To calibrate a boom sprayer for broadcast applications using this method, follow these steps:

1.     Fill the sprayer tank (at least half full) with water.

2.     Run the sprayer, inspect it for leaks and make sure all vital parts function properly.

3.     Measure the distance in inches between the nozzles.

4.     Measure an appropriate travel distance in the field based on this nozzle spacing. The appropriate distances for different nozzle spacing is as follows: 408 ft. for 10-in. spacing, 272 ft. for 15-in. spacing, 204 ft. for 20-in. spacing, 136 ft. for 30-in. spacing and 102 ft. for a 40-in. spacing. (See Extension publication AEX-520 for travel distances for other spacings, and for an explanation for selection of these specific travel distances for given nozzle spacing.

5.     Drive through the measured distance in the field at your normal spraying speed, and record the travel time in seconds. Repeat this procedure and average the two measurements.

6.     With the sprayer parked, run the sprayer at the same pressure level and catch the output from each nozzle in a measuring jar for the travel time required in step 5 above.

7.     Calculate the average nozzle output by adding the individual outputs and then dividing by the number of nozzles tested. The final average nozzle output in ounces you get is equal to the application rate in gallons per acre. For example, if you catch 15 oz. from a set of nozzles, the actual application rate of the sprayer is equal to 15 gal/acre.

8.     Compare the actual application rate with the recommended or intended rate. If the actual rate is more than 5% higher or lower than the recommended or intended rate, you must make adjustments in either spray pressure or travel speed or in both. For example, to increase the flow rate you will need to either slow down, or increase, the spray pressure. The opposite is true when you need to reduce application rate. As you make these changes stay within proper and safe operating condition of the sprayer. Remember increased pressure will result in increasing the number of small, drift-prone droplets. Using the trial-and-error method to eventually reach the intended application rate takes some time. If you follow the equations given in Extension publication AEX-520 on calibration you can find optimum travel speed and pressure much faster.

9.     Recalibrate the sprayer (repeat steps 5-8 above) until the recommended application error of +5% is achieved.


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