What is soil made from?


Quick Answer

According to Boundless, soil is a mix of varying amounts of inorganic matter, organic matter, water and air. The components in soil provide nutrients for plant uptake and can fluctuate on a daily basis, depending on water supply, cultivation practices and soil type.

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Full Answer

According to the University of Hawaii, typical soil consists of approximately 45 percent mineral, 5 percent organic matter, 20 to 30 percent water and 20 to 30 percent air. The ratio of air and water in the pore spaces often changes seasonally depending on the amount of precipitation and groundwater discharge. The mineral, or inorganic, portion of the soil consists of three particle-size classes: sand, silt and clay.

According to National Oceanic and Atmospheric Administration, sand, silt and clay are less than 2 millimeters in diameter. These particles are collectively referred to as the fine earth fraction soil, whereas larger particles, such as pebbles, cobbles and boulders, are referred to as rock fragments. The organic matter in the soil consists of a complex mixture of substances with varying chemical contents. The elemental composition of organic matter includes carbon, oxygen, hydrogen, nitrogen, phosphorus and sulfur. According to Boundless, the organic material of soil, called humus, is also made up of microorganisms and dead animals and plants in varying stages of decay.

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