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 CH4 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−2 h−1) at all the sites and was lowest during the rainy season (0.17–0.32 mg CH4 m−2 h−1). The results suggest that dryland rice soils and natural ecosystems are 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.