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loam,soil composed of sand, silt, clay, and organic matter in evenly mixed particles of various sizes. More fertile than sandy soils, loam is not stiff and tenacious like clay soils. Its porosity allows high moisture retention and air circulation. The popular confusion of loam with humushumus
, organic matter that has decayed to a relatively stable, amorphous state. It is an important biological constituent of fertile soil. Humus is formed by the decomposing action of soil microorganisms (e.g.
..... Click the link for more information. is probably due to the superior quality of both soils. According to the preponderance of their ingredients, loams are classified as sandy, clay, or silt loams. Most soils of agricultural importance are some type of loam.
a friable sandy and clayey sedimentary rock containing 10–30 percent (by weight) clay particles smaller than 0.005 mm. In soil science, loam with a higher clay content is called heavy loam, and that with less clay is called light loam. A distinction is made between coarse sandy, fine sandy, and silty loam, depending on the content of (1) sand grains of the corresponding size and (2) silty, or aleurite, particles.
The mineralogical composition of loam is varied: the more sandy loan has a high quartz content, whereas the more clayey type contains clay minerals, such as kaolinite, illite, and montmorillonite. Loam is sometimes rich in organic substances; in arid regions it may be rich in water-soluble salts. The origin of loam is usually continental; the corresponding ocean deposits are called sandy or aleurite clays. Loam is often used as a raw material for the production of brick.