施用有机肥提高土壤微生物活性的关键碳源因子及其作用机制

The application of organic fertilizer has profound influences on soil microbial community structure and function. This strategy is of great importance for maintaining soil health and promoting soil quality in agriculture. However, little is known about the key carbon sources that play vital roles in enhancing microbial metabolism in the organic fertilizations, and the functioning mechanism of those carbon sources in soil ecosystems. In this proposed project, based on the long-term fertilization experiments that include varying organic fertilization treatments in red-soil, Fluvo-aquic-soil and paddy-soil regions, we will determine the key carbon sources responsive for the elevated soil microbial metabolic activity in organic fertilization treatments by combining BIOLOG and microcalorimetric techniques. A pot experiment will be further conducted to evaluate the impacts of those key carbon sources on soil microbial function and community structures by using multiple approaches, including BIOLOG, microcalorimetry, soil enzyme assays and high-throughput pyrosequencing. Finally, by laboratory cultivation, the soil microbes driving the metabolism of those key carbon sources will be investigated by high-throughput pyrosequencing and stable isotope probing techniques. Those results will be helpful for making rational fertilization strategy, regulating soil microbial process of nutrient cycling, and promoting agricultural sustainable development, which are of significantly theoretical and applicative significance.

施用有机肥对土壤微生物群落结构及功能均具有重要影响，对于维护农田土壤健康、提升土壤质量具有重要意义。然而，施用有机肥后哪些碳源因子发挥着关键作用，其在不同土壤生态系统中的作用机理如何还有待进一步阐明。本项目拟依托我国红壤、潮土、水稻土的长期定位施肥实验平台，选取多类有机肥处理的土壤，在耦合BIOLOG与微量热技术基础上，甄别提高土壤微生物代谢活性的关键碳源因子，明确它们与土壤及有机肥种类的关系；再通过温室盆栽实验，利用BIOLOG、微量热、酶活性及高通量测序等方法，从微生物功能和多样性角度揭示关键碳源因子对土壤微生物的影响；最后通过培养实验，利用稳定同位素核酸探针等技术，揭示关键碳源因子作用下具有代谢活性的关键微生物菌群。研究结果对于优化施肥方案、调控土壤微生物养分循环功能、促进农业可持续发展具有重要的理论价值和实践意义。

施用有机肥是提升土壤地力、保持农业可持续发展的重要措施之一。但目前针对不同类型土壤中有机肥施用后提高微生物代谢活性的碳源因子的研究鲜见报道，其微生物学作用机制尚不清楚。本项目依托江西、河南及山东地区的长期定位施肥实验地，选择有机肥处理、化肥处理及不施肥土壤为研究对象，采用BIOLOG微平板及微量热技术研究影响土壤微生物代谢活性的关键碳源因子；进一步通过温室盆栽和室内培养实验，采用高通量测序等技术，研究土壤微生物群落对关键碳源因子的响应机理，结果如下：.长期施用有机肥显著提高土壤微生物碳源代谢活性及热代谢活性，效果优于化肥处理；但不同类型土壤对碳源底物的偏好存在差异。通过耦合BIOLOG及微量热技术发现，部分碳源底物对土壤热代谢活性影响显著，例如，L-精氨酸提高了江西及山东土壤热代谢活性，糖原对江西及河南土壤促进效果明显。据此推断，这两种碳源可能是提高相应土壤微生物代谢活性的关键碳源因子。采用盆栽实验研究糖原与不同类型磷肥配施对植物生长及江西红壤细菌群落的影响，发现糖原与缓效型磷肥配施显著提高植物叶片光合速率常数及土壤脱氢酶活性，降低绿弯菌门、放线菌门、酸杆菌门相对丰度，但显著提高变形菌门、拟杆菌门的比例，说明这类微生物可能参与糖原在红壤中的转化。进一步通过室内培养实验，研究糖原不同添加量对土壤酶活性、细菌群落结构的影响。结果表明，在江西红壤中，高量糖原对土壤微生物活性产生抑制效果，但中、低量糖原会提高土壤微生物活性，增加拟杆菌门、酸杆菌门的相对丰度；在河南潮土中，脱氢酶活性提高与糖原添加量无关，但添加糖原均显著增加变形菌门的比例，说明变形菌门可能是糖原促进潮土微生物代谢活性的关键微生物。本项目研究结果可为指导当地农业生产、优化施肥方案、提升土壤地力及促进农田可持续提供理论依据。