POTASSIUM SUPPLYING CAPACITY OF FLUVISOLS AND VERTISOLS IN THE MIDDLE AWASH VALLEY OF ETHIOPIA

Abstract

An investigation was carried out to study release of exchangeable
potassium, potassium-fixation, non-exchangeable potassium release anJ potassium supplying capacity under laboratory condition. The results showed that release of exchangeable K varied from 2.82 to 3.51 crnol kg-' in Fluvisol and from 2.56 to 3.76 cmol kg-t in Vertisol. Non-exchangeable K also varied from 6.73 to 8.54 cmol kg-' in Fluvisol and from 6.43 to 8.98 cmo1 kg-' in Vertiso!' The highest fixation was observed in VertisoI. Potassium fixation was high under continuous
wet moisture condition in both soils. The potassium buffering capacity was slightly high in Vertisol as compared to that of Fluvisol. The K quantity, by which the soil gains or loses potassium in reaching equilibrium, fell below zero point in the control treatment. Availability of K was slow in the Vertiso}, though its K buffering capacity/supplying was higher than in the Fluvisol.