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Three steps to accurate application

Accurate sprayer calibration is essential to know what volume of spray is being applied. Calibration is a straightforward process that, once established as a routine, takes just a few minutes and can make a significant difference to accuracy and results.

Calibration is a three stage process:

• Establish the accurate forward speed used when spraying

• Identify the output per nozzle

• Calculate the application rate per hectare

Check sprayer speed

Speed Check Lr

Sprayer Speed Check GC 

ACCURACY CHECK - At slower spraying speeds any differences dramatically affect application rate. If you aim to spray greens at four kmh, for example, but actually spray at three kmh, will increase the application rate by a massive 33%.

Check nozzle output

Check nozzle output at least twice a year, and ideally each month during busy spraying periods. Once nozzles start to wear, output rates can change very quickly and spread pattern will be affected. Firstly check for visible signs of damage.Refer to the manufacturers' nozzleoutput chart to establish expected flow rate,then measure output from each nozzle.

 

ACCURACY CHECK - Some trace element and liquid fertilizer formulations used in turf applications are particularly abrasive and can lead to high rates of nozzle wear. Check nozzles more regularly when using these products.

Nozzle Output Check GC 

ACCURACY CHECK - Always use a calibration cylinder for checking nozzle output; measuring jugs are good for measuring product, but are not sufficiently accurate for checking nozzle flow rates.

Calculate application rate

With the knowledge of the forward speed of the sprayer and the output from nozzles, the volume of spray being applied per hectare can be calculated:

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

Spray volume output can be adjusted by:

• Changing the forward speed

• Altering the operating pressure

• Changing to different sized nozzles

Use the free on-line Sprayer Set-up Calculator tools in the Syngenta GreenCast Application Zone website to see what changes are required to deliver any required water volume.

Case study calculation

To apply a water volume of 300 l/ha, using a sprayer with 0.5m nozzle spacing and operating at five kmh, for example, the GreenCast calculator shows that you require a nozzle output of 1.25 l/min.

Calculation 1 GC 

Refer to the nozzle manufacturers output charts to select an appropriate nozzle to deliver this output at an appropriate operating pressure, typically 2.5 to 3 kPa.

Having fitted the nozzles, set up the sprayer as you would use it and check the output per nozzle, you could find that the volume collected may be 1.35 l/min, for example.

 Calculation 1a GC 

The second GreenCast calculator would tell you that this combination would actually apply a water volume of 324 l/ha. With this knowledge, you could put 321 litres of water in the tank with 3 l/ha of Medallion TL, for example, and be confident that the correct product rate is being applied per m2.

However, if you want to correct the sprayer operation to deliver precisely 300 l/ha, the GreenCast Calculator shows how to adjust the sprayer speed (which in practice can be difficult to reliably achieve), or to adjust the operating pressure - which can be more precise for fine tuning, providing the spray pattern is not compromised.

Calculation 2 GC 

In this case, either increasing the speed to 5.4 kmh, or reducing the operating pressure to 2.57 kPa, would both have the desired effect.

The GreenCast calculators enable you to work out any given set of permutations to achieve the desired result.

Nozzle size choice

If any changes to required deliver a specific water volume are outside the realistic operation of a particular nozzle size, it will be necessary to change the nozzles to a smaller or larger size orifice.

For most turf applications applying foliar treatments on greens or fairways at 250 to 350 l/ ha - typically at four to seven kmh - a set of .025 and 04 nozzle will be most appropriate to cover the range. For soil target treatments requiring higher water volume, such as wetting agent or Fairy Ring fungicides, an 08 nozzle will apply a 500 - 700 l/ha at six to seven kmh.

Nozzle Set Lr 

New Syngenta XC Nozzle range available in 025, 04 and 08 sizes - to be launched at BTME in January 2013.

ACCURACY CHECK - Sprayer calibration will tell you precisely the water volume being applied, but it is equally important to know the exact size of the area being treated to ensure consistent accurate application. GPS mapping of greens and fairways is becoming increasingly available. and affordable.

 Checklist GC

• Calibrate sprayers regularly, especially during busy periods

• Inspect sprayers for leaks or damage during calibration

• Record results of nozzle set calibration and sprayer settings

Replace the whole set of nozzles if any are worn

• Use a Syngenta Calibration Checker for quick results

• Check nozzle height is 50cm

Click here or on the image below to download a PDF of this ETech Bulletin

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