Short-term impact of two liquid organic fertilizers on Solanum lycopersicum L. rhizosphere Eubacteria and Archaea diversity

•The application of two liquid organic fertilizers affected significantly the abundance and diversity of rhizospheric Eubacteria and Archaea in tomato plants, as a function of their chemical composition.•Microbial diversity indexes were higher in the soil receiving the organic fertilizers in comparison to mineral fertilization.•The Archaea and Eubacteria were not affected in the same way: Archaea were generally favored by the addition of the organic fertilizers, while Eubacteria responded differently depending on the kind of fertilizer.•The organic fertilizers induced an increase in root growth and modified root architecture.

This study evaluates the effect of two different kinds of liquid organic fertilizers and a mineral fertilizer on microbial populations (Eubacteria and Archaea) living in the tomato rhizosphere. The organic fertilizers comprised a stillage from bakery yeasts production, characterized by acidic pH and high organic nitrogen content, as well as a vermicompost extract with alkaline pH and low nitrogen content. The number of operational taxonomic units (OTUs) of Archaea species significantly increased after the addition of both the organic and mineral fertilizers, in comparison to the unfertilized control. Eubacteria OTUs increased only in plants treated with the stillage. T-RFLPs profiles identified different clusters of soil rhizospheric Archaea and Eubacteria in treatments of both organic and mineral fertilizers. However, multivariate analyses performed on indicators of genetic diversity, based on the T-RFLPs profiles, and Shannon and equitability indexes of the Archaea and Eubacteria communities, pointed out marked differences between the control (or the mineral fertilization) and the organic fertilizers. The latter treatments induced also a higher root growth and a modification of the root architecture in comparison to both control and mineral fertilizer. The results are discussed with reference to the effect of the organic products on rhizospheric soil characteristics and the relationships between the plant and the rhizospheric microorganisms.