Implementing agricultural phosphorus science and management to combat eutrophication

Abstract

Experience with implementing agricultural phosphorus (P) strategies highlights successes and uncertainty over outcomes. We examine case studies from the USA, UK, and Sweden under a gradient of voluntary, litigated, and regulatory settings. In the USA, voluntary strategies are complicated by competing objectives between soil conservation and dissolved P mitigation. In litigated watersheds, mandated manure export has not wrought dire consequences on poultry farms, but has adversely affected beef producers who fertilize pastures with manure. In the UK, regulatory and voluntary approaches are improving farmer awareness, but require a comprehensive consideration of P management options to achieve downstream reductions. In Sweden, widespread subsidies sometime hinder serious assessment of program effectiveness. In all cases, absence of local data can undermine recommendations from models and outside experts. Effective action requires iterative application of existing knowledge of P fate and transport, coupled with unabashed description and demonstration of tradeoffs to local stakeholders.

Legacy Nutrient Dynamics at the Watershed Scale: Principles, Modeling, and Implications

“…These models have been widely applied worldwide and improved our quantitative understanding of watershed nutrient dynamics for supporting the development of relevant management measures and policies. However, currently prevailing watershed models are generally lack of an explicit mechanism to describe the legacy nutrient dynamics and delivery lags (Kleinman et al, 2015;Meals et al, 2010). Lumped or statistical watershed models such as the export coefficient model, GlobalNEWS, GWLF, PolFlow, and SPARROW generally assume that the nutrient cycle to be at a steady state, either on a yearly basis or over a multiyear period (e.g., 5-year average, Alam and Goodall, 2012;De Wit, 2001;Swaney et al, 2012;Wellen et al, 2012).…”

“…The measured riverine nutrient concentration is a 27 Legacy Nutrient Dynamics at the Watershed Scale mixture of nutrient having different ages, and very often the residence time of nutrient in landscapes is much longer than the temporal extent of the calibration data available Meals et al, 2010). Due to the lack of capacity for addressing hydrological and biogeochemical legacy effects in many current watershed models, their predictions for water quality improvement after the implementation of relevant nutrient management measures rarely come true (Kleinman et al, 2015).…”

Lake Erie, phosphorus, and microcystin: Is it really the farmer's fault?

“…In effect, conservation practices are spatially and temporally variable in the effectiveness and they must be carefully matched to performance objectives. In some cases all resource objectives cannot be met, and an open dialogue is necessary to choose between the lesser of two "evils," as the tradeoffs between agronomic production and environmental outcomes may sometimes be mutually exclusive (Kleinman et al 2015).…”

Agricultural Best Management Practice Abundance and Location does not Influence Stream Ecosystem Function or Water Quality in the Summer Season

“…However, agricultural practices also have the potential to limit primary production through increased sediment loading and associated reductions in water clarity limiting light penetration to benthic habitats [7]. Growing evidence of the impacts of agriculture on the health of receiving streams and associated downstream ecosystems has made the need to implement effective management strategies to mitigate agricultural effects a major issue in agricultural regions worldwide [8].…”