Methane efflux from rice-based cropping systems under humid tropical conditions of eastern India

Tropical rice paddy is considered to be one of the major anthropogenic source of atmospheric methane (CH4). In a field study spread over the dry and wet seasons of a calendar year, the CH4 emission from upland (oilseed and pulse) crops in the dry season and a succeeding lowland rice (Oryza sativa L.) crop in the wet season was compared with rice-rice rotation in both seasons under flooded conditions. Cumulative CH4 flux from the upland crop followed by lowland rice crop was low (12.52-13.09 g CH4 m(2)) compared to that of the rice-rice rotation (39.96g CH4 m(2)). What was particularly interesting is that the seasonal mean CHI emission from the lowland rice in wet season preceded by an upland crop in dry season was low when compared to that of lowland rice in wet season preceding a dry season flooded rice. Results indicate that the cumulative CH4 emission from tropical rice ecosystem can be lowered by growing suitable upland crops to reduce the period that rice paddies are submerged during an annual cropping cycle. (C) 2000 Elsevier Science B.V. All rights reserved.