施用有机物料对潮土结构演变的影响机制研究

Soil structure is the key factor to maintain soil fertility and productivity. Typical fluvo-aquaic soils in the Huanghuaihai plain are alkaline and sandy. As a result, the soil organic matter is difficult to accumulate and soil structure is not easy to form or keep stable. Application of organic materials is the most widely used management practices for improving soil structure and soil fertility in this area. However, the influential mechanism of these management practices on the evolution dynamics of soil aggregate/pore structure and soil productivity is still unclear. .In view of this, a field experiment was setup at Fengqiu Agro-ecological Experimental Station, Chinese Academy of Sciences, taking into account of organic materials application (straw, organic fertilizer, bio-char), soil water and nitrogen transport, and crop growth dynamics. Undisturbed soil pore and root structure parameters were extracted with micro-CT scanning and digital image processing. The research on dynamic response of soil aggregates and the pore structure to organic materials may elucidate the mechanism of exogenous organic matter on soil aggregate formation, improvement of soil water and nutrient capacity and crop growth. In addition, soil structure characteristics and its production function were used together to fully evaluate the effect of organic input practices on soil structure formation, which provides basis for proposing technical schemes suitable for alluvial soils of Huanghuaihai plain.

土壤结构是维持土壤肥力和农田生产力的关键要素。黄淮海平原潮土因其呈碱性和沙性导致土壤有机质难以积累提升、土壤结构不易形成并保持稳定。有机物料施用是潮土结构改良和地力培育中应用最广的管理措施，但目前关于土壤团聚体和孔隙结构以及土壤生产力对农业管理措施的响应机制研究仍有待深入。本项目针对潮土结构改良问题，通过田间布置有机物料施用（秸秆还田、有机肥、生物炭）、土壤水肥动态和作物生长动态田间定位试验，结合土壤孔隙/根系结构CT扫描和数值模拟等手段，开展土壤团聚体及孔隙结构对有机物料施用的响应动态及其机制研究，阐明外源有机物质对土壤团聚体和孔隙结构、土壤水养容量、作物生长发育的作用机理，并在全面考虑土壤结构性状和生产功能的基础上，评价不同有机物料对土壤结构和功能的改善效果，提出适合于黄淮海平原潮土区土壤结构改良的技术途径。

土壤结构是土壤肥力和土壤生产力的关键指标。解析不同农田土壤管理措施对土壤结构形成和保持、土壤生态功能维持和改善的内在机制，对农田地力培育和调控对策的制定具有重要意义。项目针对黄淮海平原碱性砂质潮土有机质含量低、土壤结构稳定性差问题，探讨施用秸秆（MS）、有机肥（OF）、生物炭（BC）、木本泥炭（WP）、聚丙烯酰胺（PAM）、秸秆还田+有机肥（SOF）等不同有机物料条件下，土壤团聚体和孔隙结构的响应及其机制，解析外源有机物质对潮土结构及其功能演变的作用机理，评价不同有机改良措施的实施效果，为黄淮海潮土区地力培育和土壤改良提供依据。取得以下主要结果：. 1、基于4年的田间定位试验数据，通过土壤团聚体分级、孔隙结构分析和三维网络模型，揭示了不同有机改良措施对土壤表观和微观结构的影响及其机制，表明有机物料投入对容重、团聚体及其稳定性、孔径分布均有不同程度的改良效果，其中SOF处理对提高团聚体稳定性、降低容重，降低孔隙复杂度、改善孔隙连通性的效果较好。. 2、综合分析田间持水量、作物生长参数、籽粒产量等土壤功能性指标，探讨了施用不同有机物料对土壤水分库容、作物生长的影响，表明添加有机肥的处理（单施有机肥OF，秸秆还田+有机肥SOF）对提升土壤水分库容、冬小麦产量效果优于其他有机改良措施。. 3、通过聚类分析和相关分析，解析了不同措施对土壤孔隙尺度结构的影响，以及土壤孔隙特征参数与表观结构参数、土壤功能指标间的关系，表明连通孔隙度、平均配位数等孔隙连通性参数与冬小麦产量、秸秆生物量呈显著正相关。秸秆还田+有机肥联合施用（SOF）可通过增加节点孔隙和通道数量，从而增加潮土孔隙连通性、持水能力和冬小麦产量，在黄淮海潮土区具有良好的应用前景。