Australian growers are at the forefront of having access to and adopting the use of herbicide tolerant crops within their cropping rotations. Opportunities exist to use herbicide tolerant canola options and add diversity in weed control tools when planning crop rotation sequences. In this article, we look at being proactive to use canola in crop rotations to more effectively manage the weed seed bank and extend the life of ‘essential’ herbicides in faming systems.

It is important for growers and those advising them to advocate responsible stewardship of herbicide tolerant canola technologies1. The challenges are to take a longer-term seedbank and resistance risk view and strategically consider where and when alternative weed management practices can be introduced into crop rotation programs.

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At the recent DuPont Pioneer “Closing the Yield Gap” field days, the benefits and best practices from using canola herbicide technology in crop rotations were put forward:-

have a plan to utilize the benefits of canola to broaden weed management options added by its unique choice of herbicide tolerant traits and utilize crop rotations to alternate herbicide modes of action. Herbicide tolerant canola technologies provide opportunities to manage key weeds causing the greatest yield loss in winter crops including brome grass, wild radish and wild oats;;

use competitive canola hybrids to your advantage in crop rotations. Canola hybrids display stronger early vigour, larger roots and produce more biomass than most open-pollinated varieties that in turn boosts the level of weed competitiveness. Recent research findings2 confirm the advantages of varieties that have greater ability to compete with ‘weed’ pressure in term of yield performance and also to better suppress weed seed set in paddocks;

a clean start means clean seed. Always plant quality, assured seed that ensure the benefits of ‘first generation’ canola hybrids;

remove weed competition early. Canola is much more vulnerable to weed competition prior to reaching complete ground cover. Weed control timing at the 1-2 leaf stage of canola will have the most impact on protecting canola yield potential;

embrace change to preserve ‘essential’ herbicides and traits such as glyphosate3. Carefully consider alternatives in all non-crop areas such as on fence lines, road sides and in chemical fallows. Strategically use ‘essential’ herbicides to get the biggest bang for buck in your farming system;

be strategic to introduce ‘new’ weed management practices in the canola phase of crop rotations that have been refined through local farmer experience, in particular harvest weed seed control such as pre-harvest glyphosate application and narrow windrow burning;

manage canola volunteers to protect the benefits of summer fallows and avoid competition in following crops. Start with good machinery hygiene at harvest and early spraying for control of volunteer plants as seedlings (by 4-leaf stage) post-harvest;

be proactive to undertake risk assessment by testing herbicide resistance status of weed populations before planting the crop following canola.

act now to add diversity in weed management practices throughout crop rotations to control weeds and stop weed seed set such as using competitive crops & varieties; crop sequencing to allow alternate pre-emergent herbicide modes of action; agronomic practices to increase crop competitiveness; grazing and/or fodder conservation (hay/silage); crop topping; double cropping of broadleaf crops; alternative residual herbicides for summer weeds in fallows; winter cleaning of pastures in rotations and having winter fallow paddocks.

In closing, the two key ‘take home’ messages:-

  1. Herbicide tolerant canola technologies provide good opportunities to positively impact overall profitability and utility of ‘essential’ herbicides in cropping rotations;
  2. Agronomists and farm advisors need to be advocates of the industry WeedSmart 10-Point Plan4 throughout crop rotations as part of integrated weed management programs and whole farm stewardship planning. 

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Supporting references

  1. DuPont Pioneer “Herbicide tolerant canola stewardship guide” July 2015.
  2. www.pioneer.com.au
  3. Goss, S. “Crops as a weed control tool” GRDC Update, June 2015, issue 36
  4. Newman, P; Micallef, B; Mayer, L “Waste” AHRI Insight. March 6, 2015
  5. www.weedsmart.org.au