Objective The aims were to explore the synergistic effects of organic fertilizer application and appropriate irrigation strategies on soil carbon (C) emissions, crop C sequestration, and the efficiency of C emissions in farmland.

Method The field test was operated in Xingtai, Hebei, China. The test maize varieties were maize "Jinguan 220" and mung bean "Jilv 20" as experimental crops, with varying rates of organic fertilizer 0 kg ha⁻¹ (F₀), 3750 kg ha⁻¹ (F₁), 7500 kg ha⁻¹ (F₂) and irrigation quantities set according to field water capacity (θ_FC) 40%θ_FC < θ < 60%θ_FC (I₀), 60%θ_FC < θ < 80%θ_FC (I₁), 80%θ_FC < θ < 95%θ_FC (I₂). The influence of organic fertilizer and irrigation levels on soil C emission and sequestration was analyzed, along with the correlation between soil physical and chemical properties and cumulative CO₂ emissions.

Result ① Soil respiration rate initially increased, then decreased, and gradually rose with the increase of organic fertilizer and irrigation levels. ② A significant quadratic regression relationship existed between soil temperature and respiration rate (P < 0.05), with soil temperature accounting for 30.1% to 72.5% of the variance in respiration rates under different treatments. ③ Soil CO₂ emissions positively correlated with electrical conductivity, field water capacity (P < 0.05), showing a particularly strong positive correlation with organic matter (P < 0.01), while negatively correlating with pH and bulk density (P < 0.05). ④ Under various treatments, maize acted as C sink in the farmland ecosystem, with the F₁I₁ treatment yielding the highest net primary productivity and C emission efficiency.

Conclusion Considering crop yield, irrigation input, and C emission efficiency, the F₁I₁ treatment (3750 kg ha⁻¹ organic fertilizer application and 60%θ_FC < θ < 80%θ_FC irrigation level) emerged as the optimal management model for local maize/mung bean intercropping under experimental conditions.