Air induction nozzles can reduce drift 75% to 90%, but drift can still occur when farmers are spraying herbicides, insecticides and fungicides.

Farmers who were early adopters bought air induction nozzles and used them for everything, both contact and systemic herbicides. Problems started to emerge in reduced performance of some contact herbicides that had been sprayed using air induction nozzles. Causes for this reduced product efficacy were not readily apparent.

Spray Pressure Is Critical

Dr. Tom Wolf with Agriculture and Agri-Food Canada in Saskatoon, Sask.,  tested different brands of air induction nozzles and found that the optimum spray pressure is different for low pressure and high pressure air induction nozzles.

Low-pressure air induction nozzles should be operated at 40 to 60 psi for contact herbicides. High-pressure air induction nozzles should be operated between 60 and 80 psi for contact herbicides. One brand of air induction nozzle tested was found to need 80 to 120 psi operating pressure for contact herbicides.

As a result of Dr. Wolf's research, improper spray pressure was likely the cause of herbicide performance problems when applied with air induction nozzles years previous. Farmers with poor product performance were likely operating their air induction nozzles at pressures that were too low.

Farmers were buying air induction nozzle brands because they like the brand, but sprayed at 40 psi because that's what they always did. Air induction nozzles have to be operated at the correct pressure depending on the product being sprayed or the job being done.

When air induction nozzles were operated at recommended pressures according to Dr. Wolf, product performance problems all but disappeared.

Drift Reduction

Research was done by Bryan Storozinsky in Alberta to determine drift potential for different air induction nozzles compared to conventional flat fan nozzles. Drift from all nozzles was compared to the drift from Extended Range flat fan nozzles. 

Drift Potential Research Results:

• Extended Range Flat Fan                     100
• Turbo TeeJet Wide Angle Flat Fan          50
• Low Pressure Air Induction                     25
• High Pressure Air Induction                    13

Air induction nozzles can and do reduce spray drift. Air induction nozzles still produce some driftable fines that can be carried off-target by wind. The good news is the percent volume of what you are spraying that is in droplets small enough to be drift prone is very, very small but it is not zero. The only nozzle technology that has a guaranteed zero drift potential is a nozzle that is on a sprayer that is off.

Today’s Air Induction Nozzles

Every year more and more farmers purchase and use air inductions nozzles to apply a wide variety of pesticides to a host of different field and horticultural crops. Farmers have learned that spray quality or droplet size is critical for effective application for certain products.

Adjusting spray pressure to deliver a certain spray quality is helped with new droplet size information included in all nozzle catalogues. By consulting these charts a farmer can adjust his spray pressure to deliver a certain spray quality by factoring in nozzle type, nozzle size and spray pressure.

Air induction nozzles are less drift prone than nozzles that were used 10 years ago. This nozzle technology greatly reduces the number of very fine droplets produced that can be carried by the wind and could cause off-target crop damage.

This reduction in drift potential is accomplished by the shear fact that air induction nozzles generally produce bigger droplets which tend to drift less. Now, they still produce some very small droplets but considerably less than older nozzle designs. Air induction nozzles tend to stretch your spray window but there will still be days when you should not spray. Always follow label directions as to maximum wind speeds allowed for spraying,

Use your wind meter to accurately measure wind speeds at the time you are planning to spray and in the field you are planning to spray.

Farmers choose nozzle brands, sizes and operating pressures to deliver the required droplet sizes. Air induction nozzles are a tool that can help you minimize spray drift. Air induction nozzles are not a shield that will totally eliminate spray drift.

(Editor's Note: This article was written by Helmut Spieser, environmental engineer, Ontario Ministry of Agriculture, Food and Rural Affairs.)