Calibrating a Boom Sprayer: Ounces to Gallons Method
ENTFACT-804: Calibrating a Boom Sprayer: Ounces to Gallons Method | Download PDF
by Ric Bessin and tad campbell, extension entomologist and Extension Specialist
University of Kentucky College of Agriculture
- Fill the clean sprayer 1/2 full of water and find a location with terrain like what you will be spraying.
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Determine the spacing between nozzles in inches along the boom.
- Using the nozzle spacing, select the travel distance from Table 1 (on reverse side) needed to cover 1/128th acre by a single nozzle. I would add this in or move the table to the front
- Measure and mark the course length.
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Determine the tractor speed to be used during spraying (RPM & gear). Remember, the RPM must remain the same as when you will be spraying. This may take some trial and error.
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Drive the course, using the predetermined gear/RPM. Record the amount of time (seconds) it takes to cover the distance. Use a rolling start to be sure the tractor is at operating speed for the entire course. Drive the course and record the time at least twice and determine the average time.
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With the tractor in park and the engine/PTO at the predetermined RPM, engage the sprayer and catch/collect the water individually from each nozzle for the number of seconds it took to travel the course. Catch the spray in measuring pitcher.
- Calculate the average nozzle output. Clean or replace any nozzles that are more than 10% above or below the average output. If any nozzles were cleaned or replaced, repeat the nozzle catch test for all nozzles until they are all within 10% of the average output.
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The average output per nozzle measured in ounces equals the gallons per acre for the boom sprayer.
Average ounces collected per nozzle = Gallons per acre (GPA)
Table 1. Set course length based on nozzle spacing to equal 1/128th acre (340 sq ft).
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
Issued 4/2025