Submitted to: Water Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/1999
Publication Date: N/A
Citation: Heathwaite, L., Sharpley, A.N. 1999. Evaluating measures to control the impact of agricultural phosphorus on water quality. Water Science and Technology. 39:149-155. Interpretive Summary: Since the late 1960's, point sources of water pollution have been reduced due to their ease of identification and treatment. However, water quality problems remain, and as further point-source measures becomes less cost- effective, attention is now being directed towards the role of agricultural nonpoint sources in water quality degradation. In particular, nutrient management plans are now focusing on strategies that protect water resources as well as maintain adequate crop nutrient supplies. In the past, separate strategies for phosphorus and nitrogen have been developed and implemented at farm or watershed scales. Because of differing biology, chemistry, and flow pathways of phosphorus and nitrogen in soil, these narrowly targeted strategies may lead to mixed results. Thus, the prevention of phosphorus and nitrogen from watersheds with animal feeding operations needs to focus on defining, targeting, and remediating source areas of phosphorus that combine high soil phosphorus levels with high erosion and surface runoff potentials and source areas of nitrogen which coincide with soils of high permeability. Thus, differing levels of management may be appropriate for different areas of a watershed. Over the long-term, however, lasting improvements in water quality can only be achieved by balancing system inputs and outputs of both nutrients.
Technical Abstract: Current issues in phosphorus loss from non-point sources are reviewed. The need to balance both source and transport control mechanisms in field approaches aimed at controlling P loss from agricultural land is explored. Other control measures, such as P source manipulation, are evaluated. A case is made for integrating work on P loss at various research scales, from plot to hillslope to catchment, and a simple field-scale model to evaluate the factors controlling P loss in surface runoff is presented.