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This article in SSSAJ

  1. Vol. 39 No. 6, p. 1069-1072
    Received: May 21, 1975
    Accepted: July 17, 1975

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Potassium-Calcium Exchange Equilibria in Volcanic-Ash Soils1

  1. E. B. Schalscha,
  2. P. F. Pratt and
  3. L. de Andrade2



Potassium-Ca exchange equilibria were determined at potassium adsorption ratios (PAR) of 0.2, 2.0, and 20 for pH values of 4.8, 6.0, and 7.5 for four volcanic-ash soils of southern Chile. Increases in pH produced large increases in CEC which were largely balanced by increases in the amount of Ca adsorbed. The increases in exchangeable K with increase in CEC were relatively small. The relative affinities for K versus Ca at a PAR of 0.2 indicated that for each soil a small, but nearly constant, amount of negative charge had a high specificity for K. Beyond this small amount of CEC with a high affinity for K, the affinities for K were relatively low.

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