The conditions necessary for the formation of these soils are created within the steppe and forest-meadow-steppe regions of the subboreal belt of Eurasia and North America. In Europe, they are common on the Danube low-lying plains, stretching in a strip across Moldova, Ukraine, the central parts of the Russian Plain, the North Caucasus and the Volga region. To the east of the Urals, vast areas of chernozems extend in the southern part of Western Siberia and in the north of Kazakhstan. Separate areas of these soils are confined to the plains and foothills of Altai, the Minusinsk depression, as well as to the basins of Transbaikalia. In North America, chernozems are mainly formed in the Great Plains.

The climate of the zone of distribution of chernozems is continental or Moderately continental with warm summers and moderately cold or even cold winters. The annual temperature range is 30-50 0 С. During the year, precipitation ranges from 300 to 600 mm, in the North American steppes - up to 750 mm. The maximum atmospheric humidification occurs in the summer period, but at this time the highest average monthly temperatures are also noted (20-25 ° C in July), as a result of which a significant proportion of summer precipitation evaporates. Precipitation is uneven during the summer, followed by heavy rainfalls followed by long periods of drought. The average annual moisture coefficient is in the range of 0.8-0.5, and sometimes drops to 0.3 in the warm season. Thus, in summer, chernozems are characterized by periodic drying, but in spring and autumn, due to the percolation of melt and rainwater, a significant part of their profile is noticeably moistened. In a number of regions (in Western Siberia, Transbaikalia, etc.), chernozems freeze through to great depths in winter.

For the most part, chernozems develop on loamy rocks - loesses or loesslike sediments, which are distinguished by fairly good permeability, porosity and carbonate content. Chernozems of the European part of Russia, Ukraine, Western Siberia and the Central Plains of the United States are mainly confined to such breeds. In Canada, the chernozem zone penetrates into the boundaries of the ancient glaciation, where lacustrine-glacial and moraine deposits serve as parent rocks. In Kazakhstan and the Urals, these soils are sometimes formed on carbonate-free eluvium of dense rocks.

The most characteristic relief in the regions where chernozems are formed is flat, with varying degrees of development of the gully-ravine network. Chernozems are widespread on highlands (Central Russian, Dnieper, etc.), lowlands (Middle Danube, West Siberian), in the foothills (Altai, Sayan) and in extensive depressions (in Transbaikalia). As a rule, the conditions of the topography provide sufficiently good soil drainage.

Chernozems develop under herbaceous steppe associations. The nature of the vegetation cover in the areas of distribution of chernozems changes in connection with the peculiarities of hydrothermal conditions. Meadow steppes are associated with areas with a relatively high atmospheric humidity, the high and dense herbage of which is represented by various types of forbs, legumes and cereals. In moderately arid steppes, feather-grass-forb and forb-feather-grass vegetation prevails. Dry steppes are formed by feather-grass-fescue (or fescue-feather grass) more rarefied associations.

Steppe vegetation supplies a large amount of organic matter to the soil. Herbaceous plants in the steppe die off annually in whole or in a significant part, in annuals both aboveground and underground organs die off, in perennials - the entire aboveground part and a significant proportion (about one third) of root systems. Especially a lot of organic residues get into the soil in meadow steppes.

With the transition to feather-grass-forb and feather-grass-fescue steppes, the amount of plant residues entering the soil gradually decreases.

Ground and root litter of steppe vegetation is rich in nitrogen and ash elements. Compared to forest litter (especially coniferous), it contains less wax, resins, tannins, and more calcium, magnesium, phosphorus, which favors humification processes in steppe soils.

The powerful root system of steppe vegetation is a kind of biological barrier that retains many ash nutrition elements necessary for plants in soils. They are actively involved in the biological circulation of substances, and thus their leaching from the sphere of soil formation is prevented. The uncultivated chernozems are abundantly inhabited by a variety of soil fauna. The upper horizons are inhabited by worms, larvae of beetles, weevils and other insects. The upper soil horizons are loosened and mixed by small diggers, voles, etc. Large diggers also live here - marmots, ground squirrels, which make the soil even more breathable and permeable.

Chernozems are characterized by high microbiological activity, the maxima of which occur in the spring and autumn periods, when optimal hydrothermal conditions are created in the soils. In summer, microbiological activity is sharply reduced due to drying out of the soil, and in winter - as a result of its freezing.

Thus, in the areas of distribution of chernozems, the following complex of soil formation conditions is formed:

a) the presence of herbaceous vegetation supplying a large amount of organic residues rich in ash elements and nitrogen;

b) richness of parent rocks with calcium carbonates or primary calcium-containing minerals;

c) continental climate with alternating periods of moisture and desiccation, warming and freezing of soils.

The morphological profile of typical chernozems includes the horizons indicated below.

The horizon of the steppe felt lies on the surface (if the soils are plowed up, then this horizon is absent).

Below, a powerful humus-accumulative horizon Al t is developed - dark gray, almost black, fine-grained or lumpy-grainy, loose, densely penetrated by the roots of herbaceous plants (especially in the upper part) and worm holes.

A1B - transitional humus horizon, brownish-gray, downward gray color is weakening, granular-lumpy, less loose than the overlying one; in the lower part it boils and contains carbonates in the form of pseudomycelium and tubules;

In sa - illuvial-carbonate horizon, brown or pale-brown with whitish spots of nodule carbonate new formations (white-eyed); has a lumpy-nutty structure, compacted;

WITH sa - parent rock, is distinguished by a decrease in the content of carbonate accumulations and a deterioration in the structure.

According to the total thickness of the A1 h and A1B horizons, chernozems are subdivided into types: thin - less than 40 cm, medium-thick - 40-80 cm, powerful - 80-120 cm and super-powerful - more than 120 cm.

By the depth of occurrence of the carbonate horizon, subtypes of typical chernozems (the profile described above), leached and podzolized (between the A1 h and B ca horizons are developed a horizon leached from carbonates, and sometimes with signs of podzolization), as well as ordinary and southern (in which carbonates are present) respectively, in the middle part of the A1B horizon and in the lower part of the A1 horizon).

According to the humus content, among the chernozems, they are distinguished: poly-humus, or fat (more than 9%), medium-humus (6-9%) and low-humus (less than 6%). Within the humus profile, organic matter gradually decreases with depth (Figure 17.3). Chernozems are soils with the widest possible humus ratio C g / C f - from 1.5 to 2.0 and even slightly more. Among the fractions of humus, humic acids associated with calcium predominate. A significant content of nitrogen, potassium and phosphorus is observed in the humus horizon.

The reaction of the soil solution in the upper part of the profile of typical chernozems is close to neutral. In carbonate horizons, it becomes slightly alkaline. Due to the large amount of organic colloids, the absorption capacity is very high, especially in the upper horizons (from 30 to 60-70 mg × eq per 100 g of soil). The soil absorbing complex is completely saturated with bases, among which calcium predominates (75-80%). The remaining 20-25% are absorbed magnesium. The gross chemical composition is practically the same in all soil horizons, as well as the chemical composition of the clay fraction. A small silt maximum is found in the upper part of the profile. In horizon Вca, the accumulation of calcium carbonates is analytically confirmed.

Rice. 17.3. Chernozem profile. Genetic horizons: 1 - humus-accumulative humate-calcium; 2 - transitional; 3 - illuvial-carbonate; 4 - siallitic-carbonate parent rock. The composition of the mud fraction: 5 - illite-montmorillonite

Chernozems have good physical properties: water-resistant structure, high air and water permeability, significant water-holding capacity.

Most of the properties of chernozems are due to the peculiarities of the processes of humus formation and humus accumulation that take place in these soils. Significant amounts of herbaceous residues entering the soil annually, their high ash content and the richness of ash in bases are one of the determining factors for deep humification of organic matter. In relatively humid and rather warm spring and autumn periods, when the microflora (mainly bacterial) is maximally activated in chernozems, an intensive transformation of organic residues occurs in the direction of the production of mainly humic acids. In soils at this time, a neutral reaction of the environment predominates, in the sphere of humus formation there is a large amount of alkaline earth bases and, as a result, stable organo-mineral compounds of humic acids, primarily calcium humates, are formed. Fulvic acids are formed much less and only in the form associated with humic acids. There are no free, aggressive fulvic acids in chernozems.

In parallel with the humification of organic matter in the spring and autumn, its very intensive mineralization takes place. However, the results of the latter process are not manifested in a sharp decrease in the humus content, since it is significantly inhibited in summer and winter. In dry summer and cold winter seasons, chemical transformations of newly formed humic substances stop. Drying and freezing of the soil mass leads to the fact that these substances are strongly dehydrated, coagulate and pass into a sedentary state, almost irreversibly losing solubility. It is the alternation of periods of rest and active course of humus formation that contributes to the formation of large reserves of humus in chernozems.

The development of accumulative phenomena in chernozems is also favored by other features of the genesis of these soils. The combination of a large amount of organic colloids with a high absorption capacity and an almost complete saturation of the soil absorbing complex with doubly charged cations (calcium and magnesium) lead to the colloids being in a stable, strongly coagulated state. They are consolidated into structural aggregates and do not move along the profile.

The formation of a water-resistant lumpy-granular structure in chernozems is also facilitated by the abundant root system of herbaceous plants, densely penetrating the upper soil horizons. Grass roots divide the soil mass into numerous small lumps and compact them. During the decomposition of dead roots, the humic substances formed from them glue the soil particles together.

The structuring of chernozems is also associated with the activity of the abundant soil fauna, especially earthworms. Many structural aggregates in these soils are zoogenic.

A good structural state of soils creates water and air regimes of the soil that are very favorable for plant life: inside soil aggregates, capillary-suspended moisture can be retained in the capillary gaps between the parts, while the spaces between the lumps can be filled with air at the same time.

The genesis of chernozems is largely determined by the processes of movement and transformation of mineral water-soluble salts in the soil profile. As mentioned earlier, the chernozems of the steppe zone exist in a non-flush water regime. The usual soaking depth is about 2 m. As a result, the upper part of the chernozem soil profile is devoid of water-soluble salts, and illuvial salt horizons are formed at a certain depth. The illuvial carbonate horizon is especially characteristic of chernozems. Its formation involves both biogenic calcium carbonates and carbonates inherited by the soil from the rock. The mechanism of this process is as follows.

Carbon dioxide released during the decomposition of organic residues in the upper part of the soil profile combines with calcium, which is released during the mineralization of plant residues, and forms calcium bicarbonate. Part of the produced carbon dioxide, dissolving in soil moisture, contributes to the conversion of insoluble carbonates of the rock into more soluble bicarbonates according to the scheme CaCO 3 + CO 2 + H 2 0 -> Ca (HCO 3) 2. With descending streams of moisture, bicarbonates move down the profile, where they turn into various forms of carbonate neoplasms (white-eye, lime smears, pseudomycelium, etc.).

Many researchers believe that the amount of carbonates in chernozems depends on the degree of the original carbonate content of the source rocks. However, there is a point of view according to which the carbonate content of rocks is not the primary cause, but a consequence of the chernozem and, in a broader sense, steppe soil-forming process (JI.C. Berg, S.S. Neustruev, B.B. Polynov). Various facts are cited to prove this. So, on the primary carbonate-free eluvium of granites under the conditions of the steppe climate and under the steppe vegetation, soils with a carbonate horizon are formed. In this case, the entire thickness of the loose substrate in the process of soil formation is calcified due to the weathering of aluminosilicate calcium-containing minerals and the supply of a certain amount of calcium carbonates to the soil surface with atmospheric precipitation and dust masses.

In some chernozems of the most arid part of the steppe zone, at the very bottom of the profile, such readily soluble salts as gypsum, sodium and magnesium chlorides and sulfates can also be found. The formation of such illuvial-salt horizons, as a rule, is associated with the initial salinity of the rocks and the leaching of the named salts from the upper and middle parts of the profile during the process of soil formation.

Depending on the depth of soil wetting and the recurrence of relatively wet years, gypsum and salt illuvial horizons are located either directly under the carbonate horizons, marking the boundary between the soil and the parent rock, or located below the boundaries of the soil, already in the thickness of the parent rock, as is observed in most chernozems.

The age of chernozems is estimated at several tens of thousands of years. For the formation of a more or less mature chernozem soil profile with a characteristic thick humate - calcium horizon, according to various estimates, it takes time from 3-5 thousand to 10 thousand years. Some researchers believe that such properties of chernozems, such as poly-humus content, the presence of nodule carbonate new formations and a general high calcification of the profile, at least in a number of territories have a relic character and are inherited from the previous periods of the development of these soils in conditions of close occurrence of mineralized groundwater, i.e. chernozems have signs of paleohydromorphism (V.A.Kovda, E.M. Samoilova, etc.).

Chernozems are one of the most fertile soils in the world. They have chemical properties favorable for agriculture (rich in humus, mineral nutrients) and physical properties (good structure, air and water permeability). The highest yields of cereals, sugar beets, sunflowers and many other crops are obtained on these soils. At the same time, their irrational exploitation often leads to degradation - loss of humus, overconsolidation, erosion and secondary salinization.

What does black soil mean? Chernozem is a fertile land with a black shade of color, land endowed with a huge amount of humus and having a granular-lumpy structure. As a rule, chernozem soils are formed in the forest, as well as on loams and clays in a temperate continental climate.
Today, black soil can rightfully be considered the best soil for farmers, farmers and gardeners, a soil on which flowers, trees and shrubs, as well as fruit crops, such as tomatoes, cucumbers, peppers, etc. grow beautifully. Therefore, black soil is an excellent garden land, an excellent land for vegetable gardens, as well as for houseplants.
On the territory of our state, chernozem soils for the most part prevail in Western Siberia, in the North Caucasus, in the Volga region, in the central chernozem regions, and they can also be seen today on the territory of Ukraine, in North and South America, in China and a number of European states. ...

Chernozem is a land saturated with humus, for the formation of which the following conditions are important:
- temperate climate or moderate continental;
- sequential alternation of desiccation and moisture;
- positive temperature conditions.
As established by experts, for the formation of chernozems, the most favorable is the temperature regime above +5 degrees and the annual precipitation is up to 600 mm, no more.
Chernozem lands are found, as a rule, on undulating-flat relief, indented in some places by ravines, depressions and river terraces.

As for the vegetation on chernozem soil, meadow-steppe and herbaceous plants prevail here. Under appropriate climatic conditions, the process of decomposition of such vegetation takes place, as a result of which humus is formed, which accumulates in the upper soil layer over the years. Along with humus, chernozem soils also contain a number of other substances, such as mineral compounds and complex organic substances. It is thanks to them that nutrients such as phosphorus, nitrogen, sulfur and some others, important for plants growing on chernozems, begin to form in the soil.

About the properties of black soil

Chernozem differs not only in its granular-lumpy structure from other types of soils, but also in excellent water-air qualities and a huge content of calcium in its composition. The last substance in chernozem soils contains up to 90%.
Among farmers, chernozem is very valuable and people appreciate it, first of all, for its increased fertility, which in this case is associated with intense natural humification and a very high level of humus in the upper soil layer. In this case, humus is contained in the soil about 15 percent.

Types of chernozem

Specialists subdivide chernozem into 5 main types.
1. Leached. This type of chernozem is formed in the forest-steppe zone in the process of dying off of herbs and grasses.
2. Podzolized. This type of chernozem is inherent in broad-leaved herbaceous forests.
3. Ordinary. This black soil can be found in the steppe zone. It is formed, as a rule, in the process of dying off of herbaceous vegetation.
4. Typical. The formation of typical chernozem occurs on loams, in meadow-steppe zones and in forest-steppe regions as a result of the decay of herb-cereal crops.
5. Southern. This type of chernozem can be seen in the steppe zones in their southern part, and it is formed as a result of the withering away of fescue-feather grass vegetation.
Due to the high content of humus in black soil, this type of soil is valued mainly for its high level of fertility and stable yields. Black soil is sold, that is, garden soil in bags, as well as in packages weighing from 1 kilogram to several tens of kilograms.

It is worth noting that in addition to humus, chernozem contains other substances that are no less useful for fruit plants, such as phosphorus, nitrogen, iron and sulfur. According to its direct structure, the chernozem soil resembles small lumps of fertile land, and the chernozem soil of the southern zones is considered the most fertile. This soil, in another way, is also called “fatty earth” or “fatty black soil” by experts.

Today, chernozem is appreciated not only in our state, but also far beyond its borders, and all thanks to the increased fertility of such soil. At present, it is black soil that is recognized as the best soil for growing berries, fruits, vegetables, fruit bushes and trees. It is important to know that for some individual plant species, only black soil in the soil will not be very useful and it is important to mix it with other useful components, for example, with sand, peat or compost. These components help to make the black soil looser, which will allow you to get the best fruits of certain types of fruit crops.

Application of chernozem

As you know, the best soil for growing vegetables, fruits, berries, as well as fruit and berry bushes and trees is black soil, and all because this soil is very fertile. Chernozem, as the name implies, has a black color, and with it a dense composition.

Today chernozem soils are used in horticulture, horticulture and agriculture as high-quality fruit land for planting various kinds of plants, shrubs, grasses and trees. Chernozem is used today when laying out lawns, as a special plant soil, for cultivating lands endowed with a large amount of clay, as well as for diluting lands with poor drainage systems in order to create an air-water regime favorable for plant growth on such lands. Chernozem is also the best soil for seedlings, it is in it in black soil that seedlings grow stronger and begin to grow at an unprecedented rate.
Today, fertile land is sold in packages and in bags in any volume, you can buy black soil and all kinds of fertile mixtures from it personally from us at the most affordable price.

Characteristics of chernozem

Chernozem is a soil that is enriched with a huge amount of humus and the humus content is especially pronounced in the chernozem in its upper layer. At the same time, chernozem soils contain a huge amount of nutrients and microorganisms useful for plants, and visually they represent a lumpy or granular structure. Endowed with black soil and excellent water-air qualities, which no other natural soil is endowed with today.
Experts have proven that black soil contains up to 90% calcium, as well as humic acids, which today are the most valuable and simply irreplaceable fraction of humus, quickly assimilated by the roots of absolutely all types of plants.
Meanwhile, even in spite of the fact that the chernozem soil has a number of such significant advantages, it also has one drawback. Chernozem does not have friability, and therefore, when planting plants with a weak root system in this land, it is important to take care of imparting friability to the chernozem. This can be done very easily by adding a little sand, peat, or a special compost mixture to the ground, which can be purchased at any gardening or hardware store. The most optimal proportion for creating natural looseness of chernozem is three parts of chernozem itself to one part of any of the above components, that is, peat, sand or compost mixture.

It is worth noting that chernozem soil is also a very oily soil, and this can be seen by simply picking up such soil and squeezing it. On any hand, after the above actions, a black bold imprint will remain. This is what suggests that chernozem is a fertile land with a fairly high content, as already noted, of humus. Due to its such qualities, properties and less porous structure than other types of soil, black soil does not bake in the sun and does not rot under the influence of moisture, as clay soils do, for example.
Plants in chernozem feel quite vigorous and at ease, because here they are provided in abundance with all the elements and oxygen necessary for nutrition, which is so important for the growth of any living organism. In order to grow good fruits on chernozem soils, you do not need to fertilize the ground with some kind of chemistry or dietary supplements, the plants will bloom and delight you in natural conditions without any soil impurities.

Types of chernozem

Today, all farmers and gardeners rightfully call black soil the standard of soil, and this is not in vain, because it is he, the black soil, which is half humus, endows plants and fruit crops with everything they need for their life and excellent growth. Consequently, black soil is the most fertile land and this fact is undeniable.
Meanwhile, depending on where exactly the black soil was formed, it differs markedly in its composition. So, chernozem soils are poured into the following types:

Typical black soil;
- drained black soil;
- leached chernozem;
- podzolized black soil;
- carbonate-free, etc.

At the same time, despite the difference in species, black soil in any case remains the most fertile soil.
Distinguish chernozem not only by the territory of formation, but also by the percentage of humus in it. In this case, scientists divide chernozem soils into the following types:

Low-humus (contain up to 4% pure humus in their composition);
- low-humus (contain up to 5-6% of pure humus in their composition);
- medium humus (contain from 6% to 9% of pure humus in their composition);
- highly humus (contain over 9% of pure humus in their composition).

Today, fertile land is sold in bags and packages of various sizes. So, for example, garden land in packages (5,10,25,60 liters) can be purchased directly from us at a favorable price. Landscaping and landscaping of your backyard area with such land will be quick and easy. Among other things, you can buy soil for seedlings and other compositions useful for the growth and development of plants from us.

The first classification of chernozems was given by V.V. Dokuchaev, who distinguished them as an independent type and divided them according to topographic conditions into mountain chernozems of watersheds, chernozems of slopes and valley chernozems of river terraces. In addition, V.V. Dokuchaev divided all chernozems by humus content into four groups (4-7; 7-10; 10-13; 13-16%).

Considerable attention was paid to the classification of chernozems by N.M. Sibirtsev. In his classification (1901), the chernozem soil type was divided into subtypes - northern, fat, ordinary, southern.

In the future, the subtype of northern chernozems began to be called, according to S.I. Korzhinsky, degraded, and then it was divided into two independent subtypes - podzolized and leached chernozems.

In 1905 L.I. Prasolov, on the basis of studying the chernozems of the Azov and Ciscaucasia, identified a subtype of the Azov chernozems, which was later named Pre-Caucasian. The accumulation of information on the chernozems of these regions made it possible to further consider their genetic characteristics as a result of provincial and facies conditions of soil formation and not to distinguish them at the level of an independent subtype.

Based on the generalization of extensive materials on the study of chernozems in various regions of the country, the following division of the chernozem type of soils into subtypes and genera is currently accepted.

Below is a description of the main genera of chernozems.

Regular - highlighted in all subtypes; signs and properties correspond to the main characteristics of the subtype. In the full name of chernozem, the term of this genus is omitted.

Poorly differentiated - developed on sandy loam rocks, typical signs of chernozems are poorly expressed (color, structure, etc.)

Deep boiling - boil more deeply than the genus "ordinary chernozems", due to a more pronounced leaching regime due to the lightweight texture or relief conditions. Stand out among the typical. Ordinary and southern chernozems.

Carbonate-free - developed on rocks poor in silicate calcium, there is no effervescence and release of carbonates; are found mainly among the typical, leached and podzolized subtypes of chernozems.

Solonetzic - within the humus layer have a compacted solonetzic horizon with an exchangeable Na content of more than 5% of the capacity; stand out among ordinary and southern chernozems.

Solodized - are characterized by the presence of a whitish powder in the humus layer, the flow of humus color, varnishing and smears along the edges of the structure in the lower horizons, sometimes by the presence of exchangeable sodium; distributed among typical, ordinary and southern chernozems.

Deep gley - developed on binomial and layered rocks, as well as in conditions of long-term preservation of winter permafrost.

Merged - developed on silty-clayey rocks in warm facies, characterized by a high density of the horizon B. They stand out among the chernozems of the forest-steppe.

Underdeveloped - have an underdeveloped profile due to their youth or formation on strongly skeletal or cartilaginous-gravelly rocks.

All chernozems are divided into types according to the following criteria:

In terms of the thickness of the humus layer, they are super-powerful (more than 120 cm), powerful (120-80 cm), medium-thick (80-40 cm), low-power (40-25 cm) and very low-power (less than 25 cm);

In addition, chernozems are divided into types according to the severity of the accompanying process (weak, medium, highly leached, weak, medium, strongly solonetsous, etc.).

A clear zonal pattern is observed in the geographical distribution of the subtypes of chernozems. Therefore, the zone of chernozem soils from north to south is subdivided into the following subzones: podzolized and leached chernozems, typical chernozems, ordinary chernozems and southern chernozems. The most clearly indicated subzones are expressed in the European part of the country.

Chernozem soils in the forest-steppe zone are represented by podzolized, leached, and typical chernozems.

Podzolized chernozems. In the humus layer, there are residual signs of the impact of the podzolic process in the form of a whitish powder - the main distinctive morphological feature of this subtype. The humus profile of podzolized chernozems of gray, less often dark gray color in horizon A and noticeably lighter in horizon B. Whitish powder, with its abundant content, gives the profile of chernozem a grayish-ash tint. Usually it, in the form of a whitish coating, as it were, powders the structural units in horizon B 1, but with strong podzolization, a whitish tint occurs in horizon A.

Carbonates occur well below the humus layer boundary (usually at a depth of 1.3-1.5 m). Therefore, in the podzolized chernozems under the humus layer, there is a brownish or reddish-brown illuvial horizon leached from carbonates of a nutty or prismatic structure with a distinct varnish, humus smears and whitish powder on the edges. Gradually, these signs weaken, and the horizon passes into a rock containing at some depth carbonates in the form of calcareous tubes, cranes. They are divided into genera - ordinary, poorly differentiated, merged, carbonate-free.

When classifying podzolized chernozems into species, in addition to dividing by thickness and humus content, they are subdivided according to the degree of podzolization into weakly podzolized and moderately podzolized.

Leached chernozems. Unlike podzolized chernozems, they do not have silica powder in the humus layer.

Horizon A is dark gray or black in color, with a pronounced granular or granular-lumpy structure, loose constitution. Its thickness ranges from 30-35 to 40-50 cm. The lower boundary of the B 1 horizon lies on average at a depth of 70-80 cm, but sometimes it can go even lower. A characteristic morphological feature of leached chernozems is the presence of horizons V 2 leached from carbonates under the B 1 horizon. This horizon has a pronounced brownish color, humus streaks and smears, a nutty-prismatic or prismatic structure. The transition to the next horizon - BC or C - is usually distinct, and the boundary is distinguished by the accumulation of carbonates in the form of lime mold, veins.

The main genera are ordinary, poorly differentiated, carbonate-free, deep-gley, merged.

Typical chernozems. They usually have a deep humus profile (90-120 cm and even more) and contain carbonates in the humus layer in the form of mycelium or calcareous tubes. Carbonates appear more often from a depth of 60-70 cm. For a more detailed morphological characteristics of the humus layer, two horizons that are transitional in humus color are distinguished below horizon A - AB 1 and B 1.

Horizon AB 1 is dark gray with a faint brownish tint downward, while horizon B 1 already has a distinct brown tint. In the lower part of horizon AB 1, or more often in horizon B 1, carbonate efflorescence is visible.

Horizon В 2 (ВС) and the rock contain carbonates in the form of mycelium, calcareous tubules and cranes.

They are divided into the following genera: Common, carbonate-free, deep-boiling, carbonate solodized.

Chernozems of the steppe zone

Chernozems in the steppe zone are represented by ordinary and southern chernozems.

Ordinary chernozems. Horizon A is dark gray or black, with a distinct granular or lumpy-granular structure., 30-40 cm thick. Gradually passes into horizon B 1 - dark gray with a clear brownish tint, with a lumpy or lumpy-prismatic structure. Most often, the thickness of the humus layer in ordinary chernozems is 65-80 cm.

Below horizon В 1 lies the horizon of humus streaks В 2, which often coincides with the carbonate illuvial horizon or very quickly passes into it. The carbonates here are in the form of a white-eyed. This feature distinguishes ordinary chernozems from the previously considered subtypes.

The subtype ordinary chernozems is divided into genera: ordinary, carbonate, solonetzic, deep boiling, poorly differentiated and solodized.

Southern chernozems occupy the southern part of the steppe zone and directly border on dark chestnut soils.

Horizon A, 25-40 cm thick, has a dark gray or dark brown color, often with a slight brown tint, a lumpy structure. Horizon B 1 is characterized by a clear brown-brown color, lumpy-prismatic structure. The total thickness of the humus layer (A + B 1) is 45-60 cm.

In the illuvial carbonate horizon, the white-eye is usually clearly expressed. The boiling line is located in the lower part of the B 1 horizon or at the border of the humus layer.

Southern chernozems are subdivided into the following genera: common, solonetzic, carbonate, deep boiling, poorly differentiated and solodized.

INTRODUCTION

More than 10% of the world's agricultural land is located in Russia. According to media reports, our country remains the last large reserve of agricultural land on the planet, at least in the "civilized" world. Therefore, knowledge of our land resources suitable for farming has recently become extremely important. According to the founder of Russian soil science V.V. Dokuchaev “our plant-land soils (which are represented by black soil) are not some mechanical, random, lifeless mixtures, but, on the contrary, are independent, definite and subject to known laws natural-historical bodies” (1).

1. CHARACTERISTICS OF CHERNOZEM

Composition

Chernozem provides a rather heterogeneous mass: pieces of quartz, flakes of humus, and sometimes fragments of limestone, feldspar and even granite pebbles come across here.

It is very rich in humus (dark organic matter, one might say natural manure) and the most important readily soluble nutrients for plants, such as phosphoric acid, nitrogen, alkalis, etc. and composition) with the underlying rocks (subsoil), which themselves (loess) in the vast majority of cases are very rich in soluble nutrients and are endowed with excellent physical properties.

Structure

Chernozem is a plant-ground soil, the thickness of which is about 60 cm on average. Under the turf 5–8 cm thick there is a dark homogeneous loose mass - humus, consisting of grains or grains, sometimes roundish, but more often representing irregular polyhedrons. This horizon in unplowed, virgin places is filled with hundreds of thousands of living and dead underground parts of herbaceous plants. The average thickness of the horizon A (the accepted designation by V.V. Dokuchaev) is 30–45 cm. Below, the soil horizon merges completely imperceptibly with the transitional horizon, which, in all its physical and chemical characteristics, is a gradual transition from the upper (A) horizon to the lower (C) subsoil. The thickness of horizon B is also 30-45 cm. Subsoil - base (C) in the vast majority of cases consists of loess (light yellow, very loose, carbonate-rich loam), but often it is also composed of sandy loam, chalk, limestone, marl, etc. ., and always the subsoil (C) gradually passed into the upper soil horizons (A and B), giving them a strictly defined mineral character. Thus, chernozem in all natural, undisturbed (in one way or another) sections represents a gradual, closest genetic relationship with the subsoil, whatever its composition.

Types

There are the following subtypes of chernozem soils:

Podzolized chernozems,

Leached chernozems,

Typical chernozems,

Ordinary chernozems,

Southern chernozems.

Properties

1. Due to its composition, chernozem always has a more or less dark color and has a favorable attitude to heat and moisture. Color is a typical external sign: the color of black soil, whether the latter will contain humus up to 15% or no more than 3-4%, always turns out to be more or less dark,

2. The replenishment of chernozem, that is, the ability to become much more ripe (in the agricultural sense), that is, such a subsurface horizon of which is approximately the same composition in structure as the arable one.

3. Another typical constant feature is the average thickness of chernozem, which ranges from 60 to 140 cm.

2. AREAS OF DISTRIBUTION

According to V.V. Dokuchaev chernozem is always and everywhere the result of cumulative activity:

a) bedrock (subsoil), on which it lies at the present time;

b) the climate that surrounds this soil now and surrounded in the past (latitude and longitude, the nature of precipitation, temperature, winds);

c) wild vegetation that grew there and still grows to this day in places untouched by culture.

The areas of distribution of fertile plains in the world are: the steppes of Europe and Asia, the savannahs of Africa, Australia, the prairies of North America and the Pampa of South America, Venezuela, Brazil.

On the territory of Russia, chernozems are widespread in the regions of the Volga region, the Urals, the North Caucasus, the Lower Don and Western Siberia. The heart of the black earth strip is the Voronezh and Saratov regions. The massif of chernozem soils in the world is 48%, in Russia - 8.6%, which is 1.53 million km 2.

3. APPLICATION

Chernozem soils can withstand a long-term culture without any fertilization and each time, under favorable climatic conditions, they give excellent yields of rice, cereals, sunflowers, beets, fodder, fruits, grapes and other industrial and vegetable crops. The natural fertility of chernozem soils fully satisfies the population's need for food, provides a significant part of raw materials for light industry, and ensures livestock breeding.

"... the fundamental, incomparable wealth of Russia ..."
(V. V. Dokuchaev. Russian chernozem, 1898)

The parent rocks of chernozems are represented by loose loess-like sediments and loesses, but chernozems are also found on derivatives of dense rocks. As a rule, the source rocks have a silty-silty granulometric composition, contain carbonates, and their fine fractions consist of mixed-layered mica-smectite formations. The formation of chernozems is facilitated by the increased porosity and microaggregation of rocks, their good water permeability and high absorption capacity.

Chernozems are widespread both on elevated erosional plains and on low-lying accumulative plains (including terraces), as well as in foothills and intermontane basins.

The climate of the areas of distribution of chernozems as a whole is characterized by balanced moisture (Kuvl = 1–0.5) with a summer maximum of precipitation and a relatively uniform distribution of them in the rest of the time, a warm summer with a drying profile and its winter freezing. The alternation of these cycles is necessary for the formation of a kind of "black earth" humus.

Steppe forb-cereal vegetation is traditionally considered an important factor of chernozem formation due to the large mass of roots, increased ash content and easy decomposition of litter and steppe plants, high biodiversity of cenoses, and, consequently, the cyclicity of vegetation and the depth of root systems. These features of phytocenoses, in combination with a moderately warm and periodically humid soil climate, provide a high biological activity of microbocenoses, as well as meso- and macrofauna.

Chernozems occupy about 8% of the country's area; they are most diverse in the European part of Russia, where geographical models of their distribution were created. Chernozems form a number of subzonal subtypes: - podzolized, leached and typical; steppe - common and southern. The series is supplemented by facies subtypes: in the south of Russia - Azov-Ciscaucasian, and in Siberia - cryogenic-mycelial and powdery-carbonate.

Genetic horizons: The accumulative-humus (dark humus) horizon is a “visiting card” of chernozem, it is practically the same in all subtypes and types of chernozems. It has excellent macrostructure (a, b) and microstructure (c). Water-resistant aggregates, largely created by earthworms and root systems, form a granular structure and "root beads". High porosity (up to 50%) and low bulk density (~ 1 / cm3) are characteristic. The dark color is determined by the high humus content (5–8%) and its humate-calcium composition (Cr / Cfk> 2). The horizon is saturated with bases, its reaction is close to neutral. The thickness of the horizon is 40 - 120 cm.

The accumulative-carbonate horizon in its formation is associated with humus (saturation of its roots and biological activity), hydrothermal regimes of the profile and carbonate content of the rock. The accumulation of carbonates is determined by the seasonal dynamics of CO2 and soil solutions, and the forms of carbonate new formations serve as criteria for the separation of chernozems. So, the migratory forms of carbonates - tubules, pseudomycelium (d) - are characteristic of chernozems of a relatively humid and warm climate, in contrast to segregations - white-eyed (e), which form in a more continental and arid climate.

Chernozems on within the forest-steppe are found in combinations (by mesorelief) with gray forest soils. Steppe chernozems form vast homogeneous areas; on the Volga Uplands, chernozems on dense sedimentary rocks add variety to the soil cover; In the Trans-Volga region, solonetz and solonetzic soils are widespread among chernozems. In the western and central regions, medium-thick and powerful, low- and medium-humus species and subspecies of chernozems prevail; to the east, the humus content in the humus horizon increases and the thickness of the humus profile decreases. The maximum thickness of the humus profile with a low humus content is characteristic of the chernozems of the Ciscaucasia. Provincial patterns in relation to the humus profile are also traced in the zonal series of Siberian chernozems, the most complete series of which is represented in the West Siberian. To the east, the areas of chernozems become fragmented - in the foothills and intermontane basins (with forest-steppe cryogenic-mycelial chernozems); in steppe powdery-carbonate chernozems are combined with meadow-chernozem soils in depressions.

A fertile humus horizon with a high humus content and a thickness of 1 m or more is a distinctive feature of Russian chernozems. It is no coincidence that in the early soil classifications, the "fat" and "superpower" chernozems were distinguished. The increased reserves of humic substances in chernozems are associated with the peculiarities of the biological cycle, characteristic of virgin herb-feather grass and fescue-feather grass. The main background in them is made up of cereals with developed root systems, so that root litter, rich in nitrogen and ash elements, makes up 40–60% of the total input of organic residues into the soil. Their decomposition under optimal hydrothermal conditions at neutral or slightly alkaline pH values ​​contributes to the formation of humus with a predominance of complex humic acids, which are firmly fixed in the soil. During the study of Russian chernozems by the founder of Russian soil science, V.V. Dokuchaev, the level of humus in the soils of the forest-steppe and steppe zones of the then Russia ranged from 3–6% to 10–13%, which was reflected on the map of isohumus strips (humus content). V.V.'s map illustrates the level of humus content in chernozems of European Russia at the end of the 19th century; it increased from west to east, reflecting both the provincial features of chernozem formation and the longer agricultural use of chernozems in the western regions of the country.

The high fertility of chernozems determines their value in the arable fund of Russia, where they account for more than half. Large reserves of humus and basic plant nutrients (nitrogen, phosphorus, potassium), favorable water-physical properties led to the active development of chernozems, starting from the 17th – 18th centuries. In the 20th century, small areas of virgin steppes remained only in protected areas; practically the entire black earth zone of the country was plowed up.

The natural profile of chernozems used in the region changes to a lesser extent than is observed in other soils, which is associated with the high thickness of the humus horizon and the preservation of the herbaceous type of vegetation. Nevertheless, in chernozems under agrocenoses, the nature of the biological cycle of substances changes due to the withdrawal of phytomass of agricultural crops, the application of fertilizers; the microclimate and all soil regimes are being transformed; for ordinary and southern chernozems, a negative impact is added to anthropogenic impacts. Many studies have been devoted to the agrogenic degradation of chernozems, which have proven that its trigger is a decrease in the content of humus and a change in its qualitative (fractional) composition. Dehumification of soils is a consequence of the accelerated mineralization of organic matter and its entry into the arable soil in a significantly smaller volume, as well as direct losses of humus during water and wind. Even VV Dokuchaev in his work "Our steppes before and now" noted the unfavorable tendencies of the loss of humus by chernozem soils. The use of intensive technologies in agriculture in the second half of the 20th century caused the dehumification of almost all chernozems. The map, compiled by G. Ya. Chesnyak (1986) "in the footsteps of Dokuchaev" (that is, based on the results of determining the humus content in the same places as in the expedition of V.V.Dokuchaev), shows the spatial tendencies of humus losses in the Russian plains over 100 years since the publication of the book by V. V. Dokuchaev "Russian Chernozem". Especially large losses of humus are noted for the Cis-Urals, which is associated with the initial lower thickness of the humus profiles of these chernozems and the wide development of erosion processes here, caused by a combination of natural factors and a relatively low culture of agriculture.

In addition to dehumification, the general tendency during plowing is the deterioration of the soil structure due to the loss of humus, changes in its composition and multiple passes through the field of heavy agricultural machines. The transformation of the granular or lumpy-granular structure of the upper ones, with their high porosity and water permeability, into the lumpy-dusty one is accompanied by the transfer of a part of the subsurface runoff to the surface one and leads to the development of planar (rivulet) erosion. In addition, arable soils are not covered in all seasons of the year, which changes their hydrothermal regime; due to deeper and more prolonged freezing, the surface runoff of melt water increases. The development of erosion has greatly increased as a result of a reduction in the areas of watershed forests and unrestricted plowing of slopes, especially on the Central Russian and Volga Uplands with their dissected and in places thin cover of loose sediments.

With a high potential fertility of chernozems, a factor limiting the receipt of high yields may be the instability of the moisture supply of crops (especially in the southern regions and in the Volga region). Large areas of southern and common chernozems are used with regular irrigation. As a rule, when irrigated with moderate rates, secondary salinization does not threaten chernozems, but such negative consequences as alkalinization, alkalization and deterioration of physical properties are observed: the formation of a surface crust and compaction.

Concern about the fate of the Russian Chernozem forces Russian soil scientists to pay increased attention to the study of various aspects of the functioning of these soils. World recognition of the role of chernozem was manifested in the fact that 2005 was declared the Year of Chernozem - the soil that opened a new international social and scientific action "Soil of the Year". The alarming situation with the current state and use of chernozems inevitably raises the question of including a number of chernozems in the Red Book of Russian soils.