施用有机肥调控菠萝蜜园土壤有机碳库的微生态机制研究

The long-term application of chemical fertilizers in the jackfruit garden has resulted in low soil organic matter which is an important factor restricting the yield and quality of jackfruit. Returning organic materials to fields is an important way to improve soil organic matter level and crop yield. The ultimate aim for soil microbiome manipulation is to make the beneficial rhizosphere microflora based on organic inputs. Previous work done by the applicant has confirmed that the application of cow manure can induce beneficial rhizosphere microflora and increase soil organic carbon and functional microbial abundance in greenhouse experiment. However, it is still unclear about what kind of beneficial microbes were assembled in the rhizosphere, which were recruited from the bulk soil under field conditions. What works in the soil for material circulation and plant growth is a complex microbial food web. In particular, the mechanism of the interaction between multi-trophic levels such as nematodes and microbiome, and the interaction between roots and rhizosphere microflora on soil organic carbon pool has not been clearly elucidated. The research program aims to analyze the contribution of interaction among microbes, nematodes and physicochemical factors to the soil organic carbon pool by field and greenhouse experiment. This program is very important for ascertaining the key factor affecting soil organic carbon pool under the action of organic fertilizer, and is also very vital for elucidating the mechanism of rhizosphere microbiome assemblage ediated by root exudates. Finally, this project will provide the theoretical basis for the efficient use of nutrients and the rational regulation of soil ecosystem functions.

近年来菠萝蜜园长期施用化肥，导致土壤有机质含量低，树体衰弱，产量和品质受限。有机物料还田是提高土壤有机质水平和作物产量的重要途径，而基于有机投入形成有益根际微生物是区系调控的最终方向。申请人前期工作已证实盆栽试验条件下，施用牛粪有机肥能诱导有益根际微生物区系，提高土壤有机碳含量和功能微生物丰度。但此菠萝蜜根际在田间条件下从土壤中具体招募了何种微生物进行组装而形成此有益微生物区系亟待研究。土壤中对物质循环和植物生长起作用的是一个复杂的微生物食物网，尤其是结合多营养级如线虫和微生物互作以及根系与根际微生物互作影响土壤有机碳库的机制都未清楚阐明。本项目拟通过田间定位和培养试验，分析菠萝蜜根际微生物、线虫及理化因子互作对土壤有机碳库的贡献，阐明有机肥作用下影响土壤有机碳库的关键驱动因子，探明菠萝蜜根系分泌物介导下的有益根际微生物区系形成机制，为养分高效利用及土壤生态系统功能的合理调控提供理论依据。

菠萝蜜园长期偏施化肥，用养失衡，导致土壤退化，生产力下降，严重制约了产业可持续发展。有机改良土壤招募了何种微生物进行组装并通过根际互作影响土有机壤碳库有待深入研究。本项目采样高通量测序技术和土壤理化因子测定，解析了长期施用有机肥对土壤微生物群落构建和有机碳库的影响，施用有机肥显著增加土壤细菌、真菌、总线虫和食细菌线虫丰度，降低植食性线虫丰度。有机肥增加土壤与碳循环相关的功能细菌和腐生-共生型和病理-腐生型真菌类群，提高土壤pH、土壤全量N、P、K含量和有机碳组分含量；而化肥则增加了与氮循环相关的功能细菌和病理-腐生-共生型真菌类群，提高土壤速效N、P、K含量。PLS-PM分析表明施肥对菠萝蜜产量的影响包括正的直接效应和间接效应。通过土壤微培养实验，发现根系分泌物的添加对微生物群落尤其是真菌群落有显著影响。施肥土壤添加根系分泌物后显著增加土壤总线虫、杂食/捕食性线虫数量、SOC和DOC含量，土壤受到的扰动更小。有机肥土壤中添加根系分泌物后增加了土壤生态网络的交互度。初步得出施肥处理的根系分泌物中氨基酸类物质可能是介导有益根际微生物区系形成的关键物质。生物添加实验结果也表明，生物添加后土壤微生物的代谢功能类群与根系分泌物的关键碳组分变化趋势基本一致，这可能是根际有益微生物驱动根系分泌物组分的初步证据。此外，微生物α和β多样性均表明线虫的添加对土壤微生物区系形成产生显著影响，可以增加生态网络的交互度。而微生物的添加也明显影响土壤线虫群落结构，对土壤的扰动更小。本项目的研究对于解析施肥诱导根际有益微生物区系形成调控土壤有机碳库的作用机制具有一定的理论指导意义，从“根际对话”角度解析植物根系-微生物-线虫之间的互作关系，对实现土壤生态系统结构与功能的合理调控具有重要的理论和实践意义。

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