tion attributed to cogongrass interference can be as high as 70% in corn (Udensi et al., 1999), 78% in yam (Dio- Cogongrass (Imperata cylindrica (L.) Raeusch.) is a major weed scorea spp.) and cassava (Manihot esculenta Crantz) in the tropics where land is intensively cultivated and fallow duration is less than 5 yr. Field studies were conducted in 1999 and 2000 in (Koch et al., 1990), and 40% in soybean (Glycine max Nigeria to evaluate cogongrass response to combinations of five weed (L.) Merr.) (Avav, 2000). Complete crop failure usually control options. Treatment combinations were tillage (hoe tillage and occurs when crops are grown in plots slashed during no-tillage), corn (Zea mays L.), row spacing (50 and 75 cm), corn land preparation, withoutadditional weeding during the cultivar(open-pollinated (OP)and hybrid),herbicide (glyphosateand growth cycle (Udensi et al., 1999). Slashing, usually per- no glyphosate), and cover crop {velvetbean (Mucuna cochinchinensis formed using machetes, only suppresses the shoots with (Lour) A. Chev) and no velvetbean}. The treatment combinations little or no effect on the rhizomes of cogongrass (Town- were arranged in a randomized complete block design with three son, 1991; Chikoye et al., 1999; Udensi et al., 1999). replications. Integrating tillage, herbicide, and cover cropping with A period of undisturbed fallow of up to 5 yr can velvetbean gave optimal control of cogongrass. Corn height and leaf reduce the population or biomass of cogongrass by 70% area were negatively correlated with cogongrass shoot, rhizome, and total biomass. Corn grain yield was negatively correlated with cogon- and may guarantee farmers 2 to 5 yr of cropping before grass shoot biomass and total cogongrass biomass (shoot rhizome). cogongrass reinfestation (Okigbo, 1982). Long fallow Good control of other weeds was achieved through the use of narrow periods are no longer possible, owing to the increasing corn row spacing and cover cropping with velvetbean. Tillage, narrow human population pressure on limited arable land (Sie- corn row spacing, and the use of herbicide had a positive effect on bert and Kuncoro, 1987; Chikoye et al., 1999). Other corn grain yield. The use of competitive cultivars, narrow row spacing, interventions include hoe weeding, tillage, slashing, burn- covercrop,andherbicidemaybesustainableapproachestothecontrol ing, chemical control, alley cropping, and the use of cover of cogongrass and other weeds in corn. crops. Hoe weeding and slashing are the methods most commonly used by small-scale farmers to control cogon- grass; weeding is effective only if repeated at least five

Cogongrass [Imperata cylindrica (L.) Raeusch.] is a major weed in the tropics where land is intensively cultivated and fallow duration is less than 5 yr. Field studies were conducted in 1999 and 2000 in Nigeria to evaluate cogongrass response to combinations of five weed control options. Treatment combinations were tillage (hoe tillage and no-tillage), corn (Zea mays L.), row spacing (50 and 75 cm), corn cultivar [open-pollinated (OP) and hybrid], herbicide (glyphosate and no glyphosate), and cover crop (velvetbean [Mucuna cochinchinensis (Lour) A. Chev] and no velvetbean). The treatment combinations were arranged in a randomized complete block design with three replications. Integrating tillage, herbicide, and cover cropping with velvetbean gave optimal control of cogongrass. Corn height and leaf area were negatively correlated with cogongrass shoot, rhizome, and total biomass. Corn grain yield was negatively correlated with cogongrass shoot biomass and total cogongrass biomass (shoot + rhizome). Good control of other weeds was achieved through the use of narrow corn row spacing and cover cropping with velvetbean. Tillage, narrow corn row spacing, and the use of herbicide had a positive effect on corn grain yield. The use of competitive cultivars, narrow row spacing, cover crop, and herbicide may be sustainable approaches to the control of cogongrass and other weeds in corn.