Spray Application Rates Demystified: How To Apply The Right Amount Of Product

Let’s be honest.

When it comes to working out the application rate for boom spraying it’s easy to come unstuck.

And when we stuff it up it’s a costly exercise. For instance, if we put on 10% more chemical than we need, the chemical ends up costing us 10% more than we planned.

It’s actually quite simple to apply the right amount of product once you know what factors to consider.

3 questions to ask yourself when calculating your spray application rate

1. “What pressure is running through my pump?”

  • Check the pressure gauge on your equipment (or call us if it’s not working!)
  • Most boom sprayers are around 3.5 bar which is about 50psi
  • Here’s a handy calculator if you need to switch beween PSI and Bar

2. “What colour (size) nozzles am I using?”

  • Nozzle size (and therefore flow-rate) is normally identified by nozzle colour
  • Most farmers use blue (#03), red (#04) or brown (#05) for general spraying
  • The examples below for boom spraying are the latest and greatest nozzles from AIXR TeeJet (these are great if your existing nozzles are a little tired)

AIXR TeeJet tips.

3. “How fast will I be driving?”

  • Level farms are suited to speeds of around 8-10 km/h, whereas hill country is normally more like 4 km/h
  • More important than the speed itself is the consistency of speed (to ensure even application)

So What’s Next?

With a handle on the above 3 things, use the chart below to find your desired application rate.

For example, if your product calls for 200 litres per hectare, here are two of the many options available:

  • 3 Bar pressure, Red (#04) nozzle, 9kph or
  • 1 Bar pressure, Blue (#03) nozzle, 4kph

Do you have your own application rate question? Leave a comment below, or call me (Mike) on 07 847-7811.

Application Rate Chart