Several factors can directly or indirectly affect the nutritional quality of crops. Among these are soil factors, such as pH, available nutrients, texture, organic matter content and soil-water relationships; weather and climatic factors, including temperature, rainfall and light intensity; the crop and cultivar; postharvest handling and storage; and fertilizer applications and cultural practices. This paper deals primarily with fertilizer and cultural management practices, and on certain environmental factors that affect the nutritional quality of field crops and of fruits and vegetables. Earlier research that has investigated the nutritional status of crops grown with either chemical fertilizers or organic fertilizers is discussed. These studies often have given contradictory results on crop yields and on crops' mineral and vitamin contents. Other factors, such as maturity at harvest, postharvest handling and storage, anti-nutritive components, and residues of chemical fertilizers and pesticides are reviewed with respect to food safety and quality, and their implications for human and animal health. Future research needs are identified so that comparable results and valid comparisons can be obtained to identify the best management practices to ensure that food is safe and nutritious for the consumer.

Conversions from conventional to sustainable farming systems could affect local rural economies either positively or negatively, by several means: changes in income of agricultural households; backward linkages to input supply firms; forward linkages to transportation, processing, and marketing firms; and changes in consumer expenditures by agricultural and other households. We estimated these effects for five local rural economies in South Dakota, representing different agroclimatic and population settlement patterns. Whole-farm economic models of case study conventional and sustainable farms in each area were used to estimate differences in input purchase and marketing patterns. We found declines in on-farm personal income (returns to farm labor and management) in four of the five case comparisons under a conversion to sustainable farming systems if organic price premiums are ignored; we found increases in three of five cases if applicable organic premiums are included. In all five study areas, total off-farm personal income drops in the portions of local economies connected to farming through backward linkages. It also drops in four of the five study areas in the portions of local economies connected through forward linkages if organic premiums are ignored (all five if organic premiums are included). However, net forward linkage effects are usually much smaller than net backward linkage effects, and on-farm personal income effects are substantially greater than either backward or forward off-farm linkage effects in most cases. The total (on-and off-farm) personal income effect of converting to sustainable systems is positive in only one area without organic premiums, and in one additional area with premiums. The ratio of total to on-farm personal income effects within local economies, considering only first round effects on backward- and forward-linked firms, averages 1.2 without organic premiums, or 0.6 with them. Taking account of more complete multiplier effects, which also consider changes in consumer expenditures and changes in expenditures for supplies by backward- and forward-linked firms, the average is 1.8 without organic premiums, or 0.8 with them. With more time for changes in sustainable production techniques and in the structure of farms and the rural economy, the overall economic effects of conversions to sustainable farming are likely to be more positive than our estimates.

Adoption of agricultural practices that reduce or eliminate chemical use creates tradeoffs among yields and output, production costs and net income at the farm level. If widespread adoption is to occur, potential improvements in human health and the environment from reduced chemical use must be weighed against effects on aggregate farm income and consumer food prices. At present, these tradeoffs are subject to considerable debate.

I review available farm level and aggregate economic studies of reductions in total agricultural chemical use. At the farm level, available studies suggest that organic and low-input farming systems result in declines in per acre yields and in lower net returns than most conventional farming systems, although the studies do indicate that net returns for the two systems can be comparable under some conditions. Several studies suggest that low-input systems perform well with respect to risk criteria. I also discuss the potential influence of government programs on the profitability of some low-input farming systems.

All aggregate economic models conclude that widespread adoption of organic farming would result in decreased yields, decreased aggregate output, increased farm income, and large increases in consumer prices. These models have limitations, however. Recommendations are made for further economic research of the impacts of reducing agricultural chemical use at both the farm and aggregate levels.

Agroecology is the development and application of ecological theory to the management of agricultural systems, according to the specific land and other resources available. Beyond the biological and climatic dimensions of agriculture and ecology, there is growing appreciation of the influence of social, economic, and political factors on the structure and success of farming systems. This broader field is becoming known as “agroecology and sustainable development.” Expansion of the conventional curriculum to include integrative themes is essential because of the need for students to appreciate a whole farm focus for analysis, to understand the impact of socio-economic factors, and to further develop their abilities to link people and environment. Two courses are proposed and described in detail “Biology of Agroecosystems” includes study of system structure and function, cycles and interactions among components, system development and performance, and the importance of resource conservation and use. “Agroecology and Sustainable Agricultural Development” includes a survey of systems around the world, an evaluation of resources and their use, the environmental impact of agriculture, the relationships between society and agriculture, the applications of agroecology to rural development, and some projections of alternative future strategies for food production. Future agricultural professionals need to understand how improvement of agroecosystems is closely linked to economic, cultural, and political systems, and how they are both enhanced and constrained by factors beyond biology and climate.