Objectives To clarify the characteristics of nitrogen flux balance, nitrogen fertilizer use efficiency, and nitrogen loss thresholds (maximum environmentally permissible emissions) in maize fields of the Qingtongxia Irrigation District, Ningxia, and to establish a corresponding management system.

Methods This study focused on the maize field system in the Qingtongxia Irrigation District, Ningxia, using statistical data from 2018 and 2023. The NUFER (Nutrient flows in Food Chain, Environment and Resources use) model was applied to assess nitrogen flow balance, and scenario simulations were conducted to identify the potential for nitrogen fertilizer reduction.

Results Total nitrogen input in maize fields across the irrigation district increased from 47,800 t in 2018 to 65,000 t in 2023 (a 35.98% increase), primarily due to a cropland expansion of 17,100 hectares. Concurrently, environmental nitrogen emissions rose from 8,900 t (18.70% of input) to 12,100 t (18.55% of input), a 34.69% growth, with ammonia volatilization as the dominant pathway (56.98%), followed by leaching (26.54%) and runoff/erosion (9.99%). County-level nitrogen fertilizer use efficiency improved from 35.78% to 40.95% (5.17% gain) during this period. Notably, in Jinfeng District, ammonia volatilization risk decreased from 208% above the thresholds (high risk in 2018) to low risk in 2023 through fertilizer reduction, while leaching risk was effectively controlled- by 2023, only Xixia District remained at low risk, and all other counties achieving risk-free status. Scenario analysis demonstrated that balanced fertilization combined with enhanced-efficiency fertilizers (S2) strategy outperformed alternatives: compared to mere nitrogen reduction (S1), it increased fertilizer reduction potential by 5.19%−8.42%, boosted use efficiency by 4.80%−5.14%, and slashed environmental emissions by 44.13% (all below thresholds); compared with the 2023 baseline (S0), it reduced emissions by 52.50% while elevating use efficiency and reduction potential by 4.96% and 4.81% on average, respectively.

Conclusions Integrating balanced fertilization with novel fertilizers, combined with water-saving engineering measures, collectively reduces all forms of nitrogen emissions below environmental thresholds in the irrigation district.