Sprayer Nozzle Know-How

Though small, these parts can greatly influence sprayer performance.

Herbicides work best at full rates, and going full-rate on weeds can equal less resistance. Luckily, today’s sprayers can apply precisely the right amount of herbicide to every inch of your fields.

But they still need one little, essential item: spray nozzles.

“It’s a small part that has a very important job,” says Bob Wolf, owner of Wolf Consulting and Research.

One size does not fit all

Nozzles come in many types and spray patterns. Your best choice will depend on how you plan to use it.

Consider these factors:

• Application type (broadcast, band, directed, air-assisted)
• Chemical mode of action
• Chemical type (herbicide, fungicide, insecticide, fertilizer)
• Spray drift risk
• Sprayer operation parameters (application rate, spray pressure, travel speed)
• Target crop (field crops, vegetables, vineyard, shrubs and trees, etc.)

Small nozzle, big impact

Those little nozzles control a lot. They regulate the amount of liquid sprayed, which affects application rate and the variability of spray over the width of the boom.

Nozzles also influence droplet size, affecting both target coverage and spray drift risk.

Nozzles that create larger droplets work well with systemic herbicides that move through the plant. Large droplets are less likely to move off-target, which is important for post-emergence herbicide applications that could damage vulnerable plants.

Other nozzles produce smaller droplets, which is good for contact herbicides like fomesafen (Flexstar®) and glufosinate (Liberty®). Small drops enable chemicals to coat plants for optimal efficacy.

“The crop protection product used will dictate the size of droplets needed, which then dictates the nozzle choice,” Wolf says.

Back to the basics

To determine the right nozzle size, Wolf advises farmers to use a fundamental formula that allows flexibility.

Gallons/acre (gpa) x mph x w (nozzle spacing) = gallons/minute (flow rate)

5,940 (constant for calibration)

“It’s a mathematical way to pick the right nozzle size,” he says. “Plus, it allows you to account for many other factors that affect spraying, like speed and pressure.”

Once you make your calculations, it’s time to head to the manufacturer’s website. Manufacturers create charts to help you pick the right nozzle size for the right situation.

Follow the label

New technologies, including dicamba-tolerant herbicide systems, have brought nozzle selection to the forefront. Chemical companies list specific nozzles on their labels. Failure to follow these guidelines is illegal.

Wolf, who has been training applicators for more than 30 years, says labels should guide you. He reminds farmers that one spray nozzle type and size does not fit all.

“You’re not going to be applying dicamba all day, every day,” he says. “You have to have different spray nozzles to adjust to different products.”

More than nozzles

Selecting a nozzle is important, but of course, several other factors affect sprayer application. Pay attention to the spray boom height, spray angle and spray nozzle spacing on boom.

“All of these factors are critical,” Wolf says. “Poor coverage results in reduced pest control. Too much product results in crop injury, excessive drift and off-target damage.”

He suggests taking the time to calibrate your sprayer to make sure conditions are perfect.

“If you cannot calibrate the sprayer to deliver the correct number of gallons per acre, you won’t be delivering the product correctly or getting the most for your crop protection dollar,” he says.