Submitted to: Agricultural Aviation
Publication Type: Trade Journal
Publication Acceptance Date: December 24, 2002
Publication Date: January 5, 2003
Citation: Hoffmann, W.C., Kirk, I.W. 2003. Nozzle classifications and you. Agricultural Aviation. 30(1):27-29. Interpretive Summary: Aerial applicators face a number of decisions every time they make an application. Many crop protection and production materials now specify droplet size classifications for application, such as "apply as a MEDIUM spray." Studies were conducted with two nozzles that generated a "MEDIUM" spray to evaluate off-target movement of the sprayed materials. The data showed that the nozzle that had three times more spray volume in small droplets produced significantly higher downwind drift of the spray even though both nozzles met the label requirements. The results highlight the need for aerial applicators to consider all of the droplet size data, especially for the driftable portions of the spray, when selecting the most appropriate nozzle for a given application.
Technical Abstract: Aerial applicators are utilizing computer models and printed materials to comply with pesticide labels that specify droplet spectra, such as "apply as a MEDIUM spray." To help in the selection of the proper equipment selection for an application, studies were conducted to determine the spray deposition and drift from two "MEDIUM" nozzles used in an aerial application. The first nozzle (T1) generated three times more spray volume in droplets less than 200 µm than the second nozzle (T2). Droplets less than 200 µm are the droplets that are most likely to drift out of the targeted area because of their small size. The data showed very different downwind deposition occurs from the two aerial spray nozzles selected. T1 produced significantly higher downwind deposition than T2. At 50 m from the downwind edge of the spray swath, the deposition was 1.7% and 0.53% of the deposition at 0 m for T1 and T2, respectively. T1 also produced more airborne material at 50 m downwind of the spray swath edge than T2 at heights up to 10 m. These results were valid for spray applications made in crop canopies or over concrete runways. The results highlight the need for aerial applicators to consider all of the droplet spectra data when selecting the most appropriate spray nozzle for a given application situation.