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  2. USDA soil taxonomy - Wikipedia

    en.wikipedia.org/wiki/USDA_soil_taxonomy

    The soil moisture regime, often reflective of climatic factors, is a major determinant of the productivity of terrestrial ecosystems, including agricultural systems. The soil moisture regimes are defined based on the levels of the groundwater table and the amounts of soil water available to plants during a given year in a particular region.

  3. Topsoil - Wikipedia

    en.wikipedia.org/wiki/Topsoil

    Topsoil is composed of mineral particles and organic matter and usually extends to a depth of 5-10 inches (13–25 cm). Together these make a substrate capable of holding water and air which encourages biological activity. There are generally a high concentration of roots in topsoil since this is where plants obtain most of their vital nutrients.

  4. World Reference Base for Soil Resources - Wikipedia

    en.wikipedia.org/wiki/World_Reference_Base_for...

    In the topsoil, we find 20% clay, 10% sand, and 70% silt; in the subsoil, 35% clay, 8% sand, and 57% silt. Organic matter concentrations in the topsoil are intermediate. The naming of the soil consists of four steps. [1] Question 1: Does the soil have diagnostic horizons, properties and materials? The soil has the following diagnostics:

  5. Soil organic matter - Wikipedia

    en.wikipedia.org/wiki/Soil_organic_matter

    The dry matter consists mainly of carbon, oxygen, and hydrogen. Although these three elements make up about 92% of the dry weight of the organic matter in the soil, other elements present are essential for the nutrition of plants, including nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, and many micronutrients. [1]

  6. Soil in the United States - Wikipedia

    en.wikipedia.org/wiki/Soil_in_the_United_States

    Plant nutrients are also released from soil organic matter by decomposition, and organic matter is particularly significant as the major form in which soil nitrogen is stored. Organic matter contributes to aggregation and water-retention properties of soil. Soil chemical composition reflects not only the original geologic materials (e.g ...

  7. Physical properties of soil - Wikipedia

    en.wikipedia.org/wiki/Physical_properties_of_soil

    When the organic component of a soil is substantial, the soil is called organic soil rather than mineral soil. A soil is called organic if: Mineral fraction is 0% clay and organic matter is 20% or more; Mineral fraction is 0% to 50% clay and organic matter is between 20% and 30%; Mineral fraction is 50% or more clay and organic matter 30% or ...