Chemical soil reclamation briefly. Chemical soil reclamation - Knowledge Hypermarket. What does liming negative give?

Land reclamation- these are measures aimed at radical and accelerated comprehensive cultivation (expanded reproduction of fertility) of unproductive soils, protecting them from degradation and eliminating negative phenomena during land use as a result of improving their morphology, composition, properties and regimes. Among various reclamation measures aimed at improving the quality of agricultural land, chemical soil reclamation occupies one of the leading places in the intensive farming system.

Chemical soil reclamation called a set of measures aimed at radically improving its properties in order to increase the productivity of agricultural crops. This is the replacement of undesirable cations in the soil absorption complex (hydrogen, aluminum, iron, manganese in acidic soils and sodium - in alkaline soils with calcium). Excessive soil acidity is eliminated by liming, and excessive alkalinity is eliminated by gypsum. Chemical reclamation is carried out before applying fertilizers in order to create an optimal reaction of the soil solution, better absorption of nutrients from the soil and applied fertilizers. It is usually carried out once per crop rotation or after several years. The main target is to create a high buffer capacity of soils, ensure their sustainable functioning in different conditions external influences and loads. Chemical soil reclamation should not be understood too simplistically - only as a way to neutralize excess acidity or alkalinity. As its components, it is also necessary to consider methods for the radical enrichment of soils with nutrients, the use of natural and artificial ameliorants (the so-called structural ameliorants) to create a stable organo-mineral complex in it, irrigation water with additives appropriate for reclamation active substances, the involvement in reclamation action (for example, as a result of planting) of subsoil material resources and others, including indirect effects, radically change the agrochemical quality of the soil.

Chemical ameliorants - substances or mixtures of substances of natural or technogenic origin that are introduced into the soil for the purpose of chemical reclamation (gypsum, phosphogypsum, chalk, defecate, rocks containing more than 10% calcium compounds - loess, red-brown clays, calcium-iron-containing sludge from metallurgical and other enterprises, etc.).

Soils with high acidity are most common in Polesie, in the western regions of the Forest-Steppe and the Carpathian brown earth-forest region. Solonetz complexes and re-alkalinized soils are found in almost all regions of Left Bank Ukraine, but their largest areas are in the Southern Steppe.

The regions where soils are distributed are sufficiently provided with moisture (HTC> 1), with a less continental climate and a predominance of eluvial (flushing, stagnant-flushing) type of soil formation. IN southern regions On the contrary, moisture deficiency and accumulative (non-leaching) type of soil processes predominate. The soils of the Forest-Steppe occupy intermediate position- they are characterized by both eluvial and accumulative types of soil formation. They occupy almost 35% of the total agricultural land area and have varying acid-base buffering capacity. Soil acid-base buffering capacity - this is its ability to counteract the phenomena of acidification or alkalization and neutralize the addition of acid or alkali introduced into it.

Natural soil acidity is formed during the transformation of the organic part of the soil. When the content of alkaline earth metals and protein compounds in plant residues is low, primarily in an anaerobic environment, the fermentation process ends with the formation of various organic acids. They strongly acidify the soil, especially in the absence of their neutralizers.

For entering the soil large quantity In the presence of organic substances, clay processes begin to develop intensively, which weaken the crystal lattices of clay minerals and lead to the formation of free oxides of aluminum and iron. These oxides, together with reactive organic acids, form complexes and are washed out from the upper part of the soil profile.

An important role in the formation of the acid-base regime is played by the buffer properties of soils, such as their ability to resist secondary acidification or alkalization. This ability is assessed by buffer capacity - a dimensionless value, which is determined in the acid and alkaline load ranges and is usually indicated on a 100-point scale (Table 4.1).

Table 4.1. Soil classes by acid and alkaline buffer capacity(S. A. Balyuk, R. S. Truskavetsky, Yu. L. Tsapko et al., 2012)

Subject. Chemical soil reclamation. Gypsuming of solonetz soils

Basic theoretical principles

Melioration (from Latin melio - improve) this is a system of measures to improve the properties and regime of soils in favorable production and environmental directions. Reclamation ensures the creation of the most important conditions for obtaining high and sustainable yields, rational use of soils, improves production, and qualitatively changes the conditions and productivity of labor. It should be borne in mind that reclamation is only part of a complex set of measures aimed at optimizing the process of agricultural production and the total volume of soil productivity.

1. Distribution of solonetz soils and the need for their improvement

The objects of chemical reclamation are the ion-exchange and colloid-chemical properties of the soil, its acid-base characteristics, salt and microaggregate composition, which in their interrelation determine the chemical and reclamation state of the soil and can be improved using various techniques and methods. Soil colloids have absorption capacity; they are the most reactive highly dispersed part of the soil, which includes water-insoluble aluminosilicates, humic substances and organomineral compounds. This entire complex conglomerate of compounds, capable of exchanging the cations of calcium, magnesium, sodium, hydrogen, aluminum, etc. contained in it for any cations of natural and artificial solutions, is called soil absorption complex.

Solonetz soils and solonetzes are soils containing an increased amount of exchangeable sodium (or magnesium) in the PPC of one of the horizons of the soil profile - illuvial or transitional horizon B, located under the uppermost soil horizon A. The process of accumulation of absorbed sodium in the soil absorption complex is called the process of solonetsization. Typically, solonetzes are found in combination with zonal soils - brown, chestnut, chernozem, forming patches ranging in size from several square meters to tens of hectares. About 20% solonetz soils falls in the zone of chernozems, and their main areas are in the zone of chestnut soils, i.e. in areas with the most fertile soils. However, the extremely unfavorable agronomic indicators of solonetzes do not allow the use of favorable natural and climatic conditions and sharply reduce the overall productivity of zonal soils.

The share of solonetzic soils in Russian Federation accounts for 30 million hectares, which is 17.5% of agricultural land. In Siberia, solonetz soils occupy 16% of the area of ​​agricultural land and 12% (7 million hectares) of the area of ​​arable land. In the Krasnoyarsk Territory, in the forest-steppe zone (Kansky, Dzerzhinsky districts), solonetz soils with soda-type salinity are formed. In the steppe (Khakassia) and dry-steppe (Tuva) zones of the region, soils of the solonetz complex with mixed and neutral types of salinity were found; they account for 127 thousand. ha.

The beginning of an in-depth study of the genesis and reclamation of solonetzes was laid in the works of the famous soil scientist-chemist K.K. Gedroits, the author of the colloid-chemical theory of the solonetz process. According to this theory initial stage The process is the entry of sodium salts into the upper soil horizons from salt-bearing deposits or salty groundwater under the influence of capillary forces or hydrostatic pressure. When the level decreases groundwater and the cessation of their upward migration, further salinization not only stops, but the process of desalinization and leaching of salts into the lower soil horizons begins. In accordance with the theory of K.K. Gedroits, the second stage of the solonetz process begins - the formation of solonetz, in which three characteristic phases are distinguished. Firstly, the removal of soluble salts from the upper soil horizons; 2) formation of soda; 3) dispersion of soil particles and their removal down the soil profile. With desalinization and a decrease in the concentration of soluble salts below the coagulation threshold, peptization of colloids containing absorbed sodium occurs and partially transform into sol, so soil aggregates are dispersed. Peptized organic colloids are destroyed and washed out of upper layers soils into the lower ones, mineral colloids disintegrate and are redistributed, forming an illuvial horizon with a maximum content of absorbed sodium.

Although the main reason for the development of the solonetzic process is considered to be exchangeable sodium, in nature there are soils with pronounced solonetzic properties, the absorption complex of which contains a small amount of exchangeable sodium and a significant proportion of magnesium. The works of a number of researchers (A.N. Sokolovsky, 1938, A.M. Mozheiko, 1965, V.A. Kovda, 1963) have established that at a certain ratio of sodium and magnesium in the soil absorption complex, magnesium performs significant role in the formation of soil salinity. By introducing itself into the soil absorption complex, it, although to a lesser extent than sodium, increases the hydrophilicity of colloids, disrupts the connections between individual soil microaggregates, and causes the appearance of unfavorable agrochemical properties characteristic of solonetzes.

Solonetz soils have low natural fertility. This is explained, first of all, by their negative water-physical-mechanical properties. Their swelling properties increase. During the dry period, the clayey mass of solonetzes is compressed, undergoes consolidation, and turns into a dense, solid mass that cannot be processed. The solonetz horizon prevents penetration deep into the root system of plants. Compression is accompanied by ruptures. A complex network of large cracks appears. It is especially clearly manifested in the illuvial layer of solonetz, where columnar horizons are formed. Solonetzes arise under conditions of periodically leaching water regime, when a relatively short-term stage of watering the profile is replaced by drying. During the period of watering under anaerobic conditions, intensive hydration of colloids and their swelling occur. During the wet period, the illuvial horizons of solonetzes often become waterproof and absolutely impermeable, and during the dry period, the surface horizons can have very high, sometimes failing, water permeability. This explains the blocky nature of solonetzes, their low fertility and the difficulty of cultivation.

In addition to negative agrophysical qualities, solonetzes are characterized by increased alkalinity in the B horizon, which has a detrimental effect on cultivated plants and most soil microorganisms. As a result of an exchange reaction between absorbed sodium and calcium bicarbonate or carbonic acid in the soil solution of solonetzic soils, sodium carbonate salts are formed, which, being hydrolytically alkaline, create an increased alkalinity of the solution:

(P.P.K) 2Na + Ca(HCO 3) 2 (P.P.K)Ca + 2NaHCO 3. Soda, present in the surface horizons of the profile, a salt of a strong base and a weak acid, undergoes active hydrolysis: Na 2 CO 3 + 2H 2 O > 2NaOH + H 2 CO 3 .

With an alkaline reaction, the metabolism in plants is disrupted, the solubility and availability of compounds of iron, manganese, boron, phosphate salts of calcium and magnesium in the soil decreases, and photosynthesis processes are inhibited. The hygroscopicity of salts sharply reduces the amount of soil moisture available to plants. All these negative features of solonetz soils lead to a slowdown in plant development, a sharp decrease in yield, and often to the death of agricultural plants. The effect of soil salinization on the development of field crops depends on the biological characteristics of each individual crop, as well as on the degree and chemistry of salinization and on other agrochemical indicators of the soil: its moisture content, nutrient reserves. The maximum salt tolerance of agricultural crops is expressed by the permissible chlorine content in the soil for their cultivation and for most cultivated plants is in the range from 0.04 to 0.01%. Grains, sugar beets, and cotton are more resistant to salinity; melons and melons are less resistant. Among the tree crops and shrub species that are resistant to salinity are small-leaved elm, yellow acacia, Tatarian maple, and golden currant. Not all salts are equally toxic to plants. Soda is the most harmful to field crops; sodium chloride and sulfate are less toxic.

2. The meaning and essence of gypsuming of solonetz soils

Agricultural use of solonetzic and solonchak soils is possible only after their radical chemical reclamation aimed at desalinizing the soil. Reducing soil salinity can be achieved by mechanical, biological and physicochemical methods.

The improvement of solonetzic soils should be approached in a differentiated manner, depending on their degree of salinity, the amount of precipitation, and the presence or absence of irrigation. Depending on the amount of solonetzic soil, soils are divided into the following groups: non-solonetzic - containing absorbed sodium no more than 5% of the absorption capacity; slightly solonetzic 5-10%; moderately solonetzic - 10-20% and highly solonetzic (absorbed sodium more than 20%), this includes solonetses.

Solonetzes have the highest degree of salinity. Based on the nature of salinity, two groups of solonetzes are distinguished.

1) soda and soda-sulfate (alkaline) meadow and meadow-steppe types, found mainly in the chernozem zone;

2) chloride-sulfate and sulfate-chloride (neutral), common in the zone of chestnut and brown soils.

In addition to absorbed sodium, solonetzes of the first group contain water-soluble salts that have high alkalinity (NaHCO 3 and Na 2 CO 3).

The main way to radically improve these soils is gypsum, i.e. introducing CaSO 4 *2H 2 O gypsum into the soil as a reclamation agent. The theoretical justification for gypsuming solonetzes was given in the works of Academician K.K. Gedroits. When gypsum is added to solonetz soils, the following reaction occurs:

PPK] Na Na + CaSO 4 *2H 2 O >PPK] Ca + Na 2 SO 4 .

When gypsum is added to the soil, soda is eliminated from the soil solution, absorbed sodium is displaced and replaced by calcium to form a highly soluble neutral salt, sodium sulfate. Thus, this technique eliminates the alkaline reaction of solonetz soil. The replacement of absorbed sodium with calcium is accompanied by coagulation of soil colloids; Young humic substances formed during the decomposition of plant residues in the presence of calcium glue soil lumps together, so the soil acquires a strong lumpy structure, its physical properties, water permeability and aeration improve, and processing becomes easier. By eliminating alkalinity and improving the physical properties of the soil, gypsum creates favorable conditions for the development and activity of soil microorganisms. Therefore, under the influence of gypsum, the physical, physicochemical and biological properties of solonetzic soils improve, their fertility increases, and they become suitable for cultivating even very demanding crops.

3. Calculation of gypsum dose

The dose of gypsum is determined by the content of exchangeable sodium and is determined by the formula: CaSO 4 * 2H 2 O = 0.086 (Na – 0.1 * CEC) * h * d, Where

An indispensable condition for successful reclamation is the removal of by-products of the gypsum reaction (Na 2 SO 4) from the root-inhabited soil horizons, in order to avoid its secondary salinization, and this is achieved with sufficient natural moisture. Therefore, it is advisable to combine gypsum with measures that enhance soil leaching (snow retention, drainage), especially effective under irrigation conditions. Irrigation helps remove sodium salts from the soil and prevents the possibility of secondary alkalinization or salinization of the soil. Under irrigation conditions, the reclamation effect can be achieved in a relatively short period of 2-3 years. Under rainfed farming conditions, the chemical method (gypsuming) is most effective in the steppe zone with an annual precipitation of 400-450 mm for the reclamation of chernozem and meadow-chernozem solonetzes.

In the dry steppe and desert-steppe zones with an annual precipitation of 200-300 mm, chemical reclamation of chestnut and brown semi-desert solonetzes is possible only under irrigation conditions.

In the steppe zone, the best place for chemical reclamation is clean fallow. If there is a deficiency or absence of them, gypsuming is carried out for row crops. In the forest-steppe zone the best place for gypsum a field prepared for sowing sugar beets, and in the steppe corn. In forage crop rotations, gypsum is applied under perennial grasses.

The ameliorating effect of gypsum depends on the degree of its mixing with the soil. Therefore, gypsum must be incorporated under deep fall plowing so that the solonetz horizon can be better mixed with it and the upper above-solonetz horizon. Moreover, the methods of adding gypsum depend on the depth of the solonetz horizon. During conventional plowing of deep columnar solonetzes, the solonetz horizon is turned to the surface to a small extent or is not affected at all by the treatment. Under these conditions, 75% of the dose of gypsum is applied for plowing and 25% - superficially for cultivation. When plowing small solonetzes, a significant part of the solonetz horizon is turned to the surface. Half of the dose of gypsum is applied to them for plowing or scattered on the surface, followed by mixing it with the arable layer by harrowing, the second half is for cultivation. After adding gypsum, water-recharging irrigation is carried out.

Solonetzes solonchaks of soda salinity, having negative agrochemical characteristics, are also distinguished by high pH values ​​and the presence of bicarbonates and sodium carbonates, which are very toxic to plants.

In soda salinity soils, due to the alkaline reaction of the soil solution, the solubility of calcium compounds is greatly suppressed. Therefore, despite the high content of calcium carbonate in these soils, plants experience calcium starvation, and this, in turn, enhances the inhibitory effect of high Ph values ​​on plants. Due to the low solubility of calcium compounds, the use of calcium-containing ameliorants on soda solonetzes is ineffective and it is advisable to acidify the soil with strong mineral acids. Sulfuric acid is most often used for reclamation of soda-salinized soils. At acidification Soda solonetzes undergo their radical improvement: neutralization of alkalinity, decomposition of carbonates with their transition into sulfates and bicarbonates of calcium and magnesium and the formation of finely dispersed gypsum, displacing exchangeable sodium from the PPC:

Na 2 CO 3 + H 2 SO 4 = Na 2 SO 4 + H 2 CO 3 >CO2 >H2O

CaCO 3 + H 2 SO 4 = CaSO 4 + H 2 CO 3 >CO2 >H2O

PPC] 2 Na + CaSO 4 = PPC] Ca + Na 2 SO 4

As a result of these processes, coagulation of hydrophilic soil colloids occurs with a decrease in dispersity, improvement of the filtration properties of the soil, and improvement of its calcium and nutritional regimes. The acidification process is carried out by directly supplying sulfuric acid from the tank to irrigation systems, where it is diluted to a concentration of 0.8-1.0% by adjusting the water supply rate and treating the soil with the resulting solution.

For radical reclamation, the acid rate is calculated per meter layer of soil, and the leaching rates after reclamation treatment reach 17 thousand m 3 /ha. Reclamation work is carried out against the background of deep closed drainage.

In the practice of reclamation of soils affected by soda salinity, iron sulfate (iron sulfate) is also used as a chemical ameliorant.

Iron sulfate is a hydrolytically acidic salt, which, when interacting with water, forms iron hydroxide and free sulfuric acid, which affects saline soils according to the mechanism described above. The reclamation effect of using iron sulfate is enhanced by its sedimentation effect on dispersed fractions of the soil. As a result of sedimentation of hydrophilic colloids under the influence of the divalent iron cation, the structure of the soil increases, the filtration properties of the soil improve, and the process of desalination accelerates. Iron sulfate introduced into the soil enters into exchange reactions with carbonates and bicarbonates of sodium, calcium and magnesium. In this case, the soil solution is enriched with soluble sodium and magnesium salts, which are carried into the soil during subsequent leaching. drainage water. However, when ferrous sulfate is added, an increase in the concentration of mobile forms of iron in the soil is observed, which leads to the fixation of available phosphorus and a deterioration in the phosphorus supply of plants. Therefore, soils reclaimed with iron sulfate require the application of phosphorus fertilizers.

The high solubility of iron sulfate (about 20% at 20 0 C) allows the ameliorant to be applied to the soil together with irrigation water, as well as with other ameliorants, for example, phosphogypsum. Sulfuric acid formed during the hydrolysis of iron sulfate destroys the calcium carbonate film formed on gypsum grains and helps to increase its reclamation activity. The costs of complete reclamation of soda salt licks with iron sulfate are recouped in 6-8 years.

4. Gypsum ameliorants

Plastering is an expensive undertaking, and poorly soluble gypsum is a slow-acting ameliorant. Among natural compounds containing calcium in reclamation of solonetzes greatest distribution received clay gypsum, carbonate-gypsum rock, phosphogypsum, raw-ground gypsum. Clay gypsum contains 70-90% gypsum, up to 11% calcium carbonate, admixtures of magnesium, sodium, potassium, a number of trace elements: copper and manganese. Clay gypsum is an effective ameliorant, especially under irrigation conditions, and has a positive effect on the soil and its fertility for 5-6 years after application.

A similar effect on solonetz soils is exerted by carbonate-gypsum breed. It's easy to get open method and doesn't need preliminary preparation and processing, and in terms of reclamation effect it is not inferior to gypsum.

Phosphogypsum is a large-scale waste from the production of double superphosphate and precipitate. It is a very fine gray or white powder containing 75-85% gypsum, 0.5-0.6% phosphoric acid, 5-6% clay and water. Phosphogypsum is much cheaper than gypsum, has higher solubility, and the presence of water-soluble phosphorus in it enhances the reclamation effect. Its use is somewhat complicated by its high hygroscopicity, so it is recommended that phosphogypsum be dried and granulated in a factory so that it contains no more than 15% free moisture.

Raw ground gypsum obtained by grinding natural deposits of gypsum. It is a white or gray powder, contains 71-73% gypsum, and is slightly soluble in water. The fineness of its grinding is important. According to the accepted standard, all gypsum particles must pass through a sieve with a 1mm hole and at least 70-80% through a 0.25mm sieve. The moisture content of ground gypsum should not exceed 8%, otherwise it cakes and turns into lumps and lumps during storage.

5. Agrotechnical and agrobiological methods for improving solonetz soils

The study of the genetic characteristics of solonetz soils and the unique structure of their profile made it possible to develop methods for radical improvement of solonetz soils without the introduction of chemical ameliorants from the outside by using internal resources soma of the soil.

In solonetzes of the second group there is little absorbed sodium and no soda. On these soils, the agrobiological method of developing solonetzes is the most effective. It consists of a combination of mechanical, chemical and biological effects on solonetz soils in order to improve them and consists of a set of measures:

1. reclamation of soils, aimed at creating a deep arable and root layer with the involvement of calcium carbonate or gypsum from underlying horizons, due to which self-reclamation of solonetzes is carried out;
2. system of application of organic and mineral fertilizers;
3. system of moisture accumulation measures;
4. sowing of master crops.

First time appointment self-reclamation Solontsov was proposed by V.A. Kovda and A.F. Bolshakov for the reclamation of solonetzes of the Caspian lowland. The use of the method of self-reclamation of solonetzes is based on the fact that in the zone of dry steppes and desert zones in these soils gypsum and carbonate horizons lie close to the day surface. Using plantation plowing to a depth of 50-55 cm, the gypsum horizon, which lies in these soils at a depth of 35-50 cm, is mixed with solonets soil. The method of reclamation treatment depends on the thickness of the supra-solonetz and solonetz horizons and the depth of carbonates. On deep and medium solonetzes, three-tier plowing is used with a PTN-40 plow. With this treatment, the humus supra-solonetz horizon remains on the surface, and the solonetz and carbonate horizons change places.

On shallow solonetzes with shallow (up to 40 cm) carbonate deposits, plantation plowing is carried out with a PPN-50 plow. During this plowing, the humus, solonetz and subsolonetz (carbonate) horizons are mixed. After plantation plowing, the soil is treated with heavy disc harrows to destroy blocks, and measures are also taken to accumulate moisture in the soil by installing blown strips and sowing tall crops to create wings. The costs of reclamation plowing pay off in 2-3 years, and the duration of action lasts 10-12 years.

Agrobiological reclamation includes moisture accumulation, introduction of black and rock vapors, plowing of snow strips, and estuary irrigation. Thanks to this, conditions are created for an increase in reserves and the removal of harmful salts into the underlying horizons. Reclamation treatment of solonetzes is carried out in early or black fallow. When processing early fallow, the main reclamation plowing at a depth of 45-50 cm is carried out in the spring, and it is cultivated in the summer. In the early spring of next year, the solonetz developers harrow and sow crops.

When processing black fallow, the main reclamation plowing is carried out in the fall. The following year, the fallow is maintained (early spring harrowing, cultivation, autumn deep loosening).

The negative properties of highly saline soils and solonchaks can be weakened as a result biological reclamation. This type of reclamation is carried out by cultivating halophytes on saline soils. Halophytes are capable of absorbing up to 25-50% of salts from their own dry mass. Mowing and removing saltworts allows you to free the surface horizons from some of the salts. In addition, saltworts shade the soil and enrich its upper horizons with organic matter. Such plants in the zone of chestnut soils are tamarisk, oleaster, mackerel, yellow acacia, Tatarian and ash-leaved maples. With their root system they have a beneficial effect on the physical and chemical properties of the soil. Additional snow accumulation not only improves them water regime, but also contributes to the flushing of salts.

Digging as a method of reclamation, it consists in the artificial creation of a powerful fertile arable horizon on the surface of solonetz or highly saline soil. For this purpose, scrapers cut off a thin (1-2 cm) layer of the surface horizon of fertile non-solonetz soil surrounding the solonetz, which will be the arable horizon of the new profile. This technique is most effective for the reclamation of solonetzes in the chernozem zone, since cutting off the surface layers with careful implementation of this technique does not cause a noticeable change in the fertility of chernozems.

The cut fine earth of the humus horizon is stored in piles on the surface of reclaimed solonetz areas, and then leveled across the field with graders. N.V. Orlovsky, who first proposed this method of reclamation of solonetzes in the black earth zone Western Siberia, considered it sufficient to apply a layer with a thickness of 6-9 cm in several stages. Digging should be combined with an intensive system of measures to restore soil fertility in cut-off areas of the surface. The application of fertilizers, especially organic ones, and sowing of green manures are of great importance.

1. Familiarize yourself with the characteristics of solonetz soils and methods for their improvement according to the theory summary;

2. Each student receives an individual assignment, based on the materials of which it is necessary to determine:

1. soil need for gypsum;
2. calculate the dose of ameliorant;
3. propose agrotechnical methods for improving the analyzed soil.

Tasks and exercises

1. Soil southern chernozem, CEC 36 mmol/100 g, exchangeable sodium content 6.4 mmol/100 g, soil density 1.4 g/cm 3 , depth of the reclaimed layer 0–20 cm. Determine the degree of soil salinity and the dose of gypsum.

2. The dose of gypsum is 5.8 t/ha. What is the rate of application of phosphogypsum in physical mass?

3. Determine: a) the order of applying gypsum and its dose per following soils: light chestnut, heavy loamy, S = 18 mmol/100 g, Na = 2.3 mmol/100 g, humus – 2.1% for crop rotation: alfalfa – wheat – annual grasses – wheat; light chestnut sandy loam S = 12 mmol/100 g, Na = 1.8 mmol/100 g, humus – 1.2% for crop rotation: sweet clover-wheat – potatoes – oats; b) which of the indicated fertilizers will you apply to these crops (gypsum, simple or double superphosphate, phosphogypsum)?

4. Determine the degree of need for a reclamation substance and calculate its dose for the arable layer (0-20 cm) according to the following indicators:

Table 1

5. Soil – crusty solonetz, CEC – 28 mmol/100 g, exchangeable sodium content – ​​6.1 mmol/100 g, soil density – 1.5 g/cm 3 , depth of the reclaimed layer 0–18 cm. Determine the degree of soil salinity and the dose of gypsum.

6. Calculate the rate of gypsum required for reclamation of high-columnar solonetz, if S is 32.8 mmol/100 g, exchangeable sodium content is 5.5 mmol/100 g, soil density is 1.43 g/cm 3, the depth of the reclaimed layer is 0–20 cm .

Determine the degree of salinity and calculate the rate of gypsum for reclamation of chestnut soil with a humus content of 4.5%, if the content of exchangeable sodium is 3.5 mmol/100 g, CEC is 20 mmol/100 g, soil density is 1.3 g/cm3 , depth of the reclaimed layer is 0–18 cm.

8. Based on the data presented, expressed in mmol per 100 g of soil, determine: does the soil need chemical reclamation; if necessary, which one?

a) ECO=15.5; Нr=8;

b) S=8.5; Нr=4.6;

c) Na + =5; S=20;

d) ECO=28; Ca 2+ + Mg 2+ =22; pH H2O > 7;

e) S=12; ECO=20; pH H2O

e) Ca 2+ + Mg 2+ =35; ECO=40; pH H2O > 7;

g) Ca 2+ =8; Мg 2+ =3; Нr=6.

9. To create a cultural arable layer (0-20cm), you need to find out whether the soil needs a reclamation substance and in what dose according to the following indicators:

table 2

10. What can be said about the soil in terms of the composition of the absorbed cations of the soil absorption complex according to the following data, expressed in mmol per 100 g of soil?

a) Ca 2+ =29; Mg 2+ =5.8; Na + =1.9;

b) Na + =2; S=22;

c) Na + =9; ECO=28;

d) Ca 2+ =7.8; Mg 2+ =2.4; S=17;

2. Gypsuming of solonetz soils
In our country, significant areas are occupied by acidic and alkaline solonetz soils. The presence of large amounts of hydrogen and aluminum ions in an absorbed state in acidic soils, and sodium cations in solonetzic soils sharply worsen the physical, physicochemical and biological properties of these soils and their fertility. To radically improve acidic and saline soils, chemical amelioration in combination with other agrotechnical measures is necessary.

Methods of chemical reclamation of acidic and solonetz soils are based on changing the composition of absorbed cations, mainly by introducing calcium into the PPC. To neutralize acidity and increase the fertility of acidic soils, the main measure is liming, and to eliminate increased alkalinity and improve the properties of solonetz soils, gypsum is used.

The use of chemical reclamation methods on acidic and alkaline soils is the most important condition for the intensification of agriculture. production on these soils, increasing their fertility and the effectiveness of applied organic and mineral fertilizers.

The relationship between various agricultural crops to soil reaction and liming
For each plant species there is a certain environmental reaction that is most favorable for its growth and development. Most agricultural crops and beneficial soil microorganisms develop better when the environment reacts close to neutral (pH 6-7).

In relation to the reaction of the environment and responsiveness to agricultural liming. crops are divided into the following groups:

1. Cannot tolerate acid reaction alfalfa, sainfoin, root vegetables, hemp, cabbage: for them, the optimum pH lies in a narrow range from 7 to 7.5. they respond very strongly to liming even on slightly acidic soils.

2. Sensitive to increased soil acidity – wheat, barley, corn, sunflower, all legumes (except lupins and seradella), cucumbers, onions, lettuce. They grow better with slightly acidic and neutral reactions (pH 6-7) and respond well to liming of not only strongly but also moderately acidic soils.

3. Less sensitive to increased acidity rye, oats, millet, buckwheat, timothy, radishes, carrots, tomatoes. They can grow satisfactorily in a wide pH range (from 4.5 to 7.5), but a slightly acidic reaction (pH 5.5 – 6.0) is most favorable for their growth. These crops respond positively to liming of strongly and moderately acidic soils.

4. Need liming only on medium and strongly acidic soils flax and potatoes. Potatoes are little sensitive to acidity, and flax grows better in slightly acidic soils (pH 5.5 - 6.5). High rates of lime have a negative effect on the quality of the harvest of these crops: potatoes are severely affected by scab, the starch content in tubers decreases, and flax suffers from bacteriosis and deteriorates the quality of the fiber.

5. Tolerates acidic soil well and react negatively to liming lupine, seradella and tea bush, so when liming at higher rates they reduce the yield.

Thus, increased soil acidity has a negative effect on most agricultural crops, so they respond positively to liming.

The acidic reaction of the soil has a multifaceted negative effect on plants, but they can be combined into two groups: direct negative effect and indirect negative effect.

Direct negative action lies in the fact that the permeability of cell membranes deteriorates, therefore the use of water and soil nutrients and applied fertilizers becomes difficult, metabolism is disrupted, protein synthesis is weakened, and the processes of converting simple carbohydrates into more complex ones are suppressed organic compounds, growth and branching of roots worsens. Plants are especially sensitive to an acid reaction during the first period of growth, immediately after germination.

Indirect negative action acidity is also multifaceted. Acidic soils have unfavorable biological, physical and chemical properties. Their colloidal part is poor in calcium and other bases. Due to the displacement of calcium by hydrogen ions from soil humus, its dispersion and mobility increase, and the saturation of mineral colloidal particles with hydrogen leads to their gradual destruction. This explains the low content of colloidal fraction in acidic soils; therefore, they have unfavorable physical, biological, physicochemical properties, poor structure, low absorption capacity and weak buffering capacity.

The negative effects of increased acidity are largely associated with an increase in the mobility of aluminum and manganese and a decrease in the availability of phosphorus and molybdenum. In addition, in acidic soils, it is difficult for plants to receive calcium and magnesium, so their nutrition with these elements also deteriorates.
The influence of lime on the properties and nutritional regime of soil
By adding lime, free organic mineral acids in the soil solution are neutralized, as well as hydrogen ions in the soil absorption complex, that is, actual and exchange acidity is eliminated, hydrolytic acidity is significantly reduced, and the saturation of soils with bases increases.

The replacement of hydrogen absorbed by PPC with calcium is accompanied by coagulation of soil colloids, as a result of which their destruction and leaching are reduced, and the physical properties of the soil are improved - structure, water permeability, aeration.

When lime is added, the content of mobile forms of aluminum and manganese in the soil is reduced, therefore their harmful effect on plants is eliminated.

As a result of reducing acidity and improving the physical properties of the soil under the influence of liming, the vital activity of beneficial soil microorganisms and their mobilization of nitrogen, phosphorus, sulfur and other macro and microelements from the soil are enhanced. Only the mobility of boron and manganese may decrease, but this can be corrected by introducing appropriate microfertilizers.

Improved plant nutrition with nitrogen and ash elements is also due to the fact that on limed soils, plants develop a more powerful root system capable of absorbing more nutrients.

A quick method of radical reclamation of solonetz soils by earthing is that the surface of the solonetz patches is covered with a 15-20 cm layer of adjacent soil rich in calcium and humus using a scraper. chernozem soil in one go. With this amount of soil per 1 hectare, getting into the solonetz horizon improves it.

Materials used for gypsuming soils:

1. Raw ground gypsum (CaSO 4 2H 2 O) – contains 71-73% gypsum. This is finely ground natural gypsum, white or gray. Its humidity should not exceed 8%, otherwise it cakes and turns into lumps.

2. Phosphogypsum is a waste product from the production of double superphosphate and precipitate. A very fine white or gray powder containing 70-75% CaSO 4 and a small amount of P 2 O 5 2-3%.

3. Clay gypsum is extracted from natural deposits. In its natural state, it is loose and does not require grinding. Contains from 60 to 90% CaSO 4 and from 1 to 11% clay.

2. Questions about the previous lecture

1. How do crops relate to soil acidity?

2. What is the importance of soil liming?

3. What lime fertilizers exist?

4. What soils are subject to gypsum?

5. What processes occur in the soil during gypsum?

Excessive soil acidity is one of the important reasons low productivity of agricultural crops in the Non-Chernozem zone. On acidic soils, the effectiveness of fertilizers (mineral and organic) is significantly reduced and the accumulation of heavy metals in plants increases.

The high positive effect of soil liming on crop productivity was known long before the scientific explanation of the reasons behind these processes. Optimal reaction of the environment allows you to obtain high yields(40-50 c/ha) of grain crops with an average content of available nutrients in the soil, while to achieve the same yields on acidic soils the content of these elements should be 1.5-2.0 times higher.

Liming of acidic soils is the cheapest way to improve the conditions of nitrogen, phosphorus and potassium nutrition of plants, which is especially important in connection with high cost fertilizers at present. With soil reaction optimal for plants, the same increase in crop yield can be obtained with significantly lower fertilizer costs.

However, in the last 20 years, soil liming has practically not been carried out in our country, which has significantly increased the area of ​​acidic soils in the Non-Black Earth zone of Russia, reduced the effectiveness of fertilizers and the actual fertility of soils.

Currently, the area of ​​acidic and strongly acidic arable soils in our country is about 46 million hectares, or more than 50% of the total amount of arable land, and taking into account agricultural land occupied by meadows and pastures, there are 1.5 times more acidic soils.

According to long-term field experiments of VNIIA, the application of 1 ton of CaCO 3 provides for a 6-7-field crop rotation from each hectare of soil an increase in crop yield in the amount of 6-8 centners of grain units. Moreover, the higher the acidity of the soil, the greater the increase in yield from liming (Table 3.1). The importance of liming is especially great on farms that use high doses of mineral fertilizers, which is associated with an increase in the removal of calcium and magnesium by the crop and the introduction of physiological acids. Average yield increases of main agricultural crops from liming on sod-podzolic soils

(Shilnikov, 2001)

low nitrogen fertilizers. Liming has a multifaceted positive effect on soil fertility.

The addition of lime eliminates soil acidity, increases the degree of soil saturation with bases to an optimal level, increases the availability of nitrogen, phosphorus and molybdenum to plants, enriches the soil with calcium and magnesium, reduces the mobility and negative effect of aluminum and manganese on plants, increases the biological activity of soils, improves agrophysical and physicochemical soil properties, which together determine higher yields, better product quality and the effectiveness of mineral fertilizers.

It is important to note that the harmful effect of acidity on soils is due not only to the increased content of hydrogen ions, but also to the excessive accumulation of mobile aluminum, manganese and iron. The toxicity of aluminum is especially noticeable on low-humus soils, and the toxicity of manganese and iron on waterlogged soils. On peat and sandy soils, which practically do not contain mobile aluminum, the negative effect of acidity on plants affects plants much less than on loamy and clay soils Oh.

Despite the high gross content of aluminum in the arable layer of loamy and clayey soils (3-5%, or 90-150 t/ha), most of it is in the composition of insoluble compounds and does not have a harmful effect on plants. A significant increase in aluminum solubility is observed in acidic (pH 8.9) soils. Depending on the reaction of the soil, aluminum may be present in it in the form of A1 3+ cations (pH

The content of humus and exchangeable phosphorus in the soil also has a significant influence on the mobility of aluminum. With an increase in their content in soils, the amount of exchangeable aluminum noticeably decreases. This is due to the fact that Al, Mn, Fe form slightly soluble organomineral complexes with humic acids and fulvic acids of the soil, as a result of which their harmful effect on plants is significantly reduced, but complete precipitation of aluminum is observed at pH > 5.6. The positive effect of phosphorus is associated with the formation of insoluble phosphates - A1 P0 4, A1P0 4 2H 2 0, A1 2 (OH) 3 (P0 4), A1 3 (P0 4) 2 (0H) 3 5H 2 0, A1, FeP0 4 2H 2 0, Fe 2+, A1 2 (0H)(P0 4) 2 8H 2 0, etc.

Attitude of plants to soil acidity. All plants have significantly different sensitivity to acidity and react differently to increased levels of H +, mobile aluminum and manganese (Al 3+ and Mn 2+) in the soil. Depending on soil acidity and responsiveness to liming, agricultural crops are divided into five groups.

TO first group These include crops for which a slightly alkaline (pH20 7.0-8.0; pH ks, 6.8-7.5) environment is optimal: sugar, fodder and table beets, white cabbage, alfalfa, sainfoin, mustard, rapeseed, onions, garlic, celery, spinach, peppers, parsnips, currants, etc. When these crops are grown on very acidic soils, their yield is reduced by 2-3 times and the plants are severely affected by diseases. Therefore, the soils intended for their cultivation should be limed first.

Co. second group include wheat, barley, corn, peas, clover, vetch, beans, chickpeas, chickpeas, lentils, cauliflower and fodder cabbage, kohlrabi, rutabaga, turnips, lettuce, leeks, cucumber, brome, foxtail, for which the reaction is most favorable soils close to neutral (optimum pH KS1 6.0-6.5). They respond well to liming. Increasing soil acidity to pH 4.5 reduces the yield of these crops by 1.5-2.0 times and significantly increases their incidence.

IN third group includes winter rye, oats, buckwheat, timothy, tomatoes, sunflower, carrots, pumpkin, zucchini, parsley, radish, turnip, rhubarb, Jerusalem artichoke and other crops that tolerate moderate acidity and alkalinity of soils. These cultures do not have a clearly defined optimal value environmental reactions. They are greatly influenced by accompanying growth factors. Under favorable nutritional conditions and environmental conditions, as well as at a pH KC1 of 5.-7.5, they can produce high yields.

TO fourth group include potatoes, fiber flax, millet, sorghum, etc. For these crops, the optimal pH value KC1 is 5.1-5.6. They tolerate moderate soil acidity quite well and respond positively to liming when preserved in the soil optimal ratio between calcium, potassium, magnesium, boron and other nutrients.

Optimal conditions for growth and development fifth group crops (tea, coffee, cocoa, yellow and blue lupine, goat's rue, sorrel, seradella) are created at pH KS| 4.5-4.8. They are insensitive to high acidity and require liming only strongly acidic (pH KC1

Despite the different attitudes towards the acidity of adult plants, most agricultural crops require an environment close to neutral during germination and at a young age (pH KC1 5.8-6.2 or pH H2() 6.4-7.0. This reaction is the most favorable for physiological growth processes.

The physiological (biological) optimum of the environmental response required by plants may differ markedly from the ecological (technological) one associated with changes in the mobility of nutrients and the conditions for the development of diseases. So, for example, for potatoes and flax, if the plants and soil are not infected with diseases, the biological optimum of the environmental reaction is pH KS] 6.0-6.2, however, due to the damage of plants under these conditions by diseases (potatoes with a neutral and slightly alkaline reaction soils are affected by scab caused by actinomycetes, flax - by fusarium) in field conditions their yield and quality increase at pH KS1 5.2-5.6

(ecological optimum). The discrepancy between the biological and ecological optimal values ​​of the environmental response for many crops is most often caused by changes in the availability of nutrients when soil pH changes, rather than by other factors.

In this regard, it is necessary to take into account not only the relationship of different crops to the soil reaction, but also the changes in the availability of nitrogen, phosphorus, potassium and trace elements caused by liming. Liming soils to pH > 6.6 is ineffective, since the removal and leaching of introduced calcium from the soil significantly increases and the mobility of microelements, except for Mo, decreases. For different crops, the optimal pH range is not the same (Tables 3.2 and 3.3). It is advisable to carry out liming if the pH is KC1 and the degree of saturation of the PPC with bases (V, %) below the specified values.

Table 3.2

Optimal levels of environmental reaction and degree of base saturation when cultivating grain crops on soddy-podzolic soils

(Mineev, 2005)

Optimal pH values ​​| for various crop rotations

(Sheujen, 2006)

Geographically acidic soils are widespread in the region. Most of them are concentrated in the Achinsk forest-steppe zone - 46% of the total area of ​​acidic soils in the region. In the Central suburban and Kansk forest-steppe zones, their areas are almost equal (16.2 and 16.3%). There are slightly more of them in the Northern subtaiga zone - 18.5%. A small share - only 3% - falls on the southern forest-steppe zone (Tandelov, 1997).

It should be noted that, unlike their European analogues, the acidic soils of the Krasnoyarsk Territory are less podzolized, which is mainly explained by the carbonate content of the parent rocks. A characteristic feature of these soils is low structure. They quickly spray and form a crust. They have poor water permeability. As a result, water erosion develops during snowmelt and periods of intense precipitation.

The main feature of acidic soils is a lack of calcium ions and an excess of hydrogen ions in the arable horizon, which determines their extremely unfavorable agrochemical properties. First of all, calcium is an important element of plant nutrition, and its deficiency causes calcium starvation: plants develop and bear fruit poorly and cannot tolerate overwintering. A decrease in the reaction of the soil solution negatively affects the absorption of nitrogen, phosphorus, potassium and other elements by plants.

A high concentration of hydrogen ions impedes the growth and development of the plant root system, the absorption of calcium sharply decreases and sometimes completely stops, and the supply of phosphorus is inhibited, since it partially changes the composition of the protoplasm of root cells. In an acidic environment, metabolic processes in plants are disrupted with the accumulation of intermediate compounds (nitrites, simple carbohydrates, organic acids) instead of complete compounds (proteins, fats, starch). Plants lose frost and heat resistance, resistance to drought, diseases and pests, and the passage of certain phases of growth and development is delayed.

In soils with high acidity, the vital activity of beneficial microorganisms is suppressed, ammonifying and nitrifying microflora almost do not develop, which inhibits the formation of nitrates and the fixation of atmospheric nitrogen. As a result, the nitrogen nutrition of plants is disrupted. In the same time separate forms fungi (penicilium, fusarium, trichoderma), which secrete substances that are toxic to plants, develop in acidic soils, which creates unfavourable conditions for the life and development of plants.

Increased acidity reduces the solubility of compounds of a number of microelements needed by plants (molybdenum, boron, zinc and copper). Therefore, plants cultivated on eluvial soils are significantly inferior in the content of protein compounds than crops grown on chernozem soils. On the contrary, in an acidic environment, the solubility and, consequently, the content of mobile forms of aluminum and manganese, which are toxic to plants, increase.

Acidic soils are different and unfavorable physical properties. With a lack of calcium and magnesium, which form insoluble humates, humic substances are poorly retained in the soil, which not only reduces the supply of nutrients, but also deteriorates the soil structure. Eluvial soils some have, as a rule, fine-silty granulometric composition and structureless, poor in colloidal particles and humus, which is accompanied by a violation of the favorable water-air regime.

Determining the need for soil liming and calculating the dose of lime

Establishing the soil's need for liming and determining the required doses of liming materials are based on the study of soil acidity.

1. An important indicator The need for liming is the presence and magnitude of exchangeable acidity. Exchangeable acidity owes its origin to the combined presence of hydrogen and aluminum ions in soils, which are in an absorbed state, and represents a small but most dangerous part of soil acidity. It is observed in soils in which the process of leaching of bases is very intensive and the soil requires the addition of lime.

Thus, general idea Metabolic acidity can be obtained by determining the pH of the salt extract. Determined that

at pH KCl <4,5 the soil badly needs liming,

at pH KCl from 4.5 to 5.5 average need,

at pH KCl > 5,5 liming becomes unnecessary.

The degree of soil acidity is an important, but not the only indicator characterizing the soil’s need for liming.

2. The need for liming is most reliably diagnosed by the degree of base saturation (V,%):

V, % = S×100/S+ H G,

where S is the sum of absorbed bases, mEq per 100 g of soil; HG is the value of hydrolytic acidity, mEq per 100 g of soil. The need for soil liming, depending on their saturation with bases, established empirically, is expressed by the following scale (Vozbutskaya, 1968).

Soils in which V< 50%, сильно нуждаются в извести,

from 50 to 70% - moderately require the addition of lime,

V > 80% - do not require liming.

Plants, exposed to constant and long-term influence of specific conditions characteristic of certain soil provinces, reflect these conditions in their biological properties and features. In the process of natural and artificial selection in various ecological-geographical regions of agriculture, the so-called ecological-geographical types of plants were gradually formed, for which one of the essential ones was a different and specific attitude to the reaction of the soil solution. The “optimal pH range” is uncertain due to the complexity of relationships in the soil-plant system. Therefore, the soil pH value in itself cannot be a diagnostic sign of chemical reclamation of acidic soils. Cultivated plants are genetically adapted to certain growing conditions. In relation to the reaction of the environment, they can be grouped as follows.

To the first group include crops characterized by very high sensitivity to the acidic reaction of the soil environment. They grow well only with a neutral or slightly alkaline reaction and are characterized by high responsiveness to their liming - these are alfalfa, sainfoin, clover, sugar and table beets.

To the second group includes crops that are moderately sensitive to soil acidity (they grow with a slightly acidic or neutral reaction) and respond well to liming - spring wheat, corn, soybeans, beans, peas, sunflowers, onions.

To the third group include plants that grow satisfactorily in a wide pH range - those that are slightly sensitive to soil acidity (rye, oats, millet, buckwheat, timothy). They respond positively to the use of high doses of lime.

Fourth group constitute cultures:

a) intolerant of excess calcium in the soil - flax;

b) satisfactorily tolerating soil acidity and not requiring liming - potatoes.

In relation to the reaction of the soil environment, not only plant species differ, but also different varieties of the same species. The highest responsiveness to liming is found in varieties bred on soils with a neutral and alkaline environment.

The agroecological conditions of plants growing on acidic soils are largely determined by individual “acid-determining” elements.

Calculation of lime dose

When carrying out liming, it is very important to establish the optimal dose of lime in accordance with the characteristics of the soil and cultivated plants. Calculation of the dose of lime required to neutralize the soil depends on the value of hydrolytic acidity, expressed in mEq. per 100 g of soil. The dose of lime is calculated using the formula: CaCO 3 = H G × 0.05× D×G P, where

HG is the value of hydrolytic acidity, mEq/100 g of soil;

0.05 – amount of lime in grams corresponding to 1 mEq of soil acidity;

h – height of the reclaimed layer, cm;

d – density of the reclaimed layer.

When setting the dose of lime, the granulometric composition of the soil, the biological characteristics of plants and the degree of soil need for liming are taken into account. In case of strong need, the full calculated dose of lime is used, in case of medium need - 1/2 or ¾, in case of weak need - 1/3 or 1/4 dose. When choosing a place for lime in crop rotation, the relationship of crops to land reclamation is taken into account.

The main lime fertilizer - limestone CaCO 3 - is practically insoluble in water, however, under the influence of carbon dioxide contained in the soil solution, calcium carbonate gradually turns into soluble calcium bicarbonate:

CaCO 3 + H 2 O + CO 2 = Ca (HCO 3) 2.

Calcium bicarbonate dissociates into Ca 2+ and 2 HCO 3 - ions and is partially hydrolyzed:

Ca (HCO 3) 2 + H 2 O = Ca (OH) 2 + 2H 2 O + 2CO 2;

Ca (OH) 2 = Ca 2+ + 2 OH - .

In a soil solution containing calcium bicarbonate, the concentration of Ca 2+ and OH - ions increases. Calcium cations displace hydrogen ions from the soil absorption complex, and acidity is neutralized:

PPK]H + + Ca 2+ + 2 HCO 3 - → PPK] Ca 2+ + 2H 2 O +2CO 2 ;

PPK]3H + + Ca 2+ + 2OH - → PPK] H+ Ca2+ + 2 H 2 O.

Chemical ameliorants are long-acting fertilizers. With repeated mechanical tillage of the soil, they are thoroughly mixed with the entire mass of the arable layer. A full dose of lime has a positive effect on the yield of field crops on medium and heavy loamy soils for 15-20 years, and on light soils for 8-10 years. The main condition is that the maximum shift in pH towards the alkaline range coincides in time with the placement of the crop most responsive to this event on the limed field. Conversely, crops on which liming has a negative effect should be placed on this field at the moment the effect of the ameliorant subsides.

Lime fertilizers

Lime fertilizers are divided into hard (requiring grinding), soft or loose (not requiring grinding) and industrial waste.

Hard calcareous rocks contain different amounts of CaCO 3 and MgCO 3 and differ in the amount of insoluble residue (clay and sand). Based on the content of CaO and MgO, these rocks are divided into the following groups: limestones contain 55-56% CaO and up to 0.9% MgO; dolomitized limestones – 42-55% CaO and 0.9-9% MgO; dolomites – 32-30% CaO and 18-20% MgO.

Limestones and chalk– sedimentary rocks of predominantly marine origin. Limestones consist mainly of the mineral calcite, but more often they are dolomitized and, in addition to CaCO 3, contain MgCO 3. The presence of MgCO 3 increases the strength and hardness of calcareous rocks and reduces their solubility. Hard calcareous rocks are source material for the production of industrial lime fertilizers - limestone and dolomite flour, burnt and slaked lime.

Limestone or dolomite flour obtained by grinding and crushing limestones and dolomites in factories. Limestone flour consists of CaCO 3 and a small amount of MgCO 3; in terms of CaCO 3 contains 85-100%.

Dolomitized flour should be used on soils of light granulometric composition, especially when cultivating crops sensitive to magnesium deficiency, - potatoes, flax, legumes. The speed of interaction with the soil and the efficiency of ground limestone and dolomite largely depend on the fineness of the grinding. Particles of limestone and dolomite larger than 1 mm are poorly soluble and very weakly reduce soil acidity. The finer the grinding of limestone and dolomite, the better it mixes with the soil, dissolves faster and more completely, acts faster and the higher its effectiveness.

Burnt and slaked lime. When hard limestone is fired, calcium and magnesium carbonates lose carbon dioxide and turn into calcium oxide or magnesium oxide, resulting in burnt (lumpy) lime. When it interacts with water, calcium or magnesium hydroxide is formed, that is, the so-called slaked lime “fluff” - a thin crumbling powder. You can extinguish burnt lime directly in the field, sprinkling it with damp soil.

Slaked lime is obtained as a waste from lime factories and in the production of bleach. Fluff is the fastest-acting lime fertilizer, especially valuable for clay soils.

Soft calcareous rocks- secondary freshwater lime deposits . These include calcareous tuffs, marls, and natural dolomite flour. Their deposits are usually smaller, but they are often located near fields, which makes their use economically feasible; they do not require grinding, but only drying and sifting.

Calcareous tuffs also called key lime, since they are found mainly in places where springs emerge in near-terrace floodplains; contain from 80 to 90% CaCO 3 .

Marls contain mainly CaCO 3, sometimes together with an admixture of clay. Therefore, the content here ranges from 25 to 50%. Marls can be loose and dense, requiring grinding.

Dolomite flour - natural loose rock consisting of MgCO 3 and CaCO 3, with a total content in terms of CaCO 3 of 95-108%. Does not require grinding. Deposits are rare. Good lime fertilizer for soils of light granulometric composition, poor in magnesium.

Lime industrial waste. These include: oil shale ash, defecate, belite flour.

Oil shale ash. Obtained by burning oil shale industrial enterprises and power plants. It consists of silicates, oxides and carbonates of calcium and magnesium with a total content in terms of CaCO 3 - 65-80%. In addition, it contains small amounts of potassium and sulfur. Its action is similar to that of limestone flour. Oil shale ash is suitable for most field crops, including legumes, potatoes, and flax.

defect - beet sugar production waste. Contains CaCO 3 with an admixture of Ca (OH) 2 with a total content in terms of CaCO 3 of up to 70%. Good lime fertilizer for use near sugar factories. In addition to lime, defecation contains 0.3-0.5% nitrogen, 1-2% phosphorus, 0.6-0.9% potassium, and up to 15% organic matter.

Belite flour - waste from the aluminum industry, has the following chemical composition: CaO - 45-50%, Na 2 O+ K 2 O - 2.05, SiO 3 - 30, Fe 2 O 3 - 2.9, MnO -0.04, Al 2 O 3 - 3.4%, and also a small amount of phosphorus, sulfur and some trace elements.