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

Abstract Tropical rice paddy is considered to be one of the major anthropogenic source of atmospheric methane (CH 4 ). In a field study spread over the dry and wet seasons of a calendar year, the CH 4 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 CH 4 flux from the upland crop followed by lowland rice crop was low (12.52–13.09 g CH 4  m 2 ) compared to that of the rice–rice rotation (39.96 g CH 4  m 2 ). What was particularly interesting is that the seasonal mean CH 4 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 CH 4 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.