外源碳调控亚热带红壤磷素的活化效应与微生物机制

Phosphorus (P) mobilization is a key factor to improve the P uptake by crops due to the special adsorption of red soil in the subtropical areas. Microorganisms are integral to the soil P cycle and microbial mediated P mobilization process is regulated by the input of carbon quality and quantity, while the microbial molecular mechanisms of the P mobilization are not clear and urgent need to investigation. In this project, we will conduct a simulate incubation and a field observation to study transformation and availability of soil P via changed microbial community using carbon addition and microbial inhibition. We attempt to reveal seasonal dynamic changes in P fraction, microbial biomass C and microbial biomass P in situ and establish correlation to P uptake of plant. The real-time PCR and Miseq high-throughput sequencing will be applied to explore the abundance and community structure of functional genes（phoD , pqqC and BPP genes）of the inorganic/organic P mineralization, which will be better to understanding on the inorganic/organic P mineralization of molecular mechanisms. The results of this study will be expected to provide a scientific basis for the steady P supply for crop production, and design of agricultural management practices against P pollution.

亚热带典型红壤对磷素吸附强烈，活化土壤难溶磷（包括有机磷）是提高磷素利用率的关键。土壤微生物是磷循环的驱动者，外源碳输入能促进磷素（以碳促磷）的微生物活化，但其活化强度及相关功能微生物尚缺乏深入研究。本项目拟应用液相31P核磁共振、实时荧光定量PCR、Miseq高通量测序等技术，首先，通过模拟培养试验结合抑菌处理，研究外源碳调控下的土壤磷素赋存形态及其动态变化规律，比较磷素微生物转化与化学转化的相对重要性；再次，通过田间小区试验，解析碳源添加下土壤磷组分、磷转化酶、微生物量磷的季节动态变化及其与作物吸磷量的关系；最后，结合上述试验，在分子水平上研究解无机磷基因（吡咯喹啉醌合成酶）、有机磷矿化基因（碱性磷酸单酯酶，植酸酶）丰度与群落结构及其影响因素，以阐明碳源调控磷素微生物活化的分子机制。研究结果可为实现农业可持续发展的磷素供应、磷素环境污染风险规避的农业管理措施设计提供科学依据。

如何活化农业耕作土壤固持磷素是土壤学研究关注热点和难点，微生物介导的磷素活化过程受碳源质量与输入量调控。本项目应用实时荧光PCR、Miseq高通量测序技术，采用模拟培养试验与田间小区试验相结合的手段，研究碳源对土壤磷素活化程度及其相关功能微生物的影响。研究结果表明：纤维素通过微生物同化过程调控难溶性磷向易利用磷的转化，而木质素则直接通过物理竞争吸附促进磷的释放；有机物料（农家肥）投入提高碱性磷酸酶活性，改变了磷活化功能微生物群落（phoD基因），且高量农家肥投入对磷活化效果更显著；生物质炭对磷素的活化机制与木质素类似，主要通过物理化学过程（竞争吸附）提高土壤磷有效性；秸秆还田与水分管理对土壤磷素活化具有交互作用，秸秆还田能够增强淹水对土壤磷素活化的效应。在旱地土壤中，含phoD基因细菌群落结构主要受土壤有机碳和pH影响，而在水稻土中，含phoD基因细菌群落结构主要受磷组分和pH影响。总体上，碳源在旱地土壤中对磷素的活化效应优于水稻土。