Soil

Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. The outer body of soil, called the pedosphere, has four important functions:

as a medium for plant growth

as a means of water storage, supply and purification

as a modifier of atmosphere

as a habitat for organisms

All of these functions, in their turn, modify the soil and its properties.

Soil consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). Accordingly, soil scientists can envisage soils as a three-state system of solids, liquids, and gases.

Soil is also commonly referred to as dirt; some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil.