Submitted to: Encyclopedia of Water Science
Publication Type: Book / Chapter
Publication Acceptance Date: 5/20/2003
Publication Date: 10/20/2003
Citation: McDowell, R., Sharpley, A.N., Kleinman, P.J. 2003. Impacts, mechanisms and management of phosphorus loss from land to surface waters. Encyclopedia of Water Science. p. 961-964. Interpretive Summary:
Technical Abstract: Although inputs of phosphorus (P) are essential to productive agriculture, its export in watershed runoff can accelerate the eutrophication of receiving fresh waters, creating serious local and regional economic problems. Agriculture now contributes a greater share of fresh water inputs of P than 25 years ago. Thus, increasing pressures are being put on agricultural systems to sustainably utilize P in animal manures and off-farm wastes. Long-term applications of P as fertilizer or manure, at rates continuously in excess of crop removal, have resulted in soil P accumulations that are of environmental rather than agronomic concern. Moreover, current P inputs in feed and manure to agricultural systems often maintain high soil P levels or result in small and slow declines in soil P at best. Thus, remedial strategies must consider more than reducing P inputs. Options include decreasing transport potential by targeting critical source areas of both runoff and P, For example, less than 10% of watershed area and annual flow often contributes as much as 90% of P exported annually. Other options are more efficient than removal of soil P by harvesting farm produce. Finding alternative off-farm uses for manure and development of protocols to identify and target sustainable resource management systems are critical. This review discusses the general role of agricultural P management in accelerated eutrophication and where our lack of information limits improved P management.