滨海盐碱地不同外源改良物质添加下土壤氮素转化微生物驱动机制

氮是滨海盐碱地土壤质量和作物产量最重要的限制性养分。外源改良物质添加改变了土壤微环境，进而影响了微生物所驱动的氮素转化过程。然而，不同改良物质添加下土壤氮素转化关键过程间的耦合关系及其功能微生物驱动机制尚未充分揭示，成为制约滨海盐碱地氮素调控增效的主要瓶颈。选用秸秆、有机肥、生物质炭和生物菌肥4类典型外源物质开展改良试验；采用N-15稳定同位素示踪技术，研究不同改良物质添加下土壤氮素转化关键过程（矿化、硝化、同化、反硝化、硝酸盐异化还原成铵）响应特征及耦合关系；应用qPCR和高通量测序方法，明确不同改良物质添加下土壤氮循环功能（氨氧化和反硝化）微生物群落响应特征；基于数理模型和机器学习方法，阐明土壤氮循环功能微生物群落变化的主控因子；进而构建结构方程模型，揭示滨海盐碱地不同改良物质添加下土壤氮素转化关键过程的微生物驱动机制。项目可为滨海盐碱农田土壤氮素减损固持和调控增效提供理论依据。

Nitrogen is the most important limiting nutrient for soil quality and crop yield in coastal saline-alkali land. Addition of the exogenous amendments changed the soil microenvironment, and thus affecting the key transformation process of nitrogen, which driven by microorganisms. However, the coupling relationship between the key processes of soil nitrogen transformation and the driving mechanism of nitrogen-related functional microorganisms have not been fully revealed, which has become the bottleneck of nitrogen regulation and efficiency in coastal saline-alkali land. The field experiment was conducted with four typical exogenous amendments (straw, organic fertilizer, bio-char and microbial fertilizer) to reclaim coastal saline-alkali land in this project. The N-15 stable isotope dilution method was applied to investigate the response characteristics of key processes (mineralization, nitrification, immobilization, denitrification, and dissimilatory nitrate reduction to ammonia) of soil nitrogen transformation under the addition of different exogenous amendments, and the real-time fluorescence quantitative polymerase chain reaction (qPCR) and high-throughput sequencing technology were used to identify the response characteristics of soil nitrogen-related functional microorganisms under addition of different exogenous amendments. Furthermore, the key controlling factors of soil nitrogen-related functional microorganism communities were clarified based on the mathematical model and machine learning method. Finally, the structure equation model (SEM) was established to reveal the microbiological driving mechanism of the influence of different exogenous amendments additions on the key process of soil nitrogen transformation in coastal saline-alkali land. The project can provide a theoretical basis for the reduction and fixation of soil nitrogen, and the regulation and efficiency of soil nitrogen in coastal salinized farmland.