小麦蚕豆间作根际红壤磷活化及其对（无机）磷施用的响应机制

It is well documented that rational intercropping could improve soil phosphorus availability and enhance P acquisition. However, little is known about the mechanism, especially on red soil. In the previous studies we found that wheat and faba bean intercropping improved red soil phosphorus availability and increased organic acids exuded by roots, and also increased P uptake by crops. In addition, the intercropping effect was related to the amount of phosphorus fertilizer applied. Whereas, the relationship between organic acids exuded by roots in intercropping system and rhizosphere phosphorus availability on red soil is still unclear. Especially in the condition of different P levels, the mechanism of intercropping changed rhizosphere phosphorus availability on red soil is remaining unknown. Therefore, based on the former researches, the study will mainly discuss in wheat and faba bean intercropping system:(1) under the condition of different rates of inorganic P fertilizer applied on red soil, the characteristics of rhizosphere available phosphorus content, inorganic phosphorus fraction of red soil and low molecule organic acids exuded by roots; (2) the reaction mechanism among different rates of inorganic P fertilizer applied, organic acids exuded by roots in intercropping system, changing of inorganic phosphorus fraction and mobilization of rizhosphere phosphorus. The study will determine the inter-mechanism among inorganic P applied-organic acids exuded by roots- P mobilization of red soil in intercropping system. The research will have important role on theoretically and practice value for people deeply understands the mechanism of intercropping could improve resources use efficiency, and scientific fertilization is important for increaseing crop yield and farmland ecosystem productivity.

合理间作能提高土壤磷的有效性、促进作物磷的吸收利用，但合理间作提高土壤磷有效性的机制了解不多，尤其在红壤条件下的作用机制尚不清楚。前期研究中发现，小麦蚕豆间作可以提高红壤根际磷有效性、改变根系低分子量有机酸的分泌、促进作物对磷的吸收利用，且这种效应与肥料施用量有关。但间作根系有机酸的分泌与根际红壤磷有效性之间的关系如何并不清楚，尤其是不同磷水平下，间作改变根际红壤磷有效性的机制如何，尚不明确。因此，本项目主要探讨小麦蚕豆间作条件下：（1）不同无机磷用量下，间作作物根际红壤有效磷含量、无机磷组分变化和根系有机酸分泌特征；（2）不同无机磷用量与间作作物根系有机酸的分泌、无机磷组分变化、根际红壤有效磷活化的响应机制。研究可阐明间作条件下无机磷供应-根系低分子量有机酸分泌-红壤磷活化的互作机制，对深入认识间作提高养分资源利用效率，科学施肥提高产量和农田生态系统生产力具有重要理论和实践价值。

磷肥的大量施用使农田土壤成为潜在磷库，如何充分挖掘利用现有的土壤磷库是当前研究的热点。豆科禾本科间作可提高土壤磷的有效性，但研究主要集中在石灰性土壤上。红壤磷库特征异于石灰性土壤，故豆科禾本科间作提高石灰性土壤磷有效性的机制，并不能适用于红壤。研究通过连续四年的田间定位试验、水培试验和根箱试验，分析不同磷水平下单间作小麦和蚕豆根际有效磷含量、根际无机磷组分含量、红壤有效磷含量和全磷含量，探讨间作对红壤磷有效性的影响及作用机制。研究从根系及根系分泌物的角度，揭示种间互作对根系分泌物的影响，定量解析根系低分子量有机酸分泌与间作提高红壤磷有效性的关系。结果发现，磷胁迫条件下，小麦蚕豆间作降低小麦和蚕豆根际Al-P和Fe-P含量，加速根际有效磷的耗竭，提高红壤有效磷含量20-50%。说明小麦蚕豆间作主要提高了中等活性磷（AL-P和Fe-P）的有效性。在红壤条件下，小麦和蚕豆根系分泌的低分子量有机酸以柠檬酸和苹果酸为主。间作促进小麦和蚕豆根系苹果酸和酸性磷酸酶的分泌及根际淀积，但对质子的分泌无影响。在磷胁迫条件下，小麦蚕豆间作促使根系变长、增粗，提高根系苹果酸分泌量2-4倍。且低浓度苹果酸（0.5mmol L-1）的分泌，可促进AL-P的活化；当苹果酸的分泌量>1 mmol L-1时也促进Fe-P的活化。研究揭示小麦蚕豆间作提高红壤磷有效性主要是由于间作提高苹果酸和酸性磷酸酶的分泌、活化红壤AL-P和Fe-P，而与质子的分泌无关，间作刺激根系伸长和增粗是红壤磷高效吸收的基础。研究证实不同土壤条件下，种间互作提高土壤磷有效性的机制有差异，研究为深入理解豆科禾本科间作提高养分资源利用效率、实现肥料减施增效提供了依据和支撑。.项目共发表论文12篇（SCI收录2篇），待发表论文3篇（SCI1篇，中文核心2篇）。培养博士生1人，硕士生5人，本科生10人。新增云南省青年拔尖人才1人，新增国家重点研发专项子课题1项、云南省农业联合基金项目2项，培养年轻教师2人，2人晋升高一级职称。