SOIL-EROSION DUE TO SETTLED UPLAND FARMING IN THE HIMALAYA - A CASE-STUDY IN PRANMATI WATERSHED

A common concept is that upland agriculture undertaken by local commun ities is a major factor causing large-scale soil erosion and other env ironmental problems in the Himalaya. Attempts to measure soil loss fro m farm fields are limited. This study was undertaken to measure the ra te of soil loss from fields sown with crops during the rainy season an d to examine the factors determining the erosion rates in the Pranmati watershed which is characterised by settled organic farming on terrac ed slopes. About 43% of the total agricultural land in the watershed w as on low sloping terraces (<2 degrees), 32% on medium sloping terrace s (2-6 degrees) and 25% on highly sloping terraces (6-10 degrees). Pot ato was the most dominant crop, occupying 50.2% of the total cropped a rea, followed by Amaranthus paniculatus (22.6%), Eleusine coracana (11 .2%), Echinocloa frumentacea (10%) and Oryza sativa (6%). Soil loss fr om different crop covers was in the range of 0.300-0.658 t/ha/yr on lo w sloping terraces, 1-7 t/ha/yr on medium sloping terraces, and 6.037- 64.39 t/ha/yr on highly sloping terraces. Comparison of different crop s revealed the highest soil loss was from potato fields, a cash crop i n the watershed. Potato cultivation on highly sloping terraces account ed for 72.6% of the total soil loss from agricultural fields. The area under this crop is rapidly increasing because of increasing emphasis on a monetary economy. Organic manure input in potato fields (28.5 t/h a) was much higher as compared to traditional crops (7.8-15.5 t/ha). B yproducts of potato do not have any fodder value, while the traditiona l crops do have useful fodder byproducts. The increase in the area und er potato also implies more intensive pressure on the forests. The thr eat of sail erosion causing unsustainability of upland agriculture see ms to be due more to the cultivation of potato than to traditional sub sistence crops. Factors related to erosion and land-use policy aspects are discussed in the paper.