Narrow Windrow Burning (NWB)
Narrow Windrow Burning (NWB), is one of the most common HWSC methods chosen by farmers. It’s relatively easy to adopt and provides good results for weed management, but it does have its fair share of problems.
It is time-consuming; comes with a high nutrient removal cost; removes much of the ground cover from the paddock; there is a risk of fire escapes, and it is difficult to achieve a good burn contained to the windrow over the entire farm.
For these reasons, we are seeing many growers moving to some of the other tools that focus on the chaff fraction only. NWB is a bit of an art form and there are some core steps you need to take to get a job done well. Firstly, you have to harvest low. Secondly, you have to make sure you pick the right time to conduct your burn.
This is when the grass fire index is between two and 10. A light crosswind is ideal, and ideally, light up every 200-400m.
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.
Brad Jackson, Gurley NSW
Weeds are not yield-reducing on the Jackson family farms at Gurley, in northern NSW, and that’s how they want to keep it.
Brad Jackson farms ‘Bellaree’, ‘Jymoomah’ and ‘Inverness’ with his parents Peter and Janice, and brothers Phil and Matt. The 1700 ha family operation is based on a robust winter cropping program featuring wheat, barley, chickpea, canola and linseed to help keep weed numbers low and manage risk.
Brad Jackson, Gurley NSW
Each year there is wheat on about 30–40 per cent of the farmed area and several break crops. If weed numbers start building up in a paddock they use a canola–chickpea double break to help drive down the weed seed bank.
“We see annual ryegrass coming – it’s in the district and on our farm,” says Brad. “We know how bad it can get and how quickly herbicide resistant populations develop. We want to stay on the front foot.”
Having focussed on winter cropping in recent years the Jacksons, like most in NSW’s north, have been battling low rainfall for several seasons in a row. 2015 was the start of the long dry stretch and the challenges in 2016 were softened slightly with better results from some crops than expected, but it was also a year the family worked hard to manage expectations and take mental health seriously. 2017 and 2018 have been record dry years in the district where the Jacksons have been lucky to harvest their crops.
“We are heading into the 2019 winter with a completely dry soil profile, which is unheard of in living memory for this district. We have decided to ‘plant anyway’ and hope for the best,” says Brad. “In the end we usually end up with crops to harvest even though the yields have not been great. This year we desperately need ground cover so even if we don’t harvest grain we really need to invest in planting.”
In a string of very dry years, the Jacksons have planted their winter program and ‘hoped for the best’. The Boss precision planter with coulters on a parallelogram configuration allows better trash flow and they have more control over the planting depth. Last season they were rewarded with a chickpea crop establishing well from a planting depth of 20 cm.
“The rotation that has worked well here is wheat, followed by canola, then barley, then linseed. Linseed can dry out the profile but is important in the rotation to control root-lesion nematodes,” he says. “We don’t grow any summer crops so we use multiple tactics in our winter crops to keep weed numbers low.”
The Jacksons also grow grazing oats for seed production under contract so keeping the farms as weed-free as possible is very important.
Having used a conventional tined precision planter for the last 15–20 years, the Jacksons are now using a Boss precision planter with coulters on a parallelogram configuration. They are finding the trash flow is better with the coulter and they have more control over the planting depth. Last season they were rewarded with a chickpea crop establishing well from a planting depth of 20 cm.
Brad and Peter attended the 2017 WeedSmart Week in Wagga Wagga where they were convinced of the need to reintroduce the use of pre-emergent herbicides and take every opportunity to mix and rotate herbicide modes of action.
The Jacksons also use strategic tillage, optical sprayer technology and harvest weed seed control to reduce the risk of herbicide resistance in weeds. In the last few years they have introduced desiccation in chickpeas and crop-topping in canola to control late winter grasses and early summer grasses.
Re-introducing pre-emergent herbicides
In 2018 the Jacksons applied pre-emergent herbicides across 70 per cent of the farm, for the first time in 20 or 30 years. Their aim was to implement another tactic to control ryegrass, phalaris and black oats using pre-emergent applications of treflan and Avadex in linseed crops and treflan and Boxer Gold in wheat and chickpea. In the linseed and chickpeas they apply Verdict and Select in-crop.
Linseed provides multiple benefits to the Jackson’s rotation. Unlike many other growers in their area the Jacksons have chosen to grow only winter crops and so need to use several tactics to ensure sustainable weed control.
The seasonal conditions did not favour high efficacy in pre-emergent chemistry but the Jacksons found that they achieved better crop establishment with the coulter than would have been possible with their old planter, providing good support for the applied herbicides.
The Jackson’s WEEDit optical sprayer has revolutionised their herbicide program, allowing them to spray low weed density paddocks more frequently and target small, fresh seedlings. They also use it to provide a second knock following a broadacre spray on paddocks with high weed numbers. They are finding this to be a great way to reduce their reliance on glyphosate and ensure this useful chemistry is still effective in the future.
“Optical sprayer units are fairly common in this district,” says Brad. “We purchased ours in 2016 mainly to manage herbicide resistance. We couldn’t really justify the investment based on herbicide savings alone.”
The WEEDit optical sprayer has widened the herbicide options available to the Jacksons in summer.
“The desiccation or crop-topping operation is the start of our summer weed control program. After rain we use the broadacre sprayer to apply glyphosate plus a Group A fallow pre-emergent and then double knock with paraquat using the WEEDit,” he says. “It is important to start early to target barnyard grass and we are able to spray more often and target small weeds every 3 to 4 weeks if necessary with the WEEDit. The main summer weeds here are feathertop Rhodes grass, barnyard grass, and button grass.”
The Jacksons expect to see a reduction in herbicide costs over time through the use of the WEEDit but at the moment they are using it to apply more expensive herbicides that would be uneconomical to apply with a broadacre sprayer to control barnyard grass.
The Jacksons started no-till in 1990, retaining stubble for improved soil moisture infiltration and retention, and to reduce erosion on their black self-mulching clays.
Although they are committed to no-till farming there is a place for strategic use of shallow cultivation with a Kelly chain. In March 2018 they used a Kelly chain on half the farm area to kill small weeds and close the cracks that were allowing the soil to dry out at depth.
“We used the Kelly chain after harvesting chickpea and then planted imi-tolerant canola 10 cm deep. The canola went on to yield 1.2–2.2 t/ha, which was a great result given the season,” says Brad.
Harvest weed seed control
The Jacksons started harvest weed seed control in response to the unwelcome arrival of annual ryegrass. Most years they implement narrow windrow burning on about 10 per cent of their farmed area.
“We try to burn as early as possible to get hot fires – usually in February if the season allows and it’s possible to get a permit,” says Brad. “Going early also means our Big N application program can go ahead uninterrupted from December to February without running over the windrows.”
The Jacksons use a 700 mm narrow windrow chute and select paddocks based on weed pressure and crop type. They delay harvest until crop straw is fully dry and plan ahead for an extra header if necessary to cover the area. This allows for the harvester operator to go slower and cut the crop low to make sure the maximum number of weed seed heads enter the front of the header.
“If the windrow is too big there is potential for it to be blown over. To avoid that, we turn the chopper fins backwards on our New Holland harvester to make the windrow with the chopper when necessary,” he says. “This condenses the windrow substantially, keeping it knee high rather than waist high.”
Narrow windrow burning is implemented each year on about 10 per cent of the Jackson’s cropping area. They use a 700 mm narrow windrow chute and select paddocks based on weed pressure and crop type.
Care is needed when doing this as the header can become blocked up, and air from the fan can blow some weed seed out to the side and away from the windrow.
Brad says the key is to get the weed seeds in the front of the header and then to ensure they are concentrated into a zone where they can be managed strategically.
In terms of crop choice, the Jacksons find narrow windrow burning is a good option for wheat and barley provided the stubble load is not too high. It also works well for chickpea, faba bean and linseed because of the low harvest height and lower stubble loads of these crops, however it can be hard to achieve an even flow of material into the narrow windrow. The Jacksons generally do not use narrow windrow burning in canola crops and so opt for crop-topping as their main tactic to control weeds present at harvest.
While narrow windrow burning has been an effective in containing the risk of herbicide resistant weeds, the Jacksons are keenly assessing other options such as a weed impact mill, chaff lining or tramlining to avoid the need for burning and to retain more stubble in situ.
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.
Implementing the WeedSmart Big 6 on the Yorke Peninsula
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.
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.
Robert Gollasch, NSW
Narrow windrow burning for maximum effect in less time
Narrow windrow burning to destroy weed seed has been widely accepted as a useful tool, however there are risks and it can be time consuming.
Robert Gollasch has been burning narrow windrows for a few years now and has found ways to minimise the time commitment while still gaining the benefits in his weed control program.
Robert and Liz run a mixed farming operation at Wallacetown, north of Wagga Wagga, NSW. For the last 40 years they have continuously cropped most of their 2000 ha farm and currently run 1100 first cross ewes.
In the early 2000s the Gollaschs noticed increased weed burden across their cropping area and that herbicide resistance was reducing their control options. In response, Robert reassessed his cropping system and introduced more diversity in the crops grown and the weed management tools used.
“Implementing narrow windrow burning was not difficult but it did take a couple of years for us to really refine the practice on our farm,” said Robert. “Preparing for narrow windrow burning is fairly simple – the chute only takes a few hours to make and fit – and then it is down to cutting the crop short so that everything goes through the header. Although cutting short can be difficult in canola we have found that it is worth persevering with.”
Robert designed and built a chute for his Claas harvester and uses a custom-made trailer to safely and easily remove the spinners. The chute is fitted with small trolley wheels so it can be maneuvered into place and only lifted a short distance. The opening of the chute is 500 mm wide, which creates a suitable windrow without causing blockages in the header.
Simple innovations such as trolley wheels on the narrow windrowing chute and a customised trailer for the spinners off the harvester makes it easier to swap and go between crops at harvest.
After harvest the sheep are allowed to graze the narrow windrows left after harvesting cereal and lupin crops. Robert finds that the sheep don’t damage the windrows, in fact they help aerate the windrows to give a good hot burn.
“We use a low stocking rate on the crop stubble and the sheep just pick over the windrows looking for grain,” he said. “We don’t see any measurable benefits from sheep grazing the windrows but they don’t seem to spread the seed and it is making use of a resource on the farm.”
If overgrazed, sheep can create many small fire breaks in windrows. making them difficult to burn so it is important to monitor closely and remove sheep from the paddock before this occurs.
It is important not to leave the windrows sitting in the paddock for too long. Robert has found that an inch or two of rain on the windrows in autumn can make them very difficult to burn. He tries to burn the windrows as soon as permits are available in autumn and conditions are safe.
“One thing we have learned is that narrow windrow burning is most effective when you tackle a smaller area and do it well, rather than trying to windrow and burn every crop, every year,” he said. “If weed numbers are increasing in a paddock we will usually try to narrow windrow burn in that paddock for two or three years in a row to really drive down the weed seed bank.”
Robert aims to narrow windrow burn about 200–300 ha a year, usually in lupin and canola crops and finds two successive years of windrow burning in a paddock is very effective in driving down weed numbers.
Robert usually windrow burns about 200–300 ha each year, primarily in the canola or lupin phase of the rotation. To burn the windrows safely and effectively, he usually starts lighting the rows at midday and aims to have the job complete by 5 pm that day. Lighting the rows every 100 m or so produces a slow hot burn that is known to kill 99 per cent of annual ryegrass seeds present. Using a motorbike and burner, Robert lights windrows across about 50 ha a day, which takes only a few hours to burn out. He also takes into account the fact that narrow windrows in canola tend to burn slower than those following cereals and lupins.
The usual rotation Robert uses is TT canola, wheat, albus lupins, wheat and barley, then in older paddocks he establishes a lucerne pasture for five years for the sheep. The Border Leicester x Merino first cross ewes are crossed with Dorset rams and all progeny are sold.
Robert finds that ryegrass numbers tend to build up the most in cereal crops so in years where the weed numbers have increased he often bales the cereal crop rather than harvesting the grain. “Two successive years of windrow burning in the canola and lupins and then hay baling cereal crops is a very effective way to run down weed numbers,” he said.
Robert has implemented most tactics recommended in the Weedsmart 10 Point Plan to maximise the pressure on weed numbers across his farm and cropping rotation.
The barley is usually followed with a lucerne pasture phase and when Robert brings a paddock back into cropping he usually starts with canola to enable more grass weed control options followed with narrow windrow burning before planting cereals.
“We have used broadleaf cropping in our rotation for a long time, which has enabled the use of different herbicide chemistry, including pre-emergent herbicides, particularly in the lupins,” he said. “Our time with chemicals is running out so anything we can do to lessen our reliance will lengthen our use of chemicals and make our system more sustainable. We are relying heavily on clethodim for ryegrass control at the moment so being able to use Factor on lupins gives us some extra diversity in our herbicide program.”
The Gollaschs make the most of grazing livestock for weed control during the pasture phase and also use paraquat to control young grass plants toward the end of the pasture phase.
“The sheep keep the pasture short and reduce grass seed set. Each spring I spray for barley grass then ryegrass control begins in earnest in the last few years of the pasture phase,” he said. “Paraquat and simazine are applied in the second last year of the pasture to treat annual ryegrass and silver grass and then a glyphosate and paraquat double knock is used to kill the pasture in preparation for a return to cropping.”
Robert and Liz Gollasch make the most of grazing livestock for weed control after harvest and during the pasture phase on their mixed farming operation near Wallacetown, NSW.
Robert has also reduced the crop row spacing from 12 inch to 10 inch to improve yields across the farm and apply more pressure to emerging weeds. Their Bourgault Paralink seeder with hydraulic tynes works well at 10 inch row spacing but relies on the stubble either being cut shorter or burnt as inter-row sowing is harder to achieve with 10 inch row spacing. A move to narrower rows and full stubble retention would require changing to a disc seeder.
The combination of increased crop competition and harvest weed seed control go hand in hand. In competitive crops, weed seed set is reduced and weeds that do set seed tend to have seed heads held high in the canopy where they are easier to capture at harvest.
Simple innovations such as trolley wheels on the narrow windrowing chute and a customised trailer for the spinners off the harvester makes it easier to swap and go between crops at harvest.
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Windrow burning: it’s got to be hot
Growth Farms Australia manager, Chris Bunny, knew that the company was buying a property with herbicide resistant weeds when they purchased ‘Glaisnock’ near Young in 2008.
“The ryegrass on the property was known to be resistant to both Group A and Group B herbicides,” he said.
Chris and Elise Bunny, ‘Glaisnock’, Young believe narrow windrow burning is an effective non-chemical tactic to add to their weed control strategy.
“Twenty-five years of continuous wheat-canola cropping had taken its toll and changes to the farming system were obviously required.”
Over the last few years Mr Bunny has implemented drastic changes—reintroducing livestock into the system, changing herbicide application tactics, modifying the rotation and adopting narrow windrow burning—all to address the problem of herbicide resistance in weeds.
The 970 ha red earth property, ‘Glaisnock’, located between Young and Temora is well suited to cropping but continuous cropping practice has generated an unsustainable level of weed pressure. Mr Bunny is in the process of fencing paddocks and installing stock waters as they move around the property planting lucerne for stock grazing.
“About 20 percent of the property is under lucerne in any one year,” he said. “Lucerne gives us the opportunity to earn income off these paddocks while also winter cleaning with heavy grazing and paraquat in at least 3 of the 5 years of pasture.”
They run trade stock, either steers or prime lambs, so they are able to be flexible with the timing and stock density. The lucerne is also breaking up the hard pan that had developed over so many years of continuous cropping.
Triazine tolerant canola and wheat are currently sown 50:50 across the remaining farming area. Mr Bunny said the triazine-tolerant canola had proven to be a useful way to introduce different modes of action to the assault on resistant weeds. He hopes eventually to reduce the area sown to canola but for now it is playing an important part in their integrated weed management program.
During the summer fallow Mr Bunny employs double knock herbicide applications at every ryegrass germination. “Generally there are two double knock applications in the fallow,” he said. “The timing of the operations is determined by the weed size and the extent of the germination.”
“The staggered germination pattern of ryegrass can make it difficult to know when to spray,” he said. “It is also tempting to not do the second knock when the first spray appears to have worked well, but we have seen the benefits when a strip has been left un-sprayed and it is clear that the second application is essential.”
To round off their integrated weed management strategy Mr Bunny has also implemented narrow windrow burning of canola chaff as a non-chemical harvest weed seed control measure.
This year is the third year of narrow windrow burning on the property and Mr Bunny is convinced of its effectiveness in reducing the weed seed bank. “The only real problem with narrow windrow burning is the chance of the windrows getting wet before you are allowed to burn,” he said. “We try to start burning as soon as permits are available. So far we have had successful burns in 2 out of the 3 years.”
A hot fire is the key to effective narrow windrow burning to kill weed seeds.
Mr Bunny had previously used stubble burning as a weed control measure but had found that burning the whole paddock was ineffective and there was the associated loss of stubble.
“Burning the narrow windrows is a much safer operation and for negligible cost it is possible to modify the header and introduce another weapon against resistant weeds.”
The canola chaff easily generates the required 400 degrees Celsius required to kill ryegrass seed. The next challenge for Mr Bunny is to implement the strategy in harvested wheat paddocks. The main difficulty with taking this step is the need to cut the wheat lower than usual and the timing of harvest compared to when the ryegrass seed begins to fall.
“We will be working on lowering the header, aiming for ‘beer can height’, and adjusting the chute to make the windrows as narrow as possible without causing blockages,” he said.
Being able to effectively burn chaff in every paddock, every year is the aim and Mr Bunny is determined to solve any problems that stand in the way.
Mr Bunny said two people can easily burn 400 ha of narrow windrows in one afternoon. Each windrow is lit every 400 metres or so, starting soon after midday. The windrows burn quite quickly and most are burnt out by late afternoon. Mr Bunny checks the paddocks again late in the afternoon and extinguishes any that are still alight.
“With the wheat we anticipate the need to burn off smaller areas at a time and that there will be more risk of the fires spreading across the paddock,” he said.
Summer rains can cause problems with the wet windrows tending to only burn along the top where the chaff has dried off. Mr Bunny has found that even in years where the effectiveness of the burn is reduced there is still a benefit in concentrating the weed seed into narrow bands in the paddock where germinations can be more easily and cost-effectively targeted.
Growth Farms Australia recently hosted researcher Michael Walsh from the Australian Herbicide Resistance Initiative and a group of growers from Western Australia with extensive experience with herbicide resistant weeds, including annual ryegrass. Growers from the Young district were invited to meet the visiting experts and to see narrow windrow burning demonstrated.
Delta Agribusiness consultant David Crowley and GRDC funded, Charles Sturt University researcher John Broster arranged field days at Young, Griffith and Lockhart to give local growers an opportunity to meet the West Australian expert panel to discuss their experience with harvest weed seed control methods, including the Harrington Weed Destructor, chaff carts and narrow windrow burning.
Create & burn narrow windrows
The best option to maximise the weed seed bank is to harvest high and spread all of the weed seeds evenly over the paddock. This will give you something to spray next year.
If you, like most others, feel that this is a bad idea, it may be time to start narrow windrow burning. Narrow windrow burning is a good place to start to see if this harvest weed seed control caper is all it is cracked up to be.
The first step is to spend some time familiarising yourself with a beer can. The internationally accepted harvest height when trying to capture weed seeds is the height of an Australian beer can.
The next step is to work out how to modify your harvester to make narrow windrows. It’s easier than you think!
Below are a number of videos and materials to help get you started. Remember to keep an eye on this page – we’ll be keeping you up to date with everything related to windrow burning.
Windrow chute CAD drawings
AccuFire Broadacre Firelighter
Narrow windrow burning financials factsheet
Narrow windrow burning in southern NSW
Chris and Elise Bunny feature: Windrow burning – it’s got to be hot
Sensitivity analysis – grain yield factsheet
AHRI insight: Tips
AHRI insight: Burning wet windrows
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