In which zone of the soil. Soil, natural zones and landscapes

Chapter 11. CLASSIFICATION OF SOILS. MAIN TYPES OF SOILS IN DIFFERENT NATURAL ZONES

Diversity natural conditions on Earth led to the formation of various soils in natural zones. All these soils would be impossible to know, study and use rationally without their certain grouping, i.e. classification. Classificationsoils - there is an association of soils into groups according to genesis, structure, most important properties and fertility. It includes the establishment of classification principles, the development of a system of taxonomic units, nomenclature (system of scientific names) and soil diagnostics (signs by which soils can be identified in the field and on maps). Taxonomic unit determines the sequence of accounting for genetic characteristics and the accuracy of establishing the position of the soil in the classification system.

§1. Main taxonomic units of soil classification

The modern scheme of soil classification, developed by the Dokuchaev Soil Institute ("Guidelines for the classification and diagnosis of soils", 1977 ) , more fully takes into account the morphological structure of the soil profile, composition and properties of soils, the main processes and modes of soil formation. This is a genetic classification of soils, reflecting their morphological, ecological and evolutionary characteristics. It is built on a logical system of taxonomic units, where soil types are grouped according to zonal-ecological combinations, each of which is characterized by the type of vegetation, the sum of soil temperatures at a depth of 20 cm from the surface, the duration of soil freezing, and the moisture coefficient.

Main taxonomic classification unit - genetic soil type, unites soils that develop in the same type of soil formation conditions (the same type of input and transformation of organic matter, mineral mass, the nature of migration and accumulation of matter, the similarity of the profile structure, etc.) for a long time, and therefore having the same most significant and characteristic features. For example, the podzolic type is formed as a result of the long-term presence of soils under coniferous woody vegetation on a carbonate-free rock under the conditions of a leaching water regime, the chernozem type - under the influence of herbaceous vegetation under conditions of a non-leaching water regime on carbonate rocks... Genetic soil types include: subtypes, genera, species, varieties, ranks.

Subtypes -groups of soils within a type, in which an additional process is superimposed on the leading soil-forming process and the general characteristics of the soil type are supplemented by individual features in their profile. The specificity of the subtypes is due to the peculiarities of the position within the soil zone, the dynamics of the main character of the type (for example, podzolic-gley, leached chernozem).

Childbirth are isolated within a subtype to clarify local conditions related to the properties of parent rocks, the composition and depth of groundwater, the presence of relict features and anthropogenic load (chernozem.

Within the genus, there are soil types as certain groups, differing in the degree of development of the soil-forming process, manifested in the thickness of the horizons, the degree of podzolization, the intensity of accumulation of humus, carbonates, readily soluble salts, etc. For example, powerful chernozem, soddy-podzolic medium podzol.

Within the species, there are varieties of soils, reflecting their differences in grain size distribution of the upper horizons.

Discharges Soils are determined by the genetic characteristics of the parent rocks (alluvial, moraine, etc.).

The nomenclature name of soils includes all units, starting with the type. For example, chernozem (type) is ordinary (subtype), solonetzic (genus), medium humus powerful (species), medium loamy (variety) on medium loess loam (category).

§2. Soils of various natural zones

The distribution of the main types of soil on land is subject to a certain pattern. For the first time, the regularities of the geographical distribution of soils were revealed by V.V. Dokuchaev when studying the latitudinal distribution of soils of the Russian Plain, on the basis of which he formulated the law horizontal zoning... According to this law, the zoning of soil formation factors (an increase in the amount of heat and a decrease in the moisture coefficient from north to south) entails a certain, also zonal, distribution of soils on the continents of the Earth. Consequently, each soil type prevails in a certain area and forms soil zone(area of \u200b\u200bzonal soil type and accompanying intrazonal and azonal soils). They are strips of unequal width, regularly replacing each other from north to south, can disintegrate into separate islands, etc. In South America and Australia, a meridian distribution of soils is observed.

The application of the law of horizontal zoning in mountainous areas revealed the presence of vertical zoning: soil zones regularly replace each other from bottom to top, as the soil zones of plain territories change from south to north, excluding those conditions that cannot be repeated in mountainous areas. There are also soil types that are common only in the mountains, but not found on the plains (alpine mountain meadow soils, etc.).

Some soil types do not form independent soil zones, but are found within several natural zones. Such soils are called intrazonal - their formation is determined by one main factor of soil formation, the rest are insignificant (salt licks, salt marshes, malt) and azonal - underdeveloped soils, which are practically the same in all natural and climatic zones due to their youth (alluvial).

Soils of the tundra zone... The zonal type of soils in the tundra zone is tundra-gley soils, which are formed under the influence of certain factors of soil formation, the characteristics of which are given below.

Climate - cold with a low average annual temperature, long cold winters, short summers, low precipitation and low evaporation (due to low temperatures), therefore, water is retained on the soil surface and soil formation occurs with a constant excess of moisture. A characteristic feature is the presence of permafrost, above which there is a thin layer that freezes in winter and thaws in summer - an active horizon, where soil formation takes place.

Type of water regime - stagnant permafrost (KU - 1.33 - 2.0).

Parent rocks predominantly glacial, lacustrine and marine of different texture.

Relief mostly flat with low hills and depressions occupied by water.

Vegetation underdeveloped, dwarf, consists of plants adapted to a short growing season. Mosses, lichens, some sedges and grasses, such species predominate. Cloves that grow "pillows", turf. A distinctive feature of the tundra is treelessness (translated from the Finnish “tundra” - treeless places). As you move south, dwarf birch, cloudberry, lingonberry, heather, etc.

Soil-forming process goes in conditions of constant excessive moisture (since permafrost prevents moisture penetration into the depths) and a lack of heat. The short growing season and low temperatures prevent the intensive development of biological processes, the activity of microorganisms is inhibited. Chemical weathering is also weak. The vegetation produces a small annual litter, containing few ash elements, therefore the humus horizon is very small or not expressed at all, however, the presence of permafrost prevents strong leaching (leaching of elements) and podzolization of the soil. Anaerobic processes are active, resulting in the formation of ferrous compounds of iron (II), which appear externally in the form of a bluish-brown or greenish color, and the processes of accumulation of dead organic matter in the form of peat, i.e. gleying and peat accumulation are characteristic features of soil formation in the tundra.

Tundra-gley soils have a peaty litter (A 0), beneath it is a coarse-humus horizon of dark gray or brownish-gray color (A), below it is a mineral gley horizon (G) with red spots of iron oxide (III).

Agrochemical properties:humus of the sulfate type, the reaction of the medium is acidic (pH KC l \u003d 3.5 - 5.5), poor in N, P, K, Ca, low saturation with bases, cation exchange capacity (T) 5 - 8 mg × eq / 100 g of soil ...

Tundra soils are used as pasture for reindeer, mainly for greenhouse farming; it is limited possible to maintain open field culture, especially on light soils. They grow potatoes, cabbage, onions, barley for green mass, grass mixtures. To improve the microbiological and nutritional regimes, it is necessary to apply high doses of organic fertilizer (up to 150-200 t / ha) and complete mineral fertilization, and liming.

Soils of the taiga-forest zone.The taiga zone is divided into three subzones: the northern taiga with gleypodzolic soils, the middle taiga with podzolic soils and the southern taiga with sod-podzolic soils (the southern subzone includes Belarus). A large enough area causes significant changes in soil formation factors from north to south and from west to east.

Climatemoderately cold and humid enough. Compared to the tundra zone, the climate is warmer with less severe winters, more precipitation and a longer growing season. The climate of the western regions is mild, close to the sea (the influence of the Atlantic Ocean), when moving to the east it becomes more continental. The average annual temperature varies from + 4 о С to - 7 ... - 16 о С. Annual precipitation is from 600 - 700 mm in the west to 150 - 300 mm in the central part of Eurasia. The maximum precipitation occurs during the warm period, but low temperatures exclude their intense evaporation.

Type of water regime - flushing (KU - 1.10 - 1.33).

Parent rocks mainly glacial (carbonate and carbonate-free loams), water-glacial deposits, which are represented by sands, sandy loams, less often loams, lacustrine-glacial and cover loams and clays. In the central and southern regions, loess, loess-like loams and organogenic deposits (peat) occupy a large place. In the mountainous regions of the European part, Eastern Siberia, the Far East, soil-forming rocks are mainly represented by eluvium and deluvium of bedrocks. In North America, there are mainly carbonate moraines, often overlain by carbonate loess-like loams.

Relief is characterized by great variety and complexity. The plains give way to hilly rugged valleys and depressions, which alternate with hills, mountains, a system of river valleys that cross the terrain in different directions. The European part of the zone is located mainly within the Russian Plain, mountainous relief on the Scandinavian Peninsula, the Urals, Central and Eastern Siberia, the Far East, North America. AT Western Siberia there is a large West Siberian lowland with a flat relief and strong boggy. Such a variety of topography affects the redistribution of climate, changes in vegetation and causes a great diversity of the soil cover.

Vegetation.Forests are the predominant vegetation. In the northern zone there are sparse coniferous and coniferous-deciduous forests with moss and marsh vegetation. The grass cover is poorly developed. There are many bogs, mostly sphagnum. In the subzone of the middle taiga, it is represented by dark coniferous forests with a solid moss cover and highly thinned herbaceous vegetation, there are many swamps, white-moss pine forests develop on sandy rocks. In the subzone of the southern taiga, coniferous forests with an admixture of broad-leaved species and mixed deciduous-coniferous forests prevail, in Western Siberia - deciduous forests. Herbaceous vegetation is well developed.

Soil-forming processproceeds under conditions of a leaching water regime with a wide variety of soil formation factors, which determines the development of several soil forming processes: podzolic, sod and bog (see Chapters 2 and 12). Waterlogging, acidic reaction of the environment, and a large amount of sesquioxides are typical for the soils of the zone. Podzolic soils are representative of typical taiga soils.

Podzolic soilslocated mainly on terraces above the floodplain and outwash plains formed by carbonate-free sands under the canopy of coniferous forests with a moss-lichen ground cover. They are formed under the influence of the podzol-forming process (see chapter 12). Under the forest floor A 0 lies the whitish podzolic horizon A 1 A 2, flowing into A 2 B, then horizons B (B 1, B 2) and C (BC g) lie.

Agrochemical properties: humus content is small 1.0 - 2.0%, fulvate type, the reaction of the medium is acidic (pH \u003d 4.0 - 4.5), T \u003d from 2 - 4 to 12 - 17 mg × eq / 100 g of soil (low ), the degree of saturation with bases is up to 50%, the absorbed bases are mainly H +, Al 3+. The content of mobile forms of Al, Mn is often toxic to plants. Soils are poor in nutrients, have unfavorable physical properties, are structureless.

When cultivating, it is necessary to introduce a large amount of lime, organic and mineral fertilizers, regulate the water regime, and sow perennial grasses.

Soils of the forest-steppe zone. The forest-steppe zone occupies an intermediate position between the taiga-forest and steppe zones, typical for it are gray forest soils (alternating with brown forest soils, leached and podzolized chernozems).

Climateis transitional from the humid climate of the forest zone to the arid climate of the steppes - moderately warm and moderately humid, with warm summers and moderately cold winters, the severity and continentality of the climate increases from west to east of the natural zone. There is less precipitation than in the forest zone, and the maximum falls in warm weather. In general, the forest-steppe zone is characterized by a favorable ratio of heat and moisture.

Type of water regime - periodically flushing (KU - 0.8 - 1.2).

Parent rocks mainly loesses and loesslike loams containing carbonates. There are sandy and sandy loam rocks on the ancient terraces of large rivers.

Relief predominantly flat, slightly wavy, hills with elongated long slopes, heavily indented ravines as a result of erosion. The peculiarity of the relief of this natural zone is the presence on the surface of small depressions (5 - 100 m in diameter and a depth of up to 0.5 - 1.5 m), called depressions, or saucers.

Vegetation the zone is characterized by alternation of forest areas with steppe. It is represented by broad-leaved forests with a herbaceous canopy - oak, ash, hornbeam, beech, linden, birch, etc. with meadow and meadow-steppe vegetation.

Soil-forming process goes under the influence of decay of deciduous forests and grassy cover, which favors the course of the soddy process of soil formation. In such litter, there are many ash elements, among which Ca, Mg, K predominate, a lot of nitrogen, phosphorus, little difficult-to-decompose residues, which contributes to the activity of microorganisms and intense humification. A powerful humus horizon is formed. Nevertheless, in the forest-steppe zone, a podzol-forming process is also manifested, albeit to a very weak extent, as a result of the washing of the profile by descending currents of water during spring snowmelt and autumn precipitation. Partially soluble salts, bases, sesquioxides, silt particles are washed out from the upper horizon and accumulate in the illuvial horizon. There is an accumulation of quartz in the washout horizon in the form of a powder on the surface of the particles. Thus, the formation of gray forest soils occurs under the main influence of the soddy process of soil formation in combination with podzalivanie and clay (removal of silt particles from horizon A and accumulation in horizon B).

Gray forest soils on the surface have a horizon of forest bedding, or sod (A 0) 2 - 5 cm, then there is a dark gray or gray humus horizon (A1) 15 - 35 cm, below - a transitional humus-eluvial (A 1 A 2 ) 10 - 20 cm. Below it there is a brown-brown illuvial horizon B, 70 - 90 cm thick, passing into the parent rock (C), usually carbonate.

Agrochemical properties: humus content 2 - 8%, humate-fulvate type; slightly acidic (pH KC l \u003d 5.0 - 6.5), the degree of saturation with bases - 60 - 90%; T \u003d 15 - 30 mg × eq / 100 g of soil.

Gray forest soils have favorable thermal and water regimes, a supply of nutrients and, having a sufficiently high natural fertility, are suitable for growing many agricultural crops - wheat, sugar beet, corn, peas, buckwheat, millet, etc. Horticulture is widely developed on these lands. The rational use of this type of soil is associated with the use of an optimal farming system aimed at creating a more powerful arable layer, increasing the reserves of humus, nitrogen, potassium, phosphorus through the systematic application of organic and mineral fertilizers, the use of green fertilizers, sowing of herbs, liming. Since soils are easily exposed to water erosion, a complex of anti-erosion measures should be carried out: plowing across the slope, increasing subsurface runoff, planting forest belts, etc.

Soils of the steppe zone.To the south of the zone of deciduous forests in Eurasia, there is a zone of meadow steppes with typical chernozem soils, which are distributed from the west of the East European Plain to the southern border of Western Siberia and the north of Kazakhstan. In North America, they are formed within the Great Plains (USA).

Climate characterized by warm summers and moderately cold winters. The amount of precipitation is on average 350 - 550 mm, falls in the hot summer months in the form of showers and does not soak the soil to a great depth. When moving from west to east, the amount of heat and precipitation decreases, and the climate becomes more conttent.

Type of water regime - non-flushing (KU - 0.5 - 0.66).

Parent rocks are mainly represented by loess and loess-like loams of various granulometric composition, in Siberia - clayey rocks. A distinctive feature of the soil-forming rocks of chernozems is their carbonate content and a large amount of montmorillonite minerals (provides a high absorption capacity of cations with a predominance of calcium and magnesium among them).

Relief is represented in most of the territory by a slightly wavy plain.

Vegetation the steppe zone was a herb-fescue-feather grass steppes, where feather grass ( Stipa), fescue ( Festucasulcata), steppe fire, wheat grass, sedges, clover, meadow bluegrass, sage, etc. Natural vegetation has been preserved only in some areas, since the main massifs of the steppe are plowed up.

Soil-forming process flows under the cover of grassy meadow-steppe vegetation, which annually produces a large amount of litter (2 times more than in deciduous forests), and most of it falls on the share of root residues. The litter is distinguished by the highest content of ash elements (7 - 8%) and nitrogen (1 - 1.4%), rich in calcium and magnesium, which contributes to the preservation of the neutral reaction of the upper horizons and the development of abundant microflora with a predominance of bacteria and actinomycetes. A non-flush type of water regime with alternating periods of humidification - desiccation, an excess of calcium salts, sufficient oxygen access and a neutral reaction contribute to the predominance of humus formation processes. Moreover, humification proceeds with a predominance of humic acids and their rapid neutralization and fixation in the soil in the form of calcium humates, which does not cause a noticeable decomposition of soil minerals under the influence of humic substances. There are relatively few free fulvic acids, and their effect on the soil-forming process is small. During humid periods, calcium migrates down the profile and the carbonate illuvial layer forms.

Thus, the leading process of soil formation during the formation of chernozems is the sod process under the steppe vegetation, as a result of which a powerful humus-accumulative horizon develops with the accumulation of biogenic elements and a valuable granular structure.

The soil profile of chernozems consists of horizons A 0, A 1, B K, C k. The humus horizons are dark-colored, their thickness reaches 80 cm. Below is the brown horizon B with humus streaks and carbonates, then C - with the accumulation of carbonates, readily soluble salts.

Agrochemical properties: humus content - 5 - 12%, humate type, neutral (рН КС l »7), Т \u003d 40 - 60 mg × eq / 100 g of soil, high saturation with bases - up to 99%, calcium prevails in the composition of absorbed cations.

Chernozems have optimal physical properties, water-resistant structure, good water and air permeability, moisture capacity, supply of biogenic elements, i.e. have high potential fertility (trophicity), for which VV Dokuchaev called them "the king of soils." However, these lands often suffer from crop failures, the main reason for which is a lack of moisture in the soil. Droughts in summer and strong dry winds lead to wind erosion, and where the relief and soil-forming rocks are favorable, in humid times - to soil erosion and the occurrence of water erosion. Intensive agricultural use leads to soil depletion as a result of an increasing deficiency of nutrients. Therefore, in order to preserve and maintain fertility, a set of measures is needed, aimed primarily at maintaining and accumulating moisture in the soil, maintaining high fertility (planting forest belts, snow retention, deep plowing, irrigation with water without readily soluble salts, applying mineral and organic fertilizers, microelements) and combating with erosion (forest shelter belts, non-moldboard plowing, strip placement of crops).

Dry steppe soils... The zonal type is chestnut soils, replacing chernozems in the south. They are located in a narrow strip in the west of Eastern Europe along the Black Sea, which expands to the east of Eurasia and occupies the largest areas in Mongolia and Kazakhstan.

Climate sharply continental with hot, dry, long summers and slightly snowy cold winters. Little precipitation falls (180 - 350 mm), evaporation is several times higher than their amount, as a result of which a moisture deficit is created in the soil. In summer, dry winds blow, draining the earth. The dryness of the climate increases to the east and south.

Type of water regime non-flush, weakly expressed effusion (KU "0.5 - 0.6).

Soil-forming rocks most often are loess-like carbonate loams, clays, less often loess. Often the parent rocks are saline.

Relief It is a flat or slightly wavy plain with a well-defined microrelief, which causes an uneven distribution of moisture and leads to a variegated soil cover (several types of soils can be found in a small area - chestnut, salt marshes, salt licks).

Vegetation rather poor in comparison with the black earth zone, sparse, undersized. Fescue-feather-grass steppes in the north are replaced by wormwood-fescue with big amount ephemera and ephemeroids (bulbous bluegrass, tulips, irises, etc.). Vegetation does not create a continuous cover, but grows separately. Wood species (spirea, warty euonymus, oak, etc.) are confined to river valleys and gullies.

Soil-forming process goes in an arid climate under sparse grass vegetation. A small amount of plant residues, less favorable conditions for their humification (in a dry period, the activity of microorganisms is suspended, and in a wet period, rapid mineralization occurs) lead to a slower rate of humus accumulation and its small amount, i.e. the sod process is less pronounced than in the zone of chernozems. In the composition of humus, the amount of humic acids decreases, therefore the color is chestnut. During the aerobic decomposition of organic matter (especially in wormwood groups), alkali metals enter the soil along with calcium, silicon, magnesium, which are the cause of the appearance of alkalinity in this type of soil. Consequently, a feature of the soil-forming process in the dry steppe zone is the superposition of a solonetzic process on a soddy one. Soils with a light texture are less, and those of a heavy one are more alkaline; on carbonate rocks, salinity does not appear or is manifested weakly.

The genetic profile of chestnut soils consists of horizons A 0, A 1, AB, B Ca, C. Humus horizons A1 and AB (transitional) about 35 - 45 cm thick from dark gray with a brownish tint to light brown. They boil from a depth of 45-50 cm (sometimes higher). The illuvial-carbonate VK is brownish-yellow in color, there are many accumulations of carbonates in the lower part of the horizon, which gradually passes into the slightly altered parent rock C. It is lighter, gypsum and readily soluble salts (from 2 m) lie.

Agrochemical properties: humus content - 2 - 5%, humate type (but the C HA: C FA ratio is less than in chernozems), the reaction of the upper horizons is slightly alkaline (pH KC l 7.2 - 8.0), T - 8 - 40 mg × eq / 100 g of soil, high saturation with bases, in the composition of absorbed bases Ca (70 - 75%), Mg (20 - 25%), Na up to 4%. The presence of absorbed sodium and potassium affects the structure of the soil - it is less water-resistant.

Chestnut soils have high natural fertility and, with high agricultural technology, give good yields. The main drawback is a small amount of moisture, therefore, in this zone, measures for the accumulation of moisture are even more relevant: snow retention, planting forest belts, special agrotechnical techniques, irrigation reclamation. Measures to protect chestnut soils from wind erosion are of great importance (since strong winds often blow here), it is better to use them as pastures. Saline soils are improved by gypsum and organic fertilization.

Soils of a semi-desert zone. The zonal type of the desert-steppe zone (semi-desert) is brown arid soils.

Climate sharply continental, strongly arid with long hot summers and cold winters with little snow. There is little precipitation (50 - 400 mm), most of them fall in summer, and strong evaporation of 1100 - 2000 mm creates a large moisture deficit in the soil.

Type of water regime effusion throughout the year (KU "0.05 - 0.33).

Soil-forming rocksin this zone there are loess-like loams, alluvial-lacustrine deposits of varying degrees of salinity, volcanic rocks, sometimes limestone.

Relief flat, slightly wavy, mountainous in places.

Vegetation sparse (20 - 35% of the area), xerophytic, wormwood-fescue, with a large number of ephemera and ephemeroids, halophytes, woody ones are found juzgun, tamarix, in the floodplains of rivers - aspen, poplar, saxaul.

Soil-forming process proceeds under specific conditions and is due to the aridity of the climate, salinity of soil-forming rocks and low productivity of the vegetation cover (0.1 - 2.5 centners / ha, represented mainly by roots). The humification process is very short-lived and takes place only in the spring, when the soil has favorable moisture conditions. Therefore, the humus content in the soil is low. This is also facilitated by the rapid mineralization of organic matter due to the predominance of aerobic processes in the upper soil horizons (due to the high temperature and low amount of moisture). During mineralization, a large amount of ash elements (up to 200 kg / ha) accumulates, which contain a large proportion of sodium. Due to shallow leaching, sodium accumulates in the AUC and causes the development of the solonetz process. Solonetzicity is a characteristic zonal feature of brown soils.

The humus horizon A of brown soils is 10-15 cm thick and has a grayish-brown or pale-brown color. Below is the humus-illuvial B 1 of a darker brownish-brown color; under it lies the yellowish-brown illuvial-carbonate B Ca with whitish spots of carbonates; the parent rock C usually contains accumulations of gypsum or readily soluble salts.

Agrochemical properties: humus content is low - 1 - 2.5%, fulvate type, the reaction is slightly alkaline (pH KC l - 7.3 - 8.5), T - 3 - 10 mg × eq / 100 g of soil in sandy, 15 - 25 mg × eq / 100 g of soil in loamy soils, Ca, Mg predominate among the absorbed cations, and Na in a small amount.

Brown soils are characterized by structurelessness, shallow soaking depth, low moisture reserves, and low natural fertility. Therefore, most of the semi-desert soils are used as pastures. Farming is possible only with irrigation (used for growing melons, grains, some vegetables), but it must be done carefully, since secondary soil salinization is possible due to the shallow occurrence of readily soluble salts. It is also necessary to carry out measures to combat the highly developed wind erosion in this zone. To increase fertility, it is necessary to combine the regulation of the water regime with the use of fertilizers - organic and mineral (nitrogen and phosphorus). Liman irrigation can be applied (soil moistening is carried out once in the spring by flooding with melt water), which significantly increases the productivity of pastures.

Soils of dry subtropics (foothill-desert steppes).In the dry steppes of the subtropical belt, serozem is most common. They are located mainly in the foothills of Central Asia, around the Tien Shan, etc.

Climate dry and hot continental with mild, warm, short winters. The amount of precipitation increases with increasing altitude and ranges from 100 to 500, the bulk falls in the spring. Evaporation is large - 1000 - 1350 mm. Saline groundwater is deep and does not lead to soil enrichment with readily soluble salts.

Type of water regime effusion (KU "0.12 - 0.33).

Parent rocksrepresented more often by loamy eolian loess-like deposits and loess, carbonate, may contain a small amount of gypsum.

Relief - vast sloping foothill plains, turning into hilly foothills.

Vegetation predominantly cereal, many ephemerals and ephemeroids during the rains, perennials include wormwood, umbrella, in the floodplains of rivers - forests of poplar and willow.

Soil-forming process proceeds in special hydrothermal conditions, which are characterized by two sharply separated periods: spring - warm and humid, but short, and summer - dry, hot and long. In spring, vegetation and microflora are actively developing, the process of humification and, at the same time, mineralization, is intensively proceeding. From May to October, the soil is drying up and biological activity practically ceases, readily soluble salts move upward, causing seasonal salinization of gray soils, and during humid time their desalinization occurs. Little organic residues enter the soil (6 - 10 t / ha), mostly in the form of roots. Climatic conditions favor the accumulation of carbonates at a depth of 20 - 60 cm and the washing out of chlorides and sulfates down the profile during the humid period.

Serozem, despite washing in the autumn-spring period, has a poorly differentiated profile, the color of the entire profile is light gray with a fawn tint. The humus horizon A1 of a darker color gradually passes (there is a transitional A1 B) into B Ca, in which a fawn shade is more pronounced and there are accumulations of carbonates, with depth it passes into the parent rock C.

Agrochemical properties: humus content - 1 - 4%, fulvate type (but C HA: C FA is close to 1), alkaline reaction (pH KC l 8.0 - 8.5), T \u003d 8 - 10 mg × eq / 100 g soil , the composition of absorbed cations is dominated by Ca, Mg, K, Na less than 5%.

Serozem has good physical properties, reserves of phosphorus, potassium, trace elements, which are evenly distributed in the profile. The main disadvantage is the extremely low humus content, in this regard, the fragile macrostructure, and the lack of moisture. Serozem is the main area for growing cotton, melons and gourds, and some cereals. Large areas are occupied by hayfields and pastures. Fertility enhancements include organic and mineral (especially nitrogen) fertilization, irrigation (with salt control to avoid secondary salinization, and soil density).

Soils of humid subtropics. The zonal type of soils is red earth, which are common on the Black Sea and Caspian coasts, the southern islands of Japan, in Southeast and Central China, South America, Bulgaria, Italy, etc.

Climate characterized by a long growing season, warm, humid, with a large amount of precipitation (2000 - 3000 mm), falling mainly in the form of showers, evaporation of 700 - 900 mm. Long summers and mild short winters. The temperature varies slightly with the seasons.

Type of water regime flushing (KU from 1.3 to 5.0).

Parent rocksare represented mainly by the red-colored weathering crust of igneous rocks, clayey and heavy loamy.

Relief - foothills and low mountains, strongly dissected, which contributes to the widespread development of erosion.

Vegetation represented by closed deciduous forests - oak-hornbeam and beech-chestnut with evergreen undergrowth of rhododendrons, azaleas, laurels, etc., intertwined with lianas.

Soil-forming process began in the Tertiary period and was not interrupted by glaciations, proceeds in favorable climatic conditions with the vigorous activity of microorganisms. Despite the large amount of litter, relatively little humus accumulates in the upper horizons, since under conditions high temperatures and constant soil moisture is actively mineralization of organic matter. Usually, humus is evenly distributed in the soil profile. The soil-forming process takes place in a leaching regime in an acidic environment, which leads to the active decomposition of primary minerals and their leaching. The more mobile weathering products (Ca, Mg, K, Na) are leached, and as the final products, less mobile sesquioxides Fe and Al accumulate in large quantities and uniformly color the profile from bright red to yellow, depending on their ratio and amount. This process is called ferralization - the stage of weathering of rocks, at which most of the primary minerals are destroyed and secondary minerals are formed, mainly the groups of sesquioxides, there are few silicon oxides, since they are quickly weathered. The removal of degradation products indicates the presence of a podzalization process, however, signs of podzol formation appear weakly and not everywhere, since the removal of chemical elements from the upper horizons is partially compensated by a large number of bases that are formed during the decomposition of organic matter and neutralize acidic products (on basic rocks, leaching is less intense than on sour). Consequently, the leading process of soil formation in red soils is leaching, which is superimposed on the processes of metamorphism (ferralization and allitization - accumulation of aluminum).

In the profile of red soils, A 0 of a rather large thickness is distinguished - up to 10 cm, under which lies a humus A1 of a dark brown or red-brown color with a thickness of about 20 cm. The transitional horizons B are replaced by an orange- or brownish-red color with a black dots of ferrous-manganese inclusions. Below there is parent rock C, orange, red, sometimes striped, containing inclusions of manganese, iron, and silica spots.

Agrochemical properties: humus content 2 - 4%, fulvate type, the reaction of the medium is acidic throughout the profile (pH KC l \u003d 4.2 - 5.2), T - 10 - 12 mg × eq / 100 g soil (low), the degree of saturation with bases small - 10 - 30%, in the composition of absorbed cations, Al and H predominate (the acidic environment is mainly due to Al).

Krasnozems have high productivity in forest biocenoses. They are distinguished by high water permeability, porosity, moisture capacity, and water-resistant structure, but they have little available phosphorus, and nitrogen deficiency is often found. Citrus fruits, tea bush, ethereal crops, tobacco are grown. Particular attention should be paid to combating water erosion, as climate and relief contribute to it. Terracing of slopes, inter-row planting of soybeans and other legumes with their subsequent plowing as fertilizer or sodding with perennial grasses, the creation of buffer forest belts, devices for regulating surface runoff are used.

Intrazonal soils. Intrazonal soils include salt marshes, solonetzes, and solods found in semi-desert, desert, forest-steppe, steppe, taiga, and some other zones. These soils are classified as saline, i.e. contain in their profile readily soluble salts in amounts that are toxic to plants. Most often, in saline soils there are NaCl, Na 2 SO 4, Na 2 CO 3, NaHCO 3, MgCl 2, MgCO 3, CaCl 2, CaCO 3, Ca (HCO 3) 2, CaSO 4.

Salt marshes- soils containing\u003e 1% readily soluble salts from the surface. According to the composition of the predominant anions, there can be: chloride, sulfate, soda, chdoride-sulfate, sulfate-chloride, according to the composition of cations: sodium, calcium, magnesian. Formed in various ways: 1) in the presence of a saline soil-forming rock; 2) in case of close occurrence of saline ground waters as a result of their capillary rise; 3) in place of dried up lakes; 4) when salt is carried by the wind from the seas or saline lakes; 5) in case of improper irrigation (secondary salinization); 6) during the accumulation of salts by halophytic plants (after their mineralization).

Climate

Type of water regime non-flush, more often effusion (KU "0.5).

Parent rocks - clays, heavy loams, residually saline.

Relief - flat plain with microrelief in the form of saucers, depressions.

Vegetation in natural conditions, either absent or represented by a specific community of halophytic plants (saltwort, saltwort, some species of quinoa, white wormwood, black saxaul, etc.)

Soil-forming process - saline, consists in the accumulation of readily soluble salts in the soil profile.

The salt marshes have a poorly differentiated profile, a characteristic feature of which is the homogeneity of the granulometric and bulk chemical composition.

Distinguish horizon A, transitional B and parent rock C.

Agrochemical properties: humus content 0.5 - 3% (in meadow saline soils up to 8%), fulvate type, reaction of the medium from slightly alkaline (pH \u003d 7.5) in saline neutral salts to strongly alkaline (pH KC l \u003d 11) in soda salt marshes, T \u003d 10 - 20 mg × eq / 100 g of soil (low), the degree of saturation with bases is about 100%, the absorbed bases are Ca, Mg, Na.

Saline marshes are characterized by low natural fertility, since the metabolism and nutrition of plants are disturbed on saline soils. Development is possible only after reclamation measures - gypsum plastering, washing (removal of salts with fresh water). Salt-tolerant crops are planted - cotton, millet, barley, sunflower, rice, etc., or used as pasture. They use the planting of woody plants, which intensively evaporate moisture and help lower groundwater.

Salt licks - soils, the AUC of which contains sodium\u003e 20%, readily soluble salts are found not in the uppermost horizon, but at a certain depth. Most often found in dry-steppe and steppe, desert zones. They arise: 1) during desalinization of saline soils saline with neutral sodium salts; 2) as a result of the vital activity of halophytic vegetation; 3) when exposed to the soil of slightly mineralized solutions containing soda; 4) in the presence of saline soil-forming rock. As a rule, in nature there is a combined effect of several factors, which leads to a stronger manifestation of salinity.

Climatedry, hot (continental).

Type of water regime non-flushing (KU \u003d 0.6 - 0.8).

Parent rocks - clays, heavy loam carbonate residual saline.

Relief - flat plain with microrelief.

Vegetation depends on the type of salt licks. Xerophytic, often sparse, cereal-wormwood associations (black wormwood, white wormwood, saline wormwood, camphorosma, fescue, etc.)

Soil-forming process: desalinization is the process of washing out easily soluble salts from the profile. In soils where sodium salts are abundant, the absorbing complex is saturated with sodium ions by displacing other cations. Colloids enriched with sodium retain a lot of water on the surface, swell and become mobile; in an alkaline medium, the solubility of organic and mineral compounds of the soil also increases. Due to their high mobility, these components are leached from the upper horizon, at some depth they turn into gels as a result of the action of electrolytes and accumulate, forming an illuvial horizon (in in this case solonetz). Due to the large amount of Na, salt licks develop extremely poor water-physical and physical-mechanical properties.

The solonetz profile is clearly differentiated into horizons, in contrast to solonchaks. Under the humus or supra-solonetz (A1) horizon, which has the basic properties of the zonal type of soils (color, structure, etc.), lies a solonetz (B 1 - illuvial), darker, viscous in the wet state, in the dry - very dense, cracks and forms a columnar structure. Under it is podsolonets or saline B2, lighter, less dense than B 1, contains carbonates, gypsum, readily soluble salts, below is the parent rock (C).

Agrochemical properties: humus content depends on the zone of formation of solonetzes - from 1% to 6 - 8% on chernozems, humate-fulvate or fulvate-humate type, alkaline reaction (pH KC l \u003d 8.5 - 10), T \u003d 15 - 30 mg × equiv / 100 g of soil (more in chernozem), saturated with bases, in the composition of absorbed cations Na (\u003e 20%), Ca, Mg.

In their natural state, salt licks are unproductive pastures and they can be used in agricultural production only after preliminary reclamation, primarily chemical - gypsum. If the gypsum-bearing horizon is shallow, then self-reclamation is used - deep plowing to mix gypsum with the solonetzic horizon. After this method, organic fertilizer is applied to increase fertility and grass sowing is applied against the background of irrigation.

Solody - soils formed during washing and leaching of salt licks. Usually they develop in depressions of the relief, where conditions of high humidity develop, mainly in the forest-steppe, steppe zones.

Climatedry, warm. Type of water regime - mostly non-flushing.

Relief - lowering of poorly drained plains with a close location (2 - 3 m) of ground waters of the hydrocarbonate-sodium or chloride-sulfate-sodium type.

Vegetation arboreal and shrubby (aspen, willow, birch, etc.), located in chops, meadow-boggy.

Soil-forming process represents malting - the transformation of solonetzes into malts, occurs in an alkaline medium, which leads to an enhanced destruction of aluminosilicates into simple compounds (silicic acid, sesquioxides). Mobile compounds (sodium humates, oxides of iron, manganese, aluminum, etc.) are washed out from the upper horizons, forming horizon B, and silicic acid accumulates in them. The accumulation of silicates is also biogenic: after the dying off of diatoms and silicon-containing plants, they remain in the soil. Acidic decomposition products and temporary anaerobiosis contribute to the formation of fulvic acids, the replacement of most of the AUC cations by the H + ion, unsaturation with bases A1 and A2, and an acidic reaction. The upper horizons, enriched with silica, become whitish, and the malts become similar to sod-podzolic soils.

The soil profile is sharply differentiated into horizons: A 0, A 1, A 2, B (sometimes subdivided into several), C. A 1 - humus or peat, if formed in bogs, thin, A 2 - solodized, whitish, platy structure, with rusty-ocher spots, poor in silty particles and sesquioxides, rich in silica, underneath lies a brownish-brown horizon that retains remnants of the columnar structure of the solonetz horizon, many silty particles, often contains carbonates, C - yellow-brown, carbonate .

Agrochemical properties: humus content 3 - 4% (sometimes up to 10%), fulvate type, acidic reaction (pH KC l \u003d 3.7 - 6.5), neutral in the lower horizons, T \u003d 10 - 15 mg × eq / 100 g of soil (in horizon B up to 30 - 40), in the absorbed state of Ca, Mg, Na and H.

Malts - soils with low natural fertility, contain little nitrogen, phosphorus, potassium, structureless, waterlogged, processed - float heavily and form a crust, it is necessary to apply large doses of manure, lime. However, natural forest vegetation is developing well and it is better to leave these soils under the forest.

Soils of river floodplains. A floodplain is a part of a river valley that is periodically flooded during floods. Alluvial soils are formed throughout the river floodplains.

A well-developed floodplain has three parts: riverbed, central and near-terrace. The near-channel part, which is under the influence of a strong current, is usually a system of parallel shafts composed of large sandy deposits. Here, underdeveloped light soils with a poorly differentiated profile are formed. The central part is flat, with depressions, oxbow lakes, consists of dusty and silty particles, often waterlogged. The lowest and most distant from the channel is the near-terrace part, where thin silt is deposited, waterlogged and often swampy.

Vegetation formed in conditions of frequent flooding, it is represented mainly by meadow herb-gramineous groups. The richest and most diverse vegetation is in the central floodplain, the near-channel is poorer, in the near-terrace, moisture-loving vegetation is developed. Trees also grow, the composition of which is determined by the natural zone: in the forest - birch, spruce, aspen, willow, alder, poplar, in the steppe - maple, elm, oak, willow, poplar, in the semi- and desert - mulberry, saxaul, tamarix, poplar, etc.

Soil-forming process proceeds in special conditions: flooding by flood waters of the floodplain and its erosion, bringing and deposition of alluvium on its surface containing a large amount of nutrients, the development of rich herbaceous vegetation. The leading process of soil formation is sod, in some types in combination with others (gleying, solonetz, etc.).

All alluvial soils are characterized by some features:

1) soils are formed simultaneously with the parent rock, since alluvium does not require a long preparatory stage weathering is the necessary nutrients (rapid soil formation), the rock is layered and heterogeneous;

2) intermittent soil formation, uneven change in the content of humus with depth;

3) floodplain soils of different natural zones differ less from each other than out-of-floodplain soils of one zone.

Alluvial (floodplain) sod soils are formed when groundwater is deeply buried, usually on the heights of the riverbed, on sandy alluvium, and have a layered profile (layered soddy). Floodplain meadows develop on loamy alluvium of the central part with shallow groundwater, are rich in humus, have a well-defined humus horizon, with a well-defined granular structure, often gleyed below (they are also called sod granular).

Agrochemical properties: humus content ranges from 1 to 10%, depending on the subtype of soils, the reaction of the soil is from acidic to slightly alkaline, depending on the natural zone.

Alluvial soils are of great importance, primarily as natural forage lands. They are also used as arable, because they have high natural fertility (good thermal, water-physical properties, easy to process, contain many nutrients). It is necessary to apply phosphorus, potash and organic fertilizers.

Climatic conditions in different regions of the world vary considerably. As a result of these differences, various types of soils were formed, each of which has its own agrotechnical characteristics.

Soil structure, fertility and origins determine the basic characteristics that make it possible to organize soil classification.

In the classification of soils, it is customary to distinguish several nested structural units: type, subtype, genus, species, variety and category.

Soil types and their characteristics.

The main soil types are represented by the following variations:

• Soils of the tundra zone.
• Soils of the taiga-forest zone.
• Soils of the forest-steppe zone.
• Soils of the steppe zone.
• Soils of the dry steppe zone.
• Soils of a semi-desert zone.
• Soils of dry subtropics.
• Soils of humid subtropics.
• Intrazonal soils.
• Soils of river floodplains.

What are the characteristics and characteristics of the main soil types?

1) Soils of the tundra zone.

The main type of soil in this climatic zone is tundra-gley. Formed in low temperatures, with little precipitation. Moisture evaporation is negligible due to low temperatures. Because of this, there is an excess of water on the soil surface.

The depth of soil warming is low, as a result, soil formation processes take place only in the upper layers of the soil, and permafrost is located at a greater depth.

Vegetation is poorly developed on tundra-gley soils. These are mainly dwarf shrubs and trees, lichens, mosses. Some types of cereals are present. There are no forests in the tundra zone, which is hidden in the very word "tundra" - in the translation "treeless".

Excessive moisture content in tundra-gley soils, combined with low temperatures, has a depressing effect on the vital activity of microorganisms. The humus layer is thin; over time, peat accumulates.

2) Soils of the taiga-forest zone.

There are podzolic, sod-podzolic and gley-podzolic soils.

The climate is moderately humid and cold. A large number of forests and swamps. The soils are mostly acidic with high humidity. The humus content is low.

3) Soils of the forest-steppe zone.

They are subdivided into gray forest, brown forest, podzolized and leached chernozems.

The climate is moderately humid and moderately warm. The amount of precipitation is insignificant. Forests alternate with steppe expanses. The humus content is quite high, the soils have good fertility.

4) Soils of the steppe zone.

The traditional soils for this zone are chernozems.

The climate is characterized by warm summers and not very cold winters. The precipitation rate is average. Most of the territories are plains.

The humus horizon has an impressive depth, but a good supply of moisture is required to achieve high yields.

5) Soils of the dry steppe zone.

The main soils of dry steppes are chestnut.

The climate is arid with low rainfall. The relief structure is flat.

6) Soils of the semi-desert zone.

Represented by brown arid soils.

The climate is very dry with little rainfall. The relief mainly consists of plains, there are mountains.

7) Soils of dry subtropics.

Traditional soils are gray soils.

The climate is dry and hot. The relief is represented by plains and foothills.

8) Soils of humid subtropics.

For this zone, the most common soils are red soils. The climate is warm, with high humidity and high rainfall, the temperature is stable throughout the year.

The relief is low mountains and foothills.

The amount of humus is not very large. The soil is often deficient in phosphorus and nitrogen.

9) Intrazonal soils.

Usually the climate is arid and very warm, and the relief is flat.

Fertility is very low.

10) Soils of river floodplains.

A feature of floodplain soils is that they are often flooded when nearby rivers flood. There are alluvial (floodplain) sod, bog and meadow soils.

The main types of soils in Russia.

On the territory of Russia, the most common soils are:

• Soils of the tundra zone.
• Soils of the taiga-forest zone.
• Soils of the forest-steppe zone.
• Soils of the steppe zone.
• Soils of the dry steppe zone.
• Soils of a semi-desert zone.

Soils are classified by type.The first scientist to classify soils was. The following types of soils are found on the territory of the Russian Federation: Podzolic soils, gley soils, arctic soils, permafrost taiga, gray and brown forest soils, and chestnut soils.

Tundra gleythe soils are on. Formed without much influence on them. These soils are found in areas where they are (in the Northern Hemisphere). Gley soils are often places where deer live and feed in summer and winter. An example of tundra soils in Russia can serve, and in the world - this is Alaska in the United States. On the territory with such soils, people are engaged in agriculture. This land grows potatoes, vegetables and various herbs. To improve the fertility of tundra gley soils, the following types of work are used: the most saturated with moisture and irrigation of arid regions. Also, the methods of improving the fertility of these soils include the introduction of organic and fertilizers into them.

Arctic soils obtained by thawing. Such soil is rather thin. The maximum layer of humus (fertile layer) is 1-2 cm. This type of soil has a low acidic environment. This soil is not restored because of the harshness. These soils are distributed on the territory of Russia only in (on a number of islands). Due to the harsh climate and a small layer of humus, nothing grows on such soils.

Podzolic soils common in forests. The soil contains only 1-4% humus. Podzolic soils are obtained through the process of podzol formation. A reaction with acid takes place. That is why this type of soil is also called sour. Dokuchaev was the first to describe podzolic soils. In Russia, podzolic soils are common in Siberia and on. In the world, there are podzolic soils in, and Canada. Such soils must be properly processed. They must be fertilized, organic and mineral fertilizers applied to them. Such soils are more likely to be more useful in logging than in agriculture... After all, trees grow on them better than agricultural crops. Sod-podzolic soils are a subtype of podzolic soils. In composition, they are in many ways similar to podzolic soils. A characteristic feature of these soils is that they can be washed out more slowly with water, in contrast to podzolic soils. Sod-podzolic soils are found mainly in (the territory of Siberia). This soil contains up to 10% of the fertile layer on the surface, and at depth the layer sharply decreases to 0.5%.

Permafrost taiga soils were formed in forests, under eternal conditions. They are found only in a continental climate. The deepest depths of these soils do not exceed 1 meter. This is caused by the proximity to the permafrost surface. The humus content is only 3-10%. As a subspecies, there are mountain permafrost taiga soils. They are formed in the taiga, which are covered with ice only in winter. These soils exist. They meet on. More often mountain permafrost-taiga soils are found near small water bodies. Outside of Russia, there are such soils in and in Alaska.

Gray forest soilsare formed on the territory of forests. A prerequisite for the formation of such soils is the presence of a continental climate. Deciduous forests and grassy vegetation. Places of formation contain an element necessary for such a soil - calcium. Thanks to this element, water does not penetrate deep into the soil and does not erode them. These soils are gray in color. The humus content in gray forest soils is 2-8 percent, that is, the soil fertility is average. Gray forest soils are divided into gray, light gray, and dark gray. These soils prevail in Russia in the territory from to. Fruit and grain crops are grown on the soil.

Brown forest soils distributed in forests: mixed, coniferous and broad-leaved. These soils exist only under conditions. The color of the soil is brown. Usually brown soils look like this: on the surface of the earth there is a layer of fallen leaves, about 5 cm high. Next comes the fertile layer, which is 20, and sometimes 30 cm. Even lower is a clay layer of 15-40 cm. There are several subtypes of brown soils. Subtypes vary with temperatures. Allocate: typical, podzolized, gley (superficial and pseudopodzolic). On the territory of the Russian Federation, soils are common in the Far East and at the foothills. On these soils, unpretentious crops are grown, for example, tea, grapes and tobacco. It grows well on such soils.

Chestnut soilsdistributed in and. The fertile layer of such soils is 1.5-4.5%. That says the average soil fertility. This soil has a chestnut, light chestnut and dark chestnut color. Accordingly, there are three subtypes of chestnut soil, differing in color. On light chestnut soils, farming is possible only with abundant watering. The main purpose of this land is pasture. The following crops grow well on dark chestnut soils without irrigation: wheat, barley, oats, sunflower, millet. There are slight differences in soil and chemical composition of chestnut soil. Its division into clayey, sandy, sandy loam, light loamy, medium loamy and heavy loamy. Each of them has a slightly different chemical composition. The chemical composition of chestnut soil is varied. The soil contains magnesium, calcium, water-soluble salts. Chestnut soil tends to recover quickly. Its thickness is supported by the annually falling grass and leaves of rare trees in the steppe. You can get good yields on it, provided there is a lot of moisture. After all, the steppes are usually arid. Chestnut soils in Russia are widespread in the Caucasus, on

For horizons, a letter designation is adopted, which makes it possible to record the structure of the profile. For example, for sod-podzolic soil: A 0 -A 0 A 1 -A 1 -A 1 A 2 -A 2 -A 2 B-BC-C .

The following types of horizons are distinguished:

• Organogenic - (litter (A 0, O), peat horizon (T), humus horizon (A h, H), sod (A d), humus horizon (A), etc.) - characterized by biogenic accumulation of organic matter.
• Eluvial - (podzolic, glazed, solodized, segregated horizons; denoted by the letter E with indices, or A 2) - characterized by the removal of organic and / or mineral components.
• Illuvial - (B with indices) - characterized by the accumulation of matter removed from the eluvial horizons.
• Metamorphic - (B m) - formed during the transformation of the mineral part of the soil in place.
• Hydrogen accumulative - (S) - are formed in the zone of maximum accumulation of substances (readily soluble salts, gypsum, carbonates, iron oxides, etc.) brought by groundwater.
• Cow - (K) - horizons cemented by various substances (readily soluble salts, gypsum, carbonates, amorphous silica, iron oxides, etc.).
• Gleyev - (G) - with prevailing reducing conditions.
• Subsoil - the parent rock (C) from which the soil was formed, and the underlying underlying rock (D) of a different composition.

Solid phase of soils

The soil is highly dispersed and has a large total surface area of \u200b\u200bsolid particles: from 3-5 m2 / g for sandy to 300-400 m2 / g for clayey. Due to its dispersion, the soil has significant porosity: the pore volume can reach from 30% total volume in swampy mineral soils up to 90% in organogenic peat soils. On average, this figure is 40-60%.

The density of the solid phase (ρ s) of mineral soils ranges from 2.4 to 2.8 g / cm³, organogenic: 1.35-1.45 g / cm³. Soil density (ρ b) is lower: 0.8-1.8 g / cm³ and 0.1-0.3 g / cm³, respectively. Porosity (porosity, ε) is related to densities by the formula:

ε \u003d 1 - ρ b / ρ s

Mineral part of the soil

Mineral composition

About 50-60% of the volume and up to 90-97% of the mass of the soil are mineral components. The mineral composition of the soil differs from the composition of the rock on which it was formed: the older the soil, the stronger this difference.

Minerals that are residual material during weathering and soil formation are called primary... In the hypergenesis zone, most of them are unstable and disintegrate at one rate or another. Olivine, amphiboles, pyroxenes, and nepheline are among the first to be destroyed. Feldspars are more stable, making up 10-15% of the mass of the solid phase of the soil. Most often they are represented by relatively large sandy particles. Epidote, disthene, garnet, staurolite, zircon, tourmaline are distinguished by high resistance. Their content is usually insignificant, but it allows one to judge the origin of the parent rock and the time of soil formation. Quartz has the greatest stability, which wears out in several million years. Due to this, under conditions of prolonged and intense weathering, accompanied by the removal of the products of the destruction of minerals, its relative accumulation occurs.

The soil is characterized by a high content of secondary mineralsformed as a result of deep chemical transformation of the primary, or synthesized directly in the soil. Particularly important among them is the role of clay minerals - kaolinite, montmorillonite, halloysite, serpentine and a number of others. They have high sorption properties, a large capacity of cation and anion exchange, the ability to swell and retain water, stickiness, etc. These properties largely determine the absorption capacity of soils, its structure and, ultimately, fertility.

The high content of minerals-oxides and hydroxides of iron (limonite, hematite), manganese (vernadite, pyrolusite, manganite), aluminum (gibbsite), etc. strongly weathered tropical soils), take part in redox processes. Carbonates play an important role in soils (calcite, aragonite, see carbonate-calcium balance in soils). In arid regions, readily soluble salts (sodium chloride, sodium carbonate, etc.) often accumulate in the soil, affecting the entire course of the soil-forming process.

Grading

Ferré triangle

The soil can contain particles with a diameter of less than 0.001 mm and more than a few centimeters. A smaller particle diameter means a larger specific surface area, and this, in turn, means higher values \u200b\u200bof the cation exchange capacity, water-holding capacity, better aggregation, but lower porosity. Heavy (clay) soils can have problems with air content, light (sandy) soils with water regime.

For a detailed analysis, the entire possible range of sizes is divided into sections called factions... There is no single classification of particles. In Russian soil science, the N.A.Kachinsky scale is adopted. The characterization of the granulometric (mechanical) composition of the soil is given on the basis of the content of the fraction of physical clay (particles less than 0.01 mm) and physical sand (more than 0.01 mm), taking into account the type of soil formation.

In the world, the determination of the mechanical composition of the soil according to the Ferret triangle is also widely used: on one side, the share of silty ( silt, 0.002-0.05 mm) particles, the second - clay ( clay, <0,002 мм), по третьей - песчаных (sand, 0.05-2 mm) and the intersection of the segments is located. Inside, the triangle is divided into sections, each of which corresponds to a particular grain size distribution of the soil. The type of soil formation is not taken into account.

Organic part of the soil

The soil contains some organic matter. In organogenic (peat) soils, it can prevail, in most mineral soils, its amount does not exceed a few percent in the upper horizons.

The composition of the organic matter of the soil includes both plant and animal remains that have not lost the features of the anatomical structure, as well as individual chemical compounds called humus. The latter contains both nonspecific substances of a known structure (lipids, carbohydrates, lignin, flavonoids, pigments, wax, resins, etc.), constituting up to 10-15% of the total humus, and specific humic acids formed from them in the soil.

Humic acids do not have a specific formula and represent a whole class of high molecular weight compounds. In Soviet and Russian soil science, they are traditionally divided into humic and fulvic acids.

Elemental composition of humic acids (by weight): 46-62% C, 3-6% N, 3-5% H, 32-38% O. Composition of fulvic acids: 36-44% C, 3-4.5% N, 3-5% H, 45-50% O. Both compounds also contain sulfur (from 0.1 to 1.2%), phosphorus (hundredths and tenths of%). Molecular masses for humic acids are 20-80 kDa (minimum 5 kDa, maximum 650 kDa), for fulvic acids 4-15 kDa. Fulvic acids are more mobile, soluble in the entire range (humic acids precipitate in an acidic medium). The carbon ratio of humic and fulvic acids (C gc / C fc) is an important indicator of the humus state of soils.

In the molecule of humic acids, a nucleus is isolated, consisting of aromatic rings, including nitrogen-containing heterocycles. The rings are connected by "bridges" with double bonds, which create extended conjugation chains, causing the dark color of the substance. The nucleus is surrounded by peripheral aliphatic chains, including hydrocarbon and polypeptide types. The chains carry various functional groups (hydroxyl, carbonyl, carboxyl, amino groups, etc.), which is the reason for the high absorption capacity - 180-500 meq / 100 g.

Much less is known about the structure of fulvic acids. They have the same composition of functional groups, but a higher absorption capacity - up to 670 mEq / 100 g.

The mechanism of formation of humic acids (humification) is not fully understood. According to the condensation hypothesis (MM Kononova, AG Trusov), these substances are synthesized from low molecular weight organic compounds. According to the hypothesis of L. N. Alexandrova, humic acids are formed by the interaction of high-molecular compounds (proteins, biopolymers), then they are gradually oxidized and split. According to both hypotheses, these processes involve enzymes produced mainly by microorganisms. There is an assumption about a purely biogenic origin of humic acids. In many respects, they resemble the dark-colored pigments of mushrooms.

Soil structure

The structure of the soil affects the penetration of air to the roots of plants, the retention of moisture, the development of the microbial community. Depending only on the size of the aggregates, the yield can vary by an order of magnitude. The structure is optimal for plant development, in which aggregates with a size of 0.25 to 7-10 mm prevail (agronomically valuable structure). An important property of the structure is its strength, especially water resistance.

The predominant form of aggregates is an important diagnostic feature of the soil. Allocate a rounded-cuboid (granular, lumpy, lumpy, silty), prismatic (pillar, prismatic, prismatic) and platy (platy, scaly) structure, as well as a number of transitional forms and gradations in size. The first type is characteristic of the upper humus horizons and causes a large porosity, the second - for the illuvial, metamorphic horizons, the third - for the eluvial ones.

Neoplasms and inclusions

Main article: Soil neoplasms

Neoplasms - accumulations of substances formed in the soil during its formation.

Neoplasms of iron and manganese are widespread, whose migration ability depends on the redox potential and is controlled by organisms, especially bacteria. They are represented by nodules, tubes along the roots, crusts, etc. In some cases, cementation of the soil mass with ferruginous material occurs. In soils, especially in arid and semi-arid regions, calcareous neoplasms are widespread: deposits, efflorescence, pseudomycelium, nodules, and crust formations. Gypsum neoplasms, also characteristic of arid areas, are represented by raids, druses, gypsum roses, and crusts. There are new formations of readily soluble salts, silica (dusting in eluvial-illuvially differentiated soils, opal and chalcedony interlayers and bark, tubes), clay minerals (cutans - incrustations and crusts formed during the illuvial process), often together with humus.

TO inclusions include any objects that are in the soil, but not associated with the processes of soil formation (archaeological finds, bones, shells of mollusks and protozoa, rock fragments, garbage). The assignment to inclusions or neoplasms of coprolites, wormholes, wormholes, and other biogenic formations is ambiguous.

Liquid phase of soils

State of water in soil

In soil, there is a distinction between bound and free water. The first soil particles are so firmly held that it cannot move under the influence of gravity, and free water is subject to the law of gravity. Bound water, in turn, is divided into chemically and physically bound.

Chemically bound water is part of some minerals. This water is constitutional, crystallization and hydrated. Chemically bound water can be removed only by heating, and some forms (constitutional water) by calcining the minerals. As a result of the release of chemically bound water, the properties of the body change so much that we can talk about a transition to a new mineral.

The soil retains physically bound water by surface energy. Since the value of surface energy increases with an increase in the total total surface of the particles, the content of physically bound water depends on the size of the particles that make up the soil. Particles larger than 2 mm in diameter do not contain physically bound water; this ability is possessed only by particles having a diameter less than indicated. In particles with a diameter of 2 to 0.01 mm, the ability to retain physically bound water is weak. It increases with the transition to particles less than 0.01 mm and is most pronounced in credcolloidal and especially colloidal particles. The ability to hold physically bound water depends not only on particle size. The shape of the particles and their chemical and mineralogical composition have a certain effect. Humus and peat have an increased ability to retain physically bound water. The particle holds the subsequent layers of water molecules with less and less force. It is loosely bound water. As the particle moves away from the surface, its attraction of water molecules gradually weakens. The water goes into a free state.

The first layers of water molecules, i.e. hygroscopic water, soil particles attract with tremendous force, measured in thousands of atmospheres. Under such great pressure, the molecules of tightly bound water are very close together, which changes many of the properties of water. It acquires the qualities of a solid body. The soil holds loosely bound water with less force, its properties are not so sharply different from free water. Nevertheless, the force of gravity is still so great that this water does not obey the force of gravity and differs from free water in a number of physical properties.

Capillary duty cycle determines the absorption and retention in a suspended state of moisture brought by atmospheric precipitation. The penetration of moisture through the capillary pores deep into the soil is extremely slow. The permeability of the soil is mainly due to the non-capillary porosity. The diameter of these pores is so large that moisture cannot be suspended in them and seeps into the depths of the soil without hindrance.

When moisture enters the soil surface, the soil is first saturated with water to the state of field moisture capacity, and then, through layers saturated with water, filtration occurs through non-capillary wells. Through cracks, shrews' passages and other large wells, water can penetrate deep into the soil, outstripping saturation with water to the value of the field moisture capacity.

The higher the non-capillary duty cycle, the higher the soil water permeability.

In soils, in addition to vertical filtration, there is a horizontal intra-soil movement of moisture. Moisture entering the soil, encountering a layer with a reduced permeability in its path, moves inside the soil above this layer in accordance with the direction of its slope.

Interaction with the solid phase

Main article: Soil absorbing complex

The soil can retain the substances entered into it by various mechanisms (mechanical filtration, adsorption of small particles, the formation of insoluble compounds, biological absorption), the most important of which is ion exchange between the soil solution and the surface of the solid phase of the soil. The solid phase due to the cleavage of the crystal lattice of minerals, isomorphic substitutions, the presence of carboxyl and a number of other functional groups in the composition of organic matter is charged predominantly negatively, therefore the cation exchange capacity of the soil is most pronounced. Nevertheless, positive charges, which cause anion exchange, are also present in the soil.

The entire set of soil components with ion-exchange capacity is called the soil absorbing complex (AUC). The ions included in the PPK are called exchangeable or absorbed. The characteristic of the AUC is the cation exchange capacity (CEC) - the total number of exchangeable cations of one kind held by the soil in the standard state - as well as the sum of exchangeable cations, which characterizes the natural state of the soil and does not always coincide with CEC.

The ratios between the exchangeable cations of PPC do not coincide with the ratios between the same cations in the soil solution, that is, the ion exchange proceeds selectively. Cations with a higher charge are preferentially absorbed, and if they are equal, with a higher atomic mass, although the properties of the PPC components may somewhat violate this pattern. For example, montmorillonite absorbs more potassium than hydrogen protons, while kaolinite does the opposite.

Exchangeable cations are one of the direct sources of mineral nutrition for plants, the composition of the AUC is reflected in the formation of organomineral compounds, the structure of the soil and its acidity.

Soil acidity

Soil air.

Soil air consists of a mixture of different gases:

1. oxygen that enters the soil from atmospheric air; its content can vary depending on the properties of the soil itself (its looseness, for example), on the number of organisms that use oxygen for respiration and metabolic processes;
2. carbon dioxide, which is formed as a result of the respiration of soil organisms, that is, as a result of the oxidation of organic substances;
3. methane and its homologues (propane, butane), which are formed as a result of the decomposition of longer hydrocarbon chains;
4. hydrogen;
5. hydrogen sulfide;
6. nitrogen; more likely the formation of nitrogen in the form of more complex compounds (for example, urea)

And this is not all the gaseous substances that make up the soil air. Its chemical and quantitative composition depends on the organisms contained in the soil, the content of nutrients in it, the conditions of soil weathering, etc.

Living organisms in the soil

Soil is the habitat of many organisms. The creatures that live in the soil are called pedobionts. The smallest of these are bacteria, algae, fungi and unicellular organisms that live in soil water. Up to 10¹⁴ organisms can inhabit one m³. Invertebrates such as ticks, spiders, beetles, springtails and earthworms live in the soil air. They feed on plant debris, mycelium and other organisms. Vertebrates also live in the soil, one of them is a mole. He is very well adapted to living in absolutely dark soil, therefore he is deaf and practically blind.

The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment.

• For small soil animals, which are united under the name of nanofauna (protozoa, rotifers, tardigrades, nematodes, etc.), the soil is a system of micro-reservoirs.
• For the somewhat larger animals breathing air, the soil appears as a system of small caves. These animals are called microfauna. The sizes of the representatives of the soil microfauna are from tenths to 2-3 mm. This group includes mainly arthropods: numerous groups of ticks, primary wingless insects (collembolans, protora, two-tails), small species of winged insects, symphila centipedes, etc. They have no special tools for digging. They crawl along the walls of the soil cavities with the help of their limbs or worm-like worms. The soil air saturated with water vapor allows breathing through the integument. Many species lack a tracheal system. Such animals are very sensitive to drying out.
• Larger soil animals, with body sizes from 2 to 20 mm, are called representatives of the mesofauna. These are insect larvae, centipedes, enchitreids, earthworms, etc. For them, the soil is a dense medium that provides significant mechanical resistance when moving. These relatively large forms move in the soil either by expanding natural wells by pushing the soil particles apart, or by digging new passages.
• Megafauna or soil macrofauna are large diggers, mainly mammals. A number of species spend their entire life in the soil (mole rats, mole voles, zokors, moles of Eurasia, golden moles of Africa, marsupial moles of Australia, etc.). They lay entire systems of tunnels and holes in the soil. The external appearance and anatomical features of these animals reflect their adaptability to the burrowing underground lifestyle.
• In addition to the permanent inhabitants of the soil, among the large animals one can distinguish a large ecological group of burrow inhabitants (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but reproduce, hibernate, rest, escape from danger in the soil. A number of other animals use their burrows, finding a favorable microclimate in them and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but they have a number of adaptations associated with a burrowing way of life.

Spatial organization

In nature, there are practically no situations such that any one soil with properties unchanged in space extends for many kilometers. In this case, the differences in soils are due to differences in the factors of soil formation.

The natural spatial distribution of soils in small areas is called the soil cover structure (TSS). The initial unit of the SPP is the elementary soil area (EPA) - a soil formation, within which there are no soil-geographic boundaries. Genetically related EPAs alternating in space and to one degree or another form soil combinations.

Soil formation

Soil-forming factors :

• Elements of the natural environment: soil-forming rocks, climate, living and dead organisms, age and terrain,
• as well as anthropogenic activities that have a significant impact on soil formation.

Primary soil formation

In Russian soil science, the concept is presented that any substrate system that ensures the growth and development of plants "from seed to seed" is soil. This idea is debatable, since it denies Dokuchaev's principle of historicity, which implies a certain maturity of soils and dividing the profile into genetic horizons, but it is useful in understanding the general concept of soil development.

The embryonic state of the soil profile before the first signs of horizons appear can be defined by the term “initial soils”. Accordingly, the "initial stage of soil formation" is distinguished - from the soil "along Veski" to the time when a noticeable differentiation of the profile on the horizons appears, and it will be possible to predict the classification status of the soil. The term “young soils” was proposed to be assigned the stage of “young soil formation” - from the appearance of the first signs of horizons to the time when the genetic (more precisely, morphological-analytical) appearance will be sufficiently pronounced for diagnosis and classification from the general point of view of soil science.

Genetic characteristics can be given even before the profile reaches maturity, with an understandable share of predictive risk, for example, “initial soddy soils”; "Young podzolic soils", "young calcareous soils". With this approach, nomenclature difficulties are naturally resolved on the basis of general principles of soil-ecological forecasting in accordance with the Dokuchaev-Jenny formula (representation of soil as a function of soil formation factors: S \u003d f (cl, o, r, p, t ...)).

Anthropogenic soil formation

In the scientific literature for lands after mining and other disturbances of the soil cover, the generalized name "technogenic landscapes" was fixed, and the study of soil formation in these landscapes took shape in "soil reclamation". The term "technozems" was also proposed, which in fact represents an attempt to combine the Dokuchaev tradition of "-zeeds" with technogenic landscapes.

It is noted that it is more logical to apply the term “technozem” to those soils that are specially created in the process of mining technology by leveling the surface and pouring specially removed humus horizons or potentially fertile soils (loess). The use of this term for genetic soil science is hardly justified, since the final climax product of soil formation will not be a new “-zill”, but a zonal soil, for example, sod-podzolic or sod-gley soil.

For technogenically disturbed soils, it was proposed to use the terms "initial soils" (from "zero - moment" to the appearance of horizons) and "young soils" (from the appearance to the formation of diagnostic signs of mature soils), indicating the main feature of such soil formations - their time stages. evolution from undifferentiated rocks to zonal soils.

Soil classification

There is no unified generally accepted classification of soils. Along with the international (FAO Soil Classification and the WRB, which replaced it in 1998), in many countries of the world there are national soil classification systems, often based on fundamentally different approaches.

In Russia, by 2004, by a special commission of the Soil Science Institute. V.V.Dokuchaev, led by L.L.Shishov, prepared a new soil classification, which is a development of the 1997 classification. However, Russian soil scientists continue to actively use the soil classification of the USSR in 1977.

The distinctive features of the new classification include the refusal to use factor-ecological and regime parameters for diagnostics, which are difficult to diagnose and are often determined by the researcher purely subjectively, focusing attention on the soil profile and its morphological features. A number of researchers see this as a departure from genetic soil science, which focuses on the origin of soils and the processes of soil formation. The 2004 classification introduces formal criteria for assigning a soil to a certain taxon, using the concept of a diagnostic horizon, adopted in the international and American classifications. Unlike the WRB and the American Soil Taxonomy, in the Russian classification, horizons and characters are not equivalent, but are strictly ranked according to taxonomic significance. An indisputably important innovation in the 2004 classification was the inclusion of anthropogenically transformed soils in it.

The American School of Soil Science uses the Soil Taxonomy classification, which is also common in other countries. Its characteristic feature is a deep study of the formal criteria for assigning soils to a particular taxon. Soil names constructed from Latin and Greek roots are used. The classification scheme traditionally includes soil series - groups of soils that differ only in granulometric composition, and have an individual name - the description of which began when the soil bureau mapped the territory of the United States at the beginning of the 20th century.

Soil classification is a system for separating soils by origin and (or) properties.

• Soil type is the main classification unit, characterized by the generality of properties determined by the regimes and processes of soil formation, and by a single system of basic genetic horizons.
  • Soil subtype is a classification unit within a type, characterized by qualitative differences in the system of genetic horizons and by the manifestation of overlapping processes that characterize the transition to another type.
    • Soil genus is a classification unit within a subtype, determined by the peculiarities of the composition of the soil-absorbing complex, the nature of the salt profile, and the main forms of neoplasms.
      • Soil type is a classification unit within a genus, quantitatively differing in the severity of soil-forming processes that determine the type, subtype and genus of soils.
        • Soil variety is a classification unit that takes into account the division of soils according to the granulometric composition of the entire soil profile.
          • Soil category is a classification unit that groups soils according to the nature of the parent and underlying rocks.

Distribution patterns

Climate as a factor in the geographical distribution of soils

Climate, one of the most important factors in soil formation and the geographical distribution of soils, is largely determined by cosmic reasons (the amount of energy received by the earth's surface from the Sun). The manifestation of the most general laws of soil geography is associated with climate. It affects soil formation both directly, determining the energy level and hydrothermal regime of soils, and indirectly, influencing other factors of soil formation (vegetation, vital activity of organisms, parent rocks, etc.).

The direct influence of climate on soil geography is manifested in different types of hydrothermal conditions of soil formation. The thermal and water regimes of soils affect the nature and intensity of all physical, chemical and biological processes occurring in the soil. They regulate the processes of physical weathering of rocks, the intensity of chemical reactions, the concentration of soil solution, the ratio of the solid and liquid phases, and the solubility of gases. Hydrothermal conditions affect the intensity of the biochemical activity of bacteria, the rate of decomposition of organic residues, the vital activity of organisms, and other factors; therefore, in different regions of the country with different thermal regimes, the rate of weathering and soil formation, the thickness of the soil profile and weathering products are significantly different.

The climate determines the most general patterns of soil distribution - horizontal zoning and vertical zoning.

The climate is the result of the interaction of climate-forming processes occurring in the atmosphere and the active layer (oceans, cryosphere, land surface and biomass) - the so-called climatic system, all the components of which continuously interact with each other, exchanging matter and energy. Climate-forming processes can be divided into three complexes: processes of heat turnover, moisture turnover and atmospheric circulation.

The value of soils in nature

Soil as a habitat for living organisms

The soil has fertility - it is the most favorable substrate or habitat for the vast majority of living things - microorganisms, animals and plants. It is also significant that in terms of their biomass, the soil (land of the Earth) is almost 700 times larger than the ocean, although less than 1/3 of the earth's surface falls on land.

Geochemical functions

The property of different soils to accumulate differently various chemical elements and compounds, some of which are necessary for living beings (biophilic elements and trace elements, various physiologically active substances), while others are harmful or toxic (heavy metals, halogens, toxins, etc.) , manifests itself on all plants and animals living on them, including humans. In agronomy, veterinary medicine and medicine, this relationship is known in the form of so-called endemic diseases, the causes of which were revealed only after the work of soil scientists.

The soil has a significant impact on the composition and properties of surface, groundwater and the entire hydrosphere of the Earth. By filtering through the soil layers, water extracts from them a special set of chemical elements, characteristic of soils in catchment areas. And since the main economic indicators of water (its technological and hygienic value) are determined by the content and ratio of these elements, the disturbance of the soil cover also manifests itself in a change in water quality.

Regulation of the composition of the atmosphere

Soil is the main regulator of the composition of the Earth's atmosphere. This is due to the activity of soil microorganisms, on a huge scale producing various gases -

Each natural zone is defined using several features: type of vegetation, fauna, climatic conditions, etc. The type and composition of the soil also directly depends on the listed factors. In addition, moisture, volatility, and relief features affect the fertility of the land.

Soil gives life to plants, which are the beginning of ecosystem food webs. Therefore, this or that type of natural complex and climate plays a decisive role in the formation of the soil cover.

Relationship between soil and natural zones

This table proposes to consider the correspondence of ecosystem types and main soil classes.

Zone name	Soil type		Soil properties	Conditions for soil formation
Arctic deserts	Arctic	Very little	Infertile	Lack of heat and vegetation
	Tundra-gley		Low-power, gley layer	Permafrost, little heat, waterlogging
Taiga of the European part	Podzolic	Insignificantly	Wash, sour	Fallen needles strongly oxidize the soil, permafrost
Taiga of Eastern Siberia	Taiga-permafrost	Insignificantly	Infertile, cold	Eternal Frost
Mixed forests	Sod-podzolic	More than podzolic	More fertile	Flushing in spring, more plant residues
Broadleaf forests	Forest gray		More fertile	Mild climate, fallen leaves of trees are rich in ash elements
Steppe and forest-steppe	Chernozems, chestnut		The most fertile	Lots of plant residues, warm climate
Semi-desert	Brown, gray-brown	Less humus	Salinization of soils	Dry climate, thin vegetation
	Desert yellowish gray		Due to rare rains, salts are hardly washed out	Lack of moisture and poverty in organic matter
Stiff-leaved evergreen forests and shrubs	Brown		High fertility with sufficient moisture	The growing season lasts all year round
Rainforest	Red-yellow ferralite and red-brown	The share of humus is 3-10%	Good rinsing of the soil cover, high content of iron hydroxide	High humidity, year-round high temperatures, huge plant biomass

The variety of surrounding landscapes and climates affects the fertility of the land in different ways. Thus, some soils can give life to a huge number of crops, while others are practically barren.

Soil types

Soil, like vegetation, is formed under certain climatic conditions. Therefore, the tundra is overgrown with mosses and low shrubs, and, for example, the tropical forest is distinguished by lush and lush vegetation. All soil types are arranged according to geographic zonation.

Tundra

The tundra zone, which occupies about 3%, is located in the conditions of the subarctic climatic zone. The ecosystem covers the entire coast of the Arctic Ocean and the islands north of Antarctica. The land in the tundra is formed under the influence of severe frosts, excessive moisture and modest vegetation cover.

Depending on the relief and drainage, the following types of tundra soils are distinguished:

• sour brown - receive a sufficient amount of moisture and oxygen, are located in the mountain tundra or on hills;
• tundra-gley - are, on the contrary, in the lowlands, are formed under conditions of stagnant water, poor drainage and lack of oxygen;
• peat-gley - located in the southern tundra and forest-tundra, where the climate is warmer and milder than in the typical tundra;
• tundra-boggy - lie in the depressions of the relief, can form tundra salt marshes;
• soddy acidic - located in the floodplains of rivers, grasses and cereals grow on them, as a result of which these soils are relatively rich in nutrients;
• polygonal peat bogs - common in some areas of the tundra, formed during the Holocene, when there was a forest zone in these places.

The entire territory of the tundra is covered by a layer of permafrost. It is located close to the surface, as a result of which the land is highly moistened and waterlogged. Strong cooling of the soil negatively affects the processes of soil formation and vegetation development.

Podzolic

To the south of the tundra there is a huge ecosystem - taiga. The podzolic soil type is characteristic of these northern coniferous forests. Its distinctive feature is high humidity and a high oxidation state due to fallen coniferous needles.

Since the taiga zone has a large length from north to south, the podzolic type is subdivided into several types depending on climatic conditions:

• gley-podzolic - common in the northern taiga, shrubs, dwarf trees, northern conifers grow on them;
• actually podzolic - typical for a typical taiga, where spruce, cedar, fir, pine, etc. grow on a cover of moss and lichen;
• sod-podzolic - the southern taiga zone, where deciduous trees begin to mix with conifers.

In addition to distribution over subzones, podzolic soils are divided according to layer thickness, structure and character of soil formation.

Gray forest

This type of soil lies beneath the surface of broadleaf forests. It contains a significant proportion of humus, which gives the soil a shade from light to dark gray.

Depending on the content of organic matter and fertility, forest soils are subdivided:

• light gray - the humus content is insignificant (up to 5%), according to their characteristics they are close to the soddy-podzolic soils of the southern taiga;
• gray - the share of humus here can be up to 8%, humic acids are also present;
• dark gray - the amount of organic matter reaches 10%, this is the most fertile and slightly acidic type of forest soil.

This amount of organic matter is formed due to the relatively dry climate, as well as the processes of decay of fallen leaves and grassy cover.

Chernozem

Chernozem soils are formed in steppe and forest-steppe regions with a warm, dry climate and rich meadow-herbaceous vegetation. This is the richest type of soil cover in organic and mineral substances. Chernozem is rich in magnesium, iron and calcium, and the humus content reaches 15%, the layer thickness of which is 1-1.5 m.

By composition, chernozem is divided into subtypes:

• podzolized - painted in gray or dark gray, and due to podzolization processes have a characteristic whitish bloom;
• leached - unlike the podzolized subtype, they have no plaque, but contain a leached brownish horizon;
• ordinary - located in the north of the steppe zone, have a dark gray or black color, the thickness of the humus layer reaches 80 cm;
• typical - in them chernozem processes are expressed as much as possible, the thickness of humus can take more than 120 cm;
• southern ones are widespread in the south of the steppes, there is a gradual decrease in the proportion of humus (up to 7%), and the thickness of the fertile layer is about 60 cm.

At present, the areas occupied by chernozem soils are almost entirely plowed up. Only small areas in ravines, gullies, virgin fields, and also in reserves remained untouched.

Swamp

The main area of \u200b\u200bdistribution is the plains covered with tundra and taiga. Swampy areas are formed as a result of excessive moisture, as well as processes such as gleying and peat formation. The term "gleying" means that the soil is formed with the participation of microorganisms and the constant washing of a significant layer of soil. Peat is created as a result of decomposition of plant debris.

Depending on the location on the surface of the relief, the composition of vegetation and soil, swamps are divided:

• riding - occupy flat plain areas, are formed as a result of the influence of underground or atmospheric waters, the surface is covered with sphagnum mosses;
• transitional - occupy an intermediate position between the upland and lowland type, the formation occurs with alternating moistening with hard and soft waters;
• lowland - located in the depressions of the relief, sedge and cereal grasses, dwarf birches, willows, etc. grow on them.

Peat of lowland bogs has the most beneficial properties: it is characterized by a low degree of acidity and is saturated with minerals. Bog soils form best in small bodies of water and lakes with stagnant water.

Lugovaya

Meadow soils are formed in places where meadow vegetation grows.

This soil type is divided into two subtypes:

• typical meadow - formed in the area of \u200b\u200boccurrence of groundwater by 1.5-2.5 m, under the plants of meadow zones;
• wet meadow (swampy meadow) - are found in low areas of river valleys, in conditions of constant moisture, cereal and sedge grasses grow on them.

All types of meadow soil have a good humus content (4-6%), therefore they are intensively used for agriculture.

comparison table

It contains a brief description of the natural complexes, as well as their geographic location, soil and vegetation that grows there.

It can be concluded that the most favorable conditions for the development of flora are a warm climate and high, year-round humidity.

Economic value

Soil is an essential element in the formation of all living organisms on Earth. In this case, the composition of the soil is formed due to the vital processes of plants and animals. But not every type of soil can give a good harvest.

What kind of soil is best for growing certain crops is written below:

1. Clay. With the addition of peat, sand and ash, it is great for growing fruit trees, shrubs, potatoes, peas, beets.
2. Sandy. It is fertilized with peat, compost, clay or mulching. This type of soil is suitable for growing almost all crops.
3. Sandy loam. To increase fertility, fertilizers are applied, mulched, and green manure plants are planted. Almost all types of vegetables and fruits can also grow on it.
4. Loamy. It contains a large amount of nutrients, you just need to add mineral fertilizers and mulch. Suitable for most types of crops.
5. Chernozem. The most fertile soil type, which does not require fertilization at first. After a few years, it is recommended to sow green manure plants and add organic matter. All fruit and vegetable crops take root on it.
6. Peat boggy. It is recommended to apply fertilizers from sand, clay, phosphorus and organic matter into it. It is good to grow berry bushes on such soil.
7. Limestone. Requires a lot of fertilizers due to lack of manganese and iron. Suitable for plants that are not too demanding on soil acidity.

The soil is a unique natural phenomenon. When drawing up a plan for the cultivation of a plot or field, it is necessary to correctly calculate the load on the soil, because the formation of a small layer of earth takes several thousand years.

Features of soils and vegetation of different natural zones

Each natural zone is characterized by a certain set of flora, fauna, climatic features and type of soil.

1. Arctic deserts. Located in the north of Eurasia and North America. Vegetation is practically absent, the soil is infertile.
2. Tundra. Covers the coast of the Arctic Ocean. The land is covered with mosses, lichens, grasses. In the south of the zone, shrubs and dwarf trees begin to appear. The soil is thin, there is permafrost.
3. Taiga. The largest ecosystem by area. Occupies most of the temperate forests. Conifers dominate: pines, spruces, fir, larch, cedar. The soil is acidic, cold and of little use for most plants.
4. Mixed forests. They are located south of the taiga. Deciduous and coniferous trees. The land is more fertile due to more plant residues.
5. Broadleaved forests. Located in Europe, the Russian Plain, Asia, in some places in South America. Oaks, ash trees, lindens, maples grow here. The soil is fertile thanks to fallen leaves and a warm climate.
6. Steppe and forest-steppe. The Russian steppes occupy a wide strip in the south of the country. On other continents, in climatic and natural conditions, African savannas, North American prairies and South American pampas are similar to steppes. Grassy plains mixed with small forests in the north. The most fertile soil, consisting of varieties of black soil.
7. Semi-deserts and deserts. They are located in the south of Eurasia, Africa, Australia. Occasionally there are plants - shrubs, cacti, cereals and herbs. The land is saline, the hot and dry climate prevents most of the plants from growing.
8. Subtropics and tropics. Located on the Mediterranean coast. The earth is colored red-yellow due to the large amount of iron. The subtropics are heterogeneous: acacias, chestnuts, oaks, hornbeams, and beeches grow in the subtropical forests in southern Russia. In other areas of the zone, pines, oaks, ferns, bamboos and palms coexist at the same time. A huge number of thermophilic plants grow in tropical forests.

Thus, vegetation and soil composition are interconnected: the more plants, the warmer the climate, the richer and more saturated the land will be.

Animals

Natural areas are inhabited by a wide variety of animals that have been able to adapt to the conditions of these places. Consider the composition of the fauna of various ecosystems.

Arctic

The coldest zone is inhabited by animals and birds that are perfectly adapted to extreme frosts: very thick fur or feathers, white color to hide in snowy spaces, etc. The total number of inhabitants is small, but they all have their own uniqueness and beauty: polar bears, arctic foxes, arctic hares, snowy owls, walruses, seals.

Tundra

A greater variety of living organisms is already observed here. Many animals move south to the forests for the winter, but there are those who live in the tundra all year round. The main inhabitants of the tundra are represented by reindeer, arctic foxes, hares, wolves, white and brown bears, lemmings, and polar owls. There are a lot of mosquitoes and midges in the tundra due to the large accumulation of swamps.

Forest zone

Forests of a temperate climate in a wide strip stretch from the northern forest-tundra to the southern forest-steppe. The diversity of fauna also varies from north to south. Thus, in the taiga, the species composition of animals is not as diverse as in mixed and deciduous forests. But in general, the animal composition of the forest zone is approximately the same: brown bears, wolves, foxes, lynxes, elks, red deer, and hares.

Steppe

Large animals have nowhere to hide in the wide and open spaces of the steppes, so small predators and animals live here. These are mainly steppe wolves, corsac foxes, saigas, hares, marmots, prairie dogs, bustards, storks.

Desert

If the Arctic is an extremely cold desert, then the tropical type of this zone is very hot and dry. The local inhabitants have learned to do without water for a long time and have adapted to the unbearable heat: camels, antelopes, fennec foxes, monitor lizards, scorpions, snakes and lizards.

Tropics

The rainforests are home to the largest variety of animals on the planet. These forests are multi-tiered, and each tier is inhabited by thousands of different creatures. Among the main inhabitants are: leopards, tigers, elephants, antelopes, okapis, gorillas, chimpanzees, parrots, toucans, as well as a huge number of butterflies and insects.

The richest belt in vegetation

The regions with the most diverse and abundant flora and fauna are the equatorial and subequatorial climatic zones of the Earth. On ferralite red-yellow soils, multi-tiered tropical forests grow and develop. Tall trunks of palms, ficuses, chocolate, banana, iron and coffee trees are entwined with vines, mosses, ferns and orchids grow on their surface.

Such a variety of plants is due to the absence of frost: the temperature even on the coldest days does not drop below + 20 ° C. Also, the nature of the tropics is characterized by a huge amount of rainfall. During the year in the tropics, up to 7000 mm of precipitation falls in the form of heavy showers. In conditions of constant humidity and heat, most of the plants on Earth grow and develop.

Video

This video describes the soil and plants of various natural areas.