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Soil composition and structure

Soil is a colossal natural wealth. It provides animals with food, people with food, and the sphere of industry is necessary for the production of goods by raw materials. The creation of soil continued for centuries and millennia. And to date, humanity is facing the issue of the proper use of land. And this is impossible without knowledge of the structure, properties, composition and structure of soils.

History of the study of the fertile layer of the earth

Back in the 18th century, scientists noticed that the soil consists of various components. Interest in this property was renewed much later. Thus, in Germany from 1879 to 1899, research was published annually in this field, conducted by Volnya and his school. Numerous laboratory studies have established the dependence of physical properties of soils on the size of its lumps and on the content of dust.

In 1877, scientist PA Kostachev noted that after plowing virgin lands they are quickly dispersed, which leads to a decrease in yield. The soil structure was restored only after the fields were left under perennial grassy vegetation. These studies were of great importance. They proved that in agriculture the soil structure plays a great agrotechnical role.

Much attention was paid to the study of the upper layer of the earth in the 30-40-ies of the last century. At the same time, scientists attached paramount importance to the soil structure in matters of fertility. These two terms they have elevated to the rank of synonyms.

The structure of the soil and its significance were practically not considered by scientists in the 50-60s of the last century. The reason for this was the criticism of the travopoly system. Researchers began to question the role of soil structure in matters of fertility. And sometimes they completely denied it.

However, some scientists continued to engage in research in this area. And here the works of Academician VV Medvedev are especially distinguished. Scientists studied the structure of the soil and its significance using micromorphological methods. At the same time, they used modern mathematical devices that allow analysis and generalization of the data obtained. The result of Medvedev's works was a monograph published in 2008 on the structure of soils. In this work, studies were carried out which convincingly proved that the improvement of the thermal and air conditions of the upper layers of the earth directly, and also indirectly affects the growth of plants.

Basic definition

What is the structure of the soil? The definition of this term indicates that it is a collection of different aggregates (lumps) that differ in their size and shape. Each of these elements consists of substances, interconnected by plant roots, humus, etc.

The structure of soils is of great importance. It is the main factor responsible for the fertility of land. The soil structure of the upper horizon is especially important for humans. This is the layer in which the root system of plants develops. It hosts a variety of soil organisms. From this horizon, the supply of nutrients and water necessary for plant growth occurs. That is why the top layer of the soil should have an optimum ratio between its liquid, solid and gaseous phase. This proportion looks like this - 25:50:25.

Classification of soils by structure

The upper horizons of the earth can have a different appearance. They are structureless and structural. The first of these species includes granulometric elements, the state of which is characterized as a separate particle. A striking example of structureless soil is sandy. It has little humus and clay particles. Transitional types of soil structure are between structureless and structural. In them, the connections of aggregates with each other are very weakly expressed.

Fertile soil is considered structural. It is better resistant to wind and water erosion, and also crumbles easily when plowing. If the composition and structure of the soil can be attributed to the fertile soil, then the combination of air, heat and water regime is balanced in it. This factor has a positive effect on plant nutrition and the development of biological processes.

Non-structured soils can not absorb water well. In addition, rain drains on such lands cause erosion. Air and water in such soils are antagonists. Falling rain does not leave moisture in such land horizons. This is due to the intensive capillary rise of water. The soil is overdried. Plants are not provided with the necessary amount of liquid and nutrients. Despite all this, in the fields with unstructured soils, it is possible to obtain a high yield. However, this will require ongoing work that maintains high-tech farming.

Formation of the structure of the fertile layer

The upper horizon of the earth becomes suitable for the life of plants under the influence of two processes proceeding simultaneously. Thus, the formation of the soil structure occurs as a result of the mechanical separation of the layer into aggregates having various shapes and sizes. The second process is to impart internal properties and structure to the resulting elements.

Researches of scientists have shown that the formation of soil structure becomes possible under the influence of chemical, physico-chemical, biological and physico-mechanical factors.

Thus, the formation of aggregates occurs when the drying and moistening alternate, freezing and thawing. The composition and structure of the soil change under the influence of the livelihoods of burrowing animals, from the pressure exerted by the growing roots of plants. Change the properties of the upper layer of the earth and the various tool fields of the tool.

Also, the composition and structure of the soil depends on the availability of the adhesive. They, as a rule, are humic colloids. These elements, when coagulated, can transform the soil structure into a waterproof one. This characteristic depends on the amount of humus, mechanical composition, ability to retain and absorb water, and also to supply it to the surface by capillaries. After the rain on such lands, no crust forms, which reduces the access of oxygen to the roots of growing plants.

Heavy Soils

According to its mechanical composition fertile lands are divided into clay and loamy, sandy loamy, and also peat bogs. How are they determined? The mechanical composition of the soils is investigated according to the samples. Particles of the soil are taken from several places of the upper horizon, making it 20 cm deep. Further, the samples are mixed together and wetted to a doughy state with ordinary water. If you get a ball, but it can not be rolled into a cord, then the soil is classified as sandy loam. With easy implementation of such actions, the land can be classified as loam. And in the case when a cord is rolled out of the ball, which then closes into a ring, the soil is classified as clay. This type of arable layer is considered heavy. These soils have a high density and viscosity. They easily stick together and are difficult to process, confirming their name.

During the digging, clayey soil does not crumble. It forms large clods, which are difficult to break and crush. If such a land is plowed and allowed to lie down for a while, then all work will go wrong. After a while, the clumps will again stick together. The field will have to plow again.

What is the reason for this behavior of heavy soils? It is associated with a too fine structure of aggregate particles, leaving only a small space between them.

High compactness of clay soils causes their poor air permeability. This, in turn, leads to the fact that the roots of plants are not sufficiently supplied with oxygen. Restricted air access and to those microorganisms that live in such soils. A small amount of oxygen leads to a slowing down of the decomposition of organic substances to the final products of decomposition. This makes the soil poor, unable to feed the plants necessary for their growth organic substances. That is why a scant biological life is observed in clayey layers. Some parts of such lands are even called dead. They lack a developed microbiological environment.

The compressibility of aggregate soil particles is associated with such a characteristic of the land as their water permeability. Clay horizons do not form a developed capillary system. That's why the moisture passes through them badly. The roots of plants in such fields with great difficulty can get much-needed water for their lives.

In heavy soils, there is another negative feature. If water accumulates in them, it does not pass into the lower layers of the clay horizon. Significant volumes remain in the area of growth of the root system of plants, which leads to its rotting.

It can hardly be said that the best soil structure is clayey soil. And this is confirmed by the swimming of the arable layer during the rain. Falling drops break small soil aggregates. Clay clumps turn into smaller components, partially dissolving in water. The resultant fat is very tightly bound by soil aggregates. After drying, these fields are covered with a solid and very dense crust, limiting the penetration of oxygen, moisture and light to the root systems of plants. This phenomenon is called "concrete ground". The action of solar rays leads to the cracking of the soil, the structure of which for this reason becomes even denser.

Yes, clay soils are rich in trace elements and minerals. However, plants are not able to take full advantage of them. The fact is that the root system can absorb only those nutrients that are in a dissolved form, and are also the final product of processing microorganisms. Clayey soils have poor water permeability. Biological life is poor in them. This also affects the inability of normal plant nutrition.

Low yields on such lands are a consequence of the fact that the clay layers, because of their density, are poorly heated by the sun's rays. The most extreme areas for agriculture remain unheated throughout the summer period.

Improvement of heavy soils

To obtain a normal crop from clayey fields, the earth needs to be given a more loose and lumpy texture. Only in this case favorable conditions for plant growth will be created. How to improve the soil structure, which is considered heavy? This is possible with the regular introduction into the soil of loosening and lightening components. They may be peat or sand, lime or ash. In addition, to create favorable conditions for plant growth, manure and compost will be needed. These components will create a normal biological and nutrient medium in the soil .

Improvement of soil structure in terms of moisture capacity is possible when sand is introduced into it. This will simultaneously increase the thermal conductivity of the heavy ground. After the sanding procedure, clay horizons warm up, quickly dry out and are ready for further processing.

Light, or sandy soils

For such horizons is characterized by a low proportion of clay particles. The bulk of this soil is sand. Only in small amounts is found in humus.

Sandy soils are not for nothing called lungs. After all, it is not difficult to process them. And this is favored by the granular structure of the soil. Thanks to it, such horizons have high water and air permeability. However, they are prone to erosion and can not retain moisture in their layers. In addition, sandy soils not only get warm well. They also cool down very quickly.

But this is not the only reason why one can not say that the best soil structure is sandy. In such horizons the biological life is poor. This is due to a lack of nutrients and moisture for microorganisms living in such soils.

Improvement of sandy soils

To obtain a good harvest, the binding and compaction components are regularly introduced into the light soil. Improvement of the soil structure attributable to the lungs becomes possible by mixing it with peat or silt formations, drilling mud or clay. This will fill the pores between the sand particles. And for the emergence of a biological-friendly plant environment, humus and compost will be needed.

Features of sandy soils must also be taken into account in the question of their enrichment with fertilizers. Light soils perfectly pass moisture through themselves, which cleans all the useful elements out of them. That is why mineral fertilizers in such fields use only high-speed ones and often make them, but in small volumes.

Middle soils

Loamy land is the most favorable for agriculture and gardening. They have a better soil structure, the differences of which lie in granular clods. The composition of such a soil includes both solid, fairly large particles, and small dust-like components. The land on such fields is easy to process. After plowing, they do not cake or form dense lumps.

In loamy soils there are many mineral substances and nutrients, the stock of which is replenished thanks to the active vital activity of microorganisms. Such soils have high air permeability and water conductivity. They perfectly retain moisture, as well as quickly and evenly warmed by exposure to sunlight. Due to the balanced moisture in the loams, a constant temperature regime is maintained.

Improvement of medium soils

In order to keep the supply of nutrients at a proper level, loamy land must be periodically fertilized with compost. Additional mineral and organic fertilizers are introduced purposefully after a preliminary analysis of the condition of arable land.

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