News > Day Two > Don't look for silver bullets in field spraying
Selecting the correct sprayer nozzle, ground travel speed, water application rate and system pressure can make applying crop protection products a complicated task, says Tom Wolf, a research scientist with Agriculture and Agri-Food Canada in Saskatoon.

Tom Wolf (r), a sprayer technology specialist with AAFC in Saskatoon, speaks with a producer at Farm Tech in Edmonton. -- Lee Hart photo

Speaking to producers at the 2010 Farm Tech conference in Edmonton this week, Wolf says producers have to weigh a number of different factors to find the right balance between efficiency and consistency when it comes to field spraying.

"Faster travel speeds can provide efficiency, but in practice, they require nozzles that are able to operate over a wider range of flow rates than is possible with conventional technologies," says Wolf, who specializes in sprayer technology. "This limitation reduces the second priority, consistency, in terms of droplet size and pattern uniformity."

Wolf reviewed a wide range of results from research, using many of the different types of nozzles, applying products at different pressure (psi) rates, and varying ground travel speeds. There’s no perfect technology available today -- all systems have their pros and cons, he says.

While there’s no simple solution that will work with all field sprayers in all applications, he did have the following suggestions for producers:

• Know the pressure range of the nozzle you’re using.
• Know the spray pattern of that nozzle at pressure extremes. Is it going to be what you want?
• Know the spray quality (droplet size and pattern) across the pressure range of the nozzle. Good sources of information are the product catalogues produced by the nozzle manufacturers.
• Test the pressure capability of your field sprayer.
• Measure the pressure (psi) variability across the width of your spray boom. Don't just rely on the reading of the rate controller. Attaching a gauge to the nozzle outlets across the boom will provide the most accurate check on the psi applied at each nozzle.
• While spraying, go as slow as you can afford to go, given the workload for the day.

For the proper application of herbicides, Wolf said he doesn't believe faster is better. "I'm not a big advocate of speed," he says. "Often these units that travel faster are big, heavy machines. My personal preference is for spraying systems that are lighter and wide."

While some sprayers are capable of traveling 30 miles per hour, Wolf said he sees more consistent results at ground speeds of no more than 15 mph.

"Any job worth doing, is worth doing well," he says. "I say slow down if you can, although a lot depends on the time restraints of getting the job done within a certain window."

-- Lee Hart is a field editor with Grainews in Calgary.