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: dryla nd, irrigated rice, seasonally dry forest and savanna. Flux from the i rrigated rice paddies was in the range 2.14-8.23 mg CH(4)m(-2)h(-1) du ring 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 stim ulated CH4 production in irrigated rice soil while it reduced CH4 cons umption in dryland rice plots. CH4 flux measurements from nutrient-poo r, 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 res ults suggest that dryland rice soils and natural ecosystems ate potent ial sinks of CH4. Conservative extrapolation of the results indicates that to compensate for CH4 production from 1 ha of irrigated rice abou t 2.4 ha of natural ecosystems are needed. Thus there is a need of fur ther evaluation of the role of tropical dryland rice soils and natural ly dry ecosystems in the global methane budget. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.