Effects of nitrogen fertilization on soil CO 2 emission and bacterial communities in maize field on the semiarid Loess Plateau

Background and aims Nitrogen fertilization is one of the most important practices for improving of crop yield and soil quality, which also affects soil CO 2 emission. CO 2 emission is strongly influenced by soil bacterial communities. It is still unknown precisely how nitrogen fertilization affects soil bacterial communities in the semiarid Loess Plateau and how its effects are related to CO 2 emissions. Methods A field experiment was conducted with four nitrogen fertilization rates (0 (N0), 100 (N1), 200 (N2), and 300 (N3) kg N ha –1 ). Nitrogen fertilization effects soil bacterial communities, CO 2 emission, carbon emission efficiency (CEE), and their relationships were investigated. Results As a result of nitrogen fertilization, soil bacterial abundance increased, and the bacterial community composition and network changed. Soil CO 2 emission under N1, N2, and N3 were increased by 17.3%, 24.8%, and 28.9% compared to the N0 treatment, respectively. N2 and N3 exhibited the highest maize grain yield and CEE. CEE under N2 and N3 increased by 96.9%-140.9% compared to the N0 treatment. Soil bacterial abundance had a positive correlation with CO 2 emission. CO 2 emission were also affected by the bacterial composition and network, which were related to the Actinobacteria. Multiple regression analysis further suggested that CO 2 emission was jointly regulated by the abundance, composition, and network modules of the bacterial community. Conclusion Overall, our results indicated that nitrogen fertilization promoted CO 2 emission via increasing bacterial abundance and altering the composition of their community, and provided a new insight into the connection between soil microorganisms and agricultural CO 2 emission in the semi-arid region.