INFLUENCE OF WEED COMPETITION ON SUBSEQUENT GERMINATION AND SEED VIGOR OF ZEN MAYS

Small scale farmers in Africa commonly employ the practice of using ma ize (Zea mays L.) grains (F2 seed) produced in one season as seed for the next season. Experiments on cocklebur (Xanthium strumarium L.) and maize provided information on the influence of competition between th e weed and the crop on seed germination and vigour of the produced mai ze seeds. Maize was planted in 50 m rows, 2.1 m apart, with a plant po pulation of 16000 plants.ha(-1). X. strumarium was planted at five den sities between the maize. The maize seeds produced at different weed d ensities were harvested at the end of the growing season and subjected to germination and vigour tests. Both germination and vigour of maize seeds decreased with an increase in weed density. This finding should be taken into account when determining threshold values for economica l weed control.