Publications Plus online catalog
This Land
50 Ways Farmers Can Protect Their Groundwater
50 ways 57 ways 60 ways

27. Calibrate Your Sprayer


University studies have shown that about one out of every four sprayers is miscalibrated by more than 10 percent, which can mean overapplication, greater risk to water, and wasted money. With application costs at $25 per acre, overapplying chemicals by 10 percent would mean a loss of $2. 50 per acre—or $2,500 for a 1,000-acre farm.

Check the calibration of your spray equipment every few days during the season or whenever you change the pesticides being applied. New nozzles do not lessen the need to calibrate because some nozzles "wear in," which means they will increase their flow rate most rapidly during the first few hours of use.

sprayer The common way to check whether your nozzles are delivering the correct gallons per minute is to use a stopwatch and a special container marked in ounces; with these materials, you can determine the number of ounces per minute that the nozzle delivers.
An easier, more efficient way to check nozzle flow rates is to purchase a nozzle flow rate tester—an inexpensive item that can be purchased from some spray equipment suppliers. It will tell you how many gallons per minute the nozzle is delivering.
spray nozzles It's okay if the flow rate varies from the required flow rate, as long as you know that and adjust for it. However, the flow rate for different nozzles should not vary from each other by more than 5 to 10 percent. Be sure you operate spray nozzles within the recommended pressure range. This is important because as spray pressures increase or decrease, flow rates change.
nozzle Once you have calibrated your sprayer, operate it in the field at the application rate and ground speed that you selected, and at the pressure you determined. Then check the liquid level in the tank to make sure your application rate is correct. When calculating ground speed, do it under existing field conditions at the engine throttle setting and gear that you plan to use.
An electronic spray control system An electronic spray control system provides you added confidence that your sprayer is properly calibrated. However, you still need to put the correct parameters into the electronic spray control system, and that means calibrating your sprayer.

University of Illinois Logo