Soil profiles: types and description

Characteristics of soils for the purpose of determining their value are impossible without studying soil profiles. What is it, and what types of profiles are available, read in the article.

Soil profile

The process of soil formation has an effect on the mountain parent rock, as a result of which the soil properties change vertically. There is a natural change in the composition of the soil from its surface deep into the parent rock, which has not been affected by the formation of soils. This happens gradually. Soil profiles are formed under the influence of some factors. The main of them are:

• Substances entering the soil vertically from the atmosphere, or from groundwater. Their movement depends on the type of soil formation and their successiveness over the years and seasons.
• Vertical distribution of the root systems of plants living in the soil of animals, microorganisms.

All horizons of the soil profile are interrelated. 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 overlapping one 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 characteristics and properties, but also in composition. The thickness of the horizon is determined by the vertical extent. Main horizons:

• Humus soil layer.
• The transition horizon from the previous to the next layer.
• Subsoil (parent rock).

Simple profile

The structure of the soil profile can be simple and complex in more detailed consideration. A simple soil structure has the following types of profiles:

• Primitive is a thin horizon, the place of diligence is the parent breed.
• Incomplete - in the composition of this profile there are all the horizons inherent in this soil. Each horizon is low-power.
• Normal - characterized by the presence of all horizons, formed at the genetic level. Power is characteristic of non-eroded soil.
• Weakly differentiated - the horizons are poorly marked.
• Disrupted or eroded - characterized by the destruction of the upper horizons by erosion.

Advanced Profile

Types of soil profile of a complex structure are as follows:

• Relict - in the presence of this profile there are buried horizons and profiles of paleo-soil. In its composition may have traces of ancient soil formation.

• The profile is polynomial - it is formed during lithologic changes, not exceeding the limits of the soil thickness.
• Polycyclic - its formation is associated with the periodic deposition of materials forming the soil: volcanic ash, river alluvium, ash deposits.
• Disrupted or inverted - characterized by the formation of different types: 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 - is characterized not by the consistent formation of depth horizons. The change of horizons is spotted, like a mosaic pattern.

Structure of the profile according to the conditions of soil formation

Soil profiles vary. Depending on the process of formation of soils, they are divided into two types:

• The first type is characterized by the formation of soils under conditions of their washing, which are called eluvial, and the effects of moisture from the atmosphere. Precipitation coming downward from the soil moves particles and chemical elements down.
• Description of the soil profile of the second type has its own characteristics. This type of structure is characteristic of hydromorphic soils, which form with excessive moisture. The formation of soils is affected by groundwater, which enrich the soil thickness.

Structure of profiles in depth

Depending on the distribution of various substances: limestone, humus, gypsum, minerals, salts, the following soil profiles can be distinguished in depth:

• Accumulative - above the soil contains a small amount of substances: the deeper, the less they become.
• Eluvial - the amount of substances increases with depth.
• Ground-accumulative - substances accumulate from the groundwater, which are located below or in the middle of the profile.
• Eluvial-differentiated - in its upper layer, few substances accumulate, and in other layers - a lot.
• Undifferentiated - the substances are distributed evenly throughout the profile.

Profile Horizons

In addition to the three main ones, there are such horizons as:

• Peat, organogenic. Its formation occurs on the surface with constant excessive moistening. 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 grass, wood, moss, lichen, deciduous or mixed. Residues of plant origin may not be decomposed, partially preserved and fully decomposed.

• Litter forest - this layer is rich in organic substances. Its power reaches twenty centimeters. It consists of the remains of plants that have preserved their original appearance, partially or completely decayed.
• The sod layer is the surface horizon. Its formation occurs under grassy plants. Most of the volume is the roots of plants.
• Humus horizon - contains 15-35 percent of substances of organic origin. Can be structureless or have a curdled structure. The soil is black, smearing, saturated with water.
• The horizon is arable - its formation is associated with the processing of humus or underlying layers.
• Horizon humus - formed on the surface, has a dark color, contains 15 percent of organic matter.
• Horizon eluvial - 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.
• The gley horizon is called mineral. Formation occurs with prolonged or constant excessive moistening and lack of oxygen. Characteristic for the horizon is a dull color. It can be blue, gray or olive shades.
• Maternal breed - is characterized by a weak degree of influence on it of destructive factors in the formation of soils.

Color of soil

Soil horizons are characterized by such a sign as their coloration, which depends on the composition of the soil and the processes of its formation.

• Black soil. This name of the color was given to dark gray and dark brown soils. Their color depends on the content of humus or humus. The more it is in the soil, the darker the color. Black color can be attached to the soil of some minerals, as well as coal of different origin.
• White soil and all other colors of light tones. This color gives the soil limestone, gypsum, quartz, soluble salts, feldspar.
• Red soil occurs when it contains iron oxide. Purple color is obtained because of the large content of manganese oxides, yellow - iron hydroxides.
• Soil with shades of blue, blue 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 moistening).

What is the power of the horizon?

This is its length along the vertical from the surface in depth to the occurrence of the parent rock. Different types of soils have different power. On average, it ranges from forty to one hundred and fifty centimeters. For example, if the natural conditions are severe, 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 dense grassy cover - two hundred or three hundred.

The thickness of the individual horizons is judged on the value of the soils. Thus, the humus thick layer is characterized by a large stock of substances and a weak leaching. Podzolic soils are poor in nutrient content, so their value is low.

Chernozems

These are the most fertile soils. Chernozems in the past were formed from a dense grass cover, which died off annually, and decomposed under the influence of a warm summer, forming humus, which accumulated for a long time. Nowadays, almost completely the chernozems are plowed up. The soil profile of chernozem has the following structure:

• Felt steppe, power 3-4 centimeters.
• Dernina - its power is 3-7 centimeters. Has a dark gray color and dead or living remnants of roots of cereal plants. This layer can have old plow or virgin soils.
• The humus horizon is 35-120 centimeters thick. Has a dark gray color of homogeneous paint. Features of the soil profile of chernozem in its structure. It is granular and durable. The main feature is fertility.
• Transitional horizon from the humus layer to the next. Its thickness is 40-80 centimeters, its color is brownish-gray, heterogeneous, spots and humus are visible. It has a coarse, cloddy structure.
• This type of horizon has subtypes. In some of them, an illuvial-carbonate horizon with a brownish-pale color and a prismatic structure can be distinguished. The soils of the whole horizon are of molehills. They are filled with a brown mass coming from the horizons lying below. It happens that moles are filled with dark earth from the upper horizons.
• The breed that forms the soil. It has a whitish or fawn color and a prismatic structure. The soil of different depths is characterized by the presence of carbonate, salts, and gypsum.

Podzolic soils

The soil profile of podzolic soils is formed with a high level of humidity. Typical for them is the vegetation of various species. Features of the soil profile of podzolic soils in high acidity. Therefore, for their microflora, it is very important to adapt under such conditions to participate in processes of decomposition of organic matter residues. The horizons of the profile of podzolic soils are as follows:

• Forest litter - power two centimeters.
• Weakly decomposed plant remains.
• Inclusions in the form of a mycelium of fungi. The color of the soil is light brown.
• Lumpy or powdery soil structure with a dark brown color.
• The humus-accumulative layer is up to thirty centimeters thick.
• Podzolic layer with the same thickness.
• Transitional with variegated coloring layer up to fifty centimeters.
• The illuvial layer, its thickness is 20-120 centimeters.
• A layer of the parent rock.

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 not saturated with useful substances, which affects the nutrition of plants and their growth.