Deriving phosphorus export coefficients for corine land cover types

Export coefficients for phosphorus (P) have been derived for a number of CORINE land cover classes, using data obtained for 30 subcatchments of two major rivers in Northern Ireland. Multiple regression methods have been applied, with soluble reactive P (SRP), soluble orgamc P (SOP) and particulate P (PP) loads as dependent variables. Arable areal losses of phosphorus were the highest, 2.33 kg SRP ha−1 yr−1 and 2.64 kg PP ha−1 yr−1. Improved and non-improved grasslands appear to export equal amounts of TP (0.8 kg ha−1 yr−1). However, the SRP export coefficient is greater for non-improved grasslands than improved grasslands, 0.62 kg ha−1 yr−1 and 0.26 kg ha−1 yr−1, respectively. This unexpected result may be due to the undrained and compacted nature of the soils associated with non-improved grasslands, which ensures that P remains in the surface layer, limits the possibility of adsorption down the profile and encourages surface runoff. In addition, the considerable amount of organic carbon present tends to reduce the P-binding capacity of these soils.