Articles & Case Studies

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Case Study

Elton and Pam Petersen, Moonie Qld

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.
“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

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Case Study

Single family, Coonamble NSW

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.”

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Case Study

Kurt Mayne, Rolleston Qld

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.

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Case Study

Messina family, Mullewa WA

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.

Article
Case Study

Jason Rogers, Moree NSW

Jason Rogers targets summer grasses when they are small and fresh using a double knock of glyphosate and paraquat. In recent years he has moved into applying residual herbicides soon after harvest and GPS-marking any suspect weed patches to be treated with spot spraying or strategic tillage. Jason is also mixing and rotating fallow sprays to extend the efficacy of all available modes of action.
Keeping weed numbers down, managing patches and minimising weed seed set has been a high priority for Jason Rogers, Moree.
Barley and Clearfield canola provide early canopy closure and the strongest crop competition for winter weeds. Any isolated weed escapes in summer fallows or winter crops are targeted with spot spraying or chipping to maintain the low weed numbers.
Jason runs a dryland winter cropping operation on fairly uniform heavy clay soils on his farms north-west of Moree. The crop rotation across seven fields in the controlled traffic system includes wheat, barley, chickpea, canola, linseed. He no longer grows summer crops due to seasonal constraints during the extended drought and poor returns.
“Normally we grow wheat followed by barley, which gives a good amount of ground cover, and then one of the three break crops – canola, chickpea or linseed,” he says. “We have been looking at the possibility of fitting in a double-break of, say linseed and chickpea before returning to cereals.”
The advantage would be to help take pressure off the selective herbicides in the cereal phase and mix things up a bit, but Jason is also conscious of the reduction in ground cover from a double break crop.
The main weeds in the summer fallow are glyphosate-tolerant summer grasses such as windmill grass, awnless barnyard grass and feathertop Rhodes grass. Broadleaf weeds like fleabane, sowthistle and peach vine also pose a challenge, particularly because Group I hormone herbicides can not be used when nearby cotton crops are at sensitive growth stages.
“We are mixing and rotating herbicide groups as much as possible and using more residual chemistry, to keep weed numbers low in the fallow,” he says. “This can have impacts on the rotation so we work with our agronomist to plan well head to make sure the residuals have broken down enough to not cause any issues for the following crop.”
The fallow weed management program usually begins with a residual herbicide applied after harvest and then the double knock tactic is deployed multiple times during summer following any rainfall events.
Jason uses IMI residuals applied after barley harvest to give residual control of grasses over summer and then returns with a Clearfield canola crop the next winter. He then avoids using the Group B chemistry for a few years to extend its useful life in his weed control program.
For the double knock, glyphosate is often applied in a tank-mix with a Group G to help with broadleaf weed control, particularly near cotton paddocks.
“We like to get in early to treat small fresh weeds, and come back a week or so later with paraquat,” says Jason. “When dealing with predominantly glyphosate-tolerant weed species we know how important it is to prevent weeds getting too mature. If persistent wet weather means we can’t get a ground application done in time we don’t hesitate to arrange a plane to apply the herbicide.”
Jason does all the spray operations himself and takes the opportunity to map weedy patches using the John Deere software in the tractor as he travels across the paddocks. He has set up customised flags for each of the main weeds, such as feathertop Rhodes grass, windmill grass and awnless barnyard grass so he can monitor any hotspots. He then comes back to treat patches of say up to 10 m2, with strategic tillage using a chisel plough, spot spraying herbicide, or hand rouging or chipping. Jason also uses the flags to generate coordinates that he can easily send to his agronomist in Google Maps.
For winter weeds Jason finds the diversity of the crop rotation allows for effective rotation of herbicide mode of action groups and the early vigour of canola and barley assists with weed suppression.
“Using hybrid Clearfield canola varieties in the rotation gives us the ability to safely use the imi herbicides in the preceding fallow and in-crop as well as providing early canopy closure so very few weeds can grow and set seed in the canola phase,” says Jason. “Similarly in the barley, we get a free kick from solid crop competition through early vigour and high biomass production.”
Jason has used a disc seeder since 2000 with a minimum row spacing of 375 mm in their 3 m wheel spacing controlled traffic system.
Jason has used a disc seeder since 2000 with a minimum row spacing of 375 mm in their 3 m wheel spacing controlled traffic system. The high capital and maintenance cost of the seeder has been a disincentive to move to narrower rows however Jason knows there are potential weed control benefits in reducing the row spacing.
Keeping weed numbers down, managing patches and minimising weed seed set has been a high priority for Jason and his integrated weed management program is working well. An important part of the program is a robust mix and rotate program to keep all available herbicide options open for as long as possible.

Article
Case Study

Andrew Kenny, Badgingarra WA

Listen to the article being read above!

Andrew and Gina Kenny farm at Badgingarra, in WA’s west midlands using an integrated program of crop rotation, mouldboard ploughing, grazing and chaff lining to keep their weed numbers very low.
Andrew’s parents, Mike and Sara, arrived in the Badgingarra district to farm in 1959 and started clearing the land for cropping, at about the same time cropping land was also being developed around Esperance.
Badgingarra farmer, Andrew Kenny has used TT, and more recently RR, canola to take advantage of different chemistry and weed control tactics.
“There is a fault line that runs through the property with distinct soil types on either side,” says Andrew. “On one side of the line is our best cropping soil – clay through to pea gravel; on the other side is white sand with very limited water holding capacity, which we use mainly for grazing.”
 
Grazing to maximise productivity
About 60 per cent of the 4150 ha property is used for continuous cropping and the rest for grazing sheep. The Kennys grow some hay for their own use and the sheep also graze the crops – mainly barley, and sometimes wheat and canola – from mid-June to mid-August.
For over ten years the Kennys have run 5500 ewes in two flocks – a 4000-ewe self-replacing merino flock and 1500 Prime SAMM ewes mated to Poll Dorset terminal sires. Producing both wool and meat, the sheep are an important component in the business. SAMM are a dual-purpose sheep that was later further developed to produce a heavy slaughter lamb at a young age, as well as good quality wool.
“We grow mainly Bass and Planet barley, which we will graze two or three times with 2500 hoggets before allowing it to finish for grain,” he says. “These varieties both tiller well and respond quickly after grazing to the first node stage.”
Sheep utilise 40 per cent of the farm where the sandy soils do not retain sufficient moisture for cropping. The Kennys retain lupin seed, make hay, graze crops, chaff lines and stubbles and use the sheep to provide a double knock effect.
Low weed numbers allows dry sowing
Once the season breaks, the Badgingarra area can generally rely on good rainfall through the growing season. In 2018 there was a late break, resulting in Andrew taking a risk and sowing 75 per cent of their crop dry. That year he saw the benefits of earlier sowing and is confident that their weed numbers are now low enough to make dry sowing a safe practice.
“On the heavier soils we grow canola, wheat and barley. Sandier soils that are lower in the landscape have better nutrient levels than those at the top of the landscape, and are suitable for cropping lupin, wheat and barley.”
Barley has been a consistently strong performer in recent years so the area has increased. Lupins provide a good break from cereals and provide a high protein feed that is easy to store on farm and kept primarily as a drought reserve.
The Kennys introduced canola to their cropping program in the 1990s and have used TT canola, swathing and spraying under the swather with glyphosate as key tools in their weed control program. They also crop top Barlock lupins to stop seed set.
Andrew rotates herbicide modes of action through the crop cycle, particularly with the pre-emergent chemistry – using propyzamide in lupin, trifluralin in canola, Sakura in wheat and trifluralin + metribuzin in barley. He also targets weeds ahead of seeding with a double knock of glyphosate then paraquat, or uses Spray.Seed®(paraquat/diquat) on its own.
In weedy paddocks Andrew avoids growing two barley crops in a row, choosing instead to switch to canola or lupins to utilise other herbicide MOA, but in paddocks with very low weed numbers he will occasionally grow barley on barley to boost profitability.
With few in-crop options for ryegrass control, Andrew relies on having clean paddocks at seeding and robust pre-emergents. To ensure the crops get off to a good start, Andrew buys in hybrid canola seed and uses a mobile contract seed cleaner to clean farm-retained cereal and lupin seed. He has increased crop competition using a paired row boot on a 30 cm spaced tyne bar to give an effective row spacing of 7.5 cm.
“The tynes are custom built and we use them for sowing all our crops,” he says. “They probably work best in the cereals, but we don’t have any problems in the other crops either. The aim is to do everything we can to increase crop germination, which gives us more crop and less weeds for the same amount of effort.”
 
Burying glyphosate resistance
Andrew says annual ryegrass and wild radish continue to be their most challenging weeds and he has recently added RR Truflex canola hybrid to the rotation to give more options to use glyphosate.
“I am very conscious of the risk of accelerating glyphosate resistance and so we also use mouldboard ploughing to bury glyphosate resistant weed seeds and improve the wettability of the sandy soils,” he says. “Mouldboard ploughing has fixed non-wetting issues wherever we have used it and this improves crop germination, but on the very sandy soil fixing the non-wetting is not enough to sustain cropping, so these poorer soils remain under pasture.”
The benefits of mouldboard ploughing for weed control varies according to soil type. Andrew has seen it most effective on their sandy soils but found it difficult to achieve full inversion on the gravel country.
 
Chaff lining suits sheep
Ten years ago Andrew began narrow windrow burning for harvest weed seed control, mainly in cereals and only in weedy paddocks. They had good results in weedy paddocks but after eight years Andrew was looking for an alternative that would have less impact on nutrients and require less labour.
“We graze the stubbles over summer and the sheep would make tracks through the narrow windrows, which increased the number of places the windrows needed to be lit,” he says. “In 2017 we decided to give chaff lining a go.”
Although the farm is not set up for controlled traffic, Andrew does run the harvester on the same lines each year, allowing him to place the weed seed in the same place each season. With the chaff lining chute as a semi-permanent modification to the harvester, Andrew is now able to implement HWSC in all crops and all paddocks.
With the chaff lining chute as a semi-permanent modification to the harvester, Andrew is now able to implement HWSC in all crops and all paddocks – he can just forget that it’s there!
“The chute, baffle and spreader chopper were fabricated and fitted for around $6000,” he says.
In addition to concentrating the weed seed, chaff lining also concentrates any crop seed losses out the back of the harvester. This means the sheep can make use of any lost grain and Andrew expects the productivity gains from chaff lining would be similar to that measured for chaff dumps.
“In 2018 we had a high level of weed germination in the chaff lines but we did not treat them differently to the rest of the paddock,” says Andrew. “The chaff chute left clumps in the paddock and I thought this might lead to seeding blockages, but in reality, the tyne seeder easily worked through the fine chaff material.”
Andrew expects there would be some rotting of the chaff and weed seeds in years with wetter summers, but this has not yet been put to the test. What is evident though is the impact of higher soil moisture retention under the chaff lines.
Sheep graze the stubbles and do a good job of stopping seed set on any green ryegrass that escaped capture at harvest. The sheep also reduce the overall stubble load and trample the chaff lines, making sowing easier.
 
Other resources

Podcast – Mouldboarding + Chafflining + Grazing

Article
Case Study

Mat Freeman, Walkaway WA

You can listen to the article being read above!

Mat Freeman farms an aggregation of cropping properties at Mullewa and Walkaway in the Geraldton Port Zone of WA. Across the aggregation he has been systematically mouldboard ploughing since 2011 to tackle the non-wetting sands, and deep ripping has been practiced for around 30 years to alleviate compaction.
While fixing the constraints associated with non-wetting sands is the primary reason for mouldboard ploughing, there is also a weed control benefit.
Mat Freeman, Walkaway WA has used mouldboard ploughing to fix non-wetting sands and bury weed seeds.
“Having effectively buried the weed seed bank with the mouldboard ploughing, the plan is to leave the subsoil undisturbed for as long as possible,” he says. “Hard-seeded weeds such as wild radish can remain viable in the soil for several years and can germinate if they are brought back up to near the soil surface.”
Inverting the profile buries weed seed and brings some clay up from depth. Annual ryegrass and wild radish are the main weed species on the farm and Mat is making the most of the re-set value of mouldboard ploughing to keep weed numbers low going forward.
Effective amelioration operation
To achieve full inversion of the soil profile, the soil needs to be moist. The amelioration program also involves the removal of obstacles, applying limesand and then ploughing to a depth of about 35 cm.
This is usually done after a lupin crop where there is the least amount of crop residue on the soil surface. The following year Mat spreads more limesand to treat the acidic subsoil that is brought to the surface.
“Starting with a pH of around 5 on the surface and 4 in the subsoil, we are aiming for a pH around 5.5 on the surface and 5 at depth,” he says. “To achieve this requires about 4 t/ha limesand applied over the two years to treat both the topsoil and subsoil.”
“Mouldboard ploughing needs to be done well, in wet soil and with not too much crop residue on surface,” he says. “We are close to completing the ploughing program across the whole farm and expect a long-term productivity benefit from the liming and mouldboard ploughing operation as a result of improved pH.”
After using contractors for the first few years Mat now has his own mouldboard plough, and has committed to a program of ploughing 500 ha each year ever since 2011, along with regular deep ripping. When he first started deep ripping, Mat used a ripper that worked to a depth of about 35 cm but he now has a ripper that works to a depth of around 70 cm. To avoid bringing the weed seed back near the surface he uses straight, rather than C-shaped, shanks to shatter the compaction at depth without bringing weeds or clay to the surface.
Harvest weed seed control decisions
“The weed program here is about attacking them from all angles,” says Mat. “We do what we can to avoid letting weeds set seed. We have been running a Seed Terminator impact mill for a couple of harvests, having previously used narrow windrow burning for harvest weed seed control.”
Mat has replaced narrow windrow burning with an impact mill for harvest weed seed control.
Although narrow windrow burning worked well, Mat found there was a big risk of burning everything after a big cereal crop followed by lupins or canola, and it was hard to get the right weather conditions for burning. He was also concerned about the cost and long-term impact of lost nutrients.
The farm is full CTF for harvest so Mat considered chaff lining as a possibility using RTK to ensure the chaff lines went on top of each other to then be burnt. With the soils being generally low in moisture Mat thought it was unlikely that the chaff would rot and was concerned that he might ‘have the chaff lines forever’. He also considered a chaff deck but decided it was not the best option for the farm and chose instead to invest in impact mill technology.
Crop-topping in lupins has been part of Mat’s weed control program for a long time and he sees value in continuing with this tactic even though he now has the impact mill on the header.
Rotation weed control tools
“There is often 20 per cent of the farm sown to lupins and crop-topping is a good way to control any lodged or fallen grass weeds,” he says. “The outside laps in each paddock often have more weeds because it is harder to plough and the weed seeds are not always buried as well as they are in the main paddock area. Crop-topping is an effective way to help minimise weed seed set in these areas, in addition to the destruction of the weed seeds that go through the impact mill.”
Crop topping in lupins is particularly useful for stopping seed set in lodged ryegrass that might not be picked up by the harvester.
In canola Mat has previously used swathing and spraying under the cutter bar but is finding that direct heading works just as well.
Crop rotation varies slightly on different farm units but generally follows a wheat, lupin, wheat, canola sequence. Some of the very light and fragile sands have not previously been suitable for canola but Mat has been able to introduce canola on these soils following liming and mouldboard ploughing. Pre-emergent herbicides are used for all crops – except straight after ploughing where the low organic matter levels can lead to more severe crop damage.
After mouldboard ploughing and liming Mat follows a crop rotation of wheat, lupins, wheat, canola. He is planning to reduce the row spacing from 12 inch to 10 inch with his next planter to increase crop competition.
Mat uses a tyned seeder with 12 inch row spacing but plans to change to a 10 inch row spacing with the next seeder to go the next step in crop competition for weed control. Cereals are sown on the CTF lines but Mat prefers to sow canola and lupins at 30 degrees to achieve better establishment in these sandy soils. This angle gives him the option to change direction back and forth each year and is not as rough as sowing on a 45 degree angle.
Factors other than crop competition tend to influence variety choice but Mat looks to maximise crop competition through improved establishment, better soil fertility, better access to moisture and is looking to narrow the row spacing in the future.
Deep ripping for yield
In addition to the mouldboard ploughing to ameliorate non-wetting, Mat also uses deep ripping to improve crop production. Deep ripping is done every second year after lupin and canola crops and has made marginal soils profitable, which has led to a significant increase in overall farm profitability. Deep ripping trials in 2015 confirmed that there were significant benefits in addressing soil compaction and improving water penetration into the profile, particularly in wheat where ripping to a depth of 600 mm generated a yield benefit of almost 1 t/ha.
 

* Grain price wheat = $270/t and cost shallow ripping = $45/ha and deeper ripping = $75/ha.
At Walkaway deeper ripping and topsoil slotting (inclusion plates) was the highest yielding treatment. Visual observations showed more plant roots deeper in the slots than un-ripped and NDVI measurements indicated a higher biomass in the deeper ripping treatments during the season.
Source: Deeper deep ripping and water use efficiency, GRDC RCSN Geraldton GER9, by Craig Topham, Agrarian Management and Bindi Isbister, Precision Agriculture
“Deep ripping has really boosted yield and we find the crops persist better between rain events and finish better at the end of the season. The crop develops a deeper root system that can access more water at depth and the result is better yield and grain quality,” he says.
Although the mouldboard ploughing effect persists for several years, the sandy soils quickly settle and develop a hardpan at depth, even without machinery traffic. Mat aims to rip every second year if there is sufficient soil moisture in autumn, preceding sowing, taking care not to bring weed seeds to the surface.
The CTF system is based on 12.2 m centres for the sprayer, planter and harvester and was installed in each paddock after the initial mouldboard ploughing to preserve the benefit of this operation.
Using this soil amelioration program, Mat is now bringing land into crop production that was previously only used for grazing.

Article
Article

Maximising the weed control value of my crop rotation

with Kevin Morthorpe, Trait & Seed Technology Stewardship Manager, Pioneer Seeds
A diverse crop rotation is the twine that holds a good farming system together and underpins an effective weed management program.  
Kevin Morthorpe, Pioneer Seeds’ Trait & Seed Technology Stewardship Manager says herbicide tolerance traits in crop hybrids can be used to maximise competition against weeds and increase the herbicide options available to growers while optimising yield and profitability of the crop sequence in rotations.

Kevin Morthorpe (left) – Pioneer Seeds’ Trait & Seed Technology Stewardship Manager, with Dr Ray Cowley – Canola Research Scientist, Corteva Agriscience and Pioneer Seeds’ Rob Wilson – Strategic Customer & Market Development Manager and Clint Rogers – Western Regional Sales Manager & Canola Product Lead at a canola research trial near Jindera in southern NSW.
Plant breeders continue to introduce herbicide tolerance traits in a number of crops in Australia, including corn, canola, pulses, cereals, grain sorghum, summer forages and cotton.
“For example, in canola there are several herbicide tolerance traits and they are primarily available in hybrids,” he says. “This means growers get both improved crop performance due to hybrid vigour and more flexibility in herbicide use patterns.”
The increased vigour of canola hybrids also generates greater biomass production and early canopy closure that suppresses growth and seed set of weeds that germinate in-crop, complementing the use of pre-emergent herbicides.
“Hybrids super-charge crop competition through a strong root system and vigorous growth,” Kevin says. “From an economic angle, hybrids optimise yield in both high input and tough environments. In fact, we see more growers selecting hybrids when producing canola in tough conditions.”
Since the release of the first herbicide tolerant canola in 1991, the popularity of herbicide tolerance has seen a 98 per cent adoption of canola varieties with tolerance to imidazolinone (Clearfield), triazine (TT) or glyphosate (RR). In the last 15 years, the area sown to hybrid canola has risen to an impressive 47 per cent in Australia. With glyphosate tolerant canola hybrids entering South Australia in 2021 and new hybrid releases, the hybrid percentage will increase further over coming years.
With glyphosate tolerant canola hybrids entering South Australia in 2021 and new hybrid releases, the hybrid percentage will increase further over coming years.
Kevin says that Pioneer Seeds have seen increasing demand for Clearfield canola in recent years following a dip in popularity. Through strategic application of herbicide tolerant traits in diverse crop rotations it seems that farmers are overcoming the resistance problems that were prevalent with the Clearfield technology and can now re-introduce these varieties and take advantage of the weed control benefits and high yields they offer, and manage herbicide residues in the soil.
“A diverse rotation of crops and pastures is one of the WeedSmart Big 6 tactics, which Pioneer Seeds endorses wholeheartedly to protect the longevity and effectiveness of herbicide tolerance traits,” he says. “Through an effective crop rotation you can tick off all the herbicide and non-herbicide tactics needed to drive down weed numbers.”
How do I make the most of a hybrid crop?
In brief: Employ best practice agronomy.
The details: Grain hybrids are vigorous plants that produce increased biomass and grain yield. To do this, they must be supported with adequate crop nutrition. When properly fed, hybrids will provide increased crop competition and achieve greater water use efficiency compared to their conventional counterparts.
Growing a hybrid crop with herbicide tolerance traits does not equate to a full weed control program. These crops must be used within the WeedSmart Big 6 framework, within a diverse crop rotation and using herbicide tactics such as double knocking alongside cultural practices such as harvest weed seed control and crop competition to reduce seed set. They also combine well with pre-emergent herbicides to achieve excellent early weed control and suppress seed set in any late germinating weeds.
Can I use hybrid crops with herbicide tolerance to fix a weed blow-out?
In brief: No. This technology is not suitable for salvage operations.
The details: When Roundup Ready canola varieties were first released there was an expectation that these traits could be used to reverse a weed infestation. This proved not to be the case.
Hybrid crops are best used in low weed density situations where they can effectively drive down the weed seedbank. They should be grown in rotations that include an effective double-break, brown manure crop or a pasture phase.
Having hybrid crop options for both summer and winter growing seasons increases the opportunities to tackle weeds throughout the year or to use different fallow herbicides while maintaining the ability to safely grow crops in the following season.
New glyphosate tolerance traits (Truflex® and Optimum GLY®) and the stacking of herbicide tolerance traits of triazine tolerant and Clearfield® (TT+CL) have expanded the safe window for herbicide application in canola.
Are residues in grain a concern when using stacked trait herbicide tolerant hybrids?
In brief: Not if the stewardship program is followed.
The details: New glyphosate tolerance traits (Truflex® and Optimum GLY®) and the stacking of herbicide tolerance traits of triazine tolerant and Clearfield® (TT+CL) have expanded the safe window for herbicide application in canola. This gives more options, more flexibility and more crop safety through the rotation.
The stewardship program for the herbicide tolerant trait hybrids describe herbicide use patterns that growers must follow to confidently avoid the accumulation of herbicide residue in the grain and ensure that Australian maximum residue limits (MRLs) will not be exceeded. [Note that MRLs in other countries may be different to the Australian MRL. Find out more at Grain Trade Australia] 
To avoid problems with crop safety within the rotation it is important to maintain accurate paddock records to avoid applying herbicide to the wrong crop variety and ensure susceptible crops are not sown into paddocks with herbicide residues in the soil.
On the flip-side, herbicide tolerance in crops increases the options for crop selection within the rotation.
Also, keep in mind the importance of controlling any volunteers from a herbicide tolerant crop in the summer fallow or following crop.

Article
Case Study

Andrew & Jocie Bate, Gindie Qld

The idea of small, lightweight machines replacing heavy tractors was prompted by Andrew’s determination to alleviate soil compaction on the 50 to 150 cm deep black cracking clays at Bendee. Ninety per cent of the area is sown to winter crops, which are grown primarily on soil moisture stored over the previous summer.
Andrew and Jocie Bate, farmers first and foremost. A desire to alleviate compaction on their farm at Gindi, Central Queensland is the driving force behind their agtech venture into robotics.
“Central Queensland winters are generally dry and we rely on moisture stored during summer storms and retained through zero tillage and stubble cover,” says Andrew. “Wheat provides the best stubble and chickpea is our most profitable crop so we just rotate between these two crops. About one year in five we will have the opportunity to plant a summer crop and we’ll double crop a small area to mungbeans or possibly forage sorghum or dryland cotton.”
The Bates also run a cattle enterprise separate from their cropping, except for limited grazing of forage sorghum one in three years in just one paddock. They usually avoid having the cattle on the cropping paddocks due to the compaction and the proliferation of hard to control weeds that can occur.
Moisture seeking improves crop reliability
Deep, or moisture-seeking, planting has been a valuable tactic for the Bates, particularly in chickpea crops. In years where there is no summer crop in the ground they are able to plant as early as April, without waiting for planting rain.
“We plant chickpea seed up to 25 cm deep into moist soil,” says Andrew. “Wheat is more difficult to establish this way but varieties like Mitch that have a strong coleoptile can be planted up to 13 cm deep into moisture. It is still hot here in April and the temperature can reduce coleoptile length, so planter setup is critical to get even emergence from depth. If we can achieve a good even stand, the crops have access to good moisture to sustain vigorous early growth.”
Mitch is not a prime hard wheat variety so Andrew only grows it when soil moisture is limiting, knowing that it will push out of the ground even in tough conditions. Wheat stubble is essential for their farming system, so Andrew does everything necessary to ensure a good wheat crop is established.
The deep sowing technique has proven almost bullet-proof over the last 20 years with wheat being reliably established in eight years out of ten, and they have had 100 per cent success with chickpeas. In most years Andrew grows their crops on stored moisture plus one inch of early rainfall and hopes for one follow-up rainfall event in-crop.
In-crop weed control
“We put a lot of emphasis on having clean fallows and achieving strong emergence of the crop,” says Andrew. “This is critical to maintaining our low weed numbers in our winter crops. All our crops are sown on 50 cm row spacing, except sorghum, which is sown in meter rows. In the recent dry summers, we have opted to grow forage sorghum rather than grain sorghum as a risk management strategy due to limited stored moisture in the profile.”
Metsulfuron-methyl (e.g. Ally, Group B) and Tordon 242 (Group I) herbicides are providing reliable in-crop control of broadleaf weeds in wheat crops and has a useful level of soil residual activity that reduces the incidence of weeds germinating late in the season. Andrew says the dry conditions in Central Queensland winters results in minimal in-crop weeds, so there is little pressure to adopt harvest weed seed control tactics – their focus is on controlling summer fallow weeds.
Wheat provides the essential stubble cover to maximise soil moisture conservation over summer to underpin the following, and most profitable, chickpea crop.
In the chickpea and mungbean crops Andrew uses Group A chemistry, mainly haloxyfop (e.g. Verdict), to manage grass weeds. While he avoids residuals as much as possible to maintain flexibility in the rotation, he uses simazine (Group C) across all of his chickpea and isoxaflutole (Group H, e.g. Balance) on about a quarter of the chickpea area to provide long-term residual control of many problem grass and broadleaf weeds, including glyphosate tolerant feathertop Rhodes grass, sowthistle, and fleabane in crop and during the following summer fallow.
“We use minimal in-crop herbicide and rotate between chemical groups though the crop rotation,” says Andrew. “But really we rely mainly on our fallow management to have clean paddocks to plant into.”
Within the next few years all the weed control and planting at Bendee will be done by the robots. Andrew and Jocie will soon dispense with their self-propelled spray unit and just use their robots supplemented with blanket aircraft applications on less than 10 per cent of the farm area. The weediest paddocks on Bendee still only require herbicide to be applied to 20 per cent or less of the area. The robots can also do broadacre spraying but this will be more practical once the docking and refilling capability is implemented.
“We generally have dry harvest conditions so most of the soil compaction is done by the sprayer in wet conditions,” says Andrew. “Right from the start this has been a driving force behind the development of the SwarmBot concept.”
There are currently two SwarmBot-5 robots with WEEDit attachments working on Bendee. The two robots cover 24 ha/hr and can work 24 hours a day if conditions permit. With weather stations now onboard, the robots will drop into sleep mode when the weather conditions are outside acceptable parameters and then wake up and resume work when the conditions are good.
Robots and the optical WEEDit sprayer have combined to reinvent the fallow weed management system at Bendee Farming. With more passes, there are more opportunities to spray weeds when they are small and easy to kill, and rotate chemical groups more often.
Summer weeds are of greatest concern at ‘Bendee’, with sowthistle, fleabane, wild sunflower and feathertop Rhodes grass being the main targets for fallow weed management. These key species are a bigger problem in years with wet summers, where the weeds can get away during the fallow period and then haunt you in the following crop. Andrew is working on setting up the robots to wick-wipe weeds such as milk thistle growing above the canopy in chickpea and stop seed set.
Robots and the optical WEEDit sprayer have combined to reinvent the fallow weed management system at Bendee Farming. While Andrew acknowledges that calendar spraying is generally a bad idea with regular spray rigs, it is a really valuable tactic when you have robots at your disposal.
“We are doing more frequent passes with the robots applying knockdown herbicides and it works well because we are always spraying fresh, small weeds and minimising seed set, therefore reducing the risk of herbicide resistance,” he says. “We are also better able to control weeds that are considered hard to kill with glyphosate, such as wild sunflower, feathertop Rhodes, sowthistle and fleabane, which are all much more susceptible to glyphosate when they are very small.”
“With robots, it’s not about how many acres you can spray in one day – it’s more about how many passes you can do in one season. More passes, gives you more opportunities to kill weeds when they are small and easy to kill and rotate chemical groups more often.”
The benefit of the robot and optical sprayer combination is that both operate equally well at night as in the day, and so can be out spraying whenever the conditions are within the optimal range of temperature, wind speed and humidity.
Andrew can also use a wider range of knockdown options such as glyphosate (Group M), paraquat (Group L), glufosinate-ammonium (Group N), and proprietary mixes such as amitrole (Group Q) plus paraquat when spot spraying to reduce costs.
“Running the robots weekly to hit weeds hard opens up untapped potential in existing herbicides because they are being spot sprayed on small weeds only,” he says. “This avoids the need for residuals in fallow and there’s even the option to add spot cultivation if required.”
“With robots you can spot spray a paddock that an agronomist would say was not worth spraying. Having a low weed seed bank means there is less pressure to go spraying straight after rain because there will be fewer weeds germinating.”
With 4000 ha of summer fallow to keep clean Andrew is also re-evaluating their double-knock strategies using the robots. He is finding that the proprietary mix Alliance (Group Q + L) is a good double knock for glyphosate and he often puts two compatible modes of action in the same tank mix.
“The WEEDit makes double-knocking much more practical, and using the robots means the workforce and family have less exposure to chemical,” says Andrew. “We can afford to double-knock more often.”
Where weedy patches have established Andrew employs patch management strategies to prevent seed set. Intensive herbicide treatments or use of the robotic cultivator are now options at Bendee, particularly if the weed escapes are large plants.
“Ideally we are working toward the development of microwave technology for the robots rather than targeted tillage,” says Andrew. “Microwave weeding is only practical on a robotic platform and when applied using weed detection there is a big reduction in the energy required. For us, the key advantage is the zero soil disturbance – a lot of weeds thrive in a disturbed or cultivated environment even if the disturbed area is small.”
Andrew and Jocie see microwave technology as a good non-herbicide option that is compatible with robots and no-till farming systems. This prototype is proof of concept.
Along fencelines and paddock edges Andrew has reduced his use of 2,4-D in the last few years due to the impact 2,4-D has on glyphosate efficacy on key species such as sowthistle and feathertop Rhodes grass. Instead he is now doing more passes with broadleaf herbicides on borders and hand-spraying feathertop Rhodes grass.
“Buffel grass provides good competition for weeds along fences,” he says. “It is very important to just use broadleaf selectives and preserve the buffel, otherwise you end up with all sorts of weeds.”
Robotic planting
The Bates have built a planter that the SwarmBot can tow and in time they expect to have the robots completing the whole planting operation. Previously the SP sprayer was used to apply the blanket spray in front of the tractor with the planter but now the two robots can follow each other, one applying the blanket spray and one towing the planter, with both operating at 10 km/hr.
The controlled traffic system at Bendee is based on a 12 m header front, spraying band of 12 m and the 6 m robot planter will make extra wheel tracks but apply far less weight to the paddock than the conventional planter that has wheels every 4 m, with each wheel applying more weight than a whole robot.
SwarmBot planter set up for planting cotton.
Other resources:

SwarmFarm: Target small weeds year round
Robotics opens up more non-herbicide options

Article
Article

Harvest weed seed control in a nutshell

*Note: In Australia we call the whole machine a harvester, not just the cutting front.
At harvest time many weeds that have grown in the crop still have seed held in the seed head. These seeds enter the harvester along with the grain and most exit the harvester and are spread across the paddock in the chaff and straw.
Collecting these weed seeds at harvest and either destroying them or depositing them in a known location where they can be monitored and controlled later, is an excellent way to stop weeds in their tracks.
Brome grass is the most costly weed for Mallee farmers to manage, even though herbicide resistance in brome grass is currently low in the region.
If you are considering adding harvest weed seed control (HWSC) to your weed control program there are excellent resources on the WeedSmart website to help guide you through the initial decisions and the implementation of this important weed control tool.
Key messages:

Decide on which system fits your farm best.
Get maximum weed seed into the header.
Know how to manage the collected weed seed.

Which system is best?
HWSC is being rapidly adopted in Australia and other countries around the world. There are six systems currently being used on Australian farms and they have all been developed by farmers. Research has demonstrated that all are very effective weed control tactics, achieving over 80 per cent control and for some nearly 100 per cent.
There are six systems currently used to collect and manage weed seed at harvest:

chaff carts
chaff lining
chaff decks (chaff tramlining)
impact mills
Bale Direct
narrow windrow burning

While they are all effective, they vary considerably in capital and ownership cost, nutrient removal costs, operational costs and labour costs. Some HWSC tactics involve the purchase of substantial machinery – such as an impact mill, chaff cart or chaff deck – but the operational and labour costs might be lower than methods such as narrow windrow burning, which involves low set-up costs but higher nutrient losses and labour costs associated with burning. Invariably narrow windrow burning is the most expensive option in the long-run due to the high nutrient removal cost.

To calculate the cost of each method for your farm you can use a calculator developed by AHRI’s Peter Newman. https://www.weedsmart.org.au/calculating-the-cost-of-hwsc-for-your-farm/
The HWSC tools all involve some modification to the harvester. The simplest modification is for chaff lining and narrow windrow burning, where a simple chute is attached to the rear of the harvester to direct the residue into a band on the ground, running the same direction as the harvester has travelled. These chutes are often constructed and fitted on-farm.
All the other systems are commercial modifications that are fitted to the harvester – chaff decks and impact mills – or trail behind the harvester – chaff cart and Bale Direct.
WeedSmart resources:

Videos from the HWSC course outline the science and practice of HWSC https://www.weedsmart.org.au/resources/hwsc/
Calculating the cost of HWSC https://www.weedsmart.org.au/calculating-the-cost-of-hwsc-for-your-farm/
Stepping into chaff lining https://www.weedsmart.org.au/stepping-into-chaff-lining/
Using your harvester to destroy weed seeds https://www.weedsmart.org.au/using-your-harvester-to-destroy-weed-seeds/

Get the weed seeds into the header
Harvest weed seed control only works on weed seed that enters the header. Getting the weed seed into the header relies on the seed being held in the seed head at the time of harvest. The seed head must also be at harvestable height.
Consider the weed spectrum and the likelihood of seed capture. Even if some seed has shed, chances are there will be other seed heads that have not yet shed and even this will assist with reducing the amount of seed entering the seed bank.
There are four chaff-only systems and two all-residue systems.
The chaff-only systems – chaff carts, chaff lining, chaff decks and impact mills – require the harvester to be set up to separate chaff and straw, and to keep the weed seed in the chaff stream. This may require modifications to the harvester rotor and sieves and the installation of a baffle to keep the weed seed in the chaff stream.
If you choose the Bale Direct system or narrow windrow burning, all the straw and chaff ends up in the same place, so no other modification to the harvester is needed.
WeedSmart resources:

Harvester setup for HWSC https://www.weedsmart.org.au/webinars/harvester-set-up-for-harvest-weed-seed-control-hwsc-for-all-header-colours/
Getting weed seed into the chaff stream https://www.weedsmart.org.au/setting-up-harvesters-to-capture-weed-seed-in-the-chaff/
Using HWSC in different weed spectrums https://www.weedsmart.org.au/is-harvest-weed-seed-control-a-real-option-for-managing-northern-region-weeds/

Manage the weed seed after harvest
If you choose an impact mill as your HWSC tool then the tactic is completed in one pass at harvest, with nothing extra to do. All the residue is spread in the field and the weed seeds are rendered unviable.
All the other HWSC tools involve some action after harvest to remove or destroy the weed seed collected at harvest.
Chaff decks deposit the weed seed-laden chaff in one or both harvester tramlines or wheeltracks. Some growers find that the chaff rots and the weed seeds die, but in other environments growers find that it is necessary to control weeds that germinate in the tramlines using herbicide or non-herbicide tactics applied just to the tramlines.
Chaff carts can be emptied as they fill in the paddock or emptied at a central point. Many growers use chaff piles as a high nutrient value stockfeed, others burn the piles and others leave them unburned in the paddock and sow through them the following season.
Chaff lines are usually left unmanaged with the expectation that the following crop will provide adequate competition to the weeds to minimise weed growth and seed production.
The Bale Direct system results in large bales of crop residue that can be sold into suitable markets. Distance to market is usually an important factor in the success of this system for HWSC.
Narrow windrow burning uses fire to destroy the weed seed in the Autumn following harvest. There are significant labour costs and safety risks to consider along with the loss nutrients and ground cover.
Key resources to learn more:

Diversity Era online course – Harvest weed seed control 101 https://www.diversityera.com/courses/harvest-weed-seed-control-101
Kondinin Group Residue Management at Harvest – Weed Seed Options research report https://www.weedsmart.org.au/app/uploads/2018/06/RR_1802_weedsmart.pdf
Kondinin Group Harvest Weed Seed Warriors research report https://www.weedsmart.org.au/app/uploads/2020/05/RR_February_2020_Weedsmart.WS_.2020.pdf

Grower experiences:

Chaff decks and chaff lining in a high rainfall zone https://www.weedsmart.org.au/case-studies/esperance-growers-using-chaff-decks-and-chaff-lining/
Keeping pressure on brome grass with HWSC https://www.weedsmart.org.au/case-studies/bruce-family-alford-sa/

 

 

Article
Case Study

Beefwood Farms, Moree NSW

The combination allowed for more efficient and targeted use of herbicides through double knocking and more timely and frequent applications to treat weeds at their most susceptible growth phase.
 
Beefwood Farms manager, Glenn Coughran.
With low weed density across the 11,000 ha operation Glenn is able to avoid the use of pre-emergent herbicides, which have limited crop rotation choices in the past, particularly in years where summer rainfall has been low. Glenn is keen to see ‘green-on-green’ optical weed detection become a reality and is working closely with AgriFac to have this technology integrated into their spraying equipment.
Located between Goondiwindi and Moree on the western side of Newell Highway, Beefwood Farms is an aggregation of six neighbouring properties, all operated from the central workshop area. Gerrit and Pam Kurstjens, originally from Grubbenvorst, the Netherlands, purchased the aggregation in 2006 and began the transition from livestock to a controlled traffic continuous cropping operation using the latest technologies to achieve greater efficiencies.
Beefwood Farms owner, Gerrit Kurstjens (left) with his daughter Marieke and MCA Ag agronomist Stuart Thorn.
“Our cropping program has to respond to the weather, and to a lesser extent prices, but normally the sequence is wheat then barley then chickpea or left out for winter and into sorghum in summer,” says Glenn. “We are keen to try dryland cotton but unless we have conditions that result in a full profile of soil moisture it just isn’t a feasible option.”
“Each year we fallow about 20 to 25 per cent of the farm in winter in preparation for planting the summer crop,” he says. “If the sorghum is off soon enough these paddocks are usually double cropped back to chickpea the next winter. This tactic gives us two consecutive winters to work on any winter grass weeds, particularly wild oats, using different chemistry.”
But with a string of very dry years recently the opportunities to grow summer crops has been limited.
They generally avoid using residual chemistry in summer due to concerns over the possibility of insufficient late summer rainfall to breakdown the chemical prior to planting the winter crop.
“We have been caught using imazapic in a summer fallow and then we didn’t get the necessary 150 to 200 mm of rainfall needed to break down the residual,” he says. “This meant we had to grow Clearfield barley, which was a good option in the circumstances, but you are restricted to just a few varieties and we don’t want to be limited in our crop choices too often.”
The CTF system is based on 3 m machinery wheeltrack centres, 12 m headers, 24 m planters, 48 m self-propelled boom sprayers and 24 m WEEDit optical sprayer. Beefwood operates two NDF disc planters for the winter cropping program – a double bar machine planting on 33 cm row spacing and a newer single bar machine where the closest spacing they could achieve is 37.7 cm. The sorghum crops are sown on 1.5 m row spacing.
“We can’t sow the cereals any closer to increase crop competition but we have seen a response to increased seeding rates,” says Glenn. “Also, the whole farm is planted east-west to maximise shading in the inter-row. This helps a little in the sorghum too where increased seeding rates would not create any competition outside the row.”
In drier years Glenn will often increase the area sown to barley as it has a greater competitive ability and tends to perform better under marginal soil moisture conditions than wheat.
Beefwood Farms’ consulting agronomist is Stuart Thorn, a director of MCA Ag, Goondiwindi. Stuart oversees the herbicide program for the operation, including recommendations for herbicide mixes and rotation of herbicide modes of action.
“Bringing in new country into our cropping program usually involves tackling large weed populations such as a recent acquisition where barnyard grass was a big problem and we used residuals to help regain control,” says Glenn. “Residuals have also helped with feathertop Rhodes grass, and then we backed away once the problem was under control, which usually only takes a few years.”
In the fallow Glenn uses a double knock of glyphosate applied as a blanket spray and then followed up with paraquat to treat any survivors using the optical sprayer. They also use glyphosate at robust rates through the spot sprayer and no longer mix glyphosate and 2,4-D.
To stop weed seed set in-crop Glenn will often implement a late spray of a Group Z grass selective herbicide, flamprop-m-methyl, to patch out weedy areas of wild oats in wheat. Chickpeas are always desiccated to prepare the crop for harvest and this can have some weed control benefit going into the fallow.
Picloram applied in cereals to control broadleaf weeds such as sowthistle also provides a residual effect to reduce fleabane germination in July/August.
“Maintaining stubble and ground cover is our number one priority so there is no cultivation for weed control or any other purpose,” says Glenn. “Our best chance to grow competitive crops is to have stored soil moisture.”
At this stage Glenn has not implemented any harvest weed seed control measures at Beefwood but he is keeping an eye on developments. Due to the loss of stubble involved, they will not adopt narrow windrow burning but other tactics that maintain and spread stubble cover would be considered if the need arose.
Automation for spot spraying works well – but is now on hold
Having already seen the chemical savings and the weed control benefits of using optical spraying technologies for over 10 years, Gerrit and Glenn were looking for ways to extend the value of the technology to achieve even greater efficiency with chemical use, particularly in fallows.
“Gerrit has contacts with the Dutch company, Precision Makers, who had developed software for autonomous lawn mowers, and in about six months they had made the necessary modifications and installed the software on a Fendt 936 Vario tractor that we had on the farm,” says Glenn. “We found the autonomous tractor paired with the optical sprayer was a perfect fit, allowing us to spray 24 hours a day if conditions are right and to spray on the weekends without adding to our labour costs.”
After a few years they purchased a John Deere 8345 tractor, also fitted with Precision Maker equipment.
Over the last 10 years the optical spray operations have applied herbicide to an average 2 to 8 per cent of the field area, using robust rates, but this is still far more economical than blanket sprays.
The now-decommissioned automated tractor towing a WEEDit optical sprayer.
“We know it works very well when weed density is low. Now we can use the autonomous tractor to spray more frequently than you would with a driver, we have started pushing the boundaries and using the optical sprayer in paddocks with weed density of 30 per cent, knowing that we can keep coming back,” says Glenn. “Even at a higher herbicide rate this is cheaper than a blanket spray operation. The more often we go back the less large weeds there are and we are spraying smaller weeds that are easier to kill.”
In a recent spray job on 3500 ha of fallow the optical sprayer activated spray nozzles on just 0.7 per cent of the area, at a cost of 24c per ha for chemical, without a driver.
“Using the autonomous tractor is not about reducing our labour force,” says Glenn. “The person who used to drive the tractor is still looking after the spray job. The other job that is perfect for the autonomous tractor is tram track renovation.”
Every three years, usually following chickpeas when there is less crop residue, the tractor operates a TPOS flat track renovator along the 2 to 6 km long CTF wheeltracks – saving someone from a very boring job.
Having proven the value of automation to the farming system at Beefwood Farms, they have been forced to put their work in this area on hold after John Deere bought out the automated machinery component of Precision Makers in 2019 and have decided to concentrate on automated mowers for the turf industry. They are currently not servicing the automation software that Beefwood Farms had installed in two tractors.
“Unfortunately, until we find a suitable alternative, we have had to go back to fully conventional operations for spraying,” says Glenn. “It is hard to accept when we have seen the benefits of automation for these routine operations.”
A few years ago, Beefwood Farms bought a 48 m AgriFac self-propelled sprayer to increase their spraying capacity for blanket sprays and fallow spot spraying. The AgriFac sprayer is twice as wide at the WEEDit boom and can travel at twice the speed of the autonomous tractor, so even though there is a driver they are covering three to four times the area.

Green-on-green spraying
Beefwood Farms is also on the cutting edge of the latest innovation in weed detection and herbicide application, working with AgriFac and Bilberry in the testing of green-on-green spraying.
Since purchasing the AgriFac SP sprayer they have been keenly observing the advances in the artificial intelligence, or machine learning, and assisting with the field testing.
Beefwood Farms is working closely with Agrifac and Bilberry to bring green-on-green weed detection and spraying to reality.
To work in-crop the software on the sprayer needs to interpret the images from the camera, distinguish a weed from surrounding crop plants and then identify the species and size of weed. Within moments the sprayer needs to respond and deliver the correct herbicide at the right rate to the identified weed.
“The expectation is that the sprayer will be able to treat a ‘site’ of 30 cm square with exactly the right product at the right rate,” says Glenn. “This is really exciting technology and once it is fully developed we see no reason why it couldn’t be used autonomously.”

Article
Case Study

Kwinana East HWSC growers, WA

Having said that, growers in low rainfall areas have successfully implemented HWSC, even in cereal crops yielding 0.5 to 1.5 t/ha.
In 2018, GRDC invested in the collection of ten case studies with growers from the Kwinana East port zone around Merredin, WA to discover what modifications and tactics they were using to successfully collect and destroy weed seeds at harvest in this low to mid rainfall zone. The HWSC methods these growers use are narrow windrow burning, chaff lining, chaff decks, chaff carts and impact mills.
Former Planfarm agronomist, Dani Whyte, visited the growers who are all running very efficient, low cost operations to generate profits in this environment and seeing the benefits of HWSC in their farming systems.
Dani Whye, former Planfarm agronomist, visited ten growers from the Kwinana East port zone around Merridin, WA to discover what modifications and tactics they were using to successfully collect and destroy weed seeds at harvest in this low to mid rainfall zone.
“It is difficult to grow highly competitive crops in this region where the average rainfall range is 200 to 350 mm and the scale of operation often does not allow for high seeding rates and narrow row spacing,” she said. “This means that weeds such as ryegrass tend to have a prostrate growth habit and are generally not ‘held up’ by the crop at harvest. This results in a greater proportion of the weed seed being found closer to the ground where they can escape under the cutter bar, compared to what is typically seen in higher biomass crops.”
Since having the weed seeds enter the header is the critical first step to successful harvest weed seed control the growers have focussed on reducing harvest height to 10 cm or less above ground level. Because the crop biomass is low this does not impact on harvest costs but it is all the more important to ensure the paddocks are free of rocks and other obstacles.
“Along with low harvest height, many of these growers have also made minor modifications to the comb to maximise both grain and weed seed capture,” says Dani. “Sharp knives and lift kits have been shown to help gather the crop and weed seed heads onto the cutter bar in low biomass crops.”
Glen Riethmuller from DPIRD, has recommended attaching coreflute to the finger tyne reel to enhance the harvesting of low yielding crops, and this may also benefit weed seed capture. The coreflute sits approximately 25 mm longer than the reel fingers and has a sweeping action to pull grain and weed heads into the header front and prevent them falling backwards off the knife.
Farming a total area of around 7500 ha at Southern Cross, WA, brothers Clint and Wayne Della Bosca and their wives Jess and Dianne chose to add a chaff deck to their harvester for the 2016 harvest as part of their move into controlled traffic farming. Knowing where the weeds are has given them confidence to sow earlier and to use different herbicide options. It adds flexibility to the system. Having noticed that some weed seed heads were not entering the header front, even though he was harvesting as low as possible, Clint has fitted corflute to the reel and a narrow knife guard and extendable fingers to the header front to capture more weed seed and grain at harvest.
Quick tips for harvest weed seed control in low biomass crops
The most common tactics these ten grain growers used to maximise weed seed capture in low yielding or low biomass crops were to increase crop competition, make some simple modifications to the header front, cut the crop low, harvest weedy paddocks first and use their chosen form of HWSC in every paddock, every year.
WeedSmart western region agronomist, Peter Newman says growers are using these tactics and seeing benefits in their weed control, but there is limited research done to validate many of these practices.
“We do have strong evidence for some things though such as the impact of increasing crop competition any way you can, and cutting crops low to maximise weed seed capture,” he says. “The header front modifications are observed to work well and are generally relatively cheap for growers to trial on their machines and evaluate the benefits themselves.”
1. Crop competition

Establish competitive crops by sowing early, increasing seeding rates and east-west sowing where possible.
Choose competitive varieties, particularly for weedy paddocks.
Reduce row spacing to ‘hold weeds up’ in the crop canopy – a move from 12” to 10” row spacing or adopting paired row sowing can increase yield, reduce weed seed set and aid harvest of both the crop and the weed seed.

2. Header front modifications

Extended fingers and a narrow knife guard/ lift kit fitted to header front.
Sharp knife.
Narrow knife guard with plastic extension fingers to capture and hold heads on the front so they don’t fall forwards.
Coreflute attached to the finger tyne reel to pull grain and weed heads into the header front and prevent them falling backwards off the knife.

3. Harvest time

Choose a HWSC tactic that suits your farm. They all work well to reduce weed burden but there are differences in cost, additional work, nutrient concentration and stubble management.
Number 1 tactic – harvest 10 to 15 cm off the ground. Paddocks must be clear of stumps and rocks.
Harvest weedy paddocks first before weeds shed their seed or lodge. Clean down the harvester before shifting paddocks.

Chaff decks (pictured), chaff carts, impact mills, chaff lining and narrow windrow burning are all being successfully implemented in the Kwinana East zone.
Case study growers

Cusack family, Narembeen (narrow windrow burning)
Shadbolt family, Mukinbudin (narrow windrow burning)
McGinnis family, Merredin (chaff line)
Todd family, Dowerin (impact mill)
Crane family, Kondinin (impact mill)
Metcalf family, Dowerin (chaff cart)
Dolton family, Bruce Rock (chaff cart)
Turner family, Pingelly and East Corrigin (chaff cart)
Kirby family, Beacon and Nyabing (chaff deck)
Della Boscar family, Southern Cross (chaff deck)

Download whole booklet
Other resources

Podcast – Farmers share their HWSC experiences with Planfarm agronomist, Dani Whyte
AHRI Insight – Behind every successful HWSC approach is crop competition
Podcast – Harvest tips, crop topping + trifluralin resistance
Narrow row spacing: Is it worth going back? 

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