Effect of formulated glyphosate and adjuvant tank mixes on atomization from aerial application flat fan nozzles

Authors: Fritz, Bradley - Brad; Hoffmann, Wesley; BAGLEY, WILLIAM - Wilbur-Ellis Company

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2012
Publication Date: 7/12/2012
Citation: Fritz, B.K., Hoffmann, W.C., Bagley, W.E. 2012. Effect of formulated glyphosate and adjuvant tank mixes on atomization from aerial application flat fan nozzles. Journal of ASTM International. doi 10.1520/STP104451.

Interpretive Summary: Applicators are responsible for setting up their application equipment and using methods that provide maximum efficiency while reducing drift. Nozzle performance and the resulting spray droplet size are among the primary factors driving the movement and fate of applied spray. While there are a number of sources available to assist aerial applicators in setting up their spray nozzle to produce specific spray droplet spectrums, most are based on spray solutions that do not contain active products or additional spray adjuvants. This study was designed to determine if the present USDA ARS Spray Nozzle models based on water-only spray solutions could be used to estimate spray droplet size for active ingredient spray formulations using experimentally determined correction factors or if new spray nozzle models would be required. While the results did not support simple correction factor-based estimates of droplet size, they did indicate that new product specific models could potentially represent the majority of spray formulations using that specific product. New product specific models will provide applicators with better estimates of droplet size leading to more efficient and effective treatments.

Technical Abstract: This study was designed to determine if the present USDA ARS Spray Nozzle models based on water plus non-ionic surfactant spray solutions could be used to estimate spray droplet size data for different spray formulations through use of experimentally determined correction factors or if full spray formulation specific spray nozzle models are required. Twelve spray formulations were evaluated, ten of which contained active product plus additional spray adjuvant, for droplet size across multiple operational points used to define a full spray model response surface. Initial hypothesis of linear responses across the response surfaces for the different spray formulations did not hold preventing the determination of a simple linear correction factor. When compared to water or the water plus non-ionic surfactant, the changes in atomization across the different operational points was not consistent for each formulation with increases and decreases that varied from solution to solution. Attempts to apply regression fits based on solution physical properties were not successful. However, for the active ingredient used, the addition of the different adjuvants tested, with the exception of the polymer, did not significantly change the atomization properties under the high air shear regime. As a result, while there is likely a need to develop multiple atomization models for different formulated active products, the new product specific models could potentially suffice to represent the majority of spray formulation using that specific product across the range of airspeeds tested herein.