Abstract
Moderate rates of application of pre- and post-emergence herbicides tolerated by sorghum were evaluated in three ecological zones of Nigeria to find out whether low to moderate application rates of herbicides supplemented with one weeding can give yields comparable with those from higher herbicide rates not supplemented with weeding. The rates of herbicides evaluated ranged from 0.5 to 2.0 kg ai ha-1. The lower rates supplemented with one weeding gave yield that was equivalent to higher rates not supplemented with weeding and the weed-free control. Lower herbicide rates not supplemented with additional weeding, however, resulted in a significantly lower yield. The unweeded, no herbicide treatment resulted in extremely low grain yield at all locations. The results show that pre-emergence herbicides applied as low as 1.0 kg ai ha-1 and supplemented with one weeding can give optimum crop yield and will therefore be an ideal recommendation to farmers with little experience in the use of herbicides.
