Effects of Formulated Glyphosate and Adjuvant Tank Mixes on Atomization from Aerial Application Flat Fan Nozzles

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 Manuscript received October 17, 2011; accepted for publication June 3, 2012; published online September 2012. USDA-ARS, 2771 F&B Rd., College Station, TX 77845. Wilbur-Ellis Company, San Antonio, TX 78258. Copyright VC 2012 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Pesticide Formulations and Delivery Systems: Innovating Legacy Products for New Uses STP 1558, 2012 Available online at www.astm.org DOI:10.1520/STP104451 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.