Winter annual legume cover crops can reduce nitrogen (N) fertilizer requirements and provide a water-conserving mulch to a subsequent crop. A two-year study was designed to test cover crops of rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), and big/lower vetch (Vicia grandiflora Scopoli) for their ability to produce N and to conserve soil water for a succeeding corn (Zea mays L.) crop. We measured the cover crops' biomass, N yield, carbon (C) to N ratio, and influence on a subsequent corn crop grown under two tillage regimes (disk tillage or no-till). Nitrogen content in cover crop biomass at time of corn planting ranged from 37 to 187 kg/ha. Pure stands of hairy vetch and a mixture of hairy vetch plus bigflower vetch had generally higher N yields, and rye was lowest. Rye growing in association with hairy vetch had lower C:N ratios than rye growing alone. Legume C:N ratios remained generally unchanged from earlier (disked) to later (herbicide) kill dates, but total N and biomass typically increased in the last 2 to 3 weeks before corn planting. Soil water retention was affected by tillage in some cases; no-till was superior to disk incorporation in each case where there was a tillage effect. Cover crops with greater biomass resulted in greater soil water retention. Among cover crops, uptake ofNby corn was greater from hairy vetch or hairy vetch plus bigflower vetch mixture. Biological immobilization of N appeared to be reducing N uptake by corn grown in rye residues. Corn in nonlegume plots fertilized with 140 or 210 kg N/ha took up more N than corn following legumes, but there was no corresponding yield increase. Corn biomass yields following the cover crops ranged from 8.6 to 18.0 Mg/ha with no additional fertilizer N. In the second year of the study, average corn yields following hairy vetch (15.3 Mg/ha) or hairy-bigflower vetch mixtures (16.4 Mg/ha) were not statistically different from corn yields produced by a 140 kg N/ha fertilizer rate (17.4 Mg/ha). These results suggest N from a legume cover crop can replace or substantially reduce fertilizer N requirements in corn production systems in the Appalachian region.

Three hypersensitive resistant, six partially resistant (slow rusting), and one susceptible spring bread wheat (Triticum aestivum L.) cultivars were evaluated for grain yield, test weight, and kernel weight under artificially created epiphytotics of leaf rust disease (caused by Puccinia recondita f. sp. tritici) with and without fungicide protection for three years. Rusted plot yields were 4 percent lower compared to fungicide-protected plot yields for cultivars with hypersensitive resistance. In rusted plots, grain yield and kernel weight averaged 8 percent less for cultivars with partial resistance but varied from 2 to 20 percent less depending on cultivar. The susceptible check cultivar, Yecora 70, averaged 27 percent lower grain yield, 22 percent lower kernel weight, and 6 percent lower test weight in rusted plots. Slight reduction in test weight was also observed for each cultivar. Losses in grain yield could, therefore, be reduced to levels similar to those of hypersensitive resistant cultivars by the use of partial resistance. We discuss the sustainability of partial genetic resistance to leaf rust. Since partial resistance is expected to be durable, and since rust levels and effects on yield in farmers' fields are likely to be less than in this experimental plot study, partial resistance should give long-lasting resistance at a negligible cost in yield that is insufficient to justify the use of fungicides.

This paper discusses data on plant-nutrient conservation in Sweden between 1950 and 1980 and on plant-nutrient balances in conventional and alternative farming. The amounts of plant nutrients supplied in the form of artificial fertilizer in Sweden increased severalfold between 1950 and 1980. The amounts of N and P applied were four times higher than those recovered in agricultural products. This difference not only represents a loss to farmers but also a burden on the environment. This problem is a consequence of the increased separation of crop management from animal husbandry in Sweden. The flow of plant nutrients through the agroecosystem can be represented as follows: Artificial Fertilizers- > Crop Production-> Animal Husbandry- > Losses (air, water, or immobilization).

This paper suggests that all farms in Sweden can operate effectively without relying on applications of highly soluble plant nutrients. By recirculating plant nutrients in manure and cultivating nitrogen-fixing species, the need for artificial fertilizers can be eliminated while minimizing nutrient losses and their associated adverse effects on the environment. Successful alternative farms provide practical examples of how a farming system can eliminate its dependence on applications of highly soluble plant nutrients by stressing effective nutrient economy and biological activity. The strategies they use include: matching animal management practices to the farm's own production of feed, thereby reducing net removal of plant nutrients per unit area (in Sweden 0.6–0.8 animal units per ha); minimizing nutrient losses through careful manure management and by using cover crops; and supplying N by nitrogen-fixing ley species, and P and K by soil weathering and by applying supplementary soil improvement materials.

Chemical fertilizers are used only in a limited way under dry farming conditions in India because of their high cost and the risk of crop failures due to drought Several alternative strategies are being evaluated to reduce the cost of supplying N to castor bean without adversely affecting yield. We report the results of a two-year study on the possible replacement of fertilizer nitrogen by green leaves from Leucaena leucocephala for production of castor beans on a low fertility Alfisol Bean yield and dry matter production were significantly higher when 50 kg N/ha was applied as green leaves compared with 50 kg N/ha as urea. Among substitution levels, 37.5 kg N/ha as green leaves at planting followed by 12.5 kg N/ha as urea at 45 days after planting was found to be the most effective combination. Across all the substitution levels, addition of nitrogen as green leaves at planting was found to be better than application at 45 days after planting. Nutrient and water use efficiencies were higher when the N was applied as green leaves compared to urea. Nitrogen use efficiency was higher for green leaves than for urea under limited rainfall conditions. The overall data indicated that 75 percent of the fertilizer N requirement of castor bean can be supplied by leaves of Leucaena leucocephala when applied at planting.

Water harvesting technologies capture surface water runoff and recycle it for productive use. Despite the long history of water harvesting and the renewed interest in many places in the world, the technology has not been widely adopted in the United States, in part because of a lack of understanding of its economic benefits. We developed a simulation model for the economic evaluation of water harvesting systems that combines agronomic, engineering, and economic factors and daily meteorological data. The simulation model was used to investigate the economic feasibility of using a water-harvesting, supplemental irrigation system for grain sorghum production over a 44-year period at two locations in Texas. Water harvesting combined with supplemental irrigation was most successful where the precipitation is the highest. However, the net benefits were extremely variable from year to year. The modeled technique could not take advantage of the potential additional water in the wet years and did not harvest sufficient water in dry years to make water harvesting more economically attractive than conventional dryland farming. This does not mean that runoff farming cannot be of economic benefit, depending on local conditions. Widespread adoption of the technology is constrained by the limited profit potential the variability of the profits, and the knowledge required to use the technology successfully. The simulation model was a useful and simple tool for dealing with the complexity of the issues.

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.