Urea amendment decreases microbial diversity and selects for specific nitrifying strains in eight contrasting agricultural soils

Authors: STALEY, CHRISTOPHER - University Of Minnesota; BREUILLIN-SESSOMS, FLORENCE - University Of Minnesota; WANG, PING - University Of Minnesota; KAISER, THOMAS - University Of Minnesota; Venterea, Rodney - Rod; SADOWSKY, MICHAEL - University Of Minnesota

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2018
Publication Date: 4/1/2018
Citation: Staley, C., Breuillin-Sessoms, F., Wang, P., Kaiser, T., Venterea, R.T., Sadowsky, M. 2018. Urea amendment decreases microbial diversity and selects for specific nitrifying strains in eight contrasting agricultural soils. Frontiers in Microbiology. 9(634):1-13. doi:https://doi.org/10.3389/fmicb.2018.00634.
DOI: https://doi.org/10.3389/fmicb.2018.00634

Interpretive Summary: Nitrous oxide (N2O) is a potent greenhouse gas that results from the application of N-fertilizers to agricultural soils. Predictive models vary in their efficacy to predict N2O emissions based on soil chemical parameters, but incorporation of biological data can improve predictive accuracy. In this study, we expand on previous work that modeled edaphic parameters, chemical composition, and abundances of bacterial nitrification genes. Using a next-generation sequencing approach, prokaryotic communities were characterized in agricultural soils from eight fields amended with varying concentrations of urea over 21 days. Significant differences in bacterial communities were observed by site, but temporal differences and those due to urea application were inconsistent. Amendment with urea caused significant decreases in Shannon indices and variation in abundance of members of the families Microbacteriaceae, Chitinophagaceae, Comamonadaceae, Xanthomonadaceae, and Nitrosomonadaceae, in all soils. Analysis of nitrifier genera revealed diverse, soil-specific distributions of oligotypes, but few were significantly correlated with nitrification gene abundances. Results of this study suggest that the majority of the prokaryotic community is unassociated with N2O emissions but is significantly impacted by urea application. Furthermore, we reveal novel diversity within genera of nitrifiers that may have important implications regarding N2O emissions resulting from urea amendment. These results will enable more accurate N2O emissions models based on soil biochemical processes, which in turn will be useful for developing effective greenhouse gas mitigating practices.

Technical Abstract: Nitrous oxide (N2O) is a potent greenhouse gas that results from the application of N-fertilizers to agricultural soils. Predictive models vary in their efficacy to predict N2O emissions based on soil chemical parameters, but incorporation of biological data can improve predictive accuracy. In this study, we expand on previous work that modeled edaphic parameters, chemical composition, and abundances of bacterial nitrification genes. Using a next-generation sequencing approach, prokaryotic communities were characterized in agricultural soils from eight fields amended with varying concentrations of urea over 21 days. Significant differences in bacterial communities were observed by site, but temporal differences and those due to urea application were inconsistent. Amendment with urea caused significant decreases in Shannon indices and variation in abundance of members of the families Microbacteriaceae, Chitinophagaceae, Comamonadaceae, Xanthomonadaceae, and Nitrosomonadaceae, in all soils. Analysis of nitrifier genera revealed diverse, soil-specific distributions of oligotypes, but few were significantly correlated with nitrification gene abundances. Results of this study suggest that the majority of the prokaryotic community is unassociated with N2O emissions but is significantly impacted by urea application. Furthermore, we reveal novel diversity within genera of nitrifiers that may have important implications regarding N2O emissions resulting from urea amendment.