Release of potassium from some benchmark soils of India

SUMMARY Release of potassium from 15 surface samples of benchmark Alluvial, Red and Black soils of India to 0.01 M solutions of BaCl 2 , CaCl 2 , NH 4 Cl and NaCl was studied in soils either untreated or pretreated with 5 × 10 −3 M KCl. In the untreated soils, the efficacy of the extractants declined in the sequence: BaCl 2 > NH 4 Cl > CaCl 2 > NaCl. Cumulative K‐release was greatest from Black soils, followed by Red and Alluvial soils. From soils pretreated with 5 * 10 −3 M KCl, more K was released than retained, and more ‘native’ K was released than that from untreated soils. Increase in the release of ‘native’ K decreased in the sequence: Red > Alluvial > Black soils. The amounts of surface and internal K, desorption rate constants and parabolic diffusion constants were calculated from K release to the various electrolytes.