八木 一行

Rice is one of the most important cereals, especially in Asian countries. Methane (CH_4), one of the major greenhouse gases, is emitted from flooded paddy fields as a result of phenomena on various scales. This paper review studies on CH_4 emission from paddy fields, paying special attention to mitigation options from the viewpoint of their feasibility on a field scale. Field management of rice paddies is primarily carried out to obtain suitable rice yields, but it also has physical, chemical, and biological effects on CH_4 emission. Therefore, some management practices can be win-win options that sustain rice yield and mitigate CH_4 emission. For example, appropriate water management for rice growth and yield is also effective in decreasing CH_4 emission. Other practices, such as nitrogen fertilizer application and organic matter application can also have positive effects on rice yield and CH_4 emission. Recent microbial studies have been revealing the ecology of methanogens and methanotrophs in paddy soils. Further studies on a microbial scale will offer additional clues to the mitigation of CH_4 emission from paddy fields.