Calibrating a Boom Sprayer: Ounces to Gallons Method

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.
  • Determine the spacing between nozzles in inches along the boom. 

    spacing betwen nozzles

  • 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.
  • 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. 

    tractor speed

  • 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.

    time to cover distance

  • 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. 

    collect water

  • 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.
  • 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).

Table 1

Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE! 

Issued 4/2025

Categories

Contact Information

S-225 Ag Science Center Lexington, KY 40546-0091

(859) 257-7450

entchair@uky.edu