Agricultural phosphorus and water quality: sources, transport and management

  • Andrew Sharpley USDA-ARS, Pasture Systems and Watershed Management Research Laboratory, Curtin Road, University Park, Pennsylvania 16802-3702, USA
  • William Gburek USDA-ARS, Pasture Systems and Watershed Management Research Laboratory, Curtin Road, University Park, Pennsylvania 16802-3702, USA
  • Louise Heathwaite Department of Geography, University of Sheffield, Winter Street, Sheffield, S1O 2TN, United Kingdom

Abstract

Freshwater eutrophication is usually controlled by inputs of phosphorus (P). To identify critical sources of P export from agricultural catchments we investigated hydrological and chemical factors controlling P export from a mixed land use (30% wooded, 50% cultivated, 20% pasture) 39.5-ha catchment in east-central Pennsylvania, USA. Mehlich-3 extractable soil P, determined on a 30-m grid over the catchment, ranged from 7 to 788 mg kg-1. Generally, soils in wooded areas had low Mehlich-3P (<30 mg kg-1), grazed pasture had Mehlich-3 P values between 100 and 200 mg kg-1, and cropped fields receiving manure and fertiliser applications were in most cases above 200 mg kg-1. Average P concentrations for ten storms during 1996 decreased 50% downstream from segment 4 to segment 1 (catchment outlet). Flow-weighted streamflow P concentrations were more closely related to the near-stream (within 60 m) than whole catchment distribution of high-P soils. This suggests that near-stream surface runoff and soil P are controlling P export from the catchment. Remedial measures should be targeted to these critical P source areas in a catchment. Measures include source (fertiliser and manure application) and transport management (reduce surface runoff and erosion).

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Section
Articles
Published
Jan 1, 1998
How to Cite
Sharpley, A., Gburek, W., & Heathwaite, L. (1998). Agricultural phosphorus and water quality: sources, transport and management. Agricultural and Food Science, 7(2), 297-314. https://doi.org/10.23986/afsci.72855