Kinetics of Nonexchangeable Potassium Release in Relation to Clay Mineralogy in Some Calcareous Soils of Kohgilouye Province

Rate of nonexchangeable K release can significantly influence K availability. Kinetics of K+ release was studied by extraction using 0. 01 M CaCl2 in 12 surface calcareous soils of Kohgilouye Province. Results showed that cumulative K release ranged from 89. 9 to 460. 9 mg kg-1 (Average 195. 4 mg kg-1). Calcium carbonate، nonexchangeable K، cation exchange capacity and mica showed a significant correlation with K release. Maximum of potassium release was observed in Alfisols، probably because of high amount of clay content and the clay mineral of mica. The amount of K release was in the following order: Alfisols> Entisols> Inceptisols. Elovich، parabulic diffusion and power function equations could reasonably describe the K release kinetics. Fitting the data to these equations indicated that release of K is controlled by diffusion process.