Nitrogen balances for households in the mid-hills of Nepal

Sustainable production requires balanced resource use and it is the managem ent decisions at a household level that determine nutrient fluxes and the e conomic viability of enterprises. Traditionally, the agricultural systems o f the mid-hills of Nepal have relied on the close integration of forestry, livestock husbandry and crop production but increasing population and other social changes are straining these systems. This paper uses diverse source s to determine a N balance for a hypothetical household and to assess the s ustainability of current farming systems with respect to N. For a hypotheti cal household holding 1 ha of land with two-thirds of it rainfed hillside ( bari-land) and one-third irrigated lowland (khet-land), the system is curre ntly in balance with inputs across the boundary of about 26 kg Na-1 (mainly in fertilizer) and losses, excluding gases, of about 60 kg Na-1 (mainly in crop removal). Tree fodder and grasses are a major source of N (80 kg Na-1 ) to the household. A major pathway for the flow of N within the system is via the forage fed to livestock, and the subsequent application of manure t o crops. Typically, manure and compost supply 100 kg N to crops (four times that supplied by fertilizer) and produce crops with a N content in grains of 36 kg N. The N losses via soil erosion are shown to be small but the los ses via leaching and gases are largely unquantified. It is concluded that t he use of tree fodder and forage from forest areas and grasses from terrace risers as animal feed ensures a net movement of N from non-agricultural la nd to agricultural land. The magnitude of this movement is not known, becau se the quantities of Vegetation gathered from inside and outside the househ old boundaries are not known. (C) 2000 Elsevier Science B.V. All rights res erved.