Case Studies

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Case Study

Edwards family, Port Broughton SA

Stacking weed control tactics for maximum effect Farming on the sand hill swales near Port Broughton on the Yorke Peninsula, Pete Edwards is doing everything in his power to stop herbicide resistance in brome grass and wild radish. “We take a zero tolerance approach to escapes, particularly with brome grass, and have used a chemical fallow in areas with high brome numbers,” he says. “It’s a case of ‘short term pain for long term gain’ and even after a chemical fallow we will chase any survivors by hand rouging or spot sprayer. Keeping on top of brome survivors has certainly paid off and we have seen numbers decline.” L-R: Tim Edwards, Chris Davey (YP-AG) and Peter Edwards. Chaff carts have served a purpose but their time on the Edwards’ farm is limited and this harvest they will most likely introduce a chaff deck system to replace the chaff cart. In wheat Pete has had good results with non-imi chemicals such as Avadex + Sakura and Avadex + Boxer Gold, in conjunction with narrow windrow burning, which helps manage the stubble and maximises the efficacy of these more expensive herbicides. “There are very few options for wheat so it is essential that we keep pressure on brome numbers in our other crops and also give the group B herbicides a rest to help preserve the imi-tolerant crop options,” he says. “We are only a few applications away from serious resistance issues with fop and dim chemistry. When patches of weeds are not killed by our normal herbicide applications we go back and apply high rates of clethodim to achieve 95 per cent kill, and then go back again to hand rogue any survivors.” Pete is also mixing fops and dims such as Select, Verdict and Factor and the Intervix brew to extend the life of these modes of action. He has seen the value of including adjuvants such as Supercharge for Factor and ammonium sulfate to maximise the impact on hard-to-kill brome grass. The Edwards have installed a digital weather station on their farm that also provides local data to ten other growers who subscribe to access the data. Having access to local, real-time weather information, including automated Delta T calculations, means that Pete and his neighbours can avoid frosty and dewy conditions and minimise spray drift, making every application as effective as possible. When collecting seed for herbicide testing Pete looks specifically for plants that are stunted or deformed as they are likely to be indicator individuals of what might be happening in the paddock and the results help him to plan ahead with chemical choices. The Edwards family have used chaff carts for 12 years and through extensive testing have proven that operating at a slower speed really does capture more weed seed. Rather than dropping small chaff piles across the paddocks the Edwards build large chaff dumps about 200 m apart. In addition to the chaff cart, Pete has designed a narrow windrow chaff management system of his own that drops the straw on the ground and places the chaff on top. “We did conventional narrow windrow burning 10 to 15 years ago and had several years where the windrows got wet and didn’t burn the weed seeds effectively,” he says. “Putting the chaff on the top of the narrow windrow means that even if they get wet the straw underneath will still give a good hot burn to destroy the weed seed.” Pete has designed a narrow windrow chaff management system of his own that drops the straw on the ground and places the chaff on top to give a good hot burn to destroy the weed seed, even if the windrows get wet. Narrow windrow burning is done mostly in the wheat paddocks with a known brome grass history. In recent years Pete has achieved very good results using his modified narrow windrow burning system in paddocks with very high brome and ryegrass numbers. The main disadvantage of narrow windrow burning is that it removes all the crop residue. Chaff carts remove between 10 and 25 per cent of the crop residue but the rest is spread on the paddock and has a dual benefit of suppressing weeds and conserving moisture. Pete says the extra soil moisture can save a crop germination in a year with a dry start. Even so, nothing can replace narrow windrow burning completely in very high weed pressure situations so Pete will continue to use his modified narrow windrowing chute when necessary. Chaff carts have served a purpose but their time on the farm is limited and this harvest they will most likely introduce a chaff deck system to replace the chaff cart. Pete sees some advantages of the chaff deck system over chaff lining, such as less dust off the wheel tracks during spray applications and not having any piles of chaff impeding sowing. Pete reckons the iHSD will revolutionise harvest and weed seed control and thinks there could be opportunities for contractors to invest in iHSD machines to assist growers by harvesting their weediest paddocks. “Even under best operating conditions the chaff cart puts 50 per cent of the brome grass seed in the cart, 25 per cent on the ground and 25 per cent goes over the rotor and into the bin. The suction system of the iHSD reduces weed seed losses over the rotor making it a more efficient option,” he says. Pete follows a 5-year rotation of wheat, barley, lentil, wheat, lentil in large, 100–200 ha paddocks. He sows all crops on 25 cm (10″) row spacing at high seeding rate for increased crop competition and, where practical he sows paddocks east-west to gain better weed control.To improve soil fertility, chicken manure is applied at a rate of 3 t/ha every three years on paddocks that need it; often ahead of wheat. Deep ripping on the sand hills has been an effective measure to alleviate compaction and improve crop performance. Pete hopes to eventually implement a controlled traffic farming system that will help preserve the value of operations like deep ripping and also make the chaff deck system more effective. The Edwards are also lifting productivity and reducing weed pressure on their poorer sand hill soils by double sowing barley, wheat and lentil crops. In just a few years Pete has noticed a real difference in the soil structure and moisture holding capacity. Other resources: Implementing the WeedSmart Big 6 on the Yorke Peninsula
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Case Study

Kevin Simon, Halbury SA

Getting started with chaff lining Farming 4000 ha of light sandy to heavy clay soil in the medium rainfall district of Halbury and Salter Springs SA, Kevin Simon trialled chaff lining for the first time in the 2017 harvest. Kevin planted early maturing PBA Wharton field peas to help bring annual ryegrass numbers back under control. The field peas yielded around 3–4 t/ha and, being early maturing, offered an opportunity to harvest early and catch the ryegrass before it lodged or set seed. Farming in the medium rainfall district of Halbury and Salter Springs SA, Kevin Simon trialled chaff lining for the first time in the 2017 harvest. He planted early maturing PBA Wharton field peas to help bring annual ryegrass numbers back under control. Kevin plans to plant TT canola into this paddock in 2018 using a disc seeder to minimise disturbance of the chaff line. “Harvesting low and early are important to stop ryegrass seed set but it also comes with difficulties because the ryegrass is still green and can bind up the rotors in the header,” he says. Kevin plans to plant TT canola into this paddock in 2018 using a disc seeder to minimise disturbance of the chaff line. With limited in-crop herbicide options available, Kevin relies on late season cultural control. Kevin’s experience with chaff lining “We spray over the top of the canola with a self-propelled sprayer then direct harvest to control ryegrass using the chaff lining chute,” he says. “Chaff lining is also a good way to collect volunteer crop seed from the previous season. The plan is to place the canola narrow windrows on top of the previous year’s pea chaff line, and burn the narrow windrows to control weed seeds collected during the harvest process.” Last summer was very dry and so there was very limited germination of volunteers and weed seeds from the field pea chaff lines. In wetter years, Kevin expects that volunteers would be the most dominant plant type within the chaff line, with ryegrass being the next most prevalent species present. If necessary, Kevin is prepared to apply a range of chemical and cultural control measures to target the weeds growing in the chaff lines. Lime applied on other paddocks has also helped reduce the ryegrass population.  
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Case Study

Bach family, Pittsworth Qld

In 1980 the Bach family of Toowoomba diversified their farming operation to include a commercial grain storage and handling facility. With a background in grain production the family knows what’s needed to provide an efficient and safe grain handling service for other farmers. Not only do they know the importance of cleaning and grading grain to bring it ‘up to spec’, they also understand the value of removing weed contamination from seed that is being retained for planting, removing extraneous matter that can lead to problems in long-term storage and selecting the largest seed with the highest germination percentage and early vigour. David Bach from Toowoomba Grain and Storage suggests harvesting much more grain than you need for seed, getting it cleaned and keeping the largest grain aside for seed. David Bach manages the family’s grain handling facility near Toowoomba, on Queensland’s Darling Downs. He says that since retained seed must be stored for longer than most grain is held on farm, it must be stored in optimal conditions. “Grading grain at harvest will remove trash such as leaf and stem material that can attract insects and mould while the grain is in storage, either awaiting sale or being retained for seed,” he says. “Once cleaned the seed then needs to be kept cool and dry to maintain seed quality.” “When planning to retain seed on farm, select the best part of the paddock and harvest it first,” says David. “This way you will have collected the seed with the greatest vigour, which will provide the most competition for weeds in the early growth phase.” If there is not an area of the paddock that is clearly better than the rest, David suggests harvesting much more grain than you need for seed, getting it cleaned and keeping the largest grain aside for seed. “Grading it hard means that you have the best chance to remove a large proportion of the weed seeds present and you will also have a more consistent line of seed with the highest germination percentage,” he says. “It is very important that grain is cleaned at harvest, before it is stored. Clean seed that is stored and managed properly can remain viable for over 9 years.” Farming operation Peter and Kylie Bach manage the family’s farming operation—1620 ha of barley, wheat, sorghum, corn, mungbean and some faba bean—at Pittsworth, 50 km west of Toowoomba. They noticed an increasing problem with herbicide resistant crops growing as volunteers in other crops and contaminating that grain. “For example, imi-tolerant sorghum might grow as a volunteer in another, conventional crop, and will not be controlled by the herbicides applied in that crop,” says Peter. “Further cross contamination can occur if that seed is unintentionally kept for planting. It is easy to become complacent about the herbicide tolerant crop plants growing on roadsides and the potential flow of seed from roadsides into grain paddocks.” Using the stripper front and chaff deck combination in their cereal crops has gone a long way toward solving their problems with volunteer crop plants from previous seasons. “The standing stubble has given us planting opportunities for summer crops that would not have been possible after a conventional harvest,” says Peter. “Barley stubble provides an excellent environment for planting mungbeans and when the mungbeans are harvested, the paddock has much better ground cover with the previously-standing cereal stubble being retained on the soil surface.” The stripper front leaves most of the stubble standing in-situ, meaning much less material needs to be processed in the harvester. Peter and Kylie find that the barley stubble can persist for a few seasons after the growing season, providing soil moisture conservation benefits in their summer cropping program. Benefits of retaining seed Retaining seed not only represents a cost saving for them, it also provides a back-up if some or all of a paddock needs to be re-seeded for any reason. Having a good supply of seed on hand means that growers can take advantage of favourable seasonal conditions. “We try to store enough seed here to plant half of the farm’s cropping area as soon as the soil moisture conditions allow,” says David. “This way we can make last-minute decisions and be confident that the seed we plant is clean and good quality.” “Especially when the price is up it can be difficult to source seed, so we clean five times as much seed as we expect to use and store it,” he says. “To get that seed we might clean 120 tonne of grain and just keep the best 10 tonne for seed knowing that it has been thoroughly cleaned and graded.” David cites black oats as the main problem in their area for barley and wheat crops, and sees that the wild turnip is soon going to be a major concern for growers. “It pays to clean mungbean seed very hard,” he says. “Just one tonne of seed is required to sow 40 ha so it makes sense for that tonne of seed to be the very best that you have available, and free of weed seed contamination.” Johnstone grass is the most difficult weed to remove from sorghum and maize crops in summer and David sees the herbicide tolerant hybrids providing some useful options for grass control in these summer crops. Seed cleaning equipment There are several types of grain cleaning equipment available that vary in their efficiency when it comes to weed seed removal. The Bachs use a rotary screen machine that has two main sections—1. an aspirator, where a fan sucks air through the grain, removing fine particles such as dust, and light material such as husks and some weed seeds and 2. the screens, where the grain rolls around inside a drum with different sized screens that allow the grain to be separated according to size. “Usually the grain is sorted into two sizes plus the gradings or screenings, where the vast majority of weed seed is collected,” says David. “Improving the grade of the sample is usually fairly simple, but cleaning for seed is much more time consuming and therefore costs more.” “Sometimes growers think that their grain is cleaner than it really is,” says David. “On farms where the spraying is contracted out the farmer may not be as aware of the weed populations around their property.” David says the value of having a commercial grain handling contractor do the seed cleaning lies in the contractor’s knowledge about how to set the machine up to achieve the best result. “The screens are expensive but it pays to use the right combination of screens to suit the grain and the weed spectrum,” he says. “It is probably not economic for a grower to invest in the large number of screens required to do the best job in all situations.” “Grading table gear does an excellent job to remove weed seeds too,” says David. “These machines are most commonly found at commercial grain packing and processing facilities and could be a viable option for growers to use in some situations.” Research conducted in Western Australia confirms David’s comments about the value of having seed cleaned by a specialist rather than using equipment, such as sieves or in-field rotary screens, that some growers use to clean their seed on farm. Economics of seed cleaning Growing seed for future planting needs to be a planned operation—start with clean seed, sow into a clean paddock, grow a competitive crop that suppresses weeds, keep the crop weed-free by taking action if individual plants survive treatment, harvest the best, cleanest part of the paddock, clean the seed hard and store it under optimal conditions. “Seed is very valuable and is worth investing in,” says David. “If you plant clean seed into clean paddocks the cost savings in time and herbicide will soon pay for the cleaning of the seed.” To determine how many weed seeds are present in a potential seed lot, collect a 1 kg sample and separate the crop seed from all other material. 100 weed seeds per kilo of cereal or pulse seed sampled equals around one weed per square metre when the crop is sown. A survey in Western Australia by the GRDC-funded Australian Herbicide Resistance Initiative found that un-cleaned seed samples can contain over 1500 weed seeds per 10 kg planting seed, which would add extraordinary pressure on the next crop. The AHRI survey found that the gravity table method of seed cleaning consistently produces the cleanest seed sample, reducing contamination to about 25 weed seeds per 10 kg. Sieves alone can bring the number down to about 150 weed seeds per 10 kg. For more information try these links Clean weed-free seed – don’t plant weeds When is clean clean enough?
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Case Study

Warwick & Di Holding, Yerong Creek NSW

From narrow windrow burning to chaff decks and weed-lining When you know something works there is a great incentive to find solutions to any problems that might stand in the way of its implementation. The knowledge that harvest weed seed control really works has fuelled the journey that Yerong Creek growers, Warwick and Di Holding, have taken to see the practice implemented on their farms, in every crop, every year. Over a decade ago they used windrow burning as a way to control annual ryegrass plants that had evaded in-crop selective herbicides. Warwick says they saw great results but stopped due to the additional workload and fire risks. “When ryegrass numbers started to build up again we knew we had to get serious about stopping seed set in these resistant plants,” says Warwick. “We knew narrow windrow burning was effective so we started there, but we were always looking for other ways that didn’t mean extra work or create fire hazards.” In 2013 Warwick built a narrow chute for the header and they dedicated themselves to narrow windrow burning (NWB) in their canola crops, which represent 25 percent of their cropping land, for three or four years. During this time they also used NWB in some wheat and lupin crops, but the risk of burning the whole paddock and fire escapes was a real concern. To reduce the time associated with lighting the rows, and to keep traffic on the CTF tramlines, Warwick modified an old trailing boom to carry three gas burners to light the windrows at intervals while travelling along the rows rather than across them. This saved time but there were still fire risks, especially in paddocks with a heavy stubble load from previous seasons. In addition to the fire risks Warwick and Di also noticed stubble cover was dramatically reduced, variation in soil moisture was affecting planting and it appeared that nutrients were being concentrated into the narrow windrows. To get away from these disadvantages the Holdings invested in two EMAR chaff decks designed to place weed seed-laden chaff from the harvester onto permanent wheel tracks, which they used for the first time in the 2016 harvest across their 2000 ha property and 700 ha contract farming area. This coincided with 2016 being a very wet winter that resulted in a big blow-out of ryegrass in the wheat crop. In the following faba bean crop Warwick did everything possible to reduce weed numbers and contain seed set. Instead of returning to wheat in 2018 as he usually would, Warwick plans to implement a double break crop tactic by following the faba bean with canola. EMAR chaff decks designed to place weed seed-laden chaff from the harvester onto permanent wheel tracks. The Holdings have been controlled traffic farming since 2006 using 3 m centres so the chaff deck system suits their system perfectly, delivering the weed-laden chaff onto permanent, bare wheel tracks. “When I went to WeedSmart Week in WA in 2016 we visited Gary Lang at Wickepin and Trevor Syme at Bolgart and could see the results of using chaff decks in their farming systems, which are similar in many ways to ours,” says Warwick. “The idea of dropping weed seed onto wheel tracks every year was very appealing, along with only having to deal with the chaff fraction while still having the straw spread across the paddock.” “The chaff deck system ticked all the boxes for us so when we returned home we ordered two, one for each of our harvesters,” he says. “One added benefit that we hadn’t counted on is that the chaff on the wheel tracks reduces the amount of dust that is generated when spraying and we are seeing better herbicide efficacy as a result.” The chaff decks concentrate the weed seeds in the hostile environment of the wheel tracks, making it easier to deploy tactics that specifically target the (predominantly resistant) weeds that might germinate in the wheel tracks. “Many other growers who have used chaff decks for several years have assured us that most of the weed seed just rots away after harvest but we are not yet confident enough in this happening,” says Warwick. “We had quite significant germination of weeds in the tramlines after our first harvest with the chaff decks and we decided to spray these ‘weed-lines’, which represent just 8 per cent of the paddock.” The chaff decks concentrate large numbers of weeds into the bare tramlines. Warwick dismantled the gas burners he had installed on the old bar to light up narrow windrows and has rejigged the bar to carry spray lines with nozzles to spray out six tramlines (3 sets) in one pass. Warwick’s weed-lining rig can spray out three sets of tramlines in one pass. “I call it ‘weed-lining’ and use it as a cost-effective way to do site-specific weed control,” he says. “We have found that the weeds growing in the tramlines are more advanced than those growing in the paddock, so having the weed-lining spray bar means I can get on early, before the frosts, and treat the weeds in the tramlines when they are small without wasting herbicide on the rest of the paddock. A blanket spray that would cost $48/ha is replaced with a weed-lining spray costing $3.84/ha.” Being such a low-cost operation means that it is practical and economic to treat multiple germinations of weeds if necessary to ensure each application is as effective as possible and results in reduced weed numbers. “Seeing the weeds germinate in the tramlines is also encouraging in a way because you can really see that the chaff deck is capturing the resistant weed seed and putting it where you can deal with it effectively,” he says. Following the second year of harvesting with chaff decks Warwick has noticed that the chaff material is rotting better in the thicker, two-season chaff rows. The reduced dust levels continue to provide greater efficacy for the summer spraying program. A move from tine to disc seeding has meant that Warwick now uses minimal trifluralin and as a result has seen an increase in ryegrass survivors in wheat crops. The annual ryegrass on the farm is resistant to Group A dims and fops along with some Group B resistance and some resistance to glyphosate in non-crop areas. Warwick is targeting glyphosate resistance with double-knock and chipping to remove resistant plants before they enter the cropping areas. Black oats is evolving resistance to Group A on some of their heavier clay soils. Warwick and Di generously hosted other farmers and agronomists on their farm as part of WeedSmart Week 2017 in Wagga Wagga.
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Case Study

Cleave Rogan, St George Qld

Farm hygiene cottons on The release of a range of Roundup Ready (RR) crops in the USA has generated wide-spread resistance to glyphosate across their main cropping zone where RR cotton, maize and soybean were routinely grown without any other weed control tactics implemented. This is a scenario that St George farmer and cotton industry leader, Cleave Rogan, does not want to see repeated in Australia. He believes that the cotton industry must lead the way in Australia in managing glyphosate use across the rotation. Cleave and Johnelle Rogan, St George have implemented an integrated weed management plan since purchasing Bookamerrie in the mid 2000s, with an emphasis on beginning every cropping season with very clean paddocks. “Roundup Ready technology is a great tool for controlling weeds and in Australia we have RR cotton and RR canola, but unlike in the USA, these RR crops are seldom grown in the same paddocks. However, we do have a long history of relying on glyphosate in the fallow,” he says. “In the 20 plus years that we have grown RR cotton in Australia there has definitely been a shift in the weed spectrum on our farms, in favour of species that are tolerant of this mode of action.” Prior to the introduction of Roundup Ready cotton varieties, bladder ketmia was the dominant weed on the Rogan’s 425 ha irrigated farm, ‘Bookamerrie’, in the St George Channel Irrigation System. Now feathertop Rhodes grass is the main weed of concern, along with fleabane and vines; a weed spectrum now dominated by species that have a natural tolerance for glyphosate. Feathertop Rhodes grass is amongst the new suite of weeds challenging cotton production. Cleave and Johnelle purchased Bookamerrie in the mid 2000s and Cleave implemented an integrated weed management plan since day 1, with an emphasis on beginning every cropping season with very clean paddocks. “The wider spectrum of weed species makes control more challenging and requires an on-going effort to maintain a high level of farm hygiene,” says Cleave. “We keep glyphosate for in-crop weed control only and generally use Spray.Seed (paraquat + diquat) to provide broad spectrum knockdown of weeds in non-crop areas and fallow.” In-crop they use inter-row cultivation when the crop is small and apply a residual lay-by herbicide before the crop canopy closes over the row. “With the introduction of Roundup Ready technology we decided to continue the practice of a lay-by herbicide application however we have dropped out a pre-planting application of residual chemistry. Starting crops off in very clean paddocks has always been our priority.” Cultivation plays an important role in weed management between crops, starting with ripping and side-busting to 100 mm or more after the cotton is harvested. This plays a dual role in managing weeds and disrupting the lifecycle of the heliothus moths. This is followed with bed-formation, fertiliser application and seed bed preparation — providing up to three cultivations between harvest and planting. In a wet winter, weeds typically germinate in late winter or early spring and may necessitate an additional cultivation prior to bed preparation. Although the introduction of Bollgard 3 comes with a reduced requirement for pupae busting, Cleave plans to continue using the tactic as a way to control herbicide resistance risk. “We are modifying our cultivation practice to help conserve soil moisture. The 680 mm overlapping Versa Sweeps only cultivate the top 20 to 30 mm, which gives good weed control without drying out the topsoil. It also maintains the bed shape required for furrow irrigation,” he says. “This implement gives us a choice between chemical and mechanical tactics at planting, allowing us to respond to either weed pressure or bed maintenance needs of the paddock.” “Having this extra flexibility means we can rip and fertilise, then leave the paddock to conserve moisture before doing a final preparation for planting. The amount of trash in the paddock also plays a part in this decision, whether we need to cultivate to incorporate the trash.” “Bio-technology, including RR, has delivered improvements in cotton yield and quality every three to four years,” he says. “Each new variety also gives growers more flexibility in their farming system. In the early varieties, herbicide could only be applied when the crop was very small but more recent varieties allow applications of glyphosate at any stage of the crop, right up to 22 nodes.” Cleave says the majority of their weeds arrive on farm in either irrigation or flood water. “Weeds will appear first in channels and head-ditches,” he says. “Once the crop is picked and the modules delivered we start on the residual herbicide program for the roads, channels and dams. This must be complete by the end of June to allow good incorporation by winter rainfall.” There are a limited number of registered herbicide options available but Cleave rotates modes of action (MOA) as much as possible, basing herbicide choice on the likely weed species present. Cleave has installed an automatic weather station at the homestead that collects data on wind, temperature and humidity to calculate Delta-T based on local conditions. This information is presented in a visual format that allows the spray rig operator to monitor the trend in Delta-T and to change nozzles or stop spraying when conditions change. “The visual representation of the data on mobile devices means the operator can decide whether to stop spraying, re-fill or just finish the tank,” he says. Cleave’s IWM program in cotton Start clean Spray glyphosate at crop emergence Light inter-row cultivation Irrigate Spray glyphosate at 6 nodes crop stage Cultivate and apply lay-by (residual) herbicide Irrigate If necessary, apply glyphosate at 16 node stage to control late emergence weeds Crop closure — irrigation as required Defoliation of crop (no impact on weeds) Harvest Mulch and root cut cotton Ripping for pupae busting Cultivation for bedforming and seedbed preparation Cleave says growers need to be continually looking for other ways to disrupt weed growth and seed set. He says chipping out survivor weeds along roadsides, in channels and head-ditches needs to be part of every-day management, along with putting in practice ‘come-clean, go-clean’ protocols. Cropping program at Bookamerrie The Rogans are primarily cotton growers, with corn, sorghum, mungbeans, chickpea and wheat grown when seasonal conditions and water availability allows. All crops receive some irrigation and the aim is to produce high yielding, high quality crops that justify the use of irrigation. If sufficient rain falls in autumn Cleave generally looks at chickpea as a good rotational crop for cotton. With this in mind he pre-fertilises some paddocks and leaves others for chickpea in the hope that adequate rain will fall. In some unusual years, like 2016, the chickpea crop can be grown without any irrigation. “Each July we determine the base area that will go to cotton that year and we apply fertiliser to these paddocks,” he says. “If for any reason we don’t plant cotton in these paddocks, then we would plant sorghum or corn to use the fertiliser or leave the paddock until the next cotton season.” “As the water availability becomes known we can increase the area sown to cotton right up to the end of our planting window in mid to late-November.” Cleave’s farming system is based on 1 m crop rows, 2 m tractor wheel tracks, 8 m wide planter and implements and a 24 m sprayer. Avoiding the USA experience with glyphosate resistance Cleave Rogan is a strong supporter of IWM to protect the Roundup Ready technology, which is now the basis of the Australian cotton industry. Having seen the effect of glyphosate resistance on cotton systems in the USA when he toured farms in 2014, Cleave says growers need to be continually looking for other ways to disrupt weed growth and seed set. He says chipping out survivor weeds along roadsides, in channels and head-ditches needs to be part of every-day management, along with putting in practice ‘come-clean, go-clean’ protocols. “The one big mistake that growers in the USA made was to use glyphosate as their primary weed management tool in cotton and other crops as well as their fallow and non-crop areas,” he says. “Australian growers must take notice of this experience or we will face the same challenges. Dryland cotton and grain systems are most susceptible but it is also happening in irrigated systems.” When deciding on opportunity crops Cleave takes weed management and the use of different modes of action into account in both summer and winter cropping seasons. This is in keeping with the cotton industry’s Roundup-Ready stewardship recommendation of ‘2 + 2 and 0’ of two non-glyphosate control tactics both in-crop and in fallow, and a zero tolerance of survivors. “Feathertop Rhodes grass is a serious challenge for us,” he says. “We have had samples tested for glyphosate resistance, and at this stage the population remains susceptible but keeping it that way will rely on us maintaining a program that targets this weed when it is small.” Resources CottonInfo weed management page Resistance risk to knockdown herbicides on irrigated cotton farms Resistance in corn, soybean and cotton crops in the US
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Case Study

Brendan Swaffer, Clermont Qld

As an early adopter of zero tillage and controlled traffic farming in Central Queensland, Brendan Swaffer is fully convinced of the benefits, and is well aware of the potential impact of weeds like feathertop Rhodes grass. Since taking over the family farm near Clermont in 2007, Brendan and his wife Jody have been building a robust cropping program with wheat and chickpea in winter and, if soil moisture permits, dryland cotton and sorghum in summer across their 4000 ha of cultivation. Brendan and Jody Swaffer, Clermont have reintroduced tillage to their zero till controlled traffic farming system to manage weedy patches, primarily feathertop Rhodes grass. Dryland cotton has also been a useful addition to the rotation and provides another opportunity to manage FTR. “In the summer fallow our main weeds are summer grass, Johnson grass and fleabane but we are most concerned with the small patches of feathertop Rhodes grass that are appearing,” says Brendan. “We are using a mechanical and chemical double knock to manage these patches of FTR and it has been very effective for us in preventing its spread.” Early in summer Brendon targets any patches of persistent weeds – mostly feathertop Rhodes that has survived under the winter crop. Starting with cultivation of the affected areas, Brendan then follows up a few days later with an application of metolachlor (Group K) to provide short-term residual control of any new germinations that are triggered by the cultivation. “We might spend two days ploughing but only cultivate 150 ha in total,” he says. “For the rest of the year we carry a hoe in every vehicle and stop to chip out small areas of weeds when we see them. We have been enjoying the enormous benefits of zero till and controlled traffic since the 1990s – there is no going back to full cultivation, but it is a useful management tool to target weedy patches before they get out of hand.” Preventing seed set for a couple of consecutive seasons is known to rapidly rundown FTR seedbank as the seed on the surface or even slightly buried only persists for 12 to 18 months. Adding dryland cotton to their rotation has also helped minimise the spread of FTR. The Swaffers produced cotton in four of the five summers from 2010–11 to 2014–15, which enabled the application of Roundup Ready Plantshield to keep pressure on FTR and reduce seed set. Brendan has built in several non-glyphosate weed control measures including cultivation, along with other knock-down and residual herbicides, to take the pressure off glyphosate in their farming system. “Feathertop Rhodes grass is not a problem in conventional systems but the more area farmed the more difficult it is to keep clean,” he says. “It also seems to prefer scrub soils that are a bit lighter textured than the open downs country and alluvial soils we have on this property, giving us a slight advantage.” The fallow starts with spraying out sorghum in June with glyphosate to kill the crop, make harvest easier and kill the weeds. During summer, Brendan applies glyphosate, 2,4D-amine and small amount of metsulfuron (Group B) as a tank mix to target weeds when they are small and actively growing after a rainfall event. The metsulfuron is targeting parthenium and can also provide an additive effect on glyphosate when applied in a tank mix. After each spray application Brendan looks for, and manages any survivors or areas where the sprayer has missed, to minimise the number of weeds that escape and set seed later in the season. In recent years he has moved to more robust rates to ensure efficient weed control and to avoid the need to go over a paddock a second time. With the variable rainfall experienced in Central Queensland, chickpeas are now the Swaffer’s most reliable crop, using moisture seeking planting techniques. “We can plant in April or early May on rain received in February by planting the chickpea seed up to 18 cm deep,” says Brendan. “Chickpea is the only crop that has a long coleoptile that allows emergence from such depth.” Planting chickpea on 50 cm rows using moisture seeking techniques has established chickpea as the Swaffer’s most reliable crop. Brendan has found that a post-plant pre-emergence application of Terbyne (Group C) controls weeds up to canopy closure and no other in-crop herbicide is needed until the crop is desiccated prior to harvest. “Emergence can take three weeks, but we can establish a crop on stored moisture and have it up and away before in-crop rain initiates a fresh flush of weed germination, giving the crop a distinct competitive advantage.” The timing of a moisture seeking planting needs to factor in the frost risk in the district to avoid having the chickpea crop flowering when there is a high chance of frost. In some years there is moisture higher in the profile, allowing both chickpea and wheat to be planted about 10 cm deep. Wheat is also planted a little later in the Clermont district than in other areas of CQ, to avoid frost. Most growers prefer to accept the small yield penalty for planting later rather than risking a crop failure. “Strzelecki wheat is a slow maturing spring wheat of semi dwarf habit that is popular in CQ due mainly to its longer coleoptile length that allows us to plant to a depth of 10 cm,” he says. “But this variety is about to be re-classified to Hard 2 instead of Prime Hard and so many growers will be looking for alternative wheat for the future,” he says. Strzelecki wheat has been a mainstay variety in the Clermont district because of its ability to emerge from a depth of 10 cm. A change in classification of this wheat will most likely drive growers to look for a replacement variety suited to the conditions. Higher levels of crop competition can be achieved in the winter crops compared to the summer crops, with chickpea and wheat both sown on 50 cm rows. Brendan plants chickpea in his cleanest paddocks and uses a post-plant pre-emergence application of Terbyne (Group C) to control weeds up to canopy closure. No other in-crop herbicide is applied except for desiccation for harvest management. Brendon avoids using Balance due to the long plant-back period and the need for a lot of rain to breakdown the residual. Sorghum crops are sown on single skip metre rows, with cotton planted in double skip configuration of 2 in and 2 out to optimise yield and quality. Brendan previously planted sorghum in solid 1 m single rows but has changed to planting a single skip – 2 in and 1 out – and increased intra-row plant density. The soil on the Swaffer’s property requires about 200 mm of steady soaking rain to fill the profile and initiate a summer crop planting. Last season there was no summer crop planted due to a lack of soil moisture however the outlook year is looking more promising for sorghum but they have not planted cotton this season. “We are concentrating on achieving even intra-row spacing using a double disc precision planter to increase weed competition within the row,” he says. “This also promotes even maturity and reduces tillering. The combined effect encourages a shorter flowering period and makes grub and midge control easier, along with reducing the risk of ergot infection.” Sorghum is planted in January and early February following an application of glyphosate, Dual Gold and 2,4D, provided there is no cotton planted nearby. Brendan also applies atrazine and fluroxypyr to provide in-crop weed control. Metolachlor applied in the fallow ahead of cotton provides some residual weed control but the main in-crop weed control strategy is RR Plantshield. Brendan puts far greater emphasis on timeliness of weed control than on specific rates and products. At harvest, Brendan uses perforated screens in the header to remove as much Mexican poppy, and turnip weed seed and soil as possible out of the chickpea grain sample. He also keeps about 100 t of both chickpea and wheat seed that has been graded hard to ensure the cleanest possible seed goes back in the ground the following season. Brendon does all his own spraying with a John Deere 4030R self-propelled sprayer and likes to keep their spray technology up to date. He considers the sprayer to be their main tractor now and changes the sprayer unit every 5 years or so to always have new gear that works well and minimal downtime. “Our groundwater is quite hard so we use ammonium sulfate, especially when spraying out sorghum with glyphosate,” says Brendan. “Although we now have more access to rainwater, storing water is very costly so we have been assessing the difference between rain water and groundwater this year in terms of cost and efficacy on weeds. We expect to invest more in rainwater storage in the future.” Being in full control of the spray program means Brendan can ensure his neighbours are always informed regarding cotton plantings and he only sprays when conditions are suitable. “When sensitive crops are nearby it is all about working in the right conditions and being careful about product selection,” he says.
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Case Study

Darren Jensen, Biloela Qld

No-till doesn’t mean never till One of the major benefits to come from hosting research trials is that the results relate exactly to your environment and farming system. Central Queensland farmers, Darren and Tanya Jensen, were able to see for themselves the effect of a one-off tillage event on their otherwise no-till farming system. With fleabane and feathertop Rhodes grass gaining a firm hold within their 20-year no-till farming system, the Jensens wanted to know if cultivation would be an option to drive down numbers of these hard-to-kill weeds, or whether the damage to soil condition would be too severe. In 2017 Darren used the disc chain across about 40 per cent of the farm, targeting fleabane and feathertop Rhodes grass. “Yash Dang conducted tillage trials on our property near Biloela in 2012, 2013 and 2014, to investigate the effect of different types of tillage on soil properties,” says Darren. “We watched with interest and were surprised to find out that even the most aggressive tillage operations did not do much damage to the soil.” This opened up the possibility of using strategic tillage to manage the growing weed problem on ‘Grandview’ and the Jensen’s leased blocks. In 2015 Darren cultivated 1400 ha of their 1750 ha property with two passes of a chisel plough and then followed up in 2016 with one pass of a disc chain. “This meant we could drop three fallow herbicide applications from the spraying program, saving $84 thousand in chemicals,” says Darren. “In 2017 we used the disc chain again across about 40 per cent of the farm, again targeting fleabane and feathertop Rhodes grass.” “The last few years we have used cultivation to drive down weed numbers in a fairly intensive way but we would expect that, as time goes on, we will cultivate much smaller areas each year,” he says. “This intensive push has restored about 85 ha of land that had become too weedy for cropping, and lifted profits.” Having now re-introduced the use of cultivation on an as-need basis, Darren assesses the seasonal conditions in February / March and if there is sufficient moisture he will usually plant a sorghum or mungbean crop and if conditions are too dry to plant he will use the disc chain as part of his fallow management program. “Straight after harvesting the wheat and chickpea crops we apply a high label rate of glyphosate plus a residual then if there is insufficient moisture to plant a summer crop we apply a second knockdown and use the disc chain to remove any survivors. Wherever possible we will be looking to grow crops rather than weeds.” The disc chain pulls out fleabane and feathertop Rhodes grass as whole plants and also pulls out sorghum stubble. The machine only cultivates the soil surface and so is a useful tactic against weeds like fleabane and feathertop Rhodes grass that do not persist long on or near the soil surface. Darren says this might not be an effective tactic against weeds like wild turnip, which can persist for much longer if the seed is buried. “In this environment with summer dominant rainfall we often do not get a ‘spring break’ to provide a fresh flush of young weeds that can be effectively controlled with herbicide. This means that we don’t get many opportunities to do a chemical double knock,” says Darren. “The disc chain removes large plants before they set seed and also stimulates a fresh germination of weeds, which can then be treated with herbicide, after summer rain events.” Darren has also opted to purchase a Flexi-coil planter with press wheels to give him the option of a light cultivation at seeding if necessary, followed by a field roller, and he will continue to use the zero-till planter in paddocks where the weed numbers are low. “The moisture loss from the disc chain is not extreme and most crops will need a follow-up rainfall event anyway to get the secondary roots growing,” he says. “The other option is to use the disc chain ahead of the zero till planter. We are doing whatever we can to keep on top of the weeds.” “Planting with the conventional planter, followed with the roller, allows us to plant chickpeas in weedy paddocks with a pre-emergent herbicide to help with early weed control,” says Darren. “The chickpeas are sown 330 mm apart and the canopy closes over quite quickly, making them our most competitive crop.” Darren Jensen, Biloela CQ says Kyabra chickpea is his most competitive crop; sown at narrow rows and quickly achieving canopy closure. Darren has found that cultivation is a good double-knock partner to help protect his farming system from glyphosate resistant weeds and add more diversity to their weed control program. They are also using more pre-emergent herbicide options to reduce the number of glyphosate applications used across the farm. “We confine all our herbicide use to the cropped areas of the farm,” he said. “We let native grasses and other vegetation grow on roadsides and contour banks, otherwise feathertop Rhodes can gain a real hold in these areas if competition is removed.” Research gave the Jensens the confidence to adopt a weed control strategy that they were very hesitant about, and may not have used if they had not seen the evidence for themselves. As Dr Yash Dang, senior research fellow with University of Queensland says, ‘no-till does not have to mean never-till’. In a 4-year project with 15 trial sites from Emerald to Dubbo, Dr Dang investigated the effect of a range of tillage implements, used at different times and frequencies, on soil properties. “We found that neither disc nor tined tillage implements did significant damage to well-structured, high clay content soils such as vertosols,” he says. “However, more aggressive tillage has the potential to redistribute salts in sodosols and tillage at low moisture content may have detrimental effects on the aggregate structure of dermosols.” The benefits of occasional cultivation in an otherwise no-till farming system included breaking the soil- and stubble-borne disease cycle and redistributing nutrients from the surface layer into the root zone. “In terms of managing herbicide resistant weeds, or weeds that are inherently hard to kill with herbicide, the infrequent use of cultivation can certainly be considered as a viable option in the northern farming systems,” says Dr Dang. “The main consideration is when to conduct the tillage operation for maximum benefit without sacrificing a planting opportunity.” A similar trial recently conducted in southern NSW had a similar outcome, adding to the body of research that indicates occasional cultivation does not have a detrimental effect on the soil, provided other precautions are in place to protect the soil from erosion risk. Related resources: Strategic tillage tips and tactics (GRDC factsheet) Similar study conducted in sthn NSW
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Case Study

Neek Morawitz, Comet Qld

‘2 + 2 and No Survivors’ to protect RR technology At the junction of the Comet and Nogoa Rivers, 40 km east of Emerald in central Queensland, Neek and Robyn Morawitz grow a range of irrigated and dryland crops. One third of the 990 ha irrigated area is under four centre pivots and the rest is flood irrigated from their on-farm storages and the Emerald Irrigation Scheme. An additional 350 ha is operated as a minimum tillage dryland system.   Neek Morawitz grows a range of irrigated and dryland crops adjacent to the Comet River in Central Queensland. His herbicide and crop program aims to keep weed numbers low to minimise the risk of herbicide resistance. Roundup Ready Flex cotton with Bollgard 3 technology for helicoverpa control is central to the Morawitz’ business. As such Neek is keenly aware of the importance of keeping ahead of herbicide resistance. “To reduce the risk of glyphosate resistance we implement as many other weed control strategies as we can across the crop rotation,” he says. “In the fallow after an irrigated cotton crop we normally don’t use glyphosate at all, choosing to use paraquat, diquat and synthetic auxins such as 2,4-D early in the summer and then we also cultivate a few times to kill weeds, incorporate stubble and prepare the land for the next crop.” “Occasionally we will do a double knock mid-season in the fallow using synthetic auxin followed by paraquat, or glyphosate followed by paraquat. Applying MCPA in wheat crops is another opportunity to use synthetic auxins, however we restrict our use of these herbicides because of the risk of contamination of spray equipment and the potential for crop damage, particularly in cotton.” “We aim to implement the ‘2 + 2 and no survivors’ strategy of two non-glyphosate controls in-crop and two non-glyphosate controls in the fallow to extend the life of the Roundup Ready technology,” he says. “In-crop we are using inter-row cultivation, crop competition plus pre-emergent herbicide and in the fallow we use cultivation and alternative knock-downs such as paraquat and synthetic auxins.” In the following chickpea crop Neek also applies a different pre-emergent herbicide mode of action to keep weed numbers low in-crop. Cotton, sorghum and maize are grown on beds that are 960 mm apart, while wheat and chickpea crops are planted in four rows, 375 mm apart, across 2 m CTF beds. Neek pays close attention to achieving an even plant stand through precise seed placement and even germination. He says the use of GPS technology at planting has made a real difference to the competitiveness of crops by avoiding misses and overlaps. PBA Pistol, PBA Kyabra, PBA HatTrick and PBA Seamer chickpeas have all performed well in rotation with cotton, generally only requiring a pre-water and then one irrigation early in the flowering phase. “By using cultivation and strategic application of residuals along with sowing clean seed from our own farm we are getting a good even stand and very few weeds growing in our chickpea crops,” he says. Cover crop One of the centre pivot blocks has quite sandy soil that is prone to wind erosion. While soil loss is a real concern, so is the sand-blasting damage done to cotton seedlings on windy days. “We use cover crops such as wheat to protect the soil surface and the young cotton crop,” says Neek. “In fact the only wheat we have planted this winter is the cover crop on this block. Last summer we grew peanuts and baled the peanut crop residue after harvesting then planted the wheat cover crop, using a spinner, to provide surface cover for the next cotton crop.” This wheat cover crop was planted with a seed spreader to protect the sandy soil surface and conserve moisture prior to planting cotton. The cover crop was sown in mid-June after a glyphosate / paraquat double knock. In mid-September Neek brown manured the wheat with another double knock and left the crop in-situ until the cotton crop was direct drilled in late September. In addition to physical protection of the cotton seedlings Neek has seen other benefits to cover cropping, including better crop establishment and more even water distribution through the soil. Crop and herbicide rotation Much of Neek’s crop rotation centres on planning around plant-back periods for residual herbicides. On the irrigated portion of the property he chooses a mix of cotton, sorghum, maize, mungbean and soybean in summer. Neek doesn’t usually sow a summer crop on their dryland area, however, when the opportunity has arisen he has had success with dryland cotton, sorghum and mungbean. Since the introduction of Bollgard 3 cotton Neek has been taking advantage of the opportunity to plant as soon as the window opens on 1 August, particularly on the irrigated blocks. This means the crop can be harvested by late January, making both the dryland and irrigated crops more moisture efficient. The early plant also means land is free for double cropping into mungbean or sorghum if the opportunity arises. In winter, the whole farm is sown to either chickpea or wheat, if sufficient water is available. This simple rotation in winter maximises the effective use of cereal stubble for soil moisture conservation. Neek generally expects to produce three crops within a two-year timeframe, which allows for some double cropping and some fallow breaks. If necessary, Neek has the option to use irrigation to activate pre-emergent herbicide and help manage herbicide breakdown in periods of extended dry weather. “Our herbicide choices are based on balancing the expected impact on weeds and the crop safety of the following crop,” he says. “Our mix of crops allows us to be using a wider range of herbicides in both summer and winter.” “We grow some sensitive crops and so it is very important that the herbicides we apply hit their target and any drift is kept to an absolute minimum,” says Neek. “We don’t skimp on water rates and choose spray nozzles best suited to the herbicide and the conditions at spraying.” Non-crop areas and infrastructure To date, Neek has not identified any herbicide resistant weeds on the property however he has participated in a Department of Agriculture and Fisheries weed survey and is interested in seeing the results when they are released. “Feathertop Rhodes grass is our main concern here and it has the well-known tendency to establish on crop borders and non-crop areas around the farm,” he says. “To prevent movement of FTR into the cropped areas we are diligent with both herbicide and non-herbicide control methods, including using a flame-thrower to kill larger plants along irrigation channels and the like. With herbicide treatments we try to mix that up as much as possible, changing between glyphosate, paraquat, diuron and metsulfuron.” In non-crop areas such as around irrigation channels Neek has found that a flame-thrower is a good way to kill established FTR plants and prevent seed set. Other resources: Bollgard3 Roundup Ready Flex Cotton Weed Resistance Management Plan
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Case Study

John Stevenson, Lockhart NSW

Orange Park is an 8200 ha corporate dryland cropping operation with eight main blocks, all within a 30 km radius of Lockhart, NSW where John introduced the use of the double break from cereals 10 years ago.   To get the best result possible from OP canola, ‘Orange Park’ manager John Stevenson (left) has their seed professionally graded and only plants seed sized over 2 mm diameter. Karl Grocke (right) has joined the team at Orange Park on their graduate program, making the most of the opportunity to learn from great operators like John. “Our rotation is driven by herbicide resistant weed management,” he says. “A double break, such as hay/canola, pulse/canola, fallow/canola, is implemented once in a 7-year rotation. The rotation is flexible but we do what we can to avoid growing three cereal crops in a row because the result is inevitably a weed blow-out.” The main weeds on Orange Park are annual ryegrass in-crop and fleabane in summer, which has been increasing since 2005, particularly in wet years. Wild oats is a lesser but persistent weed. “We have low level glyphosate resistance and varying levels of Group A resistance to contend with,” says John. “We don’t use much Group B chemistry either, except occasionally in imi-tolerant crops, partly because of decontamination issues with canola, but mainly because of poor efficacy.” The wettest September on record in 2016 saw about 10% of the crop across the Orange Park operation inundated – compromising their weed control and nitrogen management. “Essentially we lost a year of weed control with ryegrass blow outs due to poor crop competition and not being able to do timely herbicide applications,” says John. “We also saw a shift in the weed spectrum with more carryover of weeds that thrive in wet conditions, such as toad rush and lesser loosestrife.” Crop rotation and double break cropping The rotation that is working well on Orange Park since 2008 consists of two cereals followed by canola, then another two cereals and finally a double break before returning to cereals. John incorporates as much diversity within the system as possible to maximise returns and keep pressure on weed numbers. Canola, wheat, barley, pulses (including faba bean, lentils and vetch hay), oaten hay for export, and strategic fallowing to conserve moisture, all feature in the list of options. The diversity in crops enables the rotation of herbicide groups, including pre-emergent herbicides ahead of each crop. Imi-tolerant crops such as Hurricane lentils, IT-canola, possibly barley in the future add to the mix although John often grows hybrid IT-canola conventionally simply for its inherent yield advantage. “The price of lentils is attractive however logistics are difficult, as grain needs to get to Horsham, over 6 hours away,” he says. “Realistically, canola and feed grain for poultry and feedlots are our mainstay crops.” To maximise the competitiveness of canola crops John grows some hybrid crops and also grades OP canola to 2 mm diameter as a cost-effective way to improve crop establishment and early vigour that also suppresses early weed growth. John uses TT canola when weeds become a problem issue and Clearfield canola in low weed population paddocks where he can also apply atrazine on volunteer faba beans. This year John planted 650 ha trial of lentils in a block that would normally have been fallowed. “There was good residual soil moisture from last year’s wet winter and we tried a late planting system to reduce the density of the lentil crop to keep air flowing through canopy, hopefully reducing the incidence of disease,” he says. “Weed control in the Hurricanes XT lentils has been exceptional although the crop has demonstrated the need for better pH amelioration at depth.” “Including lentils will spread the workload and we can target a different weed germination cohort,” he says. “Having a different group of herbicides available will also help add diversity to our control program.” Row spacing, CTF and stubble management John manages Orange Park as eight 1000 ha management units, where a unit may consist of several blocks in close proximity. He is looking at opportunities to implement east–west sowing in suitable blocks to maximise yield and reduce weed pressure. While on a Nuffield Scholarship trip to New Zealand, John saw crops grown on 125 mm (5 inch) row spacing where farmers were able to include ryegrass as a crop in their rotation, without concern over future weed problems. “Historically, our seeding has been on a 300 mm row spacing but we are in the process of investing in a full disc seeding system, which will allow us to narrow the row spacing to 175 mm (7 inches),” says John. The disc seeder will enable John to retain stubble from their 1.7 t/ha pulses, 3.4 t/ha wheat and 4 t/ha barley crops within their 18 m system with 3 m CTF tramlines. Harvest weed seed control John and his team have been narrow windrow burning for three years. Having tried this harvest weed seed control tactic in canola, wheat and barley crops they have found the safest and best results are achieved in canola. “Realistically, narrow windrow burning is not very compatible with the council’s fire regulations so we are looking at alternatives,” says John. “Cereal stubble burns for 4 or 5 hours, and whirlwinds can easily shift burning chaff 300 m into a neighbour’s stubble.” A downside to narrow windrow burning is that more moisture is stored under the narrow windrows, which can cause uneven crop germination the following season. John has been successfully using narrow windrow burning in canola for several years. Twelve days after sowing, this Lancer wheat crop shows the variability in germination where the rows under the narrow windrow have access to more moisture. John is looking into other options for harvest weed seed control and will probably phase out narrow windrow burning over the next few years. Chaff deck systems suit CTF and although John thinks they have merit, there are limitations on the options available when using contract harvesters. Chaff lining seems easier to implement and is likely to feature in the near future. “Narrow rows help push weed seed heads to the top of the canopy,” says John. “Two plants per m2 is too many, especially if the weed is able to adopt a prostrate habit and evade collection at harvest. The big challenge is getting inexperienced header drivers to harvest low, even though we pay the contractor a premium to have this happen.” John uses spray topping in canola, and sometimes wheat and barley, along with hay production to take out late germinating weeds. Fallow management Over summer, John uses a contractor with an optical (camera) sprayer to treat survivors with paraquat following a broadacre spray of glyphosate. He says the optical sprayer is also a valuable tool to help manage cud weed, which is becoming more prevalent. There is no routine cultivation in the system however John does incorporate lime with a speed tiller before planting and a full tillage using a flexicoil is done when there is levelling work required. “When we change over to the disc seeder we will probably need to cultivate to remove the ridges left by the tined system,” he says. “The disc seeders can’t handle too much chaff on the ground either, so burning is still an option for weed control, or when slugs and mice are a problem.” Soil fertility and weeds Across the Orange Park operation John has acidic (pH 4.5) red soil ridges and some sodic vertosols to contend with. He is using variable rate technology (VRT) to apply lime to the red ridges using rates ranging from 1 to 3 t/ha to lift the pH to 5.5. “We saw an immediate response of lower ryegrass population in low pH blocks after lime application due to stronger crop competition,” he says. “Variable rate application and soil testing has been very cost effective for us and has helped reduce weed numbers and improves herbicide efficacy. Fixing soil pH gives the best return on investment through improved nutrient availability, which supports higher yield and better weed control.” John is also using soil sensing and VRT to address constraints in nitrogen and phosphorus. The red soil ridges on ‘Orange Park’ are acidic (pH 4.5) so John is using variable rate lime applications to lift the average pH in these soils to 5.5. In doing so he has observed an immediate reduction in ryegrass numbers due to the improved crop competitiveness.  
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Case Study

Aaron McDonald, Horsham Vic

Farming with his parents, Greg and Leanne, Aaron runs 5500 ewes for wool and prime lamb production, utilising pastures, hay paddocks and crop stubble on their 4050 ha property. The McDonalds are finding a rotation of canola, wheat, canola, wheat, then a double break of canola followed by faba beans or clover hay, is profitable and enables them to keep weed numbers down. In barley crops the straw is also often baled after cutting the crop low, allowing sowing without stubble burning. Aaron does most of their oaten hay production on the poorer soils but also uses oaten hay as an effective means to clean-up paddocks that have a higher infestation of ryegrass. Their clover hay is sold locally, predominantly as cattle feed, while their oaten hay is exported most years. “Annual ryegrass and wild radish are our main problem weeds,” says Aaron. “We test for herbicide resistance every couple of years and so far the results have come back as ‘susceptible’ for most of the major groups. The main challenge we have with wild radish is the fact that it germinates all year round. With ryegrass it’s all about keeping plant numbers low.” Although the testing is not showing herbicide resistance, Aaron is seeing evidence of Select not working as well as it did in the past. To add more mode-of-action diversity to their system the McDonalds are using pre-emergent herbicides Sakura and Boxer Gold in cereals with good success and grow both hybrid (RR and 650TT) and open-pollinated (TT) canola cultivars. “The RR canola enables extra knocks with glyphosate in-crop to clean up paddocks where we are concerned over the efficacy of Select,” says Aaron. “All our other in-crop herbicides are still working well but we are trying to rotate as much as possible with Select and Edge, and using paraquat ahead of canola and glyphosate or paraquat ahead of cereals.” The McDonalds have always sown their crops on fairly narrow rows, 250 mm spacing, and use high sowing rates (wheat and oats sown at 100 kg/ha and canola at 3.6 kg/ha) to provide strong crop competition to help with weed control. The sheep grazing stubbles provides quite good control of summer weeds but some herbicide is always required. Aaron’s main summer weed concerns are melons and self-sown crop. In autumn or pre-sowing he occasionally double-knocks but often there are no survivors so the second knock is not needed. Hay making and harvest weed seed control Aaron has implemented narrow windrow burning for the last 4 or 5 years in their canola crops as a harvest weed seed control tactic to capture late germinating weeds. This is supported with strategic crop topping of the canola to desiccate and then windrowing 80 per cent of the canola area each year. In their cereals, crops are cut low and stubble is burnt on about 75 per cent of the cropped area to allow easier sowing operation, and has the added benefit of destroying some weed seed. In barley crops the straw is often baled after cutting the crop low, allowing sowing without stubble burning. Grazing stubble and burning also helps reduce mice and slug numbers. “Oaten hay production enables us to apply a desiccant over the top prior to cutting for hay,” says Aaron. “This gives us the opportunity to implement a herbicide plus non-herbicide double knock on in-crop herbicide escapes.” Aaron McDonald is using oaten hay and clover hay production as weed management tools within their mixed farming operation south of Horsham. “We graze the cereal stubble and canola narrow windrows after harvest but don’t leave the sheep on the paddocks for long,” he says. “We find that the cereals provide better feed value than the canola windrows but we also put lambs on the canola regrowth for a little extra green pick.” Each year about 5000 lambs move through the on-farm feedlot, where the McDonalds feed out gradings from the barley grain and the straw. “Feeding the grain gradings out in the feed lot also brings weed seeds into the confinement area where we can control them quite easily,” says Aaron. The feedlot adds value to the straw and grain gradings, turning off about 5000 lambs per year. Weed seeds that are brought back to the feedlot are easily managed if they survive being eaten.
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Case Study

Eagle family, Horsham

2020 mini update – Sam and Emily Eagle have introduced sheep containment yards to their operation as a means of managing weeds and optimising pasture and fodder crop production. They use sheep to graze paddocks sown to Moby barley and clover, then double knock, to make money from their cover and brown manure crops. Having used narrow windrow burning in canola for six years, Sam and Emily invested in a seed impact mill in 2018 as their harvest weed seed control tool. They spray-top their legumes, make hay and silage for on-farm use and their contract windrower sprays canola under the cutter bar, all to stop weed seed set. The Eagles continue to use herbicide resistance testing to better inform their herbicide choices and use multiple chemical groups in a broad rotation. Watch Sam’s presentation at the Horsham WeedSmart Week forum in 2019. 2017 case study: Sam and Emily Eagle run 2500 merino ewes on their 3000 ha mixed farm near Horsham, Victoria. They say the livestock and cropping activities complement each other, keeping their pastures and crops performing at their best. Herbicide resistant annual ryegrass is their main weed challenge with one test revealing resistance to glyphosate (65 per cent) and clethodim (80 per cent), and full susceptibility to chlorsulfuron (Group B, Glean). Sam and Emily Eagle run a mixed farming enterprise near Horsham, Victoria where grazing and cropping are mutually beneficial for weed management. “We test annual ryegrass from two or three paddocks each year to monitor any changes in susceptibility to the herbicides we use,” said Sam. “Knowing which herbicides are effective makes it easier to plan our herbicide use without relying solely on the products that still work. Every year we have at least one tactic in place specifically to reduce the weed seed bank.” Knowing that the tested weeds were susceptible to Glean gave Sam an opportunity to regain control of a potential blow-out situation, using a herbicide that is much cheaper than alternatives that he might have chosen if he had to make the decision without the herbicide resistance test results. The Eagle’s agronomist usually collects the seed for testing and the results are considered to be representative of the whole paddock, each one being around 35 to 70 ha. “We can fairly safely assume that all our weeds have some level of resistance so we concentrate on managing survivors, mostly treating with a double-knock whenever possible,” he said. “Annual ryegrass is our main problem weed however we are keeping a close eye on brome grass that is present on one of our lease blocks.” Triazine resistance on one block precludes the use of TT canola so the Eagles grow conventional canola on this block, aiming for the most competitive, highest yielding crop possible. Along fence lines Sam uses a 2-year program where he slashes in spring in one year and then sprays a knockdown + residual herbicide mix the next year. “When we slash, we know that the weeds will still set seed. We keep the slasher low to the ground to ensure any seed heads present at harvest are below header height so they won’t get spread,” said Sam. The pasture paddocks are de-stocked over summer with the sheep grazing on the stubble. If the stubble runs out early the sheep are returned to the containment area where they are fed screenings, hay and grain until the pastures are ready. The ewes return to the pastures to lamb in autumn. Sam and Emily use narrow windrow burning in the canola as their harvest weed seed control tool. They have had trouble using this tactic in cereals, where the fires often don’t burn right to the ground, leaving weed seed concentrated in bands. On the other hand, the canola burns well, destroying the weed seed, and Sam is able to safely burn several paddocks on the one day. Grazing the canola narrow windrows has not caused any problems with burning or with weed seed being spread. Narrow windrow burning in canola has worked very well for Sam, driving down herbicide resistant ryegrass numbers. “Canola actually gives us a few opportunities to control late germinating weeds,” said Sam. “Firstly with an over the top spray to desiccate the crop, secondly windrowing the crop early and third, using the narrow windrow chute at harvest in preparation for narrow windrow burning in autumn. We also spray top wheat and barley, with the sheep providing the second knock for any survivor weeds.” Growing faba beans, canola, wheat and malt barley enables them to use a different pre-emergent herbicide each year of the rotation. At the end of this 4-year program any paddocks that are carrying a weed burden are thoroughly cleaned using a pasture and a 3-year hay program. Moby forage barley sown with clover gives a nutrient boost to the perennial ryegrass pasture phase, which may last up to ten years. “We supply hay for export and generally grow two oat crops and one vetch,” said Sam. “Any failed crops or additional production is stored as silage in underground pits to drought-proof our breeding flock. Silage is a particularly good way to clean up weeds because we spray out when the crop is actively growing and not under any moisture or heat stress, then cut in early September.” At the end of a 4-year cropping program any paddocks that are carrying a weed burden are thoroughly cleaned using a pasture and a 3-year hay program. The Eagles supply hay for export and generally grow two oat crops and one vetch. The 2017 seeding represents the beginning of the Eagles’ fully aligned controlled traffic farming (CTF) system. The transition to 12 m wide CTF has taken several years but Sam and Emily are convinced that the efficiencies gained will be well worth the investment. They sow all crops on 300 mm row spacing and aim to achieve the most competitive crops possible. Although Sam knows 380 mm row spacing would make some management operations easier, they pick up extra yield and suppress weeds with the narrower spacing. In the seven years that Sam and Emily have been managing the farms they have seen the benefits of the rotation in keeping weed numbers low. “All of our worst paddocks have now had the ‘rotation treatment’ and we have avoided weed blow-outs,” said Sam. “Two wet years in a row could potentially challenge our weed management but having the sheep in the system gives us more options while still earning income from each paddock.” Related links 10 Point Plan – Test for resistance to establish a clear picture of paddock-by-paddock farm status Plant Science Consulting herbicide resistance testing CSU Herbicide resistance testing
Article
Case Study

Paul Slack, Moree NSW

Bringing pre-emergent herbicides back into cotton systems The new rules for managing Bollgard 3 cotton include changes to the requirements surrounding pupae busting. Dryland cotton farmer Paul Slack is considering his options but is cautious about the ramifications of a fully no-till cropping rotation on his farms east of Moree, NSW. “Weed management in cotton has seen several transitions in the last 20 years,” he said. “Before Roundup Ready cotton we applied pre-emergent herbicide in a band behind the planter and relied on chippers or shielded sprayers to remove any survivors or late emerging weeds. With the adoption of Roundup Ready Ingard, then Bollgard II cotton across the industry, growers started using less and less pre-emergent herbicide and in the last eight to ten years or so we have been heavily reliant on glyphosate.” Dryland cotton and grain grower Paul Slack (right) and his agronomist Tony Lockrey (AMPS) have been working on crop rotation options to deal with herbicide resistance in weeds. Cultivation With the only real cultural control measure being used being cultivation for the purpose of pupae busting, which also helped reduce the weed burden, there has been an over reliance on just one herbicide group. Although there is less cultivation required in Bollgard 3 production, there is still a recommendation to kill the cotton crop and any green bridge weeds or volunteers. “Cultivation may still feature in our weed management program. We would never cultivate after corn or wheat but cultivation after cotton or chickpea is a good option to fix wash-outs or deep wheel tracks while there are lower levels of stubble in the paddocks. Uneven landform presents significant challenges for spraying, especially with optical sprayers, so it is important to repair damage as soon as possible,” said Paul. “We have grown cotton every year since 1989 and know that no-till and stubble conservation in the grain phase of our dryland system is worth an additional half to one bale of cotton per hectare,” he said. Longer rotation “We got into trouble with herbicide resistance as a result of the short wheat / chickpea / wheat rotation that we used for 15 years or more, like many others in the district,” Paul said. “The legacy of this routine is our ongoing battle with Group A resistant black oats.” One strategy Paul and his agronomist Tony Lockrey, AMPS Moree have put in place is a longer rotation with summer and winter crop options across the 4850 ha of cropping land. Cotton and corn are the best fit for summer with wheat and chickpea in winter. Growing cotton and corn in summer and wheat and chickpea in winter has lengthened the crop rotation and added more options to diversify herbicide use. “Usually we can double crop from corn into chickpea and possibly also from cotton to chickpea,” said Paul. “Wheat follows chickpea before returning to cotton or corn, providing a profitable mix of commodities.” “Currently we are using a 3-year rotation and could consider lengthening this more,” said Paul. “Disease management and nematode levels influence crop rotation choices and then we plan our use of residual herbicides keeping plant-back restrictions and chemical MOA rotation in mind.” Canola and barley are both options to lengthen the winter rotation but can only slot into the rotation under certain circumstances. Barley stubble lasts longer than wheat stubble, providing better moisture conservation for the next cotton crop however there are fewer herbicide options available for grass control, putting additional pressure on Group A chemistry and risking a blow-out in black oats. Canola offers more options for nematode and black oats control. Protecting knock-downs Herbicide resistance is evident in populations of annual ryegrass, liverseed grass, barnyard grass and black oats on the property. Depending on the size of the patches Paul’s strategy includes optical spray technology and or cultivation to stop seed set. Paul is looking at ways to diversify his herbicide and non-herbicide tactics to regain control of herbicide resistance in weeds. Summer fallow sprays targeting grass weeds are usually double knocked with paraquat, and Paul rotates fops and dims (between Verdict and Select) within Group A because these active ingredients have slightly different resistance profiles. “It can take as few as seven applications of Group A herbicide to initiate resistance so this chemistry is a very short lived option if efforts are not made to control survivors,” said Tony. “To reduce this risk we have tested the use of Paratrooper (paraquat + amitrole) and paraquat + Group G herbicides (Sharpen and Sledge) this summer for ‘one shot’ control of glyphosate resistant grasses and rosette or early elongation fleabane. In some cases this was applied with other fallow residual herbicides to again take pressure off glyphosate and group A chemistry. With this approach it is essential to achieve excellent coverage so we used water rates in the range of 100–200 L/ha.” Results were very encouraging so Paul and Tony have confidence that this brings another option, albeit another herbicide option, that does not involve glyphosate and Group As. Pre-emergent resurgence In fallow prior to the summer crop, Paul is re-introducing the pre-emergent use of Terbyne (Group C). Once the crop is sown he then applies a PSPE diuron + metolachlor (Group K) mix in cotton and atrazine + metolachlor in corn for grass and broad-leaf weed control. A recent registration also allows in-crop application of Bouncer (metolachlor) in cotton. Flame is sometimes used in the fallow following chickpea and prior to the wheat crop. Balance (Group H) applied to chickpea provides effective pre-emergent grass control into the following summer as well, complementing the Flame. Balance also provides good control of volunteer cotton plants. Metolachlor, one of the pre-emergent herbicides, requires incorporation with sufficient rainfall within two weeks of application. To hedge the risk, Paul applies one shot in August prior to planting rain for cotton and corn then follows up with a second shot applied PSPE in fields with problem summer grasses. Paul currently grows conventional corn varieties however he is considering the use of imi-tolerant corn, and the soon-to-be-released IT sorghum or sunflower varieties, in the future as this would enable him to plant these crops after using Flame in the fallow without causing crop damage due to residual activity. “The release of these crops will heighten the need for growers to carefully implement the imi herbicide stewardship measures,” said Tony. “With imi tolerant options for several winter and summer crops it is essential to observe the requirement to limit Group B (imi) applications to two sprays in a 4-year period.” Crop competition Using the crop to compete with weeds is often difficult in this drier cropping zone where much of the crop growth relies on limited stored soil moisture and row spacings are often wide. Corn sown on 1-metre rows provides good shade and an opportunity to plant before the summer grasses germinate. “Corn is planted and a pre-emergent herbicide applied in August when the soil temperature hits 12 degrees C,” said Paul. “This gives the crop a competitive advantage over the summer weeds, which don’t germinate until the soil temperature reaches 14–15 degrees C. Corn also provides good canopy shade to suppress weed germination and growth as the season progresses.” “Corn also leaves more residual soil moisture for the following chickpea crop,” he said. “This is a good combination for us, generating a yield benefit of 0.4 t/ha in the chickpea crop.” In cotton, Paul is considering a change from a double skip planting configuration to a single 2.4 m wide row to better suit picking and the 3 m controlled traffic farming configuration, giving 5 rows in 12 m. Although he knows this will open the crop up to increased weed pressure the single row will favour better quality cotton and the picker will operate more efficiently. Paul is considering a change from the double skip planting configuration to a single 2.4 m wide row to better suit picking and the 3 m controlled traffic farming configuration. Although Paul knows this may open the crop up to increased weed pressure the single row will favour better quality cotton and the picker will operate more efficiently. Paul is a member of the local Dryland Cotton Group, and is hosting the group’s trial looking at the benefits of using cover crops to improve moisture conservation across the rotation. This is really a test of whether a cover crop is a viable way to improve the fallow efficiency across 5 to 7-year rotations. The group is trying different summer and winter cereals and legume species and species mixes to investigate the potential benefits of cover cropping. They are just part-way through a 3-year trial but the field pea is showing the most promise for retaining stored moisture and boosting yield in the following crop. Weed management is not the focus of this trial however there may be implications from this trial that Paul may use as he continues to fine-tune their production system. “In our hot, dry environment, organic matter in standing stubble is mostly lost to the atmosphere rather than contributing to soil organic carbon,” he says. “More nutrients and carbon return to the soil when stubble is incorporated. We will need to determine when to leave stubble standing and when to do light incorporation of the cover crop residues to maximise the benefits of both.” Related links Eradicating herbicide resistant barnyard grass Best way to protect herbicide tolerance technologies Soil behaviour of pre-emergence herbicide manual (GRDC) Pre-emergent herbicide fact sheet (GRDC)
Article
Case Study

Clemson family, Ardlethan NSW

As the 2013–2016 drought bit harder in NSW’s Riverina, Ardlethan farmers Lou and Charlie Clemson were thinking about ways to better utilise more of their property, particularly the 200 ha of non-arable country. Using a NSW State Government drought assistance grant to supplement their own funds they have installed a laneway through the middle of their property, Wongajong, to link the hilly paddocks with the stockyards and provide easy access to all the cropping paddocks between.   Lou Clemson says the laneway allows easy movement of stock through the cropping area and also provides an excellent confinement area with troughed water and creep feeders. The timbered hill paddock is key to the system’s success, providing native pasture for the breeding herd. Lou says the changes to their business and their weed management have been amazing. “We now have another income stream, and cattle have been very profitable since the drought,” she said. “And we are using less herbicide to manage weeds.” The re-introduction of livestock to Wongajong started in 2010 when the Clemsons bought 300 steers to make use of a frosted wheat crop. “We fed the steers for 5 months and made good money out of what would have otherwise been a failed crop,” said Lou. “After that we fenced off the hill and added the central laneway and watering points. We are really happy with how well this system is working and see benefits across our whole cropping operation.” “Growing early varieties is the key to maximising the feed benefit of fodder crops such as Moby barley and Brenan and Naparoo feed wheats, which we plant in February or March,” she said. “In paddocks where we have some annual ryegrass pressure we have sown feed barley in February–March, weaned calves onto it in May and grazed until September. This 73 ha paddock alone turned off 200 prime yearlings.” With some welcome rain in December, the Clemsons sprayed out the barley and took the opportunity to sow cowpeas over summer. “This year we weaned part of the herd in January and the calves went straight onto the cowpeas where they remained until late April. The cowpeas even podded up and we could have stripped them but decided to just continue grazing. The added nitrogen will also boost the next crop and build soil fertility.” Cowpeas planted opportunistically on some December rain provided perfect feed for newly weaned calves from January until late April. In addition to the feed value the cowpeas have also provided a boost to soil fertility. With two back to back seasons of crop competition and sustained grazing pressure, the ryegrass is well under control and the Clemsons have sown Condo grain wheat this winter. After removing the young stock from the cowpeas the Clemsons introduced them to creep feeders offering hay, feed barley and a magnesium calcium supplement in the central laneway. Lou said their system relies on the 200 ha of hilly country where they run their breeding herd. The cows calve in the hill paddock in July then have access to crop stubbles straight after harvest until January when the cows return to the hill paddocks and the calves are weaned onto feed. “In this system, Wongajong can carry 200 breeding cows and 50 replacement heifers but no more,” she said. “This is working so well that we are keen to build our herd and will replicate the laneway and fodder cropping system on a second property nearby. We have been expanding our area for both cropping and livestock with additional land purchased and leased.” Looking across Wongajong, the top paddock grew cowpeas that were grazed over summer, the next paddock down the hill has feed barley ready for grazing and then the laneway where the young cattle are introduced to hay and grain once their rumens are mature. The Lemken speed tiller will be used to prepare the cowpea paddock for sowing the high yielding, short season Condo wheat. “We identify paddocks that need a spell from cropping and also look at the weed burden,” said Lou. “Grazing barley is our go-to crop for weedy paddocks. It does a good job competing with annual ryegrass and gives us several options such as making hay or grazing and then spraying out.” Canola has been a mainstay crop for the Clemsons along with barley for grazing, hay and feed grain, and wheat for grazing and feed grain. The cattle strip graze the fodder crops at a density of 2 head/ha to maximise the feed value and weed control benefits. Electric fencing is used where necessary to manage the grazing intensity and provide fresh feed. Most of the fodder crops will be grazed out and sprayed in spring to clean-up for the following winter. The Clemsons are now planning to extend their fodder cropping program to hay and silage production. Forage barley has proven to be the most useful crop for livestock production and weed control. Charlie and Lou use a Lemken Helidor speed tiller to lightly cultivate paddocks that have been sprayed out after grazing. Paddocks are then rested for seven months, from late spring through summer, before they are re-sown. The combination of several non-herbicide weed control tactics such as strip grazing, fodder conservation and the speed tiller have resulted in an overall reduction in herbicide use. “Sowing early gives us the greatest number of choices,” said Lou. “Some years we would expect about 10 per cent of our crops to be frost affected, but by sowing early we can achieve higher yields and this can make up for losses to frost.” Lou said there has been a noticeable change in their attitude towards weeds with Charlie being much less stressed. Having the canola and wheat sprayed on time is important while there is more flexibility with spraying times for the grazing crops. “If there are weeds visible in the paddock we can stay relaxed knowing that once the cattle have finished grazing and been sold, the paddock will be sprayed out before the ryegrass sets seed, and any survivors will be killed with the Lemken Helidor,” she said. The Clemsons use a Lemken speed tiller straight after harvest to manage stubble and weeds. Provided there is some soil moisture present the cultivation to a depth of up to 10 cm or so causes about 80 per cent of the weed seeds to germinate, allowing a very effective spray opportunity. Cultivation with the Lemken Helidor machine stimulates weed germination and breaks up the stubble. Operating at 15–16 km/hr, the 12 m wide cultivator also breaks up and spreads the stubble and throws soil over some of the stubble to aid decomposition. The cattle still have access to valuable feed in paddocks where the Lemken has been used. This light cultivation means there is no need to burn stubble and seeding the next crop is easy. “Summer cropping opportunities seem to be more common in recent years and we have had success with both cowpeas and sorghum,” said Lou. “The Supa Sudan sorghum we grew this past summer came back three times and provided excellent feed value but it also used too much soil moisture and might limit our immediate cropping choices for that paddock.” “In winter, forage barley is followed by TT canola then a grazing wheat with the option to graze, make hay or harvest the grain.” In addition to annual ryegrass incursions the Clemsons have also seen black oats, wild radish and brome grass populations cleaned up through this combination of grazing and cropping.  
Article
Case Study

Daniel Fox, Marrar NSW

For a few years Daniel has been adding components to his system to conserve moisture and keep herbicide resistant weeds at bay. “A series of drought years got us started down this track of better soil moisture conservation,” he says. “We have been able to store more water than we expected really and this has been converted into better yields.” Daniel (left) and David Fox are pleased with the chaff lining chute they have introduced as a harvest weed seed control method on their Marrar farm near Wagga Wagga. The long-term average rainfall at Marrar, north of Wagga Wagga, NSW is 500 mm and although last year was extraordinarily wet, the 15 years prior to this were relatively dry. This long dry stretch made growers like Daniel and his father David think more about conserving soil moisture over summer and using stubble to protect the soil moisture from evaporation. As they add more strategies to their management system they are seeing yields rise from an average 2.5 t/ha for wheat to 4 t/ha in years that would have seen the crop suffer due to a lack of spring rainfall. To tackle increased pressure from annual ryegrass Daniel and David started narrow windrow burning but found that a combination of cutting the crop low at harvest and burning much of the crop residue was impacting on yields. To investigate, they participated in a trial run by Grassroots Agronomy to see if cutting the crop higher, at 30 cm rather than the recommended 15 cm for narrow windrow burning, would still be an effective harvest weed seed control measure. “The results showed a half-tonne difference between cutting barley low and cutting higher,” he says. “It seems that the taller stubble provides better protection for the soil surface and the trial with the taller stubble had better conserved moisture, which was needed to finish the crop that year, where we had no rain from early September to mid October.” Highly competitive crops, like this barley, tend to hold annual ryegrass seed heads up high in the canopy where they can be easily collected by the stripper front on the Fox’s harvester. To maintain the effectiveness of harvest weed seed control Daniel has recently purchased a Shelbourne stripper for the header to collect the grain, and weed seeds, while leaving most of the stubble standing. “Using the stripper we are putting less material through the harvester but still collect grain and weed seed in the crop canopy,” he says. “This means we are picking up yield and reducing the weed seed bank without compromising harvesting efficiency.” Having used narrow windrow burning for a few years and seeing the benefit of capturing seed from late germinated weeds at harvest, the Foxes have now built a chaff lining chute for the header and are delivering the chaff component, including weed seeds, into a 250 mm chaff line in the middle of the 12 m CTF lap. This maintains most of the crop residue evenly across the paddock and avoids the need for burning. “Having the weed seed concentrated in a narrow band reduces the amount of seed that germinates and also reduces the chance of weed seed being buried and ‘stored’ underground at planting now that we are using a disc seeder,” says Daniel. Daniel has had no problem sowing through the chaff and is also able to apply more herbicide to the tramlines if the weed numbers appear to be increasing. He is also keeping an eye on the developments of microwave weed control technology as a potential non-herbicide method to treat the tramlines in the future. “We realise that there might be an impact on soil microbes and earthworms but if the microwave is only treating the chaff lines then it could still be a good option,” he says. Croptopping in non-malting barley, canola and pulses provides an additional opportunity to stop seed set with the chaff lining providing an effective, non-herbicide second knock to support the herbicide. The cereal stubble persists across the four-year rotation of two cereal crops followed by two break crops, providing more shade and wind protection, and keeping the soil surface cooler. Daniel Fox has implemented a double break crop system where the cereal stubble is maintained on the soil surface across the 4-year rotation, conserving soil moisture and improving crop yields. The double break cropping rotation enables Daniel to have a two-year shot at both grass and broadleaf weeds using a combination of herbicide and non-herbicide tactics. “With herbicides we are using robust pre-emergent and in-crop applications and double knocking our knockdown herbicides,” he says. “The non-herbicide tools are collecting weed seed at harvest with the chaff lining chute, strong crop competition from narrow row spacing and haymaking if required. In just three years we have seen a huge reduction in the ryegrass population on the farm.” During the 2000s David stayed with the canola / wheat rotation they had in place even though it meant that they had a few failed crops, which they converted into silage. “By resisting the temptation to go with a long cereal rotation we avoided the weed blow-out that occurred on some farms,” he says. The Foxes grow wheat and barley in the cereal phase with an option for oats on their frost-prone paddocks. “Wheat is our mainstay on the higher paddocks where we sow early and the crop flowers in cooler weather, which can make a 2 t/ha difference in yield compared to sowing later,” says Daniel. “We are wanting to raise our average wheat yield from 2.5 t/ha to 3 t/ha, even in lower rainfall and lower radiation years. Likewise, for barley we are confident that significant yield gains are possible in the system we have developed.” In the broadleaf phase they grow canola and a pulse, usually lupins, and are considering faba bean and lentils as alternative pulse options. They are also investigating whether winter cover crops followed by a summer crop might have a fit in their system to give them the opportunity to use different chemistry at different times of the year to combat weeds. “No-till and glyphosate generated a big jump in productivity on this farm and now we are seeing another big improvement with new gear such as the chaff lining chute, stripper front and high clearance sprayer,” says Daniel. “We could not have got through last season without the sprayer. It has allowed us to get onto weeds when they are small and cover a big area in the best conditions.” Doing their own spraying and planting gives Daniel and David the opportunity to monitor their paddocks during the season to keep an eye on weed numbers, which also helps when they go around the farm with their agronomist to plan the weed control program. A new disc seeder has also made stubble management easier and allowed Daniel to move to 6.5 inch (165 mm) row spacing for all crops. The single disc seeder has 72 units over the 12 m span which, like the sprayer, fits within the controlled traffic system. Daniel is conscious of brome grass and black oats entering the farm from the roadside so he is spraying through the external fences with a mix of glyphosate and residual herbicide to help minimise the risk of weeds moving into the cropping areas. “We sow right up to the fence to maintain competition and if we need to, we bale the outside lap of the crop,” he says. “After harvest we plough along the fencelines as a firebreak, which is a council requirement.” The Foxes look for crop traits that provide a competitive edge such as hybrid canola over open-pollinated types and taller wheats such as Spitfire, while still maximising yield and profit from the available moisture. “The 29 year row spacing trial in WA demonstrated that narrow rows produce more crop and less weeds, and we have seen a 400 to 500 kg/ha benefit through less tiller deaths and more heads here too,” says Daniel. “To achieve this it is essential that the soil fertility is able to support the increased production. Our granite soils tend to leach nitrogen in wet years and that has a big impact on yield.” Related information Getting weed seeds into the header’s chaff stream Michael and Marnie Fels grower case study – chaff lining
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Case Study

Ben and Emily Webb – Kojonup, WA

2020 mini update Ben is still using a chaff cart for harvest weed seed control but he now burns the chaff heaps after they have been grazed. The Webbs now have an higher component of legumes, including faba beans, in their cropping program. They generally keep the cropping and livestock paddocks separate but graze the stubbles (including the chaff heaps) in summer and crop some pasture paddocks to use up excess nitrogen. From time to time they grow oats or vetch within their cropping program and defer graze these paddocks over winter, then spray top the crop.  Ben puts the sheep into confinement areas in autumn to allow the pastures and fodder crops to get away while he concentrates on the cropping program.  Any weedy patches in cropping paddocks are cut for hay or silage and Ben has also started to mow and bale two laps around cereal crops as another non-herbicide control tool to reduce weed infestation from crop borders and minimise the risk of producing herbicide resistant weeds.  Watch a short video about the Webb’s weed control program. Weed seeds have great feed value (2017 case study) For mixed farming operations like ‘Marbarrup’, west of Kojonup, WA there are a stack of good reasons not to light up chaff heaps — they are just too valuable. Ben and Emily Webb farm 2150 arable hectares and run 4500 dual purpose Merinotech ewes and their offspring on crop stubble and 935 ha of non-arable pasture. Their recent investment in a chaff cart to provide non-herbicide weed control also provides them with a valuable feed source over summer and better livestock production. Ben Webb and his consultant Kent Stone are pleased with the efficacy of the chaff cart system to collect weed seeds at harvest. “In a trial that Ed Riggall at AgPro Management ran on our property in the summer of 2015–16 the sheep gained more weight when they had access to canola chaff heaps compared to grazing a similar paddock without chaff heaps,” said Ben. “The sheep grazed the canola for six weeks over December and January, gaining an extra 3.8 kg/head over the gains made by sheep just grazing stubble.” Liveweight of sheep grazing canola chaff dumps compared to grazing paddocks without chaff dumps at ‘Marbarrup’, Kojonup WA. Note: 18 mm of rain fell at the two-week stage of the trial and a further 97 mm of rain fell eight weeks into the trial. The nutrient analysis of the canola chaff heaps showed the feed value was 7.3% crude protein and 6.1 MJ/kg DM metabolisable energy. Not only did the sheep gain additional weight, the Webbs also saved time and money on supplementary feed that would be required to achieve the same weight gain. Ed Riggall calculated the benefit of grazing chaff heaps for a typical, model farm of 2000 ha with 50% crop and running 9.5 DSE/ha would be an average saving of over $29,000/annum and an internal rate of return on investment (ROI) on a chaff cart of 36% per annum over 20 years. This is averaged across livestock weight gains achieved on canola, barley, wheat and oats chaff heaps in a detrimentally wet season. “In addition to this considerable benefit, we also saw a 25 per cent improvement in lambing percentage in the ewes grazing the canola heaps compared to those just grazing stubble,” said Ben. “This is a direct consequence of the higher productivity from heavier ewes in higher body condition.” Ben has found that the sheep do a good job of knocking down the heaps, particularly when a large mob is given access to the paddock for a short time. Prior to seeding grazed chaff heaps Ben often runs over them with a scarifier to spread the residue more evenly. This makes it easier to seed through the heaps and reduces the need to burn in autumn. “Ungrazed heaps definitely shed rainfall better but under the right conditions the grazed heaps still burn very well if we decide that’s the way to go,” he said. “The sheep do best on the canola stubble so that is our priority for grazing. The canola heaps don’t generally need much done with them after grazing but I often burn the wheat, oat and some barley chaff heaps after grazing because they can be a pain to seed through.” “We have trialled narrow windrow burning here a few times but find that it is often too wet to achieve a good result. Moving to the chaff cart and grazing the heaps has been working better for us.” Not burning the chaff heaps does allow more weeds to persist but as this photo shows, the chaff cart does a good job of cleaning up the whole paddock and concentrating the weeds in a very small area. Scientific studies have shown that sheep do not spread weed seeds as the seeds are destroyed as they pass through the sheep’s gut. A study by CSIRO scientists in 2002 concluded that less than four per cent of annual ryegrass seeds consumed could survive passage through a sheep’s digestive system and similarly a 2010 international study showed both annual ryegrass and wild radish seeds were destroyed after two days in the rumen. The Webbs use the chaff cart on all their cropping land and have seen a reduction in herbicide use across the whole farm. In addition to harvest weed seed control with the chaff cart, the Webbs have also been including as many high biomass, competitive crops in their rotation as possible. Their current program includes canola, barley, lupin and wheat, with trial paddocks of faba bean. Ben has found that growing RR and RT canola has provided excellent biomass production and allows them to restrict the use of clethodim to the lupin phase of the cropping program only. Hyola 600 RR canola (pictured) and RT canola provides a high biomass crop that competes well with weeds and produces high quality chaff heaps for the Webb’s Merinotech sheep. Frost is a concern every year and the Webbs have been heavily impacted in the last few years. One of the greatest difficulties being the unpredictability of frosts – early one year and late another. Ben sows Calingiri, a noodle wheat, and Trojan, a bread wheat as early as possible to minimise the risk of frost damage. Annual ryegrass, brome grass and wild radish are the Webb’s top-3 weed challenges and to-date the herbicide resistance status is low. A ‘quick test’ performed last year indicated that resistance to clethodim was building and this was a significant motivator for Ben and Emily to invest in the chaff cart. Prior to sowing Ben applies a double knock of glyphosate followed by paraquat mixed with a pre-emergent herbicide. Ben applies in-crop herbicides as required and hand rogues any surviving wild radish plants. To reduce seed set they also crop top lupins and spray glyphosate under the swathe when windrowing canola. Ben has also been trialling windrowing in wheat and barley, primarily as a harvest management tool that also has benefits for late frost avoidance and to reduce seed set in late germinating weeds. On the rare occasions that weeds have got out of hand the Webbs have also used hay production as a way to reduce seed set and drive down weed numbers. Planting on 229 mm (9 inch) row spacing and paired rows, Ben opts for higher end seeding rates for all crops to maximise yield and competition with weeds. Cutting the crop as low as possible and utilising the stubble as fodder makes planting on narrow rows easier to achieve. Other resources: AHRI Insight Chaff carts good for the crop and the sheep Grazing chaff heaps solved two problems Grazing chaff dumps over burning webinar

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