生物覆盖对西南“旱三熟”种植区农田土壤有机碳氮及微生物多样性的影响

The hilly regions of southwest China belong to the typical ecologically vulnerable zone where the farmlands with middle and low yield are concentrated. Due to high planting index, imbalance between land use and maintenance, and serious soil and water erosion, there are some problems such as degradation of farmland quality, low agricultural productivity and low productive benefits. Therefore, there is a realistic necessity and great potential for implementing biological mulch including straw mulch and intercropping of milk vetch. With triple intercropping system as study subject, this project will be conducted to probe the law of temporal and spatial variation of organic carbon and nitrogen in farmland soil under different modes of biological mulch. Furthermore, by adopting enzyme technology, and molecular biotechnology such as phospholipid fatty acid method (PLFA), fluorescent quantitative PCR analysis and MiSeq high-throughput sequencing analysis, the effects of biological mulch on the composition structure and ecological functional diversity of soil microbial community and the activity of enzymes relevant to carbon and nitrogen metabolism in both rhizosphere and non-rhizosphere of different crops will be investigated; the structure and encoding gene expression of functional microbes participating in soil carbon and nitrogen metabolism will be revealed; and the action mechanisms of soil microbes to the transformation of organic carbon and nitrogen as well as to crop productivity will be clarified. The study results can provide theoretical guidance for the promotion of soil quality, the improvement of ecological environment, and the high yield and high efficiency of crops in drylands in hilly regions of southwest China.

西南丘陵区是我国典型生态脆弱区和中低产田集中分布区，由于复种指数高、土地用养失衡、水土流失严重，面临耕地质量下降、农业生产力和生产效益低等问题，具有推行秸秆覆盖、紫云英间作等生物覆盖的现实必要性和巨大潜力。本项目以西南“旱三熟”种植模式为研究对象，在探讨不同生物覆盖方式下农田土壤有机碳、氮时空变异规律的基础上，运用酶学技术以及磷脂脂肪酸法（PLFA）、荧光定量PCR分析、MiSeq高通量测序分析等分子生物学技术，深入研究生物覆盖对农田不同作物根际与非根际土壤微生物群落组成结构、生态功能多样性和碳氮代谢相关酶活性的影响，揭示不同生物覆盖措施下参与土壤碳氮代谢的功能微生物结构与编码基因表达，进而阐明土壤微生物对有机碳、氮转化和作物生产力的作用机制。研究结果可为西南丘陵区旱作农田土壤质量提升、生态环境改善和农作物高产高效提供理论指导。

针对西南紫色土丘陵区水土流失严重、土地用养失衡、农业生产力低下等问题，以“旱三熟”农田为研究对象，在探讨不同生物覆盖方式下农田土壤碳、氮等养分变异规律基础上，深入研究生物覆盖对不同作物根际与非根际土壤微生物群落结构和功能多样性以及养分代谢相关酶活性的影响，进而揭示土壤微生物和酶对碳、氮等养分转化和作物生产力的作用机制。结果表明：.①秸秆、紫云英覆盖对小麦田不同养分运转产生的效应有所差异，紫云英覆盖对氮素输入与运转产生关键作用，而秸秆覆盖对磷、钾元素影响较大，两者协同覆盖可产生叠加效果。.②生物覆盖可提高大豆田土壤速效养分含量和养分循环相关酶活性，促进大豆地上部分养分积累，并提高大豆光合能力，最终提高大豆产量。.③生物覆盖可改善玉米田土壤理化性质，增加土壤微生物量碳氮和脲酶活性，利于植株干物质积累和产量增加，且以秸秆+紫云英覆盖效果最优。.④生物覆盖能改善甘薯田土壤环境，提高土壤呼吸速率和碳氮及其组分含量，利于甘薯干物质量及产量增加，且以秸秆+紫云英覆盖效果最优。.⑤生物覆盖可增加蚕豆田土壤养分含量，提高碳、氮、磷转化相关酶活性，提高细菌变形菌门、拟杆菌门丰度和真菌球囊菌门丰度，利于农田生态环境自我动态调节，促进蚕豆根系发育和产量提高。.⑥生物覆盖能有效提高“旱三熟”农田土壤有机质、总有机碳、总氮、速效氮、磷、钾等养分含量，提高土壤纤维素酶、酸性磷酸酶、蔗糖酶、淀粉酶、脲酶及蛋白酶活性，诱导土壤中草酸的累积，从而增加作物生长所需的活性养分。.⑦生物覆盖对“旱三熟”农田土壤微生物群落多样性和丰富度及其结构的调节存在空间异质性和作物类型差异性。.⑧生物覆盖能有效调节“旱三熟”农田土壤中真菌和细菌群落的物种占比，重塑微生物群落间的相互关系；能提高土壤微生物对小分子碳的代谢能力，促进土壤中碳循环的进行。.研究结果对于优化西南地区旱作农业技术措施、改善土壤质量、促进农业固碳减排具有重要理论指导意义。