## 5 Conclusions  
In conclusion, the study underscores the critical role of biochar composition and dosage in influencing soil GHG fluxes, emphasizing the need for tailored approaches to optimize its impact on microbial communities and nutrient availability. The unexpected stimulation of N\({}_{2}\)O emissions by high biochar concentrations challenges previous hypothesis, highlighting the complexity of biochar-soil interactions. Understanding the specific soil and biochar characteristics and origin is crucial for sustainable agricultural practices. Further research may be needed to identify the phyto-stimulatory or phytotoxic components in by-product organic materials and comprehend implications for crop growth and environmental sustainability. This study offers new insights into the short-term effects of anaerobic digestates and biochar on soil microorganisms, emphasizing the complexity of microbial responses. Persistence and contrasting effects on microbial functional groups highlight the need for continued research, especially exploring biochar as a tool to mitigate the impact of Clostrtidaeae in soil ecosystems influenced by digestate application. As agriculture and environmental sectors seek sustainable practices, knowledge about the resilience and recovery of soil microbiota becomes instrumental for informed decision-making regarding the repeated use of digestate as a soil amendment. Ongoing research in this area is expected to contribute further to optimizing digestate application for both agricultural productivity and environmental sustainability. Field studies with repeated digestate applications over several years, focusing on microbial communities involved in biogeochemical cycles, are essential for a holistic understanding of digestate sustainability. Limitations in the study, such as only determining the presence of functional genes without assessing their expression or quantifying enzyme activities, call for further research to establish a link between microbial functional genes and activities. Real-time PCR quantification, while suitable for characterizing soil microbial diversity, provides limited information on microbial functioning. Future research, employing metagenomic or metatranscriptomic approaches, can provide deeper insights into the mechanisms driving soil GHG emissions. Future perspectives should aim to scale up research findings from small-scale experiments to field-level application and assess the feasibility, practicality, and economic viability of using digestate and biochar as soil amendments on a larger scale. Establishing field experiments employing integrated approaches that combine digestate and biochar with other soil amendments or management practices can help to explore the synergistic or antagonistic effects between different amendments in order to optimize soil health, crop productivity and environmental sustainability. Educating farmers, agronomists, and stakeholders about the benefits, challenges, and best practices associated with digestate and biochar application is crucial for promoting the adoption of sustainable soil management practices. Conceptualization, R.P. and A.L. ; formal analysis, R.P., A.C., F.R., C.B. and A.L. ; investigation, R.P., A.C., F.R., C.B. and A.L. ; resources, E.T. and I.L. ; data curation, R.P. and A.L. ; writing--original draft preparation, R.P., A.L., E.T. and I.L. All authors have read and agreed to the published version of the manuscript. **Funding:** This study was developed in the context of the EOM4 SOIL project (External organic matters for climate mitigation and soil health), from the European Joint Program for SOIL 'Towards climate-smart sustainable management of agricultural soils' (EJP SOIL) consortium funded by the European Union Horizon 2020 research and innovation program (Grant Agreement No. 862695). **Data Availability Statement:** Data that support the findings of this study are available on reasonable request from the corresponding author.