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Title: A History of Air-Blast Sprayer Development and Future Prospects

item Fox, Robert
item Derksen, Richard
item Zhu, Heping
item Brazee, Ross

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2007
Publication Date: 4/1/2008
Citation: Fox, R.D., Derksen, R.C., Zhu, H., Brazee, R.D., Svensson, S.A. 2008. A History of Air-Blast Sprayer Development and Future Prospects. Transactions of the ASABE. 51(2):405-410

Interpretive Summary: The American Society of Agricultural and Biological Engineers are celebrating their 100th year of existence in 2007. As part of this celebration, they are publishing a series of review papers on the history, development, and future of all aspects of the Society’s technical divisions. This paper is a history of the air-blast sprayer. Pest control agents have been used on vineyards and orchards for centuries. Early application methods involved applying dusts and pastes with porous sacks and brushes. Later hand pumps and hoses with nozzle were used to apply spray water carrier mixtures. In the early 20th century engines were used to operate the pumps and later aircraft propellers were used to create air jets to transport spray droplets into the trees. Then more efficient fans were developed and the radial air-blast sprayer was introduced. Research on the air jet from sprayers resulted in numerical models of the velocity fields; velocities decreased rapidly with distance from the jet outlet. Factors effecting coverage throughout the tree canopy were evaluated in an effort to find the best match between the sprayer and the type of canopy being sprayed. Major factors include the spray droplet spectra produced by the sprayer nozzles, the velocity and volume of the air jet, and the design of the air jet outlet. Modern designs such as tower sprayers, tunnel sprayers, and multiple directed-jet sprayers, with the adoption of dwarf trees by many growers have improved the uniformity of coverage in the canopy and reduced the airborne spray drift out of the orchard. Future sprayer development will likely be required to reduce spray drift even more. As demand for organic products increases in the future, more bio-control materials will be applied. These materials will often contain living organisms and will require sprayers that do not damage these pest control agents through mechanical, thermal, or solar stress. The best application practices will include modifying the sprayer operating characteristics to match the size, shape and density of the tree canopy being sprayed.

Technical Abstract: The design and operating procedures of air-blast sprayers have been greatly improved over the past 50 years. Early tree and vine s pray application equipment used hand-guns that required large amount of water. Later, sprayers with efficient fans, producing large volumes of air at high velocities, were developed for large fruit and nut trees. Recently, growers have planted many dwarf and semi-dwarf apple trees. In general, it is easier to produce more uniform coverage with less drift when spraying small trees than when spraying large trees. Modern designs such as tower, directed jet and tunnel sprayers should reduce airborne spray drift and produce more uniform coverage. For optimum effectiveness, sprayer air-jet velocity and volume and droplet spectra should be matched to the tree size, shape and density. Future sprayers will likely be required to handle biological materials with a greater variety of physical properties than the standard ‘chemical’ materials used now. In addition, these materials will require spray systems that protect the live spray products from damage from heat, mechanical stress and other factors that may kill the beneficial organism being applied.