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Windrow to collect early shedding weed seed

Looking toward harvest, the pressure is on to get the timing right to maximise yield and grain quality. Delta Ag senior farm consultant, Tim Condon, says it is also a great time to be capturing weed seeds, particularly from wild oats plants that have escaped in-crop herbicides, using a non-herbicide tool to manage herbicide resistance.

“Windrowing, or swathing, barley has been traditionally used as a harvest management tool when growers have a number of different crops to harvest in a short time,” he says. “The really good thing about this technique is that it also gives growers another shot at collecting and destroying weed seed.”

Successful windrowing begins with cutting the crop low and, where possible at an angle to the seeding direction. When followed with any harvest weed seed management tactic, even early shedding weeds such as wild oats can be effectively controlled.

Successful windrowing begins with cutting the crop low and, where possible at an angle to the seeding direction. When followed with any harvest weed seed management tactic, even early shedding weeds such as wild oats can be effectively controlled.

Swathing barley at the earliest opportunity maintains the crop’s yield, and if done correctly, the swaths protect the grain from weathering. Mr Condon recommends checking the crop away from the paddock edges and looking for signs of physiological maturity in the barley plant. “Barley, and wheat, can be swathed when the grain is at 30 to 35 per cent moisture,” he says. “This is indicated by the peduncle [the little stem just below the head] of the grain head turning from green to brown and if you press your thumbnail into the grain there should be no dent created in the grain.”

“Once the crop is mature, the key to effective swathing – and also for the best results with weed seed collection – is to cut the crop low,” he says. “Cutting at boot or beer can height provides sturdy support for the swath, keeping the grain and the weed seed off the ground and making harvest more efficient.”

In some situations, it can also be beneficial to swath at an angle to the seeding direction to provide extra support under the swath. Good results have been seen in Western Australian crops swathed 15, 45 and 90 degrees to the seeding direction. In controlled traffic systems, using a mixer belt, or setting the belts at different speeds, is an alternative to swathing at an angle to achieve the necessary cross thatching to keep the swathed crop off the ground, maintain grain quality and allow easy pick up.

“Crops sown on narrow row spacing will also swath better, and there is good evidence that narrow row spacing also suppresses weed seed production,” says Mr Condon. “In southern NSW the main weed that we can target with swathing is wild oats. Wild oats is renowned for shedding seed before crop harvest so swathing can reduce the amount of seed shed onto the ground. Even with good control of wild oats germinations around sowing, there are often later germinated weeds that grow with the crop but are less mature at harvest than earlier germinations would have been.”

Wild oats is notorious for shedding its seed early. Windrowing is an excellent way to collect the seed from wild oats plants that have escaped in-crop herbicide treatment.

Wild oats is notorious for shedding its seed early. Windrowing is an excellent way to collect the seed from wild oats plants that have escaped in-crop herbicide treatment.

Swathing, followed with any of the harvest weed seed control tactics, becomes a very useful non-herbicide tactic to use with weed species that shed their seed early. Other potential targets with this strategy are wild radish, brome grass and annual ryegrass.

Once the swathing is done, the barley can be left for several weeks until there is an opportunity to harvest. However, there is always a risk of the windrow not drying quickly if wet weather persists, which may cause grain quality to deteriorate. Options for destroying the weed seed captured in the swath include narrow windrow burning, chaff carting, Harrington seed destructor, hay baling or chaff lining (in controlled traffic systems), all of which are detailed on the Weedsmart website.

“Narrow windrow burning can be risky in leafy crops like barley, especially in high yielding districts,” says Mr Condon. “A new technique being trialed in these situations is chaff lining, where the chaff component is dropped into a narrow band and left to rot down. Early observations suggest that weed seeds don’t survive, especially when the chaff stream is directed into the wheel tracks in a controlled traffic system.”

Avoid confusion: The terms ‘swathing’ and ‘windrowing’ refer to the same practice. In NSW and Vic ‘windrowing’ is the more commonly used term while ‘swathing’ is the more commonly used term in WA and SA. However, ‘narrow windrow burning’ is a completely different practice.

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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.


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.


Spray well – correct nozzles, adjuvants and water rates

Spray application is a technical field and growers need to make sure their equipment and application techniques are spot-on. The GRDC Spray Application GrowNote provides detailed information and about 80 videos to demonstrate key skills.

Prevent spray-drift
The focus of spraying herbicide needs to be on doing the job right so the weeds receive the correct dose and die, and this includes reducing the air borne fraction to a bare minimum.

Bill Gordon’s 10 Tips for Reducing Spray Drift

Choose all products in the tank mix carefully.
Understand the product mode of action and coverage requirements.
Select (and check) the coarsest spray quality that will provide effective control.
Expect that surface temperature inversions will form as sunset approaches and will likely persist overnight and even beyond sunrise on many occasions. DO NOT SPRAY.
Use weather forecasts to inform your spray decisions.
Only start spraying when the sun is about 20 degrees above the horizon and when the wind speed has been above 4–5 km/hr for more than 20–30 minutes, and clearly blowing away from any adjacent sensitive crops or areas.
Set the boom height to achieve a double overlap of the spray patterns.
Avoid higher spraying speeds.
Leave buffers unsprayed if necessary and come back.
Continue to monitor conditions, particularly wind speed, at the site during the spray operation

High water rates don’t have to slow you down
Some growers are concerned that increasing the water rate when applying herbicide will slow down their spray operation and cost them money. However, the biggest financial loss during spraying usually comes from a failed spray job.
To keep your spray operation as time efficient as possible when using more effective and reliable application volumes, you can:

Use nurse tanks around the farm to reduce the time spent travelling back to a central re-fill point.
Use a larger pump, e.g. 2.5 inch, to make re-filling quicker.
Pre-mix the batch while the sprayer is operating. Many mixes can be held in the mixing tank for up to 6 hours. However, wettable granules and suspension concentrates will need agitation to keep them in solution.

For pre-emergent herbicides in high stubble situations, carrier volume has a large effect on the level of control achieved. Across four trial sites Dr Borger’s research demonstrated that ryegrass control with trifluralin or Sakura® increased from 53% control when the carrier volume was 30 L/ha to 78% control when the carrier volume was increased to 150 L water/ha in high
Water quality and mixing order
Water quality is often overlooked as a possible contributor to herbicide failure and can lead to confusion over the herbicide resistance status of weeds on a property.
Water should be considered as one of the chemicals in any mix, given that water quality varies markedly depending on its source. Getting the mixing order right is essential for effective spray results.

Don’t start mixing until the water quality is right
Podcast – Mixing herbicides

Sometimes adding an adjuvant is beneficial and sometimes it is detrimental; and there is an art to knowing how to best deploy these additives.
When weeds are susceptible to the applied herbicides, the effectiveness of adjuvants generally goes un-noticed. Correctly applied adjuvants can reduce the impact of low level herbicide resistance by helping to maximise the amount of herbicide taken up by the plant.

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