关中平原作物秸秆不同还田方式对土壤有机碳和碳库管理指数的影响

Effects of different straw-returning regimes on soil organic carbon and carbon pool management index in Guanzhong Plain,Northwest China

以关中平原持续4年的小麦、玉米（麦玉）秸秆还田中长期定位试验为基础,研究了麦玉秸秆9种不同还田方式对土壤总有机碳（TOC）、活性有机碳（LOC）含量和活性有机碳分配比例（LOC/TOC）、总有机碳储量（SCS）及碳库管理指数（CPMI）的影响.结果表明：麦玉秸秆还田均可显著提高土壤（0~30 cm）TOC、LOC含量和SCS,且土壤有机碳主要集中于耕层（0~20 cm）;麦玉秸秆双季还田的TOC、LOC含量和SCS显著高于单季还田和双季均不还田,其中,与双季均不还田相比,小麦秸秆粉碎还田-玉米秸秆深松还田的TOC、LOC含量和SCS提高幅度最显著.在0~10和10~20 cm土层中,小麦秸秆粉碎还田-玉米秸秆深松还田的CPMI显著高于其他处理,其中,小麦秸秆粉碎还田较其不还田可使CPMI提高19.1%和67.9%,玉米秸秆深松还田较其不还田可提高22.6%和32.4%.相关性分析显示,CPMI较LOC/TOC更能有效表征0~30 cm土层土壤有机碳的固持和转化关系.从提高本地区土壤有机碳固持量角度来看,小麦秸秆粉碎还田-玉米秸秆深松还田为最佳还田方式.

A four-year （2008-2012） field experiment was conducted to investigate the effects of different straw-returning regimes on soil total organic carbon （TOC） , labile organic carbon （LOC） and the ratio of LOC tO TOC （LOC/TOC） as well as TOC stock （SCS） and soil carbon pool man- agement index （CPMI） in a farmland with maize-wheat double cropping system in Guanzhong Plain area, Shaanxi Province, China. The results indicated that soil TOC and LOC contents and SCS were significantly increased when wheat or maize straw was returned to field, and the increasing extent showed the rising order as follows： double straw-returning 〉 single straw-returning 〉 no straw-retur- ning. Compared to no straw returning, a significant increase of TOC and LOC contents and SCS was found in the treatment of wheat straw chopping retention combined with maize straw chopping sub- soiling retention （WC-MM）, and CPMI of WC-MM was significantly higher than in the other treat- ments in 0-20 cm soil layer. Compared to no wheat straw returning, soil CPMIs in 0-10 cm and 10-20 cm soil layer increased by 19.1% and 67.9% for the wheat straw chopping returning treat- ment, and by 22.6% and 32.4% for the maize straw chopping subsoiling treatment, respectively. Correlation analysis showed that soil CPMI was a more effective index reflecting the sequestration of soil organic carbon in 0-30 cm soil layer than the ratio of LOC to TOC. This study thus suggested that WC-MM regime is the best straw-returning regime for soil organic carbon sequestration.