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The subsoil is the depth where these weathering products accumulate. The accumulation of clay minerals, iron, aluminum, and organic compounds is called illuviation . Whereas the topsoil tends to be the depth of greatest physical, chemical, and biological activity, the subsoil is the depth of most deposition.
A plot of sugarcane yield versus depth of water table in Australia. The critical depth is 0.6 m. [4] [5] Most crops need a water table at a minimum depth. [6] For some important food and fiber crops a classification was made [7] because at shallower depths the crop suffers a yield decline. [8]
As the name implies, subaqueous and submerged soils are soils that occur under water (both fresh and salt water). The depth range of the water column where these soils may be found is not known, an arbitrary depth of 2.5 meters below the surface has been set for soil survey inventory but some states have extended this depth to 5 m (NAVD 88).
The hardpan was expected to be encountered within a depth of 6 feet. The modern concept recognizes mainly a sandy loam surface soil overlying a finer textured subsoil that has a significant clay increase, at its upper boundary or within some part of the subsoil. The subsoil rests abruptly on a mainly silica-cemented hardpan at depths ranging ...
In its broadest terms, percolation testing observes how quickly a known volume of water dissipates into the subsoil of a drilled hole of known surface area. While every jurisdiction will have laws regarding the exact calculations for the length of line, depth of pit, etc., the testing procedures are the same.
In geotechnical engineering, watertable control is the practice of controlling the height of the water table by drainage.Its main applications are in agricultural land (to improve the crop yield using agricultural drainage systems) and in cities to manage the extensive underground infrastructure that includes the foundations of large buildings, underground transit systems, and extensive ...
The water is present either permanently or cyclic within the time frame of 24 hours. Some organic soils float on water. In other cases, shallow water (i.e. water not deeper than 1 m) may cover the soil permanently, as in the case of shallow lakes, or cyclic, as in tidal flats.
Vertisols: Usually mollic epipedon; high in shrinking and swelling clays; >30% clay to a depth of 50 cm; deep cracks (called gilgai) form when soil dries; form from parent material high in clay (e.g., shales, basins, exposed Bt horizons of old soils); 2.4% of global and 1.7% of U.S. ice-free land.