tank puller and taken to a landfill or to a scrap dealer and not left on the property. Most leaks are discovered when tanks are pulled. Tank owners should check soil area around a tank for obvious releases. The owner should document all steps taken to close a tank. Documentation should include: state agencies contacted; date the tank was pulled and who pulled it; and records that indicate inspection for contamination and inspection results (Sanford, 1994). Groundwater protection from leaking underground storage tanks was enhanced with the enactment of the Georgia Underground Storage Tank Act in 1988. The program established a financial assurance trust fund and instituted corrective action requirements to clean up leaking underground storage tanks. Through
67

1991,4076 tank leak reports were received and site investigation and corrective action procedures have been completed or initiated at 1736 release sites (Georgia Dept. of Natural Resources, 1993). Unfortunately, this trust fund exempts agricultural tanks since they are not registered. The establishment of a similar fund or some sort of financial assistance would encourage more tank removals rather than attempts to conceal or ignore old abandon farm petroleum tanks.
Oil is another petroleum product that is extensively used in agriculture. Both South Carolina and North Carolina have designed programs that specifically promote oil recycling by farmers. In addition to being large oil users and potential disposal problems, farmers also present an opportunity for oil reuse as many of the used-oil incineration systems could generate heat or be used as fuel on the farm. At the very least, efforts could be coordinated with pesticide container recycling programs to collect both containers and used oil.
Protection of Water Supplies Farming accounts for some 70% of global water use (Avery, 1995). Although Georgia is
blessed with an abundance of natural rainfall, most common crops will still benefit from supplemental additions of water. This is especially true on high value crops. Irrigation requires a high investment of equipment, fuel, maintenance, and labor, but offers a significant potential for reducing the risk associated with dependance on natural rainfall. Agricultural irrigation systems in Georgia depend on both ground and surface water sources. Although center pivot systems are the most common delivery system, many other types including traveling guns, solid set systems, and low pressure, low volume systems such as drip irrigation and micro-sprinklers are available. Agriculture's dependance on water creates many pollution prevention opportunities. Since many farmers are also rural residents that are dependent on ground water for drinking purposes, it is imperative that they protect their wellheads from all possible pollutants. Water conservation can also benefit the land owners directly through fuel or power savings and improved yields or indirectly through a decreased and sustainable dependance on groundwater resources.
Wellhead Protection More than 90% of Georgia's rural residents have wells and are dependent on groundwater
to supply their drinking water and farm needs. Wells are designed to supply clean water, however, when improperly constructed or maintained they can give many farm contaminants a direct pathway to the groundwater. Once contaminated, groundwater is very difficult and costly to cleanup. Therefore, it is imperative that all rural residents do an adequate job of preventing groundwater contamination.
Well location is very important for avoiding drinking water contamination. Wells should be located up slope and away from any potential sources of contamination. Poor well design can also allow groundwater contamination by allowing surface water to reach the water table without filtering through the soil. All wells should be built with a continuous outer casing that reaches into the bearing strata and capped to prevent surface water from entering the casing. A concrete pad or clay fill should be used to elevate the cap and force drainage away from the well. Well age, type, and depth are also important as many studies have shown that old, shallow, or dug
68

wells are more likely to be contaminated than new, deep, or drilled wells. Many rural properties have abandoned or rarely used wells. These should be sealed and retired, which usually requires a permit. All connections to the water supply should be inspected to ensure that fertilizers and pesticides cannot enter by back-siphoning. Even hoses submerged in a pool ofliquid can backsiphon material if the system loses pressure. Standard ways to prevent back-siphoning are to use an air break tank, a back-flow check valve, or a reduced pressure principle zone valve. Finally, no chemicals or other potential contaminants should ever be stored in well houses.
The Cooperative Extension Service has several programs to assist rural homeowners with wellhead protection. In addition to several publications, water quality professionals will provide well inspections and well water testing upon request. Farm*A*Syst self assessments can also be used to locate many potential sources of groundwater contamination and provide the information necessary to take corrective actions. Although protection of groundwater resources has received considerable attention in the last couple of decades, the opportunities for further prevention practices, especially concerning wellhead protection, are still great.
Water Conservation Much of the vast quantity of water diverted by and for farmers never benefits a crop.
Water is lost during storage and transport via leaching and evaporation and during application via evaporation, drift, surface runoff, and plant transpiration. Worldwide, the efficiency of irrigation systems averages less than 40%. In Georgia, efficiencies are probably higher but could still be improved. Relative water use efficiencies for some common irrigation systems include flood irrigation at 35-60%, center pivot systems at 70-85%, trailing tube pivots at 85-90%, and drip/trickle systems at 85-90% (Avery, 1995). In some cases, water use is greater than aquifer recharge rates, causing a lowering of the water table and an increase in energy requirements for water delivery. Saltwater intrusion is also becoming a major issue in some areas of Georgia. These low water use efficiencies, and the resulting problems will push Georgia agriculture toward much greater water conservation measures in the coming years. Effective irrigation water management reduces the amount of applied water, subsurface drainage that requires treatment and/or disposal, leaching of nutrients, pesticides, and other toxics, and runoff. The rewards are lower water and/or energy costs, environmental protection, and often increased profits.
A summary of some practices, using current technology, that farmers can use in water conservation programs are given below (Adapted from Segars, 1995). They are not intended to be all inclusive, rather they are included to provide general examples. Only by an extensive onfarm evaluation, from a trained specialist, can one determine his/her specific conservation practices required to reduce water use and maintain profitable yields. 1. Evaluate Previous Irrigation Data
A field assessment is a key to accurately deten:nine past irrigation practices, including methods, timing and amounts. This is the data source from which to make recommendations and evaluate the effectiveness of previous irrigations. Surprisingly, many irrigators do not seriously assess previous practices and plan for needed adjustments.
69

II. Detennine Soil Characteristics
The characteristics of soils in the U.S. are well known and data on each is published by the USDA Soil Conservation Service. However, one must know the particular type of soil or soils on a given farm. Certain characteristics are of invaluable aid in irrigation. Data such as soil texture, available water-holding capacity, infiltration rates, electrical conductivity, depth to a perched water table, drainage, etc. are essential to optimize an irrigation program. Educational programs could provide growers with the tools to use such infonnation successfully.
III. Irrigation Scheduling
Effective irrigation scheduling is based on accurate knowledge of water applied, plant water use on a daily basis, and soil moisture content. Consideration of the peak water use growth periods of crops is essential for optimum scheduling. For example, grain sorghum can encounter severe drought stress at the 6-8 leafstage with little yield reduction (about 10%); however, if stressed at the heading and bloom stage, a 50% yield reduction can result. All crops have similar peak-demand growth periods. Soil moisture measurements to detennine soil water capacity should be used in humid and semi-acid climates. Instruments such as gypsum blocks and tensiometers are very effective. Since irrigation is used in these areas to supplement rainfall, soil moisture measurements are critical to development of an efficient schedule. The Cooperative Extension Service has several publications and demonstration farms that use irrigation scheduling. These efforts need to be expanded and more widely publicized.
IV. Consider Low Energy Precision Application
In the 1980's, scientists at Texas A&M University modified the traditional center pivot system and developed a process known as Low Energy Precision Application (LEPA). This technique releases water 8 to 15 inches above the ground and significantly reduces water evaporation losses. Application losses from LEPA are only 2-3 percent compared with 20-25 percent from typical impact sprinklers. Fuel consumption and costs have averaged 15-20% less than low pressure sprinklers. Texas A&M researchers have reported some tests in which LEPA averaged 10-20% higher yields than those obtained with furrow or conventional sprinkler irrigation. While some investment is required to convert existing center pivots to LEPA systems, if the effectiveness of these systems were displayed and incentives were in place, many farmers would convert to this type of system. The LEPA concept serves as an example of how scientists are developing new technology for agricultural water management. V. Calibrate Systems for Quantity and Unifonnity Center pivot systems that apply more or less water than expected, or which distribute the water non-unifonnly, will be inefficient in crop production. A Georgia study showed that some systems differed from what was projected by 50% or more. Nebraska and Florida surveys revealed that approximately 30% of center pivots could be adjusted to improve efficiency by 10% or more. The educational materials and methods to calibrate center pivots have been developed but could be improved.
VI. Drip or Trickle Irrigation
Numerous studies have shown that certain drip or trickle irrigation systems can reduce water use by 25-50% compared with conventional systems. This is especially true when
70

used in conjunction with plastic covers on the soil. Unfortunately, capital costs ($500$2,000 per acre) currently restrict its use primarily to high-income crops. VII. Conservation Tillage Systems Conservation tillage can reduce the need for preplant irrigation through improved soil moisture storage. It is defined as any tillage and planting system that maintains at least 30 percent of the soil surface covered by residue after planting to reduce soil erosion by water and/or wind. Types oftillage systems include no-till, ridge-till and mulch till. These systems conserve water by providing a surface cover to reduce evaporation and increasing the soil organic matter. Increasing soil organic matter through conservation tillage or the addition of organic residues can increase soil water retention and decrease irrigation needs.
Existing technology has been used to implement water conservation in agriculture successfully. Two examples include the Newlands Project and the Grand Valley Salinity Program. The Newlands Project irrigates more than 60,000 acres of farmland in Northern Nevada. Because of legislative action to protect an endangered species of fish, the project operators were directed to improve irrigation efficiency by 12% over five years. This was accomplished through changes in water delivery management rather than by major capital costs. After the first two years, efficiency was increased by 6%. This resulted in the conservation of20,000 acre-feet of water per year. Conservation efforts under the Salinity Program focused on two areas: (a) structural practices, and (b) irrigation water management. The structural practices included concrete-lined ditches, underground pipelines, and land leveling. Irrigation water management concentrated on: (a) irrigation scheduling and (b) uniformity of application. Preliminary data suggests that this program has the potential to significantly conserve water use on participating farms in the Grand Valley. The fact that future funding for this project has been incorporated into the 1996 Farm Bill is indicative of its success.
Studies have demonstrated that farmers are not always aware of the optimum practices needed to improve irrigation efficiency. An expanded education program is needed to show to farmers that, (a) there is room for improvement in current irrigation practices, and (b) there are techniques and technical resources available to make improvement. The Cooperative Extension Service is embarking on a pilot effort to implement water conservation planning and monitoring it Southeast Coastal Georgia. If these efforts are successful, it is likely that they will be expanded to other areas.
It is also essential that the research community continue projects to develop new and/or improved methods of water conservation. Hopefully, many innovative practices will be forthcoming. It then becomes the responsibility of those whose assignments are in technology transfer to deliver timely information, technology training, and provide necessary technical assistance to help irrigators install conservation systems and utilize proven conservation practices. While forecasting potential practices that may reduce water use is difficult, new or improved technological advances may arrive in the following areas:
(a) More efficient instruments to measure soil moisture (b) Improved cultivars of crops that require less water (c) Less costly drip irrigation systems
71

(d) Microcatchments to confine surface water runoff and rainfall (e) Organic polymers to absorb water and retain it for plant use (f) Improved purification methods so that more tailwater and subsurface drainwater
can be utilized (g) Increased use of conservation tillage (h) Increased utilization of wastewater to recharge aquifers (i) Organic chemicals to reduce transpiration in plants (j) New chemicals to reduce evaporation from impounded waters (k) Increased crop yields to reduce need for as many cropland acres (1) improved automation to achieve more optimum water distribution and delivery (m) Improved monitoring ofin-season plant water requirements (n) Affordable desalination processes
'),
(0) Increased use of xeriscaping by the landscaping industry (P) Improved methods to increase infiltration and soil moisture holding capacity (q) Increased use of composted animal wastes and bio-solids to increase moisture
holding capacity of sandy soils (r) cloud-seeding? (s) More sophisticated control systems for all types of irrigation systems (t) Greater use of crop growth models which predict water needs
Most farmers are aware ofthe need and the opportunities that exist for more efficient water management. Considerable progress has been made in improved technology and on-farm adoption of water conservation practices. Unfortunately, high capital costs and low farm profitability may hamper the adoption ofimproved water management technologies. To achieve optimum water use is a laudable goal for the agricultural community. There are, however, many challenges associated with such conservation. Changing the methods ofwater use may entail restructuring and retooling laws and agencies at the local, state and Federal level. Hopefully, legislation is not the only way to effect change. Research, incentives (such as cost-share), improved state and local programs, and most importantly, education should all be a part of the statewide water policy.
Computers and Models As with most other sectors of society, computers are changing the face of modem
agriculture. Computers make precise control ofmachinery practical; they make record keeping easier; and they make it possible for the farmer to run "what if' scenarios so that different management decisions can be tried and their many possible outcomes observed. As computers are integrated into agriculture, they present many opportunities for pollution prevention. Planning resource inputs so that only the amount needed for production is applied can be aided using computer models. This limits the amount ofnutrient and chemicals encountered in runoff and leaching. Crop management support systems are being developed to provide water and chemical management advice to obtain a maximum potential yield while reducing potential ground and surface water contamination (Broner, 1995). Models may be linked with new technologies for assessing and recording soil needs and potentials. Most of these model were mentioned inprevious sections. Models to predict crop growth, runoff and erosion, crop nutrient needs, pesticide transport and fate, and irrigation scheduling and management are all currently
72

available. While it will remain the responsibility of scientists and researchers to update and verify these models, those responsible for technology transfer must begin to put these models in the user's hands. They also need to convert these models from data hungry research tools to user friendly decision support systems that can be used on the farm.

Precision agriculture probably offers the greatest possibilities for incorporating source reduction into mainstream crop production. By managing large amounts of site specific data and pinpointing precise locations using global positioning coordinates, precision farming allows the farmer to apply inputs as effectively as possible matching crop needs to site specific soil conditions. This efficiency translates to the bottom line as it results in the maximum yields with the least possible inputs. As the size of and area that can receive individualized treatment drops from the acre level to a few square feet, inputs will be minimized and less waste will lead to a cleaner environment.

Geographical Information Systems (GIS) will not be limited to precision farming applications. They can also be used to identify and locate intensively farmed areas that may have a greater potential for environmental contamination. The systems operated by The University of Georgia are being designed to research, size, locate, and define areas contributing to pollution. This information can then be used to target funding for environmental related educational activities. The lack of such information can lead to misspent State and Federal funds and continued nonpoint pollution.

In a GIS system, the land is usually divided into watersheds. A database is then developed pertaining to land use, topography, soils data, land cover, animal density, and precipitation. A model is generated to utilize the database. Factors such as water runoff index, sediment production, animal loading index, and chemical-use indexes are modeled and given a weighting factor. The GIS-modeling system can then assess the relative potential pollutant generation and transport from agricultural lands. Ultimately, these models can be used to target sensitive areas for removal from production or increased pollution prevention efforts. An example of this type of application is the CRP. Originally, the USDA targeted highly erodible land using the USLE model and a rather extensive database. Future applications for this type of technology are boundless and range from targeting nutrient rich areas of natural fertility or animal manures to locating waste materials that could be converted to soil amendments.

Other Opportunities and Impediments Many opportunities and impediments for pollution prevention cannot be broken down

.".

into any specific categories, but instead, can apply across the board. These include items such as

environmental risk reduction, social and economic factors, and farm policy.

Risk reduction For maintaining credit ratings and property values, farmers are finding that it is a wise
business decision to document farming procedures and training, proving the accomplishment of sustainable and environmentally sound agricultural practices. Of primary concern are the chemicals that may in some way impact the viability of the land economically (Robbins and Bisset, 1994). A lender's underwriting decisions are guided by judgment, experience, and

73

investigative practices intended to prove appropriate due diligence. A significant area of due diligence consideration is environmental risk. Prevention or correction will financially benefit the property owner, thereby enhancing prospects for a viable, continuing fanning operation and a mutually beneficial customer-lender business relationship.

Banks and lending institutions are active in monitoring environmental risk. Under the

Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980,

monetary liability can be well in excess of the amount of a loan. Additionally, the local, state, or

federal government may impose fines. Third party liability suits are not uncommon. Due to

these factors, lenders must have a process for managing and monitoring environmental risk. A

lender may note the following observations (Hansen, 1995):

',.

1.

Water management - Sources ofwater, including active and abandoned wells;

compliance with health regulations; actual or alleged groundwater contamination.

2. Permits and notices - Pesticide application/storage; manure storage/discharge;

government notices of hazardous waste or site lists.

3. Storage tanks - Underground or aboveground tanks, contents, status, and condition.

4. Handling, storage/disposal of hazardous substances - pesticides and other.

5. Collection sites - Pits, dumps, lagoons, holding ponds, landfills.

6. Miscellaneous potential or actual hazards - PCB's, asbestos, radon, foam insulation,

petroleum, pipelines, drums, barrels.

Public records are used to indicate the need for additional investigation. Records may show any previously existing detrimental environmental conditions on the property or whether the customer's operations, property, or any adjacent or nearby properties or businesses present environmental risks based on prior ownership and use. Agricultural activities are noted as well as soil types, groundwater characteristics, and other geological conditions since these factors influence environmental risk. Based on information gathered during due diligence and loan monitoring, the lender can classify the property to reflect its relative environmental risk. Typical classifications are low, medium, and high. A high risk classification necessitates a professional environmental assessment to determine the extent of the problems and the need for remediation.

Because of due diligence, some lenders grant either direct or indirect reduced interest rates to fanners who implement approved sustainable agriculture plans or best management practices for soil and water conservation and protection purposes. Others participate in governmentsponsored low interest rate buy-down programs for fanners who implement sustainable practices that prevent or mitigate nonpoint sources of water pollution. Ifboth lenders and fanners could be persuaded to use pollution prevention practice as a "yardstick" of environmental awareness then there would be much greater incentive for landowners to implement these practices. For example, some lending institutions in the Midwest provide a lower interest rate to landowners that have participated in the Fann*A*Syst Program. This not only encourages greater fanner participation in pollution prevention activities, but also protects both the lending institutions and fanns. Similar arrangements should be investigated both for Georgia Fann*A*Syst and other pollution prevention programs.

74

Social and Economic Factors Some farmers choose not to use alternative practices for pollution prevention even though
they may potentially be more profitable. Much of the problem lies in the farmer's perception of the impact his practices have on the environment and other social and economic factors. In general, most farmers feel that they are not responsible for the pollution of their environment and that the use of any corrective measure will come at a cost to them (Conway and Pretty, 1991). For a farmer to adopt a pollution prevention technology it must be profitable and have a low initial cost. The solution might be increased environmental education coupled with viable demonstration projects and specific pollution control recommendations that avoid the expected economic losses.
Supalla et aI., 1995, conducted a study to assess the factors relating to why farmers choose not to use the recommended best management practices in the Central Platte Valley ofNebraska. He found that environmentally concerned, well educated, well informed, and younger producers who farmed smaller acreage were more likely to apply nitrogen at recommended rates. In Georgia, most of the farmers are not environmentally concerned, well educated, well informed, and younger producers. The USDA Economic Research Service estimates that 91 % of the farms in Georgia are owned by a single family. The average farm size is 256 acres; however, 51 % of the farms are less than 100 acres and 77% have sales ofless than $50,000. The average age of the farm manager is 55 years and most do not have a college education. Since these older and less prosperous farmers are generally not as receptive to change as younger, college educated farmers, the task of informing them and changing traditional practices is often difficult. Educational efforts to change behavior should address the linkages between management practices and environmental quality. Educational programs for nitrogen application should explain how fertilizer recommendations are developed with an emphasis on explanations for recommendations that are lower than traditional amounts. If a farmer understands why he should be concerned and economic alternatives are available, then he will be more likely to use an accepted practice.
The economic background of Georgia farmers also presents an obstacle to pollution prevention. About 54% of Georgia's farmers view farming as a secondary occupation and are therefore less likely to invest resources in improvements. A full time farmer that is dependent on his farming income will be more likely to invest in technologies with a long payback period than would a retired landowner that uses farming to supplement his income. Smaller farms are more likely to use sustainable practices since they are sensitive to a lowered break-even yield per acre as a result of being more marginally profitable. However, the small farm usually has fewer resources to expand and modify operations and less time to devote to pollution prevention practices. This displays a need for technologies that require little initial investment. In addition, educational programs should always emphasize the economic benefit of preventing pollution as both short term and long term investments, as certain technologies may only be appropriate to certain types of farmers. It is also important that these programs stress that higher productivity does not always equate to more profit, as most pollution prevention technologies could reduce both inputs and total output while increasing the profit margin.
75

Fanners and landowners are not always aware ofthe optimum practices needed to prevent pollution. An expanded education program is needed to demonstrate to fanners that, (a) there is room for improvement in current practices, and (b) there are techniques and technical resources available to make improvement. Experience has shown that direct contact with fanners is the most effective way to bring about change. However, there is no way to provide personal services to all fanners. Therefore traditional mass contact programs such as descriptive publications, mass-media distribution, newsletters, demonstrations, educational meetings, etc., must be used to reach a broad-based audience. The private sector may provide invaluable assistance in this educational effort through trained and certified consultants. The voluntary Certified Crop Advisors concept being developed by the American Society of Agronomy may provide a possible solution to broad-based recognition of qualified persons in the private sector who can assist fanners. For this to be successful, efforts to train these consultants in pollution prevention should begin immediately.
Agricultural Policy From the preceding text, much of the technology for pollution prevention in crop
production apparently exists; however, it is of little use if it is not put into practice. Obstacles deterring alternate crop production techniques and pollution prevention programs include economical constraints, lack of technical information on alternative technologies, and unwillingness of fanners to try new approaches. Most of these impediments can be overcome through education and outreach. However, many current government policies and regulations could also be changed to facilitate this process.
A number ofUSDA conservation programs share the cost of implementing conservation practices with fanners through direct payment. These include the Agricultural Conservation Program, Water Quality Incentives Projects, the Small Watershed Program, and the Rural Clean Water Program. For fiscal years 1992-1994, these programs provided about $89 million to U.S. fanners to implement environmental management practices (GAO, 1995). The main problem with this assistance is that it is often limited in terms of amount ($3,500 per year) and will only cover half of the total cost (75% in some cases). When the cost of various management practices is considered, for example $40 to $80 thousand for a lagoon, $5,000 to $20,000 for filter strips, or $8,000 to $10,000 for a poultry manure storage and composting shed, this often leaves the producer to shoulder a substantial part ofthe economic burden. Nevertheless, cost sharing is important to the implementation of conservation practices, and agricultural pollution prevention programs need to insure that appropriate pollution prevention technologies are addressed through NRCS cost share programs.
The acceptance and use of state of the art BMPs is also of primary importance as many BMPs can be implemented at little cost to the producer. In the design and implementation of these BMPs, the "whole fann" concept needs to be used to account for a variety of nutrients, conditions, processes, etc. rather than those that are most prevalent. These BMPs need to be carried out on as many fanns as possible. Generally, practices that increase net income are compatible with water quality; however, accomplishing this requires a higher level of management (Moore et aI., 1995). This management is not only supplied by the owner/grower but also requires significant participation from other sources such as extension agents, NRCS
76

staff, and fann organizations. Often these organizations each function independently rather than functioning as a team. Not only does this confuse many producers, but it also leads to substantial amounts of bureaucracy at the cost of programs that could truly benefit the farmer.
Another major obstacle to agricultural pollution prevention is a lack of funding. This comes in several layers. First, there is a real need for more research to investigate suitable agricultural pollution prevention alternatives. While some technologies exist, most require more research and are still considered "experimental". The development of new pollution prevention technologies will require substantial amounts of new research funding or the redirection of existing funding. Second, there is a need for increased funding for education and demonstration. In order for these technologies to be accepted they need to be displayed at a local level and made available to the public through local educational programs. Finally, there is a need for increased economic or regulatory incentives. Regulation will work, but it is not as politically, socially, or economically accepted as voluntary approaches. Incentive-based proposals may provide the needed information and knowledge to improve and expand pollution prevention technologies. This can come as increased cost-sharing or through the development of awards or recognition programs; however, both alternatives will require some funding.
One method of indirectly obtaining funding for all these areas is to take advantage of existing programs. Nationally established Water Quality, Integrated Pest Management, and Sustainable Agriculture initiatives receive substantial amounts of direct federal funding for both research and education. The goals ofboth programs can be obtained through agricultural pollution prevention. By allying with these programs, the agricultural pollution prevention program could take advantage of both the funding and the infrastructure already in place. Since funding is limited, it is also important that it be targeted to the most appropriate areas. While funding could be targeted using several different variables or methods, perhaps the best method is to target it to areas where the problems are the worst.
The ideas of sustainability and "whole fann planning" need to be incorporated into each ofthe pollution prevention technologies we implement at the fann level. One method of doing this is to develop sustainable guidelines. For example, if a cotton producer chooses to use regularly scheduled pesticide applications rather than an IPM program then he should document that his increased pesticide use does not have greater environmental risk. This should be accomplished through plans that insure that both the soil and water quality will not suffer from agricultural activities. If this cannot be documented, then alternative strategies should be developed. The "whole fann planning" concept that Georgia is currently testing is one method of incorporating this sustainability. Whole fann plans look at the entire fann operation rather than individual components to insure that the management decisions made in one area of the farm do not have a negative impact on another area. In addition, these plans give the fanner a tool for exploring all aspects of his operation and could be used to locate appropriate areas for pollution prevention technologies.
77

RESEARCH NEEDS
While the pollution prevention technologies discussed thus far have proven utility, more improved technologies can and will be developed. Pollution prevention is a relatively new concept. However, the concepts of maximizing productivity, conserving soil and water resources, and minimizing environmental degradation have been investigated by scientists within the agricultural community for many decades. This research has been highly successful. The USDA has estimated the investments in agricultural research return an average of 1.5 to 5 dollars per dollar invested. With returns like this, investing in agricultural pollution prevention research could be the wisest use of limited pollution prevention funds. This section highlights research needs for new and existing pollution prevention technologies that would most likely produce the greatest return in terms of efficient, usable, and beneficial technologies.
The advent and usage of conservation tillage systems represents one of the greatest pollution prevention gains of the last quarter of a century. Tillage systems that reduce soil disturbance and the number of passes made over a given field reduce soil erosion and are economically advantageous to the farmer. Therefore, these technologies have been readily adopted. While conservation tillage reduces soil erosion and increases soil quality in terms of organic matter and infiltration rates, some research has suggested that reduced tillage systems may actually increase off-site contamination with pesticide residuals. Fawcett et al. (1994) present an excellent review of this topic. Others have suggested that the use of conservation tillage systems require greater amounts of herbicide and insecticide inputs and can cause groundwater contamination since infiltration is increased. Fawcett's review of many studies contradicts both claims, however, they acknowledge that the effects of any tillage system are highly dependent on geographic, agronomic, and environmental factors and suggest further study. These investigations should not only focus on reduced tillage systems but also explore new possibilities for the development of improved tillage implements and systems.
The second major area of required research is in adequate plant nutrition. The nutrients from livestock wastes are a good source of organic fertilizer. Animal manure supplied 12% of the approximately 17 million tons oftotal nitrogen applied to U.S. cropland in the recent decade (PPI, 1992). If used to its potential animal wastes could represent a much larger percentage of the total applied nitrogen. Further research could lead to this increased use. The obstacles this research will need to overcome include the substantial energy and labor costs associated with handling and storage of the waste, the high transportation costs limiting the potential to transport to off farm areas, problems encountered in collecting representative manure samples for nutrient analysis, and the determination of application rates that provide the crop with sufficient nutrients without having adverse environmental effects.
Nutrients applied to a crop should match the needs of the crop, but the ratios ofN, P, K, and the various micronutrients within commercial fertilizers and animal wastes are generally different from those required by crops. Not only does this present problems for the development of application rate recommendations, but it can also produce nutrient imbalances in the soils and crops that receive these fertilizers. Research emphasis should be placed on determining the effects of nutrient imbalances on crop growth and environmental conditions. Historically,
78

nitrogen has been the primary element on which nutrient management plans have been developed due to its importance in optimizing crop yields and its relatively high level of mobility in the environment. Recently, more locations are moving away from the "limiting nutrient" concept and developing nutrient management plans based on other elements such as P, K, and more conservative micronutrients that may accumulate over longer periods. Future work with nutrient management planning should focus on the development of sustainable planning methodologies rather than concentrating on individual nutrients. Improved nutrient management planning strategies that limit soil nutrient imbalances rather than maximizing crop productivity (ie. consideration of elements other than nitrogen) should be developed.
Continuation of research associated with minimizing the potential for runoff and leaching under various management scenarios is also necessary. By increasing our understanding and knowledge of mineralization rates and their effects on crop growth, we could more accurately account for them in nutrient management plans. There is also ample opportunity for research on chemical amendments that would make the nutrient content of organic wastes more like that required by the crop. Methods of waste application that minimize carbon loss from the soil and organic wastes through oxidation need to be researched. Optimum rates of application of the various types of organic matter for improvement of water retention and cation and anion exchange capacities need to be formulated.
Another major waste stream in crop production that will require further research concerns pesticides. IPM represents one of the most successful pollution prevention advances of the last decade. Due to innovative IPM research, cotton growers were able to reduce insecticide use by a dramatic 70% over six years while increasing the average yield by 27% (Porterfield et al. 1995). Advances such as these could be made in other areas and for other crops through continued IPM research. This research should not be limited to strategies alone as there is plenty of room for improvement in other aspects ofIPM such as improved scouting methods, better techniques for maximizing natural predators, improved application technologies, a more thorough understanding of resistance and how to prevent it, and replacements for chemical insecticides. Investigations into the best management practices and application technologies should also be continued. For example, ultra low volume herbicide application technology using oils and surfactants is being investigated and could present some very substantial reductions in application rates. Specific guidelines for optimum soil conditions for maximizing nematode predators are needed in addition to the development of a safe effective chemical nematicide, currently not available.
'(.
Biotechnology also will provide for pollution prevention in future crop production. It has already produced plants that are resistant to certain pests and pesticides. Its potential is boundless. The ultimate goals will not only be increased yields, but also resistance to pests, droughts, and moisture plus increased tolerance for weeds and adverse soil conditions.
Another major area of increased pollution prevention research should be in the application of site specific or precision application technologies. Most ofthe research used to display the feasibility of precision farming technologies has been conducted in the Midwest. If precision farming proves to be a good deal in the Midwest there is little doubt that it would be a better deal in the
79

Southeast. The reasons it would be even more profitable in Georgia include: 1) Georgia grows high value crops such as canola, cotton, and peanuts so justifying the costs of the equipment would be easier. 2) Soil variations are greater in the South than the Midwest and 3) The level of pests and natural soil fertility are generally higher in the South (Keller, 1995). To further the use of precision farming technologies, more on-farm demonstration programs need to be established. Currently, the technology is ahead ofthe science so every operation trying precision farming is its own experiment. This results in less than optimum use and could actually cause a backlash if the experiments are not successful. Also, the abundance of small farms in Georgia may inhibit precision farming practices since large acreages are required to justify equipment purchases. Small farm needs should be evaluated. Methods such as cooperatives or commercial services that could extend this technology to the small farm should be researched. Researchers also must develop improved equipment required for precision farming. Monitors that give real time yield monitoring have been developed for all crops that are run through a combine, however, there is a need for the development of yield monitoring equipment for other crops such as peanuts and cotton. Equipment and tests for measuring soil and plant variability on the go also need to be developed. Although machine vision must come a long way to be able to scout for insects, the idea of having equipment capable of finding pests and using pinpoint pesticide applications is not too far fetched considering the advances of the last decade.
Computer technology will also be significant in other areas of agricultural pollution prevention. Farm management and operational decisions of the future will be complex because soil-water management must be integrated with improved fertilizer and pesticide application methods to insure environmentally sound agriculture. This will necessitate the use of decision support systems and environmental models. Models need to be developed that simulate seed dormancy and seedling emergence for weed species. Due to the expense and labor intensivity of long term field studies required to reliably quantify agricultural nonpoint source pollutants, computer models ofnutrient management are needed to evaluate different management scenarios and application conditions (Sharpley and Meyer, 1994). These models should be developed at different levels. Research type models that require extensive inputs should be developed to evaluate manure management alternatives for the development ofbest management practice recommendations and farm policy (Tim and Jolly, 1994 and Gelata et aI., 1994). However, a major limitation to these models is often the lack of detailed parameterization data on soil properties and climate, crop, and tillage information. There is also a need for on-farm type models that require less input data and can be used as educational tools by non-scientific users. Recent developments in geographical information systems (GIS) and advanced interfaces could make many existing models more user friendly and help them to gain broader acceptance and use. GIS systems also have the potential to be used for targeting sensitive areas and for the development of nutrient management plans for smaller areas under site-specific or "precision" conditions. There is also a need to obtain more widespread usage of existing models. This may require the development ofbetter user interfaces and databases, but existing models have been proven in research communities and should be used in the field. The WEPP model for example is a proven erosion prediction technology that could greatly benefit the agricultural community if using it was easier. Development of integrated crop ecosystem management models and decision support systems (DSS) models are also needed for most major crops grown in Georgia. These
80

models will facilitate decision making for IPM programs, fertilization, pesticide application, and irrigation requirements at the farm level or in local extension offices.

Composting can also provide a vital link in preventing pollution from all segments of society. As microorganisms digest biomass, they respire carbon dioxide emitting it to the atmosphere. Since organic carbon is valuable when in the soil and detrimental when emitted to the atmosphere, research is needed to compare the emissions of carbon dioxide and other gases from conventional composting versus soil application of biological wastes, ie. "composting" biomass in the soil. Research is needed to determine the extent to which fungi in plant canopies occurring in crops such as cotton, peanuts and soybean can be controlled by compost. The need for organic matter is great for the sandy soils of southern Georgia where most crops are grown. More research associated with the waste streams of both agricultural and non-agricultural industries could result in increased use of off-farm organic material. Potential biomass resource locations and economical hauling distances need to be identified. In doing this research, care should be taken to document the effects ofthese amendments on the soil and the value of a compost product. Many explanations behind the observed improvements from organic matter in soils that have been recorded will require further research. Studies that compare the agronomic qualities of composted manure to those of raw manure should not only highlight the benefits of using compost but also provide additional documentation on the effects of composting on pathogens, weed seeds, odors, nutrients, and soil physical properties. Better methods and equipment for processing and handling materials and improved "recipes" are needed to reduce atmospheric emissions, processing time, labor, site preparation and equipment expense associated with composting operations. Research projects should display increased emphasis on producing consistent composted products in uncontrolled environments and with variable inputs as these are the conditions likely to occur in on-farm composting.

Research needs are not limited to science but should also include policy. For example, the

Conservation Reserve Program (CRP) has proven effectiveness. Erosion on 36.5 million acres of

highly erodible land in the United States has been reduced by 90% since the initation of this

program (Porterfield et aI., 1995). However, some argue that the costs of this program are too

high and that purchasing buffer zones around sensitive environmental areas would be a better

investment than paying farmers not to produce in entire fields. A study is needed to investigate

possible incentives for the installation of vegetated buffer zones around all surface waters (ponds,

lakes, creeks and rivers). Iflong term sustainable uses that are economic and at the same time

accomplish surface water protection could be determined they would represent the most

.(

productive use of this land and save valuable tax dollars. Policy can dictate pollution prevention

techniques that are economically advantageous in the long term but have high short term costs.

81

CONCLUSIONS AND RECOMMENDATIONS
Most conventional crop production techniques tum under soil cover and add agrichemicals such as plant nutrients and pesticides that promote maximum economic plant yields. Objectives are to provide a soil environment where chosen cultivars may grow unhindered by plant competitors and to reduce crop damage from insects and disease. Conventional techniques often result in increased soil erosion, loss of soil organic matter, substantial energy requirements for farm machinery, runoff and leaching of fertilizers and nutrients, increased plant susceptibility to plant pests and pesticide consumption, and a loss of biological activity within the soil profile. Storage, handling, and application of farm chemicals also add to potential environmental contamination. The greatest opportunities for pollution prevention lie in changing to more conservative and efficient practices.
Agriculture is conducted on such a vast scale that farmers' livestock and soil management methods can have an impact on atmospheric carbon and nitrogen content. Methods that sequester carbon and nitrogen in the soil can be of benefit to soil and air quality as well as to the economic viability of the farm. In high organic soils, water is used more efficiently, less fertilizer is required, beneficial organisms can thrive, insect predators can be cultivated, and toxic chemicals are more easily degraded. Not only do farmers need to adopt methods of sustaining soil organic matter such as conservation tillage and crop rotation, but organic matter additions as animal manure, compost, crop residues, and industrial byproducts need to be investigated. Maintaining or improving soil quality should be the cornerstone of all effective pollution prevention plans.
Other pollution prevention opportunities can be broken down into the waste streams they control; runoff and soil erosion, plant nutrients, pesticides, and agrichemicals. Water quality degradation and soil erosion can often be limited or prevented through the implementation of proven techniques such as best management practices, crop rotation, vegetative buffers, and improved land management. Nutrient management plans and other demonstrated economic techniques such as soil and plant analysis, the use of organic fertility options, and the establishment of realistic yield goals should continue to be supported and implemented. More effective methods of applying both plant nutrients and pesticides should be developed and/or implemented at the field level to increase the efficiency of input use. IPM and other cultural practices can often be used to both decrease the need for agrichemical inputs and increase their effectiveness. While many improved methods of storing and handling all types of agrichemicals have been developed primarily to address human health and safety issues, they are often based firmly in the principles of reducing risk and are consistent with the goals of pollution prevention.
Economics is often the major impediment of pollution prevention. While many practices and opportunities are cost effeCtive, they often require an initial investment or have long periods. New sustainable agriculture techniques need to be demonstrated with an emphasis on economics. Research and demonstration projects should be field oriented and conducted on producers' land. Oversight ofthese projects should be conducted cooperatively between the researchers and the growers. Economic analyses of the alternatives being investigated should be incorporated into
82

the projects early in the process. Experimental practices should be implemented on a trial basis by growers willing to be trail breakers. Financial assistance should be available for those growers willing to risk time and capital on testing and implementing new pollution prevention innovations. Growers should be engaged through grower association meetings and information presented during education programs already in place. Tax credits and crop insurance could promote innovation and a quicker transition to viable, alternative approaches. Besides educational activities, there is a need for continuation of funding for applied and theoretical pollution prevention research. Research projects dealing with the fundamental processes involved with plant genetics, biotechnology, nutrient and pesticide transport and fate, atmospheric dynamics, and chemical and biological decomposition processes could all lead to development of new management practices, plants, equipment, or products that would benefit production efficiency and environmental conditions. Finally, at the core of pollution prevention technologies is the understanding that pollution is a sign of inefficiency and that effective technologies will either reduce inputs, conserve resources, or find improved uses for the by-products of production. In crop production, pesticides, fertilizers, organic carbon, and topsoil loss are the primary by-products that reach the atmosphere and water resources. There is a cost associated with these losses. Future research and outreach needs to center on technologies, practices, and policies that decrease these losses.
83

REFERENCES
Abu-Zreig, M., R.P. Retry, and W.T. Dickinson,1994. Effect of Organic Wastes on Soil Erosion. University of Guelph, School Engineering, Guelph, Ontario, Canada. Presented at the 1994 ASAE International Winter Meeting. Atlanta, GA.
Acock, B. and L.H. Allen, 1985. Crop Responses to Elevated Carbon Dioxide Concentrations. In (B.R. Strain, J.D. Cure, eds) Direct Effects of Increasing Carbon Dioxide on Vegetation. U.S. Dept. of Energy. DOE/ER-0238, Dist. Category Uc-l1.
Agbirn, N.N., B.R. Sabey, and D.C. Markstrom, 1977. Land Application of Sewage Sludge: Carbon Dioxide Production as Influenced by Sewage Sludge and Wood Mixtures. Journal ofEnvironmental Quality 6:446-451.
Ag-West Biotech Inc., 1996. Biotechnology, Agriculture, and Your Food: An Introduction to the Benefits of Biotechnology in Agriculture. Westcross House Publications, Saskatoon, Saskatchewan. (306)934-1772. 12 p.
Avery, D.T., 1995. Saving the Planet with Pesticides and Plastic: The Environmental Triumph ofHigh-Yield Farming. The Hudson Institute, Inc. Indianapolis, Indiana (317)545-1000. 432 p.
Baker, J.L., T.S. Colvin, D.C. Erbach, R.S. Kanwar, and P.A. Lawlor, 1995. Herbicide Banding to Reduce Inputs and Environmental Losses. ASAE Conference Proceedings, Vol. 1, Pesticides. Kansas City, MO.
Bodrova, E.M. and Z.D. Ozolina, 1965. Simultaneous Application of Organic and Mineral Fertilizers. Translated from Russian, Jerusalem: Published pursuant to an agreement with the USDA. pp 72-100.
Box, J. and H.I. Walker, 1968. Cotton Burrs for Soil Improvement. Texas Agricultural Extension Service, Texas A&M University, College Station, TX.
Brady, N.C., 1967. Agriculture and the Quality of Our Environment. A Symposium Presented at the 133rd meeting of the American Association for the Advancement of Science. Washington, D.C. pp 331-341.
Brady, N.C., 1990. The Nature and Properties ofSoils, tenth edition. New York: Macmillan Publishing Co. pp 519-528.
Bridges, D.C., C.K. Kvien, J.E. Hook, and C.R. Stark, 1994. An Analysis of the Use and Benefits of Pesticides in U.S.-Grown Peanuts: Southeastern Production Region. The University of Georgia National Environmentally Sound Production Agricultural Laboratory, Tifton, Georgia. NESPAL Report 1994-002.
Brock, T.D., M.T. Madigan, J.M. Martinko, and I. Parker, 1994. Biology ofMicroorganisms, seventh edition. Englewood Cliffs, N.J.: Prentice Hall. pp 668-669.
Broner, 1., 1995. Crop Management Systems to Reduce Groundwater Contamination. Fort Collins, CO: Dept. of Chemical and Bioresource Engineering, Colorado State University.
Buhler, D.D. 1995. Reducing Herbicide Use in Conservation Tillage Crop Production Systems. ASAE Conference Proceedings, VoU, Pesticides. Kansas City, MO.
Bussiere, F. and P. Cellier, 1994. Modification of the Soil Temperature and Water Content Regimes by a Crop Residue Mulch: Experiment and Modeling. Agricultural and Forest Meteorology 68:1-28.
Cabrera, M.L. and R.M. Gordillo, 1995. Nitrogen Release from Land-Applied Animal Manures. Proceedings of the 1995 Georgia Water Resources Conference, Athens, GA.
84

CAST, 1992. Preparing U.S. Agriculture for Global Climate Change. Council for Agricultural Science and Technology Report No. 119. Ames, Iowa. 77 p.
CAST. 1995. Waste Management and Utilization in Food Production and Processing. Council for Agricultural Science and Technology Report No. 124. Ames, IA. 125 p.
Chan-Muehlbauer, C. and D. Gunnink,1994. Profitability of Four Sustainable Farms in Minnesota. The Land Stewardship Project. Lewiston, MN.
Chescheir, G.M., R.W. Skaggs, J.W. Gilliam, and R.O. Evans, 1995. Effects of Water Table Management on Water Quality. ASAE Conference Proceedings, Vol. 2, Nutrients. Kansas City, MO.
Clay, S.A., D.E. Clay, K.A. Brix-Davis, and K.A. Scholes, 1995. Alachlor and Atrazine Fate in the Soil Profile. ASAE Conference Proceedings, VoU Pesticides. Kansas City, MO.
Comstock, C.R. and I. Broner, 1994. Combining Expert Systems and Neural Networks for Learning Site Specific Conditions. 1994 Winter Meeting, The ASAE, Atlanta, GA. ASAE, 2950 Niles Rd. , St. Joseph, MI.
Conservation Reserve Program, 1995. Alternatives Are Available for Managing Environmentally Sensitive Cropland. Report to the Committee on Agriculture, Nutrition, and Forestry, U.S. Senate. U.S. General Accounting Office. GAOIRCED-95-42.
Conway, G.R. and J.N. Pretty, 1991. Unwelcome Harvest: Agriculture and Pollution. Earthscan Publications Ltd., London, England. 645 P.
Cooper, S., 1996. Personal Communication. President Electrostatic Spraying Systems, Inc.
cnc, 1992. BMPs for Water Quality. Conservation Technology Information Center, 1220 Potter Drive, Room
170, West Lafayette, Indiana 47905.
Deizman, M.M., S. Mostaghimi, T.S. Dillaha, and C.D. Heatwole, 1989. Tillage Effects on Phosphorus Losses from Sludge-amended Soils. Journal ofSoil and Water Conservation 44:247-251.
Delaplane, K.S. , 1994. Pesticide Safety for Private and Commercial Applicators. The University of Georgia Cooperative Extension Service Bulletin 1105.
Deterling, D., 1995. Will Viral Insecticides Make It This Time? Progressive Farmer 86(5): 17.
Edwards, J.H., R.H. Walker, E.A. Guertal, L.D. Norton, and J.T. Eason,1994. Options for Recycling Organics on Farm Land. Biocycle 35(11 ):66-68.
Eghball, B.E., and J.F. Power, 1994. Beef Cattle Feedlot Manure Management. Journal ofSoil and Water Conservation 49(2):113-122.
EPA, 1980. Research Summary, Integrated Pest Management. United States Environmental Protection Agency, Washington D.C. EPA-600/81-80-044.
Escalada, M.M. and K.L. Heong, 1993. Human and Social Constraints to the Implementation of IPM Programs. International Rice Institute, Los Banos, Phillippines.
ESS, 1992. What Growers Should Know about Air-assisted Electrostatic Spraying. Electrostatic Spraying Systems, Inc. Watkinsville, Georgia. 13 p.
85

Fausey, N.R. and RL. Cooper, 1995. Water Table Management for Crop Production and Groundwater Quality Protection. ASAE Conference Proceedings, Vol. 2, Nutrients. Kansas City, MO.
Fawcett, RS., B.R Christensen, and D.P. Tierney, 1994. The Impact of Conservation Tillage on Pesticide Runoff into Surface Water: a Review and Analysis. Journal ofSoil and Water Conservation 49(2): 126-135.
Forcella, F., le. Barbour, C.A. Oriade, RP. King, and D.D. Buhler, 1995. Weed Emergence Modeling for a Bioeconomic Weed/Crop Management Expert System. ASAE Conference Proceedings, VoU, Pesticides. Kansas City,MO.
Foth, H.D. and B.G. Ellis, 1988. Soil Fertility. New York: John Wiley & Sons. pp 62-129.
Francis, D.D., A.L. Sims, lS. Schepers, 1995. Nitrogen Requirement, Availability, and Utilization. ASAE Conference Proceedings, Vol. 2, Nutrients. Kansas City, MO.
Free, G.R, 1949. Efficient Use of Farm Manure for Erosion Control. Journal ofSoil and Water Conservation 4: 117-118.
Frick, E.A. and C.A. Crandall, 1995. National Water-Quality Assessment Program: Water Quality in Surficial Aquifers in Two Agricultural Areas in Georgia, Alabama, and Florida. Proceedings of the 1995 Georgia Water Resources Conference. Athens, GA.
Geleta, S., G.J. Sabbagh, J.F. Stone, RL. Elliot, H.P. Mapp, D.J. Bernardo, and K.B. Watkins, 1994. Importance of Soil and Cropping Systems in the Development of Regional Water Quality Policies. Journal ofEnvironmental Quality 23(1):36-42.
Georgia Agricultural Statistics Service, 1995. Georgia Agricultural Facts. Larry E. Snipes, State Statistician. Georgia Department of Agriculture, Thomas T. Irvin, Commissioner. Athens, GA.
Georgia Agricultural Statistics Service, 1996. Georgia Farm Report 96(4): 1-4.
Georgia Department of Natural Resources, 1993. Water Quality in Georgia, Special Report from the Environmental Protection Division. Atlanta, GA.
Georgia Pest Control Handbook, 1995. Special Bulletin 28. K.S. Delaplane (ed.). Cooperative Extension Service, The University of Georgia College of Agricultural and Environmental Sciences. Athens, GA.
Georgia Soil and Water Conservation Commission, 1994. Agricultural Best Management Practices for Protecting Water Quality in Georgia.
Georgia Soil Test Handbook, periodic updates. The University of Georgia Extension Service, College of Agriculture and Environmental Sciences, Athens, GA.
Gianessi, L.P. and lE. Anderson, 1995. Pesticide Use in Georgia Crop Production. National Center for Food and Agricultural Policy, 1616 PSt., NW, Washington, DC 20036.
Gish, T.J., L. McKee, B.J. Wienhold, A. Shirmohammadi, 1995. Climate and Tillage Effects on Herbicide Volatilization. ASAE Conference Proceedings, VoU Pesticides. Kansas City, MO.
Goldman, L., 1996. EPA's Policy on Pesticides Gets Tougher. Forumfor Applied Research and Public Policy 11(1):46-53.
86

Hanks, J.E., 1995. Herbicide Use Reduction by Improved Application Technology. ASAE Conference Proceedings, VoU, Pesticides. Kansas City, MO.

Hansen, G.L., 1995. Environmental Due Diligence: Benefits to Farm Lenders and Customers. AgriBank, FCB., St. Paul,MN.

Hansen, RC., C. Marugg, H.M. Keener, W.A. Dick, and H.A.l Hoitink, 1991. Nitrogen Transformations During Poultry Manure Composting. Paper No. 914014. 1991 International Summer Meeting of the ASAE. Albuquerque, NM.

Henn, T. and R. Weinzieri, 1990. Alternatives in Insect Management - Beneficial Insects and Mites. Circular 1298, Cooperative Extension Service, Office of Agricultural Entomology, University of Illinois, Urbana-Champaign, IL.

Hickman, J., J. Jacobsen, and D. Lyon, 1994. Best Management Practices for Wheat: A Guide to Profitable and Environmentally Sound Production. National Association of Wheat Growers, 415 Second St., NE, Suite 300, Washington, D.C. 20002-4993.

Hickman, M.V., M.M. Schreiber, and G.D. Vail, 1995. Role of Controlled-Release Herbicide Formulations in Reducing Groundwater Contamination. ASAE Conference Proceedings, YoU, Pesticides. Kansas City, MO.

Hippe, D.J., H.H. Hatzell, L.K. Ham, and P.S. Hardy, 1995. National Water-Quality Assessment Program: Pesticide Occurrence and Temporal Distribution in Streams Draining Urban and Agricultural Basins in Georgia and Florida, 1993-1994. U.S. Geological Survey, Atlanta, GA., Tallahassee, FL. Proceedings of the 1995 Georgia Water Resources Conference. Athens, GA.

Hippe, D.J. and J.W. Garrett, 1995. National Water-Quality Assessment Program: Water-Quality Conditions and

Mass Transport in the Flint River, Southwestern Georgia, Related to the Flood of July 1994, Caused by Tropical

Storm Alberto. Proceeding of the 1995 Georgia Water Resources Conference. Athens, GA.

.

Hippe, D.l, D.l Wangsness, E.A. Frick, and lW. Garrett, 1994. Do the Pesticides I Use Contaminate the Rivers Everyone Uses? Water-Resources Investigations Report 94-4183, U.S. Department of the Interior, U.S. Geological Survey, National Water-Quality Assessment Program, Atlanta, GA.

Hoff, K. (ed.). 1995. Organic Cotton Monitor. Institute for Agriculture and Trade Policy. Vol. 1, No. 1. Minneapolis, MN.

Houston, J.E. and H. Sun, 1995. Cost-Sharing Incentives in the Gum Creek Watershed Agricultural Water Quality Pilot Project. Proceedings of the 1995 Georgia Water Resources Conference. Athens, GA.

Hubbard, R.K., R.R Lowrance, lG. Davis, G.L. Newton, G. Vellidis, M.C. Smith, and R Dove, 1995. Riparian Buffer Systems for Managing Effluents. Proceedings of the 1995 Georgia Water Resources Conference. Athens, GA.

Humenik, F., 1994. Protecting the Quality and Quantity of Water. Resource 1(8):14-16.

Hummel, J.W., L.M. Wax, and E.W. Stoller, 1995. Reducing Herbicide Inputs in Weed Management Systems for the Corn Belt. ASAE Conference Proceedings, YoU, Pesticides. Kansas City, MO.

ISRIC, 1992. Bi-annual report. ISRIC. Wageningen, The Netherlands.

Jaynes, D.B., 1995. Electromagnetic Induction As a Mapping Aid for Precision Farming. Ames, Iowa: USDAARS, National Soil Tilth Laboratory.

87

Johnson, D.D., J.M. Kreglow, S.A. Dressing, R.P. Maas, F.A. Koehler, and F.J. Humenik, 1982. Best Management Practices for Agricultural Nonpoint Source Control, I. Animal Waste. North Carolina Agricultural Extension Service and Biological and Agricultural Engineering Department of North Carolina State University. Raleigh, North Carolina. 67 p.
Jury, W.A., W.R. Gardner, and W.H. Gardner, 1991. Soil Physics, fifth edition. New York: John Wiley & Sons. pp 259-264.
Keller, D., 1995. Let's be Precise. Progressive Farmer 110(8):18-20.
Kellogg, R.L. and S. Wallace, 1995. Changes in Pesticide Leaching Potential Between 1982 and 1992: A National Perspective. ASAE Conference Proceedings, VoLl, Pesticides. Kansas City, MO.
Lal, R., J. Kimble, and B.A. Stewart, 1995. World Soils as a Source or Sink for Radiatively-Active Gases. In (R. Lal, J. Kimble, E. Levine, B.A. Stewart, eds.) Soil Management and Greenhouse Effect. Advances in Soil Science. Boca Raton: CRC, Lewis Publishers. pp 1-7.
Lamb, J.A., D.F. Hughes, N.R. Kitchen, and J.L. Anderson, 1995. North Central Regional Nitrogen Best Management Practices. ASAE Conference Proceedings, Vol. 2, Nutrients. Kansas City, MO.
Lan Y., D.R. Ring, J.H.Benedict, B.R. Eddleman, J.A. Landivar, and W.L. Sterling, 1994. Economic Analysis of Insect Control Strategies Using an Integrated Crop Ecosystem Management Model. 1994 International Winter Meeting of the ASAE. Atlanta, GA.
Landers, A.J., and D. Steel, 1994. Precision Agriculture - A Viable Option for Future Arable Farming in Europe. 1994 Winter Meeting, The ASAE, Atlanta, GA. ASAE, 2950 Niles Rd., St. Joseph, MI.
Larson, R.E., et aI., 1994. Water Quality Benefits of Having Cattle Manure Deposited Away from Streams. Bioresource Technology 48: 113-120.
Latimer, J.G. and others, 1995. Opportunities and Impediments to Pollution Prevention in the Ornamental Horticulture Industry. A position paper written for the Pollution Prevention Assistance Division of the Georgia Department of Natural Resources, Atlanta, Georgia.
Mannering, J.V., 1979. Conservation Tillage to Maintain Soil Productivity and Improve Water Quality. Agronomy Guide AY-222. Purdue Univ.
Maynard, A.A., 1994. Sustained Vegetable Production for Three Years Using Composted Animal Manures. Compost Science and Utilization 2(1):88-96.
Meister, B. and L. Sine (eds.), 1996. Farm Chemical Handbook. Magnolia Publishing, Clearwater, Florida. 850 p.
Moore, P.A. Jr., T.C. Daniel, A.N. Sharpley, and C.W. Wood, 1995. Poultry Manure Management: Environmentally Sound Options. Journal ofSoil and Water Conservation 50(3):321-327.
North Carolina Extension Service, 1988. Pesticides and Water Quality. Fact Sheets. North Carolina Agricultural Extension Service, Raleigh, N.C.
Olcott-Reid, B., 1991. Small but Deadly. National Gardening 5: 34.
Osmond, D.L., J. Spooner, and D.L. Line, 1995. Systems of Best Management Practices for Controlling Agricultural Nonpoint Source Pollution. RCWP Technology Tranfers Fact Sheet No.6. North Carolina Cooperative Extension Service, N.C. State University, Raleigh, NC.
88

Ozkan, H.E., 1994. Reducing Spray Drift. The Ohio State University Cooperative Extension Service, Bulletin 816.
Ozkan, H.E. and M.L. Wilson, 1994. Reducing Pesticide Waste. The Ohio State University Cooperative Extension Service, Bulletin 819.
Parker, J.H. (ed.), 1992. Environmental Handbook for Fertilizer and Agrichemical Dealers. Tennessee Valley Authority, National Fertilizer & Environmental Research Center. Muscle Shoals, AL.
Phosphate & Potash Institute, 1992. "Ten Facts Affecting Nitrogen Use for Sustainable Agriculture and Nitrate in Groundwater." PPI Brochure. Atlanta, GA.
Plank, C.O., 1988. Plant Analysis Handbook for Georgia. Cooperative Extension Service/The University of Georgia College of Agriculture. Athens, GA.
Pollution Prevention Research Center, 1995. Pollution Prevention in Agriculture: Pesticide Use Reduction. The Pacific Northwest Pollution Prevention Research Center, 1326 Fifth Ave., Suite 650, Seattle, WA 98101.
Porterfield, J.W., D.R. Parrish, and H.F. Manig, 1995. Implications of New Water Quality & Environmental Legislation for Farmers and Ranchers. Presented at the 1995 ASAE International Meeting, Paper No. 952685. ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA
Post, W.M., T-H. Peng, W.R. Emanuel, A.W. King, V.H. Dale, and D.L. DeAngelis, 1990. The Global Carbon Cycle. American Scientist 78:312-326.
Rajotte, E. G., 1987. The National Evaluation of Extension's IPM Programs. Virginia Cooperative Extension Service Publication No. 491-010.
Richards, B.N., 1987. The Microbiology ofTerrestrial Ecosystems. New York: John Wiley & Sons, Inc. pp 363.
Riggle, D., 1994. Why Farmers Become Composters. Biocycie 35(11):58-62.
Risse, L.M., M.A Nearing, AD. Nicks, and J.M. Laflen, 1993. Error Assessment in the Universal Soil Loss Equation. Soil Science Society ofAmerica Journal, 57(3):825-833
Ritter, W.F., 1990. Pesticide Contamination of Ground Water in The United States-'-A Review. Journal of Environmental Science and Health B25(1): 1-29.
Robbins, L. and D.M. Bisset, 1994. The Role of Environmental Risk Management in the Credit Process. The Journal ofCommercial Lending 94(6):18-25.
Rylant, K.E., 1996. Personal communication. Team Leader for Pollution Prevention in the Agricultural Research and Practices Department of the TVA Environmental Research Center, P.O. Box 1010, Muscle Shoals, Alabama 35660.
Rynk, R., 1994. Status of Dairy Manure Composting in North America. Compost Science & Utilization 2(1):2026.
Sanford, C., 1994. Petroleum Storage and Handling Training Manual. National Farm*A*Syst Program, Farmstead Assessment System. U.S. EPA, USDA Extension Service, Madison, WI. USDA Soil Conservation Service. Madison, WI.
Segars, W.I., 1995. Reducing Agriculture's Demand for Water. In: Proceedings of the Fifth National Conference on Environmental Issues. pp. 101-115.
89

Sharpley, A. and M. Meyer, 1994. Minimizing Agricultural Nonpoint -Source Impacts: A Symposium Overview. Journal ofEnvironmental Quality 23( 1): 1-3.
Smith, L. and W. Kemper, 1992. "Future of Animal Waste Management: Research Perspective", National Livestock, Poultry and Aquaculture Waste Management: Proceedings of the National Workshop. ASAE, St. Joseph, Michigan. pp. 16-22.
Sundquist, E.T., 1993. The Global Carbon Dioxide Budget. Science 259:934-941.
Supalla, R.J., R.A. Selley, S. Bredeweg, and D. Watts, 1995. Adoption of Nitrogen and Water Management Practices to Improve Water Quality. Journal ofSoil and Water Conservation 50(1):77-82.
Sweeten, J., 1992. "Livestock and Poultry Waste Management: A National Overview," National Livestock, Poultry and Aquaculture Waste Management: Proceedings of the National Workshop. ASAE, St. Joseph, Michigan. pp. 4-14.
Tanada, Y. and H.K. Kaya, 1993. Insect Pathology. New York: Academic Press. Pp 58-60.
Tim, U.S. and R. Jolly, 1994. Evaluating Agricultural Nonpoint Source Pollution Using Integrated Geographical Information Systems and Hydrologic/water Quality Models. Journal ofEnvironmental Quality 23(1):25-35.
Tisdale, S.L., W.L. Nelson, and J.D. Beaton, 1985. Soil Fertility andFertilizers. New York: Macmillan. pp. 655-656.
Tolar, B., 1996. The Final Rinse: Georgia Pesticide Container Recycling Program Newsletter. Georgia Department of Agriculture. Agriculture Bldg., Suite 550, Capital Square, Atlanta, Georgia 30334.
Truman, C.C., and R.G. Williams, 1994. Event and Seasonal Runoff and Soil Loss from Peanut Cropping Practices. USDA-ARS Southeast Watershed Research Laboratory, Tifton, GA. Presented at the 1994 International Winter Meeting of the ASAE. Atlanta, GA.
Tyson, A.W., P. Bush, R. Perkins, and W. Segars, 1995. Nitrate Occurrence in Domestic Wells. ASAE Conference Proceedings, Vol. 2, Nutrients. Kansas City, MO.
United State Department of Agriculture, Soil Conservation Service, 1990. Agricultural Waste Management Field Manual, Chapter 4, Organic Manure, Waste and Residue.
United States Department of Agriculture, Forest Service, and Soil Conservation Service, 1993. Final Report: Georgia Watershed Agricultural Nonpoint Source Pollution Assessment, Cooperative River Basin Study. Availible from USDA- NRCS State Office, Athens, Georgia.
United States Department of Agriculture, 1996. Agricultural Chemical Usage. Field Crop Summary Report presented by the National Agricultural Statistics Service and the Economic Research Service. Washington, D.C.
United States Environmental Protection Agency, 1991. EPA's Pesticide Programs. Pesticides And Toxic Substances (H-7506-C), 21T-1005, May 1991.
United States Geological Survey, 1994. Suspended Sediment and Agricultural Chemicals in Flood Waters Caused by Tropical Storm Alberto. U.S. Dept. Of the Interior. U.S. Geological Survey. National Water-Quality Assessment Program. Atlanta, GA.
University of Georgia, 1980. Soybeans in Georgia. Cooperative Extension Service, Bulletin 639. College of Agriculture. Athens, GA.
90

University of Georgia, 1982. Cotton Boll Rot. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1984. Controlling Nematodes on Flue-Cured Tobacco. Plant Pathology Fact Sheet, Leaflet No. 24. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1984. Tobacco Blue Mold. Plant Pathology Fact Sheet, Leaflet No. 362. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1986. Double Cropping Soybeans in Georgia. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1987. Georgia Soybean Culture. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1987. Grass Hay Crops, Circular 794. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1987. Principles and Practices of Weed Control in Soybeans. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1987. Tobacco Insect Control, Circular 413. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1987. Tobacco Production, Circular 638. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1988. Cotton Disease Control. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1989. Fertilizing Cotton. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1989. Small Grain Resource Handbook. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1990. Growing Com in Georgia, Bulletin 547. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1990. Pastures in Georgia, Bulletin 573. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1990. Producing Quality Peanuts, Bulletin 1036. Cooperative Extension Service, College

<..

of Agriculture and Environmental Sciences. Athens, Ga.

University of Georgia, 1991. Principles and Practices of Weed Control in Cotton. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1991. Small Grain Production and Utilization in Georgia. Cooperative Extension Service, College of Agriculture. Athens, GA.

University of Georgia, 1992. Forage Weed Management, Agronomy #B-1070. Cooperative Extension Service, College of Agricultural and Environmental Sciences. Athens, GA.

91

University of Georgia, 1994. Crop Enterprise Cost Analysis. Cooperative Extension Service, College of Agricultural and Environmental Sciences. Athens, GA.

University of Georgia, 1994. Cotton Defoliation and Crop Maturity. Cooperative Extension Service, College of Agricultural and Environmental Sciences. Athens, GA.

University of Georgia, 1995. Commercial Peach Integrated Crop Management Guide. Cooperative Extension Service, College of Agricultural and Environmental Sciences. Athens, GA.

University of Georgia, 1995. Cotton Production Guide. Georgia Cotton Commission and Cooperative Extension Service, College of Agricultural and Environmental Sciences. Athens, GA.

The University of Georgia, 1995. Disease and Insect IPM in the Home Orchard. Cooperative Extension Service,

...,

College of Agricultural and Environmental Sciences. Athens, GA.

University of Georgia, 1995. Annual Report. College of Agricultural and Environmental Sciences. Athens, GA 30602.

University of Minnesota, 1992. Adapting Soil-Specific Crop Management to Today's Farming Operations. A Workshop on Research and Development Issues. Eds.: P.C. Robert, R.H. Rust, W.E. Larson. Minneapolis, MN.

Von Bargen, K., G.E. Meyer, and D.A. Mortensen, 1995. Sensor-Controlled Intermittent Spraying To Improve Water Quality. ASAE Conference Proceedings, VoLl, Pesticides. Kansas City, MO.

Willis, G.H., L.M. Southwick, J.L. Fouss, J.S. Rogers, and C.E. Carter, 1995. Controlled Water Table Depth and Water Quality. ASAE Conference Proceedings, Vol. 2, Nutrients. Kansas City, MO.

Wilson, G.V., D.D. Tyler, J. Logan, G.W. Thomas, R.L. Blevins, M.C. Dravillas, and W.E. Caldwell, 1995. Tillage and Cover Crop Effects on Nitrate Leaching. ASAE Conference Proceedings, Vol.2, Nutrients. Kansas City, MO.

Wischmeier, W.H. and D.D. Smith, 1978. Predicting Rainfall Erosion Losses. USDA-ARS Agricultural Handbook 537. U.S. Government Printing Office, Washington, D.C.

Woodroff, N.P., L. Lyles, J.D. Dickerson, and D.V. Ambrust, 1974. Using Cattle Feedlot Manure to Control Wind Erosion. Journal ofSoil and Water Conservation 29:127-129.

Woolley, J.S., 1995. The Switch from Conventional to Sustainable Practices. Resource 2(4):7-9.

92

APPENDIX: AN OVERVIEW OF GEORGIA'S PRIMARY CROPS
While the main portion of this text gave an overview of the general opportunities for pollution prevention, specific crops were rarely mentioned. Often, the amount or importance of pollution prevention technology that may be applicable is highly crop specific. This appendix attempts to provide more detail on the opportunities and impediments that may be associated with the production of specific crops. Although descriptions are not meant to be crop production guides, a general overview of crop production practices is presented. The intent is to give familiarity for some major requirements for production of a specific crop. The information presented is directly from the bulletins published and distributed by The University of Georgia Cooperative Extension Service and for the most part specific references to these publications have been omitted.
A. Corn Com has been a long time staple on Georgia farms and, with new varieties and improved
management techniques, production has continued to increase. In fact, in the 1940's average com yields in Georgia were less than 10 bu/acre while today yields in excess of 100 bu/acre are common. Com represented 1.9% of total farm receipts in Georgia in 1993. A total of650,000 acres was planted. South Georgia produced more than 85% of total production, with 59% of total production in Southwest Georgia (Figure 3). More than 39 million bushels were harvested valued at $87.89 million (Georgia Agricultural Statistics Service, 1995). Even with this production, Georgia is a com deficit state that must import large quantities to meet its need for animal feed.
Nationally, com production is the most important crop in terms of acreage and value. Therefore, considerable emphasis has been placed on plant genetics resulting in continuous improvements. Hybrid selection is based on yield potential, maturity, stand ability, disease resistance, grain quality, and adaptability to different geographic areas. Early hybrids complete their life cycle at a faster rate and may need fewer irrigations and may be more suitable for use in

CORN
Production by Counties, 1994
Top 10 Counties

1. Grady 2. Bulloch

2.759.000 bu. 2;441,OOObu.

3. Coffee

2.334,OOObu.

4-1rwin

2,115,ooobu.

5. ApplIng

1,992,000 bu.

.,..

6.semJnoIe
7.scmen

1,739,000 bu. 1,732,OOObu.

8.MIlcheU

1,716,OOObu.

9.1:a1ty

1,599,000 bu.

1o.Umer

1,577,ooobu.

SIaleTolai

57,240,000 bit.

1,000,000+ bu. .

700,000-999,999 bu. _
-(1 4OlI,OOO-699,999 bu.
100,000..399,999 bit. ~ I

I .... than 100,000 bu.

I

Figure 3 Georgia com production by county. From Georgia Agricultural Statistics Service, 1995.
double-cropping programs. Early and medium hybrids generally have a lower ear setting, less lodging and higher yield. Late-maturing hybrids generally have better insect and disease resistance and shuck coverages that allow them to stand in the field for longer periods without losing grain quality. It is important that growers base hybrid selection on their specific goals. Often, factors other than yield will present better opportunities in developing pollution prevention strategies. For example, some hybrids can withstand weed infestations better and could be selected to reduce herbicide inputs.

Crop rotation is a proven management technique for increasing com yields. Yield increases of 15 to 30 bu/acre are common when corn is rotated with legumes. Crop rotation prevents disease and pest infestations. Corn can be grown under a variety of tillage systems ranging from no-till to fall plow systems. Reduced tillage is a proven soil conservation practice in Georgia and can offer economic advantages as well. Soil should not be worked any more than necessary in spring. Soil erosion considerations call for management practices to reduce soil movement especially in the Coastal Plain where wind erosion and blowing sand can damage young corn plants. Effective practices include minimum tillage planting into a small grain cover crop and discing a cover crop into the soil so that some stubble remains on the soil surface. Traffic pans should be disrupted by chisel plowing or by using an in row subsoiler during planting. In row subsoiling has increased yields tremendously on soils where traffic pans were present. Without periodic deep tillage, lime and phosphorus will not be incorporated into the soil, reducing rooting depth in soils high in aluminum.
Planting dates vary from the last of February in extreme south Georgia to the first of June in the mountains. Corn should be planted when temperature and moisture become favorable. Soil temperature in the seed zone should be 550 F or greater before planting. General recommendations call for 16,000 to 20,000 plants per acre for dryland corn and 24,000 to 30,000 plants per acre for irrigated corn depending on soil type. A 10 to 15% over planting is recommended to compensate for usual loss. Narrow rows produce greater yields due to shading the soil which reduces weed growth and reduces moisture loss from evaporation. Harvesters are now available that will harvest 30 inch rows. Surface applications of acid-forming nitrogen fertilizers will reduce the pH of the top four inches of the soil. Before planting soil pH should be checked as a pH below 5.5 can reduce yields and tie up plant nutrients.
Nutrient requirements for corn are extremely high. In 1995, 100% of Georgia corn acreage received some form of supplemental nitrogen while 96% of the acreage received phosphorus and potash (USDA, 1996). To grow 200 bu/acre corn, the plants will require 2661bs. of nitrogen, 114 Ibs. of P205' 266 Ibs. of K20, 65 Ibs. of Mg, and 33 Ibs. of S. Profitable yields require that each nutrient be supplied in adequate amounts. An unbalanced fertility program can cut yields and waste excess nutrients. Nitrogen management determines yields and profits more than any other

controllable factor. Nitrogen losses to denitrification and volatilization, especially with urea, may be greater with no-till programs. Nitrogen efficiency can be improved with split applications and nitrification inhibitors. Adequate phosphorus ensures that the farmer gets the most from his nitrogen investment. At inadequate phosphorus levels, plants cannot use all the available nitrogen and the excess is often leached through the profile. Potash gives com strong stalks and resistance to disease and drought. Com is one of very few plants that can use as much potash as nitrogen. With these nutrients and various micronutrients, it is important that they are available when the plant needs are greatest. With com, nutrient needs increase through the vegetative stages and peak at tasseling. Since this is often more than 100 days after planting, nutrients must be in a stable form. Tissue analysis can be used to detect nutrient shortages during the growing season and supplemental or foliar applications may be used.
Irrigated and com silage crops require more nutrients than dryland com grown for grain. If irrigation systems are available, only a starter fertilizer should be applied at planting. The remaining nitrogen can be applied as a side dressing or with center pivot irrigation systems (fertigation). Researchers achieved increased N efficiency and highest yield when they applied 22.5% at the six, 12, and 18 leaf stages, and 7.5% at tasseling. This method improves N uptake early in the season when root systems are small and require high N concentrations. Later in the season, this sequence of applications anticipates N requirements while minimizing the risks of nitrate leaching.
All fertilizer recommendations depend on the soil fertility level as determined by soil tests and the yield goal. Fertilization programs not based on soil tests may result in excessive and/or suboptimum rates of nutrients being applied. About three to five pounds of agricultural lime are required to neutralize soil acidity produced by every pound of ammoniacal nitrogen. A soil test taken in the fall is used to determine the requirements of the field before planting.
Com is generally fairly tolerant of most pests. Many pesticide applications in com are not needed because weed, insect and disease pressures do not justify the expense of treatment. Only when scouting shows an economic advantage should pesticides be applied. Field maps of previous pest problems must be maintained. In 1996, about 89% of the com acreage was treated with herbicides and 19% was treated with insecticides. The most common pesticide applications were

atrazine applied at an average rate of 1.53 lbs/acre and terbufos applied at an average rate of 1.10 lbs/acre.
Com grown on well-drained mineral soils rarely requires a soil insecticide. Continuous com, no-tillage com, com planted in organic soils, and com grown on set-aside acres often warrant greater use of insecticides. Insect attacks vary from year to year in com. Regular monitoring is essential. Early planting often prevents seedling damage from pests such as the lesser cornstalk borer and cutworms. Weed control can help reduce damage from com billbug, leafhoppers, and aphids that are also transmitters of com viruses. Burying residues of previous crops at planting can reduce damage from lesser cornstalk borer and cutworms. The soil should be carefully inspected when turned over for evidence of white grubs, wireworms or white fringed beetle. The Extension Service recommends treating soil that has an average of one larva per square yard if the field has a history of infestation. Nematicide is not recommended unless the field has been diagnosed to have a population that cannot be controlled by normal practices. Field com should be checked once or twice a week from the time seedlings begin emerging until the crop is mature. For most insects during the seedling stage, treatment is recommended if 10% of the plants are found to have larvae. When the crop is maturing, most insects are treated if 50% of the sampled plants contain evidence of infestation or if damage to the crop is noticed.
Although com can tolerate competition from weeds up to six weeks after emergence with little or no yield loss, weeds are fierce competitors for soil nutrients. Compared to com, common weeds take up about twice as much nitrogen. Atrazine is commonly used at planting to eliminate a previous cover crop to clear the field of any weeds. Narrow rows and uniform plant populations will reduce the time required to obtain a closed canopy to shade weed seedlings. Cultivating when weeds are small is best. Johnson grass, a host for viruses that infect com, is a critical weed to eradicate. When needed, herbicide usage may be reduced 60 to 80% by applying sprays or granules in eight to 12 inch bands over the com row. Cultivation will also be necessary to control weeds in row middles.
Pollution prevention practices for com should center on effective nutrient management practices due to the high nitrogen and phosphorus demands. Com, especially on sandy and less fertile south Georgia soils, requires large amounts of these nutrients so there is tremendous

opportunity for alternative soil amendments and organic sources of nutrients that are usually high in phosphorus. Organic matter additions in large quantities will increase moisture retention, increase the exchange capacity, and increase overall biological activity in the soil which gives multiple benefits. While com is generally tolerant of most weeds, insect pests can decrease yields so pollution prevention practices for pesticide management will also be beneficial. No-till com is a very successful option. Due to recent increases in com prices, dramatic increases in com acreage are expected in the coming years. This presents an opportunity as many new growers will be seeking advice.
B.Cotton Cotton accounted for 8.1% oftotal farm cash receipts in Georgia in 1994 and was the State's
number one cash crop. Total production was 1.54 million bales with a yield of 843 lbs. per acre. A total of 885,000 acres was planted in 1994 and an estimated 1.5 million acres in 1995. The total acreage in cotton has more than tripled since 1984. More than 92% of the cotton grown in Georgia is planted in south Georgia. Over 70% of the state's production is grown in southwest Georgia (Figure 4). The increasing competitiveness of American cotton, improved production practices, the eradication of the boll weevil and the continuing increase in demand is causing a resurgence in cotton planting in Georgia.
With the dramatic increase in cotton production, insuring that pollution prevention practices are implemented early is important as new producers are in a "teachable" mode. Proper management is extremely important in cotton production. While the nutrient requirements of cotton are not extremely high, it does require more chemical applications than most other crops. Cotton is very sensitive to both insect and weed infestations. Additionally, growth regulators and defoliants are often applied during the growing season and harvest. This makes proper chemical storage, handling and application procedures essential to cotton producers. Cotton also produces very little residue. This often leads to increased soil erosion and decreased soil organic matter levels if proper management practices are not used. In fact, many soils ofNorth Georgia are still showing the effects of years of cotton production conducted during the nineteenth and early twentieth centuries. By building up organic matter in the soil, less crusting will occur and damage from blowing sand can

COTTON
Productlon:~y,'Countles, 1994
Top 10~C()untles

1.Dooay 2. CoIqultt

96,400 bales a1AQObales

3. Mltchell 4.WOl1h

~obales
64jo'OO,bIIes

5. Decatur

58,DQO:baIea

6. Burke

53,000 bales

7. Brooks

51,800teles

a.EarIy

47,000 bales

9. Thomas

44,500 bales

10. Pulaski

4O,800balea

Stale Total 1,537,000 bale.

30,000 & over bales

-

20,000029,999 bales

7,500-19,999 bales 1~!!!mmlji!i!1:1
r'' 'I 1,000-7,499 bales .........

I Less than 1,000 baIet

I

Figure 4 Georgia cotton production by county. From Georgia Agricultural Statistics Service, 1995.
be reduced. Mulch applied to beds could decrease soil temperature and soil water evaporation decreasing relative humidity in the developed cotton canopy. Decreased humidity in the canopy can reduce damage caused by fungi that produce boll rot. Increased organic matter content can help in nematode control. Early planting and rotations can aid in weed and insect control.
While cotton production is not quite as nutrient intensive as com production, it does require a fertilization program based on a sound soil testing program. A cotton yield of750 lbs/acre requires about 105 lbs. ofN, 451bs. OfP20S' and 65 lbs. ofK20. Nationally, about 87% of the 1995 cotton

acreage received supplemental nitrogen applications while 56% and 40% received supplemental phosphates and potash (USDA, 1996). In a recommended fertility program, soil is adjusted to a pH of5.8 to 6.5. A target of60 lbs. of nitrogen per acre is applied on most soils. For deep sandy soils a basic rate of 80 to 100 lbs. per acre is recommended to offset poorer soil conditions and leaching losses. On soils with a history of rank growth, total nitrogen is reduced to 40 to 50 lbs. per acre. Peak demand for nitrogen occurs after the second week of bloom. High nitrogen levels in the early season can cause rank vegetative growth, poor fruiting and even shedding. Early season nitrogen losses can be decreased if only the amount of nitrogen to get the crop through the vegetative period are applied at preplant.
Cotton is sensitive to potassium deficiencies. Potassium deficiencies are based on soil tests. Most potassium is taken up after first bloom. Side dress applications are usually not required for soils with subsurface clay as potassium is not readily leached. For sandy soils, under irrigated situations, a 25% increase in potassium rates is required. Phosphorous is applied according to recommendations based on soil tests. Phosphorous is applied just before planting. Secondary and micronutrients are applied depending to soil tests.
In most production systems, soil is worked two to three weeks ahead of planting to allow rainfall to settle beds and enhance emergence. Fields are checked to find compacted layers so that they may be completely penetrated by subsoilers. Bedding is encouraged for all soils. Beds are 12 to 16 inches wide and of a smooth uniform surface. Hazards preventing a good stand of cotton are hard soil crusts and blowing sand. Both can be addressed with a rotary hoe or rolling cultivator operations. These implements are operated just deep enough to break the crust. Cotton grows very slowly during the initial weeks after germination, making the crop a poor competitor with weeds early in the season. Several weeks after emergence, cotton growth and leaf area increase rapidly, allowing the crop to exert a much greater influence on weeds, especially since the growth of most weeds is inhibited by shade. Rapid crop stand establishment and vigorous growth are effective means of weed suppression. If left unchecked, weeds can reduce yields as much as 80% and reduce the quality of lint.
By shortening the growing season, the threat of boll-damaging insect pests can be lessened, reducing the need for late-season insecticide treatment. An early cotton crop with more mature bolls

and fewer immature fruit is usually much less susceptible to insect damage. Early planting and managing plant maturity meant an added value of$14 to $72 per acre in a three-year study (North Carolina Extension Service, 1988). Early maturing fields typically have a higher lint quality and bring a premium price. Cotton in Georgia is planted between April 1 and May 25. Irrigated fields are planted after May 1. Ideal soil temperatures are 60 to 65 F. The crop requires 140 to 160 days to mature.
Insect pressure on cotton has a dramatic effect on the yield. Nationally, herbicides were used on 97% of the 1995 cotton acreage while insecticides were used on 75%. An additional 56% of the acreage also was treated with other agrichemicals (USDA, 1996). The cotton boll weevil is probably one of the best known plant pests. In Georgia, the boll weevil almost single handily eliminated cotton production. In 1977, cotton production dropped to a record low of less than 82,000 bales. Due to boll weevil infestations, Georgia growers were averaging more than 14 insecticide applications per growing season and were still losing lint to the boll weevil. One ofthe major success stories in agricultural pest control has been the control of the cotton boll worm. Through the boll weevil eradication program, insecticide applications have dropped drastically from double digit applications per crop to three or four applications per season. Knowledge of over wintering habits combined with coordinated multi regional planning and accurate nutrition measurement can account for much of the success. Such strategies point the way for future agriculture progress.
Cotton bollworms and budworms should be easier to control in the future with the advent of Bt cotton. lbis transgenic cultivar produces insect pathogenic toxins within plant cells that kill the boll weevil without chemical applications. Monsanto is selling Bt cotton seed in Georgia for the 1996 season and it is expected to reduce chemical loads from 60 to 75%. Naturally, this will also reduce production costs.
Early-season insect pests are controlled with a preventive insecticide (eg., Temik) treatment at planting. Foliar sprays are also used. Insect control in season is carried as needed based on scouting. Nematodes and fungi are sensitive to soil water content and temperature. Planting on a raised bed increases the probability of warmer soil and lessens the threat of nematodes. Fungicides are used on fields with a history of disease.

Crop rotations influence weed management. Some crops shade-out and eliminate weeds that may be highly competitive in a following crop. Thorough preplant tillage destroys weeds present at planting. Mechanical cultivation remains an important part of weed control. Preplant, soil incorporation of the dinitro aniline herbicides such as trifluralin and pendimethalin are the primary means of annual grass and small seeded broadleaf weed control in cotton when herbicides are the chosen method of eradication. These treatments are effective if incorporation is timely, shallow, thorough and uniform. Immediate incorporation just prior to planting usually provides the most consistent weed control. Uniform, thorough treatment is done in the absence of knowledge ofthe weed population and occurrence frequency of weed locations.
The practice of delaying planting a week or more after fmal seedbed preparation is called "stale seedbed planting." The delay allows a producer to wait for rain before planting and often allows the initial flush of weeds to be eliminated prior to cotton stand establishment. Tillage or applications of foliarly-active herbicides are used to kill seedlings. Postemergence herbicides using precision application methods are applied after cotton is more than four inches in height. For escaped broadleaf weeds, over-the-top herbicides are used. Grass infestations are often scattered, permitting spot retreatment rather than blanket broadcast applications.
Diseases reduce the Georgia cotton crop 10 to 15% per year. The major diseases include seedling diseases, wilt-nematodes, and boll rot. Seedling diseases are addressed by planting high quality, treated seed of a recommended variety. Nematodes cause stunted uneven growth and provide means of entry for other organisms. Plants resistant or tolerant to nematodes should be used when available. Rotations reduce root-knot nematodes. It is recommended that stalks be plowed up immediately after harvest to reduce nematode carryover. Nematode populations can be effectively reduced by providing a summer fallow period. Cotton is plagued by several diseases that cause economic loss, but none is more discouraging to growers than boll rot. Most of the damage is in the Coastal Plain, where many growers lose up to a bale per acre during extended periods of high rainfall at the time of boll maturity and boll opening. Several fungi and bacteria have been associated with boll deterioration. Usually boll rot organisms enter through injuries caused by insects and spray equipment or through natural openings. Anything that promotes excess vegetative growth is likely to increase boll rot. These factors include over fertilization (especially nitrogen) in

combination with high rainfall and poor insect control. Control using chemicals have not been successful. When and where boll rot is expected, growers can miminmize damage by lowering plant populations, providing good insect control, managing nitrogen applications carefully, and using a growth regulator for fields where rank. growth and boll rot are expected.
At maturity, cotton is defoliated. The purpose of defoliation is to improve lint quality, and to facilitate harvesting. Timely defoliation and harvesting reduce weathering, field losses, leaftrash, and cotton lint stain. Premature defoliation reduces yield and quality. Bolls are mature when approximately 60% of the fruits are open. Defoliation is usually advisable only after 75% of the bolls to be harvested open and the youngest bolls to be harvested are mature. It is also best to do a boll maturity check by cutting the boll and examining the seed. Harvesting is scheduled within seven to ten days after leaf drop. Organo-phosphate or cacodylic acid defoliants are often used. Defoliants are applied in two stages. A "preconditioning" application is applied one to two weeks before the final defoliant application. While these chemicals do represent additional inputs, they present few environmental concerns.
c. Peanuts
Peanuts represented 10.6% oftotal Georgia farm cash receipts in 1994 or $533 million. Total production was more than ,1.86 billion pounds with an average yield of 2,870 pounds/acre harvested from 655,000 acres. South central and southwestern regions of Georgia, accounted for more than 81 % ofthe acreage planted in 1994 (Figure 5). This is an ideal region in terms ofpotential pollution prevention as these regions also grow large amounts of cotton and com that are ideally rotated with legumes such as peanuts. While peanut yields increased substantially from 1993 to 1994, because of much larger increases in cotton acreage peanuts fell to second place in Georgia crop production values. Nevertheless, Georgia still leads the nation in peanut production producing over 40% of the nation's total supply.
The peanut is a legume that is a member ofthe pea family. It is a perennial herbaceous plant that is very sensitive to frost and is grown as an annual in most production systems. Since it is a legume, it is an excellent candidate to be grown in rotation with other crops such as com, sorghum, millet, perennial pasture grasses, and cotton that require large amounts ofN. The incidence of pests,

PEANUTS
Production by Countlest 1994 Top 10 Counties

1. Worth
2.Eart1
3.Mitchtll 4. MlIl.r
5. Decatur f. 00011 7.BuI&ach .. IrMa t. Tllmet
to. 11ft
StattTotai

108.228.000 lba.
94JJ53,oao lba.
76.824.000 Ibe. 7~77J)OO lba. 7-4.131,000'" 71;598,000 Ibe. 71,305.000 lba.
et.294,oao Ibe.
67,79&,000 Ibe. 58,11a,ooo IbIt.
1~OOOIba.

60.000.000. over lba. _
11& 3O.OO0p00.59.999,999Iba,.
1~ " ""0~ """-, 29 g. O 9991bs-. it?f;~~::,:~;;:!,~:~;::~:~*~;::~ffl
1<::::: d 1,JOQ,000-9.999,999 Ibs.

I..eA than 1.000.000 k 1_ _-,

Figure 5 Peanut production by county. From Georgia Agricultural Statistics Service, 1995.

including weeds, insects, disease causing organisms, and nematodes is high in peanuts production so efficient pest management is essential for profitable production. In fact, a recent study (Bridges et al., 1994) found that pest management costs compose a larger portion of peanut variable production costs than any other item. This study provided a detailed analysis of peanut production practices and opportunities for pesticide use reduction and should be consulted for more detailed information.
Optimum conditions for planting peanuts include good soil moisture and a four-inch soil temperature of at least 65 F for three or more consecutive days. Recommended planting dates are April 15 through May 20. Lime and fertilizer are applied first along with any preplant herbicide and then the soil is deep turned. Next the seed bed is made friable and flat by tilling. Some farmers

plant during tilling. The nutrient requirements of peanuts are rather low so fertilization is only recommended when conditions warrant it. Just after plant emergence, a three-inch deep soil sample is taken on either side of the row. Calcium levels must be 500 lbs/acre or greater and the calcium: potassium ratio must be 3: 1 in the top three inches of soil. Calcium as calcium sulfate (gypsum) is generally applied. Boron is also a critical nutrient. Boron is applied with fertilizer during land preparation. If additional boron is needed, it is applied about 40 days after planting. Since gypsum and calcium are common by-products of many industrial operations, there is considerable opportunity for developing landfill diversion programs to take advantage of the peanut's nutrient needs.
Water is a major factor in peanut production. Peanuts need about two inches of water per week after reaching the pod formation stage. If peanuts are subjected to drought stress 20 days or more before harvest, the potential for developing aflatoxin increases dramatically. Sufficient water is also important for the absorption of calcium into the peanut pod. Irrigation scheduling is highly recommended for maximum production and can aid in water conservation efforts.
Pest control is essential in peanut production as there are approximately 44 weed, 20 insect, 17 disease, and 4 nematode pests ofeconomic importance. Many chemical and non chemical control tactics are used on these pests. Initially, farmers plant fungicide treated seed and use pre-plant incorporated herbicides. Fungicides are usually used regularly throughout the season while insecticides and nematocide use is based on need. Control is critical in the early part of the growing season. Pre-emergence and at-crack herbicides are recommended to minimize later use and residual chemicals in the field. Nationally, at least one herbicide, fungicide, insecticide, or nematocide was used on 98%,98%, 70%, and 30% of peanut production acreage, respectively. In Georgia, peanuts required more pounds of total active ingredient of pesticides than any other row crop. The most common applications were the fungicide, chlorothalonil applied at a rate of 5.42 lbs/acre on 97% of the total acreage; the herbicide, paraquat applied at a rate of 0.13 lbs/acre on 90% of the total acreage; and the insecticide, aldicarb applied at a rate of 1.42 lbs/acre on 57% of the total acreage. In addition, 31 other agrichemicals were used on peanuts in Georgia in 1992 (Gianessi and Anderson, 1995).

A healthy peanut crop is tolerant and competitive. Crop management practices such as fall discing, proper fertilization and liming, bedding, use of resistant varieties, and timely planting minimizes pest problems. A three to five year rotation reduces several soil-borne pests including leafspot diseases, black root rot, southern stem rot, Sclerotinia blight and some weeds. Use of resistant cultivars also allows reduction of pesticide rates. Leaf-spot is caused by fungi and is one ofthe chiefpests in peanuts. Control calls for frequent fungicide use. Beginning in mid-May and on schedule every 10 to 14 days, fields are sprayed with fungicide. Hydraulic sprayers, air delivery sprayers, controlled droplet applicators, and aerial application are commonly used to apply fungicides. For these preventive applications, technologies that improve application effectiveness will be of most benefit to peanut producers. By following leafspot advisories, growers can eliminate one to four fungicide applications.
Peanut production poses several other opportunities for pollution prevention. Peanut harvest and tillage practices create highly erosive conditions; however, this is somewhat offset by the fact that peanuts are usually grown in rotation and in flat sandy soils. Since peanuts are legumes, there are nutritional advantages as they can fix nitrogen in the soil. A pollution prevention technology that could have future potential in peanut production is the use of soil amendments such as waste gypsum and biomass. These amendments could supply nutrients, help to conserve moisture, and control soil erosion. Since fungi cause disease in peanuts and fungi growth rate is dependent on moisture in the canopy, soil water evaporation should be lowered. Crop residues, soil amendments, and mulches can lower soil temperatures and evaporation and therefore may reduce fungicide requirements as well.
D. Tobacco Production of flue-cured tobacco totaled 80.7 million pounds in 1994. Yield per acre
averaged 2,180 pounds. Acreage harvested was 37,000 acres. Total production was valued at $136 million, 2.7% oftotal Georgia farm cash receipts. Tobacco is grown exclusively in the southern part of the state. It has been an integral part of Georgia agriculture for two centuries and has proven dependability as a marketable agricultural crop.

Pollution prevention practices may enjoy greater acceptance in a high value crop such as tobacco. Growers have large expenditures for nutrients, fumigants, herbicides, and other agrichemicals to produce optimum yields. IPM and the use of rotations are promising techniques. Increasing soil organic matter to increase soil moisture retention, encouraging growth of soil pest predators, and increasing soil fertility can decrease chemical usage. By increasing soil moisture content, soil fungus is encouraged. Soil fungi are major predators of nematodes as are certain mites. By placing mulches on the soil, soil temperature can be lowered, reducing evaporative losses of water and thereby decreasing the relative humidity in the canopy, controlling fungus growth in the canopy.
Tobacco production is limited to South Georgia as plant beds must be located in a welldrained area. A loamy soil is most desirable. Beds should be drained by a ditch 12 to 18 inches deep. While good drainage is essential, it also promotes runoff and less efficient use of nutrients. Seedlings tend to be more disease free if grown under plastic; however, plastic is an added expense and disposal cost. If plastic is not used, fields must be cultivated to keep weeds in check. Cultivation is possible only early as plants quickly form a canopy. Once established, tobacco can still be labor intensive. Not only does it require the removal of suckers (offshoots that limit productivity) and topping, but harvest and drying are done manually and are very time consuming.
All fertilizer should be applied within the first four weeks after transplanting. After this period, applications are only used in replacing certain fertilizer elements leached due to heavy rains. Excess nitrogen should be avoided as pest numbers can double by applying 30 lbs. more nitrogen than recommended. Excess nitrogen also increases the need for sucker control and delays harvest.
Tobacco is also chemical intensive. Aphids, flea beetles, vegetable weevils, budworms, cutworms, hom worms, mole crickets, green June beetles, grubs, slugs and snails can cause economic damage. Nearly 100% oftobacco acreage is treated with the insecticide acephate (average application of2.24Ibs/acre/yr) and almost half of it with ethoprop and chlorpyrifos (6.00 and 2.00 lbs/acre/yr respectively). Most farmers look on preventive insecticides as insurance against losses but scouting can be substituted for preventive treatment. Research and field demonstrations during the past several years have shown that automatic spray programs are not the best approach to insect control on tobacco. Applying insecticides when infestation has reached certain levels greatly reduces

the cost of the insect control program, and does not reduce yields. In demonstrations, the number

of insecticide applications has been reduced by more than 50% and every time, more tobacco was

harvested where the number of insecticide applications was lower. A field should be checked by

carefully inspecting 10 consecutive plants at 10 different locations each week. The exact number

of insects required to cause economic damage is not known. However, the following figures are

presented as "rules of thumb": 10 budworms, or 10 homworms, or 20 loopers per 100 plants; when

groups ofaphids can be found on the undersides of most leaves in any sizeable area within a field;

"

when flea beetle infestations are heavy enough in early season to cause extensive damage to the buds

of newly set plants. If enough damaging insects are present to justify an application, an insecticide

is used.

Mechanical practices can also be used to reduce insecticide use. Early topping and

controlling suckers decrease the prevalence of budworms and homworms. Flowering plants attract

egg-laying moths. Early topping speeds the natural decline of aphid populations, reducing the need

for chemical control and improving yield and quality. Stalk and root destruction reduces the

likelihood of pest problems in succeeding years. Crop rotation and use of disease-resistant varieties

are particularly important in any program to manage soil-borne diseases with minimal use of

chemicals.

Herbicides are only needed to control weed in the early stages oftobacco production. Weeds

are controlled only during preplant and up to four to six weeks after transplanting. Preplant

herbicides such as clomazone, isopropalin, pendimethalin and others are applied to the soil and

incorporated. After transplanting, a herbicide such as napropamide is applied after the last

cultivation. Average application rates range from one to three lbs/acre/yr.

Tobacco losses due to nematodes amount to an estimated 4 percent ofthe value of Georgia's

crop. Several species of root-knot nematodes can affect production. Plants affected are usually

stunted, wilt readily in hot weather and exhibit signs ofnutrient deficiencies. Recommended control

practices reduce the numbers of nematodes to a level where the crop can become established before

nematodes increase to damaging levels. Cultural practices alone may be adequate on some farms.

An integrated control program involves crop rotation, resistant plant varieties, setting healthy

transplants, use of nematicide based on need, and root and stalk destruction. Nematicide can be

either fumigants or non-fumigants. Fumigants (Telone II) are used when there is a large nematode population. Fumigants are injected to a depth of eight inches during bed formation and sealed in by dragging. Fumigants are phytotoxic so transplanting is not conducted until after three weeks of fumigant application. Non-fumigants (Nemacur, Mocap) are not as effective. Non-fumigants are also incorporated prior to bed formation. Sampling for nematodes in the fall can reduce the cost of nematicide use. If nematode populations are below economic threshold levels, nematicide applications can be eliminated or reduced.
Fungi cause disease damage such as black shank and blue mold disease in tobacco. Control is practiced by using clean transplants, sanitary methods, nematode control, resistant varieties, using rotations and chemicals. Preplant fungicide (Ridomil 2E) is critical for tobacco blue mold control. A four-year rotation with grass or small grain in the year preceding tobacco can reduce the occurrence of most plant diseases.
E. Soybeans Soybeans accounted for $82.9 million or 1.4% of total farm cash receipts in Georgia in 1994.
That year, a total of520,000 acres was planted and 500,000 acres were harvested. Average yield was a record 31 bushels per acre and total production was 15.5 million bushels. The Coastal Plain and the southern half of the state produced 77% of total state production. Like peanuts, soybeans are legumes that should be grown in rotations with crops that require large amounts of nitrogen. Geographically, this is possible since soybeans are predominant in similar regions as cotton and com production.
Soybeans are a crop that can be used as an effective pollution prevention tool in rotations with other crops. In fertile soils, soybeans usually do not require much if any fertilizer. While weeds are the primary pest for soybean, they can be controlled readily with cultivation or herbicides in erosive areas. In fact, biotechnology is already available for soybean production in the form of glyphosate (Roundup) ready soybean. With this new seed, one application of glyphosate can be applied after three to four weeks of growth to maintain weed control throughout the growing season. Since glyphosate is not persistent and relatively immobile, this technology is relatively environmentally sound as it would reduce cultivation and herbicide application. Highly organic soils

are desirable in soybean production for moisture retention and to foster the growth ofnematodes and

other pest predators. The suppression of high relative humidity in the canopy to prevent fungal

growth can be accomplished by practicing no-till planting and using residues and mulches on the

soil.

A three-year rotation of crops is suggested in fields where soybeans are cultivated.

Minimum-till production can be achieved and is recommended in erodible areas. When planted in

May to early June, most soybean varieties begin flowering in July, soon after night length begins to

"'",

increase. Varieties to be planted are selected according to desired maturing times, geographical

location, soil type and fertility level, moisture availability and pest resistance. Soybeans do best on

deep, well-drained fertile soils with good water holding capacity. Deep sands and eroded clays are

generally not satisfactory due to low available soil moisture. Available moisturei.s one of the main

yield-limiting factors for soybeans. Substantial yield increases can be accomplished by subsoiling,

irrigation, and other practices that increase the availability of moisture.

Liming is critical for good yields. Liming is ideally accomplished six months prior to

planting. Soil pH should be between 6.0 and 6.5. Since soybeans are legumes, they do not require

any nitrogen fertilizer. However, in 1995 Georgia farmers applied an average of 31, 50, and 62

lbs/acre on 61,67, and 66% of soybean acreage for nitrogen, phosphorus, and potash respectively.

This is primarily because most farmers were double cropping or using preformulated fertilizers but

does suggest that reductions could be made. Phosphorus and potassium are essential and should be

applied in accordance with yield goals and a soil test. Direct application ofsulfur and micronutrients

is usually not required but are usually confirmed through a soil test.

Soybeans can tolerate fairly high populations ofsome insect pests. The most commonly used

insecticides include parathion (0.5 lbs/acre/year) and carbaryl (0.8 lbs/acre/year) which were used

on 12 and 11% of the total soybean acreage. Remedial treatments should be based on timely

scouting and economic thresholds. Preventive chemical treatments are rarely justified in soybean

production. Com earwonn is a major soybean insect pest. Planting early maturing varieties early

in narrow rows that will close the canopy by bloom can reduce earworm impact. Com earworm

usually does not develop to economic threshold levels under these conditions.

Weeds are the primary pests for soybeans. Effective weed control in rotation crops can be a great aid in reducing weed problems. Timely cultivation is an important and effective practice in weed control. Research has shown that yields from soybeans cultivated four times were equivalent to yields maintained weed free by hand or with sequential herbicide treatments. It was determined that harvest losses in weedy soybeans could be diminished by reducing the speed of the combine. Harvest losses when operating at one mph in weedy soybeans were approximately equivalent to those at three mph in weed free soybeans. Herbicide use in soybeans can be either preventive or remedial and both are commonly used. While pendimethalin (33% oftotal acreage) and metribuzin (32% of total acreage) are the most commonly used herbicides, more than 20 different herbicides were used on soybeans in 1992. The preventive approach requires accurate prediction of weed problems. Prediction is based on observations from previous seasons, summarized on a weed map. Remedial weed management tends to cut pesticide use, but requires more attention and may require more labor. A combined approach is desirable both economically and to protect the environment.
No economical pesticide is available for most soybean diseases and nematode problems. Cultural practices are the primary strategy. Rotations and resistant varieties are the key management tactics. A nematode assay and a disease map are very useful in increasing effectiveness of rotations and variety resistance. In a biologically active soil, nematodes are not usually a problem. Their numbers are kept in check by predators, mainly mites and fungi. When the soil loses its biological diversity and becomes sterile, nematodes can proliferate. A rich friable organic soil can aid nematode control by producing an environment for a broad diversity of soil species that support naturally occurring nematode predators.
F. Small Grains Small grains are produced in Georgia as a cash crop, a feed grain, a forage crop, or a cover
crop in soil conservation systems. Each type of small grain (wheat, oats, barley, rye, and triticale) can be successfully grown in Georgia as either a single or double crop. The importance that each small grain occupies in a farmer's cropping system depends upon need and location in the state. Some small grains are better adapted to different regions in the state than others. In 1994, more than 20.4,3.35, and 1.89 million bushels of wheat, oats, and rye, respectively, were harvested for a total

value of $72.2 million. Most ofthese grains were grown in South Georgia and on the Coastal Plain; however, some were grown in almost every county of Georgia.
Small grains can be grown in conjunction with conservation tillage and present excellent opportunities for developing longer and more diverse crop rotations. They grow best in welldrained, fertile soil formed into a smooth, weed-free seedbed. High organic matter soils are best for grain as organic matter can increase water retention, tilth and control predators. Destruction of old crop residue aids in reducing seedling and insect losses; however, many growers use various forms ofconservation tillage to conserve organic matter. Recent research has shown that forage production will respond to some form of deep tillage. This response has been observed in wheat for many years and has now been confirmed in rye. No-till and discing produced significantly less rye and wheat forage than did chisel plowing or turning. A similar response for rye grain yields is likely. Favorable responses to deep tillage may be due to improved soil aeration, better internal drainage and root development, improved disease control due to turning under of old crop residues, and more uniform emergence and growth.
Soil fertility is one of the primary yield-building components of small grain management. Soil pH is kept between 5.8 and 6.5. For most small grains, a base rate of nitrogen application of 80 to 100 lbs. per acre is used. If the preceding crop was a legume, nitrogen is decreased. When small grains are grown for forage, the nitrogen rate may be increased by up to 60 lbs. per acre. Phosphorus and potassium requirements for most small grains are relatively low; 40 bu. of wheat contains 27 lbs. ofP20 s and 81 lbs. of~ 0, and should be based on soil tests. Recommended amounts of phosphorous and potassium are thoroughly incorporated before fall planting to ensure an adequate supply throughout the root zone. When double cropping after small grains, phosphorous and potassium are applied prior to fall planting except on deep sands. In deep sands, potassium applications are split between fall and spring crops. Lime supplies adequate amounts of calcium and magnesium on most soils.
Pest control in small grains is relatively minor with herbicides representing the majority of agrichemical use. About one third of Georgia small grains receive applications of a herbicide called 2,4-D at an average rate of 0.5 lbs/acre/yr. Some weeds causing serious problems in small grain crops in Georgia are wild mustard, wild radish, wild onion and garlic, and rye grass. Small grain

crops are very sensitive to over application of herbicides, yet poor weed control may result if too low a rate is used. It is important to calibrate the sprayer using correct volume, pressure, ground speed and boom height. The problem with weeds in small grains is that the producer cannot mechanically remove weeds by cultivation. Production practices that can help reduce weed infestations in small grains include avoiding fields with a history of problem weeds, preparing land so that no weeds survive to compete, and timely applications of herbicides at the grain's correct growth stage.
Small grains are attacked by a few insects that can cause major losses but insecticide use is limited. The primary insect pest of wheat is the Hessian fly, which has caused extensive losses throughout the Southeast in recent years. The fly can be controlled by using a systemic granular insecticide during the fall. Insecticide is applied in the furrow at the time ofplanting. Insects overall are treated on an as needed basis. Less than 20% of all small grain acreage required any insecticide in 1992.
Diseases in small grains are usually caused by fungi. Disease control measures must usually be taken before the crop is planted. Generally recommended control measures are variety selection, rotation, attention to planting dates, seed treatment, and proper fertilization. If these practices are followed, diseases do not usually cause economic damage. Foliar fungicides are used as a last resort; however, less than 18% ofwheat acreage and 1% of oat and rye acreage used any fungicide in 1992.
G. Vegetables . Total cash receipts for vegetables were $362 million in 1994 representing 7.3% of total state
farm income. In 1992, it was estimated that there was a total of 101,193 acres in vegetable production. Of this, 17,725 acres were grown using plastic covered ground and 12,661 acres were devoted to vegetables grown for processing. The remaining acreage was bareground fresh market produce. Most production is in the southern part of the state with Colquitt, Tift, Decatur, Macon, Sumter, Mitchell,. Turner and Crisp Counties all having above 2,000 acres in production (Georgia Agricultural Statistics Sendce, 1995). The southern region remains by far the area with greatest vegetable production with more than 75% of production occurring south of the fall line. The most common vegetables and their 1994 acreage and values were onions (10,300 acres and $40.5 million), tomatoes (3,500 acres and $35 million), sweet com (17,000 acres and $33.9 million), watermelons

(30,000 acres and $25.5 million), cabbage (9,000 acres and $24.3 million), cucumbers (11,500 acres and $23.8 million), snap beans (14,000 acres and $16.1 million), cantaloups (7,000 acres and $6.6 million), lima beans (5,000 acres and $4.4 million), and sweet potatoes (2,400 and $4.2 million).
Most ofthe pollution prevention opportunities for vegetable production are similar to those for other high value crops that require extensive inputs. As in peanuts and soybean, vegetables are grown in areas of the state where sandy soils predominate. These soils can receive massive amounts of organic matter to increase fertility, water retention, and nutrient holding capacity that will reduce overall chemical use. Vegetable production also offers many unique opportunities. The plasticulture industry presents several problems. There is a need to produce alternative uses and disposal methods for used plastic. When applying fertilizers through microirrigation systems under plastic, breaks or malfunctions can often go undetected. Often, these irrigation systems present numerous opportunities for pollution prevention both in how they are managed and disposed of when they are replaced. Most of Georgia's vegetable production is for the table ready fresh market. Since the majority of production does not meet these high standards, much of the product goes unused. Opportunities exist to better use vegetable culls until canning plants are built. While each vegetable is unique and presents individual opportunities, many production practices are similar enough to discuss them together.
Preparation ofthe soil is approximately the same regardless ofvegetable planted and whether plants are to be grown on bare ground or using a plasticulture system. The field is deep plowed and plant debris thoroughly incorporated. Conservation tillage is rarely used in vegetable production. Lime is used to adjust pH between 6.0 and 6.5 six weeks to several months before planting. Considerable tillage used to insure a bed free of clods.
Plasticulture systems require a unique bed preparation and utilize different procedures and equipment than bare ground culture. After soil preparation, a three foot wide bed is usually formed. Usually the soil is tracked off in rows with fertilizer placed in a three-foot band and incorporated. The rows may need to be thrown up in hills for the bed press to shape them. If possible, the bed is shaped, fumigants applied, drip tubing laid and covered with plastic mulch all in one operation.
Fertilization rates and nutrient requirements for different vegetable vary and are determined based on plant need and soil testing. Often, vegetable growers will err on the side of over

application of nutrients to insure that plant production is not nutrient limited due to the high value of the produce. Generally fertilizer is applied in a band to the side of the seed. In plasticulture systems, fertigation is often used. Here, the nutrients are applied through a drip irrigation system buried in the seedbed under the plastic. Drip irrigation facilitates the precise application-and placement of controlled amounts of fertilizer and allows the growers to supply nutrients on an "as needed" basis. This is ideal in a properly managed and functioning system; however, can produce considerable waste if the system is not calibrated correctly, malfunctions, or is improperly used.
In general, pest control in vegetables is very chemical intensive with an average of over 44.0 lbs. of active chemical ingredients applied per acre of production. Most of this use is preventive as the value of the crop can often justify regular spray schedules and "insurance" applications. This represents an excellent opportunity for pollution prevention as there is substantial room for chemical use reduction.
Weeds are a problem only for bare ground culture except for border buffers where weeds can harbor insects especially during over wintering. Successful weed control will usually require the use of both cultivation and herbicides. Generally, about half the vegetable acreage receives some type of herbicide application of products such as DCPA, Trifluralin, and Paraquat. Cultivation for weed control is used only in bare ground culture. Cultivation continues to be an effective and relatively inexpensive means of weed control. For best results cultivation should be done early when weeds are small. Care should be taken to operate sweeps, rolling cultivators, and other machinery as shallow as possible to avoid root pruning while still destroying weeds.
Due to the high value of vegetable crops, insecticides are used extensively. There are a large number of insect pests and recommended insecticides. Most are applied as sprays. Considerable opportunities exist for developing and implementing IPM programs in vegetable production. Since the value of vegetable crops are high, alternative insecticides are recommended, especially the biological control offered by Bt products. A Bt insecticide is safe to apply at harvest since it is nontoxic to humans and other mammals.
Fungicides are usually sprayed every seven to 14 days on about 90% of most vegetable acreage. Nematodes are also major problems for many vegetables and often methyl bromide fumigation has been used to reduce nematode populations. Rotations can be used to reduce both

nematode and fungi pressure. Soils with high organic matter content will encourage natural predation and lower nematode populations.
A higher price may be obtained on the organic vegetable market. The Georgia Organic Growers Association and the local County Agent can be helpful in guiding farmers into this lucrative market. Organic methods are earth friendly and can often lower the cost per acre for production. The products; however, are often less appealing to most consumers. Organic methods require close attention to the crop and unusual cultivation methods such as growing two or more species of plant in the same plot. An indepth knowledge of insect and soil ecology as well as principles in soil fertility are required for successful organic production.
H. Peaches Georgia's 1994 peach crop totaled 175 million pounds. Yield per bearing age acre averaged
8,330 pounds. The value of production was $27.5 million and represented 0.6% of total Georgia farm cash receipts. According to the 1989 Georgia Commercial Peach Tree Survey, there was a total of 2,463,908 peach trees in the state. The heaviest concentrations of orchards are in the central region of the state.
Most opportunities for pollution prevention in peach production lies in improved chemical application technology and in proper management of ground cover. Methods that can conserve surface cover within the orchard without resulting in increased pesticide use could be effective. There are also many opportunities for improved utilization of wood stock produced from pruning operations. Pruning is a key management tool in reducing loss from peach tree short life. While pruning peach trees between October 1 and February 1 should be avoided, to complete annual pruning and maintain a labor force within a manageable size, many operations are forced to prune during this period. Pruned branches, dried fruit, leaves and other refuse is destroyed, often by burning. This biomass could probably be put to more economic beneficial uses.
Deciduous fruit plants common to Georgia must be propagated asexually because they do not come true to seed. This makes it necessary to reproduce the desired fruit plants by methods such as cuttings, budding or grafting. Seedlings are often started in greenhouses and transplanted to

orchards once established. The primary rootstock for peach and nectarine trees in Georgia are Lovell peach seedling, but others used on occasion are Nemaguard and Halford.
Orchards are cultivated to provide sanitation and weed control. Cultivation controls disease and insects, provides good air circulation, and reduces competition for nutrients and water. Inseason suppression of orchard floor vegetation may be of value throughout peach fruit development but is probably most important during the initial and final swell periods of fruit development. Vegetative suppression through "chemical mowing" reduces weed competition for nutrients and moisture. Plant bug and stink bug populations are lower in chemically mowed orchards, which improves the effectiveness of insecticides used for these pests. Mechanical mowing does little to suppress insects, and it requires a greater number of trips through the orchard.
Nitrogen is applied in peach orchards annually. Research has clearly shown that optimum peach tree health and productivity requires an annual split nitrogen application--one-halfpost harvest and the remainder in late winter prior to bud break. Post harvest, 20 to 50 lbs. of nitrogen per acre are applied in the herbicide band. Late season nitrogen helps build reserves accumulated in the fall that are responsible for following spring's bud and bloom growth. Late winter before and up to bud break, 30 to 60 lbs. of nitrogen per acre are applied in the herbicide band. Excessive nitrogen invigorates excessive shoot growth, decreases red color development, delays maturity and does not increase fruit size. Potassium application is based on cropping history and soil and foliar analysis. Other plant nutrients mayor may not be required based on analysis. Rates are based on soil and leaf sampling, irrigation practices, variety, and visual indicators such as fruit yield and quality, leaf color, and terminal shoot growth.
Weed management during peach tree dormancy is critical to proper orchard pest management. Vegetative suppression, not total elimination of vegetation, is often an efficient means of maintaining a ground cover. Ofte~ vegetative suppression can be accomplished through proper timing and low herbicide rates. Certain herbicides can also be used to selectively remove broad leaf weeds from grasses. Herbicide application to the orchard floor during dormancy can be used to provide short-term elimination of orchard vegetation during peach bloom, remove broad-leaf weeds that harbor deleterious insects and mites, reduce weed competition for nutrients and moisture during initial fruit swell. While nearly all peach orchards receive some herbicides, the products are usually

rotated and application rates are low (less than 0.50 lbs/acre/yr). In 1992, diuron was used on 70% of peach acreage, terbacil on 60%, oryzalin on 50%, paraquat on 41 %, and four other herbicides on less than 25% of the peach acreage.
Insecticides are used extensively in peach production. Beyond controlling pests during the growing season, it is often necessary to control leaf curl, mites, and scale during the donnant period. During budding, bloom and fruit development there are number of disease and insect problems that generally require chemical sprays. Bacterial spot, petal fall, scab, mites, plum curculio, oriental fruit moth, June beetles, green fruit brown rot, stink bugs, scale, borers, and nematodes are commonly encountered. Recommended chemicals and application methodologies are found in the Georgia Pest Control Handbook, 1995. For blossom blight, lime sulfur, captan 50WP, Benlate 50WP, Topsin-M 70WP, Bravo 720, Funginex 1.6 EC, Nova 40WP or Orbit 3.6 WP are recommended. Alternate row middle (arm) spray application appears to offer early through mid season insect and disease control equal to conventional spraying if intervals are adjusted to account for pest pressures. Growth regulators and chemical thinners are also used to improve color, increase size under drought conditions, and advance maturity before harvest.
I. Pecans Georgia's 1993 pecan production was 150 million pounds. Georgia is the number one pecan
producing state supplying 41% of the nation's consumption. The value of production was $83.6 million or 1.8% of total state farm cash receipts. Production is predominantly in the central and southern regions of the state. A survey of pecan trees conducted in 1992 showed a state total of 2,064,679 trees on approximately 100,000 acres (Georgia Agricultural Statistics Service, 1995). Pecans produce the same pollution prevention opportunities as peaches since both are tree crops that are highly dependent on agrichemicals. One opportunity particular to pecan production is in the area of improving pesticide application efficiencies. Some pesticides are less efficient in pecan orchards simply because the active ingredient cannot reach the target area. The upper limbs and tops of many trees can be greater than 30 feet above the ground surface and few pesticide sprayers are effective at such distances.

As with peaches, most groves begin with transplanted trees. Once established orchards can continue producing annual crops for many years. Generally, cultivation should consist only of discing or harrowing at a depth of not more than three inches. Many growers manage a year-round sod system using only mowing to control vegetation. The less cultivation, (particularly in depth) the more the pecan tree roots will gro~ closer to the soil surface. Rogue trees, briars, or perennial vines are destroyed in the grove either mechanically or with chemicals. Excess vegetation such as grass and weeds should be kept down during the summer months by mowing, harrowing or use of herbicides. Cover crops are recommended during the winter and the use of legumes can cut down on fertilizer costs. Clean culture is recommended for pecan trees only on soils where slope is not more than three or 4 percent. If clean culture is practiced on soils thathave a greater slope, a system of terraces should be incorporated. A combination soil management program of chemical weed control in eight to ten foot bands within the tree row and maintenance of a mowed sod between the tree rows is gaining in popularity. The closely mowed sod is convenient for mechanical harvesting, helps in preventing erosion, reduces compaction due to machinery movement in the grove and is believed to aid in moisture absorption by the soil. Recently, some farmers have begun to use the land area within the grove as a forage system for cattle. While the effects on pecan production have not been documented, this agroforestry type system should be effective as it will enhance soil quality while providing feed to an additional crop.
Fertilization for pecan trees is similar to peach trees but greater amounts are used. Nutrients and zinc are applied at rates recommended by soil tests and leaf analysis (Plank, 1988). Late
February or early March are recommended months to fertilize pecan trees. Optimum range for pH
is 5.6 to 6.0. Lime should be applied at the recommended rate when the pH drops below 5.9. Chemical pest control in pecan groves is rather extensive. While less than half the acreage
is treated with herbicides, most is treated with insecticides and fungicides. Leaf diseases such as scab, scorch, mildew, blotch, brown spot, and downy or vein spot may cause nut shedding. Prepollination sprays are critical for control of early scab and downy spot on all pecan varieties. Trees are sprayed every 14 days from bud break until pollination with a variety of fungicides including triphenyltin hydroxide (97% of acreage at 1 lb/acre/yr), propiconazole (52% of acreage at 0.27 lbs/acre/yr), and dodine (17% of acreage at 1.01Ibs/acre/yr). Post pollination, the fungicide

is applied every 14 to 21 days until shell hardening and once after shell hardening in August. Common fungi~ides include sulfer (48% of acreage at 11.44 lbs/acre/yr), ziram (11 % of acreage at 2.13 lbs/acre/yr), and benomyl (6% of acreage at 1.48Ibs/acre/yr).
Many insects and mites can substantially effect pecan yields. Phylloxera, spittlebugs, pecan nut casebearer, mites, aphids, shuckworms, pecan weevils and kernel feeding hemipterans (stink bugs and plant bugs) are common pests in pecan groves. Insect and mite infestation levels should be estimated at least weekly based on thorough orchard sampling. If predetermined economic thresholds are reached then chemical insecticides are used. Over 18 different insecticides were used on Georgia Pecans in 1992. The most common were carbaryl (28% of acreage at 4.50 lbs/acre/yr), chlorpyrifos (45% of acreage at 1.91Ibs/acre/yr), endosulfan (47% of acreage at 1.56 lbs/acre/yr), and dimethoate (41 % ofacreage at 1.08 lbs/acre/Yr). A common problem in the chemical treatment ofpecan pests is the development of pest resistance. This is esp~cially true with aphids and mites. To prevent resistance development, insecticide use should be minimized and the products used should be rotated. Beneficial insects in pecan groves, such as ladybugs and lacewings, can also be used to control aphids and mites.
J. Pastures and Hay Farmers cut and baled 650,000 acres of hay in 1994. Value ofproduction was $119 million
or 1.8% of total Georgia cash farm income (Georgia Agricultural Statistics Service, 1995). Hay is produced from perennial grasses such as Bermuda grass and Bahia grass in south Georgia and tall fescue and Bermuda grass in north Georgia. Other grasses grown in Georgia for hay or pasture include alfalfa, lesepedeza, clover, small grains and orchard grass. The long growing season and favorable rainfall make hay a favorable crop to produce. Hay is the predominant stored feed. If pasture is included, total forage area exceeds two million acres.
Since hay crops provide substantial surface cover, have large root mass and produce large amounts of vegetative biomass, runoff and soil erosion are generally not a problem. The surface residue and plant growth can retain most nutrient and pesticide applications. Thus, hay is a very desirable crop. The primary environmental problem associated with hay production in Georgia is

the over application of animal manures such as poultry litter. This problem is more a result of inadequate land areas for application rather than poor management practice for hay production.
For best forage production, a soil pH of 6.0 is maintained with lime. Fertilizer is applied based on soil tests. Large amounts of fertilizer are sometimes used (140 to 300 lbs. nitrogen per acre). Grasses are generally harvested after four to five weeks of growth. Grass is cut using mowers from two to eight times a year depending on location. Mowers leave one to two inches of growth. In pastures, mowing is a highly effective way to control weeds. Repeated mowing depletes carbohydrate reserves in the roots and eventually kills most weeds. Carefully timed mowing treatments can also reduce the formation of weed seed. Often the best method of controlling weeds is through improved fertility programs. Most weeds cannot compete with grasses in nutrients or water are not limited.
Many insects can cause damage to grass crops. These insects can be controlled by insecticides if economic damage is encountered; however, this is rarely the case. Usually insect populations remain in check as grass harbors an abundance ofbeneficials. Wireworms, white grubs, Bahia grass borer, and white fringed beetle larvae cannot feasibly be controlled in pastures except through crop rotation where preplant broadcast insecticide applications can be applied. If heavy populations cause death and/or unthrifty grass growth, rotations should be considered.
Weeds reduce yields and lower the quality of forages. Research has shown that for every pound of weeds in a pasture, forage production will be decreased by one or more pounds. Often weed infestations result from a failure to control weeds on field borders, ditch banks, and fence rows. Since many weed species have wind-blown or animal-carried seed, it is highly important to control weeds in areas surrounding crops. This can prevent entire field applications. Weeds are rarely a serious problem in well-managed, vigorously growing grasses. One key factor in the decline of Bermuda grass stands is low soil potassium levels. As the stand thins, weeds rapidly infest the field. Besides maintaining adequate soil fertility and pH levels, other cultural control methods include using adapted cultivars, managing grazing and haying, and using supplemental irrigation. Interest in using plant pathogens or insects to control forage weeds is rapidly increasing, and research is being conducted to identify such biological weed control agents. Goats have been found to be viable

in weed control since they eat bitter sneezeweed, dogfennel, curly dock, honeysuckle, kudzu and pigweed.
Herbicides are occasionally needed for weed control in hayfields and pastures. Less than 20% of Georgia pasture acreage and 11% of hay acreage were treated with a herbicide in 1992. Herbicide was used on 36% of alfalfa grown in 1990. 2,4-D was by far the most commonly used herbicide and average application rates range from 0.5 to 1.0 lbs/acre/yr. The low percentage of forage crop acreage treated with herbicides may be due to several factors:
1. Established, well-managed forage crops compete well with weeds, 2. Producers do not consider a high level of weed control in forages important, 3. Some producers may not know much about forage herbicides, 4. Some are not willing to spend money to control weeds in forages. Herbicides are applied to forages either on a broadcast or spot-treatment basis. Broadcast treatments are mixed with either water or fluid fertilizer and uniformly applied to the field. Spot herbicide treatment is generally made on a herbicide-water percentage basis. Spot treatments are useful when infestations are spotty or sparsely scattered through the field and can significantly reduce the amount of product used.
K. Nursery, Greenhouse and Turf With Georgia's mild climate and long growing season, the state's green industry is one of
the fastest growing segments of the farm sector. Gross sales of nursery, greenhouse and turf products grown in Georgia totaled $168 million in 1993. The 31 largest firms (gross sales) accounted for 54% of the total gross sales in 1993 but represented only 3% of the total operations. The 1,050 producing firms are dispersed throughout the state. The largest concentrations are in the Atlanta and Athens areas. The south central portion of the state has the largest land area in production (turfgrass) and the second largest concentration ofproducing firms (Georgia Agricultural Statistics Service, 1994). In 1993 there were 19,500 acres in production. Turfgrass accounted for 11,700 acres. Gross sales ofturfgrass totaled $27.4 million with 65 firms in production. Sales of greenhouse produced products in 1993 totaled $65 million from 619 firms.

Pollution prevention opportunities and impediments for the green industry are discussed in detail in Latimer et al., 1995. To avoid duplication, this section will not cover much of what is considered the green industry including the commercial growth and sales of ornamental plants. It is noted that greenhouse and commercial plant producers are intensive users of fertilizers and chemicals and the potential for pollution from these operations is great. Turfgrass will be covered in this section.
Newly established turfgrass is accomplished by either seeding or sprigging into a well cultivated, loose, well-drained soil. Grasses adapted to the area and appropriate for the anticipated use should be selected. Cool season grasses should be planted in the fall and warm season grasses in early summer. A regular fertilization program is important to maintain healthy, attractive turf. Fertilization is combined with mowing, watering, and pest management. Applications of fertilizer are determined using soil test recommendations. Nitrogen materials can be divided into two groups. One is quickly available or water soluble and the second is slowly available to plants provided there is adequate soil moisture. Quickly available materials generally are less expensive, can cause flushed growth, hav~ short soil residual, can leach, and have high burn potential. Quickly available nitrogen materials include ammonium nitrate, urea, ammonium sulfate, and potassium nitrate. Slowly available materials release nitrogen more gradually and over a longer period. The rate of nitrogen release depends on microbial decomposition alone or physical and/or chemical processes along with microbial activity. Environmental factors that affect microbial activity and release of these fertilizers are temperature and moisture. Slowly available nitrogen materials are more expensive, require fewer applications, reduce losses to leaching and have low bum potential. Examples include organic matter, ureaformaldehyde, methylene urea, isobutylidine diurea and sulfur-coated urea.
Periodic irrigation is needed to maintain a healthy, actively growing turf. Water use rates depend on soil type, grass species, management level and atmospheric conditions. In general most turfgrasses grown in Georgia use about one inch of water per week. Before sunrise is considered the best time to irrigate because oflow wind and temperature. Water losses at night from irrigation are 50% less than from midday irrigation. Irrigating after dew develops on a turf will not increase disease problems. Enough water is applied to soak the soil to a depth of six to eight inches. This

is usually equivalent to about one inch ofrainfall or 600 gallons per 1000 square feet (amounts differ with soil type).
Weeds are the major pests in most turfgrasses. Turfgrass weed control consists of two basic components, use of cultural practices and the use of herbicides. Cultural practices promote vigorous growth and development. Adapted species are used along with proper fertilization, irrigation, deep root development and cultivation. Vertical mowing, aeration and top dressings are sometimes necessary. Insect and disease control will also benefit vigorous growth.
Selective and nonselective herbicides are used. 2,4-D is by far the most common herbicide and is used on about 80% ofthe sod acreage. Other pre-emergence herbicides are applied prior to weed seed germination. Preemergence herbicides form the base of chemical weed control and are used primarily to control annual grasses and certain annual broadleafweeds. Due to their persistence (tWo to four months) in the soil, preemergence herbicides control susceptible weeds for an extended period. Newly-seeded and sprigged turfrasses have a low level of tolerance to preemergence herbicides. Postemergence herbicides are applied directly to emerged weeds. They have little if any soil activity.
Most of the diseases that affect turfgrasses are favored by high relative humidity or wet conditions. Turf should be grown in well drained soils. Timing of irrigation is important. In addition to fungus, moss and algae may be introduced. Fungicides suppress fungus growth and protect the grass from attack during periods when conditions favor disease development. Preventive sprays are commonly used but applications when disease is observed is preferred and more cost effective.
Pest-free turfis not necessary. Proper management practices promote healthy, vigorous plant growth reducing the vulnerability ofturf to pests. A number of insects are of concern to the turfgrass grower including ants and imported fire ants, bees and wasps, chinch bugs, cutworms, ground pearls, millipedes, mole crickets, sowbugs and pillbugs, slugs and snails, sod webworms, spittlebugs, and white grubs. A variety of insecticides are available to control these insects. Use varies considerably
\
from year to year and is almost always based on scouting and need. Recommended insecticides and methods of treatment are found in the Georgia Pest Control Handbook, 1995.

1*Printed on Recycled Paper