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Spray Nozzle Considerations

In
the days when the Roundup Ready weed control system squelched nearly all weeds,
any glyphosate drift that occurred was incidental. After all, the odds were
high the glyphosate just drifted into glyphosate-tolerant corn or soybeans.

With
more diversified herbicide-tolerant systems and specialty crops popping up,
managing off-target movement becomes more important.

“The
importance of proper application is being reinvented and redefined,” says Jacob
Bolson, John Deere product manager, sprayer service parts.

Here are some
considerations to remember as you select nozzles for the coming spraying
season.


Coarse Droplets

The first
generation of venturi nozzles came along in the early 1990s. They created
large, coarse droplets that minimized drift.

 “The coarser the spray quality, the
better it is for off-target movement,” says Greg Kruger, University of Nebraska
Extension cropping systems specialist.

Low pressure
accompanied these air-induction nozzles. “That seemed to be common sense, as low pressure
should mean low drift,” says Bob Wolf, co-owner of Wolf Consulting and
Research.

However,
low pressure created large droplets that didn’t adequately cover weeds for
optimum control.

A second-generation
of venturi nozzles, such as HyPro’s Guardian AIR and AIXR TeeJet air-induction
XR flat spray tips, then came on the market. These droplets laced good coverage
while minimizing off-target movement.

Second-generation
venturi nozzles also tend to fare better in the rough-and-tumble world of
spraying.

“One reason
guys moved away from old air induction nozzles is they were 2.5 inches long,”
says Kruger.  “If a boom got
rocking going up and down hills, the older air induction nozzles would often snap.
The new air induction nozzles have a much shorter body, and farmers just like them
for better spray quality performance.” 


Look At
The Label

Nozzle selection is also becoming more important due to
droplet size specifications on pesticide labels.
For example, Liberty herbicide specifies a medium sized
droplet of 150 microns, about the thickness of a sewing thread.  

Bear in mind
that contact and systemic herbicides have different droplet needs, adds Kruger.
If you apply a contact and systemic herbicide in a mix, tailor nozzles toward the
contact herbicide’s droplet specification. Systemic herbicides can move within
a plant, so coverage is not as crucial as it is with contact herbicides, he
adds. 

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