Quantitative dependence of methane emission on soil properties

To identify the key soil parameters influencing CH4 emission from rice paddies, an outdoor pot experiment with a total of 18 paddy soils was conducted in Nanjing Agricultural University during the 2000 rice growing season. The seasonal average rate of CH4 emission for all 18 soils was 6.42±2.70 mg m−2 h−1, with a range of 1.96 to 11.06 mg m−2 h−1. Correlation analysis indicated that the seasonal average of CH4 emission was positively dependent on soil sand content and negatively on total N as well as NH4+-N determined before rice transplanting. Copper content of soils had a significant negative impact on CH4 emission. No clear relationship existed between CH4 emission and soil carbon content. In addition, soil type cannot explain the variability in CH4 emission. Soil parameters influencing CH4 emission were different as rice growth and development proceeded. A further investigation suggested that the seasonal average rate of CH4 emission could be quantitatively determined by a linear combination of soil NH4+-N, available copper, the ratio of available to total sulphur, and the ratio of available to total iron. Moreover, the average rates of CH4 emission in the vegetative, reproductive and ripening stages could be also respectively described by a linear combination of different soil variables.