National Academies Press: OpenBook

Alternative Agriculture (1989)

Chapter: 3 Research and Science

« Previous: 2 Problems in U.S. Agriculture
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 135
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 136
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 137
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 138
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 139
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 140
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 141
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 142
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 143
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 144
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 145
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 146
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 147
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 148
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 149
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 150
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 151
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 152
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 153
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 154
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 155
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 156
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 157
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 158
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 159
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 160
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 161
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 162
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 163
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 164
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 165
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 166
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 167
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 168
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 169
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 170
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 171
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 172
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 173
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 174
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 175
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 176
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 177
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 178
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 179
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 180
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 181
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 182
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 183
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 184
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 185
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 186
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 187
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 188
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 189
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 190
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 191
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 192
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 193
Suggested Citation:"3 Research and Science." National Research Council. 1989. Alternative Agriculture. Washington, DC: The National Academies Press. doi: 10.17226/1208.
×
Page 194

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Research and Science A UERNATIVE AGRICULTURE iS a systems approach to farming that is more responsive to natural cycles and biological interactions than conven- tional farming methods. For example, in alternative farming systems, farm- ers try to integrate the beneficial aspects of biological interaction among crops, pests, and their predators into profitable agricultural systems. Alter- native farming is based on a number of accepted scientific principles and a wealth of empirical evidence. Some of both are presented in this chapter. The specific mechanisms of many of these phenomena and interactions need further study, however. In general, much is known about some of the components of alternative systems, but not nearly enough is known about how these systems work as a whole. Examples of practices or components of alternative systems that the com- mittee has considered are listed below. Some of these practices are already part of conventional farming enterprises. These practices include: Crop rotations that mitigate weed, disease, and insect problems; in- crease available soil nitrogen and reduce the need for synthetic fertiliz- ers; and, in conjunction with conservation tillage practices, reduce soil erosion. Integrated pest management (IPM), which reduces the need for pesti- cides by crop rotations, scouting, weather monitoring, use of resistant cultivars, timing of planting, and biological pest controls. Management systems to improve plant health and crops' abilities to resist pests and disease. Soil-conserving tillage. Animal production systems that emphasize preventative disease man- agement and reduce reliance on high-density confinement, costs asso- ciated with disease, and need for use of subtherapeutic levels of antibi- otics. 135

136 ALTERNATIVE AGRICULTURE ADVOCATES AND PRACTITIONERS OF ALTERNATIVE FARMING SYSTEMS Individuals who adhere to philosophies that advocate nonconventional farming practices. Some farmers never changed to the chemically intensive, specialized approach to crop and animal production that currently domi- nates U.S. agriculture. These farmers include followers of traditional organic farming movements, such as biodynamic agriculture and the systems ad- vocated by Albert Howard and Eve Balfour [Balfour, 1976; Howard, 1943~. These individuals also include farmers who farm organically because of religious beliefs, such as some Amish and Mennonite farmers of Pennsyl- vania and the Midwest. Others have practiced a generic form of organic farming not associated with any of the established organic movements tHarwood, 1983~. Farmers looking for new ways to reduce production costs. Throughout the United States, individual farmers have recognized that heavy purchases of off-farm inputs can put them in a less competitive economic position. These farmers have modified their farming practices, often in innovative ways, to reduce production costs. Examples include a wide variety of conservation tillage systems; the use of legume-fixed nitrogen through ro- tations; interplanting; the substitution of manures, sewage sludges, or other organic waste materials for purchased inorganic fertilizers; and the use of IPM systems and biological pest control. Farmers responding to consumer interest in chemical-free organic pro- duce. Many enterprising farmers producing agronomic and horticultural crops, milk, eggs, poultry, beef, and pork without synthetic chemical inputs have taken advantage of the fact that many consumers and businesses are willing to pay higher prices for these sorts of products. In response to market demand, several commercial supermarket chains have recently be- gun to market produce grown with no or very low levels of certain syn- thetic chemical pesticides at prices roughly comparable to those of conven- tionally grown produce. Farmers responding to concerns about the adverse impact of many con- ventional farming practices on the environment. Environmental groups and soil conservation organizations have raised public awareness of the envi- ronmental hazards of conventional agricultural practices. As a result of these hazards and personal concern for the environment, some farmers have adopted alternative farming practices that are helping to reduce the deteri- oration of our nation's soil and water resources. University research scientists. Critics have attacked the colleges and schools of agriculture in the land-grant universities and the U.S. Department of Agriculture (USDA} for not researching farming systems that protect the environment and reduce dependence on synthetic chemical inputs. But many individuals at these institutions have been investigating for years practices and systems that have alternative agricultural applications. Exam-

RESEARCH AND SCIENCE pies include integrated pest management [IPM], biological controls of pests, rotations, nitrogen fixation, timing of fertilizer applications, disease- and stress-resistant plant cultivars, conservation tillage, and use of green manure crops. These research efforts have fostered some important changes in U.S. agriculture. As greater effort is made toward implementing the results of this research, more progress can be expected in the future. Much of the scientific knowledge of alternative practices summarized below is the result of research at the land-grant universities and the USDA. Alternative agriculture organizations. Groups such as Practical Farmers of Iowa, the Land Stewardship Project, the Institute for Alternative Agriculture, the Regenerative Agriculture Association, the Center for Rural Affairs, the Land Institute, and many others have worked to provide farmers with information on alternatives. They have organized research and demonstra- tion projects, lobbied state legislatures and Congress for research and dem- onstration support, and produced numerous technical publications and reports with information designed to help and encourage farmers to adopt alternatives. 137 Genetic improvement of crops to resist pests and diseases and to use nutrients more effectively. Many alternative agricultural systems developed by farmers are highly productive (see the boxed article, "Advocates and Practitioners of Alterna- tive Farming Systems," and Part Two). They typically share much in com- mon, such as greater diversity of crops grown, use of legume rotations, integration of livestock and crop operations, and reduced synthetic chemi- cal use. Although many practices show great promise, the scientific bases for many of them are often incompletely understood. During the last four decades, agricultural research at the land-grant uni- versities and the USDA has been extensive and very productive. Most of the new knowledge has been generated through an intradisciplinary ap- proach to research. Scientists in individual disciplines have focused their expertise on one aspect of a particular disease, pest, or other agronomic facet of a particular crop. Solving on-farm problems, however, requires more than an intradisciplinary approach. Broadly trained individuals or interdis- ciplinary teams must implement the knowledge gained from those in indi- vidual disciplines with the objective of providing solutions to problems at the whole-farm level. This interdisciplinary problem-solving team approach is essential to understanding alternative farming practices. Agricultural research has not been organized to address this need except in a few areas, such as IPM, the use of organic residues as an alternative nutrient source, and the use of leguminous green manure crops and rota- tions for erosion control and as a nitrogen source. Even this research has not significantly contributed to the adoption of alternative agricultural sys- tems for two principal reasons. First, most research has focused on individ-

138 ALTERNATIVE AGRICULTURE ual farming practices in isolation and not on the development of agricultural systems. This is because of the high expense of farming systems research, the intradisciplinary nature of university research, and lack of resources. Second, most research results have been implemented under policies that encouraged ever-increasing per acre yields as the best way to increase farm profits and the world food supply. In contrast, alternative farming research must include the interaction and integration of all farm operations and must consider the more comprehen- sive goals of resource management, productivity, environmental quality, and profitability with minimal government support. Only a limited amount of research has taken this comprehensive approach. Nevertheless, the sci- entific literature about specific farm practices and the empirical evidence from individual operators illustrate the efficacy and potential of alternative farming methods and provide the foundation on which to build a program of alternative farming research. Important elements of the scientific knowledge base relevant to further development of alternative agricultural systems are briefly reviewed in the following sections. Knowledge of biological systems and the management of their interactions throughout agricultural ecosystems are emphasized. CROP ROTATION Crop rotation is the successive planting of different crops in the same field. A typical example would be corn followed by soybeans, followed by oats, followed by alfalfa. Rotations are the opposite of continuous cropping, which involves successively planting the same field with the same crop. Rotations may range between 2 and 5 years (sometimes more) in length and generally involve a farmer planting a part of his or her land to each crop in the rotation. Rotations provide many well-documented economic and envi- ronmental benefits to agricultural producers (Baker and Cook, 1982; Heady, 1948; Heady and Jensen, 1951; Heichel, 1987; Kilkenny, 1984; Power, 1987; Shrader and Voss, 1980; Voss and Shrader, 1984~. Some of these benefits are inherent to all rotations; others depend on the crops planted and length of the rotation; and others depend on the types of tillage, cultivation, fertilization, and pest control practices used in the rotation. When rotations involve hay crops, on-farm livestock or a local hay market are generally required to make the hay crop profitable. Much of the literature on crop rotations refers to the rotational effect (Heichel, 1987; Power, 1987~. This term is used to describe the fact that in most cases rotations will increase yields of a grain crop beyond yields achieved with continuous cropping under similar conditions. This rota- tional effect has been shown to exist whether rotations include nonlegumi- nous or leguminous crops. Corn following wheat, which is not a legume, produces greater yields than continuous corn when the same amount of fertilizer is applied (Power, 1987~. The increase in crop yields following a leguminous crop is usually greater than expected from the estimated quan-

RESEARCH AND SCIENCE 139 Between 40 and 45 percent of the ld.S. corn crop is grown in continuous monoculture. Corn grown continuously generally requires greater use of fertilizers and pesticides than corn grown in rotation. This corn field is 10 miles from Kearney, Nebraska, which can be seen on the horizon. Credit: U.S. Department of Agriculture. tity of nitrogen supplied (Cook, 1984; Goldstein and Young, 1987; Heichel, 1987; Pimente] et al., 1984; Voss and Shrader, 1984~. In fact, yields of grains following legumes are often 10 to 20 percent greater than continuous grain regardless of the amount of fertilizer applied. Many factors are thought to contribute to the rotational effect, including increased soil moisture, pest control, and the availability of nutrients. It is generally agreed, however, that the most important component of this effect is the insect and disease control benefits of rotations (Cook, 1984, 1986~. The increase in soil organic matter, particularly in socI-based rotations, may

140 ALTERNATIVE AGRICULTURE Contour strip cropping can reduce erosion and pest infestation. When a legume is included in a rotation, such as the corn- wheat-alfalfa rotation shown here, nitrogen fertilizer needs can be decreased. Credit: Grant Heilman. be the basis for the improved physical characteristics of soil observed in rotations. This may account for some yield increase. Certain deep-rooted leguminous and nonTeguminous crops in rotations may use soil nutrients from deep in the soil profile. In the process, these plants may bring the nutrients to the surface, making them available to a subsequent shallow- rooted crop if crop residue is not removed. Another benefit common to ah rotations is the control of weeds, insects, and diseases, particularly insects and diseases that attack the plant roots (Cook, 1986~. This pest control is achieved primarily through the seasonal change in food source (the crop), which usually prevents the establishment of destructive levels of pests. As root disease and insect damage are re- duced, the healthy root system is better able to absorb nutrients in the soil, which can reduce the rates of fertilizers needed (Cook, 1984~. Healthy root systems also take up nutrients more effectively, thus reducing the likelihood of nutrient leaching out of the root zone. Rotations with particular crops or crop combinations can provide addi- tional benefits. Legumes in rotations will fix nitrogen from the atmosphere into the soil. The amount of nitrogen fixed depends on the legume and the

RESEARCH AND SCIENCE 141 management system; however, without any additional nitrogen fertilizers, leguminous nitrogen can support high grain yields (Heichel, 1987; Voss and Shrader, 1984~. The length of the rotation and yield expectations of the farmers, however, influence the level and acceptability of these yields. Hay and forage crops and closely sown field grain crops, such as wheat, barley, and oats, can provide some soil erosion control benefits in rotations. In some eroding areas with steep terrains, the practice of strip cropping corn (a row crop) with wheat (a closely sown crop) or a hay crop, such as alfalfa, is a common use of rotations to slow erosion. It must be stressed, however, that tilIage practices greatly influence the erosion control benefits of crops planted in rotations (Elliott et al., 1987~. For example, a rotation of corn, soybeans, and wheat is excellent for disease control but not for erosion control unless no tilIage or reduced tilIage is used. An indirect but important benefit of all rotations is that they involve diversification. The benefits of diversification are described in more detail later in this chapter. In general, however, diversification provides an eco- nomic buffer against price fluctuations for crops and production inputs as well as the vagaries of pest infestations and the weather. Rotations may have their disadvantages, however, particularly in the con- text of current government subsidies and requirements for federal program participation (see Chapters 1 and 4~. Rotations that involve diversifying from cash grains to crops such as leguminous hays with less market value involve economic tradeoffs (see Chapter 4~. Adopting the use of rotations may also require purchasing new equipment. As with all sound manage- ment practices, rotations must be tailored to local soil, water, economic, and agronomic conditions. PLANT NUTRIENTS Soil, water, and air supply the chemical elements needed for plant growth. Photosynthesis captures energy from the sun and converts it into stored chemical energy by transforming carbon dioxide from the air into simple carbohydrates. This stored chemical energy becomes the fuel for all life on earth. Water is also needed to provide essential elements, transport nutri- ents and sugars within plants, serve as a medium for essential chemical reactions, and provide structural form and strength by exerting turgor pres- sure from inside plant cells. Nutrient elements essential to the chemical reactions that occur within the plant are taken up from the soil through the roots. If nutrient elements or water are not adequately available at the time they are needed, plant growth and development will be affected. Growth and yield will be reduced or the plant may die. Plants need three soil-derived nutrient elements in large amounts nitro- gen, phosphorus, and potassium. These elements are frequently not avail- able in adequate amounts from soil. Nitrogen is a constituent of all proteins and a part of chlorophyll, the pigment that reacts to light energy. Nitrogen is a component of nucleic acids and the coenzymes that facilitate cell reac-

142 ALTERNATIVE AGRICULTURE lions. Phosphorus, as a component of adenosine triphosphate (ATP), is critical to the development and use of chemical energy within the cell. Phosphorus is also a constituent of many proteins, coenzymes, metabolic substrates, and nucleic acids. Unlike nitrogen and phosphorus, potassium does not have a clear function as a constituent of chemical compounds within the plant. It is important in regulatory mechanisms affecting funda- mental plant processes, such as photosynthesis and carbohydrate translo- cation. In addition to these three nutrients, other soil-supplied nutrients are essential to plant growth and development: boron, calcium, chlorine, cobalt, copper, iron, magnesium, manganese, molybdenum, sulfur, and zinc. These elements are needed in small amounts that are often available · . In SOI ,. Soil Properties anti Plant Nutrients Soil Texture The mineral particles that make up the soil are classified on the basis of their size. Clay particles are the smallest, silt is intermediate, and sand particles are the largest. The relative proportions of clay, silt, and sand determine soil texture. Soil texture has a critical influence on water and nutrient retention and movement through the soil. The large pores among grains of sand in a sandy soil allow water to pass through with relative ease, whereas the small pores formed in clay soils slow the flow and retain water. Soil particles can exist separately or they can be bound together in larger aggregates. Organic colloids and clays play a critical role in binding soil particles into soil aggregates, which increase pore space and water and air movement. Cation Exchange The molecular surfaces of clays and organic colloids have a net negative charge that interacts with the polar charge of surrounding water molecules. This causes the colloids to bind with positively charged ions of elements (cations). Because cations have differing abilities to bind with soil colloids, one cation may displace another; this is referred to as cation exchange. Displacement depends on relative bond strength and relative concentration. The cation exchange capacity of a soil is an expression of the number of cation-binding sites available per unit weight of soil (Foth, 1978~. This ca- pacity has a significant effect on nutrient movement and availability and binding of pesticides in different soils. Because hydrogen ions are cations that compete with nutrient cations for exchange sites, soil acidity, which is a measure of hydrogen ion concentration, has a marked effect on which nutrient elements are bound and which are displaced.

RESEARCH AND SCIENCE Soil Quality 143 The quality of agricultural soils is derived from their effectiveness as a medium that provides essential nutrients and water. Mineral elements in soil required for plant growth exist in soluble and insoluble forms, which affects their availability for plant uptake. For example, under acidic or alka- line soil conditions, phosphorus fertilizer is rapidly converted into less soluble compounds that may be nearly unavailable for plant nutrition. Even available forms of phosphorus are bound to clay, and organic soil com- pounds and are relatively immobile in the soil profile except as a passenger during soil erosion. In contrast, potassium ant! the ammonium and nitrate forms of nitrogen are more soluble than phosphorus. Nitrate ions are not held by negatively charged soil ant! are readily leached. Because of their positive charges, potassium and ammonium nitrogen are held on the cation exchange and will not leach appreciably except through sandy soils. Organic matter in soils influences plant growth in a number of ways. The greatest benefits of organic matter in soil are its water-holding capacity; the manner in which it alters soil structure to improve soil filth; its high ex- change capacity for binding and releasing some mineral nutrients; its pres- ence as a food source for soil microbiota that recycle soil nutrients; and its mineralization to nitrogen, phosphorus, and sulfur. The cycling of mineral nutrients between living organisms and dead organic components of the soil system provides an important reservoir of the elements needed in plant growth. Nutrients are lost from soil through removal by crops, leaching, and soil erosion. Nitrate nitrogen can also be lost from the soil by conversion to nitrogen gases (denitrification) or by volatilization of ammonia. Gaseous loss of sulfur can also occur. Some farming practices help to mitigate the loss of nutrients and in some cases replace nutrients. For example, crop rotations that include nitrogen-fixing legumes benefit the soil in several ways. Legumes, in symbiotic relationships with microbes, fix atmospheric nitrogen into nitrogen compounds available for plant nutrition. When le- gumes are plowed under as green manures, they add nitrogen and organic matter to the soil. Cover crops help hold nitrogen in the root zone during the winter. The accumulated scientific knowledge on the role and fate of mineral elements, organic matter, ant! water in crop growth provides some indica- tion of why some alternative farming practices succeed and others fail. Characteristics of a particular crop or farming system that yield maximum efficiency are not well understood, however. The task remains to assemble the interdisciplinary expertise needed to analyze and understand the com- plex relationships that contribute to the relative efficiencies of different farming systems. Nutrient Management The adequate supply of nutrients particularly nitrogen, phosphorus, and potassium and maintenance of proper soil pH are essential to crop growth.

144 ALTERNATIVE AGRICULTURE Ideally, soil nutrients should be available in the proper amounts at the time the plant can use them; this avoids supplying an excess that cannot be used by plants and may become a potential source of environmental contamina- tion. The current conventional approach is to apply nutrients in the form of fertilizers at levels needed for maximum profitability. Profitability in the context of current government programs has generally been achieved, how- ever, through maximum yield per acre, often in continuous cropping or short rotations that require significant amounts of fertilizer. The nutrients in any excess fertilizer or high levels of decomposing organic matter are subject to leaching or runoff. An alternative, more environmentally benign approach to nutrient man- agement is to reduce the need for fertilizer through more efficient manage- ment of nutrient cycles and precise applications of fertilizer. Such practices include application of organic waste residues from animals and crops, crop rotations with legumes, improved crop health that may result in better use of nutrients, and banded or split applications of fertilizers. In mixed crop and livestock operations, for example, many of the nutrients contained in the grain and residue from crops grown on the farm can be returned to the soil if the manure and crop residues are incorporated into the soil. Crop rotations that include legumes can also play an essential role in nutrient cycling, particularly for replenishing the nitrogen supply. Plant residues and manure can release nitrogen more continuously throughout the growing season than can common commercial fertilizers. However, nitrogen from organic sources may be released when crops are not actively absorbing it. In contrast, inorganic fertilizer nitrogen is relatively quickly converted to the soluble and leachable nitrate form. Efforts to provide adequate nutrition to crops continue to be hindered by inadequate understanding and forecasting of factors that influence nutrient storage, cycling, accessibility, uptake, and use by crops during the growing seasons. Soil testing and plant tissue analysis can provide the farmer with information to assure adequate nutrition for all agronomic and horticultural crops. But variable soil and climatic conditions that influence nutrient up- take and Toss make it difficult to predict the most profitable and environ- mentally safe levels of nutrients. As a result, farmers often follow broad guidelines that lead to insufficient or excessive fertilization. For example, ~ . ~ ~ .~ . ~ . . ~ ~ . ~ . ~ _ 1 _ _ _1 studies of tertlllzer recommendations revealed tnat some commercial So testing services consistently recommended the use of far more fertilizer than was needed (Olson et al., 1981; Randall and Kelly, 19871. Additionally, some farmers apply more nitrogen than is recommended. Nitrogen Nitrogen is the soil-derived plant nutrient most frequently limiting grain production in the United States. This is ironic because the atmosphere is 79 percent nitrogen by volume. Atmospheric nitrogen is in the form of inert nitrogen gas, however, which higher-order plants cannot use. Converting

RESEARCH AND SCIENCE 145 atmospheric nitrogen to ammonia and other forms that plants can use requires a high energy input. This is true for biological nitrogen fixation as wed as industrial synthesis. The biological process is fueled by photosyn- thates; the synthetic industrial process is fueled by natural gas, petroleum, coal, or hydroelectric power. The predominant process for producing syn- thetic nitrogen fertilizers involves combining hydrogen from methane gas and atmospheric nitrogen at high temperature and pressure to form am- monia. Ammonia can then be converted to nitric acid or combined with other elements to form a number of nitrogen fertilizers, including ammo- nium nitrate, ammonium sulfate, ammonium phosphate, and urea. A sig- nificant amount of energy is required to synthesize ammonia. Conse- quently, energy and methane gas costs can affect the availability and cost of synthetic nitrogen fertilizers. Neutral ammonia molecules gain a hydrogen ion when added to moist soil and become stable ammonium ions with a net positive charge. Most of the ammonium ions in soil undergo biological Vitrification, in which oxida- tion results in the formation of a nitrate ion as well as hydrogen ions that acidify the soil. Because ammonium ions have a positive charge, they are adsorbed and held on the soil cation exchange. Nitrate ions, because of their negative charge, are not adsorbed on the soil exchange complex. While readily available for plant use, the nitrate freely moves through soil in water unless it is absorbed by the plant. Although these basic processes are understood, there is a need to know much more about nutrient cycling and the behavior of nitrogen under various environmental conditions. To accomplish this, progress is needed in estimating the rates of biological reactions that control nitrogen transfor- mation in soil. .. . . , . . . . - _ - ~ . ~ . Legumes as a Source of Nitrogen Nitrogen can be provided by growing legumes in rotation with grains. For alternative farming, legumes are an effective and often profitable way to supply nitrogen. Leguminous nitrogen is consistently released through- out the growing season when temperatures are high enough to permit microbial decomposition. Combiner! with the rotational effect, leguminous nitrogen can support high yields of corn and wheat (Holben, 1956; Koerner and Power, 1987; Voss anct Shrader, 1984~. The overall contribution of leg- umes, however, depends on the management system and climate. For ex- ample, forage legumes are most effective in humid and subhumid regions (Meisenbach, 1983; U.S. Department of Agriculture, 1980~. In regions with less than 20 inches of rain a year, deep-rooted, nonirrigated legumes may decrease subsoil moisture and lead to reduced corn yields the following year (Meisenbach, 1983~. The profitability of leguminous hay crops is strongly influenced by the presence of on-farm livestock or a local hay market. Legumes supply substantial nitrogen to the soil, but the amount of nitro- gen fixed is highly variable. Different species and cultivars fix different

146 ... . i, : ~.~.~.~.~ ~~ ~~ ~~ ~~ :: A ~~ go. ~ ~~ i: ~ ~ . These fields, currently producing corn and soybeans, have received no nitrogen, phosphorus, or potassium fertilizer for 18 years. A corn, soybean, small grain, and red ALTERNATIVE AGRICULTURE i ~~ ~ ~ ~~ . ~~ ~~ i. ~ . i. ,... :: ::::::: :::: clover crop rotation and the application of manure supply nutrients. Credit: Rex Spray, the Spray Brothers Farm. amounts of atmospheric nitrogen. A number of physical and managerial factors, including soil acidity, temperature, drainage, the timing of harvest, and whether foliage is turned under as green manure, influence the amount of nitrogen fixed as well as the amount of fixed nitrogen subsequently incorporated into the soil. Nitrogen fixation by soybeans, for example, was found to vary from O to 277 pounds per acre depending on management practices, soil characteristics, and water availability. The amount of nitrate in the soil also affects nitrogen fixation. Soil rich in nitrate inhibits nitrogen fixation. In the Midwest, soybeans are managed for grain production and are commonly grown after corn in soils with residual nitrate. Where there is residual nitrate in the soil, soybean production can result in a net export of nitrogen. For example, nitrogen budget analyses on midwestern soybeans show that 40 percent of nitrogen in the crop is derived from nitrogen fixation and 60 percent is from residual nitrogen in the soil. Typically, the nitrogen removed in the soybeans at harvest exceeds the amount of nitrogen fixed, leading to a net nitrogen loss of about 70 pounds per acre. Thus, under these circumstances, soybeans may be depleting the soil of nitrogen and increasing nitrogen fertilizer needs for the subsequent crop, rather than enriching soil nitrogen as had been previously thought. In contrast, when soybeans can be managed to fix 90 percent of their nitrogen needs, the result is a 20 pound per acre nitrogen gain (Heichel, - 19871.

RESEARCH AND SCIENCE 147 Management systems also influence nitrogen made available by legumi- nous hay crops. Leguminous hays are commonly grown for their value as hay and for their ability to fix nitrogen from the atmosphere into the soil and provide nitrogen in the form of crop residue. The timing of harvest, however, dramatically affects the amount of nitrogen available for subse- quent crops. After they are cut, leguminous hays first use the reserve of nitrogen in the crown, roots, and soil to support their own growth. As the growing plant increases leaf area and photosynthesis, the energy is again nvanu~ fur n~rrogen 1lxallon. 1ne mtrogen-rlcn leaves and stems of the plant are then removed when the crop is harvested (Heichel, 19871. Heichel (1987) reported results of studies with alfalfa showing that one harvest followed by molaboard plowing of lush, late August regrowth resulted in a net nitrogen gain of 48 pounds per acre. In contrast, harvest of the August regrowth followed by plowing under of October regrowth resulted in an insignificant net nitrogen loss of 4 pounds per acre. The slight loss occurred because most of the nitrogen fixed by the lush August regrowth was re- moveu during harvest. Harvest of the October regrowth followed by plow- ing under only the roots and crowns resulted in a net nitrogen loss of 38 pounds per acre. Management also affects the amount of legume-fixea nitrogen that drains to grounuwater. Results of an unpublished Minnesota experiment (G. Ran- uall) showed that over 4 years, continuous soybean (45 bushels/acre) con- tributed two-thirds as much nitrate to drainage water as heavily fertilized corn (165 bushels/acre). Unpublished experiments in Michigan (B. Ellis) found more than twice the concentration of nitrates below crop root systems when alfalfa was plowed down than under irrigated or nonirrigateu corn. Few measurements have been made of the contribution of legumes to grounuwater contamination or, if necessary, how to minimize it. Tillage practices also influence the amount and availability of nitrogen supplied by legumes (Dabney et al., 1987; Heichel, 1987~. No-tillage systems may reduce the nitrogen available to the subsequent crop compared with a conventional tillage system such as moldboard plowing, which more thor- oughly incorporates plant matter into the soil (Varco et al., 1987~. Koerner and Power (1987) reported increased corn yield following double-disking of vetch. Corn yields were lower when vetch was left standing throughout the corn growing system or when the vetch was killed with herbicides. In a greenhouse experiment, the relative nitrogen fixation varied widely depending on species of legume, duration of growth, and temperature (Zachariassen ant! Power, 1987) (Table 3-1~. Some species performed best under low temperatures; others fixed more nitrogen at higher temperatures. For example, fava beans were found to fix 54 percent more nitrogen than hairy vetch early in the growing season (42 days) at a temperature of 10°C. But at 30°C the nitrogen fixation of the fava beans declined by 86 percent. Using legumes in a rotation, or as winter cover crops in the South, can reduce and, in some cases, eliminate the need for nitrogen fertilizers (Dab- ney et al., 1987; Goldstein and Young, 1987; Neely et al., 1987~. Cultivars ~ , 1 1 1 ~ · . ~ · . - An. .

148 ALTERNATIVE AGRICULTURE TABLE 3-t Nitrogen Fixation of Legume Species as Affected by Soil Temperature and Time Under Greenhouse Conditions Nitrogen Fixation (percent) eta: Species and Temperature (°C) 42 Days 63 Days 84 Days 105 Days Hairy vetch 10 100 108 147 223 20 46 88 67 122 30 14 8 12 30 S we e t clover 10 21 46 67 66 20 52 86 128 122 30 42 46 50 104 Fava bean 10 154 131 135 122 20 136 124 122 134 30 22 12 11 4 Lespedeza 10 0 4 3 0 20 9 29 93 145 30 16 22 60 176 Field pea 10 36 48 29 51 20 38 21 12 8 30 12 10 6 0 White clover 10 20 54 88 162 20 39 78 108 153 30 2 0 40 38 Nodulated soybeans 10 31 33 37 34 20 116 215 315 415 30 94 163 260 291 Crimson clover 10 43 43 72 107 20 54 79 86 56 30 9 2 14 5 ~ aValues are expressed as a percentage of the nitrogen fixation found in hairy vetch at 10°C for 42 days, which was arbitrarily selected as the basis for comparisons. To translate these percentages to the originally reported data (in milligrams/pot) multiply by 1.1339. SOURCE: Zachariassen, J. A., and J. F. Powers. 1987. Soil temperature and the growth, nitrogen uptake, dinitrogen fixation, and water use by legumes. Pp. 24-26 in The Role of Legumes in Conservation Tillage, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. are being developed that fix more nitrogen than their predecessors. Bacteria in the Rhizobium and Bradyrhizobium genera that fix atmospheric nitrogen in the roots of legumes are being studied extensively. Current work focuses on the mechanism of nitrogen fixation itself, the infection process that leads to a successful symbiosis, the genetic determinants and biochemical processes -that make plants receptive, and the bacteria capable of sustaining the asso-

RESEARCH AND SCIENCE TABLE 3-2 Reported Quantities of Dinitrogen Fixed by Various Legume S. pecles 149 N Fixed N Fixed Species (pounds/acre/year) Species (pounds/acre/year) Alfalfa 70-198 Ha~ryvetch 99 Alfalfa-orchardgrass 13-121 Lading clover 146-167 B~rdsfoot trefoil 44-100 Lentil 149-168 Chickpea 21-75 Red clover 61-101 Clarke clover 19 Soybean 20-276 Common bean 1.8-192 Sub clover 52-163 Crimson clover 57 Sweet clover 4 Fava bean 158-223 White clover 114 Field peas 155-174 SOURCE: Adapted from Heichel, G. H. 1987. Legume nitrogen: Symbiotic fixation and recovery by subsequent crops. Pp. 63-80 in Energy in Plant Nutrition and Pest Control, Z. R. Helsel, ed. Amsterdam, The Netherlands: Elsevier Science Publishers B. V. elation between plants and nitrogen. Improvements have already resulted from selecting for crop varieties and naturally occurring Rhizobium strains that fix large amounts of nitrogen. In a 2-year rotation with corn in Minne- sota, a new annual cultivar of alfalfa, Nitro, developed by the U.S. Depart- ment of Agriculture's (USDA) Agricultural Research Service and the Uni- versity of Minnesota Agricultural Experiment Station, fixed 94 pounds of nitrogen per acre between the last harvest in early September and the death of the plant at the first frost in October (Barnes et al., 1986~. This was 59 percent more nitrogen than was fixed after the September harvest of the commonly grown perennial cultivars used as controls in the study. About 11 percent of this increase was from the improved nitrogen-fixing capability of the legume. The remaining 48 percent was from this variety's greater productivity at the end of the growing season. Nitro alfalfa was bred as an annual crop for use in a 2-year rotation with corn. It is grown for 1 year and continues to grow and fix nitrogen until it is killed by the first frost, usually in mid-October. Commonly used alfalfa varieties, in contrast, are usually grown for 2 or more years, and (in Min- nesota) begin to go dormant and stop fixing nitrogen in early September of each year. Research conducted in northern California showed that vetch can be an economical source of nitrogen for rice. The study examined the effect of cultivar selection and time of planting. Aerial broadcast of purple vetch or Lana woolypod vetch seeder! 2 days before or after field drainage produced an excellent stand. Vetch fixed between 30 and 60 pounds of nitrogen per acre in rice stubble up to 100 pounds under ideal conditions (Williams and Dawson, 1980~. The nitrogen-fixing capabilities of various legume species are listed in Table 3-2. There is a general knowledge of the factors that affect nitrogen fixation by legumes, but little is understood about the interaction of these variables

150 ALTERNATIVE AGRICULTURE Incorporating manure into the soil soon after Between the time of its application and the application can keep nutrient losses to a emergence of the first crop, this manure tends minimum. The manure truck pictured is to be vulnerable to erosion and runoff from followed by a moldboard plow and a leveling rainfall. Credit: Rodale Press. harrow to incorporate manure into the soil. and their effect on total available nitrogen. This information is essential for determining nitrogen fertility credits of legumes and assessing the nitrate that legumes contribute to groundwater. More information is needed on nitrogen cycling in agricultural systems; the yield-boosting effects of rota- tions; the effects of tiliage practices; and how fixed nitrogen is affected by other sources of nitrogen, soil organic matter, compost, and crop residues. Manure as a Source of Nutrients Animal wastes can make a substantial contribution to nitrogen, phospho- rus, potassium, and other nutrient needs. Total supply, however, depends on the nature and size of animal enterprises and the methods used in storing and spreading the manure (Young et al., 1985~. The potential nutri- ent contribution from manure is very high in some regions (Van Dyne and Gilbertson, 1978~. Most animal manure is returned to the land. Its nutrients, however, are often inefficiently used as a result of poor storage and application practices (Smith, 1988; U.S. Department of Agriculture, 1978~. Runoff, volatilization, and leaching losses of plant nutrients in stored animal manure may be so high that only a fraction of the original nutrients remain to be applied to cropland. Poor manure hauling and spreading practices add to these losses. However, practices that increase the efficient use of nutrients may be eco-

RESEARCH AND SCIENCE TABLE 3-3 Nitrogen Losses in Manure Affected by Application Method 151 Method of Application Type of Manure Nitrogen Loss (percent) Broadcast without incorporation Solid 15-30 Liquid 10-25 Broadcast with incorporation Solid 1-5 Liquid 1-5 Injection (knifing) Liquid 0-2 NOTE: These numbers do not include losses from storage. SOURCE: Sutton, A. L., D. W. Nelson, and D. D. Jones. 1985. Utilization of Animal Manure as Fertilizer. Extension Bulletin AG-FO-2613. St. Paul: University of Minnesota. nomically costly. The cost of proper application, for example, may exceed the value of the increase in available nutrients comparer! with inefficient application methods. The effect of manure application methods on nitrogen loss, not including loss during storage, is shown in Table 3-3. Table 3-4 indicates the range of nutrient loss possible through different storage and handling systems. In many cases, manure is not applied at a time in the growing or fallow season that results in optimal use of the manure as fertilizer. For example, winter application of manure can result in significant nutrient loss. Little use is being made of animal manure in aerobic com- posting, even though comporting may offer advantages of increasing nutri- ent concentration and reducing the volume of material to be applied (Gran- atstein, 1988~. Anaerobic fermentation of manure to produce the biogas methane is not economical compared to the cost for other fuels. In addition, TABLE 3-4 Nitrogen Losses in Manure Affected by Handling and Storage Method N loss (percent) Solid systems Daily scrape and haul Manure pack Open lot Deep pit (poultry) Liquid systems Anaerobic deep pit Above-ground storage Earthen storage pit Lagoon 15-35 20-40 40 - 60 5-35 5-30 15-30 20 -40 70 - 80 NOTE: These numbers do not include losses due to application. SOURCE: Sutton, A. L., D. W. Nelson, and D. D. Jones. 1985. Utilization of Animal Manure as Fertilizer. Extension Bulletin AG-FO-2613. St. Paul: University of Minnesota.

152 ALTERNATIVE AGRICULTURE fermentation creates residue that must be disposed of or otherwise used (Smith, 1988~. Although systems are available to handle wastes in slurry form, other systems are essentially designed to dispose of the animal waste as an undesirable by-product. If animal waste is to be used more efficiently, systems and related equipment for profitably storing, handling, and spread- ing it are needed. Research is needed to devise low-cost systems of produc- ing biogas from animal manures, make efficient application systems more economical, and educate farmers about the beneficial aspects of manure. About 110 million tons (dry weight) of manure were voided by livestock and poultry in 1974. The total estimated amounts of nitrogen, phosphorus, and potassium in this manure were 4.1, 1.0, and 2.4 million tons, respec- tively. An estimated 40 percent of the total, or 1.3, 0.5, and 1.2 million tons of the nitrogen, phosphorus, and potassium voided, was estimated to be available and economically recoverable for use elsewhere. Cattle provided about 62 percent, or 800,000 tons, of the economically recoverable nitrogen from livestock manure in 1974 (Van Dyne and Gilbertson, 19781. The total nutrients economically recoverable from manure contained the equivalent of about 15 percent of the total nitrogen, 9.9 percent of the total phospho- rus, and 24.2 percent of the total potassium fertilizer applied on farms in the United States during 1974 (U.S. Department of Agriculture, 1987~. Sim- ilar data are not available for trace nutrients and organic matter supplied by , ~ manure. The amount of nutrients available from manure largely depends on how it is stored and handed. Nitrogen is most readily lost; in fact, some loss is inevitable no matter how the manure is stored or applied. Phosphorus and potassium losses are less likely except through direct runoff and leaching from open storage lots or as a result of settling in open lagoons. Table 3-5 lists the approximate nutrient content of several types of manures as a result of different storage and handling techniques. Good management in manure handling is essential to successful use of manure as a nutrient source. Farms in Lancaster County, Pennsylvania, have a high ratio of livestock per acre of cropland. Manure applications average over 40 tons per acre per year, supplying far more than the nutrient needs of the crops grown in the region. In addition, many farmers apply about 100 pounds of commercial nitrogen per acre, bringing the total nitrogen applied to corn to 350 pounds per acre (Young et al., 1985~. Many of the county's wells have nitrate levels two to three times the U.S. Environmental Protection Agency's (EPA) stan- dards for safe drinking water. Phosphorus The amount of phosphorus in solution in soil water determines the avail- ability of phosphorus for plants. There is often a substantial amount of phosphorus in agricultural soils, but it is in a form that releases phosphorus to the surrounding soil water in a slow equilibrium reaction. In soil, the soluble phosphorus in fertilizer quickly reacts with aluminum and iron

RESEARCH AND SCIENCE TABLE 3-5 Approximate Nutrient Content of Several Manures Nutrient Content (pounds/ton) 153 Type of Storage/ Ammonium Phosphate Potash Livestock Handlinga Total N (NH4+) (P2Os) Swine Solid NB 10 6 9 8 Solid B 8 5 7 7 Liquid P 36 26 27 22 Liquid L 4 3 2 4 Beef cattle Solid NB 21 7 14 23 Solid B 21 8 18 26 Liquid P 40 24 27 34 Liquid L 4 2 9 5 Dairy cattle Solid NB 9 4 4 10 Solid B 9 5 4 10 Liquid P 24 12 18 29 Liquid L 4 2.5 4 5 Turkeys Solid NB 27 17 20 17 Solid B 20 13 16 13 Horses Solid B 14 4 4 14 aNB = No bedding; B = bedding; P = pit; L = lagoon. SOURCE: Sutton, A. L., D. W. Nelson, and D. D. Jones. 1985. Utilization of Animal Manure as Fertilizer. Extension Bulletin AG-FO-2613. St. Paul: University of Minnesota. Oxide and with calcium to form compounds that are relatively insoluble and slowly available to plants. Moreover, phosphate quickly binds to clay col- Toids (Foth, 1978~. Consequently, phosphate does not readily leach but neither does it remain in a form readily available to plants in either acid or alkaline soils. Some organic farmers apply rock phosphate to their fields instead of acidulatec! phosphate. Rock phosphate found in the Uniter! States varies in solubility but generally has very low immediate availability to plants even when finely ground (Council for Agricultural Science and Technology, 1980~. Chemical treatment, or acidulation, with sulfuric or phosphoric acids significantly enhances its availability. One 24-year study showed rock phos- phate to be only one-sixth as effective as acidulated phosphate in a corn- oats-alfalfa rotation in slightly acid soils. Rock phosphate is even less effec- tive on a less acid soil (Webb, 1982, 1984~. Farmers have built up the phosphorus content of U.S. soils over the past three decades. According to the USDA (1980), growers could eliminate the use of acidulated phosphates for several years in some regions without yield loss on well-managed soils. How long the resulting mining of phosphorus from such soils could continue is not known and will vary. Application of manures and organic wastes can replenish some phosphorus but removal by crops is inevitable. Because phosphorus does not leach, replacement applications to meet crop needs are advisable. Farms cannot be self-suffi- cient in phosphorus (Eggert and Kahrmann, 19841. Phosphorus bound to sediment in runoff water is often implicated in

154 ALTERNATIVE AGRICULTURE eutrophication and decline in surface water quality. Although most farmers could reduce applications of phosphorus with little effect on crop yield, reductions are best made based on soil tests. Properly managed phosphorus applications and reduced soil erosion will be accompanied by improved water quality in watersheds with highly erodible cropland. Potassium Weathering of minerals has supplied many sods in subhumid or arid regions WIth adequate levels of available potassium. Potassium fertilizer applications, however, are especially required in humid regions and highly organic soils. Potassium has a net positive charge, so ~ Is nounu to tne soil's cation exchange complex. Potassium is available in soil water solution in an equilibrium reaction with exchangeable and fixed potassium in the soil. It is more soluble and readily available than phosphorus but has little mobility and leaches only in sandy soils. If there is excess potassium in the soil, plants will absorb more than is needed for normal physiological functioning. Forage crops such as alfalfa and clovers absorb large amounts of potassium; thus, harvest of hay or fodder (silage) leads to rapid depletion of readily available potassium in soils. Grain crops deplete potassium in the soil less rapidly, provided only the grain is removed. Potentially high levels of potassium in leguminous forages emphasize the need for conservation of manure from animals con- suming these forages. Most of the potassium ingested by animals passes through the intestinal and urinary tracts. If all of the manure is conserved and uniformly redistributed to the land, little additional potassium will be needed for soils that begin with adequate levels. Leaching of exposed ma- nure by rain can cause large losses of potassium, and this must be avoided to make recycling fully effective. , . .. . . . . .. Amending Soil Reaction One of the basic principles of soil management is to maintain a soil reaction appropriate to the crops produced. Soil reaction is measured by hydrogen ion activity and reported as pH. A neutral pH is 7.0. Most agro- nomic crops perform best between pH 6.0 and pH 7.5. The leguminous crops tend to perform better toward the upper end of the range while grain crops are usually not as responsive. Figure 3-1 illustrates the relative availability of 12 essential plant nutrients as a function of the pH of the soil (University of Kentucky, 1978~. The three primary fertilizer nutrients nitrogen, potassium, and phosphorus- have the greatest availability within the pH 6.0 to pH 7.5 range. Hence, it is understandable why crops might grow well over this range of reaction. The availability of magnesium, sulfur, copper, and boron are also well repre- sented within this range, although their availability tends to taper off as pH 7.5 is approached.

RESEARCH AND SCIENCE pH 4.5 5.0 5.5 6.0 6.5 7.O 7.5 8 0 . 1,~ MUG,', 2 · . · ' O2 · 2-2 D' ' 2 - An'. ~ 2 - ' Magnesium ~ .. o ~ ~~9~_e ~ ~ 1 ._ ~ =~_ I ' or 1i i j jlj jl j~l~l4~ 155 FIGURE 3-1 The relative availability of 12 essential plant nutrients in well-drained mineral soils in temperate regions in relation to soil pH. (Aluminum is not an essential nutrient for plants, but it is shown because it may be toxic below a soil pH of 5.2.) A pH range between 6.0 and 7.0 is considered ideal for most plants. The thirteenth essential plant nutrient from the soil, chlorine, is not shown because its availability is not pH-dependent. The saw-toothed pattern in the figure represents precipitation. SOURCE: University of Kentucky. 1978. Liming Acid Soils. Leaflet AGR-19. Lexington, Ky.

156 ALTERNATIVE AGRICULTURE The availability (solubility) of aluminum, iron, and manganese increases rapidly below about pH 5.3. The increase in the solubility of these three elements, especially aluminum, creates a toxic environment for plant roots. Growth of most plants is severely limited at low pH values. Poor plant performance, however, is not necessarily linked to low pH. Deficiencies in calcium and magnesium or toxic levels of aluminum or manganese may also affect plant growth. At low values of pH, aluminum and iron cause precip- itation of phosphate (Figure 3-1~. This can cause phosphorus deficiencies. At the upper end of the pH scale in the presence of large amounts of calcium, the calcium precipitates phosphates, but usually not to as great an extent as aluminum and iron do at the lower end. The application of agricultural limestone either calcitic limestone con- taining mostly calcium carbonate or dolomitic limestone containing a mix- ture of calcium and magnesium carbonates- can amend soils with low pH values and increase the pH to the favorable range. The procedure for deter- miriing the amount of neutralization required is a simple one involving the measurement of the pH of a soil sample suspended in a buffered solution. This pH value, compared to the pH of a suspension of the soil in water, provides a basis for measuring the total amount of acid*y that needs to be neutralized and thus the amount of agricultural limestone needed. Excess calcium carbonate usually dominates soil systems with pH values up to S.0 or S.2. This is a consequence of a soil development process that occurs mostly in drier climates. Additionally, in some crops, there may be a deficiency of iron or other micro nutrients that need to be corrected. Soils with pH values above S.3 are likely to contain sodium carbonate or potas- sium carbonate. These alkaline soils also have poor physical characteristics because of the presence of sodium. They are generally found in arid or semiarid climates. The application of gypsum (calcium sulfate) and leaching with adequate quantities of high-quality irrigation water can amend these soils. Calcium replaces sodium on the exchange complex of the soils, dis- placing the sodium that is leached out of the root zone. This results in improved soil properties. TilIage Farmers have adopted a wide range of tillage practices in the past three decades. Most of these conservation tillage practices were developed by researchers to slow soil erosion and conserve water through decreased soil disturbance. Nearly 100 million acres are farmed using some form of con- servation tillage. Most of this is in the form of mulch tillage or reducer! tillage; no tillage, strip tillage, and ridge tillage are practiced on about 16 million acres (U.S. Department of Agriculture, 1987~. While these practices may advance some of the goals of alternative farming, such as increasing organic matter in soil and reducing soil erosion, some conservation tillage practices may increase the need for pesticides, particularly herbicides (Geb- hardt et al., 19851. Conservation tiDage generally leaves a layer of crop residue on top of the

RESEARCH AND SCIENCE 157 ~~ ~~ ~~.:~ .~ :- .,,, ~~ ~~ -I ,. ,~ ~~:~: A ridge-tillage planter places seeds in a narrow band of soil scraped off the top of the ridges. This method preserves the residue cover between the rows, reducing soil and :~.2~'~ ,- ,~ ~ ,~''.; . ~ I'd i. ':'' ~ I, ' '."'..'' ' a: I. ~ water runoff. Planted last fall as a cover crop, hairy vetch helps to meet the nitrogen needs of the corn crop now being planted. Credit: Dick Thompson, the Thompson Farm. Ridge tillage is an effective alternative tillage system that can reduce erosion and costs and help control weeds without herbicides. Here, seeds are planted in a field with the residue of last year's corn crop, which protects the soil surface from erosion. Credit: Randall Reeder, Ohio State University.

158 aft. i: :~: :::::: ::~ ~ ~ ~ : ::: : I: I: : If: I: :~ : ~~ : :: ~ :: ~ ~ :: : I:: i: ~ ::~: ::: :::: ::~: :~: :: : : ~ ~ ~ :: ~::~::~:~:~ ~ :: :~ ~~ ~~ I:::: ~~ ; ~~ ~~ ~~ ~ ~~ ' :~ -: ~ '.'' ~ ~ ~ :' ~~ .'.-. .~' ;-' Aim' ;-''.;' '.' ' ' ~-'~'';~'~'~4 ALTERNATIVE AGRICULTURE ~~ ~ ~~ ~ ~~ -.-- ~~ ~~ - ~~ ~~ ~ ~~..~ ~~ ~ ~~ ~ ~ ~ . ~ ~ , ~ ~ ~ . I. ~ ~ ~ ~ - ~ ~ . . ~ ::: ::::: ::: Chisel plowing, a form of conservation tillage, mixes crop stubble into the soil, leaving the ground partially protected from wind and rain. Chisel plowing can reduce erosion by 30 to 50 percent from levels expected with moldboard plowing. Credit: John Deere Company. soil (Hendrix et al., 1986; House et al., 1984~. This residue may provide a favorable habitat to some pests. Some plant diseases overwinter in crop residues left on the soil, above and below ground insects survive, and perennial weeds may establish a foothold. The effects of these pest popula- tions are more severe if the same crop is planted the next year but may be inconsequential or minimized in a rotation. Conservation tilIage changes soil properties in ways that affect plant growth (Phillips et al., 1980~. Researchers are studying trophic interactions in croplands with no tilIage and conventional tiliage. Plant nutrients in no- tiDage soils are more stratified than those in soils under reduced or conven- tional tiDage. Nutrients also tend to concentrate in the upper portion of the soil profile. Soil under conservation tiDage practices, which leaves a surface mulch, is often 3 to 4°C cooler in late spring than soil under conventional tilIage. In the spring, the cooler temperatures can slow early season plant growth at higher latitudes. With no tillage, the soil is also more likely to be compacted, which can also reduce plant growth. In summer, however, the mulched soil is cooler and the soil surface under the residue is moister. As a result, many conservation tilIage systems have been very successful. The concentration of soil microbes and earthworms is greater in conservation tiDage systems. Inadequate research on the range of conservation tiliage practices, however, makes it impossible to draw general conclusions for most crops, soils, or climates. A number of the committee's case studies demonstrate the effectiveness of various tilIage practices in

RESEARCH AND SCIENCE .... . ~ . ~ ~ .~ ~ ~ ,, ~ I. .... .. ~~. i. .: jail ~~ ~~ ~ ~~ ~~ i: 159 ::::::: ~~ ~~ ~~.~ ~~ No tillage is another effective way to reduce erosion. Soybeans are planted into barley stubble as barley is harvested. Farmers in the South and mid-Atlantic are often able to . . ~ . ~~ ~j .~ ... .. ~~ ~~ .~ ~~ . hi. ~.~ ~~ ~~ ~ ~~ ~ ~~ ~ ~~ .. ~ ~ i.. ~ ~ ~ . ~ _ ~ . ~ ~~ ~ . ~ . . ~ ~ ~ ~ ~ ~ . . i. ~ ~ aid,. i, ~ ~~ ~~ ~ ~.~ . ~ ~ ~ ~ ~~.~ ~ ~~ ~ ..~: ~ ~~,~ ~~ ~~ .~: ~~ i., ~ .~ ~ ~~ ~ I \~ .~ ~.~ ~~ ~~ ~~,~.,~.~,~ ~~ ~~.~.~.~ ~~.~ ~~ ~~ ~.~ ~ ~ ~~ ~~,~.~.~ ~ ~ , ~ ~ ~ ~ ~ ~ I. ~ ~ ~ . . ~ ~ . ~ ~ ~ ,,'~"''~',,,.,,,t,:, :: ~ ~'~ ~ ~,~ ~~ ~~ ~~ ~ ~~ ~~, i' ~ ~ ~ ~.~'~. ~ ~ JO ,:' ~:~:~,~ ~~ :~: ~ ::: ~~ ',: I'd ',''",,,,, i' We'd ~~'~'~,,~,~'~.~ ~',~,~.~'~.~.~',,~'~:~. ,..' ~~'~,~'~',~ ~~,:~ ::: .,, t: ~ ,~. i:'., .~ : ~~:':'~ ~..~ ~ j Aid: ::~ :.:. ~:'~:'~ ..,,.: ,~: ~~ ~~:~ ~ ~~ :~ i: ~~ ~~ ~ I: :::: :t : : : : :: : : ::: :: . ~ : : :: : .: . :, ,( ~~ ::~: ~~:~:~: :: ~~ ~ i: ,~ ~ i:: : :: : :~:: ::: :::: i, ~~ ::: _:::::::::::::::::::::-~:':~ :: ~:~ ~ ::~::: ~:::~2:., ::: ~ ~~ ~~:~',~'~:~::.~, ~:'~ ~~ ~ Is i, Hi', ~.~:~ ~~:~ ~'~.~ ~ ~~ ~~ Harvest two crops in one season. Credit: Sol Conservation Service, U.S. Department of Agriculture. Corn grows on top of the ridges in a soybean Department of Agriculture. field. Credit: Soil Conservation Service, U.S.

160 ALTERNATIVE AGRICULTURE One conventional tillage method is moldboard plowing. The steel blades of the plow turn over furrows of soil. This method helps to control some diseases and insect pests by disrupting their environment and burying weed seeds. But it also leaves the soil surface fully exposed to rain and wind and increases soil erosion. Credit: Soil Conservation Service, U.S. Department of Agriculture. controlling weeds and as a component of viable alternative systems (see the Spray, BreDahI, Kutztown, and Thompson case studies). Conventional moldboard plowing, in contrast to reduced tilIage, contrib- utes to pest control by destroying some perennial weeds, disrupting the life cycle of some insect pests, and burying disease inoculum. But conventional tilIage may also disrupt the life cycle of beneficial organisms, contribute to soil erosion, and require more energy and larger tractors. Chisel plowing, the most widely used form of reduced tillage, requires large tractors but uses less energy than moldboard plowing. Conventional tiDage creates more bacterial activity and has a "boom-and-bust" effect on nutrient cycling processes (Holland and Coleman, 1937~. No tiDage or other conservation tiDage provides a slower but more even rate of nutrient release. Legumes are an effective source of nitrogen in some conservation tillage systems, although different tillage methods can influence the amount of nitrogen available to subsequent crops (Heichel, 1987~. Conservation tiliage can reduce water runoff from fields. Data reported by Hall et al. (1984) showed that compared with conventional tillage, no- tillage systems reduced runoff by 36.3 to 98.7 percent, soil losses by 96.7 to 100 percent, and the herbicide cyanazine losses by 84.9 to 99.4 percent. Glenn and Angle (1987) reported 27 percent less total runoff of water and the herbicides atrazine and simazine with no-tiDage versus conventional tilIage systems. Some forms of conservation tiDage, however, may increase the concentra- t~on of broadcast nitrogen and phosphorus fertilizers and pesticides in the

RESEARCH AND SCIENCE 161 An offset disk is a conventional tillage tool used for further soil preparation {top}. Final field preparation is accomplished with a field cultivator, which in this case is also incorporating a preplan" herbicide into the soil {bottom]. At the left, a planter follows. These conventional tillage operations work the soil into fine particles and leave almost no crop residue on the soil surface. This field could experience high soil losses if hard spring rains occur before the growing crop begins to protect the soil surface. Credits: Soil Conservation Service, U.S. Department of Agriculture {top); Grant Heilman {bottom].

162 ALTERNATIVE AGRICULTURE runoff. However, the total amount lost is generally reduced because runoff is usually less (Andraski et al., 1985; Sauer et al., 1987; Springman et al., 1986~. With conservation tilIage, fertilizer loss via runoff can be further reduced by drilling the fertilizer in the row. The effects of conservation tiDage practices on pesticide runoff are largely unknown; simulation mod- els generally show a decrease in runoff (Crowder et al., 1984~. This may be accompanied by an increase in percolation to groundwater, however. Ridge tiliage is a form of conservation tilIage with significant erosion control benefits that overcomes some of the soil temperature, weed control, and soil compaction problems associated with untilled systems. In the spring the tops of the ridges are tilled for planting (Figure 3-2~. This re- moves residue from the top of the ridges and disturbs the soil enough to create a seedbed. Soil on the ridges is also generally warmer than that between ridges or in fields without ridges. Warmer soil facilitates crop germination. Tilling only the top of the ridges disturbs fewer weed seeds, reducing weed germination. Erosion is slowed because soil and crop residue between the ridges is not disturbed. Weeds that emerge later in the growing season tend to be between the ridges. Cultivation easily controls these weeds and reduces soil compaction in crop rows, thereby enhancing plant root growth and water infiltration. The use of reduced tilIage is expected to increase primarily as a means to meet conservation compliance provisions of the Food Security Act of 1985. As its use increases, farmers and researchers will need to better understand its effects on soil structure, soil biota, plant growth, and pest populations. Research is needed to reduce the use of herbicides to control weeds in untired fields and increase the use of conservation tiliage in vegetable ancI other specialty crops. Effect of Soil Biota on Nutrient Availability Numerous free-living but plant-associated microorganisms aid in nutrient uptake (Hendrix et al., 1986~. Mycorrhizal fungi are important in the uptake of nutrients from soil and in the establishment of vigorous seedling growth in many crop and nursery species (Gerdeman, 1976~. Little is known about the genetics of these or other similar organisms or how their association benefits plants. Improvements in their use and establishment of beneficial microorganisms in the rhizosphere could make crop plants more efficient in their use of soil nutrients (Holland and Coleman, 1987~. In particular, work under way on the genetic basis of specific root associations may make it possible for free-living nitrogen-fixing bacteria to attach to the roots of cereal grasses or establish dominant relationships in the surrounding rhi- zosphere, thereby improving nitrogen use (Baldani et al., 1987~. The harmful effects of insect, nematode, and fungus pests in soil on crop growth and yields are well known and receive substantial research atten- tion. Less studied is another group of organisms that benefit crop produc- tion by decomposing leaf litter and root residues, playing an integral role in

RESEARCH AND SCIENCE Before planting 4~/,A _' O - - //// ~ After planting - _ ~ ~~~~ Before first cultivation A_ _ /// ~ ~ Last cultivation builds new riciges Old stubble ~ Residue o Seed ye Cover crop ~ Manure 163 _.,,,,- - 0 Band fertilizer FIGURE 3-2 Ridge tillage advantages in alternative production systems. The planter tills 2 to 4 inches of soil in a 6-inch band on top of the ridges. Seeds are planted on top of the ridges, and soil from the ridges is mixed with crop residue between the ridges. Soil on ridges is generally warmer than soil in flat fields or between ridges. Warm soil facilitates crop germination, which slows weed emergence. Crop residue between the ridges also reduces soil erosion and increases moisture retention. Mechanical cultivation during the growing season helps to control weeds, reduces the need for herbicides, and rebuilds the ridges for the next season. SOURCE: Dick Thompson, The Thompson Farm.

164 ALTERNATIVE AGRICULTURE making inorganic nutrients available for subsequent plant growth (Coleman et al., 1983, 1984a, 1984b; Ingham et al., 19851. The activities of these biota could influence crop nutrient needs, although their relationships with plants are not precisely understood. It is not known whether pesticides used to control soil insects and plant pathogens destroy other soil organisms. If they do, however, pesticide use may be a factor in nutrient management. Research is needed to know how pesticides affect soil biotic activity and thus influence nutrient cycles and crop nutrient requirements. Bacteria and fungi, the primary decomposers, break down sugars, poly- saccharides, and proteins in organic matter. They also assimilate mineral nutrients such as nitrogen and phosphorus into their tissues. When these organisms die, they release mineral nutrients, such as ammonium, nitrate, phosphates, and sulfates. This step is known as mineralization. A consid- erable portion of mineralization occurs when various members of the soil fauna prey on dead bacteria and fungi (Coleman et al., 1983, 1984a, 1984b; Mitchell and Nakas, 1986~. Much of this microbial and faunal activity occurs in the top few inches of the soil. A typical plow layer of 6 inches on 1 acre of farmland, which equals about 1,000 tons, contains approximately 4 tons of flora (2 tons of bacteria and an equal amount of fungi) and about 1 ton of all fauna combined (Ingham et al., 1985~. A majority of soil fauna is found in the plant rhizosphere (Ingham et al., 1985~. Current agroecosystem research on microbial flora, fauna, and or- ganic matter sources is directed toward discovering how microbial produc- tion and turnover can best be understood and managed to synchronize nutrient supply with the nutrient uptake needed for plant growth (Hendrix et al., 1986~. As a result, some farmers in the northern Great Plains are switching to spring wheat, because its growth is more synchronous with organic matter decomposition and nutrient cycles. Several ecologists and agronomists argue that farming practices matched to soil microbe activity are more energy and nutrient efficient than conventional practice (Coleman et al., 1984a, 1984b; Hendrix et al., 19861. Such factors as soil moisture, temperature, and texture must be included in decisions on timing of culti- vation, planting, and general tillage management. The relationships among soil microorganisms, nutrient cycling, pest pressure, plant growth, yield, and many other factors of crop production need further study. LIVESTOCK Livestock play an important role in many alternative farming systems in terms of nutrient cycling and their ability to make crop rotations economi- cally feasible through the consumption of forage crops (see the Spray, BreDahl, Sabot Hill, Kutztown, and Thompson case studies). Converting marginal cropland to pasture for grazing also helps promote soil conserva- tion and reduce water runoff. Nutrients not retained by the animal can be readily returned to the soil in the form of manure. Manure provides soil nutrients and enhances organic content and filth. Research in this area has

RESEARCH AND SCIENCE 165 been neglected in recent years because agriculture has focused on monocrop and monospecies systems and has increasingly separated crop and livestock activities. Much could be done to further understand and enhance crop- livestock interactions. Research is needed in the following areas to achieve the full benefits of crop-livestock systems: Crop and forage rotations and forage handling, harvest, and storage; Ruminant digestion of lignocelluTose; Quality and digestibility of pastures and forages; Animal muscle-to-fat ratio; Animal health systems; and Manure handing. - Obstacles to Greater Use of Hay anc' Forage Impressive advancements have been made in the harvesting, storage, and processing of forages for hay and silage, but major difficulties remain in integrating hay and silage into crop-livestock systems (Wedin et al., 1980~. The principal obstacles to further adoption of hay or forage crops are weather constraints and the time and labor required to harvest forage crops, particularly when cash crops require attention. Weather can interfere with harvesting; rain can seriously damage hay crops. Harvest of forage crops often occurs at peak demand times for labor and equipment and is often a lower priority than taking care of grain crops. These factors can significantly increase production costs per unit of digestible energy produced. Conse- quently, many livestock producers choose to maximize use of grains and silage and to minimize the area devoted to pastures and forages. Because pastures and forages have some advantages over row crops, such as reduced soil erosion and the potential to supply nitrogen, they are an important element in many alternative farming systems. Convincing more farmers to incorporate or expand! acreage devoted to pastures and forages, however, will require animal systems that are profitable and that save time and labor and an agricultural policy that encourages their adoption. Lignocellulose Digestion In many alternative crop-livestock systems, forages and crop residues comprise a large portion of the total diet for beef cattle, dairy cattle, and sheep, particularly in contrast to more intensive systems that rely on pur- chased feed grains. The availability of the energy stored in forages thus becomes critical to the viability of these operations. The gross energy con- tent of these celluTosic plants and crop residues is equal to that of grain and root crops. But animals do not use this energy efficiently because the cellu- lose structure is highly orclered and often associated with indigestible lignin

166 ALTERNATIVE AGRICULTURE (Council for Agricultural Science and Technology, 1986; Oltjen et al., 1980; Wedin et al., 1980~. Forage or hay crops will often be produced on land that could otherwise be in grain or other high-value crops. The economic viability of producing these crops, and ultimately the viability of incorporating livestock into an operation, therefore, will depend on the efficiency of ruminants in trans- forming these forages, hays, and crop residues into animal products. Unless corn stalks are harvested prior to maturity, as with silage, little sugar is in the stalk. When left in the field, feeding value of corn stalks is further reduced by weathering. Methods for improving the feeding value of lignoceDulose materials, such as corn stalks and small grain straw, have been studied. These methods include treatment with sodium hydroxide (Klopfenstein, 1978), a mixture of sodium and calcium hydroxides (KJopfen- stein and Owen, 1981), ammonia, urea (Ibrahim and Pearce, 1983), and, most recently, hydrogen peroxide (Keriey et al., 1985~. Because of chemical hazards, special equipment requirements, and modest improvement in feed value, the use of these intensive chemical treatments is limited. Microbiological interventions to improve the use of lignocellulose materi- als have largely concentrated on the introduction of dietary agents that will favorably influence ruminal fermentation. Several drugs, most notably the ionophores, can improve the efficiency of weight gain by reducing methane loss and increasing propionate production (Chalupa, 1980~. However, very few studies have been conducted on the genetics and genetic manipulation of ruminal bacteria (Forsberg et al., 1986; HazeTwood et al., 1986~. Research is needed to improve the bioavailability of lignocellulose. This would include plant breeding to improve the digestibility of pastures and forages and the vegetative portions of crop residues. Genetic manipulation of corn, for example, reduced the percentage of lignin by 40 percent. This resulted in a 30 percent increase of digestible dry matter from corn stover. When consumed, the forage caused a 1 pound per day increase in weight gain. Similar improvements might be possible with other forages (Council for Agricultural Science and Technology, 1986; Wedin et al., 1980~. Addi- tional research can help develop microbiological, chemical, and physical interventions that will improve the digestion of lignocellulose materials. Improving Quality of Pastures and Forages Genetic improvement in cash crops has resulted in significant increases in per acre yields. Similar yield improvement is possible for forages, al- though it has not been as widely exploited. For example, Bermuda grass yield potential has been doubled in the southeastern United States, but, in general, forages have not received the same level of research as cash crops. Improvement is also possible in nutrient availability, palatability, and the reduction of antimetabolite concentrations in plants. Reducing the amount of plant cell wall constituents, including hemicellulose, lignin, and silica, can improve nutrient availability. Palatability is important because livestock must eat the forage to benefit

RESEARCH AND SCIENCE 167 from its nutritional content. The factors affecting palatability are little un- derstood, and research could produce significant results. A variety of anti- metabolites and plant toxins are present in forage crops. Researchers are making progress in identifying and eliminating these chemicals. Plant breeders have lowered the indole alkaloid concentrations in a line of reed canary grass by one-third. Lambs fed the Tow-alkaloid canary grass gained weight at twice the daily rate of those fed the commercial variety (Marten et al., 1981~. Similar results might be possible in reducing tannins in sor- ghum and lespedeza; coumarin in sweet clovers; cyanogenic glycosides in sorghum, Sudan grass, and white clover; and saponins in alfalfa. Tall fescue is grown on 35 million acres in the United States. Poor animal performance and health problems have been reported in animals grazing some fescue pastures (Blaser et al., 1980; Goodman, 1952; Robbins, 1983; Studemann et al., 19731. The presence of the endophyte fungus Acremonium coenophialum has been implicated in poor animal performance in cattle graz- ing fescue (Hoveland et al., 19831. Improved performance has been reported in cattle grazing endophyte-free fescue. A number of fungus-free varieties have been developed; however, these varieties are more prone to insect damage due to loss of an insect toxin provided by the endophyte. Fairly convenient and accurate methods of determining forage nutritive quality are available. Improvement in methods and availability, however, would enhance forage quality research. Muscle-to-Fat Ratio One goal of agricultural research ant! farming is to improve the nutritional quality of food. Growing evidence of the link between consumption of fat and heart disease has stimulates! efforts to produce meat with lower fat content. Efficiency of conversion of feed to meat is improved when reduced fat content of meat is the goal because much more energy is required to produce fat than lean meat. Livestock fee! on pastures are leaner than those fed grains, but leaner meat sometimes lacks the taste and texture desired by consumers (National Research Council, 1988~. Perhaps more impor- tantly, the price and grading structures for beef traditionally rewarded farm- ers for producing animals with higher fat content. Recent changes in grad- ing standards have opened new markets for leaner products, but full adoption of research results is still hindered by economic incentives. Ani- mal breeding, feeding intact rather than castrated males, and genetic engi- neering are producing leaner livestock. Consumer demand! for leaner meat is growing. Genetic engineering has areas potential to accelerate this oro- T ~ V to to ~ 1 gress. Hormones are also creating opportunities for decreasing fat content in meat. For example, porcine growth hormone increases growth rate feed efficiency, and ratio of muscle to fat. Animal Health Systems Disease prevention through management has become an increasingly im- portant research objective throughout the last decade. Nonetheless, tech-

168 ALTERNATIVE AGRICULTURE nologies for disease treatment rather than management systems for disease prevention dominate current animal health systems. The subtherapeutic feeding of antibiotics and antibiotic treatment of diseased animals remain the mainstays of current animal health practices. Many alternative systems exist, however, and are widely practiced today (see the BreDahT, Kutztown, Thompson, and Coleman case studies). Some major commercial producers maintain animal health with reduced or no prophylactic feeding of antibi- otics. They are able to achieve this by modified production systems, includ- ing reduced animal confinement, improved ventilation and waste manage- ment systems, and, in certain cases, the use of alternative technologies. Antibiotics The antibiotic era ushered in with the discovery of penicillin has permit- ted treatment and control of animal disease not previously possible. The application of inexpensive antibiotics to animal feed controlled many of the disease problems that were exacerbated by the strict confinement and inten- sive management of animals. Conversely, the use of antibiotics has facili- tated the trend toward confinement housing and greater concentration of animals in production facilities (Council for Agricultural Science and Tech- nology, 1981~. About 9.9 million pounds of antibiotics are fed to livestock each year (Institute of Medicine, 1989~. The widespread! use of antibiotics in feed and to treat disease has reinforced a trend not to manage for disease prevention and to accept the costs of antibiotic feeding and use as a routine production expense. Feeds that contain antibiotics are widely used because, on the typical farm, they help animals use feed more efficiently. Research has demonstrated that the control of subclinical infection by feeding sub- therapeutic levels of antibiotics results in increased production and growth (Freedeen and Harmon, 1983~. It appears that antibiotic feeding also works by decreasing the total antigenic challenge to the animal's immune system. Immune systems that are stimulated for defense appear to channel nutri- ents to the need of the immune response and away from growth and production (Klasing et al., 19871. Antibiotics will always be needed, to some extent, for the clinical treat- ment of disease. The extensive use of antibiotics in feed and for therapy, however, has the attendant risk of promoting the selection of resistant bacterial strains that may be passed on in food, become pathogenic in humans, and resist antibiotic treatment. Research to develop new antibiot- ics for use only in agriculture may not resolve the concerns about resistant strains, because resistance in bacteria tends to occur for groups of bacteria. Moreover, the research, development, and federal approval process of new antibiotics is slow and costly, and drug companies may become unwilling to take the financial risk for new antibiotic product development (Liss and Batchelor, 1987~. It may be unwise, therefore, for animal agriculture and human medicine to assume that new antibiotics will always be developed to resolve resistance problems.

RESEARCH AND SCIENCE Alternatives to Antibiotic Use 169 The occasional adulteration of milk with antibiotics has been a problem for the dairy industry since the introduction of penicillin. To this day, peni- cillin and other antibiotic residues in milk, primarily from treatment for mastitis, remain a major concern for regulators and the dairy industry. Mastitis, a common bacterial infection of the lactating dairy cow, remains a predominant reason for the use of antibiotic therapy. Considerable re- search into mastitis has revealed that the disease is controllable and, most importantly, largely preventable. National data indicate that approximately 50 percent of the dairy cattle in the country have mastitis (National Mastitis Council, 1987~. But other studies have identified large numbers of dairy herds that have very Tow levels of mastitis, as evidenced by the low numbers of white blood cells in the commercial milk produced (Bennett, 1987~. Mastitis, like many other diseases of domestic animals, is a result of management practices. Dairy systems can be instituted and managed to reduce infection rates enough to greatly reduce intramammary use of ther- apeutic antibiotics. The opportunity to achieve this level of disease control is independent of the size of the dairy herd (Bennett, 1987~. The procedures and management for effective mastitis control have been widely published. A recent publication providing this information for pro- ducers and the allied industry is available nationwide (National Mastitis Council, 1987~. In general, effective disease control is achieved by: Pre- and postmilking disinfection of the udder; Proper milking machine function and use; Identification, diagnosis, and segregation of infected animals; Comprehensive prophylactic therapy of nonTactating animals; Maintenance of clean and dry cattle housing; and Culling chronically infected cattle. Other common dairy disease problems that may result in antimicrobial residues in milk are largely preventable, and similar control strategies have been developed (Amstutz, 1980~. The specifics of a control program must be tailored to each situation, and professional assistance is critical to the success of any program. Therefore, these systems often require a greater degree of management, knowledge, and information than is readily avail- able to producers. Swine Production The trend in swine production is toward larger confinement operations (see Chapter 1~. It is now common to find more than 1,000 sows per production unit. Without careful planning, design, and operation of these units, the risk of animal disease increases with the numbers of animals in the operation. Respiratory problems in pigs produced for market is a major

Partial confinement facilities provide shelter and open air space. Hogs raised in these systems generally have less incidence of ALTERNATIVE AGRICULTURE disease and require fewer antibiotics than those raised in confinement facilities. Credit: Grant Heilman. problem in swine production (National Research Council, 19881. A multi- tude of factors, including close proximity confinement, sanitation, and breed susceptibility, influence disease risk and the consequences of infection. The practice of feeding livestock a wide variety of antibiotics at low or subtherapeutic levels has become commonplace as producers have adopted

RESEARCH AND SCIENCE 171 confinement production systems. Animals respond to antibiotic feeding by increasing feed intake and using less feed per unit of weight gained, which improves the growth rate. The mode of action of subtherapeutic antibiotics has not been fully explained, however. Their bacteriostatic and bacteriocidal activities are probably the primary causes of improved feed efficiency and growth rate (Zimmerman, 1986~. However, additional theories have been proposed. Antibiotics may spare certain nutrients by reducing bacterial destruction of certain vitamins and amino acids or by favoring bacteria that synthesize these essential nutrients. Some studies have reporter! that anti- biotics reduce the thickness of the intestinal wall and suggested that af- fected animals may absorb nutrients more efficiently. Antibiotics may also inhibit the growth of toxin-producing bacteria within the intestinal tract. For example, antibiotics may depress bacterial urease production, which would result in lower ammonia levels in the intestine and blood (ammonia is a powerful toxin). Antibiotics may also kill or inhibit pathogenic organ- isms in the intestine, thus reducing the incidence of subclinical or clinical disease states. The significant benefits of antibiotic feeding have revealed the extent of disease problems in modern swine production. Because of the complex etiology and the pervasiveness of disease in swine, the subtherapeutic feeding of antibiotics win likely remain a simple and effective method of reducing disease loss in lieu of changes in production practices with greater emphasis on other methods of disease prevention. Alternative management systems and techniques, however, can greatly recluce reliance on subtherapeutic feeding of antibiotics (Kliebenstein et al., 1981~. Reduced confinement and the increased use of outdoor shelters and pastures are components of alternative livestock production systems that allow lowering or elimination of subtherapeutic feeding of antibiotics (see the BreDahI, Kutztown, Thompson, and Coleman case studies). Veterinary and medicine costs stemming from swine confinement production systems have been shown to be at least double those of a comparably productive pasture and hutch system. Kliebenstein et al. (1981) found that the total costs of producing 100 pounds of pork were $40.18 for the pasture system compared to $42.97 for the individual confinement unit system. In another example, veal calves raised in stall and pen confinement facilities have been shown to need five times the amount of antibiotics as hutch and yard calves (Friend et al., 1985~. Using pastures and forages may improve other aspects of production, such as waste management and nutrition. Preventive disease management, however, is not as simple as redesigning production systems and facilities. Similar disease conditions can develop in these situations as well. Hormonal Therapy A wide variety of physiological hormones modulate the natural disease defense mechanisms of animals. Research is needed to further identify

RESEARCH AND SCIENCE 173 lems or epidemics. For other important diseases, vaccinations have either not been effective or available. This is the case with acute coliform mastitis in dairy cattle. Standard antibiotic treatments are not effective against coliform mastitis. Thus, veterinarians and producers attempt treatment with different and more costly antibiotics. Gentamicin, a drug reported by the Food and Drug Administration (FDA) to occur in meat from cull dairy cows, is being used for intramammary therapy (Paige and Kent, 1987~. But advances in molec- ular immunology are beginning to reveal new opportunities for the devel- opment of effective vaccines. One vaccine developed with these techniques has been shown to modulate acute coliform mastitis in dairy cattle (Gonza- lez et al., 1988~. Often, disease problems of newborn animals are devastating and result in major economic losses. There is a need for research to develop manage- ment systems, breeding programs, and immunological interventions that will enhance immunological protection against diseases in the newborn (Anderson et al., 1980~. Parasitism Intensive use of chemical agents in the treatment and prevention of par- asitic infestation has resulted in the appearance of ecto- and endoparasites resistant to many insecticides and deworming agents. Research is needed to determine the influence of parasitism and quantify its economic effects. Integrated control programs using management, breeding, nutrition, and chemical or biological agent interventions should be developed (Anderson et al., 1980~. Parasitism of animals on pasture can be a major animal health problem and is often cited as a justification for the confinement housing and feeding of livestock. . .. . . . . . . . . Anthelmintics are administered on a regular or seasonal basis to treat subclinical parasitism before it induces a major production Toss. The FDA establishes specific label instructions for use and withdrawal periods before slaughter. The prescribed withdrawal periods and use limitations should help producers avoid high residue levels in animal products. Research on the integrated management of parasites associated with animals grazing on irrigated and nonirrigated pasture is needed in order to break the cycles of parasitic infection and reinfection. Genetic Resistance to Disease The genetic selection of animals has placed emphasis on productivity and efficiency and has potentially reduced natural disease resistance. Studies in dairy cattle have shown that as milk production increased, resistance to mammary disease decreased. It is generally thought that animals free of disease will produce more milk. It is not known, however, whether antibi-

174 ALTERNATIVE AGRICULTURE otic treatment and management or genetic resistance is the disease control strategy that will produce the most milk (AIrawi et al., 1979~. Use of genetic resistance for tolerance to disease and parasitism has been largely confined to tropical environments, where adaptation has been criti- cal to animals' survival. Research is needed to develop improved breeds and strains of livestock that are more resistant to disease or tolerant of ecto- anc! endoparasites in various climates (Anderson et al., 19801. Stress and Disease The stress response in animals is not well understood. There is a consen- sus, however, that distressed animals become less able to adjust effectively to additional change (Selye, 19501. Various stressors, such as close confine- ment, transportation, and temperature, have been shown to affect disease resistance. Although little scientific information is available that quantifies animal stress, observational research on the effects of stressors on animal health and behavior has fueled the debate on animal welfare and the signif- icance of stress (Mickley and Fox, 1987~. It is generally agreed that reducing the stress associated with confinement, transportation, and temperature decreases incidence of disease in certain cases. It has yet to be determined whether or not stress resistance can be genetically altered. There is evi- dence, however, that swine bred for high muscle content are more suscep- tible to stress, and that the stress effects of transportation reduce meat quality. Research is needed to define more fully and quantify stress in food animals. Subsequently, research may be able to determine if low stress systems offer disease protection and economic advantages. Technology and Advanced Diagnostics The performance of animals in disease-free and diseased states is difficult to measure precisely. It is very difficult to accurately diagnose diseases, particularly those that are subclinical. Immunological, biochemical, and electronic advances, however, are pro- viding new tools for the rapid and accurate determination of disease and the measurement of disease effects. Immunodiagnostics employing biotech- nological advances such as monoclonal antibodies and enzyme-linked anti- boclies have aided in disease control in virtually every food animal species. The electronic enumeration of white blood cells in cows' milk can provide every dairy producer with monthly information about the udder health status of every cow in the herd. Major advances in udder health nationwide may be possible because of this technology. A comprehensive or systems approach to the maintenance of health in food-producing animals offers perhaps some of the greatest opportunities for increasing the safety, quality, and profitability of food animal products. The academic intradisciplinary approach to research has precluded investi- gations into the larger systems approach to animal disease problems. By

RESEARCH AND SCIENCE 175 examining the interaction of nutrition, management, animal disease resis- tance, ant! the biology of disease agents, it may become possible to identify the critical control points governing the susceptibility and spread of disease and select those that win provide the most cost-effective means of disease prevention. PEST CONTROL IN CROPS Control of pests (including insects, nematodes, mites, weeds, and patho- gens) has been a major research activity in agriculture for decades. Crop management practices, rotations, genetic improvements through classical plant breeding, and synthetic organic chemicals are widely used to control pests in modern commercial agriculture. Steady progress has been made in these areas, and much of what has been accomplished is relevant to alter- native agriculture. Plant breeding that has produced many economically significant pest-resistant varieties of major cultivars is particularly relevant. Nevertheless, most of agriculture relies on synthetic chemical pesticides, even though in many cases effective alternatives are now available. Use of synthetic chemicals for pest control began in the 1940s, when the discovery of organic compounds such as dichioro diphenyl trichioroethane (DDT), benzene hexachIoride (BHC), and (2,4-DichIorophenoxy) acetic acid (2,4-D) heralded a revolution in pest management. Pesticides made it feasi- ble to control many pests and pathogens for which no effective control measure was previously available. Consequently, pesticides contributed sig- nificantly to yield increases in the 1940s through the 1960s. Pesticide use, especially of insecticides, grew rapidly. Many farmers began to apply insec- ticides on a regular schedule, often with little attention to actual infesta- tions. As a result, insecticide-resistant strains developed. Pesticides, partic- ularly insecticides and fungicides, wiped out certain beneficial species, which often led to the emergence of their prey as an even more serious pest problem. Many of the original organochiorine insecticides had detrimental environmental effects and presented unacceptable risks to human health. Most of these compounds have been removed from agricultural use and replaced with less persistent organophosphate, carbamate, and synthetic pyrethroid insecticides. Herbicide use has more than doubled since 1970, currently accounting for more than 65 percent of all pesticides applied. Today, more than 95 percent of all corn and soybean acres are treated with herbicides. As farmers con- tinue to cut input costs in response to economic conditions, researchers are seeking more effective, economical, and ecologically sound ways to control pests. Nonetheless, pesticide expenditures are about 20 percent of total input costs, although this figure varies substantially by crop and region (see Chapters 1 and 4~. Farmers and society could benefit from safer and more economical methods of controlling pests. Progress in this direction is under way as government, university, and industry researchers discover biological ant! genetic alternatives to the use of pesticides and devise a variety of

176 ALTERNATIVE AGRICULTURE cultural and biological control strategies aimed at reducing and even elimi- nating pesticide use. These efforts remain small, however, compared with the time and resources devoted to chemical pest control research. Nonethe- less, there are promising results to report. IPM Development Led by entomologists, researchers began to recognize the problems asso- ciated with dependence on extensive insecticide use in the 1950s. They developed concepts leading to what is now commonly referred to as inte- grated pest management (IPM). A central principle of {PM is the economic threshold concept, which holds that the mere presence of a pest population does not necessarily indicate an economically damaging situation where benefits will exceed the cost of control. In principle, {PM is an ecologically based pest control strategy that relies on natural mortality factors such as natural enemies, weather, and crop management and seeks control tactics that disrupt these factors as little as possible. O · ' ~ 1. Traditionally, the term IPM has been associated with insect control, in large part because formal IPM systems began with efforts to reduce insecti- cide use and avert a growing insect resistance problem, principally in cot- ton. Today, however, pest management systems that integrate a number of tactics for control of plant diseases, weeds, and other pests are widely practiced in a number of crops. For the purposes of this report the commit- tee uses the term {PM to include the integrated control of insects, diseases, and weeds. Ideally, the term IPM refers to control of all agricultural pests through the use of an integrated approach. IPM involves all aspects of crop production, including cultural practices such as cultivation, fertilization, postharvest management of fields, scout- ing for pests, tillage practices, the use of genetically improved pest-resistant varieties, rotations with other crops, and the use of biological controls (see the Florida, Pavich, Ferrari, and Kitamura case studies). However, most current IPM programs do not use all of these techniques. Current insect IPM programs generally focus on the use of improved crop varieties, scout- ing for pests, better timing of pesticide applications, and the use of more specific, less biologically active pesticides. The need for protection of natu- rally occurring biological control agents, such as predators and parasites, in the crop ecosystem is widely recognized but often overlooked in practice. In many situations, their populations cannot be preserved. Cultural prac- tices, such as increasing a crop's ability to resist pests through nutrient management techniques that promote crop health, appear to offer great promise. But these practices are not well articulated or understood. They are therefore underused and in need of quantitative research (see the Pavich case study). The common thread for all IPM programs is the concept of an economic threshold below which pest populations or damage is tolerated. The deter- mination of an economic threshold is difficult, however, because it is not a constant. It varies depending on an individual farmer's pest problems,

RESEARCH AND SCIENCE 177 stage of crop growth, and economic expectations. As economic thresholds differ, so will IPM programs. Decreased pesticide use is often associated with {PM, but it is not a mandatory component of the system. Most [PM programs decrease pesticide use, but many increase the number of pesticide applications in light of better knowledge of pest populations (Allen et al., 1987~. Significant federal support for IPM extension, research, and field studies began in 1972. The National Science Foundation (NSF) EPA and USDA ~ 1 ~ ~ ~ ~ ~ · ~ ~ . ~ ~ T ~ ~ ~ ~ · ~ Portly tuncleu thIS work known as the Hutiaker Project through the Coop- erative State Research Service (CSRS). Reauthorized in 1979 as the Consortium for Integrated Pest Management (CIPM), this project supported interdisciplinary research to develop IPM systems in alfalfa, apples, cotton, and soybeans. In 1984, the project was reorganized and decentralized. It is now administered in four regions the Northeast, North Central, South, and West. The regions set research prior- ities to match regional needs, and as a result, IPM research projects now dead with a wider range of pests on more crops. The funding for {PM research through CSRS has been about $3 million per year since 1972. The Extension Service (ES) has operated an IPM program since 1973. This program is designed to implement {PM systems and to develop an inde- pendent capacity for IPM among grower organizations, consultants, and other private parties. Allen et al. (1987) estimate that private IPM consult- ants generate $400 million per year in economic activity. Since 1979, funding for IPM activities through the ES has been steady but relatively small at about 2 percent of the total extension budget, or $7 million per year. Although effective, highly profitable, and relatively safe, {PM has been widely adopted only for some crops. Table 3-6 shows the implementation of IPM in 12 major crops. Implementing IPM programs for some crops in some regions, such as vegetables and ornamental flowers in the southeast- ern states, is particularly difficult (see the Florida fresh-market vegetable case study). The sophistication of IPM programs also varies greatly by crop, region, and individual grower. Insects and disease are an ever-present threat in hot areas with a long growing season. Some plant diseases are more consistently a problem in hot areas with high humidity, such as the south- eastern United States. Fruit and vegetable crops have a high unit value, and the loss of even a small share of the crop could be costly. Under the current federally regulated grower-operated grading system, blemish-free produce often receives a higher price. This incentive encourages uniformly sched- uled pesticide applications ant! works strongly against reductions in pesti- cicle use. Extremely low tolerance levels for insects or their fragments in high-value canned and processed foods also encourage prophylactic pesti- cide applications. Faced with this stituation, a grower has a strong incentive to eliminate any chance of damage by applying pesticides on a schedule rather than depending on monitoring and IPM. In the context of these grading standards, IPM in high-value crops may involve a very low eco- nomic threshhold that results in a greater number of pesticide applications based on increased monitoring of pest populations.

178 TABLE 3-6 U.S. IPM Use in 12 Major Crops, 1986 ALTERNATIVE AGRICULTURE Percentage of Acres Acres Total Acres Crop Planted (l,OOOs) Under IPMa (1,000 I Lnd~ LO V1 Alfalfa 26,748 1,273 4.7 Applesb 461 299 65.0 Citrusb 1,057 700 70.0 Corn 76,674 15,000 19.5 Cotton 10,044 4,846 48.2 Peanuts 1,572 690 43.8 Potatoes 1,215 196 16.1 Rice 2,401 935 38.9 Sorghum 15,321 3,966 25.8 Soybeans 61,480 8,897 14.4 Tomatoes 378 312b 82.5 Wheat 72,033 10,687 14.8 NOTE: IPM is defined broadly to include all acres where basic scouting and economic threshold techniques are reportedly used. aIncludes acres under IPM management by the Cooperative Extension Service, grower organizations, producer industries, or consultants. bData based in part on conversations with IPM entomologists in major growing regions. SOURCES: U.S. Department of Agriculture. 1987. Agricultural Statistics. Washington, D.C.; U.S. Department of Agriculture. 1987. National IPM Program. Cooperative Extension Service. Washington, D.C.; U.S. Department of Agriculture. Forthcoming. Fruit Situation and Outlook Report. Economic Research Service. Washington, D.C. Alternative Insect and Mite Control When intervention is necessary, chemical insecticides and acaricides will continue to be important ways to protect many commercially produced crops. Research shows, however, that significant progress has been made with other approaches. Incorporating pest control into the overall manage- ment of a farm by modifying cultural practices or rotating crops, for exam- ple, is essential to effective alternative pest control strategies. The most limiting factor in the adoption of these strategies is the failure to introduce them as a part of an overall farm management system. When used in the environment of conventional agriculture, the effectiveness of many alterna- tives is diminished or lost. Cultural controls for insects include modifying the pest habitat through use of crop rotations, increasing ecosystem diversity, adjusting the time of planting and harvest, precise management of water and fertilizer, modified cultivation and tiDage practices, and improved sanitation. Cultural controls have demonstrated their effectiveness in many situations against such pests as pink boDworms on cotton in Texas. There, a short-season, early-harvest crop is followed by immediate shredding and plow-down on a uniform basis (often state-mandated) throughout the area. Rotating corn with soy- beans is another common cultural practice that so far has virtually elimi- nated damage by corn rootworms.

RESEARCH AND SCIENCE 179 Before resistant varieties of wheat were developed, wheat rust annually caused millions of dollars of damage in the United States. Fungicides are sometimes still needed to control isolated infestations. Breeders continue to develop high-yielding resistant varieties to help farmers cut costs and remain competitive. Credit: Agricultural Chemicals Division, Mobay Corporation. Plant breeders have developed many widely grown cultivars with insect and disease resistance. Plant breeding, which is the science of manipulating a plant's genetic composition, has been a very effective control method for insects, mites, and particularly plant diseases. Resistant cultivars have dra- matically reduced fungicide use in wheat and peanuts and the vulnerability of wheat, corn, and alfalfa to certain pests. The potential benefits from future research remain substantial. Research and development on wheat resistant to Hessian fly and wheat stem sawfly, alfalfa resistant to spotted alfalfa aphid, and corn resistant to European corn borer cost less than $10 million. The annual savings to farmers are estimated at hundreds of mil- lions of dollars (National Research Council, 1987b). Recent developments in genetic technology promise to enhance this approach to crop improvement (Goodman et al., 1987~. Natural biological controls, such as antagonists, predators, and self-cle- fense mechanisms, suppress most pests. Biological control of pests by nat- ural enemies (parasites, predators, and insect pathogens) is partially or entirely effective on most potential pests. Additionally, this sort of control

180 ALTERNATIVE AGRICULTURE Successful biological control of pests involves attracting and keeping beneficial insects in crop fields. Here, a spined soldier bug feeds on a Mexican bean beetle larva, one of the most damaging soybean insect pests. U.S. Department of Agriculture scientists have isolated the pheromone to attract the spined soldier bug. This development may aid the biological control of the Mexican bean beetle. Credit: Agricultural Research Service, U.S. Department of Agriculture. is long-lasting if it is not disrupted by farming practices such as insecticide use, certain crop rotations, or unusual climatic conditions. Ironically, the cases in which insecticides reduce the beneficial insect population and new insect problems emerge best illustrate the importance of natural enemies (Ridgway and Vinson, 1977; Settle et al., 1986~. Importation and release of exotic natural enemies is another effective

RESEARCH AND SCIENCE 181 ~ ~ : _..~ _— .. Pheromones in the trap in this staked tomato Florida case study, can then be made in field in Florida attract insects, which are response to the actual magnitude of the pest counted to determine their populations. infestation, rasher then on a routine schedule. Pesticide applications, as described in the Credit: Will Sargent.

182 ALTERNATIVE AGRICULTURE biological control tactic (Osteen et al., 1981~. The first example of classic biological control by an introduced exotic species occurred about a century ago, when the Australian vedalia beetle was introduced into California to control the cottonycushion scale insect of citrus. Since then, the introduc- tion of exotic parasites, predators, and pathogens in the United States has controlled almost 70 insect pests (National Research Council, 1987a). Augmentation of indigenous natural enemies is an important biological control technique. It is usually accomplished by mass release of natural enemies in the target field. But this means of pest management has been very costly in some cases. Further, its effectiveness is sometimes difficult to evaluate. In several instances, however, it has been very cost-effective. One example is the use of natural enemies in controlling the alfalfa weevil (Os- teen et al., 1981~. The release of insecticide-resistant natural enemies can be very effective in certain permanent crops if monitored and managed care- fully. While this approach is not universally successful, it has shown great utility in controlling spider mite pest species in deciduous fruit and nut orchards (Hoy, 1985; Hoyt and Burts, 1974~. Insect diseases are highly selective in their action. Although these dis- eases are somewhat limited to use in special situations, some scientists are convinced of their potential, having observed epidemics caused by viral disease under natural conditions. The use of viruses to control insect pests has been inconsistent and generally disappointing in trials, however. Re- search is needed to improve virus formulation, production, and application in field situations. Bacteria have also been used successfully. For example, Bacillus thuringien- sis (Bt) controls certain lepidopterous larvae. Bt is also sometimes used for larvae "cleanup" just before the harvest of vegetable crops. Bacillus thurin- giensis israelensis, a subspecies, has demonstrated promise for use against immature mosquitoes living in aquatic environments. Genetic engineering technology creates other possibilities for Bt. Researchers have transferred the toxin gene from Bt into tobacco to control certain leaf-feeding caterpil- lars. It may also be transferred to corn seed to control European corn borer. Some entomologists, however, have serious reservations about this process because of potential resistance selection in species feeding on the plant containing the toxin. There are many types of control agents for insects that are relatively nontoxic to other organisms. Future research may prove their safety and usefulness in applied situations (National Research Council, 1987a). Recent advances in the understanding of insect ecology, biology, physiology, and biochemistry are providing new opportunities for insect control. The rear- ing and releasing of sterilized insect pests have successfully controlled the screwworm, which afflicts livestock. The technique has proved successful for eradicating new infestations of fruit fly species on the U.S. mainland. Prospects are good for similar results with other species. A similar strategy is to breed genetically altered pest species that can mate with pests to produce offspring unable to reproduce, feed, or perform other functions

RESEARCH AND SCIENCE 183 necessary tor survival. Increased knowledge of such insect hormones as brain hormones, molting hormones, and the juvenile hormone has made it possible to synthesize them. Introduction of devices that emit synthetic hormones offers the potential to disrupt normal functions such as breeding, growth, and molting, thus controlling the pest population. Insect pheromones are used commercially to monitor, detect, and predict insect populations and to control several insect pest species on a variety of crops. They have great promise for more widespread use when registration procedures under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) are completed. University, USDA, and industry scientists have identified sexual attractant or aggregation pheromones for more than 436 insect species. More than 50 companies seD about 250 of these pheromones worldwide, mostly for population monitoring and detection traps, for which they are in great demand. Pheromones dispensed over fields to confuse males and prevent mating successfully control insect pests in a number of crops, including grape leafroller, oriental fruit moth on peaches, pink bollworm on cotton, and tomato pinworm. Commercial formulations are economically competitive with insecticides, even taking application costs into account. Additionally, pheromones affect only the target species because of their extreme specific- ity. During season-Ion" pheromone disruption with no insecticides, treated grape fields in New York had crop damage below 1 percent. Similar fields treated with the insecticide carbaryl reported crop damage of 18 and 2.5 percent (Booth, 1988~. Pink bollworm disruptant has been soIc! commer- cially in the Southwest for almost 10 years and has been applied on as many as 100,000 acres per year. New formulations have held infestations to 1 percent or less throughout the season with one application; consequently, insecticide applications have been reduced by nearly 90 percent (Baker et al., in press). Oriental fruit moth infestations on peaches are routinely held to a fraction of a percent by a single season-long application of disruptant; subsequent insecticide use is eliminated (Rice and Kirsch, in press). Contin- ued development of new controlled-release technologies and cheaper syn- thetic pheromones will further improve the comnetitivene.~ of nh~romon~c .. . . . ~ .. . . ~ . . in the marketplace. Small companies specializing in pheromones will con- tinue to be the innovators in developing new pheromone products unless fees imposed by the government for entry into the registration process reach prohibitive levels and force them out of the market. Alternative Plant Pathogen Control The integration of a variety of methods has historically controlled plant diseases. The selection and development of varieties with specific or general (multigenic) resistance have helped to avoid overdependence on chemicals. Genetic resistance is the single most important defense against plant dis- ease and the proven alternative to chemical control when available.

184 ALTERNATIVE AGRICULTURE For a variety of reasons, most plant diseases cannot be directly controlled. For example, many of the fungi that infect plant roots have not been fully investigated, nor has their importance in affecting yield been quantified. In most cases, farmers cope with diseases by using good farm management practices and planting resistant varieties. When combined with the existing natural level of biological control, management and resistant varieties keep the majority of diseases in check. Nonetheless, disease can still cause sig- nificant yield loss. Moreover, germplasm for desirable resistance has not been identified for many of the worId's important crops. More research is needed to better characterize available germplasm for genetic resistance to disease and plant transformation. The development and durability of resistant varieties have been a chal- lenge to plant pathologists and plant breeders. Genetic strategies to im- prove the durability of resistance include use of multilines and cultivar mixtures as well as multigenic or horizontal resistance. Modern genetic technology will speed the development of resistant crops. It should be possible to identify genes that confer resistance to a specific pathogen. These genes would then be introduced to the appropriate plant, without incorporating other genes that may confer detrimental characteristics. This gene transfer has been achieved to produce resistance to several plant vi- ruses in tobacco plants (National Research Council, 1987a). Advances in understanding the genetic and molecular bases of disease in plants promise major improvements in plant disease control using genetic rather than chemical methods (Goodman, 1988~. Cultural practices such as crop rotations, alteration of soil pH, sanitation, and adjustment of the timing of planting and harvest to avoid peak periods of the pathogens complement genetic resistance in many situations. For example, raising soil pH with lime from 6.5 to 7.5 reduces the severity of fusarium wilts on tomato and potato crops in Florida (Jones and Woltz, 1981~. Lowering soil pH with sulfur to 5.0 controls potato scab caused by Streptomyces scabies (Oswald and Wright, 19501. Forms of nitrogen also can play a significant role in disease severity. For example, ammonium nitrogen suppresses the disease take-all in wheat but nitrate favors it (Huber et al., 1968~. Tillage practices can have effects on pathogen populations and resultant diseases. Ecofallow is a form of conservation tillage that can reduce stalk rot of sorghum but permits increases in other diseases (Cook and Baker, 1983~. Harvesting and processing practices can also influence the inception of disease. The hydrostatic pressure from tank-washing potatoes causes water infiltration of pathogens into the lenticels of the tubers, predisposing them to attack by bacterial soft rot (Bartz and Kelman, 1985~. Potatoes are then generally treated with a fungicide. There is enormous need and potential to control diseases by nonchemical methods (Cook and Baker, 1983~. But there remains a lack of understanding of the underlying mechanisms that affect disease incidence and severity.

RESEARCH AND SCIENCE 185 Synthetic chemical control of plant pathogens has become an increasingly important pest control tactic as agriculture has shifted toward intense cul- tivation of monocultures (Delp, 1983~. Practices previously used to control pathogens, such as crop rotations, are not compatible with current crop specialization (Tweedy, 1983~. Because commercial cultivars are genetically related, the loss of resistance to pathogens could cause serious problems if fungicides were not available. In California, the use of methyl bromide and chloropicrin soil fumigation resulted in huge increases in yield and quality in several crops (Wilhelm and Paulus, 1980~. This combination is widely credited with saving the strawberry industry from high production costs and foreign competition. Although the total amount of fungicides used in the United States is much less than the amount of herbicides or insecticides, the potential chronic health risk to humans is significant. Ninety percent (by weight) of fungicides applied are known to cause tumors in laboratory animals. Fun- gicicle residues in food are responsible for the largest share of potential dietary oncogenic risk from pesticides. Developing fungicides not toxic to nontarget organisms, including humans, is difficult; very few new fungi- cides have reached the market. Only four nononcogenic fungicides have been introduced in the past 15 years that have captured greater than 5 percent of any food crop market (National Research Council, 1987b). In recent years, there has been a movement toward the development of highly specific systemic fungicides, but this has accelerated evolutionary selection of fungicide-resistant plant pathogens. Research to understanc! the mecha- nisms of resistance could aid the development of chemicals with new modes of action ant! better-targeted effects. The introduction or application of biological control agents has not been very successful with plant pathogens because of the great complexity in microbial communities. Although many of the management practices that indirectly control diseases strike a balance between beneficial and deleteri- ous microorganisms, there is insufficient knowledge to effectively develop and use biological control agents commercially (Schroth and Hancock, 19851. Little is known concerning the ecology, classification, and physiology of biological control organisms or the underlying mechanisms affecting the interactions among beneficial microorganisms, pathogens, and plants. The potential to use microorganisms against microorganisms has stirred the interest of many investigators. A number of companies have pioneered efforts to develop biological control agents for plant pathogens. Several products have already reached) the market. An avirulent, antibiotic-produc- ing strain of Agrobacterium is available to control crown gall tumors of orna- mental plants and orchard trees caused by Agrobacterium tumefaciens (National Research Council, 1987a). Plans are underway to market a root- colonizing Pseudomonas bacterium as a control for Rhizoctonia and Pythium fungi in cotton. Another interesting disease control possibility is to stimulate a plant's own defense system with chemicals or by inoculation with an avirulent

186 ALTERNATIVE AGRICULTURE form of a pathogen. The citrus tristeza virus from Africa entered Brazil in the 1920s and nearly decimated the citrus industry. In the 1950s, researchers found a mild strain of the virus that protected trees from the severe strain. Commercial inoculation with the mild virus began in the late 1960s and has been very successful so far (National Research Council, 1987a). It remains unlikely, however, that disease control in continuous crop monocultures in certain regions, such as fruit and vegetable production in the East and Southeast, will be possible without use of synthetic chemical fungicides and fumigants. Disease pressures in areas with high temperatures and humid*y and long growing seasons are so severe that only dramatic changes in production systems will enable widespread adoption of alternative dis- ease control measures. Alternative Nematode Control Nematode control is particularly difficult. Strategies include genetic resis- tance, chemical control, and cultural methods such as rotations (see the BreDahT, Kutztown, Thompson, and Kitamura case studies). Genetic resis- tance is successful in only a few cases. Chemical control, which is feasible only in certain situations, relies on broad-spectrum, highly toxic, and often volatile materials. It is expensive and hazardous. The decline of basic cul- tural practices such as rotations, particularly in the Midwest, has led to an increase in nematodes in soybeans. Rotating corn with soybeans will control most nematode problems. Current research for nematode control is focusing on the development of effective cultural practices such as those traditionally practiced before the advent of broad-spectrum nematocides. Genetic research to develop nematode-resistant cultivars has been suc- cessfuT in sugar beets and tomatoes (Goodman et al., 19871. More research is necessary to determine how various nematodes damage different crops and how to modify practices if a combination of nematode species is pres- ent. Similarly, the accuracy and efficiency of techniques for estimating nem- atode populations needs to be improved. The biological antagonism level of the soil must be determined if manage- ment decisions are to be based on an understanding of the relationship between yield and population density of nematodes. A given number of nematodes will affect the same crop differently in soils of differing biota. More basic studies in biological control and interactions in the rhizosphere are required. Improved assay techniques for assessing the biological antag- onism coefficients of various soils must be developed. One promising biological control agent is the pathogenic bacterium Pas- teuria penetrans, which is effective against several economically important nematodes. It is expensive to produce on a large scale, however. A less expensive, but also less effective, biological control option is the use of plants such as CrotaZaria spectabilis that prevent the nematode from repro- ducing. Coastal Bermuda grass (Cynodon daclylon) incorporated before planting lespedeza, tobacco, or vegetable transplants protects against root-

RESEARCH AND SCIENCE 187 knot nematodes (Meloidogyne spp.) (Burton and Johnson, 1987). Coastal Bermuda grass will also reestablish itself after the annual crop is harvested. These plants could be even more effective if they could be genetically engineered to produce nematode attractants or pheromones. The selection and development of varieties for resistance and tolerance to nematode stress will continue. This may involve incorporation of appropri- ate genetic material into varieties already selected for production, economic, and marketing qualities. It is still important to develop biological and chem- ical nematocides that are systemic, easily associated with the root system, target organism specific, or a combination of these factors. These pesticides will allow flexibility in management decisions and compensation for man- agement errors that have promoted or amplified nematode stress problems in a particular production system. Alternative Weed Control Farmers in the United States depend greatly on herbicides to control weeds. Nearly two-thirds of U.S. pesticide purchases are for herbicides. But a variety of other means, such as crop rotations, mechanical cultivations, competition with other plants, and biological control through natural ene- mies can control weeds (see Spray, BreDahI, Sabot Hill, Kutztown, Thomp- son, Pavich, and Lundberg case studies). In fact, growers are often unaware of the forces naturally controlling weeds. The purslane sawfly and the leafmining weevil, for example, help control pursTane in California. These insects would be even more effective if their populations were not reduced by insecticide use. The moth Bactra verutana suppresses the weed Cyperus rotundus that infests cotton in Mississippi. More than 70 plant-feeding in- sects and plant pathogens have been introduced to control weeds in the United States; 14 weed species are now controlled in this way (National Research Council, 1987a; Osteen et al., 1981). Few weeds are controlled biologically in agriculture, however, although future opportunities are nu- merous. For example, many of the hundreds of species of carabid beetles are seed eaters and could play a role in weed control (Andres and Clement, 1984). Cultural practices are currently the most effective alternative to herbi- cides. Cultivating, rotary hoeing, increasing the density of the crop plant to crowd out weeds, intercropping, timing of planting to give the crop a competitive advantage, and transplanting seedling crop plants to give them a head start on weeds are currently practiced and effective measures. Trans- planting tomatoes to a high density has successfully controlled the growth of shade-intolerant redroot pigweed. Clover planted as an understory or living mulch reduces weed growth in corn. Several combinations of cover crops and tillage practices are effective in controlling weeds in corn and soybeans. Weed-tolerant crops and crops that produce substances toxic to weeds are potentially promising approaches that have received little research atten-

188 ALTERNATIVE AGRICULTURE lion. Naturally occurring phytotoxic allelopathic chemicals, however, may not always be safer than some of the more undesirable synthetic herbicides. Introducing weed diseases is also a possibility. The rust Puccinia chondriZZina controls the rush skeleton weed, which is a problem in wheat and pasture areas. AZternaria macrospora can inhibit the growth of spurred anode, a damaging weed in cotton production that is resistant to several cotton herbicides. The development of herbicide-resistant crops may offer opportunities to substitute safer herbicides for more dangerous herbicides. For example, efforts are being made to develop crops resistant to the herbicide glyphos- ate, a compound with very low mammalian toxicity. Like other broad- spectrum herbicides, glyphosate has limited use in crop production because it destroys crops as well as weeds and therefore must be used before crop germination or with special application methods and equipment. In re- sponse to this problem, researchers have isolated glyphosate-resistant genes and successfully transferred them to poplar trees, tobacco, and tomatoes (Della-Croppa et al., 1987; Stalker et al., 1985~. If the plants tolerate gly- phosate, the herbicide could then be used as a postemergent treatment. In certain cases, this strategy could reduce weed control costs, improve weed control quality, and reduce human health hazards. SUMMARY Alternative farming encompasses a range of farming practices, including the use of crop rotations, IPM, biological and cultural pest control, use of organic materials to enhance soil quality, different tilIage methods, and animal rearing techniques that involve less reliance on antibiotics and con- finement. The unifying premises of alternative systems are to enhance and use biological interactions rather than reduce and suppress them and to exercise prudence in the use of external inputs. Research has not fully addressed the integration of study results essential to the adoption of a number of alternative farming methods as unified systems. Although some components of alternative systems have been ex- amined, they have been generally studied in isolation. Lack of systems research is a key obstacle to the adoption of a number of alternative farming practices. On the whole, land-grant universities and the USDA have not adequately integrated the results of this research into production systems. Nonetheless, a significant amount of scientific evidence exists that sup- ports the effectiveness of a range of alternative practices. There is a large body of information about the value of legumes in fixing nitrogen, improv- ing soil quality, reducing erosion, and increasing yields of subsequent crops. {PM programs are effective, profitable, and increasingly adopted. Although biological and natural controls are underused, they have been demonstrated to be effective and warrant increased research support. Genetic engineering techniques should enhance this aspect of IPM. The integration of livestock

RESEARCH AND SCIENCE 189 into farming systems provides additional means for nutrient cycling. Im- proving forage digestibility needs further research, however. The scientific basis for some of these practices and their interaction in agricultural systems is not always understood, but they work. Many farmers have adopted them and are using them profitably. The economics of these and other alternative farming practices and systems are discussed in the following chapter. REFERENCES Allen, W. A., E. G. Rajotte, R. F. Kazmierczak, Jr., M. T. Lambur, and G. W. Norton. 1987. The National Evaluation of Extension's Integrated Pest Management (IPM) Programs. VCES Publication 491-010. Blacksburg, Va.: Virginia Cooperative Extension Service. Alrawi, A. A., R. C. Laben, and E. I. Pollack. 1979. Genetic analysis of California mastitis test records. II. Score for resistance to elevated tests. Journal of Dairy Science 62:1105-1131. Amstutz, H. E., ed. 1980. Bovine Medicine and Surgery, 2d ed. Santa Barbara, Calif.: Ameri- can Veterinary Publications. Anderson, D. P., W. R. Pritchard, l. l. Stockton, W. G. Bickert, L. Bohl, W. B. Buck, J. Callis, R. Cypess, l. Egan, D. Gustafson, D. Halvorson, B. Hawkins, A. Holt, A. D. Leman, S. W. Martin, T. D. Njaka, B. I. Osburn, G. Purchase, W. W. Thatcher, H. F. Troutt, l. Williams, and R. G. Zimbelman. 1980. Animal health. Pp. 129-151 in Animal Agriculture Research to Meet Human Needs in the 21st Century, W. G. Pond, R. A. Merkel, L. D. McGilliard, and ]. Rhodes, eds. Boulder, Colo.: Westview Press. Andraski, B. J., D. H. Mueller, and T. C. Daniel. 1985. Phosphorus losses in runoff as affected by tillage. Soil Science Society of America lournal 49:1523-1527. Andres, L. A., and S. L. Clement. 1984. Opportunities for reducing chemical inputs for weed control. Pp. 129-140 in Organic Farming: Current Technology and Its Role in a Sustainable Agriculture, Special Publication No. 46, D. F. Bezdicek and J. F. Power, eds. Madison, Wis.: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America. Baker, K. F., and R. ]. Cook. 1982. Biological Control of Plant Pathogens. St. Paul, Minn.: American Phytopathological Society. Baker, T. C., R. T. Staten, and H. M. Flint. In press. Use of pink bollworm pheromone in the southwestern United States. In Behavior-Modifying Chemicals for Insect Management: Applications of Pheromones and Other Attractants, R. L. Ridgway, R. M. Silverstein, and M. N. Inscoe, eds. New York: Marcel Dekker. Baldani, V. L. D., l. I. Baldani, and l. Dobereiner. 1987. Inoculation of field-grown wheat (Triticum aestivum) with Azospirillum in Brazil. Biology and Fertility of Soils 4:37-40. Balfour, E. B. 1976. The Living Soil and the Haughley Experiment. New York: Universe Books. Barnes, D., G. Heichel, and C. Sheaffer. 1986. Nitro alfalfa may foster new cropping system. News, November 20. St. Paul, Minn.: Minnesota Extension Service. Bartz, ). A., and A. Kelman. 1985. Infiltration of lenticels of potato tubers by Erwinia carotovora pv. carotovora under hydrostatic pressure in relation to bacterial soft rot. Plant Disease 69:69-74. Bennett, R. H. 1987. Milk quality management is mastitis management. Pp. 133-150 in Proceedings of the 26th Annual Meeting of the National Mastitis Council, Inc. Arlington, Va.: National Mastitis Council. Blaser, R. E., R. C. Hammes, Jr., J. P. Fontenot, and H. T. Bryant. 1980. Forage-animal systems for economic calf production. Pp. 667-671 in Proceedings of the XIII International Grass- land Congress. Berlin: Akademie-Verlag. Booth, W. 1988. Revenge of the "nozzleheads." Science 23:135-137. Burton, G. W., and A. W. Johnson. 1987. Coastal Bermuda grass rotations for control of root- know nematodes. lournal of Nematology 19:138-140.

190 ALTERNATIVE AGRICULTURE Chalupa, W. 1980. Chemical control of rumen microbial metabolism. Pp. 325-347 in Digestive Physiology and Metabolism of Ruminants, Y. Ruckebusch and P. Thivend, eds. Lancaster, England: MTP Press Limited. Coleman. D. C.. C. P. P. Reid. and C. V. Cole. 1983. Biological strategies of nutrient cycling in soil systems. Advances in Ecological Research 13:1-55. Coleman, D. C., C. V. Cole, and E. T. Elliott. 1984a. Decomposition, organic matter turnover, and nutrient dynamics in agroecosystems. Pp. 83-104 in Agricultural Ecosystems: Unify- ing Concepts, R. Lowrance, B. R. Stinner, and G. I. House, eds. New York: Wiley/ Interscience. Coleman, D. C., R. E. Ingham, J. F. McClellan, and J. A. Trofymow. 1984b. Soil nutrient transformation in the rhyzosphere via animal-microbial interactions. Pp. 35-38 in Inver- tebrate-Microbial Interactions, J. M. Anderson, A. D. M. Rayner, and D. W. H. Walton, eds. Cambridge, England: Cambridge University Press. Cook, R. l. 1984. Root health: Importance and relationship to farming practices. Pp. 111-127 in Organic Farming: Current Technology and Its Role in a Sustainable Agriculture, Special Publication No. 46, D. F. Bezdicek and J. F. Power, eds. Madison, Wis.: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America. Cook, R. J. 1986. Wheat management systems in the Pacific Northwest. Plant Disease 70(9):894-898. Cook, R. l., and K. F. Baker. 1983. The Nature and Practice of Biological Control of Plant Pathogens. St. Paul, Minn.: American Phytopathological Society. Council for Agricultural Science and Technology. 1980. Organic and Conventional Farming Compared. Report No. 84. Ames, Iowa. Council for Agricultural Science and Technology. 1981. Antibiotics in Animal Feeds. Report No. 88. Ames, Iowa. Council for Agricultural Science and Technology. 1986. Forages: Resources for the Future. Report No. 108. Ames, Iowa. Crowder, B. M., D. J. Epp, H. B. Pionke, C. E. Young, J. G. Beierlein, and E. J. Partenheimer. 1984. The Effects on Farm Income on Constraining Soil and Plant Nutrient Losses: An Application of the CREAMS Simulation Model. Research Bulletin 850. University Park, Pa.: Agricultural Experiment Station, Pennsylvania State University. Dabney, S. M., G. A. Breitenbeck, B. I. Hoff, J. L. Griffin, and M. R. Milam. 1987. Manage- ment of subterranean clover as a source of nitrogen for a subsequent rice crop. Pp. 54-55 in The Role of Legumes in Conservation Tillage Systems, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Della-Croppa, G., S. C. Bauer, M. L. Taylor, D. E. Rochester, B. K. Klein, D. M. Shah, R. T. Fraley, and G. M. Kishore. 1987. Targeting a herbicide-resistant enzyme from Escherichia cold to chloroplasts of higher plants. BiolTechnology 5:579-584. Delp, C. 1983. Changing emphasis in disease management. Pp. 416-421 in Challenging Problems in Plant Health, T. Kommendahl and P. H. Williams, eds. St. Paul, Minn.: American Phytopathological Society. Eggert, F. P., and C. L. Kahrmann. 1984. Response of three vegetable crops to organic and inorganic nutrient sources. Pp. 97-109 in Organic Farming: Current Technology and Its Role in a Sustainable Agriculture, Special Publication No. 46, D. F. Bezdicek and J. F. Power, eds. Madison, Wis.: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America. Elliott, L. F., R. I. Papendick, and D. F. Bezdicek. 1987. Cropping practices using legumes with conservation tillage and soil benef*s. Pp. 81-90 in The Role of Legumes in Conservation Tillage Systems, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Forsberg, C. W., B. Crosby, and D. Y. Thomas. 1986. Potential for manipulation of the rumen fermentation through the use of recombinant DNA techniques. Journal of Animal Science 63:310-325. Foth, H. D. 1978. Fundamentals of Soil Science, 6th ed. New York: Wiley. Freedeen, H. T., and B. G. Harmon. 1983. The swine industry: Changes and challenges. Journal of Animal Science 57(Suppl. 2~:110-118.

RESEARCH AND SCIENCE 191 Friend, T. H., G. R. Dellmeier, and E. E. Gbur. 1985. Comparison of Four Methods of Calf Confinement. 1. Physiology. Technical article 18960. College Station, Tex.: Texas Agricul- tural Experiment Station. Gebhardt, M. R., T. C. Daniel, C. E. Schweizer, and R. R. Allmaras. 1985. Conservation tillage. Science 230:625-630. Gerdeman, J. W. 1976. Vesicular-arbuscular mycorrhizae. Pp. 576-591 in The Development and Function of Roots, I. G. Torrey and D. T. Clarkson, eds. London: Academic Press. Glenn, S., and I. S. Angle. 1987. Atrazine and simazine in runoff from conventional and no- till corn watersheds. Agriculture, Ecosystems and Environment 18~4~:273-280. Goldstein, W. A., and D. L. Young. 1987. An agronomic and economic comparison of a conventional and a low-input cropping system in the Palouse. American Journal of Alter- native Agriculture 2~2~:51-56. Gonzalez, R. N., J. S. Cullor, D. E. Jasper, T. B. Farver, R. B. Bushnell, and M. Oliver. 1988. A mastitis vaccine? Don't laugh: New research and field tests have scientists very optimis- tic. Dairyman (May): 20. Goodman, A. A. 1952. Fescue foot in cattle in Colorado. Journal of the American Veterinary Medical Association 121:289-290. Goodman, R. M. 1988. An agenda for phytopathology. Phytopathology 78:32-35. Goodman, R. M., H. Hauptli, A. Crossway, and V. C. Knauf. 1987. Gene transfer in crop improvement. Science 236:48-54. Granatstein, D. 1988. Reshaping the Bottom Line: On-farm Strategies for a Sustainable Agri- culture. Stillwater, Minn.: The Land Stewardship Project. Hall, J. K., N. L. Hartwig, and L. D. Hoffman. 1984. Cyanazine losses in runoff from no- tillage corn in "living" and dead mulches vs. unmulched, conventional tillage. Journal of Environmental Quality 13~1~:105-110. Harwood, R. R. 1983. International overview of regenerative agriculture. Pp. 24-35 in Proceed- ings of the Workshop on Resource-Efficient Farming Methods for Tanzania, I. M. R. Se- moka, F. M. Shao, R. R. Harwood, and W. C. Liebhardt, eds. Emmaus, Pa.: Rodale Press. Hazelwood, G. P., S. P. Mann, C. G. Orpin, and M. P. M. Romaniec. 1986. Prospects for the genetic manipulation of rumen microorganisms. In Recent Advances in Anaerobic Bacte- riology, Anaerobic Discussion Group, Proceedings of the Fourth Annual Meeting, July 1985, S. P. Vorriello, ed. Boston: Martinus Nijhoff. Heady, E. O. 1948. The economics of rotations with farm and production nolirv ~nnlir~tir~nc Journal of Farm Economics 30~4~:645-664. ~ ~ _ 1 ~ ~ ~ ~ ~ ~ . _ an__ ~ ~ ~ t~ ~ ~~AA~~AVAL=- neacy, a. A., and lo. K. Jensen. -'95-~. the Economics of Crop Rotations and Land Use: A Fundamental Study in Efficiency with Emphasis on Economic Balance of Forage and Grain Crops. Research Bulletin 383, August. Ames, Iowa: Agricultural Experiment Sta- tion, Iowa State University. Heichel, G. H. 1987. Legumes as a source of nitrogen in conservation tillage systems. Pp. 29- 35 in The Role of Legumes in Conservation Tillage Systems, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Hendrix, P. F., R. W. Parmelee, D. A. Crossley, Jr., D. C. Coleman, E. P. Odum, and P. M. Groffman. 1986. Detritus food webs in conventional and no-tillage agroecosystems. Bio- science 36~6~:374-380. Holben, F. J. 1956. History of the Jordan plots: Practices, changes, and people. Pp. 5-11 in Jordan Soil Fertility Plots, Agricultural Experiment Station Bulletin 613, F. l. Holben, ed. University Park, Pa.: Pennsylvania State University. Holland, E. A., and D. C. Coleman. 1987. Litter placement effects on microbial and organic matter dynamics in an agroecosystem. Ecology 68:425-433. House, G. J., B. R. Stinner, D. A. Crossley, Jr., E. P. Odum, and G. W. Langdale. 1984. Nitrogen cycling in conventional and no-tillage agroecosystems on the southern Pied- mont: An ecosystem analysis. Journal of Soil and Water Conservation 39:194-200. Hoveland, C. S., S. P. Schmidt, C. C. King, Jr., J. W. Odom, E. M. Clark, l. A. McGuire, L. A. Smith, H. W. Grimes, and J. L. Holliman. 1983. Steer performance and association of Acremonium coenophialum fungal endophyte on tall fescue pasture. Agronomy Journal 75:821.

192 ALTERNATIVE AGRICULTURE Howard, A. 1943. An Agricultural Testament. New York: Oxford University Press. Hoy, M. 1985. Recent advances in genetics and genetic improvements in Phytosiidae. Annual Review of Entomology 30:345-370. Hoyt, S. C., and E. C. Burts. 1974. Integrated control of fruit pests. Annual Review of Entomology 19:231-252. Huber, D. M., C. G. Painter, H. C. McKay, and D. L. Peterson. 1968. Effect of nitrogen fertilization on take-all of winter wheat. Phytopathology 58:1470-1472. Ibrahim, M. N. M., and G. R. Pearce. 1983. Effects of chemical pre-treatments on the com- position and in vitro digestibility of crop by-products. Agricultural Wastes 5:135. Ingham, R. E., l. A. Trofymow, E. R. Ingham, and D. C. Coleman. 1985. Interactions of bacteria, fungi, and their nematode grazers: Effects on nutrient cycling and plant growth. Ecological Monographs 55:119-140. Institute of Medicine. 1989. Human Health Risks with the Subtherapeutic Use of Penicillin or Tetracyclines in Animal Feed. Washington, D.C.: National Academy Press. Jones, J. P., and S. S. Waltz. 1981. Fusarium-incited diseases of tomato and potato and their control. Pp. 157-168 in Fusarium: Diseases, Biology, and Taxonomy, P. E. Nelson, T. A. Toussoun, and R. l. Cook, eds. University Park, Pa.: Pennsylvania University Press. Kerley, M. S., G. C. Fakey, Jr., and L. L. Berger. 1985. ALkaline hydrogen peroxide treatment unlocks energy in agricultural by-products. Science 230:820-822. KiLkenny, M. R. 1984. An Economic Assessment of Biological Nitrogen Fixation in a Farming System of Southeast Minnesota. M.S. thesis, University of Minnesota, St. Paul. Klasing, K. C., D. E. Laurin, R. C. Peng, and D. M. Fry. 1987. Immunologically mediated growth depression in chicks: Influence of feed intake, corticosterone and interleukin I. Journal of Nutrition 117:1629-1637. Kliebenstein, J. B., C. L. Kirtley, and M. L. Killingsworth. 1981. A comparison of swine production costs for pasture, individual, and confinement farrow-to-finish production facilities. Special Report 273. Columbia, Ma.: Agricultural Experiment Station, University of Missouri. Klopfenstein, T. J. 1978. Chemical treatment of crop residues. Journal of Animal Science 46:841. Klopfenstein, T. I., and F. G. Owen. 1981. Value and potential use of crop residues and by- products in dairy rations. Journal of Dairy Science 64~6~: 1250. Koemer, P. T., and I. F. Power. 1987. Hairy vetch winter cover for continuous corn in Nebraska. Pp. 57-58 in The Role of Legumes in Conservation Tillage Systems, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Liss, R. H., and F. R. Batchelor. 1987. Economic Evaluations of Antibiotic Use and Resistance: A Perspective. Report of Task Force 6. Reviews of Infectious Diseases 9(Suppl. 3~:297-312. Marten, G. C., R. M. Jordan, and A. W. Hovin. 1981. Improved lamb performance associated with breeding for alkaloid reduction in reed canary grass. Crop Science 21:295. Meisenbach, T. 1983. Alternative Farming Task Force Report. Lincoln, Nebr.: University of Nebraska. Mickley, L. D., and M. W. Fox. 1987. The case against intensive farming of food animals. Pp. 257-272 in Advances in Animal Welfare Science 1986/1987, M. W. Fox and L. D. Mickley, eds. Boston: Martinus Nijhoff. Mitchell, M., and J. Nakas, eds. 1986. Microbial and Faunal Interactions in Natural and Agro- Ecosystems. Amsterdam: Martinus Nijhoff. Momont, H. W., and B. E. Sequin. 1985. Prostaglandin therapy and the postpartum cow, No. 17. The Bovine Proceedings (April): 89-93. National Mastitis Council. 1987. Current Concepts of Bovine Mastitis, 3d ed. Arlington, Va.: National Mastitis Council. National Research Council. 1987a. Biological Control in Managed Ecosystems. Pp. 55-68 in Research Briefings 1987. Washington, D.C.: National Academy Press. National Research Council. 1987b. Regulating Pesticides in Food: The Delaney Paradox. Washington, D.C.: National Academy Press.

RESEARCH AND SCIENCE 193 National Research Council. 1988. Designing Foods: Animal Product Options in the Market- place. Washington, D.C.: National Academy Press. Neely, C. L., K. A. McVay, and W. L. Hargrove. 1987. Nitrogen contribution of winter legumes _O_~ - --I—~^ -a to no-till corn and grain sorghum. Pp. 48~9 in The Role of Legumes in Conservation Tillage Systems, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Olson, R. A., K. D. Frank, P. H. Grabouski, and G. W. Rehm. 1981. Economic and Agronomic Impacts of Varied Philosophies of Soil Testing. No. 6695 Journal Series. Lincoln, Nebr.: Agricultural Experiment Station, University of Nebraska. OltJen, R. R., D. E. Ullrey, C. B. Ammerman, D. R. Ames, C. A. Baile, T. H. glosser, G. L. Cromwell, H. A. Fitzhugh, D. E. Gall, Z. Helsel, R. E. Hungate, L. S. Jensen, N. A. Jorgensen, L. J. Koong, D. Meisinger, F. N. Owens, C. F. Parker, W. G. Pond, R. L. Preston, and H. S. Teague. 1980. Animal Nutrition and Digestive Physiology. Pp. 69-91 in Animal Agriculture Research to Meet Human Needs in the 21st Century, W. G. Pond, R. A. Merkel, L. D. McGilliard, and J. Rhodes, eds. Boulder, Cola.: Westview Press. Osteen, C. D., E. B. Bradley, and L. I. Moffitt. 1981. The Economics of Agricultural Pest Control: An Annotated Bibliography, 1960-1980. Bibliographies and Literature of Agricul- ture No. 14. Economics and Statistics Service. Washington, D.C.: U.S. Department of Agriculture. Oswald, J. W., and D. N. Wright. 1950. Potato scab control. California Agriculture 4~4~:11-12. Paige, J. C., and R. Kent. 1987. Tissue residue briefs. FDA Veterinarian 2~6~:10-11. Phillips, R. E., R. L. Blevins, G. W. Thomas, W. W. Frye, and S. H. Phillips. 1980. No-tillage agriculture. Science 208:1108-1113. Pimentel, D., G. Berardi, and S. Fast. 1984. Energy efficiencies of farming wheat, corn, and potatoes organically. Pp. 151-161 in Organic Farming: Current Technology and Its Role in a Sustainable Agriculture, Special Publication No. 46, D. F. Bezdicek and I. F. Power, eds. Madison, Wis.: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America. Power, J. F. 1987. Legumes: Their potential role in agricultural production. American Journal of Alternative Agriculture 2~2~:69-73. Randall, G. W., and P. L. Kelly. 1987. Soil test comparison study. Pp. 145-148 in A Report on Field Research in Soils. Miscellaneous Publication No. 2(Revised)-1987. St. Paul, Minn.: University of Minnesota Agricultural Experiment Station. Rice, R. E., and P. Kirsch. In press. Mating disruption of the oriental fruit moth in the United States. In Behavior-Modifying Chemicals for Insect Management: Applications of Phero- mones and Other Substances, R. L. Ridgway, R. M. Silverstein, and M. N. Inscoe, eds. New York: Marcel Deklcer. Ridgway, R. L., and S. B. Vinson, eds. 1977. Biological Control by Augmentation of Natural Enemies. New York: Plenum Press. Robbins, J. D. 1983. The tall fescue toxicosis problem. Pp. 1-4 in Proceedings of a Tall Fescue Toxicosis Workshop. Athens, Gal: Cooperative Extension Service, University of Georgia College of Agriculture. Sauer, T. I., and T. C. Daniel. 1987. Effect of tillage system on runoff losses of surface-applied pesticides. Soil Science Society of America Journal 51:410~15. Schroth, M. N., and I. G. Hancock. 1985. Soil antagonists in IPM systems. Pp. 415-431 in Biological Control in Agricultural IPM Systems, M. A. Hay and D. C. Herzog, eds. Orlando, Fla.: Academic Press. Selye, H. 1950. The Physiology and Pathology of Exposure to Stress: A Treatise Based on the Concepts of the General Adaptation Syndrome and the Diseases of Adaptation. Mon- treal: ACTA Publications. Settle, W. H., L. T. Wilson, D. L. Flaherty, and G. M. English-Loeb. 1986. The variegated leaf hopper: An increasing pest of grapes. California Agriculture 40~7&8~:30-32. Shrader, W. D., and R. D. Voss. 1980. Soil fertility: Crop rotation vs. monoculture. Crops and Soils Magazine 7:15-18. Smith, I. S. C. 1988. Diversity of United States hybrid maize germplasm: Isozymic and chromatographic evidence. Crop Science 28:63-69.

194 ALTERNATIVE AGRICULTURE Springman, R. E., T. C. Daniel, E. E. Schulte, and L. G. Bundy. 1986. Soil fertility guidelines for conservation tillage corn. University of Wisconsin Extension Bulletin A3369. Stalker, D., W. R. Hiatt, and L. Comai. 1985. A single amino acid substitution in the enzyme 5-enolpyruvylshikimate-3-phosphate synthase confers resistance to the herbicide gly- phosate. Journal of Biological Chemistry 26:4724-4728. Studemann, J. A., S. R. Wilkinson, W. A. Jackson, and J. l. Jones, Jr. 1973. The association of fat necrosis in beef cattle with heavily fertilized fescue pastures. Pp. 9-22 in Proceedings of the Fescue Toxicity Conference. Columbia, Mo.: Cooperative Extension Service, Uni- versity of Missouri. Tweedy, B. G. 1983. The future of chemicals for controlling plant diseases. Pp. 405-415 in Challenging Problems in Plant Health, T. Kommendahl and P. H. Williams, eds. St. Paul, Minn.: American Phytopathological Society. U.S. Department of Agriculture. 1978. Improving Soils with Organic Wastes. Report to the Congress in Response to Section 1461 of the Food and Agriculture Act of 1977 (P.L. 95- 113~. Washington, D.C. U.S. Department of Agriculture. 1980. Report and Recommendations on Organic Farming. Washington, D.C. U.S. Department of Agriculture. 1987. Fertilizer Use and Price Statistics, 1960-85. Statistical Bulletin No. 750. Economic Research Service. Washington, D.C. University of Kentucky. 1978. Liming Acid Soils. Leaflet AGR-19. Lexington, Ky. Van Dyne, D. L., and C. B. Gilbertson. 1978. Estimating U.S. Livestock and Poultry Manure and Nutrient Production. Economics, Statistics, and Cooperatives Service. Washington, D.C.: U.S. Department of Agriculture. Varco, J. J., W. W. Frye, M. S. Smith, and I. H. Grove. 1987. Legume nitrogen transformation and recovery by corn as influenced by tillage. P. 40 in The Role of Legumes in Conserva- tion Tillage Systems, J. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Voss, R. D., and W. D. Shrader. 1984. Rotation effects and legume sources of nitrogen for corn. Pp. 61-68 in Organic Farming: Current Technology and Its Role in a Sustainable Agriculture, Special Publication No. 46, D. F. Bezdicek and l. F. Power, eds. Madison, Wis.: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America. Webb, J. R. 1982. Rock phosphate-superphosphate experiment. Pp. 7-9 in Northern Research Center Annual Progress Report. ORC81-14, Vol. 22. Clarion-Webster Research Center. Ames, Iowa: Iowa State University. Webb, J. R. 1984. Rock phosphate-superphosphate experiment. Pp. 5-7 in Northwest Research Center Annual Report. ORC83-29. Ames, Iowa: Iowa State University. Wedin, W. F., H. J. Hodgson, ]. E. Oldfied, K. l. Frey, C. W. Deyoe, R. S. Emergy, L. Hahn, V. W. Hays, C. H. Herbel, J. S. Hillman, T. l. Klopfenstein, W. E. Larson, V. L. Lechten- berg, G. C. Marten, P. W. Moe, D. Polin, J. M. Sweeten, W. C. Templeton, P. J. VanSoest, R. L. Vetter, and W. 1. Waldrip. 1980. Feed production. Pp. 153-191 in Animal Agriculture Research to Meet Human Needs in the 21st Century, W. G. Pond, R. A. Merkel, L. D. McGilliard, and ]. Rhodes, eds. Boulder, Colo.: Westview Press. Wilhelm, S., and A. O. Paulus. 1980. How soil fumigation benefits the California strawberry industry. Plant Disease 64:264-270. Williams, W. A., and l. H. Dawson. 1980. Vetch is an economical source of nitrogen in rice. California Agriculture 34~8&9~:15-16. Young, C. E., B. M. Crowder, J. S. Shortle, and ]. R. Alwang. 1985. Nutrient management on dairy farms in southeastern Pennsylvania. Journal of Soil and Water Conservation 40~5~:443-445. Zachariassen, J. A., and J. F. Power. 1987. Soil temperature and the growth, nitrogen uptake, dinitrogen fixation, and water use by legumes. Pp. 24-26 in The Role of Legumes in Conservation Tillage Systems, l. F. Power, ed. Ankeny, Iowa: Soil Conservation Society of America. Zimmerman, D. R. 1986. Role of subtherapeutic levels of antimicrobials in pig production. Journal of Animal Science 62(Suppl. 3~:6-17.

Next: 4 Economic Evaluation of Alternative Farming Systems »
Alternative Agriculture Get This Book
×
Buy Paperback | $49.95
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

More and more farmers are adopting a diverse range of alternative practices designed to reduce dependence on synthetic chemical pesticides, fertilizers, and antibiotics; cut costs; increase profits; and reduce the adverse environmental consequences of agricultural production.

Alternative Agriculture describes the increased use of these new practices and other changes in agriculture since World War II, and examines the role of federal policy in encouraging this evolution, as well as factors that are causing farmers to look for profitable, environmentally safe alternatives. Eleven case studies explore how alternative farming methods have been adopted--and with what economic results--on farms of various sizes from California to Pennsylvania.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!