Pesticide applicators can use a North Dakota State University Extension Service Web site to compare drift, percent coverage and droplet size of common pesticide application nozzles.

The Web site is at http://www.ageng.ndsu.nodak.edu/spraynozzles/. The Web site allows users to view video clips to compare the drift of any two selected nozzles. Users will find specific instructions included on the Web site front page.

“Each nozzle was operated in laboratory conditions applying approximately 0.2 gallons of water per minute at the manufacturer's recommended pressure,” says John Nowatzki, NDSU Extension Service agricultural machine systems specialist. “Operating at 0.2 gallons per minute corresponds to applying 8 gallons per acre with a field sprayer traveling 7.5 miles per hour. Each nozzle demonstration was repeated using 5 and 10 mph wind speeds.”

Separate laboratory experiments were conducted using water sensitive cards to compare droplet size and percent spray coverage. Pictures of the cards used in the spray experiments and the statistical analysis are displayed below each video clip. Data was collected in the laboratory using spray droplet comparison software. Each card was digitally scanned and evaluated by the software.

The statistical information includes droplet size information and percent spray coverage for each nozzle. The droplet sizes are listed in microns. One micron is 1/1,000 millimeter or approximately 1/25,000 inch. For comparison, individual strands of human hair have a diameter of approximately 100 microns.

The volume median diameter is a droplet dimension that indicates that half of the spray volume is in droplets smaller than this number and half of the spray volume is in droplets larger than this size. It also can be indicated as Dv0.5.

“Two other values also are important,” Nowatzki says. “They are 10 percent volume and 90 percent volume droplet size. These are shown as Dv0.1 and Dv0.9. The Dv0.1 value indicates that 10 percent of the spray volume is in droplets smaller than this value and are the particles most likely to drift in field applications. This number should be near or above 200 microns to help reduce drift. The Dv0.9 value indicates that 10 percent of the spray volume is in droplets larger than this. Larger Dv0.9 values indicate that some large spray drops are produced. This may result in poor coverage and wasted pesticide.”

The percent coverage value included with the statistical information indicates the amount of the water sensitive card that was covered with spray droplets. Another NDSU Extension Service Web site (http://www.ag.ndsu.edu/pubs/pests.html) has several publications on pesticide application and management practices listed.

Available on the Web site is the publication “Choosing Drift-reducing Nozzles.” The publication has more information about the data included on the spray nozzle comparison Web site.

NDSU Agriculture Communication

Source: John Nowatzki, (701) 231-8213, john.nowatzki@ndsu.edu

Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu