稻草还田方式对双季稻田耕层土壤有机碳积累的影响

选择南方典型双季稻田,研究不同的稻草还田方式对土壤不同层次有机碳的积累、表土碳密度、C/N比值及水稻产量的影响。结果表明,不同的稻草还田和耕作处理对水稻产量无显著影响;不同稻草还田处理的土壤有机碳和C/N均随土层加深而减小;3个稻草还田处理0-5 cm土层土壤有机碳质量分数显著高于不还田对照,其中,以高桩免耕处理最高,比无草翻耕处理提高13.8%（P〈0.01）;5-10 cm土层表现为高桩翻耕处理显著高于其他处理,增加幅度为1.39-1.66 g kg-1;10-15 cm为翻耕处理（包括稻草不还田和还田）显著高于各免耕处理;稻草翻耕处理（0-15 cm）的耕层有机碳密度显著高于其他处理。因此,南方双季稻田采取稻草翻耕还田方式有利于增加土壤有机碳汇。

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.