Growth and yield of forage alfalfa under a changing climate in Canada

Alfalfa ( Medicago sativa L.) is a perennial legume grown as a forage crop worldwide. More than 3 million ha of forage alfalfa is in production either as monoculture or alfalfa‐based mixtures stands in Canada. Future climate change impacts on alfalfa forage production should be investigated for potential adaptation opportunities that can leverage the beneficial climate conditions to improve yields. Our objective is to explore alfalfa growth and production under the projected future climate change in Canada using an ensemble modeling approach. Three crop models were used to simulate alfalfa growth at 61 locations across Canada using climate scenarios from five global climate models under three shared socioeconomic pathways (SSPs). Under SSP3‐7.0, temperatures are projected to increase by 1.8°C in 2030s, 3.1°C in 2050s, and 4.4°C in 2070s, with a respective increases of 31, 52, and 75 mm in annual precipitation compared to the baseline (1985–2014). The increased temperatures led to an extended growing season for alfalfa, which enabled additional harvests and shifts in crop growth dynamics. Under rainfed conditions, forage dry matter yield is projected to increase by about 1600 kg ha −1 in 2030s, 3000 kg ha −1 in 2050s, and 3600 kg ha −1 in 2070s averaged across locations. This increase is mainly due to a greater number of harvests and improved photosynthetic efficiency from elevated CO 2 under future climate change. However, at some locations in the Canadian Prairies, rainfed yield gains are considerably smaller due to precipitation deficits incurred under future conditions.