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Controlled Droplet Application

CONTROLLED DROPLET APPLICATION

by

Dr. Russell R. Hahn

Controlled droplet application is a term used to describe a new method of applying pesticides. Controlled droplet application (CDA) technology produces spray droplets that are relatively uniform in size and permits the applicator to control droplet size. On the other hand, conventional spray nozzles produce droplets that vary widely from small droplets that may drift or evaporate before reaching the target, to large droplets that concentrate too much of the pesticide in one spot.

ROTARY SPRAY NOZZLE

The key to CDA technology is a rotary spray nozzle that creates a consistent droplet size and uniform pattern width. With the rotary nozzle, spray solution accumulates at the bottom of a spinning cup and spray droplets are created by the centrifugal force of this cup as it forces spray solution up a series of grooves on the inside of the cup. When the spray solution reaches the top of the cone-shaped nozzle, droplets are thrown in a circular (hollow-cone) pattern over a six-foot diameter. The speed of the cup deter- mines the diameter of the droplets with the nozzles designed to operate at two different speeds.

The fast setting produces droplets that are 75-100 microns in diameter (a 25-micron droplet measures 1/1,000 of an inch in diameter) while the slow speed produces 250-micron droplets. The 250-micron size is con- sidered best for herbicide application, while the smaller droplets are preferred for fungicides and insecticides.

ADVANTAGES OF CDA

Proponents of the CDA technology list a number of advantages for this method of application over the use of conventional sprayers. The first is the fact that less carrier (water) is required per acre. Water require- ments may be reduced from the 20 - 30 gallons per acre used with most conventional herbicide sprayers to one gallon or less per acre with CDA.

Another claim is that the rotary spray nozzles will reduce the amount of spray drift because droplet size is controlled and fewer small droplets are produced than with conventional nozzles. Practical experience indicates that this may be true for the slow speed. However, the amount of drift may actually exceed that from conventional nozzles when the fast speed is used to produce the 75-100 micron droplets.

A third important claim is that less pesticide is required to do the job in some cases. While this might be true for certain foliar-applied, trans- located herbicides, it is doubtful that this technology will have much influence on the rates of soil-applied herbicides which depend on soil texture and soil organic matter level.

Other advantages of CDA include time and fuel savings, along with less soil compaction.

For more information, please contact Dr. Bill Duke or Dr. Russell Hahn in the Dept of Agronomy, Cornell University.

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