Opportunities with drones for spraying pesticides

By Erdal Ozkan

Currently, there is tremendous interest in using drones to spray crop-protection products. Drones are now a viable option when choosing equipment to spray pesticides, and the number of companies offering drone spraying services is rapidly increasing in Ohio and other places in the United States. A variety of names and the acronyms are associated with remotely piloted aircraft. Most used ones are: Unmanned Aerial Vehicle (UAV) and Unmanned Aerial System (UAS). However, the name used most commonly by the general public is “drone”. So, I chose the same name as I refer to this type of aircraft. 

An article appeared in the Mid-April Ohio’s Country Journal in which I gave a brief overview of different types of drones used for spraying pesticides, including the major components of a spray drone, as well as operating characteristics of spray drones. This time, I will focus on the opportunities spray drones bring us as well as their limitations, and the challenges facing drone sprayer operators. 

As I mentioned in the previous article, a rapid proliferation of lighter, easy-to-operate drones for spraying pesticides is currently underway. They are lightweight but powerful enough to lift a 10–15-gallon tank. Most commercial spray drones today are the multi-rotor type.

Opportunities spray drones bring us

Although in other parts of the world drones have been successfully used in other parts of the world, it is a fairly new concept in the U.S. However, it is becoming attractive mainly for six opportunities they bring us: 

1. The topography do not allow the use of traditional ground sprayers or conventional agricultural aircraft
2. When airplanes and helicopters are not available or are too expensive to use 
3. Drones more efficiently spray small, irregular-shaped fields 
4. When portions of a field cannot be reached by large, heavy ground sprayers because the soil is too wet, which happens frequently in some parts of Ohio 
5. Drone spraying may be the best choice to avoid soil compaction and crop damage caused by ground equipment traffic when spraying fields with established crop canopies. Even after the wet ground dries enough to allow the large ground sprayer to get in the field, the sprayer is likely to cause a significant level of soil compaction resulting in reduced crop yield, and 
6. Drones significantly reduce the risk of applicators being contaminated by the pesticides. There are also emerging problems, such as tar spot on corn, which may increase the need for aerial pesticide application by drones.

Unanswered questions about spray drones

There are many types of drones used for spraying pesticides. They all have similar components, but unfortunately no standards exist for the most optimum spray drone design, especially related to the location and configuration of nozzles on the drone. As a result, drone purchasers are faced with a number of unanswered questions:

• Is it better to have a drone with a boom under the rotors, or is it better to have nozzles directly under each rotor? 
• If a boom is better, what should the boom width and its distance from the rotors be?
• If having nozzles at the end of a drop-down hose under each rotor is a better option, what should be the length of the hose?
• What are the best type of nozzles to put on drones for different spraying jobs? 
• Is there an optimum distance between nozzles?
• Should there be one nozzle at the end of the drop hose, or multiple nozzles.

So far, drone configurations do not have the standardization seen in conventional, piloted aerial aircraft. This is because no studies have been conducted, or models developed, to determine the most optimum drone design parameters to minimize spray drift and to maximize deposition and spray coverage on the target.

Erdal Ozkan, Professor and Extension ag engineer, can be reached by email at ozkan.2@osu.edu. This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research & Development Center, and the College of Food, Agricultural and Environmental Sciences.