Subsoil is the layer of soil located beneath the topsoil, usually consisting of a mix of clay, sand, and silt, with fewer nutrients and organic matter compared to the top layer. Subsoil plays a crucial role in supporting plant root systems, storing water, and regulating drainage. While it lacks the fertility of topsoil, subsoil can provide a stable foundation for deeper roots and helps retain moisture during dry periods. In some cases, soil amendments may be needed to improve subsoil quality for plant growth.