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Soil consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). [ 1 ] [ 2 ] Accordingly, soil is a three- state system of solids, liquids, and gases. [ 3 ]
Clay is a type of fine-grained natural soil material containing clay minerals [1] (hydrous aluminium phyllosilicates, e.g. kaolinite, Al 2 Si 2 O 5 4). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide .
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.
For example, a sandy loam soil with 20% gravel would be called gravelly sandy loam. 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
For example, biological soil crusts are more dominated by green algae on more acidic and less salty soils, whereas cyanobacteria are more favored on alkaline and haline soils. Within a climate zone, the abundance of lichens and mosses in biological soil crusts generally increases with increasing clay and silt content and decreasing sand. Also ...
Soil structure refers to the size, shape and arrangement of solid particles in soil. [15] Factors such as climate, vegetation and organisms influence the complex arrangement of particles in the soil [16] Structural features of the soil include microporosity and pore size which are also affected by minerals and soil organic matter. [17]
Soil texture is the analysis and classification of the particle size distribution in soil. The relative amounts of sand, silt, and clay particles determine a soil's texture, which affects the appearance, feel and chemical properties of the soil. [12] Soil texture-by-feel method
The use of soil tests, coupled with the corresponding provisions, can alleviate issues of nutrition and irrigation that can result from non porous Ultisol. [4] Soil tests help indicate the pH, and red clay soil typically has a low pH. [5] The addition of lime is used to help to increase the pH in soil and can help increase the pH in Ultisol as ...