Climate-dependent yield–N2O trade-offs under drainage and nitrogen management: A modeling study in Southern Quebec

Controlled drainage (CD) can retain the operational benefits of subsurface drainage while reducing transport of nitrogen and phosphorus to surface water, yet its productivity–N 2 O trade-off remains poorly resolved. Here, we used the Root Zone Water Quality Model, calibrated and validated with long-term field data from southern Quebec, to evaluate how different degrees of drainage management and nitrogen (N) fertilization affect corn yield and soil N 2 O emissions under future climate projections. Drainage treatments included free drainage (FD; drain pipes installed approximately 1.0 m below the soil surface), CD with headgate settings of 75 and 55 cm below the soil surface (CD.75 and CD.55), and CD.55 combined with subirrigation (SI.55), together with four N rates (180–270 kg N ha –1 ). CD.75 represented moderate water-table elevation, whereas CD.55 and SI.55 were model-based management extensions representing greater water-table elevation. Historical simulations (1995–2014) and future simulations (2015–2054) under SSP126 and SSP585 were further evaluated across nine climate regimes defined by tertiles of growing-season precipitation (dry, normal, and wet) and mean daily maximum temperature (cool, mild, and hot). Projected growing-season conditions shifted from predominantly cool toward increasingly hot conditions, with hot–dry and hot–normal conditions becoming more frequent. Relative to FD, growing-season N 2 O emissions increased by 5.5–25.3%, depending on CD configuration and climate regime. Yield responses were similarly climate dependent: CD.55 and SI.55 increased yield by 3.2–10.4% under hot–dry conditions, whereas this benefit diminished as climate became wetter and cooler. In contrast, CD.75 maintained yields close to FD while incurring a smaller N 2 O penalty than CD.55 and SI.55 during wetter seasons. Accordingly, SI.55 and CD.55 performed most favorably under hot–dry conditions in terms of partial factor productivity of N (PFPN) and N 2 O intensity, whereas CD.75 resulted in relatively small PFPN losses and lower N 2 O risk across wetter seasons. Our simulations suggest that the productivity–N 2 O consequences of different CD configurations and N inputs depended on the dominant seasonal climate limitation, rather than indicating a universally optimal drainage–N combination.