7.3 Selecting the Correct Nozzle to Reduce Drift
Correct nozzle selection is one of the most important yet least expensive aspects of pesticide application. A nozzle's droplet size spectrum determines deposition and drift. Drift has been a major concern for many years. Off-target application wastes money, reduces deposition on the target plant, pollutes water courses, and may cause nausea in bystanders.
Conventional flat fan nozzles fitted to a crop sprayer produce droplets in the range of 10-450 microns (25,000 microns = one inch). Drift is a major problem with droplets smaller than 100 microns. Increasing the Volume Median Diameter (VMD) certainly will reduce drift, but too large a droplet will bounce off the leaves to the ground, causing pollution, wasting money, and resulting in less product on the target.34184
Conventional flat fan nozzles
Nozzles with an 80° angle produce coarser droplets than 110° nozzles at the same flow rate, but 80° nozzles require the boom to be set at 17-19 inches, whereas 110° nozzles can be set lower, and 15-18 inches above the target. (The lower the boom, the less chance of drift). Spray quality is fine to medium at 15-60 psi.34185
Pre-orifice flat fan nozzles
The internal design of these nozzles reduces the internal operating pressure compared to a conventional flat fan, resulting in coarser droplets. Available as 80° or 100° nozzles. Spray quality is medium to coarse at 30-60 psi. Drift-guard is a well-known trade name.
A turbulence chamber produces a wide-angle flat spray pattern of 150°. Spray quality is medium to coarse at 15-90 psi. Nozzles can be set at 15-18 inches above the target.
Air induction nozzles
Air induction, air inclusion, or venturi nozzles are flat fan nozzles in which an internal venturi creates negative pressure inside the nozzle body. Air is drown into the nozzle through two holes in the nozzle side and mixes with the spray liquid. The emitted spray contains large droplets filled with air bubbles (like candy malt balls) and virtually no fine, drift-prone droplets. The droplets explode on impact with leaves and produce similar coverage to conventional, finer sprays.
Air induction nozzles reduce drift even at higher pressures of 80-90 psi. They are available only at 110° fan angles, so the boom height may need to be adjusted to 15-18 inches. The use of adjuvants certainly will help create bubbles, and trials in Europe confirm this.
Air induction nozzles are regarded as expensive. The list price is three times the cost of a conventional flat fan tip, although some nozzle suppliers in New York will set them for approximately twice the cost. Manufacturers include the following:
Greenleaf TurboDrop nozzles consist of two primary components - the venturi air aspirator and the exit pattern tip. A ceramic orifice in the venturi determines the flow rate of the complete assembly. The venturi is ISO color-coded to designate the flow rate. The exit pattern tip does not affect the flow rate: it is used only to form the desired spray pattern. Pressure range is 40-90 psi.
Spraying Systems Tee Jet Air Induction (AI) nozzles comprise a plastic body with a steel tip, rated for 30-100 psi. They are plastic, with a single-piece construction.
Hardi Air Induction nozzles are similar in construction to Spraying Systems AI nozzles. They are one-piece plastic nozzles.
Albuz nozzles are similar in construction to Spraying Systems AI nozzles. They are one-piece plastic nozzles with a ceramic tip.
Trials are underway at Cornell University to compare air induction nozzles. Although the nozzles physically reduce drift, we need to see how effective they are at delivering materials used to control disease and insects. They certainly work well at delivering materials used to control weeds.