Annual legumes and mixtures of annual legumes and grasses can perform several functions as understory cover crops in pecan orchards, such as providing nitrogenrich organic matter to improve soil fertility, or by sustaining lady beetles and other arthropods that may aid the biological control of pecan pests. Remaining questions concern selection of appropriate plant materials; whether to use cover crops singly or in mixtures; how to ensure reseeding as well as a substantial N contribution; whether, when, and how to use mowing and tillage; and fertilization options. Different considerations apply when dealing with cool- vs. warm-season cover crops. With minor adjustments, growers could adapt present cultural practices to include cool-season cover crops. These could be used throughout the orchard, by establishing appropriate self-reseeding species and avoiding both excessive mowing and indiscriminate placement of N-rich fertilizers. Within alleys, alternating 2-m strips of cool-season cover crops could be tilled in mid to late April or allowed to mature. The tilled strips would supply N to pecan trees immediately, whereas the adjoining untilled (remnant) strips could be mowed after seed is mature, to ensure dispersal of seed and reestablishment of cover crops over the entire alley. Cool-season annual legumes that die or are killed in late spring will probably furnish N and other nutrients at a suitable time, particularly in orchards with sprinkler irrigation. Warm-season cover crops, if desired, should be restricted to alleys to reduce possible competition with pecan. Alleys provide better illumination than do tree rows during periods when pecan trees are in leaf, and the tillage mentioned above will encourage emergence of warm-season cover crops. If these die or are killed in late summer or early fall, timing of N release may not be optimal, in the absence of adequate irrigation. Many options and tradeoffs need to be explored before choosing a cover-crop system. Attimes, several objectives may appear to conflict, and even delicately-managed mixtures of species may not fulfill all the desired functions.

Swine production is a major component of Corn Belt agriculture; thus development of a sustainable Corn Belt agriculture depends on sustainable swine production systems. Swine are versatile enough to adapt to sustainable concepts, and swine production raises several opportunities to enhance sustainability. These include: 1) feeding with increased use of forages and by-product feeds; 2) nutrient cycling through improved handling of manure; 3) low-capital housing systems that offer an improved environment for the operator and reduced financial risk; 4) management systems suited to the swine's behavior; and 5) preventive approaches to swine health and a broader genetic base. The challenge beyond identifying the opportunities is research and technology transfer and incorporation of sustainable concepts into ecologically based swine production systems.

Combining cover crops and conservation tillage may result in more sustainable agricultural production practices. Objectives of this on-farm study were to quantify effects of cover crops on growth and nitrogen accumulation by soybean [Glycine max (L.) Merr,] and corn (Zea mays L.) on a Nicollet loam (fine-loamy, mixed, mesic Aquic Hapludoll) near Boone, Iowa, Our farmer-cooperator planted soybean in 1988 using ridge tillage into an undisturbed strip with a hairy vetch (Vicia villosa L. Roth) cover crop and into a strip where previous crop residue and a negligible amount of cover crop had been incorporated by autumn and spring disking. In each strip, we established four plots for soil and plant measurements. Our cooperator planted corn on the same strips in 1989 into a cover crop that consisted of both hairy vetch and winter rye (Secale cereale L.). We determined the source of N accumulated by the corn by applying 67 kg N/ha of 15N depleted NH4NO3 fertilizer. In the absence of cover crops, early season soil NO3-N levels in the top 30 cm were higher, and corn growth and N accumulation were more rapid. At harvest, the corn grain, stover, and cob together accounted for 36 and 39 percent of the 15N fertilizer for the ridge tillage and disked treatments, respectively. We suggest that lower net mineralization of organic matter or greater denitrification losses before planting reduced the availability of soil N, This created an early season Nstress in corn grown with cover crops that was not overcome by broadcast fertilizer N applied three weeks after planting. Our on-farm research study has helped focus continuing efforts to determine if non-recovered fertilizer N is being immobilized in microbial biomass, lost by denitrification, or leached below the plant root zone.

Phosphorus (P) and potassium (K) fertilization costs, yields, and economic returns associated with various P and K fertilization levels were evaluated on corn and soybeans in rotation in northeastern Iowa from 1979 to 1989. The treatments were 0, 20, and 40 lb P/acre and 0, 60, and 120 lb K/acre, in all nine combinations, plus the high rate (40+120) applied on alternate years. (The latter treatment applied, respectively, in odd or even years was averaged into one treatment.) The initial soil test levels averaged 57 pounds of P and 355 pounds ofK. The P-K treatments did not significantly explain the variation in corn or soybean yields. Net returns were found directly related to the cost of the treatment, so that the control treatment (0+0) achieved the highest returns. The cost of using the 20+60 treatment to maintain soil test levels in the high to very high range was $24/acre per year. Annual application of 40+120 cost $45/acre. A sufficiency approach to applying P and K could drastically reduce fertilizer costs for high-testing soils. Further research is needed to determine if recommendations from this approach can be lowered in some cases. Extension workers must continue to develop ways to aid farmers in realizing the usefulness of soil testing. Farmers must carefully evaluate their fertilization needs in conjunction with soil test results. Together, a more sustainable approach to P and K fertilization for corn and soybeans may be attained.

We surveyed shoppers at a food cooperative in New York state to measure the relationship between organic produce purchases and attitudes related to pesticide use in agriculture, food costs, and other factors affecting produce buying. Two-fifths of the co-op shoppers surveyed usually or almost always purchased organically grown produce, and one-third were somewhat or very likely to pay 100 percent more than conventional produce for residue-free produce. Those who usually or almost always purchased organic produce were less concerned than other shoppers about price when they shop for produce, had higher levels of concern about food safety, and were less concerned about insects and surface blemishes on produce. There was no relationship between income and frequency of organic purchases. Most shoppers were concerned about pesticide residues in produce, but a high level of concern appeared necessary to affect the frequency of organic purchases. In their support of organic agriculture, respondents ranked environmental protection higher than consumer protection. Educators should emphasize both the environmental and food safety benefits of organic farming to consumers.

Systems that reduce the use of fertilizers and pesticides are commonly said to do so by greater use of information and ecological understanding. However, this plausible proposition has not received much empirical examination. Different possible roles of information have not been clearly differentiated: in the development of new methods, in the farmer's decision whether to adopt them, and in their continued use. Also, the additional work that might be needed to handle information in reducedchemical systems often is not distinguished from the need for greater management ability. Typical procedures for evaluating the performance of alternative systems do not give enough attention to farmers' management ability and use of information. This is also true for research on conventional systems, even though in such systems information and management are not usually considered to have such a critical role.