Sprayer nozzle, spray volume, and adjuvant effects on herbicide efficacy, coverage, retention, and drift

Four drift-reducing nozzles significantly reduced the distance of spray drift compared to a conventional flat-fan nozzle. By reducing the amount of spray in fine droplets, the Turbo TeeJet, AI TeeJet, and TurboDrop sprayer nozzles generally reduced spray drift more than Drift Guard or conventional nozzles. Total spray coverage detected on water-sensitive cards was generally greatest for conventional and Drift Guard nozzles compared to Turbo TeeJet, AI TeeJet, and TurboDrop nozzles.;Retention of spray mixtures without adjuvants on weeds was greater for treatments applied with conventional and Drift Guard nozzles compared to Turbo TeeJet, AI TeeJet, and TurboDrop nozzles. However, spray retention among all nozzle types was similar when averaged over spray adjuvant and two weed species. Although total spray retention was greatest at 190 L/ha, dye (i.e., herbicide) retention was greater for spray applied at 47 or 94 L/ha than at 190 L/ha. Consequently, herbicide efficacy may be greater for spray applied at 47 or 94 L/ha as well.;Carfentrazone and imazamox efficacy, representing contact and translocated herbicides, respectively, usually was not influenced by changes in nozzle type (i.e., spray droplet size). Carfentrazone and imazamox were equally or more effective when applied with TurboDrop or Drift Guard nozzles than the conventional nozzle in 95% of the comparisons. In separate experiments, glyphosate, a translocated herbicide, and paraquat, a contact herbicide, provided excellent grass species control, regardless of nozzle type.;Imazamox applied at 47, 94, or 190 L/ha spray volume and carfentrazone applied at 94 or 190 L/ha spray volume provided similar control, regardless of sprayer nozzle or adjuvant. Carfentrazone applied at 47 L/ha spray volume was as effective as at 94 or 190 L/ha provided either NIS or MVO was included with 28% N in the spray mixture. Conversely, carfentrazone with 28% N alone was less effective at 47 L/ha spray volume than at 94 or 190 L/ha. Consistent species control from carfentrazone and imazamox at low spray volumes was achieved when an effective adjuvant was included in the spray mixture. Glyphosate and paraquat efficacy was similar at 47, 94, or 190 L/ha spray volume.