A review of the policies and implementation of practices to decrease water quality impairment by phosphorus in New Zealand, the UK, and the US

The improper use of phosphorus (P) on agricultural land in developed countries is related to P losses that impair surface water quality. We outline policy in New Zealand, the UK, and the US who have imposed limits for P measured as ecological status, but in some cases, also as chemical concentrations or loads. We contrast the strategies used in each country and discuss their likelihood of being able to decrease P losses and improve surface water quality. All three countries have focused on understanding pathways and catchment processes so that cause and effect can be traced across spatial and temporal scales. A poor understanding of catchment processes and critical source areas of P loss has resulted in some areas where regulation has had minimal effect on P discharges.