Does weed detection and spot-spraying machinery pay off?

Spraying technology is expensive. A new boomspray decision tool from WeedSmart is now available to test real-world spot-spraying technology options before spending any money.

Peter Newman, WeedSmart’s western extension agronomist, says the per-hectare value of plant and machinery on broadacre cropping farms has increased dramatically in recent years, making machinery investment a ‘make or break’ decision in many cases.

“Whether you are adding weed detection sensors and cameras to a new sprayer or retrofitting an existing setup, growers need to be confident that the investment will pay off,” he says. “Working off a benchmark of spending roughly ten per cent of the farm’s income on machinery depreciation is one way to ensure the business can afford the additional technology.”

The WeedSmart Boomspray Decision Tool is an interactive spreadsheet that the user can customise to suit their farm, spray requirements, and financial situation. It can also be used to compare alternative spot-spraying technologies, including cameras, sensors and drone weed maps, on self-propelled (SP) sprays, trailing booms, and robots.

“Every farm is different, but the economic principles still apply. Using your own farm numbers is the only way to know if the investment is viable,” says Peter. “The neighbour might have the latest and greatest gear, but unless you know their financial situation and whether they have over-committed or not, you can’t know if their decision will pay off.”

“Using figures that describe your own situation means that you can determine whether the technology will save you money through reduced input costs, make you money through increased yield, or both.”

Weed detection and spot-spraying technologies fit within the ‘spray efficacy – make every drop count’ pillar of the WeedSmart Big 6 integrated weed management program to minimise the risk of herbicide resistance. These technologies have been evolving in Australia for decades, with adoption rates increasing as growers seek to capture the potential savings in herbicide use and labour hours, and the yield benefits of a low-weed farming system.

Using the WeedSmart Boomspray Decision Tool

The tool is a familiar spreadsheet file with built-in formulas and editable input cells. The user inputs their farm data, such as area, proportion of cereal, on-farm fuel price and the current value of machinery.

Next, the user enters a few details about the expected number of spray passes in fallow and in-crop, along with associated chemical costs. The decision tool then calculates the total value of chemical saved through spot-spraying ‘green on brown’ in summer fallow and spot-spraying ‘green-on-green’ broadleaf weeds in cereals.

Based on this information, the decision tool displays the expected cost per hectare for an SP boomspray, trailed boom, and robot, fitted with cameras, sensors, or drone-mapping technology to complete the required herbicide spraying operations.

The final section of the decision tool provides a detailed breakdown of the boomspray ownership costs for each of the nine machinery combinations. Again, the user can enter their own figures for depreciation, spray speed, boom width, fuel usage and labour units.

What does it take to break-even on weed detection technology?

The decision tool can calculate the number of blanket sprays that weed detection and spot-spraying technology would need to replace to make the $250,000 capital cost worthwhile. The cost of owning the equipment is around $35,000 per year to cover interest and depreciation (depending on algorithm costs etc).

Using figures for an ‘average’ farm over 3500 ha, this technology would need to replace one blanket spray, equating to a chemical saving of $35,700 per year.

Repeating the process for a farm over 2350 ha, the machine would have to replace 1.5 blanket sprays per year to save $36,000 per year in chemical costs.

Take away: If buying a new sprayer, it probably pays to add weed detection and spot-spraying capability, as the savings in chemical costs will generally cover the cost of ownership. Additionally, deploying this technology can help to control hard-to-kill weeds such as glyphosate-resistant weeds, improving the sustainability of the farming system.

Is an SP or a trailing boom best for my business?

Most growers already know that an SP boomspray requires a certain scale to be cost-effective. Trailing rigs are cheaper to buy but less comfortable to use and have less clearance than an SP sprayer, which can be important for some crops such as canola. We know already that adding weed detection and spot-spraying technology will pay for itself, regardless of the machine it is fitted to.

So, let’s assume a maximum $10/ha cost to own and operate for both the SP boomspray and the trailing boom. Using the decision tool, for an average farm to afford the $1 million capital cost for a new SP boomspray, the farm needs to be cropping 4900 ha or more to achieve the $10/ha target.

In comparison, a trailing boom has a capital cost of around $450,000 and is a viable option for a farm with a cropping area of 2000 ha. This costing is for the boomspray plus half of the cost of the tractor, given that this tractor does multiple jobs.

Peter says that this comparison does not include any added benefits that might flow from the spray rig completing other operations, such as fungicide or liquid fertiliser applications.

Purchasing second-hand machinery can also be a cost-effective investment, particularly for farms with smaller cropped areas.

Could a robot pay for itself at my place?

Robots, such as Swarmbots, are finding their place on larger farms, and when you run the decision tool, it is easy to see why – they can pay for themselves.

An autonomous robot towing a boomspray with green-on-brown sensors has a capital cost of around $660,000. If this unit replaces 1.5 blanket summer fallow sprays per year on a 7000-ha farm, the cost to own and operate this machine (after chemical savings) is $0.20/ha. This combination typically remains a viable option, at less than $10/ha ownership costs, for farms with a cropping area of 4000 ha or more.

These three sample uses for the WeedSmart Boomspray Decision Tool are provided for demonstration purposes only. The beauty of the tool is that it uses the key business numbers directly from the farmer who is making these major machinery investment decisions.

Download the WeedSmart Boomspray Decision Tool.

WeedSmart provides a practical planning framework and farming systems approach to integrated weed management to keep weed numbers low, maximise crop yield and improve long-term farm profitability.

Other resources

The economics of precision weed management (GRDC publication)

Webinar – Rise of the machines