Effects of Spray Mixtures on Droplet Size Under Aerial Application Conditions and Implications on Drift

摘要

There is a concerted effort within the spray application industry to develop and implement a Drift Reduction Technology (DRT) Program, which would encourage applicators to adopt technologies that are shown to mitigate off- target movement of sprays. The use of simulated or mimic sprays for atomization studies in high-speed wind tunnels allow researchers to limit the amount of active ingredients used in spray tests and facilitate the testing and certification of DRTs. However, it is important that these simulated and mimic sprays have the same physical and atomization characteristics of sprays containing active ingredients. Studies were conducted to compare droplet size generation from four spray formulations one of which was an active ingredient and three which were potential mimics and to use the collected data to examine an application management practice as a potential DRT. These sprays were atomized using two nozzles placed in high-speed airstreams in a wind tunnel and the droplet spectra measured via a laser diffraction instrument. In general, the volume median diameter (VMD) decreased by 30% to 50% as the airspeed increased. There were significant differences in droplet size between mimic sprays and those with active ingredient sprays. Results from AGDISP modeling showed increased downwind deposition with increased airspeed as a result of the increased number of finer droplets in the spray. The AGDISP results also showed differing amounts of downwind deposition at similar airspeeds from the different formulations. Downwind deposition modeling based on a simulated multi- pass spray application with reduced airspeeds near the downwind spray area border showed that the addition of the slower-speed passes near the edge can reduce total off-target movement.