Simulated responses of canola development and growth to climate change in Canada

Canada shares 22% of the global cultivation area for canola (Brassica napus L.) and exports 90% of its canola production. Demand for canola continues to grow as the world learns more about its advantages for human health and as a source of high-quality feed and biofuel feedstock. However, meeting the demand for canola may be a challenge, especially under climate change as the projected future warmer climate is suspected to be unfavourable to cool-season crops such as canola. The CSM-CROPGRO-Canola model with two calibrated cultivars (InVigor5440 and 5030LL) grown in Canada was used to simulate the responses of canola to the projected climate change in Canada represented by Brandon (Manitoba) in the Canadian Prairies, and West Nipissing (Ontario) and Normandin (Quebec) in eastern Canada. Future climate scenarios for near (2041-2070) and distant (2071-2100) future under two representative concentration pathways (RCP4.5 and RCP8.5) were developed based on climate change simulations by a state-of-the-art regional climate model (CanRCM4). The projected climate change showed an increase in the growing season (April – September) mean temperature by 2.8 – 2.9°C (3.7 – 3.8°C) in the near future and 3.4 – 3.8°C (6.2 – 6.7°C ) in the distant future under RCP4.5 (RCP8.5) accompanied by a slight decrease in precipitation at West Nipissing and a slight to moderate increase at Brandon and Normandin. Seeding dates were estimated from air temperature, precipitation and soil moisture as advancing seeding date has been often considered as an adaptation measure to the future warmer climate. Estimated seeding dates would be 10 – 21 days earlier at Brandon, 5 – 11 days earlier at West Nipissing, but almost unchanged (3 days earlier to 2 days later) at Normandin under the future climates compared to the baseline climate (1971-2000). It implies that soil trafficability related to excessive moisture could be a limiting factor for advancing seeding date under the projected warmer climates in eastern Canada where it is currently much more humid than the Prairies. The life cycle of canola would be shortened in eastern Canada because of the projected increasing temperature while it might not change in the Prairies due to the earlier seeding date. A seed yield reduction of 40%, 20% and 10% was simulated for Brandon, West Nipissing and Normandin, respectively, in near future and of 35%, 25% and 10% in distant future, under RCP4.5, compared to the baseline climate. A larger reduction was simulated under RCP8.5, especially in distant future at Brandon and West Nipissing. The simulated seed yield responses of the two cultivars to future climates were very similar. The yield reduction under the future climate scenarios was mainly associated with a decreased harvest index and lower N/water use efficiencies (defined as yield per unit of N uptake/transpiration).