| Conservation management practices, such as no-tillage（NT） or crop residue returning, alter soil organic carbon（C） lability, thus affecting soil quality. However, inconsistent effects of conservation management practices on soil labile organic C have been commonly reported. Therefore, a field experiment was conducted to study the effects of tillage practices and wheat-straw returned to the field on soil liable organic carbon（LOC）, carbon pool management index（CPMI） and rice grain yield at the Junchuan in Hubei Province of China. Treatments were established following a split-plot design of a randomized complete block with tillage practices [plough tillage（PT） and no-tillage（NT）]as the main plot and wheat straw returning level [6000 kg·hm-2（SR3）, 4000 kg·hm-2（SR2）, 2000 kg·hm-2（SR1） and 0 kg·hm-2（SR0）] as the sub-plot treatment. The results indicated that, compared with PT, NT significantly increased the content of soil water-soluble organic carbon（WSOC） by 23%~68%（P<0.000 1）, microbial biomass carbon（MBC） by 21%~40%, easily oxidizable carbon（EOC） by 10%~63%（P<0.000 1），but didn′t have remarkable effect on the particulate organic carbon（POC）. The SR2 and SR1 significantly increased the WSOC contents by 37%~74% compared to SR0（P<0.000 3）. EOC contents increased with increasing amounts of wheat straw returning. NT significantly increased CPMI compared to PT. The effects of wheat straw returning on CPMI followed the order：SR3>SR2>SR1>SR0. SR3, SR2 and SR1 increased rice grain yield by 7.7%~16%,17%~35% and 23%~28% respectively. Correlation analysis revealed that WSOC could be a more sensitive indicator responsing to the changes of soil management practices than other indices in short-term. |
