Impact of biochar and deficit irrigation on greenhouse gas emissions reduction in maize-wheat rotation systems

Biochar application and irrigation management are widely regarded as effective strategies for mitigating greenhouse gas emissions from agricultural systems. However, the combined effects of these two approaches on greenhouse gas emissions remain insufficiently understood. This study investigated how different biochar application rates and irrigation strategies affect soil moisture and temperature, as well as the relationship between soil moisture, temperature, and greenhouse gas emissions. A two-year field experiment was conducted in the North China Plain to investigate the combined impact of deficit irrigation and biochar on greenhouse gas emissions in a summer maize–winter wheat rotation system. The experiment included three irrigation strategies (full irrigation (F: 70 %-80 % field capacity (θfc)), deficit irrigation (D: 50 %-60 % θfc) during the jointing stage of maize and wheat (DJ), and deficit irrigation during the jointing stage and filling stage of maize and wheat (DJ+F)) and 3 biochar application rates (T: 0 t ha−1 biochar, M: 15 t ha−1 biochar, and H: 30 t ha−1 biochar). The results showed that water-filled pore space (WFPS) and soil temperature were positively correlated with CO2 and N2O emission fluxes but had no significant relationship with CH4 emission flux. Decreasing irrigation and increasing biochar application led to a reduction in cumulative soil CO2 and N2O emissions, alongside an increase in CH4 absorption. The interaction between deficit irrigation and biochar application effectively reduced overall soil greenhouse gas emissions. Under high biochar application (H), deficit irrigation during the jointing stage of maize and wheat decreased the global warming potential by 15.9 %, with a minimal yield loss of only 4.86 %. These findings suggest that targeted deficit irrigation, combined with biochar application, is a promising strategy to reduce greenhouse gas emissions while minimizing crop yield losses.