Percentage of humus mineral content. What is humus? What is soil humus: composition and properties of fertilizer. Vermicompost production technology - video

Humus- a Latin word, it literally translates as earth, soil. In soil science, this term refers to a specific group of high-molecular, dark-colored substances formed during the decomposition of organic residues in the soil. These compounds are synthesized from the products of decay and decay of dead plant and animal tissues.

Anyone who has ever dug the ground knows that the top layer of soil is darker than the lower horizons. It contains a lot of small roots and humus - crushed, semi-decomposed plant residues mixed with mineral soil. All these residues that rot in the soil are material from which, with the participation of soil-dwelling microorganisms and animals, new organic compounds are formed, very stable, in which a large number of elements of mineral nutrition of plants are concentrated. This is humus.

In different natural areas, the humus layer of soil has different depths and colors. For example, in the Moscow region it is dark gray in color and only a few centimeters thick. And in the rich chernozems of Ukraine, the humus horizon is black, its thickness is more than a meter.

Soil fertility depends on the presence of essential nutrients in a form accessible to plants. Humus compounds are a reserve of nutrients. They decompose very slowly, transform into forms accessible to plants and are completely absorbed by the roots. Due to humus, the soil is able to produce stable crops for a long time. Gradually, this reserve is depleted, and if for some reason the new formation of humus is slower than its consumption, the yield begins to decline, which is what we observe on lands that are intensively exploited and at the same time improperly cultivated and fertilized.

Soil humus is a complex of different chemical compounds, in which several groups are distinguished that differ in chemical composition, properties, and degree of stability in the soil. For example, humic acids, the most stable and long-living components of humus in the soil, give it a dark color. In chernozem soils their content is very high. And in podzolic soils, so-called gray humic acids predominate - fulvic acids - more mobile, decomposing faster in the soil. That is why in the Non-Chernozem Zone the humus horizon is light and thin.

The processes of humification are very complex, their speed and nature are determined by many reasons: landscape and climatic conditions, vegetation composition, microbial and animal populations of the soil. The transformation of plant remains into humus is associated with grinding plant tissues and mixing them with mineral particles. At this stage, soil animals play an important role, feeding on such remains and digging underground passages and burrows.

Dead parts of plants first become prey for large invertebrates, which tear off, crush and grind large particles. Dead plant tissue is high in fiber and lignin. These compounds decompose very slowly in the soil and are poorly digested in the intestines of animals, but after processing in the intestinal tract of invertebrates they are greatly crushed and enriched in secretions. Then in the ground they are quickly populated by soil microflora, continuing further destruction and decomposition. Some groups of the animal population of the soil are capable of very active decomposition of fiber with the help of symbiotic microorganisms. These include, for example, woodlice, centipedes, slugs, snails, and the larvae of many insects.

In the absence of animals, the destruction of plant tissue slows down sharply. Dead roots of alfalfa, for example, retain their structure for a long time, and if they are colonized with sciarid fly larvae, they turn into an amorphous dark mass in just a few days. There is a close connection between the abundance of soil animals and the activity of humus formation.

For the formation of high-quality humus, an important condition is sufficient soil aeration. Animals constantly form a system of passages, which are constantly cleaned and maintained by their inhabitants. This system of passages creates ventilation and ensures the penetration of oxygen into the deep soil horizons, and thanks to this, aerobic processes can develop there.

Animal activity also has a known effect on soil acidity. For example, earthworms secrete large amounts of calcium carbonate during their metabolism. When the number of worms is high, this calcium significantly changes the acidity of the soil, bringing it closer to a neutral reaction. Some centipedes and woodlice have thick chitinous shells impregnated with calcium.

During molting or after the death of insects, their shells collapse, and calcium is included in metabolic soil processes. In forest-steppe oak forests, where diplopod centipedes are very numerous, the supply of calcium from their shells is up to 50 kg per hectare per year.

During their metabolism, many soil animals release a number of active compounds that are directly involved in reactions leading to the formation of humic substances. Among microorganisms, the most important in the formation of humus are bacteria, actinomycetes, and microscopic fungi. In the cells of some actinomycetes, specific dark-colored compounds are formed, the molecules of which, when interacting with each other, form humic substances. Actinomycetes are capable of synthesizing fulvic acids. Fungi that are widespread in the soil, such as penicillium and aspergillus, are involved in the initial stages of humification of plant residues.

Microorganisms also decompose humus in the soil. These are molds, actinomycetes, yeasts, and thermophilic bacteria. The decomposition and mineralization of humus is accelerated by a lack of organic material rich in nitrogen.

Soil scientists distinguish different types of humus, differing in their properties and formation characteristics. The lowest quality humus is the so-called raw or coarse acidic humus - “mor”. It forms at low temperatures, excess moisture or in poor soils. The pest contains a lot of semi-decomposed plant remains. The main agents of its formation are mushrooms. It should be noted that mushrooms secrete substances that create an acidic reaction in the soil. Thus, they prevent the settlement of animals and slow down the rate of crushing of plant tissues. As a result, many large particles rich in lignin and fiber remain in the humified mass, retaining a large amount of nutrients, which makes such humus unproductive.

Fine grinding of plant residues by animals, their secretion of mucous and alkaline products into the mass of decomposing organic matter leads to the formation of fine-grained, high-quality “sweet humus”, or “mulla”. Mull forms in soils with a high abundance of earthworms. Of great importance is the secretion of mucus by worms, which glues organic and mineral particles. They form stable, water-resistant soil aggregates that do not disintegrate for a long time and form a granular soil structure.

There are other transitional types of humus. Their formation largely depends on the composition and activity of soil organisms and the supply of organic material in the soil. In the fields, the soil is quickly depleted, and the humus content in it decreases. And the reason is that along with the harvest, the reserve of organic material, in which mineral nutrition products of plants are accumulated, is also removed. The number of animals also decreases, and subsequently the activity of humus formation decreases.

The mineralization of the humus reserve in the soil begins, and after its depletion, soil productivity drops (humus melts). The application of large doses of mineral fertilizers cannot compensate for the decrease in natural soil fertility, since plants absorb only a small part of them. And excessive concentrations of fertilizers in the soil solution and in succulent plant tissues reduce the quality of agricultural products. Nitrate poisoning of vegetables and fruits grown under conditions of excessive levels of mineral fertilizers has become widely notorious.

To maintain natural soil fertility and increase productivity, it is first necessary to apply organic fertilizers. Only they can compensate for the loss of organic material removed during harvesting. Enriching the soil with organic matter also leads to increased activity of microorganisms and animals involved in humification processes, which also contributes to the formation of a humus reserve and maintaining its balance.

For closed ground, where a small land area is intensively exploited, you can use “vermicompost” - a high-quality organic fertilizer obtained by processing various organic residues (manure, sludge, etc.) by earthworms. This is a relatively expensive fertilizer obtained in the conditions of industrial cultivation of worms, however, it will more than pay for itself in high yields of environmentally friendly products while maintaining the biopotential of the soil.

It is the most important link in the metabolism and energy between living and inanimate nature. This is a complex of organic compounds that make up the soil. Represented mainly by humus (80–90%); non-soil-specific carbohydrates; fats, proteins, as well as plant and animal remains.

Organic matter reserves in a meter layer of various soil types range from 8 to 760 t/ha. In soddy-podzolic soils (arable land) these reserves reach 90–100 t/ha, in peat bogs – 760 t/ha. The main source of organic matter in the soil is the remains of green plants. Under coniferous forest conditions, about 4–6 tons of dry matter per 1 hectare enters the soil annually in the form of litter and dead roots. In agroecosystems, the soil receives plant residues per year from 2–3 tons (row crops) to 7–9 tons of dry matter per 1 ha (perennial grasses).

The mass of microorganisms that die annually in the soil is about 0.6–0.8 tons of dry matter per 1 ha. The amount of animal residues is 0.1–0.2 tons of dry matter per 1 hectare of soil.

There are the following forms of organic matter in the soil.
1. Undecomposed or slightly decomposed remains of predominantly plant origin, brown-colored. They form forest litter, steppe felt, and peat horizons. This is the so-called rude humus, or pestilence.
2. Residues in the stage of deep decomposition, forming a loose dark brown or black mass; under a microscope - semi-decomposed remains. This form is called moder(rotten).
3. Specific organic formations, which are actually humus, making up 85–90% of the organic matter of the soil. This - mulled form.

/>The composition of organic residues entering the soil is quite complex. The bulk of them are carbohydrates - sucrose, fructose, glucose, starch, fiber. Together with organic substances, nitrogen-containing compounds enter the soil - amino acids, proteins, alkaloids, as well as lignin, tannins, resins, organic acids (oxalic, citric, tartaric).

The elemental composition of organic matter entering the soil is characterized by the fact that it is approximately 5% (in terms of dry matter) represented by carbon, hydrogen, and nitrogen; the remaining 5% is a large group of ash elements - calcium, magnesium, potassium, sodium, silicon, phosphorus, iron, sulfur, as well as trace elements - copper, boron, manganese, zinc, etc.

Organic residues entering the soil undergo various biochemical and physicochemical transformations. The rise of enzymes secreted by microorganisms changes the anatomical structure of the residues, and complex organic compounds break down into simpler ones - they are called intermediate products transformation of organic residues.

As a result of protein hydrolysis, peptones, peptides, and free amino acids are formed. When complex proteins are hydrolyzed, carbohydrates, phosphoric acid, and nitrogen-containing heterocyclic bases are formed together with acids.

The decomposition of fats is accompanied by the formation of lignin and fatty acids. The products of lignin breakdown are phenols. Many intermediate compounds are formed during the decomposition of carbohydrates - monosaccharides, organic acids, aldehydes, etc.

The range of intermediate products of the transformation of organic substances, as can be seen, is quite diverse. Most of them are oxidized to final products - carbon dioxide, water, simple salts. And the intermediate products of transformation are used by heterotrophic bacteria for nutrition and the construction of plasma and are thus re-formed into complex compounds - proteins, carbohydrates, etc. And, finally, some of the intermediate products are involved in the synthesis of humic substances.

The process of synthesis of these substances occurs under conditions of biocatalysis, the action of enzymes secreted by microorganisms. The essence of this process comes down to the fact that intermediate products of the decomposition of organic matter, falling under the influence of reactions of biochemical oxidation, polycondensation, polymerization, give qualitatively new organic compounds, which are called humus, or humus, and the process of their formation is humification. Usually under humus (from lat. humus– earth, soil) understand a group of dark-colored, high-molecular nitrogen-containing organic substances of an acidic nature, most of which are colloids. Humic substances themselves make up 85–90% of the total amount of organic compounds in the soil.

The greatest quantity and quality of humus is provided by herbaceous vegetation and its root system. The formation of humus involves the simplest animal soils and microorganisms that destroy complex organic substances. This process is called biochemical. As a result, two main groups of compounds are formed: nonspecific humus (lignin, cellulose, waxes, resins and other dilapidated compounds) and specific humus (humic and fulvic acids, humin). Specific humus is isolated using an alkaline reagent. That part of humic substances that is not extracted by alkali is called humin; extracted with alkali and precipitated during oxidation with humic acid, and the fraction remaining in the solution with fulvic acid. The structure of humus is very complex and not entirely understood. Fulvic acid is the most mobile, more aggressive with a light brown color. In Polesie it gets into wells and creates a brown color in drinking water. The best humus is one in which humin with humic acid predominates, as in our turf soils or chernozem soils (Cr: Cf > 1). In most land soils, the fulvate composition of humus predominates. Chernozems have the largest amount of benign humus (4–15%). Therefore, these soils are the most fertile.

Humus in the soil partially combines with gley and colloidal particles, creating organomineral compounds (chelates). They are useful in that they slow down the mineralization of humus (the creation of ash - oxides of chemical compounds), increase the content of valuable nutrients in an accessible form for plants and do not allow fertilizers to be carried into rivers and lakes.

The composition of humus also includes substances of initial organic residues (proteins, carbohydrates, resins, etc.), intermediate products of the transformation of organic residues (amino acids, monosaccharides, polyphenols, etc.).

The composition of humic substances includes humins - a complex of humic acids firmly bound to the mineral part of the soil.
It has been established that a combination of aerobic and anaerobic conditions with alternating periods of sufficient and insufficient moisture is favorable for the accumulation of humus. Depending on their relationship to various solvents, the following components of humus are distinguished: fulvic acids and humic acids.

Humic acids are specific organic acids of soil humus. They dissolve well in alkaline solutions, slightly in water and do not dissolve in acids. The solution of humic acids is either black in color. Consist mainly of carbon (52–62%), oxygen (31–39%), hydrogen (2.8–6.6%), nitrogen (2–6%) and a small amount of ash elements - phosphorus, sulfur, iron , aluminum, silicon, etc.

When interacting with the mineral part, humic acids form humates. Humates of monovalent cations (K+, Na+, NH-) are highly soluble in water and easily pass into the state of colloidal and true solutions and can be washed out from the upper soil horizons. The adhesive ability of these humates is low. Soils containing humates of monovalent cations do not have a water-resistant structure; when moistened, they swell and float.

Humates of di- and trivalent cations (Ca2+, Mg2+, Fe3+, AI3+) form stable, water-resistant gels that can envelop mineral soil particles and glue them into durable aggregates. That is why turf soils are characterized by a water-resistant structure. The humic acid molecule has a complex structure. The core of the molecule includes benzenepolycarboxylic acids, aromatic and heterocyclic rings. The peripheral parts of humic substances contain different functional groups (carboxyl, amino groups, alcohol, etc.), which determine various chemical and interaction of group compounds with each other, as well as with the mineral components of soil and fertilizers.

In the composition of humus, the ratio between the content of humic acids (HA) and fulvic acids (FA) is important. It is considered favorable when BG/FC >1.

The importance of humus in the formation of soils is great. The influence of humic substances on these processes is varied and very significant. With the participation of humus, many soil horizons are formed - A1 A2, B, etc., and its water-air properties are also formed. Humus increases the absorption capacity of soils and expands buffer capabilities.

Numerous plant nutrients accumulate in humus - N, P, S, K, Ca, microelements, which are released during its decomposition by heterotrophs. The decomposition processes of humic substances are accompanied by the release of carbon dioxide, which is necessary for green plants for photosynthesis.
In addition, humus is a source of biologically active substances in the soil (enzymes, vitamins, growth substances), which have a positive effect on the growth and development of plants and the mobilization of elements.

Humus also performs a sanitary and protective function: it accelerates the decomposition of pesticides, fixes pollutants (sorption, formation of complexes) and thereby reduces their entry into plants. Humic acids have a high absorption capacity - 200–600 mg equiv per 100 g of substance, their pH is about 3.4.

Fulvic acids (from lat. fulvus– yellow) have essentially the same structure as humic ones, but their core is less condensed, they contain less carbon, and more oxygen and hydrogen. Color ranges from straw yellow to orange. Fulvic acids and their salts—fulvates—dissolve well in water, acids, and alkalis. Their aqueous solutions have an acidic reaction – pH 2.6–2.8. Therefore, fulvic acids energetically destroy soil-forming rocks and promote the removal of many chemical elements from them. This is especially pronounced during podzol formation.

Thus, humic and fulvic acids differ significantly in their properties. Humic acids are able to accumulate in the soil and form its fertility. Fulvic acids actively destroy the mineral part of the soil and thereby reduce its fertility. Therefore, it is important to know not only the total amount of humus in the soil, but also its qualitative (group) composition - the ratio of humic and fulvic acids in it is an important indicator of their agrochemical assessment.

The amount of humus, its quality (Hk/Fk), and the thickness of the humus horizon in the soils of different geographical zones are not the same. Thus, a higher humus content in the upper horizon (10–14%) and its greatest thickness (70–80 cm) are characteristic of typical chernozems. To the north and south of the chernozem zone, the amount of humus and the thickness of the humus horizon decreases. To the north - 3–6% in gray forest soils and 1–3% in the humus horizon thickness of 25–30 and 15–20 cm, respectively. To the south – 3–5% in chestnut soils and 1–2% in brown soils when the thickness of the humus horizon is 20–40 and 10–15 cm, respectively.

Zonal soil types also differ in the quality of humus. Thus, in the composition of the humus of soddy-podzolic soils, fulvic acids predominate (the ratio of humic and fulvic acids is 0.6–0.8), and in chernozems, this ratio is 1.5–2.5, which indicates a clear predominance of humic acids in the composition of humus .

The granulometric composition has a great influence on humification. Thus, sandy soils contain significantly less humus (1.0–1.5%) compared to soddy-podzolic loams (2–3%).

In order for the humus balance in the soils used to be positive, it is necessary to systematically add organic fertilizers to the soil in sufficiently high quantities. It is believed that the humus content in soddy-podzolic soils will not decrease if 8–10 t/ha of organic fertilizers are applied annually. The use of green fertilizers, grass sowing, liming of acidic soils, etc. has a positive effect on increasing the humus content in the soil.

In conclusion, it should be noted that humus is not only a chemical and biological concept, but also an ecological one. Humus horizons are formed as a result of a continuous change of plant generations. Different plant communities, for example, herbaceous and woody, differ sharply in their requirements for environmental conditions and in the nature of humification. Forest litter (Ao), leaching type of water regime, fulvic type of humus - this is the ecological basis for the existence of the forest. And for herbs - humification according to the humate type, the formation of a dark-colored humus layer, the accumulation of nutrients in it.

Humus, as the ecological basis of soil fertility, directly affects the living conditions of plants, including cultivated ones.

Humus, composition - Humus is a complex dynamic complex of organic compounds formed during the decomposition of organic residues. The humus content in soils is determined by the conditions and nature of the soil-forming process; it fluctuates in the upper horizons from 1 - 2 to 12 - 15%, sharply or gradually decreasing with depth.

The composition of soil humus is divided into a specific part (85 - 90% of the total humus), represented by humic substances, and a nonspecific part (10 - 15%), represented by non-humified organic substances. The latter can be very diverse in composition and include: nitrogenous compounds (proteins, enzymes, amino acids), carbohydrates (monosaccharides, oligosaccharides, polysaccharides), lipids (fats, waxes, phospholipids), tannins (tannins, gallic acid, phlobaphenes and other polyphenols), organic acids; in addition, lignins, resins, alcohols, aldehydes.

Humic substances in the soil are represented by humic and fulvic acids, as well as humins.

Humic acids are high-molecular nitrogen-containing (up to 3 - 6%) organic acids, having a cyclic structure, insoluble in water and mineral acids, but soluble in weak alkalis and some organic solvents.

Humic acids consist of carbon (50 - 62%), hydrogen (3 - 7%), oxygen (31 - 40%) and nitrogen (2 - 6%). Their elemental composition depends on the type of soil, the chemical composition of decomposing residues, and humification conditions. Thus, humic acids in podzolic soils, in contrast to chernozems and chestnut soils, contain less carbon but more hydrogen.

Humic acids may contain from 1 to 10% ash elements, but they are not permanent components of the molecule, but are added as a result of chemical reactions.

Molecules of humic acids are not the same in size and chemical composition. Their molecular weight ranges from 4,000 to 100,000, so they are easily divided into fractions. Humic acids in soils are found predominantly in the form of gels, which are weakly hydrolyzed under the action of mineral acids, and go into solution under the influence of alkalis.

Interacting with the mineral part of the soil, humic acids form salts - humates, complex organo-mineral complexes that can be stably and firmly adsorbed on the surface of clay minerals.

Humates of alkalis (sodium, potassium, ammonium) are highly soluble in water, form true and colloidal solutions, can be washed out from the upper soil horizons, and under appropriate conditions, illuminate into the depths of the soil profile and precipitate and accumulate there. This is well expressed in solonetz and solonetzic soils.

Humates of calcium and magnesium are insoluble in water and are fixed in the soil in the form of gels. They are capable of gluing and cementing mechanical elements into aggregates and contribute to the formation of a water-resistant structure. This is observed in chernozem, meadow-chernozem and sod-carbonate soils.

Fulvic acids, like humic acids, are high molecular weight nitrogen-containing organic acids. They dissolve in water, acids, weak solutions of alkalis, sodium pyrophosphate and an aqueous solution of ammonia, forming water-soluble salts - fulvates. In addition, they dissolve in many organic solvents. Their solutions, depending on the concentration, have a color from straw yellow to orange. Their aqueous solutions have a strongly acidic reaction (pH 2.2 - 2.8). Fulvic acids are composed of carbon, hydrogen, oxygen and nitrogen, but contain less carbon and more oxygen than humic acids. On average, fulvic acids contain 40 - 52% carbon, 4 - 6% hydrogen, 40 - 48% oxygen and 2 - 6% nitrogen

Fulvic acids, due to their strongly acidic reaction and good solubility in water, energetically destroy the mineral part of the soil.

Fulysate salts (fulvates) of alkali and alkaline earth metals are highly soluble. Complex compounds of fulvic acids with iron and aluminum are also partially soluble, and fulvic acids are stronger than complexes with aluminum. The degree of mobility of such complex compounds depends on their saturation with metal. At high saturation, the complex becomes insoluble and precipitates.

Humins represent that part of humus that is not extracted from decalcified soil by alkalis. They are almost completely extracted by alternating exposure of the soil residue with humins to various acids and alkalis. Research has shown that in most cases, humins consist of the same groups of humic and fulvic acids as those extracted from humus with alkali. These acids in humins are in complex and strong bonds both with each other and with the mineral part of the soil.

The group of humins also includes inert carbonized carbon particles and incompletely humified organic residues. The humin content in humus is 15 - 20%, and in some soils even 40 - 48%.

11.Massive crystalline rocks, soil formation conditions.(6)

Massive crystalline soil-forming materials The rocks are cooled and solidified magma that has come to the surface of the earth. They have a very dense massive structure, crystalline or cryptocrystalline structure. Depending on the content and ratio of silicon and alkali compounds, on the one hand, and iron, calcium and magnesium, on the other, acidic and basic igneous rocks are distinguished.

TO acidic igneous rocks refers to granite, widespread in the mountain ranges of Buryatia. It is characterized by a high content of silica, a noticeable amount of sodium and potassium, a small content of iron, an insignificant amount of calcium and magnesium, and a relatively high content of fluorine and boron. Acid igneous rocks are usually light and brownish in color; they clearly contain crystals of quartz, feldspars and mica. These rocks contain a large amount of gases, such as CO, CO 2, H 2 S, CH3, H, N, C1, which can be released when heated. Weathering products and soils formed from acidic igneous rocks in the early stages of weathering are distinguished by the friability, sandiness and gravelly nature of the material, a more or less sufficient content of potassium associated with minerals of the mica group.

From basic igneous rocks basalts are known. They are characterized by a low silica content (40-60% by weight). Most of the silica is bound in aluminosilicate minerals. Free silica in the form of quartz is contained only in small quantities. Basic igneous rocks, in contrast to acidic ones, are mainly rich in compounds of manganese, iron, chromium, cobalt, zinc, titanium, nickel and copper. Alkaline magma rocks are distinguished by a very dark, sometimes black color, which is explained by the absence of quartz and the predominance of minerals colored in dark tones. The products of weathering and soil formation on rocks of alkaline magma usually quickly acquire a clayey character, retain an alkaline and neutral reaction for a long time, and are characterized by an increased content of soil humus and clay minerals such as montmorillonite.

Between the two main groups of massively crystalline rocks - acidic and basic - there are a number of transitional groups.

Metamorphic rocks are formed under the influence of high pressure and temperature from sedimentary rocks. Metamorphic rocks include quartzites, schists, conglomerates and gneisses, which are similar in chemical composition to granites.

Soils on such rocks have an underdeveloped profile.

Underdeveloped - formed on dense massive crystalline rocks or on steep slopes. Characterized by a complete set of horizons characteristic of a given soil type, which, however, are thin and may be discontinuous

Fertility and humus are concepts that are closely related. From Latin this term is translated as soil or earth. Although today farmers grow crops on hydroponics or artificial soil without any problems, they still cannot do without this component of fertility. To increase the percentage of yield, you first need to find out what soil humus is, and then consider the process of its formation.

Humus is...

Ecological dictionaries unanimously say that this is plant humus in tandem with organic animal waste. Even in ancient times, our ancestors noticed that the darker the soil, the more abundant and high-quality harvests it produces. It is coloring that is the first sign that indicates the presence in the soil of a nutrient medium for the root system of plants.

So how is humus formed? Complex biochemical processes occur in the upper layer of soil - the decomposition of organic remains without oxygen. They cannot occur without the participation of:

• animals;
• soil microorganisms;
• plants.

When they die, they leave behind a significant trace in soil formation. The decomposed waste products of these organisms also accumulate here. In turn, such organic substances are resistant to microbial action, which allows them to accumulate in the soil horizon.

This biomass serves as a real depot for all higher organisms. The components contained in it saturate the roots of plants with energy, and also nourish them with all the necessary elements:

• humin;
• humic acids;
• humic compounds.

The thickness of such a cover can reach (in temperate latitudes of the planet) up to 1.5 meters. In some areas it makes up 10-16% of the land, while in others it is only 1.5%. At the same time, peat bogs contain about 90% of such organic formations.

The formation of humus directly depends on the process of mineralization - the decomposition of biomass (under the influence of oxygen) into simple mineral and organic compounds. Under normal natural conditions, this occurs evenly, without compromising humification.

Compound

Before paying attention to the beneficial properties of this soil cover, you need to consider its composition. The highest concentration of useful elements is found exclusively in the upper part of the horizon. With deepening, there are fewer of them, since all the “participants” in this process live at a level of 50-70 cm from the surface. Therefore, the formation of fertile layers is impossible without:

• certain types of mushrooms;
• earthworms;
• bacteria.

The processing of organic components, as well as the excrement of invertebrate animals, leads to the formation of invaluable humus. It is the worms that are decisive in its formation. It is worth noting that about 450-500 individuals live in 1 m² of humus. Each of them eats plant debris and bacteria. The organic matter they deposit makes up a large percentage of nutritious biomass. The composition of humus includes the following chemical elements (the percentage depends on the type of soil):

1. Fulvic acids (30 – 50%). Nitrogen-containing soluble (high molecular weight) organic acids. They lead to the formation of compounds that destroy mineral formations.
2. Humins (15 – 50%). This includes elements that have not completed the humification process. At the same time, their vital functions depend on minerals.
3. Wax resins (from 2 to 6%).
4. Humic acids (7 – 89%). They are insoluble, although under the influence of alkalis they can decompose into individual elements. Each of them contains one of the leading components: nitrogen, oxygen, hydrogen and carbon. When acids come into contact with other components, salts can form in the soil.
5. Insoluble residue (19 – 35%). This applies to various saccharides, enzymes, alcohols and other elements.

The table of humus content in the main soil groups shows the amount of nitrogen and carbon for every 100 or 20 cm of soil. The measurement is carried out in t/ha. This is the general picture of fertile land reserves in Russia.

If you apply fertilizers (mineral, in particular) too often and in large quantities, this will lead to rapid decomposition of the biomass. In the first years, the yield will, of course, increase several times. But over time, the volume of the fertile layer will decrease significantly, and the yield will deteriorate.

Beneficial features

In agriculture, the most important thing is to preserve this organic horizon. Over the past half century, due to erosion in Russia and Ukraine, the top cover has decreased by almost half. Exposure to wind and water resulted in rich soil layers being blown away/washed away. The content of humus in the soil is considered by ecologists and farmers to be both a factor of fertility and the main criterion when purchasing land. After all, it is he who is responsible for the quality characteristics of the soil, and for these reasons:

Organic compounds protect lands from the harmful effects of heavy chemicals formed as a result of human activity. These elements “preserve” resinous carbons, salts, metals and radionuclides, leaving them forever in the bowels of the earth and preventing plants from assimilating them.

The only problem for all farmers is the natural area for growing crops, as well as the types of soil in which the humus content (the table is given in the article) is strikingly different. Therefore, in order to increase the fertility of your lands, you need to determine the level of biomass in them, taking the natural conditions of the region as a basis.

Map of humus reserves

In areas where the climate is very harsh, the process of soil formation is catastrophically slow. Due to weak heating of the top layer, plants and microorganisms are deprived of favorable conditions for a full existence.

Tundra

Here you can see huge areas consisting of coniferous trees and shrubs. The slopes are mostly covered with moss. In the tundra, the humus content is 73-80 t/ha in a one-meter layer. These areas are so wet that it leads to the accumulation of clay rocks. As a result, tundra soils have the following structure:

• top covering - litter consisting of undecomposed plant remains;
• humus layer, which is very weakly expressed;
• helium layer (comes with a bluish tint);
• permafrost.

Oxygen almost does not penetrate into such soils. The presence of air is essential for the microbiological activity of organisms. Without it, they die or freeze.

Taiga

Broad-leaved trees are found in this area. They form dense mixed forests. In the steppe zones, not only moss grows, but also herbal plants. Spring (often melted snow) and autumn rainy seasons excessively moisten the soil. Such flows wash away reserves of the humus horizon.

Here it forms and lies under the forest floor. Many sources provide different indicators of humus content in the taiga. For the following soil types they are as follows (per 1 m², t/ha):

• pod-golden (strong, medium and weak) - from 50 to 120;
• gray forest - 76 or 84;
• soddy-podgold - no more than 128, and no less than 74;
• taiga-permafrost contain a very low percentage.

To grow crops on such lands, you should regularly fertilize with high-quality substances. Only in this case can high yields be achieved.

Chernozem

All known varieties of black soil are considered the leader and favorite in this fertility ranking. Organic humus in them reaches a depth of 80 cm or 1.2 meters. They can rightfully be called the most fertile lands. This is favorable soil for the growth of cereals (wheat), sugar beets, corn or sunflowers. From the following list you can see the variation in humus content in different types of chernozem (t/ha, per 100 cm):

• typical (500-600);
• greened (up to 400);
• leached (within 550);
• powerful (more than 800);
• southern West Caucasian (390);
• degraded (up to 512).

It is worth understanding that the indicators for virgin, arable and developed types of land are different. To familiarize yourself with the composition of each of these groups, a table is provided. In steppe and arid regions, chestnut soils are common, which contain no more than 100-230 t/ha of humus. For desert (brown and gray types of soil cover) regions, this figure is about 70 t/ha. As a result, farmers constantly have to deal with salinization of their fields.

Drought is the main enemy of such types of land. Therefore, plantations may require abundant irrigation.

Ways to increase productivity

By understanding how the organic layer of soil is formed, the gardener will be able to increase the humus content in podzolic soils that suffer from excess moisture. In the fight for the fertility of such zones, the following actions are used:

Plant waste can be buried in your garden beds, thereby taking care of the nutrition of ground dwellers.

Such measures of caring for their land holdings will help the farmer keep the soil “alive.”
At the same time, the yield will increase several times.

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An assessment of the humus content in mineral soils of Russia is given, based on theoretical, calculated and expert approaches. A review is presented and an analysis of soil gradations based on humus content developed by the Soil Institute named after. V.V. Dokuchaeva (1977, 1985, 1997, 2001, 2003, 2004) and D.S. Orlov et al. (1978, 2004). A theoretical justification is given and a scale of Russian soils according to the degree of humus content is proposed, where the values ​​of the minimum humus content are presented as a reference point, and the objective intervals of the scale of humus content values ​​are based on the values ​​of interlaboratory permissible differences. The concept of a global assessment has been introduced, covering a wide range of soils in Russia and reflecting differences between soil types in humus content, and a differentiated assessment, characterizing differences within a soil type (subtype) in terms of the values ​​of this indicator. Methodological techniques for determining the minimum permissible, optimal and maximum permissible values ​​of humus content in arable soil horizons are outlined.
The chemical composition of soils is represented by three groups of components. These are substances that were previously part of the parent rocks; substances entering the soil with atmospheric and dust precipitation and, finally, organic substances belonging to various classes of compounds and accumulating primarily due to the remains of higher plants and microorganisms, and in soils converted into humus. The most relevant is the third group, which is almost the only source of a wide variety of organic compounds, which theoretically and practically determine both the formation of humus horizons in virtually any soil and the formation and accumulation of specific organic compounds in soils - humic substances. It is these substances that give soils their unique appearance and properties that distinguish them from other natural bodies.
According to Alexandrova, humus formation, that is, the formation of humus, is a process specific to soils, in contrast to humification, which occurs in many natural environments - peats, silts, sapropels, coals, etc. (including in soils) and leads to formation of humic substances.
The Great Russian Encyclopedia gives the following definition of humus: “Humus is a dynamic system consisting of a collection of plant and animal residues that have lost the features of their anatomical structure and undergo various stages of decomposition and synthesis; the main and most important constituent of soil organic matter.”
The US Dictionary of Soil Terms provides a different definition: “Humus is a more or less stable fraction of soil organic matter remaining after the bulk of plant or animal residues in the soil has decomposed.”
Humus is one of the most important indicators that determine the genesis and fertility of soils.
In “Classification and Diagnostics of Soils of the USSR,” the humus content is considered at the species level. Species characteristics in terms of humus content correspond to certain types of soils (Table 1).
In “Classification of Soils of Russia”, “Classification and Diagnostics of Soils of Russia”, in contrast to the previous classification system, more general criteria for identifying soils by humus content at the species level are proposed:
Types by humus content in the accumulative-humus horizon, % of soil mass (by ).

For soils with dark-humus and agro-dark-humus horizons
Type of Humus, %
1. Weakly humus<3
2. Low humus 3-5
3. Medium-humused 5-7
4. Highly humus 7-9
5. Obese >9

Table 1. Division of soil types in the USSR into types based on humus content

The system of indicators by Grishina and Orlov shows gradations of humus content generalized for all types of soil (Table 2). In their opinion, a small number of indicator levels are allocated to facilitate soil groupings. The same goal is pursued by integer limits for each Level. According to the authors, although this approach somewhat simplifies the characterization of the natural situation, each level nevertheless corresponds to some approximation to the real properties of specific soil types. Thus, a high humus content of 6-10% is indeed characteristic of chernozems, while low and very low (2-4 and<2%) — дерново-подзолистым почвам и подзолам.
In 2004, Orlov and his co-authors proposed the system “Additional indicators of the humus status of soils and their genetic horizons.” The authors believe that the previously given degrees of gradation of humus content are clearly insufficient if we take into account the characteristics of similar soils with relatively close levels of accumulation of organic matter. For the “humus content” indicator, five gradations were previously used, which is clearly insufficient. Especially when it comes to describing soils of similar genesis. They proposed introducing a more detailed gradation that more accurately covers real soil types. These estimated levels of various humus contents are presented in Table. 3. According to the authors, they significantly exceed and even expand the previously given levels, but are more consistent with the real properties of soils and seem to be much more convenient for most Russian, and perhaps many world soils.
It should be noted that the qualifiers for organic carbon content proposed in the World Correlative Soil Resources Base (WRB) for soil units - humic and hyperhumic - are based only on expert assessment.

Table 2. Humus content levels for soil grouping (by )

The rating scales of Grishina, Orlov, Orlov et al. and those given in the “Classification and Diagnostics of Russian Soils” for the degree of humus content of soils can be considered global, reflecting to a certain extent the genetic affiliation of soils. At the same time, the work of Stokozov and co-authors showed that the Grishina and Orlov system cannot be used for an objective assessment of the humus status of arable soils, since the proposed gradations were not linked to a specific soil type and its granulometric composition.
Based on bulk material, VNIPTIKHIM developed preliminary gradations for arable soils in Russia according to the degree of humus content, which are based on the soil type (subtype) and three groups according to the granulometric composition. It should be noted that earlier in the “Classification and Diagnostics of Soils of the USSR”, three subtypes of chestnut soils were divided into two groups based on their humus content, taking into account their granulometric composition.
In the above-mentioned “Temporary recommendations for the selection of soil samples for the determination of humus during agrochemical examination of arable lands in Russia,” proposed by a team of authors from VNIPTIKHIM, the Soil Institute named after. V.V. Dokuchaeva, VPNO “Rosselkhoz-Khimiya”, soils according to the degree of humus content are divided into five groups - very low, low
kaya, medium, increased, high. For chernozem soils, groups are distinguished in steps of 1% in humus content, and for other soils, with some exceptions, in the first groups the interval is 0.5%, and in the last (three) - 1%.
In our opinion, despite the available indirect express methods for establishing C min values, for a more accurate assessment of the minimum humus content, it should be determined in long-term experiments with permanent clean fallows.

Table 4. Gradations of arable soils according to humus content, %

Considering that in the vast majority of long-term stationary field experiments in Russia, options with permanent clean steam are not provided, we consider it advisable to immediately implement them. Options with permanent clean steam can be laid on old arable soil located near a station with many years of experience. After 10-15 years of fallowing, the main reserves of organic matter will be lost on this soil, and the humus content in it will be established at a level quite close to the minimum.
It was proposed that when assessing the degree of plowing of chernozems from the standpoint of their humus state, the values ​​of the minimum humus content should be used as a reference point, and objective intervals of the scale of humus content values ​​should be constructed based on the values ​​of interlaboratory permissible differences.
Interlaboratory permissible differences were calculated based on data from non-replicate analysis of Corg, determined by the dry combustion method. D = 2.8S for the difference of two single measurements, where D is the absolute interlaboratory acceptable deviation, S is the standard deviation. D is the smallest possible class size on the scale of a given soil characteristic.
As an example, we give a scale of plowing gradations for typical and leached chernozems of the Central Russian Upland according to humus content (%): heavy loamy - eroded -<5; сильно-выпаханные — 5.0—5.9; средне-выпаханные — 5.9—6.9; слабо-выпаханные - >6.9; medium loamy - eroded -<4.5; сильно-выпаханные — 4.5—5.4; средне-выпаханные — 5.4— 6.3; слабо-выпаханные — >6.3.
Taking into account the above, a scale of gradations of arable soils in Russia has been compiled according to the degree of humus content of the arable layer, consisting of four classes (Table 5). For this table, the value of D is taken from the work based on the materials of an interlaboratory certification experiment conducted in the USSR on standard samples when determining organic carbon using the Tyurin method. In case of implementation of agro analytical laboratories in the system. chem. Service of Russia, instead of methods for determining the content of organic carbon in soils using the method of dry combustion on automatic analyzers, you can use the information on the interlaboratory experiment given in the work in order to construct scales on this basis.
The first class - humus content is less than the minimum - includes soils that have partially lost the inert component of humus as a result of erosive removal of soil particles, mixing of the humus horizon with the underlying ones, mechanical removal of fine particles during harvesting of row crops, etc. The second - weakly humified, the third - medium humified - includes soils that have, to one degree or another, lost transformable organic matter in relation to its content in virgin soil as a result of biological mineralization. The fourth - highly humus - includes arable soils similar in humus content to virgin soils.
The proposed scale of gradation of arable soils in Russia provides a differentiated assessment of humus content, taking into account its transformable component, which to a certain extent characterizes the effective fertility of soils.
A very important point should be noted here. The formation and transformation of humus is a combination of physical, physicochemical, chemical, biochemical and biological processes occurring in the soil. However, its currently used division into labile, active, easily decomposed, on the one hand, and stable, inert, stable groups of fractions, on the other hand, is very conditional. So, for example, if we are talking about humic substances in chernozems, extracted directly with 0.1 n. NaOH solution, then we should talk about lability from the standpoint of chemical fractionation. If biokinetic fractionation of soil organic matter is carried out according to the scheme of Semenov et al., then it characterizes biological soil processes to a certain extent. Transformable organic matter, calculated on the basis of the formula C trans = C tot - C min, most adequately reflects the native lability of soil organic matter, which is the result of various processes.
The problem of necessary and sufficient provision of arable soils with organic matter is becoming increasingly relevant due to the disruption of natural processes in the biosphere and the task of optimizing its management to achieve sustainable and environmentally friendly agriculture.
Within the permissible range of changes in humus content, the task of regulating it on a regulatory basis is quite realistic.

Table 5. Gradations of arable soils of the Russian Federation according to the degree of humus content (humus content in the arable layer, % of the soil mass)

Table 6. Preliminary ranges of changes in humus content (% of soil mass) in typical chernozems (arable layer)

From the standpoint of agroecology, the strategy for applying organic fertilizers, given their limited resources, should be aimed at fertilizing the most plowed soils. At the same time, too high a humus content can be environmentally and economically unprofitable, since it is inevitably associated with the active release of nitrogen, especially during periods when it cannot be used by plants and, consequently, with environmental pollution. For this reason, the standards for the provision of organic matter have an upper limit.
Currently, preliminary permissible ranges for changes in humus content in the main types of arable soils in Russia have been proposed. In table 6, as an example, the ranges of changes in humus content in typical chernozems subject to agrogenic influences are considered.
The basis for determining the values ​​of the optimal humus content is based on the proposals of Kerschens and Schulz, which take into account the amounts of easily decomposed organic matter in the soils of Germany and adjusted for the conditions of Russia. According to these authors, the content of organic carbon and nitrogen in soils has relatively narrow ecological limits, which for German conditions in conventional land use systems amount to 0.2-0.6% of decomposed organic carbon and
0.02-0.06% decomposed nitrogen. When the content is below these limits, soil fertility, crop productivity and CO2 assimilation in the phyto-mass are insufficient; above these limits, losses of organic matter and environmental pollution are observed.

Conclusion
Russian scientists Grishina, Orlov, Biryukova, Rozanova and in “Classification and Diagnostics of Soils in Russia” proposed scales of soil humus content that can be assessed as global, reflecting the genetic affiliation of soils.
In contrast to the global, genetic assessment of the degree of humus content of soils, differentiated assessments have been developed that reflect differences in humus content within a soil type (subtype), including agroecological ones. A scale has been compiled for grading arable soils in Russia according to the degree of humus content, consisting of four classes: humus content is less than the minimum, low humus, medium humus, and highly humus. The proposed scale reflects an agroecological assessment of humus content, taking into account its transformable component, which to a certain extent characterizes the effective fertility of soils.
Approaches have been developed and examples of acceptable standard values ​​of humus content in the arable soil horizon are given, which are based on the proposals of various authors on minimum, maximum (highly humus-rich) and optimal levels of humus content.
Here, first of all, it should be noted that in Russia there is still no information that would allow determining the amount of optimal transformed Corg under the conditions of long-term field experiments conducted on different types of soils. To determine the optimal values ​​of humus content, an expert approach was used with extrapolation of data from other authors. According to Kershens, Schultz, the optimal amount of transformed Corg lies in the range of 0.2–0.6% of the soil mass. There is a priori information that with an increase in the gross humus content, the content of transformed Corg slightly increases; however, the dependence is not clearly defined. The range of humus content in Russian soils is much wider than that in Germany. Therefore, on soils with a Corg content of >3–4% of the soil mass, to determine the values ​​of the optimal humus content, the amount of transformed Corg was >0.6% of the soil mass. If the soils of Russia and Germany were similar in humus content, the above range for the content of transformed Corg was used to determine its optimal values.

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