Australian Herbicide Resistance Initiative (AHRI)

Can we make the canola:wheat rotation work?

Can we make the canola:wheat rotation work?

Below is the output from a RIM run we developed here at AHRI to demonstrate how the Ryegrass Integrated Management (RIM) computer model can be used to put theories to the test. Have your own theory? Click here to contact us or follow the link below.

Contact us for a RIM run


by Peter Newman

Whenever I travel to the high rainfall zone in Australia I find many growers with a continuous Canola : Wheat rotation because it makes a lot of money. I also find many growers and agronomists telling me that it is destined to fail – and it may well be!


I believe that growers should choose the most profitable rotation and throw enough weed management at it to make it work.

Can we throw enough weed control at Canola : Wheat to make it work?


C:W – no resistance to clethodim v 50% resistance to clethodim

Screenshot 1


What happens if we add some more weed control?


C:W plus chaff cart v plus chaff cart and spray/swath Canola (50% resistance to clethodim)


Screenshot 2 v2

There are many other weed control practices that we can add to this rotation. This example shows that it may be possible to use aggressive weed control to keep a tight rotation going.

The best application of RIM is to work out how to have your cake and eat it. In other words, how can we maximise profit while minimising weeds? This scenario shows that it is possible to maintain continuous crop and manage weeds.

RIM is a great tool to compare some weed control strategies using computer simulation before making the changes on farm. RIM simulates the ryegrass seedbank based on years of research data to give realistic results.

Download RIM for free and give it a try.

Download RIM


Some of the assumptions used in this simulation were:

  • High rainfall zone of Australia
  • Yields. Wheat 2.5 t/ha; Canola 1.3 t/ha. (on the low end of high rainfall zone yield)
  • Herbicide control %. Trifluralin 80%; Propyzamide 90%; Sakura 90%; Boxer Gold 85%; Glyphosate 99%.
  • Chaff cart – removed 70% of ryegrass seed in crop.
  • Spray/swath canola – 70% ryegrass seed set control.


The picture below shows some of the assumptions used for these scenarios. All of these assumptions can be adjusted to suit a particular farm.