Eutrophication of freshwater bodies caused by phosphorus (P) loss from agricultural land continues to be a major environmental problem in Northern Ireland and the Republic of Ireland. Agricultural soils are implicated as one of the main P pressures on freshwater quality, but identification of specific P hotspots on farms and in river catchments has been a major challenge. This is because P hotspots occur when high soil P concentrations that are easily mobilised coincide with hydrologically sensitive areas that are prone to surface runoff. These ‘critical source areas’ (CSA) are diffuse across the landscape but mostly occur at or within individual farm fields. This is a scale where the conditions are difficult to predict due to small field sizes and the influences of micro-topography.
However, the individual field is a meaningful scale for farmers to understand the nature of the soil P pressure. Furthermore, developing a tool that can accurately predict where these CSAs are at this small scale is seen as essential to increase farmer participation in managing this problem. It is also the correct scale for farm advisors to engage and advise farmers on a one-to-one basis, and for public sector organisations such as the Department of Agriculture, Environment and Rural Affairs (DAERA) in Northern Ireland and the Irish Environmental Protection Agency (EPA) to target and manage problem areas at regional and national scales.