Earlier this month, the Canola Council of Canada rolled out its vision for the canola industry over the next decade or so. While the plan includes growth of the domestic and export markets, the plan has also sparked some discussion on tightening canola rotations. The Canola Council has shifted its canola rotation stance slightly — it is not advocating for 1 in 2 canola rotations — however rather than making a blanket statement of what the ideal rotation may be, say 1 in 4 or 1 in 3, the council is pushing for farmers to make a rotation call based on a risk assessment for each field. As always, tightening rotations can increase disease, weed and insect pressure — farmers and/or their agronomists need to evaluate their risk based on specific areas, situations and scouting observations. Not everyone has extensive background in what they need to evaluate before pulling the trigger on shortening their rotation from 1 in 4 to say a 1 in 3. Here are just a few of the things that need to occur for this new philosophy to be successful:
Up-to-date, complete record keeping – Without recording specifics of every field on your farm you are going to be starting out behind the eight ball. The very things I will touch on later in this article such as disease, weed and insect pressure need to be understood and documented, previous fungicides, varieties/herbicide tolerance are key as well. Yield maps, to correspond with changes in management, will be essential to ensure tighter rotations aren’t sacrificing yield.
Disease – The three diseases most farmers should be worried about are sclerotinia, clubroot and blackleg. Sclerotinia levels should be monitored every year in season and then assessed again after harvest by looking at stubble. This disease is highly dependent on weather to develop, but the hard black overwintering sclerotia can build up in the field.
Blackleg should be assessed early in the season (infection occurs early, at the 2-leaf stage), throughout the season, as well as again after harvest by clipping stems. Blackleg is of particular concern in shortened rotations —the pathogen may survive as long as canola stubble is in the field. While we have access to blackleg resistant varieties, reports of new strains of the pathogen have surfaced. Again, a short rotation pressures selection. What’s more, fungicide options for blackleg control are limited, and, as noted, the application window is very early in the season and can easily be missed.
Clubroot is a serious and devastating disease of canola that is no longer limited to Alberta. Although extremely limited in Saskatchewan and Manitoba, it has been confirmed in both provinces. Clubroot spores can survive in soil for up to 20 years — for those areas not already infested, avoidance is key. A tighter canola rotation may or may not increase the risk of the disease spreading, however in areas where clubroot is prevalent, tighter rotations will increase the damage of this disease.
A few other thoughts on disease management — fungicide resistance is something many other countries are struggling with and is a growing concern in Canada. The options in disease tolerant varieties (there are now disease resistant lines for each of the above diseases, however none of the varieties will eliminate infection, only decrease it) can be a big consideration when choosing what variety to seed, but must be based on an understanding of what diseases are present and if that disease pressure is increasing, recognizing that no genetic resistance is permanent.
Weeds/Herbicides – When it comes to herbicide tolerance in canola varieties we have three options; Liberty tolerant (Gr. 10), Clearfield tolerant (Gr. 2), and Glyphosate tolerant (Gr. 9). The issue with a couple of these herbicides is their risk for resistance. Simply sticking to the same herbicide tolerance system in a short rotation is going to significantly increase the likeliness of resistance on your farm, or an increase in a specific weed that the herbicide system you choose isn’t effective on. This can cause significant issues long term when it comes to weed seed bank issues, future herbicide costs, harvest complications, sample quality and more. To top it off, the pre-burn options are limited to a select few groups which again is adding to resistance pressure. Then there is the issue of controlling the canola when it volunteers. If you only grow the same herbicide system the volunteers can throw a wrench in plant stand counts and more. To top it off, DEKALB and Bayer are releasing stacked herbicide traits with Gr. 9 and Gr. 10 tolerance in the coming years. Having a plan in place to fight resistance/weeds is key in any crop rotation, but becomes even more important in a tight rotation.
These are just a couple of the problems in a tighter rotation. There is also potential for increased insect pressure and soil health/nutrient depletion to consider. At the end of the day, for some canola pencils out better for some farms short-term, but don’t forget to think about the future of your farm (or the farm you leave for your kids) when making rotation decisions.