微生物合成土壤有机磷的碳源和底物调节

Microorganisms play a critical role in soil phosphorus (P)dynamics, especially for immobilization of soil inorganic P and mineralization of soil organic P. Organic P compounds systhesized by soil microorganisms are easily mineralized and readily available. Therefore, P immobilized by soil microorganisms are essential for plant growth. Inputs of carbon and inorganic P and soil physico-chemical properties could influence the microbial synthesis of soil organic P.However,the systematic information about the regulations of carbon and inorganic P on microbial synthesis of soil organic P is largely limited. In this study, chemical speciations and quantities of P in the community and cell scales of soil microorganisms will be investigated using two types of soils (oxusls and histosols)with verious soil pHs and clay contents after repeated addition of different carbon substrates (glucose, starch and cellulose; 3.25 g C/kg) and inorganic P fertilizers (monopotassium phosphate, single superphosphate and triple superphosphate; 50 mg P/kg) by the techniques invovling phospholipid fatty acid, the extraction of microbial cells, solution 31P nuclear magnetic resonance and resin exchange. We will identify the key factors which impact microbial systhesis of soil organic P as well as the potential role of carbon substrates on bioavailability of inorganic P fertilizers. Findings from this study will provide fundamental understaning of bioavailability of exogenous P and management practice to improve soil P fertlity.

微生物是影响土壤有机磷周转的重要因素。外源无机磷施入土壤后被微生物同化合成的有机磷具有易矿化、周转快、有效性高的特点，在植物的磷营养供应和土壤磷素肥力提高中意义重大。微生物合成土壤有机磷受到碳源、无机磷底物、土壤性质如pH和机械组成等的影响，但目前国内外尚缺乏对碳源、无机磷底物等调节微生物合成土壤有机磷的系统研究。本项目将以不同pH/粘粒含量的红壤和黑土为研究对象，利用磷脂脂肪酸、土壤微生物细胞分离、液体31P核磁共振和离子交换等技术，对土壤进行碳源（葡萄糖、淀粉、纤维素, 3.25 g/kg）和底物（磷酸二氢钾、过磷酸钙、重过磷酸钙, 50 mg/kg）重复添加处理，探讨土壤微生物群落和个体细胞尺度的有机磷数量和组分变化，探明微生物合成土壤有机磷化合物的主要影响因素及其机理，以评估碳源提高肥料磷生物有效性的潜在作用，为提高外源无机磷的生物有效性和增加土壤磷素肥力提供理论依据。

土壤微生物在土壤磷的转化过程中起着重要的调控作用。通过对4种黑土与3种红壤（其理化性质差异显著）添加不同有效性碳源及不同有效性磷底物研究。结果显示，碳源添加显著增加了土壤微生物的总量与真菌的相对丰度，其中增殖的真菌对微生物量磷的增加产生了直接贡献；而pH与有机质的增高、可溶性氮与速效磷的降低促进丛枝真菌生长，使得磷酸单酯、磷酸二酯与焦磷酸盐的含量增加。碳源有效性比较发现，淀粉添加对有机磷的合成作用较差，纤维素与速效碳源葡萄糖效果相当。磷有效性与革兰氏阴性细菌的相对丰度有较好的相关关系，但在碳源充足情况下磷源投入对有机磷合成并未产生显著影响，此时有机磷的水解与合成可能呈现着动态平衡。