In United States agricultural policy, Highly erodible land (HEL) refers to land that is very susceptible to erosion, including fields that have at least 1/3 or 50 acres (200,000 m2) of soils with a natural erosion potential of at least 8 times their T value.[1] About 101 million acres (410,000 km2) of cropland meet this definition of HEL, according to the 1997 National Resources Inventory.[2] Farms cropping highly erodible land and under production flexibility contracts must be in compliance with a conservation plan that protects this cropland.[3]