As agriculture evolves, farmers look for ways to increase yields and reduce input costs. By using precision agricultural practices, growers leverage tools and science to maximize efficiency and to produce more for a growing population. 

At Auburn University, Alabama Extension Specialist Simer Virk helps growers take their precision agriculture practices to the next level. Virk serves as an associate professor in the Department of Biosystems Engineering in the College of Agriculture and a researcher for the Alabama Agricultural Experiment Station.   

According to Virk, one of the ways growers can optimize efficiency and save some money during spraying operations is through proper sprayer calibration. This is the process of measuring the individual flow rate of nozzles on a boom sprayer. Without this process, farmers easily under or overapply pesticides, wasting time and driving up costs.  

“It seems like such a small, menial task,” Virk said. “But we are talking about thousands of dollars that growers can save just by effectively calibrating their sprayers properly.”  

In row crops, sprayer calibration is like tuning a guitar — it must be done occasionally to ensure that the sprayer output is on target. Spray nozzles wear and tear over time, causing inconsistencies in application and overapplied product.  

Virk encourages growers to calibrate their sprayer before their first pesticide applications and then as needed during the season.  

“During the season, we are likely putting out different chemicals at different rates, so you definitely need to re-calibrate for accurate applications,” Virk said. “And whenever you are changing your operational parameters, then I definitely recommend recalibrating.”  

Operational parameters like application rate, nozzle type and sprayer speeds all contribute to the performance of the spray system. When calibrated, broadcast spray booms provide uniform coverage while minimizing application gaps and streaking. 

The traditional method of sprayer calibration is as simple as grabbing a measuring jar and a stopwatch. While this process is time-consuming, it helps ensure the correct target rates — gallons per acre or GPA. GPA shows the farmer exactly how much chemical is distributed per acre based on operating conditions. 

During calibration, a common mistake growers make is not checking the flow rate of enough nozzles on the boom. This is important because general wear and tear might not be the same from one nozzle to another, and there are pressure losses across the boom.  

Virk suggests strategically checking at least 3 to 5 nozzles on each boom section during calibration to give a more realistic picture of the spray output.  

“Our typical field sprayer booms can run anywhere from 60 to 100 feet and have roughly 40 to 70 nozzles,” Virk said. “Catching flow rates from multiple nozzles can be time consuming, but there are tools like the Spot-On meter that make this task easier than the traditional method.” 

According to Virk, for around $150 a Spot-On Meter takes all the guess work out of sprayer calibration. Accurately providing the flow rate (GPM) within seconds, the tool makes a full boom calibration a much easier and cleaner process.  

While many growers rely on the in-cab display or monitor in the cab, Virk said physical spray calibration is still important to verify. 

“I know it’s easier to trust the monitor alone in the cab,” Virk said. “That may not be telling you the whole story though, as it is not accounting for worn‑out tips or plugs and sensors still go out of calibration sometimes.” 

At the E.V. Smith and Wiregrass Research and Extension Centers, two outlying units of the Alabama Agricultural Experiment Station, Virk and his team conduct various sprayer tests. These include nozzle types and using Spot-On meters for uniform applications. They also examined the precision that growers can expect from traditional rate control and advanced PWM (pulse width modulation) systems on sprayers. 

One of their recommendations is that checking pressure on individual nozzles is valuable, and growers can incorporate tools like pressure testers during calibration for precise applications. Checking spray pressure at the nozzles also helps in identifying any losses occurring across the boom, which is a common problem with sprayers due to large boom lengths.  

Even with proper calibration, spray nozzles do not last forever. So, when it is time to replace them, Virk suggests that growers stay up to date with the latest nozzle types available from different manufacturers.  

“Most nozzle manufacturers like Greenleaf and TeeJet offer online tools such as Smartphone Apps where growers can input their spray parameters,” Virk said. “Then, the app recommends the best nozzles based on their operating conditions with just a few clicks on a smartphone.”  

As growers invest in equipment, some newer sprayers are also equipped with pulse‑width modulation (PWM) technology that provides individual nozzle control capabilities. This system maintains the desired rate and droplet size by keeping spray pressure constant and consistent for more precise applications.

While PWM technology is a major up-front cost, it can save growers money in the long run, especially in large operations. With the rising cost of chemicals, more growers are adopting spray technology to improve efficiency and avoid misapplications. 

For more information about some tools for proper sprayer calibration, visit https://precisionag.auburn.edu/blog/sprayer-calibration-tools/.