Soil

Soil scientists restrict the word 'soil' to the surface material which, over a long period of time, has come to have distinct layers or horizons. A soil has certain distinctive physical, chemical and biological qualities, which permit it to support plant growth and which differentiate it from the infertile substratum lying below. While soil is composed of poth mineral and organic particles, the underlying layers may usually be composed of mineral material.

Soil is a dynamic layer-a changing and developing body-as many complex chemical, physical and biological activities continue constantly in it Soils become adjusted to conditions of climate, landform and vegetation and change internally when the controlling conditions change.

The scientific study of the characteristics, development and distribution of soils is called pedology; the process of soil formation is known as pedogenesis.