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This article in SSSAJ

  1. Vol. 66 No. 2, p. 623-631
    Received: Oct 11, 2000

    * Corresponding author(s): pvadas@anri.barc.usda.gov
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Predicting Phosphorus Desorption from Mid-Atlantic Coastal Plain Soils

  1. Peter A. Vadas *a and
  2. J. Thomas Simsb
  1. a USDA, ARS, ANRI, AMBL, B-163F Rm. 5, BARC-East, 10300 Baltimore Ave., Beltsville, MD 20705
    b Dep. of Plant and Soil Sciences, 152 Townsend Hall, University of Delaware, Newark, DE 19717


Pollution of surface waters by P from agricultural areas is a water quality issue in Delaware. The FHANTM 2.0 computer model can help identify areas with a high potential for P loss, but the model's representation of P desorption from soils to runoff waters needs re-evaluation. The equation, P d = K P o t α W β , has been proposed to predict such P desorption, but equations originally proposed to predict values for the constants K, α, and β from the ratio of soil clay content/soil organic C content may not be accurate for Delaware soils. Therefore, we measured P desorption for 23 sandy Delaware soils for times of 5 to 180 min, water/soil ratios of 10 to 1000 L kg−1, and three initial levels of soil desorbable P. Values for the constants K, α, and β were calculated and related to soil properties. We found that K, α, and β values were not well related to clay/OC, but were better related to the ratio of oxalate-extractable Fe/OC content (α) or the sum of oxalate extractable Fe and Al (β and K). These results can be used to help refine the FHANTM 2.0 model in predicting P loss from agricultural areas in Delaware and similar landscapes in the Mid-Atlantic Coastal Plain.

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Copyright © 2002. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.66:623–631.