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ARS Home » Midwest Area » Wooster, Ohio » Application Technology Research » Research » Publications at this Location » Publication #74781

Title: SHIELDS TO REDUCE SPRAY DRIFT

Author
item OZKAN, H - OSU/FOOD, AGR & BIOL ENGR
item MIRALLES, A - CEMAGREF/FRANCE
item SINFORT, C - CEMAGREF/FRANCE
item ZHU, H - OSU/FOOD, AGR & BIOL ENGR
item REICHARD, DONALD - USDA-ARS-ATRU (DECEASED)
item Fox, Robert

Submitted to: Journal of Agricultural Engineering Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Spray drift is one of the most important problems facing pesticide applicators. Drift of pesticides onto sensitive areas while spraying field, orchard, or nursery crops is a critical factor considered by USEPA and state regulator agencies in approving pesticide rates, application methods, and buffer zone widths. Spray drift can be reduced by increasing droplet size, decreasing application height, by not spraying when wind conditions are unfavorable, by using shields to protect the spray from air currents, etc. This study, conducted in a wind tunnel, measured spray deposit on the tunnel floor while shields with 9 different designs were mounted over standard nozzles on a boom. We assumed that more deposit on the floor meant that less spray drifted from the spray swath. There were large differences in spray deposit among the shield designs tested. A double-foil shield (best design) produced an increase of 59% in deposits while a shield made of plastic netting (worst design tested), increased deposit only 13% over no shield. When larger capacity nozzles (which produce larger droplets) were used without a shield, they reduced drift more than nozzles using smaller droplets used with the worst shields tested, but they were not as effective in reducing drift as the best shields. An important result of this study was that while shields do reduce spray drift, careful selection of spray nozzles can decrease drift without using expensive sprayer modifications such as shields. It is important that farmers know that by proper selection of spray application equipment and operating procedures, they can control drift with a minimum of cost and equipment changes.

Technical Abstract: The effects of several spray-boom shield designs and low-drift nozzles on spray drift are presented. Results are based on experiments conducted in a wind tunnel and computer simulations using the same experimental parameters. Performances of all experimental shields were evaluated under two spray pressures (0.15 and 0.3 MPa), and two air flow rates (2.75 and 4.80 m/s) in the wind tunnel. All nine shields tested during this study effectively reduced spray drift. Even the least effective shield design produced a 13% improvement in deposition of spray on the ground. A double-foil shield produced the best spray-deposit improvement of 59% compared to the same nozzles spraying without the shield. The shields were effective even when used with nozzles with higher flow rates (producing fewer small droplets). However, using larger capacity nozzles reduced drift more than using smaller capacity nozzles with even the most effective shield. Low-drift (LD) nozzles without a shield provided reductions in drift ranging from 20 percent to 67 percent when compared to the drift from a 0.61 L/min standard flat-fan (SFF) nozzle operating under identical conditions. The 0.61 L/min SFF nozzles operating with shield 2 (the best shield) was twice as effective in reducing drift as the same capacity LD nozzles operating without a shield. However, the low-capacity LD nozzles without a shield were twice as effective in reducing drift as the SFF nozzles of the same capacity operating with shield 5/1 (the shield with the worst performance). Without a shield, LD nozzles at higher flow rates are no more advantageous in reducing drift than SFF nozzles of similar flow rate.