A field experiment was conducted to compare the performance of pre and post-emergence herbicides for grassy and broadleaf weeds in cotton. The treatments comprised of weedy check, pendimethalin at 825 g a.i ha-1, S-metolachlorat1898 g a.i ha-1, metolachlor at 1772 g +pendimethalin at 278 g a.i ha-1, S-metolachlor at 1772 g +pendimethalin at 278 g a.i ha-1, glyphosate at 2254 g a.e ha-1, haloxyfop P-methyl at 93 g a.i ha-1and paraquat dichloride at 500 g a.i ha-1. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. The weed biomass and weed control data were recorded 30 and 60days after planting (DAP) for pre and post-emergence herbicides, respectively. At 30 DAP; the lowest biomass of both broad leave and grass weeds was recorded from pre-emergence application of S-metolachlor. Whereas, at 60 DAP, the lowest dry weights of grass and broad leaves weeds were recorded with glyphosate application and followed by paraquat dichloride. The general weed control efficiency of pre-emergence herbicides was higher at 30 DAP than 60 DAP, except for metolachlor+pendimethalin where it was improved by 4.9% for grassy weeds at 60 DAP over 30 DAP. The highest (30.9) and lowest (4.7) weed index were recorded for S-metolachlor+pendimethalin and pendimethalin alone, respectively. The maximum number of bolls per plant (22.1), boll weight (3.02 g), seed cotton yield (2099 kg ha-1) and economic returns (Rs.47638 ha-1) were recorded with S-metolachlor application.
