Agriculture, Ecosystems and Environment 188 (2014) 48–56 Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment j ourna l h omepage: www.elsevier.com/locate/agee Sustainable nutrient management at field, farm and regional level: Soil testing, nutrient budgets and the trade-off between lime application and greenhouse gas emissions James M. Gibbons, Julie C. Williamson, A. Prysor Williams ∗ , Paul J.A. Withers, Neal Hockley, Ian M. Harris, Jo W. Hughes, Rachel L. Taylor, Davey L. Jones, John R. Healey School of Environment, Natural Resources & Geography, Bangor University, Bangor, Gwynedd, LL57 2UW, United Kingdom a r t i c l e i n f o Article history: Received 28 January 2013 Received in revised form 7 February 2014 Accepted 8 February 2014 Keywords: Catchment management Diffuse pollution Environmental economics Grassland Soil acidity Water pollution a b s t r a c t Pollution from agriculture has environmental consequences at local and global scales. Managing this pollution is challenging because of diffuse sources and complex relationships between aquatic and atmo- spheric emissions. We illustrate this for a UK county that has suffered outbreaks of microbial pollution and eutrophication. We surveyed 49 livestock farms covering 12% of total agricultural grazed land. Soil nutrient status and whole-farm nutrient balances were determined, and the environmental impact of alleviating sub-optimal soil pH by liming was estimated at the county level. Only 37% of fields con- tained more P than was required for satisfactory grass growth, and soil acidity and available K were often limiting production. The mean farm N, P and K balances were similar to a modelled farm in England & Wales and EU indicators for the majority of North West Europe. This suggests that local eutrophication events linked to agriculture are more likely to relate to improper timing of nutrient application rather than over-application. None of the surveyed farmers used nutrient decision support tools, largely due to a lack of awareness and competing sources of information. Liming soils to pH 6.0 was estimated to both reduce N-leaching and N 2 O emissions; however, the net climate-change impact would be nega- tive as the direct CO 2 emissions would exceed CO 2 equivalent emissions of not liming by 394% (95% CI 201–21,232). Although liming currently presents a net cost to farmers, a sensitivity analysis suggests that reduced lime cost could lead to economic benefit to farmers but still increased greenhouse gas emissions. The results are applicable to all pasture-based agricultural systems where there is a drive to maintain or increase production through optimal soil and nutrient management. The findings demonstrate an impor- tant trade-off between reducing aquatic and atmospheric pollution and agricultural productivity, and the need to improve communication of this trade-off to farmers. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Maintaining agricultural production, while minimising diffuse pollution to water and air, is a global problem. Direct emissions from agriculture comprise roughly 11% of global greenhouse gas emissions and these emissions are projected to rise by 20% by 2030 (US-EPA, 2011). Including indirect emissions increases the total emissions from agriculture to 19–29% of the global total (Vermeulen et al., 2012). Anthropogenic activities have profoundly altered the global nitrogen and phosphorus cycles and will con- tinue to do so (Bouwman et al., 2009). Net anthropogenic nitrogen ∗ Corresponding author. E-mail address: prysor.williams@bangor.ac.uk (A.P. Williams). inputs in China, US & Northern Europe are estimated at between 2 and 3.5 t ha -1 of which 15–30% is exported in rivers (Swaney et al., 2012). Indeed, studies across the globe have shown agriculture to be amongst the largest contributor of annual nitrate and phosphate loads to river waters (Defra, 2007; Puckett et al., 2011; Liu et al., 2012). To advance sustainable agricultural production requires consid- ering the management activities at the scale of farm and field, in the context of policy at the regional or catchment level. In this paper, we consider the management of agricultural inputs and the con- sequent impact on diffuse pollution at three different scales: field, farm and region. Common field and farm management activities affecting diffuse pollution include the over-application of fertilizer (Lord and Mitchell, 1998; Withers et al., 2001), the inappropriate application of manure or slurry to land (Smith et al., 1998; Shepherd http://dx.doi.org/10.1016/j.agee.2014.02.016 0167-8809/© 2014 Elsevier B.V. All rights reserved.