Use of solid anaerobic digestate and no-tillage practices induce selective compositional changes of the total and active prokaryotic communities in two Mediterranean orchard soils with contrasting properties

Improved soil management practices have great potential to contrast loss of fertility and soil degradation in conventionally-managed Mediterranean perennial croplands. During an 18-week field experiment we investigated the impact of different tillage systems (conventional, conventional combined with the incorporation of solid anaerobic digestate, and no-tillage) on the prokaryotic community diversity in two tree orchard (olive, citrus) soils located in Southern Italy showing contrasting texture, carbonate content, pH, and prokaryotic communities. Phylogenetic diversity and compositional shifts of both total and active soil prokaryotic communities were assessed by next-generation sequencing of 16S rRNA gene templates from soilextracted DNA/RNA. In both digestate-treated soils, copiotrophic a -Proteobacteria and oligotrophic Acidobacteria, Gemmatimonadetes, and Verrucomicrobia showed animmediate (2 days) but short-lived (7 weeks) shift in abundance similar in persistence but not in magnitude. Whereas, selective soil-type dependent responses were observed for Actinobacteria, Chloroflexi, Firmicutes, and Planctomycetes. The autochthonous soil microbiota demonstrated resilience to the addition of the anaerobic digestate, which was dominated by Firmicutes, Bacteroidetes, Deinococcus-Thermus and Euryarchaeota (Methanomicrobia). Likewise, a momentary increase of copiotrophic taxa (Firmicutes, Bacteroidetes, Thaumarcheota) was observed under conventional tillage, especially in the sandy loam (citrus) soil. Conversely, no-tillagefavored the establishment of oligotrophic Chloroflexi and Verrucomicrobia in both soils. The active and the total prokaryotic communities differed from each other only in physically-disturbed soils. Soil management induced compositional shifts in the predominant microbial copiotrophic/oligotrophic lifestyle balance whose persistence was linked to the tillage system but primarily dependent on soil type for magnitude.