Horizon A is known for its rich organic material. What is it commonly referred to as?

Horizon A is commonly referred to as the humus layer because it is characterized by a high concentration of organic material, which is essential for soil fertility. This layer typically contains decomposed leaves, plants, and microorganisms that contribute to its nutrient-rich composition. The presence of these organic materials enhances soil structure, water retention, and supports diverse biological activity, making it a critical component for plant growth. The rich organic content is what distinguishes this horizon from others, such as subsoil, which is generally less rich in organic matter, or parent material, which is the underlying rock or sediment from which the soil develops. The term 'leached horizon' typically refers to a layer from which minerals and nutrients have been washed away, contrasting with the nutrient-rich conditions found in Horizon A.