Abstract
SUMMARY The decline in fertility of red ferrallitic soils in Uganda under arable cropping, and its restoration under permanent vegetation, is shown to be associated with losses and gains of major nutrients by the top-soil. A fertilizer mixture formulated to correct the losses and imitate the gains of nutrients consistently increased crop yields and maintained soil fertility over 4 years. Reasons for the success of the fertilizer mixture and its potential use in other tropical areas are discussed.