Chaff Cart are towed behind harvesters during harvest with the aim of collecting the chaff fraction as it exits the harvester.
So what do you do with the chaff? There are a few different options. Some people will opt for dumping their chaff and then perhaps grazing with sheep.
For others, burning the chaff in autumn is the preferred option. The benefits of grazing chaff dumps are that it’s beneficial for the sheep and your crop. Also, there may be no burning required
What can I do at harvest to reduce my future weed burden?
As crops mature and harvesters begin reaping, consider the potential fate of seeds ripening on weeds that escaped in-crop control measures.
Peter Newman, WeedSmart’s western extension agronomist, says harvest time is an important opportunity to assess weed burden across the farm and be proactive about driving down the weed seed bank.
“Harvest can either be a super-spreader or a weed suppressing event,” he says. “Small patches of weeds can quickly expand when seed is blown out the back of the harvester. On the other hand, the harvester can be a powerful weed management tool if any one of the harvest weed seed control options are implemented.”
WeedSmart’s western extension agronomist, Peter Newman says efforts made to reduce the spread of weed seed at harvest will soon pay off for growers.
Australian growers have led the world in inventing and adopting harvest weed seed control tools such as impact mills, chaff carts, chaff decks and chaff lining, all of which can reliably destroy over 90 per cent of the weed seed that enters the front of the harvester.
“In addition to harvest weed seed control there are several other actions in the WeedSmart Big 6 that growers can implement just prior to, during and immediately after harvest that will make a measurable difference to the weed burden in future growing seasons,” says Peter. “The WeedSmart Big 6 tactics are scientifically-proven to reduce the risk of herbicide resistance through diverse herbicide use and cultural control to prevent weed seed set.”
What can I do before harvest to manage late emerged weeds?
In brief: Scout for and map weedy patches. Consider sacrificing small areas of high density weeds. Swathing can be a very effective way to stop seed set of late emerged or resistant weeds. Collect weed seeds for herbicide susceptibility testing.
The details: Growers across Australia use a variety of methods to map weeds – from the simple to the sublime. ‘Dropping a pin’ using the tractor’s GPS mapping system as you travel through a weedy section when spraying or harvesting is easy and provides useful information about the distribution of weeds in the paddock. Many growers have their own drones and use them the collect images or video footage of the crop that can be viewed or analysed to identify high density weed patches.
Collect seed for herbicide susceptibility testing – knowing what still works is vital information for planning next season’s herbicide program. There are three herbicide testing facilities in Australia that are equipped to test weed seed samples – Plant Science Consulting, CSU Herbicide Resistance Testing and UWA Herbicide Resistance Testing.
Collecting weed seed before or at harvest is the most common method used. The collected seed must be mature, from green to when the seed changes colour. Before harvest, collect 30 to 40 ryegrass seedheads or several handfuls of wild oats seed. After harvest, it is common to find seedheads still in the paddock or samples of contaminated grain can be sent for analysis.
Keep samples from different locations separate and details noted on the bag. Only use paper bags (double layer) to collect and send seed samples. Ensure bags are sealed so that the samples don’t mix during transit.
Which harvest weed seed control tool is best for my situation?
In brief: There are six harvest weed seed control tools used in Australia – impact mills, chaff decks, chaff lining, chaff carts, bale direct and narrow windrow burning. Choose the one that best suits your system and budget.
The details: Impact mills are best suited to continuous cropping situations. Residues are retained and evenly spread. Chaff decks have lower capital cost and are well-suited to controlled traffic situations. Chaff carts are popular with grain producers who also run livestock. Bale direct is also expensive but has a good fit in locations where there is access to straw markets. Chaff lining is currently the best ‘entry level’ system and can be used in CTF or non-CTF systems, with best results where the harvester runs on the same track each year. Chaff lining has essentially superseded narrow windrow burning, overcoming the time required and risks involved in burning and reducing the loss of nutrients from the system.
If you haven’t used harvest weed seed control tools before, it doesn’t take long to build and fit a chaff lining chute ready for use this harvest season.
What should I be ready to do straight after harvest?
In brief: Spraying weeds immediately after harvest is fairly common practice. Weeds present may be close to maturity or fresh germinations of summer-active weed species.
The details: Some growers get in early with knockdown herbicide applied under the cutter bar when swathing barley or canola. Consider using the double knock strategy, heavy grazing pressure and possibly a soil residual herbicide that is compatible with your planned crop rotation. Pay particular attention to any weedy patches identified before or during harvest. Stopping seed set at every opportunity is the crux of an effective weed management program.
Give some thought to what might be the underlying cause of weedy patches – fixing problems such as pH and soil nutrition imbalances, waterlogging and spray practices that routinely deliver low doses of herbicide.
Chaff carts were made for feeding livestock
Chaff carts were invented in Canada in the 1970s as a fodder collection system, so they have always had an association with livestock. In the late 1980s they were introduced to Australia and used as one of the first harvest weed seed control (HWSC) tools to manage herbicide resistant ryegrass and wild radish in Western Australia.
Depending on the grower’s situation, chaff heaps in Australia have been burned, grazed then burned, sold as loose chaff for horse feed, grazed or knocked down then seeded through (unburned) and most recently, baled and used on-farm as conserved fodder.
Different model chaff carts incorporate more or less straw with the chaff, which can affect the feed value of the bales.
This latest method fits very well with the move to confinement feeding of sheep and brings the use of the chaff cart almost full circle. Given the long-standing association with fodder conservation, the value of the chaff as a feed source is well known, particularly for sheep.
A HWSC Calculator developed by WeedSmart western extension agronomist Peter Newman, now enables growers to quickly estimate the potential value of baling chaff from chaff heaps and feeding it out in on-farm confinement areas. Upper Eyre Peninsula mixed farmer, Bruce Heddle, instigated the addition of the new feature to the calculator and provided the energy figures from his own testing of different chaff types. Planfarm livestock consultant, Paul Omodei, worked with Peter to make sure the calculator took into account the important considerations for livestock production.
Although there is variability in feed value results, ballpark energy figures are in the order of 6.7 MJ/kg DM for wheat chaff, 7.7 MJ/kg DM for barley chaff, and 8 MJ/kg DM for canola and pulse chaff. Peter says the cost to deliver baled barley chaff to an on-farm feedlot is around 1.5 c/MJ compared to barley grain for 2.3 c/MJ, based on these feed values that Bruce Heddle provided.
“Chaff carts incorporate more or less straw with the chaff depending on the cart model, and while some extra straw makes baling and handling easier, it also reduces the feed value slightly, so that needs to be factored in,” he says. “Some growers are already set-up for hay making while others might choose to employ a contractor.”
Bruce has a contractor to bale their wheat, barley, canola and lentil chaff dumps, and feeds the bales along with barley grain and a lick feeder to sheep held in confinement from January to the end of seeding. All the chaff is beneficial although the canola and lentil chaff has the highest feed value.
Bruce says having the sheep confined during this period reduces their workload as the sheep are easy to look after and feeding out is only needed once a week. They are able to easily monitor the flock and attend to any problems quickly, and don’t have to spend time moving sheep around during seeding.
The pastures also benefit from a spell from grazing for these months, so the sheep are turned out into refreshed pasture after their confinement.
Jarred Tilley is another mixed farmer who has been making chaff bales for use in their family’s sheep enterprise at Kapunda in South Australia for the last two years. Jarred has been fencing off less productive areas on their farms and using them as confinement yards for their sheep in May and June. Their high density baler creates large bales that weigh 500 to 550 kg each from chaff dumps that are knocked down using a telehandler and then raked to save time when baling. Having their own hay-making equipment helps justify the chaff baling operation.
“We have fed 500 ewes in an 8 hectare paddock for six weeks with a diet of chaff bales, regular hay and a lick feeder,” he says. “The benefits are probably marginal for us using wheat chaff, but the canola and pulse chaff is a better feed supplement. The feed quality of the chaff is not always as good as we would like.”
Jarred says that the sheep spread the chaff out in the confinement paddocks and often leave more ground cover in those paddocks than when the sheep went in.
Chaff is a low-cost feed that is only sufficient for maintenance energy levels for sheep. Other feeds need to be included in the feed ration to promote growth or support lactation. Studies that Ed Riggall at AgPro Management conducted at multiple sites in Western Australia over three years demonstrated that sheep with access to chaff heaps from various crops gained an average of 2 kg in the first three weeks. This was 500 g more than sheep grazing stubbles where the chaff was spread out by the harvester.
Livestock containment paddocks boost productivity while stopping the spread of herbicide resistant weed seeds.
At the end of six weeks grazing the sheep with access to chaff piles had gained about 100 g, while sheep without access to the chaff piles had lost almost 2 kg compared to their starting weight. Additional benefits might be expected in a confinement feeding situation where the chaff is easier to forage and is potentially available to the stock for longer as part of a mixed ration.
By making use of the chaff within their own operations these growers are gaining benefit from a resource that is otherwise wasted, and avoid the risks associated with burning chaff heaps.
All harvest weed seed control methods provide similar levels of weed control – collecting, concentrating or destroying over 90 per cent of the weed seed that enters the front of a well set-up harvester. Australian farmers are spoiled for choice when it comes to the options for collecting and destroying weed seed at harvest and keeping downward pressure on herbicide resistance. The WeedSmart HWSC Calculator tool allows growers and agronomists to test different scenarios using their own figures to estimate the costs and benefits of the different systems available.
Download the HSWC costs calculator
More lambs, less weeds in confinement systems
Sheep can turn weed seeds and chaff into cash
Ben & Emily Webb case study
Regional Update – Adrian Perks, Farmer, Esperance, WA
In this edition of the Regional Update we’re heading to the Western Region and catching up with farmer, Adrian Perks. Adrian is based in Condingup in WA, which is 70 kilometres north east of Esperance.We’ll be visiting Adrian’s farm as part of Esperance WeedSmart Week, so we’ll find out more about that and get a weed focused update for his region.
WeedSmart Week Esperance is 17-19 of August. To find out more about this event and to buy tickets, click here.
Wagga WeedSmart Week; chaff lining + carts + cotton update
In this choc-a-block podcast, hosts Jessica Strauss and Peter Newman investigate chaff lining and chaff carts, get an overview of WeedSmart Week and a seasonal overview of cotton.
Mick McClellend farms in the Mallee in Victoria and has been using chaff lining in his farming system for the last three years. He gives an overview of the successes he has had using it.
Tom Lewis from Tecfarm manufactures chaff carts. He chats about the benefits of using one for weed control. Chaff carts can be used in mixed and broadacre farming systems.
WeedSmart Week is not far away, with the forum kicking off on August 21, and the farm visits following on August 22 and 23. Greg Condon talks about who will be presenting and what farmers and advisors can expect from the day. For more information about WeedSmart Week in Wagga and to register, click here.
The Cotton Research and Development Corporation (CRDC) has recently jumped on board as a sponsor of WeedSmart. We welcome them aboard and get a seasonal update and find out what they’re doing weed management-wise from CottonInfo’s Regional Extension Officer Annabel Twine and Tech Specialist Eric Koetz.
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.
AHRI Insight Chaff carts good for the crop and the sheep
Grazing chaff heaps solved two problems
Grazing chaff dumps over burning webinar
Andrew Boultbee, WA
Grazing chaff heaps solved two problems
For many growers burning crop residue to kill weed seeds collected at harvest goes against the grain. Along with the loss of nutrients and ground cover there is significant risk, stress and discomfort associated with burning, even in autumn.
Andrew Boultbee wanted to stop burning chaff heaps. His solution: first graze the chaff heaps, then lightly scarified before seeding right across them.
Andrew and Marjorie Boultbee run a predominantly cropping operation near York, Western Australia, with land they own and lease spread across their district. As annual ryegrass became increasingly difficult to control with herbicides the Boultbees adopted narrow windrow burning as a harvest weed seed control method. They soon saw how effectively this technique drove down weed seed numbers on their farm and decided to invest in chaff carts.
Andrew has seen many growers in his district adopt the use of chaff carts only to stop using them because of the costs and dangers associated with burning the heaps. “We soon found that burning the chaff heaps consumed all our attention and the smoke was unpopular with our neighbours,” he says. “Having properties spread out also caused logistic difficulties and with the heaps smouldering over several days we had a few close calls and sleepless nights.”
To keep the weed control benefits without all the problems Andrew and Marjorie decided to stop burning and to start using the chaff heaps as a feed resource for their sheep over summer.
Andrew has found canola and wheat chaff heaps to be very effective for weed control, even if the heaps are not burned. He allows sheep to graze on the heaps first which makes use of the feed resource while also knocking down the heaps to allow him to seed through them the following autumn. This works very well in canola however Andrew has found that running the scarifier lightly along the cereal heaps prior to seeding helps to spread the heaps more and minimises the chance of blockages at planting.
“The sheep eat down and flatten the canola heaps to the point where we can pass through with the seeding equipment and the crop grows through the remaining residue,” says Andrew.
The cereal chaff heaps are also well grazed, however Andrew always runs a scarifier along the row of heaps, knocking them down to about 30 cm in height. Doing this at right angles to the sowing direction means the seeder is able to seed through the chaff zone without blocking up.
“It is important to seed across the line of chaff heaps, not along them,” he says. “We make a habit of creating the heaps in a line across the paddocks at harvest.”
It takes a couple of years for the heaps to disappear altogether and return to full production but the heaps cover only about 1 per cent of the total cropping area. Once the heaps have disappeared there is a noticeable increase in the crop production in those patches, more than compensating for the small loss of production in the first year.
“The remaining residue in the 30 cm deep cereal chaff layer slowly composts during the winter rains,” Andrew says. “Two years after grazing a chaff dump we can notice the difference in that part of the paddock, with stronger crop growth and few weed issues.”
The Boultbees also choose crops and cultivars that they are confident will perform well within their weed management program. Andrew says they look for cultivars that are high yielding, very competitive in the early growth stages and have hard grain that is not damaged by the harvest settings that remove the most weed seeds.
“It pays to set everything up well before attempting to use harvest weed seed control tactics like chaff carts,” he says. “The paddocks must be free of rocks so that there is no impediment to cutting low to the ground and the header must have sufficient power and the correct settings so that weed seeds are taken in the front and end up on the sieve.”
Cutting low is particularly important for soft-seeded weeds like annual ryegrass that do not stay dormant in the soil for many years. Andrew says that leaving low growing or lodged weeds in the paddock in the first year effectively selects for the trait that exposes the weakness of this weed control method.
“It is important to harvest as low as possible right from the start and to have other strategies to deal with weeds that ‘survive’ collection,” says Andrew. “The next step is to make sure the header is set up for optimal performance and to collect as much seed as possible in the chaff.”
It is important to run at high rotor speed and to open the back of the concave up so that seed and straw is efficiently separated. The harvester needs to have the capacity to handle the increased amount of straw and must be set up so weed seeds end up on the sieve and not out the rotor. Andrew also avoids harvesting on cold damp nights where separating the harvested material efficiently is more difficult.
Annual ryegrass and wild radish no longer dictate the Boultbee’s cropping rotation as they once did. The chaff carts keep weed pressure low and allow the Boultbees to take advantage of seeding or marketing opportunities for their crops, with spin-off benefits for their sheep enterprise.
Australian Herbicide Resistance Initiative leader of communications, Peter Newman, says chaff carts capture about 75 to 85 per cent of annual ryegrass seeds and 85 to 95 per cent of wild radish seeds that are present in a crop, without slowing harvest operations.
In a cost comparison of harvest weed seed control methods, WeedSmart estimated that running a chaff cart, including the cost of nutrient removal, costs $14/ha (assuming 2000 ha wheat at 2 t/ha), or even less is a second-hand chaff cart is used.
In Andrew’s situation there is less nutrient removal costs and less costs associated with burning. He identifies rock-picking the paddocks as one of the major costs in his operation but estimates the cost of running the chaff carts is only $8/ha.
A few years after grazing, improved growth and crop productivity can be easily observed with the chaff heap zones growing larger crops.
Better results in barley
Barley crops play an important part in the Boultbee’s weed management program. Andrew chooses the most competitive barley varieties available to suppress weed germination and growth in-crop. When sown on 260 mm row spacing the tall dense stand lessens lodging in the annual ryegrass, keeping it erect and protecting the seed heads from shedding in the wind.
By swathing the barley they introduce more diversity into the rotation so that every few years each paddock will be cut early rather than later. Barley windrows maintain their shape well and are easy to pick up with the header. There is less shedding of barley grain and weed seed due to the early swathe timing.
“Swathing barley means there is a greater proportion of the cropping area that is cut early,” says Andrew. “With harvest potentially extending through to the end of December the weeds have quite a long time available to mature and shed their seed and so evading capture through any harvest weed seed control measure.”
Then graze and burn in-crop
There are some challenges that arise when barley chaff heaps are not burned. Barley chaff heaps are prone to thatching, which helps protect seeds on the soil surface from getting wet and composting during winter.
“Even after grazing, the soil under the chaff heaps stays dry enough to preserve both barley seed and weed seeds,” says Andrew. “Volunteer barley growing in our wheat crops became a problem that we had to solve and so we have tried in-crop burning of barley chaff heaps in winter.”
From their previous experiences with narrow windrow burning and burning chaff heaps, the Boultbees knew that burning was an effective way to drive down weed numbers quickly but they did not want to go back to the traditional autumn burning method.
“We are seeing good results from in-crop burning of barley chaff heaps when the winter crop has reached the mid-tillering growth stage,” Andrew says. “Unlike burning chaff heaps before sowing, these in-crop burns are very safe, with virtually no risk of escape. Because of the minimal risk involved, one person can easily set fire to heaps across 1000 ha in one day.”
The small fires are well contained and burn out within a day or two rather than continuing to smoulder for several days. Burning in winter makes it easier to predict the wind and Andrew takes the wind direction and location of their neighbours into consideration when burning. “There is no stress or urgency associated with burning in winter and there is much less smoke,” he says.
The Boultbees are using the same idea in high weed density wheat paddocks and Andrew thinks it could also work well in paddocks with a high burden of wild radish in canola.
In-crop burning of the barley heaps after grazing is very safe and has proven to be very effective in destroying the weed seed that can evade grazing and composting.
Extracting the feed value from chaff heaps
Grazing the chaff heaps over summer fills a feed gap for the Boultbee’s 3000 sheep, and has lifted the lambing percentage of the flock to over 100 per cent—quite an achievement for Merino ewes.
The ewes are put in to graze the canola heaps first and on mating they are moved onto the barley heaps. After mating the ewes are moved onto the wheat heaps where they will stay until planting. Once the lambs are weaned they remain on the cereal paddocks with access to barley in a lick feeder to finish them.
The grazing value of the chaff heaps enables the Boultbees to run more sheep over summer and the sheep do better than those that don’t have access to this resource. Andrew says that there is an opportunity to use the chaff in a lot-feeding situation but he has not done this as yet.
Sheep selectively graze the most digestible portion of the chaff heaps including fine leaf material, whole and broken grain and weed seeds, chasing the seeds to the bottom of the heaps. Annual ryegrass, wild radish and wild oats seeds along with some broken cereal grains constitute about nine per cent of the material in the chaff heaps. The sheep seek these seeds and fragments out and spread the remaining plant material as they feed and trample the heaps. The nutrients from the heaps are then redistributed in the paddock via the manure, particularly when the chaff heaps are located some distance from watering points.
To gain maximum nutritional benefit, the Boultbees put the sheep in to graze the chaff heaps soon after harvest, and move them to new paddocks when they have extracted all the feed value from the chaff heaps and stubble. Providing a protein-rich feed such as barley seed in a lick feeder is a great way to finish the weaners very cost-effectively.
The chaff heaps provide an additional feed resource and allow the Boultbees to increase the number of animals they can run over summer, especially in difficult years when there is more small seed left in the paddock at harvest.
There are risks associated with feeding chaff to livestock that farmers should be aware of. High levels of toxins such as the bacterium associated with annual ryegrass toxicity, phomopsin in lupins that cause lupinosis and ergot, which can cause illness and even fatalities in sheep and cattle. Monitoring the health of the animals while they are grazing, and testing for toxicity in the chaff will reduce the risk of disease.
Research has shown that less than three per cent of ryegrass seeds that the sheep consume from chaff heaps will survive digestion. In contrast, almost one-third of ryegrass seeds ingested by cattle remain viable in the faeces.
Research has shown that less than three per cent of ryegrass seeds that the sheep consume from chaff heaps will survive digestion. The sheep shown in this image are not grazing on the Boultbee’s property.
Want more? You can also watch the recording of the webinar where Andrew and Peter discuss the value and practicalities of grazing chaff heaps and stubble.
Chaff carts conserve more
A change in chaff cart technology has increased the adoption of the carts as a harvest weed seed control method.
Australian Herbicide Resistance Initiative researcher, Dr Michael Walsh, said the change in the chaff delivery system, from cross augers and blowers to a simple conveyor system, has significantly improved their operation.
WA farmer Lance Turner has developed a new conveyor belt style chaff cart that increases the straw content of the chaff heaps, making the heaps safer to burn.
“An additional benefit that comes from this change is that more straw is being collected in the chaff cart and this is helping to aerate the chaff heaps so they burn out faster than they do when only chaff is collected,” he said.
“In the last two or three years an estimated 200 of the new-style chaff carts have been introduced into Western Australia and growers are particularly pleased with the faster burns, which are much safer than the chaff-only heaps that can smoulder for several days.”
A long-time advocate for all harvest weed seed control measures, Dr Walsh is encouraged by the rapid uptake of narrow windrow burning across South Australia, Victoria and southern NSW.
After a series of workshops were held in the southern grains region in 2011 to demonstrate the benefits of harvest weed seed control, Dr Walsh was pleasantly surprised to hear of the immediate trialling of the techniques, mainly narrow windrow burning.
“In just a few years we have seen adoption of narrow windrow burning go from zero to about 20 per cent of growers across the southern region,” he said. “Most growers begin harvest weed seed control by modifying their harvester to create narrow windrows that are then burnt the following autumn. A move from narrow windrow burning to using chaff carts is a natural progression, particularly in high yielding cereal crops.”
Dr Walsh said the benefit of using a chaff cart is that less crop residue is removed from the paddock and so the soil still gains the benefits of more ground cover and the return of nutrients.
One barrier to the adoption of the new chaff cart technology in the southern states is the lack of chaff cart manufacturers. Growers who want to invest in the technology will find it difficult to locate a chaff cart manufacturer in this region.
“The carts are not difficult to manufacture and many farmers are probably capable of building their own, but this takes time and time is something most farmers don’t have enough of,” said Dr Walsh. “We are encouraging machinery manufacturers to consider offering to build chaff carts on demand for clients in the southern states.”
All harvest weed seed control methods are equally effective when it comes to destroying weed seeds that are still attached to the plant at harvest time. Weeds such as annual ryegrass, brome, wild oats and wild radish are the usual targets.
“For these weed control tactics to be effective the weed seed heads must pass through the harvester so it is important to cut the crop low,” said Dr Walsh. “While this might slow harvester speed the potential weed control benefits are far more important for growers.”
Tow a chaff cart
“Weeds dictate everything that we do. It’s a whole systems approach. The chaff cart is not a silver bullet, but it’s a pretty big linchpin in the whole system.” – Lance Turner, AHRI & WeedSmart 2013 Resistance Champion.
After completing an AHRI Ryegrass Integrated Management (RIM) workshop in 1996, Lance realised the most economic choice to drive down weed numbers was to use a chaff cart at harvest.
Towing a chaff cart for the past seven years in combination with a range of other tactics has been the key to Lance’s ongoing success with weed control.
Lance admits he initially had reservations about adopting a chaff cart due to the perception that it slows down harvest and because of the extra work required burning chaff dumps. However, he has developed a system that works well on his farm.
His tips and tricks are below, along with other material to help you. Remember to keep an eye on this page – we’ll be keeping you up to date with everything related to the chaff cart.
Chaff cart NEW financials factsheet
Chaff cart SECOND-HAND financials factsheet
Sensitivity analysis – grain yield factsheet
AHRI insight: Rules of thumb (weed seed retention at harvest)
AHRI insight: Spoiled rotten (all HWSC)
AHRI insight: To win the war you must win the battles (all HWSC)
GRDC IWM hub: managing weeds at harvest