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Fragipan
A fragipan is a diagnostic horizon in USDA soil taxonomy. They are altered subsurface soil layers that restrict water flow and root penetration. Fragipans are similar to a duripan in how they affect land-use limitations. In soil descriptions, they are commonly denoted by a Bx or Btx symbol. They often form in loess ground. The first record of fragipans is probably that by John Hardcastle in New Zealand in the 1880s. Characteristics The Required Characteristics of a fragipan according to the "Keys to USDA soil taxonomy, tenth edition, 2006" are #The layer is 15-cm or more thick; ''and'' #The layer shows evidence of pedogenesis within the horizon or, at a minimum, on the faces of structural units; ''and'' #The layer has very coarse prismatic, columnar, or blocky structure of any grade, has weak structure of any size, or is massive. Separations between structural units that allow roots to enter have an average spacing of 10 cm or more on the horizontal dimensions; ''and'' #A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
USDA Soil Taxonomy
USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate Soil classification, classification of soil types according to several parameters (most commonly their properties) and in several levels: ''Order'', ''Suborder'', ''Great Group'', ''Subgroup'', ''Family'', and ''Soil series, Series''. The classification was originally developed by Guy D. Smith, Guy Donald Smith, former director of the U.S. Department of Agriculture's soil survey investigations. Discussion A taxonomy is an arrangement in a systematic manner; the United States Department of Agriculture, USDA soil taxonomy has six levels of classification. They are, from most general to specific: order, suborder, great group, subgroup, family and series. Soil properties that can be measured quantitatively are used in this classification system – they include: depth, moisture, temperature, texture, structure, cation exchange capacity, base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duripan
{{Short description, Subsurface soil horizon cemented by silica A duripan is a diagnostic soil horizon of the USDA soil taxonomy that is cemented by illuvial silica into a subsurface hardpan. Similar to a fragipan, Petrocalcic Horizon and petrogypsic horizon, it is firmly cemented and restricts soil management. In soil descriptions, they are most often denoted by the symbol Bqm. The closest equivalent in the Canadian system of soil classification is called a duric horizon, although it does not mean exactly the same thing as a duripan in the United States. They form almost exclusively in arid or Mediterranean climates, and can be as hard as concrete, which makes plowing very difficult or impossible. Soils that include duripans are generally used for grazing or wildlife habitat, and are seldom cultivated. Characteristics The required characteristics for a duripan, according to the "Keys to USDA soil taxonomy, Tenth Edition, 2006" are: # The pan is cemented or indurated in more th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Horizon
A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. These may be described both in absolute terms (particle size distribution for texture, for instance) and in terms relative to the surrounding material, i.e. 'coarser' or 'sandier' than the horizons above and below. The identified horizons are indicated with symbols, which are mostly used in a hierarchical way. Master horizons (main horizons) are indicated by capital letters. Suffixes, in form of lowercase letters and figures, further differentiate the master horizons. There are many different systems of horizon symbols in the world. No one system is more correct—as artificial constructs, their utility lies in their ability to accurately describe local conditions in a consistent manner. Due to the different definitions of the horizon sym ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pedogenesis
Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order (anisotropy) within soils. These alterations lead to the development of layers, termed soil horizons, distinguished by differences in color, structure, texture, and chemistry. These features occur in patterns of soil type distribution, forming in response to differences in soil forming factors. Pedogenesis is studied as a branch of pedology, the study of soil in its natural environment. Other branches of pedology are the study of soil morphology and soil classification. The study of pedogenesis is important to understanding soil distribution patterns in current ( soil geography) and past ( paleopedology) geologic periods. Overview Soil develops through a series of changes. The starting point is weathering of freshly accumulated parent material. A variety of soil microbes (ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parent Material
Parent material is the underlying geological material (generally bedrock or a superficial deposits, superficial or drift (geology), drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are often classified based upon their contents of consolidated or unconsolidated mineral material that has undergone some degree of physical or chemical weathering and the mode by which the materials were most recently transported. Consolidated Parent materials that are predominantly composed of consolidated rock are termed residual parent material. The consolidated rocks consist of igneous, sedimentary, and metamorphic rock, etc. Residual Soil developed in residual parent material is that which forms in consolidated geologic material. Unconsolidated This parent material is loosely arranged, particles are not cemented together, and not stratified. This parent material is classified by its last means of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Structure
In geotechnical engineering, soil structure describes the arrangement of the solid parts of the soil and of the Pore space in soil, pore space located between them. It is determined by how individual soil granules clump, bind together, and Soil aggregate stability, aggregate, resulting in the arrangement of soil Pore space in soil, pores between them. Soil has a major influence on water and air movement, Soil microbiology, biological activity, root growth and seedling emergence. There are several different types of soil structure. It is inherently a dynamic and complex system that is affected by different biotic and abiotic factors. Overview Soil structure describes the arrangement of the solid parts of the soil and of the pore spaces located between them. Aggregation is the result of the interaction of soil particles through rearrangement, flocculation and Cementation (geology), cementation. It is enhanced by: the precipitation of Oxide, oxides, hydroxides, Carbonate, carbonate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Carbonate
Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues. Chemistry Calcium carbonate shares the typical properties of other carbonates. Notably, it: *reacts with acids, releasing carbonic acid which quickly disintegrates into carbon dioxide and water: : *releases carbon dioxide upon heating, called a thermal decomposition reaction, or calcination (to above 840 °C in the case of ), t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnesium Carbonate
Magnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and Base (chemistry), basic forms of magnesium carbonate also exist as minerals. Forms The most common magnesium carbonate forms are the anhydrous salt called magnesite (), and the di, tri, and pentahydrates known as barringtonite (), nesquehonite (), and lansfordite (), respectively. Some basic forms such as artinite (), hydromagnesite (), and dypingite () also occur as minerals. All of those minerals are colourless or white. Magnesite consists of colourless or white trigonal crystals. The anhydrous salt is practically insoluble in water, acetone, and ammonia. All forms of magnesium carbonate react with acids. Magnesite crystallizes in the calcite structure wherein magnesium, is Coordination geometry#Crystallography usage, surrounded by six oxygen atoms. The dihydrate has a triclinic structure, while the trihydrate has a monoclinic structure. Refe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek () 'most' and (; Latinized as ) 'new'. The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, oscillating between cold Glacial period, glacial periods and warmer Interglacial, int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
