Stop spraying and then start again. Stop and then start. Farmers who do this 10 to 15 times a second can control everything from the rate of application to the fineness of the droplets.
Called pulse width modulation, this new spray system is said to result in better drift management and chemical use, more precise application and a greater range of use from one set of nozzles.
It relies on technology found in the latest diesel engine injectors and aerospace applications that are used to control sprayer nozzles.
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Case International has offered the Aim Command system with its Case/Tyler Patriot line of sprayers since 1998 and as a stand-alone retrofit unit for any sprayer.
The “on-off” system electronically stops and starts each nozzle on a sprayer using durable solenoid valves.
By controlling how long the nozzle is turned off, the operator can maintain high or low pressures in the boom, thus controlling the spray pattern at the nozzle, independent of ground speed.
Not all of the nozzles are off at once, allowing complete coverage of plants even though some nozzles are closed.
System pressure varies only slightly because the extra pressure of closed nozzles is absorbed by the open nozzles and the swelling and contracting of system components.
A computerized controller divorces ground speed from system pressure.
Until now, if a producer wanted to travel faster or apply lower or higher rates, nozzles would have to be changed to accommodate higher system fluid pressures caused by greater flow rates. Restricting the system with a bypass only cut flows or increased pressure.
By turning nozzles on and off, the pressure can remain constant independent of flow rates. This also allows for reduced carrier volumes and improved herbicide efficacy for some pesticides, such as glyphosate.
A new pattern from a single nozzle can be created by adjusting the amount of time the nozzles are on or off, which in turn adjusts the pressure.
Low pressure generates larger droplets with fewer fine droplets that are prone to spray drift. High pressure generates finer patterns with better leaf adhesion and spray coverage.
Tom Wolf of Agriculture Canada in Saskatoon says this alone is a major time saver for producers.
“This means farmers only need one nozzle for everything. No more changing nozzles.”
The system isn’t cheap, costing an average of $10,000 to add to a 90 foot sprayer. However, Wolf said this isn’t out of line considering the advantages.
Wolf, a leading spray system researcher, said many farmers start at the wrong end when designing a new sprayer.
He said farmers buying a new sprayer or retrofitting an older unit should consider building backward from the booms.
“Farmers spend the least on these parts. They buy everything else on the list first, but a sprayer is really just the nozzles and the fluid system. Everything else is extra as far as doing the best job possible in the field.”
The pulse width modulation equipment will add a lot of wiring to the sprayer, creating the potential for system failures if a wire breaks. However, Wolf said if that happened, farmers could turn off the computer and revert to the original application system until the equipment can be repaired.
The unit also provides instant, no-drip, shutoff for the sprayer. This reduces stop-and-start misses and the need to back up the sprayer and respray some areas, which in turn reduces plant damage in herbicide-sensitive applications.
