Classification of fertilizers, their properties

Classification of fertilizers, their properties The enormous importance of fertilizers in increasing the fertility of soils and crop yields is proved by numerous experiments of scientific institutions, and is also confirmed by the practice of world agriculture. According to experts, about half of the entire increase in crop yields is due to the use of fertilizers. The effectiveness of fertilizers in different climatic conditions is not the same and depends on the properties of the soil. Positive effect is exerted by fertilizers on all soils under irrigation and in areas with sufficient moisture. Mineral fertilizers, when properly used, significantly increase the yield, and also improve the quality of the products, so that their use causes a high economic effect.

The whole history of world agriculture testifies to the existence of direct dependence of crop yields on the amount of fertilizers used. The use of fertilizers is of great importance in solving important national economic problems, for example, in increasing the production of grain, wheat and in providing livestock with fodder. The effectiveness of mineral fertilizers depends on their proper application in combination with organic, chemical reclamation techniques in combination with the use of chemical plant protection products, as well as growth regulators in growing varieties with high productivity.

All of the above conditions for the effective use of fertilizers are taken into account with modern technologies of crop cultivation, one of the most important elements of which is to ensure the optimal regime of plant nutrition during vegetation with the help of fertilizers. Fertilizers can be classified into mineral and organic. Mineral fertilizers, in turn, are divided into nitrogen, nitrate, phosphoric, potassium, microfertilizers. Organic include manure, slurry, bird droppings, peat composts, and green fertilizer.


Mineral fertilizers contain nutrients in the form of various mineral salts. Depending on what nutrients enter into them, fertilizers are divided into complex and simple.

Mineral fertilizers are a powerful means of influencing the physical, chemical and biological properties of the soil and the plants themselves. In soil, mineral fertilizers undergo various transformations that affect the solubility of the nutrients contained in them, the ability to move in the soil and accessibility to plants. The nature and intensity of these transformations depend on the properties of the soil. Mineral fertilizers enrich the soil with nutrients, change the reaction of the soil solution, affect microbiological processes, etc. Since the nutrition of plants is mainly through the roots, the introduction of mineral fertilizers into the soil makes it possible to actively influence the growth and development of plants and, consequently, the overall biological productivity of the field, meadows, etc. Proper use of mineral fertilizers is the most effective means of increasing yields Agricultural crops and product quality (technological properties of spinning fiber fibers, sugar beet sugar content, fruits and berries, grain protein content, sunflower oil content Single et al.). The level of provision of mineral fertilizers 1 ha of sowing is one of the main indicators of the intensification of agricultural production crops and its most important industry - agriculture.

Almost all mineral fertilizers are produced by the chemical industry (obtained by processing agronomic ores or by synthesis), in a relatively small amount in agriculture natural salts, such as potassium, sodium (Chilean) nitrate, and industrial wastes are used. For agronomical purposes, mineral and fertilizers are distinguished directly and indirectly. Direct mineral fertilizers (containing elements of direct plant nutrition - N, R, K, Mg, B, Cu, Mn, etc.) are divided into unilateral and complex. Unilateral mineral fertilizers contain predominantly any one nutritive element. These include nitrogen fertilizers (ammonium, sodium, calcium nitrate, ammonium sulfate, urea, etc.), phosphoric (superphosphate, phosphorite flour, precipitate, etc.), potassium (potassium chloride, 30 and 40% potassium salt, Sulfate of potassium, etc.), microfertilizers. Complex fertilizers (double and triple) contain two or more nutrients (nitrophos, ammophos, etc.). Indirect mineral fertilizers are used to improve the agrochemical and physico-chemical properties of the soil and to mobilize its nutrients (for example, calcareous fertilizers, gypsum). The same fertilizer can have a direct and indirect effect.

So, the introduction of phosphate flour not only increases the level of phosphorus nutrition of plants, but also weakens the acidity of the soil. Mineral fertilizers are solid - powdery and granulated (most of them) - and liquid - ammonium water, liquid ammonia, ammonia. Depending on the effect on the reaction of the soil solution, physiologically acidic, alkaline and neutral mineral fertilizers are distinguished. Physiologically acidic include fertilizers whose cations are better absorbed by the soil than the anions, and the latter acidify the soil solution. To physiologically alkaline belong fertilizers, the anions of which are better assimilated by plants, and cations gradually accumulate and alkalinize the soil. Physiologically neutral mineral fertilizers do not change the reaction of the soil solution. The effectiveness of mineral fertilizers is increased in conditions of irrigation and high technology of cultivation. Mineral fertilizers in the crop rotation are used in a certain system, which is called the fertilizer system. It provides for their distribution according to the fields, norms, timing and methods of application, determined from agrochemical analysis of the soil and the results of field experiments.

Mineral fertilizers are applied in autumn or spring (main fertilizer), simultaneously with sowing (seed fertilizer) and during vegetation (fertilizing plants). Ways of application: scattered (with fertilizer drills, from an airplane) with soil plow, cultivator or harrow - the fertilizers are mixed with the soil of the entire arable layer; Local - in rows or holes with the help of combined seeders and planters when sowing seeds, planting tubers, seedlings, seedlings. Mineral fertilizers also process seeds before sowing (dusting, soaking in solution). Incorrect application of mineral fertilizers (for example, excessive doses, poor sealing) can reduce the fertility of the soil, cause the death of plants and animals, pollution of rivers and water bodies. Nitrogen fertilizers, their classification Nitrogen is one of the main nutrients that are necessary for plant life.

Nitrogen plays an extremely important role in the metabolism. It is a part of such important organic substances as proteins, nucleic acids, nucleoproteins, chlorophyll, alkaloids, phosphatides, etc. On average, its content in proteins is 16-18% of the mass. Nucleic acids play an important role in the metabolism of plant organisms. They are also carriers of hereditary properties of living organisms. Therefore, it is difficult to overestimate the role of nitrogen in these vital processes in plants. In addition, nitrogen is the most important constituent of chlorophyll, without which the process of photosynthesis cannot proceed and, therefore, organic substances essential for human and animal nutrition cannot be formed. It should also be noted that nitrogen is an important element in the composition of enzymes, catalysts of life processes in plant organisms. Nitrogen is part of organic compounds, including the most important of them - the amino acids of proteins. Nitrogen, phosphorus and sulfur together with carbon, oxygen and hydrogen are the building blocks for the formation of organic substances and, ultimately, living tissue. The nitrogen content of plants varies significantly, depending on their type, age, soil-climatic conditions of cultivation, methods of farming, etc.

For example, in a family of grain crops nitrogen contains 2-3%, in beans - 4-5%. The greatest content of nitrogen is noted in the vegetative organs of young plants. As they age, the nitrogenous substances move into newly emerged leaves and shoots. Sources of nitrogen for plants can serve as salts of nitric and nitrous acids (nitrates, nitrites), ammonia forms of nitrogen, some organic compounds of nitrogen - urea and amino acids. Bean plants, as is known, assimilate the molecular nitrogen of the atmosphere (N2) with the help of nodule bacteria. However, in whatever form mineral nitrogen enters the process of plant nutrition, in the synthesis of amino acids, proteins and other nitrogen-containing organic substances, it can participate only in the reduced form in the form of ammonium. Therefore, the nitrate nitrogen that enters the plants as a result of the oxidation of carbohydrates is reduced to the anion of nitrous acid, and then to ammonia. The whole complex cycle of synthesis of nitrogenous organic substances in plants begins with ammonia, and their decay ends with its formation.

The nitrogen reserve in the soil is to a certain extent replenished with nitrogen from atmospheric precipitation. Usually it comes in the form of ammonia and, in part, nitrates. These nitrogen compounds are formed in the atmosphere and under the influence of lightning discharges. According to the data of the majority of specialists, from 2 to 11 kg of nitrogen are received annually for each hectare. The listed sources of replenishment of natural nitrogen reserves are of undoubted practical interest, but they deliver only a part of nitrogen, which is carried out with crop yields. Therefore, it is necessary to take measures for -optimal increase in soil fertility and, first of all, replenishment of the stocks of organic and mineral fertilizers. Lack of nitrogen is often a factor limiting crop growth. In nature, there are numerous ways of nitrogen loss.

The main ones are:

  1. Immobilization, that is nitrogen consumption by soil microflora.
  2. Leaching, and especially nitrate forms of nitrogen in groundwater.
  3. Volatilization of ammonia, nitrogen oxides and molecular nitrogen in the air.
  4. Fixation of ammonium in soil or its non-absorption.

Nitrates can accumulate in plants to a certain limit without harm. In addition, the transition of nitrates to ammonia occurs as it is used to synthesize amino acids. There is no synthesis - there is no ammonia from nitrates. Nitrates are the best form of plant nutrition at a young age, when the leaf surface is small, so that photosynthesis is still weak in plants and carbohydrates and organic acids are not formed in sufficient quantities. With the increase in the leaf surface photosynthesis of carbohydrates is intensified, during the oxidation of which organic acids are formed, which, in turn, promotes the binding of ammonia with dicarboxylic acids to form amino acids and then proteins. For crops that contain a sufficient amount of carbohydrates (for example, potato tubers), ammonia and nitrate forms of nitrogen at the beginning of plant growth are almost equivalent. For crops in which carbohydrates contain little (for example, sugar beet), nitrate forms of nitrogen have an advantage over ammonium.

Conditions of nitrogen nutrition have a great influence on the growth and development of plants. With a shortage of nitrogen, their growth sharply worsens. Especially strongly affects the lack of nitrogen on the growth of leaves: they grow smaller, have a light green color, prematurely turn yellow. The stems become thin and branch slightly. Such plants give a low yield. Under normal nitrogen nutrition of plants, the synthesis of protein substances increases, the growth is accelerated and the aging of the leaves slows somewhat. The leaves are intensely green in color, the plants form powerful stems, grow well and bush. Excess nitrogen nutrition during vegetation retards development of plants, they form a large vegetative mass at the expense of reproductive organs.

To develop the leaf surface of the plant at the beginning of life, it is necessary to strengthen the supply of nitrogen. But the excess of ammonia nitrogen during the germination of seeds, poor in carbohydrates, has a negative effect. Ammonia nitrogen in this UANe is not fully used by the plant, accumulates in tissues, causing ammonia poisoning. This is not the UANe with nitrate nutrition. All vegetable crops have high requirements for nitrogen nutrition throughout the growing season. The most intensive increase in cabbage yield is observed in July-August, at which time it absorbs the bulk of nitrogen. Carrots most of all nitrogen assimilates in late August - early September. The intake of nitrogen in cucumbers increases gradually, reaching a maximum during the period of maximum growth of the ovaries. It has been experimentally proved that only 3-4 weeks after the emergence of the shoots, the majority of vegetable crops use the nutrients of the fertilizers applied before sowing to a depth of 20 cm. Lack of nutrition during the initial period of growth, when the root system is still weak and does not penetrate deeply, significantly reduces the subsequent crop.

Therefore, in order to obtain a high crop of vegetable crops, it is necessary to introduce small doses of fertilizers into rows and holes immediately after sowing seeds and planting seedlings, which ensures normal nutrition at an early age. The main place in the range of produced nitrogen fertilizers is occupied by concentrated forms of nitrogen: ammonium nitrate, urea, anhydrous ammonia, as well as complex fertilizers; The share of low-percentage fertilizers, for example, calcium and sodium nitrates, ammonia water, ammonium sulfate, is constantly decreasing. Nitrogen fertilizers are divided into the following groups: - nitrate fertilizers (saltpeter), which contain nitrogen in nitrate form; - Ammonium and ammonia fertilizers (solid and liquid), which contain nitrogen in ammonium and ammonia form; - ammonium nitrate fertilizers, they contain nitrogen in ammonium and nitrate form (ammonium nitrate); - fertilizers in which the nitrogen is in the amide form (urea, or urea); - aqueous solutions of urea (carbamide) and ammonium nitrate, which were called UAN (urea ammonium nitrate).

The production of various nitrogen fertilizers is based on the production of synthetic ammonia from molecular nitrogen and hydrogen. Nitrogen is obtained by passing air into the generator with burning coke, and the sources of hydrogen are natural gas, oil and coke gases. Synthetic ammonia is used not only for the production of urea, ammonium salts and liquid ammonia fertilizers, but also nitric acid, from which ammonium nitrate fertilizers are obtained. Nitrate fertilizers Nitrate fertilizers - sodium and calcium nitrates - make up about 1% of produced nitrogen fertilizers. Sodium nitrate (sodium nitrate, Chilean nitrate) contains 16% nitrogen and 26% sodium. It is a by-product in the production of nitric acid from ammonia and is a fine crystalline salt of white or yellowish-brown color, highly soluble in water. It has a weak hygroscopicity. If this fertilizer is stored in unsuitable conditions for it, then it may be clogged. With proper storage, it retains good dispersibility. Calcium nitrate (calcium nitrate) contains about 13% nitrogen.

It is obtained by neutralization of nitric acid with lime, and also as a by-product in the production of complex fertilizers - nitrophos - by the nitric acid processing of phosphates. Calcium nitrate is a white crystalline salt that is highly soluble in water. Has high hygroscopicity. If the storage conditions are incorrect (for example, if the humidity in the room is too high), it becomes damp, cracks and fades. Store and transport it in a special waterproof packaging. To reduce hygroscopicity, calcium nitrate is granulated using hydrophobic coatings. Calcium and sodium nitrates are physiologically alkaline fertilizers. Plants consume more anions than cations. The use of calcium nitrate on acidic, poor soils gives good results. When it is applied, the acidity decreases, and the physical properties of the soil improve.

In a humid climate or with abundant irrigation, nitrate nitrogen can be washed out of the soil, and also lost as gaseous products during denitrification. It is not recommended to add saltpeter in autumn, it is better to seal them in spring under pre-sowing cultivation. These fertilizers can be used as top feeding of winter and tilled crops, and sodium nitrate - in the sowing of sugar beet, fodder and table roots in rows. The effectiveness of sodium nitrate is associated with the role of sodium. It increases the outflow of carbohydrates from the leaves, which increases the yield of root crops and the content of sugar in them. Ammonium and ammonium fertilizers Solid ammonium fertilizers account for approximately 4% of the total production of nitrogen fertilizers. The production of solid fertilizers is constantly increasing. Solid ammonium fertilizers include ammonium sulfate and ammonium chloride.

Ammonium sulphate contains about 21% nitrogen. Ammonium sulphate is a crystalline salt that is highly soluble in water. The hygroscopicity of the fertilizer is weak, under normal storage conditions it is cracks little and retains good dissipation. Ammonium sulfate is obtained by trapping ammonia from sulfuric acid from gases that are formed during the coking of coal, or by neutralization of spent sulfuric acid by synthetic ammonia by various chemical industries. A large amount of ammonium sulfate is produced as a by-product in the production of caprolactam. Synthetic ammonium sulfate is white, and the coke oven has a gray, bluish or reddish color. Fertilizer contains 24% sulfur and serves as a good source of this nutrient for plants.

Ammonium chloride is a by-product of soda production. Fertilizer contains about 25% nitrogen. For crops it is of little use, since it contains a large amount of chlorine. Ammonium sulphate and ammonium chloride are physiologically acidic fertilizers. With a single application of moderate doses of these fertilizers, acidification of the soil is not observed, but if used continuously, low-buffered soils are significantly acidified. After application to the soil, ammonium fertilizers quickly dissolve in soil moisture and enter into exchange reactions with cations.

Absorbed ammonium is readily available to plants. Its mobility in the soil and the danger of washing out under normal humidification conditions are reduced. Ammonium fertilizers are best made with the help of special machines in the autumn under plowing. For fertilizing it is better to use nitrate fertilizers, ammonium is used before sowing as the main fertilizer. Over time, the difference in mobility of nitrate and ammonium fertilizers is smoothed, as ammonium nitrogen is gradually subjected to nitrification and passes into the nitrate form. Ammonium chloride is nitrified more slowly than ammonium sulfate, which is due to the negative effect of chlorine on the activity of nitrifying bacteria. With the constant use of ammonium fertilizers, especially in low-buffered and weakly cultivated sod-podzolic soils, active, exchange and hydrolytic acidity increases, the degree of soil saturation with bases decreases, the content of mobile forms of aluminum and manganese increases. As a result, the conditions for plant growth deteriorate and the effectiveness of fertilizers decreases. There is a growing need for liming. Acidifying effects of ammonium fertilizers are strongly affected by cultures sensitive to soil acidity, such as wheat, barley, cabbage, beet.

For these plants, ammonium fertilizers have been less effective than nitrates since the first years of their use. Good soil filling with manure, increasing its buffering, also reduces the negative effect of these fertilizers on soil properties and is of great importance for more effective use. Liquid ammonium fertilizers include anhydrous ammonia and ammonia water. Anhydrous ammonia contains 82% nitrogen. It is obtained by liquefying gaseous ammonia under pressure. In appearance, colorless, mobile liquid, boiling point 20°C. When stored in open vessels quickly evaporates. Anhydrous ammonia has a high vapor pressure, so it is stored and transported in steel cylinders or cisterns that withstand high pressures.

Ammoniac water is an aqueous 25% - and 22% ammonia solution, produced in two varieties with a nitrogen content of 20, 5% and 18%. The solution is a colorless or yellowish liquid with a sharp smell of ammonia. The vapor pressure is small. Transport and storage of ammonia water is necessary in hermetically sealed tanks, which are designed for low pressure. The advantage of liquid nitrogen fertilizers lies in the fact that production and use of them are much cheaper than solid ones. In the production of liquid ammonium fertilizers, there is no need to build nitric acid plants, as well as crystallization, evaporation, granulation, drying, which significantly reduces the capital investment for the construction of a nitrogen fertilizer plant of equivalent capacity. When used correctly, liquid nitrogen fertilizers produce the same crop yield increases as an equal dose of nitrogen in ammonium nitrate.

Liquid ammonium fertilizers are introduced by special machines, which ensure their immediate fixation to a depth of 12 cm on heavy soils and up to 18 cm on light soils. The superficial application of these fertilizers is unacceptable, since ammonia rapidly evaporates. With a small embedding, its significant losses are possible, especially on light sandy and sandy loamy soils. Of the moist soil, the loss of ammonia is much less than that of dry soil. With the introduction of liquid ammonium fertilizers, the ammonium ion is absorbed and therefore weakly moves in the soil. In the first days after fertilization, the soil becomes alkaline, and then, as the ammonia nitrogen is nitrified, its reaction shifts toward acidification. When fertilizer nitrogen is nitrified, its mobility in the soil increases.

In the zone of the introduction of anhydrous ammonia, temporary sterilization of the soil occurs and the rate of nitrification slows down. Liquid ammonia fertilizers can be used for basic application to all crops not only under pre-sowing cultivation, but also in autumn under plowing. They can also be used for fertilizing tilled crops. In this UANe, in order to avoid burns of plants, fertilizers are closed in the middle of the rows or at a distance of not less than 12 cm from the plants. When working with liquid ammonia fertilizers, observe safety rules, as ammonia vapor causes irritation of the mucous membranes of the eyes and respiratory tract, asphyxiation and coughing. When inspecting and repairing containers from these fertilizers, precautions should be taken, since the ammonia-air mixture is explosive. Ammonium nitrate fertilizers Ammonium nitrate is the main nitrogen fertilizer, which contains 34% of nitrogen. Fertilizer is released in the form of white crystals or granules up to 3 mm in size (spherical, in the form of scales, plates).

Ungranulated crystalline ammonium nitrate has a high hygroscopicity, it is caked when stored, so it should be stored in waterproof bags in a dry place. Granulated nitrate, produced for agriculture, is less hygroscopic, less cracks, retains good dissipation, especially if special conditioning additives are introduced into it in the process of obtaining fertilizer. Ammonium nitrate is a highly soluble, highly concentrated, universal fertilizer. It can be applied to any crops and on all soils before planting, when planted in rows or wells and as a fertilizer. In fertilizers, half of the nitrogen is in the nitrate, half in the ammonium form. Ammonium nitrate is a physiologically acidic fertilizer, but it acidifies the soil weaker than ammonium sulfate. On soils saturated with bases, calcium nitrates are formed in the solution, and the soil solution does not acidify even with a constant application of high doses of fertilizer. For such soils, ammonium nitrate is one of the best forms of nitrogen fertilizers. On acid sod-podzolic soils containing little calcium and many hydrogen ions in the absorbed state, as a result of which the soil solution is acidified, acidification is temporary, since it disappears with the consumption of nitrate nitrogen by plants.

At first, especially with the introduction of a large dose of ammonium nitrate and its uneven sieving, pockets with high acidity can be created in the soil. With long-term use of ammonium nitrate on low-buffered sod-podzolic soils, acidification can be very strong, as a result, the effectiveness of this fertilizer, especially when applied under crops sensitive to increased acidity, is markedly reduced. To increase the efficiency of ammonium nitrate on acidic soils, their liming is of great importance. On acid soddy-podzolic soils, a higher effect, especially with constant use, yields neutralized, or calcareous, ammonium nitrate. It contains up to 23% nitrogen and is obtained by fusing or mixing ammonium nitrate with an equivalent amount of lime, chalk or dolomite.


Urea (carbamide) contains at least 46% nitrogen. It is obtained by synthesis from ammonia and carbon dioxide at high pressures and temperatures. White fine crystalline product, highly soluble in water. Hygroscopicity at a temperature of up to 20 ° C is small. Under good storage conditions, little cracks, preserves normal sowing. Granular urea has good physical data. During the granulation of urea, a biuret is produced which has a toxic effect, but its content in the granulated fertilizer does not exceed 1% and is almost harmless to plants in the usual ways of use. In the soil under the influence of urobacteria secreting the urease enzyme, urea is ammoniated for 2-3 days to form ammonium carbonate. In the first days after the introduction of urea due to the formation of a hydrolytic alkaline salt, local alkalinization of the soil takes place.

The resulting alkaline salt is absorbed by the soil and gradually nitrified, with the nitrification proceeding more quickly, and the temporary alkalinization of the soil is replaced by some acidification. On low buffered light soils, the shifts in the reaction of the soil solution can be particularly noticeable. Urea is one of the best nitrogen fertilizers and is equivalent in efficiency to ammonium nitrate. It can be used as the main fertilizer or as a fertilizer for all crops and on various soils. When urea is applied to the soil, it must be pre-insulated in advance, since with the surface placement of the fertilizer, nitrogen losses are possible due to the volatilization of ammonia from ammonium carbonate, which readily decomposes in the air.

Significant losses in the form of ammonia can occur when using urea in top feeding in meadows and pastures, since the sod has a high urease activity. In addition, urea can be used for foliar top feeding of vegetable and fruit crops, as well as for late fertilizing of wheat in order to increase the protein content in the grain. Unlike other nitrogen fertilizers, urea does not even burn the leaves, even in high concentrations, and at the same time is well absorbed by plants. Also, urea is used in animal husbandry as a nitrogen supplement to carbohydrate feeds. Aqueous solutions of ammonium nitrate and urea As liquid nitrogen mixtures, ammonia and UAN are used. Ammonia is a solution obtained by the combined or separate dissolution in ammonia water of a predetermined amount of ammonia or calcium nitrate, carbamide or other nitrogen-containing substances.

UAN is called liquid nitrogen fertilizers, consisting of aqueous solutions of carbamide and ammonium nitrate. Unlike liquid ammonia fertilizers, UAN almost does not contain free ammonia, it can be introduced with the help of high-performance ground assemblies without simultaneous sealing in the soil. UAN with a corrosion inhibitor can be transported in conventional rail tank cars and tank trucks, especially the transportation of UAN by pipelines and by water transport. The low temperature of crystallization and freezing makes it possible to transport and store UAN throughout the year, especially in buried natural storage tanks of concrete and asphalt with internal film coating, reinforced fiberglass or mild steel. UAN has a high density, which allows to significantly reduce capital investments for transportation and storage. When using the UAN, a high accuracy of dosing and uniformity of application over the entire area is ensured. For transportation and application of the UAN, the same technique as for liquid complex fertilizers and ammonia water can be used.

The use of UAN in agriculture has its advantages over solid fertilizers.

  1. First, full mechanization of all loading and unloading operations, reduction of costs for production and use.
  2. Secondly, working conditions improve, the consumption of packaging, ensuring the uniformity of nitrogen application and dosing is eliminated.
  3. Thirdly, it is easy to prepare the necessary fertilizers, including those with the addition of trace elements and pesticides.

Liquid nitrogen fertilizers lack the drawbacks that are often observed in solid fertilizers. They have free flowing, do not dust or cake. Raw weather and even rain do not have a negative impact on them. Also they are much cheaper than solid, and less labor costs for their introduction. In the soil, liquid nitrogen fertilizers are introduced by trailed or mounted machines in a unit with plows or cultivators to a certain depth (to avoid ammonia losses): ammonia water and ammonia - by 10-12 cm, liquid anhydrous ammonia - by 15-20 cm (depending on Mechanical composition of the soil). Liquid fertilizers can be used not only in spring, but also at the end of summer (under winter crops sowing) and in autumn (for spring next year harvest).

Solutions of ammonium nitrate and urea (up to 30-32%) do not contain ammonia, so they can be applied as a fertilizer, spraying on the surface of the soil. Doses of liquid fertilizers (nitrogen) are the same as for solid nitrogen fertilizers. Complex liquid fertilizers are aqueous solutions containing up to 27% nitrogen, phosphorus and potassium. With the introduction of stabilizing additives, for example colloidal clay, bentonite, which protect the solution from crystallization, the concentration of nutrients in the fertilizer can be increased to 40%. Complex liquid fertilizers do not contain free ammonia, so they can be applied superficially for plowing, cultivation or harrowing and in rows when sowing. From the point of view of consumer properties, the use of solutions (suspensions) makes it possible to completely mechanize labor-consuming processes of loading and unloading fertilizers and introducing them into the soil. Increasing the effectiveness of nitrogen fertilizers Until recently, it was believed that plants use up to 80% nitrogen fertilizers.

The coefficient of nitrogen use by plants was determined by the difference method (by the difference in nitrogen removal with the yield when nitrogen was introduced and without application) and expressed as a percentage of the applied amount of fertilizer. The use of the method of labeled atoms in agrochemical studies made it possible to establish that in the field conditions plants absorb directly from fertilizers only 30-50% of nitrogen. However, when nitrogen fertilizers are introduced, the mineralization of soil nitrogen and its assimilation by plants are intensified. The coefficients of nitrogen use of various forms of nitrogen fertilizers do not differ significantly.

The conversion of nitrogen into an organic form increases sharply when an organic substance with a low nitrogen content is soaked into the soil. Fixed nitrogen is slowly mineralized and poorly absorbed by plants. Nitrogen losses during the denitrification of nitrates formed during the nitrification of ammonium nitrogen in soil and ammonium nitrogen fertilizers and urea, as well as from nitrate nitrogen fertilizers, are very significant. Nitrogen fertilizer losses increase sharply in steaming soil and reach 50%. The most intensive gaseous losses of nitrogen during biological and indirect denitrification occur in the first 20 days after the introduction of nitrogen fertilizers and under conditions of limited biological absorption in the soil. With increasing doses of nitrogen fertilizers, losses increase. Nitrogen fertilizer losses due to leaching of nitrates on cohesive soils are insignificant, and on lightly drained soils with a washing regime of moistening can be significant.

Large losses due to volatilization of ammonia are observed when the technology of introducing ammonium forms of liquid nitrogen fertilizers is violated, as well as in the UANe of surface application and untimely termination of urea in carbonate and alkaline soils. Increasing the efficiency of fertilizer nitrogen and reducing losses are provided by increasing the amount of nitrogen absorption by agricultural crops by optimizing the regime and conditions of plant nutrition, as well as agrotechnical measures and creating a favorable water regime and soil response. Under the influence of nitrogen fertilizers, the mineralization of organic matter intensifies, and not only the absorption of soil nitrogen by plants, but also its loss. Losses of nitrogen fertilizers can be reduced by increasing the immobilization or inhibition of mineralization of organic matter of soils by introducing organic fertilizers, including straw, agrotechnical soil conservation and conservation measures, cultivation of stubble and intermediate crops, cultivation of grasses, use of green fertilizer.

To avoid nitrogen losses and eliminate the danger of contamination with plant nitrates and the environment, new forms of nitrogen fertilizers are being developed-slowly soluble, nitrogen-capsulated at a controlled rate of nitrogen release, modified with nitrification inhibitors. The last preparations, when applied to the soil in small doses, inhibit nitrification within two months and preserve the mineral nitrogen of soil and fertilizers in ammonium form. By suppressing the nitrification of fertilizer nitrogen, inhibitors reduce its losses in gaseous form by 2 times as a result of leaching of nitrates. As a result, yields of different crops and the efficiency of nitrogen fertilizers are increasing. Phosphorus fertilizers Phosphorus (more precisely, its oxide P2O5) - a relatively common in nature element. Its content in the earth's crust is 0, 08-0, 125% of the total mass. Today there are about 120 known minerals, which include phosphorus.

Apatite ores, contained in phosphoric ores, are used for the production of phosphorus fertilizers. Phosphoric ores, in turn, are included in the concept of agronomic ores used in the production of mineral fertilizers. Phosphoric ores are divided into very rich in content, they contain up to 35% phosphorus; The rich, containing 28-35% of phosphorus; Medium quality - 18-28% phosphorus; Poor - 10-18% of phosphorus; Very poor - 5-10% phosphorus; Phosphate-containing - 0, 5-5% phosphorus. In their origin, phosphorus ores are divided into apatites, rocks of endogenous origin, and phosphorites, rocks of exogenous origin. The pure mineral of apatite contains up to 42% of phosphorus, but in production the percentage of apatite in the ore is slightly lower (15-20%) because of the presence of other minerals in it. Apatite is a colorless mineral with a greenish or yellowish-green tinge with a hexagonal shape of crystals.

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