What does it mean to “calibrate” an airblast sprayer?

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.

When I’ve asked sprayer operators to define calibration during workshops, their responses cover a wide range of activities. Here are the three most common definitions:

  1. Sprayer inspection (e.g. is it worn out, broken or leaking?).
  2. Adjusting the sprayer settings to match the crop and the environmental conditions (e.g. should semi-dwarf trees in high wind be sprayed like nursery whips in high humidity?).
  3. Confirming sprayer output (e.g. is the rate actually sprayed per hectare what it should be?).

Convention would suggest that answer number three (confirming sprayer output) is the correct definition for sprayer calibration. However, I feel that calibration is holistic and includes elements from all three answers – it’s simply a matter of knowing when to do what and why.

Why should I calibrate?

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.

No matter the definition, regular airblast sprayer calibration is essential because:

  • Calibration confirms the sprayer is functioning correctly.
  • Calibration confirms each nozzle is delivering the desired rate (e.g. L/min. or gal./min.) and spray quality.
  • Calibration ensures the desired rate (e.g. L/ha or gal./ac) is applied to the crop.
  • Calibration improves coverage and reduces product wastage (i.e. saves money and reduces unnecessary environmental impact).

When should I calibrate?

This depends on which of the three definitions you have in mind:

The operator should perform a sprayer inspection at the beginning of every spray day. Think of this activity as preventative trouble-shooting or a safety check. It should not be confused with the more involved pre-season maintenance inspection.
Ideally, minor changes should be made to the airblast sprayer set-up to match the physical size, shape and density of the crops (both between blocks and over the season), to account for environmental changes, and to reflect product mode-of-action and target location. The operator might make these changes several times a day based on relatively simple visual tests.
The operator should confirm that the sprayer is emitting the correct rate at the beginning of the season and after any significant change to the sprayer set-up. That includes new nozzles, new tractor tires, using a different tractor or after replacing a pump or any lines/hoses. These changes require the dreaded “sprayer math” which ultimately determines how much pesticide is put in the tank.

Where do I calibrate?

Again, this depends on which of the three definitions you have in mind:

Operators should perform the inspection in the yard where they store, maintain and/or fill the sprayer. That’s where it’s easiest to deal with any mechanical problems.
Operators should adjust settings throughout the spray day, while in the target planting, to reflect changing conditions as required. Don’t hesitate to get down from the tractor cab and make adjustments. Not only does it improve the spray job, but it helps alleviate operator fatigue.
Operators should confirm sprayer output in the target planting (i.e. the vineyard, nursery, orchard, hop yard, etc.) to avoid false readings. For example, ground speed can be up to 15% faster on pavement compared to the planting because sprayers move slower on soft ground. Tire slippage is one cause for ground speed inaccuracies. Additionally, hilly terrain can cause a tractor to lug, resulting in a slower ground speed; where possible, calibrate on level ground.
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. 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.

 

The obvious question of “how do I calibrate” is a huge topic, and way too much for a single article. It is a requirement of Good Agricultural Practices (GAP) to calibrate any sprayer, but presently, GAP doesn’t specify the calibration method. Be sure to regularly perform all three varieties of calibration according to use and your sprayer manufacturer’s maintenance schedule, and keep your records up to date.

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.