HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dufey, J. E. Articles by Delvaux, B. Search for Related Content PubMed Articles by Dufey, J. E. Articles by Delvaux, B. Agricola Articles by Dufey, J. E. Articles by Delvaux, B.

Modeling Potassium-Calcium Exchange Isotherms in Soils

University of Louvain, Soil Science Unit

Bruno Delvaux

IRFA/CIRAD, Place Croix du Sud 2, B-1348 Louvain-la-Neuve, Belgium

*Corresponding author.

ABSTRACT

Ion exchange equilibria involving K cannot be described by a constant selectivity coefficient for all surface compositions. The main reason is that the soil exchanger contains various types of sites with different affinities for K ions. This paper makes use of a multi-site model, the main assumption of which is that the exchange reaction is governed by single values of the Vanselow selectivity coefficient, K_v, for each type of site. The simplest model—i.e., the two-site model—is tested. Three parameters must be adjusted: the proportion of high and low selective sites, and the K_v's for these two classes of sites. Simulated K-Ca exchange isotherms are shown, with various combinations of the parameters. The model has been adjusted to experimental K-Ca exchange data, using a non-linear regression procedure. A fair agreement between the experimental and calculated curves is obtained. As a consequence, this simple model proves to be a powerful tool for a quantitative description of exchange data involving K ions.

Received for publication October 14, 1988.