Soil Biophysical Processes Involved In Decomposition Of Rice Straw Incorporated In Upland Soils Under Wetting And Drying Cycles For Stabilization Of Soil Carbon Pools And Soil Structure

Incorporation of rice straw into degraded upland soils is not only important to sequestrate more carbon, which otherwise is burnt in the paddy fields as a tradition, but also to improve soil structure against soil degradation by soil and water erosion. Decomposition of rice straw in the upland soils after incorporation is affected by soil moisture regime and soil microbial community, which in turn may be related to stabilization of soil carbon pools and soil structure. Low level of soil water repellency can reduce soil wetting rate and prevent soil slaking due to compressed air within the aggregates during wetting. The low level of soil water repellency is reportedly related to soil moisture regime and soil microbial community as well as dissolved organic carbon. It is unclear whether the low level of soil water repellency may occur during rice straw decomposition after the incorporation under wetting and drying cycles. Laboratory incubation experiments were carried out with <2 mm sized 5% rice straw-soil mixture filled in soil cores. During the incubation the soil cores were treated with repeated wetting drying cycles under different drying intensities (strong-drying (SD), Middle-intensity drying (MD), and Low intensity drying (LD). The objectives of this investigation were to study the effects of different intensities and numbers of drying and wetting cycles on: (1) dynamics of soil organic carbon (SOC) pools; (2) changes in soil structure and stability; (3) soil dissolved organic carbon (DOC) and soil water repellency; (4) changes in soil microbe community; (5) the interaction of soil biological and physical factors in relation to soil stability.The 120-day incubation revealed that the content of soil organic carbon was...