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Soil Science Society of America Journal Abstract -

Phosphorus Transport during Transient, Unsaturated Water Flow in an Acid Sandy Soil


This article in SSSAJ

  1. Vol. 60 No. 1, p. 42-48
    Received: July 28, 1994

    * Corresponding author(s): chen@soilwater.agr.okstate.edu
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  1. J. S. Chen ,
  2. R. S. Mansell,
  3. P. Nkedi-Kizza and
  4. B. A. Burgoa
  1. Dynamac Corp., 3601 Oakridge Blvd., Ada, OK 74820
    Soil and Water Science Dep., Univ. of Florida, Gainesville, FL 32611
    Univ. of Tennessee, Knoxville, TN



Sorbent-sorbate interactions heavily retard the movement of P during water flow in most soils. The effect of soil/solution ratio on sorption kinetics and movement of P during unsteady unsaturated water flow were investigated. A series of batch experiments with soil/solution ratios ranging from 0.1 to 6.4 Mg m-3 were conducted to obtain sorption rate coefficients. Aqueous P solutions (100–800 g m-3) were applied at two constant fluxes (1.4 × 10-6 and 6.9 × 10-6 m s-1) to columns of an air-dry spodic soil. The experimental data were simulated with a parallel two-site nonlinear, nonequilibrium transport model during unsteady, unsaturated water flow. Phosphorous sorption followed Freundlich-type reversible kinetics with a very fast reaction occurring in Type I sites and a slow reaction occurring in Type II sites. The sorption reaction of P in batch experiments was satisfactorily described by the model but the rate coefficients varied with the soil/solution ratio. Experimentally determined rate coefficients described P movement in column experiments at an influx rate of 6.9 × 10-6 m s-1, but not for the slower influx rate of 1.4 × 10-6 m s-1, hence calibration of rate coefficients was necessary for describing P movement during the slower water influx. We developed a technique for determining rate coefficients under water saturated-unsaturated conditions that provides a way to validate P transport models during transient, unsaturated water flow.

Florida Agric. Exp. Stn. Journal Series no. R-04647.

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