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Soil Science Society of America Journal Abstract -

Self-Diffusion of Phosphorus in Clays and Soils: II. The Effect of pH1


This article in SSSAJ

  1. Vol. 32 No. 5, p. 657-660
    Received: Mar 4, 1968
    Accepted: May 15, 1968

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  1. G. A. Place,
  2. R. E. Phillips and
  3. D. A. Brown2



The effect of pH on the self-diffusion coefficient of 32P was measured in kaolinite, montmorillonite, illite, Dundee silt loam, and Sharkey clay. Six fractions of soil phosphorus were evaluated and related to the effect of pH on the self-diffusion coefficients of 32P by multiple linear regression analysis. The free iron oxide content was determined in each medium and related to the variation in self-diffusion coefficients between media.

The self-diffusion coefficients were significantly affected by pH in all media. A multiple regression analysis for individual clays and soils where self-diffusion was the dependent variable and water soluble-P, Al-P, Fe-P, occluded Fe- and Al-P, and Ca-P were the independent variables revealed that water soluble P in kaolinite was positively correlated (R2 = 0.673) and occluded Al-P in montmorillonite was negatively correlated (R2 = 0.402). There were no significant terms in the other media. The magnitude of the self-diffusion coefficients between media was kaolinite > montmorillonite > Dundee silt loam > illite > Sharkey clay. When the self-diffusion coefficients and phosphorus fractions were averaged over all pH values, self-diffusion increased as the water soluble- and Al-P concentrations increased and the Fe-P and free ion oxide contents decreased.

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