Bioefficacy of sequential application of herbicides in cotton

Abstract

A field experiment was conducted for two years during kharif 2011-12 and 2012-13 to study the bio-efficacy of sequential application of herbicides in Bt cotton. Ten weed control treatments were tested in randomised block design and they were replicated thrice. The mean of two years data indicated that, all the herbicide treatments significantly reduced dry weight of weeds over unweeded control. Among the herbicide treatments sequential application of Pyrithiobac sodium at 0.125 kg/ha as pre emergence followed by (fb) Pyrithiobac sodium at 0.125 kg/ha as post emergence, Butachlor at 1.5 kg/ha fb Butachlor at 1.5 kg/ha and Pendimethalin 38.7% CS 0.68 kg/ha fb Pendimethalin 38.7% CS 0.68 kg/ha were quite effective in controlling weeds which reflected in significantly decreased weed dry weight and increased weed control efficiency. These three herbicide treatments also recorded significantly higher yield (2863, 2830 and 2725 kg/ha, respectively). The growth and yield parameters followed similar trend as that of yield. The weed index was also lower in the above three treatments (11.43, 12.45 and 15.45 %, respectively) compared to un weeded control (76.56 %).