The most used unit of soil classification is called the “soil series.” Series are determined by studying the horizon characteristics. Such characteristics as number of horizons, color, thickness, texture, erosion phase, slope, organic content, and depth to hardpan are used to differentiate among series. Series are the smallest unit that soils are subdivided into except for the soil type and phase. Soil type subdivides the series on the basis of surface texture, while phases are determined by slope, erosion, or salt content. All soils given the same soil series name would possess the same characteristics across the landscape. Examples of soil series are Holdrege, Nora, Sharpsburg and Valentine. (See Table 1.4) Soil series names are often taken from a nearby town or area where the soil was first described. A soil series, type and phase name might be, for example: Sharpsburg silty clay loam, 5 to 9 percent slope, eroded.
The soil series relates a soil to a specific group of other characteristics that are described by the soil’s complete name. This would be comparable to a person’s given name. Nan’s given name was Nancy Marie Wilson Johnson. Similarly, a Valentine soil’s given name is Valentine loamy fine sand, rolling, mixed, mesic, Typic Ustipsamment.
Soil complex Mapping unit
Soil complex Mapping unit used to denote the distribution of soils: it is more precise than a soil association, and is used where soils of different types are mixed geographically in such a way that the scale of the map makes it undesirable, or impractical, to show each one separately.
Agrilearner: A soil monolith is a vertical section of the soil profile that is extracted from the field and mounted for display and teaching purposes. Scientists remove the soil slice carefully, preserve the layers in a wooden frame, and stabilize it with a hardening compound like glue. The natural appearance of the soil, including its horizonation, colour, and structure is preserved using this technique.
The soil monoliths featured at this website are displayed in the MacMillan Building at the University of British Columbia, Vancouver. The profiles sampled are representative of soil types found in British Columbia and in parts of Alberta and Yukon. The University of British Columbia has the 2nd largest collection of soil monoliths in Canada. Over the decades, the collection has become underutilized in teaching because of its inadequate display and storage status. The goal of this project was to improve accessibility of UBC’s collection to learning community. by developing an interactive, web-based tool that combined existing teaching resources (soil monoliths) with on-line soil science educational resources developed by the Virtual Soil Science Learning Resource group.
The most general level of classification in the USDA system of Soil Taxonomy is the Soil Order. All of the soils in the world can be assigned to one of just 12 orders (Table 5.1). Soil orders are frequently defined by a single dominant characteristic affecting soils in that location, e.g., the prevalent vegetation (Alfisols, Mollisols), the type of parent material (Andisols, Vertisols), or the climate variables such as lack of precipitation (Aridisols) or the presence ofpermafrost (Gelisols). Also significant in several soil orders is the amount of physical and chemical weathering present (Oxisols, Ultisols), and/or the relative amount of Soil Profile Development that has taken place (Entisols).
This lesson will examine each of these 12 soil orders in turn: Entisols, Inceptisols, Andisols, Mollisols, Alfisols, Spodosols, Ultisols, Oxisols, Gelisols, Histosols, Aridisols, and Vertisols. To get the most out of this lesson, the student should carefully study each soil order, including the supplementary material provided by the embedded links. Agrilearner
A soil phase is a unit of soil outside the system of soil taxonomy. It is a functional unit that may be designed according to the purpose of the survey. Phases of taxa at any categorical level, from order to series, may be defined. Also, areas not classified in soil taxonomy such as rockland and steep slopes may be designated as phases on soil maps. The two general reasons for differentiating soil phases are
to recognize and name soil and landscape properties that are not used as criteria in soil taxonomy, for example, slope or erosionto recognize and name, at a relatively high categorical level, soil properties that are used as differentiae at a lower categorical level. For example, depth to a lithic layer is a family criterion, but it can be used as a phase criterion at the order, great group, and subgroup levels such as, Brunisolic soils, very shallow lithic phase. Agrilearner
soil type usually refers to the different sizes of mineralparticles in a particular sample. Soil is made up in part of finely ground rock . Hard surface of base is called hard strata soil particles, grouped according to size as sand and silt in addition toclay, organic material such as decomposed plant matter.
Each component, and their size, play an important role. For example, the large particles, sand, determine aeration and drainage characteristics, while the tiniest, sub-microscopic clay particles, are chemically active, binding with water and plant nutrients. The ratio of these sizes determines soil type: clay,loam, clay-loam, silt-loam, and so on.
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