SPRAYER SPEED AND VENTURI–NOZZLE EFFECTS ON BROADCAST APPLICATION UNIFORMITY

Sprayer speeds up to ~26 kmh –1 did not reduce quantity or increase variation in field spray deposit across a 27.4–m boom when using Ultra Plus Low Drift (UPLD) venturi nozzles at pressures of at least 276 kPa. Sprayer speeds of 12.9, 19.3, and 25.7 kmh –1 with the UPLD nozzles produced water sensitive paper coverage of ~19% that was not significantly different than the ~20% produced by an extended range (ER 4) single elliptical orifice nozzle. A 6.4 kmh –1 treatment with UPLD 15 nozzles resulted in lower coverage (~14%) attributed to large droplets. Laser measured volume median diameters (Dv0.5 ) for the UPLD 15, 2, 4, and 5 nozzles corresponding to sprayer speed treatments of 6.4, 12.9, 19.3, and 25.7 kmh –1 were 663, 474, 579, and 513
m, respectively. The ER 4 nozzle produced a Dv0.5 of 187
m. UPLD nozzles resulted in spot densities ranging from 44.9 to 104.6 spot cm –2 , compared to 233.4 spot cm –2 for the ER 4, all at 93.5 Lha –1 spray rate. Overall, field applied coefficients of variation (CV) in deposit ranged from ~13% to 21% for all nozzles compared to ~4% to ~16% for a static spray pattern uniformity test. The static test determined an optimum nozzle height, based on minimization of CV, of 71 cm for UPLD nozzles. This was higher than 41 cm for the ER 4 nozzle. Slight nuances in coverage under nozzles versus between nozzles, between left, middle, and right boom were noted, including reduced coverage along the centerline of the sprayer for some speed/nozzle combinations.