不同秸秆还田年限对稻麦轮作土壤团聚体和有机碳的影响

Effect of Years of Straw Returning on Soil Aggregates and Organic Carbon in Rice-wheat Rotation Systems

为了揭示稻麦轮作不同秸秆还田年限下土壤团聚体稳定性以及有机碳组分的变化特征及其响应机制,采用大田小区试验,考察不同秸秆还田年限(0,3,4,5,6,7,8,9a)对土壤团聚体分布特征和团聚体稳定性指数(平均重量直径MWD、几何平均直径GMD、分形维数D)的影响,并研究其与土壤有机碳组分的相关性。结果表明,秸秆还田条件下土壤大团聚体数量R_(0.25)、MWD和GMD均显著提升,分形维数D则显著降低,随还田年限越长趋势越明显,但短期秸秆还田(5a以内)对土壤MWD和分形维数D的改善效果不显著;长期秸秆还田显著提升了土壤总有机碳TOC,但短期秸秆还田(5a以内)与不还田处理差异不显著,长期和短期秸秆还田均对活性有机碳AC的提升效果显著;多元回归分析显示,相比AC,土壤团聚体结构稳定更能促进TOC的增长,GWD与土壤有机碳组分的拟合度最高,更适合用于揭示团聚体与有机碳组分之间的关系。

In order to reveal the change characteristics and the response mechanisms of the soil aggregate stability and organic carbon fractions to different years of straw returning in rice-wheat rotation systems, a field experiment was conducted to determine the effects of years of straw returning on the soil aggregate distribution characteristics and soil aggregate stability indexes （Mean Weight Diameter MWD, Geometric Mean Diameter GMD and Fractal Dimension D）, and to study their relationships with soil organic carbon fractions. The results of the study showed that under the condition of straw returning, soil macroaggregate content R025, MWD and GMD increased significantly, and the fractal dimension D decreased significantly, and the trend was more obvious with the increase of years of straw returning, but the improvement effect on MWD and fractal dimension D under short-term straw returning （within 5 years） was not significant. The long-term straw returning significantly increased soil total organic carbon TOC, but there was no significant difference in TOC between the treatments of short-term straw returning （within 5 years） and no straw returning. Both long-term and short-term straw returning could enhance the active organic carbon AC significantly. The multiple regression analysis showed that compared to AC, soil aggregate structure stability could promote the growth of TOC. GWD had the most significant correlation with soil organic carbon fractions, and it was more suitable for revealing the relationship between soil aggregates and organic carbon fractions.