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

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.