More efficient spray application saves money

Posted: June 9, 2005

• The basics of sprayer calibration
• The art and science of assessing nozzle wear
• Field sprayer calibration steps

Statistic Canada figures show that between 40 and 50 percent of Canadian farmers calibrate sprayers at the beginning of the crop season and fewer do it more than once during the spraying season.

While it takes time to properly calibrate a sprayer, it can easily pay off. The Canola Council of Canada uses the example of an 800-gallon sprayer operated on a quarter section of canola, to make the economic point.

If the miscalibrated sprayer applies eight percent more product than intended, the lost profits are considerable. If the sprayer is used to apply products for grass control, broadleaf weed control, sclerotinia and a single pass for flea beetle control, the Council estimates total cost of over-application of the various pesticides at about $550. For the three hours it might have taken to calibrate the sprayer, the producer could have paid himself $180 per hour. And that's just on 160 acres.

How often is equipment off calibration? North Dakota researchers testing 100 farm sprayers found it is surprisingly common.

Out of 100 farms they found:

• 60% calibration error greater than + or - 10% from the owner's prediction
• 43% greater than + or - 10% variation in discharge from individual nozzles (nozzle wear).
• 32% inaccurate travel speed from what the owner predicted.
• 27% improper boom height for the nozzle spacing and nozzle discharge angle.
• 13% inaccurate pressure gauges. Many of the gauges indicated too low pressure.
• 8% inadequate hose size to supply nozzles. When large nozzles are installed on a boom, the hoses may be too small, causing uneven pressure in the system.

One of the confusing complications of calibrating sprayers in Canada is the mix between Imperial, U.S. and metric measures. Most nozzle manufacturers are still calibrating in gallons/acre, while pesticide registration labels specify product use in litres/acre, gallons/acre and milliliters/acre. Often some degree of conversion is needed.