AUTHOR=Fudjoe Setor Kwami , Li Lingling , Anwar Sumera , Shi Shangli , Xie Junhong , Yeboah Frederick Kwame , Wang Linlin 

TITLE=The impact of fertilization on ammonia-oxidizing bacteria and comammox Nitrospira communities and the subsequent effect on N2O emission and maize yield in a semi-arid region

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1249668

DOI=10.3389/fmicb.2023.1249668

ISSN=1664-302X

ABSTRACT=<p>The control of nitrous oxide (N<sub>2</sub>O) emissions through nitrification and the optimization of maize yield are important in agricultural systems. However, within the semi-arid region, the impact of fertilization on the function of nitrification communities and its connection with N<sub>2</sub>O emissions in the rhizosphere soil is still unclear. Our study investigates the influence of fertilization treatments on the communities of ammonia-oxidizing bacteria (AOB) and the complete ammonia oxidizers of the <italic>Nitrospira</italic> known as comammox (CAOB) in a maize agroecosystem. Nitrous oxide production, potential nitrification activity (PNA), maize yield, and nitrogen use efficiency (NUE) were determined for the same samples. The fertilizer treatments included a control group without fertilization (NA), inorganic fertilizer (CF), organic fertilizer (SM), combined inorganic and organic fertilizer (SC), and maize straw (MS). The SC treatment indicated a lower cumulative N<sub>2</sub>O emission than the CF treatment in the 2020 and 2021 cropping seasons. The AOB community under the CF, MS, and SM treatments was predominantly composed of <italic>Nitrosospira</italic> cluster 3b, while the SC treatment was associated with the comammox <italic>Nitrospira</italic> clade A.1 lineage, related to key species such as Ca. <italic>Nitrospira inopinata</italic> and Ca. <italic>Nitrospira nitrificans</italic>. Network analysis demonstrated a positive potential for competitive interaction between hub taxonomy and distinct keystone taxa among AOB and comammox <italic>Nitrospira</italic> nitrifiers. The structural equation model further revealed a significant positive association between AOB nitrifiers and N<sub>2</sub>O emission, PNA, soil pH, SOC, <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:msubsup></mml:mrow></mml:math></inline-formula>-N, and DON under organic fertilization. The keystone taxa in the comammox <italic>Nitrospira</italic> nitrifier and network Module II exhibited a positive correlation with maize productivity and NUE, likely due to their functional activities stimulated by the SC treatment. It is noteworthy that the AOB community played a more significant role in driving nitrification compared to the composition of comammox <italic>Nitrospira</italic>. Collectively, combined inorganic and organic fertilizer (SC) treatment exhibits high potential for reducing N<sub>2</sub>O emissions, enhancing maize productivity, increasing NUE, and increasing the sustainability of the nitrogen dynamics of maize agroecosystems in the semi-arid Loess Plateau.</p>