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Kinetics of Potassium Desorption in Soil using Miscible Displacement
Author(s) -
Sparks D. L.,
Zelazny L. W.,
Martens D. C.
Publication year - 1980
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/sssaj1980.03615995004400060014x
Subject(s) - desorption , chemistry , soil water , diffusion , potassium , analytical chemistry (journal) , adsorption , kinetics , mineralogy , environmental chemistry , soil science , geology , thermodynamics , physics , organic chemistry , quantum mechanics
Kinetics of K desorption were conducted on samples from the Ap, A2, B21t, and B22t horizons of two Dothan (Plinthic Paleudults) soils. Aluminum‐ and calcium‐ saturated samples were equilibrated with K for 96 hours and then continuously leached with 0.01 M CaCl 2 until K was not detected in the leachate. The rate of K desorption from all samples increased rapidly initially and levelled off with time. Desorption was nearly complete in approximately 3 to 4 hours for the Ap, A2, and B21t horizons, and in 8 to 9 hours for the B22t horizons. Approximately 95–98% of the adsorbed K was subsequently desorbed suggesting K adsorption‐desorption in the Dothan soils was reversible. A linear relationship between time ½ and percent K desorption indicated that diffusion was the predominant mechanism of K desorption in these soils. Diffusion‐controlled exchange would be expected due to the vermiculitic clay minerals present in the soils. Potassium desorption conformed to first‐order kinetics. Apparent desorption rate coefficients ( k′ d ) ranged from 0.3 to 1.3 hour −1 . The magnitude of the k′ d values decreased as clay content increased in the soils. This was ascribed to increased intraparticle transport and to increased diffusion in the more clayey samples. The k′ d values were generally higher in the Al‐than in the Ca‐ saturated samples. The effect of flow velocity on rate of K desorption was investigated using velocities of 0.5, 1.0, and 1.5 ml min −1 . The rate of K desorption increased only slightly with flow velocity.