Effect of pre-sowing and pre-emergence glyphosate applications on weedsin stale seedbed cotton

The effect of pre-emergence or pre-sowing glyphosate treatments in stale seedbed cotton was evaluated in 2005, 2007 and 2008. Main soil tillage at the experimental fields was carried out in early April to allow weed emergence before sowing. Glyphosate was applied on plots with or without seedbed preparation as pre-sowing or pre-emergence treatments. Efficacies of glyphosate treatments were compared with untreated control and plots which received seedbed preparation + trifluralin. 2 and 4 weeks after cotton emergence, weed cover was visually estimated and weed biomass determined, respectively. A combination of stale seedbed technique with glyphosate treatment can be considered an effective alternative weed control system to reduce weeds by up to 90% during the critical period. This would reduce the intensity, costs and negative environmental impact of mechanical and chemical treatments.