耕作方式对紫色水稻土有机碳及土壤质量影响研究

he impact of conservation tillage practices on carbon sequestration has been of great interest in recent years. Changes in the soil organic carbon (SOC) as influenced by tillage, is more noticeable under long-term rather than short-term tillage practices. This experiment analyzed the organic carbon status of soils sampled at depth increments from 0 to 60 cm after 20 years of five tillage systems (in treatments in a purple paddy soil). The tillage experiment was established in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China, located in the farm of Southwest University (30 26′N, 106 26′E), Chongqing. In this paper five tillage treatments including conventional tillage with rice only system (DP), conventional tillage with rotation of rice and rape system (SL), no-till and ridge culture with rotation of rice and rape system (LM), no-till and plain culture with rotation of rice and rape system (XM) and tillage and ridge culture with rotation of rice and rape system (LF) were selected as research objectives to measure SOC storage and stratification ratio of SOC (CSR). The SOC storage under different tillage systems was calculated based on an equivalent soil mass. The CSR can be used as an indicator of soil quality because surface organic matter is essential to erosion control, water infiltration, and the conservation of nutrients. Results indicate that SOC contents under DP, SL and LF treatments decreased equably with the increase of soil depth; however, no-tillage (NT) practices increased the SOC concentration in soil surface. The difference of SOC contents between the five tillage systems was the largest in the top soil and the lowest in the bottom soil. The order of SOC storage was LM (158.52 Mg C/ hm2) >DP (106.74 Mg C/ hm2) >XM (100.11 Mg C/ hm2) >LF (93.11 Mg C/ hm2) >SL (88.59 Mg C/ hm2), LM treatment was significantly higher than the other treatments. The SOC storage of the five treatments in 2009 all increased when compared to 2003, and the increase was the highest in LM treatment. Stratification ratios of soil organic carbon (CSR) were 2.14, 2.70, 2.65 under LF, XM and LM, meanwhile the values under DP and SL were only 1.54, 1.92. Setting CSR>2 be an indication that soil quality might be improving. Conventional tillage DP and SL treatment both resulted in degraded conditions, however LM, XM and LF improved soil quality. Overall, long-term LM treatment is a valid strategy for increasing SOC storage and improving soil quality in a purple paddy soil in Southwest China.