M.Kimura, H.Ando and H.Haraguchi@@@@@@@@
Enveron. Sci.(Β«Θwο) 4-1, 15-25 (1991)
Key words: carbon dioxide, Japan, methane, paddy field,
soil type
The potential CO2 and CH4 production in Japanese paddy
fields were estimated from chemical properties of paddy soils of respective
soil series, their acreage and thermal regimes during rice growing period.
Total carbon meniralization (CO2 plus CH4) was calculated from the estimation
of nitrogen mineralization of soil organic matter under anaerobic incubation.
the assignment of mineralized carbon to CH4 portion was calculated from
the ratio of oxidation capacity, represented by free iron content of soil,
to reduction capacity, represented by estimated NH4 production during rice
growing period.
The CO2 production from Japanese paddy fields were estimated
to be 3.8x1000000 and 9.6x10000 ton-C/one crop season, respectively. Silos
classified to Gray Lowland Soil Series Group (SSG) produced most (37% and
41% of the total CO2 and CH4 production), followed by soils of Gley Soil
SSG (26% and 20%).
As for the CO2 and CH4 production per the unit area,
soils of Andosol SSG produced most in CO2 (2.4 ton-C/ha) and soils of Gleyed
Andosol SSG most in CH4 (73kg-C/ha). The CH4 production increased sharply
as the fields located more south. The CH4 production was influenced more
by the temperature during rice growing period and by the the of SSG than
the CO2 production.