Evaluation of some pre-emergence herbicides on cotton (Gossypium hirsutum L.) at Samaru, Nigeria

Chemical weed control is the most viable method of checking the menace of weeds under large scale cotton production. In the humid tropical grass lands of Nigeria, some pre-emergence herbicides were evaluated alone and as mixtures with karmex (diuron) on cotton at Samaru in 1999, 2001 and 2002. Igran combi gold at 2.0-2.4 kg a.i ha(-1), mixtures of diuron with alachlor and metolachlor each at 0.8 + 1.5 -2.00 kg a.i ha(-1) and diflufenican at 0.8 + 0.4 kg a.i ha(-1) and diflufenican applied alone at 0.3-0.4 kg a.i ha(-1) followed by supplementary hoe weeding (fb SHW) controlled weeds and increased seed cotton yield over the weedy check. Some of these treatments depressed seedling emergence and stand count, but also resulted in comparable, and in some cases, higher yields than hoe weeding at 3 and 6 weeks after sowing (WAS). It was observed that Igran combi gold was generally the safest herbicide on cotton. Unchecked weed growth caused 74%, 87% and 24% seed cotton yield reductions compared to the highest yields obtained in 1999, 2001 and 2002, respectively.