Response of Bt. cotton to post emergence herbicides in Vertisols of Krishna zone.

ABSTRACT

Cotton, a long duration crop coupled with heavy rains during the early vegetative stage inhibit manual and mechanical methods of weed control causing heavy yield loss . A field experiment was conducted to evaluate the efficacy of different post emergence herbicides applied at 45 DAS viz; glufosinate ammonium 15% SL @ 300 g a.i ha-1, glufosinate ammonium 15% SL @ 375 g a.i ha-1, glufosinate ammonium 15% SL @ 450 g a.i ha-1, paraquat 24 SL @ 300 g a.i ha-1, glyphosate 4l SL @1025 g a.i ha-1 on productivity of Bt. cotton entry NCS 145 BG II against Cyprus rotundus, Commalina bengalensis, Corchorus acutangulus, Amaranthus viridis, Abutilon indicum, Phyllanthus niruri ,Celosia argentia, Parthenium sp etc from 2008 to 2010 in vertisols under rainfed conditions at Regional Agricultural Research Station, Lam, Guntur. The seed cotton yield increased significantly due to all the treatments to the magnitude of 66-75% as compared to weedy check. The highest seed cotton yield of 3094 kg ha-1 was recorded with glufosinate ammonium 15% SL @ 375g a.i ha-1 followed by hand weeding at 20, 40 and 60DAS (3062 kg ha-1) and glyphosate 41 SL @ 1025 g a.i ha-1 (2902 kg ha-1). The weed density and weed dry matter recorded were lowest with the application glufosinate ammonium 15% SL @ 375g a.i ha-1 and glufosinate ammonium 15% SL @ 450g a.i ha-1 when compared to other treatments.