Evaluating the potential of a winter canola-soybean relay intercrop in Ontario

Objectives:

• Assess the potential of winter canola-soybean relay intercropping on-farm.
• Determine the optimal winter canola density and soybean seeding date that facilitates relay intercropping (RI) of these crops under Ontario conditions.

• Evaluate the cost of production of relay intercrop systems in comparison to conventional soybean production practices.

Impacts:

• The development of relay intercropping as a cropping system will help increase the per acre profitability of Ontario grain farmers.
• The adoption of relay intercropping by Ontario farmers will promote year-round soil cover, thereby improving soil health and reducing the potential for soil erosion or nutrient loss in groundwater.

• The addition of winter canola will help diversify crop rotations and will serve as a second high value oilseed option for Ontario farmers.

Scientific Summary:

Farmers in Ontario have recently been exploring relay intercropping as an alternative to annual monocropping. Interest in relay intercropping can be traced to its potential for increasing net on-farm income, as well as its benefits to soil health and reducing erosion. While winter wheat and soybean have been the most frequently evaluated relay intercrop, the recent expansion of winter canola acres in Ontario opens the possibility of an alternate winter crop to pair with soybean in a relay system. To date, there has been no research in Ontario or elsewhere exploring relay intercropping with winter canola and given the economic potential of these crops, a relay partnership represents a significant opportunity to enhance the sustainability and profitability of cropping systems in Ontario.

In this research we proposed to evaluate a winter canola-soybean relay intercrop and several of the agronomic factors that may drive its success as a cropping system. The distribution of resources, both spatially and temporally, between crops in a relay intercrop is key for the success of the overall cropping system. Resource distribution can be modified through row spacing, seeding density and crop growth habit. As such, we proposed to evaluate the impact of winter canola seeding density and soybean seeding date on the phenology, physiology, and yield of both crops in a relay intercrop. Experiments were conducted across southern Ontario, both on farm and on research stations in order to determine the feasibility of a winter canola-soybean relay intercrop and to optimize the agronomic factors that contribute to its success. Through the development of a winter canola-soybean relay intercrop, this research will help increase the per acre profitability of Ontario grain farmers, while reducing erosion and improving soil health through the implementation of continuous cover cropping systems.

Results:

A two relay-intercropping research trial was initiated at four sites across southern Ontario (Elora, Woodstock, Harrow and Woodslee). The first trial examined the seeding of soybean into an established winter canola crop (spring relay intercropping) and the second trial evaluated seeding of winter canola into a mature soybean stand (fall relay intercropping). Key agronomic factors evaluated in these studies included nitrogen fertilization, plant density, planting date, and seeding method. In the spring intercropping trial, results indicated that while spring nitrogen boosts winter canola yields by an average of 0.9 Mg ha⁻¹, it reduces soybean yields, emphasizing the need for balance to maximize system productivity. In fall intercropping, results indicate that early planting dates for canola improve establishment and yield but also caused a decline in soybean yields. This decline was at least in part attributed to the size of winter canola rosettes in early plant dates and the need to adjust combine headers, which may have left some soybean pods unharvested. The seeding method had minimal impact on soybean performance, though planted canola achieved better yields than broadcast due to superior establishment.

The economic analysis of spring relay intercropping highlights the trade-offs between system productivity and profitability. Sole crop systems generally yield higher net returns, but relay intercropping systems can remain economically viable with careful management of inputs. The findings underscore the potential of relay intercropping to enhance land-use efficiency and system resilience, aligning with sustainable intensification goals. However, achieving widespread adoption will require addressing challenges such as crop competition, optimizing planting techniques, and managing environmental variability to ensure consistent economic returns for farmers.

Recommendations:

Farmers looking to adopt relay intercropping with winter canola and soybean can take several practical steps based on the findings of this research. In spring relay intercropping, managing nitrogen fertilizer is key—while nitrogen boosts winter canola yield, excessive application can reduce soybean yields. Farmers should aim for moderate nitrogen rates to balance productivity between the two crops. For fall relay intercropping, winter canola should be planted as early as possible, as earlier planting dates lead to better establishment and higher yields. However, this can increase competition with the soybean crop, so balancing planting dates is essential. Using precise planting methods, such as row planting instead of broadcasting, improves winter canola establishment and yield. Adjusting plant densities is another critical factor; for example, lower soybean densities can reduce competition and allow winter canola to thrive, but excessively low densities may compromise soybean yields. While relay intercropping can improve land use efficiency and productivity, careful management of inputs, planting schedules, and crop competition is essential for economic success.

External Funding Partners:

Rubisco Seeds

Ontario Canola Growers Association  

Project Related Publications:

None.