Spray Drift Reduction

What factors should be considered to reduce spray drift?

• Boom height

• Wind speed (Force 2 is ideal - 2mph to 4mph)

• Spray quality

• Speed and pressure

How does the boom height help reduce spray drift?

It should be as low as possible without compromising the evenness of spray deposition

Why is spraying in Force 2 (2-4mph) wind conditions ideal?

It reduces volatilisation by promoting gentle air movement that disperses vapours, improves spray deposition, and prevents temperature inversions that trap chemicals near the ground.

What is the standard droplet size used when spraying?

Medium (compromise between droplet size and potential for drift)

When would a fine droplet size be used when spraying?

When small cotyledon weeds need to be targeted - boom height can be lower if crop is not drilled/not emerged to reduce drift

When must you not use a fine spray quality?

If the product label indicates “Toxic”, “Very Toxic”, “Corrosive” or “Risk of serious damage to the eyes”

When would a coarse spray quality be used?

If you are wanting to target the soil under a dense canopy (eg: applying Kerb or Astrokerb in OSR in late November to target weeds under the canopy)

What is a flat fan nozzle?

• Produce a spray deposit pattern which peaks directly under the nozzle - when boom height is correct so the deposition of alternate nozzles meets, the overall spray coverage is even across the boom

• Most common angle is 110 degrees, however 80 degrees is used for band spraying in row crops

When would an even spray nozzle be used?

For band spraying and on hand lances / knapsack sprayers

What is an even spray nozzle?

• Produces a full deposit across the full width of their pattern as the individual nozzle patterns are not overlapped

• Nozzles are mounted at a slight angle to the boom to reduce potential for interference between patterns from adjacent nozzles

What is a twin outlet flat fan nozzle?

Angled to give forward and backward spray trajectories which can increase the coverage in dense crops or on vertical targets

What is a pre-orifice flat fan nozzle?

Pressure drop chamber within the nozzle which reduces the number of small droplets in the spray (the spray quality is made coarser)

How does an air induction flat fan nozzle work?

• Draw air into nozzle chamber by Venturi action

• Air and the spray water mix = droplets which contain air bubbles

• Bubble bursts on the leaf to produce a finer spray quality

What is a benefit of using air induction flat fan nozzles?

They lead to improved coverage and retention on the target in comparison to equivalent conventional nozzles user under the same parameters

What is a twin-fluid nozzle (air-tec)?

• Injects compressed air into the nozzle body

• Results in both air inclusion and an enhanced effect on spray penetration of the canopy

What is a benefit of using twin-fluid nozzles (air-tec)?

They allow for very low water volumes to be used giving a more concentrated spray solution which allows for a reduced number of tank fill ups

What is a negative when using twin-fluid nozzles (air-tec)?

Cost and maintenance higher that conventional set ups

What is the process of hydraulic sprayer calibration?

• Determine the required spray volume, product dose and spray quality

• Measure the time taken to cover 100 metres

• Calculate the speed: 360 / Time = Speed in kmph

• Measure nozzle spacing (typically 0.5m)

• Calculate the nozzle output

• Select the correct nozzle to produce the required output and quality

• Check the nozzle output (for at least 4 nozzles) using a jug or flow meter, nozzle pattern and alignment. Replace nozzles which vary by +/- 10%.

• Check the spray volume / ha achieved

• If necessary, alter the pressure and repeat steps 7 and 8 until the required spray volume is achieve.

• Record all details of the calibration