Effects of Formulated Glyphosate and Adjuvant Tank Mixes on Atomization from Aerial Application Flat Fan Nozzles
Abstract : This study was designed to determine if the present USDAARS spray-nozzle models, which were based on spray solutions of water plus non-ionic surfactant, could be used to estimate spray droplet-size data for different spray formulations through use of experimentally determined correction factors. Twelve spray-solution treatments were evaluated, ten of which contained a formulated glyphosate product and nine of these contained an additional tank-mix adjuvant. Droplet-size testing was conducted across multiple operational points (nozzle-orifice size, nozzle orientation spray pressure, and airspeed), in a high-speed wind tunnel, which corresponds to the response surface experimental model used to develop the present spray-nozzle models. The hypothesis that the different treatment solutions would respond linearly across a range of operational parameters and that a correction factor from relative to water plus non-ionic surfactant solution was proven false. When compared to water or the water plus non-ionic surfactant, the changes in atomization across the operation spectrum of the nozzle were not consistent and varied by formulation. Attempts to apply regression fits for a correction factor based on solution physical properties were not successful. With the formulated glyphosate tank mix used, none of the adjuvants tested, except the polymer, showed significant changes in droplet size under the high air shear regime. Whereas there is likely a need to develop formulated product-specific atomization models, the further addition of adjuvants do not significantly change the atomization characteristics and, as such, should not require a unique spray-nozzle model.
Measurement of drop spectra from rotary cage aerial atomizers
Abstract The drop spectra produced by various examples of Micronair AU3000 rotary cage atomizer were measured using a laser-based Particle Measuring Systems optical array probe. To simulate aerial application by fixed-wing aircraft, the atomizers were mounted in an open jet wind tunnel operating in the range 130–225 km h−1. An empirical model which predicted the volume median diameters (VMDs) and volume quartiles of the spectra was developed. The model showed a high degree of correlation with the experimental results. The model took into account not only the speed of rotation of the cage, but its diameter, the liquid flow rate, and the air speed of the aircraft. The model showed general agreement with research into rotary disc atomization. Although a water-based liquid was used in the tests, it was concluded that the model would be suitable for use as a performance guide for most pesticide formulations.
Evaluation of the AgDISP aerial spray algorithms in the AgDRIFT model
A systematic evaluation of the AgDISP algorithms, which simulate off‐site drift and deposition of aerially applied pesticides, contained in the AgDRIFT® model was performed by comparing model simulations to field‐trial data collected by the Spray Drift Task Force. Field‐trial data used for model evaluation included 161 separate trials of typical agriculture aerial applications under a wide range of application and meteorological conditions. Input for model simulations included information on the aircraft and spray equipment, spray material, meteorology, and site geometry. The model input datasets were generated independently of the field deposition results, i.e., model inputs were in no way altered or selected to improve the fit of model output to field results. AgDRIFT shows a response similar to that of the field observations for many application variables (e.g., droplet size, application height, wind speed). However, AgDRIFT is sensitive to evaporative effects, and modeled deposition in the far‐field responds to wet bulb depression whereas the field observations did not. The model tended to overpredict deposition rates relative to the field data for far‐field distances, particularly under evaporative conditions. AgDRIFT was in good agreement with field results for estimating near‐field buffer zones needed to manage human, crop, livestock, and ecological exposure.