Open AccessSoil C and N statuses determine the effect of maize inoculation by plant growth-promoting rhizobacteria on nitrifying and denitrifying communities
Author(s) -
Alessandro Florio,
Thomas Pommier,
Jonathan Gervaix,
Annette Bérard,
Xavier Le Roux
Publication year - 2017
Publication title -
scientific reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.24
H-Index - 213
ISSN - 2045-2322
DOI - 10.1038/s41598-017-08589-4
Subject(s) - denitrifying bacteria , rhizosphere , inoculation , nitrification , denitrification , microbial inoculant , biology , agronomy , ammonium , rhizobacteria , nitrate , horticulture , chemistry , nitrogen , ecology , bacteria , organic chemistry , genetics
Maize inoculation by Azospirillum stimulates root growth, along with soil nitrogen (N) uptake and root carbon (C) exudation, thus increasing N use efficiency. However, inoculation effects on soil N-cycling microbial communities have been overlooked. We hypothesized that inoculation would (i) increase roots-nitrifiers competition for ammonium, and thus decrease nitrifier abundance; and (ii) increase roots-denitrifiers competition for nitrate and C supply to denitrifiers by root exudation, and thus limit or benefit denitrifiers depending on the resource (N or C) mostly limiting these microorganisms. We quantified (de)nitrifiers abundance and activity in the rhizosphere of inoculated and non-inoculated maize on 4 sites over 2 years, and ancillary soil variables. Inoculation effects on nitrification and nitrifiers (AOA, AOB) were not consistent between the three sampling dates. Inoculation influenced denitrifiers abundance ( nirK , nirS) differently among sites. In sites with high C limitation for denitrifiers (i.e. limitation of denitrification by C > 66%), inoculation increased nirS -denitrifier abundance (up to 56%) and gross N 2 O production (up to 84%), likely due to increased root C exudation. Conversely, in sites with low C limitation (<47%), inoculation decreased nirS -denitrifier abundance (down to −23%) and gross N 2 O production (down to −18%) likely due to an increased roots-denitrifiers competition for nitrate.