Types of Soil Erosion

Concept of erosion. Soil erosion – the process of destruction of soil cover. Soil erosion includes removal, transport and redeposition of soil mass. Depending on the destruction factor, erosion is divided into water and wind (deflation).

Water erosion– the process of destruction of soil cover under the influence of melt, rain or irrigation water.

Based on the nature of the impact on the soil, water erosion is divided into planar and linear.

Planar (surface) erosion– washout of the upper soil horizon under the influence of rain or melt water. The mechanism of surface erosion is associated with the destructive impact force of raindrops and the impact of surface runoff of rain and melt water.

Linear (gully) erosion– erosion of soils into depth by a more powerful stream of water flowing down the slope. At the first stage of linear erosion, deep streaky erosions (up to 20-5 cm) and gullies (depth from 0.3-05 to 1-1.5 m) are formed. Their further development leads to the formation of ravines. Linear erosion leads to the complete destruction of soil.

In mountainous areas, along with the development of normal forms of water erosion, mudflows (mudflows). They are formed after rapid snowmelt or intense rains, move at high speed and carry away a huge amount of material in the form of fine earth, pebbles and large stones. The fight against them requires the construction of special anti-mudflow structures.

Based on the rate of development, a distinction is made between geological (normal) and accelerated erosion.

Geological (normal) erosion- a slow process of washing away particles from the soil surface covered with natural vegetation, in which the loss of soil is compensated for during soil formation. This type of erosion occurs everywhere, causes virtually no harm and does not require soil protection.

Accelerated erosion occurs when natural vegetation is removed and soil is misused, resulting in a sharp increase in the rate of erosion. This type of erosion leads to a decrease in soil fertility, and sometimes to the complete destruction of soil cover, and requires soil protection.

Wind erosion (deflation)– the process of destruction of soil cover under the influence of wind. Depending on the size of the particles, they can be transported by the wind in suspension, jumping or sliding along the surface. There are dust (black) storms and everyday (local) deflation.

Dust storms repeat once every 3-20 years, carry away up to 15-20 cm of the surface layer of soil. In this case, large soil particles move short distances, stopping at various obstacles and in depressions of the relief. The smallest soil particles (<0,1 и <0,001 мм) в виде воздушной суспензии перемещаются на десятки, сотни и даже тысячи километров.

Everyday Deflation more slowly but regularly destroys the soil. It manifests itself in the form of top erosion and drifting snow. At crown erosion and soil particles rise high up in the vortex (turbulent) movement of air, and when drifting snow they roll over the surface of the soil with the wind or move spasmodically at a small height from the soil.

When rolling and jumping, particles hit and rub against each other, which increases their destruction. This contributes to increased deflation.

Erosion areas. Water erosion is most common in zones of gray forest soils, chernozem, chestnut soils, in agricultural areas of the taiga-forest zone, and in mountainous regions.

Wind erosion is common mainly in areas of insufficient moisture and low relative air humidity: in areas of unstable moisture, in arid areas, in deserts and semi-deserts.

Ecological consequences of erosion. As a result of erosion, a decrease in soil fertility occurs (with surface water erosion and deflation) or complete destruction of the soil cover (with linear water erosion). The decrease in fertility is associated with the gradual removal of the most fertile upper layer and the inclusion of less fertile lower horizons into the arable horizon. The degree of fertility reduction depends on the degree of washout or deflation.

As a result of erosion, the physical, chemical and biological properties of the soil deteriorate. The content and supply of humus decreases, its qualitative composition often deteriorates, the reserves of nutrients (nitrogen, phosphorus, potassium, etc.) and the content of their mobile forms decrease. The structural condition and composition deteriorate, porosity decreases and density increases, which leads to a decrease in water permeability, an increase in surface runoff, a decrease in moisture capacity and reserves of moisture available to plants. The loss of the upper most humified and structured layer leads to a decrease in the biological activity of soils: the number of microorganisms and mesofauna decreases, and the microbiological and enzymatic activity of soils decreases.

In addition, water erosion is accompanied by a number of other unfavorable phenomena: loss of melt and rainwater, reduction of water reserves in the soil, dismemberment of fields, siltation of rivers, irrigation and drainage systems, other reservoirs, disruption of the road network, etc.

Ultimately, the deterioration of the fertility of eroded soils leads to a decrease in the yield of agricultural plants.

Conditions for the development of erosion. Distinguish natural And socio-economic conditions development of erosion. In the first case, the natural conditions themselves are predisposed to the manifestation of erosion processes. In the second case, the development of erosion is facilitated by improper human use of land. Natural conditions include climate (the number, intensity and size of raindrops; the thickness of the snow cover and the intensity of its melting), relief (steepness, length, shape and exposure of the slope), geological structure of the area (the nature of rocks - their susceptibility to erosion, washout and deflation, the presence of dense underlying rocks), soil conditions (grain size distribution, structure, density and moisture of the upper horizon) and vegetation cover (the presence and nature of vegetation cover, the presence of turf and litter).

Forces such as surf, glaciers, gravity; in this case, erosion is synonymous with denudation. For them, however, there are also special terms: abrasion ( wave erosion), exaration ( glacial erosion), gravitational processes, solifluction, etc. The same term (deflation) is used in parallel with the concept wind erosion, but the latter is much more common.

According to the rate of development, erosion is divided into normal And accelerated. Normal always occurs in the presence of any pronounced runoff, occurs more slowly than soil formation and does not lead to noticeable changes in the level and shape of the earth's surface. Accelerated is faster than soil formation, leads to soil degradation and is accompanied by a noticeable change in relief.

For reasons they highlight natural And anthropogenic erosion. It should be noted that anthropogenic erosion is not always accelerated, and vice versa.

Wind erosion [ | ]

Dust raised by the wind from a plowed field. Iowa, USA, 1890.

Wind erosion manifests itself in the destructive effect of wind on rocks. It is one of the leading geological agents in changing the topography of desert and semi-desert areas and has a great influence on agricultural lands. Wind erosion is also one of the main causes of soil degradation, desertification, dust pollution and damage to agricultural land. Wind erosion includes deflation and wind corrosion.

Deflation represents the blowing and fluttering of loose rocks - sands, forests, plowed soils, the occurrence of dust storms. It is divided into two types: areal and sor. Areal deflation covers large areas, leading to the blowing out of the surface layer of loose rocks and a gradual lowering of the earth's surface. During sor deflation, the destructive geological activity of the wind is concentrated in certain areas, mainly confined to dry logs and plump salt marshes. In the latter case, specific deflationary relief forms are formed - deflationary basins (“deflation basins”", Holwegs): negative forms, elongated in the direction of the prevailing winds, the latter are formed in areas of development of loess and loess-like deposits.

A significant proportion of geological work in wind erosion occurs during dust (sand) storms. They occur almost everywhere, but are most typical for territories with arid and semiarid climates with weak development of vegetation or its absence. The beginning of a dust storm is associated with certain wind speeds, however, due to the fact that flying particles cause a chain reaction of new particles breaking off, it ends at significantly lower speeds. The most severe storms occurred in the USA in the 1930s (“Dust Bowl”) and in the USSR in the 1960s, after the development of virgin lands. Most often, dust storms are associated with irrational human economic activity, namely, massive plowing of land without any implementation, which leads to active soil erosion.

Wind corrosion occurs when wind-blown sand and dust particles impact hard rock outcrops. As a result of wind grinding of rocks, stones, buildings and mechanisms, blowing niches, mushroom-shaped formations and other specific shapes are formed in protrusions of hard or rocky rocks.

Water erosion [ | ]

Water erosion occurs under the influence of temporary flows of atmospheric water (rainfalls, melt water, etc.).

Drip erosion[ | ]

Destruction of soil by impacts of raindrops. Structural elements (lumps) of soil are destroyed under the influence of the kinetic energy of raindrops and are scattered to the sides. On slopes, downward movement occurs over a greater distance. When falling, soil particles fall on the film of water, which facilitates their further movement. This type of water erosion is of particular importance in the humid tropics and subtropics

Planar erosion[ | ]

Planar (surface) erosion is understood as a uniform washout of material from slopes, leading to their flattening. With some degree of abstraction, it is imagined that this process is carried out by a continuous moving layer of water, but in reality it is produced by a network of small temporary water flows.

Surface erosion leads to the formation of and, and on a larger scale, colluvial deposits.

Linear erosion [ | ]

Unlike surface erosion, linear erosion occurs in small areas of the surface and leads to the dismemberment of the earth's surface and the formation of various erosion forms (gulleys, ravines, gullies, valleys). This also includes river erosion caused by constant flows of water.

The washed material is deposited usually in the form of alluvial fans and forms proluvial deposits.

Types of linear erosion[ | ]

In every permanent and temporary watercourse (river, ravine), both forms of erosion can always be found, but in the first stages of development, deep erosion predominates, and in subsequent stages, lateral erosion.

Mechanism of water erosion[ | ]

The chemical impact of surface waters, which include river waters, is minimal. The main cause of erosion is the mechanical effect on rocks of water and the fragments it carries of previously destroyed rocks. When there is debris in the water, erosion increases dramatically. The higher the flow speed, the larger the fragments are transported, and the more intense the erosion processes.

The resistance of soil or soil to the action of water flow can be assessed by critical speeds:

For soils and polydisperse soils, the concept of non-erosive velocity has no physical meaning, since even at the lowest velocities the smallest particles are removed. In a turbulent flow, particle separation occurs at maximum pulsation velocities, so an increase in the amplitude of flow velocity fluctuations causes a decrease in the critical velocities for a given soil.

Erosion of technogenic origin[ | ]

The decisive factor in stabilizing soils and protecting soils from all types of erosion is vegetation cover. Trees and shrubs, grass with a developed root system effectively reduce the speed of surface air flows in the wind, ensure the absorption of the energy of falling drops during rain and the dissipation of water flows on the surface.

Therefore, with anthropogenic impacts associated with soil exposure, for example, ground work during construction, quarrying, construction of slurry storage facilities, etc., there is a danger of a sharp increase in the volume of soil loss with erosion. For example, when constructing an arable field on heavy loamy sandy soil with a slope steepness of 10°, the erosion rate increases by 50-250 times (compared to grass cover), and 7000-35000 times (compared to a forested area). In the absence of anti-erosion measures, soil loss can be 1-10 cm per year. Forms of water erosion (drip, surface and linear) differ in the impact of soil loss. On the test slope (sandy soil, slope 11°), soil loss was distributed in the proportion 1:20:950. As the percentage of silt particles increases, the tendency to erosion increases.

Soil erosion is a significant risk factor in the implementation of infrastructure, construction and agricultural projects, therefore, after ground work, it is recommended to immediately apply grass seeding (“grassing”) to restore the damaged surface and strengthen the slopes. To ensure sufficient protection of the soil during the period between grass sowing and obtaining a stable vegetation cover, a protective coating is often applied along with sowing: manually - biomats, mechanically - hydromulching / hydroseeding.

Spread of erosion[ | ]

Erosion processes are widespread on Earth. Wind erosion prevails in arid climates, water erosion - in humid climates.

Soil erosion control[ | ]

To prevent soil erosion, the correct ratio of land (arable land, forests, meadows) for a given geographical zone and area is ensured, thorough tillage of the soil and also its fertilization and change of crops, change of fallow and sowing, so that soil fertility increases, so that the cultural horizon of the soil increases and is enriched , and did not shrink or leach, wash off or blow out.

see also [ | ]

Notes [ | ]

1. // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
2. Yandex.Pictures (Russian). yandex.ru. Retrieved July 17, 2017.
3. SOILS. Terms and Definitions. UDC 001.4:502.3:631.6.02:004.354
4. Wind erosion // Geological Dictionary: [in 3 volumes] / Ch. ed. O. V. Petrov. - 3rd ed., revised. and additional - St. Petersburg. : VSEGEI, 2010. - T. 1. A - J. - ISBN 978-5-93761-171-0.

The destructive effect of water, wind and anthropogenic factors on the soil and underlying rocks, the removal of the most fertile upper layer or erosion is called erosion. Erosion causes great harm.

As a result of its activity, the humus horizon is washed away, the reserves of energy and nutrients in the soil are depleted, and, consequently, the energy potential decreases and fertility decreases. Suffice it to say that every centimeter of soil washed away is a loss of about 167472 * 10 6 J of energy from 1 hectare of field. These factors lead to disruption of the stability of the ecosystem, and these changes can be profound and even irreversible.

Types of erosion. Based on the rate of manifestation of erosion processes, a distinction is made between normal, or geological, and accelerated, or anthropogenic, erosion.

Normal erosion flows everywhere under forest and grassy vegetation. It manifests itself to a very weak extent; the soil is completely restored within a year thanks to soil-forming processes.

Accelerated erosion develops where natural vegetation is destroyed and the territory is used without taking into account its natural features, as a result of which the process of soil erosion is not covered by the processes of its self-healing. There are ancient and modern soil erosion. The ancient one is represented by a hydrographic network (hollow, ravine, ravine, valley). The ancient erosion has ceased to operate. Modern erosion occurs against the backdrop of ancient erosion; it is caused by both natural factors and human economic activity.

The most common types of soil erosion are: water planar (washout) and linear or vertical (washout);

wind (deflation); irrigation; industrial (technogenic); abrasion (collapse of the banks of reservoirs); grazing (soil destruction by livestock); mechanical (soil destruction by agricultural machinery).

Planar erosion - This is the washing away of the upper soil horizons on slopes when rain or melt water flows down them in a continuous stream or streams. Based on the degree of erosion, soils are classified into weakly, moderately and strongly washed away. Slightly washed away soils include soils in which the upper horizon A has been washed away to half its thickness, moderately washed away - horizon A has been washed away by more than half, heavily washed away - horizon B has been partially washed away. On slightly washed away soils, the grain yield is reduced to 25%, on moderately washed away soils - by 50%, and on heavily washed away soils. - by 70%.

Linear erosion caused by melt and rainwater flowing down in a significant mass, concentrated within the narrow confines of a slope area. As a result, the soil is eroded into depth, deep gullies and potholes are formed, which gradually develop into ravines. Depending on soil and climatic conditions, the growth and formation of a ravine occurs at a rate of 1-3 to 8-25 m per year.

Planar erosion is especially dangerous, giving impetus to the development of ravines, primarily because its manifestation is barely noticeable. If a layer of soil with a thickness of only 1 mm per year is washed away from an arable land of 1 hectare, i.e. approximately 10 tons, this goes unnoticed, although in many cases the natural regeneration of the soil is much lower. Another example is even more clear. If a ravine 100 m long, 5 m wide and 2 m deep has formed on a field of 100 hectares, then the loss of soil and subsoil is 600-800 m 3. The losses from washing away the most fertile top layer 1 cm thick from the same area (100 hectares) are equivalent to the loss of approximately 10,000 m 3 of soil. To more clearly imagine the magnitude of the damage, it should be borne in mind that the permissible level of erosion for thick chernozems is 3 t/ha, for ordinary and southern soils - 2.5, for dark chestnut soils - 2 t/ha. However, actual soil losses often exceed the specified limits of its natural recovery.

With the increase in arable land, the fight against this phenomenon is becoming increasingly important. Therefore, constant attention should be paid to the widespread protection of forests and all vegetation cover, especially in mountainous and hilly areas, and their proper exploitation.

Wind erosion, or deflation, observed on both light and heavy carbonate soils at high wind speeds, low soil moisture and low relative air humidity. Therefore, it predominantly occurs in the arid steppe regions of the country. Plowing light soils and loosening them is especially dangerous in the spring, when they are deprived of a protective green cover, which makes them vulnerable to deflation. Wind erosion manifests itself as daily or local deflation and as dust or black storms.

Dust storms, like winter snowstorms, scatter the loose layer, lift light and small particles and transport them to one or another distance. The lightest soil particles rise high into the air and are carried far beyond their location, while the heavier ones move spasmodically or waddle to the first obstacle. The greatest danger is caused by jumping soil particles. When they hit the soil, they destroy it, increase blowing, and when they encounter fragile crops or perennial grasses, they mark and cover them. In large open spaces, jumping soil particles, like a chain physico-chemical reaction as the hurricane moves forward, cause more and more destruction in the soil. Dust storms along their path partially or completely destroy crops over large areas, fill up roads, irrigation canals, various buildings, and irrevocably demolish the top, most fertile layer of soil. Dust storms, polluting the environment, water, air, negatively affect the health of humans, domestic and wild animals.

Wind erosion due to deforestation and plowing of new lands covers all new areas up to the forest-steppe and even taiga ^Ulyanovsk region, Kazan Trans-Volga region, Lena River basin.

Irrigation erosion often observed in areas of irrigated agriculture; in the zone of its activity, permanent and temporary reclamation networks are disabled. The main reasons for its erosion are weak fixation of the bottom and slopes of canals, an insufficient number of connecting structures when reinforcing them, an increase in slopes, weak infiltration capacity of the soil, subsidence of soil leading to disruption of the normal profile of canals, their clogging, increased water consumption in irrigation furrows or strips. When operating irrigation systems in certain areas, up to 20-45% of water is lost for various reasons due to filtration and leakage, which also contributes to soil erosion. Irrigation erosion manifests itself even in conditions of small slopes with increasing irrigation flow. Irrigation without taking into account irrigation norms and weather conditions of the growing season leads to the accumulation of salts in the topsoil, which sometimes not only reduces soil fertility, but also completely removes such areas from agricultural use.

Industrial erosion arises as a result of mining, especially open-pit mining, construction of residential and industrial buildings, laying highways, gas and oil pipelines.

With erosion, called abrasion(collapse of river banks and other bodies of water), the area of ​​arable land and pastures is reduced, and water bodies become silted.

Due to the overload of pastures with livestock, significant areas are exposed to pasture (trail) erosion. It manifests itself when grazing norms are violated, it is carried out without taking into account the number of livestock, the capacity of pastures and meadows, when cattle are driven through the same areas, without watering the pasture areas with sprinkling in hot weather.

Erosion is the enemy of fertility. It is estimated that every minute on the globe 44 hectares of land go out of agricultural use. More than 3 thousand hectares are irretrievably lost from erosion every day, and in total more than 50 million hectares of fertile land have already been lost. As a result of soil washout, erosion and blowing away, the yield of all agricultural crops is reduced on average by 20-40%. However, the damage caused by erosion does not end there. The formation of gullies, hollows and ravines on the soil surface makes it difficult to cultivate the land and reduces the productivity of tillage and harvesting equipment. Soil erosion, and consequently the destruction of the habitats of plants and animals in biogeocenoses, leads to a disruption of the existing biological balance in natural complexes.

It should be noted, however, that accelerated erosion is not an inevitable process. A high level of agricultural technology ensures timely implementation of comprehensive erosion protection.

Factors of manifestation of erosion processes

relief. Alternation of flat plains and hills as a result of glacial activity. Novogrudok – 330m, Minsk – 350 m, Grodno region. 200-250m

climate. 3 climatic zones (northern, central and southern)

Soil cover and parent rocks(flat on loams, wind on peatlands) Northern and Central parts - water erosion, Southern - wind erosion

vegetation,

Fighting soil erosion.

Erosion occurs as a result of irrational economic activities, improper use of land, and poor agricultural practices in some farms. Grazing of animals without observing the norm of grazing and loading livestock on the slopes of gullies and ravines, plowing the soil and inter-row cultivation along the slopes, ill-conceived road construction, etc. Against the background of ancient erosion, they contribute to the emergence and rapid growth of new foci.

The washout and erosion of lands lead to siltation of water bodies, shallowing of rivers, and clogging of the irrigation network. Fishing, transport, and energy sectors also suffer losses. Damage in agriculture from drought, plant and animal diseases, etc. significantly less than from soil erosion.

The fight against this phenomenon is one of the leading links in a high culture of agriculture. For each natural zone, in accordance with its physical and geographical conditions (soil, climate, topography), farming systems have been developed. The success of erosion control depends largely on compliance with the basic agricultural practices applied in a particular area and on the nature of the land use.

In areas where wind erosion is widespread, soil-protective crop rotations with strip placement of crops and fallows, wings, grassing of heavily eroded lands, buffer strips of perennial grasses, fertilization, snow retention, consolidation and afforestation of sand and other lands unsuitable for agricultural use, regulation of livestock grazing, cultivation of field protection are necessary. forest belts, as well as

non-moldboard tillage leaving stubble on its surface.

In areas where water erosion develops, tillage and sowing of agricultural crops should be carried out across the slope, using contour and ridge plowing, deepening the arable layer, slitting and other methods of treatment that reduce surface water runoff; Soil-protective crop rotations, strip placement of agricultural crops, grassing of steep slopes, fertilization, cultivation of field-protective and anti-erosion forest strips, afforestation of ravines, gullies, sands, banks of rivers and reservoirs, construction of anti-erosion hydraulic structures (changes, ponds, terracing, embankment of the tops of ravines and etc.).

In mountainous areas, anti-mudflow structures, terracing, afforestation and grassing of slopes and alluvial fans, regulation of livestock grazing, and conservation of mountain forests are necessary.

All of the listed activities are usually divided into groups: organizational and economic, agrotechnical, forest reclamation and hydraulic engineering.

For the practical implementation of anti-erosion work, a number of organizational and economic measures are first required. These include proper organization of the territory. On collective farms and state farms, areas are identified that are subject to varying degrees of water and wind erosion, soil erosion plans are drawn up, on which categories of lands subject to water and wind erosion are applied for the differentiated application of anti-erosion measures.

In the United States, in the fight against water erosion, soil cultivation along horizontal lines or contour farming is widely and successfully used, which has increased the productivity of leading crops - corn, cotton, potatoes, etc. Contour farming on slopes of slight steepness ensures the conservation of moisture, the protection of soil from washout, and increased her fertility. In this case, some deviation from the horizontal lines is allowed in case of their strong tortuosity.

The retention of precipitation and the transfer of surface runoff into intrasoil flow is facilitated by the deepening of the arable layer. As a result of this technique, surface runoff in our country was reduced by approximately 25%, which reduced the destructive effect of melt and rainwater.

Vegetation cover plays a particularly important role in protecting the soil from both slope runoff and rainfall.

The high density of vegetation also ensures uniform distribution of snow on the fields. The root system of plants determines erosion resistance and soil structuring. Dead parts of plants and their litter also help reduce runoff and, in addition, improve the vital activity of microflora and mesofauna, and enhance the biological activity of the soil.

Perennial legume-grass grass mixtures stabilize the soil most reliably. They improve the physical properties of the soil and also enrich it with nitrogen, phosphorus, and calcium. Nodule bacteria that develop on the roots of leguminous grasses increase the nitrogen content in the soil by fixing it from the air. At the same time, the importance of annual crops in the fight against erosion cannot be denied, although they are less resistant to it and have less ability to restore the fertility of eroded lands.

All crops can be divided into three groups according to their anti-erosion properties. The first group, which best protects the soil from erosion, includes perennial ladders, the second group includes annual crops, which are significantly inferior to them in this regard. Row crops have the weakest protective effect, and in certain cases, if they are placed along a slope, they can contribute to increased runoff and thereby erosion.

It is generally accepted that, compared with soil washout under perennial grasses, soil washout under grain crops is 4-5 times higher, and under row crops – 25 times higher. Of the annual crops, winter crops protect the soil relatively well, since in spring and autumn they form erosion-resistant vegetation cover. However, row crops in the second half of summer and early autumn provide high projective cover and at this time reliably protect the soil from erosion. On slopes, it is effective to create buffer strips across the slope from the same crop, but with an increased dose of fertilizers and an increased seeding rate, control snowmelt by strip compaction, etc.

Anti-erosion methods also include other methods: non-moldboard tillage with preservation of stubble, embankment and furrowing of plowed land, mole cutting, slicing, mulching with straw at the rate of 1-2 t/ha. For every ton of straw, 10 kg of nitrogen should be applied. Mulching the soil on slopes with substandard straw at a dose of 1-3 t/ha reduces erosion by 3-5 times. Mulch also reduces the depth of soil freezing, which means it promotes early spring runoff absorption, reduced runoff, and increased crop yields.

On erodible soils, the creation of a wind-resistant surface layer is important. For this purpose, special stubble seeders are used, and strip placement of crops and grasses is used.

The use of anti-erosion tools ensures the preservation of stubble on the soil surface, helps retain snow in the fields, improves the soil structure and sharply reduces wind erosion. Blow-resistant soil has 60% particles larger than 1 mm in the top 5 cm layer and persists even at a wind speed of 12.5 m/s at a height of 0.5 m.

On soils subject to deflation (blowing), soil-protective crop rotations with sowing buffer strips of perennial grasses have especially proven their worth. On sandy soils, the area under perennial grasses should be increased to 50%. On less deflated soils, it is advisable to occupy 30% of the arable land with them.

Creating curtains from tall plants (sunflower, corn) improves snow distribution in the fields, reduces the erosive energy of individual streams of water, i.e. reduces soil erosion in general.

In winter, to reduce erosion processes, it is necessary to create snow banks across the slope.

It should also be noted that the application of fertilizers on erodible lands is more effective, since as a result of the application of the entire complex of anti-erosion measures, the loss of soil, and therefore the nutrients added to it, is sharply reduced.

In the fight against water and irrigation erosion, slotting is effective, helping to increase the water permeability of heavy soils. Another way is to use sprinklers with low and medium rain intensity (up to 0.3 mm/min). This makes it possible to increase the irrigation rate to 700-800 m 3 of water per 1 hectare without the formation of surface runoff, save water, avoid salinization and decrease in soil fertility.

Forest reclamation is also an important part of the anti-erosion complex.

PROTECTION OF SOILS FROM SALINIZATION, ACIDIFICATION AND WATERLOGING

These processes contribute to a sharp disruption of the normal functioning of the soil-plant system.

Soil salinization - accumulation of soluble salts and exchangeable sodium in concentrations unacceptable for normal growth and development of plants. Among saline soils, there are solonchak soils with a high concentration of soluble salts; saline, containing more than 5-10% of exchangeable sodium; salt marshes and salt licks. Even with weak salinity, the yield of corn, for example, decreases by 40-50%, wheat - by 50-60%.

Every year, 200-300 thousand hectares of irrigated land around the globe go out of use due to salinity. Saline lands need to be washed with fresh water, but this raises another problem - the discharge of saline rinsing waters, which form huge salty swamps. The discharged waters are saturated with fertilizers, pesticides and defoliants that are toxic to humans and animals.

One of the salinity factors is wind. It captures salty dust and transports it long distances into the interior of the continents. A similar phenomenon is observed in the Aral Sea region, where the wind intensifies the removal of salts and dust from the dried seabed and their transfer to the region.

Soil salinization is possible due to improper agricultural practices, turning saline layers to the surface, and excessive livestock load on pastures. The cause of soil salinization may be the irrigation water itself if it contains elevated concentrations of soluble salts.

There have been cases of accumulation of easily soluble salts (up to 500 kg per 1 ha) under the influence of halophytic vegetation.

Most often, salinization occurs due to the enrichment of the soil with salts contained in groundwater. Simultaneously with the increase in their level, moisture rises through the capillaries into the rhizosphere zone, where salts accumulate as the water in it evaporates. The drier the climate and the heavier the soil in granulometric composition, the more pronounced this process is, the more pronounced the toxicity of salts to plants. An increased content of salts in the soil causes an increase in the osmotic pressure of the soil solution, which complicates the water supply of plants, they are chronically starved, and their growth is weakened. This primarily affects the root system, which loses turgor and dies. Sodium carbonate is especially dangerous for plants. If the soil contains 10-15% of the exchangeable sodium absorption capacity, the state of the plants is depressed; when its content is within 20-35%, the inhibition is very strong.

With increased irrigation rates and losses of irrigation water from canals, the groundwater level also increases. The process when salt accumulation in the soil occurs as a result of disruption of the irrigation regime and water filtration in irrigation canals is called secondary salinization.

As a preventive measure to combat secondary salinization, it is necessary to drain the area using pottery, plastic and other pipes laid to a depth of 1.0-1.8 m with a distance between drains of 5 to 15 m. Irrigation by sprinklers with low to medium rainfall intensity (up to 0.3 mm/min) is also safe in this regard. Subsoil, drip, fine and pulse irrigation are promising. The common advantage of these methods is water saving. Thus, with subsurface irrigation, the irrigation rate can be reduced to 100-300 m 3 /ha. The water flow rate for pulse sprinkling is only 0.01 mm/min. Due to low irrigation rates, the likelihood of salinization and waterlogging decreases. An important advantage of new irrigation methods is the reduction of evaporation from the soil surface, and, in the case of fine irrigation, transpiration. With drip irrigation, water in the form of a drop is supplied directly to the roots. The use of these irrigation methods prevents irrigation erosion, so they can be used on slopes.

The creation of forest belts along canals also ensures a constant groundwater level, as trees intercept and transpire filtered water, acting as biological drainage. To remove salts from the soil, flushing with fresh water is used.

With an increase in soil acidity (pH below 7), its productivity also decreases: the concentration of mobile aluminum increases and at the same time the nutrient content decreases. Acidification depends on the absorption capacity, particle size distribution, water permeability, biological activity of the soil and the humus content in it. Physiologically acidic nitrogen fertilizers increase soil acidity. Therefore, liming and the application of fertilizers rich in calcium are recommended on such lands. Without the use of lime, the effectiveness of fertilizers decreases.

Waterlogging of the soil, leading to waterlogging, is widespread in a number of areas of the Non-Chernozem Zone, and is also observed in other areas near canals, reservoirs and undamped artesian wells. About 8% of the world's land is subject to waterlogging and flooding.

To drain wetlands, slot drains are installed, cut into the ground. On heavy soils, drains are created using mole plows. In the Far East, complex drainage is used, which is a combination of tubular drains with a network of molehills. Other preventive measures are effective: the optimal method of watering and strict adherence to the irrigation regime for crops. Closed drainage has an advantage over an open drainage network, since in this case the usable area is not lost.

However, drainage should be carried out within reasonable limits. A decrease in the groundwater level when draining swamps more than 1.5 m from the soil surface contributes to the rapid oxidation of peat and the removal of nutrients into drainage ditches. With a further decrease in their level, the root horizon becomes detached from the capillary fringe, which leads to the death of forests.

The development of new lands must be carried out taking into account nature protection. Sometimes there is still an opinion that swamps cause great harm, so they need to be drained. However, it should be remembered that swamps perform an important water management function, feeding rivers and groundwater, and purifying polluted atmospheric precipitation.

Reclamation of wetlands must be carried out taking into account the protection of natural resources from depletion and undesirable impacts on the nature of the Non-Black Earth Zone. In this regard, great attention should be paid to environmental control and broad discussion of projects.

Erosion- destruction of rocks and soils by surface water flows and wind, including the separation and removal of fragments of material and accompanied by their deposition.

There are water and wind erosion.

Types of water erosion: gully (linear, streamy), planar and irrigation (irrigation).

Drip erosion

Destruction of soil by impacts of raindrops. Structural elements (lumps) of soil are destroyed under the influence of the kinetic energy of raindrops and are scattered to the sides. On slopes, downward movement occurs over a greater distance. When falling, soil particles fall on the film of water, which facilitates their further movement. This type of water erosion is of particular importance in the humid tropics and subtropics

Planar erosion

Planar (surface) erosion is understood as a uniform washout of material from slopes, leading to their flattening. With some degree of abstraction, it is imagined that this process is carried out by a continuous moving layer of water, but in reality it is produced by a network of small temporary water flows.

Surface erosion leads to the formation of washed away and reclaimed soils, and on a larger scale - colluvial deposits.

Linear erosion

Unlike surface erosion, linear erosion occurs in small areas of the surface and leads to the dismemberment of the earth's surface and the formation of various erosion forms (gulleys, ravines, beams, valleys). This also includes river erosion caused by constant flows of water.

Causes of soil erosion.

• Climate influences the development of erosion processes as a result of fluctuations in temperature, amount and intensity of precipitation, and wind force.
• wind. The erosive force of the wind begins to manifest itself at a speed of 8-12 m/s at a height of 10 m from the soil surface, it becomes significant at 12-15 m/s, and strong at 16-25 m/s.
• Relief is the main cause of water erosion. The length and steepness of the slope, the size of the watershed, and the shape of the slope surface determine the degree of development of erosion processes. The longer the slope and the greater its steepness, the larger the area and with greater intensity the erosion develops.
• Intensity Soil loss depends on the shape of the slope. On convex slopes it is greater, on concave slopes it is less. Often slopes have a complex shape: convex in one place, straight or concave in another.
• Condition and characteristics of soils Thus, well-structured, humus-rich soils of light and medium loamy mechanical composition are characterized by looseness and good water permeability, and therefore washout and erosion on them are sharply reduced. On the contrary, on destructured, sprayed, compacted soils of heavy mechanical composition, water is slowly absorbed, accumulates on the surface and flows into low areas of the relief, causing washout and erosion of the soil.
• The occurrence and development of erosion is largely determined mechanical composition of the soil. Under natural conditions, soils of light mechanical composition - sandy and sandy loam - are more susceptible to deflation. Heavy (clayey) soils are susceptible to air erosion only in a loosened, sprayed state or after the destruction of the top layer as a result of grazing. Calcareous soils - chernozem and chestnut - are easily destroyed by wind. Solonetz soils and solonetzes are wind-resistant.
• Destruction of woody vegetation
• Overgrazing

Soil protective crop rotations

To protect soils from destruction, it is necessary to correctly determine the composition of cultivated crops, their rotation and agricultural practices. In soil-protective crop rotations, row crops are excluded (since they poorly protect the soil from being washed away, especially in spring and early summer) and the crops of perennial grasses and intermediate subsowing crops are increased, which protect the soil well from destruction during erosion-hazardous periods and serve as one of the best ways to cultivate eroded soils.

Agrotechnical anti-erosion measures.

The simplest measures to regulate the surface runoff of melt water are plowing, cultivation and row sowing of crops across the slope, if possible parallel to the main direction of the horizontal lines. One of the most effective soil protection techniques on sloping lands is the replacement of moldboard plowing with tillage without soil rotation.

Forest reclamation measures

They include planting forests and creating protective forest strips for various purposes:

• wind-protective, created along the boundaries of crop rotation fields;
• field protection, laid across slopes to retain surface runoff of colluvial waters;
• ravine and ravine; forest plantations along slopes and bottoms of beams and ravines; water-protective forest plantations around reservoirs, lakes, canals;
• forest plantations for general environmental purposes on lands unsuitable for agriculture.

Water erosion is divided into planar and linear.

Plane erosion is the washing away of the upper soil horizons on slopes when melt and rainwater flows down, forming a network of small streamy gullies and potholes as they move. Such erosion is hardly noticeable, but is catastrophic due to the scale of its manifestation.

Linear erosion is the erosion of soil in depth with the formation of potholes and deep gullies that grow into ravines. This erosion is caused by significant water flows concentrated in narrow sections of the slope. They lead to the complete destruction of soils.

Irrigation erosion is a type of water erosion. With irrigation erosion, soils are washed away and eroded by irrigation water. In mountainous areas, mudflows develop after rapid snowmelt or intense rains, during which mud-stone mass (fine earth, crushed stone, stones of various sizes with water) is transferred from the mountains to the foothill plains.

Based on the rate of development of erosion processes, a distinction is made between normal (geological) and accelerated (anthropogenic) erosion.

Normal erosion occurs under natural vegetation under the influence of geological and other natural causes, when soil losses do not exceed the rate of soil formation, that is, losses are restored during the soil formation process. Such erosion is practically not harmful. It is otherwise called the permissible erosion rate. The issue of erosion rates was considered by A. M. Burykin, M. E. Belgibaev, M. I. Dolgilevich and other scientists, who calculated the annual permissible norms (values) in mm: for soddy-podzolic soils - 0.87, for chernozems - 0.28, for chestnut soils - 0.36 and for gray soils - 0.27. With an average volumetric mass of 1.25 g/cm, the permissible erosion rate for soddy-podzolic soils is 10.9 t/ha, for chernozems - 3.5, for chestnut soils -4.4, for gray soils - 3.4 t/ha . In the USA, the permissible erosion rate varies from 2.25 to 11.5 t/ha, depending on the permeability and thickness of the soil.

Accelerated erosion is associated with human economic activity. It manifests itself when natural vegetation is destroyed and soils are plowed up with slopes steeper than 2°.

For planar erosion, the following gradations according to the intensity of annual soil erosion have been established: insignificant (average annual erosion up to 0.5 t/ha), weak (0.5... 1 t/ha), medium (1...5 t/ha), strong (5... 10 t/ha), very strong (more than 10 t/ha).

For linear erosion, the following gradations according to the intensity of erosion have been established: weak (average annual growth of ravines less than 0.5 m), medium (0.5...1.0 m), strong (1...2 m), very strong (2... 5 m), extremely strong (more than 5 m).

Accelerated erosion is observed in zones of gray forest soils, chernozems, chestnut soils, in agricultural areas of the taiga-forest zone, as well as in mountainous areas. The most common erosion is on the right bank of the Dnieper, Volga, Don, Northern Donets, Desna, Dniester and their tributaries, on the Central Russian, Volyn-Podolsk, Donetsk, Volga, Klin-Dmitrov and Stavropol uplands, on the General Syrt, in the High Trans-Volga region, in the Ob zones and Irtysh, in the Far East, in the foothills and mountains of Crimea, the Carpathians, the Caucasus, the Urals, and Central Asia.

Erosion causes enormous harm to agriculture. Thus, with weak soil erosion, the yield is reduced by 20%, with average - by 40% and strong - by 60...80%. It has been established that when a 20-centimeter layer of chernozem is washed away on each hectare, 150...200 tons of humus, 10...15 tons of nitrogen, 5...6 tons of phosphorus, 40...60 tons of potassium, 50...60 tons of t calcium. The loss of 1 cm of soil layer is equivalent to the return of the history of its development by 1000 years. Consequently, the level of fertility depends on the degree of washout, since as a result of washout, the reaction of the environment, the composition of exchangeable cations, the chemical composition of soils change, the reserves of humus and nutrients decrease, the activity of enzymes, the number of microorganisms and mesofauna decrease. Losses of humus and calcium lead to the destruction of soil structure, reducing their water permeability and moisture capacity. Thus, water erosion leads to a significant decrease in soil fertility or to its complete destruction (linear erosion).

As erosion develops, rivers become shallower, the productivity of valuable agricultural land sharply decreases, and the road network is disrupted.

The main reasons for the development of water erosion are the destruction of natural vegetation, non-compliance with anti-erosion measures, poor farming standards, excessive grazing, improper road construction, etc. The intensity of erosion development is also influenced by natural conditions: climate, topography, vegetation, geological structure of the territory, soil properties .

Among climatic conditions, the amount, mode, intensity, duration of precipitation and its distribution over the seasons of the year, as well as temperature, play a major role in the occurrence of erosion. Dry, deeply frozen soils in regions with heavy rainfall are more likely to be eroded, especially in areas devoid of vegetation. Severe erosion is caused by melt water if thin thawed soil layers are oversaturated with water.

In the development of water erosion, relief is of particular importance (the depth of the local erosion base, that is, the difference in heights of the highest and lowest points of the drainage basin, the steepness, length, shape and aspect of the slopes). With a large depth of the base of erosion, there is a great danger of its manifestation. In the forest zone, soil loss occurs at a slope steepness of 1...1.5°, and in the forest-steppe - 2°. The steeper the slope, the greater the soil loss.

The most dangerous in terms of erosion are convex slopes, since the lower, steeper part of it is washed away by the water collected above. On the southern, south-eastern and south-western slopes the risk of erosion increases.

The influence of the geological structure of the territory on the development of erosion is associated with the different susceptibility of rocks to erosion and washout. Loess and loess-like loams are easily eroded, cover loams are worse, moraine loams are significantly resistant to erosion. Fluvioglacial and ancient alluvial sandy-sandy loam deposits are characterized by good water permeability and are therefore resistant to water erosion.

Soil conditions (particle-size and mineralogical composition, structure, thickness of the humus horizon, humidity, density) significantly influence the development of erosion processes. The soils are light in granulometric composition, well structured, loose, with a thick humus horizon and better resist water erosion. Soils with low humus and a destroyed structure have weak anti-erosion resistance.

Vegetation is an effective means of protecting soils from erosion, as it absorbs the impact of raindrops. Plant roots hold soil particles together, thereby preventing soil washout and erosion. They also help transfer surface runoff into soils. Plants reduce the speed of water flow. Forest litter and turf prevent siltation of pores. Vegetation makes it possible to accumulate more snow and thus weaken soil freezing and ensure better absorption of water into the soil. Violation of vegetation cover leads to the development of erosion. Erosion is most intense on slopes devoid of vegetation (pure fallow, where the erosion hazard coefficient is K = 1).

According to the degree of erosion, soils are divided into weakly washed away, moderately washed away and highly washed away. Below is a soil diagnostics for the main soil types in Russia.

The fight against water erosion includes a whole range of anti-erosion measures: organizational and economic, agrotechnical, forest reclamation and hydraulic engineering, taking into account zonal moisture conditions, topography, and the degree of erosion.

Organizational and economic measures provide, first of all, for the rational land management of the territory, in which plans for anti-erosion measures and their implementation are developed.

Agrotechnical measures include anti-erosion soil cultivation (cultivation across slopes, furrowing, embanking, digging up plowed land and fallows, plowing with soil deepening, slitting, mowing, making storm furrows, leveling gullies and potholes), snow retention, regulation of snow melt, the use of various types of fertilizers, the use of strip agriculture, regulation of livestock grazing. Particular attention is paid to planting soil protection crops, crop rotations rich in perennial grasses, and buffer strips consisting of annuals and perennials. Crops of perennial grasses have the greatest soil-protective efficiency (the erosion hazard coefficient is very low - 0.08...0.01).

Forest reclamation measures are mainly aimed at creating field protection, water-regulating forest and shrub strips laid across slopes, forest plantations (near ravines, near ravines and on the slopes of ravines and ravines).

The task of hydraulic engineering measures includes the retention and regulation of surface slope runoff using various hydraulic structures: terraces of various types, shafts, drainage channels on slopes to intercept and drain the runoff of melt and storm water, summit watercourses, as well as leveling the slopes of ravines, dams in ravines and beams, etc.

In irrigated agriculture, the main attention is paid to preventing irrigation erosion. In this case, soil cultivation techniques and irrigation methods play an important role.