The soil structure is studied in different ways, the choice and application of which is determined by the specific needs of specialists. Moreover, there are universal methods for presenting the characteristics of soil layers, thanks to which scientists can visually get acquainted with the qualities and general features of the land cover of a particular area. For example, there are atomic, aggregate, and crystal-molecular levels of representation of the structure, which make it possible to study the soil with one or another detail. The fourth level of representation is formed by soil horizons. Thus, for example, the earth can be reflected in the section, the profile of which was formed by several geological layers for a certain period of time.
Underlying horizons
This is in some way a fundamental and basic soil formation layer, which acts as a mother rock in terms of the formation of subsequent layers towards the surface. Such layers are heterogeneous and have different characteristics. Specialists distinguish sandy, clayey, forest litter, as well as combined strata that are of special origin.
It is important to note that maternal horizons are called basic for a reason. They are located in the lower part, but at the same time have a serious effect on the upper layers. This is manifested in the ability to form chemical, mineralogical and mechanical characteristics, as well as the physical qualities of the fertile layers. Accordingly, forest litter will have more attractive agrotechnical qualities than parent species, the mechanical properties of which are determined by sand or clay compositions.
Types of soil structure
Evaluation of the characteristics of a horizon is impossible without determining its structure. Structurality is understood as a set of aggregates or individual particles capable of randomly decaying. That is, this property that determines the mechanical state of aggregation of the soil mass. One of the parameters that make it possible to attribute soil horizons to one or another structure is the strength of the connection between the individual elements and microaggregates of the studied composition. To date, in soil science there are three categories of structures that differ in particle size, as well as their relative position. These are prismatic, cuboid and platy structures.
In prismatic soil masses, particles develop mainly along the vertical axis, the cuboid structure assumes a uniform distribution of particles along three planes that are perpendicular to each other. Plate-like soils are formed in two axes with obvious shortening in the vertical direction. If the mass does not decompose into individual particles, but is initially characterized by a loose state, then it is called a single-particle structureless. This group includes dust and sand. In turn, stony soil can be called massive structureless. Such structures are characterized by the presence of large shapeless blocks.
The value of particle size distribution
If the structure determines the mechanical distribution of individual elements in the soil mass, then the particle size analysis allows you to find out the agronomic properties by directly evaluating the particles. For example, experts give a morphological characteristic of the soil profile with fixation of the compositional features. So, the desert soil will be predominantly sandy, and the main task for researchers will be to determine the uniformity of the composition and the predominance of a particular fraction. In such analyzes, various measurement methods are used, including using metrological equipment.
The value of soil color
The color of the soil mass is one of the most striking morphological characters by which to determine the genetic horizon in the profile. In addition, the earth in the context of indicating the shades of the layers helps to fix the boundaries of horizons in such studies. However, the concepts of coloring and color performance are not equivalent in this case. Color refers to the general characteristic of heterogeneity and spotting. On the other hand, the color of the soil mass indicates a combination of tones, intensity and other chromatic qualities. By the way, many varieties of soils get their name precisely by their color characteristics - these include serozem, red earth and chernozem.
The color of the horizon can be heterogeneous and homogeneous. In the first case, the mass is painted in different tones, while the differences are traced not only by chromatic signs. Color often determines the physical characteristics that stand out with the shade. The uniform color, for example, has desert soil, and its particles are clarified to the lower layers.
Humus horizons
This is an extensive group of soils that are formed in the processes of biological decomposition. Separate layers of the horizon differ in height, physical qualities, composition of organic elements, etc. In this case, the shade tends to be more in the range from gray to black. The characteristic locations of the humus horizon are the steppe and forest-steppe. Actually, maternal forest underlying platforms largely contribute to the formation of the upper layers of this type. In particular, there are sod horizons, gray humus and light humus. Sod layers are more often found in tundra and taiga regions. The humus horizon with humus is also widespread. It is usually found in waterlogged landscapes in the south. The light masses of horizons of this type are widely spread in soils of semi-desert and dry-steppe lands, in which a warm arid climate prevails.
Organogenic horizons
This category includes soil horizons in which the content of organic components reaches 30% or more. Most often these are the upper layers of the profile. For example, the surface layer represents a peat horizon, the height of which is 10 cm. It is formed by decomposing remains of vegetation, grassy steppe felt, etc. The humus layer is also included in this group. Thanks to it, chernozem soils are formed, which can have both dark brown and black shades. Such strata usually occur under the litter-peat layers. There are other subspecies of this horizon, which may include mineral elements. But the main unifying morphological property of all soils included in this complex is the origin based on organic materials. That is, soil formation in this case occurs under the influence of biological decomposition.
Middle soil horizons
A distinctive feature of horizons of this type is the tendency to soil formation processes directly inside the structure without external influence on the masses. A typical representative of this species is the alpha-humus horizon. It is characterized by the presence of humic-iron film inclusions on the surface of aggregates or mineral particles. As for color, in this case there are no strict characteristics - a lot depends on the specific composition, which can give the soil both dark and yellowish-light shades. Typically, mid-level soil horizons are found in sandy or sandy soils. A good example of this distribution will be the texture horizon. This is a brown mass, also distinguished by a multi-order structure and an abundance of multilayer films. However, this horizon can also be found in the prevalence of clay soils.
Eluvial horizon
In the profile of the cover lying under the organogenic or humus layers, this is the lightest horizon. It is distinguished by a light particle size distribution and a variety of elements included in it in terms of physical properties. These horizons include podzolic, humus-eluvial and subeluvial strata. For example, podzolic masses are distinguished by a sandy and sandy loam granulometric base, and in some cases a structureless lumpy base. This horizon is characterized by an arrangement in the structure of humid and alfegumus landscapes. By the way, according to some structural characteristics, an illuvial horizon is similar to such layers, although the dominance of brown color still causes pronounced external differences.
Arable horizon
Soils included in arable horizons are usually superficial. But not every surface layer can relate to fertile soils. A particular quality of this horizon is precisely the set of favorable conditions for the cultivation of cultivated plants. The composition and agrotechnical characteristics of the fertile layer allow the root system to draw the necessary elements from the soil mass. Natural conditions for this are created by chernozem soils, but often the necessary characteristics are increased by special means. For example, using the technology of cultivating the arable horizon, applying fertilizers and by correcting the hydrological support of the land.
Parent rocks
These are superficial mother layers, which become the basis for the formation of new soils. As a rule, the granulometric set of such rocks is made up of mineral components - up to 80%. The only exception is the peat horizon, in which the volume of mineral content can be within 10%. It is noteworthy that such layers can become the optimal platform for the formation of fertile arable soil with high agronomic properties, but they themselves are not always suitable for cultivation. It can be mountainous or rocky soil, the basis of which is formed by igneous, sedimentary and metamorphic rocks. But, despite the scarce characteristics from the point of view of fertility, such layers become a good basis for the development of more attractive integuments for agriculture.
Conclusion
Agrotechnical enterprises and forestry are the main customers and users of materials in which maps are developed with land sections and an indication of the profile of the soil horizon. Such data are required for a more complete understanding and current picture of the characteristics of a natural resource and an idea of future processes of its development. In particular, soil horizons make it possible to predict what further corrections in the soil composition may be. To study such horizons, an extensive range of methods is used, supported by modern technical means. In addition, companies interested in such studies often themselves carry out activities aimed at changing the structure and characteristics of certain horizons.