Carbon and Nitrogen Flow in the Traditional Land Use System of the Himalaya Region, Nepal

Traditionally, agricultural systems in the Himalayan region of Nepal rely on livestock, forestry, and crop production. The extraction of litter, tree fodder, and grasses from the forest ensures a net movement of carbon (C) and nitrogen (N) from the forest to the agricultural land. This study assessed the sustainability of farming systems by computing the C and N input and output of the agroecosystem. The study was conducted in the buffer zone of Sagarmatha National Park in Nepal. A questionnaire survey, field measurements, and laboratory analysis of samples were used to determine the C and N inputs and fluxes in the systems. Forest litter is a major source of C and N for agricultural land, as is fodder from the forest fed to livestock (lopping of trees, grazing). Amounts that are fairly significant are supplied by human waste. To produce the average amount of 40 kg N ha(-1) per year applied as compost, 25 kg N from forest litter, 23 kg N from forest fodder, 9 kg N from human waste, and 3.5 kg N from field grazing and straw are required. Losses are attributed to volatilization, denitrification, and leaching. Harvest residues amount to 14 kg N ha(-1). Rather than discouraging the use of litter toilets, a modernized version of indigenous waste management and composting practices could reduce dependency on forests for fuelwood, fodder, and litter. To maintain the present fertility status, each household needs an estimated 2-5 ha of forest land.