The soil, nutrient and water conservation is the main problem faced by farmers and investigators under the corn crop-based systems in Central America and Mexico. Several farmers from Honduras have come up with an efficient technology for the corn planted on hills, in which the bean manure is planted in rotation with corn during the dry season. The results from the conducted survey, at the Departamento de Atlantida in Honduras, indicate that 66 % of the farmers grow most of the corn through the protective mat produced by the beans during the rainy season. Among the advantages of this rotation, compared to the traditional burned and cleared land, are the higher yields with les ser dependency of external imputs, shorter rest periods, lower land preparation costs, less soil erosion and lower risk of drought damages. The problems linked to the diffusion ofthe system include the risk ofland slides and a higher plague's incidence (rats) on the corn planted through the manure mat. Usually, the amount of land available in the regionalland markets is the determining factor on the diffusion of this system, and not the size of the farm nor the form of land tenancy.

The increase of agricultural productivity and the conservation of natural resources are announced as desirable objectives of agricultural research. They are, however, frequently presented as substitutes. Reaching one it should make necessarily to coast of sacrificing the other. This work presents the idea that both objectives could be complementary to each other through the development and transfer of technologies that simultaneously enhance productivity and conserve resources (PERC technologies). This idea is illustrated with the case of conservation tillage wih crop residue managements. Finallu the work lists the costs and benefits of technologies that are available or that are in advanced stages of development in the region.

For the recommendation domain 1 (RD1), characterized by high initial content for P in the soil and a low level of organic matter (OM), optimal economic rates were 184 kg N/ha and no P application. For the RD2, low P and high level of MO, the optimal rates were 72 kg N/ha and 51 kg P2O5/ha. For the DRl the profitability of fertilizer application was found to be significantly superior to that found in RD2. For fertilization to be profitable in the RD1 the minimum rate of return acceptable to farmers must be inferior to 42%, while in RD2 this rate must be inferior to 93%.