Context: Irrigation and nitrogen application are essential agronomic practices for enhancing crop yields, yet they also represent potential levers for mitigating agricultural greenhouse gas (GHG) emissions in cropping systems. Objective: This study aimed to identify optimal water-nitrogen management strategies that maximize grain yield while minimizing GHG emissions in winter wheat-summer maize rotations within the Guanzhong Plain. Methods: The Denitrification-Decomposition (DNDC) model was rigorously calibrated and validated using empirical field datasets. Individual and synergistic effects of irrigation levels (spanning 0-120 % field capacity, FC) and nitrogen application rates (0-300 kg N ha-1) on GHG emissions were evaluated through systematic simulations of 88 distinct water-nitrogen management scenarios. Results and Conclusions: Maximum yields were achieved at 85 % FC irrigation coupled with 225 kg N ha-1 for winter wheat (8431 kg ha-1) and 85 % FC irrigation with 250 kg N ha-1 for summer maize (9806 kg ha-1), beyond which yields plateaued. Cumulative N2O emissions ranged from 0.07 to 0.75 kg N ha-1 (wheat) and 0.10-1.37 kg N ha-1 (maize). CO2 emissions initially increased with inputs before stabilizing at 3050 kg C ha-1 (wheat) and 2464 kg C ha-1 (maize) under optimal regimes. Precision management (85 % FC + crop-specific N) synchronizes yield optimization with GHG mitigation, achieving 18-22 % emission reduction relative to con-ventional practices while maintaining 95-97 % of maximum yield potential. Significance: This work establishes a scientifically validated framework for climate-smart cereal production in semi-arid regions. The identified water-nitrogen regimes (85 % FC + 225 kg N ha-1 wheat; 85 % FC + 250 kg N ha-1 maize) enable sustainable intensification by concurrently addressing food security and decarbonization goals in global cropping systems.