Water Erosion

Water erosion is one of the most significant agricultural problems throughout the world. This erosion occurs due to the energy of water as it falls toward the earth and flows over the surface. Almost any area where crops are grown and food is produced has to deal with this problem. It was estimated in the early 1970s that as much as 4 billion Mg (metric tons) of soil were lost in the United States to the water erosion processes of detachment, transport and deposition each year. That number is somewhat less today, however, due to government conservation programs.

The main variables affecting water erosion are precipitation and surface runoff. Raindrops, the most common form of precipitation, can be very destructive when they strike bare soil. With impacts of over 20 mph, raindrops splash grains of soil into the air and wash out seeds. Overland flow, or surface runoff, then carries away the detached soil, and may detach additional soils and then sediment can be deposited elsewhere.

Sheet and interrill erosion are mainly caused by rainfall. However, some of the more severe erosion problems such as rill erosion, channel erosion, and gully erosion all result from concentrated overland flow. Other types of erosion by water include landslides.

One of the best ways to control interrill and rill erosion is through proper management of crop residues. The stems, leaves, and stalks from previously harvested crops can protect the soil surface from raindrop impact and detachment, as well as help to reduce soil surface sealing and maintain water infiltration. Crop residues also act as flow barriers in rill channels, slowing the water flow and reducing the erosive potential of the runoff. Proper management of soil roughness through properly-timed tillage operations can also help to reduce sheet and rill erosion by forming roughness elements that act as miniature reservoirs to trap any detached sediment. The combination of residue and soil roughness management is generally known as conservation tillage.

Other water erosion control practices

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