Methane emissions from rice: mitigation options
Neue, H.U. | Wassmann, R. | Lantin, R.S. (International Rice Research Inst., Los Banos, Laguna (Philippines). Soil and Water Resources Div.)
Emission of methane from ricefields is the net result of strictly anoxic bacterial methane production and aerobic oxidation. A complex set of parameters linking physical and biological characteristics of flooded soil environments with specific management practices governs methane fluxes. With current cultivation technologies, methane emission from ricefields is expected to increase as rice production increases in the next decades. Field and laboratory studies show readily metabolizable carbon, soil reduction, soil pH, soil structure and texture, soil temperature, the fermentation chain and microbial synergisms and antagonisms, rice cultivars and crop biomass, and cultural practices are the major factors that control methane fluxes. Irrigated rice has obviously the highest potential to produce and emit CH4 because of assurred flooding and high rice production. Methane emission in rainfed rice varies widely and is generally lower because of periodic droughts. Deepwater rice may emit more methane because of the extended period of submergence. Upland rice is not a source of methane because it is never flooded. Research has begun to identify the mechanisms of methane fluxes in ricefields that allow the development of technically and socioeconomically feasible mitigation technologies without sacrificing rice yields. The most promising no-regret options are modifying water and soil management, minimizing inputs of easily degradable carbon sources, and selecting rice with lower emission potential. By using a combination of feasible mitigation techologies, there is great potential to stabilize or even reduce methane emission from ricefields while increasing rice production without dramatically changing cultural practices
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