Natural perfection of black soil. Chernozem soil type Chernozems are the most fertile soils in the world
The first classification of chernozems was given by V.V. Dokuchaev, who singled them out 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 subdivided 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. Siberians. In his classification (1901), the chernozem soil type was divided into subtypes - northern, rich, ordinary, southern.
Later, 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 the study of the chernozems of the Azov and Ciscaucasia, identified a subtype of the Azov chernozems, later called the Ciscaucasian. The accumulation of information on the chernozems of these regions made it possible in the future to consider their genetic features as a result of the provincial and facies conditions of soil formation and not to single them out 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 soil type into subtypes and genera is currently accepted.
Below is a description of the main genera of chernozems.
Ordinary - stand out in all subtypes; signs and properties correspond to the main characteristics of the subtype. In the full name of the chernozem, the term of this genus is omitted.
Weakly differentiated - developed on sandy loamy rocks, typical features of chernozems are poorly expressed (color, structure, etc.)
Deep-boiling - boil more deeply than the genus "ordinary chernozems", due to a more pronounced flushing regime due to a lighter mechanical composition or relief conditions. stand out from the typical ones. Ordinary and southern chernozems.
Non-carbonate - developed on rocks poor in silicate calcium, there is no effervescence and release of carbonates; are found mainly among typical, leached and podzolized subtypes of chernozems.
Alkaline - within the humus layer, they have a compacted solonetzic horizon with an exchangeable Na content of more than 5% of the capacity; stand out among ordinary and southern chernozems.
Solodified - characterized by the presence of a whitish powder in the humus layer, leakage of humus color, varnishing and smearing along the edges of the structure in the lower horizons, sometimes the presence of exchangeable sodium; common among typical, ordinary and southern chernozems.
Deep gley - developed on two-membered and layered rocks, as well as under conditions of long-term preservation of winter permafrost.
Merged - developed on silt-clay rocks in warm facies, characterized by a high density of 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-rubble rocks.
All chernozems are divided into types according to the following criteria:
According to the thickness of the humus layer - super-thick (more than 120 cm), powerful (120-80 cm), medium-thick (80-40 cm), thin (40-25 cm) and very thin (less than 25 cm);
In addition, chernozems are divided into types according to the degree of severity of the accompanying process (weakly, medium, strongly leached, weakly, medium, strongly solonetzic, etc.).
In the geographical distribution of subtypes of chernozems, a clear zonal pattern is observed. Therefore, the zone of chernozem soils from north to south is divided 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.
Chernozems are podzolized. In the humus layer, they have residual signs of the impact of the podzolic process in the form of a whitish powder - the main distinguishing morphological feature of this subtype. The humus profile of podzolized chernozems is gray, less often dark gray in horizon A and noticeably lighter in horizon B. Whitish powder, with its abundant content, gives the chernozem profile a grayish-ashy tint. Usually, in the form of a whitish coating, it seems to powder the structural units in the B1 horizon, but with a strong podzolization, a whitish tint also occurs in the A horizon.
Carbonates occur significantly below the boundary of the humus layer (usually at a depth of 1.3-1.5 m). Therefore, in podzolized chernozems under the humus layer, a brownish or reddish-brown illuvial horizon of a nutty or prismatic structure leached from carbonates with distinct varnishing, humus smears and whitish powder on the edges is distinguished. Gradually, these signs weaken, and the horizon turns into a rock containing carbonates at a certain depth in the form of calcareous tubules, cranes. They are divided into genera - ordinary, poorly differentiated, fused, carbonate-free.
When classifying podzolized chernozems into types, in addition to dividing according to thickness and humus content, they are subdivided according to the degree of podzolization into slightly podzolized and medium podzolized.
Chernozems are leached. Unlike podzolized chernozems, they do not have silica powder in the humus layer.
Horizon A is dark gray or black in color, with a distinct granular or granular-cloddy structure, loose texture. Its thickness ranges from 30-35 to 40-50 cm. The lower boundary of horizon B 1 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 under horizon B 1 of horizon B 2 leached from carbonates. This horizon has a clearly expressed brownish color, humus streaks and smudges, and 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 common, weakly differentiated, carbonate-free, deep-gley, merged.
Chernozems are typical. Usually they 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 tubules. Carbonates appear more often from a depth of 60-70 cm. For a more detailed morphological characteristic of the humus layer, two horizons transitional in humus color, AB 1 and B 1, are distinguished below horizon A.
Horizon AB 1 is dark gray with a faint, brownish tinge downwards, and B 1 is already distinguished by a distinct brown tint. In the lower part of the AB 1 horizon, or most often in the B 1 horizon, carbonate efflorescences are visible.
Horizon B 2 (BC) and the rock contain carbonates in the form of mycelium, calcareous tubules and cranes.
They are divided into the following genera: Ordinary, non-carbonate, deep-boiling, carbonate solod.
Chernozems of the steppe zone
Chernozems in the steppe zone are represented by ordinary and southern chernozems.
Chernozems are ordinary. 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 B 1 lies the horizon of humus streaks B 2, which often coincides with the carbonate illuvial horizon or very quickly passes into it. The carbonates here are in the form of white-eye. This feature distinguishes ordinary chernozems from the previously considered subtypes.
The subtype of ordinary chernozems is divided into genera: ordinary, carbonate, solonetzic, deep-boiling, poorly differentiated and solod.
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, and a lumpy structure. Horizon B 1 is characterized by a clear brownish-brown color and a 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 effervescence line is located in the lower part of horizon B 1 or at the boundary of the humus layer.
Southern chernozems are subdivided into the following genera: ordinary, solonetsous, carbonate, deep-boiling, weakly differentiated, and solodized.
Chernozem is a highly fertile land, dark in color, chernozems are rich in humus, with a pronounced granular-cloddy structure, usually chernozem is formed in forests, loams or clays, in a temperate continental climate.
Chernozem is rightfully considered the best soil for agriculture, while chernozem is formed under perennial herbaceous vegetation, in the climatic conditions of the steppe and forest-steppe territorial zones.
On the territory of our country - chernozems are located in the central black earth regions, the Volga region, in Western Siberia and the North Caucasus, there are many black earth lands in Ukraine, as well as in some European countries, China, South and North America.
Chernozem, as soil, is rich in humus, is formed on loess-like loams or clays, as a rule, in a temperate continental climate, with periodic precipitation, under perennial vegetation, usually herbaceous.
Soil formation conditions for chernozems
For stable soil formation of chernozems, the following conditions are necessary - the climate is temperate, or moderately continental, there must be an alternation of moisture and desiccation, with the dominance of a positive temperature regime. The average annual temperature should not be below +3 +7 degrees Celsius, and the annual amount of precipitation is 300-600 mm.
The relief of occurrence of chernozems is wavy-flat, in some places it is cut by depressions, ravines, river terraces.
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The vegetation on the chernozems is perennial herbaceous, meadow-steppe. Under appropriate climatic conditions, it decomposes, as a result of which humus compounds are formed, which, accordingly, accumulate in the upper layers of the soil.
Together with humus in the chernozem soil, in the form of complex organic, mineral compounds, such nutrients are formed for plants, such as nitrogen, iron, phosphorus and sulfur, etc. site/node/2879
About the properties of chernozem
Chernozems in their properties - have fairly good water-air qualities, but the chernozem is distinguished by a lumpy or granular structure, a high content of calcium in the soil from 70 to 90%, inherent in chernozem - a neutral or almost neutral reaction.
Chernozem on earth is valued for its increased fertility, natural and intensive humification, and rather high, about 15%, humus content in the upper layers of the soil.
What are the types of black soil
Chernozems are divided into the following types:
Podzolized chernozem - these chernozems are common in broad-leaved grassy forests;
Leached chernozem - such chernozems are formed under the meadow forb-cereal steppes of the forest-steppe zone;
Typical chernozem - the formation of this type of chernozem occurs under forbs and cereals, i.e. meadow-steppe, vegetation in forest-steppe zones, loess-like and mantle loams;
Common chernozem - these chernozems can be found in the northern part of the steppe zone, and they are formed under forb vegetation;
Southern chernozems - these chernozems are formed under fescue-feather grass vegetation; they can be found in the southern part of the steppe zone.
Chernozem, which has a large amount of humus in its composition, is valued as a highly fertile soil that gives a high and stable yield. It also contains a fairly large amount of other useful substances for fertility, which are so necessary for plants: nitrogen, sulfur, iron and phosphorus. The chernozem in its structure has a dense cloddy structure, and one of the most fertile is the southern chernozem, it is even called "fat chernozem".
Because of its fertility, black soil has always been valued throughout the world. And now, in modern times, black soil is the best type of land for growing vegetables, fruits, berries, trees and shrubs on it. Although it is worth knowing that for some plants, when planting them in the ground (chernozem), peat, sometimes sand or compost, should be mixed in to loosen the ground (soil), because the chernozem itself is quite dense, it does not differ in high friability.
Chernozem application
As we already know, black soil is the best soil for plants. As the name suggests, chernozem is the earth (soil) of dark color and very fertile.
Chernozem is used as a vegetable soil and is used when laying out lawns, in horticulture and as garden soil, etc. Chernozem is also used when cultivating land with a large composition of clay, land with poor drainage, to create a favorable air-water regime, and also, if necessary, to create a loose, lumpy soil structure.
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Moving from the forest region to the region of the southern steppes, we observe completely new conditions for the formation of soil. The terrain here is more flat. The climate is much warmer and drier. Summers are long and hot, winters are short. Already in February, the breath of spring is felt, and in March the steppe begins to turn green and resounds with the singing of a lark. The average temperature of each of the summer months is not lower than 20°. Precipitation in the main part of the zone is less than in the neighboring forest belt: in different places from 300 to 700 mm in year. This amount is not enough to wet the soil and soil to the level of deep-lying groundwater. Therefore, the water regime here, in the steppe, is non-flushing. Through wetting of the soil is observed only in round funnel-shaped depressions called potuscules (according to Vysotsky), but in these depressions the soils are already different (salt licks, solods, various marshy soils).
At the same time, glacial deposits of loam, clay, sand, interbedded with boulders and pebbles, characteristic of the taiga zone, are replaced here by various loess-like rocks and loess, porous loam of the smallest particles with a high content of lime. Boulders are not found in the loess at all. These rocks were deposited by glacial and rainwater, as well as winds.
The vegetation of the virgin chernozem steppes is forb, consisting of cereals, legumes, wormwood and other plants. The steppes stretched for hundreds and thousands of kilometers. Forests are located here on flat watersheds, along beams and river valleys. But under the forests and the soil is already forest.
In the ordinary steppe, without human help, trees suffer, especially in the first years of their life, for many reasons. They do not tolerate dry air and soil, they are scorched by the hot sun; sometimes they are destroyed by a large amount of soluble salts in the soil; on some poor breeds, they starve due to a lack (in the deep horizons of the soil where the roots go) of nutrients, such as phosphorus and potassium. Finally, until the trees have gained strength and closed their crowns, they are suppressed by grassy vegetation. A person can significantly weaken or even completely eliminate the causes that harm forests, and then they successfully develop in the steppe chernozem spaces.
The virgin, unplowed and unirrigated steppe lives to the fullest only in spring and in the first half of summer, when lush grassy vegetation develops on it. It should be noted that at present, after the plowing of virgin and fallow lands, the chernozem steppes untouched by agricultural crops have been preserved almost exclusively in reserves. This is Streletskaya (2 thousand sq. ha), Cossack (1200 ha) and Yamskaya (500 ha) steppes of the Central Black Earth State Reserve in the Kursk and Belgorod regions; The Starobelskaya steppe on the border of the Rostov and Voroshilovgrad regions, the Askania-Nova reserve in the south of Ukraine (its steppe part is 7 thousand years old). ha).
Virgin black earth steppes are just small islands against the backdrop of plowed lands. In table. 3 shows various lands for the main soil zones of the USSR. This table shows that in the zone of ordinary and southern chernozems, about 63% of the entire territory is currently developed for arable land, fallows, vegetable gardens and orchards. The rest of the area goes under hayfields, pastures, pastures, forests and shrubs, ravines or is occupied by buildings, roads and other structures. The same table shows the percentage of developed land in other soil zones of the USSR .
Chernozem steppes spread over large areas: from Moldova to the Far East, from Stavropol and Kuban to Kursk and Penza. As an example, we will describe the northern Streletskaya forb steppe in spring (on virgin soil).
The steppe is good at this time. In May, her green carpet is adorned with thousands of bright flowers, among which multi-colored irises are especially striking. Later, chamomile, bluebells, carnations, peas, St. John's wort, fragrant cheber (Bogorodskaya grass) and many dozens of other flowers bloom. Sometimes there are thickets of hawthorn, blackthorn and wild rose - favorite places of partridges, shrikes and other birds. In spring, these shrubs delight the eye with bright greenery and flowers, and in autumn - no less bright and pleasant fruits. Depending on which plants have blossomed, the shade of the steppe changes. She either turns blue or blushes, then turns yellow or is adorned with a colorful carpet. And in June, silver waves of feather grass sway in its open spaces. The air, especially in the evening and morning dawn, literally rings from the songs of the lark, from the “chilling” of partridges, from the cries of quails, twigs and other birds, from the whistling of gophers and the hubbub of other animals.
By the middle of summer, the steppe is scorched by the sun and has a gray appearance; however, even at this time, many cereal grasses, astragalus, wormwood and some other plants continue to vegetate.
The soils in the non-chernozem steppe are well ventilated and warmed up by the sun, but there is not enough water in them in the summer during the rainless period. For this reason, plant and animal remains decompose slowly. It turns out a lot of dark, poorly soluble humus in water. It combines with iron and calcium in the soil, and is firmly fixed in it. There are fulvic acids in the humus of chernozems, as well as other steppe soils, but they differ from the fulvic acids of podzolic soils and, apparently, are humic acids of a simplified structure (according to the works of Kononova). A lot of humus has accumulated in the soil, and it is contained in a significant thickness of it (sometimes up to a meter depth or more). The soil, due to the large amount of humus, acquired a black color, which is why it was called chernozem.
The chernozem of different areas of humus contains different amounts. For example, in the northern chernozem, on the border with the forest, there are only 4-6 parts of humus per 100 parts of soil, while in the regions of Ulyanovsk or Ufa it contains up to 13 16 and even 20 parts per 100 parts of soil. The deeper the soil layer, the less humus in it; the dark color of the soil also gradually fades away and is replaced by pale tones of the parent rock (fig. 63 and 64).
The humus in the soil firmly sticks together the smallest soil particles, and therefore in chernozems, especially unploughed ones, a lumpy-granular structure is clearly expressed. This is also facilitated by the richness of the soil with lime, one part of which - calcium - is included in the absorbing complex of the soil, saturates it.
The absorption capacity of chernozems is the best of all soils. In the humus horizon (A 1) it is 5-10 times higher than in the same horizon of podzolic soils.
Together with calcium, but in a much smaller amount (4-5 times), magnesium is also included in the absorbing complex of the soil. The total amount of absorbed calcium and magnesium reaches 1% or more by weight of the soil.
A lump of chernozem soil from its upper horizon, when crushed in the hand, is divided into rounded and angular pieces the size of a buckwheat grain and a little more. Such a structure is called granular. Separate structural pieces of soil, bonded with humus and lime, are distinguished by high porosity (about 50%) and at the same time significant water resistance: they easily and quickly absorb water, but are hardly washed away by it. In these lumps, even in damp soil, air is also contained in large pores (see Fig. 47). Air is also retained in the non-capillary pores between the lumps. This combination of water and air in the soil, as we have already noted, favors the development of cultivated plants.
As they deepen into the soil, its structural units grow in size and turn into lumps, and then (below 50 cm) and into lumps, which also break up into lumps, grains and dust.
The formation of a good structure in the chernozem is greatly facilitated by the root system of plants. A dense network of herb roots, penetrating the soil in all directions, provides material for humus formation and at the same time divides the soil, especially its upper layer, into small pieces.
We have already talked about the activity of earthworms in the chernozem soil. It must be said that the activity of other burrowing animals, especially before the plowing of land, was extremely pronounced here. This was noted at the beginning of the book. Moles, hamsters, marmots, ground squirrels, earth hares, mice and other diggers have in the past furrowed the soil with their burrows in all directions. A lot of earth thrown out by them to the surface. It is worth digging a hole in the black soil, and immediately you can notice the filled, and sometimes fresh holes. On the wall of the pit, they appear as round, oval or oblong spots, depending on the direction in which the hole is cut with a shovel. In the lower parts of the wall, the spots are more often black in color, because earth from the upper layers of the soil was poured here and brought by excavators. Above the spots are light - yellow-brown, dirty-yellow. Little processed loam was pulled out from the lower layers of the soil (see Fig. 63). These spots are called molehills. In some places, especially on watersheds, chernozem is completely processed by excavations, and therefore it is called molehill.
Moisture in the second half of summer chernozem is poor. The humus in it is “sweet”, mainly from humic and ulmic substances. Fulvic acids are few. The reaction is almost neutral. Due to the long stay of the soil in the dried state in the summer and the low content of acids in it, the minerals in the soil are slowly weathered. Various parts of the destroyed minerals are weakly washed out by water and linger in the soil. It accumulates, for example, salts containing substances necessary for plants, potassium and phosphorus. Washing out of the destroyed particles is significantly prevented by humus, which cements them. Nevertheless, the most soluble salts from the upper soil horizons are washed out by water with carbon dioxide dissolved in it. Of these salts can be called sodium sulfate, sodium chloride (table salt), gypsum, lime carbonate. Some of them were deposited in the lower layers of the soil. Above all other salts, now under the humus layer, and sometimes in itself, poorly soluble carbonic lime has accumulated. It can be observed here in the form of separate efflorescences, veins resembling a mycelium, and sometimes also in the form of rounded pieces the size of a pea or more (see Fig. 63). These last formations are called white-eyed or cranes. If you drop any acid on the crane and the soil surrounding it, it will hiss. The soil is said to "boil". This releases carbon dioxide after lime is broken down by acid. Such effervescence cannot be found in any layer of podzolic soils formed on non-calcareous moraine, because, with rare exceptions, they do not contain lime.
There are chernozems that have been more washed out with water and have even lost some of their humus. In this case, they acquire a grayish tint and lose their granular structure. Soluble salts from their upper horizons are washed out and washed out to a considerable depth. Such chernozems are usually located in depressions where water flows, and on the borders with the forest, where the soils are better moistened than in the open steppe.
Let us give a brief description of the chernozem soil as a whole.
The upper horizon (in Fig. 63 it is marked with the letter A 1) is painted black or dark gray, slightly brighter downwards. It accumulates most of the humus. In the surface part, the horizon breaks up into grains and small lumps, which increase in size with depth. The thickness of this horizon for the chernozem shown in the figure (fat chernozem), 35-40 cm
The second horizon (B 1) is somewhat lighter than the upper one, but it is difficult to draw a boundary between them. There is less humus in this horizon. It has a brownish coloration, intensifying in the lower part. It breaks up into larger pieces. The thickness of the second horizon is about 30 cm. Lightening downwards, it cuts into the third, yellowish or dirty-yellow loamy horizon (C 1 and C 2) with indistinct brown tongues and spots.
Some of the salts washed out from the upper parts of the soil, mainly carbonic lime, were deposited here. On fig. 63 its clusters are visible in the form of white spots (white-eyed, or cranes).
Throughout the horizons A and B in the dried soil, vertical and transverse cracks can be observed. During the period of snowmelt and during rains, water with salts dissolved in it and partly humus usually seeps through vertical cracks. Humus is deposited in the area of cracks in the form of individual spots, weak streaks and tongues. Wormholes and molehills can be observed in all three soil horizons. Live worms and some insects are often found. In different chernozems, the described three horizons have different thicknesses.
It should also be noted that in addition to loamy chernozems, there are clayey, sandy loamy, and occasionally sandy chernozems. They are scattered in spots and stripes over the entire area of occurrence of chernozems. There are chernozems formed on stony rocks.
The chernozem soils of our country stretch in a wide strip (800-1070 km) from the southwest of the European part of the USSR to the northeast. They are also common beyond the Urals and occupy significant areas in Siberia. .
Since the climate, vegetation and parent rocks in the vast expanses of the chernozem zone are different and the chernozems themselves are not the same in age, it is natural that, as we have already noted, they will be characterized by special properties in different parts of the zone. In those cases when chernozems stand out sharply from the zonal series according to some features, for example, by carbonate content, the thickness of the humus horizon, they are grouped into separate “provinces” - the Azov chernozem province, the Western Ciscaucasian, etc. Chernozems are distinguished mainly by three main features: thickness of the humus horizon, which ranges from about 40 to 150 cm; by humus content; its amount in the upper part of the humus horizon (A 1) varies from approximately 4 to 20%; according to the degree of washing, leaching of chernozem from lime and other salts. There are chernozems containing lime in their entire thickness and effervescent from acid from the very surface: they are called carbonate chernozems. In other cases, they boil with acid from 10, 20, 30, 40 cm etc. In the most leached chernozems, lime is found only in the thickness of a second meter of soil.
The smaller the humus horizon and the poorer it is in humus, the less naturally fertile the chernozem will be.
Such chernozems are common in the southernmost, driest part of the chernozem zone: in the south of Moldova and Ukraine, in the Rostov region, in the south of the regions of Saratov, Kuibyshev, Chkalov, in some regions of Siberia. Since these soils lie in the southern part of the chernozem zone, they were called southern chernozems, and due to the fact that they have an insignificant humus horizon (40; 50; 60 cm), they are also called weak. The last name is correct. It clearly distinguishes these chernozems from others, also located in the south, but with a powerful humus horizon, such as the Kuban or Stavropol.
There is relatively little humus in thin chernozems (4-6%), so their color is dark gray, with a reddish tint downwards. They are weakly washed out by sediments. From acid boil at shallow depths (from 10; 20; 30 cm), and sometimes from the surface. The latter is observed in the case when the chernozem is heavily dug up by excavations or its surface layer is washed away by rainwater. If you make a cut (dig a hole) in a field with thin chernozems, then at a shallow depth, immediately under the humus horizon, and sometimes in its lower part, clear accumulations of lime will be found. Gypsum can sometimes be found in the thickness of the second meter of soil.
In contrast to the southern (thin) chernozems, powerful chernozems (located much to the north), as their name shows, have a powerful humus horizon (about a meter or more in depth), and often, especially on rocks rich in lime, and a high content of humus (up to 10% or more); then they are also called fat (these are the most fertile soils in the world). The high content of humus in these soils causes their black color. When raw, they are as black as a raven's wing. These soils are common in some places in the Vinnitsa region, north of Kharkov, south of Kursk, in the regions of Voronezh, Tambov, Penza and in the east of the European part of the USSR: in the Ulyanovsk region and especially in Bashkiria, as well as in some regions of Siberia. As we move to the northeast, the thickness of these chernozems sharply decreases, and their obesity increases.
So the fat chernozems of Bashkiria, formed on carbonate (calcareous) rocks, have the thickness of the humus horizon (A+B) only 60-70 cm(see Fig. 63), and the humus content in them reaches 15, and sometimes 20%.
In different areas, thick and fat chernozems are washed from lime and other salts in different ways, but always much more than southern (thin) chernozems. Most often, from acid, they boil from 40-50 cm, sometimes even lower. For example, the rich chernozem of the Belebeevsky region of Bashkiria, shown in Fig. 63, boils at a depth of 39 cm, and on the horizon WITH starting from 75 cm it contains a significant content of white-eye and other inclusions of lime (lime veins, lime deposits along cracks, etc.).
Between thick and fat chernozems, on the one hand, and thin chernozems, on the other, there is a wide strip of chernozems that are intermediate in their properties. These are the so-called ordinary, or medium, chernozems. Significant areas of them are noted in Moldova, in the north of Odessa and Kherson, in the southern parts of Kharkov and Voronezh, in the north of Rostov, in some places of the Saratov, Kuibyshev, Chkalovsky regions and in Siberia.
These are soils with a humus horizon of up to 70 cm and somewhat more, with the content of humus in horizon A 1 7-10%. The upper part of their profile is usually washed from lime to half a meter and deeper. Gypsum in them can be found only in the thickness of the third meter, and visible efflorescence of easily soluble salts (sodium sulfate, sodium chloride and others) - only at a depth of four meters and below. These soils, especially in their wet state, are black in color and fully correspond to their name of chernozems. They are very fertile by nature.
In the north of the black earth zone - along the border with the forest-steppe - the climate becomes noticeably cooler and wetter. The soil here more often than in other parts of the zone is in a damp state and is more easily washed out by atmospheric precipitation. This leads to the fact that local chernozems are washed not only from easily soluble salts, but also from lime. They boil from acid well below the humus horizon - usually at the end of the first or in the thickness of the second meter. These are leached chernozems.
The thickness of the humus horizon and the content of humus in these soils are different. It depends on what kind of chernozem they formed as a result of washing it with precipitation: from powerful, fat or ordinary, medium. More often than not, the thickness of their humus horizon (A+ IN) not less than 70 cm, and the amount of humus in the surface horizon is not lower than 5-7% by weight of the soil.
Let us also note some features of the chernozems common in the southwest of the Rostov region, in the Krasnodar Territory, in the western and southwestern parts of the Stavropol Territory. These are the so-called Azov and Ciscaucasian chernozems. They also differ from each other, but for most plain soils, two characteristic features can be noted. By the size of the humus horizon, these are mainly the most powerful chernozems: the humus layer in them ranges from 100 to 170 cm. At the same time, the content of humus in these soils is relatively low: in most cases, in horizon A 1 4-5%. Only on the elevated plains of the Stavropol region are they significantly enriched in humus (up to 8-10%).
The chernozems located on the shores of the Sea of Azov are very rich in lime. Often they boil with acid directly from the surface. They are called so - Azov carbonate chernozems. They apparently developed from carbonate solonchaks, which we will discuss below.
Another part of the Ciscaucasian chernozems, located mainly in the western foothill plains of the Kuban Territory, for example, in the Krasnodar region, where up to 700 mm and more, along with a powerful humus horizon, it is distinguished by strong leaching and leaching. From acid, they boil only in the thickness of the second meter, in the lower part of which one can also find visible inclusions of lime. The humus horizon of these soils usually reaches 150 cm and more. These are leached western Ciscaucasian chernozems and, in terms of the size of humus horizons, the most powerful soils in the world.
Let us also name the Central Pre-Caucasian chernozems occurring on the elevated plains of the North Caucasus, for example, in the Stavropol region, where the climate is wetter and cooler than in the neighboring, lower steppes. As we have already noted, the soils here are relatively rich in humus (in the horizon A 1 6-10%). In terms of flushing (leaching), they occupy an intermediate position between the Azov carbonate and Western Ciscaucasian leached chernozems. From acid, they boil at various depths, but not lower than 50-60 cm. The thickness of their humus horizon ranges from 100 to 150 cm.
The three categories of soils noted here in the North Caucasus are among the most fertile soils in the world.
We have given a brief overview of chernozems, pointing out their differences in the thickness of humus horizons, humus content, and degree of precipitation leaching. It is obvious that these chernozems are also sharply different in their other properties: water, air and thermal regimes, the supply of nutrients, and structure. In particular, fat, thick and ordinary chernozems have the best cloddy-granular structure.
In general, black soil is the best soil. It is richer in humus, nutrients. True, with inept use, black soil can also be depleted. So, in some northern black earth regions, the soils in the pre-revolutionary past were already so plowed up that in order to obtain high yields, they need the mandatory use of mineral and organic fertilizers. Fertilizers, especially phosphate fertilizers, have long been introduced for sugar beet in other regions of the black earth region. And in recent years, the experiments of the leading workers of socialist agriculture have proved the significant effectiveness of fertilizers on chernozems and for grain crops. Mineral fertilizers are effective even on the most fertile chernozems of the Rostov Region, Stavropol and Krasnodar Territories.
Nevertheless, it should be noted that there are much more nutrients in the chernozem than in podzolic and other soils.
The roots of grasses and cultivated plants freely penetrate the entire chernozem thickness and develop in it in a continuous network, gradually decreasing with depth (Fig. 65-67).
Plants on the black soil no longer suffer from hunger, but from drought, and in search of water they send their roots to great depths.
The farmer has to save every drop of water here and keep it in the soil through reasonable cultivation and tireless struggle against weeds - the enemies of cultivated plants. The main processing of chernozem soils should be deep, 25-30 cm. An obligatory place in the crop rotation, especially on the more arid chernozems - ordinary and southern, should be found in pure fallows, and on all chernozems - tilled crops and grasses. In order to control weeds and retain moisture, the top layer of fallow soil, as well as other fields, must be kept in a loose, weed-free state so that water does not evaporate by weeds and the soil surface itself (due to capillary rise).
It is necessary to plow and loosen the soil as moist as possible, so as not to break or spray structural lumps. Dispersed soil after rains swims in a harmful crust, and in winds it flutters and spreads. There are black storms. The wind picks up the sprayed particles of the earth and carries them over long distances. Crops are dried up, and sometimes fall asleep. Especially harmful are storms on unstructured soils, which are more easily blown by the winds, and therefore the struggle for structural soil is at the same time a struggle against this disaster.
It should also be noted that the better the plant is provided with nutrients, the more economically it consumes water, so the struggle for nutrients in the soil will be at the same time a struggle for water, with drought.
An interesting industrial experience in the cultivation of meadow-chernozem soils is being carried out in Western Siberia (the Zavety Ilyich collective farm of the Shadrinsk district, Kurgan region) by the foremost agricultural worker T. S. Maltsev. The peculiarity of the agricultural technology used by him is as follows: the main plowing of the soil is carried out in a fallow field with a moldboardless plow to a depth of 50 cm. When the fallow is doubled (plowing the field at the end of summer), the soil is loosened to the same depth crosswise to the first direction of plowing. Further, in four-, five- and six-field crop rotations until the second rotation, deep tillage is not carried out, but its surface is often and thoroughly loosened by disc cultivators, which, along with loosening, helps to destroy weeds and reduce the evaporative capacity of the soil.
Positive in the Maltsev system is deep tillage without eversion of the subarable low-humus clay layer to the surface. Loosen up to 50 cm the layer absorbs atmospheric moisture well, and frequent loosening of the soil surface reduces the physical evaporation of water. Ultimately, the soil with such cultivation is better provided with moisture than with "normal" plowing with a plow with a moldboard to a depth of 20-22 cm. The systematic control of weeds also contributes to the conservation of moisture (and nutrients). Maltsev, using his system, gets grain crops on average about 20 c grain per hectare.
The weak points of the Maltsev system, in our opinion, are as follows:
a) there is no provision for plowing organic fertilizers (primarily manure) and a layer of grasses, as well as deep incorporation of mineral fertilizers;
b) continuous tillage without reversal of the layer can further lead to destructurization of the surface layer of the soil with all the negative consequences of this phenomenon.
While maintaining the positive qualities of the Maltsev system (deep tillage and systematic weed control), it is necessary to find a way to eliminate the shortcomings noted in it. In our opinion, this can be achieved by replacing non-moldboard tillage with a plow with a moldboard and disc skimmers, as well as with a ploughshare that loosens the lower layers of soil without turning them to the surface. Plowing with seam turnover on chernozems should be carried out to a depth of 25-30 cm, and further deepening of plowing without turning the lower layers to the surface - up to 50-60 cm.
The main deep plowing in a crop rotation should be carried out even on chernozems at least once every three years.
The use of a moldboard plow with skimmers and a subsoiler will make it possible to deeply loosen the soil and at the same time wrap the upper part of the layer while applying organic and mineral fertilizers.
The black earth zone is the granary of the USSR. The most valuable crops are cultivated here: wheat, barley, oats, millet, sunflower, sugar beets, corn, all kinds of vegetables, as well as fruit crops (Fig. 68 and 69). On the chernozem soils of the south of Ukraine, the Rostov region, Stavropol and Kuban, peanuts are now grown, and in some places castor beans are successfully grown, from which castor oil, which is so necessary in technology and medicine, is extracted. With careful care, these crops give high yields.
Earlier we described the virgin steppe in the Kursk region. Plowed chernozem soils look different. Occupied by a particular culture, they turn bright green in the spring. Next to the emerald of greenery, black areas of fallows stand out: here arable land is being prepared for winter crops.
In June in the south and in July in the north of the zone, the fields are eared with golden wheat and barley, panicles of oats, and heavy bunches of millet.
Beet fields are covered with rosettes of large juicy leaves. Walls are green massifs of corn and sunflowers. The latter first pleases the eye with bright yellow highlights of flowers, and later bends the tops under the weight of fruit "baskets". The greenery of corn and sunflower is so high (for example, in the Kuban) that in its shade one can hide from the heat; a rider on a horse can hide in it (Fig. 70).
Good for melons and gardens: they are decorated with golden melons, rolling green and colorful watermelons and pumpkins, red bunches of tomatoes and many other fruits - a product of soil fertility and human labor.
In August and September the fields are empty. The steppe now smells of wormwood, dry grass and compressed bread. Long stacks of straw grow. Harvest sunflower, corn, sugar beets, potatoes, fruit crops. Grain threshing is coming to an end. And nearby they are already preparing arable land for future harvests: they are peeling stubble, sowing winter crops, taking manure to fallow land and black fallows, plowing them.
And when the days become noticeably shorter and cooler, the autumn rain will drizzle, and strings of birds will stretch to the south, the steppe, saying goodbye to summer, will again be adorned with emerald greenery: it is winter grains that have risen and are gaining their first strength.
In November-December, the steppe will be covered with snow and fall asleep until spring.
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 agriculture has recently become of exceptional importance. According to the founder of Russian soil science V.V. Dokuchaev “our vegetative-terrestrial soils (represented by chernozem) are not some kind of mechanical, random, lifeless mixtures, but, on the contrary, are independent, definite and subject to known laws, natural historical bodies” (1).
1. CHARACTERISTICS OF CHERNOZEM
Compound
Chernozem provides a rather heterogeneous mass: pieces of quartz, humus flakes, and sometimes fragments of limestone, feldspar and even granite pebbles come across here together.
It is very rich in humus (dark organic matter, one might say, natural manure) and the most important, readily soluble nutrients for plants, which are: 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 such a plant-terrestrial soil, the average thickness of which is about 60 cm. Under the sod, 5–8 cm thick, there is a dark homogeneous loose mass - humus, consisting of grains or grains, sometimes roundish, but more often representing irregular polyhedra. This horizon in unplowed, virgin areas is overflowing with hundreds of thousands of living and dead underground parts of herbaceous plants. The average thickness of horizon A (the accepted designation according to V.V. Dokuchaev) is 30–45 cm. At the bottom, the soil horizon merges completely imperceptibly with the transitional horizon, which in fact, in all its features (physical and chemical), is a gradual transition from the upper (A) horizon to the lower (C) subsoil. The thickness of horizon B is also 30-45 cm. The subsoil - base (C) in the vast majority of cases consists of loess (light yellow, very loose loam rich in carbonates), 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, the chernozem in all natural, undisturbed (in one way or another) sections represents a gradual, closest genetic connection with the subsoil, whatever its composition may be.
Types
There are the following subtypes of chernozem soils:
Podzolized chernozems,
leached chernozems,
Chernozems are typical,
ordinary chernozems,
Southern chernozems.
Properties
1. In connection with its composition, chernozem always has a more or less dark color and is favorable to warmth and moisture. Color is a typical external sign: the color of black soil, whether the latter contains up to 15% humus 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 that the 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 the 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) bedrocks (subsoil) on which it still lies;
b) the climate that surrounds this soil now and surrounded it 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 savannas of Africa, Australia, the prairies of North and the pampas of South America, Venezuela, Brazil.
On the territory of Russia, chernozems are common in the regions of the Volga region, the Urals, the North Caucasus, the Lower Don and Western Siberia. The heart of the black earth belt is the Voronezh and Saratov regions. The mass of chernozem soils in the world is 48%, in Russia - 8.6%, which is 1.53 million km 2.
3. APPLICATION
Chernozem soils withstand long-term cultivation without any fertilizer and every time, under favorable climatic conditions, give excellent yields of rice, cereals, sunflowers, beets, fodder, fruits, grapes and other industrial and vegetable crops. The natural fertility of chernozem soils makes it possible to fully satisfy the population's need for food products, provides a significant part of the raw materials for light industry, and ensures livestock breeding.
Chernozem is not only a type of soil that is rich in humus, has a dark color and a granular structure, and is also actively used in agriculture due to its high fertility. This natural resource is one of the largest carbon stores in the world, home to almost a third of living organisms and is subject to restoration, because it takes more than 1000 years to form 1 cm of soil.
The formation of the described soil type occurs under perennial herbaceous vegetation in such natural zones as the steppe and forest-steppe, which are under conditions of a temperate continental climate type.
Due to the granular structure, chernozems are characterized by excellent air permeability, as well as a humus content of up to 15%. Also, in the soil, such important elements for plant nutrition as nitrogen, iron, phosphorus and others are accumulated and fixed in the form of mineral compounds of organic origin. In addition, the calcium content varies from 70 to 90%, which in turn ensures neutral reactions.
Depending on the place of formation, the thickness of the humus layer and the percentage of humus to chernozem, the described type of soil has several gradations.
The modern classification distinguishes 5 subtypes of chernozem - leached, podzolized, ordinary, southern and typical.
Leached chernozems are formed in the steppes under grasses and herbs. Broad-leaved forests, rich in herbaceous vegetation, serve as a place for the formation of podzolized chernozems. Ordinary chernozem is formed in the steppes with forbs located in the northern regions. Southern chernozem can be found in the southern parts of the steppe, rich in fescue-feather grass vegetation. Covering and loess-like loams covered with grasses and herbs serve as a place for the formation of typical chernozems.
According to the depth of humus occurrence (thickness of the humus layer), 4 groups are distinguished - thin (less than 0.4 m), medium-thick (from 0.4 to 0.8 m), powerful (from 1.2 to 0.8 m) and heavy-duty ( over 1.2 m).
The classification of chernozem according to the percentage of humus distinguishes 5 groups, which are characterized by their own color of the soil. Fat or highly humus soil has more than 9% humus and is painted in rich black. Medium-humus soils are painted black and the percentage of humus varies from 6 to 9. Dark gray color is typical for low-humus soil with a humus content of 4 to 6%. Low-humus soils are gray in color; the humus content in these soils is less than 4%. Microhumus soils contain less than 2% humus and are light gray in color.
Option 2
Under the steppe landscapes of Eurasia, North America (prairies) and South America (pampas), there are chernozem soils with a high quality of fertility. These are due to the presence of humus, formed from the remains of vegetation.
Soil conditions.
The temperate climatic zone is characterized by annual temperatures up to +7 0 C, with annual precipitation from 300 to 600 mm.
The vegetation cover is represented mainly by cereal crops of the herbaceous life form. In the upper soil layer, plant residues decompose under the influence of climatic conditions and bacteria. In addition to organic matter, inorganic substances are formed in the soil: nitrogen, phosphorus, sulfur and iron. The soil horizon becomes black.
Profile:
A - humus horizon (thickness 40-120 cm);
B - transitional horizon;
C is the parent breed.
Soil properties:
- the structure is lumpy, granular;
- 70-90% Ca in horizon B;
- neutral chemical reaction;
- 15% humus content in horizon A (the classification marks the highest degree of fertility in the southern subtype, allowing for an excellent harvest).
Soil color:
The whitish color is formed as a result of intensive washing out of mineral products. The process of formation of solonchaks and solonetzes begins. You can determine the presence of kaolin, gypsum and magnesium in the composition.
The study of chernozems:
1. M.V. Lomonosov, essay "On the Layers of the Earth", 1763. The concept of "chernozem" was introduced.
2. M. I. Afonin collected soil samples for exhibition in museums in 1771.
3. V. M. Severgin "Detailed mineralogical dictionary" 1807
4. The greatest contribution to the science of soil science was made by V. V. Dokuchaev, having spent the years 1876-1882 in scientific works. Compiled a detailed description and classification of chernozems. Wrote "Russian Chernozem" in 1883.
5. In the French capital of Paris in 1889, an exhibition was held, where they showed the exhibit "chernozem".
It should be noted that it took hundreds of years to form a fertile humus horizon. It takes much less time to lime it. So in the steppes of North America, the intensive development of chernozems led to dust storms in the 20th century.
