Dissertation Research: Phosphorus mobilization by legume cover crops in agricultural systems

农业生产力通常受到土壤养分（包括磷）的限制。土壤中磷的有效性是有限的，因为大多数土壤磷不能直接提供给植物，自然投入不足以取代收获去除的磷。因此，需要施用化肥或粪肥来维持土壤肥力和产量，但经济上可行的磷储量正在下降，农业系统的磷损失使水生生态系统退化。该项目评估覆盖作物，特别是豆科作物，是否可以提供磷肥力的经济作物，同时减少磷投入的需求，通过动员土壤磷（转化为植物有效形式的土壤矿物和有机质结合的磷）。中心目标是确定如何不同种类的覆盖作物可以调动P.要做到这一点，互补的方法？在长期实验，温室研究和磷预算的计算现场测量？将用于将采取措施的不同形式的土壤磷，过程中动员磷，从覆盖作物到经济作物的磷转移率，和整体的重要性，覆盖作物相对于其他磷通量在农场scale.This项目将有助于替代施肥策略的发展，可以保持土壤肥力，同时减少昂贵的磷投入。它将测试使用覆盖作物是否有助于实现这一目标，并提供更好地了解不同植物物种生长的土壤中的磷转化。由于该项目的结果应与农场从业人员直接相关，因此该研究将与推广活动相结合，以广泛传播结果，包括公开数据，为覆盖作物数据库做出贡献，并通过学术界以外的活动（实地考察日，非技术出版物）转让知识。该项目还将涉及本科生，并为他们提供生态系统科学方面的基本培训。

Agricultural productivity is often limited by the availability of soil nutrients, including phosphorus (P). Phosphorus availability in soils is limited because most soil P is not directly available to plants and natural inputs are insufficient to replace P removed by harvest. Applications of fertilizers or manures are thus required to maintain soil fertility and yields, but economically viable P reserves are declining and P losses from agricultural systems degrade aquatic ecosystems. This project evaluates whether cover crops, especially legumes, could provide P fertility for cash crops while reducing P input requirements by mobilizing soil P (converting P bound to soil minerals and organic matter into plant-available forms). The central objective is to identify how different species of cover crops could mobilize P. To do so, complementary approaches ? field measurements in long-term experiments, greenhouse studies, and computation of P budgets ? will be used. Measures will be taken of different forms of soil P, processes that mobilize P, transfer rates of P from cover crop to cash crop, and the overall importance of P mobilization by cover crops relative to other P fluxes at the farm scale.This project will contribute to the development of alternative fertilization strategies that could maintain soil fertility while reducing costly P inputs. It will test whether using cover crops could contribute to this goal and provide a better understanding of P transformations in soils where different plant species grow. Because results from this project should be directly relevant to farm practitioners, this research will be coupled with outreach activities to disseminate results widely, including making the data publicly available, contributing to cover crop databases, and transferring knowledge through activities held outside of academic circles (field days, non-technical publications). This project will also involve undergraduate students and provide them with basic training in ecosystem science.