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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #98698
Title: INTEGRATING PHOSPHORUS AND NITROGEN MANAGEMENT AT WATERSHED SCALES

Author
item HEATHWAITE, LOUISE - UNIVERSITY OF SHEFFIELD
item Sharpley, Andrew
item Gburek, William

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/1999
Publication Date: N/A
Citation: N/A

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: Integrated approaches to derive BMPs that accommodate the spatial variation in phosphorus (P) and nitrogen (N) loss from agricultural land are examined using simple P and N indexing systems. We show that the primary flow pathways and critical source areas of P and N loss differ. We demonstrate that BMPs are more effective if narrowly targeted to watershed areas where the source and transport factors governing P and N loss coincide. Current legislation that focuses on source controls alone (e.g. soil P concentrations) may prove unnecessarily restrictive and may not achieve the desired reduction in nutrient loss from non-point sources.