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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Soil Management and Sugarbeet Research » Research » Publications at this Location » Publication #413802
Research Project: Agricultural Management for Long-Term Sustainability and Soil Health

Location: Soil Management and Sugarbeet Research

Title: A review of the development and implementation of the critical source area concept: A reflection of Andrew Sharpley’s role in improving water quality

Author
item MCDOWELL, R - Agresearch
item Kleinman, Peter
item HAYGARTH, P - Lancaster University
item McGrath, Justin
item Smith, Douglas
item HEATHWAITE, A - Lancaster University
item IHO, A - Natural Resources Institute Finland (LUKE)
item SCHOUMANS, O - Wageningen University
item NASH, D - University Of Melbourne

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2024
Publication Date: 2/28/2024
Citation: McDowell, R.W., Kleinman, P.J., Haygarth, P.M., McGrath, J.M., Smith, D.R., Heathwaite, A.L., Iho, A., Schoumans, O., Nash, D. 2024. A review of the development and implementation of the critical source area concept: A reflection of Andrew Sharpley’s role in improving water quality. Journal of Environmental Quality. https://doi.org/10.1002/jeq2.20551.
DOI: https://doi.org/10.1002/jeq2.20551

Interpretive Summary: Managing agricultural nutrients for water quality protection can be quite complicated given the array of sources that need to be controlled. Critical source areas are small areas of a field, farm, or watershed that account for most contaminant loss by having both a high contaminant availability and transport potential. The critical source area concept has been readily grasped by scientists, farmers, and policy makers across the globe. An international team of phosphorus scientists, including scientists from USDA's Agricultural Research Service, evaluated the science and application of critical source areas related to phosphorus in agricultural watersheds. They found that use of critical source area management for watershed phosphorus mitigation is most effective when applied to smaller watersheds.

Technical Abstract: Critical source areas (CSAs) are small areas of a field, farm, or catchment that account for most contaminant loss by having both a high contaminant availability and transport potential. Most work on CSAs has focused on phosphorus (P), largely through the work in the 1990s initiated by Dr. Sharpley and colleagues who recognized their potential value in targeting mitigation efforts. The CSA concept has been readily grasped by scientists, farmers, and policymakers across the globe. However, experiences and success have been mixed often caused by the variation in where and how CSAs are defined. For instance, analysis of studies from 1990-2023 shows that the proportion of the annual contaminant load coming from a CSA decreases from field to farm to catchment scale. This finding could be due to the increased buffering of CSAs with scale or variation in the definition of CSAs. We therefore argue that to help target strategies to cost-effectively mitigate contaminant losses from land to water the definition of CSAs should remain as small areas that account for most contaminant loss. This article sheds light on the development and utilization of CSAs, paying tribute to Dr. Sharpley's remarkable contributions to the improvement of water quality, and reflecting upon where the CSA concept has succeeded or not in reducing contaminant (largely P) loss.