Soil absorption capacity: what is it and the role in fertility, 6 types

Soil is a complex system that includes coarse dispersion particles, finer fragments and molecular elements. At the same time, the absorption capacity of the soil is considered one of the key parameters. This term is understood as the ability of the substrate to retain valuable elements. This is of great importance when using soil for agricultural purposes.

What is soil absorption capacity

The absorption capacity of the soil is provided by the absorbent complex, which is a combination of minerals, organic and organomineral components of the solid phase.Scientists interpret this term as the ability of the earth to retain elements that come into contact with its solid phase through the water circulating in it.

At the same time, various substances can linger in the soil - coarse suspensions, solutions, minerals, living microorganisms and organic elements. Depending on the nature of absorption, there are different types of absorption capacity.

Role in fertility

This characteristic of the soil affects not only the formation and evolution of soils. The success of growing plants directly depends on it. The absorption capacity of the soil affects the ability to retain various kinds of soluble elements, including substances biologically important for crops.

Types of soil absorption capacity

Scientists distinguish a number of varieties of soil absorption capacity. Each of them has certain features.

Mechanical

This term is understood as the ability to mechanically retain particles in the pores of the soil. At the same time, suspensions of organic and aluminosilicate fragments and colloidally sprayed particles are retained. This helps to preserve ameliorants, colloidal fractions and top dressings that are poorly soluble in water.

The intensity of mechanical absorption is affected by the presence of pores in the soil and their size. The dispersion of the substance is also of great importance. Therefore, clay soil types and loams are characterized by a greater mechanical absorption capacity compared to sandy and sandy loamy soils. This characteristic is very important for the correct distribution of microorganisms in the structure of the earth.

Physical

This type of absorption is the ability to retain organic and mineral elements on the surface of the solid phase of the soil.This effect is associated with the action of absorption forces. Physical absorption is associated with the presence of a highly dispersed earth phase. Due to this, it is possible to attract and accumulate groundwater and the substances contained in them.

In this case, the absorption capacity depends on the type of soil. In coarse-grained soils, adsorption forces are low. Therefore, they have a low absorption capacity. As the fineness increases, the absorption properties increase.

Chemical

This characteristic is associated with the formation of insoluble or sparingly soluble compounds. This is due to the appearance of chemical reactions between individual soluble s alts in the soil structure.

This property plays a special role in the transformation of phosphorus in the soil. When using water-soluble preparations based on this substance, a pronounced chemical binding of phosphorus is observed in the soil.In acidic soil types, which include many sesquioxides, the chemical absorption of this substance is accompanied by the release of iron and aluminum phosphates, which are difficult to dissolve.

Due to chemical absorption in the soil, phosphates accumulate, which become available when the reaction of the environment changes, otherwise they act as ballast in the soil. In such a situation, chemical assimilation performs a negative function.

Biological

This characteristic represents the absorption of nutrients, air and fertilizing by cultivated plants and soil microflora. During the life of plants and soil microorganisms, organic elements accumulate. They contain ash and nitrogen.

A distinctive feature of biological absorption is selectivity. The root system of crops and microorganisms absorb the substances they require from the soil.

The severity and pace of this process depends on the following parameters:

• air ground mode;
• content of organic elements and plant residues in the soil;
• thermal conditions of the soil;
• reactions of the environment.

Crop root secretions are used as an easily accessible source of energy for microorganisms. Therefore, microbiological processes are especially successful in the rhizosphere.

To regulate the characteristics of the substrate, you can make organic and mineral top dressing. Also for this purpose, crop rotation rules, the use of bacterial fertilizers and other agricultural practices are used.

Physico-chemical

This absorption capacity is also called exchange capacity. This term is understood as the ability of the soil to absorb and exchange ions located on the surface of colloidal fragments for ions of the soil solution.

When the potential-determining layer of soil colloids is negatively charged, cations are exchanged. If the charge is positive, anion exchange is observed. The key features of the exchange assimilation of cations include the following:

1. The exchange is carried out in equivalent volumes. This happens according to the basic laws of chemical reactions.
2. Any absorbed cation can be replaced by another cation in the soil solution.
3. The energy of absorption and displacement of cations is significantly different. It is influenced by valency and atomic mass.

Non-exchange absorption of cations is also observed in the soil. As a result, they are fixed by clay minerals, which have a three-layer crystal lattice.

Non-exchange absorption of potassium and ammonium has wide limits - it all depends on the basic characteristics of the soil.This indicator is directly affected by the mineralogical and granulometric composition of the substrate. In chernozems, it is much more pronounced than in the soddy-podzolic type of soil.

Also, this kind of absorptive capacity increases in the case of periodic moistening and drying of the earth. Therefore, the shallow incorporation of potassium and ammonia compounds into the soil structure, which is subject to irrigation and drying, enhances the non-exchange absorption of potassium and ammonium. These substances are more slowly converted into available forms compared to exchange-absorbed.

Fixing capacity of soils

This capacity of the soil is due to the relation to cations, and it depends on the granulometric composition. This characteristic is determined by the content of humus. The higher this parameter and the heavier the substrate, the higher its ability to absorb cations.

The absorption capacity of the soil directly affects the process of growing cultivated plants. That is why it is so important to consider this parameter and its varieties.

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