On the North China Plain, the winter wheat season is poorly synchronized with precipitation, making the traditional winter wheat–summer maize system heavily dependent on supplemental irrigation and associated carbon inputs. Based on a split-plot field experiment in Shenzhou, Hebei, from October 2022 to October 2025, this study evaluated the trade-off between annual system yield and area-scaled carbon emission among six cropping systems under conventional irrigation (CK) and rainfed management (R). The winter wheat–summer maize system (WM) maintained the highest grain-oriented annual system yield (22.91 t ha−1 yr−1 under CK), but it also showed the highest area-scaled carbon emission (11.97 t CO2-eq ha−1 yr−1). The winter wheat–summer maize–spring maize system (WMM) reduced area-scaled carbon cost relative to WM (8.97 vs. 11.97 t CO2-eq ha−1 yr−1 under CK), whereas its product-scaled carbon footprint remained comparable to or slightly higher than that of WM. Under a unified dry-matter basis, the double silage-maize system (FM) showed the lowest dry-matter-scaled carbon footprint (CFDM; 193.85 and 175.71 kg CO2-eq t DM−1 under CK and R, respectively). Soil respiration in 2025 varied mainly with observation date and cropping-system configuration, and soil organic carbon (SOC) stock at the 2025 harvest differed among cropping systems, water-management regimes, and soil depths. Overall, WM remained the highest-yielding option under a grain-supply objective, whereas FM, the ryegrass–early-summer maize system (RM), and the forage winter wheat–early-summer maize system (FWM) were relatively more suitable under multifunctional biomass-supply and low-carbon-transition objectives.
Li et al. (Wed,) studied this question.