Field studies were conducted at the Alabama Agricultural Experiment Station near Shorter, AL, from 1998 to 2000 to evaluate six commercial spray adjuvants and their effects on glyphosate applied to cotton with an air-assisted sprayer. Each adjuvant was evaluated with a conventional sprayer calibrated to deliver 94 L/ha solution and a low-volume, air-assisted sprayer calibrated to deliver 19 L/ha solution. Glyphosate was applied to two-leaf pitted and entireleaf morningglory growing in glyphosate-resistant cotton. Visual control of pitted and entireleaf morningglory was more dependent on the rate of herbicide application than on a particular adjuvant or sprayer, with glyphosate at 0.42 kg ae/ha providing 70% control 21 d after treatment. Pitted and entireleaf morningglory biomass measurements generally reflected visual control data. Ammonium sulfate and formulated glyphosate consistently gave the highest visual control and the greatest biomass reduction. Glyphosate application rate was more important than adjuvant addition or sprayer type, with the higher rates of application providing greater control. No differences in weed control were observed between spray systems; therefore, air-assisted sprayers may be used on a field-scale basis with consistent and adequate results.
Nomenclature: Glyphosate; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray #3 IPOHE; pitted morningglory, Ipomoea lacunosa L. # IPOLA; cotton, Gossypium hirsutum L. ‘Paymaster 1220BG/RR’.
Additional index words: Glyphosate-resistant cotton, IPOHE, IPOLA, surfactant.
Abbreviations: AMS, ammonium sulfate; COC, crop oil concentrate; DAT, days after treatment; GLY , formulated glyphosate; NIS-1, nonionic surfactant; NIS-2, nonionic wetter–spreader–penetrant; NIS-3, nonionic surfactant–penetrant–acidifier; POST, postemergence; PPI, preplant incorporated; WCA, water conditioning agent.
