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Spray Capture by a Riparian Barrier

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2007 ASAE Annual Meeting  071148.(doi:10.13031/2013.23364)
Authors:   Harold W Thistle, George (or initial) Ice, Richard (or initial) Karsky
Keywords:   Riparian Barrier, Deposition, Pesticide, Drift, Aerial Spraying, Forestry Herbicide

A field study was conducted west of Corvallis, Oregon in the Coastal Range to evaluate the effectiveness of riparian barriers, as defined by the Oregon Forest Practice Act rules, in preventing herbicide deposition to streams. A helicopter sprayed two tracers (BSF and LiCl) over 4 transects (two each into a Medium Stream and a Small Stream barrier). Twenty trials were conducted resulting in over 1400 tracer samples. The preliminary conclusion of this study is that riparian barriers as currently defined in Oregon are effective at reducing the amount of deposition to streams. The effect is strongest when the potential for near field drift driven by wind speed is greatest with reductions shown here ranging from 58 to 96% of the fine droplet (driftable) fraction when compared to modeled controls. The reduction is less clear under low wind speed conditions but these conditions are not generally high drift scenarios and absolute deposition to downwind streams is low in these scenarios in any case.

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