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Easy steps to sprayer calibration | Ask the Industry

Senior Solutions Development Manager, Scott Mathew
Senior Solutions Development Manager, Scott Mathew

Too little or too much can have a big impact when making applications to vegetable crops. Syngenta Senior Technical Services Lead Scott Mathew provides practical advice on how growers can calibate their spray units to apply the precise quanties required.

My spring column included a checklist for those wanting to be well prepared for the busy spray season ahead. Following on from that article, I’d like to remind growers of the importance of maintaining an accurately calibrated spray unit throughout the year.

Correctly calibrated equipment really is the foundation for applying crop protection products evenly and at the recommended rate. Too much product can damage the crop and harm the environment. It‘s also a waste of money. A failed result from under dosing can cost you even more when the control isn’t what it should be.

There are different ways to calibrate a spray boom; however, I find that the following steps are simple and accurate:

Step 1

We need to start the calibration with a machine that is correctly set-up and in good working order. All filters and nozzles need to be clean and the spray pressure must be correct for the selected nozzles. Output across the boom must be uniform. Replace nozzles that have 5% or more variation from the manufacturer specifications. If more than two nozzles fail the flow rate test, it’s best to replace the whole set.

Nozzle output should be measured in L/min.

Using the Syngenta 11004 Potato nozzle as an example, the output at 3 bar (43.5psi) should be close to 1.58L/min.

Step 2

Check the driving speed. Mark out 100 meters and measure the time taken (in seconds) to travel that distance and use the following driving speed formula.

Driving speed (km/hour) = Distance driven (m) X 3.6

                                                Time (sec)

As an example, if it takes 45 seconds to travel the 100 metres, then the calculation would be:

100 multiplied by 3.6, divided by 45 gives a driving speed of 8 km/hour.

You should do your speed test under field conditions. A speed test done on the road may vary significantly from what you do in the paddock.

Step 3

Calculate the application volume or boom output using the following formula:

Boom output (L/ha) = Nozzle output (L/min) x 600

                                    Nozzle spacing (m) x Speed (km/hour)

Using the Syngenta 11004 Potato nozzle as an example with:

nozzle output of 1.58L/min (per nozzle)
nozzle spacing of 0.5m
driving speed of 8km/hour

the application volume calculation of the boom spray would be:

Boom output (L/ha) =  1.58 x 600
  0.5 X 8

The application volume equals 237 L/ha.

And that’s all there is to it. Sprayer calibration is not difficult and doesn’t take a lot of effort. It’s worth taking the time to ensure your equipment is operating efficiently and monitoring the output over the season. Don’t forget to update your calculations a few times a year, at least.


Handy conversions

Thumbing through some old notes I found some useful conversions that relate to spraying when comparing our metric system with imperial. You might find them handy, especially if you read a lot of US articles.

  • 1 ton per acre equals 2.24 tonnes per hectare
  • 1 pound per acre equals 1.12 kilogram per hectare
  • 1 gallon per acre equals 9.35 litres per hectare
  • 1 fluid ounce per acre equals 73 millilitres per hectare
  • 10 metres is approximately 11 yards
  • 10 square meters is approximately 12 square yards
  • 10 cubic metres is approximately 13 cubic yards