Principles of Preventive Weed Control on a Tropical Black Clay

Summary Grasses, sedges and broadleaved weeds compete seriously with crops during the rainy season on the dark clay soils of the Kafue Pilot Polder in Zambia. Quantitative evidence is shown how they can be reduced to manageable proportions by leaving the perennial grass vegetation of the Flats intact as long as possible before cropping begins, by maintaining thorough weed control from year to year, by selective stimulation of crops with effective pre-rain planting and concentration of fertiliser, by early and frequent weeding with light shallow working hoes and, if necessary, by discriminate use of chemical weedkillers.