Research shows that the risk of spray drift increases substantially when spray equipment travels fast during higher wind speeds.
A Canadian study has shown that during higher wind speeds of about 20 kilometres per hour, machinery travelling at about 30km/h almost doubled the amount of chemical contributing to spray drift risk compared with machinery travelling at 8km/h.
The same study revealed that spray drift risk was not affected by travel speed during slower wind speeds of 7 to 8km/h (under daytime conditions).
Spray operators are therefore advised to avoid travel speeds above 16 to 18km/h during higher wind speeds unless there is excellent boom height control and equipment is set up to minimise airborne droplets by providing spray quality that is coarse or larger.
The fact sheet, developed by the GRDC in conjunction with Bill Gordon of Bill Gordon Consulting, contains advice to reduce spray drift including:
- make the most of favourable weather conditions, especially wind speed;
- avoid spraying during surface temperature inversion conditions;
- use the coarsest spray quality that will provide efficacy;
- maintain boom height to achieve double overlap, but no higher;
- try to minimise your travel speed; and
- use unsprayed, downwind vegetative buffers.
Bill Gordon Consulting,
firstname.lastname@example.org, 0429 976 565
A fact sheet on practical tips for spraying is available at: www.grdc.com.au/GRDC-FS-SprayPracticalTips
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