The Art of Application

With spray nozzles being the final point of delivery, it is crucial that they are working accurately and efficiently, if operators are going to get the spray on target, reports Tom Robinson of Syngenta.

All nozzles wear over time; the rate of wear being dependent on the amount of use and the products being applied; coarse liquid fertiliser or trace element products typically cause faster wear - low quality iron products can be like sandpaper going through the nozzle.

I would always recommend checking nozzle output at least twice a year, and possibly each month during busy spraying periods. One thing to look out for is if you expect to spray eighteen greens on a 400-litre tank, and you have run dry after seventeen, then the nozzles may be to blame.

There is some opportunity to adjust pressure or speed to get the right application rate if all the nozzles have worn evenly (see calibration section below) but, if nozzles wear too much, then the spray pattern will be affected and that will influence the leaf coverage and the potential performance of products.

More typically, and of greater concern, is if one nozzle has worn more than others and is applying at a higher rate. Overall the machine may be applying the required volume across the six metre width but, if one nozzle is applying 20% more than others, for example, then some areas will be getting too much fertiliser that may cause scorch or striping or, if applying fungicides, plants sprayed with the lower output nozzles may not be getting the vital protection they require.

Operators need to check the individual output from each nozzle and that it is consistent across all the nozzles. Once the output per nozzle has been established, the other variable operators need to know exactly is how fast they are spraying? With these two facts, the precise spray volume can be calculated and any adjustments made to select nozzle choice and pressure to achieve the desired output.

Checking sprayer speed

It is very easy to check the spraying speed. Accurately measure out a run of 100m on a turf surface, using a cane to mark each end. Start the timing as you drive over the first cane at spraying speed; stop the clock as you drive over the second cane.

Divide 360 by the time taken to drive the 100m in seconds = speed in km/h.

Repeat if different spraying speeds are used for different areas, e.g. greens and fairways.

Checking nozzle output

To check the consistency of nozzle output across the boom, fill the tank with clean water, set the pump to the standard operating pressure and collect the output from each nozzle for 30 seconds, using a Syngenta Sprayer Checker calibration cylinder.

Note down the output from each nozzle. Add up the total and divide by the number of nozzles to give the average output per nozzle across the boom. Calculate the difference from average for each nozzle.

If the output from any nozzle is +/- 4% of the average, nozzles are unacceptably worn and the complete nozzle set should be replaced.

Top Tip: Always use a calibration cylinder for checking nozzle output; measuring jugs are good for measuring product, but are not sufficiently accurate
for checking nozzles

Calculating application rate

With the knowledge of the forward speed of the sprayer and the output from nozzles, the calculation to work out the volume of spray being applied per hectare is:

Spray volume (l/ha) = Nozzle output (l/min) x 600 ÷ forward speed (km/hr) ÷ nozzle spacing (m)

This can also be turned around so that you can calculate the nozzle output per minute required to apply a given spray volume:

Nozzle output (l/min) = Spray volume (l/ha) x forward speed (km/hr) x nozzle spacing (m) ÷ 600

Changing the forward speed or the operating pressure would adjust the spray volume application rate; increasing pressure or slowing down raises application rate, lowering pressure or speeding up will decrease application rate. For greater changes in the water volume different sized nozzles may be required.

Any changes can be worked out and checked with the manual calculations, or using the on-line sprayer calculations available free on the Syngenta GreenCast Application Zone.

Top Tip: If you have collected nozzle output for 30 seconds in you nozzle check, don't forget to double it to get the output per minute for the spray volume calculation

Course Manager's comments

We use the sprayer repeatedly throughout the year, not just for disease control, but also for all the fertiliser as liquid feed, trace elements, worm treatments and wetting agents, reports Alec MacIndoe of Newbury & Crookham Golf Club.

"It is really essential for us that the sprayer is operating efficiently and accurately. Andy has been on training courses for spray application and calibration and keeps up to date with new developments."

"Whilst we check, adjust and maintain the mowers through the workshop every week, it's fair to say that we possibly haven't given the sprayer the same level of attention in the past. If we are going to get the best results from the inputs used within the available budget, it makes economic and environmental sense to get the application and the timing as accurate as possible in the future."

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