Soil Conservation - History, How Soil Erodes, Soil Conservation Methods, Barrier Approaches, Cover Approaches

Soil conservation refers to maintaining the productivity of agricultural land by control of the erosion of soil by wind or water. Soil conservation practices use the land according to its needs and capabilities.

Erosion is any process by which soil is transported from one place to another. At naturally occurring rates, land typically loses about one inch (2.5 cm) of topsoil in 100-250 years. A tolerable rate of soil erosion is considered to be 48-80 lb of soil per acre (55-91 kg per hectare) each year. Natural weathering processes that produce soil from rock can replace soil at about this rate. However, cultivation, construction, and other human activities have greatly increased the rate of soil erosion in most regions. Some areas of North America are losing as much as 18 tons of soil per acre (40 tonnes per hectare) per year.

Soil erosion not only results in the loss of soil particles, but also organic matter and nutrients. The first 7-8 in (18-20 cm) of soil is the surface layer (topsoil) that provides most of the nutrients needed by plants. Because most erosion occurs from the surface of the soil, this vital layer is the most susceptible to being lost. The fertilizers and pesticides in some eroded soils may also pollute rivers and lakes. Eroded soil damages dams and culverts, fisheries, and reservoirs when it accumulates in those structures as sediment (this is known as sedimentation).