The chapter identifies phosphorus transfer (PT) as a multidisciplinary issue and focuses areas where future research is required. Potentially mobile P (PMP) is a useful concept because it attempts to weight soil P status in terms of environmental significance rather than by means of conventional soil measurement. The chapter describes agronomic management strategies, but the approaches are orientated towards agronomic rather than environmental concerns. The most significant area for further developing understanding of P transfer is hydrology, with its complexities of spatial and temporal variability. The chapter also describes new model approach that allows improved integration, which is of particular relevance when assessments of management effects and options for mitigation strategies are required. The new model structure provides a simple means for classifying and rationalizing P transfer and a basis for a spatial land use model. Moreover, it provides a basis for discussion and a means for defining future research needs on diffuse P transfer and its effects.