Journal of the Indian Society of Soil Science

The release of non-exchangeable potassium with different concentrations of different acids, viz. HNO₃, oxalic and citric acids was studied in four soil samples differing in parent materials and texture. Total amount of non-exchangeable potassium released by oxalic acid was more than nitric and citric acids. These values were higher when extraction was done in hot (on boiling water bath) than in cold (at room temperature). Potassium was released in two steps, an initial rapid release from edge sites, followed by slower release from interlayer sites within the clay mineral.