How to Calibrate a Boom Sprayer


Correct calibration of a sprayer is extremely important in using pesticides. If you apply too much chemical, you waste money and could contaminate the environment. If you don't apply enough, effective control of the pest may not be achieved. There are several ways to calibrate a boom sprayer. The tank refill method is the simplest.

Things You'll Need

  • Two wooden stakes
  • Brightly colored surveyors' tape
  • Measuring tape, 100 or 200 feet long
  • Graduated bottle
  • Graduated gallon bucket
  • Check the sprayer thoroughly to ensure there are no worn nozzles, dirty screens, worn belts or faulty air pressure gauge.The sprayer supports and frame should be sturdy and the spray tank free of rust and sludge. Take off the end caps of the boom and run water through the boom to ensure that it is unobstructed.

  • Put water in the spray tank, start the sprayer, adjust the pressure regulator to operating pressure and collect spray in a graduated bottle from each nozzle for 30 seconds. If output from any nozzle varies more than 10 percent of the average flow between the other nozzles, replace the bad nozzle.

  • Set two stakes 660 feet apart in an area that has vegetative cover, soil firmness and terrain similar to the field that is to be sprayed. Tie surveyors' tape on the top of each stake so that they can be easily seen.

  • Fill the spray tank with clean water and mark the fluid level on the tank. Select an operating speed and pressure before beginning calibration. When the tractor speed is set, record the tachometer reading or mark the throttle setting. When applying the pesticide, use the same speed and pressure that was selected for calibration.

  • Park the tractor approximately 25 feet from the first stake with the sprayer shut off. Set the tractor brakes and increase engine speed until the correct RPMs are reached.

  • Release the brakes on the tractor and let it move forward without moving the throttle. When the boom passes the first stake, turn on the sprayer. When the boom passes the second stake, turn off the sprayer.

  • Refill the spray tank with a graduated bucket while recording the amount of water that is required to bring the fluid level to the previously marked line on the tank.

  • Use the following formula to determine the application rate of the sprayer.

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

Tips & Warnings

  • Graduated jars and buckets can be purchased from agricultural chemical dealers.
  • Never blow on nozzles or screens for cleaning. Use a soft bristle brush.

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