Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2010
Publication Date: 7/13/2011
Citation: Kleinman, P.J.A., Sharpley, A.N., Buda, A.R., McDowell, R.W., Allen, A.L. 2011. Soil controls of phosphorus runoff: management barriers and opportunities. Canadian Journal of Soil Science. 91:329-338. Interpretive Summary: Despite decades of activity aimed at restricting nutrient losses from agricultural soils, the loss of phosphorus in agricultural runoff remains a concern across North America. Managing phosphorus in runoff is complex and cannot rely upon traditional conservation practices to achieve water quality goals. Research increasingly points to the lingering effects of past management on today’s problem. We identify an array of barriers to phosphorus runoff mitigation, historical and current, as well as opportunities for improving today’s management strategies.
Technical Abstract: The persistent problem of eutrophication, the biological enrichment of surface waters akin to aging, has produced a vast literature on soil phosphorus (P) effects on runoff water quality. This paper considers the mechanisms controlling soil P transfers from agricultural soils to runoff waters, highlighting obstacles to and opportunities for water quality mitigation. Historical emphases on soil conservation and control of sediment delivery to surface waters demonstrate that comprehensive strategies to mitigate sediment-bound P transfers can produce long-term water quality improvements at a watershed scale. More difficult to control are dissolved P releases from soils that have received historical applications of P in excess of crop requirements. While prevention of further P additions to such soils ensures that dissolved P losses will not continue to be exacerbated, the desorption of “legacy P” will persist for long periods of time. Articulating the role of legacy P in delaying the response of watersheds to remedial programs remains an underserved area of scientific communication. Furthermore, hydrologic flow paths can activate such legacy P and undermine broader efforts to curtail P losses. In the short term, strategies that take advantage of the tremendous capacity of soils to buffer dissolved P losses offer short-term solutions. This includes employing periodic tillage to diminish severe vertical stratification of P in no-till soils. In some cases, more aggressive strategies may be required that enhance buffers along critical flow paths of P transfer.