A review of phosphorus and sediment release from Irish tillage soils, the methods used to quantify losses and the current state of mitigation practice.

Abstract

Throughout the European Union (EU), agricultural soils with high phosphorus (P) status due to a surplus input of fertiliser have been identified as a landscape pressure impacting on water quality. In the Republic of Ireland, approximately 80% of agricultural land is devoted to grass, 11% to rough grazing, and 9% to arable cereal and crop production. Consequently, the majority of erosion research has focused on quantifying nutrient and sediment losses from grassland. Tillage soils are, however, more susceptible to erosion than grassland soils and, in general, have higher levels of soil P. This paper reviews the current state of research, and the regulatory regime relating to diffuse P and sediment loss for tillage soils. It identifies the key threats to soil quality associated with cultivated soils, and proposes the targeting and remediation of critical source areas for effective mitigation of P losses from tillage soils. A multi-scaled approach is recommended, in which catchment and field-scale monitoring is complemented with controlled laboratory and small plot-scale rainfall simulation experiments to identify areas where P loss and soil erosion are at critical levels and may pose a threat to water quality. Catchment scale research will help to link critical source areas of sediment and P loss with hydrological pathways to surface waters in the catchment. These areas can then be targeted for remediation in the River Basin Management Plans.