New spray nozzles deliver better coverage, less drift

Ten years ago, spray nozzles were like the Model T. You could have whatever colour you wanted as long as it was black. In the case of nozzles, the only model available was the conventional nozzle.

According to Tom Wolf, Research Scientist with Agriculture and Agri-Food Canada in Saskatoon, the conventional nozzle performed well but it came with drift issues. Times have changed and so have sprayer nozzles.

“Since that time the industry has introduced air-induced low drift nozzles,” says Wolf. “Our surveys show that up to 50% of producers are using these nozzles but that hasn’t happened without some growing pains. One of the issues is that the nozzles can be used improperly, resulting in poor performance of the pesticide.”

Wolf says that the first step to ensure effective performance is to spend some time making the right selection.

“There are a number of different nozzles available and producers need to consult with an expert to choose the nozzle that is right for them,” he advises.

Four types of nozzles are available in the western Canadian market. Here are Wolf’s comments and recommendations about each type summarized from his research:

Conventional

• Available in 80 and 110 degree flat fan.
• At low pressure, the pattern collapses and the spray is coarser.
• At high pressure, the pattern forms nicely but can become drift prone.
• 110 degree fan angle allows for a wide pressure range.
• With these tips the spray gets excessively fine at higher pressures, particularly the 110, making drift a problem.

Pre-orifice (low drift version)

• The nozzle uses a pre-orifice to reduce the pressure at the tip. At the conventional pressure of 40 psi, there is less drift with this nozzle.
• At lower pressures the pattern is slightly lost, pressure has to be slightly elevated.
• Between 40 and 50 psi is a good operating range.
• At higher pressures, like all nozzles, these become more drift prone but never have the drift potential of conventional tips.

Low pressure air-induced

• Like the pre-orifice tip with a venturi in the middle to introduce air for coarse spray.
• Optimal range of 50 - 70 psi provides a consistent spray pattern with low drift and good coverage.

High pressure air-induced

• Same design as the low pressure air-induced nozzles except designed for coarser spray requiring even higher pressure.
• At low pressure these nozzles produce poor patterns but with increased pressure, as much as 100 psi, they provide good pest control.
• With higher pressures the drift potential increases but never as high as with conventional tips.

Four important rules for effective coverage

For growers using air-induced low drift nozzles, there are four rules for effective coverage and environmental protection.

1. Select the right nozzle for your needs and that are suitable for the product you are spraying. Growers can choose nozzles that give spray from fine to extra coarse. Consult an independent expert, such as Tom Wolf, Ph.D. with Agriculture & Agri-Food Canada at wolft@agr.gc.ca.
2. Operate at the right pressure for the particular nozzle – 60 to 100 psi is common for air-induce nozzles.
3. Use the appropriate water volume. If you go to a coarser spray, you may require higher water volumes.
4. Make sure your pattern is appropriate. A wider overlap may be required for a low-drift nozzle, compared to a conventional nozzle. Ensure that the edge of a spray pattern projects to the middle of the adjacent pattern at target height.

Check sprayer performance

Wolf recommends that growers double check their sprayer performance by making an infield pass over water sensitive paper and compare their results with this chart.

“For products like contact herbicides, ensuring spray pattern performance that is similar to the top left corner of the chart, is important for product performance,” advises Wolf. “Using higher water volumes and correct spray pressures will help reduce efficacy issues with these types of products.”

Getting the job done

The saying “make hay while the sun shines” applies to spraying as well. According to Blaine Woycheshin, Bayer CropScience Portfolio Manager Oilseed & Pulse Crop Herbicides, growers should be spraying Liberty® in full sunshine, when temperatures are greater than 10° C and plants are actively growing in good moisture. Avoid heavy dew and spraying in high humidity, if possible, as it reduces the product performance.

“The better the coverage you get on the plants, the better control you’ll see,” advises Woycheshin. “So it’s important that growers keep in mind how travel speed, droplet size, pressure, boom height and water volume each contribute to product efficacy. Get those working in your favour and you’ll get the best results.”