Controlling Barley Grass Report 2020

0

Demonstrating and validating the implementation of integrated weed management strategies to control barley grass in the low rainfall zone farming systems

Author and organisation: Helen McMillan, Central West Farming Systems

Key messages

  • Pre-sow knockdown still shows promise for barley grass control on this farm
  • Seeding rate did not impact barley grass numbers at this site in 2020, but is a proven technique to reduce weed numbers and seed set so should still be considered for integrated weed management
  • Trifluralin and pyroxasulfone (Sakura) both worked well to control barley grass at this site in 2020

Barley Grass Project Background

Over the last few years there have been increases in barley grass infestations in cereal crops in southern Australia.

Evolution of herbicide resistance to group A and B herbicides is contributing to the increase in barley grass in cropping areas of southern Australia. There is evidence to show that barley grass from cropping areas has developed longer seed dormancy than those from non-cropping areas.

Along with these two man made selections, barley grass possesses several biological traits that make it difficult for the growers to manage it in the low rainfall zone. This includes early onset of seed production, which reduces effectiveness of crop-topping or spray-topping in pastures. This species has also been shown (GRDC project UA00156) to shed its seeds well before crop harvest. Therefore, harvest weed seed control tactics are likely to have a much lower effect on barley grass management as compared to weeds such as ryegrass which has a much higher seed retention.

Barley grass management may also be a little more challenging in the low rainfall zone because the growing seasons tend to be more variable in terms of rainfall, which can affect the performance of the pre-emergence herbicides. Furthermore, many growers in these areas tend to have a lower threshold for expenditure on management tactics.

Aim

The proposed project plans to undertake coordinated development research with target farming systems groups to demonstrate tactics that can be reliably used to improve management of barley grass. These tactics will include herbicide options within relevant rotations in the target area. (Sourced from Barley Grass GRDC project submission, Gill 2019). In 2020 the project demonstrated two seeding rates and two pre-emergent herbicide strategies to determine if high inputs offered better barley grass control compared to grower standard practice.

Paddock Details

  • Location: North Condobolin
  • Rainfall Condobolin Airport:
    2020 Total: 670 mm (2019 144.2 mm)
    2020 GSR (April-Oct): 364 mm (2019 62.8 mm)
  • Paddock history
    2019: Fallow
    2018: Wheat
  • Soil type: Sandy loam

Trial Details 2020

  • Variety: Lancer wheat
  • Treatments: Pre-emergent herbicide 1.5 L/ha trifluralin vs 118 g Sakura. Paddock had a knockdown weed control of glyphosate and amine seven days prior to sowing.
  • Sowing rate: GSP 27 kg/ha, double seed rate 48 kg/ha.
  • Sowing date: 27/4/20 into good moisture.
  • Fertiliser: 60 kg/ha MAP, none in crop.
  • Harvest date: 18/11/20.