Flight parameters for spray deposition efficiency of unmanned aerial application systems (UAAS)

Authors: CAPUTTI, THIAGO - Auburn University; DE OLIVEIRA, LUAN - University Of Georgia; RODRIGUES, CAMILA - Auburn University; CREMONEZ, PAULO - Auburn University; FOSHEE, WHEELER - Auburn University; Simmons, Alvin; DA SILVA, ANDRE - Auburn University

Submitted to: Drones
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2025
Publication Date: 6/27/2025
Citation: Caputti, T., De Oliveira, L.P., Rodrigues, C., Cremonez, P., Foshee, W., Simmons, A.M., Da Silva, A.L. 2025. Flight parameters for spray deposition efficiency of unmanned aerial application systems (UAAS). Drones. https://doi.org/10.3390/drones9070461.
DOI: https://doi.org/10.3390/drones9070461

Interpretive Summary: Unmanned aerial application systems (UAAS) can be useful for sustainable agricultural practices. However, there is no standard for ensuring the optimal use of UAAS for pesticide applications in specialty crops (such as fruits and vegetables). A study was done to evaluate the effects of flight speed, droplet size, and application volume on spray deposition by UAAS. Flight speed, droplet size, and application volume influenced spray deposition; a slower flight speed (4.4 yards per second) and higher application volume (3 gallons per acre) increased coverage and droplet density, which is desirable for specialty crops. However, the effective swath width and spray uniformity were maximized at a flight speed of 8.7 yards per second with a droplet size of 350 micrometers (0.00035 inches). Results from this study are useful to help researchers and the farming community optimize UAAS-based pesticide applications by increasing efficiency and reducing environmental impact to facilitate their use in specialty crop production.

Technical Abstract: The use of unmanned aerial application systems (UAAS) for precision pesticide applications has increased alongside the demand for sustainable agricultural practices. However, limited studies have standardized the necessary flight parameters ensuring the optimal use of UAAS in specialty crops (e.g., fruits and vegetables). Thus, the objective of this study was to evaluate the effects of flight speed, droplet size, and application volume on the spray deposition of UAAS, creating guidelines to facilitate their use in specialty crops. Field experiments were conducted in a three-factorial experimental design of three flight speeds (4, 7, and 10 m/s), three droplet sizes (150, 250, and 350 µm), and two application volumes (18.75 and 28.10 L/ha). Spraying droplet parameters (coverage, droplet density, and droplet spectra, and application uniformity), measured through the effective swath width, were recorded to assess spray deposition efficiency. Flight speed, droplet size, and application volume significantly influenced spray deposition. Treatments with slower flight speeds (4 m/s), but higher application volumes (28 L/ha), increased coverage and droplet density, which is desirable for specialty crops. Ultimately, the effective swath width and spray uniformity were maximized at a flight speed of 7.93 m/s with a droplet size of 350 µm. These results help optimize UAAS-based pesticide application, increasing efficiency and reducing environmental impact; however, understanding pesticide translocation dynamics (i.e., systemic or contact) on plants is key for growers to determine flight parameters.