Long-Term Phosphorus Fertilization Impacts Soil Fungal and Bacterial Diversity but not AM Fungal Community in Alfalfa |
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Authors: | M S Beauregard C Hamel Atul-Nayyar M St-Arnaud |
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Institution: | 1. Institut de recherche en biologie végétale, Université de Montréal and Jardin botanique de Montréal, 4101 Sherbrooke Street East, Montreal, QC, Canada, H1X 2B2 2. Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, 1 Airport Road, P. O. Box?1030, Swift Current, SK, Canada, S9H 3X2
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Abstract: | Soil function may be affected by cropping practices impacting the soil microbial community. The effect of different phosphorus
(P) fertilization rates (0, 20, or 40 kg P2O5 ha−1) on soil microbial diversity was studied in 8-year-old alfalfa monocultures. The hypothesis that P fertilization modifies
soil microbial community was tested using denaturing gradient gel electrophoresis and phospholipids fatty acid (PLFA) profiling
to describe soil bacteria, fungi, and arbuscular mycorrhizal (AM) fungi diversity. Soil parameters related to fertility (soil
phosphate flux, soluble P, moisture, phosphatase and dehydrogenase assays, and carbon and nitrogen content of the light fraction
of soil organic matter) were also monitored and related to soil microbial ribotype profiles. Change in soil P fertility with
the application of fertilizer had no effect on crop yield in 8 years, but on the year of this study was associated with shifts
in the composition of fungal and bacterial communities without affecting their richness, as evidenced by the absence of effect
on the average number of ribotypes detected. However, variation in soil P level created by a history of differential fertilization
did not significantly influence AM fungi ribotype assemblages nor AM fungi biomass measured with the PLFA 16:1ω5. Fertilization
increased P flux and soil soluble P level but reduced soil moisture and soil microbial activity, as revealed by dehydrogenase
assay. Results suggest that soil P fertility management could influence soil processes involving soil microorganisms. Seasonal
variations were also recorded in microbial activity, soil soluble P level as well as in the abundance of specific bacterial
and fungal PLFA indicators of soil microbial biomass. |
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