Controlling Weeds in Nursery and Landscape Plantings

Bulletin 867

Handy Worksheet For Calibrating A Boom Or Backpack Sprayer

(copy as needed)

Please read the complete instructions in the text before using this worksheet

1. Using the table on the backside ofthis sheet, choose a calibration distance that corresponds with the band width if using a single nozzle, or with nozzle spacing if using a boom.

   Calibration distance = __________________________

2. Determine the number of seconds required to travel the calibration distance at the speed you will use for the actual application. For a tractor mounted sprayer, record the following settings so that identical settings are used for the actual application:

   Gear = ________________________ engine R.P.M.s = __________________________

   Time to travel calibration distance (sec) = _________________________

3. While stationery, engage pump. Pressure regulator should be set at an appropriate pressure (between 15 and 50 psi for herbicides); you will use this same pressure during actual application. Using only water in the sprayer, collect the spray output from one nozzle for the number of seconds required to travel the calibration distance. For hand-pump sprayers without pressure regulators, you must apply a consistent stroke during calibration as well as the during the actual application. THE NUMBER OF FLUID OUNCES COLLECTED EQUALS THE GALLONS PER ACRE (GPA) APPLIED.

4. Record the number of fl. oz. collected. For spray booms, repeat step three two more times on different nozzles, and record the average nozzle output volume. Ideally, differences among nozzles will not exceed 10%.

   Average # fl. ounces collected _______________ = Gallons per acre (GPA) _______________

5. Divide the capacity ofthe tank by the GPA. This give the area, in acres, covered by one full tank.

   _______ Your tank capacity 4 _______ GPA recorded in step 4 = _______ Acres covered by full tank

6. How much to add to tank? Multiply the desired application rate of the product per acre by the acres covered by a full tank (from step 5).

   _______ desired rate of chemical per acre x _______ acres covered by full tank = _______ amount to add to a full tank

Calibration Distance To Use, Based On Nozzle Spacing Or Band Width

Select the calibration distance to use 1) according to nozzle spacing if broadcast applying with a spray boom, or 2) according to the width of the spray band if band applying with a single nozzle. Band width will depend on how high the nozzle is maintained above ground level.