Glyphosate selectivity by non-transgenic methods and efficacy of weed control in cotton (Gossypium hirsutum L).

Abstract

Glyphosate is a non-selective, broad spectrum and systemic weedicide and cannot be sprayed directly on crop without protective mechanism. Application of glyphosate at early stage of weed growth requires minimal dose. Higher dose also could be used by employing protective mechanism to crop plants. Glyphosate phytotoxicity could be reduced by pre-conditioning of plants by chemicals. Keeping the above facts in view, this experiment this experiment was conducted during 2013-14 at Central Institute for Cotton Research, Coimbatore with objective to assess glyphosate based weed control in cotton by achieving crop selectivity for glyphosate. Higher rate of crop phytotoxicity grade of 2.5 and 2.0 were registered by application of 2.5 ml/L of glyphosate along with 0.625 ml/L of Quizalofop ethyl at 20 and 40 DAS without protective mechanism (T6). The same treatment, with pre conditioned application of NiCl @0.01% on crop plants two days before application of glyphosate combination observed less phytotoxicity grade of 1.25 for both 20 and 40 DAS (T8). The significantly least weed DMP was estimated with application of glyphosate @ 5 ml/L at 20 and 40 DAS with protective mechanism(T9). Manual weeding at 20 and 40 DAS (T2) had registered significantly the highest seed cotton yield (2087kg/ha). The results was on par with application of glyphosate @ 5 ml/L at 20 and 40 DAS with protective mechanism (T9) and also comparable with glyphosate @ 2.5 ml/L with 0.625 ml/L of quizalofop ethyl at 20 and 40 DAS with protective mechanism/ pre conditioned by application of NiCl on crop plants ( T7 & T8). Application of Glyphosate @5.0 ml/L at 20 & 40 DAS with protective mechanism registered the significantly highest net return (Rs. 61, 875/ ha) and benefit cost ratio (2.56).