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Corn+Soybean Digest

Proper Application Minimizes Drift, Data Shows

If you apply pesticides correctly, only a tenth of 1% of the chemical should drift.

So confirm ground application studies coordinated by the Spray Drift Task Force (SDTF), a consortium of 38 ag chemical firms.

The SDTF was established in 1990 after EPA ruled that the 2,000 existing and any future products would need spray drift data to become registered.

"One of the things we've proved is that what you're spraying only has a relatively small effect on drift," says David Johnson. Johnson is director of Stewart Agricultural Research Services, the firm hired to manage data generation.

The studies' goal was to determine how much chemical drifts from ground and aerial applications and from chemigation.

The collected data will help develop computer models that EPA can use to estimate drift. The models are being jointly developed by EPA, SDTF and USDA.

The most extensive research, Johnson points out, has been done on aerial application. An aerial-drift computer model is nearlycomplete.

Ground application research was not as in depth, he says.

"How you set up your sprayer is not as important in ground application as in aerial. The drift is very low from ground."

In fact, in a typical full-field ground application, more than 99.9% of the applied active ingredient stays on the field.

A typical application? A 1,200 foot- wide, 20-swath field, using 8004 flat fan nozzles at 40 psi, 20" nozzle height and 10-mph crosswind.

The task force recommends ways to minimize ground drift:

* Apply the coarsest droplet- size spectrum that gives enough coverage and pest control.

* Use the lowest nozzle height that gives uniform coverage.

* Apply pesticides when wind speeds are low and blowing away from sensitive areas.

Chemigation drift potential is also very low. High-pressure irrigation systems cause more drift than low-pressure systems; they release droplets higher.

Adding an end gun to a high-pressure system doesn't affect drift much. But adding one to a low-pressure system substantially increases drift when droplets are released at 12 foot.

Despite SDTF findings, Bob Wolf, University of Illinois ag engineer, believes farmers should still be concerned about drift from ground sprayers.

"Even if it's a very low percentage, when drift occurs, it has the potential to cause problems," states Wolf. "It's important to make sound application decisions to minimize drift so crop protection products won't be lost through regulation."

For more information or copies of study results, contact David Johnson or Andrew Hewitt, Stewart Agricultural Research Services, Inc., P.O. Box 509, Macon, MO 63552. Phone: 660-762-4240.

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