Efficacy of Glyphosate with or without Additives/Herbicides for the Control of Purple Nutsedge (Cyperus rotundus L.) in Soybean

Field trial was carried out during 1994–95 and 1995–96 to find out the residual and cumulative effect of glyphosate with or without additives/herbicides for the control of purple nutsedge (Cyperus rotundus L.) in soybean. Efficacy of glyphosate at 1.0 kg/ha was increased substantially when applied in combination with either ammonium sulphate (2%), urea (2%) or 2, 4-D (1.0 kg/ha) as compared to sole application of glyphosate at same dose. The synergism was, however, marginal at 2.0 kg/ha glyphosate. The efficacy of glyphosate was lowered by the additon of oxyfluorfen (0.10 kg/ha). Repeating the application during both the years was relatively more effective in controlling C. rotundus than one year application. The treatment which gave good control of C. rowndus realised higher productivity of soybean. There was 15–50 and 30–81% increase in seed yield due to one year (direct effect) and two year (cumulative effect) applications, respectively.