The effects of nitrogen and period of weed interference on the fibre yieldof kenaf (Hisbiscus cannabinus L.) in the northern Guinea Savanna of Nigeria

The effect of weed interference on kenaf was evaluated at three nitrogen ap plication rates. The vegetative phase was reduced but the growth and yield were increased by N (86 kg N/ha was the optimum N-rate). Plots kept weed-fr ee had better growth and yield than the weed infested. Unchecked weed growt h reduced fibre by 31.5-53.3% compared to the highest yield in the trials. The critical period of weed competition was between 3 and 6 WAS. Within thi s range, additional initial weed-free period of 1 day increased fibre yield by 19.1 kg/ha, while additional weed infestation period of I day reduced t he yield by about 13.0 kg/ha. (C) 2001 Elsevier Science Ltd. All rights res erved.