The primary function of the severance layer of soil, also known as the E horizon, is to facilitate the process of leaching. This layer is typically located beneath the topsoil (A horizon) and above the subsoil (B horizon) in a soil profile. It is characterized by the loss of minerals and organic matter, leading to its lighter color and lower fertility compared to the layers above it. The severance layer plays a crucial role in soil formation and the movement of nutrients and water. It helps regulate the flow of water and minerals through the soil profile, impacting plant growth.