Methane flux from irrigated paddy and dryland rice fields, and from seasonally dry tropical forest and savanna soils of India

Methane flux was measured from four tropical, Indian ecosystems: dryland, irrigated rice, seasonally dry forest and savanna. Flux from the irrigated rice paddies was in the range 2.14-8.23 mg CH(4)m(-2)h(-1) during the crop period. In contrast, the dryland rice soil consumed 0.12-0.90 mg CH4 m(-2) h(-1). Application of wheat straw + fertilizer stimulated CH4 production in irrigated rice soil while it reduced CH4 consumption in dryland rice plots. CH4 flux measurements from nutrient-poor, well-drained dry deciduous forest and savanna soils indicated heavy methane consumption. Maximum CH4 consumption was observed during the winter season (0.46-0.95 mg CH4 m(-1) h(-1)) at all the sites and was lowest during the rainy season (0.17-0.32 mg CH4 m(-1) h(-1)). The results suggest that dryland rice soils and natural ecosystems ate potential sinks of CH4. Conservative extrapolation of the results indicates that to compensate for CH4 production from 1 ha of irrigated rice about 2.4 ha of natural ecosystems are needed. Thus there is a need of further evaluation of the role of tropical dryland rice soils and naturally dry ecosystems in the global methane budget. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.