ObjectiveTo investigate the effects of combined application of biochar and microbial fertilizer on greenhouse gas emissions and sunflower yield in saline-alkali soil under plastic film mulching and drip irrigation.MethodsField experiments were conducted in saline-alkali soil in the Hetao Irrigation Area of Inner Mongolia, with different combinations of biochar (0, 7.5, 15 t/hm²) and microbial fertilizer (0, 112.5, 225 kg/hm²). Greenhouse gas emissions were monitored using static chamber-gas chromatography method. Changes in soil physicochemical properties, global warming potential (GWP), and sunflower yield were analyzed.Results1) Compared with the control (0 t/hm² biochar+0 kg/hm² microbial fertilizer), the treatment of 7.5 t/hm² biochar+225 kg/hm² microbial fertilizer increased soil organic carbon, available phosphorus, and available potassium contents by 63.9%, 155.7%, and 46.8%, respectively. 2) Compared to the control, the treatment with 7.5 t/hm² biochar +225 kg/hm² microbial fertilizer reduced cumulative CO₂ emissions from 4 373 kg/hm² to -394.3 kg/hm², increased cumulative CH₄ emissions from -0.08 kg/hm² to 0.1 kg/hm², reduced cumulative N₂O emissions from 0.23 kg/hm² to -0.09 kg/hm², and decreased GWP from 4 438.3 kg/hm² to -417.2 kg/hm². 3) Under the treatment of 15 t/hm² biochar+225 kg/hm² microbial fertilizer, sunflower yield reached 4 137.5 kg/hm², which was increased by 39.4% compared with the control (2 968 kg/hm²). 4) Mantel test analysis revealed that sunflower yield was extremely significantly correlated with soil physicochemical properties (p < 0.01); CO₂ emissions were significantly correlated with ammonium-nitrogen content and soil moisture, N₂O emissions were significantly correlated with nitrate-nitrogen content, and CH₄ emissions were extremely significantly correlated with nitrate-nitrogen content (p < 0.05).ConclusionCombined application of biochar and microbial fertilizer can simultaneously improve saline-alkali soil, reduce greenhouse gas emissions, and increase sunflower yield, with 7.5 t/hm² biochar+225 kg/hm² microbial fertilizer being the optimal combination. This technique provides a new strategy for reducing greenhouse gas emissions in agricultural production and increasing crop yields on saline-alkali soils.