Soil composition

Soil is the medium and the main condition for the development of plants. In the soil, plants take root and from it they draw all the nutrients and water necessary for life. By the term soil is meant the uppermost layer of the solid earth crust, suitable for processing and growing plants, which in turn consists of sufficiently thin humidified and humic layers. The humidified layer of is of a dark color, has an insignificant thickness of several centimeters, contains the largest number of soil organisms, it has a violent biological activity. The humic layer is thicker;if its thickness reaches 30 cm, you can talk about a very fertile soil, it is inhabited by numerous living organisms that process plant and organic residues into mineral components, as a result of which they are dissolved by groundwater and absorbed by the roots of plants. Below are the mineral layer and the parent rocks. Mineral layer, or subsoil horizon, has limited biological activity, it has fewer living soil organisms, but contains a huge amount of nutrient minerals. Mineral substances are processed by soil organisms and acquire a form that is available for assimilation by plants.

layer of the parent rock is biologically inactive, any organic processes in it are very limited, the rocks are subject to slow washing out and weathering.

Soil consists of of various solids, air and water. The more space between the particles, the more permeable to air and water is the soil. solid particles are essentially the main soil mass and can be of organic and inorganic origin. Solid soil particles of inorganic origin are sand, rocky residues and clay. Clay particles in the optimal

amount are very important for the quality of the soil, they have the ability to bind the soil, creating larger cloddy formations, and to retain water with nutrients dissolved in it. The organic part of the soil consists of humus, or humus, and the so-called soil fauna. The humus, which follows from the name of this substance, is formed as a result of the decomposition of organic and plant remains by bacteria and other soil organisms. This process itself is the basis of the life of the soil and, consequently, of the plants rooted in it, since only living soil organisms are able to process organic residues in the process of vital activity in an accessible form suitable for consumption by plants. The process of decomposition of organic substances in the soil is called humification, and its final result is a product such as humus, which determines the degree of soil fertility. In a simplified form, this process can be described as follows: soil bacteria and other organisms decompose plant and organic residues, as a result of which mineral compounds vital for the development of plants are released. It is important that the decomposition process occurs with sufficient access to oxygen, otherwise it will take the form of decay.

According to the degree of humus content, the soils are subdivided into poorly thawed slightly humic( 1% humus and less), moderately humic( up to 2 % humus), medium-humid ( 2-3 %) and, finally, humus, containing more than 3% humus. Favorable for the cultivation of any crops is soil containing at least 3-5 % humus.

An important constituent of the soil is soil water, filling the space between the solid particles. In it, in the dissolved form, the nutrients of the soil are contained, so that in fact it is no longer water in pure form, but a kind of soil solution. Water enters the soil through precipitation, from the air, to a small extent as a result of groundwater recharge or by targeted irrigation. Supplying the soil with water is the main condition for the development of all life processes in it. Spaces, or pores, between the solid particles of the soil are filled with water and, as a result of the action of the capillaries, serve as conductors of water to the roots of plants, and also serve as a drainage preventing the processes of excessive accumulation and stagnation of water.

/. The moistened layer of soil, fastened by the roots of plants, its thickness is no more than a few centimeters.

2. Humus layer, which is the basis of soil fertility, 100 cm thick.

3. The subsoil layer is characterized by a decreased activity of biological life.

4. Maternal rocks

The ability of different types of soils to absorb and retain moisture is not the same. Sand soils absorb the best moisture, where the space between soil particles is the largest, but they are not able to retain it due to the same factor. Clay soils, because of their dense structure and small spaces between solids, absorb water more poorly and get rid of its excess, due to the impossibility of forming capillaries in the coalesced mass of soil. Clay soils are most susceptible to stagnant processes. Ideal option is the humus soils, which have a balanced structure with an optimum ratio of solid particles and the space between them, they absorb moisture well, keep it inside and through the system of capillaries are supplied to the roots of plants.

Soil moisture, in addition, plays the role of a regulator of soil temperature and maintains a temperature balance. The more the soil is moistened, the more slowly it heats up and slowly cools. This is affected by the compensating effect of water.

Humus is the most valuable organic and biologically active part of the soil. For plants, humus is the main source of nutrients, which, dissolving in water, enter the plant through the roots and saturate it primarily with nitrogen. Humus is formed as a result of humification processes of decomposition products of organic residues, carried out by soil bacteria and other microorganisms.

Nutrients in humus are processed in such a way that they become available for the suction roots of plants, and hence can be completely absorbed by the plant. In addition, when in a bound state, they are not washed out of the soil.

High content of humus in the soil means a rich reserve of nitrogen, which is extremely necessary for plant life.

Humus has a stabilizing effect on all reactions and processes in the soil, including the processes of oxygen and water metabolism.

Humus binds solid soil particles, turning them into friable lumps with pores, creates an optimal loose structure of the soil, which greatly increases its ability to absorb and retain moisture, and also has a decisive influence on the air permeability of the soil.

Humus has a dark brown to black color, which gives it the ability to accumulate and retain heat. Humus soils warm up much faster.

Soil air is also contained in cavities between solid soil particles and determines the viability of a specific soil environment. Soil air contains more carbon dioxide than atmospheric, which is explained by the specificity of the vital activity of plant roots, which use oxygen for breathing and produce carbon dioxide. As a result of the presence of exchange products, the proportion of carbon dioxide in the soil air increases. Air is necessary for soil to ensure the breathing of the root system of plants and soil organisms. The lack of oxygen in the soil inhibits the growth of the root system, adversely affects the absorption of soil moisture by plants and the assimilation of nutrients dissolved in water. Therefore, even in a soil with a sufficient degree of hydration, the growth of

plants can be suppressed due to a lack of soil air and a lack of adequate nutrient absorption. Soil air contains about 90 % water vapor, therefore in hot weather the content of water vapor in soil air decreases and the soil temperature starts to approach the temperature of atmospheric air. As a result, plants experience an extreme lack of moisture in drought.

Humus is called by the immune system of the soil, because due to its action, the soil structure is maintained and improved, its basic functions are maintained and the health of the soil environment is maintained. Humus activates the natural resistance of plants to diseases and pests, prevents the mass development of pathogens.

Due to the optimal balance of humus in the soil, its filtering and binding capabilities are maintained and improved. Nutrients are retained in the organic surface layer of the soil with a developed root system, the harmful substances disintegrate or in the colloids are deactivated and do not pose a danger to the soil fauna and plants.

The introduction of unreasonably high doses of various mineral fertilizers and irrational management of an economy is reflected in the biological state of humus, which is the main criterion of its value. It follows that the quantitative assessment of the humus content of in soil is not yet indicative of its fertility. Essential in the evaluation of humus is its biogenic state or the indicator of humus itself. In soils with a relatively high humus content, a very low biogenic state of humus can be observed as a result of years of improper treatment, so only the absolute content of humus together with its biological value can provide a true picture of the humus balance in the soil.