Phosphorus losses in subsurface flow before and after manure application to intensively farmed land

A study was conducted to examine the loss of P in subsurface flow from three cultivated soils of varying soil P concentrations. Measurements were made in flow waters from the soils before applying manure and then 3 weeks after sowing the soils to grass. An additional measurement of P in flow waters was made 1 year later. Dissolved reactive P ŽDRP. concentrations measured in flow water before Ž0.15 0.20 mg l 1. and after Ž0.39 0.51 mg l 1. manure application exceed current estimates of those required to promote surface water eutrophication Ž0.05 mg l 1.. Concentrations of DRP 1 year after manurial application increased compared to 3 weeks after application and was attributed to the slow movement of P down the cultivated soil. Concentrations of soil P were significantly increased down the soil profile and attributed to the P saturation of soils before manurial application. The results suggest that despite the establishment of fast growing grass, P concentrations would not be mitigated in the short-term Ž 1 year., due to the large contribution of P in subsurface pathways.