Earthworm population dynamics and contribution to nutrient cycling during cropping and fallow phases of shifting agriculture (jhum) in north-east India.
Sampling of earthworm populations during 5- and 15-yr-old cropping phases and in 5-, 10- and 15-yr-old fallow phases of shifting agriculture at Shillong, Meghalaya, showed that while Tonoscolex horaii and Amynthas diffringens occurred during cropping and fallow phases up to 15 yr old, Nelloscolex strigosus and Drawida assamensis occurred only in samples from fallows 5 or 15 yr old. Population size decreased significantly after slashing and burning. Seasonal fluctuations with maximum population size during the wet season were observed for all species except Amynthas diffringens, which peaked during the winter. Population size was significantly correlated with soil moisture, temperature and organic matter. Wormcasts had a higher pH and better nutrient status than soil, and showed local concentrations of nutrients. The results show that in highly leached soils of the humid tropics, earthworm activity is beneficial because of rapid incorporation of detritus into the mineral soil.