Soil C and N statuses determine the effect of maize inoculation by plant growth-promoting rhizobacteria on nitrifying and denitrifying communities

TitleSoil C and N statuses determine the effect of maize inoculation by plant growth-promoting rhizobacteria on nitrifying and denitrifying communities
Publication TypeJournal Article
Year of Publication2017
AuthorsFlorio A, Pommier T, Gervaix J, Berard A, Le Roux X
JournalScientific Reports
Volume7
Pagination12
Date PublishedAug
Type of ArticleArticle
ISBN Number2045-2322
Accession NumberWOS:000408106000002
Keywordsammonia-oxidizers, annual grassland, available, azospirillum-lipoferum crt1, carbon, field conditions, genetic-structure, microbial communities, rhizosphere microorganisms, root development, Science & Technology - Other Topics, zea-mays
Abstract

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 N2O 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 N2O production (down to - 18%) likely due to an increased roots-denitrifiers competition for nitrate.

Alternate JournalSci Rep