Shift and resilience dynamics in soil bacterial communities upon addition of different fertilizers

Assessing the response of microbial communities to nutrient inputs in man-managed soils is of primary importance in understanding elemental cycling in the environment as well as improving crop productivity. In this study a low-nutrient soil was supplemented with seven different fertilizers including matrixes of plant, animal, fungal or synthetic origin and dosed to deliver the same amount of nitrogen. Growth of a grass crop (Cynodon dactylon) was recorded and the fertilizers were scored by the plant yield obtained. Soil cores were sampled at 9 and 58 days after the addition and bacterial community composition was analyzed through pyrosequencing of 16S rRNA gene amplicons. Over 900 bacterial genera were detected, belonging to 21 described and 19 candidate phyla. Specific groups were fostered by given fertilizers, in particular marked effects on some phyla were displayed by a yeast-based fertilizer which was also most effective in plant productivity. The main shifts were observed shortly after the supplementation and followed by a gradual stabilization of the equilibria and by a rise in community evenness. In the two-month time a decrease in the abundances of Firmicutes and Bacteroidetes was observed in parallel to a rise of Acidobacteria, Actinobacteria and part of the Proteobacteria.