COMPARING DOWNWIND SPRAY DROPLET DEPOSITS OF FOUR FLAT-FAN NOZZLE TYPES MEASURED IN A WIND TUNNEL AND ANALYZED USING DROPLETSCAN. SOFTWARE

Wind tunnel experiments were conducted to examine the ability of four flat-fan nozzles designed for herbicide applications to reduce the downwind movement of spray droplets (drift). The nozzles were compared at 47 and 94 L/ha in crosswind and headwind application scenarios at a constant wind speed of 4.6 m/s. Each nozzle was used at the common recommended field operating pressure of 173 kPa for the extended range (XR) flat-fan, 242 kPa for the turbo (TT) flat-fan and the Combo-Jet (DR) flat-fan, and 345 kPa for the venturi (AI) flat-fan. Downwind droplet movement used as an indicator for drift was collected on water-sensitive paper (wsp) positioned 2, 3, and 4 m downwind from the nozzle. The wsp was scanned and DropletScan. software was used to measure percent area coverage for each treatment as a basis for separating differences. For the crosswind orientation, the XR flat-fan measured significantly more downwind droplet coverage than the TT, DR, and AI flat-fans. The TT flat-fan had significantly less downwind droplet movement than the XR flat-fan at 47 L/ha, but not at 94 L/ha. The DR and AI flat-fans were not significantly different from each other, but did produce significantly less droplets moving downwind than both the XR and TT flat-fans. For the XR flat-fan, increasing the application volume from 47 to 94 L/ha significantly reduced the amount of downwind droplet movement. This finding did not hold true for the TT, DR, and AI flat-fans. Similar trends were measured with the headwind nozzle orientation. As evidenced in this study, even when used at the recommended pressure, the four nozzles compared produced significantly different amounts of downwind coverage on the wsp. Based on the findings, using nozzles specifically designed for reducing drift (TT, DR, and AI flat-fans) will significantly reduce drift when compared to conventional XR flat-fans.