A diesel exhaust fluid (DEF) control system includes: a target module configured to determine a target rate of injection of a DEF by a DEF injector; an adjustment module configured to determine an adjustment based on a concentration of urea in the DEF; an adjusting module configured to adjust the target rate based on the adjustment to produce an adjusted rate of injection of the DEF by the DEF injector; and an injector control module configured to control injection of the DEF by the DEF injector based on the adjusted rate.