There was also some evidence of a response to this reduced P source pressure in closed Penicillin G P concentrations and losses in the catchment stream, particularly in Quick flow and Interflow concentrations, but there were no clear trends of improving biological quality over the three years. This suggests a diminished response to policy between P source pressure and P delivery and impact, at least over the short time scale of this study (3 years), where the strength of any observable trend along this cascade of responses is greater closer to the source end of the nutrient transfer continuum. Therefore, significant time lags can be expected between implementation of policy, decreases in nutrient source pressures and improvements in water quality impact and policy monitoring and assessment efforts will need to be cognisant of this.
AcknowledgementsThe authors wish to acknowledge the heterotrophs farmers and landowners for access to catchment farms and Teagasc technical and advisory staff for data collection. The Aquatic Services Unit, University College Cork, was contracted to gather stream ecological data. This research was funded by the Department of Agriculture, Food and Marine and administered by Teagasc under the Agricultural Catchments Programme.