Soil
Soil is a natural body consisting of layers (soil horizons) that are primarily composed of minerals which differ from their parent materials in their texture, structure, consistency, colour, chemical, biological and other characteristics. It is the unconsolidated or loose covering of fine rock particles that covers the surface of the earth. Soil is the end product of the influence of the climate (temperature, precipitation), relief (slope), organisms (flora and fauna), parent materials (original minerals), and time. In engineering, soil is referred to as regolith, or loose rock material: this is the 'drift deposit' lying on top of the 'solid geology'. However, in horticulture, the term 'soil' is defined as the humic layer of topsoil, or the depth of regolith containing organic material that influences and has been influenced by plant roots and may range in depth from centimetres to many metres. Expressions such as lunar soil or Martian soil are commonly used for extraterrestrial regolith, even though there is no known biological component.
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Famous quotes containing the word soil:
“Forever float that standard sheet!
Where breathes the foe but falls before us,
With Freedom’s soil beneath our feet,
And Freedom’s banner streaming o’er us!”
—Joseph Rodman Drake (1795–1820)
“An underground grower, blind and a common brown;
Got a misshapen look, it’s nudged where it could;
Simple as soil yet crowded as earth with all.”
—Richard Wilbur (b. 1921)
“The constant abrasion and decay of our lives makes the soil of our future growth.”
—Henry David Thoreau (1817–1862)