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research programs around the world, as scientists become better prepared for basic investigations and the glamour of genetic engineering and high technology solutions pervades the scientific community, In contrast to the range of ecological situations where farmers produce crops, the research establishments have relatively few experiment stations. Much of the research performed on these stations is reductionist in nature, with limited regard for the incorporation of new innovations into the total farming system. For these reasons, there is comparative advantage to conducting at least some of the research in a wider array of sites with collaborating farmers.
Another compelling reason for. working directly with individual farmers and groups relates-to distance from the controlled research site to the farm where results will be applied. This 'distance" may take several forms (Francis et al., 1990). Geographic space in miles or kilometers from one site to another is the most commonly used measure of distance. Farmers are willing to travel certain distances to visit other sites, depending on culture and infrastructure (Rzewnicki, 1991). More important, perhaps, is the 'ecological distance' from one site to another. For example, a low lying area with poor drainage and heavy soils may be a very short physical distance from a well drained, lighter soil on a hillside, yet the soil conditions, appropriate cultural practices, and crops or varieties that are appropriate may be quite distinct. Finally, there may be *conceptual* or .psychological distances" between researcher and farmer, based on differences in education or experience, and these need to be bridged in order to effect a working partnership and a fully participatory system of research and extension. On- farm activities among people who have mutual respect for each others' talents and potentials to contribute can help to overcome these social distances.
The potentials of a participatory network of farmers and rese-"chers can perhaps best be illustrated through: use of an- exampl-.. Th&unique. contributions of the farmer in the total research process is highlighted; -A number of additional: examples,. especially in farmer contributions to ideas for weed management, were recently summarized by Francis and Doll (19 91).
Maize yield resoonse to nitrogen in crop rotations. In order to study the effect of nitrogen applications on maize yields in continuous maize and sorghum compared to rotation of these cereals in Nebraska, a network of about thirty farmers was established to work with a project of the University of Nebraska. There has been great concern about the energy costs of this input in maize production, as well as potential for nitrate contamination of ground water supplies that are frequently used for human and animal consumption. Supported in part through a grant from the Nebraska Energy Office, a university technician established contact with a number of farmers, many of whom were members of the Nebraska Sustainable Agriculture Society. All were interested in more efficient use of nitrogen, and in finding ways to quantify the effects of a cereal-legume rotation on response to this important nutrient.
In cooperation with farmers, fields and experimental sites were chosen, soil samples were taken, and lab test results discussed. Together- the team determined realistic yield goals. and developed nitrogen budgets considering all sources of this major nutrient. Each farmer thus derived a conservative but optimum level of nitrogen for the. coming season. In most fields this N rate and a one-half rate were included, and in. some fields a zero rate as well. On many fields these treatments were applied in replicated strips across the entire field. For the years 1988, 1989, and 1990 there was a predicted yield response to rates of 80 to 150 pounds N/acre, although the
-actual economic optima were lower in most fields (Franzluebbers, 1991). Following soybean, sweet clover, or alfalfa there was no -economic response to applied nitrogen by either maize or sorghum under rainfed conditions. In irrigated fields, there was no economic response of maize yields. to nitrogen if the maize followed alfalfa. The conclusions from this three-year project. as interpreted by farmers and project personnel, was that nitrogen generally is over applied under many conditions in Nebraska.