Soil organic matter: composition and sources, general scheme of formation

Soil organic matter is understood as a combination of organic components that are present in the form of humus, plant residues and animal waste products. In fact, this component is a complex of complex organic components that are biogenic in nature. Their content affects the fertility of the soil. Therefore, with a decrease in the level of organic matter, appropriate measures must be taken.

Sources of soil organic matter

Soil organic matter is formed in natural conditions. They enter the soil as a result of the death of plants and microorganisms. Also, income groups include ground animals and products that remain after their life.

On arable areas, the general scheme for the formation of matter is based on plant residues and organic fertilizers that give soil fertility. The advantage of using plant residues is to reduce the cost of using organic fertilizers.

Meaning and composition

The organic matter of the soil accumulates reserves of nitrogen and potassium. It also contains phosphorus, carbon and other valuable components. Thanks to the balance of nutrients, it is possible to achieve the required soil regime, prevent erosion, and reduce the effects of toxins.

With the help of organic substances, it is possible to regulate the consumption of nutrients and prevent unproductive losses associated with leaching. They also make mineral fertilizers more efficient.

Deficiency of organic matter in the soil structure provokes a violation of chemical, physical and biological characteristics. Due to its high absorption capacity, humus prevents the migration of cations along the soil profile, absorbs toxins, and increases biological activity.

The organic components of the soil are divided into 2 categories:

1. Humic substances of a specific nature, which are resistant to decomposition, and humic acids. Also included in this category are humin and fulvic acids.
2. Non-humified or non-specific constituents that may be of vegetable or animal origin. Also included in this group are some decomposition products of an intermediate nature. For example, cellulose, fiber, protein elements. In addition, this category includes starch and amino acids. The share of this part of the substance is 10-15% of the total reserve in the soil structure. It decomposes easily and serves as a food source for plants.

Soils that contain a lot of humus are considered more biologically active. They are characterized by a high content of microorganisms, good enzymatic activity, intensive formation of carbon dioxide.

At the same time, the volume of humus differs significantly depending on the type of soil. For example, the percentage of this substance in podzolic soils is inferior to that of chernozems.

The specific content of humus in different types of soil is presented in the table:

Amount of humus in the upper layer, %Humus reserves, tons per 1 hectarelayer from 0 up to 20 centimeterslayer from 0 to 120 centimetersSod-podzolic South chernozem Leached black earth 7-8192500-600 10-12 650-800Common black soil6-8 137400-500Grey forest podzolized4- 6 109150-300Krasnozem5-7 153150-300 37

Soil type
2-4	53	80-120
4-5	-	300-350
			Powerful black soil
224
		Sierozem	1-2
50

Humic substances

About 90% of organic elements are represented by humus components. These include humic acids, humin and fulvic acids. By their nature, these elements are resistant to decomposition. 50-60% of their composition is carbon, and 30-45% is oxygen. Only 2.5-5% of the total is nitrogen. The structure also contains phosphorus, sulfur and other components.

Humic acids

They are a variety of humic acids that have a dark color. They dissolve in alkalis, but are resistant to acids. These components are organic acids containing nitrogen. They differ in cyclic structure.

Depending on the type of soil and the concentration of these components, humic acids may have a black or brownish color. Their structure includes carbon and hydrogen. It also contains nitrogen and oxygen.

The content of these components is affected by the type of soil, the composition of residues, and the features of humification. Chernozem components contain the maximum amount of carbon. Agriculture slightly changes the elemental structure of such acids.

Fulvic acids

This concept includes the category of humic acids, which are easily soluble in water. They also mix easily with acids and alkalis. These are organic acids that include nitrogen and carbon. They also contain hydrogen and oxygen. In the composition of fulphonic acids, there is a smaller amount of carbon and a larger amount of oxygen, unlike humic acids.

These components have a yellowish or brown tint. They are characterized by a more mobile structure and relatively easy to move along the soil profile. For fulphonic acids, a pronounced acid reaction is characteristic. They easily mix with water and easily destroy the mineral components of the soil.

However, the effect of fulvic acids on the minerals present in the soil mainly depends on the content of humic acids in it. The less humic acids present in the soil, the more pronounced the effect of fulvic acids.

Like humic acids, they have functional categories that are able to absorb cations. They can also form calcium and magnesium s alts, which have a soluble structure.

Fulvic acids are more mobile. The nitrogen components in their composition do not have such a strong bond. That is why they are more easily hydrolyzed by acids than the nitrogen components present in humic acids. Fulvic acids include 20-40% of soil nitrogen, and humic acids - 15-30%.

Gumins

This term is understood as a combination of humic and fulvic acids. At the same time, by their nature, humins are closer to humic acids. They differ from fulvic acids in a stronger bond with the mineral part of the soil and high resistance to microorganisms.

Humins do not dissolve in alkalis and acids. Also, they are not affected by organic agents. The structure of these soil components contains 20-30% of the nitrogen contained in the soil.

Different types of soil differ not only in the volume of humus, but also in the proportions of humic acids and fulvic acids. So, for sod-podzolic types of soil, indicators are at the level of 0.4-0.6, while in chernozems they are 1-1.5. That is why organic matter in soddy-podzolic soils is much more mobile compared to chernozem.

Non-humified substances

The share of non-humified components accounts for 10-20% of the total volume of organic soil components. It is a source of nutrition for plants and biota. Some of these substances activate or inhibit the development of living microorganisms. This is reflected in the transformation of soil nutrients and fertilizers from forms that cannot be absorbed by plants.

Approximately 10-30% of non-humified components take part in the formation of humus. The lack of such elements negatively affects the nutritional regime of all organisms living in the soil.

The influence of various farming practices on the organic matter regime and the humus state of soils

Today there are many agricultural practices that help increase the content of humus and other valuable components in the soil.

Cereals

To create a positive balance of organic components in the soil structure, it is necessary to increase the share of grain crops in the crop rotation. You can also use perennial legumes and legumes.

Utilization of fertilizers

The use of mineral fertilizers is often the main factor that contributes to the increase in yield parameters.However, the yield is not considered an absolute parameter of fertility. Reproduction of soil organic matter helps to achieve high efficiency of using increased volumes of mineral dressings.

Agronomic importance of soil organic matter and ways of its regulation

In order to achieve the desired results in the cultivation of cultivated plants, it is important to accompany the introduction of organic top dressing with a whole range of agrotechnical measures. It includes the following:

• lime or gypsum soil;
• rational application of mineral supplements;
• correction of the structure of sown areas.

Humus reproduction

For the reproduction of humus, it is recommended to cultivate perennial grasses. This helps to achieve positive results due to the accumulation of a large amount of plant residues and slowing down the mineralization of humus.

Key ways to make up for losses include the following:

• application of various types of organic top dressings in combination with minerals;
• plowing green manure and residues of roots;
• Introduction of legumes and legume-cereal crops into crop rotation.

Why is the humus content low in mountain soils

Mountain types of soil contain a minimum amount of humus, as they are based on hard rocks. When mixed with soil during precipitation, mud is formed that resembles clay in structure.

Soil organic matter is an important component that affects the degree of its fertility. In order to increase the content of valuable elements in the soil structure, it is necessary to apply appropriate agricultural practices.

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