EVALUATING 2ND YEAR CROPPING ON JHUM FALLOWS IN MIZORAM, NORTH-EASTERN INDIA - PHYTOMASS DYNAMICS AND PRIMARY PRODUCTIVITY

Cropping on jhum fallows in north-eartern India is predominantly done for one year in a jhum cycle. If second year cropping is done, expanse of the forest land required for slashing and burning could be reduced significantly. We tested this hypothesis in a young (6 yr) and an old (20 yr) jhum fallow. We also evaluated if the productivity during sec ond year cropping could be alleviated by auxiliary measures such as ti lling the soil or application of fertilizers (chemical or farm-yard ma nure or both in combination). The results demonstrate that the ecosyst em productivity (total dry matter production) and economic yield (rice grain production) decline with shortening of jhum cycle. Second year cropping causes a further decline in ecosystem productivity in old jhu m field, but not in young jhum field. Economic yield from second year cropping in its traditional form (without any fertilizer treatment) is not much lower than that in the first year, and can be improved furth er by manuring the soil. Tilling of soil improves neither ecosystem pr oductivity nor economic yield. Different fertilization treatments resp ond differently; while inorganic manuring enhances ecosystem productiv ity, a combination of inorganic and organic mauuring improves economic yield.