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

The variety of natural conditions on Earth has led to the formation of various soils in natural zones. All these soils would be impossible to know, study and rationally use without their certain grouping, i.e. classification. Classification soils - there is a union 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 morphological structure soil profile, composition and properties of soils, basic 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 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 common features soil types are complemented 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, sod-podzolic medium podzol.

Within the species, there are varieties of soils, reflecting their differences in the granulometric composition 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 ​​zonal 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. V South America, Australia is observed meridian distribution of soils.

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, just as the soil zones of plain territories change from south to north, excluding those conditions, the occurrence of which 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 types of soils 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 lies 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 mainly glacial, lacustrine and marine of different texture.

Relief mostly flat with low hills and depressions filled with water.

Vegetation underdeveloped, dwarf, consists of plants adapted for 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. are found.

Soil-forming process goes in conditions of constant excessive moisture (since permafrost prevents moisture penetration into the depths) and a lack of heat. A short growing season and low temperatures prevent the intensive development of biological processes, the activity of microorganisms is suppressed. 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 dark-gray or brown-gray coarse humus horizon (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 = 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, cultivation is limited. open ground 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, to carry out liming.

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

Climate moderately cold and moist 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 predominantly glacial (carbonate and carbonate-free loams), water-glacial deposits, which are represented by sand, sandy loam, less often loam, lacustrine-glacial and cover loams and clays. In the central and southern regions, a large place is occupied by loess, loess-like loams and organogenic deposits (peat). In the mountainous regions of the European part, Eastern Siberia In the Far East, soil-forming rocks are represented mainly 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 terrain on the Scandinavian Peninsula, the Urals, Central and Eastern Siberia, the Far East, North America. In Western Siberia, there is a large West Siberian lowland with a flat relief and strong swampiness. Such a variety of topography affects the redistribution of climate, changes in vegetation and causes a great diversity of the soil cover.

Vegetation. The dominant vegetation is forests. 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 solid moss and highly sparse 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 process proceeds under the 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 swamp (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 typical taiga soils.

Podzolic soils are located 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 action of a podzol-forming process (see chapter 12). Under the forest floor A 0 lies a 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 = 4.0 - 4.5), T = 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 domesticating, it is necessary to introduce a large amount of lime, organic and mineral fertilizers, regulation of water regime, sowing of 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).

Climate is transitional from the humid climate of the forest zone to the arid climate of the steppe - 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 by ravines as a result of erosion. A feature of the relief of this natural zone is the presence on the surface of small depressions (5-100 m in diameter and depth 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, there is a lot of nitrogen, phosphorus, little difficult-to-decompose residues, which contributes to the activity of microorganisms and intensive 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 (A 1) 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 KS l = 5.0 - 6.5), the degree of saturation with bases - 60 - 90%; Т = 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. Rational use 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 broad-leaved 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 north of Kazakhstan. On the territory of North America, they are formed within the boundaries of 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. 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 loesslike 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 high capacity absorption of cations with a predominance of calcium and magnesium among them).

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

Vegetation steppe zone was a forb-fescue-feather grass steppes, where feather grass ( Stipa), fescue ( Festucasulcata), a 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. Relatively few free fulvic acids are formed, and their effect on the soil-forming process is insignificant. During humid periods, calcium migrates down the profile and a carbonate illuvial layer is formed.

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, the 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 (pH KC l »7), T = 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 the lack of moisture in the soil. Droughts in summer time 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, 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).

Soils of the dry steppe zone... The zonal type is chestnut soils, replacing chernozems in the south. 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, poorly expressed effusion (KU "0.5 - 0.6).

Soil-forming rocks most often are loesslike 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 zone of chernozems, sparse, undersized. Fescue-feather grass steppes in the north are replaced by wormwood-fescue steppes with a large number of 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, and 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 zone of dry steppes is the imposition of a solonetzic process on a soddy one. Soils with a light texture are less, and those of a heavy one are more solonetzic; on carbonate rocks, salinity is not manifested or 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) with a thickness of about 35 - 45 cm from dark gray with a brownish tint to light brown. 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 harvests... The main disadvantage 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 for the protection of 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 plastering and organic fertilizers.

Soils of the 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 it falls 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 rocks in this zone there are loess-like loams, alluvial-lacustrine deposits of varying degrees of salinity, volcanic rocks, sometimes limestone is found.

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, among woody ones, juzgun, tamariks, in the floodplains of rivers - aspen, poplar, saxaul.

Soil-forming process proceeds in 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 c / 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. Agriculture is possible only with irrigation (used for growing melons, grains, some vegetable crops), however, it must be carried out 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 used (soil moistening is carried out once in 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. The 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 rocks represented more often by loamy aeolian 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, there are many ephemerals and ephemeroids during 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, and 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 desalinization occurs during wet time. Little organic residues get into 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 leaching 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 pale yellow 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 = 8 - 10 mg × eq / 100 g of soil , in the composition of absorbed cations, Ca, Mg, K, Na less than 5% predominate.

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 some cereals. Large areas occupy 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 from season to season.

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

Parent rocks 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 in conditions of high temperatures and constant soil moisture, the mineralization of organic matter is actively going on. Usually humus is evenly distributed in the soil profile. The soil-forming process takes place under the conditions of 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- stage of weathering rocks, on 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 quickly erode. The removal of degradation products indicates the presence of a podzalization process, however, signs of podzol formation are weakly manifested and not everywhere, since the removal chemical elements from the upper horizons, it 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 acidic ones). Consequently, the leading process of soil formation in red soils is leaching, which is superimposed by 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. black dots of ferrous-manganese inclusions. Below is the 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 = 4.2 - 5.2), T - 10 - 12 mg × eq / 100 g soil (low), the degree of saturation with bases small - 10 - 30%, the composition of absorbed cations is dominated by Al and H (the acidic environment is mainly due to Al).

Krasnozems are highly productive in forest biocenoses. They are distinguished by high water permeability, porosity, moisture capacity, 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 are used, followed by plowing them as fertilizer or turfing perennial herbs, creation of buffer forest belts, devices for regulation of surface runoff.

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. The most common in saline soils 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> 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) at close occurrence of saline ground waters as a result of their capillary rise; 3) in place of dried up lakes; 4) when salts are carried by the wind from the seas or saline lakes; 5) with 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 micro-relief 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 = 7.5) in saline neutral salts to strongly alkaline (pH KC l = 11) in soda salt marshes, T = 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. Use fit woody plants, which intensively evaporate moisture and contribute to the lowering of groundwater.

Salt licks - soils, the AUC of which contains sodium> 20%, readily soluble salts are 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 low-mineralized solutions containing soda; 4) in the presence of a saline soil-forming rock. As a rule, in nature, a combined effect of several factors is observed, which leads to a stronger manifestation of salinity.

Climate dry, hot (continental).

Type of water regime non-flushing (KU = 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 - the process of washing out easily soluble salts from the profile. In soils with a lot of sodium salts, 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 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 the 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 podsolontsovy or saline В 2, lighter, less dense than В 1, contains carbonates, gypsum, readily soluble salts, below - parent rock (C).

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

In their natural state, salt licks are unproductive pastures and 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 reception, to increase fertility, make organic fertilizer and use grass sowing 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.

Climate dry, 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-sulphate-sodium type.

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

Soil-forming process represents malting - the transformation of solonetzes into malts, occurs in an alkaline environment, which leads to increased 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 promote 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 peaty, if formed in swamps, 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 = 3.7 - 6.5), neutral in the lower horizons, T = 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. Underdeveloped light soils with a poorly differentiated profile are formed here. 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, represented mainly by meadow herb-gramineous groups. The richest and most varied 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 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 of weathering and there are necessary nutrients (rapid soil formation), the rock is layered and heterogeneous;

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

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

Alluvial (floodplain) soddy 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, 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, since 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 the 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 in combination 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 warm summer period 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 to the soil 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.

The fertility level 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 the semi-desert zone.

summaries of other presentations

"The main natural zones of the Earth"- Natural areas. Biosphere. Altitudinal zonality. Organisms and environment... Protection of Nature. Terrestrial dry land. Tropical humid forests. Temperate forests. Subequatorial humid forests. Equatorial belt. Zone of temperate semi-deserts and deserts. Main biogeographic zones of land. Basic approaches. Forest-steppe and steppe. Subtropics. Tundra. Evolution of the biosphere.

"Latitudinal zoning and altitudinal zonality"- The predominance of reptiles. High soil fertility. Podzolic soils. What soils are typical for the natural zone of the steppes. Traveler. Chernozem soils. The geographic shell of the Earth. Natural area. What soils are typical for the natural zone of the taiga. A traveler who flew from the Volgograd Region to the Vologda Region. Climatic zone. Mixed forests. Tundra.

"Main natural areas"- Conditions of existence in deserts. Fast moving animals. Steppe. Deserts. Yakamara. Golden lion tamarin. Wild deer. Polar bear. Savannah. Distribution of tropical rainforests in the world. Lichens. Penguins and walruses. Constantly blowing winds. Animals. Brown bear. Plants. Natural zones of the Earth. Forest zone. Soil quality. Seals. Savannahs are characteristic of South America. Young gazelle.

"Geography" Natural Zones "- Natural zones of the Earth. Distinctive features tundra. Wild animals. The reason for the zoning. Monkey. Natural areas. Forests temperate latitudes... Arctic and Antarctic deserts. A huge number of plant and animal species. Lack of moisture. The number of land animals. Savannah. Animal world. Change of vegetation. Equatorial forests. Concretize concepts. Zonal complexes. Dry summer. The number of ungulates.

"Natural areas and their features"- Polar willow. Tundra. Hare. Brown bear. Dryad. Bison. Animals of the tundra. Natural zones of the Earth. Change in the number of plant species. Animals of the arctic deserts. Plan for the study of the natural area. Desert. Fill the table. Mixed and deciduous forests. Plants of arctic deserts. Steppe. Larch. European spruce. Deciduous forest animals. Arctic deserts. Capercaillie. Natural zones of Eurasia.

"Geographical zoning"- Geographer S.V. Kalesnik. Streams of air, water. Landscape zones. Geographic envelope component. Geographic zones. Physical and geographical phenomena. Geographic zones are divided into sectors. Zoning is gradually disappearing. Location of zones. Zoning of thermal conditions. Climatic zones. Unity of the geographical system. Geographic zoning. Radiation belts. Heat zones. Seven climatic zones.