氮的微生物固持与矿物固定间相互转化特征及其对秸秆还田的响应

Microbial immobilization-mineralization and clay minerals fixation-release of fertilizer nitrogen (N) were the important pathways of N conservation and supply in soils. However, the relationship between these processes is lack of systematic investigation to date. Using the red soil, meadow brown soil and black soil, this study focuses on the processes of N in microbial immobilization-mineralization and soil minerals fixation-release based on the long-term experiment in Shenyang Agricultural Station, Chinese Academy of Sciences. A series of incubation and pot experiments will be conducted with multiple techniques, including the techniques of isotope tracer, double labeling, microorganism culture and isotope dilution. Based on the systematic research on the mutual transformation characteristics of N in microbial immobilization-mineralization and minerals fixation-release and its response to straw returning, the specific aims of this proposal are to: (1) clarify the effects of microbial immobilization-mineralization process and minerals fixation-release process on N conservation and supply in soils, and the contributions of these processes on N use efficiency; (2) reveal the mutual transformation characteristics of microbial immobilization and minerals fixation, and quantify the relationship between these processes; (3) elucidate the cycling rates of N in microbial immobilization-mineralization and minerals fixation-release processes; and (4) construct the mathematical N-cycling models in soils, including the biotic and abiotic processes. The results will improve the soil N-cycling theroy system, and provide the theoretical basis and technical support for optimizing N management and scientific operation.

肥料氮的微生物固持-矿化和粘土矿物固定-释放是其在土壤中保存与供给的重要途径，但两者之间的关系至今尚缺乏系统研究。本项目以旱地红壤、潮棕壤和黑土为研究对象，以中科院沈阳生态实验站及相关长期定位试验为平台，以同位素示踪及双标记技术、微生物纯培养技术和同位素稀释技术为主要手段，以培养和盆栽试验为技术途径，围绕土壤微生物固持-矿化和粘土矿物固定-释放这一核心，系统研究肥料氮的微生物固持-矿化和矿物固定-释放之间的转化特征及对秸秆还田的响应，明确微生物固持-矿化和矿物固定-释放过程在保氮和后续供氮中的作用及其对氮肥利用率的贡献；揭示微生物固持和粘土矿物固定之间相互转化的关联影响，量化两者之间的数量关系；明晰微生物固持-矿化和矿物固定-释放过程的循环周转速率，构建有非生物过程参与的土壤氮素循环模型。相关成果可以完善土壤氮素循环理论体系，并为农田氮素优化管理和科学运筹提供理论依据和技术支撑。

肥料氮的微生物固持-矿化和粘土矿物固定-释放在土壤保氮供氮中的作用至关重要，但相关过程受土壤类型及外源有机物输入的影响。因此，本研究将以这两个过程为核心，阐明不同类型土壤生物和非生物的耦联过程及其对秸秆还田的响应。.对于固定态铵的释放，微生物固持和硝化作用分别在固定态铵释放的前期和后期占主导地位。低量秸秆还田对固定态铵的释放有促进作用；中量和高量秸秆则抑制其释放，同时，黑土的释放潜力要高于潮棕壤。秸秆还田提高了固定态铵释放后进入有机氮库的比例。.微生物来源氮矿化后可以被粘土矿物所固定，但其量不足固定态铵总量的1‰。黑土标记微生物来源氮矿化后大部分被硝化细菌所利用；而潮棕壤大部分则仍保存在有机氮库。秸秆还田显著增加了黑土标记微生物氮含量和潮棕壤标记非微生物有机氮含量。.就供氮能力而言，生物过程保氮供氮能力强于非生物过程，但就对肥料氮的保存与供给而言，则粘土矿物固定-释放作用大于微生物固持-矿化过程。秸秆还田有利于提高生物过程在保氮与供氮中的作用，而秸秆还田量对铵态氮的矿物固定与释放影响存在阈值效应。残留的肥料氮主要以有机氮形态，尤其是非微生物有机氮形态留存于土壤之中，残留率明显高于土壤其他氮库，表明土壤中残留的肥料氮大部分是经微生物介导以更为稳定的形态保存在土壤中。.综上所述，合理的秸秆还田量与方式有利于提高玉米产量、减少肥料氮的损失、使更多的肥料氮稳定留存于土壤之中，供后续作物利用。