Effects of Conservation Tillage on Organic Carbon and Carbon Management Index in Paddy Soil

Effects of different tillage systems on organic carbon and carbon management index (CMI) in paddy soil of long-term experiment site (since 1990) were studied. The experiment included three tillage treatments: conventional tillage with rotation of rice and winter fallow (CT-r) system, no-tillage and ridge culture with rotation of rice and rape (RT-rr) system, and conventional tillage with rotation of rice and rape (CT-rr) system. Soil labile organic carbon measured by oxidation of KMnO4 respond rapidly to carbon supply changes, and it is considered as an important indicator of soil quality. Compared with CT-r system, long-term RT-rr system significantly increased total organic carbon and labile organic carbon in surface soil (0-10 cm and 10-20 cm). The proportion of labile organic carbon to total organic carbon under RT-rr system was higher than other tillage systems. The carbon management index (CMI) is derived from the total soil organic carbon pool and carbon lability and is useful to evaluate the capacity of management systems to promote soil quality. The CMI increased in each layer under RT-rr system, while it decreased under CT-rr system. This indicated that conservation tillage improved the capacity of the management system into promoting soil quality in Sichuan Basin of China.