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Feb 17, 2023 · Each of these layers is called a soil horizon, and when these layers are arranged sequentially one above the other, it forms the soil profile. In other words, the soil profile is the vertical section of the soil exposed by a soil pit.
An A horizon is a mineral horizon meaning it contains ≤ 17% organic C (about 30% organic matter) by weight. It forms at or near the surface in the zone of leaching or eluviation of materials in solution or suspension, or of maximum in situ accumulation of organic matter or both.
A chemical compound in which a molecule (in soils usually an organic acid) wraps around and bonds to a polyvalent metal cation (eg ferric or aluminium ions). Chelation can increase the solubility of ions like aluminium and iron in soils.
Most soils have three major horizons (A, B, C) and some have an organic horizon (O). The horizons are: O (humus or organic): Mostly organic matter such as decomposing leaves. The O horizon is thin in some soils, thick in others, and not present at all in others. A (topsoil): Mostly minerals from parent material with organic matter incorporated.
describing a subsoil horizon that has both an accumulation of organic matter and an illuvial accumulation of silicate clays. This is an example of a horizon with both properties of an A and a
Each horizon is the result of a number of geological, chemical, and biological processes that have been in progress for over thousands of years. If you look carefully, you will see that the soil horizons are best formed and delineated from each other in older soils.
Plants absorb nutrients out from the upper layers of soil, changing the soil chemistry and possibly colour, depending on the nutrients remaining. Chemical Acidic solutions in the water can react with minerals and rocks, altering the appearance, texture, and chemistry of that horizon.
