Widespread resistance to selective postemergence herbicides has led to increased use of preemergence herbicides to control rigid ryegrass (Lolium rigidum Gaudin), the major weed of southern Australian cropping systems. Seeds of L. rigidum are dormant at maturity, leading to staggered germination across the growing season and avoidance of pre-sowing knockdown herbicides by the later-germinating cohorts. Although it is well known that this selects for higher seed dormancy in intensively cropped areas, there is less information on whether dormant seeds respond differently to preemergence herbicides applied at sowing. To address this, seeds of field-collected L. rigidum populations were divided into dormant and nondormant (afterripened) subsamples and treated with sublethal rates of three preemergence herbicides in order to monitor seedling emergence and seed persistence over 6 mo. The presence of prosulfocarb and pyroxasulfone eliminated the nearly 4-fold increase in seedling emergence that typically results from afterripening, while trifluralin was partially inhibitory. In all treatments, the proportion of viable seeds remaining in the soil after 6 mo was negligible (≤3% of the viable seeds originally sown) for both the dormant and nondormant seeds. Application of radiolabeled herbicides to soil and seeds showed that the herbicides persisted in the seed tissue for longer than in the bulk soil. Therefore, the presence of dormant L. rigidum seeds in the soil seedbank is unlikely to result in cohorts that can avoid preemergence herbicides.