Kinetics of potassium desorption by Alfisols of Greece

Abstract

Kinetics of K desorption was studied on Alfisol Haploxeralf samples of central Greece. Calcium‐saturated samples were equilibrated with different potassium concentrations and pH for 96 hours at pH 5.0, 6.0, 7.0 and 8.0 and initial potassium concentrations of 7, 35, 54 and 112 ppm. Samples were continuously leached with 0.01 M CaCL₂ until K was not detected in the leachate. Desorption was nearly complete in approximately 3 to 4 hours for the Alfisol Haploxeralf. When the initial K concentrations varied between 0–7, 7–35, 35–54 and 54–112 ppm, then approximately 95–97%, 93–98%, 75–96% and 18–75%, respectively, was subsequently desorbed from Alfisol Haploxeralf samples. Three mathematical models (first order, power function and parabolic diffusion) were used to describe cumulative potassium release at different values of pH and initially adsorbed K. Comparisons of coefficients of determination (r²) indicated that the first order, power function and parabolic diffusion equations adequately described cumulative potassium release for all studied pH and initially adsorbed potassium. Apparent potassium desorption rate coefficients (k) ranged from 4.3 x 10^‐3 to 11.4³ × 10^‐3 min^‐1. The magnitude of the k values decreased as adsorbed potassium and pH increased. Finally all the studied models were transformed to pH‐dependent forms.

Notes

Postal address of the corresponding author: A. Ioannou, 14 Thermopillon Street, Pallini, 15344, Greece.

National Agricultural Research Foundation, Soil Science Institute of Athens, 1 S. Venizelou Street, Lycovrissi, 141 23, Greece.