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A SwarmFarm robot, ‘Oscar’, has added another dimension to Elton and Pam Petersen’s integrated weed management program, which features the majority of the WeedSmart Big 6 tactics.
In two summer fallows the Petersens have regained control of glyphosate resistant feathertop Rhodes grass (FTR) and awnless barnyard grass (BYG) that was threatening their 2000 ha dryland cropping operation at Moonie, on the Western Downs.
Elton and Pam Petersen, ‘Traighli’ near Moonie on the western Darling Downs.
The Petersens have achieved this remarkable feat after deploying ‘Oscar’ with a 12 m weedIT boom attachment. In the 20 months that Oscar has been spraying weeds in the summer fallow, ‘he’ has clocked up over 3000 hrs and passed over more than 25,000 ha.
Elton and Pam purchased ‘Traighli’, a 2370 ha grain and cattle property 5 km north of Moonie, on the western Darling Downs, in 2015. Previously they had farmed on the Fraser Coast growing sugarcane, soybeans and pineapples, and running cattle.
At the time of purchase, weeds that adapt well to conservation cropping systems had established populations that were impacting on the profitability of grain production. Elton’s initial plan was to use cultivation and blanket spraying to regain the upper hand, particularly of the herbicide resistant summer-growing grass weeds.
“Cultivation certainly helped reduce weed numbers, but was never intended to be a long-term, sustainable solution to manage these weeds. It was also too costly to use the blanket sprayer frequently enough to prevent seed set,” said Elton. “We were interested in optical spot spraying technology and everyone we spoke to who used this technology gave very positive feedback – except that it was still not practical to spray as frequently as is required to target small weeds.”
After further investigation the Petersens decided to invest in technology that would maximise the efficacy of the optical spot sprayer in their weed control program.
“Our choice was between a 36 m tow-behind weedIT boom and a 12 m weedIT boom mounted on a SwarmFarm robot,” said Elton. “We saw the robotic platform as a way for us to really hit our grass weed problem hard and to drive down the weed seed back as quickly as possible, with minimal operator input.”
The Petersens with SwarmFarm founders Andrew and Jocie Bate and SwarmFarm team members Tom Holcombe and Jarrod Jackson.
“In such a short space of time we have dramatically reduced the seed bank to the point where Oscar can work for up to 40 hours scouting and spraying weeds without the spray tank needing to be refilled,” said Elton. “This fact alone is incredibly important. It gives us much more freedom without compromising the weed management program.”
Elton has also experienced a significant mind-set change to weed management as a result of deploying Oscar. Applying constant pressure to small, fresh weed seedlings has seen the weed seed bank dwindle as no new seed has been produced for two summers.
When blanket spraying, Elton knew he was compromising on water and chemical rates in the interests of saving money and time. He said the focus was always on trying to make the spray operation more efficient and this often resulted in some weeds being larger than ideal when the herbicide was applied.
“With a tow-behind optical boom we would have improved our chemical and water application rates but not solved the frequency and consistency problem we had with the blanket spray system,” he said. “Automation brings the consistency. If Oscar goes out spraying and finds only a few weeds it only costs us $0.50/ha in diesel, and we are paying for the machine whether we use it or not.”
In the 2020/21 summer fallow, chemical costs totalled just $12.80 per ha for all the summer weed control and the pre-plant knockdown spray. Elton says this is equivalent to the cost of a single blanket spray in the past.
“In our old system we were never on top of resistant weeds and although the new system probably has similar costs, we are achieving a much better result,” said Elton. “We have essentially invested in technology that does a better job with less chemical – the long-term benefits have been realised more quickly than we dared to hope. The saving in chemical cost is even greater than I expected.”
Summer fallow spray program
In the 2020-21 summer fallow Oscar completed seven passes of the whole farm between mid-November 2020 and May 2021. For the 25-week fallow period, the property received around 650 mm of rainfall (more than the annual average for the property), with the longest stretch without rain being just 10 days. Being able to send Oscar out spraying almost immediately after rain has allowed the Petersens to treat each new germination of weeds while still very small. Elton also has Oscar set to only spray when the conditions are cool, to maximise herbicide uptake.
BYG sets seed very quickly, even quicker than FTR, so there is no opportunity to stop seed set other than killing the seedling before it seeds. Elton believes he is on track to eradicate both of these grass weeds within the next few years and will be able to reduce or eliminate the use of Group A herbicide in the summer fallow.
He says they are currently applying Group A herbicide in three passes, but each round is only using one drum of Group A product, across the 2000 ha cropped area.
The other fallow sprays are glyphosate immediately after harvest and after the first rain (for crop volunteers) and then the pre-seeding knockdown.
“The glyphosate / paraquat double knock has been replaced with frequent spraying using the robots to target small, fresh weeds,” says Elton. “There is limited opportunity to double knock as each paddock is sprayed roughly every 21 days.”
“This property is heavy grey cracking clay soil and melon hole country, so we have really noticed a difference in being able to access the paddocks with such a light machine much sooner after rain than is possible with a tractor,” said Elton. “Everything is centred on hitting weeds when they are very small and at their most susceptible to herbicide. This has resulted in a large reduction in the amount of chemical used.”
Another feature that Elton uses to enhance the efficacy of the pre-plant herbicide treatment is to slow Oscar down and increase the sensitivity of the optical detection to ensure that the very smallest of weeds are ‘seen’ and sprayed. This essentially saves them the cost of a pre-plant blanket knockdown.
Very clean fallow in the background compared to two passes that were missed due to an error in the robot’s instructions.
Winter weed control tactics
The Petersen’s winter cropping program is limited to growing chickpea, wheat and barley, so although they rotate the available chemistry, their options are restricted. When the opportunity arises they plant a summer crop followed by a winter fallow to target black oats and phalaris.
“We do one in-crop spray in wheat to target these grass weeds and are aware of the risk of Group A resistance in black oats, and a second in-crop spray is to control broadleaf winter weeds,” says Elton. “We use robust rates and ensure there are no survivors. A targeted winter fallow program would also go a long way to reducing the impact of herbicide resistance in black oats.”
Chickpea crops are now sown on the same 375 mm (15 inch) row spacing as the cereals, which is proving beneficial in both higher yield and weed suppression compared to the 760 mm (30 inch) spacing used previously in chickpea. Pre-emergent herbicide is applied ahead of chickpeas and in summer crops.
“We set our planting date to avoid frost risk and want to get the crop in as quickly as possible and have the option to use moisture seeking techniques in dry years,” says Elton. “You can’t overestimate the effect of canopy closure on weeds and evaporation.”
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SwarmFarm: Targeting small weeds all year

Tony and Sharon Single farm with Tony’s parents John and Mary, south east of Coonamble in northern NSW with views of the Warrumbungle Range.
Across the 4500 ha cropping area at ‘Narratigah’, the weed numbers are low as a result of the Single’s ‘farming moisture’ philosophy, which involves planting whenever there is sufficient subsoil moisture to establish a competitive crop on their heavy clay soils. Their location allows a mix of summer and winter cropping, so if there is an opportunity for a summer crop they take it, even if that might result in missing the winter crop.
Tony (left) and John Single use their Single Shot weed detecting drone to scout for and map weeds to create a prescription map for their tractor mounted boomspray.
“Farming moisture is our risk management strategy and it has paid off time and time again,” says Tony. “We are really farming with probability and by reducing our risk we have been able to maximise profits. If there is insufficient subsoil moisture we just don’t plant. This means we have very few failed crops and we take advantage of the intermittent winter fallows to run down the seedbank, particularly for winter-active grass weeds.”
Tony says the area has a slightly summer dominant rainfall pattern but rainfall is very variable. The main crops grown are wheat, chickpea and sorghum, along with any other crop that might fit a certain planting opportunity.
While their cropping decisions are very water responsive, there can be situations where the need for ground cover outweighs other considerations. This can occur after a chickpea crop and if they feel it is necessary, Tony and John will plant a crop just to produce stubble, knowing that the yield will most likely be low.
“Generally, if it is too dry to plant we will choose to fallow to build up the soil moisture profile knowing that this is the least-risk strategy and gives the best result in the long term,” says Tony. “We can effectively gain good weed control for the full 12 months through the use of cropping and fallowing in both winter and summer.”

Resistance status
Herbicide resistance is considered the biggest threat to their business even though they currently have resistant weeds well under control. Glyphosate resistance was first confirmed at ‘Narratigah’ in 2005 in annual ryegrass, and Tony and John are also aware of some small areas of glyphosate resistant barnyard grass.
“These are our most important weeds and keeping a lid on resistance is crucial to prevent them becoming limiting factors in our cropping choices,” says Tony. “We also have other weeds including milk thistle, fleabane, blow-away grass and feathertop Rhodes grass – the full suite of northern region weeds really.”
Tony says their efforts to consistently drive down the weed seed bank, and having regular winter fallows, minimises the impact of herbicide resistance on their business.
“Our weed seed bank is low and weeds do not dictate our cropping decisions,” he says. “Ryegrass has a relatively long growing season so we have ample opportunity to stop seed set through a winter fallow. There are also several chemical options for use with our spot spraying technology and new pre-emergent herbicide options too, along with cultural controls such as chipping.”
“We are more concerned about the implications of resistant barnyard grass, which washed in from up-stream. Barnyard grass has the ability to germinate and very quickly set seed, making it more difficult to contain.”
To avert the risk of more seed being deposited by overland flow, the Singles have constructed a number of diversion banks on the up-stream side of their cropping area to divert water.
Tony is also noticing ‘rate creep’ as weeds like milk thistle that are slow to metabolise herbicide, become harder to control. He says they are needing to use a higher rate of paraquat in the double-knock applications. The Singles are managing this through regular double-knocking in fallow and strategically using saflufenacil with paraquat to enhance control.
Black oats currently has a low resistance profile due to the use of winter fallows and fop chemistry is still effective in many paddocks.
The Singles use their proprietary drone weed mapping system ‘Single Shot’ to scout for and map weeds, helping them to better plan for and implement each herbicide application.
Their integrated weed management system is an excellent example of the WeedSmart Big 6 in practice.
#1 – Diversity in cropping
The combination of winter cereals, winter pulses and summer cereals provides many opportunities for controlling weeds pre-season and in-crop.
“The decision to plant sorghum is driven by weed and disease pressure in winter crops,” says Tony. “In a paddock that is becoming difficult to manage, we would rather change to sorghum than turn to a heavy reliance on pre-emergent herbicides and in-crop spraying of winter weeds in winter crops. Swapping to a summer crop gives us the opportunity to target problematic weeds using a winter fallow phase.”
This practice, plus the persistent drought in recent years, has resulted in more fallow area and allowed them to drive down the weed seed bank of annual ryegrass and black oats. It is now very rare for them to target grass weeds in-crop in winter cereals.
Using their drone and sensor to scout for and map weeds in the fallow periods has been a powerful tool to attack the weed seed bank in both summer and winter. Decoupling the weed detection and spraying operations opens up opportunities for more diverse weed control.
Tony and John can use the drone to map the presence of weeds just before, or soon after, significant rainfall events. Once they are able to get on the paddocks with the sprayer they can target previously existing weeds with spot spraying an effective herbicide mixture while applying a blanket rate to the new germination of weeds following the rain.
Knowing exactly what is in the paddock before they start spraying means they can consider a wider range of potential chemical options or techniques. Once the plan is made, they know how much product they will need and the cost. Knowing that they will only be treating say 5 ha in a paddock, they can afford to use chemicals that they would never consider for a blanket spray application.
#2 – Mixing and rotating MOA
Tony and John use some preemergent chemistry strategically in fallows to maximise weed control diversity while keeping their options open for cropping.
They aim to use a preemergent application to control key broadleaf and grass weeds after harvest, which takes the pressure off glyphosate without compromising planting opportunities the following autumn.
A combination of soil residual herbicides such as picloram, Balance and Flame has given good results early in the summer fallow, followed with a pre-sowing double knock of glyphosate and paraquat, giving a total of five chemical groups targeting fallow weeds. When it suits the program, they use chemistry mixes such as Sharpen + paraquat in the double knock, increasing the modes of action and increasing the efficacy of the treatment on the weed spectrum.
In addition to the use of preemergent chemistry, winter grass weeds are also targeted in broadleaf crops, usually with clethodim (Group A, Group 1), but the Singles are aware of the resistance risk and are looking to introduce Clearfield canola as alternative means of grass control in break crops, and to bring more diversity to their system.
Using their drone mapping technology, Tony and John can merge multiple flights of a paddock during the year into one map to show the location of all the weeds detected. This map can then be used to apply a site-specific soil residual herbicide for the next season to say 15 to 20 per cent of the paddock. In treating smaller areas, they can afford to consider chemistry that might otherwise be too expensive, add more diversity to chemicals used and reduce their plant-back risks.
#3 – Crop competition
The Singles consider crop competition to be their #1 weed control tactic, simply because it is the only one that provides season-long in-crop weed control.
“We do everything we can to maximise the crop’s ability to suppress weeds,” says Tony. “This starts at planting, where we have invested in planting gear with moisture seeking capability so we can plant crops on time and ensure good establishment. We take great care to ensure there are no gaps for weeds to exploit, and always square-off the headlands.”
Planting at 330 mm row spacing allows for inter-row sowing and stubble retention, and planting rates are chosen to maximise yield – with long-season wheat sown at 40 to 60 plants/m2, and later plant wheat sown at 80 to 100 plants/m2. The slope of each paddock dictates the tramline direction to be perpendicular to the overland flow, which results in most paddocks being sown north south.
For all crops Tony aims to achieve 100% knockdown prior to planting with a double knock treatment, followed with a well-established, vigorous crop.

#4 – Double knock
The Singles started using the double knock tactic twenty years ago in their winter fallows, and introduced it to summer fallows about ten years ago.
“The double-knock strategy hasn’t added significantly to our overall weed control costs,” he says. “When we first started using the double-knock we counted it as a direct cost to the system, but we now see the second knock with paraquat as a preemptive strike on future weeds – an investment in lowering the weed seed bank, and we are picking up savings with lower volumes of chemical required in subsequent weed control applications.”
The double knock tactic is now embedded in their weed management strategy and they have invested in spray gear to allow them to cover their area within the recommended 7 to 8 day window. Tony says the high level of control they achieve with the double knock means there are fewer and fewer weeds each year and this reduces the cost of the operation, particularly now they have the capacity to spot spray weeds with highly consistent weed detection.
“This tactic puts a significant dent in the weed seed bank and reduces the number of large and potentially stressed plants being sprayed,” says Tony. “This makes it a very effective resistance tool, particularly for our hard to kill weeds.”
#5 – Stopping seed set
The Singles are aiming for 100 per cent weed control in fallow, particularly for annual ryegrass and BYG, by managing paddocks in a site specific way at a square metre level using their drone scouting technology.
“The drone can effectively scout for weeds at a rate of 200 ha/hr, which makes it very quick and easy to scout a paddock and then go out and chip the five or so plants that might be left growing in a paddock,” says Tony. “This moves us closer to achieving 100 percent weed control. We have really driven down our weed numbers and significantly reduced the impact of herbicide resistance in our operation.”
Occasionally, Tony will drive along the tramlines in the side-by-side and chip out any grass weeds in chickpeas that have either escaped control or germinated late in-crop. Then prior to harvest, Tony and John look for any patches of weeds that have escaped control and take action to prevent seed set.
“If we find there is a patch of weeds getting away from us we don’t hesitate to sacrifice small areas of the crop to prevent seed set,” says Tony. “In 2020 we had a three or four hectare patch of ryegrass and decided to use a small slasher to mow the crop and weeds then sprayed the area with paraquat. That way we made sure the weeds did not set seed and prevented the spread of resistant weed seed at harvest.”
The Singles do not spray any selective herbicides outside their cropped area and prior to harvest they slash a 2 m width of crop along fencelines to stop the header bringing weeds into the paddock from the fenceline.
#6 – Harvest weed seed control
Several years ago, the Singles trialed narrow windrow burning for harvest weed seed control but decided that the negative effects outweighed the weed control benefits.
“For us, ground cover is supremely important for erosion control, reducing evaporation and increasing infiltration through the heavy clay soils,” says Tony. “We are watching the developments in impact mill technology and will most likely go down that path if we feel harvest weed seed control is needed in the future.”

Preserving the option for opportunity cropping is critical for Rolleston grain grower Kurt Mayne, but this means he needs to be careful with pre-emergent herbicides in his fallow weed control program.

Kurt and his family operate a 6000 ha mixed farming operation of dryland grain production and backgrounding steers for feedlots at ‘Broken Plains’, 13 km east of Rolleston in Central Queensland. They grow chickpea and wheat every winter and summer crops when the opportunity presents on the 1400 ha of farmed country previously used for finishing cattle on leucaena (AKA tagasaste).
Kurt Mayne bought a secondhand 36 m weedIT in early 2019 and can now spot spray their entire cropping area within two days.
Wanting to keep one step ahead of herbicide resistance, Kurt took the opportunity to join a GRDC Grower Solutions study tour that included attending the 3-day WeedSmart Week event in Narrabri in 2018.
He returned from the tour convinced that he needed to take extra steps to minimise the risk of herbicide resistance before it began to impact on his crop choices and profitability.
“Optical spraying technology was the tactic that really stood out for me on the study tour,” says Kurt. “We bought a weedIT boom soon after I returned from the trip and I have been impressed with the benefits that have come with the addition of an optical sprayer to our weed control program.”
“In our farming system it is hard to incorporate pre-emergent herbicides in the fallow because that can restrict our options for opportunity cropping over summer,” he says. “The optical sprayer makes fallow weed management much more effective, and when that’s combined with pulses in the rotation we are able to keep on top of grass weeds like feathertop Rhodes grass, which was getting increasingly difficult to manage.”
The main weeds at ‘Broken Plains’ are feathertop Rhodes grass (FTR), milkthistle and fleabane – all notoriously hard to kill in fallow situations. Kurt bought a secondhand 36 m weedIT in early 2019 and can now spot spray their entire cropping area within two days. He also uses a tow-behind sprayer for their broadacre spray applications.
Kurt says the pressure from FTR had led to an increasing need for cultivation to stop seed set and he saw that optical spray technology would mean he could reduce the amount and frequency of cultivation.
“We use the weedIT to spot spray weeds with a double knock of glyphosate plus a Group I [Group 18], followed with paraquat; targeting these hard to kill weeds when they are small,” says Kurt. “No residuals are used in fallow because they can limit our options for summer cropping particularly.”
“The aim is to keep the fallows weed-free so we have low weed numbers at planting,” he says. “Once a crop is planted we do use residuals to give it the best chance to grow ahead of any weeds that might emerge on the planting rains.”
The weedIT has markedly reduced the amount of chemical applied in the fallow and reduced the time needed to do an application across the cropped area. Kurt is finding it much easier to apply the double knock tactic for glyphosate within the optimal timeframe.
“Being able to get a proper double knock done when you need to, means you can get on with other jobs, knowing that you have done the best control treatment possible on the weeds,” says Kurt.
Crops and varieties are chosen to maximise yield potential and this also means there is maximum suppression on weeds. Their crops are sown on 50 cm row spacing in a 12 m controlled traffic system, except for sorghum, which is grown on 1.5 m spacing.
“We are basically farming moisture here, so if there is suitable rainfall we want to be in a position to take that opportunity to plant,” he says. “Sorghum and mungbean are the usual summer crop options, and we aim to be cropping for 10 months of the year if conditions allow.”
In drier years the winter crops are sown deep, about 15 cm, to access available moisture. Chickpeas are particularly well suited to moisture seeking planting techniques. Kurt grades his own chickpea and wheat seed to remove weed seeds and ensure that the largest and most vigorous seeds are planted. He buys in mungbean and sorghum seed each season to maximise seedling vigour and establishment, and ensure the seed is weed-free.
Chickpeas are particularly well suited to moisture seeking planting techniques. Kurt grades his own chickpea and wheat seed to remove weed seeds and ensure that the largest and most vigorous seeds are planted.
Kurt uses a tyned planter and a single disc for nitrogen application. He has recently embarked on a program to apply ‘deep P’ across the cropped area. The phosphorus is applied about three months before planting at a rate of 250 kg/ha MAP at a depth of about 30-45 cm using a dozer. He has been very impressed with the crop response to the phosphorus application, which has clearly demonstrated that low phosphorus levels have been a constraint on production.
The Maynes are seriously considering adding harvest weed seed control to their weed management program. Kurt sees real benefits in the chaff deck system that delivers the chaff onto the tram lines – both as a weed control tactic and a means of reducing the frequency of tram line renovation.
On the cattle side of their business the Maynes buy in about 1600 feeder steers and run them for less than 12 months on 2800 ha of buffel and leucaena pasture.

Mullewa growers Andrew and Rod Messina have been on a long and dedicated journey of weed management. Their 12 thousand ha dryland cropping enterprise is based on a predominantly sandplain soil type and the region generally expects 250 to 350 mm annual rainfall, but seasonal variability is often a challenge.
The most recent innovations to be tested and adopted are real-time and localised herbicide application technology and impact mills for harvest weed seed control.
The soils and rainfall limit the Messina’s crop choices but they use the available options of wheat, canola and lupins to their best advantage for herbicide and non-herbicide tactics to keep downward pressure on the weed seed bank.
Mullewa farmer Andrew Messina says it’s amazing how quickly weed numbers come down after two or three years of integrated weed management practices, including harvest weed seed control. Photo: Fiona Mann
“We have been doing whatever we can to reduce the seed bank for weeds, and we’ve been doing that for a long time now, particularly with mouldboard ploughing and harvest weed seed management,” Andrew said. “Weeds rule broadacre farming, there are no two ways about that – weeds and rainfall.”
Over the years their efforts to reduce the weed burden across their controlled traffic farming operation have also included narrow windrow burning, chaff carts, autumn tickles, crop topping and double knocking glyphosate.
“We find that when we buy a new property it always has a lot of weeds but after two or three years of integrated weed management practices, including harvest weed seed control, it’s amazing how quickly weed numbers come down,” Andrew said.
Wild radish has always been the main weed challenging crop production on the Messina’s Spring Park Farms on the Eradu sandplain east of Geraldton. When herbicide resistant wild radish populations established on the farm the Messinas added pre-emergent to the in-crop herbicides in their weed management strategy.
In 2020 the family sold their collection of chaff carts and bought three Integrated Harrington Seed Destructors (iHSD) in anticipation of a harvest dominated by cereals across 10,000 ha. The impact mills performed well through the 2020 harvest and the Messinas are very pleased to have dispensed with burning chaff dumps for harvest weed seed control.
At the same time they have also moved into camera spot-spraying technology, initially for summer and fallow spraying but also for future potential for in-crop spot-spraying.
Teaching technology to recognise weeds
Their new 8000-litre Agrifac Condor Endurance II machine is equipped with weed-identifying cameras developed by French firm Bilberry, allowing for real-time weed detection and tailored herbicide application.
“To have mechanically driven weed destructing mills on our harvesters, and this camera technology … it’s the most exciting thing I have seen in my farming life,” said Andrew.
The system – called AiCPlus – uses optical cameras and microprocessors to identify weeds ahead of the 48-metre spray boom. Individual nozzles are then triggered as the boom passes overhead to spot spray the weeds. The cameras are fixed at 3 m apart, with each linked to the independent operation of nozzles within a set of 12 nozzles.
Green-on-brown is the only commercially available technology available for this machine at present, but the Messinas have been busy assisting the system’s developers to trial its green-on-green capabilities.
Arriving on farm in January 2020, a little later than expected, the Messinas used it to finish the summer weeds program on about 400 ha of their sandplain soils. Once the crops were planted, they then used it for nine days in young wheat crops in July and then again in August, traversing 14,000 ha at an average speed of 19 km/h.
AiCPlus uses optical cameras and microprocessors to identify weeds ahead of the 48-metre spray boom. Photo Fiona Mann
Its target was wild radish growing in paddocks of Scepter, Devil, Chief and Zen wheat. With each pass, the cameras captured images that depicted both the crop and weed at different times of day and under various light conditions. These images are being used to better inform the algorithm behind the technology. In 2021 the Messinas will be working with Bilberry to gather images to identify blue and white lupin in wheat crops.
For the trial, they had allowed the radish plants to grow to a size that the cameras could easily detect, approximately 10 cm2, with the sprayer first being put to work on a paddock with a high weed burden, something that they would not usually do.
In paddocks with high weed burdens, their aim is to knock out weeds early in their growth via a blanket spray, in a bid to conserve crop-available moisture. This would usually occur around the three-leaf stage in wheat.
Andrew expects the efficiencies from green-on-green technology to come in subsequent sprays that targeted the low number of radish plants from later germinations.
As a result of the family’s persistent weed-fighting efforts, most of their paddocks host only low densities of radish. In these paddocks, Andrew said a blanket spray would generally not be necessary.
Having the impact mills fitted to their harvesters gives the Messinas full confidence to be involved with the development of the weed identification and spraying technology because they know that any weeds that escape treatment will be destroyed at harvest.
“But when we were walking through the paddock, most of the weeds had been hit,” said Andrew.
The 48 m Agrifac sprayer runs on the same trams as the harvester rather than the trams used by their other sprayers. By going to a wider boom and operating at 19 km/hr they can get over the same area as their 36 m sprayers running at 26 km/h.
Addressing soil constraints
The family started exploring soil constraints in 2008, mainly to determine if soil acidity, aluminium toxicity or nutrient deficiencies were limiting yields.
Testing uncovered pH levels of around 5.3 to 5.5 at the surface and 4.4 to 4.6 at depth (30 cm). Non-wetting properties and compaction were also identified as potential limiting factors.
They then embarked on a liming and mouldboard ploughing program to adjust the pH, treat non-wetting and bury weed seed. Their soils now feature pH levels in the range of 5.5 to 6.2.
“For the past five years we have been deep ripping to depths of 60 to 70 cm prior to seeding wheat to maximise the ability of crops to access moisture and nutrition in the profile,” said Andrew. “We also spread two tonnes of lime per hectare ahead of the ripper every three years.”
The overall result is better soil, better crop competition and less weeds. Andrew says the deep ripping has the potential to bring weed seed back to the surface, but this has only been evident on the edge of tram lines in a couple of paddocks where brome grass has re-surfaced.
Stopping seed set at every opportunity
The Messinas aim to stop seed set at every stage of the crop production and weed life cycle.

Mouldboard ploughing and liming re-set the seed bank and removed soil constraints related to pH and non-wetting.
Deep ripping ahead of planting (autumn tickle) stimulates a germination of weeds that are treated with a knockdown herbicide or double knock. Deep ripping also opens up the sandy profile to accept soil moisture and incorporate lime every three years. This encourages roots to seek nutrients and moisture and sets the crop up to compete well with weeds and reach the yield potential for the season.
Pre-emergent herbicides are applied to give the crop a head start on weeds.
One or two post-emergent sprays are applied as required in wheat for wild radish control. The AiCPlus camera sprayer will change broadacre spraying into spot-spraying for this key weed.
Lupins and canola are crop-topped if required but crop-topping has not been necessary in recent years.
All crops are treated with harvest weed seed control. The Messinas have achieved excellent weed seed control since they began with windrow burning in 1997 then moved to chaff carts in 2012 and now use iHSD impact mills.
Summer spraying will now focus on spot-spraying with the AiCPlus camera sprayer.

This case study is based in part on an original article written by Ann Rawlings with permission from the Society of Precision Agriculture Australia (www.spaa.com.au) and other sources.