Abstract

A field investigation was carried out at Tamil Nadu Agricultural University, during winter 2011- 12 to evaluate the new formulation of potassium salt based glyphosate (Roundup Crop Shield 460 SL) on weed control in winter irrigated cotton. Experimental results revealed that, post- emergence application of glyphosate at 1800 g a.e. ha-1 at 35 and 70 days after sowing + Intercultural operation as earthing up at 45 and 55 days after sowing resulted in lower weed density, weed dry weight and higher weed control efficiency. With respect to the relative weed density, broad-leaved weeds were higher at initial stages and grassy weeds were predominant at later stages of cotton. Higher seed cotton yield was obtained with POE glyphosate at 1800 g a.e. ha-1 at 35 and 70 DAS with + Intercultural operation at 45 and 55 DAS (2930 kg ha -1 ), which was comparable with PE pendimethalin at 750 g a.i. ha -1 + Intercultural operation at 45 and 55 DAS (2710 kg ha -1 ). Compared treatments without intercultural operation, intercultural operation carried out treatments performed better and recorded more seed cotton yield.

Keywords: Cotton, Glyphosate, Weed density, Weed control efficiency, Yield.