## 4 Discussion
Specifically, higher pyrolysis temperatures tend to yield biochar with an increased content of NO\({}_{3}\)\({}^{-}\), while lower temperatures favor the presence of NH\({}_{4}\)+. Moreover, biochar produced through fast pyrolysis exhibits a larger surface area compared to biochar produced through slow pyrolysis methods. This increased surface area in fast pyrolysis enhances its capacity to adsorb inorganic N compounds or facilitating microbial N-immobilization [73]. In simpler terms, biochar produced through fast pyrolysis may possess a greater ability to capture and retain N compounds, either through physical adsorption or by fostering microbial processes that immobilize N. All of these variations have implications for biochar's potential impact on N-cycling within soil ecosystems [73]. In our mesocosm experiment, the soil treated with 10% biochar exhibits the lowest abundance of bacteria compared to the other treatments. Nevertheless, no particular relationship between bacterial abundance and treatment is evident. Similarly, the abundance of soil nitrifiers and denitrifiers does not show a particular influence due to the application of digestate and/or biochar. This contrasts with the findings of [PERSON] et al. [5], who documented alterations in these microbial functional groups following the application of biochar and digestate. Specifically, they recorded those soils receiving biochar significantly suppressed the abundance of _amoA_ gene, while soils amended with digestate show an increase in the abundance of denitrification (_narG_, _nrA_, _nrK_, _nosZ_) and nitrification (_amoA_, _amoB_) genes. Contrasting results were obtained by [PERSON] et al. [69] in a pot trial under greenhouse conditions, revealing no significant responses to biochar in bacterial-_amoA_, _nrS_, and _nrK_ gene transcripts, while archaeal-_amoA_ and _nosZ_ gene transcription was significantly stimulated. Our results could be explained by the short-incubation period of the mesocosm experiment, which does not provide sufficient time for significant changes in functional microbial groups due to the application of digestate and/or biochar. The additional N dose from both manure-based digestate and biochar, along with labile C substrates suppliedby digestate [5], appears to primarily affect the activity of microorganisms involved in the initial steps of denitrification process. This influence might not have enough time to exert substantial modifications on the overall microbial functional potential related to the N-cycle in the soil. Nevertheless, changes in the structure of the denitrifying community provide limited predictive power for N\({}_{2}\)O emissions [79]. Denitrification is a facultative process that relies on specific environmental conditions, and key enzymes are synthesized accordingly. Thus, _mirK_, _mirS_, and _nosZ_ abundances may not be significant factors. Understanding the physiological and ecological dynamics of N\({}_{2}\)O-reducing communities is crucial for devising strategies to mitigate N\({}_{2}\)O emissions. While our study sheds light on the initial impacts of digestate and biochar application on soil microbial communities, a longer incubation period may be necessary to observe more significant changes in microbial function and N-cycling dynamics.