ENTFACT-805: Calibrating a Boomless Sprayer: Pints to Gallons Method  |  Download PDF

by Ric Bessin and tad campbell, extension entomologist and Extension Specialist
University of Kentucky College of Agriculture

Supplies needed: PPE, measuring tape and/or wheel, stopwatch, 5-gallon buckets, 1” hose 4 ft in length (one
for each nozzle), and measuring pitcher.

• Fill the clean sprayer 1/4 full of water and find a location with terrain similar to what you
  will be spraying
• Determine the width covered by the sprayer in feet. Operate the stationary sprayer at
  desired pressure and engine/PTO RPM. Measure the total width of the spray swath (ft),
  calculate the effective width of the spray swath as 80% of the total width (this accounts for
  needed overlap to provide uniform coverage). The nozzles must be at the same height and
  orientation used during spraying.

• Using the effective spray width, select the travel distance from Table 1 needed to cover
  1/8th acre. If your spray width is not shown, simply divide 5445 (1/8th of an acre) by the
  effective spray width.
• 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 it was when the spray swath was measured. This may take
  some trial and error.

• 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.

• With the tractor engine/PTO at the predetermined RPM, engage the sprayer and catch/collect
  the entire spray output for the number of seconds it took to travel the course. Catching
  all of the spray output can be challenging. Place a 1” hose over each nozzle so the output can
  be directed into a collection bucket. The technique may vary depending on your sprayer’s
  nozzle configuration, as a collection bucket may be needed for each nozzle due to the output
  volume. There will be several gallons of spray to be collected.

• Measure the amount of water collected. The number of pints (16 ounces) collected equals
  the sprayers output in gallons per acre (GPA).
   

  

  Pints collected = Gallons per acre (GPA)
   

  Table 1. Set course length based on effective spray width to equal 1/8th of an acre.
  Spray Width (ft) Course Length (ft)

  

  
  
  Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
  Issued 4/2025