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A Simple Method to Predict Dissolved Phosphorus in Runoff from Surface‐Applied Manures
Author(s) -
Vadas P. A.,
Kleinman P. J. A.,
Sharpley A. N.
Publication year - 2004
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/jeq2004.7490
Subject(s) - surface runoff , phosphorus , environmental science , simple (philosophy) , hydrology (agriculture) , surface water , environmental chemistry , environmental engineering , chemistry , geology , geotechnical engineering , ecology , biology , philosophy , organic chemistry , epistemology
Computer models are a rapid, inexpensive way to identify agricultural areas with a high potential for P loss, but most models poorly simulate dissolved P release from surface‐applied manures to runoff. We developed a simple approach to predict dissolved P release from manures based on observed trends in laboratory extraction of P in dairy, poultry, and swine manures with water over different water to manure ratios. The approach predicted well dissolved inorganic ( R 2 = 0.70) and organic ( R 2 = 0.73) P release from manures and composts for data from leaching experiments with simulated rainfall. However, it predicted poorly ( R 2 = 0.18) dissolved inorganic P concentrations in runoff from soil boxes where dairy, poultry, and swine manures had been surface‐applied and subjected to simulated rainfall. Multiplying predicted runoff P concentrations by the ratio of runoff to rainfall improved the relationship between measured and predicted runoff P concentrations, but runoff P was still overpredicted for dairy and swine manures. We attributed this overprediction to immediate infiltration of dissolved P in the freely draining water of dairy and swine manure slurries upon their application to soils. Further multiplying predicted runoff dissolved inorganic P concentrations by 0.35 for dairy and 0.60 for swine manures resulted in an accurate prediction of dissolved P in runoff ( R 2 = 0.71). The ability of our relatively simple approach to predict dissolved inorganic P concentrations in runoff from surface‐applied manures indicates its potential to improve water quality models, but field testing of the approach is necessary first.

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