Field experiments were conducted to evaluate the effect of five spray-nozzle types and three drift-control adjuvants (DCA) on glyphosate spray drift. The extended-range (XR) flat-fan nozzle at 280 kPa was used as the standard comparison. DCAs were evaluated for drift reduction with the use of the XR and air-induction (AI) nozzles. Wind speed ranged from 1.3 to 9.4 m/s (3 to 21 mph). Lethal drift (DL) and injury drift (DI) were determined by downwind visual observation of grain sorghum response. Drift distances were measured from the spray swath edge. The Turbo FloodJet and AI nozzles reduced DL distance by 34%. All four drift-reducing (DR) nozzles reduced DI distance by 22 to 32%. Reducing the pressure of the XR flat-fan nozzle from 280 to 140 kPa did not reduce DL or DI distance. When applied through AI nozzles, each DCA increased droplet volume diameter, one DCA reduced DI distance and none reduced DL distance when applied through XR tips. The DCAs did not affect DL or DI distance.
Nomenclature: Glyphosate; grain sorghum, Sorghum bicolor (L.) ‘Topaz’.
Additional index words: Drift-control adjuvant, flat-fan nozzle, flood nozzle.
Abbreviations: AI, air induction; AMS, ammonium sulfate; DAP, days after planting; DAT, days after treatment; DCA, drift-control adjuvant; DG, preorifice flat fan; DI, injury drift; DL, lethal drift; DR, Combo-Jet; GR, glyphosate resistant; HRC, herbicide-resistant crops; TD, TurboDrop; TF, Turbo FloodJet; TT, Turbo TeeJet; VMD, volume median diameter; XR, extended range.