For larger areas such as field nurseries, golf fairways, or other large turfgrass areas, follow these seven steps to calibrate your sprayer:
1. Find an area that best represents the average topography for the area to be sprayed. Measure it and mark off the calibration distance that coincides with your nozzle spacing or your band width.
Calibration distance = __________ feet
2. Walk or drive across the area, maintaining an even speed. If using a tractor-mounted sprayer, notice what the engine RPM is, plus what gear, and write it down so that you use the same speed during calibration and application.
___________ RPMs ____________ gear
3. Record the number of seconds it takes to travel the calibration distance and write it down.
__________ seconds
4. Fill your sprayer, engage the pump and adjust the pressure regulator to the boom pressure you want (between 15 and 50 psi for pesticides).
Collect all the water from one nozzle for the same number of seconds you have written above.
With a 20-inch nozzle spacing, if it took 35 seconds to travel 204 feet, collect the discharge of one nozzle for 35 seconds.
The number of fluid ounces collected equals the gallons per acre ( GPA ) of output of that nozzle. ( 20 ounces collected equals 20 GPA )
5. Repeat Step 4 two more times, collecting water from a different nozzle each time. The average number of ounces collected from each of the three nozzles is equal to the gallons of water applied per acre for that boom. Also remember to maintain the same pressure and travel speed when spraying.
6. Divide the capacity of the tank by the number of gallons of water applied per acre (GPA) to find out the area (in acres) you can cover with a tankful of spray.
200 gal./tank divided by 20 GPA = 10 acres covered/tank
7. To find out how much control product you need to add to the spray tank, multiply the application rate of the product per acre by the acres covered per tank. Then add that amount of pesticide to your sprayer tank.
2 qts per acre x 10 acres/tank = 20 qts., or 5 gal./tank