This study investigated the effects of nitrogen reduction and controlled-release nitrogen fertilizer on soil nitrogen dynamics in continuous cropping of potato under rainfed conditions in the mountainous areas of southern Ningxia.Field experiments were conducted with three treatments:conventional farmer fertilization(CON)，14%N reduction(KF)，and an optimized integrated fertilization(BMP，28%N reduction combined with controlled-release fertilizer).Soil sampling，laboratory analysis，and biostatistical methods were employed to evaluate the impact of these nitrogen management practices on soil nitrogen accumulation and temporal dynamics in the potato monoculture system.The results demonstrated that compared to CON，both KF and BMP treatments significantly reduced nitrate-nitrogen accumulation in the 0-100 cm soil layer.Post-harvest nitrate-nitrogen accumulation decreased by 20.93%-32.67%，19.06%-31.75% and 15.77%-33.34% in 2018，2019 and 2021，respectively.BMP treatment further reduced nitrate-nitrogen by 20.86%，18.74% and 20.86%，compared to KF treatment.Nitrate-nitrogen accumulation was significantly higher during the flowering stage than at harvest，while ammonium-nitrogen levels showed no significant variation.However，neither nitrogen reduction nor controlled-release fertilizer exhibited significant correlations with potato yield，nutrient uptake，or partial factor productivity.Based on these findings，reducing nitrogen application by 14%(N 180 kg/hm²)or 28%(N 150 kg/hm²，combined with controlled-release fertilizer at 515.7 kg/hm² and calcium superphosphate at 66.3 kg/hm²)in rainfed potato systems of southern Ningxia were recommend.These practices effectively mitigated soil nitrate accumulation in continuous cropping systems，reduced risks of agricultural non-point source pollution，enhanced economic returns，and were suitable for large-scale adoption in the region.