62. The Role of Soil Phosphorus in Controlling Sediment Associated Phosphorus Transfers in River Catchments

Many of the models used to determine phosphorus (P) transfers within river catchments use soil-P concentrations as one of the main input data sets. Such soil-P values are often based on bulked soil cores. To test the validity of using such data, depth profiles of total-P and Olsen-P were determined for arable and grassland fields in the catchment of the Hampshire Avon, UK. For the soils under grassland, maximum soil-P values occur at or near the surface and decrease with depth. For soils under arable, total-P values are broadly constant within the plough layer, whereas for Olsen-P maximum values are located at or near the surface, below which values are broadly constant to the plough depth. These findings have important implications for the use of bulked soil-P data to represent the concentrations of P at the soil surface, particularly for modelling P transfers associated with soil erosion and overland flow.