长期保护性耕作下豆-麦轮作体系黄绵土团聚体稳定性差异机制研究

Soil aggregate stability has a great influence on maintaining soil fertility and preventing soil erosion in the Loess Plateau rainfed farmland with loessial soil. Our present research on different conservation tillage measures and two phase rotation system with spring wheat and field pea has shown differences in soil aggregate stability. It showed that different tillage measures have effected the soil aggregate stabilitys of both wheat and pea fields . Also the stability of soil aggregates were variety between wheat and pea plots under the same tillage measure. However, the interaction between tillage and crop rotation and it effect on soil aggregate stability leaves many questions in the minds of many researchers. Issues such as “what is the major source in the difference of Relative index of soil aggregate stability? What is the difference in contribution between tillage and crop rotation? How are they coupled? These unanswered questions require further study. Based on a long-term experiment setting up in 2001, in situ visualization, laboratory analysis, multiple regression analysis and principal component analysis methods would be used to monitor the different characteristics in soil aggregate stability, construct the difference in soil generated by physics, chemistry, biology research on mechanism of the system, revealing the differences in the result in terms of the dominant factor and their interaction and clarifying the above factors and their relationship between the difference in soil aggregate stability for the two phase rotation system with different tillage measures. The study would provide some references for clarifying the response patterns of different tillage and crop rotation systems and characteristics of soil aggregates stability. The study would also perfect soil aggregate formation and disintegration mechanism under different cultivation measures and making reasonable decision to promote soil macro-aggregate formation stability and enhancing soil control measures.

土壤团聚体稳定性是影响黄土高原黄绵土农田肥力及侵蚀的重要因素。前期研究发现：长期保护性耕作措施下豌豆-春小麦轮作土壤团聚体稳定性存在差异：一方面，不同耕作措施下，同种作物农田各层土壤团聚体稳定性有差异；另一方面，同一耕作措施下，春小麦和豌豆田各层土壤团聚体稳定性也不同。但耕作与轮作交互作用下，上述差异的主要来源是什么？其对差异的贡献有多大？它们是如何耦合的？还有待深入探究。本研究拟借助2001年布设的耕作与轮作长期定位试验，采用原位观测、室内分析、多元回归分析、主成分分析等方法，监测土壤团聚体稳定性差异特征，构建差异产生的土壤物理、化学、生物学机制研究体系，揭示导致差异的主导因子及其交互作用，理清上述因子与保护性耕作措施及轮作黄绵土团聚体稳定性差异间的关系，可为掌握土壤团聚体特性对不同保护性耕作措施和轮作的响应规律，合理制定促进旱作农田土壤团聚体形成和稳定性增强的调控措施提供依据。

本研究基于布设在黄土高原旱作农田的春小麦、豌豆双序列轮作长期保护性耕作试验（共设4个处理：传统耕作+不覆盖、免耕+不覆盖、传统耕作+秸秆还田、免耕+秸秆覆盖4个处理）研究了不同耕作措施下土壤团聚体组成和稳定性特征及其影响机制。主要结论如下：.该区水稳性团聚体崩解主要是由于水分入渗而引起的，且水分快速入渗时的破坏最大；同时，免耕结合秸秆覆盖处理可有效提升土壤团聚体的水稳性，更有利于该区农田水土保持。. 秸秆添加处理（T和NTS处理）下5-30cm土层的根际土壤团聚体稳定性高于非根际土壤，表明添加秸秆可改善土壤根系生长，进而促进根系对土壤团聚体稳定性的提升。. 添加秸秆可提升土壤有机碳及其组分含量，特别是活性组分。秸秆添加处理下土壤团聚体固碳能力较强，总体来看NTS处理的效果最好。这表明免耕配合秸秆覆盖对土壤团聚体固碳效应最优，为团聚体的形成和稳定性的改善提供了良好的有机胶结物质，进而促进土壤团聚体稳定性的提升。. 团聚体中酶活性随着粒级的减小而升高，保护性耕作措施可改善土壤团聚体中酶活性，进而改善团聚体供给养分的能力。.