KEYNOTE Diffuse pollution from agriculture: The phosphorus story and how it got complicated

Diffuse pollution from agriculture has focussed on phosphorus (P) transfer from land to aquatic environments. Research on P loss has typically focussed on understanding the sources and pathways of P loss to water and the P... [ view full abstract ]

Diffuse pollution from agriculture has focussed on phosphorus (P) transfer from land to aquatic environments. Research on P loss has typically focussed on understanding the sources and pathways of P loss to water and the P transfer continuum provided a conceptual model of P loss to guide research and emphasised the complex, inter-disciplinary nature of the problem. Whilst current policy instruments in water quality (EU Water framework Directive, WFD), seek to derive measures for agriculture, policy makers need to be mindful of the complexities that a variable biochemical and physical landscape brings. Pre-WFD research on P loss from agriculture assumed a direct and linear relationship between P in soil and potential losses to water and these results formulated the basis for our current restrictions on P usage on farms in Ireland and across EU. Post-WFD, we now know that these relationships are not linear, and that confounding factors such as lag times for nutrient transfer, nutrient attenuation in the landscape and hydrological connectivity create a complex biogeophysical setting upon which policy makers are expected to impose mitigation measures and risk assessment. In this paper, we document the significant components of diffuse pollution research during the past 20 years that shaped our understanding of P loss from agriculture, and we identify current research and knowledge gaps that present challenges for policy makers and practitioners, as the EU WFD moves into the second cycle to devise programmes of measures.