Low drift spraying – Why and How ?
The Plant Protection Products (Sustainable Use) Regulations 2012 require that the application of pesticides must be confined to the land, crop, structure, material or other area to be treated. The spray must not drift outside the area of application.
We all want to reduce spray drift for economic, environmental and health reasons, and the impact of spray drift can not be over-emphasised.
Therefore, users of pesticides must ensure that all reasonable precautions are taken to prevent spray drift. Reasonable precautions include using the right spraying techniques and equipment, taking account of weather conditions and the need to protect neighbours’ interests and other members of the public, wildlife and the environment.
The Plant Protection Products (PPP) Code states that the safest conditions in which to spray are when there is a steady force 2 light breeze (leaves rustle and you can feel the wind on your face, 3.2 to 6.5 kilometres an hour - 2 to 4 miles an hour) blowing away from any sensitive areas or neighbours’ land. There is a table in the PPP Code which provides a guide to wind speed and when spraying should take place, called the Beaufort Scale.
Buffer Zones and LERAPs
When spraying near water with certain pesticides, it might be necessary to leave an unsprayed strip of crop at the field margin to prevent spray drifting out of the treated area. This unsprayed area is called a buffer zone. The product label (and approval) gives details of buffer zones which must be used.
Only certain plant protection products have an aquatic buffer zone requirement when applied by horizontal. If you want to reduce this aquatic buffer zone, there is a legal obligation to carry out and record a Local Environment Risk Assessment for Pesticides (LERAP). For horizontal boom sprayers it is only possible to reduce buffer zones of 5 metres; buffer zones of greater than 5 metres cannot be reduced.
If you just want to apply the buffer zone specified on the label you don’t have to carry out a LERAP. But you are still legally obliged to record this decision as normal in your spray records
LERAP rates initially assigned a 2 or 3 star rating to low drift products which gave a 50% or 75 % reduction in drift potential respectively. Recently the UK Cemical Regulations Directorate (CRD) introduced a more stringent LERAP band of 4 star rating for equipment reaching 90% drift reduction. This has a significant impact on reducing off-target contamination, and protection of water, and should not be overlooked as an option.
What causes spray drift?
A combination of factors may affect spray drift including:
- wind velocity at spray nozzle height (boom height),
- stability of the local atmospheric conditions,
- wrong nozzles choice for the prevailing weather conditions,
- incorrect pressure affecting spray quality,
- vehicle forward speed,
- poor equipment maintenance,
Spray drift can cause much damage to wildlife and is a common result of the misuse of pesticides and a potential source of friction between farmers and their neighbours.
To avoid spray drift, and its adverse environmental effects, the following must be adhered to:
- check the weather forecast before starting off; do not spray if the wind direction and speed would cause spray to drift onto sensitive areas, taking into account unexpected gusts of wind
- keep the spray boom as low as possible, consistent with an even spray pattern at the correct target height
- check spray angles and adjust height accordingly
- choose an 80º angled fan pattern nozzle, which naturally produce fewer fine droplets
- use the coarsest appropriate spray quality at all times
- when using a boom sprayer, reduce the operating pressure and forward speed but maintain the dose, volume and spray quality within the recommendations on the label
- consider not treating the crop or part of the crop closest to the boundary
- alternative systems for spray application that are available may help to reduce spray drift when used according to the manufacturer’s instructions
- reducing the dose of the product you apply will reduce the amount of product which could potentially drift off target;
- in orchards, consider having appropriate natural windbreaks, such as other trees, around the treated area;
- use one of the various spraying systems which are available to help reduce spray drift. Suitable drift-reducing systems may include twin-fluid nozzles, air-induction nozzles, rotary atomisers, pre-orifice nozzles, air-assistance for field crop sprayers, shrouded-boom sprayers for sports turf and other amenity areas, and re-circulating tunnel sprayers for spraying fruit bushes and trees. Sprayers and nozzles meeting the needs for low-drift equipment under the LERAP schemes will give lower levels of drift than conventional systems when used correctly;
- use an authorised drift-reducing additive to pesticides in appropriate situations (depending on the type of equipment being used and the nature of the spray solution).
In a nutshell what can I do as a spray operator:
- Slow down
- Reduce system pressure
- Increase water volume applied
- Lower the boom height
- Use low drift nozzles (air inclusion)
- Use an 80° angled nozzle when appropriate
- Learn the Beaufort Scale and get a good weather app
- Follow LERAP guidelines
BfS have always been specialist “low drift” nozzle designers and manufacturers based entirely in the UK. The company introduced the first air inclusion nozzle, the Billericay Bubble Jet, to the UK agricultural market in the early nineties. Prior to this if you wanted to add air into a spray liquid stream you had to pump it there using a twin fluid nozzle and supply from a compressor. These were “Airtech” machines and very effective at reducing spray drift. These were superceded by air inclusion nozzles due to cost and effectiveness, and the simplicity to be able to retrofit to existing sprayers.
Air inclusion nozzles produce droplets containing air, so are bigger. They have a larger VMD (volume median diameter), and are less prone to drift. Nozzle manufacturers usually publish the droplet size classification for their products.
The most drift prone droplets are ones less than 150 microns and these must be avoided wherever possible, so choose a nozzle producing medium, coarse or very coarse droplets to ensure drift is minimised.
BfS Air Bubble jets give 75% DRT relative to a flat fan.
BfS ExRay XC give 90% DRT relative to a flat fan.