Spraying advice for dense canopies

STENAN, Sask. — Even experts can learn something new.

It happened recently to Tom Wolf while demonstrating spray nozzle penetration techniques and canopy densities in breezy conditions at the Ag In Motion farm show earlier this summer.

“We learned that no matter what we did with a double nozzle — low boom, high boom, fast, slow, coarse, fine — it always deposited in the direction of the wind,” he said during the Canola Harvest Innovation Demo Day in Stenen hosted by BASF.

“I couldn’t deposit it against the wind. So wind conditions can trump this.”

He said two key factors stand out for successful spraying under windy and challenging conditions: twin fan coarse spray nozzles and a low boom height.

The twin fan nozzle allows the spray to go forward and backward, while a low boom height gives the droplets maximum opportunity to fly backward at the target.

“Make the spray as coarse as you can. We want the droplets to actually move forward and backward despite the wind, and low booms help that,” he said.

“I’m spraying at a fairly low boom height to give the droplets maximum opportunity for actually flying backwards at the target height. That’s the key thing.”

The importance of water volume and timing is critical in a year of dense canopies, whether spraying fungicides or desiccating.

“Your biggest hammer is more water, and I achieved it by going slower,” he said.

The bottom third of the stand received no benefit during Wolf’s field demonstration when spraying at about 10 gallons of water per acre over a thick canopy.

“The canopy is incredibly powerful at attenuating the spray,” he said. “The more difficult it is to see through the canopy, the more water you should be applying.”

Wolf recommended slowing high clearance sprayers to about 10 m.p.h. and applying 15 gallons per acre using a coarse tip.

“You can use that same tip for your late season desiccation work, but now you’re going 10 m.p.h. and doing 15 gallons an acre.”

However, he said 20 gallons are even better for penetrating to the bottom third.

“The number one thing is the value of more water in terms of canopy penetration to get deeper into a canopy and to have better coverage lower in the canopy.”

Producers with a lot of ground to cover and not enough time should not hesitate to use aircraft.

“The application method is not as important as the timing,” he said.

“The nozzle choice is much less important than water volume.”

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