The Spatial Heterogeneity of Crop Carbon Emissions: Effects of Cropping Patterns Changes in China’s Grain Hubs

Agriculture contributes 23% of global carbon emissions, with crop cultivation now exceeding livestock as China’s primary emission source, yet how cropping structure evolution drives regional differentiation remains insufficiently quantified. This study examines the Northeast Plain, Huang-Huai-Hai Plain, Middle-Lower Yangtze River Plain, and Xinjiang-Gansu using carbon accounting, LMDI decomposition, and correlation analysis (2000–2021). Cropping structure dominates spatial emission heterogeneity: the Northeast’s shift to corn monoculture (63.6% share) created a carbon hotspot; Huang-Huai-Hai’s wheat–corn rotation (>64%) generated the highest northern intensity; the Yangtze region maintained moderate growth through diversification; and Xinjiang-Gansu showed “scale-intensity dual growth” under arid constraints. Structural effects drove cumulative growth (+1.85 Mt and +1.33 Mt), while regional drivers differed—mechanization scale (r = 0.90), fertilizer dependency (r = 0.84), irrigation–carbon coupling (r = 0.94), and irrigation–fertilizer synergy. The 2015 fertilizer policy marked a turning point in intensity. Differentiated strategies—rotation optimization, input efficiency, water–heat synergy, and water-saving technology—can synergize food security with carbon neutrality.