AbstractInformation is lacking on the long‐term impact of tillage systems on NO3 losses to surface and groundwater. An 11‐yr (1982–1992) study was conducted to assess NO3 losses to subsurface, tile drainage for corn (Zea mays L.) grown with continuous conventional tillage (CT) and no tillage (NT) on a poorly drained Webster clay loam soil (fine‐loamy, mixed, mesic Typic Haplaquoll) at Waseca, MN. Nitrogen was applied at an annual application rate of 200 kg ha−1. Mean annual subsurface drain flow during the 11‐yr period was 35 mm higher for NT (315 ram) compared with CT (280 mm). Flow‐weighted nitrate‐nitrogen (NO3‐N) concentrations increased dramatically in the wet years (1990 and 1991) following the dry period of 1987 to 1989. Flow‐weighted NO3‐N concentrations during the 11‐yr period averaged 13.4 and 12.0 mg L−1 for CT and NT, respectively. Although subsurface drain flow was 12% higher with NT, NO3‐N losses were about 5% higher with CT mainly due to higher NO3‐N concentrations with CT in the last 2 yr. Corn grain yields and N removal were significantly higher in 6 out of 11 yr with CT compared with NT with no difference between tillage systems in the other 5 yr. Grain yields averaged 8.6 Mg ha−1 with CT and 7.3 Mg ha−1 with NT during the 11‐yr period. Multiple regression equations showed that annual flow‐weighted NO3‐N concentration is best predicted from residual soil NO3 in the 0‐ to 1.2‐m profile and spring rainfall while NO3‐N flux can be predicted well from May and June rainfall. Results from this long‐term study indicate that on this poorly drained soil, CT had a positive effect on corn grain yield and N removal compared with NT, but tillage systems had minimal impact on NO3 losses to subsurface drain flow. Higher drain flow with NT does not necessarily result in higher NO3‐N fluxes lost via subsurface drainage.