Effect of patterns of straw returning to soil on the cultivated soil organic carbon accumulation in double-crop rice system

Changes of organic matter carbon(SOC),density of organic carbon(DOC),carbon/nitrogen ratio(C/N) in cultivated soil layer(0-15 cm) of paddy fields and rice yields under different patterns of rice straw returning to paddy soil were conducted by 3 years fixed-position field experiment.The result indicated that there was not remarkable effect on rice yields among the five treatments.With soil layer deepening,the content of SOM and C/N in the treatments of all straw returning to paddy soil was being decreased.The SOC in 0-5 cm soil layer in the treatments of straw returning to paddy soil was evidently higher than that of the treatments of no straw returning.The SOC in HSNT was highest than that of the other treatments,which were increased by 13.8%(P0.01) compared with the NST.The SOC in 5-10 cm soil layer in TS was significantly higher than the other treatments and increased by 1.39-1.66 g·kg-1.The SOC in 10-15 cm soil layer in the two plowing tillage treatments was remarkably higher than that of the no-tillage treatments.The statistical analysis result was showed that the DOC of the cultivated soil layer(0-15 cm) existed the significant differences among treatments and that of the HST and NST was remarkably higher other treatments.Therefore,the double-crop rice system in Southern China could increase SOM sequestration by combining straw returning to paddy soils with plowing tillage.