A Wind Tunnel Investigation of Airborne Liquid Particle Behavior: Adjuvant Effects on Deposition

摘要

Application techniques, spray adjuvants, buffer zones, and windbreaks are all important tools for management of spray drift. However, a wide variety of vegetative types may be used for both buffer zones and windbreaks and therefore it is expected thatthese might capture the driftable fraction of the spray cloud differently depending on the physical properties of the spray mixture being utilized. The studies described here set out to evaluate the influence of adjuvants on the capture efficiency of various weed species and plant densities that might be found in buffer zones. Data were generated in a wind tunnel constructed at the Laboratory for Pest Control Application Technology (LPCAT). Water sensitive papers and passive dosimetry were utilized toassess droplet interception and capture respectively. Spray clouds were generated using either a TeeJet XR8001VS hydraulic fan nozzle or a Micron Ulva + spinning disc sprayer placed at the opening of the tunnel. Water, an hydroxy-propyl guar (HPG polymer), two crop oil concentrates, a non-ionic surfactant, and an invert suspension were utilized to impart different physicochemical characteristics to the spray cloud. Two mL/L of Rhodamine WT were added to each mixture for fluorimetry work. Three plant species were utilized, barnyard grass (Echinochloa crus-galli), velvetleaf (Abutilon theophmsti), and smooth pigweed (Amaranthus hybridus). Each treatment was replicated five times.The results showed that for bamyard grass, collection efficiency was different for the polymer compared to the other treatments. These results have implications for the vegetative composition of buffer zones and for drift risk assessment as applied to different crops.