Spray technology

Three years deposition experience

Robert Brunel has often used a deposition agent in his Apache high clearance sprayer in the past three years.

WinField’s InterLock has cost him $1 to $3 per acre, depending on wind, the crop and the product he’s spraying. He said it’s a small price to pay for the benefit he receives, especially compared to other inputs he puts in the tank.

“I use it when it’s a little windier than I like. This year has been fairly windy so we used a fair amount,” said Brunel, who farms near St. Rose du Lac, Man.

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“I use it sometimes with our fungicides and some of the contact herbicides like Liberty. And we use it a lot when we’re spraying Roundup and there’s a neighbouring crop. It helps put the Roundup down in the canopy so there’s not as much drift.

“It seems to make all the contact products work a little better, so we get better performance from the products we apply and we have fewer issues with spray drift.”

Put droplets through their paces

In its quest to reduce drift, WinField’s spray particle analysis lab can test virtually any combination of nozzle, water volume, wind speed, wind direction, adjuvant, active product, pressure and flow rate.

The company’s main tool is a laser camera in a spray analysis chamber, located in River Falls, Wisconsin.

“It’s one of only three such labs in the world today,” said WinField’s David Van Dam.

“We’ve invested a lot of money in finding that secret sauce.”

Designed specifically for this purpose by WinField researchers, the lab has a fully enclosed wind tunnel with a fluid delivery system for precise testing of active ingredients with any nozzle.

Test solutions, which are identical to tank mixes used on the farm, are pressurized and delivered into the system through typical agricultural spray nozzles. A laser beam passes through the spray sheet and sends data to the computer, which determines droplet size and distribution of spray.

No smoke, mirrors or mysterious magic

Deposition adjuvants are not smoke and mirrors and magical chemistry, says a renowned application expert who has been closely involved in testing them for drift reduction and product efficacy.

“In defense of the mysterious nature of the product, I have seen the data and believe them to be correct,” Tom Wolf of Agrimetrix said in an email.

This behaviour sets such products apart from low-drift nozzles and low spray pressure as drift reducing tools. Lowering spray pressure or using a lower drift tip eliminates fines but also adds large droplets and may reduce coverage.

Deposition adjuvants can prevent that.

“It’s important not to confuse ‘coverage’ with ‘dose,’ ” Wolf said. “Keep in mind that 50 percent more coverage probably doesn’t mean it will work 50 percent better. It may just mean you have a better chance of achieving the intended outcome.”

Wolf said a spray sheet includes a wide range of droplet sizes ranging from a few microns in diameter to as large as a few millimetres. Deposition adjuvants reduce the proportion of the total volume contained in the finest droplets and reduces drift potential.

The proportion of volume in the largest drops typically doesn’t change much, so the overall proportion of the spray in a usable size fraction increases. These are the droplets that are neither too big nor too small.

“The performance of adjuvants depends on many things, such as type of nozzle, product being applied, spray pressure and more. So it’s important to ask the manufacturer for data that supports any specific use intention.

“The two companies are doing a great job of backing up their claims with data. They’re doing a better than most companies.”

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