Tight crop rotations reduce canola yields
Crop rotations significantly influence canola yields, showing a 7.5% yield reduction in continuous canola rotations compared to canola grown after a cereal crop. Conversely, canola yields increased by 3.8% when grown after lentils and 4.7% after peas compared to canola grown after a cereal crop.
In western Canada, canola acreage has increased in recent years, which has led to shorter rotations between canola crops. Field trials and other research suggest that canola yields are reduced by shorter rotations. Under shorter rotations, incidences of the main soil-borne canola diseases including sclerotinia stem rot, blackleg and clubroot were also higher, impacting crop yields. The current recommendation by agronomists in western Canada is to grow canola only once every 3 to 5 years in rotation to minimize impacts of pests and diseases on yield.
The goal of this study was to analyze the effect of crop rotations on canola yields in Saskatchewan. The project used regression models to analyze over 20 years of observational data in Saskatchewan, representing 61% of canola acres. The project examined factors such as soil zones, soil moisture conditions, yield distribution and their relationship to the impact of rotations. Crop insurance yield data from 1998 to 2021 provided by the Saskatchewan Crop Insurance Corporation (SCIC) was used in the analysis.
Data from SCIC and Agriculture and Agri-Food Canada’s (AAFC) crop inventory dataset from 2009 to 2021 were also used to determine crop rotations used on the same land in the previous four years. The percentage change in canola yields grown on previous cereal crops was compared to the results from growing canola, peas, lentils, and fallow in prior years.
7.5% yield reduction
The project results confirm that crop rotations significantly influence canola yields. The analysis showed a 7.5% yield reduction in continuous canola rotations compared to canola grown after a cereal crop, suggesting that profits from canola are significantly reduced when grown in a continuous rotation. According to the Saskatchewan Crop Planning guide in 2022, a 7.5% reduction in yields would reduce the profits from growing canola by 48% in the Black/Gray soil zone, 59% in the Dark Brown soil zone, and 86% in the Brown soil zone.
As expected the negative effects of consecutive canola plantings were more pronounced in wetter regions and under higher disease levels, and in lower yielding crops. In comparison, the results showed that growing pulse crops in prior years increased canola yields across all of the models. The results showed an increase in canola yields of 3.8% grown after lentils and 4.7% after peas compared to after a cereal crop.
Although the yield effects observed in this study are generally smaller than field trial results, overall the findings align showing similar yield reductions from consecutive canola plantings and yield improvements from prior plantings of pulse crops. The differences may result from the more controlled conditions of field trials as compared to the observational data used in this analysis.
Although the study did not identify optimal rotations, the results show that rotations have a significant impact on farm profitability. This in turn has an impact on the cost of publicly subsidized insurance, which is important for policymakers and crop insurance providers. Under current crop insurance programs, premiums do not account for differences in crop rotation practices, effectively shielding producers from the financial impact of a tight crop rotation, reducing their incentive to diversify rotations. The findings suggest that insurance policies should consider crop rotation strategies to better reflect yield risks and encourage more sustainable farming decisions.
The project was funded by the Saskatchewan Wheat Development Commission and Saskatchewan Pulse Growers.
Lassoued, F., Slade, P., & Dyck, A. (2025). Crop rotations and canola yields: Evidence from field-level data in Western Canada. Agronomy Journal, 117, e21739. https://doi.org/10.1002/agj2.21739
