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Title: Spray spectrum modifications through changes in airspeed to minimize drift

item Fritz, Bradley - Brad
item Hoffmann, Wesley
item Lan, Yubin

Submitted to: National Agricultural Aviation Association Meeting
Publication Type: Proceedings
Publication Acceptance Date: 12/8/2008
Publication Date: 12/8/2008
Citation: Fritz, B.K., Bagley, B., Hoffmann, W.C., Lan, Y. 2009. Spray spectrum modifications through changes in airspeed to minimize drift. National Agricultural Aviation Association Meeting. Paper No. AA08-002.

Interpretive Summary: Drift from aerial application of crop protection materials is influenced by many factors such as meteorological factors, spray material properties, and equipment setup, but the spray droplet size has long been recognized as the primary factor. Smaller droplets typically result in greater spray drift, with higher airspeeds resulting in increased atomization and therefore smaller droplets. High-speed wind tunnel measurements of spray droplets were incorporated in a mathematical model of spray drift to explore several scenarios of applications at decreased airspeeds near a field edge in order to increase droplet size and decrease drift. Results showed optimum reduction in drift potential with two or three near field edge swaths being made. These results will help applicators apply crop protection materials with maximum on-target deposition and minimum off-target drift.

Technical Abstract: Management of droplet size is one of the key components to minimizing spray drift, which can be accomplished in-flight by changing airspeed. Studies were conducted measuring spray droplet spectra parameters across airspeeds ranging from 100-140 mph (in 5 mph increments). In general the volume median diameters decreased 30-50% as airspeed increased with similar increases in the percent of the spray volume less than 100 µm. To determine the extent to which these changes in droplet spectra data impacted downwind drift, AgDISP was employed to estimate how varying airspeed along sequential flights swaths near a downwind field edge impacted total off field spray drift. Spray drift was modeled across multiple sequential spray swaths at both constant airspeeds across all swaths and at scenarios where near field edge swaths were flown at lower airspeeds (thus larger droplet sizes) to determine the level to which spray drift is reduced.