The papers in this issue of the American Journal of Alternative Agriculture are devoted to the proceedings of a symposium, “The Role of Ecology in Lower-Input, Sustainable Agriculture.” This symposium was sponsored by the Ecological Society of America as a part of its annual meetings with the American Institute of Biological Sciences at The Ohio State University, Columbus, August 10, 1987. The symposium was organized for the purpose of relating ecological approaches and concepts to sustainable agriculture. Additionally, it was our intention to indicate research opportunities for ecologists in agricultural systems.

Conventional agriculture has caused economic problems associated with overproduction of crops, increased costs of energy-based inputs and lessened farm incomes. It has also produced ecological problems such as poor ecological diversity, soil erosion, and soil and water pollution. The adoption of integrated systems of agricultural production involving lower inputs of fertilizer, pesticides and cultivations can alleviate these economic and ecological problems. Such systems are dependent upon a good understanding of the nature of interactions between the four main components of such systems, which are fertilizers, pesticides, cultivations and rotations and how these interactions influence crop yields and farm income. Alternatives to energy-based inputs include legume rotations, use of waste organic matter as well as that from animals and crops, integrated pest management, pest and disease forecasting, biological and cultural pest control, living mulches and mechanical weed control, conservation tillage methods, and specialized innovative cultural techniques, including intercropping, strip cropping, undersowing, trap crops, double-row cropping. Two commercial farms in Europe operated on integrated lower input systems have increased farm incomes by 5–20 percent. Further research on such techniques is needed, as well as computer-aided management systems, appropriate extension aids and farmer education.

The variable costs and net returns for a conventionally managed rotation and for a low-input, legume-based rotation were compared under 1986 economic conditions in the Palouse region of Washington. The conventional system was a four-year wheat/barley/wheat/pea rotation with fertilizers and pesticide inputs each year. The low-input system was a three-year pea-medic/medic/wheat rotation with pesticide inputs used only on peas. As the biennial medic was allowed to set and drop seed and revolunteer in subsequent stands of spring peas, the system was called the “perpetuating-alternativelegume-system” or “PALS”. Identical wheat yields were assumed between the two systems as field trials showed that wheat which followed medic without fertilizer produced similar yields to wheat after cereals with fertilizer. Pea yields were assumed to be lower under PALS due to competition from the medic. Medic was neither harvested nor grazed. For PALS, herbicides on wheat were replaced by harrowing because trials showed that wheat after medic competed better with weeds than wheat after cereals. Variable costs for PALS were only 44 percent of those for the conventional system ($56.82 versus $129.40/acre/year). Fertilizers, pesticides, and application accounted for 56 percent of the costs for the conventional system, but only 26 percent for PALS. The conventional system generated higher gross returns because a crop was harvested every year. Because of its lower production costs, PALS generated higher net returns when crops were sold for market prices. The conventional system was more profitable than PALS only when wheat and barley were valued at current government target prices. Under high and low yielding conditions PALS was more profitable than the conventional system when wheat prices were lower than $3.50 and $5.36/bushel, respectively. Government target and local market wheat prices in 1986 were $4.38 and $2.40/bushel, respectively. If world market competition and domestic policy pressures reduce crop price supports and grain prices in the future, low-input systems would become more profitable than conventional practices. PALS is promising but requires further agronomic evaluation before recommendations can be made.

The accelerated use of agricultural chemicals over the past 20–30 years has increased production and generally has been profitable, but it has also had an adverse impact on ground water quality in many major agricultural areas. The contamination of ground water, related to nitrogen fertilizers and pesticides, from widespread, routine land application, as well as from point sources has become a serious concern. Ground water contamination also impairs surface water quality. Research, world-wide, has shown increases in NO3-N in ground water concurrent with major increases in N-fertilization. Many shallow ground water supplies now exceed recommended NO3-N drinking water standards. While many sources contribute N into the environment, synthetic fertilizers have become the major component. There are clear economic incentives to improve management; harvested crops often account for less than 50 percent of the purchased fertilizer inputs. Pesticides are appearing in ground water with unanticipated frequency, and while their concentrations are generally below acute toxic levels, many are of concern for possible chronic effects. Such widespread contamination is of real concern because of the potential for long-term and widespread exposure of the public through drinking water. Surveys of farmers indicate a desire to improve management practices and reduce chemical inputs. Promoting the principles of alternative, sustainable agriculture is a necessary element in the resolution of these problems.

Microbial activities important to effects on crop productivity and nutrient cycling can be altered by agricultural management practices. This study was conducted to determine whether soil microbial populations and their N cycling activities differ between conventional and alternative management practices. Physical, chemical, and microbial soil properties were measured at soil depth intervals of 0 to 7.5, 7.5 to 15, and 15 to 30 cm at a site in southeastern Pennsylvania during the second and fifth years after conversion from a conventional, chemically intensive system to alternative systems utilizing legumes and animal manure as N sources. In the second year after conversion, populations of fungi and bacteria, dehydrogenase activity, and soil respiration in the surface soil layer were greatest with alternative systems planted to red clover (Trifolium pratense L.). Differences in soil biological factors between management systems were related primarily to crop characteristics and, to a lesser extent, to soil physical properties. Levels of microbial populations and activities with conventional management were the same as with alternative management systems when similar crops such as corn (Zea mays L.) or soybean [Glycine max (L.) Merrill] were grown. Soil NO3-N contents, at most sampling depths, were markedly increased by application of fertilizer N or recent plow-down of red clover or hairy vetch (Vicia villosa Roth). The growth of red clover in the second year or hairy vetch in the fifth year was accompanied by significantly increased microbial biomass and potentially mineralizable N (PMN) reserves in the top 30-cm soil layer-these changes being most pronounced in the surface 0- to 7.5-cm layer. Nitrogen deficiency symptoms and lower corn grain yields in a legume/cash grain rotation as compared with conventional management in the second year were associated with lower soil NO3, levels and a greater proportion of N present as weed biomass and belowground microbial biomass. In 1985, management systems comparisons were limited to corn as the main crop; soil NO3 levels during the growing season were inversely related to soil microbial biomass and PMN levels where hairy vetch was overseeded and incorporated as green manure by plowing before corn planting. Under the conditions of this study, the use of chemicals had little effect on microbial populations, their activity, or the cycling of nitrogen. Cropping systems-in particular, the growth of red clover or hairy vetch—profoundly influenced soil microbial biomass levels and soil pools of organic and available NO3-N during the growing season. Competitiveness of alternative management systems employing legumes as? sources for grain crops may depend largely on the grower's ability to synchronize supplies of available soil N with periods of maximum uptake by grain crops.

A mailed survey was sent to 174 Midwestern organic farmers originally studied in 1977. We obtained information on 133 of this group, 96 of whom are still farming at the same location, although 12 no longer use organic methods. Fifty-eight currently active farmers returned a detailed questionnaire that covered their perceptions of the advantages and disadvantages of organic farming, some of their practices, and their financial status. Most farmers who employed organic farming methods stated they did so out of concern for the health of themselves, their families, and their livestock. Compared to ten years ago, philosophical or religious considerations were less frequently mentioned as an advantage of organic farming. In contrast, some agronomic and management disadvantages of organic f arming were mentioned more often. The farmers now are more tolerant, in principle, of some chemicals not generally accepted in organic farming, but regular use of soluble fertilizers and synthetic pesticides has not increased appreciably. The farmers reported little change in the institutional and social environment for organic agriculture, including available markets, information sources, and the attitudes of their neighbors.

Editor's note: At conferences with a focus on scientific and political information about alternative agriculture, the live stories of how individual farmers “made the switch” from chemical intensive to low-chemical farming help us to stay in touch with the issues as the farmer sees them. At the IAA symposium, Kansas farmer John Vogelsberg told the story of his choice to make that transition, delighting the audience with his dry humor, warmth, and wisdom. Following are excerpts from his reflections.

This paper has three goals: (1) to convince ecologists and evolutionary biologists to study the evolution in insects of the ability to overcome crop protection measures, (2) to provide insights into the kinds of data needed to develop methods for retarding the evolution of such traits, and (3) to suggest that the study of these phenomena can further our understanding of evolution. The evolution of resistance to chemical insecticides often results in higher application rates and constant development of new classes of these potentially environmentally degrading toxicants. Moreover, it is important to understand resistance phenomena related to alternative crop protection measures involving plant genetic resistance and biological insecticides so that these less environmentally damaging control measures can be maintained. Insecticide resistance evolves in insect populations in response to selection by chemical compounds. Similarly, selection by host-plant defenses of resistant crops leads to the evolution of virulence to those varieties. The evolution of these traits constitutes an important subject of applied evolutionary biology. In the context of single-gene evolutionary models, this article reviews the most common strategies that have been suggested for retarding the evolution of insecticide resistance. These models are also used to illustrate the effects of ecological factors and genetical properties of insect populations on the evolution of resistance. Where appropriate, the relevance of these models to the evolution of virulence to resistant crop varieties is also described. Durability in the insecticidal effectiveness of a plant protective chemical is not incompatible with the requirement for health safety in the same material.

A survey of organic farmers in New York State identified problems in need of university research. Weed management was the most frequently mentioned problem by far, identified as significant by two-thirds of the organic farmers. Only a few other problems were listed as significant, including insufficient time for farm work, lack of markets, low prices, and lack of appropriate tools. These were cited by more than a third of the farmers. Drought, insect management, and a lack of a dependable supply of labor were cited by about one-third of the respondents. The survey also examined organic farmers' information sources. They do not use conventional sources of agricultural information, such as the extension service and conventional agricultural media, as much as books, magazines, and newsletters on organic f arming, other organic f armers, and on-farm experiments. Many respondents noted that local extension agents did not know very much about non-chemical solutions to organic production problems. They considered University Extension to be accessible, but not very useful in solving problems specific to organic farming, and had many suggestions to improve Land Grant research in organic agriculture.

Low external-input agriculture seeks to optimize interactions between species that permit processes at the ecological community level to shift inputs away from nonrenewable or synthetic sources. This goal can be reached through the study of the ecological basis of an array of plant-plant and plant-insect interactions, especially in intercropping systems where particular plant mixtures are of benefit to the entire crop community. These polyculture systems can be managed for nutrient cycling efficiency and pest and disease regulation using knowledge of multi-trophic level interactions and application of recent developments in mutualism and competition theory. A mechanistic model of additive and removal reactions on the environment is proposed as a means of studying species interactions.

Editor's note: First-hand accounts of how conventional farmers are attempting to “make the switch” from chemical-intensive to low chemical farming help us understand the problems involved in this transition process. At the IAA symposium, Indiana farmer Jess (Josh) C. Andrew III presented a highly informative talk on these critical issues and questions from the perspective of the conventional farmer. The following is based upon his formal presentation and additional written materials which he submitted.

Riparian forests situated adjacent to agricultural uplands were studied to test the hypothesis that riparian forests intercept and utilize nutrients lost from these uplands. Production rates, tissue nutrient concentrations, and nutrient accretion rates of woody plants were compared between sites that were contiguous to agricultural areas (test sites) and sites that were separated from agricultural areas by grass buffer zones (reference sites). Net primary production was 10,344 kg ha–1yr–1, but trees within a riparian forest that received runoff directly from a pigpen (test site) had production rates that were 2.5 times higher than the average for all other sites. Above ground forest nutrient accretion rates were also highest at the pigpen test site. Woody plants in test site forests had, on the average, higher branch wood and leaf nutrient concentrations than plants in reference site forests. The data provide evidence that riparian forest communities within agricultural environments absorb and retain nutrients lost from agricultural uplands. As such they are important components of agricultural ecosystems helping to maintain acceptable stream water quality. It is suggested that ecologically sound agricultural practice should include longterm maintenance of natural riparian vegetation zones within agricultural areas.

The mining of sand and gravel deposits and excavation oftopsoil in urban areas have left extensive tracts of exposed subsoils that do not support plant growth because of adverse soil chemical and physical properties. Such degraded and marginal soils, or spoils, are infertile, low in organic matter, often acidic, and subject to severe erosion and surface runoff Many of these lands are owned by small and part-time farmers who wish to restore their aesthetic value and agricultural productivity. Research has shown that with liming and the proper use of organic amendments such as animal manures and sewage sludge compost, these lands can be restored to a high level of productivity in as little as three years. The methods and techniques for improving the productivity of marginal soils described in this paper can be of considerable benefit to some farmers in developed and developing countries where there is no other choice but to farm marginal soils because of the lack of highly productive agricultural lands. With increased efforts to restore the productivity of degraded and marginal soils through the use of organic amendments, conservation tillage, and crop rotations, future research should address the effect of best management practices on crop yields, the nutritional quality of crops, and the bioavailability of plant nutrients to both animals and humans.

The energy crisis of the late 1970's has raised the question of the wisdom of depending upon fertilizer nitrogen as the primary source of N input into crop production systems. While present and past price structures have favored fertilizer-N over biologically fixed N, there are a number of other benefits of legumes in a cropping system in addition to their effects on N availability. Among these are less potential for environmental degradation and improved soil physical conditions and water relations, but it is difficult to assign economic value to many such benefits. In addition to the economics of the present price structure, disadvantages of using legumes could include reduced total production and increased need for livestock in a farming enterprise (these could be considered assets from some aspects). Legumes are presently used in shortterm rotation, such as corn-soybean, or in continuous corn with a legume winter cover crop. These systems are finding widespread use and offer the producer many benefits, as well as helping to solve several major environmental problems associated with N use in agriculture.

Developing reduced-input agroecosystems is a challenge to researchers and practitioners in a number of disciplines. In particular, because of the complexity of managerial inputs, understanding the effects of decreases in levels of one or several inputs presents a difficult experimental problem. Moderate reductionism is proposed as an appropriate hierarchical analysis, which first characterizes system level behavior and then explains it in terms of system components and their interactions. An example is given using reduced nitrogen fertilizer inputs; higher nitrogen use efficiency at lower levels of input is explained by increased nutrient recycling between soil and plant subsystems. Transition from conventional to reduced-input management involves changes in both economic and ecological properties of agroecosystems. Biological, chemical and physical changes, including increased species diversity, tighter nutrient recycling, and longer-term perennial effects, may parallel ecological succession. Hypothetical trends for several such changes are discussed.