Potential role of pyrolysis temperature for brewer’s spent grain biochar on mitigating ammonia emissions from urea-fertilized soils

Nitrogen (N) management in urea-fertilized soils is essential for enhancing crop productivity and preventing secondary environmental pollutions.This study aimed to evaluate the potential role of pyrolysis temperature for biochar production and its effect on ammonia (NH 3 ) volatilization and soil chemical properties.The biochar was produced by brewer's spent grain (BSG) and pyrolyzed at 300C, 500C, and 700C, abbreviated as BSG 300 , BSG 500 , and BSG 700 , respectively.The aforementioned biochars were treated at 3% (by soil weight) in urea-fertilized soils.The pH and nutrient content of BSG biochars were improved by the increase in the pyrolysis temperature from 300C to 700C, whereas the EC value was the lowest in BSG 700 at 0.71 dSm -1 .Additionally, total carbon content of BSG biochars had the positive correlation with the pyrolysis temperature, resulting from BSG 300 , BSG 500 , and BSG 700 were represented the 59.40%, 66.12%, and 69.23%, respectively.The soil chemical properties represented the similar trend with the chemical characteristics of BSG biochars, and the soil pH and organic matter content in the BSG 700 treatment were the highest at pH 6.54 and 4.02%, respectively.However, despite the BSG biochar treatment, the soil pH, exchangeable Ca 2+ , and exchangeable Mg 2+ contents in the BSG 300 and BSG 500 treatments did not exhibit the statistically significant differences with the initial soil.The NH 3 volatilization decreased significantly by the BSG 300 and BSG 500 amendments at 7.34 kgha -1 and 10.36 kgha -1 , respectively, while the BSG 700 treatment (11.83 kgha -1 ) was 1.12-fold higher than urea-only treatment (10.57kgha -1 ).Therefore, although BSG 300 had the relatively low improvement in soil fertility and carbon sequestration, the BSG biochars pyrolyzed at below 500C were recommended for effectively N management in urea-fertilized soils.