Now’s the time to make sure your boom sprayer is calibrated correctly. The following steps will help you do just that. The process is based on spraying 1⁄128 of an acre per nozzle and collecting the spray that would be released during the time it takes to spray the area. Because there are 128 oz. of liquid in 1 gal., this results in liquid caught from one nozzle being equal to the application rate in gallons per acre (gpa). For example, if you catch an average of 15 oz. from a set of nozzles, the application rate of the sprayer is equal to 15 gpa. The table below shows the distance you must travel to cover 1⁄128 of an acre for different nozzle and row spacings.
1. Fill the sprayer tank with water.
2. Run the sprayer, inspect it for leaks and make sure all vital parts are functioning properly.
3. Measure the distance in inches between the nozzles. Then determine an appropriate distance in the field based on this nozzle spacing, as shown in the table below.
4. Drive the appropriate distance in the field at your normal spraying speed and record the travel time in seconds. Repeat this procedure and average the two travel times.
5. 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 amount of time averaged in step 4.
6. Calculate the average nozzle output by adding the individual outputs and dividing by the number of nozzles tested. If an individual sample is more than 10% higher or lower than the average, check for clogs, clean the tip or replace the nozzle.
7. Repeat steps 5 and 6 until the variation in output rate for all of the nozzles is within 10% of the average.
8. If these changes don’t bring variations to within 10% of the average, you might have to select a new set of nozzles with smaller or larger openings.
9. The final average output in ounces is equal to the application rate in gallons per acre: Average output (oz.) = application rate (gpa).
For additional calibration tips, visit www.FarmJournal.com/calibrate_sprayer