The need for reclamation by climatic zones. Drainage reclamation, methods and methods of drainage

General patterns placement of land reclamation. The location of land reclamation is determined by both natural and socio-economic conditions, and the level of development of the productive forces of society. Soil and climatic conditions determine the need for certain types of land reclamation. Hydrological, hydrogeological and geomorphological conditions determine the possibility of reclamation in a particular territory. The complexity and order of their implementation. From natural conditions And biological features crops depend specific ways and land reclamation techniques. Zonal natural factors (climate, soil) determine the zonal nature of the location of reclamation sites. Azonal natural factors (relief, tectonics, lithology, etc.), as well as the degree of continental climate, determine the provincial characteristics of natural reclamation factors. Socio-economic conditions influence both the development and location of land reclamation and their effectiveness. To the number economic factors, affecting the placement of reclamation activities include:

• 1) general economic factors (population and labor resources, level of development and location of settlements, level of technical progress, state and development of transport and transport networks, specialization and concentration of production, level of intensity of land use);
• 2) special agricultural (position in relation to populated areas, water and energy systems, enterprises processing agricultural products, agro-industrial enterprises, material resources);
• 3) economic demands (expanding agricultural production, reducing production costs, faster payback on land reclamation costs).

The influence of the above factors determined the following patterns of land reclamation placement in Russia:

• 1. Drainage reclamation is common in the northern part of the temperate zone, in areas of excessive landscape moisture.
• 2. Irrigation reclamation areas are located mainly in steppes, deserts and semi-deserts.
• 3. Anti-erosion reclamation is carried out in forest-steppe and steppe landscapes.
• 4. Anti-deflation measures are practiced in deserts and semi-deserts.
• 5. Chemical reclamation has been developed in different regions of the country: gypsum - in areas of soil salinity, liming - on acidic soils, salt enrichment reclamation - everywhere where soil fertility is declining.
• 6. Agroforestry is more common in forest-steppe landscapes, hydroforestry - in areas of excess moisture - in Polesie, Western Siberia.
• 7. Microclimatic reclamation is used in suburban farms. For example, growing vegetables indoors. Thermal reclamation is practiced in areas of permafrost.
• 8. Snow reclamation is carried out in arid steppe and forest-steppe landscapes in order to accumulate additional moisture in the spring and insulate wintering crops.
• 9. Specialization and concentration of agricultural production is carried out on reclaimed lands. For example, the production of vegetables in suburban farms, the production of fodder crops on drained lands in the Non-Black Earth Region.

Land reclamation - basic concepts and definitions. Goals and objects of drainage reclamation. Melioration as a participant in the water management complex.

Agricultural reclamation – a set of technical, organizational, economic and socio-economic measures aimed at radically improving unfavorable natural conditions and increasing soil fertility in order to obtain high sustainable crop yields.

Land reclamation actively influences the development of agriculture and helps improve human life.

Reclamation, changing the water regime of soils in the direction necessary for agricultural production, simultaneously affects the air, nutritional, thermal and agrobiological regimes of soils, increases their fertility and creates conditions for obtaining high and sustainable crop yields.

The formation of excess or lack of moisture in the soil depends on zonal and local topographical, hydrogeological, hydrological, soil and climatic factors.

With the help of a set of reclamation, agrotechnical, cultural, organizational and technical measures, a person changes in the necessary direction the unfavorable influence of local factors on agricultural production, and when these measures cover a large territory, the zonal factors also change.

Different zones require different types of reclamation. In conditions of excessive moisture, the main reclamation measures are aimed at removing excess water, increasing aeration, increasing soil temperature, and developing aerobic processes of decomposition and mineralization of organic matter. In conditions of insufficient moisture, reclamation measures are aimed at replenishing moisture deficiencies in the soil, reducing soil evaporation and temperature, and changing the microclimate of the ground layer of air.

Agrotechnical measures consist of choosing appropriate crop rotation schemes that ensure soil fertility with high-yielding varieties of crops corresponding to natural conditions, soil cultivation and fertilization systems.

Cultural and technical measures include the removal of hummocks, shrubs and woody vegetation, stones, uprooting of stumps, surface leveling, liming and gypsuming of the soil.

On saline or predisposed to salinity soils, reclamation, agrotechnical and organizational and technical measures are carried out to prevent and combat salinization.

The tasks of agricultural reclamation also include the prevention and control of soil erosion and the sliding of canal slopes formed as a result of reclamation, as well as due to the natural conditions of the basin.

A further sustainable increase in agricultural production is possible only by increasing productivity on existing lands and introducing new acreage as a result of their reclamation.

The development of land reclamation as a means of increasing agricultural productivity is inextricably linked with the development of agriculture, the growth of productive forces, changes in production relations, and its social conditions.

Great importance is attached to improving environmental protection: preserving agricultural land, combating erosion, salinization, waterlogging, flooding and drying out of soils; protection of water sources from depletion and pollution.

Particular attention is paid to reclamation in the waterlogged zone.

Drainage reclamation on agricultural land is designed to actively and regulated the water regime of soils, creating optimal water and associated air, thermal and nutrient regimes in order to increase soil fertility and ensure rational farming.

Drainage reclamation, being a powerful anthropogenic factor in soil formation, leads to the formation of new soils.

Drainage reclamation is necessary in the zone of excess moisture, that is, in areas where precipitation exceeds evaporation. In addition, waterlogging may be a consequence of poor conditions for the outflow of excess water. On watersheds, outflow can be difficult due to the low slope of the surface, its high roughness, and the low water permeability of soils and soils. In low-lying areas, waterlogging is facilitated by the influx of surface and underground waters and their insufficient outflow due to the poor natural drainage of the territory: shallow depths and slopes. River floodplains are often subject to waterlogging. It may be a consequence of human activity: flooding and periodic flooding of lands along the banks of reservoirs; reducing the capacity of watercourses during the construction of bridges, roads and dams; destruction of forest vegetation on slopes, etc.

An important problem for the development of land reclamation and the country's productive forces is water shortage.

Irrigated agriculture consumes 143 million m3, or 45% total number water consumed in the national economy, and its consumption will increase in the future. Therefore, at present, the problem of saving and strictly rationing water consumption and combating losses is urgent, which will increase yields in the irrigation zone, as well as use water to introduce additional areas of irrigated land into agricultural production.

To use water more efficiently, increase the efficiency of systems and the coefficient of land use of irrigated lands, channels in the earthen bed are lined, replaced with pipelines, reinforced concrete trays, high-performance sprinkler equipment is used, and subsoil irrigation methods are introduced.

The inclusion of irrigation reclamation in the WHC is not always obvious for a number of reasons. On the one hand, the regime of water consumption by plants depends on weather conditions, and therefore it is impossible to unambiguously determine the required amount of resource at each moment of the growing season. This is especially evident in the zone of unstable moisture. On the other hand, the yield of an irrigated field depends not only on the availability of water resources, but also on the amount of photosynthetically active radiation, thermal and nutrient regimes, the timeliness of agrotechnical measures and other factors. Therefore, the inclusion of land reclamation among the participants in the water-chemical complex must be justified taking into account the stochastic nature of the main factors, and primarily water.

The rationale for the need for reclamation can be formulated as follows: determine the probability of a discrepancy between environmental conditions and the optimal range of plant requirements at each moment of the growing season.

Scientific and technological progress plays an important role in land reclamation. Reclamation systems have been created to ensure high and sustainable crop yields; the land use ratio has increased significantly; losses of irrigation water have decreased, the efficiency of irrigation systems has increased; conditions for the efficient use of agricultural machinery have improved; the necessary water-salt and other regimes are created; Much attention is paid to the automation of reclamation systems.

Land reclamation is a national and national task. It is designed to increase soil fertility, protect agriculture from adverse weather conditions, carry out a radical restructuring of agriculture, and increase its intensity.

IN textbook The main types of soil reclamation, the structure of drainage and irrigation systems, the types and chemistry of soil salinization and methods of their reclamation, and issues of agroforestry are considered.

3Reclamation of excessively moist soils: drainage reclamation

3.1 The concept of drainage reclamation

Drainage reclamation began in ancient times: for several millennia, the population of Egypt, Burma, India, Vietnam, and China built dams in the valleys of large rivers to protect floodplains from floods. The Greek historian Herodotus described one of the first drainage systems in the Nile Valley more than 2,000 years ago. Drainage as a reclamation measure became widespread in the ancient period in Greece. Later, the Roman writer Cato (1st century BC) in his treatise “On Agriculture” described open drainage systems used in Ancient Rome for draining soils in vineyards and olive plantations. Many of these systems are still in effect today. In the 10th century In Europe, work began on the installation of drainage systems in the North Sea basin. They were especially intense in the 12th – 14th centuries. Large swamps, coastal lowlands, river deltas, and lake depressions were drained.

In England, in 1252, under King Henry III, the first law on the drainage of agricultural land was passed, which became the basis for the development of land reclamation in subsequent centuries. The first closed drainage system in Europe was apparently built in this country under Henry V at the end of the 15th century.

The intensive development of drainage work in Russia was initially associated with the activities of Peter I. He undertook the drainage of swamps in connection with the development of the coast of the Gulf of Finland, the construction of St. Petersburg and other cities, fortresses, and factories. The action of open drainage systems was described by M.V. Lomonosov in his work “The Livonian Economy” (1738). At the end of the 18th century. A.T. Bolotov developed issues of drainage of the northern regions of Russia. However, in the post-Petrine period until the second half of the 19th century. work in the field of soil drainage in Russia was carried out on a very limited scale. The abolition of serfdom and the rapid development of capitalism were the driving factors for soil reclamation.

Drainage reclamation is one of the main ways to increase the productivity of agricultural land, which occupies 10% of the planet's land area. A sixth of these lands have been reclaimed, and from 40% to 50% of all agricultural products produced are obtained from them.

Dehumidification (drainage) plays important role in the creation of transport communications, industrial and civil purpose, sports facilities, airfields, etc.

The objects of drainage reclamation are swampy and swampy soils. When they are reclamated, wetting and plant diseases are eliminated, and favorable conditions for mechanization and processing of fields, increases labor productivity. Very often, land reclamation turns out to be not only the main link in agricultural and forestry production, but a necessary condition optimization of human life in humid landscapes.

3.2 Design of the drying system

The drainage method, that is, the fundamental focus of reclamation measures, determines the causes of soil waterlogging. Thus, when soils become swamped with groundwater, the method of drainage will be to lower the groundwater level; When swamping with alluvial slope waters, the main goal is to intercept these waters and accelerate their discharge beyond the drained territory. When soils are swamped by alluvial channel waters, the drainage method consists of protecting territories from flooding by alluvial channel waters, etc. If soil waterlogging is associated with the simultaneous action of different factors, then drainage methods in this case can become more complex.

Drying system is a complex of structures necessary to remove excess gravitational moisture from the horizons of the soil profile. A properly constructed drainage system should provide: optimal water-air regime in the area where plant root systems are located and the possibility of (free) accessible regulation; the possibility of early sowing; accessibility to the use of a variety of agricultural machinery and the possibility of transporting crops from the drained area. Typically, the drainage system consists of the following components (elements) - Figure 3.1:

1) drained territory;

2) fencing network;

3) regulating network of dryers or drainage;

4) conductive collector network;

5) main canal;

6) water intake;

7) structures on the drainage network.

Applying all or individual elements fencing network due to the reasons for waterlogging of the soils of the drained object. Elements of the fencing network include dams, protective shafts, upland and trap canals.

Conductive collector network collects water from the regulating network of dryers and transports it to the main canal. This network plays mainly a water supply role. It is represented by open channels or closed material pipelines made of plastic, ceramic and other materials. Dryers flow into second-order collectors. From these collectors, water flows into first-order collectors (collectors) and finally enters the main channel of the drainage system.

1 – river-receiver, 2 – main canal, 3 – open collector, 4 – open drainers, 5 – catch canal, 6 – closed collector, 7 – drains, 8 – track road, 9 – crossing pipe, 10 – wellhead structure , 11 – observation well, 12 – upland canal, 13 – trapping canal, 14 – protective dam.

Figure 3.1 – Elements of the drainage system

Dryer network or drainage(English drain - drain, drain) is a system of underground drains (pipes, cracks, passages in the ground), as well as open channels for draining water from the soil. Closed drainage helps to increase the use of land, eliminate the breeding grounds of weeds, and improve the conditions for mechanization of work. This type of drainage is more durable, causes less costs for the construction of transitions and repairs of an open system, helps to increase soil fertility, agricultural culture, increase labor productivity and reduce production costs (Figure 3.2).

Figure 3.2 – Closed drainage

Water intake called a reservoir or watercourse into which drainage and surface water flows from the main canal or from the main collector. The receiving water can be a river, lake, natural thalweg or other watercourses. The water intake must maintain or ensure a regime that prevents stagnation of water masses and deterioration of water quality as a result of the discharge of drainage water.

Depending on the specific conditions, they can be used for reclamation of swampy soils. various types drainage systems, usually having all or part of the components listed above. In areas with periodic flooding followed by drying out of the territory, systems with two-way regulation of the water regime or drying and humidification systems are used (Figure 3.3.)

A – meadows, B – fodder crop rotation, C – vegetable crop rotation; 1, 2 – holes in the embankment dam to regulate the flooding of the floodplain with flood waters, 3 – irrigation pumping station, 4 – drainage pumping station, 5 – sluice on the river, 6 – reservoir on the tributary, 7 – main drainage canal, 8 – collectors, 9 – mountain canals (they are also water supply canals for humidification), 10 – drains, 11 – open collectors, 12 – embankment dam. The meadows are drained by a system of open collectors, and the areas under crop rotation are drained by drainage. During the spring flood, the floodplain is flooded through openings 1, 2 for a given period; excess water is discharged by gravity or pumped out by a pumping station. Meadows are moistened during spring flooding, vegetable crop rotation lands are moistened by sprinkling, fodder lands are moistened by subsoil moistening through drains. Water for irrigation can be taken from the river above lock 5, from the reservoir on the tributary and by pumping station 3. The arrows show the direction of water movement.

Figure 3.3. – Scheme of the drainage-humidification system in the river floodplain

Soil drainage in irrigated areas is necessary to remove excess moisture and salts and maintain groundwater at a level that prevents secondary salinization. The drainage network on the irrigated area provides the possibility of stable and efficient exploitation of reclaimed lands. Currently, data have accumulated confirming high efficiency this event. The collector-drainage network on an irrigated area is a special complex of hydraulic structures consisting of drains, collectors, and pumping stations that ensure the collection and removal of groundwater from irrigated areas.

Drying systems differ significantly in their fundamental design features. These differences are determined by hydrological conditions and the nature of the water intake, the genesis and composition of soils, parent rocks, causes of waterlogging and other factors.

1 Based on the fundamental design features and the nature of water flow into the water intake, drainage systems are divided into gravity and polder systems.

Gravity drainage systems allow excess moisture to be removed from the drained area only under the influence of gravitational forces, by gravity. The movement of water is carried out due to the slope of the drainage and collector lines into the main canal and then into the water intake.

Polder drainage systems, confined to sea coasts, large deltas or floodplains, are usually built in conditions where the water level in the water intake is higher than or at the hypsometric mark of the drained massif. Therefore, the water from the drainage system cannot be discharged by gravity into the receiving water. For this purpose, the entire drained area is embanked, a pumping station is built on the dam, which pumps water into the area behind the dam into the water intake from the supply main canal. Polder systems can be non-flooded (winter polders) or flooded (summer polders). There are sea and river polders, depending on their location on floodplains and deltas or on the sea coast. Polder systems that provide two-way pumping of water (from the supply main canal to the water intake and from the water intake during the dry period to the conductive network of the drainage system to the polder territory) allow effective two-way regulation of the water regime. Polder systems are, under certain conditions, more environmentally friendly than gravity-fed ones. They eliminate the need to regulate the water intake (river), straighten it and deepen the channel and, as a consequence, a general decrease in the base of erosion and groundwater levels of the entire reclaimed landscape.

2 Based on the relation of the control network of dryers to the slope of the surface, drying systems are divided into longitudinal and transverse. With a longitudinal arrangement, the control network of dryers is laid normally to the horizontal lines; when transverse - along the horizontal lines or at a slight angle to them across the slope.

3 According to the location of the control network of dryers in the plan, depending on the structure of the soil cover, systematic or selective drainage is used. Systematic drainage is necessary in areas formed only by marshy and swampy soils. In this case, the entire drained massif is covered with a systematic network of drains (channels).

Selective drainage is used when the structure of the soil cover is complex, which includes both automorphic and hydromorphic non-swampy soils and swampy ones (for example, a combination of soddy-podzolic non-gleyed and deeply gleyed soils that do not require drainage for any use, and heavily swampy soddy-podzolic gley and peaty soils). gley soils, the drainage of which is necessary for any agricultural use). In this case, the regulating network of dryers is confined only to the contours of the actual wetland soils, while in the territory formed by non-wetland soils, only a conducting network passes.

4 Based on the combination (or lack of combination) of a set of hydraulic engineering and agro-reclamation measures for organizing surface and subsurface runoff, drainage systems are divided into combined and non-combined.

Combined drainage systems are used on soils with low values ​​of the filtration coefficient of the subsurface horizon (Kf< 0,1 – 0,3 м/сут). В этом случае наряду с закрытым дренажем или открытой сетью каналов предусматривают выполнение мероприятий по организации поверхностного и внутрипочвенного стоков.

3.3 Types of drainage

Depending on the location, drainage can be vertical or horizontal.

Vertical drainage system ensures a decrease in groundwater levels by mechanically pumping them out of wells (Figure 3.4). It is a complex structure consisting of a water intake (a system of deep wells equipped with filters) with hydraulic equipment and a ground complex. The latter includes the energy sector (high-voltage power line, transformer substation, low-voltage line, starting equipment, electrical equipment), automation, telemechanics and communications equipment, water intake facilities and drainage network, and operational roads. Vertical drainage of irrigated lands is a relatively new method of lowering groundwater levels. It was first used in the United States in the 1920s for drainage and irrigation of agricultural lands in Arizona. During this period, a vertical drainage system of 159 wells was built, which served an area of ​​21,000 hectares. In our country, the first vertical drainage well on irrigated lands was built in 1928 in the Golodnaya Steppe N.V. Makridin and M.M. Reshetkin.

1 – aquifer; 2 – waterproof; 3 – depression curve; 4 – casing pipes, pump, filter.

Figure 3.4 – Scheme of vertical drainage operation

Vertical drainage allows you to actively regulate the groundwater level at the site; it occupies a small area, does not interfere with the mechanization of agricultural work, and allows the use of non-mineralized groundwater for irrigation. On average, one vertical drainage well can serve an area of ​​50 to 100 hectares, and its flow rate ranges from 30 to 200 l/s. The disadvantages of vertical drainage include high operating costs, the need for electricity and high-quality filters.

Vertical drainage is used to solve three main problems:

1) for raising water for irrigation of fresh pressurized groundwater with simultaneous desalinization of soils;

2) to prevent the rise of mineralized groundwater on new irrigated lands;

3) when replacing mineralized groundwater with fresh water.

The most favorable results when using vertical drainage were obtained in highly permeable soil strata with a high well yield.

Horizontal drainage system is a set of horizontal drains and collectors with hydraulic structures, intended for drainage of the irrigated area (Figure 3.5).

1 – drainage pipe; 2 – gravel filling; 3 – layer of sand (second layer); 4 – holes in the drainage pipe.

Figure 3.5 – Horizontal drainage diagram

Drains receive and remove groundwater directly from the reclaimed area, and collectors transport it to the receiving water. If gravity drainage of drainage water from the irrigated area is impossible, water lifting with the help of drainage is provided. pumping station. The collector network of the drainage system is located along the lowest elements of the relief, taking into account the boundaries of farms, crop rotations and other factors. The design flow of open main sewers should provide for the passage of flood flows of 10% probability, taking into account drainage discharge flows. Closed horizontal drains can be ceramic, reinforced concrete, expanded clay concrete, polyethylene, asbestos cement. To protect pipes from silting during construction, trench filters made of sand, gravel and other materials are used.

Dryers on reclamation drainage systems have different designs, shapes, and are made of different materials. Their types currently used in production are shown in Figure 3.6. The diagram shows that horizontal dryers are divided into open and closed.

Open drainage. Drainage channels in reclamation systems are always installed in excavations. The parameters of drainage channels are related to the economic use of drained lands. In meadows and pastures, the depth of the channels is taken to be from 0.8 to 1.0 m, in field lands - from 1.0 to 1.2 m, in gardens - from 1.2 to 1.4 m. The length of the channels is from 600 up to 1200 m, bottom slope - from 0.0005 to 0.005 m. Depressions - flattened channels with a depth of 0.3 to 0.6 m with a slope coefficient of 5.6. Depressions serve to drain surface water. They are used in conditions of surface swamping on heavy, poorly permeable soils. In conditions of ground swamping, the use of hollows to create a control network of dryers is ineffective.

Closed drainage divided into trench and trenchless. Trench drainage includes pottery, plastic, wood, stone, gravel, fascine and others, and trenchless drainage includes mole and slot.

Trench drainage Most often used to drain excessively moist mineral soils. The most famous and more common are pottery and plastic drains. In forest areas and peat bogs, wooden drainage is used from boards, poles, fascines - bundles of brushwood (small branches or willow grass) tied with wire with a diameter of 20 cm to 30 cm. When constructing trench drainage, a trench is laid in which pottery or other drains are laid on the appropriate depth. Taking into account the largest mass of plant root systems in the soil, the depth of the drains also depends on the depth of freezing of the soil and soil.

Figure 3.6 – Types of dryers (F.R. Seidelman, 2003)

Trenchless drainage It is also used primarily for draining deep peat bogs and heavy mineral soils.

Mole drainage is a system of molehills, pipe-like holes with a diameter of 6 to 10 cm, made by a special tool at a depth of 40 to 70 cm. The working parts of this tool, called a plow, are knives and a drainer - a steel cylinder pointed at the front with an increased diameter at its end. . A knife is attached to the plow body, which forms a gap, and a drain, attached by a cable to the bottom of the knife at the required depth, forms a drain (molehole) with compacted walls when the tool moves. The formation of drains begins with an open channel into which water will subsequently flow from them (Figure 3.7).

Figure 3.7 – Design of various types of drains

Biological drainage – a drainage method based on the use of plants with high transpiration capacity for soil drainage. This method was first used in Colchis in the early 30s. Eucalyptus was used as a drying plant. This method, however, is not widely used in land reclamation practice.

3.4 Causes of soil waterlogging

Waterlogged and swampy soils arise as a result of various causes of waterlogging. Based on the tasks of land reclamation and agricultural production, under cause of waterlogging understand the hydrological factor(s) that causes long-term anaerobiosis due to stagnation of moisture in the horizons of the soil profile. It leads to the suppression or death of agricultural crops, the appearance of characteristic signs of soil hydromorphism, and deterioration of the conditions for agricultural and other work. Elimination of these causes with the help of hydraulic engineering and agro-reclamation measures creates favorable conditions for the growth and development of agricultural crops and field work. Wetlands and marsh soils, which are part of the broad group of hydromorphic soils, are formed under the influence of mainly five hydrological factors: atmospheric, alluvial slope, alluvial channel, ground and ground-pressure waters(Figure 3.8).

In addition, waterlogged and swampy soils can result from overgrowing of reservoirs or under the influence biogenic swamping. Thus, swampy and swampy soils are formed under the influence of seven factors (or seven causes) of waterlogging (five hydrological factors of land swamping, overgrowing of water bodies and biogenic waterlogging).

Figure 3.8 – Hydrological causes of waterlogging of land soils

In terms of reclamation, diagnosing the causes of soil swamping is of significant interest, since they determine the method of drainage, the fundamental focus of reclamation measures (for example, lowering the groundwater level when soils become swamped with groundwater, accelerating surface and intrasoil runoff when swamping with alluvial slope waters, etc. ).

There is a certain zonality of the causes of waterlogging. Thus, in the north, in the cold zone, the emergence of hydromorphic soils is associated exclusively with the influence of precipitation, causing the formation of supra-permafrost perch. In the warm temperate zone, within the vast outwash plains, hydromorphic soils, formed under the influence of groundwater, dominate. On moraine, glaciolacustrine, Permian, cover loams and clays of watersheds, predominantly soils swamped by alluvial slope waters are common. In the forest-steppe zone, soil swamping is caused mainly by the wedging out of groundwater and pressure water in the floodplains of rivers. The causes of soil waterlogging are closely related to the geological and geomorphological structure of the territory and vegetation cover.

3.4.1 Signs of soil waterlogging by groundwater and pressure water

Passing through the thickness of loose or highly fractured sediments, ground and pressure waters in places where they pinch out are unloaded from previously leached and dissolved compounds. Therefore, the accumulation of various salts in soils is often a reliable diagnostic sign of waterlogging of soils by groundwater, groundwater, or pressure water. In areas of humid climate, in zones of ground swamping, abundant accumulations of iron oxide, calcium and magnesium carbonates, and less often gypsum are deposited. Ferrous compounds often occur in soils in cases where the drainage area of ​​the basin is formed by sandy soils and especially when groundwater migrates through rocks containing sulfides, carbonates and iron hydroxides. Filtering through such soils, sediments, under the conditions of gley formation prevailing in this territory, dissolve films of iron oxide and bring these compounds into the ground stream in the form of ferrous organic and mineral salts. In aeration zones, these forms of ferrous iron undergo intense oxidation and precipitate in the form of iron hydroxide. With subsequent dehydration, layers of swamp ore are formed in places where hydroxide accumulates, often reaching high power(several decimeters). The accumulation of carbonates in the form of bog marl, tuff, nodules and other formations occurs in cases where groundwater or pressure water passes through a layer of fractured limestone or loose Quaternary sediments enriched with fragments of limestone rocks. In this case, groundwater transports calcium and magnesium salts in the form of bicarbonates, which are retained in solution only at a high concentration of free carbon dioxide. In the discharge zone of these waters, a sharp decrease in the partial pressure of carbon dioxide occurs; bicarbonates turn into carbonates and precipitate.

Therefore, in soils swamped by groundwater and pressure waters, peculiar new formations arise that have important diagnostic value in reclamation surveys and research.

Soils swamped by groundwater develop under the cover of specific vegetation. Thus, in the southern taiga zone in near-terrace depressions, communities of black alder, willow and birch are widespread. Meadowsweet, black currant, and stinging nettle grow on alder trees. The trees are often entwined with hops. Between the cobles, soddy sedge, sharp sedge and others form rare hummocks of considerable height, and in heavily watered areas - marsh cinquefoil, trifoliate sedge, marsh marigold, marsh whitewing, floating manna, vesicular sedge, and false sedge. This plant cover is usually confined to mineral soils of alder swamps, as well as to well-decomposed high-ash peat soils enriched with ash and nitrogen nutrition elements.

When swamped by less mineralized groundwater, birch-grass communities and communities of large hummock sedges often settle. Long-leaved speedwell, common loosestrife and valerian grow on sedge hummocks. In this community, along with tall forbs, common reed and various types of reed grass inhabit this community. Reed communities formed by reeds, broad-leaved and narrow-leaved cattails, and lake reeds are usually confined to areas with running water.

In places where hard groundwater pinches out, hypnomoss communities settle; in conditions of swamping with soft waters on swamp soils - sedge-hypnum and hypno-sedge, on mineral soils - wet communities of white grass, communities of small sedges, etc.

However, vegetation is not an exclusive indicator of the causes of waterlogging, since close associations often occur under different waterlogging conditions and different communities occur under homogeneous conditions.

3.4.2 Signs of soil swamping by atmospheric and alluvial slope waters

Atmospheric and alluvial slope waters enter directly into the territory under consideration or travel a relatively short path along the surface of the catchment area. Their chemical composition and the amount of transported fine earth are determined by the size, composition of the rocks and the nature of the drainage area.

The water regime of soils swamped by atmospheric and alluvial slope waters is characterized by pronounced seasonal cyclicity. Their abundant water supply during precipitation and spring snowmelt is replaced by a sharp drop in the level of high water or its complete disappearance during the dry period. Soils swamped by atmospheric and alluvial slope waters are usually confined to massifs formed by rocks of loamy and clayey mechanical composition. At the same time, soils with such waterlogging can also be confined to rocks with a two-membered structure (the upper light sediment of sandy or sandy loam granulometric composition is underlain by acidic, carbonate moraine or cover loams and clays).

In the north, in the cold zone, supra-permafrost perched water can form in soils associated with any rock. The genesis of these soil-forming rocks is different.

In the Urals, soils swamped by surface, predominantly alluvial slope waters are formed on loamy and clayey red-colored eluvium of carbonate Permian rocks.

Soils confined to fluvioglacial sands, underlain at shallow depths by moraine loams, are widespread in the middle part of the zone.

The formation and development of soils under the influence of surface swamping occurs under the cover of plant associations that are undemanding to the conditions of ash nutrition - cereals-forbs-small grasses, wet small sedges, sedge-reed grasses, etc.

End of introductory fragment.

An external sign of lands, the normal use of which requires drainage reclamation, is excessive moisture in the root layer. The main types of excessive soil moisture: mineral permanently or temporarily excessively wet soils, wetlands and swamps.

Excessively moistened mineral soils- these are territories in which the sod-podzolic process of soil formation is widely developed and which are subject to periodic waterlogging (in spring, autumn and summer during periods of prolonged rains), as a result of which the timing of field work is delayed, sparseness of seedlings and soaking of crops is observed, which in total leads to a decrease or complete loss of the crop. It is advisable to drain such lands periodically, depending on the type of crops grown, and it is necessary to control the moisture content in the soil.

Wetlands are lands whose excessive moisture has led to the development of moisture-loving vegetation on them and the beginning of the peat formation process (the peat layer on the surface is less than 30 cm). The feasibility of their drainage is determined depending on the soil-forming factors and the nature of agricultural use. The largest areas of wetlands are in the northern regions, where precipitation usually exceeds evaporation.

Swamp- this is a separate area of ​​the earth's surface with constant excess moisture, with typical hydrophilic vegetation on which organic matter accumulates, i.e. the process of peat formation is underway. Bogs, depending on their location in the relief and the type of composing peat, are divided into lowland (eutrophic), transitional (mesotrophic) and raised (oligotrophic). The most valuable for agriculture are lowland bogs composed of sedge, alder and other types of herbaceous and woody peats, high-ash and well-decomposed.

Lowland marshes(Fig. 3.2.1) are usually formed on low relief elements, in the coastal strip of lakes and in river floodplains and have a concave surface. The process of overgrowing reservoirs begins with the deposition of amorphous peat and silt, called sapropel, on its bottom. On this layer, starting from the banks, characteristic vegetation, green (hypnotic) moss, develops and dies, gradually filling the reservoir. In addition to surface water, the swamp is also fed by groundwater, rich in mineral soil particles. Therefore, the ash content (the content of mineral particles as a percentage of dry weight) of the lowland swamp is significant and reaches 10-20%. The thickness of peat in lowland bogs varies within a wide range of 7-10 m.

Unlike the lowland raised bogs(Fig. 3.2.1) are a convex surface with poor vegetation and white moss (sphagnum). Raised bogs are formed in elevated areas - watershed plateaus composed of heavy soils, in basins and depressions of coastal terraces under conditions of moistening by precipitation.

These swamps do not receive nutrients from ground and surface waters. Raised bogs are independent formations or represent the final stage of development of lowland bogs as the peat layer increases and the connection with groundwater is lost. Raised bog peat is characterized by a low ash content (2-5%), low degree of decomposition, acidic reaction, and high moisture capacity. After drainage, peat from raised bogs is used for fuel or for bedding in livestock buildings, and after enrichment with organic substances, it is used to fertilize fields.

Transitional swamps characterized by properties intermediate between highland and lowland bogs. Here you can find green and white moss, wild rosemary, cranberries, and cloudberries. The ash content of peat in transitional bogs is 5-10%. After drainage, agricultural use of the land of these swamps requires the application of fertilizers and lime.

Fig.3.2.1. Types of swamps: 1-raised swamp; 2 - transitional swamp; 3 - lowland swamp;
4 – sapropel

3.2.2. Requirements of agricultural production for the water-air regime of the soil. Norm for drainage of agricultural land. Drying methods

For the growth and development of crops, light, heat, air, water and nutrients are necessary, and none of these factors can be replaced by another. Light and heat are cosmic factors and man cannot control them; he can control the remaining factors, for which it is necessary to know the conditions imposed by the plant on external environment(duration of flooding, need for water, air and food elements).

Flooding of drained lands by spring floods is not allowed when they are used for winter crops. The duration of flooding of perennial grasses should not exceed 20-25 days. The smaller the flood layer and the higher the water temperature, the shorter the permissible period of flooding.

Flooding of the surface of drained lands by summer floods during the growing season without reducing agricultural yields is possible for no more than 0.5 days for grain crops, 0.8 days for vegetables, silage crops, root crops and 1-1.5 days for perennial grasses on soils of heavy mechanical composition. Duration of drainage of excess water from the arable horizon up to 30 cm deep during the growing season: for grain crops 1-2 days, vegetables 1-1.5 days, grasses 2-3 days, from the subsoil layer (30-50 cm) regardless of the crop - over the next 2-3 days, and from the horizon 50-80 cm in another 4-5 days. To ensure the aeration necessary for root respiration and decomposition of organic matter, constant gas exchange must occur in the soil, in which the entire volume of air in its active layer could be renewed within a short period of time - 8 days. The volume of air contained in this layer should be: for grasses - no less than 15-20% of the soil porosity or total moisture capacity, for grain crops - no less than 20-30 and for root crops - no less than 35-40%. Consequently, the highest soil moisture in the active layer for grasses should be about 80-85% of the total moisture capacity, for grain crops 70-80 and for root crops 60-65%. Soil moisture depends on the groundwater level, precipitation, evaporation, soil properties and agricultural technology.

The most characteristic indicator on which the moisture content of peat soil depends is the groundwater level. According to the definition of A. N. Kostyakov, the groundwater level that provides the most favorable water-air regime of the soil for a particular crop during the growing season is called dehumidification rate.

Dehumidification rate agricultural land depends on the type of crops, water-physical properties of soil, period of year and weather conditions. For plants that are less demanding on aeration conditions, have a shallow root system and high water consumption, it is less; It is also lower for soils with a low capillary rise, as well as for drier and warmer years.

Table 3.2.1

Values ​​of drying norms in cm

The drainage rate for agricultural crops depends on the type of crop, the nature of the soil and reaches a maximum during the growing season. During the sowing period, its value is reduced by 20÷30%.

Drying methods

Drainage methods are technical and agrotechnical methods and means by which one or another drainage method is carried out. The following drainage methods are recommended depending on the type of water supply, soil, geological conditions and economic use of the drained land:

1. Drainage with single channels and a systematic open network on permeable mineral soils (sands, sandy loams, light loams).

2. Drainage with open channels and closed horizontal drainage in combination with agro-reclamation measures on poorly permeable mineral soils (heavy loams, clays).

3. Thin peatlands, underlain by poorly permeable soils, are drained for arable land and pastures using closed drainage. Thick peatlands (more than 1.5÷2 m) are pre-drained with open channels and mole drainage, and then after the peat settles, closed drainage is laid on them.

4. Peatlands of non-confined ground feeding, underlain by permeable soils (k> 5 m/day), when used for arable land and pastures, are drained by open canals in combination with sparse closed drainage.

5. At alluvial water supply sites (alluvial and deluvial types), river regulation and the construction of upland catch and head canals are used. For surge waters, the polder drainage method is used.

6. To combat flooding during infiltration feeding, coastal, ring and head drainages are used.

7. For ground-pressure water supply, vertical drainage is applicable under appropriate hydrogeological conditions.

Lands that have a water regime unfavorable for agricultural plants and require reclamation include excessively wet land areas. Total area Such lands in the territory of the former USSR amount to approximately 235 million hectares, including swamps and wetlands - 190 million hectares, mineral permanently or temporarily wetted lands (floodplains, flooded lands in areas of reservoirs and lakes) - 45 million hectares. Significant areas of excessively wet lands are located in the tundra zone and forest zone, and the share of wetland and bog soils in the taiga and taiga forest zones accounts for 19-26% of the total area of ​​the zone. Approximately 135 million hectares of excessively wet land are suitable for agricultural use, while the share of agricultural land in Russia is 24% of the area of ​​all swamp and semi-swamp soils.

Drainage of excessively moistened lands, depending on the types of water supply and the reasons for excess moisture, is carried out by lowering the level of groundwater, reducing its pressure, accelerating the flow of surface water and draining water from the arable horizon, fencing the drained area from inflows from surface and groundwater. For this purpose, various types of drainage (horizontal and vertical) and open channels are used. Arable lands are drained mainly by closed horizontal drainage.

At any land use site, due to the variety of types of water supply and the reasons for excess moisture, not one, but several methods and methods of drainage are used in various combinations.

By draining excessively wet lands, the water-air regime of the root-inhabited soil layer is regulated. However, such lands remain infertile and uncultivated and, as a result, are not prepared to produce high yields of agricultural crops. Therefore, drainage is considered as the beginning of work on the reclamation of swamp lands. After drainage, in order to transform these lands into agricultural land, a set of cultural and technical measures are carried out, such as preparing or improving the topography of the land plot, creating and cultivating the arable layer.

The use of a complex of agrotechnical and reclamation techniques, such as the application of optimal doses of fertilizers, loosening and moistening of soils, makes it possible to annually obtain high and sustainable crop yields. Thus, the drained lands of many regions of the Non-Chernozem Zone of Russia, with a share of 3(M0%) of the total arable lands, provide a harvest of flax, perennial grasses, potatoes and root crops, amounting to 50 to 70% of the dump.

With proper operation and intensive use of drained land, the costs of constructing drainage systems pay off in 7-10 years.

However, with an incorrect drainage regime in the territories, there is a decrease in the groundwater level to unacceptable limits, which causes drying of the land, wind erosion, rapid mineralization of peat, changes in the quantitative composition of water, vegetation and wildlife.

Drainage of excess soil moisture is combined with irrigation, which is necessary for the normal growth and development of agricultural crops suffering from summer periods from a lack of moisture in the root layer of the soil. Guaranteed water supply for drained swamps protects peat soils from possible fires, the occurrence of which is caused by the ability of peat to spontaneously combust as a result of the decomposition of organic matter under favorable temperature conditions and peat humidity. A modern drying-humidifying system consists of two parts: drying and humidifying, providing additional moisture to plants during dry periods.

Land drainage is a type of drainage reclamation, and it consists of removing excess ground moisture from them, as well as surface water, including swamps and wetlands. With proper drainage reclamation, high productivity of agricultural and forest lands is achieved. When lands dry out, soil degradation occurs. In them, especially in peats, organic reserves are depleted, and plants experience moisture deficiency. There is also a risk of fires.