Dealing With Drift

Increasing efficacy. Minimizing drift. Maximizing productivity. These are by-products of an accurate and efficient spray application program. They are also a major focus of CropLife Media Group’s two-part Webinar series “Dealing With Drift,” featuring Robert Wolf, professor of biological and agriculture engineering at Kansas State University and an expert on drift.

Wolf discussed nozzle technology and calibration (Part 1) and equipment and adjuvants (Part 2) in his two presentations. Attendees were awarded CCA CEU credits for the Webinars, which were sponsored by Greenleaf Technologies (TurboDrop), AGCO‘s RoGator, and BASF‘s Status herbicide.

Nozzle Technology And Calibration

In “Dealing With Drift: Nozzle Technology And Calibration” (Part 1), Wolf presented an overview of nozzle designs past and present, and issues related to efficacy and drift control.

“Many technological changes have occurred in the spray industry in recent years,” Wolf said. “Much attention has been given to application equipment to increase efficiency and minimize spray drift. This presentation is designed to highlight some of these application technologies in ground application.”

Nozzles are important because they control the amount (GPA), determine the uniformity of application, affect the coverage, and influence the drift potential, according to Wolf.

“Today’s nozzles are being designed to reduce drift, with greater emphasis on improved drop size control and spray quality,” he said. However, he reminded applicators must keep in mind the number one goal is to control the undesired pest. While doing so, they must minimize drift.

Wolf compared several nozzle types available on the market today, from the extended range to the air-induced/Venturi design, and examined their droplet size, spray distribution, and pressure range.

“Beginning with the ‘extended range’ flat fan nozzle (all major manufactures have one), continuing with the design of ‘preorifice inserts’ and ‘turbulation chambers’, and now with the ‘Venturi’ style nozzle design, manufacturers have worked to develop nozzles that are improving the quality of spray emitted,” Wolf said.

Wolf also addressed the role of Standard ASABE S-572.1 — Spray Nozzle Classification by Droplet Spectra — and how applicators need to calibrate for a label-specified droplet size in the future.

“Calibration for droplet size is the next phase for applicators,” he said. “Ensuring that the spray droplet spectrum is what it is supposed to be to maximize efficacy while minimizing drift.”

Equipment And Adjuvants

In “Dealing With Drift: Equipment And Adjuvants” (Part 2), Wolf emphasized the importance of canopy penetration, as well as how application strategies may vary by crop protection product (e.g., herbicides vs. fungicides vs. insecticides). He also provided a comprehensive review of spray equipment technologies that impact efficacy and drift control, including air-assist and pulse width modulation.

“Air-assist sprayers are popular for applications of fungicides and insecticides in heavy crop canopies,” he said. ” A curtain of high speed air is used to assist with particle movement after leaving the nozzle. In some designs, the spray and air are combined prior to exiting the boom, while in others a shield of air is directed parallel or into the spray stream.”

Wolf also explained the use of pulse width modulation, which allows operators to control pressure independent of speed or rate.

“Using high-speed solenoid valves to regulate flow, pulse width modulation allows you to retain both a set rate and a set pressure whenever a speed change requires a change in the liquid flow,” Wolf said.

The influence of tank mix solutions on flow rate and droplet spectra was also covered in the Webinar.

“What we’re finding is droplet spectra is affected by certain products,” Wolf said. “The need to evaluate droplets of solutions is starting to be accomplished at various labs across the country.”

Operators should be open minded to the adoption of drift reduction additives (e.g., adjuvants), especially if used with other drift control strategies, Wolf said.

“Initially, many people thought the addition of drift control additives alone would be the cure all. But that hasn’t been the case,” he said. “Still, technological advancements are occurring that are showing promise with these products in reducing drift.”

Finally, Wolf offered a long list of strategies for reducing drift, including using lower pressures, avoiding high application speeds, and considering buffer zones.

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