The problem of soil deflation in Africa, Europe, Asia, America is very relevant. This is one of the key difficulties associated with the ecological state of the soils of our planet. Ecologists and geologists urge to pay special attention to it, arguing that underestimation of this disaster can result in a global crisis. Indeed, deflation is a serious threat to the future of the globe. What is it and how is it expressed?
General information
The problem of water and wind erosion of soils is extremely urgent, since every year such phenomena affect impressive zones. Deflation is commonly understood as soil destruction due to moving air currents, as well as the removal of the top layer of soil by the wind. Deflation occurs when the wind speed exceeds the limit that the ground can resist. The destructive power of the natural phenomenon becomes so great that no amount of ground stability can save the earth.
Soilparticles begin to move due to the force of the wind due to the mutual influence of statics, dynamics. Such forces appear when an air flow flows around a particle located on a ground surface. When the air flow moves, it acts on a spherical element on the ground surface. Since the particle is located freely, it is subject to the complex influence of gravity, frontal air pressure, and atmospheric pressure. They play the role of lifting and traction forces.
Power and influence
Erosion of soils and lands due to the influence of wind, studied by geologists and ecologists, made it possible to understand the peculiarities of the correlation of the influence of forces on individual particles. If the combination of gravity, atmospheric pressure, cohesive force practically corresponds to the force of the frontal air pressure, the soil element begins to move, dragging along the surface. If gravity, air pressure, and cohesion are collectively weaker than the uplift force, the soil element is in a suspended moving state.
The reason for the appearance of lift is the difference in wind speeds at different heights available to the ground element. A certain flow enters under the spherical lump. The soil top is somewhat rough, so the speed of such a flow is relatively low. Soil density plays a role. Above the particle, a zone is formed in which the pressure level is lower than in the surrounding space, and below it the opposite occurs, that is, a region appears, which is characterized by a relatively high pressure. This leads to the emergence of a lifting effect on the soil element.strength.
Complex phenomenon
The development of soil erosion is a set of interrelated processes. They include not only detachment of soil particles, but also their movement with subsequent deposition. In some cases, the wind affects the underlying varieties, affects the soil-forming varieties. Deflation is observed if there is a wind whose speed is quite high, so it provides the movement of particles. Deflation is divided into everyday (or local) and dust storms. For division, what is happening is analyzed: intensity, duration in time, amount of damage. Daily inflation is observed at relatively low speeds of movement of air masses. They can very slightly exceed the critical indicators for the soil. The everyday phenomenon is very limited in scale, it covers a field or several nearby ones. All stages of the process are observed within this area - the soil is blown out, sediments are deposited. To some extent, any arable land is subject to this phenomenon.
When a very strong wind causes soil deflation, there is a dust storm. This word denotes a phenomenon initiated by the wind, which is much stronger than the critical one carried by the soil. The influence of air masses leads to the movement of large dust volumes. At the same time visibility drops. During a storm, a large height of the rise of soil elements into the atmosphere is observed - it is calculated in hundreds of meters. The range of movement is great - it is estimated in hundreds, thousands of kilometers.
Intensity
To assess the process of soil erosion under the influence of wind, it is necessary to characterize the intensity of the phenomenon. Evaluation of this factor provides data on the quantitative side of what is happening. Take into account how intensively the soil is blown away. The result is measured in t/ha during the year. Another assessment option is to analyze how thick the soil layer was lost over a certain time period (month, year).
To analyze how high the risks of deflation are, it is necessary to correlate the known intensity and speed of the process of the emergence of new soil. The average indicator of this parameter is estimated in millimeters per year. To determine the value, correlate the power of the humus level and the duration of its formation.
Deflation: Factors
All factors of soil deflation are usually divided into those determined by climate, topography, human activity, soil. Studying the climate, they take into account the speed, direction of the wind, the level of heating of the environment at different times of the year, the amount of precipitation inherent in the area. Soil deflation is more common where the level of soil moisture is low, moisture evaporates more actively than precipitation falls. The risk of deflation is greater if during the warm season the temperature of the environment warming up is very high, and the relative level of atmospheric mass humidification is below the norm. Deflation is especially pronounced in the Central Asian lands, characteristic of the western Siberian regions and Kazakhstani territories. If we evaluate the state of the soil in Altai, we can see that more than 75% of the western terrain is subject to this destructive process. Approximately 64.1% of allarable land - areas for which the process under consideration is dangerous. About 45% have already become its victims.
The strength of soil erosion and deflation is determined by the intensity of air mass movement. As a standard, the wind speed increases during the day, is maximum by noon, and subsides in the evening. The longer the wind is observed, the greater the losses if the speed of movement of air masses exceeds the critical one for the ground. To evaluate the critical one, it is necessary to determine the speed of air movement at a height of no more than 10 cm from the ground surface. The critical wind will be the one in which the grains of sand are obviously moving. To assess the speed of air movement at a height of 10-15 meters above the surface, special instruments are used - they are located at weather stations. There are recorders designed to measure the speed and direction of air movement. Cup anemometers are used.
About speed in more detail
In order to study soil deflation, it is necessary to indicate the features of the winds inherent in the region. Measurements of speed, directionality are recommended to be done with three-hour pauses. It is taken into account that the speed changes from season to season, and all changes are natural. The strongest wind is observed at the end of winter, beginning of spring. Often this stage is fixed at a time when there is no vegetation yet, so negative processes quickly spread to large soil areas.
One of the main characteristics of the wind regime is the direction of air masses that pose a danger to the area. To define ituse the wind rose, that is, the rhumb chart. The wind rose gives an idea of which directions prevail and allows you to assess which soils are at particular risk.
Precipitation and warming
As you can see from special reference books, some degree of soil protection from erosion and deflation is provided by precipitation, if it is moderate. They moisten the soil, enhance the adhesion between media in different states of aggregation, increase the ability of the soil to resist deflation, and also mechanically affect the soil structures. If the wind is dry, strong - the soil dries up, so the resistance to deflation drops. The mechanical effect of precipitation is determined by the size of the drops, the duration of rainfall and its intensity, the qualities of the soil and the number of cycles of drying and filling with moisture, thawing and subsequent freezing.
Temperature greatly affects the quality of the soil. The alternation of positive temperatures and frost, observed during the day, leads to constant freezing with subsequent warming of the soil. If this is observed very often, the soil is moistened, the level of its resistance to destruction decreases.
Topography
To a large extent, soil deflation depends on the topography of the area. It affects how meteorological features will affect the ground, and therefore determines the strength of deflation. Wind is one of the strong, significant factors that shape the terrain. If we are talking about areas used in agriculture, then the wind here is a tool for shaping the relief at the nano level,microparticles. Due to it, sediments (bumps, spits) appear behind small obstacles. These are, for example, plant stems and tree trunks. Under the influence of the wind, ramparts appear in place of forest belts intended to protect fields. The relief elements are different from each other. If we analyze a plain with broken sections, we can see, with equal wind parameters, an increase in wind speed when air masses move up the slope, and the reverse phenomenon on the descent. The change in the speed of air masses, depending on the relief, largely controls deflation, determines the patterns of soil development in the region.
In the conditions of a flat rugged relief with the same wind in a free atmosphere, its speed at the level of the soil surface increases when moving up the slope and decreases when moving down the slope. Accordingly, protruding sections are more susceptible to aggression than leeward ones. The level of deflation becomes more significant as you move up. The steepness, geometric features of the slope largely determine the strength of the influence of the wind on the nuances of the relief. The effect of deflation is most pronounced if the slope is convex. If it has a concave shape, the aggressive factor is affected to the least extent possible.
Human Influence
Currently, people are thinking about what to do to prevent soil erosion more effectively. In many ways, the relevance of this is due to the fact that deflation often begins precisely because of human activity, the organization of industry, and the management ofsome lands. Serozem, light chestnut soil, brown soil are most susceptible to processes. First of all, semi-desert, desert areas, chestnut areas of dry steppe regions, as well as steppe chernozem suffer. Soil qualities responsible for the level of deflation are divided into those that affect its stability and those that have an indirect effect. The first category includes the composition, density, adhesion of particles. Indirectly, chemical, physical, combined processes affect, due to which the quantitative parameters of the soil change.
Among all the factors of deflation, one of the strongest is anthropogenic. Because of it, the aggregate qualities of the upper level used for arable land change cyclically every year. Man changes the density of this layer. Often the result is unfavorable for nature, especially if the work is carried out with the involvement of special machines. A person adjusts interaggregate coupling.
Parameters and composition
One of the important soil parameters is lumpiness. It allows you to understand how many elements in the soil with dimensions of more than a millimeter. The higher the lumpiness, the less the region is subject to deflation. The structural state largely depends on the granulometric composition. Among the lands in the steppe plowed by man, the most risky, most severely affected by deflation zones are those that are heavy or lighter than average in terms of particle size distribution. In the first case, the structure is too porous, the second option is accompanied by a lack of binder material, dust, whichnecessary for the appearance of large, durable elements.
Soil can be protected from deflation to some extent if measures are taken to improve its composition. It is believed that the process is less dangerous if the soil is 27% silt. If there is enough dust in the soil, it is more resistant to deflation. In this case, the very nature of destruction is largely determined by the granulometric composition. The wind transports the elements while simultaneously destroying them, abrading the surface of the ground as small structures move across it. All this leads to an increase in the volume of small elements in the soil. These are easily carried by the wind.
Organics
To a large extent, soil deflation is determined by the presence of organic compounds. At their expense, the terrain is more fertile, but less resistant to destruction. With equal processing procedures, chernozem enriched with humus will have more small-sized inclusions. Such territory is more susceptible to deflation. Embedding vegetation residues in the ground gives a worse effect than leaving it in the top layer. Being at the top, the plants decompose more slowly, replenish the soil with adhesive ingredients longer, protecting it from destruction. Lands enriched with humus are destroyed faster, since the surface crust appears more slowly here. The formation of such a crust increases resistance to deflation. The intensity of deflation becomes somewhat less, the amount of loss is reduced.
Water and greenery
Soil erosion control involves monitoring soil moisture saturation. Filling with water creates more weight. Moreindicators of the speed of movement of air flows become critically dangerous for the area. Humidification leads to the appearance of a water film. When the particles are closed, there is a cohesion due to different aggregate states of substances. Such forces make the soil more resistant to destruction. Deflation is declining.
In the fight against soil erosion, vegetation comes to the aid of man. It determines the quality of the soil, air, flows in it. Plants correct deflation almost always in a positive direction, and also affect human agricultural activities. The air flow due to plants becomes more turbulent, the average speed drops. Due to the plants, a turbulent wake appears, that is, a layer in which the turbulence phenomenon is especially strong. Such a trace, due to a group of plants, becomes a kind of buffer, which weakens the exchange between different air layers. Using this, it is possible to think over the location of the vegetation on the field in such a way that the areas containing deflation cover the entire surface. Then the region will be protected as effectively as possible. The higher the air speed, the smaller the area protected by the plant. Strong winds can move particles despite protective vegetation.
What to do?
If you ask geologists, ecologists, what measure protects the soil from deflation, many will advise using vegetation. Comprehensive work is expected. The surface of the territories that need to be protected from an aggressive phenomenon is mulched. It is recommended to sow intermediatevarieties. Crops are arranged so that the stripes alternate. It is necessary to create the so-called wings of tall plants that protect fields and forest plantations. The strongest cover is formed by varieties of legumes.
To understand how relevant different measures are, you need to check the condition of the soil. All varieties of territories are divided into weakly, medium, strongly deflated. Having determined belonging to a particular group, they choose measures to protect the area. In any case, the measures must be comprehensive. Wind speed should be reduced over areas prone to erosion. To do this, create obstacles - windbreakers. Their role is played by forests, backstage of tall plants. Equally important is the formation of a protective soil cover. Its area of responsibility is to perceive wind blows, which otherwise could destroy the ground.
Many agronomists know what measure protects the soil from deflation - the introduction of chemical products that make the adhesion of particles more powerful, thereby increasing the strength of the soil.
Complex measures
Soil protection from erosion involves agrotechnical work, organized agricultural, forest reclamation. Agricultural require a rational arrangement of places for cultivation. Studying the qualities of different areas allows you to determine which zones are more susceptible to aggressive factors. Such places are sown with perennial plants, forests are planted here. Technologies designed to protect the soil must be used.
On HS-heavy soils, this is a soil-protective cultivation technologygrain crops in a five-field grain fallow crop rotation. 20% of arable land in this crop rotation is allocated for fallow. Tillage is carried out here leaving stubble. Sowing - stubble planters.
If the soil is light, sow so that the crops grow in stripes. When cutting fields, distribute them so that the long side is oriented across the main dangerous air flow.
The task of agrotechnical work is to make up for the lack of nutrients, to accumulate water in the soil. It is necessary to organize work so that the plow horizon becomes structural, and the speed of air movement near the ground is minimized.
The level of soil protection in different seasons depends on the biological qualities of the crop that a person cultivates. The highest level of protection is in areas reserved for perennials. The fallow fields are the least protected. Areas occupied by cabbage, onion and similar crops also have practically no protection. The biological mass of these plants is too small, so it is not possible to protect the area from soil blowing. Effective include corn, cotton. Planting sunflowers will benefit the soil.
