ABSTRACT
Subsoil is the stratum of soil immediately below the surface soil or topsoil and can be naturally occurring or manufactured. Like topsoil, it is composed of a variable mixture of small particles such as sand, silt, and clay, but with a much lower percentage of organic matter and humus, and the macroscopic and microscopic organisms that make the topsoil rich with organic matter spend little time in the subsoil layer. Subsoil performs many vital functions in landscaping, including drainage, water storage, and providing anchorage for trees and shrubs. Although subsoil is much less fertile than topsoil, it can be amended to increase its plant-growing capacities. British Standard BS 8601:2013 Specification for subsoil and requirements for use provides guidance as to the structure, composition, and treatment of subsoil. In creation of landscaping schemes, the treatment of the subsoil is often overlooked, but it is as equally important to the survival and performance of trees, shrubs, grass, and other plants as topsoil.
