Phosphorus transport pathways to streams in tile-drained agricultural watersheds

L. E. Gentry, M. B. David, T. V. Royer, C. A. Mitchell, K. M. Starks

Research output: Contribution to journalArticlepeer-review


Agriculture is a major nonpoint source of phosphorus (P) in the Midwest, but how surface runoff and tile drainage interact to affect temporal concentrations and fluxes of both dissolved and participate P remains unclear. Our objective was to determine the dominant form of P in streams (dissolved or particulate) and identify the mode of transport of this P from fields to streams in tile-drained agricultural watersheds. We measured dissolved reactive P (DRP) and total P (TP) concentrations and loads in stream and tile water in the upper reaches of three watersheds in east-central Illinois (Embarras River, Lake Fork of the Kaskaskia River, and Big Ditch of the Sangamon River). For all 16 water year by watershed combinations examined, annual flow-weighted mean TP concentrations were >0.1 mg L-1, and seven water year by watershed combinations exceeded 0.2 mg L-1. Concentrations of DRP and particulate P (PP) increased with stream discharge; however, participate P was the dominant form during overland runoff events, which greatly affected annual TP loads. Concentrations of DRP and PP in tiles increased with discharge, indicating tiles were a source of P to streams. Across watersheds, the greatest DRP concentrations (as high as 1.25 mg L-1) were associated with a precipitation event that followed widespread application of P fertilizer on frozen soils. Although eliminating this practice would reduce the potential for overland runoff of P, soil erosion and tile drainage would continue to be important transport pathways of P to streams in east-central Illinois.

Original languageEnglish (US)
Pages (from-to)408-415
Number of pages8
JournalJournal of Environmental Quality
Issue number2
StatePublished - Mar 2007

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution
  • Management, Monitoring, Policy and Law


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