A comparative study of the energy budget of hill agro-ecosystems with emphasis on the slash and burn system (JHUM) at lower elevations of North-Eastern India

Abstract

The present study is a comparison of the energy efficiency of three types of shifting agriculture, known locally as 'jhum', in north-eastern India. Longer cycles of 30 and 10 years, which are rather rare now, are compared with the more common 5-year cycle of the present time. Of the three land use practices, jhum and valley agricultural systems are more efficient from the energy viewpoint, with higher output/input ratios compared with terrace cultivation, which is least efficient due to heavy fertiliser input requirements. For jhum, a 10-year cycle, however, is more efficient from the energy and land use points of view, with an effective energy output of 5660·1 MJ compared with 1892·2 MJ under a 30-year cycle or 4771·6 MJ under a 5-year cycle. Cereal cultivation, if its is to be sustained, must be on the basis of valley cultivation, which is sustainable year after year, or on basis of a 10-year jhum cycle. The implications of these findings are discussed in the light of the relative significance of land and energy constraints.