Performance of Venturi-type Nozzles

The number of postemergence herbicide applications has increased in recent years. This has increased our awareness and concern about drift management. One factor to consider in managing drift is setting up equipment so that it sprays larger droplets. This can be accomplished by using nozzles that are designed to produce larger droplets. Venturi or air induction nozzles are a newer nozzle type that produce a larger spray droplet. However, there is a potential that larger spray droplets may not provide the same level of weed control with all herbicides. To test this question, a group of scientists from the University of Tennessee compared the performance of 11003 XR Teejet (flat fan) nozzles against 110015 AI Teejet venturi nozzles and 110015 and 11003 Raindrop Ultra venturi nozzles for controlling weeds. The tests compared cocklebur and broadleaf signalgrass control when spraying Liberty, Gramoxone Extra, and Roundup Ultra with the different nozzle types. Spray volumes were fairly low in the tests, especially for the contact herbicides. Spray volumes of 5 and 11 gal/acre were used with all nozzles and herbicide combinations.

The researchers found that cocklebur control was 95% and slightly greater with the AI and XR Teejet nozzles than the 90% control with Raindrop Ultra nozzles when averaged over the three herbicides. The same trend occurred with each individual herbicide. In broadleaf signalgrass, results were similar. AI (95%) and XR (94%) nozzles were just slightly better at controlling this grass weed compared to the Raindrop Ultra (91%) nozzles. The droplet size (volume mean diameter or VMD) produced by the XR flat fan nozzles was measured at 175 microns and the AI Teejet venturi nozzles produced droplets with a VMD of 450 microns. The Raindrop Ultra produced a slightly larger droplets with a VMD of over 600 microns. Cocklebur control with the contact herbicides (Liberty and Gramoxone Extra) and broadleaf signalgrass control with Liberty were slightly reduced with increasing droplet size. Droplet size did not affect the performance of glyphosate, which is a translocating herbicide. The researchers concluded that venturi nozzles that produce droplets with a VMD of 450 microns can provide weed control that is similar to the level obtained with flat fan nozzles. However, it appears that there is potential for reduced weed control if contact herbicides are being sprayed with venturi nozzles that produce droplets larger than 450 microns.

Source: Etheridge et al. 2001. Effect of venturi-type nozzles and application volume on postemergence herbicide efficacy. Weed Technology 15:75-80.

April, 2001


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