Residual herbicides are those that continue to control weeds for some time after application. Residual herbicides extend the period of weed control, increasing the efficiency of weed management efforts. However, they may persist longer than desired and injure or kill subsequent rotational crops. Herbicide persistence, or the length of time a herbicide remains in the soil, varies greatly with climatic conditions, soil type, and cultural practices. Find out more about herbicide risk and persistence with this detailed fact sheet (10 pages).