Pedocal

A pedocal is a soil order in the USDA soil taxonomy, characterized by the accumulation of calcium carbonate (CaCO3). The name "pedocal" is derived from the Greek words "pedon" (soil) and "calx" (lime). These soils typically occur in arid and semi-arid regions where evapotranspiration exceeds precipitation, leading to upward movement of soil water and subsequent precipitation of carbonates near the surface.

Pedocals often have a light color and relatively high pH due to the presence of calcium carbonate. The horizon where the carbonate accumulation is most pronounced is called the calcic horizon, which is a diagnostic horizon used in defining pedocals. The depth of the calcic horizon varies depending on the local climate and parent material. In some cases, the accumulation can be so extensive that it forms a hardpan layer.

Vegetation associated with pedocals is generally drought-tolerant and includes grasses, shrubs, and trees adapted to dry conditions. These soils are often used for grazing and, with irrigation, can be productive for agriculture. However, the high pH and potential for calcium carbonate precipitation can limit the availability of certain nutrients to plants.

Pedocals are an important indicator of past and present climatic conditions and play a significant role in the carbon cycle by sequestering carbon in the form of calcium carbonate. They are found extensively in the western United States, as well as in other arid and semi-arid regions around the world.