Atrazine was used to control Japanese brome in conjunction with nitrogen fertilization to determine if herbage production could be increased more than by fertilization alone. Atrazine treatments included a single application, application in alternate years, and application for two or three consecutive years. Atrazine did not significantly increase production more than fertilizer alone and caused some decreases in western wheatgrass production at low rates of N in one year at one location. Unless atrazine was applied in two or more years, Japanese brome was a prevalent the second growing season after application as where it had never been controlled. Application of atrazine in consecutive years increased shortgrass production at one location. Japanese brome (Bromus japonicus) is an introduced annual from Eurasia. A winter annual, it is similar to downy brome (II. tectorum) but becomes more abundant than downy brome as soil moisture supplies increase (Hulbert 1955). Both species occur in South Dakota, but Japanese brome is more abundant on rangeland. Japanese brome is a newcomer to parts of South Dakota. In western South Dakota, Lewis et al. (1975) observed Japanese brome in one small area of their research pastures in 195 1. By 1955
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