To till or not to till, that is the question

Image of grower Richard Pye and his sons

Grower Richard Pye (centre) with his two sons, Josh (left) and Matt at a recent GRDC Update in Dalby, Queensland. Richard uses occasional tillage to remove problem weeds on his properties.

PHOTO: Tom Dixon

No-till farming has been practised in the northern grains region for more than 30 years, but new research shows that its time may be running out. Researchers on the Darling Downs have been trialling strategic tillage as a way to extend no-till.

No-till has many advantages for soil health including increased moisture-holding capability and fewer problems with soil erosion. However, an increase in herbicide-resistant weeds could make no-till unviable within a few years unless new methods of weed control are found.

Like the rest of Australia’s grain-growing regions, herbicide resistance is now a worsening problem in the northern region. 
Many northern farming systems rely heavily on herbicides to control weeds, and the resulting herbicide resistance is likely to hit growers hard.

Weeds in the northern region are developing glyphosate resistance at an alarming rate says Tony Cook, technical weeds specialist with the New South Wales Department of Primary Industries.

“Glyphosate became the north’s herbicide of choice due to the move away from cultivation and a high frequency of rain on fallows,” he says.

“Fortunately, resistance has been slower to develop because the diverse crop rotations in the north allow more crop and herbicide choice, and switching between summer and winter crops.”

But it seems that herbicide-resistant weeds are now here to stay, leaving growers to learn how to best deal with new cases of herbicide resistance. One option is a return to strategic tillage as part of an integrated weed management strategy.

Strategic tillage

“The key to successful no-till farming into the future is likely to be flexibility and the introduction of strategic tillage,” says Dr Yash Dang, a GRDC-funded researcher at the Queensland Department of Science, Information Technology, Innovation and the Arts in Toowoomba.

Dr Dang has been evaluating the effects of strategic tillage in no-till systems on weeds and soil health. “Strategic tillage allows growers to keep most of the associated soil health and labour benefits of no till, with many of the advantages of a tillage system,” Dr Dang says.

“Weeds such as fleabane and feathertop Rhodes grass are now a real problem in the north,” he says. “Herbicides are becoming less effective against many weeds around Australia, and we are seeing the effects of this creeping into the northern grain-growing region.”

Many growers are already reintroducing some tillage to their properties, and are excited to see the results of Dr Dang’s research.

Dr Dang says initial results are looking good. “One-time tillage with tyne or disc in long-term no-till paddocks has helped growers to control winter weeds and improve grain yields, while also retaining the soil-quality benefits of no-till farming systems,” he says. “This has the potential to save on herbicide and other treatment costs of hard-to-kill weeds.”

“The short-term effects of returning to a single-tillage system include reduced protective cover, soil loss from increased run-off and erosion, loss of carbon and reduced microbial activity,” Dr Dang says. “But these effects are likely to be minimal and prove a good trade-off against removing problematic weeds.

“This project is all about exploring some of the longer-term issues of a return to strategic tillage. It’s imperative to find out whether a one-time return to tillage has detrimental effects on the soil’s physical, chemical and biological health. We also want to find out how long it would take the soil to return to pre-tillage conditions.

“The other key questions are how long do the beneficial effects of one-time tillage such as weed removal last, and how frequently would growers have to carry out tillage to be an effective management tool for problem weeds.

“Hopefully, within a few years we’ll have answers to many of these questions,” Dr Dang says.

Grower perspective: Richard Pye

Grower Richard Pye from near Miles, Queensland, has been using no-till on his property for the past 12 years, but is gradually bringing in more tillage.

Mr Pye predominantly grows wheat, but as well as using some strategic tillage to control weeds, he also puts in break crops and summer crops to rotate his program.

“We farm about 1416 hectares over four properties,” Mr Pye says. “We always plant 1000ha of wheat, but we’ll also have 400ha or so planted to oats, chickpeas or sorghum in rotation to help break the weed and disease cycle.”

“We’ve seen some resistance developing in both fleabane and feathertop Rhodes grass,” he says.

Rotations do not always break the cycle though. “Every now and then we’re going back to tillage, bringing in a chisel plough, a deep chisel plough or an offset disc,” Mr Pye explains, “especially when we’re trying to get on top of fleabane or feathertop Rhodes grass.”

More information:

Tony Cook
02 6763 1250
tony.cook@industry.nsw.gov.au

Dr Yash Dang
07 45291245
yash.dang@science.dsitia.qld.gov.au

Richard Pye
07 4627 6465
pyes.transport1@bigpond.com

End of Ground Cover Issue [#109] (Northern edition)
Read the accompanying Ground Cover Supplement:

Ground Cover Supplement issue #109 - Frost

Previous:

A bridge too far – weeds a reservoir for hidden diseases

GRDC Project Code ERM00003

Region North, South, West