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This article in JEQ

  1. Vol. 31 No. 4, p. 1294-1299
     
    Received: Oct 16, 2001
    Published: July, 2002


    * Corresponding author(s): rmaguire@udel.edu
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doi:10.2134/jeq2002.1294

Effect of Mixing Soil Aggregates on the Phosphorus Concentration in Surface Waters

  1. R.O. Maguire *a,
  2. A.C. Edwardsb,
  3. J.T. Simsa,
  4. P.J.A. Kleinmanc and
  5. A.N. Sharpleyc
  1. a Dep. of Plant and Soil Sci., Univ. of Delaware, Newark, DE 19717-1303
    b Macaulay Land Use Research Inst., Craigiebuckler, Aberdeen, AB15 8QH, UK
    c USDA-ARS, Pasture Systems and Watershed Research Unit, Curtin Road, University Park, PA 16802-3702

Abstract

At any time, the phosphorus (P) concentration in surface waters is determined by a complex interaction of inputs of soluble P and sorption–desorption reactions of P with sediments. This study investigated what factors control P in solution when various soil aggregates were mixed, seen as being analogous to selective soil erosion events, transport, and mixing within river systems. Fifteen soils with widely differing properties were each separated into three aggregate size fractions (2–52 μm, 53–150 μm, and 151–2000 μm). Resin P, water-soluble phosphorus (WSP), and the phosphorus buffer capacity (PBC = resin P/WSP) were measured for each aggregate size fraction and WSP was also measured for 11 mixes of the aggregate fractions. The smallest aggregates tended to be enriched with resin P relative to the larger aggregates and the whole soils, while the opposite was true for WSP. As the PBC was a function of resin P and WSP, the PBC was greatest in the 2- to 52-μm aggregate size fraction in most cases. When two aggregate size fractions were mixed, the measured WSP was always lower than the predicted WSP (i.e., the average of the WSP in the two individual aggregates), indicating that WSP released by one aggregate fraction could be resorbed by another aggregate fraction. This resorption of P may result in lower than expected solution P concentration in some surface waters. The strength with which an eroded aggregate can release or resorb P to or from solution is in part determined by that aggregate's PBC.

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Copyright © 2002. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.31:1294–1299.