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Soil erosion is the loss of soil by transport in water or wind, and is one of the major types of soil degradation. The effects of erosion are also quite visible either on fields as topsoil loss, in fields and landscapes as rill erosion or formation of gullies, or at the landscape level as sedimentation of soil in water bodies. The impacts of soil erosion affect soil processes including loss of topsoil and reduced soil depth and rooting zone; loss of nutrients, soil organic matter, and biota in the topsoil; and contamination of water resources with nutrients, agrochemicals, and soil. All combined, these changes may affect the primary productivity of ecosystems depending on the soil type, climate, and soil management practices put into place.
Conversion of soils from natural systems to agriculture removes the vegetative cover of soils. In addition, the level of organic inputs that are returned to the soil are reduced. This results in declines in SOM, soil aggregate stability, increases in bulk densities, and compaction. These degradation processes result in reduced water infiltration and increased water runoff and soil erosion. The major reason that sets off this series of processes is that removal of the vegetative cover exposes the soil surface to rainfall impacts and wind. If the soil is also tilled, the soil structure is further disrupted, exposing more of the soil to rainfall and higher temperatures and leading to further loss in aggregate stability, soil organic matter, and infiltration rates which translate to more runoff and erosion.