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Run down the summer grass seedbank in mungbeans

With investment from GRDC, researchers led by Professor Bhagirath Chauhan at the University of Queensland, have shown that both windmill grass and feathertop Rhodes grass can greatly reduce yield in mungbean, yet both weed species retain a large portion of their seed when the mungbean crop is ready for harvest. This gives growers the opportunity to use several tactics to reduce the seedbank of these two species while growing mungbean. Professor Chauhan says that even at the most competitive row spacing of 50 cm, mungbean yield was halved when there were around 40 windmill grass plants/m2 or just 11 feathertop Rhodes grass plants/m2 growing in the crop. Feathertop Rhodes grass competes strongly and produces masses of seed if it gains a foothold in a mungbean crop. “The good news is that both species have a high level of seed retention at harvest because mungbean is such a quick growing crop,” he said. “This gives growers the chance to vastly reduce the amount of new seed entering the seedbank.” “Even though these weeds have high seed retention at harvest they also produce a huge quantity of seed,” he says. “At peak weed density in our field trials feathertop Rhodes grass produced over a quarter of a million seeds per metre square and windmill grass produced around 100,000 seeds per metre square. So, even if a small portion of this seed enters the seedbank it can still equate to a large number of seeds to potentially germinate the following spring.” Feathertop Rhodes grass is known to begin germinating in late winter and early spring, well before a mungbean crop is planted so every effort should be made to eliminate all flushes of this weed prior to planting mungbean. Haloxyfop is currently registered for fallow control of feathertop Rhodes grass ahead of mungbean production and can be used to reduce the weed burden prior to planting mungbeans in the most competitive configuration of 50 cm row spacing. To reduce the risk of Group A resistance, use a double knock in this pre-plant situation to control any Group A herbicide survivors of these difficult grass weeds. Paraquat is the usual chemical double-knock partner in these situations and should be applied to small, unstressed weeds within 7 to 10 days after the application of haloxyfop. Both these weed species can germinate close to the same time as the mungbean crop, so early weed control is essential to maximise yield and minimise early weed competition. Although these two grass species are susceptible to several pre-emergent herbicides, only flumioxazin (Valor) is registered for use in mungbean. This Group G herbicide can be applied at least two months pre-sowing to provide enhanced knockdown and residual control of feathertop Rhodes grass in mungbeans, taking care to follow the ‘critical comments’ to avoid crop injury. Extra emphasis should be put on ensuring the paddock is as clean as possible prior to planting mungbeans. Inter-row cultivation may be an option provided the young plants are not injured, as wounds can allow entry of diseases such as tan spot or halo blight. Clethodim applied before the mungbeans begin to flower will provide effective in-crop control of small, late germinating grass weeds. Mungbean crops are commonly desiccated prior to harvest using either Reglone or glyphosate. Both of these Chloris weed species are generally unaffected by these herbicides as mature plants, so the desiccation of the crop is unlikely to stop weed seed set. Mechanical options such as swathing are currently under investigation and may provide a more reliable way to stop seed set on these weeds prior to harvest. Professor Bhagirath Chauhan, University of Queensland, says windmill grass and feathertop Rhodes grass both retain a large portion of their seed at the time of mungbean harvest, making harvest weed seed control an practical option to help reduce the weed seedbank. “Mungbean is a good candidate for harvest weed seed control, using chaff lining, impact mills and the like, because the crop is harvested at ground level so any weed seed held on the plants should enter the harvester front,” says Professor Chauhan. The WeedSmart Big 6 approach to help manage resistant and hard to control weeds combines the power of multiple tactics throughout the year and across a full crop sequence to reduce weed seed set. Although feathertop Rhodes grass and windmill grass both produce vast quantities of seed, the seed is very short-lived. If left on the soil surface the seed remains viable for only one to two years. All efforts to prevent seed set will be rewarded with a rapid decline in the weed seedbank for these two difficult grasses. GRDC has recently updated the ‘Integrated weed management of feathertop Rhodes grass’ manual, which provides detailed information on the ecology of this important weed, along with the tactics and strategies that can be used throughout a cropping sequence to manage the seedbank. Other resources Giving summer legumes the competitive edge FTR grass demands attention to stop seed set  Creating stiff competition for summer weeds GRDC manual: Integrated weed control for feathertop Rhodes grass 2020 update
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Cover crops can swamp fallow weeds

Whether they are resistant to herbicide or not, weeds generally do not compete well with vigourous crops, but in the fallow they can rapidly take advantage of the lack of competition for resources. Department of Agriculture and Fisheries researcher, Dr Annie Ruttledge has been running experiments at Kingaroy to investigate the benefits of bringing crop competition into the fallow phase of cropping systems in southern Queensland. Dr Annie Ruttledge, Department of Agriculture and Fisheries, Queensland weeds researcher is conducting trials to identify cover crop species suited to southern Queensland that have weed-suppressive traits. With investment from GRDC the cover crop project, led by Charles Sturt University, is investigating the weed-suppressive power of various cover crop species suited to either summer or winter fallows at three locations in the northern grain growing region – Kingaroy, Narrabri and Wagga Wagga. At the Kingaroy site, both winter and summer-growing cover crops were shown to suppress weeds by over 85 per cent and up to 95 per cent, compared to an untreated fallow where the sown weeds were not inhibited by a cover crop. While this level of control is worthwhile on its own, it is also backed up with either a chemical or non-chemical tool to terminate the cover crop and kill any survivor weeds. “In winter in Kingaroy, the best cover crops for weed control were grazing oats and tillage radish,” says Annie. “These species provided early season ground cover and suppressed our mimic annual grass weed, Italian ryegrass, by up to 94 per cent relative to the weeds-only fallow. None of the cover crop species we tried were able to suppress the quick-growing mimic broadleaf weed, Oriental mustard.” Winter-growing cover crop monocultures and mixtures. In summer, Annie says the best cover crop options for Kingaroy were white French millet, Japanese millet, forage sorghum and buckwheat. Again, early-season biomass and ground cover was the key to suppression of both grass and broadleaf weed mimics by up to 95 per cent when compared to the weeds-only fallow. Summer-growing cover crop monocultures and mixtures. So far in this trial, there has been no measurable weed suppression benefit in sowing mixed species cover crops rather than monocultures. However, a mixed species cover crop may be preferred if a grower is wanting to achieve multiple outcomes. For example, grazing oats may be selected as a fast growing and highly competitive species and teamed with a less competitive legume to boost soil nitrogen stores. “Obviously, the species selected will depend on the growing region and soil type,” she says. “Cover crops also provide many other services to the farming system and so the grower could select a cover crop species, or mix of species, that would also provide a break from disease or insect pressure, increase moisture infiltration, build up organic matter or break down compaction.” Source: Charles Sturt University Cover crops are an extension of the WeedSmart Big 6 tactic of providing crop competition to suppress weed growth and reduce the weed seed bank in an integrated weed management program. Annie says that light interception is a critical driving force in the effectiveness of cover cropping for weed control. In selecting cover crops for weed suppression, choose species that grow well in your locality and that restrict light penetration to the soil through strong early growth and the development of a dense canopy. For greatest benefit, terminate cover crops at maximum biomass, which should coincide with the beginning of flowering; however, earlier termination may be required if soil moisture is limiting. There is a large body of research work now underway to investigate other aspects of incorporating cover cropping into farming systems in various regions. While this work focuses on weed suppression, other researchers are looking into soil water and nutrient use efficiency under different conditions and in various cropping systems. Other resources Summer cover crops video DAF Day family case study Cotton cover crops Cover crops research update video presentation GRDC Update paper – Cover crops to provide groundcover in dry seasons
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Hit your target when spraying

The three things that the spray operator can and must control are nozzle choice, boom height and ground speed of the spray rig. Recently, there has been plenty of attention on some of the new technologies involving weed detection and artificial intelligence (AI), and companies like Goldacres are keen to deliver these to growers as they come to market, but their sales and marketing operations manager, Stephen Richards says the technologies behind effective and reliable droplet delivery to the target remain central to their spray rig designs. Goldacres sales and marketing operations manager, Stephen Richards says the technologies behind effective and reliable droplet delivery to the target are central to their spray rig designs. “At the end of the day, if the droplets of product don’t hit the target at the required rate you might as well have left the spray rig in the shed,” he says. “The best way to ensure the correct dose is applied and avoid spray drift is to pay close attention to setting the rig up correctly and operating it well.” In the last 20 years there has been a quiet revolution in nozzle design and much of this has been driven by the need to eliminate the risk of spray drifting downwind or being caught up in temperature inversion layers. “Years ago the standard nozzle was the XRT-jet flat fan nozzle that operated at a pressure of 1 to 4 bar, which gave good coverage in ideal spray conditions, but also produced more fine droplets that easily drift,” says Stephen. “Modern nozzles have been designed with the emphasis on producing medium to coarse droplets and using higher water rates to achieve adequate coverage.” The modern nozzles also have a wider pressure range of 1 to 6, or 1 to 8 bar, making the one nozzle type suitable for a variety of applications. When considering ground speed, Stephen says the technologies behind even rate delivery through the boom have made it possible for machinery manufacturers to build sprayers that can operate at higher speeds and cover more area in a day. “The Goldacres self-propelled sprayers have had a 3-tier nozzle system for about 20 years, where the first set of small nozzles come on when the machine is operating at 5 to 10 km/hr then the second and third sets activate when the machine is operating at higher speeds,” he says. This ensures that the correct product rate is applied at the headlands and wherever the operator needs to slow down. Another option is the ‘pulse width modulation’ system to adjust the volume through the nozzles in response to changes in ground speed. “Pulsing is particularly good for turn compensation with a large boom, where nozzles near the outside tip are typically moving twice as fast as nozzles near the machine,” says Stephen. “This means product would be under-applied at the tip and over-applied near the centre. Consistent under-dosing of herbicide is a particular risk in the evolution of herbicide resistance.” As boom length increases so does the need for high tech suspension and rate compensation for variable speed and turning. The boom height is also critical in reducing drift risk associated with the air turbulence behind the spray rig. A 20 cm change in height from the recommended 50 cm above ground to 70 cm can quadruple the quantity of air-borne droplets. “With booms now as wide as 48 m the suspension system is more important than ever,” says Stephen. “Goldacres machines use a system that minimises yaw, roll and pitch of the boom to give a stable spray platform and optimise spray coverage in undulating or uneven paddocks.” Before heading out to spray Stephen recommends operators check for blocked nozzles and at the start of each season, do a jug test to check for nozzle wear. The large investment in spray technology can be undone if nozzle choice and maintenance is neglected. “The jug test needs to show that each nozzle is delivering within 10 per cent of the nominated volume per minute for the specific nozzle type and size,” he says. “The cost of a new set of nozzles pales in significance against the cost of product wastage, a spray failure or the evolution of herbicide resistance on your farm.” Before heading out to spray Stephen recommends operators check for blocked nozzles and at the start of each season, do a jug test to check for nozzle wear. The WeedSmart Big 6 tactics that form an integrated weed management program to reduce the risk of herbicide resistance in weeds are supported by companies like Goldacres, who understand the importance of effective and safe herbicide application. Goldacres is working with Bilberry to perfect the artificial intelligence systems required to bring green-on-green weed detection to Australian farmers. These systems, along with the optical spraying technology that has been used for spot-spraying in fallows for over 20 years, are expected to deliver more targeted herbicide use into the future.
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Keeping glyphosate resistance rare

This has been the key message of weed management experts in Australia ever since 1996, when Australia’s worst weed, annual ryegrass, was found to be resistant to our most useful herbicide, glyphosate.   A few years later, the Australian Glyphosate Sustainability Working Group (AGSWG) was set up under the CRC for Australian Weed Management (Weeds CRC) to bring together commercial and research expertise from around the country with a determination to ‘keep glyphosate resistance rare’. With investment from the Grains Research and Development Corporation, AGSWG established a database of confirmed cases of glyphosate resistance in Australia and developed information products for all users of this important weed control tool. After guiding growers and agronomists through a critical 15 years of managing glyphosate resistance in Australia the AGSWG has been disbanded, however the work of advising farmers and other weed managers will continue. Keep weed numbers low and do everything you can to prevent resistant weeds from setting seed. Australian Herbicide Resistance Initiative (AHRI) director, Professor Hugh Beckie, says glyphosate means so much more than weed control to Australian farmers, particularly for dryland cropping. “This herbicide has been the means of achieving incredible productivity increases in dryland crop production, initially providing an alternative to tillage for fallow weed control and thus conserving soil moisture over summer,” he said. “It is also now used as a broad spectrum knockdown pre-seeding and post-harvest in many crops and in RoundUp Ready cotton and canola.” “As predicted, the incidence of glyphosate resistance is ramping up, having been heavily relied on for weed control since its introduction to Australia in 1976,” said Prof Beckie. “It is important to understand that glyphosate is not only used extensively on farms but also along roadways, fence lines, railway lines, in public parks and in home gardens. This means that resistance can, and does, evolve in many different settings and can move across the landscape in weed seeds and pollen.” According to the International Herbicide-Resistant Weed Database there are currently 20 species and thousands of populations known to have evolved resistance to glyphosate in Australia.    While this is a serious situation, and glyphosate resistance can no longer be considered ‘rare’, it is still possible to regain control of weed populations that have evolved resistance. One of the useful products that AGSWG published was a series of factsheets outlining the practices that should be followed and those that should be avoided. These factsheets have recently been updated and published on the WeedSmart website. There is a factsheet for each of the main glyphosate user groups – grain producers, cotton growers, horticulturalists, orchardists and vinegrowers, irrigators and managers of public lands and utilities. While the principles remain the same for all industries, there are some practical variations in implementation. Using a diverse weed control program and taking care to apply glyphosate in the optimal way can tip the scales in the grower’s favour and keep this valuable product as an option well into the future. Download glyphosate factsheets Northern grains and cotton factsheet Winter grains and irrigation factsheet Orchards and vineyards factsheet Roadside and railways factsheet Vegetable production factsheet

Podcasts

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Green on green technology ready to hit the market

Welcome to the last WeedSmart podcast of 2020! What a year it’s been. On this episode we take a deep dive into spot spraying. We’re joined by Bilberry CEO, Guillaume Jourdain who provides us with an update on their green on green spot spraying technology. WA Farmer Andrew Messina also was part of trial work Bilberry did on this technology and he joins us to share his experience. As this is the final 2020 podcast, we’d like to thank you – our listeners – for listening over the year. We love bringing you the latest information in the weeds space and look forward to sharing more stories with you in 2021. On the podcast we mentioned that even though things are winding up, we do have some new content filtering through. Our latest Ask an Expert is with our Northern Extension Agronomist, Paul McIntosh. Paul answers the question: What alternatives are there for desiccation and crop topping? Check it out here. Have a lovely break over the festive season! We’ll see you in the new year! ___________________________________________________________________________ Podcast presenters: Jessica Strauss & Peter Newman Podcast producer: Jessica Strauss Photos: Fiona Mann
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Regional Update – Paul Nelson, Croppa Creek, NSW

This is our last Regional Update for 2020. This was a new concept we brought about initially as a way to connect with you more due to COVID-19 disrupting in-person events, but it went so well we decided to keep it. So you can expect more Regional Updates in 2021! On this episode, we caught up with Total Ag Services Agronomist, Paul Nelson, from Croppa Creek in NSW. Paul gives us an update on the Northern region, with a focus on how they’re dealing with weed burdens over the Summer period.
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Grazing and baling chaff dumps and Mateno Complete overview

Today on the podcast we chat with WA farmer Clayton South about his experience with grazing chaff dumps. We also hear from Bayer’s Australian Field Leader of Integrated Weed Management, Craig White about their new herbicide product “Mateno Complete” and how to use it effectively and sustainably in your farming system. As mentioned on the podcast, our latest Ask an Expert on soil degradation can be found here. ___________________________________________________________ Podcast presenters: Jessica Strauss & Peter Newman Podcast producer: Jessica Strauss

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Andrew Kenny, Badgingarra WA

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
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Case Study

Mat Freeman, Walkaway WA

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.
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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
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.”

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