Assessment of some herbicides for the control of purple nutsedge (Cyperus rotundus) in soybean (Glycine max (L.) Merrill)

Field experiment was conducted at the Teaching and Research Farm, Faculty of Agriculture, Kogi State University, Anyigba in 2014 to assess the effects of some herbicides on the control of purple nutsedge in soybean. The field used for the trial was left fallow for about five years and predominantly infested with purple nutsedge. It was then ploughed, harrowed and ridged. The treatments applied consisted oflinuron [N-(3, 4-dichlorophenyl)-N-methoxy-N-methyl urea] at 2.0 and 2.5 kg a.i/ha;  2,4-D [ (2,4-dichlorophenoxy) acetic acid ] at 2.0 and 3.0 kg a.i/ha; glyphosate [N- (phosphonomethyl) glycine] at 2.0 and 2.5 kg a.i/ha;  a tank mixture of glufosinate [2-amino-4- (hydroxymethylphosphinyl) butanoic acid] + fluazifop [ (R) -2-[5-(trifluoromethyl)-2- pyridinyl ] oxy] phenoxy] propanoic acid] at 2.5 and 3.0 kg a.i/ha, manual hoe weeding  at 3,6 and 9 WAS and the weedy check. In this trial,the application of 2.0 and 2.5 kg a.i/ha of glyphosate was found to be most efficacious in the control of purple nutsedge. Glyphosate applied at both rates compared favourably with hoe weeding at 3,6 and 9 WAS in the control of purple nutsedge and resulted in the highest grain yield of soybean in the area. A tank mixture of glufosinate + fluazifop at 3.0 kg a;/ha equally gave a good control of purple nutsedge and the soybean grain yield produced therein was comparable to that obtained from plots treated with both rates of glyphosate or that were hoe weeded. Results obtained in this study suggest that glyphosate applied at 2.5 kg a.i/ha could provide alternative management option for the control of purple nutsedge to manual hoe-weeding and for ensuring higher grain yield of soybean.