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What is the basis of the soil. What is soil and what does it consist of? Animals have two key functions

Soil is the most superficial layer of land on the globe, resulting from changes in rocks under the influence of living and dead organisms (vegetation, animals, microorganisms), solar heat and precipitation. The soil is a very special natural formation, having only its inherent structure, composition and properties. The most important property of the soil is its fertility, i.e. ability to ensure the growth and development of plants. In order to be fertile, the soil must have a sufficient amount of nutrients and a supply of water necessary for plant nutrition, it is precisely in its fertility that the soil, as a natural body, differs from all other natural bodies (for example, a barren stone), which are not able to meet the needs of plants in the simultaneous and the joint presence of two factors of their existence - water and minerals.

Soil is the most important component of all terrestrial biocenoses and the biosphere of the Earth as a whole, through the soil cover of the Earth there are numerous ecological connections of all organisms living on earth and in the earth (including humans) with the lithosphere, hydrosphere and atmosphere.

1.2 The doctrine of the soil

The science of the origin and development of soils, the patterns of their distribution, the ways of rational use and increasing fertility is called soil science. This science is a branch of natural science and is closely related to the physical, mathematical, chemical, biological, geological and geographical sciences, based on the fundamental laws and research methods developed by them. At the same time, like any other theoretical science, soil science develops on the basis of direct interaction with practice, which checks and uses the revealed patterns and, in turn, stimulates new searches in the field of theoretical knowledge. To date, large applied sections of soil science for agriculture and forestry, irrigation, construction, transportation, mining, health and environmental protection.

From the moment of the systematic occupation of agriculture, mankind first empirically, and then with the help of scientific methods, studied the soil. The most ancient attempts to evaluate various soils are known in China (3 thousand BC) and Ancient Egypt. In ancient Greece, the concept of soil developed in the course of the development of ancient natural-philosophical natural science. During the period of the Roman Empire, a large number of empirical observations on the properties of the soil were accumulated and some agronomic methods of its cultivation were developed.

The long period of the Middle Ages was characterized by stagnation in the field of natural science, but at the end of it (with the beginning of the disintegration of the feudal system), interest in the study of soils reappeared in connection with the problem of plant nutrition. A number of works of that time reflected the opinion that plants feed on water, creating chemical compounds from water and air, and the soil serves them only as a mechanical support. However, by the end of the 18th century. this theory was replaced by the humus theory of Albrecht Thayer, according to which plants can only feed on soil organic matter and water. Thayer was one of the founders of agronomy and the organizer of the first higher agronomic educational institution.

In the first half of the 19th century The famous German chemist Justus Liebig developed the mineral theory of plant nutrition, according to which plants absorb minerals from the soil, and only carbon in the form of carbon dioxide from humus. J. Liebig believed that each crop depletes the supply of minerals in the soil, therefore, in order to eliminate this deficiency of elements, it is necessary to introduce into the soil mineral fertilizers factory prepared. The merit of Liebig was the introduction of the use of mineral fertilizers into the practice of agriculture.

The value of nitrogen for the soil was studied by the French scientist J.Yu. Bussengo.

By the middle of the 19th century. extensive material has been accumulated on the study of soils, but these data were scattered, not brought into a system and not generalized. There was no single definition of the term soil for all researchers.

The founder of soil science as an independent natural-historical science was the outstanding Russian scientist Vasily Vasilievich Dokuchaev (1846–1903). Dokuchaev first formulated the scientific definition of soil, calling soil an independent natural-historical body, which is the product of the combined activity of the parent rock, climate, plant and animal organisms, soil age, and partly the terrain. All the factors of soil formation that Dokuchaev spoke of were known before him, they were consistently put forward by various scientists, but always as the only determining condition. Dokuchaev was the first to say that the formation of soil occurs as a result of the combined action of all factors of soil formation. He established the view of the soil as an independent special natural body, equivalent to the concepts of a plant, animal, mineral, etc., which arises, develops, continuously changes in time and space, and in this way he laid a solid foundation for a new science.

Dokuchaev established the principle of the structure of the soil profile, developed the idea of the pattern of spatial distribution of certain types of soils covering the land surface in the form of horizontal or latitudinal zones, established vertical zonality, or zonality, in the distribution of soils, which is understood as the regular replacement of some soils by others as they rise from the foot to the top of high mountains. He also owns the first scientific classification of soils, which was based on the totality of the most important features and properties of the soil. Dokuchaev's classification was recognized by world science and the names he proposed "chernozem", "podzol", "salt marsh", "salt" became international scientific terms. He developed methods for studying the origin and fertility of soils, as well as methods for mapping them, and even in 1899 compiled the first soil map of the northern hemisphere (this map was called the "Scheme of Soil Zones of the Northern Hemisphere").

In addition to Dokuchaev, a great contribution to the development of soil science in our country was made by P.A. Kostychev, V.R. Williams, N.M. Sibirtsev, G.N. Vysotsky, P.S. Kossovich, K.K. Gedroits, K. D. Glinka, S. S. Neustruev, B. B. Polynov, L. I. Prasolov and others.

Thus, the science of soil as an independent natural formation was formed in Russia. Dokuchaev's ideas had a strong influence on the development of soil science in other countries. Many Russian terms have entered the international scientific lexicon (chernozem, podzol, gley, etc.)

Important studies for understanding the processes of soil formation and studying the soils of different territories were carried out by scientists from other countries. This is E.V. Gilgard (USA); E.Ramann, E.Blank, V.I.Kubiena (Germany); A. de Zigmond (Hungary); J. Milne (Great Britain), J. Aubert, R. Menin, J. Durand, N. Lenef, G. Erar, F. Duchaufour (France); J. Prescott, S. Stephens (Australia) and many others.

For the development of theoretical concepts and successful study of the soil cover of our planet, it is necessary business connections different national schools. In 1924 the International Society of Soil Scientists was organized. For a long time, from 1961 to 1981, a large and complex work was carried out to compile the Soil Map of the World, in which Russian scientists played a large role.

What is soil made of? It seemed like a simple question. We all know what it is. Every day we walk on it, we plant plants in it that give us a harvest. We fertilize the land, we dig it up. Sometimes you can hear that the land is barren. But what do we really know about soil? In most cases, only that it is the topmost layer of the earth's surface. And this is not so much. Let's see what components the earth consists of, what it can be and how it is formed.

Soil composition

So, the soil is the top fertile It consists of various components. In addition to solid particles, it includes water and air, and even living organisms. In fact, the latter play a crucial role in its formation. The degree of its fertility also depends on microorganisms. In general, the soil consists of phases: solid, liquid, gaseous and "living". Let's look at what components form them.

Solid particles include various minerals and chemical elements. It includes almost the entire periodic table, but in various concentrations. The degree of soil fertility depends on the solid particles component. Liquid components are also called soil solution. It is water in which chemical elements dissolve. There is liquid even in desert soils, but there are meager amounts of it.

So, what does soil consist of, apart from these basic constituents? The space between solid particles is filled with gaseous components. Soil air consists of oxygen, nitrogen, carbon dioxide, and thanks to it, various processes occur in the earth, for example, respiration of plant roots and decay. Living organisms - fungi, bacteria, invertebrates and algae - are actively involved in the process of soil formation and significantly change its composition, introducing chemical elements.

Mechanical structure of the soil

What the soil consists of is now clear. But is its structure homogeneous? It's no secret that the soil is different. It can be sandy and clay or rocky. So, the soil consists of particles of different sizes. Its structure may include huge boulders and tiny grains of sand. Usually, the particles entering the soil are divided into several groups: clay, silt, sand, gravel. This is essential for agriculture. It is the structure of the soil that determines the degree of effort that must be applied to cultivate it. It also depends on how well the earth will absorb moisture. Good soil contains equal percentages of sand and clay. Such soil is called loamy. If there is a little more sand, then the soil is crumbly and easy to process. But at the same time, such soil retains water and minerals worse. Clay soil is damp and sticky. She doesn't drain well. But at the same time, it contains the most nutrients.

The role of microorganisms in soil formation

The properties of the soil depend on what components it consists of. But not only this determines its qualities. From the dead remains of animals and plants, organic matter enters the soil. This is due to microorganisms - saprophytes. They play an important role in the processes of decomposition. Thanks to their vigorous activity, the so-called humus accumulates in the soil. It is a dark brown substance. The composition of humus includes fatty acid esters, phenolic compounds and carboxylic acids. In the soil, particles of this substance stick together with clay. It turns out a single complex. Humus improves soil quality. Increases its ability to retain moisture and minerals. In swampy areas, the formation of humus mass proceeds very slowly. Organic residues are gradually compressed into peat.

Soil formation process

The soil is formed very slowly. In order for its mineral part to be completely renewed approximately to a depth of 1 meter, at least 10 thousand years are needed. What the soil is made of is the products of the constant work of wind and water. So where does soil come from?

First of all, these are particles of rocks. They are the basis of the soil. Under the influence of climatic factors, they are destroyed and crushed, settling on the ground. Gradually, this mineral part of the soil is populated by microorganisms, which, processing organic remains, form humus in it. Invertebrates, constantly breaking through passages in it, loosen it, contributing to good aeration.

Over time, the structure of the soil changes, it becomes more fertile. Plants also play a role in this process. Growing, they contribute to changing its microclimate. Soil formation is also affected by human activities. He cultivates and cultivates the land. And if the soil consists of infertile components, then a person fertilizes it, introducing both mineral and organic fertilizers.

composition

In general, there is currently no generally accepted classification of soils. But still it is customary to divide them according to their mechanical composition into several groups. This division is especially relevant in agriculture. So, the classification is based on how much the soil consists of clay:

Loose sandy (less than 5%);

Connected sandy (5-10%);

Sandy (11-20%);

Light loamy (21-30%);

Medium loamy (31-45%);

Heavy loamy (46-60%);

Clayey (more than 60%).

What does the term "fertile" soil mean?

What parts the soil consists of affects the degree of its fertility. But what makes the earth so? The composition of the soil directly depends on many factors. This is the climate, and the abundance of plants, and the presence of living organisms that live in it. All this affects the chemical composition. The degree of its fertility depends on which components are contained in the soil. Mineral components such as calcium, nitrogen, copper, potassium, magnesium, and phosphorus are considered very useful for high yields. These substances enter the ground during the decomposition of organic residues. If the soil is rich in mineral compounds, then it is fertile. Plants will thrive on it. Such soil is ideal for growing vegetables and fruit crops.

Classification of soil pollution.

Formation of various types of soils.

Soil, soil structure.

LAND RESOURCES AND SOIL PROTECTION.

Lecture 4

4. Soil erosion. Soil protection measures against erosion.

5. Salinization and land reclamation.

The soil - this is the surface layers of the earth's crust, which is formed and develops as a result of the interaction of vegetation, animals, microorganisms, parent rock and is an independent natural formation.

The founder of scientific soil science is the Russian scientist V.V. Dokuchaev (1846-1903), who first defined the concepts: "soil" and "soil profile", identified the main distinctive properties and revealed the essence of the soil-forming process. To the five factors of soil formation established by V.V. Dokuchaev: parent rock, climate, relief and time, plant and animal organisms, water (soil and ground) was later added and economic activity person.

Any soil can be considered as a heterogeneous system consisting of three phases: solid (mineral skeleton, organic and biological components), liquid (soil solution) and gaseous (soil air).

solid phase Soil contains the main supply of nutrients for plants. It consists of 90 % and more from complex minerals and about 10 % and less from organic matter, which play a very important role in soil fertility. Almost half of the solid phase of the soil is bound oxygen, one third is silicon, more than 10 % - for aluminum and iron, and only 7% for other elements.

The totality of finely divided (colloidal) particles of soil and organic matter constitutes the soil-absorbing complex (SPC). The total charge of the PPC of most soils is negative, and thus it retains on its surface in the absorbed state mainly positively charged ions - cations.

soil solution- the most mobile and active part of the soil, in which various chemical processes take place and from which plants directly absorb nutrients. Nutrients in the soil solution are the most accessible to plants.

soil air serves as the main source of oxygen for the respiration of plant roots. It differs from the atmosphere by a high content of carbon dioxide and a slightly lower content of oxygen.

Soil structure is characterized by a combination of genetic horizons. Genetic horizons are those that were formed as a result of the general soil-forming process, so that the formation of each of the horizons present in the soil is closely related (or even due) to the formation of other horizons. This is most easily illustrated by the example of the structure of some soils. If you lay a soil section (dig a hole) with a vertical front wall, then the sequence of genetic horizons will become clearly visible on the latter.

As a result of the movement and transformation of substances, the soil is divided into separate layers, or horizons, the combination of which makes up the soil profile.

Each of us who is at least a little familiar with biology understands that the success of growing horticultural crops immediately depends on a combination of many versatile factors. Climatic conditions, planting dates, variety, timeliness and literacy of agricultural practices - these are far from all that have a direct impact on the harvest.

Chernozem, humus-rich soil. © NRCS Soil Health

One of the fundamental points that often plays a dominant role in the outcome of laying a garden and laying out a vegetable garden is the type of soil. It is on what kind of soil is on your site that the possibility of growing certain crops, the need for certain fertilizers, the frequency of watering and weeding will depend. Yes Yes! All this can have significant differences and be beneficial or harmful if you do not know what kind of soil you are dealing with.

Main types of soils

The main types of soils that gardeners in Russia most often encounter are: clay, sandy, sandy loam, loamy, calcareous and swampy. Each of them has both positive and negative properties, which means it differs in recommendations for improving and selecting crops. In their pure form, they are rare, mostly in combination, but with a predominance of certain characteristics. Knowing these properties is 80% of the success of a good harvest.

Clay soil. © nosprayhawaii

It is quite easy to determine the clay soil: after digging, it has a coarse-grained dense structure, sticks to the feet in rainy weather, does not absorb water well, and easily sticks together. If you roll a long sausage from a handful of such earth (wet), it can be easily bent into a ring, while it will not crumble into pieces or crack.

Due to the high density, such soil is considered heavy. It warms up slowly, is poorly ventilated, and has a low water absorption coefficient. Therefore, growing crops on it is quite problematic. However, if clay soil is properly cultivated, it can become quite fertile.

To facilitate and enrich this type of soil, it is recommended to periodically apply sand, peat, ash and lime. Sand reduces moisture content. Ash enriches with nutrients. Peat loosens and increases water-absorbing properties. Lime reduces acidity and improves soil air conditions.

How much to contribute is an individual question, directly related to the indicators of your particular soil, which can only be accurately determined in laboratory conditions. But, in general: sand - no more than 40 kg per 1 m², lime - about 300-400 g per m², for deep digging once every 4 years (on soils with a slightly acidic reaction), there are no restrictions for peat and ash. If there is a choice of organics, then the best option for increasing the fertility of clay soils is horse manure. It will not be useless to sow green manure, such as mustard, rye, oats.

Plants on clay soils have a hard time. Poor warming of the roots, lack of oxygen, stagnant moisture, the formation of a soil crust do not work in favor of the crop. But still, trees and shrubs, having a fairly powerful root system, tolerate this type of soil well. From vegetables on clay, potatoes, beets, peas and Jerusalem artichoke feel good.

For other crops, it is possible to recommend high beds, planting on ridges, using a smaller depth of seed and tuber placement in the soil, planting seedlings in an oblique way (for better warming of the root system). Among agricultural practices, special attention should be paid to loosening and mulching on clay soils.

Sandy soil. © extension

Sandy soil refers to light soil types. It is also not difficult to recognize it: it is loose, free-flowing, easily passes water. If you pick up a handful of such earth and try to form a lump, nothing will work.

All the qualities inherent in sandy soils are both their plus and minus. Such soils warm up quickly, are well aerated, are easily cultivated, but at the same time cool quickly, dry out soon, and weakly retain minerals in the root zone (nutrients are washed out by water into the deep layers of the soil). As a result, they are poor in the presence of useful microflora and are poorly suited for growing any crops.

To increase the fertility of such soils, it is necessary to constantly improve their compacting and binding properties. Regular application of peat, compost, humus, clay or drill flour (up to two buckets per 1 m²), the use of green manure (with incorporation into the soil), high-quality mulching after 3-4 years give a decent stable result.

But even if the site is still in the process of cultivation, it is possible to grow carrots, onions, melons, strawberries, currants, fruit trees on it. Cabbage, peas, potatoes and beets will feel somewhat worse on sandy soils, but if you fertilize them with fast-acting fertilizers, in small doses and often enough, you can achieve good results.

For those who do not want to mess with cultivation, there is another way to improve these soils - the creation of an artificial fertile layer by claying. To do this, in place of the beds, it is necessary to arrange a clay castle (lay out clay with a layer of 5-6 cm) and pour 30-35 cm of sandy or loamy soil taken from the side onto it.

Sandy soil. © pictonsandandsoil

Sandy loamy soil is another variant of soils that are light in texture. In terms of its qualities, it is similar to sandy soils, but contains a slightly higher percentage of clay inclusions, which means it has a better holding capacity for mineral and organic substances, not only warms up quickly, but also retains heat for a long time, passes moisture less and dries out more slowly, is well aerated and easy to process.

You can determine it by the same method of squeezing a handful of moist earth into a sausage or lump: if it forms, but does not hold its shape well, you have sandy loam soil in front of you.

Anything can grow on such soils, with the usual methods of agricultural technology and the choice of zoned varieties. This is one of the good options for gardens and orchards. However, methods of increasing and maintaining fertility for these soils will also not be superfluous. It is recommended to regularly apply organic matter (in normal doses), sow green manure crops, and mulch them.

Loamy soil. © gardendrum

Loamy soil is the most suitable type of soil for growing horticultural crops. It is easy to process, contains a large percentage of nutrients, has high air and water permeability, is able not only to retain moisture, but also to evenly distribute it over the thickness of the horizon, and retains heat well. If you take a handful of such earth in the palm of your hand and roll it up, then you can easily form a sausage, which, however, cannot be bent into a ring, since it will fall apart when deformed.

Due to the combination of existing properties, loamy soil does not need to be improved, but it is only necessary to maintain its fertility: mulch, apply manure for autumn digging (3-4 kg per 1 square meter) and, if necessary, feed the crops planted on it with mineral fertilizers. Everything can be grown on loamy soils.

lime soil. © midhants

Lime soil belongs to the category of poor soils. Usually it has a light brown color, a large number of stony inclusions, is characterized by an alkaline environment, quickly heats up and dries out at elevated temperatures, poorly gives iron and manganese to plants, and can have a heavy or light composition. In crops grown on such soil, foliage turns yellow and unsatisfactory growth is observed.

To improve the structure and increase the fertility of calcareous soils, it is necessary to regularly apply organic fertilizers, not only for the main cultivation, but also in the form of mulch, sow green manure, and apply potash fertilizers.

Everything is possible to grow on this type of soil, but with frequent loosening of row spacing, timely watering and thoughtful use of mineral and organic fertilizers. Potatoes, tomatoes, sorrel, carrots, pumpkins, radishes, cucumbers and lettuces will suffer from low acidity, so they need to be fed with fertilizers that tend to acidify rather than alkalize the soil (for example, ammonium sulfate, urea).

Peat medium decomposed horizon of soddy-podzolic soil. © own work

swampy soil

Marshy or peaty soils are also used for laying out horticultural plots. However, it is rather difficult to call them good for growing crops: the nutrients contained in them are not very accessible to plants, they absorb water quickly, but they also give it away just as quickly, they warm up poorly, and often have a high acidity index. But, such soils retain mineral fertilizers well and are easy to cultivate.

In order to improve the fertility of swampy soils, it is necessary to saturate the earth with sand (for this it is necessary to carry out deep digging in such a way as to raise the sand from the lower layers) or clay flour, apply abundant liming on especially acidic options, take care to increase the content of beneficial microorganisms in the soil (apply manure, slurry, compost, do not bypass microbiological additives), do not forget about potassium-phosphorus fertilizers.

If you plant a garden on peat soils, then it is better to plant trees either in pits, with soil individually laid for cultivation, or in mounds, from 0.5 to 1 m high.

Carefully cultivate the ground under the garden, or, as in the variant with sandy soils, lay a clay layer and already fill it with loam mixed with peat, organic fertilizers and lime. But if you grow only gooseberries, currants, chokeberries and garden strawberries, then you can do nothing - just water and weed, since these crops on such soils work out without cultivation.

Chernozem. © carlbagge

Chernozems

And, of course, speaking of soils, it is difficult not to mention chernozems. In our suburban areas, they are not so common, but worthy of special attention.

Chernozems are soils of high potential fertility. A stable granular-cloddy structure, a high humus content, a high percentage of calcium, good water-absorbing and water-retaining abilities allow us to recommend them as the best option for growing crops. However, like any other soil, they tend to deplete from permanent use, therefore, already 2-3 years after their development, it is recommended to apply organic fertilizers to the beds, sow green manure.

In addition, chernozems can hardly be called light soils; therefore, they are often loosened by adding sand or peat. They can also be acidic, neutral and alkaline, which also requires its own adjustment.

Chernozem. © Axel Hindemith

To understand that you really have black earth in front of you, you need to take the guest of the earth and squeeze it in your palm, a black greasy print should remain on your hand.

Some confuse chernozem with peat - there is also a trick for checking: a wet lump of soil must be squeezed out in your hand and put in the sun - peat will dry instantly, while chernozem will retain moisture for a long time.

The content of the article

THE SOIL- the most superficial layer of land on the globe, resulting from changes in rocks under the influence of living and dead organisms (vegetation, animals, microorganisms), solar heat and precipitation. The soil is a very special natural formation, having only its inherent structure, composition and properties. The most important property of the soil is its fertility, i.e. ability to ensure the growth and development of plants. In order to be fertile, the soil must have a sufficient amount of nutrients and a supply of water necessary for plant nutrition, it is precisely in its fertility that the soil, as a natural body, differs from all other natural bodies (for example, a barren stone), which are not able to meet the needs of plants in the simultaneous and the joint presence of two factors of their existence - water and minerals.

The role of the soil in the human economy is enormous. The study of soils is necessary not only for agricultural purposes, but also for the development of forestry, engineering and construction. Knowledge of soil properties is necessary to solve a number of health problems, exploration and extraction of minerals, organization of green areas in the urban economy, environmental monitoring, etc.

Soil science: history, relationship with other sciences.

The science of the origin and development of soils, the patterns of their distribution, the ways of rational use and increasing fertility is called soil science. This science is a branch of natural science and is closely related to the physical, mathematical, chemical, biological, geological and geographical sciences, based on the fundamental laws and research methods developed by them. At the same time, like any other theoretical science, soil science develops on the basis of direct interaction with practice, which checks and uses the revealed patterns and, in turn, stimulates new searches in the field of theoretical knowledge. To date, large applied sections of soil science have been formed for agriculture and forestry, irrigation, construction, transport, mineral exploration, public health and environmental protection.

In the first half of the 19th century The famous German chemist Justus Liebig developed the mineral theory of plant nutrition, according to which plants absorb minerals from the soil, and only carbon in the form of carbon dioxide from humus. J. Liebig believed that each harvest depletes the supply of minerals in the soil, therefore, in order to eliminate this deficiency of elements, it is necessary to introduce mineral fertilizers prepared at the factory into the soil. The merit of Liebig was the introduction of the use of mineral fertilizers into the practice of agriculture.

The value of nitrogen for the soil was studied by the French scientist J.Yu. Bussengo.

The founder of soil science as an independent natural-historical science was the outstanding Russian scientist Vasily Vasilievich Dokuchaev (1846–1903). Dokuchaev was the first to formulate scientific definition soil, calling the soil an independent natural-historical body, which is the product of the combined activity of the parent rock, climate, plant and animal organisms, the age of the soil, and partly the terrain. All the factors of soil formation that Dokuchaev spoke of were known before him, they were consistently put forward by various scientists, but always as the only determining condition. Dokuchaev was the first to say that the formation of soil occurs as a result of the combined action of all factors of soil formation. He established the view of the soil as an independent special natural body, equivalent to the concepts of a plant, animal, mineral, etc., which arises, develops, continuously changes in time and space, and in this way he laid a solid foundation for a new science.

For the development of theoretical concepts and successful study of the soil cover of our planet, business ties between different national schools are necessary. In 1924 the International Society of Soil Scientists was organized. For a long time, from 1961 to 1981, a large and complex work was carried out to compile the Soil Map of the World, in which Russian scientists played a large role.

Soil study methods.

One of them is comparative geographical, based on the simultaneous study of the soils themselves (their morphological features, physical and chemical properties) and soil formation factors in different geographical conditions with their subsequent comparison. Currently, soil research uses various chemical analyzes, analyzes of physical properties, mineralogical, thermochemical, microbiological and many other analyses. As a result, a certain relationship is established between the change in certain soil properties and the change in soil-forming factors. Knowing the patterns of distribution of soil-forming factors, it is possible to create a soil map for a vast territory. It was in this way that Dokuchaev in 1899 made the first world soil map, known as the "Schemes of Soil Zones of the Northern Hemisphere".

Another method is the method of stationary studies It consists in the systematic observation of a soil process, which is usually carried out on typical soils with a certain combination of soil-forming factors. Thus, the method of stationary studies refines and details the method of comparative geographic studies. There are two methods for studying soils.

Soil formation.

The process of soil formation.

All rocks covering the surface of the globe, from the very first moments of their formation, under the influence of various processes, began to immediately collapse. The sum of the processes of transformation of rocks on the surface of the Earth is called weathering or hypergenesis. The totality of weathering products is called the weathering crust. The process of transformation of the original rocks into the weathering crust is extremely complex and includes numerous processes and phenomena. Depending on the nature and causes of the destruction of rocks, physical, chemical and biological weathering is distinguished, which usually comes down to the physical and chemical effects of organisms on rocks.

The processes of weathering (hypergenesis) extend to a certain depth, forming a zone of hypergenesis . The lower boundary of this zone is conditionally drawn along the roof of the upper horizon of groundwater (formation) waters. The lower (and larger) part of the hypergenesis zone is occupied by rocks that have been altered to some extent by weathering processes. Here, the most recent and ancient weathering crusts, formed in more ancient geological periods, are distinguished. The surface layer of the hypergenesis zone is the substrate on which soil is formed. How does the process of soil formation take place?

In the process of weathering (hypergenesis), the original appearance of rocks, as well as their elemental and mineral composition, changed. Initially massive (i.e. dense and hard) rocks gradually passed into a fragmented state. Grass, sand, and clay can serve as examples of rocks crushed as a result of weathering. Becoming fragmented, rocks acquired a number of new properties and features: they became more permeable to water and air, the total surface of their particles increased in them, which increased chemical weathering, new compounds were formed, including easily water-soluble compounds and, finally, mountain rocks acquired the ability to retain moisture, which is of great importance for providing plants with water.

However, the weathering processes themselves could not lead to the accumulation of plant food elements in the rock, and, consequently, they could not turn the rock into soil. Easily soluble compounds formed as a result of weathering can only be washed out of rocks under the influence of atmospheric precipitation; and such a biologically important element as nitrogen, consumed by plants in large quantities, is not contained at all in igneous rocks.

Loose and capable of absorbing water, rocks became a favorable environment for the vital activity of bacteria and various plant organisms. Gradually, the upper layer of the weathering crust was enriched with the products of vital activity of organisms and their dying remains. The decomposition of organic matter and the presence of oxygen led to complex chemical processes, which resulted in the accumulation of elements of ash and nitrogen food in the rock. Thus, the rocks of the surface layer of the weathering crust (they are also called soil-forming, bedrock or parent rocks) became the soil. The composition of the soil, therefore, includes a mineral component corresponding to the composition of bedrocks, and an organic component.

Therefore, the beginning of the process of soil formation should be considered the moment when vegetation and microorganisms settled on the weathering products of rocks. From that moment on, the crushed rock became soil, i.e. a qualitatively new body, possessing a number of qualities and properties, the most significant of which is fertility. In this respect, all existing soils on the globe represent a natural-historical body, the formation and development of which is associated with the development of all organic life on the earth's surface. Once born, the soil-forming process never stopped.

Soil formation factors.

The development of the soil-forming process is most directly influenced by the natural conditions in which it proceeds; its features and the direction in which this process will develop depend on one or another of their combinations.

The most important of these natural conditions, called factors of soil formation, are the following: parent (soil-forming) rocks, vegetation, wildlife and microorganisms, climate, terrain and soil age. To these five main factors of soil formation (which Dokuchaev named) are now added the action of water (soil and ground) and human activity. The biological factor always plays a leading role, while the remaining factors are only the background against which the development of soils in nature occurs, but they have a great influence on the nature and direction of the soil-forming process.

Soil-forming rocks.

All existing soils on Earth originated from rocks, so it is obvious that they are directly involved in the process of soil formation. The chemical composition of the rock is of the greatest importance, since the mineral part of any soil contains mainly those elements that were part of the parent rock. Also of great importance physical properties parent rock, since such factors as the granulometric composition of the rock, its density, porosity, thermal conductivity most directly affect not only the intensity, but also the nature of the ongoing soil-forming processes.

Climate.

The climate plays a huge role in the processes of soil formation, its influence is very diverse. The main meteorological elements that determine the nature and characteristics of climatic conditions are temperature and precipitation. The annual amount of incoming heat and moisture, the peculiarities of their daily and seasonal distribution determine quite definite processes of soil formation. The climate affects the nature of rock weathering, affects the thermal and water regimes of the soil. The movement of air masses (wind) affects the gas exchange of the soil and captures small soil particles in the form of dust. But the climate affects the soil not only directly, but also indirectly, since the existence of this or that vegetation, the habitat of certain animals, as well as the intensity of microbiological activity are determined precisely by climatic conditions.

Vegetation, animals and microorganisms.

Vegetation.

The importance of vegetation in soil formation is extremely high and diverse. Penetrating the upper layer of soil-forming rock with their roots, plants extract nutrients from its lower horizons and fix them in the synthesized organic matter. After the mineralization of dead parts of plants, the ash elements contained in them are deposited in the upper horizon of the soil-forming rock, thereby creating favorable conditions for the nutrition of the next generations of plants. So, as a result of the constant creation and destruction of organic matter in the upper horizons of the soil, the most important property for it is acquired - the accumulation, or concentration of elements of ash and nitrogen food for plants. This phenomenon is called the biological absorption capacity of the soil.

Due to the decomposition of plant residues, humus accumulates in the soil, which is of great importance in soil fertility. Plant residues in the soil are a necessary nutrient substrate and the most important condition for the development of many soil microorganisms.

In the process of decomposition of soil organic matter, acids are released, which, acting on the parent rock, increase its weathering.

The plants themselves, in the course of their life activity, secrete various weak acids with their roots, under the influence of which sparingly soluble mineral compounds partially pass into a soluble, and therefore, into a form assimilated by plants.

In addition, vegetation cover significantly changes microclimatic conditions. For example, in the forest, in comparison with treeless territories, the summer temperature is lowered, the humidity of air and soil is increased, the strength of the wind and the evaporation of water over the soil are reduced, more snow, melt and rain water accumulates - all this inevitably affects the soil formation process.

Microorganisms.

Thanks to the activity of microorganisms inhabiting the soil, organic residues are decomposed and the elements contained in them are synthesized into compounds absorbed by plants.

Higher plants and microorganisms form certain complexes, under the influence of which various types of soils are formed. Each plant formation corresponds to a certain type of soil. For example, under the plant formation of coniferous forests, chernozem will never form, which is formed under the influence of a meadow-steppe plant formation.

Animal world.

Animal organisms are of great importance for soil formation, and there are a lot of them in the soil. Invertebrates living in the upper soil horizons and in plant remains on the surface are of the greatest importance. In the course of their life activity, they significantly accelerate the decomposition of organic matter and often produce very profound changes in the chemical and physical properties of the soil. An important role is also played by burrowing animals, such as moles, mice, ground squirrels, marmots, etc. By repeatedly breaking the soil, they contribute to the mixing of organic substances with minerals, as well as increasing the water and air permeability of the soil, which enhances and accelerates the processes of decomposition of organic residues in the soil. . They also enrich the soil mass with the products of their vital activity.

Vegetation serves as food for various herbivores, therefore, before getting into the soil, a significant part of the organic residues undergoes significant processing in the digestive organs of animals.

Relief

has an indirect effect on the formation of soil cover. Its role is reduced mainly to the redistribution of heat and moisture. A significant change in the height of the terrain entails significant changes in temperature conditions (it gets colder with height). The phenomenon of vertical zonality in the mountains is connected with this. Relatively small changes in altitude affect the redistribution of precipitation: low areas, depressions and depressions are always more humid than slopes and elevations. The exposure of the slope determines the amount of solar energy entering the surface: the southern slopes receive more light and heat than the northern ones. Thus, the features of the relief change the nature of the impact of climate on the process of soil formation. Obviously, soil formation processes will proceed differently under different microclimatic conditions. Of great importance in the formation of the soil cover is also the systematic flushing and redistribution of fine earth particles by atmospheric precipitation and melt water over the elements of relief. The significance of the relief is great in conditions of heavy rainfall: areas deprived of the natural flow of excess moisture are very often swamped.

Soil age.

Soil is a natural body that is in constant development, and the form that all soils on Earth have today is only one of the stages in a long and continuous chain of their development, and individual present-day soil formations, in the past, represented other forms and in in the future may undergo significant transformations even without drastic changes in external conditions.

There are absolute and relative age of soils. The absolute age of soils is the period of time elapsed from the moment the soil appeared to the current stage of its development. The soil arose when the parent rock came to the surface and began to undergo soil formation processes. For example, in Northern Europe, the process of modern soil formation began to develop after the end of the last ice age.

However, within the boundaries of different parts of the land that have simultaneously freed themselves from water or ice cover, soils will by no means always go through the same stage of their development at each given moment. The reason for this may be differences in the composition of soil-forming rocks, in relief, vegetation and other local conditions. The difference in the stages of soil development in one common area with the same absolute age is called the relative age of the soils.

The time of development of a mature soil profile for different conditions is from several hundred to several thousand years. The age of the territory in general and soil in particular, as well as changes in the conditions of soil formation in the process of their development, have a significant impact on the structure, properties and composition of the soil. Under similar geographical conditions of soil formation, soils of different age and history of development can differ significantly and belong to different classification groups.

The age of soils is therefore one of the most important factors to be taken into account when studying a particular soil.

Soil and groundwater.

Water is the medium in which numerous chemical and biological processes take place in the soil. Where groundwater is shallow, it has a strong effect on soil formation. Under their influence, the water and air regimes of soils change. Groundwater enriches the soil with the chemical compounds it contains, sometimes causing salinization. Waterlogged soils contain an insufficient amount of oxygen, which causes the suppression of the activity of certain groups of microorganisms.

Human economic activity affects some factors of soil formation, for example, vegetation (cutting down forests, replacing it with herbaceous phytocenoses, etc.), and directly on soils through mechanical processing, irrigation, application of mineral and organic fertilizers, etc. As a result, often soil-forming processes and soil properties change. In connection with the intensification of agriculture, human influence on soil processes is continuously increasing.

The impact of human society on the soil cover is one of the aspects of the overall human impact on the environment. Now the problem of destruction of the soil cover as a result of improper agricultural tillage and human construction activities is especially acute. The second most important problem is soil pollution caused by chemicalization of agriculture and industrial and domestic emissions into the environment.

All factors do not affect in isolation, but in close interconnection and interaction with each other. Each of them affects not only the soil, but also each other. In addition, the soil itself in the process of development has a certain influence on all factors of soil formation, causing in each of them certain changes. Thus, due to the inseparable connection between vegetation and soils, any change in vegetation is inevitably accompanied by a change in soils, and, conversely, a change in soils, in particular, their moisture regime, aeration, salt regime, etc. inevitably entails a change in vegetation.

Soil composition.

The soil consists of solid, liquid, gaseous and living parts. Their ratio varies not only in different soils, but also in different horizons of the same soil. A decrease in the content of organic matter and living organisms from the upper soil horizons to the lower ones and an increase in the intensity of the transformation of the components of the parent rock from the lower horizons to the upper ones are regular.

Mineral substances of lithogenic origin predominate in the solid part of the soil. These are fragments and particles of primary minerals of various sizes (quartz, feldspars, hornblende, mica, etc.) formed in the process of weathering of secondary minerals (hydromica, montmorillonite, kaolinite, etc.) and rocks. The sizes of these fragments and particles are varied - from 0.0001 mm to several tens of cm. This variety of sizes determines the friability of the soil. The bulk of the soil is usually fine earth - particles with a diameter of less than 1 mm.

The mineralogical composition of the solid part of the soil largely determines its fertility. The composition of minerals includes: Si, Al, Fe, K, Mg, Ca, C, N, P, S, much less trace elements: Cu, Mo, I, B, F, Pb, etc. The vast majority of elements are in oxidized form. Many soils, mainly in the soils of insufficiently moistened territories, contain a significant amount of calcium carbonate CaCO 3 (especially if the soil was formed on a carbonate rock), in the soils of arid regions - CaSO 4 and other more easily soluble salts (chlorites); soils, humid tropical areas are enriched with Fe and Al. However, the realization of these general regularities depends on the composition of parent rocks, the age of soils, topography, climate, and so on.

The composition of the solid part of the soil also includes organic matter. There are two groups of organic substances in the soil: those that have entered the soil in the form of plant and animal residues and new, specific humic substances. substances resulting from the transformation of these residues. There are gradual transitions between these groups of soil organic matter; in accordance with this, the organic compounds contained in the soil are also divided into two groups.

The first group includes compounds contained in large quantities in plant and animal residues, as well as compounds that are waste products of plants, animals and microorganisms. These are proteins, carbohydrates, organic acids, fats, lignin, resins, etc. These compounds in total make up only 10–15% of the total mass of soil organic matter.

The second group of soil organic compounds is represented by a complex complex of humic substances, or humus, resulting from complex biochemical reactions from compounds of the first group. Humic substances make up 85–90% of the organic part of the soil; they are represented by complex high-molecular acidic compounds. The main groups of humic substances are humic acids and fulvic acids. . Carbon, oxygen, hydrogen, nitrogen, and phosphorus play an important role in the elemental composition of humic substances. Humus contains the main nutrients of plants, which, under the influence of microorganisms, become available to plants. Humus content in the upper horizon different types soil content varies widely: from 1% in gray-brown desert soils to 12–15% in chernozems. Different types of soils differ in the nature of the change in the amount of humus with depth.

The soil also contains intermediate decomposition products of organic compounds of the first group.

When organic matter decomposes in the soil, the nitrogen contained in them is converted into forms available to plants. Under natural conditions, they are the main source of nitrogen nutrition for plant organisms. Many organic substances are involved in the creation of organo-mineral structural units (lumps). The structure of the soil thus arising largely determines its physical properties, as well as water, air and thermal regimes.

The liquid part of the soil or, as it is also called, the soil solution - this is the water contained in the soil with gases dissolved in it, mineral and organic substances that got into it when passing through the atmosphere and seeping through the soil layer. The composition of soil moisture is determined by the processes of soil formation, vegetation, general features of the climate, as well as the season, weather, human activities (fertilization, etc.).

The soil solution plays a huge role in soil formation and plant nutrition. The main chemical and biological processes in the soil can only take place in the presence of free water. Soil water is the medium in which the migration of chemical elements occurs in the process of soil formation, the supply of plants with water and dissolved nutrients.

In non-saline soils, the concentration of substances in the soil solution is low (usually does not exceed 0.1%), and in saline soils (saline and solonetz soils), it is sharply increased (up to whole and even tens of percent). A high content of substances in soil moisture is harmful to plants, because. this makes it difficult for them to receive water and nutrients, causing physiological dryness.

The reaction of the soil solution in soils of different types is not the same: acid reaction (pH 7) - soda solonetzes, neutral or slightly alkaline (pH = 7) - ordinary chernozems, meadow and brown soils. Too acidic and too alkaline soil solution adversely affects the growth and development of plants.

The gaseous part, or soil air, fills the pores of the soil that are not occupied by water. The total volume of soil pores (porosity) ranges from 25 to 60% of the soil volume ( cm. Morphological features of soils). The ratio between soil air and water is determined by the degree of soil moisture.

The composition of soil air, which includes N 2, O 2, CO 2, volatile organic compounds, water vapor, etc., differs significantly from atmospheric air and is determined by the nature of many chemical, biochemical, and biological processes occurring in the soil. The composition of soil air is not constant, depending on external conditions and seasons, it can vary significantly. For example, the amount of carbon dioxide (CO 2 ) in the soil air varies significantly in annual and daily cycles due to different rates of gas release by microorganisms and plant roots.

Between soil and atmospheric air there is a constant gas exchange. The root systems of higher plants and aerobic microorganisms vigorously absorb oxygen and release carbon dioxide. Excess CO 2 from the soil is released into the atmosphere, and atmospheric air enriched with oxygen penetrates into the soil. The gas exchange of the soil with the atmosphere can be hindered either by the dense composition of the soil or by its excessive moisture. In this case, the oxygen content in the soil air sharply decreases, and anaerobic microbiological processes begin to develop, leading to the formation of methane, hydrogen sulfide, ammonia, and some other gases.

Oxygen in the soil is necessary for the respiration of plant roots, so the normal development of plants is possible only under conditions of sufficient air access to the soil. With insufficient penetration of oxygen into the soil, plants are inhibited, slow down their growth, and sometimes die completely.

Oxygen in the soil is also of great importance for the vital activity of soil microorganisms, most of which are aerobes. In the absence of air access, the activity of aerobic bacteria ceases, and in connection with this, the formation of nutrients necessary for plants in the soil also ceases. In addition, under anaerobic conditions, processes occur that lead to the accumulation of compounds harmful to plants in the soil.

Sometimes the composition of soil air may contain some gases that penetrate through the strata of rocks from their places of accumulation; this is the basis for special gas geochemical methods for prospecting for mineral deposits.

The living part of the soil consists of soil microorganisms and soil animals. The active role of living organisms in the formation of soil determines its belonging to bioinert natural bodies - the most important components of the biosphere.

Water and thermal regimes of the soil.

The water regime of the soil is a combination of all phenomena that determine the inflow, movement, consumption and use of soil moisture by plants. Soil water regime – the most important factor soil formation and soil fertility.

The main sources of soil water are precipitation. A certain amount of water enters the soil as a result of condensation of steam from the air, sometimes closely spaced groundwater plays a significant role. In areas of irrigated agriculture, irrigation is of great importance.

The flow of water is as follows. Part of the water entering the soil surface flows down in the form of surface runoff. The largest amount of moisture entering the soil is absorbed by plants, which then partially evaporate it. Some water is used for evaporation , moreover, part of this moisture is retained by the vegetation cover and evaporates from its surface into the atmosphere, and part evaporates directly from the soil surface. Soil water can also be consumed in the form of subsoil runoff, a temporary phenomenon that occurs during periods of seasonal soil moisture. At this time, gravitational water begins to move along the most permeable soil horizon, the aquiclude for which is a less permeable horizon. Such seasonally existing waters are called perched waters. Finally, a significant part of soil water can reach the surface of groundwater, the outflow of which occurs along an impervious bed-water barrier, and leave as part of the groundwater runoff.

Atmospheric precipitation, melt and irrigation water penetrate the soil due to its water permeability (ability to pass water). The more large (non-capillary) gaps in the soil, the higher its water permeability. Of particular importance is the permeability for the absorption of melt water. If in autumn the soil is frozen in a highly moistened state, then usually its water permeability is extremely low. Under forest vegetation that protects the soil from severe freezing, or in fields with early snow retention, melt water is absorbed well.

The water content in the soil determines the technological processes in tillage, the supply of water to plants, the physicochemical and microbiological processes that determine the conversion of nutrients in the soil and their entry with water into the plant. Therefore, one of the main tasks of agriculture is to create a water regime in the soil that is favorable for cultivated plants, which is achieved by the accumulation, conservation, rational use of soil moisture, and, if necessary, by irrigation or drainage of land.

The water regime of the soil depends on the properties of the soil itself, climate and weather conditions, the nature of natural plant formations, on cultivated soils - on the characteristics of the cultivated plants and the technique of their cultivation.

The following main types of soil water regime are distinguished: leaching, non-leaching, effusion, stagnant and frozen (cryogenic).

Pripromyvny In the type of water regime, the entire soil layer is annually soaked to groundwater, while the soil returns less moisture to the atmosphere than it receives (excess moisture seeps into groundwater). Under the conditions of this regime, the soil-ground stratum is, as it were, annually washed with gravitational water. The leaching type of water regime is typical for a humid temperate and tropical climate, where the amount of precipitation is greater than evaporation.

The non-leaching type of water regime is characterized by the absence of continuous wetting of the soil layer. Atmospheric moisture penetrates the soil to a depth of several decimeters to several meters (usually no more than 4 m), and between the soaked soil layer and the upper boundary of the capillary fringe of groundwater, a horizon with constant low humidity (close to the wilting point) appears, called the dead horizon of drying. . This regime differs in that the amount of moisture returned to the atmosphere is approximately equal to its entry with precipitation. This type of water regime is typical for a dry climate, where the amount of precipitation is always significantly less than evaporation (a conditional value that characterizes the maximum possible evaporation in a given area with an unlimited supply of water). For example, it is characteristic of the steppes and semi-deserts.

effusion the type of water regime is observed in a dry climate with a sharp predominance of evaporation over precipitation, in soils that are fed not only by atmospheric precipitation, but also by the moisture of shallow groundwater. With an effusion type of water regime, groundwater reaches the soil surface and evaporates, which often leads to soil salinization.

The stagnant type of water regime is formed under the influence of the close occurrence of groundwater in a humid climate, in which the amount of precipitation exceeds the sum of evaporation and absorption of water by plants. Due to excessive moisture, perched water is formed, resulting in waterlogging of the soil. This type of water regime is typical for depressions in the relief.

The permafrost (cryogenic) type of water regime is formed on the territory of continuous distribution of permafrost. Its peculiarity is the presence of a permanently frozen aquifer at a shallow depth. As a result, despite the small amount of precipitation, in the warm season, the soil is supersaturated with water.

The thermal regime of the soil is the sum of the phenomena of heat transfer in the system of the surface layer of air - soil - soil-forming rock, its characteristics also include the processes of transfer and accumulation of heat in the soil.

The main source of heat entering the soil is solar radiation. The thermal regime of the soil is determined mainly by the ratio between the absorbed solar radiation and the thermal radiation of the soil. The features of this ratio determine the differences in the regime of different soils. The thermal regime of the soil is formed mainly under the influence of climatic conditions, but it is also influenced by the thermophysical properties of the soil and its underlying rocks (for example, the intensity of absorption of solar energy depends on the color of the soil, the darker the soil, the more solar radiation it absorbs) . Permafrost rocks have a special effect on the thermal regime of the soil.

The thermal energy of the soil is involved in the phase transitions of soil moisture, being released during ice formation and condensation of soil moisture and consumed during ice melting and evaporation.

The thermal regime of the soil has a secular, long-term, annual and daily cyclicity associated with the cyclicity of the receipt of solar radiation energy on the earth's surface. On a long-term average, the annual heat balance of a given soil is zero.

Daily fluctuations in soil temperature cover the thickness of the soil from 20 cm to 1 m, annual fluctuations - up to 10–20 m. soil cooling). The depth of soil freezing rarely exceeds 1–2 m.

Vegetation has a significant influence on the thermal regime of the soil. It delays solar radiation, as a result of which the temperature of the soil in summer can be lower than the air temperature. Forest vegetation has a particularly noticeable effect on the thermal regime of soils.

The thermal regime of the soil largely determines the intensity of mechanical, geochemical and biological processes occurring in the soil. For example, the intensity of the biochemical activity of bacteria increases with an increase in soil temperature to 40–50°C; above this temperature, the vital activity of microorganisms is inhibited. At temperatures below 0 ° C, biological phenomena are sharply slowed down and stop. The thermal regime of the soil has a direct impact on the growth and development of plants. An important indicator of the provision of plants with soil heat is the sum of active soil temperatures (i.e. temperatures above 10 ° C, at these temperatures there is an active vegetation of plants) at a depth of the arable layer (20 cm).

Morphological features of soils.

Like any natural body, the soil has a sum of external, so-called morphological features, which are the result of the processes of its formation and therefore reflect the origin (genesis) of soils, the history of their development, their physical and chemical properties. The main morphological features of the soil are: soil profile, color and color of soils, soil structure, granulometric (mechanical) composition of soils, soil composition, neoplasms and inclusions.

Soil classification.

Each science, as a rule, has a classification of the object of its study, and this classification reflects the level of development of science. Since science is constantly developing, the classification is being improved accordingly.

In the Dodokuchaev period, it was not the soil (in the modern sense) that was studied, but only its individual properties and aspects, and therefore the soil was classified according to its individual properties - chemical composition, granulometric composition, etc.

Dokuchaev showed that the soil is a special natural body, which is formed as a result of the interaction of soil formation factors, and established character traits soil morphology (primarily the structure of the soil profile) - this gave him the opportunity to develop a classification of soils on a completely different basis than previously done.

For the main classification unit, Dokuchaev took the genetic types of soils formed by a certain combination of soil formation factors. This genetic classification of soils is based on the structure of the soil profile, which reflects the development of soils and their regimes. The modern classification of soils used in our country is a developed and supplemented by Dokuchaev's classification.

Dokuchaev singled out 10 soil types, and in the supplemented modern classifications there are more than 100 of them.

According to the modern classification used in Russia, one genetic type combines soils with a single profile structure, with a qualitatively similar soil formation process that develops under conditions of the same thermal and water regimes, on parent rocks of a similar composition and under the same type of vegetation. Depending on the moisture content, the soils are combined into rows. There are series of automorphic soils (i.e. soils that receive moisture only from atmospheric precipitation and are not significantly affected by groundwater), hydromorphic soils (i.e. soils that are significantly affected by groundwater) and transitional automorphic soils. -hydromorphic soils.

Soil genetic types are subdivided into subtypes, genera, species, varieties, categories, and they are combined into classes, series, formations, generations, families, associations, etc.

The genetic classification of soils (1927) developed in Russia for the First International Soil Congress was accepted by all national schools and contributed to the elucidation of the main regularities of soil geography.

Currently, a unified international classification of soils has not been developed. A significant number of national soil classifications have been created, some of them (Russia, USA, France) include all the soils of the world.

The second approach to the classification of soils took shape in the 1960s in the United States. The American classification is based not on an assessment of the conditions of formation and related genetic characteristics of various soil types, but on taking into account easily detectable morphological features of soils, primarily on the study of certain horizons of the soil profile. These horizons were called diagnostic .

The diagnostic approach to soil taxonomy turned out to be very convenient for compiling detailed large-scale maps of small areas, but such maps could hardly be compared with survey small-scale maps built on the basis of the principle of geographic and genetic classification.

In the meantime, by the early 1960s, it became clear that a world soil map was needed to determine a strategy for agricultural food production, the legend of which should be based on a classification that eliminated the gap between large-scale and small-scale maps.

Experts from the Food and Agriculture Organization of the United Nations (FAO), together with the United Nations Educational, Scientific and Cultural Organization (UNESCO), have begun to create an International Soil Map of the World. The work on the map lasted more than 20 years, and more than 300 soil scientists from different countries took part in it. The map was created during discussions and agreements between various national scientific schools. As a result, a map legend was developed, which was based on a diagnostic approach to determining the classification units of all levels, although it also took into account individual elements of the geographic and genetic approach. The publication of all 19 sheets of the map was completed in 1981, since then new data have been obtained, certain concepts and formulations in the map legend have been clarified.

Basic regularities of soil geography.

The study of the regularities of the spatial distribution of different types of soils is one of the fundamental problems of the Earth sciences.

The identification of regularities in soil geography became possible only on the basis of V.V. Dokuchaev’s concept of soil as a result of the interaction of soil formation factors, i.e. from the standpoint of genetic soil science. The following main patterns were identified:

Horizontal soil zonality. In large flat areas, soil types that arise under the influence of soil formation conditions typical for a given climate (i.e., automorphic soil types that develop on watersheds, provided that precipitation is the main source of moisture) are located in extensive strips - zones elongated along strips with close atmospheric humidification (in areas with insufficient moisture) and with the same annual sum of temperatures (in areas with sufficient and excessive moisture). Such types of soils Dokuchaev called zonal.

This creates the main regularity of the spatial distribution of soils in the flat areas - horizontal soil zoning. Horizontal soil zonality does not have a planetary distribution, it is typical only for very vast flat areas, for example, the East European Plain, part of Africa, the northern half of North America, Western Siberia, the flat spaces of Kazakhstan and Central Asia. As a rule, these horizontal soil zones are located latitudinally (i.e., they are elongated along the parallels), but in some cases, under the influence of the relief, the direction of the horizontal zones changes dramatically. For example, the soil zones of the western part of Australia and the southern half of North America extend along the meridians.

The discovery of horizontal soil zonality was made by Dokuchaev on the basis of the theory of soil formation factors. This was an important scientific discovery, on the basis of which the doctrine of natural zones was created. .

From the poles to the equator, the following main natural zones replace each other: the polar zone (or the zone of the Arctic and Antarctic deserts), the tundra zone, the forest-tundra zone, the taiga zone, the mixed forest zone, the broad-leaved forest zone, the forest-steppe zone, the steppe zone, the semi-desert zone, the zone deserts, a zone of savannahs and light forests, a zone of variable-moist (including monsoon) forests and a zone of humid evergreen forests. Each of these natural zones is characterized by quite definite types of automorphic soils. For example, on the East European Plain, latitudinal zones of tundra soils, podzolic soils, gray forest soils, chernozems, chestnut soils, and brown desert-steppe soils are clearly expressed.

The ranges of subtypes of zonal soils are also located inside the zones in parallel stripes, which makes it possible to distinguish soil subzones. So, the zone of chernozems is subdivided into subzones of leached, typical, ordinary and southern chernozems, the zone of chestnut soils - into dark chestnut, chestnut and light chestnut.

However, the manifestation of zoning is characteristic not only of automorphic soils. Certain zones have been found to be associated with certain hydromorphic soils (i.e., soils that are formed under a significant influence of groundwater). Hydromorphic soils are not azonal, but their zoning manifests itself differently than in automorphic soils. Hydromorphic soils develop next to automorphic soils and are geochemically associated with them; therefore, a soil zone can be defined as the territory of distribution of a certain type of automorphic soils and hydromorphic soils that are in geochemical conjugation with them, which occupy a significant area, up to 20–25% of the area of soil zones.

Vertical soil zonality. The second pattern of soil geography is vertical zonality, which manifests itself in the change of soil types from the foot of the mountain system to its peaks. With the height of the terrain it becomes colder, which entails regular changes in climatic conditions, flora and fauna. In accordance with this, soil types also change. In mountains with insufficient moisture, the change in vertical belts is due to a change in the degree of moisture, as well as the exposure of slopes (the soil cover here acquires an exposition-differentiated character), and in mountains with sufficient and excessive moisture, it is due to a change in temperature conditions.

At first, it was believed that the change in vertical soil zones was completely analogous to the horizontal zonality of soils from the equator to the poles, but later it was found that among mountain soils, along with types common both on the plains and in the mountains, there are soils that form only in mountainous conditions. landscapes. It was also found that very rarely a strict sequence of vertical soil zones (belts) is observed. Separate vertical soil belts fall out, mix, and sometimes even change places, so it was concluded that the structure of the vertical zones (belts) of a mountainous country is determined by local conditions.

The phenomenon of facies. I.P. Gerasimov and other scientists found that the manifestation of horizontal zonality is corrected by the conditions of specific regions. Depending on the influence of oceanic basins, continental spaces, large mountain barriers, local (facies) climate features are formed on the path of the movement of air masses. This is manifested in the formation of features of local soils up to the appearance of special types, as well as in the complication of horizontal soil zonality. Due to the phenomenon of facies, even within the distribution of one soil type, soils can have significant differences.

Intrazonal soil subdivisions are called soil provinces . A soil province is understood as a part of the soil zone, which is distinguished by the specific features of subtypes and types of soils and the conditions of soil formation. Similar provinces of several zones and subzones are combined into facies.

Mosaic of the soil cover. In the process of detailed soil-surveying and soil-cartographic work, it was found that the idea of the homogeneity of the soil cover, i.e. The existence of soil zones, subzones, and provinces is very conditional and corresponds only to the small-scale level of soil research. In fact, under the influence of meso- and microrelief, variability in the composition of parent rocks and vegetation, and the depth of groundwater, the soil cover within zones, subzones, and provinces is a complex mosaic. This soil mosaic consists of varying degrees of genetically related soil areas that form a specific soil cover pattern and structure, all of whose components can only be shown on large-scale or detailed soil maps.

Natalia Novoselova

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