Airblast calibration – clearing up confusion

“Sprayer calibration is an important part of any crop protection program.” Everyone says so, so it must be important. But what exactly are they asking you to do, and why?

When delivering presentations I often take the opportunity to ask audiences to define airblast sprayer calibration. Their responses cover a wide range of activities that can be rolled up into three related, but quite different, definitions:

  1. Sprayer maintenance inspection
  2. Adjusting sprayer configuration
  3. Validating sprayer output
Ask a group of managers, sprayer operators, agrichemical reps, gov’t regulators and equipment manufacturers to define “calibration”. Be prepared for very different answers.

Traditionally, calibration refers to Number 3: Validating sprayer output, but all three are required to ensure a safe, effective and efficient application. Don’t panic – your workload didn’t just triple.

There is a time and a place for each of these activities. Some should be performed more often than others, but none of them are difficult. This is easier to accept when you realize that only a portion of the spray-day is actually spent spraying. Filling, travel time, cleaning and calibration-related activities are all essential components.

Let’s consider each activity.

Sprayer maintenance inspection

This is more maintenance than calibration (e.g. is it properly connected, is it worn out, is it plugged, is it leaking?). It should not be confused with spring start-up or winterization. For those lucky readers in temperate regions, “winterization” is preparing the sprayer for long-term storage post season… we just use antifreeze.

The maintenance inspection is the morning walk-around, no different from what any operator of heavy machinery must do before starting their work day. Learn more about sprayer inspection and download a helpful checklist in this article.

Here are some nasty disc & cores revealed during a calibration workshop. It certainly explained the poor performance the operator was complaining about. Is it time to replace yours? Photo credit – Dr. H. Zhu, Ohio.
Here are some nasty disc & cores revealed during a calibration workshop. It certainly explained the poor performance the operator was complaining about. Is it time to replace yours? Photo credit – Dr. H. Zhu, Ohio.

Adjusting sprayer configuration

This is an ongoing process whereby an operator makes minor sprayer adjustments (e.g. pressure, travel speed, air settings) to reflect environmental conditions, the product’s mode of action and the nature of the target. Would you apply an insecticide to semi-dwarf pears in high wind using the same sprayer settings to apply a fungicide to nursery whips in high humidity? I hope not.

The process is more intensive at the beginning of the spray season and again around mid-season (e.g. petal fall or whenever the crop changes sufficiently to require a reassessment). It’s described step-by-step in many articles on this website as well as in Airblast101.

Yes, it requires an investment of time and effort, but the feedback makes subsequent adjustments faster, easier and more intuitive. There are strategies to reduce the number of adjustments required. Large operations can assign sprayers to blocks with similar crop architecture (e.g. one sprayer works large orchards, another sprayer works young or high-density orchards). Smaller operations can change the order in which crops are sprayed.

Validating sprayer output

This accounting activity ensures the sprayer is applying the intended rate at the intended speed. “Sprayer math” is really only theoretical; It helps the operator plan for how much pesticide and water must go in the tank and how long the job will require. How the sprayer actually performs may be a different story.

According to 1992’s “Tools for Agriculture” a horse can deliver 500 watts of power over 10 hours, but the camel can deliver 650 watts over six. Ontario might not employ camels for spraying, but the old adage still applies: “the right tool for the right job”. Photo Credit – R. Derksen, Ohio. Date and location of photograph is unknown.
According to 1992’s “Tools for Agriculture” a horse can deliver 500 watts of power over 10 hours, but the camel can deliver 650 watts over six. And you thought establishing tractor speed was difficult. Photo Credit – R. Derksen, Ohio. Date and location of photograph is unknown.

Validating output, or calibrating, confirms that each nozzle delivers the desired rate and that the sprayer travels at the desired speed, so the crop receives the correct dose with no unexpected left-overs or shortages.

The operator should perform these activities at the beginning of the season and after any significant change to the sprayer set-up. Examples include new nozzles, new tractor tires, using a different tractor or after replacing a pump or any lines/hoses.

The validation (i.e. calibration) process is explained in our articles on testing airblast sprayer sprayer output and travel speed.

Conclusion

Be sure to perform all three calibration-related activities as required. This will keep records up-to-date, improve your spray coverage, and save you from unexpected sprayer malfunctions – almost all of which are preventable.

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