Drone spraying

By James Hoorman, Hoorman Soil Health Services

Aerial Drones are being used in agriculture.  Alan Leininger, OSU Extension Educator, Henry County is doing agricultural research on drone applications.  Drones have several advantages over ground-based spray equipment. 

First, they economically apply small rates of spray (herbicides, insecticides, fungicides, nutrients), seed (small seeded cover crops) and are battery operated.  Second, they fly in the air, so there is no soil compaction.  They extend the application season.  If it is too wet, applicators can still spray.  There is no wheel damage to standing crops.  Applicators can precision apply product at the ideal time during the growing season to address a nutrient or pest problem.  Drones are also autonomous meaning they fly themselves on a set pattern.  Humans still have to be present for fill ups and to trouble shoot problems (low flying planes, helicopters, towers, telephone lines, tree, etc).

There are several different kinds of drones with various prices.  Avoid buying cheap drones on the internet.  Most have to be flown manually and have low quality.  They may be alright for aerial pictures, but they have little power for product application.  The DJI drone holds up to 10 gallons, has a 36-foot swath, and can apply material at 2 gallons/acre (gpa) or 52 acres/hour (aph).  The cost is around $20,000 to $40,000.  Hylio drones (AG272) have a larger capacity (18 gallons) 40-foot swath, 2 gpa and 50 aph.  They cost more at around $55,000 to $75,000.  The Hylio is quite large, similar in size to about 2-4 long tables. The XAG is a much smaller drone often used with a spreader box to spread cover crop seed. 

Drones cannot be used for all pesticides due to label restrictions.  Glyphosate (Roundup) needs a minimum of 3 gpa of water.  Liberty needs 10 gallons water, and some fungicides and insecticides need more water to spread the product.  Drones are prohibited from spraying the following products: Enlist, Acuron (Atrazine), Harness Extra, Xtend Max (Dicamba).  The pesticide label is the law, so until these labels are changed, drones use is at least limited or prohibited on these products.  For this reason, ground-driven application equipment will still be needed to apply these products. 

Using a drone requires several certifications.  First the FAA (Federal Aviation Administration) requires a Part 107 pilot license to fly commercial drones.  Recreational drones do not need this license.  Part 137 is required to aerial apply pesticides, similar to crop dusters.  It takes longer to get the certifications than it does to learn to fly a drone which may only take 1-2 days. Drones are limited to flying only 400 feet high but usually operate at 20-40 feet above the crop canopy.  Drones do not have the right of way and have to yield (get on the ground) when airplanes or helicopters, etc. are in the vicinity.   According to the USDA, drone pesticide applicators need a commercial pesticide license (Category 1).

As a general rule, drones must weigh less than 55 pounds.  A small drone typically weighs 24# plus 2 gallons of water (17#) so they are under.  If you have a larger payload (10-18 gallons of water) plus the drone weight, you need a special exemption which will cost more money.  Another rule, all drones must maintain a line of sight by the operator.  They may be self-flying, but the operator is responsible for watching for incoming flying traffic or any other problems that may occur.  Drones are restricted from flying near airports (Class B, C, D) or within the boundaries of air traffic control.  Most small county airports are exempt, but you still have to land the drone if a plane or helicopter flies in.  Generally, drones cannot be operated above 15 mph wind speed which is similar to ground-spray equipment.  Most drones can stay on course at 5-10 mph but operate the best at 0-5 mph wind speed.

Alan Leininger has done some research on spray effectiveness using drones.  Turbo Jet spray tips spraying 2-2.5 gpa had less variation and more consistent coverage, but the spray droplets were smaller.  Air Induction nozzles had larger droplet size but wider variation in spray coverage.  When compared to over-the-top boom sprayers (ground driven), both had similar results on fungicide application and control.  Drones often move the canopy when they fly over tasseled corn, which helps move the product down into the leaves, but it may not be consistent across the whole spraying swath. Most drones need at least 4 batteries that last 12 minutes in flight before being replaced.  Larger drones need more batteries. There needs to be much more research done on drones, but they are here to stay. Except more relaxed restrictions and larger payloads in the future.         

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