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  2. Humus - Wikipedia

    en.wikipedia.org/wiki/Humus

    It is also used to describe a topsoil horizon that contains organic matter (humus type, [4] humus form, [5] or humus profile [6]). Humus has many nutrients that improve the health of soil, nitrogen being the most important. The ratio of carbon to nitrogen of humus commonly ranges between 8:1 and 15:1 with the median being about 12:1. [7]

  3. Bulk density - Wikipedia

    en.wikipedia.org/wiki/Bulk_density

    The bulk density of soil depends greatly on the mineral make up of soil and the degree of compaction. [3] The density of quartz is around 2.65 g/cm 3 but the (dry) bulk density of a mineral soil is normally about half that density, between 1.0 and 1.6 g/cm 3.

  4. Topsoil - Wikipedia

    en.wikipedia.org/wiki/Topsoil

    The United States loses almost 3 tons of topsoil per acre per year. [16] 1 inch (2.5 cm) of topsoil can take between 500 [17] and 1,000 years [18] to form naturally, making the rate of topsoil erosion a serious ecological concern. Based on 2014 trends, the world has about 60 years of topsoil left. [18] [19]

  5. 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:

  6. Unified Soil Classification System - Wikipedia

    en.wikipedia.org/wiki/Unified_Soil...

    For example, GW-GM corresponds to "well-graded gravel with silt." If the soil has more than 15% by weight retained on a #4 sieve (R #4 > 15%), there is a significant amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change. For example, SP-SM could refer to "poorly graded SAND with silt ...

  7. Soil gradation - Wikipedia

    en.wikipedia.org/wiki/Soil_Gradation

    A poorly-graded soil is a soil that does not have a good representation of all sizes of particles from the no. 4 to no. 200 sieve. A poorly-graded gravel is classified as GP, while a poorly-graded sand is classified as SP. Poorly-graded soils are more susceptible to soil liquefaction than well-graded soils. [1]

  8. Soil loss tolerance - Wikipedia

    en.wikipedia.org/wiki/Soil_loss_tolerance

    Soil loss tolerance for a specific soil, also known as the T value, which can be calculated with = + [1] formula, is the maximum average annual soil loss expressed as tons per acre per year that will permit current production levels to be maintained economically and indefinitely.

  9. Soil test - Wikipedia

    en.wikipedia.org/wiki/Soil_test

    In precision agriculture, soil samples may be geolocated using GPS technology in order to estimate the geospatial distribution of nutrients in the sampled area.The geolocated samples are collected using a distribution and resolution that allows for the estimation of the geospatial variability of the soil area where the crop will be grown.