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Boom Sprayer Calibration

Boom sprayer basics

Boom sprayers, or sprayers with multiple nozzles, are used to apply liquid products more efficiently to larger areas than with a single-nozzle sprayer. However, many homeowners do not know how to properly calibrate sprayer output for these types of sprayers. This can lead to improper application of fertilizers, pesticides, or other liquid products, which ultimately wastes money and can be harmful to the turfgrass and the environment. An easy method for determining sprayer output is based on a procedure described as the 1/128th-acre method for boom sprayers. This calibration method is appropriate for handheld units to boom sprayers attached or pulled behind tractors or ATV. Follow the simple steps below to properly calibrate your boom sprayer.

Boom sprayerpng

3-nozzle boom sprayer

Setting up a calibration area

Step 1: Measure the distance between two adjacent nozzles. This is referred to as nozzle spacing. Nozzle spacing should be the same between adjacent nozzles across the boom.

Measuring nozzle spacingpng

Step 2: The area of calibration will be determined based on nozzle spacing. Convert the nozzle spacing distance from inches to a distance in feet. (12 inches = 1 foot)

Nozzle spacing (inches) ÷ 12 = Nozzle spacing (feet)

Example: 18 inches ÷ 12 = 1.5 feet

Step 3: Divide 340 square feet by the nozzle spacing in feet. This is the distance that will be traveled during the calibration procedure.

Calibration area (square feet) ÷ Nozzle spacing (feet)* = Calibration travel distance (feet)*

Example: 340 square feet ÷ 1.5 feet = 226.7 feet

*See table below for calculated calibration travel distances (feet) for common nozzle spacing (inches).

Nozzle spacing (inches)Calibration travel distance (feet)

Step 4: Using a tape measure, mark the calibration travel distance. The calibration travel distance by nozzle spacing is approximately equal to 1/128th of an acre, or 340 square feet.

Measuring calibration travel distancepng

Boom sprayer calibration

Step 1: Read the label of the product you want to apply to determine the gallons per acre (GPA) of solution needed for proper application.

Step 2: Make sure the sprayer and nozzles are clean and working properly. Broken or clogged parts should be replaced. Improperly working sprayers affect the calibration and application of products.

Step 3:Fill the sprayer tank with enough water to complete the calibration. Use only clean water when calibrating.

Step 4: Time how long it takes to travel (walking or driving, depending on type of sprayer) the calibration travel distance at a reasonable application speed. This step may need to be repeated several times to calculate an average time to travel the calibration distance.

Step 5: Using a container that will measure volume in fluid ounces, collect output from a single nozzle for the number of seconds timed in step 4. Repeat this for several nozzles to ensure consistency across nozzles.

Step 6: The fluid ounces collected from a single nozzle will equal the application rate of the sprayer in gallons per acre (GPA).

Tip: The speed you walk or drive will affect the calibration. To increase the GPA delivered, decrease speed when applying water to the calibration area. To decrease the GPA, increase speed when applying water to the calibration area.

Collecting sprayer output volumepng

Collecting sprayer output volume

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