Weeding out a costly foe
Author: Natalie Lee | Date: 09 Mar 2016
WA grower Dean Levett uses a variety of integrated weed management strategies including a chaff cart on his property between Walkaway and Mingenew.
Developing weed management strategies while ensuring the suite of herbicides available to growers doesn’t lose efficacy is one of the biggest challenges facing the Australian grains sector.
According to the Grains Research and Development Corporation (GRDC), weeds cost the Australian grains industry a staggering $3.27 billion annually in control measures and lost production.
Grower-driven research and development (R&D) priorities shared by the GRDC’s Western Regional Panel and Regional Cropping Solutions Network groups in Western Australia consistently identify management of weeds – especially herbicide resistant weeds – as one of the biggest limiting factors to productivity.
GRDC research compiled by the CSIRO has found WA growers incur losses of about $25/ha due to the impact of weeds on crop yields and it is estimated WA growers spend up to $85/ha annually on weed control on cropped land.
They’re figures that ring true for WA grower Dean Levett, who crops 5000 hectares in the grainbelt between Walkaway and Mingenew.
Mr Levett grows wheat, canola and lupins, and he also runs Dorper sheep, turning off close to 4000 lambs a year.
The sheep are a key part of Mr Levett’s integrated weed management strategy, which includes a number of other non-herbicide tools, such as using a chaff cart, mouldboard ploughing and seed cleaning before planting.
“Our biggest weed issues are the two Rs – radish and ryegrass. Couch grass is starting to become another problem but it’s on country that we’ve brought in to the enterprise and it’s all adjoining this property,” he said.
“Our biggest problem is just trying to get that weed seed bank down to start with and then you can tackle it with things like mouldboarding, double-knock herbicide applications and chaff carts.
“Anything that can reduce your weed seed numbers is the first thing you apply to it. That’s why we still run livestock – they’re very good at cleaning up country that is out of crop.
“What goes through a sheep’s gut is the equivalent of a chaff cart being run over the country.
“While we can get a tool that’s non-herbicide, we grab it.”
Mr Levett said the cost of controlling just one weed was approximately $40/ha annually and with radish and ryegrass his two main issues, his annual costs to control weeds was about $80 to $85/ha.
“If you don’t try to control weeds, you’re going to definitely put a hole in your bottom line,” he said.
“Not only that, with the product that you’re trying to produce - in the form of either wheat or lupins - you’ve got another cost in there in terms of grading to get it up to receival standards.
“It’s still cheaper to spray a crop to control weeds then it is to grade it after it’s harvested.
“To put in a cereal crop during the winter, we normally go with a double-knock first up prior to planting.
“A lot of the programs we’ve put in place are to lower the impact on Roundup® because it’s so crucial to us.
“Even during our summer spraying, we try to use things that aren’t related to Roundup®. If we can use SpraySeed® we will, not because of cost but to keep the pressure off Roundup®.
“We’ve just started delving during the past three years into mouldboarding ... to get areas of land back to square one, and I’ve not only got rid of weed seeds, but also non-wetting sands as well and that strategy has been huge to us.
“We’re in the process of going to tramlining on that sort of country as well – going back to say a 40-foot tramline set-up as well. That’s all to keep lengthening out the time and effect of the mouldboarding so that we may be getting out to 10 or 15 years with a bit of luck before we’ve got to think about it again.”
Mr Levett said due the variable soil types in his cropping operation, he would continue to need to employ a range of weed management strategies.
As a result, he’s an advocate for the research being carried out by GRDC.
“GRDC’s set-up has been good for us. The panels are very accessible, their feedback is very easy to get to and the scientists they’ve got in there are doing a bloody good job.”
Mr Levett said he was starting to see the results of his integrated weed management strategy, with increased yields - particularly in mouldboard ploughed areas. As an example, he said wheat yields were up by 0.5-0.8t/ha.
GRDC has a $1.5 million annual investment in the Australian Herbicide Resistance Initiative (AHRI), based at The University of Western Australia.
AHRI Director Stephen Powles leads a team of researchers at UWA focused on cropping, weed control and herbicide resistance.
Professor Powles said Australian growers were spending close to $1 billion a year on herbicides and ongoing investment into integrated weed management strategies was vital.
“I will count AHRI to be a great success if we collectively – that is the whole industry – especially the growers, can keep herbicides working on their farms,” Professor Powles said.
“Farmers know that herbicides are simply the best way to control weeds and it’s almost impossible to imagine modern farming without herbicides, and yet that is the threat we face.
“Collectively through the research we’re doing and the practice of farmers, we can keep these herbicides working for future harvests and future farmers.
“It’s quite a challenge but we can do it, and it’s through diversity and it’s through integrated farming systems, it’s through not relying on the same tool all the time, so when we’re on a good thing, not sticking to it.
“And if we practice all these integrated, sensible, diverse strategies, we will keep our herbicides working and have more crop with less weeds, and that is the objective.”
Work already undertaken by Professor Powles and his team and funded by GRDC has supported the introduction and widespread adoption of harvest weed seed control tools such as chaff carts and the Harrington Seed Destructor.
The introduction of the Group K herbicide, Sakura®, into the range of herbicides available to Australian farms was also the result of GRDC-funded research.
AHRI worked with Japanese R&D company Kumiai, and then Bayer, to demonstrate the value of introducing Sakura® to Australian cropping operations.