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United States Department of Agriculture

Agricultural Research Service

Title: Atmospheric effects on the fate of aerially applied agricultural sprays

Authors
item Fritz, Bradley
item Hoffmann, Wesley

Submitted to: International Agricultural Engineering Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 26, 2008
Publication Date: August 10, 2008
Citation: Fritz, B.K., Hoffmann, W.C. 2008. Atmospheric effects on the fate of aerially applied agricultural sprays. International Agricultural Engineering Journal. X:08008.

Interpretive Summary: Drift from aerial application of crop protection materials is influenced by many factors such as wind speed, temperature, relative humidity, and atmospheric stability. Applicators are responsible for making all possible efforts to reduce drift. Generally, greater drift has been associated with greater atmospheric stability. Field trials were conducted to assess the degree of downwind deposition and airborne concentration resulting from aerial spray applications for various meteorological and atmospheric stability conditions. Wind speed was found to increase the transport distance of larger spray droplets as well as increase downwind drift and deposition. These results will help applicators apply crop protection materials with maximum on-target deposition and minimum off-target drift.

Technical Abstract: Drift from aerial application of crop protection materials is influenced by many factors such as mean wind, temperature, relative humidity, and atmospheric stability. The applicator is responsible for making all possible efforts to reduce drift. Atmospheric conditions and stability must be considered and adjusted for on the basis of real-time observations and past experience. The objective of this research was to further document the effects of atmospheric conditions and stability on the deposition, drift, and deposited droplet size characteristics of aerial sprays. Twelve replications using a fine aerial spray treatment were conducted over the course of a day. Ground deposition and airborne concentrations at multiple heights were collected at multiple downwind locations using mylar cards and nylon screen cylinders, respectively. Results indicated that wind speed was more dominant than stability, and increased wind speeds resulted in increased downwind ground deposition, suspended concentrations, and transport of larger droplets downwind. There were no significant differences in either ground depositions or airborne concentrations past 75 m downwind, regardless of atmospheric stability. Overall, the results indicated that wind speed was the most dominant meteorological factor in the transport and fate of aerially applied sprays.

Last Modified: 4/16/2014
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