X-ray Derived Crystallite Size of Mica Particles in Genetically Different Soil profiles of India in Relation to Potassium Release

Profile soil samples from an Alfisol, a Vertisol and an Entisols were collected and fractionated into coarse clay(0.2–2.0 μm) and fine clay (< 0.2 μm) fractions. X-ray diffractogram of each sample was deconvoluted and curve fitted to get full width at half maximum (FWHM) of corresponding mica peak which were transformed to crystallite size. The crystallites of micaceous minerals were found to be largest in coarse clay fractions of Entisols followed by Alfisols and Vertisols. In almost all the profiles of Alfisol, Vertisols and Entisols, the crystallite size of micaceous minerals was found to increase along the depth of the profile. Crystallite size was found to be related to release of non exchangeable K from soil by oxalic acid extraction and to that released by intensive Sudan grass cropping.