Weed management, fiber quality, and net returns in no-tillage transgenic and nontransgenic cotton (Gossypium hirsutum)

Studies on weed management systems with bromoxynil-resistant, glyphosate-resistant, and nontransgenic cotton cultivars in a no-tillage environment were evaluated in North Carolina and Tennessee in 1997 and 1998. All weed management systems in nontransgenic and bromoxynil-resistant cotton controlled sicklepod 72 to 78%, whereas sicklepod was controlled at least 94% in glyphosate-resistant cotton. Entireleaf and pitted morningglory, smooth pigweed, and common cock-lebur were controlled at least 92% with all management systems. Fiber quality was also measured in Tennessee. Micronaire and fiber strength ranged from 4.35 to 4.55 units and 28.6 to 30.1 g/tex, respectively, in bromoxynil-resistant and glyphosate-resistant cultivars that received postemergence over-the-top (POT) herbicides. Harvest trash content ranged from 0.80 to 1.15% in systems where POT and late postemergence-directed (LAYBY) herbicides were used and was 1.65% where multiple glyphosate applications were used with no LAYBY herbicides. Cotton lint yield and net returns were generally highest in systems that included bromoxynil or pyrithiobac POT followed by cyanazine plus MSMA LAYBY or multiple glyphosate treatments where no LAYBY herbicides were used.