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Phosphorus Transport Pathways to Streams in Tile‐Drained Agricultural Watersheds
Author(s) -
Gentry L. E.,
David M. B.,
Royer T. V.,
Mitchell C. A.,
Starks K. M.
Publication year - 2007
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0098
Subject(s) - tile drainage , surface runoff , hydrology (agriculture) , streams , environmental science , ditch , particulates , watershed , nonpoint source pollution , phosphorus , drainage , water quality , soil water , surface water , environmental engineering , ecology , chemistry , geology , soil science , computer science , biology , computer network , geotechnical engineering , organic chemistry , machine learning
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 particulate 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, particulate 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.