秸秆还田对土壤压缩回弹特性的影响机制

The organic matter content in the farmland of Northeast China has decreased year by year, and the soil compaction is seriously degraded. Straw returning is an effective measure to increase soil organic matter content. Determining soil compression-resilience characteristics will greatly reduce the risk of soil compaction. However, the compression-resilience characteristics of the soil in the area under long-term straw returning conditions are not well understood. In this study, the typical black soil and brown soil in the northeast region are used as experimental materials. The combination of field experiment and indoor simulation are carried out to study the mechanism of the compression-resilience of soil under different straw returning conditions (different straw returning amount and returning time). Based on the determination of soil structural indicators and clay-carbon ratio, the uniaxial compression test method is used to determine the compression curve of soil and calculate the deformation characteristic values such as pre-consolidation pressure value, compression index and rebound index; The law of soil structural indicators and clay-carbon ratio changes with straw returning amount and returning time are analyzed. The influence of various indicators on soil compression-resilience characteristics are quantitatively evaluated, and the mechanism of straw returning to the soil compression-resilience characteristics is clarified. The research results not only help to deepen the understanding of the soil compaction mechanism, but also provide a theoretical basis for the regulation of soil organic carbon content and soil compaction risk by straw returning in the black soil region of Northeast China.

东北农田有机质含量逐年下降，土壤板结退化严重。秸秆还田是提高土壤有机质含量的有效措施，明确土壤压缩-回弹特性将大大降低土壤板结发生风险。然而，到目前为止该地区在秸秆还田条件下土壤的压缩-回弹特性不十分清楚。本研究拟以东北地区典型黑土和棕壤为试验材料，采用大田试验和室内模拟相结合的方法，研究秸秆还田条件下，不同秸秆还田量和还田时长对土壤压缩-回弹特性的影响机制。在测定土壤结构性指标和黏粒饱和度的基础上，同时利用单轴压缩试验方法测定供试土壤压缩曲线并求算预固结压力值、压缩指数和回弹指数等形变特征值；分析土壤结构性指标和黏粒饱和度随秸秆还田量和还田时长的变化规律，定量评价各指标对土壤压缩-回弹特性的影响，阐明秸秆还田对土壤压缩-回弹特性的影响机制。研究结果不仅有助于深化对土壤板结机理的认识，还将为东北农田秸秆还田调控土壤有机碳含量、降低土壤板结风险提供理论依据。

东北农田有机质含量逐年下降，土壤板结退化严重。秸秆还田是提高土壤有机质含量的有效措施，明确土壤压缩-回弹特性将大大降低土壤板结发生风险。然而，到目前为止该地区在秸秆还田条件下土壤的压缩-回弹特性不十分清楚。本研究拟以东北地区典型黑土和棕壤为试验材料，采用室内模拟的方法，研究了秸秆还田量和不同水势条件下棕壤的压缩回弹特性，探讨了秸秆还田对土壤压缩回弹特性的短期影响；同时，研究秸秆还田条件下，不同秸秆还田量和还田时长对土壤压缩-回弹特性的影响机制，明确了长期秸秆还田对土壤压缩回弹特性的长期效应。研究结果表明，秸秆添加量、土壤基质势及其二者间的交互作用对压缩曲线最大曲率、预固结压力值、压缩指数和回弹指数的影响都达到显著性水平，秸秆添加有助于提高土壤回弹和抗压缩特性。秸秆添加量和秸秆还田时长与土壤的压缩指数和预固结压力都呈现正相关关系。随着秸秆添加量和秸秆还田时长的增加，回弹指数呈现先增加后降低的趋势。不同秸秆还田量和还田时长处理下的团聚体稳定性差异显著。研究结果不仅有助于深化对土壤板结机理的认识，还将为东北农田秸秆还田调控土壤有机碳含量、降低土壤板结风险提供理论依据。