LAUSR

In the last two decades, a change in land use has taken place in Europe. Manures that used to be applied to agricultural soils are now used in biogas reactors, and instead, digestate is applied. Here, we simulated soil amendment with either fresh or anaerobically digested cattle manure. The aim was to investigate the resilience of the resident microbiota and detect differences in the microbial biomass and activity after fertilizer amendment. Furthermore, the physiological community profile and the role of the indigenous microbial community was elucidated. In a microcosm experiment, two kinds of agricultural soil (γ-irradiated versus non-irradiated) were amended with either treatment. The effect of amendments on the community composition and physiological activity was tested immediately, after 1 and 3 months of incubation through 16S rRNA gene amplicon sequencing (initial soil community), genetic and physiological profiling (PCR-DGGE and MicroResp™), and measurement of basal respiration and microbial biomass. Either fertilizer did not affect the community composition of dominant fungi and bacteria in non-irradiated soils. This indicates the ability of the indigenous microbiota to outcompete allochthonous microorganisms. Soil microbial biomass was not changed, whereas basal respiration was significantly higher after amendment, especially when using fresh manure. MicroResp™ revealed slightly higher respiration for some substrates after 1 month; this finding was, however, not persistent and similar for manure and digestate. Generally, after 1 month, treatments returned to control levels for all parameters. In conclusion, amendment with anaerobically digested manure did not have a greater impact on soil microbial properties.