Chernozem where. Chernozems, properties of chernozems, types of chernozems, earth - chernozem

Let's stop first at short description soil formers characteristic of the steppe zone.
We can characterize the climate of the steppe zone, generally speaking, as continental, dry, especially in the eastern part of the described zone. At the same time, the dryness of the climate here is determined not so much by the small amount of precipitation, but by the nature of their precipitation and other meteorological conditions. Indeed, in the steppe zone during the year, on average, precipitation from 400 to 500 mm falls, which almost corresponds to the amount of precipitation in some northern regions of Russia. Ho, firstly, precipitation falls in the steppe zone, usually in the form of showers, which, due to the fine earth content and poor water permeability of chernozem soils, do not have time to be completely utilized last and, for the most part, drain uselessly into low places, ravines, etc. Further, Precipitation these are confined mainly to the summer months, when, due to the high temperature, their evaporation reaches a maximum (their approximate distribution during the year is as follows: about 200 mm in summer, about 100 mm in autumn, about 80 mm in spring and about 70 mm in winter).
The low relative humidity of the air in the steppe zone, which sometimes reaches no more than 45% in the summer months, also contributes to a large evaporation of precipitation. Let us add here the withering effect of the so-called "dry winds" - such common winds for the described zone, the withering effect of a powerfully developed system of ravines and gullies, creating, as it were, natural drainage of the area and increasing the surface of contact of the soil with air, etc.
Thus, the soils of the described type are for most of the year under conditions of such moisture, which explains to us the relatively low leaching of these soils, which can be expressed in the removal from the soil stratum of only easily soluble salts (sodium and calcium) that were present in the original parent rock and formed in the process of weathering of the latter; on the other hand, there is a relatively weak decomposition of the remains (vegetable and animal) accumulated in their surface horizons.
However, it should be noted that by the beginning of the growing season, i.e., by spring, the surface horizons of soils of the type of soil formation under consideration, undoubtedly, are still more or less provided with moisture for the production of a huge amount of plant mass, which is expressed by herbaceous flora with a short vegetation period. period: melt water and spring precipitation, due to the relatively low temperature at this time of the year and still relatively weak evaporation, still water the soil to a large extent. But, since there are few moisture reserves in the soil (due to the above reasons), by the middle of summer they are already drying up, and the steppe begins to burn out, taking on a dull look. The production of a huge plant mass is also facilitated by the comparative richness of the described soils in nutrient minerals, which we will discuss below. Thus, chernozem soils annually receive a huge amount of material for the construction of humus compounds.
The parent rocks on which chernozem soils are formed are very diverse. In the European part of Russia, the chernozem region is characterized by the extensive development of loess and loess-like rocks that replace it. In addition, chernozems often occur (in the northern part of their distribution) on various moraine sediments (clays, loams), on red-brown clays (in the south), on marine solonetsous variegated clays and on sandy deposits (very, however, rarely) of the Aral-Caspian sea ​​(southeast).
You can often find rocks and more ancient systems as parent parent rocks - Jurassic marl clays (for example, in the southeast of the Gorky region), Jurassic gray clays (for example, in the Oryol region), limestones, sandstones and other rocks of the Upper Cretaceous, Tertiary and Jurassic deposits (for example, in the Saratov region of the Ulyanovsk region, etc.). Finally, chernozem soils are described that form directly on the products of weathering of crystalline rocks (for example, olivine-basalts in the Lori steppe in Transcaucasia, etc.). In Siberia, the parent rocks for chernozem soils are loess-like loams, shale clays, tertiary clays, weathering products of crystalline rocks, etc.
The chernozem type of soil formation is most pronounced precisely on loess and loess-like rocks, i.e., substrates characterized by fine earth, fine porosity and richness in calcium carbonates (CaCO3), as well as all other minerals necessary for higher plants. To a greater or lesser extent, these properties are also inherent in all other parent rocks on which chernozem soils are formed and which we discussed above.
The characteristic features that loess and loess-like rocks possess leave a very definite imprint on the soils that form on them and predetermine the question that the absorbing complex of these soils (both mineral and organic) will be saturated with calcium (and magnesium) CO with all the numerous resulting hence the consequences (the resistance of the humate and aluminosilicate parts of the soil to the decomposing and dissolving action of soil water, the strength of the structure, etc.).
The acquisition of this basic property by soils of the chernozem type of soil formation is, of course, also favored by those climatic features that we spoke about above (the relatively small amount of water entering the described soils, due to which, of course, there can be no place for the hydrogen ion in the absorbing complex of these soils). ).
Relief. Except for the northern subzone of the steppe zone with the so-called northern - degraded and leached - chernozems, which is characterized by an undulating relief (with relatively small plains, slightly sloping spaces), coinciding with the development of glacial deposits, then for the rest of the chernozem zone (middle and southern) the most typical is a flat relief with very soft contours (at present it seems to be dissected by ravines and gullies of the latest formation, especially the middle part of the described zone).
Such a monotonous and flat relief, protecting the parent rock during the processes of soil formation undergoing by it from the phenomena of erosion, washing away and alluvium, contributed in the best possible way to the calm course of the mentioned processes and the formation as a result of the latter of those highly organized natural bodies, which are typical and "fat" chernozems occupying just plain watersheds. Except for steep slopes, gullies and ravines and strongly dissected elevated areas occupied by forest soils, then throughout the rest - often huge - we can observe an extremely uniform soil cover; along the flat watersheds, we see the so-called "mountain" chernozems (typically developed "fat" chernozems), and along the gentle slopes - lighter differences: loamy and sandy loam ("valley" chernozems).
Thus, the mentioned soil former (relief) also contributes to the creation and formation of certain properties and features of the described soil type.
Flora and fauna. At present, it can be considered established that our steppe zone was originally treeless and that it was steppe vegetation (represented by cenoses of grass and shrub-grass steppes), and not forest, that took part in the formation of chernozem soils. The latter, as we will see below, cannot form the chernozem soil type, and if, due to certain conditions, it begins to take possession of the steppe spaces, it inevitably leads to the degeneration (degradation) of these soils, pushing them along the path of podzol formation processes. The forest, as they say, "eats up the black soil." We will return to this issue in more detail below. We consider it necessary to make a reservation that we can talk about the eternal treelessness of our steppes only insofar as we consider this phenomenon from the time of the deposition of those soil-forming rocks (loess, loess-like loams, etc.) on which modern soils began to develop (i.e., soils). since the end of the Ice Age). Until that time, the picture of the distribution of vegetation on the European continent was, as is known, completely different - in connection with a completely different distribution of climatic conditions.
The composition of steppe vegetation, even within the same European part of Russia, is very diverse. In general, two subzones can be outlined here: the subzone of feather grass steppes, which cover the chernozems of the drier southern regions (with tyrsa, fescue, fine-legged, wheatgrass, etc.), and the subzone of meadow steppes, confined to less arid regions (in addition to various cereals, we see here is a rich flora of dicotyledonous plants, we will name some representatives of both: meadow bluegrass, wheatgrass, chapoloch, clover, adonis, sage, astragalus, sainfoin, tumbleweed, and many others).
The steppe vegetation involved in the formation of chernozem soils must be characterized biologically as a set of forms that have a relatively short growing season, enabling them to complete their development cycle by the onset of that dry period that reaches the steppe zone by about mid-July (see above for the description climate of the steppe zone) and more or less freely endure that comparative excess of mineral salts, which we generally observe in soils of the chernozem type.
The richness of humus in chernozem soils, which is so characteristic of them, is partly explained by the enormous amount of organic matter that is annually delivered to these soils precisely by grassy, ​​steppe vegetation; a special role in this regard must be assigned to the underground organs of this vegetation, represented by a whole "lace" of a surprisingly branched and powerfully developed root system of the latter. Forest vegetation, on the other hand, in the form of only falling leaves and a relatively poor herbage, can never provide the soil with such abundant material for the construction of humus substances.
In the nature of the development of the root system of steppe plants, penetrating the soil in all directions and braiding it with its thinnest and numerous branches, we can partly see the reason for that strong granular structure that is so characteristic of virgin representatives of chernozem soils; direct observations show that in this case, indeed, "the soil turns out to be broken up into grains or grains, as if interspersed in the loops formed by the roots" (Keller).
As for the animal world, being represented in the steppe zone by a diverse fauna of various burrowing and digging animals, it also makes a significant contribution to the construction of the soils we describe; the systematic mixing of the material of various soil horizons and the soil with each other, which leaves a very definite imprint on certain morphological features of the chernozem soils, and the highly perfect and intimate mixing of organic substances with mineral substances are due to a large extent to the work of precisely those excavators who huddle in such a large number in soil soils of the chernozem zone.
Having become acquainted in general terms with the nature of those soil-forming agents under the influence of which the soil chernozems develop, we will now proceed to a direct study of these latter.
For chernozem soils, namely for their typical representatives, the following basic and characteristic properties inherent in them can be noted.
1. Rich in humus substances (and in particular the "humate" part of the absorbing complex). The amount of humus in typical ("powerful" and "fat") chernozems sometimes reaches a huge value - 18-20%.
Such a wealth of humic substances is due, on the one hand, to the huge amount of organic material annually delivered to the soil by dying vegetation, in the face of both the ground and, in particular, its underground part, on the other hand, the fact that the processes of decomposition of this organic material proceed quite vigorously. only during the spring months, when the surface horizons of the soil are still sufficiently watered melt waters, and also during the autumn months, when, due to the relatively weak evaporation from the soil of atmospheric precipitation, the moisture content of this soil is still sufficient to support, although weak, but still the continuous course of the processes mentioned. During the rest of the year, these processes almost freeze: in the summer months due to the rapid depletion of moisture reserves (for the reasons we have discussed above), in winter - due to low air and soil temperatures.
Thus, for humification processes (i.e., the processes of transformation of organic constituent parts plants into constituents of soil humus) in the chernozem zone there are quite favorable conditions, but there is not enough moisture for further decomposition and mineralization of the resulting humic substances - and just at the very time when, due to very favorable temperature conditions the latter processes could have received a sharp expression.
Further, the very processes of humification of dying organic residues in chernozem soils reach the stage of mainly humic (black) substances, and only in spring and autumn periods can advance to the stage of more oxidized and more mobile compounds, which, as we know, are "crepe" and "apocrene" substances. Thus, the main components of humus that accumulate in chernozem soils are those compounds that, as we know, are characterized by extremely low solubility and low mobility (the fact of the low mobility of humus in chernozem soils has now been proven by direct experimental data). And in this circumstance, we cannot fail to see a new explanation for the fact that chernozem soils are highly enriched in humus substances.
Finally, if we take the modern point of view and accept that humus substances (or at least a certain part of them) can be in a colloidal state (see above), then bearing in mind the abundance of typical representatives of chernozem soils in such strong coagulants of colloidal particles as are calcium salts, we must assume that the humic substances of the soils under consideration will be in a firmly coagulated state, protecting them from the spraying, dissolving and decomposing action of water. From this it becomes clear to us why the humate part of the absorbing complex in chernozem soils reaches such an enormous value.
In connection with the richness of chernozem soils in humus substances, there is also a very high comparative content of nitrogen in them, the amount of which in "fat", for example, chernozems can reach 0.4-0.5%.
The richness of chernozem soils in phosphorus (0.2-0.3%) must also be connected with the high content of humus in them.
2. Rich in minerals (in particular, the "zeolite" part of the absorbing complex). This characteristic property of typical representatives of chernozem soils is a consequence, on the one hand, of the general richness in mineral compounds of those parent soil-forming rocks (loess and loess-like rocks), on which the described soils get their greatest development and best expression, on the other hand, their relatively low leaching as the result of a certain combination of climatic conditions already known to us in the chernozem zone; finally, the presence in the soils of the chernozem type a large number such an energetic coagulator as Ca-ion, explains to us the fact why, in particular, the "zeolite" part of the soils described (the aluminosilicate part of the absorbing complex), acquiring special strength and resistance against the spraying and dissolving action of water, can reach such a large value (often above 30% of dry soil weight).
This "zeolite" part of chernozem soils is very rich in bases: it can be considered that the sum of all bases in it reaches on average up to 50% (the remaining 50% are SiOj).
3. The saturation of their absorbing complex with bases, and the "saturating" ion is exclusively calcium (and magnesium). The climatic features of the steppe region are combined, as we already know, in such a way that only such readily soluble salts as sodium and potassium salts can be removed from the soil stratum in the process of soil formation in significant quantities. Ground waters lie in the described area (due to the same conditions) so deep that the possibility of a reverse rise of these salts into the upper soil horizons is excluded.
On the other hand, in the area described there are all favorable conditions for the preservation at one or another depth in the soil stratum in a large amount of such relatively sparingly soluble compounds, such as alkaline earth metal carbonates.
Thus, taking into account the relatively negligible concentration of alkaline cations in the soil solution of chernozem soils, on the other hand, recalling that calcium generally has a significantly higher absorption energy (or displacement energy) compared to sodium and potassium (and also magnesium), and magnesium, in turn, has a higher absorption energy (or displacement energy) compared to both of the above-mentioned unambiguous ions, it is not difficult to conclude that the absorbing complex of the soils we describe should contain calcium (primarily) and partly magnesium among the absorbed cations. There is no need to even talk about the hydrogen ion: it cannot compete with alkaline earth cations in any way for a place in the absorbing complex of chernozem soils, since the latter are formed and develop under conditions of insufficient moisture supply to them.
The following table illustrates this situation quite clearly (E.N. Ivanova according to K. Gedroits).

The saturation of the absorbing complex of chernozem soils with calcium (and magnesium), which determines its special strength and resistance to the destructive action of soil water, explains to us, on the one hand, the fact that we noted above is very rich in the described soils in the "zeolite" and "humate" parts (the total value absorbing complex in chernozem soils can reach 50% or more), on the other hand, it causes the presence in typical (“fat” clayey) chernozems of the granular - very strong - structure so characteristic of the latter (due to the sharp coagulating ability inherent in the calcium cation). Such structure, creating a favorable air regime in chernozem soils, provides them with the correct course of aerobic biochemical processes and thus excludes the possibility of formation in them of any incompletely oxidized or ferrous compounds.
The above-noted richness of the absorbing complex of chernozem soils explains to us the very high absorbing capacity, which distinguishes these soils so much.
In conclusion, in order to complete the description of the characteristic properties and features of typical chernozems, let us recall the main difference that exists between soils with saturated and unsaturated bases. As is known, the latter contain a hydrogen ion in their colloidal (aluminosilicate and humate) part in the absorbed state. Although this absorbing complex is insoluble in water, nevertheless this hydrogen ion is capable of vigorous exchange reactions on the surface of the elements of this absorbing complex with any cations of those salts that are in the soil solution. As a result of such a reaction, the acid of those anions with which such exchange decomposition took place begins to accumulate in the soil solution. Thus, soils unsaturated with bases (for example, podzolic ones) can always maintain the presence of strong acids in soil solutions - in view of the appearance in the latter acids of anions of those salts that are formed in these soils during their soil formation.
As for soils saturated with bases, to which, as we saw above, chernozems belong, when the elements of their absorbing complex meet with neutral solutions of various salts, bases from the latter are also, of course, absorbed, but with a return to this salt solution the same amount (in molecular terms) of other bases (in this case, calcium and magnesium), as a result of which the soil solution does not change its reaction; changing only its composition.
From this we conclude that the process of chernozem formation usually proceeds in a neutral or even slightly alkaline medium and that, due to the above reasons, the possibility of the formation of free acids in soil solutions of the described soils is excluded (which circumstance, together with the enrichment of chernozem soils with organic substances, creates a very favorable environment for biological processes). Only in certain periods of the life of these soils, due to the vigorous processes of decomposition of organic matter in them (in spring and autumn), can we sporadically state a weakly acidic reaction due to the accumulation of carbon dioxide and bicarbonate carbonates.
The neutral (or weakly alkaline) environment in which the soil-forming process of chernozem soils takes place and the low supply of moisture to them makes it even more understandable for us the fact that we have already noted above that the described soils are relatively little affected by leaching processes: only easily soluble salts are washed out of the soil stratum in typical chernozems. (potassium and sodium); as for the more sparingly soluble calcium and magnesium carbonates, they are not deeply washed out, and their abundant accumulations are usually ascertained even in relatively shallow horizons; finally, for washing out oxides of silicon, aluminum and iron and not at all suitable conditions: in the form of true solutions, they cannot move deeper - due to the absence of a favorable reaction of soil solutions, in the form of pseudo-solutions - due to the presence of such a strong coagulant, which is calcium.
The above considerations, in turn, make clear to us the facts of a relatively uniform and homogeneous distribution of all elements over the various horizons of the described soils: the upper horizons, in comparison with the deeper ones, are enriched only in humus substances, and the deep-lying horizons seem to be more enriched in lime and magnesia; the rest of the soil remains almost unaffected by leaching processes and, therefore, seems to be rather homogeneous throughout the entire thickness, which is not difficult to verify by comparing the figures for layer-by-layer analyzes (see below).
The chemical composition of typical chernozems (“fat”, “powerful”) can be characterized on average by the following numbers of their surface horizons:

Water-soluble compounds typical representatives of chernozem soils contain about 0.1%; Approximately half of this amount is mineral and half is organic.
Of the minerals that pass into the water extract, calcium is in the first place.
As an illustration of the layer-by-layer distribution of individual components in chernozem soils, we present (in abbreviated form) an analysis of the Saratov (K. Schmidt) and Tobolsk (K. Glinka) chernozems.


The uniformity and homogeneity of the distribution over the various horizons of the described soils of individual components (of which we spoke above) emerge even more clearly if we list the figures given for the anhydrous, carbonate-free and humus-free mineral mass.
For the Tobolsk chernozem, the corresponding quantities (in%) will then be as follows:

Some of those chemical properties and features that are characteristic of typical chernozems and about which we spoke above find a rather vivid expression in a number of peculiar morphological features these soils.
Morphology of typical chernozems. Horizon A (humus-eluvial) - black, especially when wet. Its power is very large, measured 60 cm and above. The structure is granular, very strong; structural aggregates - rounded or ribbed, 2-3 mm in diameter.
In virgin (virgin) representatives of the described soils, one can observe on the very surface a “steppe felt” 1-3 cm thick, consisting of a semi-decomposed intertwined mass of the remains of roots and stems with an admixture of clay powder particles.
Horizon B (eluvial) is hardly distinguishable from horizon A. Dark, almost black in color. The thickness is 50-70 cm. The structure is somewhat coarser: in the upper subhorizons of the described horizon it is granular-nutty, in the lower - lumpy. These last sub-horizons show already distinct effervescence with hydrochloric acid (presence of exudates of carbonic lime).
Thus, the entire humus horizon of the described representatives of chernozem soils (A + B) reaches a huge thickness, sometimes measured 1-1.5 m. Its characteristic feature is a very gradual (not abrupt) decrease in the amount of humus downwards.
Horizon C (illuvial). Structurality, one might say, is absent; fine porous structure; power measured 40-60 cm; pale gray color. Abundant excretion of calcium carbonates; first in the form of false mushrooms, deeper - in the form of various shapes and sizes of concretions (white-eyed, cranes, etc.). Violent effervescence with hydrochloric acid.
Horizon D (parent rock) - usually loess and loess-like rocks, porous structure, fawn color; vertically fissured.
The abundant fauna of chernozem soils, represented by numerous representatives of burrowing and digging animals, leaves certain traces of their life activity on the soil section of the described soils. Numerous wormholes furrowing the soil profile in all directions, molehills: pale yellow in horizons A and B (as a result of their filling with underlying loess-like rock) and dark in horizon C (as a result of filling them with soil from overlying horizons), etc. - all these neoplasms are fairly common companions of typical representatives of chernozem soils.
To complete the consideration of the main morphological features of these soils, we note that sometimes (in loess areas) at a depth of 2-3 m one can observe very original formations in the form of the so-called "second humus horizon", which is an indistinctly formed accumulation of dark humus substances.
In most cases, this phenomenon is not associated with the soil-forming process of modern chernozem soils and is a remnant of buried soils (for example, “former” chernozems buried by layers of loess, on which the soil cover that is modern to us was later formed). Ho, of course, it cannot be denied that in some cases this phenomenon is of purely illuvial origin. We already know that in some periods of the life of chernozem soils (spring and autumn), the processes of decomposition of organic substances can proceed quite vigorously, with the formation, perhaps, of such easily mobile humus components as "crepe" and "apocrene" compounds. Washing out to a certain depth and getting into conditions of insufficient aeration, these compounds will be restored and turn into less mobile dark forms of "humic" substances.
In cases where we observe “the second humus horizon is not too deep, such an explanation of the genesis of the latter is quite appropriate.
Above we have described characteristic features that difference of chernozem soils, which is called "typical" chernozem. The named difference sometimes receives the name of "fat" or "powerful" chernozem.
However, the vast steppe zone is not in all its parts a homogeneous region in terms of climate. In connection with a decrease in precipitation and an increase in temperature, this zone, as we saw above, can now be subdivided into a number of subzones, changing from northwest to southeast. Each subzone corresponds to its own special difference in chernozem, bearing traces of the climatic features of this subzone. In this regard, all the morphological and physicochemical features described above, which are characteristic of typical chernozems, undergo in nature a wide variety of variations and deviations from general scheme on either side. In view of the fact that the transition of some varieties to others is extremely gradual and often even imperceptible, there is no need and opportunity to dwell on a detailed description of the properties and features of all chernozem varieties observed in nature. Therefore, in the future we will only note the main features characteristic of each of them.
Let us preliminarily point out that chernozem soils can now be subdivided into the following differences: 1) northern (or degraded or podzolized) chernozem, 2) leached chernozem, 3) typical chernozem (“powerful”, “fat”), 4) ordinary chernozem, 5) southern chernozem and 6) Azov chernozem.
We will not talk about degraded chernozem now, because it carries all the typical signs of another type of soil formation (namely, podzolic), so we will postpone its description until the time when we will talk about the degradation of chernozem in general.
The leached chernozem is characterized by a significantly lower amount of humus (4-6%) compared to rich chernozems, and a lower thickness of the humus horizon - due to the relatively small amount of dying vegetation and a more vigorous rate of its decomposition. The solubility of humus is somewhat higher (1/200-1/250 of its total content) - as a result of more vigorous decomposition of organic residues (due to a less arid climate, with the possible, therefore, partial formation of more mobile components of humus such as "crepe" and " apocrenic acids).
The described difference of chernozem soils seems to be more depleted in calcium carbonates, both due to the greater poverty of this compound in the parent underlying rocks (which are often various moraine sediments - clays and loams), and due to the greater amount of atmospheric precipitation entering these soils. In view of this, the effervescence horizon in the described difference of chernozem soils is much deeper than that of their typical representatives.
The comparative depletion in calcium is the reason for the comparatively lower strength of their absorbing complex; this circumstance, in turn, determines the fact of the relative depletion of their "zeolite" (and, as we indicated above, "humate") part.
The depletion of leached chernozems in such an energetic coagulator as the calcium ion explains to us that interesting fact that in some of the “most leached” representatives we can state hints of the phenomena of the movement of sesquioxides (Al2O3 + Fe2O3) from the upper horizons to the lower ones, i.e., phenomena that are so characteristic of degraded chernozems (and even more so for podzolic soils, see . below), but never observed in typical ("powerful") chernozems.
The presence of a brownish illuvial horizon in some representatives of leached chernozems, as established by a number of researchers, must apparently be connected precisely with the processes just mentioned.
As for the ordinary chernozem, we do not dwell on its characteristics: representing the transition from the typical (“fat”) chernozems we have considered above to the southern ones (see below), it carries all the signs of intermediate formations.
The southern chernozem is characterized, in comparison with the ordinary (and even more so with powerful chernozem), by a significantly lower humus content (4-6%) due to the greater aridity of the climate and some alkalinity of this variety, which phenomena cause a relatively small increase in plant organic mass.
The mentioned solonetzicity (of deep horizons) is the result of a relatively small amount of moisture entering it (strong evaporation, etc.), as well as the nature of the parent rocks on which it usually forms (red-brown clays, marine solonetzic variegated clays, etc.). ).
Hence, we understand the genesis of the gypsum horizon, which is so often present in the section of southern chernozems. Being soluble in water, gypsum (CaSO4.2.H2O) does not find favorable conditions for its isolation and accumulation in all the above varieties of chernozems, undergoing processes of removal from the soil layer almost completely. In this case, due to lack of moisture, it concentrates at a certain depth (usually deeper than the white-eye horizon) and stands out in the form of various shapes and sizes of aggregates consisting of whitish-yellow crystals.
The gypsum horizon is thus a fairly characteristic new formation for southern varieties of chernozem.
There are fewer traces of the life activity of excavators (molehills, wormholes, etc.) than in typical chernozem, in view of the relatively poorer fauna.
In the regime of the absorbing complex of the described difference of chernozem soils, sodium begins to play a certain role (in any case, still very insignificant - and then only in some individual periods of the life of these soils) due to the low leaching of these soils in general and the alkalinity of the underlying parent rocks in particular, which circumstance explains to us some specific features of these soils, which distinguish them from the previously considered varieties and bring them closer to soils of the desert-steppe type of soil formation (chestnut and brown), for example, the emerging division of horizon A into two subhorizons, of which the deeper one seems to be somewhat darker and somewhat more compacted, the existence of the same compacted horizon under the humus layer, etc.
In view of the fact that southern chernozems very gradually and often imperceptibly pass into chestnut soils, in which the above-mentioned specific features are revealed much more clearly, we will say a little more about these features below when we talk about chestnut soils.
The Azov (or Ciscaucasian) chernozem, described by L. Prasolov, is a peculiar difference of chernozem soils, in the genesis of which the water-thermal conditions created by the proximity of the Sea of ​​\u200b\u200bAzov played an important role. From the morphological side, these chernozems are described in sufficient detail (the enormous thickness of the humus horizon, measured almost 1.5 m; its not too dark color, indicating a relatively small amount of humus substances in it; nutty-lumpy structure; the presence of needle-like crystals already in the surface soil horizons calcium carbonates; poor development of the white-eye horizon, etc.). The details of the soil-forming process of the described variety of chernozem soils seem, however, unclear.
Currently, another variety of chernozem soils is highlighted - "mountain chernozems", common in some intramountain valleys of Dagestan and Transcaucasia, in Armenia, in the foothills of Altai, etc.
As for the mechanical composition of chernozem soils, in this respect we observe a very wide variety among them: starting from heavy clay soils and ending with sandy and even skeletal ones, we can find in nature varieties of chernozem soils that differ greatly in mechanical composition. Loamy varieties, however, are undoubtedly predominant (within the Russian steppes) due to the predominant type of parent rocks in the steppe zone (loess, loess-like loams), which are distinguished by their fine earth content.

Chernozem is formed at a temperature above +5 degrees, and also subject to an annual income of up to 600 mm. Deposits of chernozem lands are located on a wavy-flat relief, characterized by the presence of river terraces, ravines or depressions in some places.

The peculiarity of the chernozem soil is that a large number of meadow and steppe plants grow on it. The decomposition of such vegetation leads to the formation of humus, which gradually accumulates in the upper layers of the soil. Chernozem also contains other substances: organic and mineral compounds that make it possible to obtain phosphorus, nitrogen, sulfur and other components that feed the soil.

Properties

A distinctive feature of chernozem is its structure, it is a granular-cloddy mixture. This soil contains a lot of potassium. Chernozem is also characterized by special water-air qualities. Farmers appreciate it for its excellent fertility associated with a high percentage of humus in the top layer. The composition of such soil includes up to 15% humus.

Types of chernozem

There are 5 main types of black soil:

• Leached is formed in the forest zone due to the death of cereal plants;
• Podzolized is formed in broad-leaved grassy forests;
• Ordinary is present in the steppe zone, and is formed after the death of forb plants;
• Typical is formed on loams, in forest-steppe regions, meadow-steppe zones during the decay of forb and cereal crops;
• The southern can be found in the southern part of the steppe zones, and its formation is associated with the death of fescue-feather grass vegetation.

Chernozem application

This is the most fertile type of soil, which is actively used in horticulture, horticulture, agriculture as a fertile land for growing plants, herbs, shrubs and trees. Chernozem is used in the cultivation of lands that contain a lot of clay, to dilute soils that have a poor drainage system in order to form an air-water regime favorable for plant growth.

Chernozem is sold in bags or packages of any size. You can order black earth in bulk in our company. Delivery is carried out in Moscow and the Moscow region on the day of the order.

V. V. Dokuchaev called chernozems the “king of soils” due to their high fertility. There are various hypotheses and theories about the origin of chernozems. Some researchers were inclined to the marine origin of chernozems, that is, they considered them as marine silt left after the retreat of the Caspian and Black Seas. Other scientists considered the chernozem to be a product of redeposition by the glacial sea and icebergs of black Jurassic shale clay. Then the theory of swamp origin of chernozem was put forward, according to which the chernozem zone in the past was a heavily swampy tundra. During the drainage of the territory with the onset of a warm climate, the decomposition of marsh and tundra vegetation, marsh silt and the settlement of terrestrial vegetation took place, as a result of which chernozems were formed.

More accurate ideas about the origin of chernozem belong to M.V. Lomonosov, who in his work “On the Layers of the Earth” (1763) wrote that chernozem is not primitive or primordial matter, but came from the decay of animal and plant bodies over time.

The theory of the plant-terrestrial origin of chernozems was expressed by F. Ruprecht in his work "Geobotanical research on chernozems" (1866). He considered the emergence of chernozems as a result of the settlement of herbaceous plants and the accumulation of humus during their decomposition, without attaching importance to other soil-forming factors.

P. A. Kostychev in his work “The Soils of the Chernozem Region of Russia” (1886) assigned a special role to the root systems of herbaceous plants in the accumulation of humus.

V. R. Williams believed that the genesis of chernozems is the result of the development of the sod process under the meadow steppes.

The origin of chernozems on a scientific basis was proved by V.V. Dokuchaev in his work “Russian Chernozem” (1883). He considered the formation of chernozems to be the result of the accumulation of humus in the rock "from the decay of grassy steppe, and not forest vegetation, under the influence of climate, the age of the country, vegetation, terrain and parent rocks." He associated the type of vegetation, the rate of its development, the nature and speed of the processes of decomposition of plant residues with the climate.

Subsequently, the Chernozems were studied by many researchers (N. M. Sibirtsev, I. V. Tyurin, P. G. Aderikhin, E. A. Afanas’eva, E. A. Samoilova, M. M. Konokova, etc.), whose works established that chernozems are soils formed under perennial herbaceous vegetation of the forest-steppe and steppe under conditions of non-leaching or periodically leaching water regime. The leading process of soil formation is an intensive soddy process, as a result of which a powerful humus-accumulative horizon A develops, nutrients accumulate and the soil is structured.

The herbaceous community consists mainly of grasses and forbs with a strong reticulate fibrous root system.

The annual litter is 20...30 t/ha, but most of it (65...75%) falls on the root mass, which is rich in protein nitrogen, bases (calcium, magnesium). The litter is decomposed mainly by spore-forming bacteria and actinomycetes with sufficient access to oxygen, optimal moisture, without intensive leaching in a neutral environment. Annually, 600...1400 kg/ha of nitrogen and ash elements come with the litter. Ash content of litter 7... 8%.

In spring, with a sufficient amount of moisture, organic matter quickly decomposes, and plant nutrients are released. In summer, the moisture reserve is reduced to the wilting point. Under such conditions, the mineralization of organic residues is suspended, as a result of which humus is formed and accumulates. Due to the shallow filtration of atmospheric precipitation waters, nutrients accumulate in the upper horizons. Calcium contributes to the fixation of humus. Winter cooling and freezing of soils also contribute to the accumulation of humus, since humus denaturation occurs at low temperatures. In summer, during the period of drying up and in winter, during freezing, humic substances are fixed and become more complex. Humic acids and calcium humates predominate in their composition, leading to the formation of a water-resistant granular structure. This is also facilitated by carbonate soil-forming rocks, high ash content of plant residues, and saturation of ash with bases. The most favorable conditions for chernozem formation are characteristic of the southern part of the forest-steppe. In the steppes, there is a moisture deficit, the amount of incoming litter decreases, therefore, the intensity of humus formation decreases.

The classification of chernozems was first given by V.V. Dokuchaev, who singled them out in independent type and subdivided into watershed, slope and terraced. Much attention was paid to the classification of chernozems by N. M. Sibirtsev, S. I. Korzhinsky, L. I. Prasolov, P. G. Aderikhin, and others. At present, chernozems are combined into facies: warm South European, temperate East European, cold West and East Siberian, deep freezing East Siberian. The facies of the zone are divided into subzones-subtypes: in the forest-steppe - podzolized, leached, typical, and in the steppe - ordinary and southern chernozems. The optimal conditions for the formation of chernozems are formed in the southern part of the forest-steppe (typical chernozems), where the largest amount of plant mass is concentrated and a favorable hydrothermal regime has been established.

Chernozems are subdivided into types according to the thickness of the humus horizon, according to the content of humus and according to the degree of severity of the accompanying process. According to the thickness of the humus horizon (A + AB), chernozems are divided into super-thick (more than 120 cm), powerful (80 ... 120 cm), medium-thick (40 ... 80 cm), thin (25 ... 40 cm), very low-power (less than 25 cm). According to the content of humus, fat (more than 9%), medium-humus (6% ... 9%), low-humus (4% ... 6%), low-humus (less than 4%) chernozems are distinguished. According to the severity of the accompanying process, chernozem soils can be slightly-, medium-strongly solonetzic; slightly, medium, strongly leached, etc.

The profile of chernozems in a generalized form has the following morphological structure: A d - steppe felt up to 5 cm thick, consists of roots and intertwined grass stems on virgin soil, absent in arable soils; A - humus-accumulative horizon with a thickness of 40 ... 130 cm or more, dark gray or black, granular or granular-cloddy, with beads on the roots of plants; AB - transitional dark gray humus horizon, granular-cloddy in structure, with a noticeable browning downwards of the horizon or with dark brown spots; B - horizon of humus streaks with a thickness of 40 ... 80 cm, brownish-gray, lumpy, often subdivided according to the structure and degree of humus content into subhorizons B 1, B 2, B 3; these horizons contain calcium carbonates in the form of pseudomycelium, cranes, white-eye (with the exception of highly leached and podzolized chernozems); VS K - illuvial-carbonate horizon transitional to the parent rock, brownish-pale, lumpy-prismatic; C - fawn soil-forming rock with carbonate secretions, and in southern chernozems with gypsum. Molehills occur along the entire profile, the transitions between horizons are gradual.

Podzolized chernozems (Fig., a) are developed under broad-leaved herbaceous forests on loess-like and mantle loams and loess. The thickness of the humus horizon (A + AB) varies from 30...50 cm (cold western and Central Siberian facies) to 70...100 cm (warm South European facies). Horizon A is predominantly dark gray, with a granular structure, and when plowing, it becomes lumpy. In the AB horizon, a grayish hue is observed (a whitish coating of silica powder SiO 2 on structural units). Horizon B has a nutty or nutty-prismatic structure; brown films, humus smears, and siliceous powder are noted on the faces of structural units; denser, with a gradual transition to the soil-forming rock C. Soils boil up from a depth of 130 ... 150 cm. The BC K horizon contains carbonates in the form of calcareous tubules, cranes, and dutik.

Slightly podzolized chernozems have a silica powder in the lower part of the AB horizon and in the B horizon, and medium podzolized chernozems - throughout the humus layer and in the B 1, B 2 horizons.

Podzolized chernozems are subdivided into the main genera: ordinary, merged, poorly differentiated, carbonate-free.

The reaction of the upper horizons is slightly acidic or close to neutral (рН 5.5...6.5). The absorption capacity is 30...50 mg eq/100 g of soil; the soil absorbing complex is saturated with bases, and the AB horizon contains exchangeable hydrogen (up to 3%). Horizon A contains 5...12% humate humus. In horizon B, an increase in the content of silt is observed.

Leached chernozems (Fig., b) are formed under forb-grass vegetation. Their profile has a well-defined dark gray humus horizon A. It is loose or slightly compacted, has a lumpy-granular structure. There is no whitish siliceous powder in this horizon. Horizon AB with a thickness of 30...50 cm in the East Siberian facies to 80...150 cm in the warm facies, dark gray with a brownish tinge. Under it lies a compacted brownish carbonate-free horizon B 20–50 cm thick, with humus streaks, smudges and films along the edges of a lumpy-nutty or lumpy-prismatic structure; the transition is gradual. Horizon VS K - illuvial-carbonate, pale yellow, compacted, nutty-prismatic, with efflorescences, veins, mycelia, powdery accumulations, carbonate cranes. C to - pale carbonate soil-forming rock. Gypsum and easily soluble salts are absent.

The following types of leached chernozems are distinguished: weakly leached (the effervescence line runs no more than 20 cm from the lower boundary of the AB), medium leached (at a depth of 20 ... 50 cm from the boundary of the humus layer), strongly leached (below 50 cm from the boundary of the AB) . A feature of these soils is the absence of free carbonates in horizons A and AB.

Typical chernozems (Fig., c) are formed under forb-grass vegetation on loess, loess-like and mantle loams. They are characterized by a large thickness of the humus layer - from 50 ... 70 cm (cold facies) to 100 ... 190 cm (warm facies), the presence of carbonates in the form of mycelium, calcareous tubules in the AB horizon. More often carbonates are observed from a depth of 60...70 cm. Horizon A up to 130 cm thick is black or grayish-black, granular, and AB is dark gray with a barely noticeable brownish tinge, often with darker streaks. Below AB lies a grayish-brown compacted illuvial-carbonate horizon Bk with tongues and streaks of humus, lumpy-prismatic structure, with carbonates mainly in the form of mycelium, efflorescence, cranes. This horizon gradually turns into horizon VS K - pale-brown, transitional to rock, with a significant amount of carbonate veinlets and cranes. C to - carbonate, soil-forming rock of pale color. Gypsum and easily soluble salts are absent in the entire soil profile. There are many molehills in the soils.

Ordinary chernozems (Fig., d) are common under steppe forb-fescue-feather grass vegetation. These soils are less powerful than typical chernozems. Their humus horizon ranges from 35...45 cm (cold East Siberian facies) to 80...140 cm (warm facies). The soils have a brownish tint against a general dark gray background and a cloddy structure of the AB horizon. Horizon B (of humus streaks) often coincides with the carbonate horizon or Bk or BC K. The structure of this horizon is prismatic, brownish-yellow in color. Carbonates are represented by spots of white-eye and pseudomycelium, mealy impregnation. Sometimes, at a depth of 200...300 cm, readily soluble salts and gypsum stand out. C to - pale carbonate soil-forming rock. There are many molehills in the soil profile.

Rice. Profile structure of chernozems: a - podzolized; b- leached; c - typical; g - ordinary; d - southern

Southern chernozems (Fig., e) were formed under fescue-feather grass steppe vegetation. They have a small humus layer (from 25...30 to 70...80 cm). Horizon A, 20–30 cm thick, dark gray with a brown tint, cloddy and granular-cloddy structure. Horizon AB (30...40 cm) brownish-dark gray, nutty-lumpy, compacted. Below lies the carbonate horizon Bk, brown with humus streaks, compacted, nutty-prismatic, containing mycelia, efflorescences, mealy carbonates. VS K - brownish-pale illuvial-carbonate horizon, compacted, prismatic, with a large amount of white-eye. C - pale carbonate rock, from a depth of 150 ... 200 cm gypsum precipitates are found, and from a depth of 200 ... 300 cm - easily soluble salts. Molehills are observed in the soil profile.

Ciscaucasian chernozems form a peculiar group. They have a dark gray color with a brownish tinge from the surface, a powerful humus horizon (120 ... 150 cm and more). These soils boil up already in horizon A.

Meadow-chernozem soils develop under conditions of increased moisture on poorly drained plains, in low relief elements (depressions, hollows, estuaries) under grass-forb vegetation. Groundwater occurs at a depth of 3...6m. Meadow-chernozem soils are semi-hydromorphic analogues of chernozems. They are distinguished by a darker color of the humus horizon, increased humus content, stretching of the humus horizon, and the presence of deep gleying.

According to the type of water regime, the degree of severity of soil hydromorphism is divided into subtypes: meadow-chernozem and meadow-chernozem.

Meadow-chernozem soils are formed as a result of increased temporary surface moisture at deep occurrence. ground water(4...7 m). The profile has the following structure: A - humus-accumulative horizon, black or dark gray, granular, loose, with increased thickness compared to chernozems, contains a lot of roots, molehills; the transition is gradual; AB - the lower humus horizon, dark gray with a brownish tinge, granular or lumpy-granular, loose, contains many plant roots, molehills, sometimes carbonate pseudomycelia are observed in the lower part. The total thickness of horizons A + AB ranges from 50...80 to 100...120 cm; B - heterogeneously colored (brown with a large number of dark gray, brown-gray humus streaks in the form of tongues to a depth of 100 ... 150 cm) transitional horizon, nutty and prismatic-nutty, may contain carbonates in the form of pseudomycelium, molehills, plant roots; Ск - soil-forming rock of yellow-brown and fawn color, pseudomycelia, carbonate lubrication are found, rusty-ocher spots are observed from a depth of 2 ... 3 m.

Soils are subdivided into types according to power, humus content and related processes as chernozems.

Due to the warm and mild climate, the southern European chernozems (Moldova, southern Ukraine, Ciscaucasia) are characterized by an intense biological cycle, a large digging of the profile as a result of the activity of earthworms, and periodic washing of the profile. These soils are distinguished by a large thickness of the humus horizon with a low humus content (less than 8%), the absence of easily soluble salts and gypsum, and abundant carbonate content in the form of blooms, cobwebs, veins, etc. in the upper horizons and micellar forms in the lower ones. Micellar forms of carbonates testify to their migration and seasonal pulsation in soils. These soils are called "micellar-carbonate".

In the chernozems of the Eastern European group, due to the drier and colder climate, the thickness of the humus horizon is less, and there is more humus (7 ... 12%); the profile is washed from easily soluble salts only in the forest-steppe, while in the steppes at a depth below 2 m, new formations of gypsum are observed.

The chernozems of Western Siberia are characterized by deep streaks of humus along the cracks formed when the soil freezes, a high content of humus (up to 10...14%) with a rapid decrease in its amount with depth, as well as the presence of gypsum in the steppe part.

In Eastern Siberia, the biological cycle of elements is significantly suppressed by low temperatures, so the humus content in them is low (4 ... 9%), the thickness of the humus horizon is insignificant. These soils are often referred to as low-calcareous or non-calcareous soils, since they contain little or no carbonates (powdery).

The granulometric composition of soils depends on parent rocks and varies from sandy loamy to clayey, but loamy varieties dominate.

Chernozems are characterized by the absence of noticeable changes in the granulometric composition during soil formation. Only in podzolized and leached chernozems is an increase in the amount of fine dust fraction down the profile observed. In all soils, compared with the parent rock, the profile is enriched with silt. The composition of the silt of the South European chernozems is dominated by the montmorillonite group, hydromicas contain less than 25%, and kaolinite is not observed. Hydromicaceous minerals and hydromicaceous-montmorillonite mixed-layer formations predominate in Eastern European chernozems. Minerals of the kaolinite and chlorite type are present in very small amounts. The micromorphology of the clay material is closely related to the depth of carbonates in the profile. In soils in which the carbonate horizon follows the humus horizon, the clay substance is coagulated together with humus and fixed. The lowering of the carbonate horizon entails clay peptization and some movement along the profile.

Chernozems are characterized by looseness, high moisture capacity, good water permeability. The structural composition of virgin chernozems is dominated by water-stable granular aggregates, which is especially pronounced in typical, leached, and ordinary chernozems. Podzolized and southern chernozems contain less water stable aggregates. When using chernozems in agriculture, there is a decrease in the content of lumpy-granular, granular, dusty fractions, a decrease in water resistance and a decrease in the size of structural units.

Chernozems are characterized by a high content of humus in the humus-accumulative horizon A, which gradually decreases with depth, except for the soils of Eastern Siberia (table). The amount of humus in chernozems ranges from 3...5% (reserves are 270...300 t/ha) in the southern to 5...8% (450...600 t/ha) in the typical South European group, from 4 ...7% (300...450 t/ha) in southern ones up to 8...12% (600...750 t/ha) in typical Eastern European ones, from 4...6% (200... 300 t/ha) in southern up to 10...12% (450...500 t/ha) in typical Western Siberia, from 3.5...5.0% in southern to 5...7% ( 200...300 t/ha) in the leached areas of Eastern Siberia. The humus composition of horizons A and AB is dominated by black humic acids associated with calcium. The amount of humic acids associated with R2O3 and the clay fraction is insignificant. Stk ratio: Sfk = 1.5...2.6. In chernozems, compared to other soils, fulvic acids are the lightest, with the lowest optical density and an insignificant content of the aggressive fraction.

Soil reaction is slightly acidic or close to neutral in humus horizons of leached and podzolized chernozems or neutral and slightly alkaline in chernozems of other subtypes. In the lower horizons, the soil reaction is predominantly weakly alkaline, less often alkaline.

Zone	Chernozem	Humus content, %	Humus stock, t/ha
Southern part of Europe	Southern	3...5	270..	.300
	Typical	3...8	450..	.600
Eastern Europe	Southern	4...7	300..	.450
	Typical	8...12	600..	.750
Western Siberia	Southern	4...6	200..	.300
	Typical	10...12	450..	.500
Eastern Siberia	Southern	3,5...5	200..	.250
	leached	5...7	200..	.300

Chernozems have a high absorption capacity (50...70 mg equiv / 100 g of soil for loamy varieties), a significant saturation of the absorbing complex with bases, and high buffering capacity. The composition of exchange cations is dominated by calcium, then magnesium (15-20% of the total). Hydrogen is present in the absorbing complex in podzolized and leached chernozems. In ordinary and southern chernozems, in addition to calcium, sodium is present in the composition of absorbed cations, and the content of magnesium increases.

The soils are characterized by a significant gross content of nutrients. For example, in typical heavy loamy chernozems, the amount of nitrogen reaches 0.4 ... 0.5% (10 ... 15 t / ha), phosphorus - 0.15 ... 0.35%. The content of mobile forms of nutrients depends on the climate, agricultural practices and cultivated crops. The largest number of them is contained in the arable layer of cultivated chernozems.

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 Danubian lowland plains, stretching in a strip through 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 into the southern part of Western Siberia and northern Kazakhstan. Separate areas of these soils are confined to the plains and foothills of the Altai, the Minusinsk basin, and also to the basins of Transbaikalia. In North America, chernozems are mainly formed in the spaces of the Great Plains.

The climate of the zone of distribution of chernozems is continental or temperate continental with warm summers and moderately cold or even cold winters. The annual temperature range is 30-50 0 C. During the year, from 300 to 600 mm of precipitation falls, in the North American steppes - up to 750 mm. Atmospheric humidification peaks in summer, but at this time the highest average monthly temperatures are also observed (20-25 °C in July), as a result of which a significant proportion of summer precipitation evaporates. Precipitation falls unevenly throughout the summer, with heavy rains followed by long periods of drought. The average annual moisture coefficient is in the range of 0.8-0.5, and in the warm period of the year it sometimes drops to 0.3. Thus, in summer, chernozems are characterized by periodic desiccation, but in spring and autumn, due to the seepage of melt and rainwater, a significant part of their profile becomes noticeably moistened. In a number of regions (in Western Siberia, Transbaikalia, etc.), chernozems freeze to a great depth in winter.

For the most part, chernozems develop on loamy rocks - loess or loess-like deposits, which are distinguished by fairly good water permeability, porosity and carbonate content. Chernozems of the European part of Russia, Ukraine, Western Siberia and the Central Plains of the USA are mainly associated with such rocks. In Canada, the chernozem zone penetrates within the boundaries of ancient glaciation, where glaciolacustrine and moraine deposits serve as soil-forming rocks. In Kazakhstan and the Urals, these soils sometimes form on carbonate-free eluvium of dense rocks.

The most characteristic relief in the areas of formation of chernozems is flat, with varying degrees of development of the ravine-beam network. Chernozems are widespread in the uplands (Central Russian, Dnieper, etc.), lowlands (Central Danube, West Siberian), in the foothills (Altai, Sayan) and in extensive depressions (in Transbaikalia). As a rule, the terrain conditions provide enough good drainage soils.

Chernozems develop under grassy steppe associations. The nature of the vegetation cover in the areas of distribution of chernozems is modified in connection with the peculiarities of hydrothermal conditions. Meadow steppes are confined to areas with relatively high atmospheric moisture, high and dense herbage of which is represented by various types of herbs, 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 sparse associations.

Steppe vegetation supplies the soil with a large amount of organic matter. Herbaceous plants in the steppe die off annually in whole or in large 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 enter the soil in the meadow steppes.

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

The ground and root litter of steppe vegetation is rich in nitrogen and ash elements. Compared to forest litter (especially coniferous), it contains less waxes, 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 in the soil many elements of ash nutrition necessary for plants. They are actively involved in the biological cycle of substances, and thus their leaching from the sphere of soil formation is prevented. Unplowed chernozems are abundantly populated by diverse soil fauna. The upper horizons are inhabited by worms, larvae of beetles, weevils and other insects. The upper horizons of the soils are loosened and mixed with small diggers, voles, etc. Large diggers live here - marmots, ground squirrels, which make the soil even more air and water 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 the drying of the soil, and in winter - as a result of its freezing.

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

a) the presence of herbaceous vegetation that supplies the soil with a large amount of organic residues rich in ash elements and nitrogen;

b) richness of soil-forming rocks in 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 following horizons.

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

Below, a powerful humus-accumulative Al t horizon is developed - dark gray, almost black, fine-grained or lumpy-granular, friable, densely permeated with roots of herbaceous plants (especially in the upper part) and burrows of worms.

A1B - transitional humus horizon, brownish-gray, gray color weakens downwards, granular-cloddy, less loose than the overlying one; boils in the lower part and contains carbonates in the form of pseudomycelium and tubules;

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

FROM sa - soil-forming rock, distinguished by a decrease in the content of carbonate accumulations and deterioration of the structure.

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

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

According to the content of humus, among the chernozems are distinguished: high-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 (Fig. 17.3). Chernozems are soils with the widest possible ratio in the composition of humus C g / C f - from 1.5 to 2.0 and even a little more. Humic acids associated with calcium predominate among the humus fractions. The humus horizon contains a significant content of nitrogen, potassium and phosphorus.

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 weakly alkaline. The absorption capacity due to the large amount of organic colloids 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% is absorbed magnesium. The bulk chemical composition is practically the same in all soil horizons, as is the chemical composition of the clay fraction. A small silt maximum is found in the upper part of the profile. In the Bca horizon, 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 - siallite-carbonate parent rock. The composition of the clay 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 occurring in these soils. Significant amounts of herbaceous residues annually entering the soil, their high ash content and richness of ash in bases are among the determining factors of deep humification of organic matter. In relatively humid and fairly warm spring and autumn periods, when the microflora (mainly bacterial) is maximally activated in chernozems, there is an intensive transformation of organic residues in the direction of producing mainly humic acids. In the soils at this time, the neutral reaction of the environment prevails, the sphere of humus formation contains a large amount of alkaline earth bases and, as a result, stable organo-mineral compounds of humic acids are formed, primarily calcium humates. 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 periods, its very intense mineralization occurs. However, the results of the latter process do not manifest themselves in a sharp decrease in the humus content, since it is significantly slowed down in summer and winter. In dry summer and cold winter time 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 dormancy and active 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 number of organic colloids with a high absorption capacity-1 and the almost complete saturation of the soil absorbing complex with doubly charged cations (calcium and magnesium) lead to the fact that the colloids are 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 cloddy-granular structure in chernozems is also facilitated by the abundant root system of herbaceous plants, which densely penetrates the upper soil horizons. Grass roots divide the soil mass into numerous small lumps and compact them. When the dead roots decompose, the humic substances formed from them glue the soil particles together.

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

The good structural state of the soil creates very favorable water and air conditions for plant life: inside the soil aggregates, capillary-suspended moisture can be retained in the capillary spaces between the parts, while the spaces between the clods 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 conditions of a non-leaching water regime. The usual depth of wetting 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 from the rock by the soil. The mechanism of this process is as follows.

The carbon dioxide released during the decomposition of organic residues in the upper part of the soil profile combines with calcium released during the mineralization of plant residues and forms calcium bicarbonate. Part of the produced carbon dioxide, dissolving in soil moisture, contributes to the transfer of insoluble rock carbonates into more soluble bicarbonates according to the CaCO 3 + CO 2 + H 2 0 -> Ca (HC0 3) 2 scheme. With descending moisture flows, bicarbonates move down the profile, where they turn into various forms carbonate neoplasms (white-eye, lime lubrication, pseudomycelium, etc.).

Many researchers believe that the amount of carbonates in chernozems depends on the degree of initial carbonate content of parent rocks. However, there is a point of view according to which the carbonate content of rocks is not the root 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, soils with a carbonate horizon are formed on the initially carbonate-free eluvium of granites under the conditions of a steppe climate and under steppe vegetation. 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 influx of a certain amount of calcium carbonates on 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, chlorides and sulfates of sodium and magnesium can also be found. The formation of such illuvial-salt horizons is associated, as a rule, with the initial salinity of rocks and the washing out of these salts from the upper and middle parts of the profile during soil formation.

Depending on the depth of soil wetting and the frequency of relatively wet years, the gypsum and saline illuvial horizons are located either directly below the carbonate horizons, marking the boundary between the soil and the parent rock, or are located below the soil boundaries, 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. In order to form a more or less mature chernozem soil profile with a characteristic powerful humate-calcium horizon, according to various estimates, it takes from 3-5 thousand to 10 thousand years. Some researchers believe that such properties of chernozems as high humus content, the presence of carbonate nodules and the general high calcification of the profile, at least in a number of areas, are of a relic nature and are inherited from past periods of development of these soils under 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 favorable for agriculture chemical (rich in humus, mineral nutrition elements) and physical properties (good structure, air and water permeability). On these soils, the highest yields of cereals, sugar beets, sunflowers and many other crops are obtained. At the same time, their irrational exploitation often leads to degradation - loss of humus, overconsolidation, erosion and secondary salinization.

Chernozem is one of the most fertile soil types. This is a kind of separate ecosystem, widely used in all regions of our country. That is why gardeners will not be out of place to know what black soil is, what characteristics it has and how it differs from other types of soil.

Chernozem is created only by nature. It is impossible to make artificial black soil with the help of various fertilizers. It is formed in natural areas dominated by a temperate continental climate. The place of formation of chernozem is loess-like loams or clays, loess. Necessary conditions for its formation: periodic changes in humidity and temperature, soil suitability for the life of microorganisms and invertebrates, abundant and perennial grass vegetation. But nowadays you can buy black soil in the Moscow region with the supply of soil to any region of Russia, which expands the possibilities of summer residents to improve the soil on their own. personal plot.

Chernozem characteristics

The main characteristics of this soil are:

• lumpy structure (the soil “breathes” and passes moisture well);
• high humus content (the soil does not have time to quickly deplete);
• a high percentage of calcium (it is necessary for absolutely all plants);
• balance and easy availability of microelements useful for plants (iron, nitrogenous compounds, phosphorus, sulfur);
• neutral or near-neutral acid-base reaction (suitable for more plants);
• as a consequence of all of the above - the high fertility of these soils.

There are five main varieties of this soil:

• ordinary chernozem (have a more lumpy structure, good moisture capacity);
• southern (with the highest content of humus);
• typical (has the most striking basic characteristics of such soils, the most balanced chernozem);
• podzolized (has a slightly acidic reaction and a small supply of humus);
• leached (contain a lot of calcium and magnesium).

Distinctive features of black soil

What is the difference between manure, humus and peat from black soil? Manure is the waste products of animals and birds. Humus is formed from manure due to its overheating and processing by worms, insects and microorganisms for a long time. Chernozem is initially a fertile soil layer, and humus and manure can be called fertilizers to increase its fertility.

Peat, like chernozem, is formed due to the decomposition of plant residues. But this decomposition takes place in swampy areas, and its main plant component is moss. For these reasons, black soil can retain moisture, while peat cannot.

Real, undiluted chernozem has a rich black color and a coarse-grained or lumpy structure. If it is wetted, then by its properties it will resemble clay: the same consistency and a long drying process.

Distinctive feature of this soil - a greasy trace on the hand, after compression of a lump of black soil. This is due to the high percentage of humus in it.

People who have a dacha or their own garden know that it is better not to find black soil. It contains a lot of humus and nutrients. However, many people forget that everything loses its properties over time. And sooner or later even black soil will have to be “fed” with fertilizers.

It is not recommended to fertilize vegetable and flower crops with black soil. They have a too weak root system, so the soil may soon become compacted, which means that the air and water permeability of the chernozem will drop sharply.

Most often, summer residents use a mixture of black soil, peat and simple garden soil. Ornamental perennials get along well in the soil with black soil introduced into it, it is also often used when planting plants in greenhouses and greenhouses.

Chernozem is dug up only with a pitchfork to maintain its density. To restore the acid-base balance in slightly acidic black, lime or wood ash is added, and in slightly alkaline, fertilizers with high acidity are added.