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Soil Erosion

Erosion is the removal of soil particles by the forces of wind and water. Wind and water erosion can threaten the long-term productivity of soils through the loss of valuable, nutrient-rich topsoil. Erosion occurs naturally, but some land use practices can accelerate its rate. Soil erosion is estimated to reduce annual net profits by an average of $12 per cropped hectare. Where soils are deep enough, topsoil can be rebuilt, but only at a very slow rate (generally much slower than the rate of soil erosion).

Most soil loss due to water occurs because of high runoff events, such as heavy rainstorms. Soils are subject to water erosion throughout Alberta. Extreme rainstorms have led to serious soil loss events on farmland from Medicine Hat to Fort Vermilion. Measurements on a continuously cropped farm field near Tofield reported soil losses as high as 10 tonnes per hectare for the summer of 1996 as a result of a number of moderate rainstorms.

The Dust Bowl of the 1930s was a vivid example of wind erosion - unprotected topsoil blackened the skies, and drifted into ditches and along fence lines. The result was unproductive fields and ruined crops. Since then, the agriculture industry has made great progress in controlling and preventing wind erosion. Nonetheless, agricultural land across Alberta is still subject to periods of drought and strong winds, particularly on open prairies. During the recent drought of the 1980s, wind erosion damaged an estimated 900 000 hectares of agricultural soils in Alberta. Strong and continuous winds along with dry, bare soils contributed to serious topsoil loss. Valuable nutrients were also removed with the topsoil, reducing the soil's ability to produce crops. Factors that increase the risk of wind erosion include a sparse or absent plant cover, large fields and strong winds, and a loose, dry, smooth soil surface. Soil texture and structure also affect wind erosion risk.