The Impact of Bio Compost Use on the Agricultural Soil Microbiome: Evidence from a Laboratory-Scale Study

Composted organic amendments are increasingly recognized as viable alternatives to synthetic fertilizers, driven by the rising interest in organic waste recycling and sustainable soil management. This study aims to evaluate the long-term effects of bio compost, derived from organic waste, on the chemical and microbiological properties of agricultural soils. A one-year laboratory-scale experiment was conducted using nine microcosm replicates with increasing doses of compost (ratios 1:1, 1:2, 1:4), applied in both powder and granular forms, with and without the addition of water. Microbiological analysis based on 16S rRNA gene sequencing revealed significant shifts in microbial composition. The results demonstrated a consistent increase in microbiological DNA concentration in samples amended with bio-compost, showing a 50% increase from the initial concentration. Furthermore, regarding species composition, bio-compost altered the bacterial population in favor of the predominant species introduced into the soil, indicating a selective enhancement of the bacterial community. Additionally, the addition of water did not affect either the quantity or quality of the bacterial composition. Microbial biomass significantly improved following compost application, with powdered formulations proving more effective than granular ones, and drought conditions often eliciting more pronounced responses. These findings demonstrate that the amendment can improve soil quality by minimizing disruption to microbial communities and promoting long-term soil fertility. Adopting this approach appears beneficial for circular, bio-based agricultural systems.