ABSTRACT

The Potassium chemistry of soils obtained from. two locations (Ajata Ibeku and Amakama in Abia State, Nigeria) of contrasting parent materials were studied in the laboratory. Potassium properties studied on the soils included: Potassium adsorption and desorption characteristics, forms and distribution of potassium and Potassium sorption behaviour. The kinetics of Potassium adsorption and desorption on these soils were determined using batch technique. Potassium adsorption and desorption conformed to first order reactions, which were resolved into two linear portions indicating that adsorption and desorption consisted of two concurrent reactions. The first reaction was relatively faster than the second, indicating differences in accessibility of the adsorption sites. The first reaction was ascribed to easily accessible planar sites of 1: 1 clay minerals while the second and relatively slower reaction involved the interlayer spaces of 2: 1 clay minerals. The rate of adsorption and desorption were higher in Ibeku soil than Amakama soil (and this was indicated by higher potassium adsorption and desorption rate coefficient). The sorption capacity in Ibeku soil was higher than the sorption capacity of Amakama soil. Potassium sorption isotherm conformed well to the Freundlich equation. The inability of the langmuir equation to describe tile data indicated that there are several discrete types of potassium sorption sites each with a different selectivity for potassium in these soils. Ibeku soil was found to be higher in the various forms of potassium than Amakama soil. The result of this study therefore showed that Ibeku soil would sustain crop production without potassium fertilization. Amakama soil on the other hand would require K fertilizer application for optimum crop performance.