AUTHOR=Fudjoe Setor Kwami , Li Lingling , Anwar Sumera , Shi Shangli , Xie Junhong , Wang Linlin , Xie Lihua , Yongjie Zhou 

TITLE=Nitrogen fertilization promoted microbial growth and N2O emissions by increasing the abundance of nirS and nosZ denitrifiers in semiarid maize field

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1265562

DOI=10.3389/fmicb.2023.1265562

ISSN=1664-302X

ABSTRACT=<p>Nitrous oxide (N<sub>2</sub>O) emissions are a major source of gaseous nitrogen loss, causing environmental pollution. The low organic content in the Loess Plateau region, coupled with the high fertilizer demand of maize, further exacerbates these N losses. N fertilizers play a primary role in N<sub>2</sub>O emissions by influencing soil denitrifying bacteria, however, the underlying microbial mechanisms that contribute to N<sub>2</sub>O emissions have not been fully explored. Therefore, the research aimed to gain insights into the intricate relationships between N fertilization, soil denitrification, N<sub>2</sub>O emissions, potential denitrification activity (PDA), and maize nitrogen use efficiency (NUE) in semi-arid regions. Four nitrogen (N) fertilizer rates, namely N0, N1, N2, and N3 (representing 0, 100, 200, and 300 kg ha<sup>−1</sup> yr.<sup>−1</sup>, respectively) were applied to maize field. The cumulative N<sub>2</sub>O emissions were 32 and 33% higher under N2 and 37 and 39% higher under N3 in the 2020 and 2021, respectively, than the N0 treatment. N fertilization rates impacted the abundance, composition, and network of soil denitrifying communities (<italic>nirS</italic> and <italic>nosZ</italic>) in the bulk and rhizosphere soil. Additionally, within the <italic>nirS</italic> community, the genera <italic>Cupriavidus</italic> and <italic>Rhodanobacter</italic> were associated with N<sub>2</sub>O emissions. Conversely, in the <italic>nosZ</italic> denitrifier, the genera <italic>Azospirillum</italic>, <italic>Mesorhizobium</italic>, and <italic>Microvirga</italic> in the bulk and rhizosphere soil reduced N<sub>2</sub>O emissions. Further analysis using both random forest and structural equation model (SEM) revealed that specific soil properties (pH, NO<sub>3</sub><sup>−</sup>-N, SOC, SWC, and DON), and the presence of <italic>nirS</italic>-harboring denitrification, were positively associated with PDA activities, respectively, and exhibited a significant association to N<sub>2</sub>O emissions and PDA activities but expressed a negative effect on maize NUE. However, <italic>nosZ</italic>-harboring denitrification showed an opposite trend, suggesting different effects on these variables. Our findings suggest that N fertilization promoted microbial growth and N<sub>2</sub>O emissions by increasing the abundance of <italic>nirS</italic> and <italic>nosZ</italic> denitrifiers and altering the composition of their communities. This study provides new insights into the relationships among soil microbiome, maize productivity, NUE, and soil N<sub>2</sub>O emissions in semi-arid regions.</p>