Effects of winter cover crop straw recycling on soil organic carbon and soil carbon pool management index in paddy fields

Research on total organic carbon (TOC), carbon pool activivty (CPA) and carbon pool management index (CPMI) of paddy fields with different double cropping rice patterns could enhance the exploitation of winter cover crop and the assessment of paddy rice cropping patterns. This paper discussed soil TOC, CPA and CPMI in double cropping rice systems with straw recycling of different winter cover crops. Experiments were conducted in field plot trials of ryegrass and double cropping rice (T1), Chinese milk vetch and double cropping rice (T2), rape and double cropping rice (T3) and fallow and double cropping rice (CK). The results showed that recycling of winter cover crop straws significantly increased soil TOC and CPA over CK. The order of TOC content and CPA under different cropping patterns was T2 > T1 > T3 > CK at the early and later rice harvest stages. Compared with CK, T1, T2 and T3 averagely increased soil TOC content respectively by 6.73%, 10.53% and 4.79% at early rice harvest in 2011 and 2012 and by 4.16%, 6.20% and 2.37% at later rice harvest in 2011 and 2012. However, no significant difference existed in TOC content among T1, T2 and T3 treatments. The CPA under treatments T1 and T2 with winter cover crop straw recycling was also higher than that of CK. Compared with CK, CPA under treatments T1 and T2 on average increased respectively by 10.52% and 21.52% at early rice harvest and by 11.99% and 15.59% at later rice harvest in 2011 and 2012. Also compared with CK, CPA, activity index (AI), carbon pool index (CPI) and CPMI under treatments T1, T2 and T3 improved at early and later rice harvest stages. The results further showed that CPA, AI, CPI and CPMI increased with winter cover crop straw recycling. The order of CPA, AI, CPI and CPMI under the different cropping patterns were T2 > T1 > T3 > CK. Thus winter cover crop straw recycling significantly influenced TOC content, AC and CPMI in paddy fields. Winter cover crop straw recycling had the best effect with Chinese milk vetch, followed by ryegrass and then rape.