Read time: 5 minutes

Edwards family, Port Broughton SA

Stacking weed control tactics for maximum effect

Farming on the sand hill swales near Port Broughton on the Yorke Peninsula, Pete Edwards is doing everything in his power to stop herbicide resistance in brome grass and wild radish.

“We take a zero tolerance approach to escapes, particularly with brome grass, and have used a chemical fallow in areas with high brome numbers,” he says. “It’s a case of ‘short term pain for long term gain’ and even after a chemical fallow we will chase any survivors by hand rouging or spot sprayer. Keeping on top of brome survivors has certainly paid off and we have seen numbers decline.”

L-R: Tim Edwards, Chris Davey (YP-AG) and Peter Edwards. Chaff carts have served a purpose but their time on the Edwards’ farm is limited and this harvest they will most likely introduce a chaff deck system to replace the chaff cart.

In wheat Pete has had good results with non-imi chemicals such as Avadex + Sakura and Avadex + Boxer Gold, in conjunction with narrow windrow burning, which helps manage the stubble and maximises the efficacy of these more expensive herbicides.

“There are very few options for wheat so it is essential that we keep pressure on brome numbers in our other crops and also give the group B herbicides a rest to help preserve the imi-tolerant crop options,” he says. “We are only a few applications away from serious resistance issues with fop and dim chemistry. When patches of weeds are not killed by our normal herbicide applications we go back and apply high rates of clethodim to achieve 95 per cent kill, and then go back again to hand rogue any survivors.”

Pete is also mixing fops and dims such as Select, Verdict and Factor and the Intervix brew to extend the life of these modes of action. He has seen the value of including adjuvants such as Supercharge for Factor and ammonium sulfate to maximise the impact on hard-to-kill brome grass.

The Edwards have installed a digital weather station on their farm that also provides local data to ten other growers who subscribe to access the data. Having access to local, real-time weather information, including automated Delta T calculations, means that Pete and his neighbours can avoid frosty and dewy conditions and minimise spray drift, making every application as effective as possible.

When collecting seed for herbicide testing Pete looks specifically for plants that are stunted or deformed as they are likely to be indicator individuals of what might be happening in the paddock and the results help him to plan ahead with chemical choices.

The Edwards family have used chaff carts for 12 years and through extensive testing have proven that operating at a slower speed really does capture more weed seed. Rather than dropping small chaff piles across the paddocks the Edwards build large chaff dumps about 200 m apart.

In addition to the chaff cart, Pete has designed a narrow windrow chaff management system of his own that drops the straw on the ground and places the chaff on top. “We did conventional narrow windrow burning 10 to 15 years ago and had several years where the windrows got wet and didn’t burn the weed seeds effectively,” he says. “Putting the chaff on the top of the narrow windrow means that even if they get wet the straw underneath will still give a good hot burn to destroy the weed seed.”

Pete has designed a narrow windrow chaff management system of his own that drops the straw on the ground and places the chaff on top to give a good hot burn to destroy the weed seed, even if the windrows get wet.

Narrow windrow burning is done mostly in the wheat paddocks with a known brome grass history. In recent years Pete has achieved very good results using his modified narrow windrow burning system in paddocks with very high brome and ryegrass numbers.

The main disadvantage of narrow windrow burning is that it removes all the crop residue. Chaff carts remove between 10 and 25 per cent of the crop residue but the rest is spread on the paddock and has a dual benefit of suppressing weeds and conserving moisture. Pete says the extra soil moisture can save a crop germination in a year with a dry start. Even so, nothing can replace narrow windrow burning completely in very high weed pressure situations so Pete will continue to use his modified narrow windrowing chute when necessary.

Chaff carts have served a purpose but their time on the farm is limited and this harvest they will most likely introduce a chaff deck system to replace the chaff cart. Pete sees some advantages of the chaff deck system over chaff lining, such as less dust off the wheel tracks during spray applications and not having any piles of chaff impeding sowing.

Pete reckons the iHSD will revolutionise harvest and weed seed control and thinks there could be opportunities for contractors to invest in iHSD machines to assist growers by harvesting their weediest paddocks.

“Even under best operating conditions the chaff cart puts 50 per cent of the brome grass seed in the cart, 25 per cent on the ground and 25 per cent goes over the rotor and into the bin. The suction system of the iHSD reduces weed seed losses over the rotor making it a more efficient option,” he says.

Pete follows a 5-year rotation of wheat, barley, lentil, wheat, lentil in large, 100–200 ha paddocks. He sows all crops on 25 cm (10″) row spacing at high seeding rate for increased crop competition and, where practical he sows paddocks east-west to gain better weed control.To improve soil fertility, chicken manure is applied at a rate of 3 t/ha every three years on paddocks that need it; often ahead of wheat. Deep ripping on the sand hills has been an effective measure to alleviate compaction and improve crop performance. Pete hopes to eventually implement a controlled traffic farming system that will help preserve the value of operations like deep ripping and also make the chaff deck system more effective.

The Edwards are also lifting productivity and reducing weed pressure on their poorer sand hill soils by double sowing barley, wheat and lentil crops. In just a few years Pete has noticed a real difference in the soil structure and moisture holding capacity.

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Ryegrass management in the High Rainfall Zone – What have we learnt?

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Rod Birch on how the Big 6 is keeping weeds at bay at Catalina Farms

Catalina Farms is approximately 13,000 ha of 100% cropping, with 65% wheat, with the other 35% comprising of 20% canola and 15% lupins. The longterm rainfall is about 330ml per year and around 250-280ml of growing season rainfall.
Taking on a new property usually has its challenges, but there can be upsides too. Some of the challenges at Koobabbie were related to the fact it had been a livestock property and cropping machinery had never having been run through it. However, Rod explained that they have had some great news about the herbicides they are able to use.
Through the University of Western Australia’s resistance testing service, run by Dr Roberto Busi at AHRI, they found out some older chemistries were still effective, which was a pleasant surprise. Daniel Birch explains below in the Regional Update Podcast what they found out and how they used this information in their planning.

Video breakdown

1:10 Crop rotations – Rod’s favourite rotation is Lupins – wheat – canola – wheat. It provides a lot of diversity for Modes of Action, as well as allows for nitrogen to go back into the soil through the lupin phase.
2:10 Crop Competition – the Birches are big fans of crop competition and it’s an essential part of their approach to controlling weeds.
3:00 Double knock – conditions haven’t been suitable for a double knock since 2016, but when the opportunity arises, it’s an important tool.
4:21 Mix and rotate herbicides – the crop rotations used at Catalina allow for really diverse chemical groups to be used, which is a great tactic to keep resistance at bay.
5:52 Stopping weed seed set – the Birches are trying to eliminate as many weeds in the crop as possible. Crop topping is a tool that they employ, as well as late spraying where necessary.
6:49 Harvest weed seed control – seed destruction is on the horizon at Catalina, but logistically has been a bit tricky.
7:21 Acquiring Koobabbie – it has been exciting for the Birches to be able to introduce more diverse rotations. They’ve been able to use Modes of Action which have never been used before.
9:48 Soil amelioration  – liming has been a really beneficial tool for Catalina Farms. They also put out pot ash and gypsum. Deep ripping has also been a great tool to remove the compaction layer.
11:29 Big 6 benefits  – controlling weeds is such an important strategy at Catalina Farms. Rod Birch said “We’ll never have a ceasefire on the war on weeds!”.



WeedSmart Week Forum Day Videos

List of videos

Interviews with the Esperance Pioneers. Chair: Lisa Mayer, interviewing Neil Wandel & Theo Oorschot
Rotating buys you Time, mixing buys you shots
Efficacious use of the new pre-ems, Brent Pritchard
Delivering regionally focused research
Crop competition in wheat and canola, Hugh Beckie
Summer weed control
Strategies for control of ryegrass, marshmallow, fleabane, portulaca, Greg Warren
Farmer Experience
Rotations to stop seed set and preserve chemistry, Tom Longmire
Soil Amelioration, Tom Edwards
Crop competition: Reduced row spacing, higher seeding rates, east-west sowing, precision seed placement & competitive varieties, Theo Oorschot
Farmer Experience – Utilising crop competition strategies and the Big 6, Mic Fels
Weed control – farmer systems discussion panel – Chair: Peter Newman, with Mark Wandel and Laura Bennett
What’s next in spray technology? Andrew Messina
What’s next in spray technology 2? Guillaume Jourdain
Innovation Panel – Chair: Ben White, with Guillaume Jourdain, Andrew Messina
Stacking the Big 6 in farming systems in WA presented by Greg Condon, with Peter Newman


Ryegrass management in the High Rainfall Zone – What have we learnt?

This webinar was hosted by Jana Dixon, WeedSmart’s High Rainfall Zone extension agronomist.

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