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Title: Wind Tunnel Evaluation of Drift Reduction Potential and Spray Characteristics with Drift Retardants at High Operating Pressure

item GULER, H - OSU
item Zhu, Heping
item OZKAN, H - OSU
item Derksen, Richard
item Krause, Charles

Submitted to: American Society for Testing and Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2006
Publication Date: 5/10/2006
Citation: Guler, H., Zhu, H., Ozkan, H.E., Derksen, R.C., Krause, C.R. 2006. Wind Tunnel Evaluation of Drift Reduction Potential and Spray Characteristics with Drift Retardants at High Operating Pressure. American Society for Testing and Materials. 3(5):1-9.

Interpretive Summary: Spray drift can be a serious concern in pesticide spray applications since it causes inefficient use of pesticide, damage on crops in adjacent fields, and pollution of air and water resources. During past decade, many new drift retardants to minimize the pesticide drift potential were introduced into the market; however, limited information is available about their effectiveness at high operating pressures. In this study, spray drift reduction potential for spray carriers with drift retardants containing different active ingredients were investigated with spray nozzles discharging a large fluid capacity at high pressure in a wind tunnel. Test results indicated that, compared to the spray carrier with water only, drift retardants containing nonionic colloidal and polyvinyl polymers at high operating pressure reduced the drift potential while the polyacrylamide drift retardant did not show any significant reduction in drift potential. Therefore, pesticide applicators should investigate carefully the basic chemistry composition of any drift retardants they select for adding to their spray mixtures; also, chemical formulators must be familiar with the active ingredients in any drift retardants added to pesticide formulations.

Technical Abstract: Although considerable research has been done on effectiveness of drift retardants for many years, answers to some questions are still unclear to applicators. Laboratory tests were conducted to evaluate drift potentials associated with off-target ground and airborne spray deposits discharged with a hollow cone nozzle spraying three different drift retardants at a high operating pressure and various wind velocities in a wind tunnel. Droplet sizes and spray widths were also determined with a laser imaging system and a portable spray patternator. At 1655 kPa pressure and 4.65 L/m flow rate, the volume median diameters of droplets from the hollow cone nozzle discharging spray mixtures containing water only, polyvinyl polymer, nonionic colloidal polymer and polyacrylamide polymer drift retardants were 201, 222, 239 and 210 µm, respectively. The major spray pattern width was not changed after drift retardants were added into the spray carrier. For the wind velocity from 1 to 5 m/s in the wind tunnel, the polyacrylamide drift retardant produced the highest airborne deposit among the three drift retardants, followed by polyvinyl, and then nonionic colloidal. Also, the polyacrylamide drift retardant produced the highest ground drift potential, followed by nonionic colloidal and then polyvinyl. According to the results from this laboratory study, both nonionic colloidal and polyvinyl polymer drift retardants reduced the drift potential compared to the spray carrier containing water only.