Enclosing the spray pattern with a shield can significantly reduce spray drift compared to that of a standard boom sprayer, provided a nozzle producing a coarse spray quality or larger is used. This may provide the opportunity for greatly reduced downwind buffers (no-spray zones) for the application of some products, as drift- management strategies become recognised on product labels.

After selecting a coarse or larger spray quality, the next most important factor for preventing droplet escape (leakage) from a shielded sprayer is the gap between the bottom of the shield and the ground. Minimising the gap as low as possible will further reduce leakage.

The air flow past the nozzle can also be important. This will be a combination of travel speed, prevailing wind (speed and direction i.e. a trailing or head wind) and any openings within the shield that can allow air flow into the shield.

Maintaining shield height and minimising the gap between the base of the shield and the ground is important for reducing leakage which can lead to crop damage. Paddock selection for the use of shielded sprayers can be important, depending on how the height of each shield is maintained. Most shields will have a skid plate to assist with keeping the shield close to the ground, which may be less effective in ‘rough’ paddocks.

Generally, shielded sprayers should be maintained at spraying speeds of not more than 10 kilometres per hour.

Even at low spraying speeds, with fully enclosed shields, air will still enter the shield as it passes over the ground. Any air entering the shield will also leave the shield potentially carrying small droplets out of the shield. The combination of spraying speed and wind speed needs to be taken into consideration, particularly in headwind situations as this will have the greatest impact on ‘leakage.’

Some shields have an open top, which should be fitted with an appropriate mesh or shade cloth to reduce droplet escape. This would require regular cleaning and decontamination to minimise the risk to the operator when changing or adjusting nozzles.