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Title: Spray deposition inside tree canopies from a newly developed variable-rate air assisted sprayer

item CHEN, Y - The Ohio State University
item OZKAN, H - The Ohio State University
item Zhu, Heping
item Derksen, Richard
item Krause, Charles

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2013
Publication Date: 12/22/2013
Citation: Chen, Y., Ozkan, H.E., Zhu, H., Derksen, R.C., Krause, C.R. 2013. Spray deposition inside tree canopies from a newly developed variable-rate air assisted sprayer. Transactions of the ASABE. 56(6):1263-1272.

Interpretive Summary: Trees in nurseries and orchards have great variations in shapes, sizes, canopy densities and gaps between in-row trees. The variability requires future sprayers to be flexible to spray the amount of chemicals that can match tree structures. A variable-rate air-assisted sprayer implementing high-speed laser scanning technology was developed to achieve the requirements. The new sprayer performance was evaluated in an orchard by quantifying its spray deposition inside canopies at different plant phenological stages. The spray deposition quality was also compared with conventional constant-rate spray applications. Field tests demonstrated that the new variable-rate sprayer produced significantly more consistent spray deposit and coverage inside tree canopies over different growth stages than the conventional sprayers, consequently resulting in less off-target loss and less pesticide use. Therefore, use of the new sprayer to deliver pest control agents will bring great benefits to growers economically and environmentally.

Technical Abstract: Conventional spray applications in orchards and ornamental nurseries are not target-oriented, resulting in significant waste of pesticides and contamination of the environment. To address this problem, a variable-rate air-assisted sprayer implementing laser scanning technology was developed to apply appropriate amount of pesticides based on tree canopy characteristics such as tree height, width, volume, foliage density and occurrence of trees. The new sprayer performances were evaluated in an apple orchard by quantifying spray deposition at three different growing stages (April, May and June) with three sprayer treatments: the new variable-rate sprayer, the same sprayer without the variable-rate function and a conventional air blast sprayer. Their spray coverage and deposits inside canopies were measured and compared with water sensitive papers and nylon screens. The three sprayer treatments provided fairly consistent spray coverage and deposit in spray direction (or canopy depth direction) in April test when tree foliages were in the early growth stage. The variations in spray coverage and deposit in spray direction increased considerably for S2 and S3 in May and June tests. S1 produced better uniformity in spray deposit and coverage across tree height direction than S2 and S3 at all growth stages. Compared to conventional constant-rate sprayers, the new variable-rate sprayer only consumed 27% to 53% of the spray mixture while it still achieved adequate spray coverage inside canopies. Also, the spray deposition from the new sprayer was very consistence regardless of the canopy growth stages. Therefore, the new sprayer increased spray efficiency and improved spray accuracy by lowering the overspray possibility greatly, resulting in reduced spray costs and potential environmental pollutions.