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Soil Science Society of America Journal Abstract -

Evaluation of Potassium Quantity-Intensity Relationships by a Computer Model Employing the Gapon Equation1


This article in SSSAJ

  1. Vol. 50 No. 1, p. 58-62
    Received: Mar 20, 1985
    Accepted: July 19, 1985

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  1. V. P. Evangelou and
  2. A. D. Karathanasis2



The influence of cation exchange selectivity coefficients on quantity-intensity (Q/I) relationships of soil systems was evaluated by the Gapon equation. Computer simulations of potassium Q/I plots revealed that the linear potential buffering capacity for K+ (PBCK), when exchangeable K+ constitutes a minor portion of the CEC, depends on the magnitude of the soil CEC and the Gapon exchange selectivity coefficient (KG). This dependency is valid only if the Q/I plot is directly K-(Ca + Mg) interaction dependent. Upon increasing the CEC and KG, PBCK increases since PBCK = CEC KG. At low KG values the CEC has a lesser influence on increasing the PBCK, and at low CEC values the KG has a smaller influence on the magnitude of the PBCK. The PBCK is also inversely related to soil K-loading but the influence of K-loading on the magnitude of PBCK, appears to be important only when exchangeable K+ represents a significant portion of the CEC. The influence of K-loading on the magnitude of PBCK, however, appears to be considerable only at K-loading values much higher from those encountered in most agricultural soils. These findings are supported by data available in the literature.

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