Kinetics of K adsorption reaction in Ca-and Al-saturated soils conformed to second order reaction, modified Freundlich and modified Elovich equations. Higher rate constants of K adsorption in Ca-soils (8.4 x 10−5 to 19.9 X 10−5 mg−1 h−1) over Al-soils (6.4 x 10−5 to 14.9 x 10−5 mg−1 h−1) were due to valence effect. Similarly higher diffusion coefficient was observed in Ca-soil(3.1 x 10−11 to 4.6 X 10−11 cm2 S−1)than that of AL-soil (3.0x 10−11 to 3.7X10−11 cm2 S−1). The diffusion coefficient increased with increase in clay and organic matter content of soil. Half-life time for disappearance of K from soil solutes on reaction with soil ranged from 176.7 x 103 to 505.4 X 103 h. Higher values of ‘m’ calculated from modified Freundlich equation for Al-saturated soil indicated the slow release of K with the time of equilibration. The products of the calculated values of ‘α’ and ‘β’ were much greater than one which support the assumption made in deriving the Elovich equation. A decrease of ‘β’ and/or increase of ‘α’ showed enhancement of reaction rate.
Kinetics, potassium, adsorption, rate constant, diffusion coefficient, half-life, calcareous soil
