Simulating Climate Change Impacts and Management Strategies on Crop Yield and Soil Organic Carbon Dynamics in Eastern Canada

Highlights Warmer climate and enhanced CO2 levels are projected to generally increase crop yields and SOC levels in Eastern Canada. Average crop yields and SOC significantly increased under all future climate scenarios compared to the baseline. Managing the impacts of climate change on crop growth and SOC ensures long-term sustainability of the agriculture sector. Abstract. The agricultural sector in Eastern Canada is facing growing challenges from climate change, with regional warming occurring at twice the global average, necessitating the development of effective adaptation strategies. This study aimed to assess changes in crop growth and soil organic carbon (SOC) under current and projected future climate, exploring the potential implications of climate change on diverse crop rotations combined with long-term application of different manure and tillage types. The Denitrification-Decomposition (DNDC) model was calibrated and validated against historical data to simulate crop yields and SOC and was then used to project the impacts of climate change on these cropping systems from 1981 to 2100 with reporting for three future periods: Near-term (2030s), mid-term (2050s), and distant future (2070s). Simulations were conducted under three Shared Socio-economic Pathways (SSPs) scenarios (SSP 1-2.6, SSP 3-7.0 and SSP 5-8.5) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) for Eastern Canada. Three cropping systems were considered including cereal monoculture, cereal-perennial legume hay rotation (1989-2010) on a silty clay soil near Normandin, Quebec and an annual crop rotation (wheat-corn-soybean) from 2009-2016 on a sandy loam soil near St-Augustin-de-Desmaures, Quebec. The DNDC model demonstrated satisfactory performance in simulating yields at the experimental sites for annual crops, legume hay, and SOC stock. Compared to the 2000-2029 baseline scenarios, the average yields and SOC significantly increased under all future climate scenarios at Normandin due to a longer growing season, and the beneficial effects of elevated atmospheric CO2. However, SOC showed minimal change, as increased carbon inputs from crop residues were offset by higher SOC mineralization rates under elevated temperatures. In contrast, diversified rotations, such as barley-hay and corn-soybean-wheat, demonstrated further yield increases and SOC gains. These improvements were linked to reduced crop nutrient stress and enhanced soil water-holding capacity associated with higher simulated SOC levels. As expected, increasing the proportion of perennials in rotation, particularly leguminous forages, enhances both yields and long-term soil organic carbon (SOC) accumulation. However, diverse annual cropping systems also show potential for improving soil health and resilience, which could, in turn, boost economic returns for farmers.

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