Soltani, N., Robinson, D. E, Miller, R. T. and Sikkema, P. H. 2015. Length of residual activity of saflufenacil/dimethenamid-p in soybean (Glycine max). Can. J. Plant Sci. 95: 727-733. A total of six field studies were conducted over a 2-yr period (2009, 2010) at three Ontario locations to determine the length of residual activity of saflufenacil/dimethenamid-p applied preemergence (PRE) for the control of annual weeds in soybean. As the rate of saflufenacil/dimethenamid-p increased from 0 to 980 g a.i. ha^-1 the maximum cumulative emergence percentage for common lambsquarters, redroot pigweed and common ragweed decreased. Additionally, as the saflufenacil/dimethenamid-p rate increased from 0 to 980 g a.i. ha^-1, the cumulative emergence of common lambsquarters, redroot pigweed and common ragweed slowed down over time. Times to 10% emergence were 1.0, 1.0, 2.1, 3.2, 3.9, 6.6 and >12 wk for common lambsquarters, 1.4, 1.6, 1.8, 2.6, 4.3, >12 and >12 wk for redroot pigweed and 0.8, 1.0, 2.2, 2.7, 3, >12 and >12 wk for common ragweed with saflufenacil/dimethenamid-p applied at 0, 30.625, 61.25, 122.5, 245, 490 and 980 g a.i. ha^-1, respectively. Based on these results, saflufenacil/dimethenamid-p applied PRE at the labelled use rate of 245 g a.i. ha^-1 can provide as much as 3.9, 4.3 and 3wk of effective control of common lambsquarters, redroot pigweed and common ragweed, respectively in soybean.