Technical
Application
foliar nozzle, for example, produces under 3% small sub 100 micron-sized droplets that are highly susceptible to drift, compared to 14% with a traditional flat fan nozzle. The extra velocity of the larger droplets means they are significantly less susceptible to drift. In practice, the drift reduction typically gives an average three to four extra days per month suitable for spray application - enabling more timely treatments essential to achieve better results. Managing drift is especially important in amenity situations that are under public scrutiny.
Nozzle size selection
The size of the nozzle orifice primarily dictates the spray water volume, within the parameters of the sprayer speed and the operating pressure. The outputs are standardised, with an 04 nozzle giving twice the output of an 02 at any given speed and pressure, whilst an 08 will give twice the output of an 04, etc.
Forward speed also has an effect on the water volume physically applied. Reducing the speed from six to four km/h, for example, will increase the water volume, and therefore the product application rate, by 50%. This is a factor to consider when spraying greens, for example, where there is a tendency to slow down at the start and end of each run.
Raising the operating pressure will also
increase the water volume but, as a result, will tend to increase the number of small droplets and. therefore. the risk of drift, especially with traditional flat fan nozzles. Reducing the pressure will reduce the driftiness of a nozzle, but can compromise the spray pattern and the velocity of droplets to hit and stick on the target. Most nozzles are designed to work most efficiently at three to four bar. Variable Pressure (VP) nozzle design is a useful development in that the nozzles can be operated at a wider range of pressures, in some instances down to as
low as one bar. This can really help if the wind gets up during spraying, when lowering the pressure could help get the job finished; albeit possibly not spraying quite as efficiently. Remember you will have to adjust your forward speed accordingly, but a good understanding of the relationship between speed and pressure will facilitate that. Whilst one nozzle size can deliver
different water volumes by adjusting speed and pressure, you can be more efficient and precise in your accurate application of the most appropriate water volume by selecting different nozzles sizes. A good selection to have available for consistent application in most turf situations at two to three bar would be a set of 025 nozzles for greens, delivering a water volume of 200 - 300 l/ha at four to five km/h; 04s applying 220 - 380 l/ha at five to seven KPH on fairways and a set of 08s that will deliver 450 - 770 l/ha at five to seven km/h.
That is very easy if you have a sprayer DECEMBER/JANUARY 2013 PC 107
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