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Calibrate your sprayer

03/20/2013 @ 9:58am

Pesticide is expensive and essential. Yet, if you aren’t applying it properly, you are wasting it.

“Research has shown what the right amount of pesticide is,” says Bob Klein, University of Nebraska specialist. “This is what you want to hit to make sure you don’t waste money and you get good control from your products. Having the right rate is so important.”

1. Equal pressure.

Uneven pressure equals uneven application of pesticides. The first step you should take in calibrating your sprayer is ensuring that spray pressure is equal throughout the boom.

Check pressure all along the boom, because if there’s a restriction in the line, there will be uneven pressure. If the pressure isn’t even, it’ll be a waste of your time to calibrate the sprayer. Next, compare the cab pressure with pressure in the boom, making any adjustments that are necessary.

2. Speed.

Holding all other factors constant, if you run your tractor twice as fast, you’ll apply half the rate. Maintaining a consistent speed is important for an even application.

If you have to spray around obstacles or touch up areas, Klein suggests using an ATV or UTV. You may want to use a GPS to calibrate your sprayer.

“A lot of people spray with ATVs, but with these speedometers it’s difficult to maintain a consistent speed,” explains Klein. “Taping a GPS to the dash makes it easier.”

3. Nozzle spacing.

While the standard nozzle spacing is 20 inches, Klein points out several reasons to switch to 30-inch nozzle spacing. If 110° nozzles are used, 30-inch nozzle spacing is just as effective; most new air-induction nozzles are only available in 110°. If you have 30-inch rows, then this spacing is ideal.

The spacing also allows for 50% larger nozzles, which provides a lower application rate. Nozzles that require less than a 50-mesh nozzle screen should be avoided, as the smaller screens tend to plug up.

4. Nozzle flow rate.

Nozzle orifice size, pressure, and solution density will all affect the flow rate. Anything heavier than water will come out more slowly; anything lighter will come out more quickly.

Also, Klein notes that new nozzles may put out more than their ratings. In his tests, he found they ranged from 0% to about 15% more than the capacity rating, with an average of 7% above.

To ensure the correct flow rate, you can calibrate your sprayer the old-fashioned way by driving a known distance, measuring the amount delivered, and using that information to calibrate the sprayer. However, Klein recommends using a tool to aid the process. He has had good results with the SpotOn Spray Calibrator from Innoquest.

“With this tool, nobody has to time or measure,” says Klein. “Just put it under the nozzle and it will automatically measure the gallons applied per minute (gpm).”

The SC-1 calibrator is available for flow rates below 1 gpm and the SC-4 for flow rates between 1 gpm and 4 gpm. Prices range from $149.95 to $219.

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