Elevated CO₂ improved soil nitrogen mineralization capacity of rice paddy

Elevated CO₂ would increase rice yields and may lead to nitrogen limitation and potentially influence the sustainability of agricultural production. Blindly increasing the amount of chemical fertilizer will damage the environment and is very unwise. Therefore, clarifying the response of soil nitrogen mineralization capacity to elevated CO₂ is critical for both sustainable agriculture production and environmental protection. Here, we relied on Free-Air CO₂ Enrichment (FACE) platform and used a waterlogged incubation method to investigate the effects of elevated CO₂ on soil nitrogen mineralization capacity under different fertilization levels when planted different rice cultivars (strong and weak-CO₂ response rice). According to the first-order kinetic equation fitting, compared with Ambient, elevated CO₂ increased soil potential mineralized nitrogen (N_p) by 16.18%. Path analysis indicated that fertilization status, rice cultivar, soil organic carbon and soil C: N ratio might affect N_p. There was a significant positive correlation between soil nitrogen mineralization rate and N_p. Under different fertilization conditions and rice cultivars, the improvement degree of soil nitrogen mineralization capacity (Np and soil nitrogen mineralization rate) by elevated CO₂ was different. These findings suggest that more parameters and influencing factors should be taken into account when studying soil nitrogen cycle models under the condition of global change.