Evaluation of the Efficacy of Application Time and Rate of Metribuzin Herbicide on Weed Population and Grain Yield of Maize (Zea mays L.) cv. KSC 704

This experiment was conducted in 2007 and 2008 to evaluate the efficacy of metribuzin herbicide on weeds control and yield of maize، at research farm of the Agricultural Research Center of Safi Abad Dezful، Iran. The experimental design was a randomized complete block with 13 treatments in three replications. Treatments included preplant، preemergence and postemergence application of metribuzin at 3-4 leaf stage of maize and weeds each at 0. 35 and 0. 52 kg ai ha-1، preplant، preemergence and postemergence application of atrazine + metribuzin at 3-4 leaf stage of maize and weeds each at (0. 6 + 0. 175) kg ai ha-1، nicosulfuron at 0. 08 kg ai ha-1at 3-6 leaf stage of maize and preemergence application of atrazine + alachlor at (1. 2 + 1. 9) kg ai ha-1، together with weedy and weed free checks. The results indicated that compared to the weedy check، postemergence application of metribuzin at 0. 35 kg ai ha-1 and atrazine + metribuzin with 79 and 75% control، respectively، were the most effective treatments in reducing total number of weeds. Application of atrazine + alachlor، postemergence application of metribuzin at 0. 35 kg ai ha-1 and atrazine + metribuzin and nicosulfuron with 89، 87، 86 and 85% control، respectively، were the most effective treatments in reducing dry weight of weeds. Compared to the weedy check، postemergence application of metribuzin at 0. 52 and 0. 35 kg ai ha-1، atrazine + metribuzin and premergence application of atrazine + alachlor with 50، 44. 44 and 37% increase، respectively، were the most effective treatments in yield increase. According to these results، for weed control and yield increase of corn، postemergence application of metribuzin at 0. 52 or 0. 35 kg ai ha-1، atrazine + metribuzin or premergence application of atrazine + alachlor each at the abovementioned rates can be recommended.