A Realistic Look at UAVs and Aerial Application in Agriculture

Unmanned aerial vehicles (UAVs), also referred to as drones, have captured the attention of almost every industry, including the fields of medicine, retail, media, and real estate. The agriculture industry is no exception to this, with PrecisionAg recently publishing a three-part series titled “Three Agricultural Spray Drone Models That Promise to Be Breakthroughs.”


With technology progressing at a breathtaking pace, every day brings new and exciting innovations that can ensure an abundant food supply for the world’s ever-growing population. The National Agricultural Aviation Association (NAAA), representing 1,800 aerial application operators and pilots, views UAVs as a complementary tool to manned aerial application methods, not a wholesale replacement.

Aerial application by manned aircraft is by far the fastest and most effective method of application. Every year aerial application pilots treat approximately 127 million acres of cropland in the U.S. This equates to 28% of all commercial cropland in the country. A relatively small number of pilots accomplish this feat by using agricultural aircraft holding between 400 and 800 gallons of product. UAVs do not have payloads approaching anywhere near this size, nor do they achieve speeds even close to the 90 to 150 mph speeds manned ag aircraft travel across a field during an application.

The article series correctly mentions aerial application by UAVs is popular in Japan. However, it should be noted the average farm size in Japan is approximately 5 acres, compared to 441 acres in the U.S. This is where UAVs can complement manned aircraft nicely, by making applications on small plots of land that are not suitable for traditional airplanes or helicopters. The UAVs used in Japan have found their niche in the U.S. as well, making applications to small vineyards on steep terrain where they offer an effective replacement to backpack spraying, areas larger manned aircraft are unable to reach.

There is also no available evidence to suggest UAVs make more efficacious applications and create less unintentional drift than manned aircraft. Those promoting UAVs for aerial application have described UAVs’ downwash effect as “unique,” enabling products to penetrate deeper into the crop canopy. The same aerodynamics apply to manned aircraft. Furthermore, the downwash effect is greater with manned aircraft because manned aircraft are generally larger than UAVs, causing more air to be displaced moving the applied products deep into the crop canopy for excellent coverage.

Additionally, thanks to extensive research done by the USDA’s Aerial Application Technology Research Unit and the EPA, manned aircraft have sophisticated spray nozzle models showing how products applied aerially are dispersed based on aircraft size, aircraft speed, wake vortices, windspeed, temperature, boom length, droplet size, and many other factors. However, these models only apply to traditional manned aircraft that are either single-rotor helicopters or single prop airplanes moving at high speeds. The models are not applicable to multi-rotor drones moving much slower and weighing much less. New spray models applicable to unmanned aircraft with two, three, four, or even eight rotors need to be developed before anyone can confidently state the efficaciousness of UAVs. The efficacy and drift aspects are things that pesticide manufacturers, state regulators, and the EPA are concerned about and are looking into.

The article series also included a quote claiming UAVs can make applications at night when it is too dark for pilots to take off. Aerial applicators can and do operate at night. Night operations are conducted with the use of high-performance lighting systems or night vision goggles. Seven percent of aerial operations conduct applications after dark, treating a total of 1.9 million acres.

Additionally, the claim was made application by UAVs is safer because UAVs have chemical products loaded into them on site and do not have to ferry with the chemicals from an airstrip. There are numerous EPA regulations that must be followed to mitigate risk for the mixing and loading of pesticides that apply no matter where the loading is being conducted. Manned aircraft are most often loaded over pads specifically designed to capture any spills. They use check valves and a suck-back system to ensure there are no leaks during the ferry. Loading at the field actually has the potential to be more hazardous to the environment — there is no permanent structure in place to contain any spills that do occur, and the operators and loaders are near the field which could provide exposure issues.

NAAA welcomes the use of UAVs in agriculture and other industries, but also wants to see them meet the high standard already applied to manned aerial applicators. Additionally, NAAA believes these aircraft must be equipped with certain safety equipment to ensure they do not collide with manned aircraft. Under the right conditions NAAA believes UAVs can be a valuable tool for growers, not just for aerial application but for aerial imaging as well.

Aerial application is a 98-year-old industry that has evolved through decades of research to become not only the fastest method of application but also exceptionally effective, reliable, and precise. There is not one technology available on UAVs, be it GPS, electrostatic spray systems or “downwash,” that is not already available on manned aircraft. NAAA encourages those seeking to bring UAVs into the agriculture space to build on this legacy through collaboration and not make misleading claims or assertions that have not been proven.

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Avatar for Bill Lavender Bill Lavender says:

Mr. Moore is exactly correct in his statements. One of the more important aspects is the high potential for drift by UAVs. First, there are no agricultural chemicals labeled to be applied at ultra low volume rates that UAVs use. Next, I have not seen any published data where UAV applications have been tested for droplet size and swath width. If so, I would like to read the data.

As Mr. Moore stated, UAVs can be a valuable resource in agriculture from imaging to specific applications. Our industry welcomes their participation, but at a professional level that does not create problems for all.

Bill Lavender/Publisher
AgAir Update