Soil water properties: types and types of regime, ways of its regulation

Everyone involved in agriculture is advised to pay attention to the water properties of the soil. Soil scientists note the importance of the issues of moisture inflow, movement and accumulation. They are associated with the features of accumulation, movement and leaching of organic substances, which are products of soil-forming processes. Under the water regime is understood the totality of all processes of moisture entering the soil structure, its state in the soil and the process of spending.

Categories of soil water, characteristics, availability to plants

Water in the structure of the earth has a heterogeneous structure, and therefore differs significantly in physical characteristics.

Hard

This form of water is ice. It is considered a potential source of liquid and vaporous moisture. Ice formation is seasonal or perennial. At temperatures above 0 degrees, it becomes liquid or vapor.

Chemically bonded

This type of water is present in the composition of minerals in the form of a hydroxyl group or whole molecules. In the first case, moisture is called constitutional. It is removed from the soil by calcination up to 400-800 degrees. Water presented in the form of molecules is called crystallization water. It can be removed by heating the earth to 100-200 degrees.

Chemically bound water is considered the most important parameter by which one can understand the composition of the soil. This substance is present in the composition of the solid phase of the earth and does not belong to independent physical bodies. The composition does not move, has no solvent characteristics and is not available to plants.

Steamy

This substance is present in the soil air and in the pores in the form of water vapor. Vaporous moisture is able to move with the current of soil air and depends on the moisture capacity of the soil.

Although the volume of vaporous moisture is no more than 0.001% of the mass of the soil, it is very important for the correct redistribution of soil moisture and helps protect the root hairs of crops from drying out. When condensing, the vapor transforms into a liquid.

Sorbated

This substance is formed as a result of sorption of vaporous and liquid water on the surface of solid soil elements. It is also called physically bound. Such water is divided into strongly bound and loosely bound. This gradation is based on the strength of the connection with the solid phase of the earth.

Tightly bound or hygroscopic water is formed due to the adsorption of molecules from the vapor state on the soil surface.The ability of the earth to pass and absorb vaporous moisture is called hygroscopicity. Strongly bound water is fixed on the surface by increased pressure. This forms a thin film on the soil particles.

During the contact of soil particles with water, its additional absorption is observed, and loosely bound water is formed. It is not so firmly fixed and slowly moves from fragments with a larger film to particles with a smaller one.

Free

This water is located in the active layer of soil on top of loosely bound. It is not connected with soil fragments by forces of attraction. Free water in soil can be either capillary or gravitational.

Capillary

This type of moisture resides in the thin capillaries of the earth. It moves under the influence of capillary forces that appear at the interface of all phases - solid, liquid and gaseous. This type of moisture is considered the most accessible to plants.

Water properties of soils

Soils differ in certain properties and characteristics. Gardeners should definitely take this into account.

Water holding capacity

This term is understood as the ability of the soil to retain moisture associated with the influence of sorption and capillary forces. The maximum volume of water that can retain soil by certain forces is called moisture capacity.

Depending on the form in which the moisture is held by the soil, there are total, capillary, minimum and maximum molecular moisture capacity.

Soil water permeability

This concept includes the ability of the earth to absorb and pass water through itself. There are 2 stages of water permeability:

1. Absorption - represents the absorption of water by the soil and its passage in unsaturated soil.
2. Filtration - this term is understood as the movement of moisture in the soil under the influence of gravity and pressure gradient with full saturation of the soil with moisture.

Water permeability is measured by the volume of water that flows through a certain unit area of soil per unit time at a water pressure of 5 centimeters. The indicator is constantly changing. The balance of water permeability is determined by the granulometric composition and chemical characteristics of the soil. It is also affected by their structure, density, humidity.

Heavy texture soils have lower water permeability compared to light soils. The presence of sodium or magnesium in the composition of the earth, which cause it to swell rapidly, makes the structure almost waterproof.

Water-lifting capacity

This term is understood as the ability of the soil to provoke the upward movement of the moisture it contains, due to the action of capillary forces. The height of the rise of moisture in the soil and the rate of its movement are affected by the granulometric and structural composition of the soil.

Also, the rate of rise in moisture is determined by the degree of mineralization of groundwater. Highly mineralized waters are characterized by a lower height and rate of rise. But the high location of mineralized waters increases the risk of rapid soil salinization. This danger arises when they are located at a level of 1-1.5 meters.

Types of soil water regime

Water regimes come in a variety of forms, each with specific features.

Cryogenic

This water regime is common in permafrost conditions. At the same time, the frozen part of the soil is water resistant. It is an aquiclude, over which there is a permafrost perch. It leads to saturation of the upper part of the thawed soil with water. This mode of regulation is observed throughout the growing season.

Flushing

According to the theory, this regime is observed in regions in which the total amount of annual precipitation exceeds their evaporation. The entire soil profile is subjected every year to through wetting to groundwater and rapid leaching of soil formation products. Under the influence of the washing type, red soils, yellow soils, podzolic soils are formed.

If there is a close location of groundwater, and soils are characterized by poor water permeability, a swamp subtype of the water regime is formed. This leads to the formation of bog and podzolic-bog soil types.

Periodic flushing

This variety is characterized by an average balance of precipitation and evaporation. At the same time, limited wetting of the soil in dry years alternates with through wetting in wet periods.

Flushing of land with excess rainfall occurs 1-2 times over several years. This type of water regime is typical for gray forest soils, leached and podzolized chernozems. Soils are characterized by unstable moisture supply.

Non-flushing

This mode is distinguished by the distribution of precipitation, mainly in the upper layers of the soil. However, it does not reach groundwater. Moisture is exchanged by moving it in the form of steam. This type of water regime is typical for steppe soil types. These include chestnut, gray-brown desert, brown semi-desert soils and chernozems.

In such soils, there is a decrease in precipitation and an increase in evaporation. To assess the water regime, a moisture coefficient has been developed. In this case, it decreases from 0.6 to 0.1.

The water reserves that were accumulated in the steppe soil during the spring are actively spent on transpiration and physical evaporation. By the time autumn comes, they become very low. In desert and semi-desert areas, it is impossible to farm without irrigation.

Effluent

This regime of saline soils is typical for the steppe, desert and semi-desert zones. It has a high groundwater table. Soils with good water permeability are characterized by ascending moisture flows. With increased mineralization of groundwater, easily soluble s alts penetrate into the ground, which provokes its salinization.

Irrigation

This water regime is formed when the soil is additionally moistened with irrigation water. With proper rationing of water for irrigation, it is possible to obtain a non-flushing type with the highest moisture coefficient close to unity.

How to regulate the water regime

Proper regulation of the water regime is of great importance in conditions of intensive agriculture. At the same time, it is important to apply special techniques that are aimed at eliminating adverse factors.

To achieve the desired results, it is important to try to balance the amount of moisture that enters the soil, with its consumption for physical evaporation. As a consequence, the moisture factor should be as close as possible to 1.

Regulation of the water regime is carried out on the basis of taking into account climatic and soil conditions. The need for crops in moisture is also of great importance.

To improve the water regime of poorly drained soil in zones of excessive moisture, it is necessary to plan the surface and level different types of depressions. It is in these places that stagnation of moisture is observed.

In soil with temporary excess moisture, excess moisture must be removed. To do this, it is recommended to make ridges in the fall. Swamp soils require drainage reclamation.

The water properties of the soil are of great importance for successful farming. Therefore, it is so important to familiarize yourself with them before planting certain plants.

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