Case Studies

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Case Study

Esperance growers using chaff decks and chaff lining

Ten growers from the Esperance region of Western Australia who have adopted either chaff lining or chaff tramlining to help manage weeds have provided insights into their experience with these harvest weed seed control tactics.
Each grower spoke to Planfarm Agronomist, Nick McKenna, who documented their experience as part of a GRDC investment into the practical adoption of HWSC in the area in 2018.
Adrian Perks – Esperence grower using an EMAR chaff deck system for harvest weed seed control.
Nick says the growers all felt that they needed to use HWSC tactics to stay ahead of the weed pressure on their farms. One grower indicated that he would need to return to a mixed farming operation if he did not take action to reduce the weed numbers in his farming system.
“Several growers in and around Esperance had used narrow windrow burning and chaff carts in the past but had found it was often difficult to get a clean and safe burn on the residue, either because summer rain had made them too damp, or because the risk of fire escaping meant it required too much attention to burn safely,” he says. “Changing to chaff lining or chaff tramlining was an easy decision for these growers because there is no further effort required after harvest to get a kill on the weeds.”
Experience with chaff decks
The chaff lining system involves dropping a narrow line of chaff, including weed seed, behind the harvester. A chaff deck directs the weed seed-laden chaff into the permanent wheeltracks in a controlled traffic system. In both systems the chaff is left undisturbed.
Two of the ten growers interviewed were using the chaff lining system and eight had installed chaff decks on their harvesters. Each grower was satisfied with the results they were getting with the system chosen and there were few differences between the two systems.
“The two growers with chaff lining chutes had both built their chaff chutes themselves at minimal cost,” says Nick. “One person had moulded plastic chutes with a hot air gun and some tek screws and the other was made of metal sheeting. Both were attached to the harvester with pins and R-clips, making them easy to drop off to access the rear of the harvester. The total cost for materials and labour was about $1000.”
Chaff decks are a more expensive option – usually around $15,000 to $20,000 when fitted to new harvests. The commercially available chaff decks have two conveyor belts running at an angle to the harvester to deposit the chaff onto the wheeltracks. Installation on the harvester involves moving the chopper a fair way back to make room for the chaff deck. None of the growers Nick spoke to had experienced any operational problems with their chaff deck systems.
“One grower had made his own chaff decks specifically for John Deere S670, S680, S690 harvesters,” says Nick. “His system had two conveyors running across the back of the harvester, and did not involve as much modification work at the back of the harvester. It looked to be a simpler system, and cost about $13,000.”
Chaff decks deliver the weed-laden chaff onto the harvester wheeltracks.
The growers Nick spoke to all considered annual ryegrass to be their main weed. When using chaff decks the growers had observed greater germination of weed seeds on the high traffic wheeltracks, compared to the low traffic wheeltracks.
“Growers using chaff chutes said that very little grass germinates in the chaff lines,” says Nick. “I think this was partly because there is very little seed soil contact in the fluffy chaff left in chaff lines, and the chaff lines seem to do a good job of shedding water.”
“Clearly it is not essential to have a full controlled traffic system in place, but it is best if the harvester runs on the same tracks each year,” he says. “Some might consider that having no disturbance and very little germination is better than having weeds germinating on a portion of the wheeltracks; but either way they are concentrated and not spread across the whole paddock.”
When it came to seeding, none of the growers had run into difficulties when seeding through chaff lines. Some growers were running disc units either side of the chaff to minimise disturbance of the chaff and maximise the crop competition, so that the crop would suppress any weeds that did germinate.
“One advantage of the chaff deck is that the quantity of chaff is split between the two wheeltracks rather than all going into the one chaff line,” says Nick. “The growers all said that using a chaff deck or chaff lining allowed them to sow early with confidence, knowing they wouldn’t have an excessive number of weeds germinating in-crop.”
Those using a chaff deck observed that the ‘carpet of chaff’ on the wheeltracks significantly reduced the amount of dust generated during spray operations, giving them better coverage behind the boom, especially in hot conditions. In the day or two after rain the chaff can cause wheel slip during seeding on some soil types.
The experiences of these ten growers are documented in ‘Investigating the harvest weed seed control tools chaff lining and chaff tramlining (chaff deck) in the Esperance area – Grower case studies from the Esperance Port Zone’. The project was an initiative of the Esperance Port Zone Regional Cropping Solutions Network and the report was prepared by Nick McKenna and Peter Newman, Planfarm.
Nick McKenna, Planfarm agronomist visited 10 growers around Esperance, WA who have adopted chaff decks or chaff lining for HWSC.
The growers featured in this report are:

Mick Shutz – EMAR chaff deck
Adrian Perks – EMAR chaff deck
Col de Gussa – chaff tramlining using chutes
Carl Rasich and Henry Barlow – EMAR chaff deck
Steve Marshall – EMAR chaff deck
Elliot Marshman – EMAR chaff deck
Con Murphy – EMAR chaff deck
Mark and Hayley Wandel – chaff deck (continuous conveyor at 90 degrees to the direction of travel)
Patty Barber – chaff line (metal chute)
Mic Fels – chaff line (plastic chute)

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Case Study

Tim Rethus, Horsham Vic

Tim Rethus and his brother Luke farm with their father Geoff and workers Glenn and Dale in the central and southern Wimmera, where they are contending with Wimmera annual ryegrass, brome, wild oats, vetch, bifora, sow thistle and prickly lettuce.
“Our approach to weed control centres on keeping weed germination levels low and using diverse farming practices,” says Tim. “Dad was an early adoptor of minimum tillage back in the early 1980s and we have progressively moved to farming systems that involve less and less disturbance. One of the major benefits is that we are leaving the weed seeds on the soil surface where they are exposed to the weather and don’t have the soil contact they need, and this really reduces weed seed germination.”
Wimmera grower Tim Rethus and his family are taking an integrated approach to the weed management with a strong focus on weed-free crops.
A key element to the Rethus’ success is their determination to achieve near-zero disturbance at planting. When they adopted a 40-foot CTF system in 2008 their min-till single disc seeder did a good job and reduced soil throw but ten years on, the removal of machinery traffic from the cropping zone had led to the single discs often stalling in the softer soil and the depth control was no longer adequate.
This led the Rethus’ to invest in a zero-till precision planter to provide more precision at planting, including inter-row sowing for lentils, and to make best use of the newest chemistry available.
The planter the family has built with minimal soil disturbance in mind, to reduce weed germination at sowing.
“This precision seeder was a good unit but it was complex and didn’t suit all our crops,” says Tim. “So, we decided to combine the precision row units with twin-disc openers on a new 80-foot NDF frame but use an air-seeder to deliver the seed.”
To further reduce soil throw, residue managers are not used. Instead ‘PTT Sabre-tooth’ discs are used to cut through the residue and reduce pinning. The two discs are slightly different in size, so they rotate at slightly different speeds, providing a cutting action to keep residue out of the seeding furrow.
“Adding side-shifting rams to the toolbar means we can also inter-row sow our lentils and we have a seeder that meets all our requirements, especially in terms of maintaining low weed seed germination at seeding while still sowing at 15-inch row spacing.”
The seeder also has moisture sensors along it that are linked to the depth control of each individual row to try and put all of the seed in the same level of moisture, ensuring an even strike.
Zero disturbance planting in CTF beds is working a treat to minimise weed seed germination.
The Rethus family practice a diverse crop rotation of wheat, barley, durum, canola, lentils, beans and oats, and use shielded spraying, hay production, brown manuring, spray topping and diverse herbicide strategies to minimise weed seed set. Tim says the reality of herbicide resistance means non-chemical tools are very important to maintain low weed numbers and this is one of the driving forces behind their efforts to fully integrate hay production into their CTF system.
“Within the rotation we usually have about 35 to 45 per cent legumes for their soil health benefits and the additional herbicide options available,” he says. “We practice chemical double-knock and mix and rotate our chemistry, realising that herbicide resistance is inevitable but we can delay onset and do all we can to maintain low weed numbers.”
The Rethus’ herbicide program starts with a pre-sowing double-knock where the pre-emergent is mixed with the paraquat if the season permits. They aim to apply the pre-emergent as close to crop emergence as possible so very little of the active life of the herbicide is wasted, this is particularly important when dry sowing so they delay application of the pre-emergent until breaking rains fall.
They mix and rotate pre-emergents where possible and are careful when planting two cereal crops in a row to not use Sakura both times, favouring Boxer Gold for barley crops. Legumes offer a number of Group C options to rotate between and in oaten hay they have found Dual Gold and diuron is a good mix provided care is taken to use the correct rate for different soil types.
The mobile chemical storage and mixing truck the family uses to ensure their herbicides are mixed and applied safely and effectively.
In-crop they use multiple modes of action where possible, with legumes presenting serious limitations for in-crop broadleaf weed control due to the limited products available.
At the end of the season cover crops are terminated using multiple modes of action and a double-knock and lentils, canola, and sometimes barley, are crop-topped.
The Rethus’ routinely test weeds for susceptibility to the herbicides used across the cropping program to ensure they are using effective products and mixes. They use either a quick test in season or seed test at harvest if there are unusual weed escapes.
To avoid producing herbicide resistant weeds along the farm’s roadsides and tracks the Rethus’ choose to mow, rather than spray, the vegetation growing there.
For the last 15 years hay production has been an important mechanical control method to stop weed seed set – particularly for annual ryegrass. The Rethus’ will do up to three years of hay production in a row to drive down the ryegrass seed bank before returning to the grain cropping rotation.
“We run a controlled traffic operation and that makes hay production challenging,” says Tim. “Over the years we have developed systems and machinery that make it possible to keep to the wheeltracks throughout the hay-making process.”
“We use a front-mounted and side-mounted mower/conditioner to make three small windrows per CTF pass. The three windrows across the 40 ft CTF run are then raked together ahead of the baler. This provides a solid, constant feed into the baler travelling along the CTF wheeltracks, from crops that produce a biomass of typically 7 to 8 t/ha.”
“The final trick is to move the bales from the centre of the wheeltracks to the side so they can be picked up by the stacker. Our uncle built a hydraulic lifter that is mounted on the front of the tractor and simply lifts each bale and places it to the side where it is picked up by the stacker running behind the tractor. We stack all the bales at one end of the paddock making it easy for the telehandler operator and truck drivers,” he says. “We can bale, stack and store 600 bales a day this way without running off the CTF wheeltracks.”
The camera guided shielded sprayer is used to target vetch in lentils to avoid grain contamination.
In-crop, the Rethus’ use a camera-guided shielded sprayer for inter-row spraying in lentils. The Crop Stalker recognises the crop rows and follows between them, not relying on the crop to guide the shields.
Crop rotation is also used to manage persistent hard-seeded weeds, such as seven years without lentils for vetch control and four years without barley for wild oats control. Tim has found that even when they leave out their most profitable crop, lentils, for an extended period the paddock can remain very profitable.
“Another strategy we use for stopping seed set is to include multiple termination dates in the rotation, so the crop-topping, brown manuring and hay cutting all happen at different times,” says Tim. “Adding another layer of diversity reduces the selection for early maturity in weeds.”
Vetch has long been the brown manure used to build soil health but the Rethus’ are now using a multi-species cover crop for even better soil outcomes and reducing the build-up of vetch seed, which is a persistent weed in their system.
When it comes to crop competition the Rethus’ CTF system is set up for 38 cm (15 inch) row spacing, so they look for other ways to increase the crop’s competitive advantage. Starting with clean seed, their highest priority is minimal soil disturbance at sowing and maintaining standing stubble throughout the rotation. With the seeder only disturbing a very narrow band of soil there is little stimulation of weed seeds to germinate between the rows.
“We also sow early to take advantage of warm soils for maximum early growth and choose competitive varieties such as RGT Planet barley, Jumbo II lentils and hybrid canola,” says Tim. “It is very important that the crops we grow reach canopy closure by the time the pre-emergents have run out, and investing in good crop nutrition to support high biomass production in good years pays off.”
Choosing competitive crops and varieties is a very deliberate weed control strategy used.
Tim and Luke are avid adoptors of new precision agriculture tools to map weeds, in-crop green-on-green spot spraying with best chemical rates to target persistent weeds like vetch, bifora, wild oats and brome and spot spraying summer weeds to reduce chemical use.
The Rethus’ robust integrated weed management system incorporates all of the WeedSmart Big 6 tactics except harvest weed seed control. With their focus on multiple in-crop strategies to minimise weed germination and seed set they find that their crops are almost weed-free at harvest.

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Case Study

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.
Optical sprayer
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.
Strategic tillage
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.

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Case Study

Chris Reichstein, Esperance WA

In late 2008, Chris Reichstein, bought a new property near Esperance knowing that glyphosate resistant ryegrass was widely established. He was confident in his ability to bring the problem under control and set about using every tactic possible to reduce weed seed numbers on the farm.

Starting with herbicide resistance testing to find out what still worked, Chris established a rotation plan to make the most of crop and herbicide combinations, including swathing and croptopping, narrow windrow burning, chaff carts, autumn tickle and a triple knock strategy of two chemical applications followed with a competitive crop. Containing the problem is now a permanent part of his farming system.
More information:

Glyphosate resistant weeds – beat them before they beat you
It’s time for a glyphosate intervention
AHRI Insight – Don’t waste glyphosate

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Case Study

Trevor Syme, Bolgart WA

A few years ago they began an extensive liming and clay delving and spading program across 50 per cent of the 3500 ha cropping area to improve the water holding capacity of the natural non-wetting sands. With 75 per cent of the affected area now treated Trevor is looking forward to having this expensive but very beneficial operation behind him.
Treating the non-wetting soils has assisted with weed control through 40 per cent higher yielding crops, more even crop germination and better efficacy with the pre-emergent herbicides.
“Treating the non-wetting soils has assisted with weed control through 40 per cent higher yielding crops, more even crop germination and better efficacy with the pre-emergent herbicides,” says Trevor. “It has also enabled us to grow canola in paddocks that were previously not an option and crops seem to finish better and are less prone to frosting.”
They have also achieved good results building soil organic matter with brown manured cereal rye crops. Trevor has trialled summer crop brown manuring too but the results over three seasons were unreliable and he has decided to look for other options to reduce evaporation over summer and reduce the need for summer weed control.
The Symes’ farming system is 100 per cent controlled traffic and stubble retention with a long winter crop rotation of lupins, wheat, canola, wheat, barley, with brown manured cereal rye grown on the soils not suited to canola.
Information on the summer fallow spray program
The summer fallow spray program involves 2,4-D ester, triclopyr and glyphosate to control melons, caltrop, fleabane, sowthistle and volunteer cereals. For the last 5–6 years Trevor has applied a double knock of glyphosate followed with paraquat in preparation for sowing. “We try hard to get the timing right and target the right size weeds with the double knock,” he says. “We also avoid mixing a pre-emergent in with the paraquat because the aim is to get the paraquat on weed leaves using a high water rate and fine droplet size, whereas the aim with the pre-emergent is to achieve even coverage of the soil. Doing the pre-emergent spray separately costs us more but I believe it is worth using the right boom set up for the two jobs.”
“Rotating crops and herbicide modes of action, and using the double knock tactic, are critical to our weed management program,” he says. “RR canola, Clearfield barley and lupins all have a fit in the crop rotation and allow us to rotate herbicides effectively. The imi-tolerant barley has enabled quite effective control of brome grass and we croptop the canola with glyphosate.In the lupins we are using a pre-emergent propyzamide application followed with clethodim in-crop and finish with a croptopping spray of paraquat.”
Trevor is finding that weed control in the lupin phase is more critical than it used to be, but the value of lupins in boosting yields in the following wheat crop motivates him to look after the lupin crops, plant into clean paddocks and do everything he can to keep weed numbers low.
The Symes have had good success with high biomass canola on sandy soils where multiple germinations of wild radish are the norm. They usually plan their crop and herbicide program with their agronomist at the end of September and then revise it in February or March.
Trevor is going away from the current move toward narrow row spacing and disc seeders. “We are changing back from a disc seeder at 305 mm spacing to tines on 381 mm with a split boot to sow cereals in paired rows and canola and lupin in single rows,” he says. “We are working on the idea that less rows equals less disturbance equals less weeds in a controlled traffic system. The slightly wider row spacing also makes it easier to handle the stubble load accumulated over several years and allows us to inter-row sow.”
He has found that high tillering wheat varieties, such as Magenta, offer an alternative way to increase crop competition through additional shading of the inter-row.
In the 2015 harvest the Symes added a chaff deck to their weed control progam, directing all the chaff, and weed seeds, into the harvester wheel tracks. Trevor harvests weedy paddocks first to maximise the value of harvest weed seed control and has found the chaff deck easy to use and results in relatively few weeds surviving in the tramlines.
The biggest benefit of the chaff deck is that weed seeds are collected across the whole farm every year, and concentrated in the inhospitable tramlines.
“The biggest benefit is that we can collect weed seed across the whole farm every year where previously we have only really been able to do narrow windrow burning in the canola phase. Now at harvest the whole job is done, with no need to return to burn.”
“It is great to know where the weeds are and they are dumped on a hard, inhospitable surface,” he says. “Any escapes are easily collected at the next harvest. We also have a back-up plan to use a shielded sprayer to weeds in the tramlines, but we really want to avoid using this option.”
“In fields with high weed numbers in the tramlines we have tried simply driving a tractor, without any implement, along every tramline to achieve a crimp-rolling effect. This seems to have been a cost-effective way to stop seed set in weedy tramlines.”
In fields with high weed numbers in the tramlines Trevor has tried simply driving a tractor, without any implement, along every tramline to achieve a crimp-rolling effect (right).
Annual ryegrass, wild radish and brome grass are the main weed challenges on the Symes’ property. Trevor has done some herbicide resistance testing but generally takes the approach that all weeds present are likely to have some level of resistance. “The key is to keep weed numbers low so we take care to spray when weeds are small and avoid frost windows and high temperatures when the sprays are less effective,” he says. “We also use quite high water rates – 80 L/ha for most post-emergent herbicides and 120 L/ha for pre-emergent herbicides and paraquat – and have two sprayers so we can cover as much ground as possible when the conditions are right.”
“Fencelines and fire breaks are a weak point in our farming system as a source of glyphosate resistant weeds,” he says. “We have removed as many fences as possible, now that we don’t run any livestock, and are actively looking for an alternative herbicide that is not used in crop to manage weeds on the firebreaks.”
Trevor takes considerable care when choosing seed production paddocks, ensuring weed numbers are low to start with and then treating the paddock as a nursery. He harvests the seed crops early and cleans the seed prior to planting.

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Case Study

Lance Wise, Bowenville, Qld

Lance and Fallon Wise and Lance’s parents, Murray and Janette crop 1600 ha and run cattle on 45 ha of non-arable rocky ridges. The locality and soft black plains enable the Wises to grow a range of crops including sorghum, mungbean, chickpea, barley and wheat, along with the occasional crop of faba bean, millet and canola.
In an effort to reduce their reliance on glyphosate and overcome some of the disadvantages of long-term no-till farming, the Wises have reintroduced light cultivation and are moving toward more targeted application of glyphosate and other herbicide products using an optical sprayer.
“Our usual rotation is a legume followed by a cereal, such as mungbean, to sorghum and chickpea to wheat or barley,” says Lance. “We use either a short fallow or double crop to change from a winter to summer crop program and aim for at least one crop every 12 months from each paddock.”

Having been no-till farming for 25 years the Wises have seen the weeds transition to those species that proliferate in the absence of cultivation; weeds like fleabane, urochloa, feather top Rhodes grass, cow vine and bladder ketmia.
In an effort to reduce their reliance on glyphosate and overcome some of the disadvantages of long-term no-till farming, the Wises have reintroduced light cultivation and are moving toward more targeted application of glyphosate and other herbicide products using an optical sprayer.
Nine years ago they had success using the Kelly disc chain to manage urochloa on their less well-structured red earth soils. More recently they have used this implement to target herbicide tolerant feathertop Rhodes grass and fleabane on their main black clay soils.

“We are using a chemical / tillage double knock to good effect on feathertop Rhodes grass in the fallow,” says Lance. “We apply glyphosate and then follow up five days later with the Kelly chain, which does a terrific job of pulling out sick, dead and small plants at an operation speed of 11 to 12.5 km/hr.”
“The same system works well on fleabane too, pulling up plants with foot-long roots from soft soil, although a higher rate of glyphosate is required. It doesn’t work well for weeds like prairie grass that have deep, fibrous root systems.”
The Wises have found the chemical / tillage double knock to work well on feathertop Rhodes grass and fleabane.
Used in reverse order, Lance has found the light cultivation is an effective way to stimulate germination after a poor sorghum crop to sprout volunteers and then spray out the crop.
Along with the benefits of partial stubble incorporation on soil microbial activity and ease of sowing, Lance says the two short chains in the middle fill in the 3 m wheel track to even out the paddock, avoiding the need to do extra wheeltrack renovation operations.
About the Kelly chain
“We also use the Kelly chain to incorporate pre-emergent herbicide after sowing to a maximum depth of 2 cm. This does not disturb seed, which is all sown at least 4 cm deep with a presswheel, and the soil is moved sideways without destroying the cracks in the soil or drying out the profile,” he says. “Weed seed is not buried deeply so it doesn’t come back to haunt you years later.”
Lance avoids using the Kelly chain more than once in a season on the red soils, which can get very dusty and are prone to hardsetting on the surface.
At the end of harvest Lance and Murray assess the stubble load and weed pressure in each paddock. They usually spray glyphosate after a rain event and either double knock with the Kelly chain or spray paraquat through their Weedseeker optical sprayer.
After using the Kelly chain, Lance follows 30–45 days later with the Weedseeker rig to clean up any survivors.
“The Weedseeker is a new fallow option for us and means that we can treat weeds that we might otherwise ignore, apply higher rates, and use more expensive products to control small areas or patches of weeds,” says Lance. “The 36.6 m boom carries 96 sensors so there are not many weeds that go undetected in the fallow.”
At the end of last year, the Wises started sub-soil ripping to a depth of 35 to 40 cm on 75 cm spacing to increase water capture and break up the sub-soil compaction to improve crop growth.
Six weeks ahead of planting they apply the final glyphosate spray and then add fertiliser, which they incorporate with the Kelly chain, with the added benefit of removing any weeds present. Liquid fertiliser applied at seeding promotes early seedling vigour and growth, which gives the crops a competitive advantage over weeds.
They plant using a Tobin planter that achieves a good even strike in stubble, starting on the red soils as soon after rain as possible, then moving onto the black soils.
Pre-emergent herbicide is applied after sowing legume crops and incorporated using the Kelly chain. Herbicide is applied in crop as well as for desiccation purposes in sorghum, mungbeans and chickpea.
Being a spray contractor, Lance has also invested in an air boom on his sprayer that enables him to have much greater control of droplet size to match the environmental conditions, while also covering a larger area in a day.

He says the elliptical cone delivers spray in both a forward and rear motion to achieve better coverage, even at lower water volumes. The controls in the cab allow the operator to adjust the spray quality from fine to extra course without changing nozzles on the boom and there is no need to have all the different nozzles to suit different conditions and products.
The Wises operate a 12 m controlled traffic system and plant all their crops on 375 mm row spacings. Lance has increased the planting rate in sorghum from plants 40 cm apart in the row to 25–30 cm apart to quickly to shade the interspace and suppress weed growth.

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Case Study

Krui Pastoral Co, Condamine, Qld

East-west sowing between shade lines
Half an hour west of Condamine on the western Darling Downs, Jake and Felicity Hamilton work with Jake’s father to farm 4500 ha of brigalow scrub, which was originally cleared for cattle grazing in the decades since 1975. Although the cattle are all gone now, the Hamiltons have maintained the shade lines of native vegetation left when the property was cleared and which occupy about 10 per cent of the farm’s area.
Jake says the thick stand of buffel grass in the shade lines prevents other weeds from establishing and the buffel doesn’t move into crop areas. Most of the fencelines are also timbered, with the low soil moisture keeping a lid on weeds.
Jake and Scott Hamilton, are well aware of the impact of herbicide resistance on their farm near Condamine, Qld.
“When the farm was cleared, the shadelines were left running east west to maximise the shading effect for the livestock and now we are cropping east west in fairly large, square paddocks,”says Jake. “We are now taking advantage of the shading effect on the inter-row to suppress weed germination and growth.”
Crop rows run east-west, parallel with tree lines left when the property was cleared, to provide shade for stock.
Growing wheat / chickpea / wheat, with few opportunities for summer cropping in recent years, Jake has been working hard to keep on top of herbicide resistance in summer growing species including barnyard grass, liverseed grass, button grass and feathertop Rhodes grass.
Not being able to grow summer crops on a regular basis, Jake has implemented a robust fallow management program to keep these weeds under control.
“We try to double knock the glyphosate applications with paraquat, especially if the weed burden is high, there are large weeds present or weeds are not dying like they should,” he says. “And we always use full label rates to avoid herbicide resistance.”
Jake regularly employs casual labourers to go around the farm on the ‘Gator with the spot spray rig to deal with any individual weed survivors, or if there are weedy patches they use the 6 m boom on the ‘gator’.
Spot and patch spraying is time-consuming but very worthwhile.
“Spot spraying summer grasses is quite time consuming but incredibly effective and cost efficient,”he says. “We also employ an agronomist to visit the farm once a fortnight to assist with monitoring and planning the weed control program.”
“We know we are losing Group M [glyphosate] and can see resistance to Group A [grass selective] chemistry on button grass, which will leave us with very few herbicide options. We rotate crops as best we can so we can use different methods of weed control to try and break the resistance.”
Button grass is proving to be quite a challenge to control with herbicide.
Following two reasonable winter seasons, the 2016–17 summer was too hot for summer cropping, with no rain falling between September and February. Jake took this opportunity to do more laser levelling to remove the melon holes that are characteristic of brigalow scrub soils. Levelling brings about an immediate increase in yield and more even crops.
“We purchased a second hand Caterpillar D11R and fitted it with TopCon GPS,”says Jake. “With the dozer we are able to cut 10 cm below grade on our first pass, which creates a good blend of topsoil with any exposed subsoil to avoid ‘scalping’the paddock.”
Every four years the Hamiltons also incorporate 10 t/ha of manure to a depth of 15 cm and plan to utilise variable rate technology to apply manure to ameliorate some areas of soil fertility decline.
“After using a chisel plough for several years to incorporate the manure, we are moving toward a program of deep ripping and deep application of phosphorus fertiliser to a depth of 40 to 50 cm, on 50 cm spacings,”says Jake.
Since 2001 the farming system has been controlled traffic with 12 m bays, to suit 36 m sprayer, 24 m planter and 12 m header. Their new planter is configured for 375 mm (15″) spacings for wheat and barley, 750 mm (30″) for chickpeas, faba beans and mungbeans and 1500 mm (60″) sorghum and cotton. Jake also uses high seeding rates to maximise crop competition, along with their efforts to improve overall soil fertility and boost crop competitiveness.
Although there are some risks associated with the short crop rotation Jake says residuals are doing a good job controlling weeds in-crop, with no late germinations evident. “We use residuals plus picloram and aminopyralid for fleabane control in wheat,” he says. “In chickpea we apply simazine and Balance and follow with an in-crop application of a Group A herbicide.”
“If there are weeds present in-crop they usually don’t seed before harvest,” he says. “Black oats is a potential problem though if there is a spray miss.”
They also apply pre-emergence herbicides Balance + Flame + diuron in some paddocks to keep them clean over summer while leaving their summer cropping options open in other paddocks.”
The Hamiltons store planting seed on farm and grade all their seed through a mobile grader on the Easter long weekend, aiming to achieve a good clean sample –99 per cent purity.
Jake spreads their frost risk by planting 50 per cent of the wheat area to Gregory in early May then sowing the chickpea area the following week. The remaining wheat area is sown later to Suntop or Crusader.
After suffering severe frost damage in late August 2017 the Hamiltons changed their planting schedule to reduce their frost risk. Jake says late frosts can be a problem in the Condamine area and can badly affect chickpea crops if the temperature drops to zero or below during flowering or podding.
“We aim to have all our wheat planted between 7 and 21 May and then plant chickpeas after that,”he says. “Our new planting equipment has superior breakout force, compared to our old machine, which allows us to plant chickpeas to a depth of 200 mm (8″). Planting at this depth delays seedling emergence until after the first week of June, pushing the flowering window back a fortnight, closer to the warmer weather of spring.”
“Chickpea makes a huge difference to our farming system with better wheat yields, less fertiliser and softer soil.”

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Case Study

Bruce family, Alford SA

Keeping pressure on brome grass with HWSC
Brothers Gary, Paul and Bronte Bruce farm at Alford on the Yorke Peninsula, SA have used harvest weed seed capture as an important tool in their weed management program to bring down grass weed numbers in their continuous cropping business.
For the last 15 to 20 years the Bruce family has followed a 3-year rotation of wheat – barley – legume, having exchanged field peas for lentils in the legume phase in recent years. They found that producing export hay on grassy paddocks was a very effective way to manage grass weed seedbank, to the point where they had only one paddock of hay in 2016 and no hay in 2017.
Gary Bruce, together with the family’s agronomist Chris Davey, YP-AG sets out a plan for the season, including our weed management program, with different strategies used depending on whether there is a wet or a dry start.
“Hay production is hard work and now that we don’t have much of a grass weed problem we are taking hay out of the rotation for a while,” says Gary. “The hard work was certainly worth it in terms of regaining control over herbicide resistant weeds on the farm. Now we’d like to keep more crop residue on the paddocks to improve the hardsetting nature of the soil here.”
Having used a chaff cart for many years, the Bruce’s were well aware of the benefits of capturing weed seed in the chaff stream but Gary was very interested to hear HWSC advocate and WA grower, Ray Harrington, speak at a field day about chaff lining. In 2017 harvest they used chaff line chutes on two headers for the first time. As usual they learnt a lot in their first harvest and have plans to make even better use of the system this season.
Gary is very aware of the fact that there is very limited research on the long-term impact of chaff lining on weed management.
“Our farm is partially set up for controlled traffic with 12 m and 36 m gear so the chaff line ends up on a spray track every third run,” he says. “We found starting the harvester on a spray track at the edge makes the best use of the wheeltracks. If we go to a full CTF system we will probably change to using a chaff deck system but the chaff lining chute is certainly a cheap and effective way to confine weeds to a small area of the paddock while also retaining the stubble.”
Gary’s farm is partially set up for controlled traffic with 12 m and 36 m gear so the chaff line ends up on a spray track every third run. So far they have found using the chaff lining chute is a cheap and effective way to confine weeds to a small area of the paddock while also retaining the stubble.
HWSC and late germination
Brome grass is the most problematic weed on the Bruce’s farm with limited options for control in the cereal phase. There are limited chemical control options to kill early germinating brome grass before seeding and so Gary relies on HWSC to take care of late germinating cohorts. They recognise that hay making has played an important part in keeping this weed in check and acknowledge this could be more difficult if they get out of hay production altogether.
All crops are sown to achieve greatest crop competition possible using 25 cm row spacing and cultivars that are well suited to the different soil types. Two-thirds of the farm is inter-row sown while paddocks with hardsetting topsoil generally follow the same furrow as the previous year. As the soil improves through increased residue retention Gary hopes most of the farm will eventually be sown in the inter-row.
Generally they find, Scepter wheat yields better than Mace, Compass barley produces the most straw, PBA Bolt lentils give salt and boron tolerance where it’s needed and PBA Hurricane lentils offer Group B herbicide tolerance.
“Early in April we usually speak with our agronomist, Chris Davey, about a plan for the season, including our weed management program,” says Gary. “For example, wet and dry starts need different strategies such as ensuring there is sufficient moisture to activate metribuzin and propyzamide before sowing lentils. We have also experienced more summer rainfall recently and often need to do two sprays for summer weed control.”
Other resources:

Implementing the WeedSmart Big 6 on the Yorke Peninsula

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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.

Article
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

Article
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.

Article
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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