Agriculture is the main source of livelihood for most people in hillside areas of Nepal, and soil fertility is largely maintained through the use of organic manure. Discussions with farmers indicated five principal soil fertility management practices (manure, chemical fertilizer, compost based on leaf litters, growing legume crops, and in-situ manuring). Farmers identified five soil productivity indicators (crop productivity, soil characteristics (particularly soil colour), management requirement, species of weeds, diseases, and pests, and termites). Historical trends (increasing crop intensification, decreasing livestock numbers, increasing use of chemical fertilizers, reduced labour availability, and change in the climate over the last 30-40 years) showed a decline in soil productivity. Scored causal diagrams on soil fertility drawn from focus group discussions indicated that the primary causes of declining soil fertility and crop productivity are a decrease in available manure, increased cropping intensity, low use of chemical fertilizers, and change in climate. Scientific evaluation confirmed that altitude, farming system, and land types affected the availability of soil nutrients. Organic C, total N, available P and exchangeable K increased in less intensive farming systems, which were at higher altitudes. These nutrients as well as available Fe, Mn, and B in soil significantly increased in rainfed upland (bari) compared with irrigated lowland (khet). Covering manure with black plastic sheets resulted in faster decomposition as well as increased total N and exchangeable K. Covered manure applied to summer rainfed maize and upland rice as well as irrigated lowland spring maize increased grain and straw yields between 13 and 36% when compared with uncovered manure. Both farmers' indigenous knowledge and their criteria were as useful as scientific evaluation in assessing soil fertility improvements. Therefore, farmers' knowledge and criteria should be considered when monitoring soil fertility and crop productivity in farmer trials.
