Ultisol , commonly known as red clay soil , is one of twelve soil orders in the United States Department of Agriculture soil taxonomy . The word "Ultisol" is derived from "ultimate", because Ultisols were seen as the ultimate product of continuous weathering of minerals in a humid, temperate climate without new soil formation via glaciation . They are defined as mineral soils which contain no calcareous ( calcium carbonate containing) material anywhere within the soil, have less than 10% weatherable minerals in the extreme top layer of soil, and have less than 35% base saturation throughout the soil. Ultisols occur in humid temperate or tropical regions. While the term is usually applied to the red clay soils of the Southern United States , Ultisols are also found in regions of Africa, Asia, Australia and South America.
63-668: In the World Reference Base for Soil Resources (WRB), most Ultisols are known as Acrisols and Alisols . Some belong to the Retisols or to the Nitisols . Aquults are typically Stagnosols or Planosols . Humults may be Umbrisols . Ultisols vary in color from purplish-red, to a bright reddish-orange, to pale yellowish-orange and (in cooler areas such as Pennsylvania ) even some subdued yellowish-brown or grayish-brown tones. They are typically quite acidic , often having
126-564: A pH of less than 5. The red and yellow colors result from the accumulation of iron oxide (rust), which is highly insoluble in water. Major nutrients , such as calcium and potassium , are typically deficient in Ultisols, which means they generally cannot be used for sedentary agriculture without the aid of lime and other fertilizers , such as superphosphate . They can be easily exhausted, and require more careful management than Alfisols or Mollisols . However, they can be cultivated over
189-409: A 2- to 3-inch layer of compost and manure should be mixed into the soil to match a shovel's depth. The addition of organic material also helps to improve the drainage, while decreasing the overall weight of the soil. However, microorganisms in the soil consume the same nutrients that plants use to grow so certain nutrients will remain unavailable to plants until the microorganisms completely break down
252-421: A map unit not just one soil is indicated but an association of soils. For this purpose, WRB uses the following nomenclature: Soils representing smaller areas are ignored in the denomination of the map unit. For codominant and associated soils, it is allowed to use less principal qualifiers than would correspondent to the used map scale level. The use of specifiers is not recommended due to the generalization that
315-457: A minimum thickness and therefore a horizontal appearance. The diagnostics have names (e. g. argic horizon, stagnic properties, fluvic material). The classification comprises two levels: The first level has 32 Reference Soil Groups (RSGs). At the second level, for further differentiation a set of qualifiers is added to the name of the RSG. There are 202 qualifiers in total. For every RSG, there
378-528: A relatively wide range of moisture conditions. Ultisols can have a variety of clay minerals, but in many cases the dominant mineral is kaolinite . This clay has good bearing capacity and no shrink–swell property . Consequently, well-drained kaolinitic Ultisols such as the Cecil series are suitable for urban development. Ultisols are the dominant soils in the Southern United States (where
441-400: A soil to a certain RSG. In a defined sequence, the key asks for the presence or absence of certain diagnostics in a certain depth range. In addition, the key asks for single characteristics, e. g., a certain clay content or a certain base saturation. The soil belongs to the first RSG, for which it fulfils the set of criteria. The qualifiers available for use with a particular RSG are listed in
504-519: A soil-forming process) apply. Stagnic is found further up in the list. Therefore, the soil has to be named until now Albic Stagnic Luvisol. From the list of the supplementary qualifiers, Siltic (silty from 0 to 60 cm), Loamic (loamy from 60 cm downwards), Aric (ploughed), Cutanic (clay coatings), Differentic (the clay migration led to a significant difference in clay content), Endic (the argic horizon starts below 50 cm) and Ochric (relatively small concentrations of organic carbon) apply. Bringing
567-453: A soil. Depending on the purpose of the map or according to national traditions, at any scale level, elective qualifiers may be added. They may be additional principal qualifiers from further down the list and not already used in the soil name, or they may be supplementary qualifiers. They are placed using the above-mentioned rules for supplementary qualifiers; principal qualifiers first, then supplementary qualifiers. The WRB recommends that on
630-449: Is Stephan Mantel ( International Soil Reference and Information Centre (ISRIC), The Netherlands, since 2018). Chairs of the WRB working group and responsible first authors of the WRB editions are: Seppe Deckers (Belgium, 1st edition 1998), Erika Michéli (Hungary, 2nd edition 2006) and Peter Schad (Germany, 3rd edition 2014 and 4th edition 2022). The WRB working group has a homepage that
693-512: Is a list of available qualifiers, which are subdivided into two types: Qualifiers may be principal for some RSGs and supplementary for others. The names of the RSGs and the qualifiers start with capital letters. They must be given in English and must not be translated into any other language in order to guarantee that a certain soil has the same name all over the world. A key is used for allocating
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#1732772400899756-402: Is amorphous; it may gradually decay over several years or persist for millennia. It has no determinate shape, structure, or quality. However, when examined under a microscope, humus may reveal tiny plant, animal, or microbial remains that have been mechanically, but not chemically, degraded. This suggests an ambiguous boundary between humus and soil organic matter, leading some authors to contest
819-541: Is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the fourth edition 2022. It is edited by a working group of the International Union of Soil Sciences (IUSS). Since the 19th century, several countries developed national soil classification systems. During the 20th century, the need for an international soil classification system became more and more obvious. From 1971 to 1981,
882-554: Is approximately 16% pore space, 2% organic matter and 82% mineral. The use of mulch is widespread in the Piedmont region of the United States as a solution to the high temperatures and saturation of the soil. The addition of mulch helps to make the soil more porous. Adding manure and compost can help boost the amount of organic material present in the soil, which in turn helps add essential nutrients . Specifically, adding
945-642: Is currently hosted by the ISRIC. It provides the following: The classification is based on diagnostic horizons , diagnostic properties and diagnostic materials , altogether called diagnostics . Diagnostic materials are materials that significantly influence soil-forming processes ( pedogenesis ). They may be inherited from the parent material or be the result of soil-forming processes. Diagnostic properties are typical results of soil-forming processes or reflect specific conditions of soil formation . Diagnostic horizons are typical results of soil-forming processes showing
1008-507: Is formed from the slow oxidation ( redox ) of soil carbon after the incorporation of finely powdered charcoal into the topsoil , suggested to result from the grinding and mixing activity of a tropical earthworm. This process is speculated to have been important in the formation of the unusually fertile Amazonian terra preta do Indio . However, some authors suggest that complex soil organic molecules may be much less stable than previously thought: “the available evidence does not support
1071-441: Is light-coloured, and the upper part is darker. In the clay-richer horizon, we observe redoximorphic features; the oximorphic and the reductimorphic features sum up to 30% of the exposed area, the intensive colours found in the interiors of the aggregates. In spring, reducing conditions occur. The soil is ploughed regularly. Laboratory characteristics: The laboratory analyses confirm the high cation exchange capacity per kg clay in
1134-597: Is mainly taken from Table 2 (Chapter 1) of the WRB Manual. Soils with thick organic layers Soils with strong human influence Soils with limitations to root growth Soils distinguished by Fe/Al chemistry Pronounced accumulation of organic matter in the mineral topsoil Accumulation of moderately soluble salts or non-saline substances Soils with clay-enriched subsoil Note: The exchangeable base cations are given in cmol c kg . Soils with little or no profile differentiation Our example soil has
1197-412: Is optional: The number of qualifiers used in a map legend depends on the scale. The WRB distinguishes three map scale levels : Correlating the map scale levels with concrete scales is difficult because selecting a map scale level depends very much from the homogeneity/heterogeneity of the landscape. The principal qualifiers are added before the name of the RSG following the rules explained for naming
1260-427: Is quickly transformed by white-rot fungi , is one of the primary precursors of humus, together with by-products of microbial and animal activity. The humus produced by humification is thus a mixture of compounds and complex biological chemicals of plant, animal, and microbial origin that has many functions and benefits in soil. Some judge earthworm humus ( vermicompost ) to be the optimal organic manure . Much of
1323-474: Is required when making maps. In map legends, the names of the RSGs are given in plural; in all other cases they are given in singular. The WRB Manual comprises seven chapters and six annexes. The seven chapters are followed by six annexes: This is the list of the 32 Reference Soil Groups in the sequence of the key (Chapter 4 of the WRB Manual), including the codes (Chapter 6 of the WRB Manual). This list
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#17327724008991386-406: Is sometimes composted and used as a soil amendment . The primary materials needed for the process of humification are plant detritus and dead animals and microbes, excreta of all soil-dwelling organisms, and also black carbon resulting from past fires. The composition of humus varies with that of primary (plant) materials and secondary microbial and animal products. The decomposition rate of
1449-476: Is that soil climate is regarded only as a soil-forming factor and not as a soil characteristic. The WRB is not meant to replace national soil classification systems, which, for their area, may be more detailed than the WRB. The WRB is edited by a working group of the International Union of Soil Sciences (IUSS). The current chair of the working group is Cezary Kabala ( Wroclaw University of Environmental and Life Sciences , Poland, since 2022). The current vice-chair
1512-463: Is used to describe mature or natural compost extracted from a woodland or other spontaneous source for use as a soil conditioner . It is also used to describe a topsoil horizon that contains organic matter ( humus type , humus form , or humus profile ). Humus has many nutrients that improve the health of soil, nitrogen being the most important. The ratio of carbon to nitrogen ( C:N ) of humus commonly ranges between 8:1 and 15:1 with
1575-752: The Carboniferous period when forests first developed. Though known from far north of their present range as recently as the Miocene , Ultisols are surprisingly rare as fossils overall, since they would have been expected to be very common in the warm Mesozoic and Tertiary paleoclimates. The lack of organic matter in Ultisol makes it difficult for plants to grow without proper care and considerations. Soil amendments are generally required each year in order to sustain flourishing plant life in regions with primarily Ultisol soil. The use of soil tests, coupled with
1638-628: The Food and Agriculture Organization (FAO) and UNESCO published the Soil Map of the World , 10 volumes, scale 1 : 5 M). The Legend for this map, published in 1974 under the leadership of Rudi Dudal , became the FAO soil classification . Many ideas from national soil classification systems were brought together in this worldwide-applicable system, among them the idea of diagnostic horizons as established in
1701-487: The soil matrix , molecular soil humus should be considered to be of significance in removing the atmosphere's current carbon dioxide overload. There is little data available on the composition of humus because it is a complex mixture that is challenging for researchers to analyze. Researchers in the 1940s and 1960s tried using chemical separation to analyze plant and humic compounds in forest and agricultural soils, but this proved impossible because extractants interacted with
1764-698: The '7th approximation to the USDA soil taxonomy' from 1960. The next step was the Revised Legend of the Soil Map of the World, published in 1988. In 1982, the International Soil Science Society (ISSS; now: International Union of Soil Sciences , IUSS) established a working group named International Reference Base for Soil Classification (IRB). Chair of this working group was Ernst Schlichting [ de ] . Its mandate
1827-615: The Cecil series is most famous), southeastern China, Southeast Asia, and some other subtropical and tropical areas. Their northern limit (except fossil soils) is very sharply defined in North America by the limits of maximum glaciation during the Pleistocene , because Ultisols typically take hundreds of thousands of years to form—far longer than the length of an interglacial period today. The oldest fossil Ultisols are known from
1890-438: The analysed organic matter and created many artefacts. Further research has been done in more recent years, though it remains an active field of study. Microorganisms decompose a large portion of the soil organic matter into inorganic minerals that the roots of plants can absorb as nutrients . This process is termed mineralization . In this process, nitrogen ( nitrogen cycle ) and the other nutrients ( nutrient cycle ) in
1953-430: The clay-richer horizon and the dominance of exchangeable base cations over exchangeable Al in the subsoil. In the topsoil, we find 20% clay , 10% sand , and 70% silt ; in the subsoil, 35% clay, 8% sand, and 57% silt. Organic matter concentrations in the topsoil are intermediate. The naming of the soil consists of four steps. Question 1: Does the soil have diagnostic horizons, properties and materials? The soil has
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2016-506: The codes of Chapter 6 of the WRB Manual gives us the following short name: LV-stn.abm-sia.lon-ai.ct.ed.oh. Humus In classical soil science , humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter . It is rich in nutrients and retains moisture in the soil. Humus is the Latin word for "earth" or "ground". In agriculture , "humus" sometimes also
2079-536: The corresponding provisions, can alleviate issues of nutrition and irrigation that can result from non porous Ultisol. Soil tests help indicate the pH , and red clay soil typically has a low pH. The addition of lime is used to help to increase the pH in soil and can help increase the pH in Ultisol as well. Generally, gardeners aim to have 45% mineral, 5% organic matter and 50% pore space in their soil. The composition of Ultisol in North Carolina, for reference,
2142-568: The decomposed organic matter are recycled. Depending on the conditions in which the decomposition occurs, a fraction of the organic matter does not mineralize and instead is transformed by a process called humification . Prior to modern analytical methods, early evidence led scientists to believe that humification resulted in concatenations of organic polymers resistant to the action of microorganisms, however recent research has demonstrated that microorganisms are capable of digesting humus. Humification can occur naturally in soil or artificially in
2205-400: The decomposition of sugars and starches from carbohydrates, which decompose easily as detritivores initially invade the dead plant organs, while the remaining cellulose and lignin decompose more slowly. Simple proteins, organic acids, starches, and sugars decompose rapidly, while crude proteins, fats, waxes, and resins remain relatively unchanged for longer periods of time. Lignin, which
2268-484: The depth-related specifiers Ano- and Endo- to construct the subqualifiers Anosiltic and Endoloamic. The stagnic properties occur only in the subsoil and the albic horizon around 50 cm. This means that we can use the subqualifiers Endostagnic and Amphialbic. Using these specifiers does not change the position of the qualifiers in the soil name. Now, the soil name is: Amphialbic Endostagnic Luvisol (Anosiltic, Endoloamic, Aric, Cutanic, Differentic Endic, Ochric). Using
2331-432: The different compounds will affect the composition of the humus. It is difficult to define humus precisely because it is a very complex substance which is still not fully understood. Humus is different from decomposing soil organic matter . The latter looks rough and has visible remains of the original plant or animal matter. Fully humified humus, on the contrary, has a uniformly dark, spongy, and jelly-like appearance, and
2394-416: The exception of deep horizons of podzolic soils enriched with colloidal humic substances which have been leached down the soil profile. The importance of chemically stable humus is thought by some to be the fertility it provides to soils in both a physical and chemical sense, though some agricultural experts put a greater focus on other features of it, such as its ability to suppress disease. It helps
2457-618: The first edition of the WRB was published. At the same congress, the ISSS endorsed the WRB as its correlation system for soil classification. (In 2014, the USDA soil taxonomy also received the status of a correlation system.) At the 18th World Congress of Soil Science in Philadelphia in 2006, the second edition of the WRB was presented, and at the 20th World Congress of Soil Science in Jeju in 2014,
2520-473: The following characteristics: Field characteristics (described according to Annex 1 of the WRB Manual): A soil developed from loess shows a marked clay increase in around 60 cm depth and clay coatings in the clay-richer horizon. According to the landscape setting, we presume that high-activity clays dominate. In the field, a pH of 6 is measured in the subsoil. The lower part of the clay-poorer topsoil
2583-547: The following diagnostics: Question 2: To which RSG does the soil belong? We have to go through the key, RSG for RSG. This soil is not a Histosol, not an Anthrosol, not a Technosol etc. Finally, we end up with the Luvisol . This is the first RSG in the key, the criteria of which our soil completely fulfils. Question 3: Which qualifiers apply? From the list of the principal qualifiers, Stagnic (stagnic properties and reducing conditions) and Albic (light colours resulting from
Ultisol - Misplaced Pages Continue
2646-480: The formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds.″ Humus has a characteristic black or dark brown color and is organic due to an accumulation of organic carbon. Soil scientists use the capital letters O, A, B, C, and E to identify the master soil horizons , and lowercase letters for distinctions of these horizons. Most soils have three major horizons:
2709-599: The humus in most soils has persisted for more than 100 years, rather than having been decomposed into CO 2 , and can be regarded as stable; this organic matter has been protected from decomposition by microbial or enzyme action because it is hidden (occluded) inside small aggregates of soil particles, or tightly sorbed or complexed to clays . Most humus that is not protected in this way is decomposed within 10 years and can be regarded as less stable or more labile . The mixing activity of soil-consuming invertebrates (e.g. earthworms , termites , some millipedes ) contribute to
2772-480: The key, along with the RSG. Their number is from 40 to 79. All applying qualifiers must be added to the soil name. The principal qualifiers are added before the name of the RSG. The sequence is from right to left, i. e., the uppermost qualifier in the list is placed closest to the name of the RSG. If no other principal qualifier applies, the Haplic qualifier is used. The supplementary qualifiers are added in brackets after
2835-444: The list are separated by a slash (/), only one of them can be used. The slash signifies that these qualifiers are either mutually exclusive (e. g. Dystric and Eutric) or one of them is redundant with the redundant qualifier(s) listed after the slash(es). In the soil name, supplementary qualifiers are always placed in the order of the alphabet (exception: supplementary qualifiers related to the texture, see above), even if their position in
2898-611: The list differs from the alphabetical sequence due to the use of the slash. It is a general rule that qualifiers conveying redundant information are not used. Example: If a soil has the Calcaric qualifier (carbonates present) the Eutric qualifier (high base saturation) is not used. Qualifiers may be combined with specifiers (e. g. Epi-, Proto-) to form subqualifiers (e. g. Epiarenic, Protocalcic). The depth-related specifiers referring to layers are of special importance, although their use
2961-475: The median being about 12:1. It also significantly improves (decreases) the bulk density of soil. Humus is amorphous and lacks the cellular structure characteristic of organisms . The solid residue of sewage sludge treatment , which is a secondary phase in the wastewater treatment process, is also called humus. When not judged contaminated by pathogens , toxic heavy metals , or persistent organic pollutants according to standard tolerance levels, it
3024-583: The more systematic IRB approach. Otto Spaargaren ( International Soil Reference and Information Centre ) and Freddy Nachtergaele (FAO) were nominated to prepare a draft. This draft was presented at the 15th World Congress of Soil Science in Acapulco in 1994. At the same congress, the WRB was established as an ISSS working group replacing the IRB. At the 16th World Congress of Soil Science in Montpellier in 1998,
3087-443: The more when associated with cations (e.g. calcium ), and in providing a very large surface area that can hold nutrient elements until required by plants, an ion exchange function comparable to that of clay particles. Soil carbon sequestration is a major property of the soil, also considered as an ecosystem service . Only when it becomes stable and acquires its multi-century permanence, mostly via multiple interactions with
3150-408: The name of the RSG and are separated from each other by commas. The sequence is from left to right. Supplementary qualifiers related to the texture, if applicable, are the first in the list. If several ones apply, they are placed in the sequence from the top to the bottom of the soil profile. All other supplementary qualifiers follow them and are used in alphabetical order. If two or more qualifiers in
3213-908: The organic material and release nutrients. Living organisms within the soil use, and subsequently convert, organic material into usable humus . To avoid the delay presented by this process, adding manure in the fall is advisable. Some gardeners who live in areas with large amounts of red clay soil use raised beds or Hügelkultur to avoid having to amend the soil. By using raised beds, gardeners avoid having to deal with Ultisols altogether. Plants found native to regions with high amounts of Ultisol can thrive. Generally, these species adapt to poorly drained, damp soils. The Missouri Botanical Garden recommends tickweed , spotted jewelweed , mealycup sage , Camassia , spring starflower , ostrich fern , sideoats grama , Bouteloua curtipendula , and prairie dropseed . World Reference Base for Soil Resources The World Reference Base for Soil Resources ( WRB )
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#17327724008993276-418: The original plant material (foliage, wood, bark), in part from similar molecules that have been produced by microbes . During decomposition processes these polyphenols are modified chemically so that they are able to join up with one another to form very large molecules. Some parts of these molecules are modified in such a way that protein molecules, amino acids, and amino sugars are able to attach themselves to
3339-495: The original work is properly cited. The WRB has two hierarchical levels (see below) and has in that sense a similar approach as the French référencial pédologique (1992, 1995, 2008). Contrary to that, the USDA soil taxonomy is strongly hierarchical and has six levels. The classification in WRB is based mainly on soil morphology (field and laboratory data) as an expression of pedogenesis . Another difference with USDA soil taxonomy
3402-421: The polyphenol “base” molecule. As protein contains both nitrogen and sulfur, this attachment gives humus a moderate content of these two important plant nutrients. Radiocarbon and other dating techniques have shown that the polyphenolic base of humus (mostly lignin and black carbon ) can be very old, but the protein and carbohydrate attachments much younger, while to the light of modern concepts and methods
3465-416: The production of compost . Organic matter is humified by a combination of saprotrophic fungi, bacteria, microbes and animals such as earthworms, nematodes, protozoa, and arthropods (see Soil biology ). Plant remains, including those that animals digested and excreted, contain organic compounds: sugars, starches, proteins, carbohydrates, lignins, waxes, resins, and organic acids. Decay in the soil begins with
3528-461: The situation appears much more complex and unpredictable than previously thought. It seems that microbes are able to pull protein off humus molecules rather more readily than they are able to break the polyphenolic base molecule itself. As protein is removed its place may be taken by younger protein, or this younger protein may attach itself to another part of the humus molecule. The most useful functions of humus are in improving soil structure , all
3591-424: The soil retain moisture by increasing microporosity and encourages the formation of good soil structure . The incorporation of oxygen into large organic molecular assemblages generates many active, negatively charged sites that bind to positively charged ions (cations) of plant nutrients , making them more available to the plant by way of ion exchange . Humus allows soil organisms to feed and reproduce and
3654-471: The stability of humus by favouring the formation of organo-mineral complexes with clay at the inside of their guts , hence more carbon sequestration in humus forms such as mull and amphi, with well-developed mineral-organic horizons , when compared with moder where most organic matter accumulates at the soil surface. Stable humus contributes few plant-available nutrients in soil, but it helps maintain its physical structure. A very stable form of humus
3717-427: The supplementary qualifiers into the correct order (first the textural qualifiers from the top to the bottom of the soil profile, then all others in alphabetical order), the soil is an Albic Stagnic Luvisol (Siltic, Loamic, Aric, Cutanic, Differentic, Endic, Ochric). Question 4: Which specifiers can be used to form subqualifiers? The soil is Siltic from 0 to 60 cm and Loamic from 60 cm downwards. We can use
3780-432: The surface horizon (A), the subsoil (B), and the substratum (C). Some soils have an organic horizon (O) on the surface, but this horizon can also be buried. The master horizon (E) is used for subsurface horizons that have significantly lost minerals ( eluviation ). Bedrock, which is not soil, uses the letter R. The richness of soil horizons in humus determines their more or less dark color, generally decreasing from O to E, to
3843-641: The third edition. An update of the third edition was issued in 2015. Whereas the second edition was only suitable for naming soils, the third and the following edition can additionally be used for creating map legends. At the 22nd World Congress of Soil Science in Glasgow in 2022, the fourth edition was published. The 4th edition is an open access document under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided
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#17327724008993906-527: The use of the term humus and derived terms such as humic substances or humification , proposing the Soil Continuum Model (SCM). However, humus can be considered as having distinct properties, mostly linked to its richness in functional groups , justifying its maintenance as a specific term. Fully formed humus is essentially a collection of very large and complex molecules formed in part from lignin and other polyphenolic molecules of
3969-455: Was to develop an international soil classification system that should better consider soil-forming processes than the FAO soil classification. Drafts were presented in 1982 and 1990. In 1992, the IRB working group decided to develop a new system named World Reference Base for Soil Resources (WRB) that should further develop the Revised Legend of the FAO soil classification and include some ideas of
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