ESTIMATION OF THE INCREASE IN CH4 EMISSION FROM PADDY SOILS BY RICE STRAW APPLICATION

The relationship between the amount of CH4 emission to the atmosphere from submerged paddy soils with rice plants and the application level (0-8 g kg(-1)) of rice straw (RS) in soil was investigated in a pot experiment. Amounts of CH4 emitted from pots with respective RS levels differed between a clayey yellow soil and a silty gray lowland soil. However, the increase in cumulative amounts of CH4 emission with the increase in the application level of RS was similar in pattern between the two soils, and the increase (Y) was formulated with a logistic curve: Y = k[a/(1+be(-cx))]; x, application level of RS; k, a coefficient for relative CH4 emission. Since the seasonal variations in coefficients a, b, and c in the logistic equation were also formulated as the function of the sum of effective temperature (E, Sigma(T-15); T, daily average temperature), the increase in cumulative amounts of CH4 emission from any paddy soil by any level of RS application was known to be estimated by the following equation: Y = k[a(E)/(1+b(E)e(-c(E)x))].