This research was conducted in the upper reaches of

Improved grassland dominates the catchment (76% by area), along with acid grassland (10%) and arable land (6%), with 2.88 livestock units (LU) ha− 1 (cattle and sheep). The average Olsen P concentration from across 38 fields (14% of catchment) is 23.6 mg kg− 1 (σ = 9.9 mg kg− 1) with a range of 8–46 mg kg− 1.