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Paired-rows give entry level crop competition

Higher crop yield and less weeds naturally flow from increased crop competition, but the costs involved in changing machinery and farming systems can be a barrier to achieving these benefits.

Narrowing row spacing, while maintaining the same seeding rate, is generally accepted as the simplest way to increase crop competition, but growers who are not ready to change over their machinery can gain much of the weed suppression benefit using paired-row sowing systems. If this is coupled with east-west sowing the benefits are even greater.

Peter Aikman, Annuello, Victoria has used a paired-row system to maintain crop competition to suppress weeds while gaining seeding efficiencies through slightly wider row spacing. This crop of Compass barley was dry sown in April 2018 and germinated on 12 mm rainfall on 4 May.

Peter Newman, WeedSmart western extension agronomist says paired-row systems such as the Stiletto Boot, which is popular in West Australian sandy soils, are a cheap way to increase crop density and achieve earlier canopy closure.

“Generally, there is not a yield response over single row seeding but yield is maintained in weedy situations, taking some pressure off in-crop herbicides without adding significantly to the weed seed bank,” he said. “Paired-row systems reduce the ‘auto allelopathy’ effect that suppresses plant growth when the seeds of crops like wheat are planted very close along the row. Spreading the seed out, essentially in a slightly wider band, gives each crop seed more room to germinate and grow without impacting on the growth of neighbouring crop plants.”

In southern Australian farming systems there has been steady adoption of paired-row systems, such as Rootboot and Groundhog, to improve seedbed utilisation (SBU), which is a measure of the seed and fertiliser spread relative to the row spacing.

Southern WeedSmart extension agronomist Greg Condon says the paired-row systems help avoid the problems with fertiliser toxicity that can occur in single wide row systems.

“Older paired-row setups moved too much soil and left the seedbed very rough,” he says. “They also had poor stubble handling capacity, used more fuel, achieved poor seed-soil contact and growers had problems with pre-emergent herbicide safety in some situations.”

“Most of these constraints have been fixed with the newer configurations now available on the market. Growers who might have had bad experiences before will probably find that paired-row boots now move less soil, have narrower openers and fit better with a wider press-wheel setup.”

Greg says that although paired-row systems are a good interim option, the best long-term solution is to change to narrow single-row spacing, no wider than 250 mm for tynes or 190 mm for disc planters.

Good establishment in paired-row sown canola.

Paired-row system technology options

Dr Jack Desbiolles, senior agricultural research engineer at University of SA has undertaken extensive trials investigating the benefits of increasing the space between seeds in the seedbed. Paired-row sowing is one way to effectively achieve this and can deliver both increased yield and useful suppression of weeds.

“When it comes to paired-row seeding systems, the technology can be categorised into either split or integrated designs,” said Dr Desbiolles. “The split designs use a Y-splitter tail located further behind the opener, which delivers seeds into a furrow backfill. While seed spread can be more limited, seed placement can be accurate, but seed is often exposed to diluted furrow moisture and contamination from residue and pre-emergence herbicide, all of which can reduce the rate of crop establishment.”

Dr Jack Desbiolles says when it comes to paired-row seeding systems, the technology can be categorised into either split or integrated designs.

While these Y-splitter design solutions represent easy and low-cost upgrades for compatible single row seeding systems, the newer, integrated paired-row designs are becoming more mainstream.

“The integrated designs are compact and streamlined, sitting closely behind the opener and are designed to deliver seeds onto an undisturbed ledge on each side of the trench that the opener creates,” he said. “The accuracy of seed placement depends mostly on the primary furrow shape not affecting the integrity of side ledges. These paired-row configurations are more expensive but often achieve good seed-soil contact without diluting soil moisture or allowing residue or herbicide contamination.”

One grower’s experience

Farming at Annuello in the north-west of Victoria, Peter Aikman (pictured at the top) started using a Rootboot paired-row system in 2014 as part of their strategy to increase sowing efficiency after buying additional land and doubling their cropped area.

Peter’s Horwood Bagshaw seeder had been set up on 30 cm, single row spacing for cropping wheat, barley and legumes in rotation. To cover more area per day at seeding Peter changed to 35 cm row spacing but did not want to lose the crop competition benefits that he had seen at 30 cm spacing.

“Widening the tine spacing allowed us to increase sowing speed and add two more tynes to increase the seeder width. Together these changes increased our seeding efficiency from 12 ha/h to 16 ha/h, which means we save seven days at seeding time and can finish planting the whole area on time,” he said. “To keep the crop competition benefits we turned the row direction to east-west where practical, and use the Rootboot opener to seed 10 cm paired-rows on 35 cm tyne spacing.”

Peter has found that this paired-row system moves some soil around, but in some instances this can be a good thing as it helps to fix any small areas left bare after a legume crop or slightly eroded after using the self-propelled sprayer on sand hills.

“Brome grass is one of our major weeds and we are trying to reduce its germination and seed set by using the combination of the paired-row system and east-west sowing, together with other strategies such as robust crop and herbicide rotation, monitoring for weeds, acting early to prevent weed blow-outs and using harvest weed seed control.”

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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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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

Adjuvants
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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