DISSOLUTION OF POTASSIUM-FELDSPAR ROCKS IN SOILS IN OPEN-LEACHING ANDCLOSED-INCUBATION SYSTEMS

The dissolution of two finely ground potassium feldspar rocks (KFR), f rom Malawi and Sri Lanka, was examined in four indigenous acid soils u sing open-leaching and closed-incubation systems. Increases in fractio ns of soil potassium (K), compared to the control, indicated that the extent of dissolution of KFR was usually substantially enhanced in the leaching system. Because the leaching system represents the field sit uation more closely, it is the most appropriate for assessing the diss olution of potassium feldspar rocks (KFR) in soils and their potential as direct-application K fertilisers.