POTASSIUM FRACTIONATION AND ADSORPTION CHARACTERISTICS OF SOILS OF KAFTA HUMERA DISTRICT UNDER DIFFERENT LAND USES, WESTERN TIGRAY, ETHIOPIA

Abstract

Potassium in soil system found in different forms in different soil types and land use systems. Information on the forms and characteristics of potassium in different soils under different land use types is vital for the management of potassium fertility of the soils. This study was aimed at investigate the forms of potassium and its adsorption characteristics in soils of Kafta Humera district under different land use types. The bulk soil samples were collected randomly from adjacent surface soil (0-20 cm) of the different soil type and land uses below 5% slope. The samples were analyzed for the selected soil physiochemical properties; texture, pH, EC, CEC, exchangeable bases (Ca2+, Mg2+, Na+ and K+), OM, total N, available P, fractionation of different forms of K and adsorption characteristics. Water Soluble K ranged from 0.01 cmol(+)/kg Chromic Vertisols of bare land to 0.19 cmol(+)/kg Eutric Cambisols of grass land with a mean value of 0.05 ± 0.05 cmol(+)/kg. Exchangeable K fraction varied from 0.07 cmol(+)/kg Chromic Vertisols of bare land to 2.31 cmol(+)/kg Eutric Cambisols of grass land with a mean value of 0.38 ± 0.42 cmol(+)/kg. Non exchangeable K varied from 0.39 cmol(+)/kg Chromic Vertisols of bare land to 7.32 cmol (+)/kg) from the Eutric Nitisols of cultivated land and had a mean value of 0.82 ± 0.44 cmol (+)/kg. Lattice K of the study site varied from 11.59 cmol (+)/kg within Orthic Luvisols of cultivated land to 35.82 cmol (+)/kg Lithosols of cultivated land with a mean value of 23.73 ± 6.78 cmol (+)/kg. There order of potassium (K) fraction in magnitude were water soluble K < exchangeable K < non exchangeable K < lattice K (structural). The large amount of potassium was reserved in the lattice form. Adsorbed K in the different land uses of Chromic Luvisols was wood land < bare land < grass land < cultivated land <bush land where as bush land < bare land < grass land < wood land < cultivated land in Chromic Vertisols. Cultivated land had a greater adsorption characteristics. Adsorbed amount potassium under cultivated land of different soil types was Eutric Nitisols < Lithosols < Eutric Cambisols < Orthic Luvisols < Chromic Luvisols < Chromic Vertisols. The adsorption was high within Chromic Vertisols than the other soil types due to fine soil texture that can hold more soil nutrients.