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Chaff-fed sheep help break weed cycle

Weed seed collection at harvest, grazing chaff dumps instead of burning, and swathing barley crops are key weapons growers Andrew and Marjorie Boultbee have in their arsenal for their war on weeds on their property at York, Western Australia.

The couple’s priority is to implement a farming system where crop rotation choices are uninhibited by planting date, weed density or herbicide resistance pressures.

“To optimise profits, we want to be able to change our rotation quickly – if necessary – in reaction to shifts in commodity prices or seasonal conditions,” Andrew says.

“This is made possible by having a low weed seedbank.”

A man standing in a shed next to equipment

York, Western Australia, grain grower Andrew Boultbee is using chaff cart weed-seed collection at harvest and swathing to reduce the weed seedbank on his property.

Historically the Boultbees used herbicide, rotation and some narrow windrow burning after harvest to control weeds.

However, Andrew says he found burning windrows was costly (he estimates $4 per hectare), time consuming, hard on machinery, unhealthy – keeping him awake at night worrying about fires up to 70 kilometres away – and not conducive to stubble retention.

In 2002, he decided to use chaff carts as an alternative way to capture weed seeds at harvest, lower the property’s overall weed seedbank and facilitate ongoing continuous cropping.

Instead of burning the chaff heaps, the Boultbees started grazing this resource during summer. The sheep flatten the chaff heaps to a very small pile and help to redistribute some of the nutrients in these heaps back out to the paddock.

It is a win-win for achieving good weed control and filling a sheep feedgap that, in turn, has contributed to boosting lambing percentages.

Andrew says the sheep eat down canola heaps and the minimal amount of residue remaining is sown through with no extra treatment.

“The cereal chaff heaps are well grazed, but there is a small pile left,” he says. “So we run a scarifier through this residue, straight down the row of heaps to knock the tops off, levelling it to a height of about 30 centimetres.

“This effectively joins the heaps together into a continuous strip at 90 degrees to the seeding direction, which the seeder can easily go over.”

Research has shown that only three to six per cent of ryegrass seeds that sheep pick up from chaff heaps survive digestion.

“What we are finding is that the weed seeds that get through the chaff carts and sheep digestion have little protection against the composting effect of the 30cm layer of chaff on the ground during the winter rains and they rot,” Andrew says.

“Even though we don’t burn the chaff dumps, we don’t see many weeds in them at all. Two years after leaving a dump, it is the best part of the paddock – big crop growth and very few weeds.”

Andrew says he now uses two chaff carts and the system is a cost-effective tool that is destroying enough weed seeds to lower the seedbank.

However, he says there are costs involved in clearing paddocks of rocks to drop the front of the harvester to cut stubble as low as eight to 10cm and in reducing harvest speeds to about 8km/hour.

Andrew estimates the cost to run the chaff carts is about $5 to $6/ha – similar to the cost of narrow windrow burning.

“Using such a low cut height at harvest and with an increased volume of straw, we have had to upgrade our header size and run two headers, at considerable expense,” he says.

“That has been the biggest downside to moving to weed seed collection at harvest.

“The benefits are that our time of sowing and crop choice is less inhibited by weed pressures, we don’t have to burn chaff heaps and our stock are doing well on this feed resource.”

Using chaff carts, the Boultbees also retain full stubble cover and are noticing increased stored soil moisture at seeding, less waterlogging after big rain events, less wind erosion, increased soil microbial activity and fewer weeds.

Annual ryegrass is their highest-priority weed and another tool to tackle this is to swathe barley crops.

“The idea is to get as many seeds into the front of the harvester as possible and stop any lodging or shedding of ryegrass and brome grass seeds,” Andrew says.

“The same goes for wild radish, which is usually dry and shedding, or green, and therefore it’s hard to get weed seeds down on the sieve.”

Swathed barley crops are left for up to four weeks, allowing standing crops, which have priority, to be harvested.

Andrew says the system depends on swaths being laid “just right”, requiring crops to be cut low and consistently to enable effective weed seed and barley grain collection.

“If you are going to get into the swathing barley game you have to get it right,” he says.

“We use Buloke barley because it is tall and competitive, so it makes a good windrow.

“It also has a hard seed, so we can thresh it hard to make sure that we get most of the weed seeds into the cart.

“We don’t like using Hindmarsh barley for this purpose because it is too short to make good swaths and the seed is soft, so will crack if we thresh it too hard.”

Andrew says in high weed burden areas, two or three consecutive barley crops are grown and swathed in the rotation using this system.

He says canola follows the second barley crop if conditions are right, or is dropped out if prices or the season appear unfavourable.

Andrew now rarely uses post-emergent herbicides for ryegrass control in cereals. Herbicides are rotated with crops, there are long breaks between using the same herbicide in a paddock twice and minimal glyphosate is used prior to seeding.

To hear Andrew Boultbee discuss his chaff cart and integrated weed management system, watch the GRDC Ground Cover video below.

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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


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.

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