Prediction of Bioavailable Phosphorus Loss in Agricultural Runoff
- Andrew N. Sharpley * and
- S.J. Smith
The loss of bioavailable P (BAP) in both soluble (SP) and participate (BPP, bioavailable particulate P) forms in agricultural runoff, can accelerate the eutrophication of surface waters. Bioavailable P represents P that is potentially available for algal uptake. Although prediction of BAP loss would provide a more reliable assessment of the impact of agricultural management on surface water eutrophication than just SP or total P (TP), currently no predictive equations are available. Bioavailable P transport in soluble and particulate forms in runoff from 20 agricultural watersheds in the Southern Plains over a 5-yr period, was predicted using kinetic and enrichment ratio approaches, respectively. Measured and predicted SP and BPP concentrations of individual runoff events were similar for all watersheds and management practices over a range of 7 to 3522 and 3 to 4059 µg L−1, respectively. Calculated as the sum of SP and BPP, BAP loss in runoff was predicted accurately, with only a 12% error in measured mean annual loss (662 g ha−1 yr−1). Although BAP loss below 100 g ha−1 yr−1 was underestimated, above this value measured and predicted values closely followed a 1:1 relationship. Inclusion of these equations in comprehensive water quality models will improve the prediction of agricultural management on the biological response of receiving water bodies.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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