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This article in SSSAJ

  1. Vol. 37 No. 6, p. 851-855
    Received: Nov 13, 1972
    Accepted: July 3, 1973

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Calcium-Magnesium-Potassium Equilibria in Some California Soils1

  1. R. M. Carlson and
  2. J. R. Buchanan2



Ion exchange equilibria in several soils were studied to seek equilibrium equations that could be used in chromatographic models dealing with movement and distribution of fertilizer potassium in soil profiles. Soil samples were equilibrated with mixtures of CaCl2, MgCl2, and KCl solutions and then extracted with NH4OAc to determine exchangeable cation compositions at equilibrium. It was necessary to correct the exchangeable cation concentrations by subtracting the cations extracted from nonexchangeable sources by NH4OAc. Vanselow's, Davis', Gapon's, or Kerr's equations would not describe the equilibria. Empirical equations of the form: did describe the equilibria with all three cations present, and over a wide range of composition, for all soils studied. In these equations Ai is the solution ion activity, k is the distribution coefficient, Ei is the equivalent fraction of the exchangeable cation, and Di and Pi are arbitrary constants that are characteristic for each soil and each cation.

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