Spraying with Drones

By John Fulton (Associate Professor), Chris Wiegman (graduate student), Erdal Ozkan ( Professor), and Scott Shearer (Professor), Ohio State University Department of Food, Agricultural and Biological Engineering

Drones or Unmanned Aircraft Systems (UAS) have become a common technology in agriculture. As of early 2019, there were around 1.3 million registered drones in the U.S. and over 116,000 registered drone operators within the commercial sector. Within agriculture, drones have been mainly used for scouting purposes. Today, uses of drones include collecting remotely sensed imagery, tissues samples, and water samples. Spraying with drones is also available through some manufacturers.

Drone spraying has been used Southeast Asian countries such as China, Japan and South Korea for several decades. In fact, the use of this type of spraying in Japan can be traced back to the 90’s. Currently, we are seeing a significant increase in the number of drones used in these countries, mostly in rice production that requires applications done when the field is flooded with water, making entry of motorized vehicle to the field impractical. Drone spraying has also been considered as the most effective and safe way to treat crops grown in steep hills.

Drone spraying is becoming increasingly available for specialty crops and row-crop production. Here is the U.S., drone spraying was approved in 2015, but under strict policies in the state of California. The Yamaha RMAX from Japan was the first drone sprayer tested in California prior to approval. Most recently, drone manufacturers such as DJI (https://www.dji.com/) have started offering high payload rotor drones that include sprayers. Spray applications using drones has arrived in Ohio as well.

Spraying with drones is a unique practice since it is conducted autonomously. Drone sprayers are equipped with almost all the parts of any other sprayer: a tank, a pump to push liquid through the hoses to the nozzles, filters and a pressure gauge. But there are limitations, mostly on the size of these components because of the power required to keep the drone sprayer in flight mode for a reasonable time.

Companies have been testing using this technology globally since spray drones carry unique characteristics when applying liquid products. First, the application is different from ground-based machines (i.e. high clearance sprayers) but not the same as typical aerial applications completed with helicopters or crop dusters. These small drones are typically flown 3 to 10 feet above the crop or target area with their rotors creating turbulence or what we call vortices. While the turbulence created by the rotors can help spray droplets penetrate into a crop canopy and provide good coverage on the top and bottom of leaves, these vortices cause drift concerns. Research is being conducted to determine spray deposition, coverage and drift from drone sprayers in comparison to other methods used for pesticide application. Therefore, it is too soon to come to a conclusion on effectiveness and drift potential of drone sprayers. Unique features for drone sprayers includes vertical or altitude adjustments for topography or height, autonomous swath control, and safety, which are standard features on most commercially available systems today.

In general, spray drones for applying products to row-crops here in Ohio will have 4- to 5-gallon tanks with a spray width between ranging 10 and 15 feet. The application rate will be 1 to 2 gallons per acre, which is important when making sure applications are made in accordance with product labels. Today, multi-rotor drones have a flight time of around 10 minutes allowing a tank to be dispersed before needing to land to refill plus change out batteries for the next flight. Most manufacturers provide estimates on application rates in minutes per acre with most drones spraying an acre within 3 to 4 minutes.

While spray drones can cover complete fields, it seems more likely economics will dictate they be used for spot spraying within row crops. Drones can easily be used to clean up fields, spray drowned out spots, control resistant weed escapes, or other small areas within a field versus using a high-clearance sprayer. In addition, they will be useful for conducting field research for new products since applications can be made to smaller areas without needing to traffic crops, especially for later season studies with fungicides.

For drones to work effectively for spot- or small-area spraying, weed infestation or other areas of interest will need to be mapped in advance of application to support path planning for automated systems. On-going research at Ohio State is addressing this need with projects focusing on utilization of artificial intelligence (AI) for classification of crop stressors including weed infestations, nutrient stress, disease and insect infestations. Stress mapping will allow the spray drone to fly to these spots or areas and then spray, thus maximizing the limited flight times and payload capacities of drones. Today, the mapping process is more accurate and efficient given the development of AI representing an essential step forward in technology.

The regulatory landscape for drone spraying continues to evolve at the federal level given recent attention to remotely piloted aircraft systems (RPAS). RPAS regulations must evolve to include drone spraying in parallel with appropriate labeling of pesticides. Currently, companies developing and testing these systems have been successful in applying to the FAA for an exemption under Section 333 resulting in the FAA potentially issuing a Certificate of Waiver or Authorization (COA for Certificate of Authorization) to facilitate testing in the United States. Significant development is also under way in other countries with less restrictive air spaces. Producers can purchase spray drones today but, understand at a minimum, you will need following three items to operate:

  1. Private Pesticide Applicator License – https://agri.ohio.gov/wps/portal/gov/oda/divisions/plant-health/licenses/pesticide-licenses
  2. Part 107 Certificate through the FAA – https://www.faa.gov/uas/commercial_operators/https://www.faa.gov/uas/commercial_operators/become_a_drone_pilot/
  3. Part 137 Certificate through the FAA – https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afx/afs/afs800/afs820/part137_oper/

Further, owners are required to register their drones (any drone between 0.55 and 55 pounds) with the FAA: www.faadrone.org/?gclid=Cj0KCQjw09HzBRDrARIsAG60GP9kV-npW7Qj0o2rq0DCziyxtsggrxddA6he8RB4eF0S0IU9fsBYs9gaAoNrEALw_wcB.

There is no doubt that we need to prepare for drone spraying here in Ohio. It will not be uncommon to see demonstrations in 2020. But understand, ongoing drone spraying research is looking into topics including drift, application efficacy, and proper drone sprayer set-up meet pesticide products labels. If interested in learning more, here are a few examples of spray drones in the marketplace with the understanding other manufacturers offer similar products as well.

Yamaha RMAX and FAZER Helicopters



Hylio Agrodrone

  • https://www.hyl.io/
  • Electric with 8 rotors
  • 4.5- gallon tank
  • Typically 1 gpm
  • 15-foot spray width
  • 6-nozzle boom

Be on the lookout for drone sprayers in 2020. While there is still work on the regulatory landscape and application quality, spray drones provide unique capabilities over manned aircraft and ground spraying equipment. Spot or small area spraying are logical applications for drone sprayers on Ohio farms. Please keep up evolving drone spraying technology and other digital ag information at the Ohio State Digital Ag Website https://digitalag.osu.edu.

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