Impact of biochar on enzyme activity, respiration, and microbial population in irrigated farmland

Purpose This study investigated the effects of different biochar application rates on wheat yield, soil microbial activity, enzyme function, and CO 2 emissions under two nitrogen fertilization levels, aiming to identify an optimal strategy for improving soil health and reducing emissions. Methods A randomized block design was used with eight treatments combining two nitrogen rates (conventional N1: 300 kg·ha −1 , reduced N2: 255 kg·ha −1 ) and four biochar doses (0, 10, 20, 30 t·ha −1 ). Soil microbial community, respiration, enzyme activities, and CO 2 emissions were analyzed. Results Biochar enhanced overall soil microbial activity and diversity. The highest microbial activity indices occurred with conventional nitrogen and moderate biochar (N1B2). All biochar treatments increased microbial diversity, with ester consumption as the primary carbon source. The combination of reduced nitrogen and moderate biochar (N2B2) lowered cumulative CO 2 emissions by 4.42% compared to reduced nitrogen alone. Both nitrogen and biochar increased sucrase, urease, and catalase activities. Conclusion The application of reduced nitrogen (255 kg·ha −1 ) with moderate biochar (20 t·ha −1 ) is identified as an optimal strategy to enhance the soil micro environment and mitigate CO 2 emissions in irrigated wheat fields, though its long-term effects require further assessment.