Subsurface, layer (stratum) of soil immediately below the topsoil, consisting predominantly of minerals and leached materials such as iron and aluminum compounds. The remains of humus and clay accumulate in the subsoil, but the macroscopic and microscopic microorganisms that make the soil rich with organic matter spend little time in the subsoil layer. Beneath the subsoil is a partially disintegrated layer of rock, and the underlying rock. Clearing the topsoil while clearing the land for crop growth or commercial development exposes the subsoil and increases the rate of erosion of soil minerals.
Residing below the topsoil, the subsoil does not have high concentrations of organic matter, but offers rich minerals for the search for root systems. Varying in colors like red and yellow, this hidden layer of soil is directly affected by the movement of water. Minerals from the top layer of the soil find their way down into the subsoil through runoff from the water; clays are also concentrated under the fertile topsoil. As a result, mineral deficiencies in the topsoil force roots to dig deeper into nutrients while allowing them to settle deeper into the soil structure.
Soil is the first link in the food chain for terrestrial animals; growing plants nurture herbivores and omnivores with nutrient-rich fruits, roots, and foliage. The soil is not a lifeless mound of soil that supports plant roots, however. In fact, every square centimeter contains some form of life, mineral or vitamin, for healthy plant growth. Soil layers, such as topsoil, subsoil, and bedrock, provide distinct habitats for continually recycling this important resource.
