The most important types of soils, their characteristics, advantages and disadvantages. Soil structure and main types Samples of soil rocks with descriptions

Soil types

Soil formation conditions

Soil properties

Natural area

1. Arctic

Little warmth and vegetation

Not fertile

Arctic desert

2. Tundra-gley

Permafrost, little heat, waterlogging

Low-power, have a gley layer

3. Podzolic

To uvl. > 1

Chilly. Plant residues - pine needles, pepper leaching

Washing, sour, low-fertility.

4. Sod-podzolic

More plant residues by flushing the soil in spring

More fertile, acidic

Mixed forests

5. Gray forest, brown forest

Temperate continental climate, remnants of forest and herbaceous vegetation

Fertile

Broadleaf forests

6. Chernozems

Lots of heat and plant residues

The most fertile, granular

7. Chestnut

To uvl. = 0.8, 0.7

Lots of heat

Fertile

Dry steppes

8. Brown and gray-brown

To uvl.< 0,5

Dry climate, little vegetation

Soil salinization

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

Diversity natural conditions on Earth led to the formation of different soils in natural zones. All these soils would be impossible to know, study and rationally use without their specific grouping, i.e. classifications. Classification soils - is the unification 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 (a system of scientific names) and soil diagnostics (characteristics 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 soil in the classification system.

§1. Basic taxonomic units of soil classification

Modern soil classification scheme developed by the V.V. Dokuchaev Soil Institute (“Instructions for classification and diagnostics of soils”, 1977 ) , more fully takes into account the morphological structure of the soil profile, the composition and properties of soils, the main processes and regimes 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 by 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.

Basic taxonomic unit of classification – genetic soil type, unites soils that develop under the same type of soil formation conditions (same type of input and transformation of organic matter, mineral mass, nature of migration and accumulation of matter, similarity of profile structure, etc.) for a long time, and therefore have 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 non-carbonate rocks under percolative water conditions, while the chernozem type is formed under the influence of herbaceous vegetation under non-percolative water conditions on carbonate rocks. Genetic types of soils include: subtypes, genera, species, varieties, categories.

Subtypes – groups of soils within a type in which some 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 determined by the peculiarities of the position within the soil zone, the dynamics of the main characteristic of the type (for example, podzolic-gley, leached chernozem).

Childbirth allocated within a subtype to clarify local conditions related to the properties of soil-forming rocks, composition and depth of occurrence groundwater, the presence of relict features and anthropogenic load (chernozem.

Within the genus there are types of soils as certain groups that differ 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, easily soluble salts, etc. For example, thick chernozem, soddy-podzolic medium podzolized.

Within the species there are soil varieties, reflecting their differences in the granulometric composition of the upper horizons.

Rank soils are determined by the genetic characteristics of soil-forming rocks (alluvial, moraine, etc.).

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

§2. Soils of various natural zones

The distribution of the main types of soils on land is subject to a certain pattern. For the first time, the patterns of geographical distribution of soils were identified by V.V. Dokuchaev when studying the latitudinal distribution of soils on the Russian Plain, on the basis of which he formulated the law horizontal zoning. According to this law, the zonality 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 globe. Consequently, each soil type predominates in certain territory 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, and can break up into separate islands, etc. In South America and Australia, a meridian distribution of soils is observed.

The application of the law of horizontal zonation in mountainous areas revealed the presence of vertical zonation: soil zones naturally replace each other from bottom to top, just as soil zones in lowland areas change from south to north, excluding those conditions whose occurrence cannot be repeated in mountainous areas. There are also types of soils that are common only in the mountains and are 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 (solonetzes, solonchaks, solods) and azonal– underdeveloped soils, which are almost 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 are tundra-gley soils, formed under the influence of certain soil-forming factors, the characteristics of which are given below.

Climate– cold with low average annual temperature, long cold winter, short summers, low precipitation and low evaporation (due to low temperatures), so 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 occurs.

Water mode type– stagnant-permafrost (KU – 1.33 – 2.0).

Soil-forming rocks predominantly glacial, lake and marine of different mechanical composition.

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, species of this family predominate. Cloves, which grow in “pillows” and turfs. A distinctive feature of the tundra is treelessness (translated from Finnish “tundra” means treeless places). As you move south, you encounter dwarf birch, cloudberries, lingonberries, heather, etc.

Soil formation process occurs under conditions of constant excess moisture (since permafrost prevents moisture from penetrating deeper) and lack of heat. Short growing season and low temperatures prevent the intensive development of biological processes, the activity of microorganisms is inhibited. Chemical weathering is also weak. Vegetation produces small annual litter containing few ash elements, so the humus horizon is very small or not expressed at all, but the presence of permafrost prevents strong leaching (washing out 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 accumulation of dead organic matter in the form of peat, i.e. characteristic feature soil formations in the tundra are gleying and peat accumulation.

Tundra-gley soils have a peaty litter (A 0), under it there is a coarse humus horizon of dark gray or brown-gray color (A), below there 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 KS 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 deer, mainly for greenhouse farming; crop cultivation is limited open ground, especially on light soils. They grow potatoes, cabbage, onions, barley for green mass, and 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 full mineral fertilizer, and carry out liming.

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

Climate moderately cold and fairly humid. 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 soft, close to maritime (influence of the Atlantic Ocean), but when moving to the east it becomes more continental. The average annual temperature varies from + 4 o C to – 7…– 16 o C. The annual precipitation ranges from 600 – 700 mm in the west to 150 – 300 mm in the central part of Eurasia. The maximum precipitation falls during the warm period, but low temperatures prevent intense evaporation.

Water mode type– flushing (KU – 1.10 – 1.33).

Soil-forming rocks predominantly glacial (carbonate and non-carbonate 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 organic deposits (peat) occupy a large place. In the mountainous regions of the European part, Eastern Siberia, and the Far East, soil-forming rocks are represented mainly by eluvium and colluvium of bedrock. In North America, they are mainly carbonate moraines, often overlain by carbonate loess-like loams.

Relief characterized by great diversity and complexity. The plains give way to hilly, rugged valleys and depressions, which alternate with hills, mountains, and a system of river valleys crossing the area in various 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, and North America. In Western Siberia there is a large West Siberian Lowland with flat topography and heavy swampiness. This diversity of relief affects climate redistribution, changes in vegetation and causes greater diversity of soil cover.

Vegetation. The predominant vegetation is forests. In the northern zone there are sparse coniferous and coniferous-deciduous forests with moss and swamp vegetation. The grass cover is poorly developed. There are many swamps, mostly sphagnum. In the middle taiga subzone it is represented by dark coniferous forests with a solid moss cover and very sparse herbaceous vegetation, there are many swamps, and 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 broad-leaved-coniferous forests predominate, in Western Siberia - deciduous forests. Herbaceous vegetation is well developed.

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

Podzolic soils located mainly on floodplain terraces and outwash plains formed by non-carbonate sands under the canopy of coniferous forests with a moss-lichen ground cover. They are formed under the influence of the podzol formation process (see Chapter 12). Under the forest floor A 0 lies a whitish podzolic horizon A 1 A 2, which gradually passes 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 mEq/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 and Mn is often toxic to plants. The soils are poor in nutrients and have unfavorable physical properties, unstructured.

When cultivating, it is necessary to apply 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 of it are gray forest soils (alternating with brown forest soils, leached and podzolized chernozems).

Climate is a transition 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, with the maximum falling in warm weather. In general, the forest-steppe zone is characterized by a favorable ratio of heat and moisture.

Water mode type– periodically flushing (KU – 0.8 – 1.2).

Soil-forming rocks mainly loess and loess-like loams containing carbonates. Sandy and sandy loam rocks are found on ancient terraces of large rivers.

Relief mostly flat, slightly undulating, hills with elongated long slopes, heavily indented by ravines as a result of erosion. A peculiarity 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 alternating forest areas with steppe areas. 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 formation process occurs under the influence of litter from broad-leaved forests and herbaceous cover, which favors the course of the turf soil formation process. This litter contains a lot of ash elements, among which Ca, Mg, K predominate, a lot of nitrogen, phosphorus, and few difficult-to-decomposable residues, which contributes to the activity of microorganisms and intensive humification. A powerful humus horizon is formed. Nevertheless, in the forest-steppe zone, the podzol formation process also manifests itself, although to a very weak extent, as a result of the washing of the profile by downward currents of water during spring snowmelt and autumn precipitation. Partially soluble salts, bases, sesquioxides, and silty particles are washed out from the upper horizon and accumulate in the illuvial horizon. There is an accumulation of quartz in the leaching 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 podzing and claying (removal of silt particles from horizon A and accumulation in horizon B).

Gray forest soils on the surface have a forest floor horizon, or turf (A 0) 2 - 5 cm, followed by a dark gray or gray humus horizon (A 1) 15 - 35 cm, below is a transitional humus-elluvial horizon (A 1 A 2 ) 10 – 20 cm. Below it there is a brownish-brown illuvial horizon B with a thickness of 70 – 90 cm, which passes 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), degree of saturation with bases – 60 – 90%; T = 15 – 30 mg×eq/100 g of soil.

Gray forest soils have favorable thermal and water regimes, a supply of nutrients and, having a fairly high natural fertility, are suitable for growing many agricultural crops - wheat, sugar beets, 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, and phosphorus through the systematic application of organic and mineral fertilizers, the use of green fertilizers, sowing grass, and liming. Since soils are easily subject to water erosion, a set of anti-erosion measures should be carried out: plowing across the slope, increasing subsoil flow, 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 the north of Kazakhstan. In North America they form within the boundaries of the Great Plains (USA).

Climate characterized by warm summers and moderately cold winters. The average precipitation is 350 – 550 mm, falling in the hot summer months in the form of showers and does not wet the soil to a great depth. As you move from west to east, the amount of heat and precipitation decreases, and the continentality of the climate increases.

Water mode type– non-washing (KU – 0.5 – 0.66).

Soil-forming rocks are mainly represented by loess and loess-like loams of various granulometric compositions; 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 (providing a high absorption capacity of cations with a predominance of calcium and magnesium).

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

Vegetation The steppe zone consisted of forb-fescue-feather grass steppes, where feather grass ( Stipa), fescue ( Festucasulcata), steppe brome, wheatgrass, sedges, clover, meadow bluegrass, sage, etc. Natural vegetation has been preserved only in certain areas, since the main tracts of the steppe have been plowed.

Soil formation 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), with most of it being root residues. The litter has the highest content of ash elements (7–8%) and nitrogen (1–1.4%), and is 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-flushing type of water regime with alternating periods of wetting and drying, an excess of calcium salts, sufficient access of oxygen and a neutral reaction contribute to the predominance of humus formation processes. Moreover, humification occurs 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 noticeable decomposition of soil minerals under the influence of humic substances. Relatively few free fulvic acids are formed, and their influence on the soil-forming process is small. During wet periods, calcium migrates down the profile and forms a carbonate illuvial layer.

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

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

Agrochemical properties: humus content – ​​5 – 12%, humate type, neutral (pH KS l » 7), T = 40 – 60 mg×eq/100 g of soil, high saturation with bases – up to 99%, calcium predominates in the composition of absorbed cations.

Chernozems have optimal physical properties, a water-resistant structure, good water and air permeability, moisture capacity, and a reserve of nutrients, i.e. have high potential fertility (trophicity), for which V.V. Dokuchaev called them “the king of soils.” However, these lands often experience crop failures, the main reason for which is a 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 wet times - to soil erosion and the occurrence of water erosion. Intensive agricultural use leads to soil depletion as a result of increasing deficiency of nutrients. Therefore, to preserve and maintain fertility, a set of measures is necessary, aimed primarily at preserving and accumulating moisture in the soil, maintaining high fertility (planting forest belts, snow retention, deep plowing, irrigation with water without easily soluble salts, applying mineral and organic fertilizers, microelements) and to combat with erosion (forest shelterbelts, moldless plowing, strip placement of crops).

Soils of the dry steppe zone. 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 cold winters with little snow. There is little precipitation (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, greatly drying out the land. The dryness of the climate increases in the eastern and southern directions.

Water mode type non-flushing, mild effusion (CU" 0.5 - 0.6).

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

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

Vegetation quite poor compared to the chernozem zone, sparse, low-growing. Fescue-feather grass steppes in the north are replaced by wormwood-fescue steppes with a large number of ephemerals and ephemeroids (bulbous bluegrass, tulips, irises, etc.). Vegetation does not create a continuous cover, but grows separately. Tree species (spirea, warty euonymus, oak, etc.) are confined to river valleys and ravines.

Soil formation process travels in arid climates under sparse grass vegetation. A small amount of plant residues, less favorable conditions for their humification (in the dry period, the activity of microorganisms is suspended, and in the wet period, rapid mineralization occurs) lead to a slower rate of accumulation of humus and its small amount, i.e. the turf process is less pronounced than in the chernozem zone. The amount of humic acids in the composition of humus decreases, so the color is chestnut. During aerobic decomposition of organic matter (especially in wormwood groups), calcium, silicon, and magnesium enter the soil. alkali metals, which are the cause of the appearance of solonetzity in this type of soil. Consequently, a feature of the soil-forming process in the dry steppe zone is the superposition of the solonetzic process on the turf one. Soils of light mechanical composition are less, and soils of heavy mechanical composition are more solonetzic; on carbonate rocks, salinity does not manifest itself or is weakly manifested.

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

Agrochemical properties: humus content – ​​2 – 5%, humate type (but the ratio of CHA: CFA is less than in chernozems), the reaction of the upper horizons is slightly alkaline (pH KS l 7.2 – 8.0), T – 8 – 40 mg× eq/100 g of soil, high saturation with bases, the composition of absorbed bases is 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, produce good harvests. The main disadvantage is a small amount of moisture, therefore, in this zone, measures to accumulate moisture are even more relevant: snow retention, planting forest belts, special agricultural practices, 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 gypsuming and adding 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, very arid with long hot summers and cold winters with little snow. There is little precipitation (50 - 400 mm), most of it falls in the summer, and strong evaporation (1100 - 2000 mm) creates a large moisture deficit in the soil.

Water mode type effusion throughout the year (CU » 0.05 – 0.33).

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

Relief flat, slightly undulating, mountainous in places.

Vegetation sparse (20 - 35% of the area), xerophytic, wormwood-fescue, with a large number of ephemerals and ephemeroids, halophytes, among the trees there is juzgun, tamarix, in the floodplains of rivers - aspen, poplar, saxaul.

Soil formation process occurs under specific conditions and is caused by arid climate, salinity of soil-forming rocks and low productivity of vegetation (0.1 - 2.5 c/ha, represented mainly by roots). The process of humification is very short-lived and occurs 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 high temperatures and low amounts of moisture). During mineralization, a large amount of ash elements accumulates (up to 200 kg/ha), which contain a large proportion of sodium. Due to shallow leaching, sodium accumulates in the PPC and causes the development of the solonetz process. Salinity is a characteristic zonal feature of brown soils.

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

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

Brown soils are characterized by lack of structure, shallow depth of wetting, 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 salinization of soils is possible due to the shallow occurrence of easily soluble salts. It is also necessary to take measures to combat wind erosion, which is highly developed in this area. To increase fertility, it is necessary to combine regulation of the water regime with the use of fertilizers - organic and mineral (nitrogen and phosphorus). Estuary irrigation can be used (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 zone, gray soils are 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 falling in the spring. The evaporation is large – 1000 – 1350 mm. Saline groundwater lies deep and does not lead to the enrichment of the soil with easily soluble salts.

Water mode type effusion (CU" 0.12 - 0.33).

Soil-forming rocks are often represented by loamy aeolian loess-like deposits and loess, carbonate, and 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, among perennials there are wormwood and umbelliferous, in the floodplains of rivers there are forests of poplar and willow.

Soil formation process occurs under special hydrothermal conditions, which are characterized by two sharply separate periods: spring - warm and humid, but short-lived, and summer - dry, hot and long. In spring, vegetation and microflora actively develop, and the process of humification and, at the same time, mineralization proceeds intensively. From May to October, the soil dries out and biological activity practically ceases; easily soluble salts move upward, causing seasonal salinization of gray soils; in wet times, 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 leaching of chlorides and sulfates down the profile during the wet period.

Gray soils, despite washing in the autumn-spring period, have a poorly differentiated profile, the color of the entire profile is light gray with a fawn tint. The humus horizon A 1 of a darker color passes gradually (there is a transitional A 1 B) into B Ca, in which the fawn tint is more pronounced and there are accumulations of carbonates, with depth it passes into the soil-forming rock C.

Agrochemical properties: humus content – ​​1 – 4%, fulvate type (but CHA: CFA approaches 1), alkaline reaction (pH KS l 8.0 – 8.5), T = 8 – 10 mg×eq/100 g soil , the composition of absorbed cations is dominated by Ca, Mg, K, Na less than 5%.

Gray soils have good physical properties, a supply of phosphorus, potassium, and microelements, which are evenly distributed in the profile. The main disadvantage is the extremely low humus content, and therefore the fragile macrostructure, and lack of moisture. Serozems are the main growing area for cotton, melons, and some grains. Large areas are occupied by hayfields and pastures. Measures to increase fertility include the application of organic and mineral (especially nitrogen) fertilizers, irrigation (with control of salt content to avoid secondary salinization, and soil density).

Soils of humid subtropics. The zonal type of soil is red soil, which is common on the Black Sea and Caspian coasts, the southern islands of Japan, 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 700 - 900 mm. Long summers and mild short winters. Temperatures vary slightly between seasons.

Water mode type flushing (KU from 1.3 to 5.0).

Soil-forming rocks are represented mainly by the red 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 It is represented by closed deciduous forests - oak-hornbeam and beech-chestnut with an evergreen undergrowth of rhododendrons, azaleas, cherry laurel, etc., intertwined with vines.

Soil formation process began in the Tertiary period and was not interrupted by glaciations; it occurs in favorable climatic conditions with the active activity of microorganisms. Despite the large amount of litter, relatively little humus accumulates in the upper horizons, since under conditions of high temperatures and constant soil moisture, organic matter is actively mineralized. Typically, humus is evenly distributed in the soil profile. The soil-forming process occurs under leaching conditions in an acidic environment, which leads to active decomposition of primary minerals and their leaching. More mobile weathering products (Ca, Mg, K, Na) are leached, and as final products, less mobile sesquioxides of Fe and Al accumulate in large quantities and uniformly color the profile from bright red to yellow, depending on their ratio and quantity. This process is called ferralitization- the stage of rock weathering, at which most of the primary minerals are destroyed and secondary minerals are formed, mainly groups of sesquioxides; there are few silicon oxides, since they quickly weather. The removal of destruction products indicates the presence of a podzolization process, however, signs of podzol formation appear weakly and not everywhere, since the removal chemical elements from the upper horizons is partially compensated by a large amount of bases, which 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 metamorphic processes (ferralitization and allitization - accumulation of aluminum).

In the profile of red soils, A 0 is distinguished with a fairly large thickness - up to 10 cm, under which lies humus A 1 of a dark brown or red-brown color with a thickness of about 20 cm. It is replaced by a transitional horizon B of orange or brownish-red color with a thickness of 40 - 70 cm with black dots of ferromanganese inclusions. Below is the parent rock C, orange, red, sometimes striped, containing inclusions of manganese, iron, and spots of silica.

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

Red soils have high productivity in forest biocenoses. They are distinguished by high water permeability, porosity, moisture capacity, water-resistant structure, but have little available phosphorus, and nitrogen deficiency is often detected. They grow citrus fruits, tea bushes, essential crops, and tobacco. Particular attention should be paid to the control of water erosion, as climate and topography contribute to it. Terracing of slopes, inter-row planting of soybeans and other legumes with their subsequent plowing as fertilizer or turfing are used. perennial herbs, creation of buffer forest strips, devices for regulating surface runoff.

Intrazonal soils. Intrazonal soils include solonchaks, 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 easily soluble salts in quantities toxic to plants. Most often found 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% of readily soluble salts from the surface itself. The composition of the predominant anions can be: chloride, sulfate, soda, chdoride-sulfate, sulfate-chloride; the composition of cations: sodium, calcium, magnesium. They are formed in various ways: 1) in the presence of saline soil-forming rock; 2) with close occurrence of saline groundwater as a result of their capillary rise; 3) on the site of dry lakes; 4) when salts are transported by wind from seas or saline lakes; 5) with improper irrigation (secondary salinization); 6) during the accumulation of salts by halophyte plants (after their mineralization).

Climate

Water mode type non-washing, often effusion (KU" 0.5).

Soil-forming rocks– clays, heavy loams, residually saline.

Relief– a flat plain with microrelief in the form of saucers and depressions.

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

Soil-forming process– solonchak, consists of the accumulation of easily soluble salts in the soil profile.

The solonchaks have a poorly differentiated profile, the characteristic feature of which is the uniformity of the granulometric and gross chemical composition.

There are horizon A, transitional B and source rock C.

Agrochemical properties: humus content 0.5 – 3% (in meadow solonchaks up to 8%), fulvate type, the reaction of the environment from weakly alkaline (pH = 7.5) in those saline with neutral salts to highly alkaline (pH KS l = 11) in soda solonchaks, T = 10 – 20 mg×eq/100 g of soil (low), the degree of base saturation is about 100%, the absorbed bases are Ca, Mg, Na.

Salt marshes are characterized by low natural fertility, since the metabolism and nutrition of plants is disrupted on saline soils. Development is possible only after reclamation measures - gypsuming, washing (removing 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 contribute to a decrease in groundwater.

Solonetz – In soils whose PPC contains sodium > 20%, easily soluble salts are not located in the uppermost horizon, but at some depth. Most often found in dry steppe and steppe, desert zones. Occurs: 1) during desalinization of salt marshes saline with neutral sodium salts; 2) as a result of the vital activity of halophytic vegetation; 3) when the soil is exposed to weakly mineralized solutions containing soda; 4) in the presence of saline soil-forming rock. As a rule, in nature there is a combined action of several factors, which leads to a stronger manifestation of salinity.

Climate dry, hot (continental).

Water mode type non-flushing (KU = 0.6 – 0.8).

Soil-forming rocks– clays, heavy carbonate loams, residually saline.

Relief– flat plain with microrelief.

Vegetation depends on the type of solonetzes. Xerophytic, often sparse, grass-wormwood associations (black wormwood, white wormwood, solonchak wormwood, camphorosma, fescue, etc.)

Soil-forming process: desalinization is the process of washing out easily soluble salts from the profile. In soils where there are 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, and the solubility of organic and mineral compounds in the soil also increases in an alkaline environment. 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, solonetzic). Due to the large amount of Na, solonetzes develop extremely poor water-physical and physical-mechanical properties.

The profile of solonetzes is clearly differentiated into horizons, in contrast to solonchaks. Under the humus or supralonetzic (A 1) horizon, which has the basic properties of the zonal type of soil (color, structure, etc.), lies the solonetzic (B 1 - illuvial), darker, viscous in the wet state, very dense in the dry, cracks and forms a columnar structure. Below it is subsolonetz or saline B 2, lighter, less dense than B 1, containing carbonates, gypsum, and easily soluble salts, below is the soil-forming 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 KS l = 8.5 - 10), T = 15 - 30 mg× eq/100 g of soil (more in chernozem soils), saturated with bases, containing absorbed cations Na (> 20%), Ca, Mg.

In their natural state, solonetzes 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 the gypsum with the solonetz horizon. After this technique, to increase fertility, organic fertilizer is applied and grass sowing is used against the background of irrigation.

Solody– soils formed by washing and leaching of solonetzes. Usually develop in depressions of the relief, where conditions arise high humidity, mainly in forest-steppe and steppe zones.

Climate dry, warm. Water mode type- mostly non-washable.

Relief– depressions of poorly drained plains with close proximity (2 – 3 m) of groundwater of the sodium bicarbonate or chloride-sulfate-sodium type.

Vegetation tree and shrub (aspen, willow, birch, etc.), arranged in clumps, meadow-swamp.

Soil-forming process represents solodization - the transformation of solonetzes into malt, 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. Silicates also accumulate biogenically: after diatoms and silicon-containing plants die, they remain in the soil. Acidic decomposition products and temporary anaerobiosis contribute to the formation of fulvic acids, the replacement of most of the PPC cations with the H + ion, unsaturation with the bases A 1 and A 2, 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 silt particles and sesquioxides, rich in silica, underneath lies a brownish-brown horizon, preserving the remains 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 KS l = 3.7 – 6.5), neutral in the lower horizons, T = 10 – 15 mg×eq/100 g of soil (in the B horizon up to 30 - 40), in the absorbed state of Ca, Mg, Na and H.

Soils - soils with low natural fertility, contain little nitrogen, phosphorus, potassium, are structureless, waterlogged, cultivated - they float heavily and form a crust, it is necessary to apply large doses of manure and lime. However, natural forest vegetation develops well, and these soils are best left under forest.

Soils of river floodplains. A floodplain is a part of a river valley that is periodically flooded during high water. Alluvial soils are formed everywhere along river floodplains.

A well-developed floodplain has three parts: riverbed, central and near-terrace. The riverbed part, which is under the influence of a strong current, usually represents 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, and is often waterlogged. The lowest and most distant part from the riverbed is the near-terrace part, where thin silt is deposited, which is waterlogged and often swampy.

Vegetation is formed under conditions of frequent flooding and is represented mainly by meadow forb-grass groups. The richest and most diverse vegetation is in the central floodplain, the riverine vegetation is poorer, and moisture-loving vegetation is developed in the near-terrace. 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 semi- and desert - mulberry, saxaul, tamarix, poplar, etc.

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

All alluvial soils have some characteristics:

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

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

3) floodplain soils of different natural zones differ less from each other than non-floodplain soils of the same zone.

Alluvial (floodplain) turf soils are formed when groundwater is deep, usually on the elevations of the riverbed part, on sandy alluvium, and have a layered profile (layered turf). Floodplain meadows develop on the 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 at the bottom (they are also called turf granular).

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

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

Any gardener knows that when growing garden crops, the yield on his plot depends primarily on the soil, its composition and properties. It is known that every natural area correspond to their own special climatic conditions. Due to such differences in weather conditions, different types soils that have different characteristics.

Basic soil properties

All soils are different appearance, structure and many other characteristics. They evaluate the composition of the soil and assign it to one type or another. Here are the main criteria for soil quality:

Color is an external property, a description of the soil, according to which it can be classified as chernozem, gray soil, red soil or yellow soil. Of course, the color depends entirely on how moist the soil is and what is included in its composition. For example, a greater amount of humus turns the soil dark or even black. A whitish color indicates the presence of salts - calcium, magnesium, gypsum, silicon and the leaching of minerals. Red and brown tones indicate the presence of iron and manganese in the rock.

This indicator is not as simple as it seems. Humidity depends not only on meteorological conditions.

Simply put, if you saturate the soil with moisture different types then it will look different. They are influenced by underground flows, groundwater levels, and the mechanical composition of the soil mixture.

For example, the predominance of large sand particles does not retain moisture, allowing it to pass into the lower layers. Water also evaporates quickly from this type of soil. The presence of clay particles leads to an increase in its moisture capacity.

Description and characteristics of species

The soils that gardeners, gardeners, and agronomists most often work with are:

• sandy;
• sandy loam;
• loamy;
• clayey;
• peat

Properly organizing planting means knowing the characteristics of the soil and how to improve its properties through proper cultivation, application of the necessary minerals and fertilizers.

This is a light type of soil consisting mainly of sand grains and a small portion of clay particles. It allows water to pass through well and is extremely free-flowing. If you take a handful of earth in your palm, you won’t be able to form a lump out of it. She's falling apart. Its other qualities are high breathability, thermal conductivity, and easy workability. It is difficult to apply fertilizers to such soil. They do not stay there, they go along with the water into deeper ground layers.

Such lands are poor and not very suitable for growing crops. But grow garden trees, as well as carrots, onions and strawberries on it are quite acceptable. To cultivate sandstone, it is good to introduce peat, humus and clay flour.

Sandy loam type

This soil has the best properties, is similar in composition to sandy, but still contains a higher percentage of clay impurities. By taking a handful in your hand and squeezing it, you can get a lump. But it doesn't hold its shape well. The qualities of such soil are more valuable. It retains moisture better and minerals, breathable, dries out more slowly, warms up better, easier to process. You can grow all crops, not forgetting about methods of increasing soil fertility. Ways to improve such soil: applying potash and organic fertilizers, mulching, green manure and fairly frequent loosening.

Loamy lands

The best type of soil in terms of characteristics is also called loam. Contains the largest percentage of nutrients. It retains moisture well and is endowed with the ability to distribute it throughout the horizon. Easy to handle and retains heat. Such a sample forms a lump well and can be rolled out into a “sausage”, but cannot be bent into a ring. This is a special technique in agronomy for determining the mechanical composition of the soil. Such land does not need to be improved, but only to maintain its fertile properties, for which purpose it is mulched and humus is added when digging in the autumn.

The soil is clay

Or clayey, as it is also called. Clay content up to 80%. It is very heavy and dense, does not absorb water well, and sticks to shoes when wet. The structure is lumpy.

If you take a lump of damp earth, you can easily form a long sausage and roll it into a ring. At the same time, it will not crack or tear.

We can say that it looks like plasticine. Accordingly, its quality deteriorates: it contains little air, does not warm up well and allows water to pass through. It is not easy to grow garden crops on such land.

Proper cultivation will help such land become fertile. To do this, lime, ash, compost, and manure are regularly added. Careful loosening and mulching will also be beneficial.

Acid balance

Soil acidity plays a huge role in growing crops., the optimal value of which is called acid-base balance. It is one of the most important indicators of the quality of fertile land. Acidity is indicated by the “pH” symbol. When this value is equal to seven units, the acidity is called neutral. If the pH is below seven the earth is acidic. A pH above seven is called alkaline.

With increasing acidity, there is an increase in the content of aluminum and its salts in the soil, as well as manganese and other minerals. This prevents plants from developing normally. Moreover, in such soil, pathogenic bacteria, microorganisms and pests begin to actively multiply. The applied fertilizers do not decompose. All this leads to soil imbalance.

Determining acidity is very easy at home. To do this, use a simple method of litmus indicators. Soils are very often acidified. The most common method is liming. At the same time, lime displaces aluminum and its salts from the top layer of the earth, replacing them with calcium and magnesium. This reduces the toxic effect on the plant.

Amount of lime per square meter depends on the type of soil and its characteristics. The table shows the rates for applying lime to reduce acidity.

The principle is simple: the heavier and clayier the soil, the more more she needs lime. It is important to remember that when applying lime, boron fertilizers are applied at the same time. Acidity should be checked periodically if adjustments need to be made.

After all, this indicator affects the fertility of the land, and, accordingly, the yield.

types of soils

Type is the main unit of soil classification. It is allocated in accordance with the profile of the earth. V.V. Dokuchaev first classified the types in 1886.

Soils that arose during the cultivation of areas that were previously unsuitable for agricultural development belong to a special group.

Some species do not form groups (zones) and are found in separate areas within zones. This is largely due to the characteristics of the rocks, moisture, and terrain.

Zonal soil types are considered the most common. They (together with plant and other landscape elements) form natural areas.

Soil types

1. Swamp lands. are formed during prolonged or excessive constant moisture (swamping). As a rule, they form in forest areas of temperate zones.
2. Brown forest. These soil types are mainly found in areas with warm-temperate, humid climates.
3. Brown semi-desert, desert-steppe. These types of soils are formed in areas with a dry climate, in the temperate zone, under desert-steppe plant species.
4. Mountain. They are a group formed in mountainous areas. Almost all types of soils included in this category are characterized by gravelly, low thickness and the presence of primary minerals.
5. Chestnut. Distributed in semi-deserts and steppes of the temperate zone.
6. Meadow soils are formed under meadow plant species, in areas of high surface moisture or areas exposed to continuous influence of groundwater.
7. Salted. They are common in arid areas with a high concentration (more than 0.25%) of mineral salts that are easily soluble in water - magnesium, calcium, chloride carbonates.
8. are formed in mixed forests and taiga, under temperate continental and continental climates. They experience excessive moisture and are constantly washed by seeping water.
9. Gray soils are common in the subtropical zone.
10. Confluent soils are formed in subtropical, tropical soils. In their profile they have a confluent horizon, which, when wet, swells greatly and acquires high plasticity; when dry, it remains hard and dense.
11. Tundra. They are a combination of soils in the Northern Hemisphere and its tundra zone. This category includes tundra humus-carbonate, soddy, podzolic and other soils.
12. Chernozems. These soils are common in the steppe and forest-steppe zones of the temperate zone.

An important indicator when classifying soil is its composition.

Light - sandy - soils include a large amount of sand, a small proportion of humus, and a small volume of clay particles. Soils of higher density are classified as heavy clay soils. They do not crumble during processing; on the contrary, they form large lumps, which makes digging very difficult.

Rocky soils are common on the slopes of mountains or hills and are not fertile. Most of their composition is occupied by

The basis is largely organic matter. They are rich in nitrogen, contain little potassium and very little phosphorus. However, there are also peat-vivianite soils in which, on the contrary, there is a high concentration of phosphorus.

Sandy loam soils endowed with many of the properties of sand with a more balanced ratio of components, they belong to the intermediate variety. These soils are considered favorable in all respects for plant cultivation.