MAINTAINING SOIL FERTILITY UNDER INCREASING LAND-USE PRESSURE IN THE MIDDLE MOUNTAINS OF NEPAL

Nepal is facing a serious problem of being unable to maintain soil fer tility in agriculture and forestry. Land use practices initiated over the past 10-15 years have resulted in insufficient nutrient inputs, wh ile biomass use and production have increased. Changes in forest soil fertility have resulted from intensive use of forest biomass for anima l feed and collection of forest litter for use in agriculture. The agr icultural fertility changes have resulted from intensifying annual cro p rotations from 1.5 to 2.5 crops and insufficient inputs. The removal of biomass from the forest has curtailed the natural organic cycle by virtually eliminating nutrient inputs. The soils are very acidic and have little C, N, P and exchangeable bases, but have large amounts of active iron. Basic nutrients are not sustained in agriculture and diff erences in inputs and management between irrigated and rainfed agricul tural systems are becoming visible. Irrigated fields show the largest cation content because of input from irrigation water. Rainfed agricul tural sites, which receive the most nutrients (fertilizers and manure) , have the highest pH values and C and N contents. All soil fertility conditions are marginal and put into question the long-term sustainabi lity of current levels of production. Alterations in the cropping inte nsity are needed and the introduction of nitrogen fixing trees and cro ps seems to be the most viable option towards sustainability.