Cultivars vary considerably in how they respond to moisture stress throughout crop development. In areas of the Pacific Northwest with less than 250 mm of annual rainfall, win ter wheat is under moisture stress most of the time from planting to harvest. Cultivars must be ab le to absorb moisture, germinate, and emerge under high temperature, poor seed zone moisture, and deep seed cover. Moisture stress slows emergence and seedling development and reduces most yield components, including number of tillers, seeds per spike, seeds per unit area, seed size, and seed weight per unit volume. Additionally, leaf senescence and maturity are earfy under moisture stress conditions. A cultivar cannot obtain its potential yield with less than adequate moisture; therefore, under moisture stress fewer tillers and seeds are produced. Which plant structures are reduced is determined by the growth stage of the plant during stress, while the extent of this reduction is determined by the severity of moisture stress and the genotype of the cultivar.

Biodynamic agriculture is an organic farming system that utilizes fermented herbal and mineral preparations as compost additives and field sprays. This study was conducted to determine whether biodynamic preparations affect lentil and wheat growth and yield, soil fertility, or weed populations in the short run. Each of four nutrient treatments, biodynamically prepared compost, non-biodynamic compost, mineral NPK fertilizer, and no fertilizer, were tested with and without biodynamic field sprays. Crop yield, crop quality, and soil fertility were similar in plots treated with mineral NPK fertilizers, biodynamic compost, or non-biodynamic compost. Use of compost raised soil pH from 6.0 without compost to 6.5 with compost. Compost application reduced the broadleaf weed population by 29% and reduced the grass weed population by 78%. Biodynamic sprays altered soil and grain N chemistry, but the effects are of unknown biological significance. Use of the biodynamic field sprays correlated with higher yield of lentil per unit plant biomass, lower grain C and crude protein contents, greater content in soft white spring wheat, and greater content in soil. In general, soils and crops treated with biodynamic preparations showed few differences from those not treated. Application of composts with or without the preparations produced similar crop yields with lower weed pressure, compared with equal nutrients supplied by mineral fertilizer, but any additional short-term benefits from biodynamic preparations remain questionable.

New crop production technologies developed in response to growing concern over environmental contamination from agriculture may be neither more profitable nor higher yielding than the systems they replace, but they often reduce environmental contamination or improve soil and water quality. Systems designed with environmental objectives cannot be evaluated fairly just by productivity, which is what often is done in economic studies of alternative systems. We review 58 recent studies comparing alternative crop production systems to identify the key criteria for system comparisons, the system characteristics important in designing the analysis, and the methods most suited for comparing alternative systems.

The four key criteria we looked for in system comparisons are expected profit, stability of profits, expected environmental impacts, and stability of environmental impacts. Most economic studies of crop production focus exclusively on profitability, and incorporate neither environmental criteria nor the dynamic characteristics inherent in alternative systems. We identify promising new approaches that take account of specific environmental characteristics and attempt to balance the objectives of profitability and environmental risk management. Balanced environmental-economic analysis is most likely to be achieved by integrating biophysical simulation models with economic optimization methods to model the trade-offs among profitability, environmental impact, and system stability (both financial and environmental).

Many farmers view with skepticism the dominant agricultural research and extension education model, in which new knowledge on f arming practices is developed by researchers and delivered through extension programs. The participatory research and education model is designed to support a shared vision of research and education as a learning process among partners working in community. The participatory model is offered as a way to achieve better communication and enhanced cooperation among farmers, researchers and extension educators.

Moderate to large scale California growers (as well as small scale ones) manipulate cropping patterns in a number of ways to reduce pest problems. Crop rotation, which can be defined as diversifying crops over time, is used to manage selected pests, primarily weeds, pathogens, and nematodes. As a substitute for pesticides, crop rotation has been most rewarding in the control of nematodes; sugarbeet cyst and root knot nematode examples are detailed. Some pests that invade fields from nearby areas can be managed by modifying adjacent cropping patterns or practices; Pierce's disease of grapes, sugarbeet yellows and border harvesting of alfalfa are given as examples. Finally, multiple crops can be grown within a single field or orchard. Although this approach is not widely practiced by many California growers, two examples of systems where intercropping has been shown to limit pest numbers without the use of pesticides are described: intercropping of cotton with alfalfa and companion planting oats when seeding alfalfa. These examples show that using crop diversification to manage pests is feasible, but growers must be strongly motivated to make the necessary changes in cropping patterns. Most of the systems that have been widely adopted are those for which few other economically feasible methods were available.

The most widely used and successful cultural practices for managing plantparasitic nematodes are resistant cultivars and some elements of cropping systems, such as rotation crops, cover crops, or nematode-antagonistic crops. Exclusion and sanitation practices, such as use of nematode-free planting material, site selection, and weed management, are useful in limiting infestations. Soil solarization, organic amendments, biological control, fallow, flooding, timing of planting dates, or tillage practices may be helpful in some areas, but additional research is needed to optimize their use. Most management methods emphasize reduction of nematode populations, but improvement of crop tolerance to nematodes should not be overlooked. For their successful use, most of these alternative methods require detailed knowledge of nematode and plant biology and ecology, and it may be necessary to integrate several practices for maximum nematode suppression. Although the basic principles of nematode management are generally known, detailed data often are lacking on specific combinations of nematodes and host crop cultivars. Consequently, the availability of such data will likely determine whether nematodes can be managed successfully in a particular situation.

Serious side effects from the conventional use of traditional chemical pesticides for routine arthropod pest management have prompted the investigation and development of alternate strategies for the minimization of pest damage. Insect sex pheromones have been proposed as a potential group of alternative control agents for over twenty years. The possible uses of these substances for insect control are discussed and factors influencing their development for pest management are presented. The scientific research and commercial development of oriental fruit moth mating disruption is presented as a case study for the commercialization of this approach. Advantages and limitations of pheromone-based control tactics are presented. Mating disruption technology is starting to find its place in a number of diverse cropping situations. The use of pheromones for pest control promises to be an important component of the ongoing challenge to develop alternatives that may help to solve major environmental and human health problems associated with chemical pesticide use in agriculture.

A simple method of estimating changes in biologically active soil carbon (C) could help evaluate soil quality impacts of alternative management practices. Most reports of permanganate for active C determination use highly concentrated solutions (0.333 M) that are difficult to work with and tend to react with a large fraction of soil C that is not well distinguished from total organic C. We report on a highly simplified method in which dilute, slightly alkaline KMnO4 reacts with the most readily oxidizable (active) forms of soil C, converting Mn(VII) to Mn(II), and proportionally lowering absorbance of 550 nm light. The amount of soil C that reacted increased with concentration of KMnO4 used (0.01 to 0.1 M), degree of soil drying (moist fresh soil to air-dried for 24 hour) and time of shaking (1–15 minutes). Shaking of air-diy soil in a 0.02 M KMnO4 solution for 2 minutes produced consistent and management-sensitive results, both in the laboratory and with a field kit that used a hand-held colorimeter. Addition of 0.1 M. CaCl2 to the permanganate reagent enhanced settling of the soil after shaking, eliminating the need for centrifugaron in the field kit. Results from the laboratory and field-kit protocols were nearly identical (R2 = 0.98), as were those from an inter-laboratory sample exchange (R2 = 0.91). The active soil C measured by the new procedure was more sensitive to management effects than total organic C, and more closely related to biologically mediated soil properties, such as respiration, microbial biomass and aggregation, than several other measures of soil organic C.

Panels of 40 to 60 “non-expert” consumers attempted to distinguish between the taste of organically and conventionally grown fruits and vegetables. Wherever possible, samples of the two types of produce were obtained by picking them in the growing orchards/fields to avoid any question of authenticity, and cold-stored without treatment under the same conditions, for periods reflecting their shipping time to markets. Some physical, chemical, and instrumental analytical tests were also performed. No consistent preference pattern emerged. For grapefruit, grapes, carrots, spinach, sweet corn and tomatoes, the differences in hedonic ratings and scores between the two types of produce were not significant. For mangoes and orange juice, the conventional type was preferred, while the reverse was true for bananas; in each of these three instances the result could be ascribed to fruit being tasted closer to its optimum maturity.

Screening tests were performed to detect any traces, at the parts-per-billion level, of chlorinated hydrocarbons and organophosphorus compounds used as pesticides, or their degradation products. No traces were detected in any of the samples examined (bananas, grapes, carrots, spinach, sweet corn or tomatoes), whether organically or conventionally grown. In those samples examined (bananas, grapes, carrots, spinach, sweet corn and tomatoes) by quantitative tests for the three major fertilizer elements used conventionally (NPK), nitrogen and phosphorus concentrations were not consistently greater, while potassium concentrations were either equal or greater, than in the organically grown samples. Among the anion analyses performed on orange juice, grapefruit juice, carrots, spinach and tomatoes, nitrates and particularly nitrites either were not detected, or occurred at negligible concentrations in all samples. Phosphates were found at higher concentrations, but not significantly so, in four of the five organic products tested; no phosphates were detected in either type of tomatoes.

Excessive nitrogen fertilizer use in corn production has resulted in widespread nitrate pollution of ground water and economic losses for farmers. In addition, reliance on nitrogen fertilizers produced with large amounts of fossil fuels may not be economically or environmentally sustainable in the future. Although leaching of significant amounts of nitrate to the ground water is inherent in growing corn, several techniques are available for more environmentally and agronomically sound management. The following management practices are discussed in this article: sidedress as the main method of N fertilizer application; the pre-sidedress (Magdoff) nitrate soil test; farm-based nitrogen sources (manures, green manures, and rotations with sod crops); cover crops for lowering profile nitrate during the most likely period for leaching; and the end of season stalk nitrate test.

Soil physical and biological properties often change when different cropping, tillage, or management systems are imposed. Changes occasionally occur quickly, but usually become evident only after months or years. Infiltration rates are affected by several soil properties and may provide the most sensitive indication of changes in soil properties. To evaluate the use of infiltration measurements for detecting changes in soil properties, we conducted infiltration tests on a cropping systems experiment, a tillage experiment, and two beef cattle grazing experiments. In Pennsylvania, significant changes in infiltration rates did not occur until more than four years after converting from a conventional to a low-input cropping system. Infiltration rates were higher on 14th-year no-till plots compared with moldboard plow and chisel treatments in an Iowa tillage study. Earthworm populations and activity were highest in the no-till treatment. Infiltration rates correlated negatively with increased stocking rates in a long-term beef grazing study in Oklahoma. The number of earthworms did not correlate positively with infiltration in this study, suggesting a complex interaction. A short-term study of overwinter beef corn-stalk grazing in Iowa did not show consistent patterns in infiltration rate or other soil properties with different stocking rates. Infiltration appears to be a good indicator of soil structural changes associated with cropping, tillage, and management systems.

Traditional agricultural systems that have met the test of sustainability have not been able to respond adequately to modern rates of growth in demand for agricultural commodities. A meaningful definition of sustainability must include the enhancement of agricultural productivity. At present, the concept of sustainability is more adequate as a guide to research than to farming practice.

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.

Understanding farmers' knowledge of soil quality and health is essential to ensure transfer of appropriate technology for on-farm assessments. The objective of this study was to evaluate farmers' knowledge of soil quality by comparing their perceptions of soil conditions for “good” and “problem” soils on their farms with values of soil quality indicators as determined by established assessment protocol. Twenty-four conventional and organic farmers throughout eastern Nebraska were paired within regions of similar climate, topography, and soil type and their perceptions of soil quality indicators were queried using a written questionnaire. Questionnaire data were compared directly to values of soil quality indicators and perception accuracy indices were calculated. Overall, perception accuracy of soil quality indicators did not differ between conventional and organic farmers. Farmers' perceptions of soil quality indicators tended to be more accurate for “good” soils as compared to “problem” soils. Indicators that were incorrectly estimated at a frequency greater than 33% included available nitrogen and phosphorus, soil color, degree of compaction, and infiltration rate. Despite this, farmers' perceptions were correct or nearly-correct over 75% of the time for the majority of indicators evaluated in the study. Evaluation of social and managerial factors indicated that perception accuracy of soil quality indicators declined as the time of on-farm tenure increased. Results from this study indicate that agriculturists should seek out farmers' knowledge of soil characteristics as a first iteration to pointscale evaluation of soil quality.

Agricultural research conducted in the United States since establishment of the U.S. Dept. of Agriculture and Land-Grant University System in 1862 has shown that regular and proper additions of organic materials are very important for maintaining the tilth, fertility, and productivity of agricultural soils, protecting them from wind and water erosion, and preventing nutrient losses by runoff and leaching. Several millennia earlier, Roman agriculturists were advocating crop rotations, green manuring, composts, legumes, farmyard manures, crop residues, wood ashes, seaweed, and sewage wastes for supplying humus and nutrients to restore or enhance soil productivity. Even earlier, Asian farmers also used these practices to maintain healthy and productive soils. Today the most serious problem in U.S. agriculture and agriculture worldwide is the widespread degradation of agricultural soils through erosion and the consequential decline in productivity. In view of how much information is available on the benefits of organic recycling on agricultural lands, one wonders why we aren't doing a better job of protecting and conserving our land resource base. We discuss strategies for using organic resources more effectively to achieve a more sustainable agriculture for the future.

In this paper, we criticize recent definitions of sustainable agriculture as being overly based on short-term economic criteria, rather than long-term ecological criteria. A concise definition of sustainable agriculture is put forth, premised on the assumption that the ecological parameters of energetics and ecosystem integrity ultimately determine the long-term viability of farming systems. We share with others the view that, in designing sustainable farming systems, a broad array of social and economic factors should be taken into consideration. We believe, however, that these factors are not intrinsic to a sustainable agriculture, but rather separate, desirable goals.

In many respects the long standing and vigorous debates over alternative agriculture and organic farming are becoming less strident and less polarized. However, despite the mounting evidence that key elements of both the conventional and alternative agricultural communities are beginning to “build bridges” to each other, and to establish formal institutional programs and arrangements for improved communication and program development, important differences continue to separate the proponents and opponents of alternative agriculture. In part, these lingering differences result from the lack of adequate and reliable data, misinformation, and faulty data analyses. In order to clarify those issues which continue to divide the critics and advocates of alternative agriculture, this reappraisal of the debate begins with a methodological critique of comparison studies of conventional and organic farms. Also included is an assessment of fertilizer and pesticide use in American agriculture, the environmental impacts of conventional and reduced-input systems, the relationship between alternative agriculture and efforts to save the family farmer, and the prospects for increased public sector research on reduced-input farming systems.

Conventional and organic semidwarf Granny Smith apple production systems were compared during three years of conversion to certified organic management. Because of differences in fruit load with hand thinning compared with chemical thinning, apple tonnage was higher in the organic production system (OPS) in 1989 and 1991. The organic system was higher than the conventional system in number and weight of fruit per tree, but smaller in average fruit size. Using grower-receivedfarmgate premiums of 38% (1990) and 33% (1991) for unsorted, certified organic apples, comparative cost accounting showed greater net return per hectare for the OPS. The OPS required higher material and labor inputs in all years.

Greater terminal growth in the conventional production system (CPS) in 1991 was the only significant difference in growth indicators between systems. N was generally higher in leaf and new wood bark tissues in the CPS. P was generally higher in the leaf and new wood bark tissues in the OPS. No decline in yield was associated with increased weed biomass in the OPS. There was no difference in fruit damage caused by codling moth between production system treatments (codling moth granulosis virus and pheromone-based mating disruption vs. synthetic insecticide). In 1991, secondary lepidopterous pests (apple leafroller and orange tortrix) caused greater fruit scarring in the CPS. In all years, tentiform leafminers caused greater leaf damage in the CPS. Apple leafhopper density and leaf damage were greater in the OPS in 1990 and 1991.

Soil nutrient levels showed few significant changes during conversion to organic management. Soil bulk density and water holding capacity were useful indicators of changes in soil physical characteristics. Potentially mineralizable nitrogen andmicrobial biomass-C were more sensitive indicators of system change than total N or organic C. Two soil biological ratios, the respiratory ratio and biomass-C/total organic-C, were similar in the two production systems. Earthworm biomass and abundance increased in the OPS in the third year. The introduction of Lumbricus terrestris into the OPS greatly increased litter incorporation rates.

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.