Characterization of soils in order to determine their value is impossible without studying soil profiles. What is it and what types of profiles are available, read the article.
Soil profile
The process of soil formation affects the rock mother, as a result of which the soil properties change vertically. There is a regular change in the composition of the soil from its surface inland to the parent rock, which was not affected by the process of soil formation. This happens gradually. Soil profiles are formed under the influence of some factors. The main ones are:
- Substances entering the soil vertically from the atmosphere or from groundwater. Their movement depends on the type of soil formation and their changeability over years and seasons.
- The vertical distribution of the root systems of plants living in the soil of animals, microorganisms.
All horizons of the soil profile are interconnected. It happens that the soils of horizons of different types have similar properties and signs.
Soil profiles: structure
Layers of soil alternating vertically are soil horizons. Their structure and properties are different. Soil horizons successively lying one after another are soil profiles. Their structure for each soil is specific.
The structure of the soil profile is closely related to the process of natural soil formation and their use in agriculture. Soils of horizons of different types differ not only in features and properties, but also in composition. The thickness of the horizon is determined by the vertical extent. The main horizons:
- Humus soil layer.
- The transition horizon from the previous to the next layer.
- Subsoil (mother breed).
Simple profile
The structure of the soil profile with a more detailed examination is simple and complex. The simple structure of the soil has the following profile types:
- Primitive is a low-power horizon, the place of diligence is the mother breed.
- Underdeveloped - this profile contains all the horizons characteristic of this soil. Each horizon is thin.
- Normal - characterized by the presence of all horizons formed at the genetic level. Power is peculiar to non-eroded soil.
- Weakly differentiated — horizons are poorly marked.
- Disturbed or eroded - characterized by the destruction of the upper horizons by erosion.
Complex profile
The types of soil profile of a complex structure are as follows:
- Relict - this profile has buried horizons and paleo-soil profiles. In its composition may have traces of ancient soil formation.
- Polynomial profile - formed during lithological shifts, without going beyond the soil thickness.
- Polycyclic - its formation is associated with the periodic deposition of materials forming the soil: volcanic ash, river alluvium, ash deposits.
- Disturbed or inverted - is characterized by the formation of a different type: natural or artificial. In the first case, the human factor played a role, in the second - the natural factor, when the underlying horizons moved to the surface.
- Mosaic - characterized by not sequential formation of horizons in depth. Change of horizons occurs in spots, like a mosaic pattern.
Profile structure according to soil formation conditions
Soil profiles vary. Depending on the process of soil formation, they are divided into two types:
- The first type is characterized by the formation of soils under conditions of leaching, which are called eluvial, and the influence of moisture from the atmosphere. Precipitation flowing down from the soil moves particles and chemical elements down.
- The description of the soil profile of the second type has its own characteristics. This type of structure is characteristic of hydromorphic soils, which are formed with excessive moisture. Soil formation is influenced by groundwater, which enriches the soil stratum.
Depth structure
Depending on the distribution of various substances: limestone, humus, gypsum, minerals, salts, the following soil profiles can be distinguished in depth:
- Accumulative - on top of the soil there is a small amount of substances: the deeper, the less they become.
- Eluvial - the amount of substances increases with depth.
- Soil-accumulative - substances accumulate from groundwater, which are located below or in the middle of the profile.
- Eluvially differentiated - few substances accumulate in its upper layer, and a lot in other layers.
- Undifferentiated - substances are distributed evenly throughout the profile.
Profile Horizons
In addition to the three main distinguish such horizons as:
- Peat, organogenic. Its formation occurs on the surface with constant excess moisture. A characteristic feature is the specific conservation of substances of organic origin, which do not turn into humus and do not burn. The composition of peat is grassy, woody, mossy, lichen, deciduous or mixed. Residues of plant origin may not be decomposed, partially preserved and completely decomposed.
- Forest litter - this layer is rich in organic substances. Its power reaches twenty centimeters. It consists of the remains of plants that have retained their original appearance, partially or completely decayed.
- The turf layer is the surface horizon. Its formation occurs under herbaceous plants. Most of the volume is plant roots.
- Humus horizon - contains 15-35 percent of substances of organic origin. It can be structureless or have a curdled structure. The soil is black, spreading, saturated with water.
- Arable horizon - its formation is associated with the processing of humus or underlying layers.
- Humus horizon - formed on the surface, has a dark color, contains 15 percent organic matter.
- The horizon is eluvial - is formed under the organogenic horizon. The soil is whitish, clarified.
- Mineral horizon - the place of its formation - the middle part of the profile. It can be illuvial, solonetzic, carbonate, salt, gypsum or mixed.
- Glue horizon - it is called mineral. Formation occurs with prolonged or constant excessive moisture and a lack of oxygen. Characteristic of the horizon is a dull color. It can be blue, gray or olive shades.
- Parent rock - characterized by a weak degree of exposure to destructive factors in the formation of soils.
Soil color
Soil horizons are characterized by such a feature as their color, which depends on the composition of the soil and the processes of its formation.
- Black soil. Dark gray and dark brown soils received this name of color. Their color depends on the content of humus or humus. The more it is in the soil, the darker the color. Compounds of certain minerals, as well as coal of various origins, can give black color to the soil.
- White soil and all other colors of light colors. This color gives the soil limestone, gypsum, quartz, soluble salts, feldspar.
- Red soil happens when iron oxide accumulates in its composition. The purple color is obtained due to the high content of manganese oxides, yellow - iron hydroxides.
- Soil with shades of blue, cyan and green. This is due to the fact that ferrous iron compounds are present in the soil. Its content in the soil is a consequence of anaerobic conditions (excessive moisture).
What is horizon power?
This is its vertical extent from the surface inland to the bedding of the parent rock. Different types of soils have different capacities. On average, it ranges from forty to one hundred and fifty centimeters. For example, if environmental conditions are harsh, the process of soil formation affects the upper part of the rocks. The thickness of such soil reaches twenty to thirty centimeters. In the steppe zones under a thick grassy cover - two hundred and three hundred.
The power of individual horizons is used to judge the value of soils. Thus, a thick humus layer is characterized by a large supply of substances and weak leaching. Podzolic soils are poor in nutrients, so their value is low.
Black earth
These are the most fertile soils. In the past, chernozems were formed from a dense grass cover, which died off annually, and decomposed under the influence of warm summer, forming humus, which accumulated for a long time. Currently, almost all black soil is plowed up. The soil profile of chernozem has the following structure:
- Felt steppe, power 3-4 centimeters.
- Dernina - its power is 3-7 centimeters. It has a dark gray color and dead or living remains of the roots of cereal plants. This layer may have old arable or virgin soils.
- Humus horizon - its power is 35-120 centimeters. It has a dark gray color uniform paint. Features of the soil profile of chernozem in its structure. It is grainy and durable. The main feature is fertility.
- Transition horizon from the humus layer to the next. Its thickness is 40-80 centimeters, the color is brownish-gray, heterogeneous, spots and smudges of humus are visible. It has a rough, lumpy structure.
- This type of horizon has subtypes. In some of them, an illuvial-carbonate horizon with a brownish-yellow color and a prismatic structure can be distinguished. Soils of the entire horizon have molehills. They are filled with brown mass coming from horizons below. It happens that molehills are filled with dark earth from the upper horizons.
- The rock that forms the soil. It has a whitish or fawn color and prismatic structure. Soils of different depths are characterized by the presence of carbonate, salts, gypsum.
Podzolic soils
The soil profile of podzolic soils is formed at a high level of moisture. Typical for them is the vegetation of various species. Features of the soil profile of podzolic soils in high acidity. Therefore, it is very important for their microflora to adapt in such conditions in order to participate in the decomposition of residues of organic substances. The horizons of the profile of podzolic soils are as follows:
- Forest litter - power two centimeters.
- Weakly decomposed plant residues.
- Inclusions in the form of fungal mycelium. The color of the soil is light brown.
- Lumpy or powdery soil structure with a dark brown color.
- Humus-accumulative layer with a capacity of up to thirty centimeters.
- Podzolic layer with the same power.
- Transitional with a variegated color layer with a capacity of up to fifty centimeters.
- The illuvial layer, its thickness is 20-120 centimeters.
- The layer of the parent breed.
Soils of this type in the wild have low fertility, the humus layer is practically absent, the soil reaction is acidic. Podzols poorly absorb moisture, are poorly saturated with nutrients, which affects the nutrition of plants and their growth.