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Soil testing has been an accepted agricultural management practice for decades. Interpretations and fertility recommendations based on soil analyses and the information obtained with soil samples on cropping systems, tillage practices, soil types, manure use, and other parameters have contributed to the increased efficiency of agricultural production. Recently, however, analyses of long‐term trends in soil test P values have shown that soil P in many areas of the world is now excessive, relative to crop P requirements. The role of P in the eutrophication of surface waters and emerging concerns about the human health impacts of toxic algal/dinoflagellate blooms have heightened public awareness of nonpoint source pollution by agricultural P. The greatest concerns are with animal‐based agriculture, where farm and watershed‐scale P surpluses and over‐application of P to soils are common. The need for nutrient‐management plans based on N and P is now an issue of intense debate in the U.S. and Canada. This paper addresses three issues: Should the applications of organic wastes and fertilizers be based on soil P and, if so, what is the most appropriate testing method to assess environmental risk? How can our knowledge of soil P chemistry be integrated with the expertise of hydrologists, agronomists, aquatic ecologists, and others to assess the risks that P in agricultural soils poses to surface waters? And, finally, how can we use soil P testing to evaluate new best management practices (BMPs) now being developed to reduce P transport from soil to water?

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Kay, P., Edwards, A. C., Foulger, M. (2009). A review of the efficacy of contemporary agricultural stewardship measures for ameliorating water pollution problems of key concern to the UK water industry. Agricultural Systems, 99 (2-3), 67-75.The UK water industry faces a number of water quality issues which mean that capital must be spent on treating raw water in order to meet regulatory standards. Moreover, other policies exist that require improved water quality (e.g. the Water Framework Directive) and contemporary regulation is encouraging water companies to deal with the problem at Source, rather than relying exclusively on 'end-of-pipe' treatment solutions. Given that much of this Pollution results from agricultural practices, agricultural stewardship measures could offer a means of source control. Although numerous schemes are available that encourage farmers to adopt environmentally friendly farming practices, uncertainty exists as to the specific impacts of these measures on water quality. This study has, therefore, reviewed the scientific literature to establish those agricultural stewardship measures that have been proven to impact water quality for three pollutant groups of key concern to the UK water industry, namely dissolved organic carbon, nutrients and pesticides. It has been found that, whilst for many measures there is little or no evidence for impacts on water quality, a range of stewardship practices are available that have been proven to improve water quality. Their effectiveness is subject to a number of factors though (e.g. soil type and pollutant chemistry) and so they should be implemented on a case-by-case basis. Further research is needed to ascertain more fully how contemporary agricultural stewardship measures really do impact water quality. (C) 2008 Elsevier Ltd. All rights reserved.Peer reviewe

1. The elemental composition and stoichiometry of aquatic plants has often been suggested to reflect the nutrient enrichment of aquatic habitats. However, the relationship is often weak. Moreover, uncertainties remain in the relevance of laboratory derived critical plant tissue nutrient concentrations to maximum yield or growth rates in the field. 2. Aquatic vascular plants and bryophytes, overlying water and sediment samples were collected to test whether freshwater aquatic macrophytes: (i) show tissue nutrient deficiencies when growing in oligotrophic freshwater habitats, and (ii) have strict homeostatic stoichiometry. 3. Plant nutrient concentrations were significantly related to total inorganic nitrogen (or nitrate), total dissolved phosphorus and sediment total phosphorus. However, these relationships were weak. Virtually all the variance in plant tissue nutrient concentrations, however, could be explained by species (taxon) identity. 4. Critical tissue nutrient concentrations for 95% maximum yield or 95% maximum growth rate in aquatic angiosperms, determined from laboratory bioassays, suggested that nutrients should not limit yield in wild aquatic macrophytes. However, there were a substantial number of samples where potential growth rate limitation was possible, particularly due to phosphorus. 5. Strict C : N : P stoichiometric ratios were found for both vascular plants and bryophytes, suggesting little scope for plants as indicators of nutrient enrichment, but provide robust stoichiometric data for studies on ecosystem metabolism and nutrient cycling.

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