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This article in SSSAJ

  1. Vol. 44 No. 2, p. 260-264
    Received: July 26, 1979
    Accepted: Nov 7, 1979

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Kinetics of Dissolution of Phosphate Rocks in Soils1

  1. S. H. Chien,
  2. W. R. Clayton and
  3. G. H. McClellan2



A modified Elovich equation in the form of Ct = C0 − (1/β)ln (αβ) − (1/β) ln t was derived to describe the kinetics of dissolution of three phosphate rocks (North Carolina, central Florida, and Tennessee) in three soils (one soil from Florida and two Nigerian soils). The equation fitted the experimental data the best among various models of kinetics. Comparisons of dissolution rates of various phosphate rocks in a given soil or a given phosphate rock in various soils can be made by comparing the values of three parameters—C0, α, and β—in the equation where C0 is the maximum P concentration in the soil solution that a phosphate rock can provide in a soil (Ct is the P concentration at time t), and α and β are constants. It was found that C0 increased as α increased and/or β decreased in a given system.

Temperature was found to have no significant effect on the dissolution of phosphate rock in the soil. This implies that phosphorus retention by the tropical soils treated with phospate rock may be much less affected by temperature as compared with water-soluble P fertilizers such as concentrated superphosphate.

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