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A conceptual approach for integrating phosphorus and nitrogen management at watershed scales

Research output: Contribution to journalJournal article


<mark>Journal publication date</mark>2000
<mark>Journal</mark>Journal of Environmental Quality
Issue number1
Number of pages9
Pages (from-to)158-166
<mark>Original language</mark>English


Since the late 1960s, point-sources of water pollution have been reduced due to their ease of identification and treatment. As water quality problems remain and further point-source measures become less cost-effective, attention is directed toward reducing agricultural nonpoint-sources of P and N. In the past, separate strategies for P and N were developed and implemented at farm or watershed scales. Because of differing biology, chemistry, and flow pathways of P and N in soil, these narrowly targeted strategies may lead to mixed results. In some cases, N management of manures has increased soil P and subsequent P enrichment of surface runoff, while no-till has reduced P losses but increased nitrate leaching. Thus, an integrated approach to nutrient management is needed, with best management practices (BMPs) targeted to critical areas of a watershed that contribute most of the P and N exported. We have developed indices that identify critical sources and transport pathways controlling P and N export. These indices are applied to a mixed land use watershed in Pennsylvania. Areas most vulnerable to P loss are limited to small, well-defined areas of the watershed (<20% of area) near the stream channel. In contrast to P, larger areas contribute to nitrate leaching and generally occur on the upper boundaries of the watershed (60%), where freely draining soils and high manure and fertilizer N applications are made. Thus, differing levels of nutrient management may be appropriate for different areas of a watershed.

Bibliographic note

A conceptual approach for integrating phosphorus and nitrogen management at watershed scales

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