| Themes > Science > Earth Sciences > Geology > Soils > Soil Morphology > Physical Properties > Textural classes |
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The principal textural classes are: Clay, sandy clay, silty clay, clay loam, sandy clay loam, silty clay loam, loam, sandy loam, silt loam, sand, loamy sand and silt. The physical properties and the chemical composition of the small and large particles differ greatly. the coarse fraction, gravel and sand which are mainly composed of rock fragments or primary minerals act as individual particles. They have low specific surface and are relatively non-reactive. They do not hold large amounts of water or nutrients. Owing to large voids between them, they transmit air and water easily. The silt particles are intermediate between sands and clays. Mineralogically, the particles of silt are similiar to those of sand, as they are largely composed of primary minerals. They are more reactive than sands because of the higher specific surface. The clay fraction controls of the important properties of the soils. They are chiefly composed of secondary minerals--crystalline alumino silicates. They have high specific surface and are most reactive. They have high capacity to retain water and nutrients. The textural classes differ
not only in the particle size analysis, but also in their bearing on some
of the important factors affecting plant growth, such as Sandy soils are very permeable and well drained but are less water retentive and hence need more frequent irrigation for successful crop growth than fine textured soils. The clayey soils can hold more moisture, but they have high wilting percentage. The rate of water intake of these soils is low. They are subject to water-logging resulting in poor aeration and workability. The moderately fine-textured soils e.g. loams, caly loams, or silt loams are by far the excellent soils for plant growth, since they have the advantages of both sands and clays. |
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