Impact of Biochar on Nitrogen-Cycling Functional Genes: A Comparative Study in Mollisol and Alkaline Soils.

Biochar has gained considerable attention as a sustainable soil amendment due to its potential to enhance soil fertility and mitigate nitrogen (N) losses. This study aimed to investigate the effects of biochar application on the abundance of key N-cycling genes in Mollisol and alkaline soils, focusing on nitrification (AOA, AOB, and ) and denitrification (, , and ) processes. The experiment was conducted using soybean rhizosphere soil. The results demonstrated that biochar significantly altered the microbial community structure by modulating the abundance of these functional genes. Specifically, biochar reduced and abundance in both soil types, indicating a potential reduction in NO emissions. In contrast, it promoted the abundance of , particularly in alkaline soils, suggesting enhanced nitrite oxidation. The study also revealed strong correlations between N-cycling gene abundances and soil properties such as pH, EC (electrical conductivity. Biochar improved soil pH and nutrient availability, creating favorable conditions for AOB and Nitrospira populations, which play key roles in ammonia and nitrite oxidation. Additionally, the reduction in / ratios in biochar-treated soils suggests a shift towards more efficient NO reduction. These findings highlight biochar's dual role in enhancing soil fertility and mitigating greenhouse gas emissions in Mollisol and alkaline soils. The results provide valuable insights into the sustainable management of agricultural soils through biochar application, emphasizing its potential to optimize nitrogen-cycling processes and improve soil health. Further research is needed to explore the long-term impacts of biochar on microbial communities and nitrogen-cycling under field conditions.