Planting vegetation as a drift barrier
GroundCover™ Supplement Issue: 122 | 02 May 2016 | Author: Dr Andrew Hewitt, Dr Chris O’Donnell, Dr Gary Dorr, Jason Ferguson and Rodolfo Chechetto
Vegetative barriers can be effective in mitigating the downwind movement
of spray particles released during normal pesticide-application operations
Vegetative barriers are areas of trees or shrubs deliberately planted to act as ‘filters’ to minimise spray drift risk and to potentially reduce odour and noise.
However, remnant vegetation should not be used as a barrier: it should be protected from spray drift.
Vegetative barriers can be permanent, such as planted strips of trees and shrubs, or temporary, such as strips of forage sorghum adjacent to paddocks that are sprayed regularly.
A permanent vegetative barrier is typically a narrow strip of trees and shrubs (about 20 metres wide) that has been deliberately planted close to the edge of sprayed fields to trap airborne spray droplets that may be carried away from the field by wind. Vegetative barriers do not need to be particularly tall or wide to be effective.
The height of the vegetative barrier depends on the release height of the spray.
At 50 per cent porosity (ratio of light to dark when viewed side on), the height of the vegetative barrier should be at least one-and-a-half times the release height of the spray. If the porosity of the barrier is 40 per cent, it is recommended that its height be increased to about twice that of the release height of the spray.
Immediately behind a vegetative barrier will be a reduction in drift, which is directly related to the porosity of the barrier. As distance downwind of the barrier increases, the reduction in drift decreases. However, a long distance (beyond 100 metres downwind) from the buffer, the drift will be at the level of no barrier (Figure 1).
Dr Andrew Hewitt,
University of Queensland,
Queensland Department of Natural Resources and Mines, Planning Guidelines:
Separating Agricultural and Residential Land Uses
PSIC (SCARM) Report 82, 2002, Spray Drift Management: Principles,
Strategies and Supporting Information
Victoria DPI Agriculture Notes, AG0860, 2002, Using Buffer Zones and
Vegetative Barriers to Reduce Spray Drift
GRDC Project Code UQ00072, UQ00047
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