Effects of differently aged biochar to soil NH3 volatilization, N2O emissions and microbial diversity, and interaction

Abstract

Abstract Biochar has been considered an effective tool to alleviate soil ammonia (NH3) volatilization and nitrous oxide (N2O) emissions. However, there is often an aging phenomenon after the application of biochar, which brings uncertainty to the effectiveness of different aged biochar in alleviating global warming for a long time. The effect of aged biochar on soil NH3 volatilization, N2O emissions, and microbial diversity remains to be explored. In this study, different aged biochar was obtained by artificially accelerating physical, chemical, and biological aging and the intensity of biochar aging was quantified by an index. Then, the effects of aged biochar on soil NH3 volatilization, N2O emissions, and microbial diversity were determined through field control experiments and high-throughput sequencing. The results showed that biochar aging increased the acidity, oxygen content, specific surface area (SSA), total pore volume (PV), and the number of oxygen-containing functional groups in biochar, and effectively inhibited NH3 volatilization in soil. Compared with raw biochar, aged biochar by oxidation and mineralization significantly reduced NH3 volatilization by 14.71% and 9.39%. However, aged biochar increased the emission of soil N2O. Compared with raw biochar, biochar aged by oxidation and mineralization increased the N2O emissions by 30.34% and 26.36%. Biological and physical aging had no significant effect on soil NH3 volatilization and N2O emissions. Raw biochar increased the diversity of soil bacteria and decreased the diversity of nitrogen (N) fixing bacteria, but aged biochar just had converse effects on them. The alpha diversity of bacteria and fungi promoted NH3 volatilization and N2O emissions. The work clarifies the effects of different aged biochar on biochar properties, NH3 volatilization and N2O emissions, and soil microbe diversity.