Decomposition of Rice Straw in Soils as Affected by Some Management Factors

Decomposition of rice straw contained in nylon bags was measured in field experiments at two different locations during winter and spring months. Incorporated straw decomposed more rapidly than did straw on the soil surface, and least decomposition occurred in straw samples suspended above the soil surface as in a windrow. Decomposition rates were not affected by chopping straw. Laboratory decomposition experiments conducted at 8 and 25C and at 60 and 150% water holding capacity showed more effect of low temperature in retarding straw decomposition than excess water. Additional nitrogen stimulated straw decomposition in Stockton adobe clay during the first few weeks but had little effect in Sacramento clay. After 2 months' initial decomposition the soil samples treated with straw were dried and rewetted to 60% water holding capacity (WHC), then incubated another 2 months. During this period straw decomposition in Sacramento clay samples which had received additional N was significantly depressed. Additional P and S had no effect on rice straw decomposition.