• Jialin Hu, University of Tennessee, Knoxville
• Jonathan D. Richwine, University of Tennessee, KnoxvilleFollow
• Patrick D. Keyser, University of Tennessee, KnoxvilleFollow
• Lidong Li, USDA, Agricultural Research Service, Lincoln, NebraskaFollow
• Fei Yao, University of Tennessee, Knoxville
• Sindhu Jagadamma, University of Tennessee, KnoxvilleFollow
• Jennifer M. DeBruyn, University of Tennessee, KnoxvilleFollow

2021

PeerJ Microbiology (2021) 9: e12592

doi: 10.7717/peerj.12592

Background: Fertilizer addition can contribute to nitrogen (N) losses from soil by affecting microbial populations responsible for nitrification. However, the effects of N fertilization on ammonia oxidizing bacteria under C₄ perennial grasses in nutrient-poor grasslands are not well studied. Methods: In this study, a field experiment was used to assess the effects of N fertilization rate (0, 67, and 202 kg N ha⁻¹) and grass species (switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii)) on ammonia-oxidizing bacterial (AOB) communities in C₄ grassland soils using quantitative PCR, quantitative reverse transcription-PCR, and high-throughput amplicon sequencing of amoA genes. Results: Nitrosospira were dominant AOB in the C₄ grassland soil throughout the growing season. N fertilization rate had a stronger influence on AOB community composition than C₄ grass species. Elevated N fertilizer application increased the abundance, activity, and alpha-diversity of AOB communities as well as nitrification potential, nitrous oxide (N₂O) emission and soil acidity. The abundance and species richness of AOB were higher under switchgrass compared to big bluestem. Soil pH, nitrate, nitrification potential, and N₂O emission were significantly related to the variability in AOB community structures (p 0.05).

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