Spray application manual
31 January 2025
Module 18: Single line and multi-step systems
18.3 Operating range for a 4-nozzle multi-step system
Published 24 January 2025 | Last updated 20 January 2025
A four-nozzle multi-step system may be set up by using four nozzles per outlet across the boom (e.g. at 0.5m), or by having two nozzles per outlet, using half the normal nozzle spacing (e.g. 0.25m). Table 6 provides an example of the equivalent flow rates that can be achieved using a four-nozzle multi-step system.
Depending on the nozzle orifice sizes chosen, a four-nozzle system can offer 10 or more steps, which can provide flow rates ranging from the equivalent of an 01 orifice through to the equivalent of an 07 (or larger) orifice.
A grower's view on multi-step systems
24 January 2025A grower's view on multi-step systems. Another video from GRDC's Spray Application GROWNOTES™ series.
Graham Betts: We're at Ashley Wakefield's property in Tingarra which is halfway between Maitland and Middleton in South Australia and we're looking at the arag seletron four fold system, and I'd just like to ask Ashley why did you go to the expense and the trouble of putting this system on Ash.
Ashley Wakefield: Basically I was wanting to get smaller sections. I had always tried to get down to smaller section sizes so we didn't have as much overlap and doubling up on our chemical and causing crop damage. To me when I saw this system individual nozzles was to me one of the most exciting things I've seen in the spraying industry, just being able to turn off each individual nozzle one at a time on its own was fantastic.
Graham Betts: Reliability Ashley - how is it going for reliability? because it is electrics and electronics in the past have been a bit hit-and-miss.
Ashley Wakefield: Touch wood it's been really reliable so far. I've just had it on nearly two years now and haven't had any problems whatsoever with the electronics so hopefully it'll keep going that way.
Graham Betts: And what speed range have you been able to achieve with this?
Ashley Wakefield: The beauty of this system because we've got the fourfold is I can vary my water rate, my speed and my droplet nozzle size without having to change any of the nozzles. We've got four nozzles there and manipulating pressure and also speed we can get exactly the right spray quality we want to do the job I want.
Graham Betts: So it's not be all that ends all, you can't not swap your nozzle and you've got a fertilizer nozzle on here.
Ashley Wakefield: That's correct, yeah. So if I want to go and do fertiliser spraying I'll use the fertiliser nozzle, but for all my spray applications I can leave those spray nozzles on there and do almost just about every job I want.
Graham Betts: So all your systemic, contacts, soil products, residual products, you use the same nozzle combination, just vary your pressures and settings.
Ashley Wakefield: Correct, yep. So just by using lowering my maximum pressures for courser droplets and increasing the pressure for finer droplets I can manipulate all those spray qualities just by using those four nozzles.
Graham Betts: In your farming career, and you say to me it's about 40 years what are the things that have had the biggest influence on your farming practice?
Ashley Wakefield: Probably one of the first things that came in with GPS, we knew exactly where we were in the field, followed closely by auto-steer, because of GPS obviously, so saves a lot on overlap and therefore costs, and to me the next thing along was the seletron. Because we can do each individual nozzle we're not over-spraying, so I'm not spraying any more than probably half a square metre on my property at any one time. So I think that's been a real cost saving.
The nozzles engaged and equivalent flow rates possible for a four-nozzle multi-step system
Tip
When using a half nozzle spacing where different nozzle orifice sizes are operating at the same time (e.g. 01 and 015, or 015 and 02 at a 0.25m nozzle spacing), set the boom height to achieve a double overlap for each orifice size, which would be equivalent to using a 0.5m nozzle spacing.
For the example included in Table 1, when operating with 01, 015, 02 and 025 orifices fitted to a four-nozzle system and applying a rate of 100L/ha, this system could operate from about 4.3km/h up to more than 40km/h (although driving at 40km/h is possible when the tank is empty, it is not recommended for spraying). Alternatively, this combination of nozzles could apply more than 200L/ha at spraying speeds of up to 21km/h.
Nozzle type and transition points
When planning the transitions between nozzles, the operator needs to consider what the minimum flow rate of the next nozzle in the desired sequence will be, and to ensure that the spraying system has reached that flow rate before the transition occurs.
For example, if an operator has selected to use a multi-step system fitted with four low-pressure air-induction nozzles per outlet (a four-nozzle body and each outlet is fitted with 01, 015, 02 and 025 orifice sizes), then the transition from the 01 orifice to the 015 orifice should not occur before the 01 orifice has a flow rate of 0.48 litres per minute per nozzle, which is equivalent to the flow rate of a 015 orifice at 2 bar (refer to Table 2 for an example).
Table 2 also shows that the transition from the 015 to the 02 should not occur until the flow rate of the 015 has reached at least 0.65L/min per nozzle (equivalent to the flow rate of an 02 orifice at 2 bar).
This process should be followed for each transition between orifice sizes or combinations of the orifice sizes (see Table 2). The minimum flow rate of any combination of nozzles can be calculated by adding the minimum flowrate (at 2 bar for low pressure air induction) for each nozzle in that combination:
e.g. 035 minimum flowrate = 015 min (0.48L/min) + 02 min (0.65L/min) = 1.13 L/min
The first 4 transitions possible between nozzles for a 4 nozzle multistep system
With small increases in the orifice size between each step it is possible to transition between nozzles (or combinations of nozzles) before the maximum pressure of each nozzle is reached. This allows for greater control of the pressure at the nozzle to achieve the desired spray quality, provided the flow rate per nozzle is sufficient to operate the next nozzle (or combination of nozzles) in the programmed sequence.
In the example given in Table 2, once the 025 orifice size is reached, there are two possible transitions shown, from 025 at 3bar to the 03 equivalent (red arrows), or from the 025 at 4 bar directly to the 035 equivalent (green arrows). The choice of when to transition between orifice sizes must consider the preferred spraying speed and application volume/s and also the spray quality produced.
Avoid spraying at speeds that align with transition points between nozzles.
Achieving the desired spray quality
Once the nozzle orifice sizes have been selected and maximum pressure for transitions between each has been established, a nozzle chart can be consulted to find nozzles that produce the spray quality required (see Table 3).
From Table 3 we can see that the Lechler IDK-120 nozzles between 01 orifice and 025 orifice sizes can all produce a coarse or larger spray quality at pressures of 4 bar or lower, and all orifice sizes produce a medium spray quality at 6.0 bar.
If selecting this nozzle type, it would allow the operator to change spray quality by changing when the transitions between nozzles occurs to match the required operating pressure.
For a coarse spray quality or larger the transition should occur at 4 bar and for a medium spray quality the nozzles would need to be operated at 5 to 6 bar.
Spray qualities produced by a selection of air-induction nozzles from 01 to 025 orifice sizes
Steps and transitions for a four-nozzle multi-step system to achieve a Coarse spray quality or larger at 100 L/ha
When using a four-nozzle multi-step system, to provide for the lowest practical spraying speed it is useful to consider starting with the 01 orifice nozzle. However, there are few low-pressure air-induction nozzles available of the 01orifice size that can produce a coarse or larger spray quality (see Table 3).
Typical steps when operating a four-nozzle multi-step system
Tables 4 and 5 show the first 7 steps for a four-nozzle multi-step system. The tables highlight suitable spraying speeds (green boxes) to achieve a coarse spray quality or larger at an application volume of 100L/ha using Lechler IDK 120 at 0.5m nozzle spacing.
Guide to reading tables 4 and 5
Select spraying speeds highlighted in bright green boxes
Avoid spraying at speeds with highlighted by orange boxes
Set the rate controller to transition between the current nozzle and the next nozzle/s listed in each step (on the left of each table) at speeds where a red box with larger white text exists, or at flowrates (litres per minute per nozzle) highlighted by bold red numbers, or at pressures which align with either of these.
Where a minimum hold function exists in the controller (set as a pressure or flowrate for each nozzle), this is suggested as bold black text. For low pressure air induction nozzles this is usually at a pressure of 2 bar).
Failing to set appropriate transitions can lead to inappropriate spray qualities being produced and/or exceeding suitable operating parameters for the nozzles.
Step 1 to 4 for a four-nozzle multi-step system fitted with 01, 015, 02 and 025 orifice size
From Table 4, showing steps 1 to 4 for an application volume of 100L/ha, the operator can determine suitable minimum spraying speeds to achieve a coarse spray quality or larger at 100 L/ha.
By carefully evaluating the range of operating pressures, spray quality produced and spraying speeds that align with these pressures, the transition points can be determined. This information should be recorded in a spray plan, as well as in the rate controller.
Tables 5 shows the next 4 steps possible for a four-nozzle multi-step system applying a rate of 100L/ha to achieve a coarse spray quality or larger. Note that one of the possible steps (using the combination equivalent to a 04 orifice flowrate) does not improve the speed range or spray quality, so has not been suggested as a step to be programmed into the controller.
Step 5 to 7 for a four-nozzle multi-step system
The ideal rate controller for a multi-step system would allow the operator to ‘save’ or ‘store’ a programmed sequence for a coarse spray quality and another sequence for medium spray quality. Where such a function is not available, the operator should produce a spray plan and record where the transition points should be programmed when changing between spray qualities (e.g. from coarse to medium). While it may take several minutes to enter the information into the controller to tell the system when new transitions should occur to change the spray quality, this will still be much faster than changing a complete set of nozzles.
Steps and transitions for a four-nozzle multi-step system to achieve a Very Coarse spray quality or larger at 100 L/ha
Where a Very Coarse (VC) or larger is required with 01 to 025 orifice sizes, the TeeJet TTI (from Table 3) with a minimum pressure set to 2 bar could be used, or the operator could choose high pressure air induction nozzles such as the Lechler ID3 (see Table 6).
A change to higher pressure air induction nozzle would require the minimum pressure for each nozzle to be increased to 3 bar, which in turn requires a higher flowrate before transitioning from one nozzle to the next.
Examples of high-pressure air induction nozzles between 01 and 025 orifice sizes
Where the operator is seeking to use a 4-nozzle multistep system to apply 100L/ha with high pressure air induction nozzles, it can be seen if a Lechler ID3 was chosen, a VC spray quality can be achieved up to 5 bar for the 01 through to 025 orifice sizes, so this is the logical transition pressure between each nozzle or combinations of nozzles.
Tables 12 and 13 show the first 8 steps possible for a four-nozzle multi-step system. The tables highlight suitable spraying speeds (green boxes) to achieve a Very Coarse (VC) spray quality or larger at an application volume of 100L/ha using Lechler ID3 nozzles at 0.5m nozzle spacing.
Guide to reading tables 12 and 13
Select spraying speeds highlighted in bright green boxes
Avoid spraying at speeds with highlighted by orange boxes
Set the rate controller to transition between the current nozzle and the next nozzle/s listed in each step (on the left of each table) at speeds where a red box with larger white text exists, or at flowrates (litres per minute per nozzle) highlighted by bold red numbers, or at pressures which align with either of these.
Where a minimum hold function exists in the controller (set as a pressure or flowrate for each nozzle), this is suggested as bold black text. For high pressure air induction nozzles this is usually at a pressure of 3 bar).
Failing to set appropriate transitions can lead to inappropriate spray qualities being produced and/or exceeding suitable operating parameters for the nozzles.
Step 1 to 4 for a four-nozzle multi-step system fitted with 01, 015, 02 and 025 orifice sizes
Steps 5 to 8 for a four-nozzle multi-step system fitted with 01, 015, 02 and 025 orifice sizes
Considerations for operating four nozzle multi-step systems
Understand why you may need a multi-step system before considering a purchase. Unless you have large variations in spraying speed in single paddocks, or large variations in application volume between paddocks, it may not be necessary for your situation.
Work out the transition points between nozzles, based on the minimum pressure required to operate the next nozzle (or combination) in the sequence.
Do not operate any nozzle outside of the manufacturer’s recommended range of operating pressures.
Avoid selecting spraying speeds near a programmed transition point between nozzle orifice sizes. If this is not practical, the operator should consider changing the transition point in the rate controller to avoid the transition between nozzle sizes occurring at speeds close their preferred spraying speed (this may impact spray quality and therefore nozzle choice).
Avoid spraying at speeds where the nozzles are operating at the lower end of the operating pressure, or the spray quality is too coarse for the target and tank mix with the selected nozzle type.
Select nozzles that produce the required spray quality or larger within the pressure range for each transition, noting that it is unlikely that a single nozzle type or model can do every job.
Understand how to change transition points in the rate controller to achieve different spray qualities and be prepared to do this when required. e.g. where a transition may currently be set to occur at 4 bar for a particular nozzle and orifice size to maintain a coarse spray quality or larger, this may be able to be increased to 6 bar to obtain a medium spray quality or larger.
Consider a range of spraying scenarios, such as combinations of different nozzle types to achieve each of the spraying jobs you are likely to encounter. This may take two complete sets of nozzles to achieve.