Characterization of soils in order to determine their value is impossible without studying soil profiles. What is it, and what types of profiles are, read the article.
Soil Profile
The process of soil formation affects the rock parent rock, causing soil properties to change vertically. There is a regular change in the composition of the soil from its surface deep down 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 turnover over the years and seasons.
- Vertical distribution of the root systems of plants living in the soil of animals, microorganisms.
All soil profile horizons are interconnected. It happens that soils of horizons of different types have similar properties and characteristics.
Soil profiles: structure
Soil layers alternating vertically are soil horizons. Their structure and properties are different. Soil horizons, sequentiallylying one after another are soil profiles. Their structure is specific for each soil.
The structure of the soil profile is closely related to the process of natural soil formation and their use in agriculture. The 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. Main Horizons:
- Humus soil layer.
- The transition horizon from the previous to the next layer.
- Subsoil (mother rock).
Simple profile
The structure of the soil profile in more detailed consideration can be simple and complex. A simple soil structure has the following profile types:
- Primitive is a thin horizon, the place of diligence is the parent rock.
- Incompletely developed - 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 inherent in non-eroded soil.
- Weakly differentiated - the horizons are weakly distinguished.
- Disturbed or eroded - characterized by the destruction of the upper horizons by erosion.
Complex profile
Types of complex soil profile are as follows:
Relic - this profile has buried horizons and profiles of paleo soils. In its compositionmay have traces of ancient soil formation
- Polynomial profile - formed during lithological changes, without going beyond the soil thickness.
- Polycyclic - its formation is associated with the periodic deposition of materials that form the soil: volcanic ash, river alluvium, ash deposits.
- Disturbed or inverted - characterized by the formation of a different type: natural or artificial. In the first case, the human factor played a role, in the second - natural, when the underlying horizons moved to the surface.
- Mosaic - characterized by inconsistent 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 their washing, which are called eluvial, and the influence of moisture from the atmosphere. Precipitation descending from the soil moves particles and chemicals down.
- 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 layer.
Profile structure by depth
Depending on the distribution of various substances: limestone, humus, gypsum,minerals, s alts, the following soil profiles can be distinguished by depth:
- Accumulative - the top of the soil contains a small amount of substances: the deeper, the less they become.
- Eluvial - the amount of substances increases with depth.
- Soil-accumulative - accumulates substances from groundwater, which are located at the bottom or in the middle of the profile.
- Eluvial-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 horizons, such horizons are distinguished 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 herbaceous, woody, moss, lichen, deciduous or mixed. Remains of plant origin may be undecomposed, partially preserved or completely decomposed
- Forest litter - this layer is rich in organic matter. Its thickness reaches twenty centimeters. Consists of the remains of plants that have retained their original appearance, partially or completely rotted.
- The turf layer is the surface horizon. Its formation occurs under herbaceous plants. Most of the volume is plant roots.
- Muscular horizon - contains 15-35 percent of substances of organic origin. It may be structureless or have a curdled texture. The soil is black, smudged, 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.
- Eluvial horizon - formed under the organogenic horizon. The soil is whitish, clarified.
- Mineral horizon - the place of its formation - the middle part of the profile. May be illuvial, solonetzic, carbonate, saline, gypsum or mixed.
- Gley horizon - it is called mineral. Formation occurs with prolonged or constant excessive moisture and lack of oxygen. A characteristic feature of the horizon is a dull coloration. It can be blue, dove or olive hues.
- Parent rock - characterized by a low degree of impact on it of destructive factors during soil formation.
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. This color name 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. The black color of the soil can be due to compounds of certain minerals, as well as coal of various origins.
- White soil and all other light colors. This colorimparts limestone, gypsum, quartz, soluble s alts, feldspar to the soil.
- Red soil occurs when iron oxide accumulates in its composition. 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 presence of ferrous iron compounds in the soil. Its content in the soil is a consequence of anaerobic conditions (excessive moisture).
What is the power of the horizon?
This is its vertical extent from the surface to the depth of the parent rock. Different types of soils have different thicknesses. On average, it ranges from forty to one hundred and fifty centimeters. For example, if natural 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 dense grassy cover - two hundred or three hundred.
The value of soils is judged by the thickness of individual horizons. Thus, the powerful humus layer is characterized by a large supply of substances and weak leaching. Podzolic soils are poor in nutrients, 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 under the influence of warm summers decomposed, forming humus, which accumulated for a long time. At present, almost completely chernozems are plowed up. The soil profile of chernozem has the following structure:
- Steppe felt, thickness 3-4 cm.
- Turf - its capacity 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.
- The humus horizon is 35-120 centimeters thick. It has a dark gray uniform color. Features of the soil profile of chernozem in its structure. It is grainy and strong. The main feature is fertility.
- Transitional horizon from the humus layer to the next one. Its thickness is 40-80 centimeters, the color is brownish-gray, heterogeneous, spots and streaks of humus are visible. Has a rough, lumpy texture.
- This horizon type has subtypes. In some of them, one can distinguish an illuvial-carbonate horizon with a brownish-pale color and a prismatic structure. The soils of the entire horizon have molehills. They are filled with brown mass coming from the horizons lying below. It happens that molehills are filled with dark-colored earth from the upper horizons.
- Rock 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, s alts, 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 to such conditions in order to participate in the decay processes.residues of organic matter. The profile horizons of podzolic soils are as follows:
- Forest floor - two centimeters capacity.
- Weakly decomposed remains of plants.
- Inclusions in the form of mushroom mycelium. The color of the soil is light brown.
- Lumpy or powdery soil structure with a dark brown color.
- Humus-accumulative layer up to thirty centimeters thick.
- Podzolic layer with the same thickness.
- Transitional variegated layer up to fifty centimeters thick.
- The illuvial layer, its thickness is 20-120 centimeters.
- Parent layer.
Soils of this type in the wild have low fertility, the humus layer is practically absent, the soil reaction is acidic. Podzols do not absorb moisture well, are not saturated with useful substances, which affects the nutrition of plants and their growth.
