Parameterized Soil Chemical Properties for Evaluating Methane Production from Rice Paddies.
Weiguo Cheng1, Hiroko Akiyama2, Seiichi Nishimura2, Shigeto Sudo2, Kazuyuki Yagi2, Anne Hartley1, and J. Patrick Megonigal3. (1) Florida International Univ, Dept of Environmental Studies, Miami, FL 33199, (2) Natl Inst. for Agro-Env. Sci., Tsukuba, Ibaraki, 305-8604, Japan, (3) Smithsonian Environmental Research Center, PO Box 28, Edgewater, MD 21037-0028
For understanding which parameters are more important in soil chemical properties for deciding the CH4 production from rice paddies, nine kinds of rice soils were collected around Japan and anaerobically incubated at 30ºC for 16 weeks in laboratory condition, After 1, 2, 4, 8 and 16 weeks of incubation, CO2, CH4 and Fe2+ were measured for understanding soil organic matter decomposed and iron reduction. Available N also was measured at end of incubation. The results showed that decomposable C and reducible Fe are two key parameters to decide the CH4 production (PCH4). There was a significant relationship between decomposable C and available N (Nava) (r2=0.975**). Except a sand-gley soil samples, also, a significant relationship between total-Fe (Fetotal) and reducible Fe was found (r2=0.837**). From this experiment, a simple CH4 production model was pulled draw as: PCH4 = 1.593Nava – 2.460Fetotal/1000(each unit was µg g-1 soil). After simulated CH4 production by two soil chemical properties as above, there was shown a significant consistency between by model simulation and by actual measurement (r2=0.831**). Key Words: available N, CH4 production, decomposable C, reducible Fe, total-Fe