宁夏青铜峡灌区县域尺度玉米田氮素投入及损失风险评价OA

[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]From 2018 to 2023,total nitrogen input in maize fields across the irrigation district increased from 47800 t in 2018 to 65000 t in 2023,an increase of 35.83%,primarily due to a cropland expansion of 17100 hectares.Concurrently,environmental nitrogen emissions rose from 8900 t(18.70%of input)to 12100 t(18.55%of input),a 34.69%growth,with ammonia volatilization as the dominant pathway(accounting for 56.98%of total environmental emissions),followed by leaching(accounting for 26.54%of total environmental emissions)and runoff/erosion(accounting for 9.99%of total environmental emissions).The nitrogen fertilizer use efficiency in the irrigation district reached 42.92%in 2023,an increase of 5.72 percentage points compared with 2018.Notably,in Jinfeng District,ammonia volatilization risk decreased from 208%above the threshold(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 achieved risk-free status.Balanced fertilization combined with enhanced-efficiency fertilizers(S2)was identified as the optimal strategy.Compared with nitrogen reduction alone(S1),S2 increased nitrogen fertilizer reduction potential by 5.19-8.42 percentage points,improved use efficiency by 4.80-5.14 percentage points,reduced total environmental emissions by 44.13%(with all loss pathways below thresholds),and decreased environmental emissions by 52.50%while increasing nitrogen fertilizer use efficiency by 12.45 percentage points,compared with the 2023 baseline(S0).[Conclusions]Integrating balanced fertilization with enhanced efficiency fertilizers,together with water saving engineering measures,can reduce all forms of nitrogen emissions below environmental thresholds in the Qingtongxia Irrigation District,representing a key technological pathway for achieving regional agricultural green development and nitrogen emission mitigation.