Spray Drift Characterization of a Remotely Piloted Aerial Application System

Abstract

Highlights RPAAS drift study with 12 replications at fine spatial resolution (0.5 m). RPAAS produced more drift than a tractor-mounted boom sprayer up to 10 m off field. Data confirmed use of an extra coarse nozzle best mitigated spray drift. Swath offset proved to be a BMP for RPAAS drift mitigation and regulatory consideration. Abstract. The phenomenal growth of remotely piloted aerial application systems (RPAASs) in recent years has raised questions about their impact on off-target movement of crop protection products. Few quality field data currently exist to improve the understanding of the fundamental factors that govern spray drift and deposition for RPAASs and to compare such data with conventional ground application platforms. A field study was conducted to compare spray deposition and downwind drift from a 10-L RPAAS with a conventional tractor-mounted boom sprayer. Applications were made with two different agricultural spray nozzles, which produced medium and extra coarse spray droplet spectra. Spray drift and deposition were measured up to 100 m downwind, and airborne drift was determined up to 50 m downwind at heights of 0.2 and 2 m. Regardless of the delivery platforms, overall spray drift was greater for the medium nozzle than that for the extra coarse nozzle, indicating that the applied droplet size was a critical factor governing spray deposition. The RPAAS had significantly higher ground spray deposition than the tractor-mounted boom sprayer for both the medium and extra coarse nozzle treatments out to 10 and 6 m downwind without swath offset, respectively. With swath offset, these distances were reduced to 4.5 and 2.7 m downwind, respectively. Utilizing swath offset to account for displacement of the swath caused by wind-driven off-target movement could be effective in reducing drift for the RPAAS platform, particularly for the medium nozzle treatment. The use of swath offset with careful consideration of wind speed proved to be a best management practice for mitigating spray drift for RPAAS applications and is recommended for consideration for ongoing regulation development on spray drift characterizations. Keywords: Boom sprayer, RPAAS, Remotely piloted aerial application system, Spray deposition, Spray drift, Spray drone, Tractor-mounted boom sprayer, UAS, UAV.