Nature of Soil
The soil is a natural body embracing not only the topsoil, but also the subsoil and other layers above its parent rock. It is a product of its environment – of the rock waste which is its parent material, of the climate under which it weathers, of the kind of topography upon which it is situated, of the vegetation and other organisms with which it develops, and of the length of time during which it has been developing.
From the standpoint of land use the soil is regarded as a medium of plant growth, but it is not a passive medium. It is an active body comprising not only mineral and organic constituents, but also the soil processes that are continually going on, as well as soil temperature and moisture regimes that keep these processes operating. The dynamic or active soil, as defined in this way, correlates well with the kinds and distribution of soil organisms, with plant growth, with land capability, and with land use.