Machinery prices have sky-rocketed in recent years, leaving many growers wondering whether new technologies, like optical spot sprayers, can pay their way.
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Peter Newman, Planfarm farm business consultant and WeedSmart western extension agronomist, has run some figures for his clients to help them with boomspray purchase decisions, and found that the benefits often outweigh the upfront cost of weed detection technology.
"Generally, optical sprayers will pay for themselves through herbicide savings in situations where a grower is doing at least one pass for summer weed control and spraying broadleaf weeds in cereals," he said.
"Our growers are often contending with high levels of resistance in broadleaf weeds such as wild radish in cereals. While the numbers are low due to good management over many years, the resistant individuals cost a fortune to control."
However, if growers are still achieving good broadleaf weed control in cereals with cheap (e.g. $10/hectare) herbicides, green-on-green weed detection in crop may not pay its way.
Some growers are also starting to notice an increase in glyphosate-resistant ryegrass numbers, and weed detection cameras will help to control the survivors with alternative knockdown herbicides registered for use at higher rates through optical sprayers.
Mr Newman based his analysis on the average WA farm from the 2022 Planfarm Benchmarks. This average farm has a total area of 4600ha, growing 2400ha of cereals and 1200ha of break crops, with the remaining 1000ha winter-fallowed or pasture. The assumed cost of a summer spray was $15/ha, and the four levels of broadleaf weed control in cereals ranged from a cheap, single spray of $10/ha to a high-cost, two-spray strategy at $45/ha just for the herbicides.
The initial investment to fit weed detection cameras or sensors from Bilberry, WEED-IT, WeedSeeker or See & Spray Select to a 36 metre boom was set at $150,000, and the analysis included the ongoing algorithm fees (for the Bilberry system). These systems can save around 90 per cent of herbicide cost for both green-on-brown and green-on-green (in-crop) spraying, but for the analysis, Peter used an 85pc saving. He depreciated the equipment at 10pc per year and included $2 to $4/ha for repairs, depending on the boomspray type.
The results of the analysis for this average WA farm suggest that if summer spraying the whole 4600ha farm with a blanket application costs $69,000, swapping to a spot sprayer will reduce the herbicide cost by 85pc, down to $10,350 using a green-on-brown system such as WEED-IT, WeedSeeker or See & Spray Select, or $21,850 if using the Bilberry system, taking into account the annual algorithm fee.
All optical sprayers are very useful for the second or third knock in fallow systems to control surviving weeds, including glyphosate resistant weeds.
Assuming the wild radish is hard to kill in the cereals, the analysis is based on blanket spraying one-third of the 2400ha cereal crops with herbicide costing $21/ha, one-third costing $35/ha and one-third costing $45/ha, giving a total herbicide cost for broadleaf weeds in-crop of $80,000.
Only the Bilberry system can detect weeds in-crop (green-on-green). Assuming the spot-sprayer reduces chemical usage by 85pc, the herbicide cost is $12,000 plus the annual algorithm fee of $19,000.
For this average farm, the chemical savings with a WeedSeeker, WEED-IT or See & Spray Select system for summer spraying are about $58,000, and using a Bilberry system for summer spraying and controlling wild radish in cereals, the saving is $96,000 per year.
"If a grower has a summer weeds problem and is using an expensive broadleaf spray over a low density of weeds in cereals, the worst thing they can do is simply buy a new SP boomspray and continue to blanket spray their whole area," Mr Newman said.
Although optical sprayer technology involves a high initial outlay, the return on investment is rapid in the right situation. While green-on-green detection is currently limited to select broadleaf weeds in cereals, there are other algorithms in development for detecting weeds in break crops such as lupins, canola and lentils, and this will add to the return on investment in the future.
If you are looking at buying a new sprayer it is definitely worth running the numbers for your farm to see if you would benefit from adopting this technology, and maybe even adding automation using a robotic platform.
Spray efficacy is one of the WeedSmart Big 6 tactics to ensure every drop of herbicide applied is effective, underpinning profitable crop production.
For more information about herbicide efficacy, please visit the website: www.weedsmart.org.au
