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[B-2.3 Emission of Methane and Nitrous Oxide from Agricultural Lands]

[Contact Person]

Haruo Tsuruta
Head, Laboratory of Environmental Impact Assessment
Department of Environmental Planning
National Institute of Agro-Environmental Sciences
Ministry of Agriculture, Forestry, and Fisheries
3-1-1 Kan-nondai, Tsukuba, Ibaraki 305 Japan
Phone +81-298-38-8276, Fax +81-298-38-8199
E-mail tsuruta@niaes.affrc.go.jp

[Total Budget for FY1990-1994]

79,974,000 Yen (FY1994 17,852,000 Yen)

[Abstract]

　Methane(CH₄) emission from rice paddy fields in Japan and Thailand were studied to estimate the annual emission rate of CH₄, and to find major factors controlling the CH₄ emission. Nitrous Oxide(N₂O) emission from fertilized soils and rice paddy fields were also studied to estimate the N₂O emission rate during a cultivated season. Annual CH₄ emission rate from rice paddy fields in Thailand was estimated to be 3.7 TgCH₄/year from the flux measurements in the rice experiment stations between 1991-1994 under the collaborative study with the DOA, Thailand. The annual CH₄ emission rate in rice paddy fields of Japan was also estimated to be 0.26 TgCH₄/year. Major factors controlling the CH₄ emission from rice paddy fields were soil biochemistry, water management, and the amount of organic matter application. A modelling of CH₄ transport from paddy soils to the atmosphere was proposed by field and incubation experiments. N₂O was emitted to the atmosphere from fertilized soils mainly through nitrification rather than denitrification. N₂O was also emitted after final water drainage through a fallow season in rice paddy fields, and which were identified as one of the sources of atmospheric N₂O. Nitric Oxide(NO) was also emitted from the soils with the application of nitrogen fertilizers, and much higher in emission rate than N₂O.

[Key Words]

Methane, Rice Paddy Fields, Nitrous Oxide, Fertilized Soils, Emission Rate