Incongruous variation of denitrifying bacterial communities as soil N level rises in Canadian canola fields |
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| Institution: | 1. College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China;2. Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China;3. Agricultural Quality Standards and Testing Technology Research Institute, Shandong Academy of Agricultural Sciences, Jinan, Shandong 250100, China;4. Soil Resources and Land Use, Institute of Soil Science and Site Ecology, TU Dresden, Germany;1. Landcare Research, P.O. Box 40, Lincoln 7640, New Zealand;2. Landcare Research, Private Bag 3127, Hamilton 3240, New Zealand;3. Department of Earth and Ocean Sciences, University of Waikato, Hamilton 3240, New Zealand;4. Landcare Research, Private Bag 11052, Palmerston North 4442, New Zealand;1. College of Life Sciences, Nanjing Normal University, Nanjing 210023, China;2. College of Resources and Environment, Linyi University, Linyi 276000, China;3. Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, School of Geography Sciences, Nanjing Normal University, Nanjing 210023, China;4. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China;5. Jiangxi Institute of Red Soil, Nanchang 331717, China;1. Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, Building 1, DK-2100 Copenhagen Ø, Denmark;2. Technical University of Denmark, Department of Environmental Engineering, Miljøvej, 2800 Kgs. Lyngby, Denmark;3. Technical University of Denmark, Department of Chemical Engineering, Søltofts Plads 229, 2800 Kgs. Lyngby, Denmark;1. College of Agriculture, Henan University of Science and Technology, Luoyang 471003, PR China;2. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, PR China |
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| Abstract: | Soil N fertilization stimulates the activity of the soil bacterial species specialized in performing the different steps of the denitrification processes. Different responses of these bacterial denitrifiers to soil N management could alter the efficiency of reduction of the greenhouse gas N2O into N2 gas in cultivated fields. We used next generation sequencing to show how raising the soil N fertility of Canadian canola fields differentially modifies the diversity and composition of nitrite reductase (nirK and nirS) and nitrous oxide reductase (nosZ) gene-carrying denitrifying bacterial communities, based on a randomized complete blocks field experiment. Raising soil N levels increased up to 60% the ratio of the nirK to nirS genes, the two nitrite reductase coding genes, in the Brown soil and up to 300% in the Black soil, but this ratio was unaffected in the Dark Brown soil. Raising soil N levels also increased the diversity of the bacteria carrying the nitrite reductase gene nirK (Simpson index, P = 0.0417 and Shannon index, 0.0181), and changed the proportions of the six dominant phyla hosting nirK, nirS, and nosZ gene-carrying bacteria. The level of soil copper (Cu) and the abundance of nirK gene, which codes for a Cu-dependent nitrite reductase, were positively related in the Brown (P = 0.0060, R2 = 0.48) and Dark Brown (0.0199, R2 = 0.59) soils, but not in the Black soil. The level of total diversity of the denitrifying communities tended to remain constant as N fertilization induced shifts in the composition of these denitrifying communities. Together, our results indicate that higher N fertilizer rate increases the potential risk of nitrous oxide (N2O) emission from canola fields by promoting the proliferation of the mostly adaptive N2O-producing over the less adaptive N2O-reducing bacterial community. |
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| Keywords: | Denitrification Pyrosequencing Soil nitrogen level Canola Nitrous oxide emissions |
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