Residual soil NO₃-N (RSN) is susceptible to loss during the non-growing season. This 5 yr study investigated the effects of three N fertilizer sources [ammonium nitrate (AN), ammonium sulfate (AS), and polymer-coated urea (PCU)] applied at four rates (60, 120, 200, and 280 kg N ha^-1) plus an unfertilized control on RSN following potato production and on overwinter NO₃-N changes in an irrigated sandy soil in Quebec, Canada. Composite soil samples were collected at the 0–15, 15–30, 30–60, and 60–90 cm depths immediately after potato harvest in fall and again in the following spring from 2008 to 2012. Residual soil NO₃-N content within the 0–30 cm depth (RSN_0–30) was highly correlated with the RSN content in the 0–90 cm depth (RSN_0–90), indicating that RSN_0–30 can be used as an indicator of soil profile NO₃-N accumulation. Overall, RSN_0–90 increased with fertilizer N application rate, particularly for above the minimum fertilizer N rate required to maximize yield (N_max), and was generally higher for years with greater pre-plant soil NO₃-N. The split application of AN and AS resulted in lower RSN_0–90 than the single application of PCU at above N_max. Overwinter losses of soil NO₃-N were generally increased with increasing RSN_0–90 in fall. The results suggest that reducing the fertilizer N rate is more important than the choice of N source in managing RSN.