Controlling barley grass on the Eyre Peninsula
Senior research officer Amanda Cook is currently doing trials and on farm monitoring to look at alternative options for weed control in low rainfall farming systems other than relying on current chemical options for barley grass control.
Research by the University of Adelaide has shown that barley grass has developed high levels of dormancy in cropping situations, due to selection pressure from practices such as knockdown herbicides. Barley grass seeds taken from paddocks had much higher levels of dormancy, well into winter, compared to fence-lines or pastures.
The longer term use of winter cleaning barley grass in low rainfall systems has resulted in some Group A herbicide resistance being detected in paddocks.
“The development of dormancy means we can’t effectively control barley grass before sowing with knockdowns, and the early seed shedding habit means we are unsure of control levels at harvest with options like weed seed collection,” Ms Cook said.
“Other options which still need to be researched in low rainfall systems are increased crop competition, two year breaks for lowering weed seed banks, other cultural methods and alternative in-crop herbicides.”
Barley grass is particularly difficult to control using weed seed collection compared to ryegrass because the weed sheds seeds before harvest. The level of weed seed capture is being investigated in farm paddocks at the Minnipa Ag Centre and at local farmer Bruce Heddle’s property with weed seed capture systems in place.
“Stubble retained systems create a further challenge, because of the reduced effectiveness of pre-emergent herbicides. A trial with three different stubble management systems; a windrow system, spread stubble and stubble removed by burning, has been established at the Minnipa Ag Centre this season to investigate chemical performance and barley grass weed control,” Ms Cook said.
Another trial being performed at the Minnipa Ag Centre by University Adelaide researcher Ben Fleet is aiming to reduce the barley grass weed seed bank by using two years of alternative control options, such as pasture topping or cutting for hay before seed shedding.
While some chemical options may be too expensive for growers in low rainfall systems, using two year breaks within rotation of break crops may be useful in lowering the seedbank to manageable levels.
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GroundCover Supplement: Herbicide Resistance
GRDC Update paper: Evolution of herbicide resistance in Barley grass populations across cropping systems of SA
GRDC Project Code DAN00170, UA00105, EPF00001, CWS00020