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Heterovalent Cation Exchange Equilibria in Soils with Variable and Heterogeneous Charge
Author(s) -
Munns D. N.
Publication year - 1976
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1976.03615995004000060015x
Subject(s) - chemistry , oxisol , divalent , adsorption , soil water , cation exchange capacity , vertisol , leaching (pedology) , saturation (graph theory) , inorganic chemistry , potassium , ion exchange , analytical chemistry (journal) , environmental chemistry , ion , soil science , geology , mathematics , combinatorics , organic chemistry
Divalent cations were incrementally displaced, from limed and unlimed samples of three soils, by suspending the soils in increasing volumes of 2m M KCl. Mass action coefficients for exchange between Ca and Mg were constant. But for the exchange of divalent cations by K, the exchange coefficients of Kerr, Vanselow, Gapon, Krishnamoorthy and Overstreet, and Gaines and Thomas increased markedly as potassium saturation or pH increased. For each cation species, separate fractions which were relatively tightly or relatively loosely adsorbed could be estimated by a simple regression analysis. The loosely adsorbed Ca, which may control Ca availability to plants, could be independently estimated by a leaching procedure. Mass action exchange coefficients for the loosely adsorbed cations were approximately constant under all conditions tested. The variable charge mobilized by liming differed from the fixed charge in having a slightly higher proportion of sites with high divalent affinity, in an Oxisol, and a much lower proportion in a Vertisol and a Mollisol.