| Popis: |
Determining the supply and uptake of K nutrient and the dynamic equilibrium (adsorption-desorption) reactions among the K forms in the soils are not commonly addressed in the highlands of Ethiopia. A study was therefore initiated to determine the adsorption capacity of the exchangeable K and the release kinetics of the non-exchangeable K in the soils of the Qenberenaweti Sub-watershed. Twelve disturbed surface (0–20 cm) soil sub-samples were collected from every farmland which was representative of each pre-identified soil type (Vertic Cambisols, Pellic Vertisols, Pisoplinthic Luvisols, Relictistagnic Cambisols, Pisoplinthic Cambisols, and Plinthofractic Cambisols). A composite sample was made in duplicate for the determination of K adsorption capacity and desorption kinetics per soil type. The mean maximum (69.47 ± 4.31 %) and minimum (56.16 ± 6.04 %) K adsorption rates were obtained from the Plinthofractic Cambisols and Vertic Cambisols, respectively. Among the tested isotherm models, the goodness of the Freundlich was better fit the data of all experimental soils; hence, a modified equation of this model (qe = aCeb/a) could be used to describe the theoretical doses of K fertilizers required to develop K levels in soil solutions. The highest constant K releases from the Plinthofractic Cambisols (47 mg kg−1), Pisiopllintic Cambisols (46 mg kg−1), and Pisoplinthic Luvisols (44 mg kg−1) were attained at the 9th extraction. In comparison, it was noticed at the 7th and 11th extractions of the Relictistagnic Cambisols (45 mg kg−1) and both Pellic Vertisols (48 mg kg−1) and Vertic Cambisols (42 mg kg−1), respectively. The equation of power function was the best to successfully describe the released K+ from all the experimental soils. Eventually, determining the adsorption capacity and release kinetics of K at a site-specific level helps to know the relative potential of the soils to supply K and also plan for an effective K fertilization strategy. |
