b'Room for nutrient improvement: A Field Scale Audit ofP Management and soil P Trends in two Mixed-Use CatchmentsMcDonald NT1, Wall DP2, Mellander P-E1 , 2, Buckley C3, Shore M4, Shortle G1, Leach S1, Burgess E1, OConnell T1 and Jordan P51Agricultural Catchments Programme, Teagasc, Johnstown Castle Environment Research Centre, Wexford, Co. Wexford, Ireland2Crops, Environment and Land Use Programme, Teagasc, Johnstown Castle EnvironmentResearch Centre, Wexford, Co. Wexford, Ireland3Agricultural Economics and Farm Surveys, Teagasc, Athenry, Co. Galway, Ireland4 Local Authority Water Support and Advice Team, Limerick County Council, Co. Limerick, Ireland5School of Geography and Environmental Sciences, Ulster University, Coleraine, N. IrelandAccounting for the distribution of soil phosphorus within fields is crucial in identifying hotspotsof agronomic underperformance and/or environmental risk to water as a consequence ofinadequately managed P disruption. There is also a need to understand how P use and legacy soil P evolves under the Nitrates Action Programme (NAP) regulations from the European Union (EU) Nitrates Directive. In an Irish case study the aim was to provide a detailed audit of P balance and soil P responses and trends in two mixed land use agricultural catchments (Arable A- Castledockrell and B-Dunleer) across a four year study period. Driven by increased chemical P inputs the field balances in the Arable A catchment had an average surplus P, ranging from 1.9 to 7.5 kg ha-1 yr 1. However, during the study period 2010 to 2013, the average soil test P (STP)levels declined, with the area of excessive soil P concentrations decreasing by 8%. Similarly, in the Arable B catchment the average annual P inputs increased the surplus field P from -0.42to 25.5 kg ha-1 yr-1, but the area of excessive soil P concentrations increased by 4%. To some extent, this increase is attributed to some fields receiving excess applications of organicnutrient forms above crop requirements. Whilst, the legacy soil P (i.e. levels excess of croprequirement) declined in the Arable A catchment indicating a response to NAP, for bothcatchments it is evident that the distribution of P sources within farms was poor and P inputs often did not match crop and soil P requirements at the field scale. This study highlights the need for improved support to knowledge transfer mechanisms so as to deliver better farm and soil specific nutrient management planning strategies that offer dual benefits of improved water quality and increased crop outputs.2'