Soil is essential for life on this planet by storing water and nutrients, providing habitats, and taking up and releasing gases (such as oxygen and greenhouse gases). In light of World Soil Day on December 5, first designated in 2014 to focus on the importance of healthy soil and sustainable management of soil resources by the UN General Assembly, below are some facts on this life-giving substance that covers 25% of the Earth.
Ideal soil is said to be 50% pore space (for water and air), 5% organic matter (organisms, sugars, and plant matter), and 45% minerals (such as sand, silt, and clay).
Soil is considered a renewable resource but with an extremely slow formation rate—one inch of topsoil can take hundreds to over a thousand years to form depending on the region.
Soil is categorized into six horizons (layers) given by a single letter: O, A, E, B, C, and R. For simplicity, “O” is the organic layer (with humus), “A” is topsoil, and “R” is bedrock.
Earthworms are beneficial to soil by increasing its porosity (for water), excreting materials with beneficial microbes, and consuming dry matter and mixing it with the soil.
The US Department of Agriculture has a Soil Textural Triangle to help determine the type of soil based on percentage of clay, silt, and sand found once separated. For example, soil that is 30% sand, 35% clay, and 35% silt is clay loam.
To raise awareness about the importance of creating and maintaining healthy soil, the UN Food and Agriculture Organization (FAO) established World Soil Day in 2014.
According to the FAO, “33% of the Earth’s soils are already degraded and over 90% could become degraded by 2050.”
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