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Diverse approach to feathertop Rhodes grass control

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.

Other resources

Mark Congreve explains the key features of FTR, considerations when developing a control strategy, fallow herbicide options and fallow application recommendations in a new series of Grains Research and Development Corporation (GRDC) Know More videos.

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What to expect at WeedSmart Week 2021

Big 6 at WeedSmart Week 2021 – Double knock to protect glyphosate
The WeedSmart Forum is set for Tuesday 17 August, 2021 at the Civic Centre in Esperance WA. The program features growers, agronomists and researchers discussing ways to use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
Greg Warren from Farm and General in Esperance will be sharing his thoughts on the control of weeds like summer-germinating ryegrass, marshmallow, fleabane and portulaca.
He says the growers around Esperance are tackling glyphosate resistance in annual ryegrass, along with brome and barley grass and other emerging weeds using a range of integrated control tactics. The double knock plays a key role in preserving glyphosate (and soil moisture) and providing a clean seed bed for planting crops.

 
Big 6 at WeedSmart Week 2021 – Increase crop competition
WeedSmart Week 2021 is set for Tuesday 17 to Thursday 19 August, 2021 in and around Esperance WA. The last two days feature local growers hosting visits to their farms and discussing how they use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
One of the farms hosting a visit during WeedSmart Week is Warrakirri’s 12,800 cropping operation at Condingup. Farm manager Con Murphy has implemented a variety of tactics to combat their main weeds – annual ryegrass and wild radish. Since 2015 the farm has undergone an intensive soil amelioration program to improve the drainage and ameliorate the sandy soils across the farm.
Con says the benefits have been seen in better germination and establishment that sets their cereal, pulse and canola crops up to compete strongly with weeds. There is also a benefit at the end of the season where rain in August or September enters the soil profile without causing waterlogging, and providing a better finish for their crops.
Since 2016-17 about 80% of the farm has been ripped and a portion has been ripped 2 or 3 times because the sandy soils tend to slump after substantial rainfall events, recreating the hardpan.
Con will be showing the WeedSmart tour group how their ripping, drainage, liming and spading program has helped grow more crop and less weeds!
Listen to the podcast with Warrakirri’s Con Murphy talking about the impact of improved drainage on crop competition

Big 6 at WeedSmart Week 2021 – Implement harvest weed seed control
The WeedSmart Week machinery display is set for Wednesday 18 August, 2021 at Dave Campbell’s shed near Esperance WA. The 3-day WeedSmart Week program features growers, agronomists and researchers discussing ways to use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
We’ve saved the harvest weed seed control discussion for the machinery session on Wednesday 18 August. Ben White from Kondinin Group will host the machinery session with spray and harvesting gear on display including impact mills from Seed Terminator, Redekop and iHSD (both hydraulic and belt-driven), Emar chaff deck, and spray technologies including Goldacres’ G6 Crop Cruiser series 2, and weed detection technologies using drones and weed identifying cameras (green on green).
Ben White, Kondinin Group (Photo: Melissa Powell, courtesy of GRDC)
Growers doing the WeedSmart Big 6
WeedSmart Week 2021 is set for Tuesday 17 to Thursday 19 August, 2021 in and around Esperance WA. The last two days feature local growers hosting visits to their farms and discussing how they use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
One of the growers who will open up their farm for a visit is Adrian Perks who farms at Condingup, 70 km north-east of Esperance. Adrian runs a continuous cropping program on his 4300 ha property, growing canola, wheat, barley, faba beans and lupins. This diverse rotation allows him to mix and rotate both chemical and non-chemical weed control tactics. Over half of Adrian’s farm is sandplain, on which he has implemented a soil amelioration program to address non-wetting to increase the competitiveness of his crops. He currently uses chaff decks for harvest weed seed control and is introducing an impact mill this season. Adrian monitors the tramtracks for weed growth and if he feels the weed pressure is too high, he uses a shielded sprayer to reduce seed set. The bus tour will include four farm visits and a machinery display.
Listen to Adrian on the Regional Update podcast.
Adrian Perkins, Condingup WA
 

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WeedSmart agronomist set to tackle high rainfall zone weeds

Every locality has its own spectrum of weeds, and growers face different opportunities and challenges regarding the control tactics they can employ.
The WeedSmart Big 6 approach is a practical way to ensure that an integrated weed management program is put in place that disrupts weed seed production and the evolution of herbicide resistance.
Commencing in January 2021, Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria.
Jana will add to the dedicated and experienced extension agronomists on the WeedSmart team with Peter Newman in the Western region, Chris Davey in the South, Greg and Kirrily Condon in the East and Paul McIntosh in the North.
Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria.
Jana hails from the Mid North of SA, and began working at Pinion Advisory (previously Rural Directions) while she was studying agriculture at the University of Adelaide. She has been employed full-time at Pinion Advisory since January 2019 as an agribusiness consultant, based in Clare, and spends most of her time delivering agronomy and farm business advice to clients from a wide range of cropping regions in South Australia.
Pinion Advisory is a foundation WeedSmart sponsor and Jana has been involved in two WeedSmart Week events already – the first as a participant and grower group organiser at the Horsham event in 2019 and then as the local organiser for WeedSmart Week 2020 in Clare.
In welcoming her to the WeedSmart team, program manager Lisa Mayer says Jana brings energy, commitment and insight to deliver communications focussed on the southern region’s high rainfall regions.
“Growers in the southern high rainfall zones are facing some serious issues with herbicide resistance influencing their farming decisions,” says Ms Mayer. “Jana will be engaging with agronomists, growers and researchers in each of the distinct high rainfall zones to understand the complexities and look for practical ways to apply the WeedSmart Big 6 in various cropping scenarios.”
“We plan to deliver WeedSmart Week in Esperance, part of Western Australia’s high rainfall cropping zone, in August 2021 and Jana will play a key role in the planning and delivering of our annual 3-day flagship event.”
Jana says her experience with the WeedSmart program has been very positive and she has been particularly impressed with the support the program has from all sectors of the grains industry.
Newly appointed WeedSmart extension agronomist, Jana Dixon (green cap) leading discussions with farm visit host, Ben Marshman, Owen SA, and growers and agronomists attending WeedSmart Week 2020 in Clare.
“I have spoken to many growers and agronomists who have found real value in the information that the WeedSmart program delivers,” she says. “For many it is as much about considering another operator’s philosophy on dealing with weeds, and taking a fresh look at their own systems, rather than just learning about a new tactic or the traits of a new herbicide in isolation from the big picture.”
She says the high calibre of industry people who contribute their time and expertise to the program is testament to the value WeedSmart has to agribusiness, growers, agronomists and researchers alike.
In taking on the responsibility for delivering information tailored for the high rainfall zones Jana says she is pleased to have an extensive network of contacts through Pinion Advisory, with offices in a number of high rainfall areas to provide easy access to local agronomists and growers. She is also aware that there are major differences in weed spectrums and farming systems in each high rainfall zone and plans to take full advantage of the opportunity this role presents to expand her understanding of different approaches to weed management.
“The long and favourable growing season and the associated prolonged periods of weed germination, is a key factor that I see potentially impacting on a grower’s weed management strategies in these regions,” she says. “On the other hand, access to highly diverse rotations and a focus on crop competition are two strategies that can play an important role in achieving excellent weed management in these regions.”
“I am keen to engage with anyone working and farming in the high rainfall zones to build my knowledge and understanding,” she says. “And to create opportunities to develop and extend the WeedSmart Big 6 strategies, both herbicide and non-herbicide, that work in each area and in different situations.”
WeedSmart is the industry voice delivering science-backed weed control solutions with support from the Grains Research and Development Corporation (GRDC), major herbicide, machinery and seed companies, and university and government research partners, all of whom have a stake in sustainable farming systems.
You an follow Jana on Twitter and keep up to date with the HRZ here.

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Never cut the herbicide application rate

Scientific studies have demonstrated that resistance can rapidly evolve in weeds subjected to low doses of herbicide. Some weeds can develop resistance within a few generations.
Full rates when mixing herbicides too!
When mixing herbicides it is important that each product is still applied at the full label rate to ensure high mortality.
Applying different chemicals in one mix can provide an additive advantage. It is important to understand the mode of action of each herbicide on the plant when preparing a herbicide mix. This is just as important for pre-emergent grass weed mixes as it is for post-emergent mixes aimed at broadleaf weed control. ALWAYS READ THE LABEL.
Surrounding weed seeds with a combination of pre-emergent herbicides with different modes of action can give a high level of control and help extend the useful life of all the chemicals used. The high level of control must be supported with additional control measures for all survivors. All products with different modes of action must be applied at full label rates for this to be an effective strategy.

 
Mixing two chemicals with the same mode of action can achieve some additional efficacy, however, the mix should deliver the combined full rate to ensure a lethal dose. The amount of stubble present and crop safety are all important considerations when mixing chemicals. For example, when using a tank mix of Avadex® and trifluralin to control ryegrass in wheat, the rates used will vary depending on the sowing system and level of stubble retention. Be sure to get good advice.
Many herbicides on the market are a combination of two or more modes of action within the one product. These products must be applied at the full label rate to be effective. Having dual action does not negate the need to change herbicide products and rotate modes of action. Repeated use of any single strategy will reduce the effectiveness of that strategy over time.
 

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