Ministry of Agriculture of the Republic of Azerbaijan State Agrarian University Department of Agrochemistry subject: Agrochemistry topic: Application of gypsum and lime Lecturer

Ministry of Agriculture of the Republic of Azerbaijan

Azerbaijan State Agrarian University

Department of Agrochemistry

SUBJECT: Agrochemistry
TOPIC: Application of gypsum and lime

Lecturer :M.E.Bahmanli


Application of gypsum and lime
Gypsuming of soils
Gypsum is added to the soil to improve its chemical, physical and biological properties.

In our country, saline and saline soils are widespread in the plains, dry steppe and desert-steppe zone. These lands are more widespread in the Mil-Garabagh, Mugan-Salyan, Shirvan plains, Samur-Davachi lowland, Nakhchivan plain and Absheron peninsula.

The relatively low elements of the relief in the Kur-Araz lowland, the alluvial salinity form for the alluvial plains of the low terraces of the Caspian Sea are typical. In two-thirds of the Kur-Araz lowland, the groundwater level is shallower than 5 m above ground level. During the irrigation season in summer, the groundwater level rises further, and in autumn it falls. Mineral groundwater close to the soil surface enters the top layer of the soil by the action of capillary forces and salinizes the soil as a result of evaporation.

Deluvial and deluvial-proluvial salinization forms are found in the cones and valleys of mountain rivers in the foothill plains of the republic. Atmospheric precipitation falling on watersheds and mountain crops in these areas dissolves salts close to the surface and carries them to the foothills. The various salts collected here cause salinization of the soil . In the form of deluvial-proluvial salinization, salinization of river cone and river valley soils occurs due to salts brought by river waters

The saline soils of the republic are divided into different groups according to the ratio of anions and cations of salts and morphological features. According to the chemical composition of water-soluble salts, these soils can be divided into the following groups: 1) chloride salts; 2) sulfate salts; 3) soda salts; 4) saline soils with mixed salts.

The most dangerous of these are soda salts, which are called salinity by experts. Salinities also belong to the category of saline soils. However, unlike salinities, easily soluble salts are not located on the surface of the soil, but at a certain depth of the profile.

As a result of a sharp increase in the dispersion of organic and mineral parts of the soil under the process of salinization, it is understood that sodium ions enter the absorption complex, the resistance of colloids to water decreases and the soil alkaline reaction occurs.

More precisely, soils containing large amounts of absorbed sodium and magnesium in the illuvial layer are called salinities.

To improve these soils, it is necessary to change its reaction and the composition of cations. This can be achieved by applying gypsum to those soils.

Saline soils are divided into the following groups according to the amount of absorbed sodium:

a) Non-saline - the amount of sodium absorbed does not exceed 3-5%,

b) Weakly saline - 5-10% Na,

c) Saline - 10-20% Na,

d) Salinity - more than 20% Na.

In addition, salinities are divided into three subtypes according to water regime and complex properties (salt regime characteristics, humus accumulation): 1) autorphic salinities (groundwater is located at a depth of 6 m); 2) semi-hydromorphic salinities (groundwater is located at a depth of 4 m); 3) hydromorphic salinities (groundwater is located at 3 m). A characteristic feature of the granulometric composition of salinities is the sharp stratification of sludge particles along the profile. The general chemical composition of salinities is the profile distribution of a number of oxides (SiO2, Fe2O3, Al2O3, CaO, MgO, SO3, P2O5, K2O, Na2O). The amount of humus varies greatly depending on the area where the salts are formed and the granulometric composition.

Salinities are a great source of reserves for the expansion of agriculture. However, due to the low fertility of these soils, their use is not possible without major improvements. The most basic method is to gypsuming these soils.

Gypsum is the most suitable way used to increase the fertility of soda-saline soils, which are distinguished by the high content of absorbed sodium and the alkalinity of the soil solution. This method is also called chemical reclamation.

Organic fertilizers are widely used to increase the effect of gypsum on saline soils. If the amount of sodium in the absorption capacity is more than 10%, it is important to carry out gypsum measures. Weakly saline soils can be improved by deep plowing with high doses of manure, compost and other organic fertilizers. Sometimes it can be improved by bringing fertile soils (500 t / ha) to saline areas (once every 3-5 years). However, this is not considered effective because it requires a lot of effort.

When applying gypsum to the soil, the following reaction occurs:

Na₂CO₃ + CaSO₄ → CaCO₃ + Na₂SO₄,

+CaSO₄ → + Na₂SO₄

Na₂SO₄ is a neutral salt and will not harm plants if it is formed in small amounts in the process. However, if the absorption capacity is more than 20%, it is important to discharge it to the collectors through irrigation. As a result of this work, the alkaline reaction of the soil is eliminated, the physical-chemical properties and biological properties are improved, cultivation is facilitated and the aeration process is normal. In addition, in the process of washing Na2SO4, large amounts of humus and other nutrients needed by plants are released from the soil. Therefore, after these measures, high doses of manure, compost and other mineral fertilizers should be applied to the soil.

The amount of gypsum is determined by the amount of sodium exchanged. If the amount of absorbed sodium in the absorption capacity is 10-20% or more, the dose of gypsum is 10-15 t / ha and more, if it is less than 10%, it is advisable to give 5-8 t / ha. Deep plowing, application of local and industrial fertilizers and snow storage are the main measures to increase the efficiency of gypsuming. Among mineral fertilizers, ammonium sulfate and simple superphosphate are considered more suitable.

The amount of gypsum (t / ha) is used to replace the absorbed sodium with calcium, and the following formula is used to calculate it.

CaSO₄ · 2H₂O = 0,086 (Na-0,1 T) · H_n:d_v

Here: Na - the amount of sodium absorbed, in 100 g of soil in mg · eq);

T - absorption capacity per 100 g of soil;

(0,1 · T) - in the calculation it is possible to keep less than 10 ,,,,,,% of sodium in the absorption capacity;

Hn - thickness of the soil layer to be gypsiming (cm);

dv - volumetric mass of saline layer (gm / cm3)

0.086 - 1 m · eq gypsum index.

In general, the amount of calcium absorbed in the dry-steppe and semi-steppe zones of the republic is sufficient. However, as salinity develops in these areas, the amount of calcium absorbed decreases, and the amount of sodium and magnesium absorbed increases. In the process of salinization, the main part of calcium is replaced by sodium, and some - by magnesium. Salinities are formed under the following conditions:

1) calcium is replaced by sodium when the total amount of sodium in the cations is more than 10%; 2) replaces calcium in a certain part when the sum of cations contains more than 30% of magnesium; 3) when less than 70% of the total cations in the absorbing complex are calcium.

When calculating the need of saline soils for chemical ameliorants, the state of calcium saturation of the soil absorption complex should be taken into account.

Due to the degree of calcium saturation of salts, it can not be called calcium saturated. Because its content in the absorbing complex is less than 70%. Therefore, the dose of gypsum for these soils should be determined using the above formula.

Calcium unsaturated salts are divided into high-sodium (typical) and low-sodium (less than 10% Na in cations). When determining the norm of gypsum for high-sodium salts, it is necessary to take into account 10% of sodium absorbed by total cations and 30% of magnesium:

G=0,086 (Na-0,1T) + ( Mg - 0,3T) H_n·d_v

The following formula is used when calculating chemical ameliorants for low-sodium salts according to the amount of magnesium absorbed.

G= 0,086 ( Mg - 0,3T) H_n·d_v

If soda is predominant in saline soils, it is advisable to give more gypsum. Only in this way can the toxic effects of soda on plants be eliminated. It is advisable to give a high dose of gypsum gradually over 2-3 years.

Effective results can be obtained if the application of raw ground gypsum and phosphogypsum in such soils as fertilizers.