by Courtney Llewellyn
There are three different ways to improve the precision of existing orchard spraying systems. That’s what Dr. Jason Deveau of the Ontario Ministry of Agriculture, Food and Rural Affairs, and author of the seminal “Airblast 101,” believes. And when you’re trying to improve accuracy, the best advice for one sprayer isn’t necessarily what’s best for another.
- Match vertical flow distribution to your canopy. Deveau said you need to match the spray coming out of your sprayer to the height of your target. An unadjusted sprayer produces highly variable coverage and wastes a lot of spray. “Ninety percent of the battle is how you adjust your air,” Deveau said. “An old school way to do that is with lengths of 10-inch ribbon. You can also drive ribbons through the canopy itself. You always want the top of the canopy wiggling, because you see a lot of disease issues up high. You always want to vector air close to the top.”
If the sprayer blows a ribbon out 90º, its throw is too far. Your goal is simply to displace stagnant air with spray-laden air in the canopy – a ribbon blown out to 30º is the ideal throw. This is the easiest way to assess where the air you’re spraying is aimed.
- Match horizontal distribution to space. There are a lot of gaps in trees – places where there isn’t a target for a sprayer. Deveau said machines first introduced in 1980s used sonar to recognize empty space. Turning the boom off between targets could result in about 25% savings over a season, but there are concerns about lead and lag, because you want to have a little spray being released before the sprayer is even with a tree.
- Hold your rate constant by matching flow to travel speed. Rate controllers maintain a constant application rate by altering the flow relative to travel speed using pressure. But there’s a drawback to this on uneven land. Going downhill, speed increases, which reduces dwell time; going uphill, the opposite occurs. By keeping your rate constant, you can reduce higher residue on inclines and improve crop protection on declines. “Experience has shown that when you improve coverage uniformity, operators can safely spray at minimal rates,” Deveau noted.
Even small operations can benefit from rate controllers. A good rate controller option will monitor and adjust pressure. It will have the fewest moving parts, a simple interface and have the lowest cost for what your orchard needs.
“A better option would monitor and adjust flow, not pressure,” Deveau said. “It alerts the operator to changes in flow.”
The best option would monitor flow and pressure and adjust flow. This would result in the best likelihood of consistent application. These systems have alarms or will automatically compensate flow and pressure. But they also have the highest cost and steepest learning curve.
Saving time, money and resources are all end benefits of improved precision, however.