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This article in SSSAJ

  1. Vol. 46 No. 2, p. 276-279
    Received: Sept 9, 1981
    Accepted: Nov 24, 1981

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Dissolution Rate of EDTA-extractable Phosphate from Soils1

  1. A. B. Onken and
  2. R. L. Matheson2



The kinetics of phosphorus (P) dissolution in EDTA (ethylenedi-aminetetraacetic acid) solution were investigated for several soils for the purpose of determining if the dissolution rate constants could be related to crop response to applied P. Eight kinetic models were evaluated using coefficients of determination (R2) and standard errors of estimate (SE). Additionally, the effects of temperature and soil-solution ratio on P dissolution in the EDTA solution were determined.

Relatively high values of R2 and low values of SE indicated that P dissolution in EDTA solution for the soils used was most often best described by the two-constant rate equation, the Elovich-type equation, and the differential rate equation. None of the models best described the dissolution for all soils. Using R2 and SE for evaluation, the best relationships found between dissolution rate constants and yield response to applied P were for the two-constant rate equation (R2 = 0.97; SE = 2.58) and the differential rate equation (R2 = 0.95; SE = 2.69). Soil-solution ratio affected the values of dissolution rate constants, with those obtained from the differential rate equation most sensitive. The Arrhenius equation described reasonably well the effect of temperature on values of the dissolution rate constants.

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