Why should you be concerned about where your pesticide application ends up? Jason Deveau, application technology specialist with the Ontario Ministry of Farm & Rural Affairs in Canada, answered with three words: “Everyone is watching.”
Deveau presented “Catch My Drift: Keeping Pesticides Where They Belong” at the recent Soybean & Small Grains Congress.
“Pesticide misuse is a public concern and a political theme of agricultural sustainability,” Deveau said. “Given the economic, environmental and health impacts, drift management is a primary concern of federal regulators. A grower’s right to farm is contingent on public trust. This implies a social contract wherein the sprayer-operator promises to make every reasonable effort to reduce the environmental impact.”
Drift also has effects very close to home. Neighbors have the right to expect growers to keep spray off their property.
Deveau said, “Training or empowering operators is great. Situational awareness is important. But it comes down to attitude. We get lax until one year, something happens.” Experiencing problem-free year after problem-free year can contribute to lower levels of diligence.
Drift can occur in several ways: through the air directly from nozzles or off sprayed surfaces; from the point sources, including leaky storage, carryover, spills while filling, rinsate (contaminated water used to wash equipment) while cleaning and priming; and runoff in groundwater and from the atmosphere.
To help reduce spills while filling tanks, closed transfer systems can help. Cleaning equipment properly is also important; however, the rinsate can spread chemicals where they’re not wanted.
How long is long enough for washing a sprayer? That depends upon how sensitive the next crop is to sprays and the potency of the previous chemical used. But only 0.16% of field rate XtendiMax left in a sprayer can cause 10% yield loss in non-trait soybeans.
“Even when sprayers are ‘empty,’ they’re not,” Deveau said. “The draw is higher than the bottom of the tank.”
The suction line, pump, agitators and bypass circuits, nozzle bodies, boom ends, inductor, fence post nozzle line and exterior can all hold residue. Sprayer cleanout should include minimizing the standing volume, diluting the residual pesticide and decontaminating equipment. Leaving a used sprayer dry allows residue to harden inside it.
Deveau encouraged farmers to fill it with water if they cannot clean it right away. “Otherwise, it’s harder to knock out later,” he said.
For cleaning the equipment, farmers should use multiple low-volume rinses, which Deveau said dilutes better than a single, high-volume rinse.
“Read your label,” he advised. “Soak and scrub nozzles and filters in some of the second rinse solution. An amazing amount of chemicals are stuck on self-cleaning filters. Clean the exterior too.” He encouraged operators to carefully follow package directions.
Managing rinsate can include bioremediation (microbial degradation), evaporation/dehydration, physio-chemical means and photocatalytic (UV degrading).
Drift in the air includes primary movement (the initial off-target drift of droplets caused by turbulent conditions) and secondary movement (a form of off-target drift that usually occurs over a longer time period).
“This is the stuff everyone sees,” Deveau said. “It has destroyed neighborly relations. It’s not just neighbors. You can screw up your own day. Drift can burn you too.”
Buffer zones and windbreaks help reduce the effects of drift, but Deveau said the best way to deal with drift is to not do it in the first place. When spraying under sunny, breezy conditions, “82% lands on swath. Another 15% is two feet away. One percent is 16 feet away. Two percent is in the atmosphere.”
Reducing this takes several strategies, including decreasing the droplet energy by increasing its size and velocity with low drift nozzles and air assist. It also helps to decrease exposure time and reduce equipment force with shrouds, reduced distance and speed and optimized air energy. Nozzles rated as coarse and higher by the manufacturer provide the ideal droplet size.
Longer booms may save time, but Deveau said their variations in height make them less accurate and more prone to causing drift.
“Driving faster and with a higher boom creates small pressure zones that flings them into the air,” Deveau said. “Low and slow is the way to go.”
He also cautioned about thermal inversion, which can make drift unpredictable. Cooler air sinks to the ground and warmer, pesticide-laden air rises. This can cause the pesticide to move elsewhere even after the operator has parked the sprayer. Humidity helps slow thermal inversion, as does timing spraying between 8 a.m. and 4 p.m.
“Inversions don’t form every summer night, but depending on where you are, they can form more often than not,” Deveau said.
“Managing off-target pesticide movement should outweigh all other concerns,” he concluded.
by Deborah Jeanne Sergeant
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