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United States Department of Agriculture

Agricultural Research Service

Research Project: AERIAL APPLICATION RESEARCH FOR EFFICIENT CROP PRODUCTION Title: Determination of selection criteria for spray drift reduction from atomization data

Authors
item Hoffmann, Wesley
item Fritz, Bradley
item Bagley, William -
item Gednalske, Joe -
item Elsik, Curt -
item Kruger, Greg -

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2012
Publication Date: September 15, 2012
Citation: Hoffmann, W.C., Fritz, B.K., Bagley, W., Gednalske, J., Elsik, C., Kruger, G. 2012. Determination of selection criteria for spray drift reduction from atomization data. ASTM Special Technical Publication 1558 STP. p. 65-79.

Interpretive Summary: When testing and evaluating drift reduction technologies (DRT) as part of a U.S. EPA program, there are different measurements that can be used to determine if the technology reduces spray drift as compared to a reference system. These measurements can include reduction in percent of fine drops, measured spray drift from a field trial, or computer modeling of spray drift based on the application system and the droplet size distribution resulting from the specified operational conditions. Studies were conducted in the USDA-ARS Aerial Application Technology group’s low- and high-speed wind tunnels to determine the best droplet size classification measurement to objectively evaluate DRT technologies. The percent of spray volume contained in droplets with diameters less than 80-105 um (one-millionth of a meter) provided the most robust separation of treatments. These results will provide applicators, growers, and regulators with general guidelines to ensure that technologies sold as a DRT do effectively reduce spray drift.

Technical Abstract: When testing and evaluating drift reduction technologies (DRT), there are different metrics that can be used to determine if the technology reduces drift as compared to a reference system. These metrics can include reduction in percent of fine drops, measured spray drift from a field trial, or computer modeling of spray drift based on the application system and the droplet spectrum resulting from the specified operational conditions. While the percent reduction in fines is commonly used and reported in the literature, there are often different droplet size values used, such as 100, 105, 141, 150, 200, and 210 um. These values are of interest as they potentially relate to the volume fraction of the spray that has the greatest potential for drift. The percent of spray volume contained in droplets with diameters less than 80-105 µm provided the most robust separation of treatments. The interaction between active ingredient, nozzle, and adjuvant must be considered when making DRT determinations. This study illustrates that adjuvants do not behave the same with every nozzle. Different types of adjuvants alter the spray distribution in different ways. The oil concentrate in this study uniformly narrowed the entire spray distribution while in contrast the polymers widened the spray distribution due to a greater increase in spray volume made up of large droplets with only a modest increase in spray volume made up of smaller droplets. When evaluating different spray technologies, it is critical that the overall spray distribution is considered and used as a comparative measure between multiple technologies, particularly with active formulations and spray solution modifiers.

Last Modified: 10/23/2014