Tutorial:Soil Calcification


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[edit] Calcification and Salinisation

Unlike eluviation, podzolisation and leaching processes, which involve the net down profile movement of soil components, calcification and salinization involve the upwards movement of soluble salts in the soil water.

Calcification tends to occur in semi-arid and arid area, where evapotranspiration exceeds rainfall. Seasonal percolation of water down through the profile takes soluble salts down to the lower horizons, but isn’t sufficient to totally leach them out of the profile. This is augmented by some upward capillary movement of groundwater bringing with it more salts. This leads to the deposition of calcium carbonate (or in some cases gypsum) in the lower soil horizons. The calcium carbonate may precipitate throughout the soil as fine powdery crystals, or it may form discrete concretions and nodules.

Salinization occurs in arid areas where rainfall is insufficient to leach soluble salts from the soil, whilst evapotranspiration causes the capillary movement of ground waters containing soluble salts, up though the profile. This leads to increased salinity in the upper soil horizons and can lead to the formation of a salt crust.

Saline soils are toxic to many plants, hence salinization has implications for agricultural sustainability. Increasing soil salinity, for example, is thought to have been an increasing problem in Mesopotamian agriculture (ref.).

These alkaline deposits help preserve calcareous materials such as shell and bone, but are not good for the preservation of ecofacts such as pollen. Pottery and other ecofacts may be affected by the formation of salt and calcareous compounds on their surface.

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