Phosphorus from agricultural sources is a component of diffuse P pollution delivered to surface waters in Ireland.

Understanding the sources and pathways of P loss from grassland soils has become the central theme of much of the research undertaken at laboratory, field and catchment scales in recent years.

Mechanistic and process-orientated research on soil P cycling and hydrological pathways tends to be carried out in isolation at laboratory and field scales.

Catchment-scale research allows an integration of sources and pathways of P loss that provides an understanding of how these processes interact and contrive to deliver losses to water.

Modelling P loss from catchments moves P research from a fundamental level to an applied level, so that results can provide a decision support for catchment managers.

Recognised processes in soil P pools and hydrological pathways are combined with agricultural activities (landuse patterns, P usage, timing of applications, stocking density) to generate predictive amounts of P in surface waters.

Catchment characteristics, such as arrangement of soil types, land-use patterns and rainfall, can be incorporated into some models to provide a profile of a catchment to determine losses based on the catchment’s response to P sources and water movement.

Full executive summary in report.