NAAA has rebutted two recent articles espousing the virtues of drones in agriculture that erroneously suggested crop spraying UAVs are superior to professionally piloted manned agricultural aircraft from an efficacy, precision and cost-savings standpoint.

“Automating Farming from the Sky,” an article published Aug. 2 on AirSpaceMag.com, the website of Air & Space/Smithsonian magazine, flatly stated:

Drones are increasingly replacing traditional aircraft in crop dusting, technically known as “aerial application” of herbicides, fertilizer, pesticides, and even seeds. Because drones fly lower and slower than manned crop dusters, they can spray crops much more efficiently and accurately, reducing costs to the farmer, mitigating pesticide drift, and reducing the chance of accidents. 

On Aug. 1, Business Insider published “Exploring agricultural drones: The future of farming is precision agriculture, mapping, and spraying” on BusinessInsider.com. In this piece, the author’s claims about drones’ superior crop spraying capabilities were downright puzzling:

Drones such as [Yamaha’s RMAX helicopter UAV] are capable of spraying crops with far more precision than a traditional tractor. This helps reduce costs and potential pesticide exposure to workers who would have needed to spray those crops manually. 

NAAA members know that such assertions are absurd—so much so that NAAA could not let them go unchallenged. NAAA sent detailed letters to the editors of both publications that pointed out the flaws in their articles’ assertions about drones’ crop spraying capabilities and made clear that the efficacy of manned aerial applications over unmanned ones is irrefutable.

NAAA Executive Director Andrew Moore’s letter to Air & Space magazine is reprinted in full below.

August 10, 2017

AIR & SPACE Magazine
Smithsonian Institution
PO Box 37012
MRC 513
Washington, DC 20013-7012

Dear Editors:

While there is no question exciting possibilities exist for the use of drones in agriculture, in “Automating Farming from the Sky,” contributing editor Ed Darack couldn’t be more incorrect in his assertion that “Drones are increasingly replacing traditional aircraft in crop dusting.” Certainly in the United States, that’s simply not possible now or for the foreseeable future. The notion drones are superior to manned crop dusters in terms of efficiency, accuracy and costs to the farmer is also far-fetched. Mr. Darack’s statements about the perceived advantages unmanned agricultural aerial applications have over manned aerial applications don’t square with the speed, efficiency and economic benefits America’s agricultural pilots provide to their customers, nor with the size and scope of the farms they treat by air.

Looking outside the U.S., Yamaha’s RMAX helicopter drones have been spraying crops in Japan for more than 20 years, but Japanese agriculture bears little correlation to agriculture in America. Japan’s 1.63 million commercial farms manage small plots—only 4.8 acres, on average, according to the USDA’s Economic Research Service. In contrast, with an average size of 442 acres, U.S. farms are more than 90 times larger.

In the U.S., it is not uncommon for ag pilots to cover hundreds of acres in a single load and treat thousands of acres per day. For example, a 500-gallon ag plane can treat a 100-acre field in 20 minutes or less—far faster than a drone equipped for aerial application. Researchers at UC-Davis conducted field tests using a remote-controlled RMAX helicopter that sprayed about five acres per hour. Therefore, it would take the UAV 20 hours to treat what an ag plane could do in 20 minutes. Thinking of hiring a fleet of UAVs instead? It would take 60 UAVs to complete the work in the same 20 minutes as the 500-gallon ag plane, and each UAV would need to have a separate licensed drone pilot operating it and a significant number of troops to constantly reload and refuel the UAV fleet. If that sounds like a lot of labor costs, you’re right. In either instance, using a single drone or a fleet of them to treat a field instead of manned ag aircraft is going to be much more expensive for the farmer.

The claim drones can apply crop protection products more precisely than professional ag pilots also is false and absent of any credible study attesting to such a benefit. Flying “lower and slower than manned crop dusters” does not give drones a leg up over manned ag aircraft or even ground rigs in terms of coverage, deposition or accuracy. All aircraft, both fixed-wing and helicopters, push air down toward the ground and away as they fly. Any wing, be it fixed or rotary, creates downwash. The amount of air pushed down is exactly proportional to the weight of the aircraft the air is holding up. A 140-pound helicopter drone does not displace much air. With ag planes typically weighing around 10,000 pounds or more fully loaded, a manned ag aircraft can generate far more downward air pressure. Helicopters operate on the same principle as a rotorcraft UAV, but at a much greater weight and a corresponding increase in spray product moving down into the crop canopy, increasing plant coverage and protection.

Finally, there is much more to performing aerial application work safely and effectively than UAV evangelists may think. There is no substitute for the experience, mindfulness and judgment it takes on the part of the pilot to minimize the possibility of drift. Notwithstanding the positive hype and publicity surrounding UAVs’ potential commercial uses, there is simply no comparison between the efficacy of manned aerial applications versus unmanned ones.

Sincerely,

Andrew D. Moore

Executive Director

National Agricultural Aviation Association

NAAA’s response to Business Insider made many of the same points, but also debunked some false assumptions specific to Business Insider’s article. Excerpts of NAAA’s letter to Business Insider appear below:

Business Insider cited four agricultural drones ranging in price from $3,300 to $12,000. Those UAVs are used for of aerial imaging, not spraying. A 140-pound RMAX helicopter UAV—currently the only UAV legally able to spray in the U.S.—is easily over $100,000. Reportedly, Yamaha plans to charge about a hundred dollars per acre for vineyard spraying. Ag aircraft operators typically charge between $6 and $14 per acre depending on the crop.

The suggestion that using a drone to apply pesticides somehow makes it safer for workers also is off base. Pesticide labels require Personal Protective Equipment (PPE) for both applicators and loaders (workers who mix the pesticide spray and load it into the spraying system). The recently revised compliance manual for the U.S. EPA’s Worker Protection Standard for Agricultural Pesticides exempts aerial applicators from many of the PPE requirements because the cockpit is an enclosed cab, which prevents exposure to the pesticide spray. Ground-based application equipment have the same exemption. The greatest exposure risk for pesticide handlers is during the mixing and loading phase, not the actual application. During mixing and loading, the worker is exposed to the concentrated pesticide formulation. An applicator is spraying a solution that has the pesticide concentrate diluted in water, greatly reducing the exposure risk. UAVs have small tanks with very limited capacities, which means they will need to be loaded many more times than a manned agricultural aircraft for any given application.

Looking back at the comparison between the RMAX and the 500-gallon ag plane treating the 100-acre field, let’s assume a spray application rate of 2 gallons per acre, a rate used both by UC-Davis in its research and commonly applied by manned agricultural aircraft. That means every acre of the field will receive 2 gallons of spray. The 100-acre field therefore needs 200 gallons of spray. Because the ag plane can hold 500 gallons of spray, it would only need to be loaded once for the field. The RMAX can only hold 4.2 gallons of spray, which means it would need to be loaded 48 times to treat the 100-acre field. This greatly increases the risk of exposure to the workers.