Evaluating second year cropping on jhum fallows in Mizoram, north-eastern India: Soil fertility

Abstract

Changes in soil fertility were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern India in response to various operations involved injhum such as slashing and burning of vegetation, cropping period, and intervening fallow period between first and second year cropping. The results demonstrate that the soil is richer in nutrients in old than young field prior to the start of jhum cultivation. Slash burning depletes soil acidity, carbon and nitrogen but elevates phosphorus and cations. Soil fertility declined during first cropping phase, and further declined during second cropping phase. After two cropping years, soil fertility of old field was almost at par with that of young field, signifying that the loss of soil fertility was more in old than young field. A short intervening fallow period between first and second year of cropping did not show any pronounced improvement in soil fertility, though it provided some biomass for second burning. Tilling caused maximum loss to soil fertility. The fertilizer treatments ended with comparable or better soil fertility in comparison to no-treatment plot. There seems to be none of the fertilizer treatments superior over others from the standpoint of ending soil fertility. The unifying conclusions of this series of investigations support the hypothesis that the second year cropping holds promise to reduce the demand for forested land for jhum, and lengthen the jhum cycle substantially.