Xing, Z., Chow, L., Rees, H. W., Meng, F., Monteith, J. and Stevens, L. 2011. A comparison of effects of one-pass and conventional potato hilling on water runoff and soil erosion under simulated rainfall. Can. J. Soil Sci. 91: 279-290. Hilling plays an important role in potato production, but is found to be inducing soil loss. An artificial rainfall simulation system was used to evaluate the differences between one-pass hilling (OPH, hilling performed when planting, or shortly after planting) and conventional hilling (CH, hilling performed approximately 35-45 d after planting) as well as their combination with a cover crop (ryegrass; _R) on runoff and soil loss. A three-replicate randomized block experimental design with constant rainfall intensity (120 mm h^-1) was used in this study. No significant differences in runoff were found between different hilling methods. The soil losses, however, showed significant differences both among treatments, among canopy cover classes, and among their interaction terms (all P<0.001). The mean soil loss for CH was significantly higher than that for OPH, by 40%, and the mean soil loss for CH_R was higher than that for OPH_R by 57%. On average, the CH treatments (CH and CH_R) induced greater soil loss than the OPH treatments (OPH and OPH_R) by 47%. Further, the effects can vary with different canopy cover percentages. The OPH treatments (OPH and OPH_R) induced more soil loss than CH treatments (CH and CH_R), by 4.4 to 12.8%, in the <30% canopy cover group, while soil loss in the CH treatments was greater than that in OPH treatments for both the 30-70% and >70% canopy cover groups by 21-94%. Irrespective of treatment, soil loss before canopy forming was 2.4 to 8.9 times higher than the soil loss for the partial to full canopy period. With a cover crop, the CH and OPH treatments can reduce soil loss by 37-55%. One-pass hilling initiated runoff earlier than CH. The water runoff and soil loss with respect to the elapsed time since initialization of water runoff and soil loss could be modeled by a three-parameter Sigmoid function with r²≥0.94. The information generated from this study could be used in landscape modeling to study the impacts of potato production on soil and stream water quality.