How to Calibrate a Crop Sprayer

Updated March 23, 2017

Correctly calibrating a crop sprayer is important when using pesticides because applying too much chemical could waste money, ruin crops and harm the environment. Not applying enough pesticide could be ineffective at pest control, and crops might still be damaged. One way to make sure you are applying the adequate amount of chemical is to correctly calibrate your crop sprayer. The tank refill method is a simple way to calibrate your crop or boom sprayer.

Inspect the sprayer for defective parts such as worn belts, faulty air pressure gauge, worn nozzles or dirty screens. Make sure that the sprayer frame and supports are in good working condition and that the tank does not contain any rust or dirt. Pull off the end caps on the boom and flush the boom with water to make sure it is unclogged.

Fill the spray tank with water and turn on the sprayer. Switch the pressure regulator to operating pressure and fill a graduated bottle from each nozzle for about 30 seconds. If the output varies greatly from one nozzle to the other, then replace the nozzle with the least output.

Position two stakes at 660 feet apart in an area of the field that has firm soil and a coverage area similar to the area you are set to spray. Secure surveyor's tape to each stake, so you can easily locate them.

Add water to the spray tank and draw a mark at the fluid level on the tank. Set an operating pressure and tractor speed before calibrating. Record the tachometer reading after you set the speed. Use the same speed and pressure that you used for calibration when applying the pesticide.

Leave the sprayer off until the correct RPMs are reached on the tractor. After you pass the first stake, turn the power on to the sprayer. Turn off the sprayer when you reach the second stake.

Fill the spray tank by using a graduated bucket until it reaches the mark you previously made on the tank. Record the amount of water that was needed. The following formula can be used to calculate the rate of the sprayer.

Gallons per acre (GPA) = Gallons to refill X 66 /spray width (feet)


Agriculture chemical dealers have buckets and graduated jars available for sale. Use a soft bristle brush to clean the screens or nozzles.

Things You'll Need

  • Two wooden stakes
  • Brightly coloured surveyors' tape
  • Measuring tape, 100 or 200 feet long
  • Graduated bottle
  • Graduated gallon bucket
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About the Author

Dianne Christensen began writing professionally in 2003 for the "Muskegon Chronicle" in Muskegon, Mich. She has a Bachelor of Science in journalism from Grand Valley State University in Allendale, Mich.