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This article in SSSAJ

  1. Vol. 27 No. 1, p. 31-34
    Received: Mar 8, 1962
    Accepted: May 22, 1962

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Effect of Exchangeable Potassium Level and Drying on Release and Fixation of Potassium by Soils as Related to Clay Mineralogy1

  1. R. H. Dowdy and
  2. T. B. Hutcheson Jr.2



The effect of exchangeable K level and drying over H2SO4 upon K release and fixation by six soil series was studied in the laboratory. Differences in behavior seemed to be related very closely to clay mineralogy of the soils. Illite appeared to be the source of K released by drying, whereas fixation at moisture levels higher than 4% was associated with vermiculite and fixation at lower moisture levels with montmorillonite.

Further evidence indicates the moist K equilibrium value of these soils to be 0.45 ± 0.10 me. exchangeable K per 100 g. of soil. When exchangeable K values are above that level for field-moist samples, K is fixed on drying, whereas it is released when the initial K level is lower. The magnitude of release or fixation appears to be directly related to the clay mineralogy.

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