秸秆还田方式对旱地草甸土活性有机碳组分的影响

为阐明不同秸秆还田方式下草甸土活性有机碳组分的分布特征，基于玉米田间定位试验，分析了不同耕作与秸秆还田方式下三个深度土层土壤有机碳及其活性组分的变化。结果表明：频繁的翻耕加速了表层（0~20 cm）土壤有机碳的矿化分解，使有机碳含量下降；免耕秸秆覆盖还田有利于表层土壤有机碳的增加，秸秆翻耕还田促进了中层（20~40 cm）土壤有机碳的积累；秸秆连续翻耕还田提高了中层土壤高活性和中活性有机碳的含量及土壤碳库管理指数，秸秆浅翻还田对表层和中层低活性有机碳的影响显著高于深翻还田与覆盖还田，但短期内秸秆连续浅翻还田与深翻还田对提高土壤碳库管理指数的差异不大。研究表明，土壤高活性和中活性有机碳对耕作深度的响应更加敏感，而秸秆还田主要使低活性有机碳增加，这也是玉米增产的主要原因。

Effects of different straw returning methods on labile organic carbon distribution in upland meadow soil

This study used field positioning experiments to clarify the distribution of organic carbon under different methods in which straw was returned to upland meadow soil. The labile organic carbon components of three deep soil layers in each treatment were compared to summarize the changes in soil organic carbon and labile components under different tillage and straw return methods. The results showed that the mineralization and decomposition of organic carbon in topsoil(0~20 cm) was accelerated and its content decreased under frequent tillage methods. This content increased in the same layer under no-tillage straw returning; tillage with straw returning increased the accumulation of organic carbon in the middle layer(20~40 cm). Continuous tillage with straw returning improved high and medium labile organic carbon content in this middle layer and the soil carbon management index. Furthermore, shallow tillage with straw returning increased low labile organic carbon in the surface and middle layers significantly more than that obtained when deep tillage with straw and no-tillage with straw were used. However, the difference in the soil carbon management index under tillage with straw returning treatments was not significant in the short-term experiment. Our results indicated the high and medium labile organic carbon levels in the soil were sensitive to changes in tillage depth while straw management methods mainly increased the content of low labile organic carbon and was the main reason for the increase in maize yield.