Soil is a mixture of minerals, organic matter, gases, liquids, and countless organisms that together support life on Earth. Soil is a natural body called the pedosphere which has four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of Earth's atmosphere; it is a habitat for organisms; all of which, in turn, modify the soil.
- Miller, Austin (1953). The Skin of the Earth (1st ed.). London, United Kingdom: Methuen. https://ia902705.us.archive.org/26/items/skinoftheearth032705mbp/skinoftheearth032705mbp.pdf. Retrieved 11 June 2017.
- Chesworth, Ward (2008). Encyclopedia of soil science. Dordrecht, The Netherlands: Springer. ISBN 978-1402039942. http://data.lib.hutech.edu.vn/mucluc/f2e0a00788a82be82718e64d734d1a50.pdf. Retrieved 11 June 2017.