Bioefficacy of chlorimuron ethyl for weed control in soybean (Glycine max)

Bioefficacy of chlorimuron ethyl (Classic 25% wp) @ 3, 6, 12, 24 and 48 g/ha was evaluated at 15 and 21 days after sowing for weed control in soybean [Glycine mar (L.) Merr.]. it was compared with fluchloralin 1.0 kg/ha pre-plant incorporation, butachlor 2.5 kg/ha pre-emergence, fluazifop-p-butyl 0.25 kg/ha post-emergence 21 days after sowing, 1 hand-weeding add a weedy control. Ail the broad-leaf weeds and purple nutsedge (Cyperus rotundus L.) were susceptible to chlorimuron ethyl at all the rates and stages, especially at 15-day stage. The efficacy increased with increase in its rate. Among grasses, hairy crabgrass [Digitaria adscendens (H.B.&K.) Henr.] and dinebra (Dinebra spp) were also killed, but barnyard grass [Echinochloa crus-galli (L.) P. Beauv.] showed only cessation in growth. All the rates except 3 g/ha reduced the weed biomass compared with the weedy control. The weed-control efficiency was 52-68%. Chlorimuron ethyl caused yellowing of the leaves and cessation of growth in soybean also, which became normal after a week. The highest mean yield was noted under hand-weeding (2 234 kg/ha), followed by fluchloralin (2 010 kg/ha) and fluazifop-p-butyl (1 944 kg/ha). These treatments gave more yield than chlorimuron ethyl, as the field was dominated by barnyard grass which was not controlled by it. However, chlorimuron ethyl gave significantly higher yield than the weedy control (750 kg). Therefore chlorimuron ethyl can be used to control broad-leaf weeds and sedges @ 12-24 g/ha al 15-day stage.