Optimizing Dose, Volume Rate and Time of Application upon Post-emergence Use of Metribuzin for Weed Control in Soybean

The dose, volume rate and time of application of metribuzin as post-emergence for controlling weeds including Cyperus rotundus L. (purple nutsedge) in soybean, have been optimized through a field experiment undertaken for two years at the Indian Agricultural Research Institute, New Delhi. We observed that, upon post-emergence use, metribuzin at 0.1 kg/ha was superior to 0.2 kg/ha; volume rate at 200 L/ha superior to 400 L/ha; and time of application at 20 d after sowing (DAS) superior to 30 DAS. A significant interaction of the third order revealed that metribuzin at 0.1 kg/ha with 200 L/ha of water applied at 20 DAS resulted in a more suppression of Cyperus rotundus, and caused a considerable reduction in total weed population and dry weight compared to metribuzin at 0.2 kg/ha with 400 L/ha of water applied at 30 DAS. The metribuzin 0.1 kg/ha with 200 L/ha of water applied at 20 DAS, therefore, resulted in higher soybean seed yield than those in other combinations of the dose, volume rate and time of application of metribuzin, and was superior to others.