GrowNotes

Spray application manual

Module 5: Completing a spray plan

5.2 Where to start

Published 24 January 2025 | Last updated 20 January 2025

There are two things to establish before you prepare a spray plan:

the speeds you will spray at and how the products you are using need to be applied.

Determine the actual range of spraying speeds for all paddocks

Experience will tell most operators what a reasonable spraying speed is for their current sprayer. However, when operating a new spray rig or tractor, a reasonable spraying speed will need to be established before you can make the best decision about the types and orifice size of nozzles that will be required.

It is important to check and record what the range of travel speeds is in each paddock.

Identify paddocks where the layout, obstacles, contour banks, washouts or sandhills are likely to affect spraying speed. Determine what the constant or average travel speed will be in each paddock and work out what the minimum average/constant and maximum travel speeds are likely to be.

This helps to determine the minimum pressure, flow and speed for each nozzle type you are considering, as well as the possible need for minor adjustments to the application volume and/or speed to ensure the nozzles are operating correctly and the spray quality is appropriate.

Make a list of the products likely to be used

Once the speed range of the sprayer has been established, consider what types of products are likely to be applied throughout the season. This allows you (the spray operator) to select and purchase all of your required nozzles, gaskets and caps before the start of the season and to prevent delays later on.

Discuss your product requirements with your adviser or agronomist. List all of the jobs you are likely to do and the typical application volumes (litres per hectare) for each.

Consult each of the product labels for the spray quality and buffer (no-spray zone) requirements.

Tip

Group similar job and application requirements together before purchasing nozzles. With thoughtful consideration and planning, the majority of broadacre spray applications can typically be achieved with two or three different set of nozzles

For example, spray jobs that most grain growers would undertake throughout the season would include:

fallow spraying;

  • translocated herbicides (60 to 80L/ha, coarse or larger, with a minimum of Very Coarse or larger for 2,4-D products)*; and

  • contact herbicides or double-knocks (80 to 100L/ha, medium or coarse)*.

pre-emergents (100L/ha, coarse or larger)*;

early broadleaf control (70 to 80L/ha, coarse)*;

grass-selective sprays in-crop (80 to 100L/ha, medium or coarse)*;

fungicide and insecticide in-crop (80 to 150L/ha, medium or larger)*; and

pre-harvest desiccation: (80 to 120L/ha, coarse or medium)*.

Tip

These application volumes and spray qualities are examples only. Your requirements may vary depending on product label, stubble load, canopy size, conditions, and the presence of sensitive areas.

Find out more

Further information: Nozzle Selection Guide

Identify how many nozzle set-ups will cover the range of applications you may need to do

Summarising the examples listed in section 2.2 above, we could come up with at least four set-ups to cover most situations:

•                low volume very coarse (60 to 80L/ha);

•                high volume coarse (80 to 100L/ha);

•                low volume medium (80 to 100L/ha); and

•                high volume medium (120 to 150L/ha).

If maintaining a reasonable travel speed to ensure good timing is your priority, then these four set-ups may require four different sets of nozzles. However, if you are willing to adjust your travel speed (without sacrificing too much efficiency or timeliness), it may be possible to achieve these four set-ups with just two or three sets of well-chosen nozzles.

For example, by slowing down and increasing the application volume, it may be possible to use the same nozzle set-up for translocated herbicides as for pre- emergent herbicides or for pre-harvest desiccation. Similarly, the nozzle set-up used for grass-selective sprays may be used for fungicides if the spraying speed is reduced and the application volume increased.

Consider sensitive areas, buffer requirements and suitable conditions for spraying

Good farm maps highlighting sensitive areas are essential for planning applications and are important for spray operators to have available when spraying. Knowing where the sensitive areas may be on your property and on neighbouring farms is important to consider for any spray job, particularly in relation to wind direction and label buffer zones.

Where sensitive areas are downwind of the common prevailing wind patterns it will be important to also ensure that a set of extremely coarse or ultra coarse nozzles are available and are utilised for initial spray passes along the edge of the paddock closest to the sensitive area. Often when using these drift reducing nozzles the application volume will need to be increased to compensate for the smaller number of droplets produced.

As the spraying operation moves further away from the sensitive area it may be appropriate to switch back to a more conventional droplet size and water rate.