Evaluation of Glyphosate as a Harvest‐Aid Chemical on Cotton1

Abstract

AbstractRegrowth is sometimes a problem after defoliation of cotton (Gossypium hirsutum L.). Glyphosate [N‐(phosphonomethyl) glycine], a systemic herbicide, has been suggested as a regrowth suppressant. Glyphosate rates of 1.12 to 4.48 kg/ha were used in greenhouse studies to measure effects on leaf abscission and regrowth inhibition. Treatments of DEF (S,S,S,‐tributylphosphorotrithioate) at 1.26 kg/ha mixed with glyphosate at either 0, 1.12, 2.24, or 3.36 kg/ were used in a field experiment to determine effects of these treatments on defoliation, regrowth, yield, and various boll, seed, and fiber properties. Bolls that dehisced 0 to 25 days after treatment were used for boll, seed, and fiber property measurements.Glyphosate suppressed regrowth development when used either alone or in combination with DEF, and enhanced defoliation when the two chemicals were applied as a mixture. Seed cotton yield and most boll components were not affected by glyphosate treatments. Seed index was reduced by glyphosate treatments of 3.36 kg/ha, and a significant interaction between glyphosate rates and boll development was indicated for seed vigor. This research indicates that glyphosate can be an effective harvest‐aid on cotton when used in combinations with the defoliant chemical DEF.