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[B-1.3.2 Quantitative Analysis of Carbon Cycle System in Paddy Field]

[Contact Person]

Tomoyuki Hakamada
Head, Earth Environment Research Team, National Institute of
Agro-environmental Sciences, Ministry of Agriculture, Forestry and
Fishery, 3-1-1 Kan-nondai, Tsukuba 305 Japan

[Total Budget for FY1993-FY1995]

8,292,000 Yen (FY1995: 2,319,000 Yen)

[Abstract]

A quantitative study of carbon cycle system was made from 1993-1995 on a well controlled paddy field in which rice was cropped yearly from May to September, at Tsukuba in central part of Japan. In paddy field system, carbon contents of solid phase(soil and rice plant), aqueous phase(flooded water, irrigation water and percolated water) and gaseous phase(carbon dioxide and methane) were analyzed. Following results were given. Carbon content of plow layer soil and rice plant produced was estimated to be 4600 and 650 kg/10a, respectively. In rice plant, carbon was distributed throughout paddy(233), straw(263), stubble(136) and tiller(16kg/10a) after harvest. Carbon content of flooded water, irrigation water and percolating water were estimated to be 1.6, 8.1 and 30kg, respectively. Yearly input of C to paddy field ecosystem per 10a was estimated to be 1200kg/10a and 10kg/10a as gaseous C(CO₂ fixation) and aqueous C(irrigation and precipitation), respectively. Yearly output of C was estimated to be 500kg and 10kg as respiration and methane formation respectively. Consequently, net CO₂ fixation was calculate to be 700kg/10a/year. In 700kg, 650kg was fixed in rice plant and 30kg was leached to underground water.

[Key Words]

Paddy field, Carbon, Soil organic matter, Irrigation water, Percolating water, Methane flux, Carbon dioxide flux