Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 20, 2004
Publication Date: February 16, 2005
Citation: Hoffmann, W.C., Kirk, I.W. 2005. Spray deposition and drift from two medium nozzles. Transactions of the ASAE. 48:5-11. Interpretive Summary: Application of crop protection materials by air is an important tool used by American farmers in the production of their crops. Labels for many crop protection and production materials now specify droplet size classifications for application, such as "apply as a MEDIUM spray." Therefore, aerial applicators now use computer models and technical documents to comply with these labels. Studies using two "MEDIUM" nozzles showed that the nozzle that had three times more of the spray volume in small droplets produced significantly higher downwind movement of the spray. The results highlight the need for aerial applicators to consider all of the droplet size data when selecting the most appropriate spray nozzle for a given application.
Technical Abstract: Many crop protection and production materials are requiring specific droplet sizes for application, such as "apply as a MEDIUM spray." Therefore, aerial applicators are utilizing computer models and printed materials to comply with these labels. This study determined the spray deposition and drift from two "MEDIUM" nozzles used in an aerial application. With an application rate of 28 L/ha (3 gal/acre), CP nozzles were configured to produce a volume median diameter (VMD) of 272 µm (T1) and Spraying Systems D8 straight stream nozzles were configured to produce a VMD of 413 µm (T2). Under the ASAE nozzle classification system, both would be classified as Medium sprays; however, the spray volume contained in droplets less than 200 µm was 23.4% and 8.7% for the CP and D8 nozzles, respectively. These studies show that very different downwind deposition can occur from two aerial spray nozzles that are classified as MEDIUM based on droplet spectra. T1 contained three times more spray volume in droplets less than 200 µm than T2. As a result of this difference, 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.