Which soil constituents move downward to produce the B horizon of a soil?

Soil is divided into different layers called horizons. These horizons are labeled O, A, B, and C. The O and A horizons make up the surface layers, where organic matter accumulates. The B horizon is a subsoil layer, which is typically characterized by one or more of these structures: clay, organic matter, iron, aluminum, and/or soluble salts. The C horizon is the parent material that underlies all other horizons.

The process by which soil constituents move downward through the soil profile is called "leaching" or "eluviation." Water transports dissolved and suspended materials downward, leading to the deposition of these materials in the lower soil layers. Leaching enables the transport and accumulation of certain constituents in the B horizon.

The following soil constituents are commonly found to move downward and accumulate in the B horizon of a soil: 1. Clay - Small particles of weathered rock and minerals that get redistributed from A horizon to the B horizon. 2. Organic matter - Decomposed plant and animal residues which are moved through eluviation process. 3. Iron - Water-soluble ions that are transported to the B horizon, where they precipitate and form iron oxide or hydroxide minerals. 4. Aluminum - Similar to iron, soluble aluminum ions move downward and accumulate as aluminum oxide or hydroxide minerals in the B horizon. In summary, clay, organic matter, iron, and aluminum are among the soil constituents that move downward through the soil profile, eventually forming the B horizon.