Influence of biochar on soil N2O emissions and bacterial community structure

Biochar has emerged as a promising strategy for greenhouse gas mitigation in agriculture. When applied to soils, environmental interactions can alter its physicochemical properties. Understanding biochar’s behavior over time is crucial to assessing its effectiveness in mitigating N₂O emissions and modulating nitrogen-cycle-associated microbial communities. Gas samples were collected during a 44-days greenhouse experiment with maize cultivation, and microbiological analyses were conducted to quantify functional genes involved in the nitrogen cycle using real-time quantitative polymerase chain reaction (qPCR). The experiment followed a randomized design with four treatments: i) soil control; ii) soil + nitrogen fertilizer (NF); iii) NF with biochar (NF+BC); iv) NF with aged biochar (NF+BCA). The main results indicated a reduction in carbon content and changes in carbon bonding in the NF+BCA treatment, suggesting that chemical alterations may influence biochar interaction with soil nitrogen cycle, affecting its N₂O mitigation potential. Daily N₂O emissions were lower in biochar treatments, and cumulative emissions were reduced by 48% with NF+BC and by 30% with NF+BCA compared with NF. Bacterial community composition varied across treatments: the control was characterized by high Actinobacteriota diversity, whereas biochar application enhanced Proteobacteria associated taxa. The NF treatment showed an intermediate profile, with increased Actinobacteriota abundance. These shifts suggest that the treatments shaped bacterial dominance and community composition, with potential implications for the ecological functionality. These results highlight biochar as an effective strategy for N₂O mitigation and support its potential long-term role in sustainable agriculture.