Spray drift mitigation transcript
Spray drift is the movement of ag chemicals outside the intended target area, and this movement outside the target area can be as droplets, as particles or as volatile vapours. Spray drift has obvious economic impact for the farmer too. Spray drift is lost chemical and that means it's chemical that's not getting to the target area.
It's absolutely critical to minimise spray drift to ensure the chemical reaches the target area so it can be more effectively used. While more spray is lost within the target area, it is the spray that leaves the target area that is of the greatest concern to us. Factors that contribute to drift include: droplet size, boom height, inversions, wind speed, wind direction, relative humidity/temp delta T, and formulation type.
Recommendations to mitigate spray risk can be summarised by: slowing down next to neighbouring properties and sensitive areas, changing nozzle size in high risk areas for larger spray droplets, and building a buffer zone at the perimeter of the spray job. Spray jobs generally start in favourable weather conditions. This is the best time to cut out any perimeter or any sensitive area buffer zones. Build these out of the job and then check weather conditions every tank load or significant change of weather. Stick flagging tape along the fence adjacent to sensitive areas to indicate wind direction.
Weather conditions should always be measured at the site of application. Travel speed is an important consideration when planning and calibrating for a spray job. Slowing down around sensitive areas will allow for larger droplets to be produced. For this job, an average speed of 20 kilometres an hour is required to achieve the desired spray quality. In perimeter risk areas, slow down to the minimum speed where the nozzles are still working properly, in this case, 16.2 kilometres an hour. This will produce a coarser spray quality and lowers risk of drift without efficacy change.
Two laps like this around the perimeter will provide a suitable buffer zone. You can then speed up to 20 kilometres an hour for the rest of the paddock. One outside lap may not be enough on the perimeter to allow for an effective spray job. If we consider a 36 metre boom and we do two outside laps that'll allow 72 metres on the buffer of the perimeter. Now we have enough room to turn the sprayer, line it up and ensure that it's working when we hit the 72 metre mark.
To enable this, we may need to consider a wider headland with the seeder, so four passes of the seeder to facilitate two passes of the spray unit. As the day progresses, conditions may deteriorate so the greater the buffer zone, the further you are away from your perimeter and the safer your job will be in terms of spray drift.
Without a buffer zone, you are right on the fence every time. Some sprayers have a pressure spike each time the system switches on, so being only one boom width out from the perimeter will still potentially have a big pulse of fine droplets close to the fence as the sprayer kicks into gear. This increases the risk of off-target drift. The added benefit of wider headlands is that it reduces the risk of under-applications when turning the sprayer around at the beginning and the start of the runs.
It's impossible to turn the sprayer in one lap without having a teardrop on every run in the corners. e completed the spray drift management course that was sponsored by the VFF and run to try and stop the 2.4-D issue with the horticultural areas, so we participated in that and learnt a lot about managing drift and also about nozzle selection. Since we've been able to reduce the drift, we're so much more confident about working besides paddocks where there is newly germinated crops, we can use glyphosate now through the fence and know that we're safe where before, with our old flat fan nozzles, we were very, very concerned.
We have to be very careful here because we border onto grapes and it's just very, very imperative that we make the right selection with nozzles and chemicals and spraying conditions. Getting your head around AI's was a bit difficult first up because there's low pressure and high pressure induction jets, but once you made the selection and you use the correct pressures, they're very good jets to use. We can physically see a lot less drift, as well as we're not having any issues with the grapes being next door now.
View the Spray drift mitigation video.