Soil erosion is the carrying away of soil thru the free movement of water over the surface of the land. If all the rain falling on the soil were absorbed, erosion could not occur. But the precipitation is sometimes so rapid and so great and such a small portion is taken up by the soil, that many cultivated fields are subject to extensive losses by the washing action of water. Bare bluffs and hillsides are particularly in danger of erosion and gullies formed in such locations may extend for miles and render large areas partially or wholly unfit for cultivation.

Loess soils are apt to be injured by erosion when the topography is hilly or rough and it is these soils which are affected to the greatest extent in Iowa. Large acreages in the Missouri loess, the Mississippi loess and the Southern Iowa loess soil areas are frequently rendered untillable or even entirely useless because of excessive erosion. The adoption of proper methods of preventing or controlling the washing away of valuable land is therefore important.