Agriculture, phosphorus and eutrophication: a European perspective

The enrichment of European waters with anthropogenic sources of nutrients (nitrogen (N) and phosphorus (P)) contributing to eutrophication, and the resulting impairment of water use for recreation, industry and drinking, has become a major environmental issue in recent decades. Concern over eutrophication first emerged in Europe’s coastal waters with subsequent commitments by bordering countries to reduce nutrient emissions to the sea (De Walle & Sevenster, 1998). National surveys of standing and flowing freshwaters in different EU countries also identified a widespread incidence of eutrophication and led to the development of various indicators to monitor trends in water quality (EEA, 2003). Whilst both N and P contribute to eutrophication, there is ample evidence that the main focus for reducing eutrophication should remain with phosphorus (Sundareshwar et al., 2003; Foy, 2005). With the introduction of the EU Water Framework Directive (WFD) in December 2000, there is now a legislative framework to implement catchment controls over P inputs to EU waters from all sources, including those from agriculture. According to EEA (2005), the agricultural contribution to total annual P loads in EU waters is often about 50% (range 25–75%) with higher proportional contributions in countries where point-source P inputs have been markedly reduced by wastewater treatment. Controls over transfers of P from agricultural land have therefore been judged a necessary part of the integrated catchment management needed to achieve the good ecological status demanded by Europe by 2015. Until the early 1990s, there had been very little EU research conducted on phosphorus transfer in runoff from agricultural land. As the potential linkages between agricultural intensification, increased P concentrations in land runoff and eutrophication became more widely appreciated (e.g. Tunney et al., 1997; Edwards & Withers, 1998), research to quantify the accumulation, loss and impact of P from land to water increased amongst different disciplines. In July 1997, EU COST Action 832 (Quantifying the Agricultural Contribution to Eutrophication) was set up to help co-ordinate this research activity in order that the agricultural contribution to eutrophication could be more uniformly assessed across Europe. The specific aims of the Action were to develop a common conceptual understanding of the processes of P transfer to water and to identify appropriate methodologies for quantifying the use, cycling, transfer and impacts of phosphorus in runoff from agricultural land. The Action involved 18 countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Norway, Poland, Romania, Spain, Sweden, Switzerland, the Netherlands and the UK) and over 140 scientists participated. This special issue of Soil Use and Management draws together the knowledge base and selected research studies conducted across Europe as part of COST 832 and supporting national research programmes. It succeeds an earlier special issue of Soil Use and Management that summarized research into phosphorus loss from agriculture in the UK (Edwards & Withers, 1998). The COST Action adopted the P transfer continuum theme outlined by Haygarth et al. (2005), in which four working groups discussed P inputs to agricultural land (sources), release of P from the soil or P amendments (mobilization), P transfer from the point of mobilization to the stream (delivery) and the fate of P on entering different types of water body (impacts). This is illustrated conceptually in Figure 1. This theme is continued in this special issue and complements other publications from the COST Action (Chardon & Schoumans, 2002; Kronvang, 2002; Chardon & Withers, 2003). The first four papers describe the range in P surpluses, the relative importance of the different processes of P transfer and the main controlling factors prevalent in the diverse landscapes of Europe. What is clear is the very large spatial and temporal variability in P transfer that occurs between different countries and also within countries as a result of differences in climate, topography, soil type, land use patterns and P surpluses, and the way in which these surpluses are managed. The role of intensive livestock farming, soil P accumulation and consequent leaching of P Correspondence: P. J. A. Withers. E-mail: Paul.Withers@adas.co.uk Soil Use and Management