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Calcium‐Magnesium‐Potassium Equilibria in Some California Soils
Author(s) -
Carlson R. M.,
Buchanan J. R.
Publication year - 1973
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/sssaj1973.03615995003700060019x
Subject(s) - potassium , chemistry , magnesium , soil water , composition (language) , calcium , ion exchange , ion , equilibrium constant , range (aeronautics) , inorganic chemistry , mineralogy , analytical chemistry (journal) , thermodynamics , geology , environmental chemistry , soil science , organic chemistry , materials science , physics , linguistics , philosophy , composite material
Ion exchange equilibria in several soils were studied to seek equilibrium equations that could be used in chromatographic models dealing with movement and distribution of fertilizer potassium in soil profiles. Soil samples were equilibrated with mixtures of CaCl 2 , MgCl 2 , and KCl solutions and then extracted with NH 4 OAc to determine exchangeable cation compositions at equilibrium. It was necessary to correct the exchangeable cation concentrations by subtracting the cations extracted from nonexchangeable sources by NH 4 OAc. Vanselow's, Davis', Gapon's, or Kerr's equations would not describe the equilibria. Empirical equations of the form:A CaA Mg= k Ca ‐ Mg( E Ca − D Ca)P Ca( E Mg − D Mg)P MgandA CaA K 2= k Ca ‐ K( E Ca − D Ca)P Ca( E K − D K )2 P Kdid describe the equilibria with all three cations present, and over a wide range of composition, for all soils studied. In these equations A i is the solution ion activity, k is the distribution coefficient, E i is the equivalent fraction of the exchangeable cation, and D i and P i are arbitrary constants that are characteristic for each soil and each cation.