Carbon neutralization potential and carbon sequestration efforts in a wheat-maize rotation system in the North China Plain

Agricultural C neutralization is an effective method of using industrial carbon dioxide (CO₂) in agricultural production. Aiming at the national goal of “peaking CO₂ emissions before 2030 and achieving carbon neutrality before 2060”, we defined the agricultural non-energy C balance in the North China Plain (NCP) by using the “static chamber-eddy covariance-biomass monitoring method”. Simultaneously, C emissions from agricultural energy were determined based on the sampling survey data of farmers and the C emission coefficients of agricultural activities. Thus, the C neutralization potential of croplands in this region was calculated. Our results showed that in the NCP, the net amount of organic C (including grains and returned straw) for winter wheat and summer maize was 604 g(C)∙m⁻² and 540 g(C)∙m⁻², respectively. Considering the ecosystem autotrophic respiration consumption, the net C sequestration of non-energy C was −359 g(C)∙m⁻² and −143 g(C)∙m⁻² in the wheat and maize seasons, respectively. Energy C emissions in the system were further studied. The C emissions of pesticides, chemical fertilizers, agricultural diesel, and irrigation in the wheat season were 3.74, 90.70, 5.68, and 2.05 g(C)∙m⁻², respectively; and those in the maize season were 2.89, 53.70, 10.20, and 2.05 g(C)∙m⁻², respectively. Combined with the non-energy and energy C budget, both the winter wheat and summer maize seasons were C sinks, −257 g(C)∙m⁻² for the winter wheat season and −74 g(C)∙m⁻² for the summer-maize season. For example, in Luancheng (located in Hebei Province), a typical intensive and high-yield grain region in the NCP, the annual C sequestration potential of winter wheat and summer maize croplands was 3.8×10¹⁰ g C and 9.4×10⁹ g C, respectively. In addition, strengthening cultivated land management, promoting low-C agriculture, and developing C-rich agriculture can be effective strategies for C sequestration in this region. In conclusion, we identified the C sink intensity of winter wheat and summer maize rotation cropland in the NCP, estimated the C neutralization potential in Luancheng, Hebei Province, and proposed effective C sequestration efforts.