Read time: 3 minutes

Getting weed seed into the header’s chaff stream

All harvest weed seed control methods rely on getting the weed seed in the front of the header and then onto the sieve, along with the harvested grain and chaff. Sounds easy enough, however experience has shown that doing some modification to the header set up can capture more weed seed and prevent it going out the rotor along with the straw.

The bonus that comes from making adjustments that capture more weed seed is that you will also capture more grain—another win win.

In the back end of the harvester, a separator baffle can be installed to split the air flow from the rotor and the air flow from the sieve. The 20–25 cm high baffle stops the weed seed from being blown over the top of the chaff stream and into the straw spreader.

In the back end of the harvester, a separator baffle can be installed to split the air flow from the rotor and the air flow from the sieve. The 25–30 cm high baffle stops the weed seed from being blown over the top of the chaff stream and into the straw spreader.

Ray Harrington, a West Australian grain grower and long-time innovator, believes that all modern harvesters need some adjustment so they are better setup to target weed seed during harvest. It is critical that all the weed seeds exit in the chaff for harvest weed seed control (HWSC) systems such as chaff carts, Harrington Seed Destructor and chaff tramlining.

Assuming that the harvester is operated low to the ground, with the front cutting no higher than beer can height, most weed seeds that are present at harvest will go into the harvester.

Once inside the machine the key for successful weed seed capture is to make sure that the weed seed and the grain all comes out of the rotor and onto the sieves. To achieve this Ray recommends modifying the second concave, such as removing every second wire in the concave frame in the Case 8230. Other harvesters have different construction but the principle remains the same.

Since the straw component is still very long at this point of the process Ray says there is no need to have narrow slots in the second concave. Keep experimenting until you find the perfect set up for your machine.

Likewise, there can be a benefit derived from making larger holes in the harvester grates of some models. In the Case 8230 Ray has found that the grates don’t need modification as the holes are already quite large.

With harvested material only being in the rotor for a few seconds, it is important to make sure that the inside wall of the concave is not lined with straw, making it difficult for the weed seed and grain to go through the gaps and onto the sieve. Ray has installed an extra bar inside the rotor to help keep all the harvested material moving as it flows through, maximising the opportunities for weed seed and grain to separate from the straw and fall through the concave.

For each model, and even for different crops, there needs to be a different set up. Ray recommends experimenting and adjusting until maximum weed seed and grain are being collected on the sieve.

He knows from his own farm that a surprising amount of grain, let alone weed seed, can travel in the front and straight back out on the paddock if the settings are not right. In canola particularly Ray has seen more than 0.5 t/ha of grain going back out through the spinners.

In the back end of the harvester Ray is using a separator baffle to split the air flow from the rotor and the air flow from the sieve. The 25–30 cm high baffle stops the weed seed from being blown over the top of the chaff stream and into the straw spreader.

Ray says that because the weed seed has a kernel it will not rise higher than the baffle height and so joins the chaff stream and is directed into the Harrington Seed Destructor, onto the chaff cart belt or down the narrow windrow chute.

Keeping a 25–30 cm gap around the baffle allows the high volume, low pressure air flow to efficiently separate the grain from the chaff and weed seed, and the baffle keeps the weed seed from being caught up in the straw as it flows over the top through the choppers and out through the spinners.

In the diagram below, drawn by engineer Nick Berry, shows how a separator baffle can be used to divert more weed seeds into the Harrington Seed Destructor (HSD) mills. These baffles come in all shapes and sizes, and are often custom made by grain growers to fit their harvesters. The aim is to divert the weed seed containing chaff fraction below the baffle to collect at least 95 to 98% of the weed seeds with one of the many HWSC tools.

This diagram, drawn by engineer Nick Berry, shows how a separator baffle can be used to divert more weed seeds into the Harrington Seed Destructor (HSD) mills. The same concept applies for chaff carts and chaff lining.

This diagram, drawn by engineer Nick Berry, shows how a separator baffle can be used to divert more weed seeds into the Harrington Seed Destructor (HSD) mills. The same concept applies for chaff carts and chaff lining.

Once everything is correctly set up, Ray says his experience, and trials conducted by Dr Michael Walsh from AHRI, indicate that it is realistic to expect that only 2 per cent of the weed seed that enters the header will end up evading harvest weed seed capture.

Dr Michael Walsh from AHRI conducted 25 trials across Australia comparing weed seed capture of the chaff cart, narrow windrow burning and the Harrington Seed Destructor. He and Charlie Aves did ryegrass counts in the following autumn and found that the three HWSC tools performed equally, reducing the ryegrass germination by 56% on average. If there were significant rotor losses, and weed seeds were spread with the straw, the narrow windrow burning treatment would be expected to perform better than the other treatments because windrow burning removes all of the straw and chaff while the chaff cart and HSD remove the chaff only.

Listen to Ray talk with AHRI’s Peter Newman about setting up your harvester:

Related Articles

View all
Article
News

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
 

Article
News

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.

Article
News

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.
 

Subscribe to the WeedSmart Newsletter