Pre-emergence applications can be high risk for drift due to bare soils that release stored heat causing air/spray to rise and have no crop to intercept spray; cooling air temperatures; high loading of ai/ha; and inverse weather conditions.
Product drift not only reduces efficacy but also risks contaminating ‘non target’ areas. Crop protection chemistry is already under significant political and public pressure so minimising residue detection through controlling drift is key to protecting products in the future.
There are four main areas to consider for drift reduction:
The biggest influence on drift is the wind speed, ideal wind conditions are force 2 on the Beaufort scale. Higher speeds can cause spray to be carried away from its target. Avoid spraying in completely still conditions which could cause spray to hang in the air. Double the wind speed; double the drift.
Excessive speeds can lead to decreased boom stability and create turbulence behind the boom, which may lead to increased drift and reduced product efficacy. The optimum speed for applying pre-emergence herbicides in 2016 trials was below 12 kph, this delivered the best balance of work rate and efficacy.
With a steady forward speed, the next step is to ensure correct boom height. In trials reducing the boom from 100cm above the crop to 50cm efficacy went up from 70% to 87% control. To aid stable and correct boom height ensure correct tyre pressure, grease the boom suspension, lubricate bushes and bearings and check wear, attach a Syngenta cable tie to the boom which guides 50cm boom height, set-up sensitivity of boom-levelling system for minimal drift.
Coarse to extra coarse droplet size will reduce drift further. Current application work has shown strong performance from 90% drift reduction nozzles, proving drift reduction doesn’t have to compromise efficacy.
2017 recommended pre-emergence nozzles
|Nozzle||Water volume (l/ha)||Pressure (bar)||Speed (kph)||Drift reduction rating|
|Perfect spray conditions|
|Compromised spray conditions|
|Teejet TTI1 10-05||200||2.0||10||90%|
|Teejet AI/AIC 110-05VP/VS||200||2.0||10||90%|
Ongoing trials work allows us to continually update our best application advice to fit with the changing agronomic and environmental landscape. The Syngenta 3D Nozzles still remain a class leading nozzle for efficacy against grassweeds, however their drift reduction operating pressures are low, therefore in sub optimal conditions, a drift reduction nozzle with higher operating pressures should be used. We have seen that Drift Reduction Nozzles can also offer the same level of controls as the 3D.
If using 3D Nozzles, it is important to choose a Nozzle with a larger orifice size which will allow you to apply higher water volumes with coarser droplet to minimise drift.