Modified cornstalk biochar can reduce ammonia emissions from compost by increasing the number of ammonia-oxidizing bacteria and decreasing urease activity

Abstract

This study examined how the addition of modified cornstalk biochar (CB) affected ammonia (NH₃) emissions during composting. Four treatments were established, including a control (CK) with layer manure and sawdust only, and the CK mixtures adding 10% HNO₃ CB (NA), 10% H₂O₂ CB (HP) and 10% HNO₃- H₂O₂ CB (MI). As the results showed, NH₃ emissions was reduced by 47.83% (NA), 61.69% (HP) and 45.69% (MI) when the modified CB used as a compost additive (P < 0.05). According to the data analysis, the addition of modified CB significantly increased the number of ammonia-oxidizing bacteria (AOB), inhibited urease activity and decreased the abundance of narG and nirS at rising temperatures and high temperatures (P < 0.05). Redundancy analysis demonstrated a negative correlation between NH₃ emissions and AOB and a positive correlation with urease activity, narG and nirS. Thus, the modified CB helped reduce NH₃ emissions by regulating nitrification processes.

Keywords: Ammonia; Biochar; Composting; Layer manure; Nitrogen functional gene.