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, geologists urge to pay special attention to it, arguing that underestimation of this disaster may end in a global crisis. Indeed, deflation poses a serious threat to the future of the globe. What is it and what is it expressed in?
general information
The problem of water and wind erosion of soils is extremely urgent, since annually impressive areas suffer from such phenomena. Deflation is usually understood as soil destruction due to air moving flows, as well as the demolition of the upper soil layer by the wind. Deflation is observed if the wind speed exceeds the limit value that the soil can resist. The destructive power of a natural phenomenon becomes so great that no soil stability can save the earth.
Soil particles begin to move due to wind force due to the mutual influence of statics and dynamics. Such forces appear when an air stream flows around a particle located on a ground surface. When the air stream moves, it acts on a spherical element on a dirt 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.
Strength and Influence
Erosion of soils and lands due to the influence of wind, studied by geologists and ecologists, made it possible to understand the features of the correlation of the influence of forces on individual particles. If the combination of gravity, atmospheric pressure, traction practically corresponds to the force of the frontal air pressure, the soil element starts moving, dragging along the surface. If gravity, air pressure, and grip are in total weaker than the lifting force, the soil element is in a suspended moving state.
The reason for the appearance of the lifting force is the difference in wind speeds at different heights available to the soil element. A certain flow enters under a spherical lump. The soil top is somewhat rough, so the speed of such a flow is relatively low. Soil density plays a role. A zone is formed above the particle in which the pressure level is lower than in the surrounding space, and the opposite occurs under it, that is, a section appears that is characterized by a relatively high pressure. This leads to the appearance of a lifting force affecting the soil element.
Complex phenomenon
The development of soil erosion is a set of related processes. They include not only the separation of soil particles, but also their movement with subsequent deposition. In some cases, the wind affects the underlying varieties, affects soil-forming varieties. Deflation is observed if there is a wind whose speed is quite high, so it ensures the movement of particles. Deflation is divided into everyday (or local) and dust storms. For the division, what is happening is analyzed: intensity, time duration, amount of damage. Everyday inflation is observed at relatively low speeds of movement of air masses. They can slightly exceed critical indicators for the soil. Everyday phenomenon in scale is very limited, it covers a field or several located nearby. All stages of the process are observed within this area - the soil is blown out, deposits are deposited. To some extent, any arable land is subject to this phenomenon.
If a very strong wind becomes the cause of soil deflation, a dust storm is observed. This word designates the phenomenon initiated by the wind, which is significantly stronger than the critical transported 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 high elevation of soil elements into the atmosphere is observed - it is hundreds of meters. The range of travel is great - it is estimated in hundreds, thousands of kilometers.
Intensity
To evaluate the process of soil erosion under the influence of wind, it is necessary to characterize the intensity of the phenomenon. Evaluation of this factor gives 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 much the thick soil layer has been lost over a certain time period (month, year).
To analyze how high the risks of deflation are, you need to correlate the known intensity and speed of the process of 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 caused by climate, topography, human activity, and soil. Studying the climate, 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 likely to occur where the level of soil moisture is low, moisture evaporates more actively than precipitation. There is a greater risk of deflation if, during the warmer months, the temperature of the medium is very high, and the relative level of humidification is lower than normal. Deflation is especially pronounced in the Central Asian lands, characteristic of the western Siberian regions and Kazakhstani territories. If you evaluate the condition of the soil in Altai, you will notice that more than 75% of the western area is subject to this destructive process. About 64.1% of all arable land is land for which the process in question is dangerous. About 45% have already become his victims.
The force of erosion, deflation of the soil is determined by the intensity of movement of air masses. Standard wind speed becomes greater during the day, maximum by noon, subsides in the evening. The longer the wind is observed, the greater the loss if the speed of movement of the air masses exceeds the critical value for the soil. To evaluate the critical, you need to determine the speed of air at a height of not more than 10 cm from the soil surface. The wind will be critical, in which grains of sand obviously move. To assess the speed of air movement at an altitude of 10-15 meters above the surface level, special instruments are used - they are located by weather stations. There are recorders designed to measure speed, direction of air movement. Use cup anemometers.
About speed in more detail
In order to study soil deflation, it is necessary to identify the features of winds inherent in the region. It is recommended that measurements of speed and direction be made with three-hour pauses. Take into account that from season to season the speed changes, and all changes are natural. The strongest wind is observed at the end of winter, the beginning of spring. Often this stage is fixed at a time when there is no vegetation yet, therefore negative processes quickly spread to large soil territories.
One of the main characteristics of the wind regime is the direction of the air masses, which are a danger to the terrain. To determine it, they use a rose of winds, that is, a diagram along the rhumb. The wind rose gives an idea of ​​which directions prevail and allows you to evaluate which soils are at particular risk.
Precipitation and warming up
As can be learned from special reference books, to some extent, soil protection from erosion and deflation is provided by precipitation, if moderate. They moisturize the soil, enhance adhesion between the media in a different state of aggregation, increase the ability of the soil to withstand deflation, and also mechanically affect soil structures. If the wind is dry, strong - the soil dries up, so the resistance to deflation decreases. The mechanical effect of precipitation is determined by the size of the droplets, the duration of rainfall and its strength, soil quality and the number of cycles of drainage and moisture filling, thawing and subsequent freezing.
Temperature greatly affects the quality of the soil. The alternation of plus temperatures and frost, observed during the day, leads to constant freezing with subsequent heating of the soil. If this is observed very often, the soil is moistened, its level of resistance to destruction decreases.
Topography
In many ways, soil deflation depends on the topography of the area. It affects how the meteorological features will affect the soil, and therefore determines the strength of deflation. Wind is one of the strong, significant factors that shape the terrain. If we are talking about the areas used in agriculture, then the wind here is a tool for shaping the relief at the level of nano-, microparticles. At his expense, sediments (mounds, scythes) appear behind small obstacles. These are, for example, plant stems and tree trunks. Under the influence of wind, shafts appear on the site of forest strips intended to protect the fields. The relief elements are different from each other. If we analyze a plain with crossed sections, we can see, with equal wind parameters, an increase in wind speed with the movement of air masses along an uphill slope, and the opposite phenomenon on a descent. The change in the speed of air masses, depending on the topography, largely controls deflation, determines the patterns of soil development in the region.
Under the conditions of a flat, rugged topography 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, the protruding areas are more prone to aggression than the lee. The level of deflation becomes more significant when moving up. The steepness, geometric features of the slope largely determine the strength of the influence of 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 acts to the least extent possible.
Human influence
Currently, people are thinking about what to do to prevent soil erosion is more effective. 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 housekeeping on some lands. Most of all processes are subject to serozem, light chestnut soil, brown. First of all, semi-desert, desert areas, chestnut territories of dry steppe regions, as well as steppe black soil are affected. Soil qualities responsible for the level of deflation are divided into those that affect its stability and have an indirect effect. The first category includes composition, density, particle adhesion. Chemical, physical, combined processes are indirectly affected, due to which the quantitative parameters of the soil change.
Among all the factors of deflation, one of the strongest is considered anthropogenic. Because of it, the aggregate qualities of the upper level used for arable land change annually. Man changes the density of this layer. Often the result is unfavorable for nature, especially if the work is carried out using special machines. A person adjusts inter-aggregate coupling.
Parameters and composition
One of the important soil parameters is lumpiness. It allows you to understand how many elements in the soil are larger than a millimeter. The higher the lumpiness, the less susceptible the region to deflation. The structural state largely depends on the particle size distribution. Among the lands in the steppe that are cultivated 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, which is necessary for the appearance of large, strong elements.
To some extent, soil can be protected from deflation if measures are taken to improve its composition. It is believed that the process is less dangerous if the soil is 27% formed by sludge. If there is a lot of dust in the soil, it is more resistant to deflation. Moreover, the nature of the destruction itself is largely determined by the particle size distribution. The wind carries the elements, while destroying them, erasing the surface of the soil when small structures move along it. All this leads to an increase in the volume of small elements in the soil. Such are easily carried by the wind.
Organics
In many ways, 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 treatment procedures, chernozem enriched with humus will have more small-sized inclusions. Such a territory is more susceptible to deflation. Embedment of vegetation residues in the soil gives a worse effect than leaving in the upper layer. Being at the top, plants decompose more slowly, replenish the soil with adhesive ingredients for longer, protecting them from destruction. Humus-enriched lands are destroyed faster, as the surface crust appears more slowly here. The formation of such a crust increases the resistance to deflation. The intensity of blowing becomes somewhat less, the volume of loss is reduced.
Water and greens
Soil erosion control involves monitoring soil moisture saturation. Filling with water creates more weight. Critically hazardous for the area indicators of the speed of movement of air flows become more. Moistening leads to the appearance of an aqueous film. When the particles are closed, cohesion appears due to different aggregate states of substances. Such forces make the soil more resistant to destruction. The intensity of deflation decreases.
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 way, and also affect human agricultural activity. The airflow due to plants becomes more turbulent, the average speed decreases. Because of the plants, a turbulent wake appears, that is, a layer in which the phenomenon of turbulence is especially strong. Due to the group of plants, such a footprint becomes a kind of buffer that weakens the exchange between different air layers. Using this, you can think of the location of vegetation on the field so that the deflation-inhibiting sections cover the entire surface. Then the region will be able to protect as efficiently as possible. The higher the air velocity, the smaller the area protected by the plant. With increased wind, particles can be moved regardless of the protective vegetation.
What to do?
If you check with geologists, ecologists, which measure protects the soil from deflation, many will advise using vegetation. Complex work is supposed. The surface of the territories to be protected from the aggressive phenomenon is mulched. Recommended to sow intermediate varieties. Crops are arranged so that the stripes alternate. It is necessary to create the so-called backstage from tall plants, protecting fields, forest plantings. The strongest cover is formed by varieties of legumes.
To understand how relevant the various measures are, you need to check the condition of the soil. All varieties of territories are divided into weak, medium, and highly deflated. Having determined belonging to a specific group, choose measures to protect the terrain. In any case, the activities should 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 from tall plants. Equally important is the formation of a protective soil cover. His area of ​​responsibility is to perceive wind shocks that could otherwise destroy the soil.
Many agronomists know what action protects the soil from deflation - the introduction of chemical products that make particle adhesion more powerful, thereby increasing the strength characteristics of the soil.
Comprehensive measures
Soil protection from erosion involves agrotechnical work, organized agricultural, forestry and land improvement. . , . , . , .
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The level of soil protection in different seasons depends on the biological qualities of the culture that man cultivates. The highest level of protection is in areas reserved for perennial plants. Steam fields are protected to a minimum. Areas occupied by cabbage, onions and similar crops also have virtually no protection. The biological mass of these plants is too small, so it is not possible to protect the area from blowing soil. Effective include corn, cotton. To the benefit of the soil will be the planting of sunflower.