有机肥促进红壤中非晶形纳米矿物形成的机制研究

Soil organic matter (SOM) content is one of the critical factors influencing the formation and evolution of soil fertility, and the formation of organo-mineral complex is the main mechanism of SOM sequestration. Our previous investigation showed that the content of SOM in the manure fertilization (M) and chemical plus manure fertilization (NPKM) treatments of a long-term fertilization station (22 years), located in Qiyang, Hunan Province, was significantly higher than that of no fertilization (CK) and chemical fertilization (NPK) treatments. This result may be attributable to the formation of noncrystalline nanominerals in soils from the M and NPKM fertilization treatments rather than CK and NPK fertilization treatments, which possess the huge specific surface area and the strong adsorption capability for organic matters. Therefore, fertilization treatment may modify the structure and morphology of minerals, form the organo-noncrystalline nanominerals complex, and improve soil fertility. This project aims to 1) characterize the formation and property of soil noncrystalline nanominerals in the different fertilization treatments; 2) study the relationship between noncrystalline nanominerals and soil bioavailability as well as adsorption/storage capability; 3) understand the role of organic matter and microbiology during the formation of noncrystalline nanominerals; 4) explore the factors limiting the bioavailability and adsorption/storage capability of soil noncrystalline nanominerals; 5) investigate the mechanism and strategy of SOM sequestration. In summary, the project will provide a new opinion about the sequestration and stability of SOM. Knowledge on the structure and morphology of soil noncrystalline nanominerals contributes to our understanding of the sequestration of SOM and provides novel information for scientific research and engineering application.

土壤有机质是土壤肥力形成和演变的关键因子，矿物-有机复合体的形成是土壤有机质稳定和提升的关键。申请人在前期研究中发现，长期定位试验点有机施肥和有机-无机配施的土壤有机质含量显著高于不施肥和化肥施肥的土壤，这可能归因于有机施肥的土壤中可以形成具有较大比表面积和较强吸附性能的非晶形纳米矿物，而化肥施肥的土壤中不能形成非晶形纳米矿物，仅能形成晶形矿物。因此，有机施肥可以改变土壤矿物的结构和形貌特征，形成非晶形纳米矿物-有机复合体，提升土壤有机质和土壤肥力。本申请项目拟从深入表征长期施肥土壤的非晶形纳米矿物的结构特征和形成机制出发，明确非晶形纳米矿物的结构和形貌特征及其与吸附/储存性能及生物稳定性的动态联系，理解有机物和微生物在土壤非晶形纳米矿物形成中的关键作用，找出限制土壤非晶形纳米矿物吸附和稳定性能的关键因子。该研究也将为土壤有机质提升机制探讨提供新思路。

土壤是全球最大的陆地碳库。矿物-有机物相互作用、团聚体的物理保护和气候因子是影响土壤有机碳稳定的主要机制。然而，由于土壤有机碳和矿物本身的高度异质性、动态变化等原因，至今很多科学家仍然将矿物-有机复合体作为一个“黑箱”进行研究，而缺乏对土壤有机碳稳定机制的深入理解。全面了解土壤有机碳的稳定机制对于充分发挥土壤的生态功能至关重要，也有助于管理人员制定相宜的土壤管理措施。鉴于此，本项目紧紧围绕相关研究的基础科学问题和国家需求，利用国内外长期定位试验站（25 年，160 年和175 年）、微宇宙试验（Microcosms）和室内同位素示踪试验，结合同步辐射（XANES/EXAFS/STXM/μ-XRF/SR-FTIR）、纳米粒子探针（NanoSIMS）、高分辨透射电子显微镜（HRTEM）和高通量测序（MiSeq）等创新技术平台，对1）土壤纳米矿物提升及其稳定土壤有机碳机制，2）土壤纳米矿物形成中的微生物学机制和3）土壤纳米矿物减缓土壤酸化、重金属有效性机制等方面进行了系统的研究。研究结果表明：长期施有机物可以提升土壤纳米矿物含量，增加有机碳固持、缓解土壤酸化和减少重金属有效性。同时，施肥措施改变了土壤微生物群落结构，影响了土壤铁循环和纳米矿物的形成。真菌可以直接转化常规矿物为纳米级矿物。研究成果增加了对土壤固碳、土壤肥力提升和土壤修复的认识，对于寻找合适的土壤培肥途径和制定土壤固碳决策等具有重要的意义。