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Soil types by clay, silt and sand composition as used by the United States Department of Agriculture. Loam (in geology and soil science) is soil composed mostly of sand (particle size > 63 micrometres (0.0025 in)), silt (particle size > 2 micrometres (7.9 × 10 −5 in)), and a smaller amount of clay (particle size < 2 micrometres (7.9 × 10 −5 in)).
Dark soil color imparted by organic matter in Illinois, US. Dark brown or black colors typically indicate that the soil has a high organic matter content. [4] Organic matter coats mineral soil particles, which masks or darkens the natural mineral colors. [1] Sodium content also influences the depth of organic matter and therefore the soil color.
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.
A fourth term, loam, is used to describe equal properties of sand, silt, and clay in a soil sample, and lends to the naming of even more classifications, e.g. "clay loam" or "silt loam". Determining soil texture is often aided with the use of a soil texture triangle plot. [5] An example of a soil triangle is found on the right side of the page.
A study of a single winter rye plant grown for four months in one cubic foot (0.0283 cubic meters) of loam soil showed that the plant developed 13,800,000 roots, a total of 620 km in length with 237 square meters in surface area; and 14 billion root hairs of 10,620 km total length and 400 square meters total area; for a total surface area of ...
Each plant species achieves maximum growth in a particular pH range, yet the vast majority of edible plants can grow in soil pH between 5.0 and 7.5. Soil scientists use a soil classification system to describe soil qualities. The International Union of Soil Sciences endorses the World Reference Base as the international standard. [2]
The table below displays the deal bulk densities that both allow and restrict root growth for the three main texture classifications. The porosity of a soil is an important factor that determines the amount of water a soil can hold, how much air it can hold, and subsequently how well plant roots can grow within the soil. [14] Soil porosity is ...
Soil bulk density, when determined at standardized moisture conditions, is an estimate of soil compaction. [3] Soil porosity consists of the void part of the soil volume and is occupied by gases or water. Soil consistency is the ability of soil materials to stick together. Soil temperature and colour are self-defining.