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This article in SSSAJ

  1. Vol. 43 No. 2, p. 301-304
    Received: July 7, 1978
    Accepted: Oct 24, 1978

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Adsorption of Magnesium and Calcium by a Soil with Variable Charge1

  1. K. Y. Chan,
  2. B. G. Davey and
  3. H. R. Geering2



The subsoil of a xanthic ferralsol was used to determine the effect of varying ionic strength and pH on the cation exchange capacity and the amounts of Na, K, Ca, and Mg in exchangeable form.

The cation exchange capacity increased with both pH and ionic strength from 2.6 meq/100 g at pH 2.5 and 0.01M ionic strength to 6.9 meq/100 g at pH 9.5 and 1.0M ionic strength.

Sodium and K remained completely exchangeable over all the ionic strengths (0.01 to 1.0M) and pH range 2.5 to 9.5. By contrast Mg became fixed in nonexchangeable forms as the pH increased so that 62% of Mg originally exchangeable at pH 4.0 was fixed at pH 9.5 and 1.0M ionic strength. Calcium also appeared to become fixed in nonexchangeable form as the pH increased, but to a much lesser extent than Mg.

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