充分挖掘农田土壤遗留磷（legacy phosphorus）资源为农业节肥增效与可持续发展独辟蹊径。玉米‖大豆间作可提高土壤磷有效性，而面对当前停/减施磷肥的国家需求，针对我国不同土壤类型，玉米‖大豆间作对土壤遗留磷供给的调控特征与分子机制仍不清楚。本项目拟针对我国典型土壤类型，采用根系分隔盆栽试验，探索玉米‖大豆间作土壤遗留磷的作物有效性及供给特征；利用同步辐射X射线吸收近边结构谱、微探针、X射线扫描透射显微术和液相磷-31核磁共振等前沿微结构分析技术，揭示根际土壤遗留磷形态转化的分子机制；以鸟枪法宏基因组测序探明根际微生物磷功能基因组成及微生物群落结构，并从土壤-根系-微生物多角度综合分析，甄别土壤遗留磷供给的关键驱动因子，最终系统阐明玉米‖大豆间作对土壤遗留磷分子形态及作物有效性的调控机制，为评估、挖掘、调控我国土壤遗留磷资源提供前瞻性理论依据。

Full exploitation of legacy phosphorus (P) currently present in soils is an innovation way towards less dependence on fertilizer and sustainable development in agriculture. It is well documented that maize/soybean intercropping can improve soil P availability. With the current national demand for stopping/reducing P fertilizer, however, little is known about the regulation characteristics and mechanism of maize/soybean intercropping on crop utilization of soil legacy phosphorus in Chinese soils with different soil types and P fertility. Selecting typical soil types with common P fertility in China, this project aims to study P availability and supply of soil legacy P under maize/soybean intercropping based on pot experiments with and without root separation. Utilizing state-of-the-art techniques, including synchrotron-based X-ray absorption near-edge structure, microprobe, X-ray scanning transmission microscopy and solution P-31 nuclear magnetic resonance, we investigate the molecular speciation and its transformation of soil legacy P. Furthermore, the composition of P functional genes and the microbial community are investigated by shotgun metagenomic sequencing. Then, we also identify the key driving factors regulating P supply of soil legacy P from multiple aspects of soil, root, and microbe. Finally, the regulation mechanisms of maize/soybean intercropping on molecular speciation and crop availability of soil legacy P are systematically clarified. Results should provide prospective information to assess, mine, and regulate the legacy soil P reserves in China.