Choosing and justifying the right sprayer

Take home messages

  • There are many variables to consider when choosing a sprayer, and each will be weighted differently from business to business depending on the farming model utilised, (enterprise mix, farming system, typical rotation, spread of farming operations, etc.), the need or want to optimise efficiency, and availability of labour and lifestyle decisions. Make sure you get the right horse for your course regardless of what the neighbour has.
  • Before upgrading the sprayer there may be options to increase overall efficiency of the existing sprayer.
  • The capital invested can be similar between a self-propel (SP) and a tow-behind outfit when aiming to match field capacity.
  • Alternative uses for the sprayer, and the likelihood of spraying where higher clearance is required, are key determinants in type of machine and cost-of- ownership.
  • Tank size and boom width can sometimes be a trade-offs against spraying speed.


Choosing the right sprayer and justifying its ownership cost can be a challenging task. There’s a lot of variables and trade-offs to consider when making the decision, and the importance of each varies from business to business. The sprayer is often the most used implement on the farm, and therefore, it’s important to get the decision right. Taking a structured decision making approach can help take the stress and uncertainty out of making this decision.

Structured decision making approach

Step 1. What spraying tasks and timelines do I need to achieve?

Spraying objectives, or targets around getting the spraying done on time, can vary considerably from business to business. While often not written down, each business usually has a number of ‘spraying objectives’ they aim for to ensure timeliness of operations. Examples of some spraying objectives include:

  • Complete post-emergent grass selective herbicide application early (i.e. before tillering of weeds).
  • The ability to spray the area of susceptible cereal crop varieties in three days should a stem rust incursion break out.
  • The ability to get clethodim out within a 4hr/day ‘window of opportunity’ during winter in the Western district to minimise the effect of frost on herbicide efficacy.
  • The ability to apply herbicides during late stages of crop development (crop-top) to any crop type with minimal crop damage and good spray coverage.

Step 2. What will affect these timelines?

Besides physical limitations such as sprayer clearance height, the ability for your spraying outfit to meet your spraying objectives in a timely manner, will be influenced by the ‘work rate’ of your sprayer inside the paddock and efficiencies impacting on timeliness outside the paddock.

Inside the paddock

Work Rate (Effective field capacity)

The theoretical capacity (ha/hr) of a machine to perform its work whilst in the paddock is defined as ‘Theoretical Field Capacity’ = width of boom (m) x speed of travel (km/hr) / 10
However, we know that there are factors that affect the ability for a machine to operate at its maximum width or speed at all times, while in the paddock. Hence the theoretical field capacity of a machine is adjusted down by a factor known as the Field Efficiency Percentage (FE %), which is the percentage of time the machine operates at its fully rated speed and width while in the paddock. The result is the Effective Field Capacity, or true ‘Work Rate’ that can be used to assess true productivity in the paddock.

‘Work Rate’ (Effective field capacity) = (width of boom (m) x speed of travel (km/hr) / 10 ) X FE % 

An example is provided in Table 1.

Table 1. Calculation of Work Rate.

  Units Example
Boom width Metres 36m
Spraying speed Kilometres/hour 25km/hr
Theoretical field capacity Hectares/hour 90ha/hr
Field efficiency Percentage 80%
Work Rate (Effective field capacity) Hectares/hour 72ha/hr

Examples of factors that affect the width or average speed of the spraying unit whilst in the paddock include:

  • Water rate limitations (will this limit speed due to inadequate pump capacity, or nozzle size or number?).
  • Spray efficacy limitations
    o Wind
    o Dust
    o Technology to allow correct droplet size at increased speed (e.g. AIM Command®, Three Tier System (3TS)®).
  • Paddock landform and topographic feature limitations
    o Soil type and steepness can affect trafficability.
    o Paddock shape, undulation, obstacles (trees, dams, channels, swamps, etc.) and terrain (rocks, corrugations) can all limit speed and width (overlap).
  • Overall power, gearing, weight and balance
    o an underpowered machine will restrict speed
    o inadequate gearing range can affect speed
    o is the machine too heavy for the rainfall zone and soil type, hence may sink?
    o an unbalanced machine may have a restricted speed
  • Downtime
    o Breakdowns, blocked nozzles; could these be eliminated with better preventative maintenance?

Efficiencies impacting on timeliness outside the paddock

With a spraying outfit, there are significant factors outside the paddock that also impact on the overall timeliness of the spraying operation. These factors can often be improved for low cost regardless of which spraying outfit you use.

Examples of efficiencies outside the paddock, and what influences them, include:

  • Fill time
    o Pump and hose size (e.g. 1.5” connection to chemical shuttle =60L chemical/min; 4” water hose faster than 3” > 2”, etc.).
    o Induction technology.
    o Batching plant (often requires additional labour).
    o Mounted pump.
    o Quick fill systems (for example, overhead water loading, nose connector)
  • Travel time
    o Spread of farming operations and/or distance between paddocks.
    o Road speed (empty and loaded).
    o Block cropping (less clean-outs).
    o Distance to fill points (versus a ‘nurse tank’ could be used to take water to the sprayer instead, however this may require extra labour which will be need to be accounted for).
  • Clean out time
    o Flush technology.
    o Block-cropping.
  • Tank size – if tank size is matched to paddock size (subject to weight considerations) this can mean less time spent travelling and filling.
  • Breakdowns (lack of preventative maintenance?).

Efficiency factors both inside and outside the paddock can be highly variable between farms. Growers should continually ask themselves what could I be doing differently to improve current efficiencies, and therefore, overall timeliness of the operation.

Step 3. What options do I have to achieve my timelines?

The main options as with most plant and machinery is self-ownership, use of contractors, or a combination of the two. The key questions to ask with respect to each include:-

Self ownership:

  1. Do you need:
    • Alternative uses – am I looking for a dedicated spraying outfit or do I also need a ‘third’ tractor (for example, front end loader (FEL), spreader or chaser tractor), or self-propel (SP) that can be used for windrowing also? An alternative use can effectively subsidise the cost of ownership of a machine.
    • Clearance height – what’s the likelihood of needing to spray where higher clearance is required (for example, taller crop types (e.g. canola, sorghum/corn) or late season applications (e.g. fungicides/insecticides/desiccation/crop-topping, late season liquid N)). If likely, are contractors available if you haven’t got the clearance?
  2. What can I afford? (refer later section)

Contractors usually come with the latest and greatest machines, which can usually handle all applications and are modern, economically justified machines due to the area that they cover which increases the utilisation of the equipment. Are you confident you can get them in a timely manner and not compromise productivity? Is it cost effective to own your machine? (refer later section)

For example, by owning a tow-behind you get the alternative use from the tow-tractor and you can engage a contractor for the high-clearance spraying. The consideration for operations, is can you get the contractor when needed?

Step 4. Ownership & costs – What can I justify?

Table 2 provides a comparison of different types of sprayers. In summary however a few features of each type of sprayer are listed. (Note: Less attention has been paid to truck mount sprayers given the limited number operating on Victorian farms):

  1. Tow-behind
    • Handles most applications.
    • Choice of larger tank sizes.
    • Clearance issues late in season.
    • Multiple alternative uses for towing tractor.
  2. Truck or tractor mount
    • Fastest road speed full or empty.
    • Choice of larger tank sizes.
    • Clearance issues late in season.
    • Visuals sometimes compromised.
    • Limited alternative use.
  3. Self-propel
    • Great clearance - specifically designed for spraying hence suitable for all spray applications.
    • Great traction.
    • Best comfort.
    • Superior visuals.
    • Good road speed.
    • Modern technology (for example, AIM Command®).
    • Higher fuel use (hydrostat).
    • Limitations on tank size.
    • Limited alternative use.

Table 2. Comparison of different types of sprayers.


Justifying an investment in a machine is a balance of financial and non-financial considerations.

The primary financial consideration is cost of ownership, which will be influenced by:

  • Capital cost (i.e. the loss in value of the machine each year, plus the appreciation in value of its replacement and an allowance for the opportunity cost of the money invested into purchasing the machine which could have been invested via another means). This ‘changeover’ cost can be 35-40% of the total cost, so keeping it to a minimum has a big influence on overall ownership cost. Factors that affect changeover cost include:
    o Engine hours on trade.
    o Age of trade
      - Obsolete model or technology.
      - Access to parts.
      - Poor condition.
    o New technology – the sky’s the limit so be critical on what you really need. For example, do I need auto-height, auto-greaser, etc.?
    o No-trade discount.
    o Factory incentives.
    o Exchange rate.
    o Poor reputation.
    o Poor dealer support.

Table 3. Some ‘actual’ variations in capital cost of SP sprayers sold within various regions of Victoria (Source: ORM Pty Ltd).

  Wimmera Western District North Central
Age (years) 5 4 3.6
Changeover price ($) 205,000 192,000 142,000
Engine hours 2,000 1,950 2,550
Hours per year 400 488 676
Changeover (depreciation)/year ($) 42,000 48,000 39,628
Changeover (depreciation)/Eng. hr ($) 103 98 56


Some growers have a defined policy around changeover time based on engine hours (for example, 2000 hours), age (for example, 5 years old) or model (for example, within one model of current model). Whereas others will keep an active eye on the market and buy whenever the price is right (for example, Wimmera grower in Table 3 will upgrade whenever changeover is < $100/

The full scale of financial benefits of ownership, needs to be evaluated as an offset to the costs, these benefits will be driven by the following factors:

  • Field capacity and field and non-field efficiencies, as outlined in Step 1.
  • Alternative uses for machine - can ‘subsidise’ the sprayer costs.
  • The percentage of spraying needed to be done by contractors.
  • Other fixed costs (interest, rego/insurance) – can be up to 25% of total costs which is a big contributor.
  • Fuel usage – hydrostat SP can use double the amount of a tow-behind, but overall fuel cost is influenced by field capacity and field efficiency.
  • Labour cost – dependent on machine hours.
  • Scale – spread of costs (particularly the fixed costs) over area sprayed per annum ($/ha).

When assessing cost of ownership, it is advisable to compare it to the cost of using a contractor. Once this comparison has been made an informed assessment can be made as to whether ownership is cost-effective. The final decision will however also be impacted by non-financial considerations and the timing of the planned upgrade.

Non-financial considerations include:

  • Job satisfaction – the sprayer is the most widely used implement on farm, operator comfort, health considerations (e.g. bad back) should be considered.
  • Interest and/or expertise in machinery – sometimes it’s easier to let the contractor worry about ownership issues and access to labour, and get the latest and greatest technology turn up each year.
  • Attracting and retaining employees – varies between regions.
  • No financial pressure.
  • Family time.
  • Stress – being able to get the contractors when you want them.
  • OHS

Non-financial considerations are harder to quantify than financial considerations. Each grower has to put their own weighting and dollars on these variables depending on their personal preferences.

In regards to timing, sometimes a decision to upgrade can be justified based on a simple cost : benefit analysis, but there may be other immediate priority uses for that capital or existing financial commitments that already limit cash flow. Some useful overall machinery investment benchmarks to consider include:

  • Alternative/priority uses for capital – i.e. what other ‘big-ticket’ items are coming due for an upgrade and will investing a certain amount of capital in improving your spraying capacity limit you from getting the balance and timeliness right in other areas?
  • Overall capital invested in machinery – ORM benchmarking show that the typical investment in machinery is $1 for every $1 of income generated, or a ratio of 1:1. Some businesses can maintain a 0.8:1 ratio without compromising timeliness, which means in a farm business generating $1,000,000 income, $200,000 of capital can be invested elsewhere.
  • Total (horse) power, machinery and labour cost (TPML) – what is the total annual cost of machinery capital, machinery operating costs (fuel, repairs, contractors), and labour (including your own). A figure under 40% of income is good, under 35% is great
  • Cash flow implications – machinery is often financed over five years and too much spent on machinery upgrade all at once can run down cash flow, particularly in a poor income year. Machinery repayments (principal and interest) below 13% of income is generally OK if other key-cost areas in the business are balanced.


Choosing and justifying the right sprayer doesn’t have to be a difficult process. Taking the time to fully evaluate what capability you need, and the options and costings associated with achieving that capability, will ensure that you get the right horse for your course.

Contact details

Brett Symes
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