Podsol

Podsol (also spelled Podzol, or known as Spodosol) is the typical soil of coniferous, or Boreal forests. The name is Russian for ash soil (due to the appearance of the E horizon), and it is found in areas that are wet and cold (for example in Northern Ontario or Russia).

The bleached soil, which is usually 4–8 cm thick, is low in iron and lime, and is formed under moist and cool conditions. It is found under a layer of organic material in the process of decomposition, which is usually 5–10 cm thick. In the middle, there is often a thin layer of 0.5 to 1 cm. The bleached soil goes over into a red or redbrown horizon called rusty soil. The colour is strongest in the upper part, and change at a depth of 50 to 100 cm progressively to the part of the soil that is mainly not affected by processes; that is the parent material. The soil profiles are designated the letters A (transitional layer with organic matter), E (bleached soil), B (rusty soil) and C (parent material).

In podzols, translocation has meant the leaching out from the A horizon of clays, humic acids, iron, and alluvial compounds. These constituents may then accumulate to form a hardpan or iron band. Podzolization occurs when severe leaching leaves the upper horizon virtually depleted of all soil constituents except quartz grains. Clay minerals in the A horizon decompose by reaction with humic acids and form soluble salts. The leached material from the A horizon is deposited in the B horizon as a humus-rich horizon band or as a hard layer of sesquioxides.