Methane production potentials of twenty-eight rice soils in China

Soil CH4 production potentials were investigated by incubating air-dried soils under anaerobic conditions in the laboratory. Twenty-eight soils from different fields and locations were collected for this study. Soil CH4 production during a 100-day incubation differed greatly and were significantly correlated with soil organic content: (r=0.61, P<0.01), The statistical significance increased when soils were grouped according to soil reduction rates. A significant correlation was also found between CH4 production and total N content: (r=0.64, P<0.01) and between CH4 production and soil particle sizes of 0.25-0.05 mm (r=0.48, P < 0.05). tk negative exponential correlation was found between CH4 production and aerobic soil pH (r=-0.74, P<0.01). The 28 soils were stratified into four groups on the basis of variation in CH4 production rates which were associated with the soil reduction rare and soil organic content. The faster the Eh of soil fell, the more CH4 was formed. Adding rice straw to Hangzhou and Beijing soils increased CH4 production. The increase in CHS production was more pronounced in the soil with the lowest organic matter content and slowest reduction rate than in the soil with highest organic matter and fastest reduction rate. Inorganic fertilizer had no significant influence on CEC production potentials of either type of soil.