The water regime of the soil is restored. Techniques for regulating water regime in agriculture

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Lukin Andrey Sergeevich, candidate of economics. Sciences, Associate Professor, Department of Management, Vyatka Socio-Economic Institute, [email protected]; Papyrin Vladimir Borisovich, candidate of economics. Sciences, Associate Professor, Department of Management, Vyatka Socio-Economic Institute.

5. Metodicheskie ukazaniya po opredeleniyu ehko-nomicheskoj ehffektivnosti udobrenij i drugih sredstv himizacii, primenyaemyh v sel "skom hozyajstve. M.: Ko-los, 1979. 30 s.

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Lukin Andrey Sergeevich, Candidate of Economic Sciences, Associate Professor, Vyatka social and economic institute, [email protected]; Papyrin Vladimir Borisovich, Candidate of Economic Sciences, Associate Professor, Vyatka social and economic institute.

UDC 631.432:631.433:631.445.4(571.1) GRNTI 68.05.41 L.V. Yushkevich, A.G. Shchitov, V.L. Ershov

OPTIMIZATION OF WATER-AIR REGIME OF CHERNOZEM SOILS IN THE FOREST-STEPPE OF WESTERN SIBERIA

The results of observations of the agrophysical state of chernozem soil in a long-term stationary experiment in the forest-steppe of Western Siberia are presented. Tillage systems in crop rotation for growing spring grain crops were compared. The optimal (0.7-0.8) ratio between air and moisture in the upper layer of chernozem soils for sowing grain at the current density (1.04-1.08 g/cm3) can be achieved when soil moisture is up to 36-40%, what is observed after the snow melts. It is more advisable to bring the density of the top layer for sowing to optimal parameters -1.10-1.15 g/cm3. In this case, soil moisture up to 30-32% due to moisture-accumulating agricultural practices while minimizing the cultivation of chernozem soils optimizes the ratio between air and moisture for sowing grain crops.

Key words: tillage system, predecessor, soil density, porosity, yield.

L.V. Yushkevich, A. G. Shchitov, V.L. Ershov

OPTIMIZATION OF WATER-AIR REGIME CHERNOZEM SOILS OF FOREST-STEPPE OF WESTERN SIBERIA

Presents results of observations of the state of agrophysical chernozem soil in long-term stationary experiment in forest-steppe of Western Siberia. We compared tillage systems in rotation with the cultivation of spring crops. The optimum (0.7-0.8), the ratio between the air and the moisture in the upper layer of chernozem soil for sowing of grain at the current density (1.04-1.08 g/cm3) can be achieved when the soil moisture up to 36- 40% that observed after snowmelt. Furthermore it is advisable to bring the top layer density for seeding to the optimal parameters of 1.10-1.15 g/cm3. In this case, soil moisture up to 30-32% at the expense of the moisture-accumulating processing while minimizing the processing chernozem soils optimizes the ratio between air and moisture for sowing crops.

Keywords: system of processing of the soil, predecessor, soil density, porosity, productivity.

© Yushkevich L.V., Shchitov A.G., Ershov V.L., 2016

Introduction

The development of resource-saving soil protection tillage systems on the chernozem soils of the forest-steppe of Western Siberia requires justification and a comprehensive assessment of the optimal parameters of agrophysical properties under the conditions of chemicalization of agriculture. With a change in the mechanical load on the top layer of chernozem soils, from the use of fertilizers and pesticides, the mass of plant residues on the surface of the field increases, which over time affects the elements of soil fertility, reduces erodibility, increases the content of water-resistant aggregates, optimizes density, water regime and water consumption per unit of production .

The agrophysical state of the top layer of chernozem soils directly affects the life of plants. The primary and determining factor in all soil physics is its density. The water, thermal and air regimes of the soil are directly related to it; it is a significant factor in fertility. Both loose and over-compacted soil are harmful to the crop, and its optimal composition creates the best conditions for plant life.

It has been established that for the life support of most grain crops, it is not so much the parameters of the composition of the top layer that are important, but rather the optimal ratio of soil phases in it, especially in arid climates and a shortage of water resources. Studies of agrophysical parameters show that the most optimal soil conditions for plant life are created with the following ratio of soil phases: solid - 43-44%, liquid - 34-35% and gaseous - 21-23% of the soil volume. Research data on chernozem soils of Western Siberia are extremely limited.

The purpose of the research is to establish the influence of treatment systems on the optimization of the water-air regime in the upper layer of chernozem soils in the forest-steppe of Western Siberia.

Objects and Methods

The studies were carried out in the forest-steppe soil-climatic zone of the Omsk region in a long-term (since 1973) stationary grain-fallow crop rotation of the agriculture department of the Federal State Budgetary Scientific Institution Siberian Research Institute of Agriculture in 2001-2010.

The soil of the experimental plot is meadow-chernozem, medium-thick, heavy loamy with a humus content of up to 7-8%. The density of the top layer is, depending on the soil treatment option, 0.90-1.15 g/cm3, increasing down the profile to 1.40-1.60 g/cm3, and the density of the solid phase, respectively, is 2.50- 2.59 and 2.60-2.70 g/cm3. The total porosity of the humus horizon is 55-63%, below it it decreases to 40-50%. The total porosity is dominated by micropores less than 3 μm and active capillary pores (60-3 μm). The capacity of absorbed bases is 29.5-36.0 mg equivalent/100 g of soil, of which 80-90% is the Ca++ cation. There is no salinity (aqueous pH 6.7-6.8).

The growing season of the agricultural landscape is 162-165 days, the sum of active temperatures above 10 °C is 1800-2000 °C. The average annual precipitation is 350-400 mm, including 190-220 mm during the growing season. Dry winds are usually observed in May and in the first half of summer.

The agrophysical parameters of the top layer of meadow-chernozem soil under various tillage options were studied using generally accepted methods.

Research results

It has been established that for local chernozems the optimal soil density limits are close to the range of 1.0-1.2 g/cm3. V.N. Slesarev (1984) refined these parameters, and the optimal density for grain crops (wheat, barley) was 1.10 ± 0.10 g/cm3. The yield of grains on loose (0.9 g/cm3) and dense (1.3 g/cm3) soil is reduced by 16-32%. Even with a density close to the equilibrium and optimal state, an increase in the proportion of the gaseous phase and a decrease in the liquid phase in the upper layer before sowing grain crops contributes, with insufficient moisture and increased aeration, to the deterioration of the agrophysical parameters of the fertility of chernozem soils.

Observations of the water-physical state of the upper layer of meadow-chernozem soil indicate that even with periodic refusal of the main cultivation to sowing spring wheat, the optimal relationship between air and moisture does not occur, which indicates a shortage of water resources (Table 1).

Table 1

The ratio of solid (t), liquid (l) and gaseous (g) phases in the soil on the second wheat after fallow, %

Basic tillage

Layer Moldboard Flat-cut Minimal

soil, to depth to depth to depth

cm 20-22 cm 12-14 cm 5-6 cm

t f g t f g t z g

After processing

0-10 34 21 45 36 22 42 39 23 38

10-20 33 22 44 39 21 40 44 23 33

20-30 40 18 42 45 19 36 49 20 31

0-30 36 20 44 40 21 39 44 22 34

Before sowing

0-10 30 25 45 29 25 46 29 27 44

10-20 34 27 39 35 28 37 37 28 35

20-30 45 28 27 46 29 25 48 30 22

0-30 36 27 37 37 27 36 38 28 34

The relationship between air and moisture in the upper layer of chernozem soils is largely determined by the method and depth of the main tillage, seasonality and moisture. In autumn, after the main tillage, due to insufficient compaction (less than 1.0 g/cm3) and moistening, the gaseous phase in the upper (0-30 cm) layer significantly (1.5-2.2 times) exceeds the liquid phase, and the ratio between air and moisture increases with decreasing soil density.

Thus, with minimal processing the ratio was 1.55, with flat-cut processing - 1.86, and with moldboard processing it reached 2.20, and this ratio narrows with depth.

For sowing spring wheat, the ratio of soil phases relative to autumn indicators

changes in the direction of a slight increase in solid and liquid and a decrease in gaseous due to the assimilation of non-vegetative sediments and compaction of the upper layer of chernozem. If the amount of the liquid phase practically does not change according to the variants of tillage of the stubble predecessor soil, then the gaseous phase decreases with compaction from 37.0 to 33.7%.

The obtained data on the agrophysical parameters of the upper layer of meadow-chernozem soil indicate that the optimal relationship between the gaseous and liquid phases of the soil does not occur. In the moldboard version of soil cultivation, this ratio in the arable layer of 0-30 cm is the highest - 1.37; with flat-cut tillage it decreases to 1.33 and with minimum tillage it decreases to 1.21. The relatively unfavorable ratio between air and moisture on stubble backgrounds for sowing grain crops is mainly due to insufficient compaction (less than 1.15 g/cm3), and as a result - increased porosity of the top layer, reaching 58-62%. Lack of moisture in the spring and a limited amount of non-vegetative precipitation lead to the sowing and growing season of the crop to an excessive content of the gaseous phase. Calculations show that with moisture equal to the lowest moisture capacity (MC), the air content in the upper layer with optimal compaction can decrease to 20-30% of the soil volume.

It has been established that the use of moisture accumulation techniques in the arid steppe zone (snow retention, high-cut stubble) on the second wheat after fallow increases the content of the liquid phase by 2.7-3.0%, and in a fallow field with curtains it brings its ratio closer to the optimum (1: 0.80) .

According to the fallow predecessor, where moisture conditions are most favorable in arid territories, in the upper layer of chernozem soils the ratio between air and moisture to sowing spring wheat approaches one (Table 2).

At the end of fallowing, the soil cultivation technology had a noticeable effect on the density and moisture content of the top layer. Thus, in the variant with dump steam treatment, according to the early type, the soil density in the 0-30 cm layer was 0.98, with minimal treatment - 1.07 g/cm3, porosity 62 and 56%, respectively. Excessive looseness and porosity of the treated layer in combination with insufficient moisture (close to the water-cooling factor) contributed to

The ratio of solid (t), liquid (l) and gaseous (g) phases in soil on wheat after the steam predecessor, %

Soil layer, cm Basic tillage

Dump to a depth of 20-22 cm Minimum to a depth of 6-8 cm

t | f | g t | f | G

After processing

0-10 35 23 42 34 25 41

10-20 37 24 39 40 26 34

20-30 42 24 34 51 24 25

0-30 38 24 38 42 25 33

Before sowing

0-10 39 31 30 38 33 29

10-20 37 28 35 39 29 32

20-30 42 27 31 43 26 31

0-30 39 29 32 40 29 31

both in terms of dump and minimum cultivation, unfavorable ratio between air and moisture (1.58 and 1.32, respectively).

By the time of sowing spring wheat, the density and porosity of the upper layer as a result of moistening and volumetric deformations of the upper layer practically did not differ among the steam preparation options. The increased porosity of the soil, despite the increase in moisture, contributed to a decrease in the gaseous phase to a minimum. In general, by the time of sowing spring wheat, the ratio between air and moisture decreased with depth, and in the 0-30 cm layer it was 1.10 in the moldboard version of steam preparation, and 1.07 in the minimum.

Similar studies carried out using various methods of processing pure and occupied fallows showed that in pure fallow the ratio between air and moisture before sowing spring wheat in a layer of 0-30 cm was 1.07 for plowing, 1.00 for shallow flat-cutting and the minimum was 0.89, that is, when minimizing processing, it approached the optimal parameters. At the same time, in the occupied (rapeseed) fallow field before sowing spring wheat, the ratio between air and moisture according to the steam treatment options was 1.37, respectively; 1.04 and 0.96. This ratio, in general, due to a decrease in density and spring moisture in a field with occupied fallow, increased with a tendency to optimize while minimizing tillage.

In connection with the introduction of intensive technologies for cultivating grain crops in the region and the application of chopped straw to the field surface, it is important to establish their influence

to optimize the water-air regime Table 3 in the upper layer of chernozem soils. Observations showed that in the closing field of the grain-fallow crop rotation (barley), the systematic use of complex chemicalization, with minimal processing, contributed to an increase in plant residues in the 0-20 cm layer from 0.86 to 1.44 t/ha (by 67.4%), which in general had a positive effect on optimizing the water-physical state of the soil before sowing the crop (Table 3).

The systematic use of chemicals and crushed straw in the variant with moldboard processing did not have any positive changes in the water-physical state of the top layer for sowing barley. With minimal tillage, leaving the bulk of plant residues on the field surface, the amount of liquid phase in the 0-30 cm layer increased to 30% (by 10.7%) while the gaseous phase decreased from 29 to 25%. In this option, the ratio between air and moisture is reduced to 0.81 and approaches the optimal parameters.

Conclusion

Thus, the optimal (0.7-0.8) ratio between air and moisture in the upper layer of chernozem soils for sowing grain at the current density (1.04-1.08 g/cm3) can be achieved when the soil is moistened to 36- 40%, which is observed more often after snowmelt. It is more advisable to bring the density of the top layer for sowing to optimal parameters -1.10-1.15 g/cm3. In this case, soil moisture up to 30-32% (close to NV) due to moisture-accumulating agricultural practices and complex chemicalization while minimizing the cultivation of chernozem soils optimizes the ratio between air and moisture for sowing grain crops.

References

1. On the issue of providing plants with moisture 1. K voprosu obespechennosti rasteniy vlagoy i

and air at different soil compaction / A. Kanarake, R. Thaler // Soil Science. 1962. No. 5. P. 106-113. R. Taller // Pochvovedenie. 1962. No. 5. S. 106-113.

Ratio of solid (t), liquid (l)

and gaseous (g) phases in the soil before sowing barley, depending on cultivation technology, %

Basic tillage

Soil layer, dump Minimum

cm to a depth of 20-22 cm to a depth of 5-6 cm

t f g t f g

After processing

0-10 38 28 34 39 29 32

10-20 43 29 28 44 28 28

20-30 44 27 29 45 28 27

0-30 42 28 30 43 28 29

Before sowing

0-10 37 29 34 39 30 31

10-20 42 30 28 45 31 24

20-30 44 28 28 47 31 22

0-30 41 29 30 44 31 25

2. Soil density as a fertility factor and some features of its determination / L.S. Rock-tanen // Soil density and its regulation by cultivation. Tselinograd, 1973. P. 3-36.

3. Buyankin N.I., Slesarev V.N. Agrophysics and kinetics in minimizing the main cultivation of chernozems / Ros. acad. agricultural Sci. Kaliningrad: Yantarny Skaz, 2004. 160 p.

4. Dospehov B.A. Field experiment methodology. M.: Kolos, 1973. 336 p.

5. On the essence of the concept of volumetric mass and soil density / V.N. Slesarev // Siberian Bulletin of Agricultural Science. 1992. No. 1. P. 3-5.

6. Scientific principles of minimal tillage / I.B. Roar // Agriculture. 1970. No. 2. P. 17-23.

7. Slesarev V.N. Agrophysical foundations for improving the basic cultivation of chernozems in Western Siberia: abstract of thesis. dis. ... Dr. Agricultural Sciences Sciences: 06.01.01. Omsk, 1984. 32 p.

8. Cherepanov M.E. Snow retention in conservation agriculture in Western Siberia. Novosibirsk: Science. Sib. department, 1988. 160 p.

Yushkevich Leonid Vitalievich, doctor of agricultural sciences Sciences, Professor, Siberian Research Institute of Agriculture, [email protected]; Shchitov Alexander Grigorievich, Ph.D. agricultural Sciences, SibNIISKH; Ershov Vasily Leonidovich, Doctor of Agriculture. Sciences, Professor, Omsk State Agrarian University, [email protected].

2. Plotnost pochvyi kak faktor plodorodiya i nekotoryie osobennosti ee opredeleniya / L.S. Roktanen // Plotnost pochvyi i ee regulirovanie obrabotkoy. Tselino-grad, 1973. S. 3-36.

3. Buyankin N.I., Slesarev V.N. Agrofizika i kinetika v minimizatsii osnovnoy obrabotki chernozemov / Ros. akad. s.-h. nauk. Kaliningrad: Yantarnyiy skaz, 2004. 160 s.

4. Dospehov B.A. Methodika polevogo opyita. M.: Kolos, 1973. 336 s.

5. About suschnosti ponyatiya ob"emnoy massyi i plot-nosti pochvyi / V.N. Slesarev // Sibirskiy vestnik selsko-hozyaystvennoy nauki. 1992. No. 1. S. 3-5.

6. Nauchnyie osnovyi minimalnoy obrabotki pochvyi / I.B. Revut//Zemledelie. 1970. No. 2. S. 17-23.

7. Slesarev V.N. Agrofizicheskie osnovyi sover-shenstvovaniya osnovnoy obrabotki chernozemov Zapadnoy Sibiri: avtoref. dis. ... d-ra s.-h. nauk: 01/06/01. Omsk, 1984. 32 s.

8. Cherepanov M.E. Snegozaderzhanie v pochvoza-schitnom zemledelii Zapadnoy Sibiri. Novosibirsk: Nauka. Sib. otd-e, 1988. 160 s.

Yushkevich Leonid Vitalyevich, Doctor of Agricultural Sciences, Professor, Leading Researcher, Siberian Research Institute of Agriculture, [email protected]; Shchitov Alexander Grigoryevich, Candidate of Agricultural Sciences, Siberian Research Institute of Agriculture; Ershov Vasiliy Leonidovich, Doctor of Agricultural Sciences, Professor, Omsk SAU; [email protected].

The state of water in the soil is highly dynamic. Under the influence of various factors (natural and anthropogenic), soil moisture continuously changes both over time and within the soil profile, soil moisture passes from one form to another. The totality of all phenomena of moisture entering the soil, its movement and consumption, and changes in its physical state is called the soil water regime. A quantitative characteristic of the soil water regime is its water balance, which takes into account the incoming and outgoing items of moisture.
The general water balance equation has the form:

The left side of the equation includes income items of the water balance, the right side includes expenditure items. The water balance is characterized by an annual cycle, after which all the processes of moisture inflow and outflow that make it up are repeated, although, if necessary, the water balance is compiled for any observation period.

Depending on fluctuations in weather conditions, the values ​​of the water balance vary significantly and the water reserve in the calculated soil layer at the end of each specific year increases or decreases. However, if there is no progressive climate change, then the water reserves in the soil at the beginning and end of the average long-term cycle are considered equal: W 0 = W 1 . The amount of moisture entering the soil as a result of condensation of water vapor is very small compared to other items of the water balance, and is not taken into account in practical calculations. On flat elevated areas (plateaus, plains) there is no surface and lateral inflow of moisture, and on slope elements of the relief, surface and lateral inflow of moisture are balanced by surface and lateral runoff. After these assumptions, the water balance equation takes the following form:

For example, the roots of forest vegetation penetrate to a depth of 6-10 m, in cereals and grain legumes they reach a depth of 1-2 m, in sunflower - more than 3 m. In the first year of alfalfa’s life, its roots penetrate to a depth of 2-3 m, and in subsequent years - up to 10 m. Therefore, when groundwater occurs at a depth of 5-10 m, the roots of some plants greatly influence the water balance of the soil due to its water-lifting capacity, reaching 3-5 m in loamy varieties. In this case, the water balance is for the entire soil-ground thickness from the surface to the groundwater level. When groundwater is deep, the balance is drawn up for the layer that is annually wetted by precipitation.

Types of water regime. The formation of the water regime of soils occurs under the influence of various factors: climatic conditions, terrain features, lithology of soil-forming rocks, vegetation, depth of the groundwater level, water-physical properties of the soil, and human activity. The nature of the combination and the degree of expression of these factors determine the quantitative ratio of incoming and outgoing items of the water balance. The scale of moisture reserves and the preferential direction of movement of moisture in the soil profile in seasonal and annual cycles depend on this. i.e. the type of water regime.

The foundations of the doctrine of the water regime of soils and its types were laid by G.N. Vysotsky. He identified four types of water regime - leaching, non-flushing, effluent and water-stagnant. This problem was further developed in the works of A. A. Rode, who identified six types of water regime, further dividing them into subtypes. Currently, the following types of soil water regime are distinguished.

Frozen type characteristic of soils formed in the area of ​​permafrost. For most of the year, soil moisture is in the form of ice. During the warm period, under the thawed part of the soil profile there is a frozen layer of soil that serves as a waterproof layer. An aquifer is formed above it - supra-permafrost perch. Due to this, during most of the growing season in the thawed layer, soil moisture is maintained in the range from the maximum field moisture capacity to the full water capacity.

Water-saturated or water-stagnant type is characteristic of marsh soils. In normal years of moisture, soil moisture is at the level of full moisture capacity. In dry years, it decreases to the level of maximum field moisture capacity and even lower.

Washing the type is formed in the case when the amount of precipitation fallen in a year exceeds the amount of evaporation for the same period, i.e., when Ku > 1. In annual and long-term moisture cycles, downward moisture currents prevail over upward ones. In spring and autumn, there is an annual through wetting of the soil thickness down to groundwater, due to which all soluble and geochemically mobile products of weathering and soil formation occur outside the soil profile. A water regime of this type is typical for soils in forest zones: podzolic, soddy-podzolic, brown forest, etc. In spring, the upper part of the profile of these soils is often in a waterlogged state and perched water forms at a certain depth; in the lower part of the profile, the moisture content is almost never lower maximum field moisture capacity.

Intermittent flush type corresponds to climatic conditions with an average long-term balance of precipitation and evaporation (BC = 1), as, for example, in the northern part of the forest-steppe zone, where podzolized and leached chernozems are formed. Through wetting of the soil profile (leaching type of water regime) occurs only in wet years (1-2 times every 10-15 years). In normal wet and dry years, limited soil wetting occurs, which is typical for a non-flushing type of water regime; moisture circulation is carried out within the soil profile. In the lower part of the profile, the soil periodically dries to the moisture content of capillary rupture, in the upper part - to the wilting moisture content.

Not washed in new type is formed in the soils of the steppe and dry-steppe zones (ordinary and southern chernozems, chestnut soils), where the average annual precipitation rate is less than the evaporation value (EV<1). Мощность почвенного профиля, вовлекаемая в годовой влагооборот, чаще всего не превышает 2 м. При этом атмосферные осадки не достигают верхней границы капиллярной каймы грунтовых вод. Связь между атмосферной (почвенной) и грунтовой влагой осуществляется через слой с постоянно низкой влажностью, близкой к влажности завядания. Этот слой Г.Н.Высоцкий назвал мертвым горизонтом. Передвижение воды через мертвый горизонт в том или ином направлении осуществляется в форме пара или пленочной влаги.

In the upper part of the profile, the moisture content of soils formed under conditions of a non-flushing water regime fluctuates in accordance with precipitation from full moisture capacity to wilting moisture content. In the lower horizons, soil moisture throughout the year is between wilting moisture and capillary rupture moisture.

Soils formed under conditions of a water regime of a non-leaching type differ from soils with a water regime of periodically leaching and leaching types in that they are less leached from mobile products of soil formation. The profile of such soils always contains horizons enriched with water-soluble compounds (gypsum, calcium carbonates, etc.) located below the depth to which the average long-term wetting of the soil by precipitation occurs.

Arid or dry type characteristic of desert and semi-desert soils - brown, gray-brown, etc. In such soils, the evaporation rate is significantly higher than the annual precipitation rate (KU = 0.1-0.3). Throughout the year, soil moisture levels within the profile are at wilting moisture levels or even lower. Sporadically, higher humidity levels are observed in the upper horizons.

Sweat type is formed in soils with shallow groundwater levels in the steppe and especially semi-desert and desert zones, i.e., where evaporation noticeably exceeds the amount of precipitation. Under such conditions, there is an intense upward movement of moisture through capillaries from groundwater to the soil surface and its subsequent evaporation. If the groundwater is mineralized, then the upper horizons are enriched with water-soluble salts, which leads to the formation of a large group of saline soils and meadow solonchaks of different chemistry and degree of salinity.

Destructive-effusion type differs from effusion in that the moisture coming from groundwater through capillaries is absorbed by the root systems of plants at one or another depth in the soil profile. At the same depth, salts contained in groundwater precipitate. This type of water regime is typical for meadow and semi-hydromorphic soils.

There are two periods in the moisture cycle regime. After abundant moisture, the soil profile is soaked to the groundwater level. During this period, the downward flow of moisture prevails and the soils are characterized by high humidity throughout the entire profile. As the soil subsequently dries, the downward flow of moisture is replaced by an upward flow, which dominates in the second period, when the capillary fringe of groundwater reaches the root layer and evaporates at a certain depth. In the lower part of the soil profile, moisture remains at a high level, but the upper horizons can dry out to a moisture content lower than the wilting moisture content.

Flood type characteristic of soils periodically flooded by river, slope, and rainwater. In this case, depending on the zone, the geomorphological position of the soil (floodplain, under, slope plume), and the depth of groundwater, periodic flood flooding of the soil is replaced in the inter-flood period by a water regime of another type .

Irrigation type is formed during artificial irrigation and is distinguished by a wide variety of categories depending on the type of irrigation (aerosol irrigation, sprinkling, surface irrigation, subirrigation) and irrigation norm, the depth of seasonal fluctuations in groundwater levels, the presence and nature of artificial drainage. The water regime of this type is divided into:

· irrigation-non-flushing, at which KU>1 taking into account irrigation. There is no through wetting of the soil profile after successive spills;

· irrigation-periodic flushing, at which KU = 1. After watering, in some cases, through wetting of the soil profile occurs.

· Irrigation and flushing, at which KU>1. Through wetting of the soil profile is observed after each irrigation and contributes to a rapid rise in the groundwater level.

DRY TYPE is formed on artificially drained swampy and swampy soils. Its specific characteristics are determined by the type of drainage and the degree of regulation.

The considered types of water regime reflect the general patterns of moisture circulation in long-term cycles. In any soil zone, the conditions of the water regime in certain periods of the year may differ significantly from the annual average, i.e., several types of water regime will be combined in the annual cycle. For example, in the taiga-forest zone in podzolic soils, the annual cycle of moisture circulation is dominated by the leaching type water regime. At the same time, in the early spring, as a result of snowmelt and precipitation, water stagnation regimes of varying durations arise in these soils, and in the summer months they are predominantly in conditions of a non-flushing type water regime. It is important to take these features into account when assessing the processes occurring in soils and optimizing the soil water regime.

Regulation of water regime. Optimization of the water regime is the most important link in a set of measures aimed at creating conditions favorable for the growth and development of agricultural crops. Without a stable supply of moisture, even with an optimal combination of all other life factors, plants are not able to fully realize their biological potential and, therefore, it is impossible to obtain high yields of crop products.

Optimal conditions for the growth and development of cultivated plants are created when the amount of moisture entering the soil balances its consumption for transpiration and physical evaporation.

When regulating the water regime, climatic, lithological, geomorphological and soil conditions are taken into account, as well as the characteristics of water consumption of cultivated crops. To create an optimal water regime, surface runoff is regulated, the water-physical properties of soils are improved, and irrigation is used. drainage, forest reclamation, various agricultural practices. Usually, a set of measures is carried out aimed at artificially changing the incoming and outgoing items of the water balance and, accordingly, the total and productive reserves of moisture in the soil.

In the zone of excess moisture, the improvement of the water regime of poorly drained areas is associated with the removal of free gravitational moisture through agro-reclamation measures to accelerate surface and subsurface runoff. To speed up surface runoff, the surface is leveled and profiled, narrow-paddock plowing is carried out, and ridges and beds are cut.

With the help of leveling, depressions in the area are leveled, in which moisture stagnates for a long time in the spring and after heavy summer rains. Profiling the surface consists of giving it a directional slope, thereby removing free gravitational moisture. With narrow paddock plowing, split furrows are formed between the developing wide ridges, along which surface water, if there is the necessary slope, is diverted outside the drained field. Ridgeing and ridgeing are methods of intensive local drainage of surface horizons and increasing their evaporation capacity. Surface water flows out of the field along the furrows between the ridges and ridges.

To accelerate intrasoil runoff, mole cutting and deep reclamation loosening are used. Mole formation is the installation of earthen drains, which redistributes excess moisture from the surface to the subsoil layers of the profile and their aeration. As a result of deep reclamation loosening, compacted water-resistant horizons are destroyed, optimal density and water permeability of the upper part of the soil profile with a thickness of at least 0.6 m are ensured.

Regulation of the water regime of swamp-type soils, as well as mineral swampy soils (swamp-podzolic, sod-gley) is carried out using drainage reclamation - the installation of closed or open drainage to remove excess moisture outside the drained massif.

At the same time, regulation of the water regime in the zone of excess moisture cannot be considered only as a one-sided measure to remove excess moisture. This is due to the fact that here periods of severe waterlogging of the soil can be replaced by periods of intense drying. Thus, in the zone of loamy soddy-podzolic soils, summer drought always occurs. Its duration within the European part of the country, depending on the availability of precipitation, can reach 2-5 weeks. In this case, the upper part of the soil profile can dry out to the point where plants wilt. In sandy and sandy loam soils, which are characterized by lower moisture capacity, the period with a clearly pronounced deficit of moisture available to plants is even longer. In this regard, in the Non-Chernozem Zone, an effective way to optimize the moisture supply of cultivated plants is the two-way regulation of the water regime. If there is excess moisture in the soil, it is removed from the fields through drainage pipes into special water intakes, and, if necessary, it is supplied back to the fields through the same pipes or using sprinklers.

To optimize the water regime, all measures aimed at soil cultivation are important, since they contribute to the accumulation and preservation of productive moisture reserves in the root layer. Such measures include: increasing the thickness of the arable layer and improving its agrophysical properties (structural state of porosity, density), liming, applying organic and mineral fertilizers, green manure, loosening the subarable layer, etc.

In zones of unstable moisture and in arid regions, regulation of the water regime is primarily aimed at maximum accumulation of precipitation moisture in the soil and its subsequent rational use. Since by the end of summer in such regions the reserves of moisture available to plants in the root layer of the soil are reduced to an extremely low level, measures to accumulate autumn-winter precipitation in the soil, which accounts for up to 70% of its annual amount, are of particular importance. Therefore, precipitation in the autumn-winter period plays a decisive role in the formation of the crop; to accumulate it, stubble peeling is carried out after harvesting grain crops, early autumn plowing, slotting, snow retention, and spring strip thawing of snow. The soil protection farming system developed under the leadership of A.I. Baraev is characterized by high efficiency. It is based on flat-cut tillage, after which up to 80% of the stubble is retained on the soil surface. Thanks to the presence of stubble, evaporation is reduced and precipitation is better accumulated, snow accumulates and is more evenly distributed on arable land, the soil freezes less and better absorbs melt water in the spring, as a result of which surface runoff and soil erosion are significantly limited. The moisture-accumulating effect is enhanced when sowing curtains of tall plants.

Clean vapors play an important role in the system of moisture accumulation measures to improve the water regime, the greatest effect of which is manifested in the steppe zone. With proper care by spring, in clean fallows, 130-160 mm or more of moisture available for plants accumulates in a meter layer of soil, which ensures a sustainable water supply for agricultural crops sown in fallows. In some areas, back-and-forth pairs are preferred over pure ones.

An effective method for accumulating and preserving soil moisture is the creation of a system of forest shelterbelts that contribute to a noticeable humidization of the microclimate. Compared to the open steppe, more snow accumulates in fields protected by forest belts (25-30%) and the depth of soil freezing decreases. In spring, the soil thaws faster, resulting in increased infiltration of meltwater. Therefore, surface runoff is significantly reduced or stopped altogether, and the amount of productive moisture increases by 80-100 mm. In fields protected by forest belts, wind speed decreases by 30-40%, and air temperature in summer by 2-3 0 C, resulting in a decrease in unproductive evaporation of moisture from the soil surface. The greatest effect is observed in the case of creating openwork and openwork-blown forest strips.

Moisture accumulation measures are of particular importance on slope areas, where there is a real danger of moisture loss as a result of surface runoff. In such areas, fall plowing is carried out across the slope, strip placement of crops, hole digging, slicing, intermittent furrowing, buffer strips of perennial grasses and other techniques are used.

In the spring, it is important to preserve moisture accumulated in the soil from physical evaporation, losses due to which can amount to 60% or more of the total precipitation. Thus, in steppe regions, up to 40-45 tons of water are lost per hectare of unfenced plowland in one hot day. To prevent unproductive loss of moisture, surface loosening, which promotes mulching of the top layer, and harrowing are used. When the continuous water body of the soil is disturbed, the topmost layer dries out and protects the moisture of the underlying part of the soil profile from evaporation.

Irrigation is an effective method of regulating the water regime, the use of which can quickly eliminate moisture deficiency in the soil and maintain microclimatic conditions at an optimal level during the growing season. At the same time, in the steppe and especially in the forest-steppe zone, irrigation should be considered only as a technique that complements the entire complex of agrotechnical measures for the accumulation and preservation of precipitation moisture in the soil.

In arid regions where there is an insignificant amount of precipitation, the use of the most advanced moisture-accumulating agricultural technologies is not enough to accumulate the required amount of moisture in the soil. Therefore, in such regions, irrigation is used to regulate the water regime. At the same time, a system of measures to prevent the unproductive consumption of irrigation moisture, especially for infiltration, is of paramount importance, in order to prevent a rise in the level of mineralized groundwater and secondary salinization of irrigated soils.

Water in the soil is one of the most important factors in plant fertility and productivity. It plays a significant and versatile role in soil processes and in the creation of agronomically important soil properties. This role is determined by the special position of water in nature.

Water is a special physical and chemical very active system that ensures the movement of substances in space. The rate of weathering and soil formation, humus formation, biological, chemical and physicochemical processes are related to the water content in the soil. Nutrients dissolve in water and enter the plants from the soil solution. Since the evaporation of water consumes a huge amount of heat, water is also a thermostat for soil and plants, protecting them from overheating by solar radiation.

Water enters the soil in the form of precipitation, groundwater, condensation of water vapor from the atmosphere, and irrigation. The main source of water in the soil under rain-fed agriculture is precipitation.

Plants contain 80-90% water. In the process of their life, they spend a huge amount of it. To create 1 g of dry matter, 200 to 1000 g of water is required. With a lack of water in the soil, unstable and low crop yields are formed.

The water supply of plants depends not only on the amount of water entering the soil, but also on its water properties. With equal absolute humidity, soils can contain different amounts of available water, which is determined by the granulometric composition of the soil, structural state, humus content and other indicators that determine their water properties.

Understanding the patterns of behavior of soil moisture, processes of water consumption by plants, water properties and water regime is of great importance for managing and optimizing the water regime in order to obtain high and sustainable crop yields.

A. A. Izmailsky, G. N. Vysotsky, and P. S. Kossovich made a great contribution to the study of the patterns of relationships between water, soil and plants. The fundamentals of the study of the water properties of soils and water regimes are set out in the works of A. F. Lebedev, S. I. Dolgov, A. N. Rode, N. A. Kachinsky and other scientists.

CATEGORIES (FORMS) OF SOIL WATER, THEIR CHARACTERISTICS AND AVAILABILITY TO PLANTS

Water in soils is heterogeneous. Its different quantities have different physical properties (thermodynamic potential, heat capacity, density, viscosity, chemical composition, osmotic pressure, etc.), caused by the interaction of water molecules with each other and with other phases of the soil (solid, liquid, gaseous). Amounts of soil water that have the same properties are called categories or forms of soil water.

According to the classification developed by A. A. Rode (1965), there are five categories (forms) of soil water in soils: solid, chemically bound, vapor, sorbed and free.

Solid water is ice. This category of water is a potential source of liquid and vapor water. The appearance of water in the form of ice can be seasonal (seasonal soil freezing) or perennial (permafrost). Ice turns into liquid and vapor when the water temperature is above 0°C.

Chemically bound water is part of chemical compounds (minerals) in the form of a hydroxyl group - the so-called constitutional water or as whole molecules - crystallization water (CaSO 2H 2 O, Na 2 SO 4 10H 2 O).

Constitutional water is removed from the soil by calcination at a temperature of 400-800 °C, crystallization water by heating the soil to 100-200 °C. Chemically bound water is an important indicator of soil composition; it is part of the solid phase of the soil and is not an independent physical body, does not move, does not have solvent properties and is inaccessible to plants.

Vaporous water is contained in the soil air, in pores free of water, in the form of water vapor. Vaporous moisture can move along with the flow of soil air, as well as diffusely from places with greater elasticity of water vapor to places with lower elasticity.

Despite the fact that the total amount of vaporous water does not exceed 0.001% of the soil mass, it plays a large role in the redistribution of soil moisture and protects plant root hairs from drying out.

As the steam condenses, it turns into liquid water. In the soil, vaporous moisture moves from warm layers to colder ones. In this regard, ascending and descending seasonal and daily flows of water vapor arise. Due to the upward movement of water vapor in winter, up to 10-14 mm of moisture is accumulated in a meter layer of soil in arid areas.

Physically bound, or sorbed, water is formed by the sorption of vapor and liquid water on the surface of solid soil particles. Physically bound water, depending on the strength of the bond with the solid phase of the soil, is divided into tightly bound and loosely bound (film).

Strongly bound (hygroscopic) water is formed as a result of the adsorption of water molecules from a vapor state on the surface of solid soil particles. The property of soil to sorb vaporous water is called soil hygroscopicity, and sorbed water is called hygroscopic. Strongly bound hygroscopic water is held on the surface of soil particles by very high pressure, forming thin films around the soil particles.

In terms of physical properties, hygroscopic water approaches solids. It has a high density (1.5-1.8 g/cm3), low electrical conductivity, does not dissolve substances, has high viscosity, freezes at temperatures from -4 to -78 ° C, and is inaccessible to plants.

The maximum amount of water that can be absorbed by the soil from a vapor state at a relative air humidity close to 100% is called maximum hygroscopic (MH) water. When soil moisture equals MG, the thickness of the film of water molecules reaches 3-4 layers.

The values ​​of hygroscopicity and MG depend on the granulometric and mineralogical composition and humus content. The more clay, especially colloidal, fraction and humus in the soil, the higher the hygroscopicity and MG.

In mineral low-humus sandy and sandy loam soils, the maximum hygroscopicity ranges from 0.5 to 1%. In highly humified loamy and clayey soils, the maximum hygroscopicity can be 15-16%, and in peat - up to 30-50%.

However, due to the absorption of vaporous water, the sorption forces of the surface of soil particles are not exhausted, even if the soil moisture reaches maximum hygroscopicity. When soil particles come into contact with water, additional absorption occurs and loosely bound, or film, water is formed. It is held less firmly by soil particles and moves very slowly from soil particles with a larger film to particles with a smaller film. The thickness of the film reaches several tens of water molecules and can exceed the value of maximum hygroscopicity by 2-4 times. Film moisture has a density slightly higher than the density of free water, has a reduced dissolving ability, freezes at a temperature of -1.5...-4 °C, and is partially accessible to plants.

Free water is the water contained in the soil above the loosely bound one. It is not connected by forces of attraction with soil particles. There are two forms of free water in the soil: capillary and gravitational.

Capillary water is located in the thin capillary pores of the soil and moves through them under the influence of capillary forces that arise at the interface between the solid, liquid and gaseous phases. This water is most accessible to plants.

Depending on the nature of moistening, capillary-suspended and capillary-backed water are distinguished. When the soil is moistened from above by precipitation or irrigation water, capillary-suspended water is formed. When the soil is moistened from below due to groundwater, capillary-backed water is formed in the soil. The zone of capillary saturation above groundwater is called the capillary fringe (CB).

Gravity water is located in large non-capillary pores and freely seeps down the profile under the influence of gravity. A distinction is made between gravitational seepage water and aquifer moisture. The latter above the impermeable layer forms soil and groundwater, as well as a temporary horizon of upper waters.

WATER PROPERTIES OF SOIL

The main water properties of soils are water holding capacity, water permeability and water-lifting capacity.

Water-holding capacity is the property of soil to retain water due to the action of sorption and capillary forces. The greatest amount of water that the soil can hold by one force or another is called moisture capacity.

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

Total (maximum) moisture capacity (MC), or water capacity, is the amount of moisture retained by the soil in a state of complete saturation, when all pores (capillary and non-capillary) are filled with water.

For soils with normal moisture, the moisture state corresponding to full moisture capacity may occur after snowmelt, heavy rains, or when irrigated with large amounts of water. For excessively wet (hydromorphic) soils, the state of full moisture capacity can be long-term or permanent.

With a long-term state of soil saturation with water to full moisture capacity, anaerobic processes develop in them, reducing its fertility and plant productivity. The optimal soil humidity for plants is considered to be within 50-60% of PV.

However, as a result of swelling of the soil when it is moistened and the presence of trapped air, the total moisture capacity does not always exactly correspond to the total porosity of the soil.

The lowest moisture capacity (LC) is the maximum amount of capillary-suspended moisture that the soil can retain for a long time after abundant moistening and free drainage of water, provided that evaporation and capillary moistening due to groundwater are excluded.

When NV in the soil, 55-75% of the pores are filled with water, creating optimal conditions for moisture and air supply to plants. The value of HB depends on the particle size distribution, humus content and soil composition. The heavier the soil is in granulometric composition, the more humus it contains, the higher its minimum moisture capacity. Very loose and highly dense soils have a lower moisture capacity (MC) than soils of medium density. For loamy and clayey soils, the NV value ranges from 20 to 45% of absolute soil moisture. The highest NV values ​​are characteristic of humus-rich soils of heavy granulometric composition with a well-defined macro- and microstructure.

As water evaporates and is consumed, plants lose their continuous filling of capillaries with water, and the mobility of water and its availability to plants decrease. The humidity corresponding to capillary rupture is called capillary rupture humidity (CBR). This is the hydrological constant of the soil, characterizing the lower limit of optimal moisture. For loamy and clayey soils, the WRC is 65-70% of the NV.

The maximum amount of capillary-backed moisture that can be contained in the soil above the groundwater level is called capillary water capacity (KB).

Maximum molecular moisture capacity (MMC) corresponds to the highest content of loosely bound water retained by sorption forces or forces of molecular attraction.

At a humidity close to the MW, plants usually begin to wilt steadily, so this humidity is called wilting moisture (WM) or the “dead” moisture reserve in the soil, inaccessible to plants. For different plants, as well as different periods of their growth (seedlings or mature plants), the wilting moisture content will be different. Seedlings are especially sensitive to critical soil moisture conditions.

The moisture content of plants withering is determined by the seedling method according to S.I. Dolgov or by calculation using the percentage of water in the soil equal to the maximum hygroscopic moisture. It is taken into account that the ratio of wilting moisture to maximum hygroscopic moisture in different soils for different plants ranges from 1 to 3; for non-saline soils it is often 1.3-1.5, for saline soils it is slightly higher. Wilting humidity (in%) is equal to the maximum hygroscopic humidity (in%) multiplied by a factor of 1.34 (according to the recommendation of the hydrometeorological service) or 1.5 (according to the recommendation of N. A. Kachinsky):

B3 = MG × 1.34 (1.5).

Wilting moisture content varies depending on soil type and texture (Table 33).

33. Wilting moisture content in soils of different granulometric compositions

(according to Francesson)

In peat soils, the wilting moisture content reaches 50% of the mass of absolutely dry soil.

The wilting moisture content is the most important hydrological constant. Based on the VZ data and the total moisture content in the soil, the reserve of productive moisture is calculated, i.e., the moisture that is available to plants and spent on crop formation.

The amount of productive moisture is usually expressed in mm of the thickness of the water layer. In this form, water reserves are better compared with precipitation data. 1 mm of water on an area of ​​1 hectare corresponds to 10 tons of water.

Productive moisture reserves (in mm/ha):

W=0,l×d v ×h(B-B3),

where 0.1 is the coefficient of conversion of moisture reserves from m 3 /ha to mm of water layer; d v - soil density, g/cm 3 ; h is the thickness of the soil layer, cm, for which the reserve of productive moisture is calculated; B - field soil moisture, % for absolutely dry soil; VZ - wilting moisture content, % for absolutely dry soil.

The optimal reserves of productive moisture (according to A.M. Shulgin) in a meter layer of soil during the growing season of plants are on average in the range from 100 to 200 mm.

Both excess moisture (more than 250 mm) and insufficient moisture (less than 50 mm) negatively affect the development of plants and their productivity.

Soil permeability is the ability of soils to absorb and pass water through itself. There are two stages of water permeability: absorption and filtration. Absorption is the absorption of water by the soil and its passage through soil that is not saturated with water. Filtration (seepage) is the movement of water in the soil under the influence of gravity and pressure gradient when the soil is completely saturated with water. These stages of water permeability are characterized by absorption and filtration coefficients, respectively.

Water permeability is measured by the volume of water (mm) flowing through a unit area of ​​soil (cm2) per unit of time (hour) at a water pressure of 5 cm.

This value is very dynamic, depending on the granulometric composition and chemical properties of soils, their structural state, density, porosity, and moisture.

In soils of heavy granulometric composition, water permeability is lower than in light soils; the presence of absorbed sodium or magnesium in the PPC, which contributes to the rapid swelling of soils, makes the soils practically waterproof.

The assessment of soil water permeability is carried out according to the scale proposed by N.A. Kachinsky (1970).

If water permeability is insufficient, moisture either stagnates on the soil surface, creating conditions for crops to soak, or flows down the slope of the area, contributing to water erosion.

With very high water permeability, moisture does not accumulate in the root layer, it is quickly filtered deep into the soil profile; under irrigated farming conditions, losses of irrigation water occur, the groundwater level rises, and there is a danger of secondary soil salinization.

Water-lifting capacity is the ability of soil to cause upward movement of the water contained in it due to capillary forces.

The height of water rise in soils and the speed of its movement are determined mainly by the granulometric and structural composition of soils and their porosity.

The heavier and less structured the soil, the greater the potential height of water rise, and the slower its rise rate.

The rate of water rise is also affected by the degree of mineralization of groundwater. Highly mineralized waters are characterized by lower height and rate of rise. However, the occurrence of mineralized groundwater close to the surface (1 - 1.5 m) creates the danger of rapid soil salinization.

WATER REGIME OF SOIL

The water regime is understood as the totality of the phenomena of moisture entering the soil, its retention, consumption and movement in the soil. It is expressed quantitatively through the water balance, which characterizes the flow of moisture into the soil and the flow out of it.

The general water balance equation is expressed as follows:

V 0 + V os + V g + V k + V pr + V b = E isp + E t + V i + V p + V s + V 1

where Vo is the initial moisture reserve; In os - the amount of precipitation during the observation period; In g - the amount of moisture coming from groundwater; In k - the amount of moisture condensing from water vapor; In pr - the amount of moisture entering as a result of surface inflow; B b - the amount of moisture coming from the lateral inflow of soil and groundwater; E isp - the amount of moisture evaporated from the soil surface (physical evaporation); E t - the amount of moisture consumed by transpiration (deduction); B and - moisture infiltrating into the soil-ground thickness; V n is the amount of water lost due to surface runoff; In c - moisture lost during lateral intrasoil runoff; B 1 is the moisture reserve in the soil at the end of the observation period. If over a long period of time progressive wetting or drying of the territory does not occur, the inflow and flow of water in the soil are equal, the water balance equation is equal to zero. In this case, the water reserves in the soil at the beginning and at the end of the observation period can be equal: B 0 = B 1 For slope elements of the relief, the amount of water coming from the lateral inflow of soil and groundwater is equal to the amount of water lost during lateral flow: B b = In s. The content of moisture condensing in the soil is small compared to other balance items and can be neglected. Taking into account these clarifications, the water balance equation takes the following form:

V os + V g + V pr = E isp + E t + V i + V p.

The equation for the water balance of equivalent territories with deep groundwater has an even simpler form:

B 0 + Vos = E + B 1

where E is total evaporation, or evapotranspiration.

Depending on the nature of the annual water balance in the ratio of its components - annual precipitation and annual evaporation - the main types of water regime are formed.

The ratio of annual precipitation to annual evaporation is called the humidification coefficient (HC). In different natural zones, CU ranges from 3 to 0.1.

For various natural conditions, G.N. Vysotsky established 4 types of water regime: flushing, periodically flushing, non-flushing and effluent. Developing the teachings of G.N. Vysotsky, Professor A.A. Rode identified 6 types of water regime, dividing them into several subtypes.

1. Permafrost type. Distributed in permafrost conditions. The frozen layer of soil is waterproof and is an aquifer, over which the supra-permafrost perch flows, which causes the upper part of the thawed soil to become saturated with water during the growing season.

2. Flushing type (KU > 1). Characteristic of areas where the amount of annual precipitation is greater than evaporation. The entire soil profile is annually subjected to through wetting to groundwater and intensive leaching of soil-forming products. Under the influence of the leaching type of water regime, soils of the podzolic type, red soils and yellow soils are formed. When groundwater occurs close to the surface and the soils and soil-forming rocks have low water permeability, a bog subtype of water regime is formed. Under its influence, bog and podzolic-marsh soils are formed.

3. Periodically flushing type (KU = 1, with fluctuations from 1.2 to 0.8). This type of water regime is characterized by an average long-term balance of precipitation and evaporation. It is characterized by alternating limited wetting of soils and rocks in dry years (non-flushing conditions) and through wetting (flushing regime) in wet years. Soil washing by excess precipitation occurs 1-2 times every few years. This type of water regime is characteristic of gray forest soils, podzolized and leached chernozems. Soil water supply is unstable.

4. Non-flush type (KU< 1). Характеризуется распределением влаги осадков преимущественно в верхних горизонтах и не достигает грунтовых вод. Связь между атмосферной и грунтовой водой осуществляется через слой с очень низкой влажностью, близкой к ВЗ. Обмен влагой происходит путем передвижения воды в форме пара. Такой тип водного режима характерен для степных почв - черноземов, каштановых, бурых полупустынных и серо-бурых пустынных почв. В указанном ряду почв уменьшается количество осадков, увеличивается испаряемость. Коэффициент увлажнения снижается с 0,6 до 0,1.

Moisture circulation covers a thickness of soil and soil from 4 m (steppe chernozems) to 1 m (desert-steppe, desert soils).

The moisture reserves accumulated in steppe soils in the spring are intensively spent on transpiration and physical evaporation and by autumn they become negligible. In semi-desert and desert zones, farming is impossible without irrigation.

5. Exhaustive type (KU< 1). Проявляется в степной, полупустынной и пустынной зонах при близком залегании грунтовых вод. Преобладают восходящие потоки влаги по капиллярам от грунтовых вод. При высокой минерализации грунтовых вод в почву поступают легкорастворимые соли, происходит ее засоление.

6. Irrigation type. It is created by additionally moistening the soil with irrigation water. With proper rationing of irrigation water and compliance with the irrigation regime, the water regime of the soil should be formed according to the non-flushing type with a WC close to unity.

REGULATION OF WATER REGIME

Each soil-climatic zone is characterized by certain types of soil water regime, which, depending on the characteristics of the cultivated crops, require appropriate measures to regulate it.

In the taiga-forest soil-climatic zone and in other zones where excessive soil moisture is observed, various agrotechnical techniques are used aimed at removing excess moisture from the upper soil horizons: bedding and raking, leveling micro- and meso-depressions. If necessary, drainage is carried out using open ditches, closed drainage, embankment, colmatage and other reclamation methods.

Excessive moisture can be eliminated by creating a thick, well-cultivated arable layer and loosening the subarable horizon, which increases the moisture capacity of the soil and allows moisture to penetrate into the lower layers. During dry critical periods of the growing season, this moisture serves as an additional reserve for the plants being grown.

In the taiga-forest zone, there are sometimes dry years, when agricultural crops sharply reduce their yields due to a lack of productive moisture. For example, in the Moscow region, out of 100 years, 29 are dry, 23 are excessively wet, and 48 are normal. Therefore, even in this zone in some years it is advisable to accumulate and conserve moisture from atmospheric precipitation.

In forest-steppe and steppe zones with unstable and insufficient soil moisture, the main tasks of regulating the water regime come down to the accumulation, conservation and productive use of moisture from precipitation to maintain the necessary supply of cultivated crops. In these zones, measures aimed at weakening surface water flow, snow retention, and reducing the physical evaporation of water from the soil are of great importance.

An important role is played by the soil cultivation system, clean fallows, weed control, and forest belts. Thus, autumn tillage, providing a loose structure of the arable layer, promotes better absorption of rain and melt water, reduces surface runoff and reduces moisture loss due to physical evaporation. This improves the moisture supply of agricultural crops and increases their yield.

In the arid regions of the Volga region and Western Siberia, rocker pairs are effective, helping to increase the reserves of productive moisture in the meter layer to 50 mm or more (Shulgin). Unproductive moisture losses due to physical evaporation are significantly reduced when carrying out spring harrowing of fields, as well as when loosening the surface soil horizons after rains, preventing the formation of crust. Post-sowing soil compaction changes the density of the surface layer of the arable horizon compared to the rest of its mass. The difference in soil density causes capillary flow of moisture from the underlying layer and helps the condensation of water vapor in the air. The use of mineral and organic fertilizers contributes to more economical use of moisture; water consumption per 100 kg of grain is reduced by an average of 26% (Listopadov, Shaposhnikova).

In vegetable growing, soil mulching with various materials is widely used to preserve moisture.

In desert-steppe and desert zones, the main method of regulating the water regime is irrigation. In irrigation, it is especially important to strive to reduce unproductive water losses to prevent secondary salinization. Optimization of the water-physical properties of soils and their structural state helps to improve the moisture supply of plants in various soil-climatic zones.

Test questions and assignments

1. Name the categories (forms) of water in the soil. What is their bond strength with the solid phase of the soil and accessibility to plants? 2. Give the concept of soil-hydrological constants, list the main ones. 3. What is called productive moisture? How to calculate it? 4. Name and characterize the water properties of soil. What soil properties determine water properties? 5. Give the concept of water regime. 6. Describe the types of water regime and methods of their regulation.

Most of the soils in the country require special measures, either adaptive or reclamation, to regulate the water regime of soils under conditions of excessive or insufficient moisture.

Overcoming excess hydration. Waterlogging occurs almost everywhere in the taiga-forest zone. Spring and summer-autumn waterlogging in many soils is quite long, often enough to cause soaking and death of not only winter grains that are very sensitive to waterlogging, but also other crops. F.R. Zaidelman developed an ecological and hydrological principle for assessing the feasibility of soil drainage, based on an analysis of the water regime of soils in years of different moisture and crop productivity. Rational selection of crops allows you to obtain the greatest environmental effect with minimal investment.

As soil swampiness increases, selective or continuous drainage is used. Unlike light soils, where drainage is achieved by lowering the groundwater level by drainage, heavy soils require a complex system of measures, which should not only reduce the level of perched water in deep layers, but also eliminate excess water in the arable horizon and the upper part of the profile.

To optimize the water regime of the territory, a landscape approach to regulating surface runoff is promising. In this regard, on slopes it is advisable to carry out deep autumn tillage in order to reduce runoff, and on soils prone to waterlogging to increase runoff, replacing autumn tillage with spring plowing is effective. Such a replacement reduces the time it takes for the soil to mature for cultivation, improves the operating conditions of agricultural machinery, and increases the bearing capacity of the soil. The last circumstance is extremely important, because the duration of unfavorable soil moisture for the operation of heavy wheeled equipment during the spring work can be quite long. As is known, violation of the conditions for the operation of equipment occurs when soil moisture is equal to or greater than 0.75 of the full moisture capacity. This value for heavy soddy-podzolic soils corresponds to the maximum field moisture capacity, when the soil does not release water either to drainage or to runoff. A situation arises when the equipment is standing still, but the excess moisture cannot be removed. There is only one way out of the situation in such conditions - in changing the system of machines, in reducing their pressure on the soil, in replacing heavy wheeled equipment with tracked vehicles, and in the use of tractors with dual wheels. In this case, the maximum pressure of the propellers on the soil should not exceed 60-80 kPa.

Despite the fact that the territory of the taiga-forest zone in the long-term cycle is characterized by excessive moisture, during the year and growing season, agricultural plants in average and especially dry years may experience insufficient moisture. Therefore, in the Non-Black Earth Region, watering vegetable plantations, pastures, gardens, and many forage crops is often justified, especially on soils that are light in texture. On thick fluvioglacial sands and sandy loams with groundwater deeper than 3 m, plants lack moisture not only in dry and averagely humid years, but also throughout the entire growing season of wet years.

Considering that in this zone long periods of stable and deep drying are not often observed and they are often interspersed with rains and downpours, vegetation irrigation with large irrigation rates (except for garden trees) can be very dangerous. In combination with unexpected precipitation, they can lead to waterlogging of soils and the development of gley processes. Therefore, frequent watering with small norms in the amount of daily moisture deficits turns out to be more justified in the Non-Black Earth Region.

Accumulation and retention of moisture in dry conditions. In arid areas, especially in the steppe and dry-steppe zones, almost all elements of agriculture must be optimized in terms of accumulation, conservation and rational use of moisture. The initial conditions are the choice of rational crop rotations with a certain proportion of clean fallow and the use of soil protection systems for tillage, leaving crop residues and preferably all straw on the surface. Weed control, fertilizers, a clean steam care system, maneuvering sowing dates in accordance with the dynamics of soil moisture availability and the likelihood of precipitation, and seed sowing rates are very important.

Among the special measures for moisture accumulation, the most important is snow retention. In addition to additional moisture accumulation, the creation of a sufficiently thick snow cover serves as reliable protection for winter crops and perennial grasses from freezing. By reducing the freezing depth, runoff and soil washout are reduced. Increasing the efficiency of using winter precipitation is a major reserve for agriculture. For example, in the Volga region, the average loss of snow in the plowed land due to snow drift into the hydrographic network is 30-40%. Snow blowing, depending on its condition, begins at wind speeds of more than 4-10 m/sec, which is a common occurrence in steppe regions. Therefore, to retain snow, it is necessary to leave stubble and create scenes of tall plants (mustard, sunflower, etc.), and use snow plows to increase the thickness of the snow cover.

A known role in regulating the microclimate and, accordingly, the water regime of soils is played by forest shelterbelts, which reduce wind speed and, accordingly, the intensity of moisture evaporation, contributing to the retention of snow. At the same time, however, a precise system for their organization is required (the design of forest belts, the distance between them, a reasonable choice of tree species).

Soil moisture availability, especially in complex landscapes, is largely related to the intensity of surface runoff. The greatest runoff is observed when the soil, wet since autumn, is severely frozen and there are no measures to retain melt water. Measures that ensure the weakening and elimination of melt water runoff include leaving stubble, mulching the soil surface with straw, mechanical tillage, contour organization of the territory, strip placement of crops and clean fallows, etc.

The increase in the moisture reserve in the soil due to melt water depends on the rate of its absorption. On well-permeable soils, if they go into winter in a non-waterlogged state, the absorption of melt water occurs quickly. If autumn is damp and the surface layer is waterlogged, then when it freezes it turns into a solid monolith, which thaws slowly and is a strong obstacle to the absorption of melt water. Therefore, during a wet autumn, it is advisable to treat the soil on the slopes with chisels, after which complete freezing does not occur and the infiltration of melt water improves. On perennial grasses, for this purpose it is very effective to cut slits to such a depth that during the period of snow melting the bottom of the crack is in the already thawed soil.

The technique of so-called “vertical mulching” is very useful, in which in the fall cracks are cut to the freezing depth of the soil and filled with strands of straw. Through these cracks, melt water flows deep into the soil. The technique can be performed in fields with a large amount of post-harvest residues.

The water regime is the totality of the phenomena of moisture entering the soil, its movement, retention in soil horizons and consumption from the soil. The water regime of soils characterizes the flow of water into the soil and its consumption from the soil for outflow into groundwater or other relief elements, for evaporation and transpiration. The last two phenomena are often combined under the single term total evaporation (evapotranspiration) - due to the difficulty of defining them separately. Typically, the water regime is characterized by the following parameters: moisture regime (changes in water content in the soil depending on weather conditions and the influence of plants) and soil water balance (assessment of the influx and consumption of water in soils in the annual cycle). Recently, to these known parameters, characteristics of the hydrological profile and hydrological horizons of soils have been added. The water regime is important for understanding the genesis of soils and their ecological functions, which are manifested in maintaining a certain vegetation cover under given conditions.

The water balance, which characterizes the flow of water into the soil and its flow from it, is quantitatively expressed by the formula:

Vo+Vos+Vgr+Vk+Vpr+Side=V 1 +Vs+Vi+Vp+Esp+Etr

where B is the moisture reserve in the soil at the beginning of observations; Vos is the amount of precipitation during the observation period; Vgr - the amount of moisture received from groundwater; Vk - amount of condensing moisture; Vpr - surface moisture influx; Sideways - lateral inflow of soil and groundwater; B 1 - the amount of moisture in the soil at the end of observations; Sun is the amount of moisture in the side runoff; Vi is the amount of infiltrated moisture; Вп - amount of moisture of surface runoff; Esp - the amount of evaporated moisture; Etr - the amount of moisture for transpiration (deduction).

The left side is income items, the right side is expenses.

In most cases, progressive drying or wetting of the territory does not occur and the water balance equation is equal to zero. Water balance is characterized by annual cycles with repeating processes of moisture supply and consumption. By eliminating weakly significant and compensating components of the balance, we can write the equation approximately

Vo+Vos+Vgr+Vpr=V 1 +Vi+Vp+Esp+Etr

In natural soils, the water balance in the long-term cycle is compensated, i.e. The consumption and inflow of water in an annual period of time are on average equal. It is not compensated only in a number of irrigated soils, where water can enter groundwater and increase its capacity and water supply in the soil-soil column, and with directed climate change. You can view the routes of night buses in St. Petersburg on the website Peterburg.ru

Thus, the water balance characterizes the main feature of the soil water regime, its cyclicity, and the total volume of water passing through the soil under given conditions. Any supply of moisture existing in a given soil is restored after a certain time, within which the flow and inflow of water ultimately equalizes. Therefore, assessing the water regime of soils based on moisture balance cannot serve as a reliable characteristic of it. It only talks about the volume of water that passed through the soil during a hydrological year.

For a mossy spruce forest, located 3 km from the oak-spruce forest, down a very flat catena, the water balance equation looks slightly different:

755 (precipitation) = 323 (outflow) + 88 (evapotranspiration) + 88 (soil moisture after drying up to NV) + 236 (retained by plant canopy, loss due to wetting of trees and moss layer).

The main result of assessing the water balance of the studied ecosystems is that it was possible to identify the amount of water used to supply water to plants. It is equal to 80-120 mm depending on the type of parcel (ecosystem).

The water balance can be compiled in relation to different soil layers, the entire soil thickness or a certain depth. Most often, moisture reserves, consumption and income items are expressed in mm of the water layer or in m 3 /ha. Moisture content is calculated separately for each genetic horizon, since moisture content and density vary greatly across different layers of the soil profile. Water reserves in a separate horizon are determined by the formula:

B=a*OM*N

where a is field humidity, %; OM - volumetric mass (density); n - horizon thickness, cm

To convert water reserves calculated in m 3 /ha into millimeters of water layer, a coefficient of 0.1 must be entered.

Water reserves in the soil, which are taken into account throughout the growing season, make it possible to judge the moisture supply of cultivated plants. In agronomic practice, it is useful to take into account the total and useful water reserves. The total water supply is the total amount for a given soil thickness, expressed by the equation:

OZV = a 1 *OM 1 *N 1 +a 2 *OM 2 *N 2 +a 3 *OM3 3 *N 3…. + an *OMn *Hn

The useful supply of water in the soil is the total amount of productive, or plant-available, moisture in the soil thickness.

To calculate the useful supply of moisture in the soil, you need to calculate the total supply of moisture and the supply of hard-to-reach moisture, which is calculated similarly to the previous formula, but instead of field moisture, the moisture content of stable wilting of plants is taken. The difference gives the amount of useful moisture in the soil.

EZV=OZV-ZTV

For a layer of 0-20 cm, reserves of more than 40 mm are considered good, 20-40 - satisfactory, less than 20 - unsatisfactory. For a layer of 0-100 cm, reserves of more than 160 mm are considered very good, 130-160 - good, 90-130 - satisfactory, 60-90 - bad, less than 20 - very bad.

Types of water regime. The water balance is different for different soil-climatic zones and individual areas of the area. Depending on the relationship between the main items of the annual balance, there may be several types of water regime.

In practice, the nature of the water regime is determined by the ratio of average precipitation and evaporation. Evaporation is the greatest amount of moisture that can evaporate from an open water surface or from the surface of constantly waterlogged soil under given climatic conditions (mm). The ratio of annual precipitation to annual evaporation is called the humidification coefficient (HC). It ranges from 0.1 to 3 in different natural zones.

The type of water regime determines the characteristics of the movement of substances in the soil, the degree of destruction of minerals and rock fragments in soils, and the very preservation of certain types of minerals. Thus, soils with a leaching type of water regime are washed away in most cases from soluble salts and carbonates. On the Russian and American Plains, a pattern can be observed of a decrease in the depth of carbonates by 30 cm with an increase in the amount of annual precipitation by 100 mm. On the contrary, effusion soils are usually gleyed and may be enriched with soluble salts. In this case, the composition of salts is determined by the type of water regime of uplands (watersheds and gentle slopes). In the arid zone these are chlorides, sulfates and carbonates of calcium, sodium, magnesium, in the humid zone - calcium carbonates and iron compounds.

The water regime determines the water content in the soil during the year and its individual periods, its movement in the groundwater-soil-plant-atmosphere system. The water regime affects plant growth (usually in agricultural production 1000 tons or more of water are spent per 1 ton of products).

The chemical composition of soils and their acidity are related to the water regime. Thus, the most likely pH values ​​for the upper horizons (A, B) of soils with leaching water regime are less than 6.

The water regime determines the fate of contaminated soils. The leaching regime can gradually lead to self-purification of the soil; under conditions of the non-leaching regime, pollution becomes a constant factor.

G.N. Vysotsky identified 4 types of water sludge, A.A. Rohde developed his teaching, identifying 6 types.

1. Permafrost type. Occurs in areas of permafrost. The frozen layer of soil, being a waterproof layer, causes the presence of supra-permafrost perch, so the upper part of the thawed soil is saturated with water during the growing season. The soil thaws to a depth of 1-4m. The annual water cycle covers only the soil layer.

2. Flushing type (KU > 1). Characteristic of areas where the amount of annual precipitation is greater than the amount of evaporation. In the annual cycle of water circulation, downward currents predominate over upward ones. The soil layer is annually subjected to through wetting to groundwater, which leads to intensive leaching of soil-forming products. The annual moisture cycle covers the entire soil layer. In drier regions it occurs only with a light particle size distribution. Under such conditions, soils of the podzolic type, red soils and yellow soils are formed. The swamp subtype of water regime develops when groundwater occurs close to the surface, or the soil-forming rocks have low water permeability.

3. Periodically leaching type (KU = 0.8-1.2; average 1) is characterized by an average long-term balance of precipitation and evaporation. The annual moisture turnover covers only the soil layer (non-leaching conditions) in a dry year and the entire layer up to groundwater (leaching conditions) in a wet year. Flushing happens every few years. This water regime is typical for gray forest soils, leached and podzolized chernozems.

4. The non-flushing type of water regime (KU less than 1) is characteristic of areas where precipitation moisture is distributed only in the upper horizons and does not reach groundwater. The connection between atmospheric and groundwater occurs through a layer with very low humidity, close to the WS (dead layer). Moisture exchange occurs through the movement of water in the form of steam. This water regime is typical for steppe soils - chernozems and chestnut, brown semi-desert and gray-brown desert soils. In this series of soils, the amount of precipitation decreases and evaporation increases. The humidification coefficient decreases from 0.6 to 0.1. The annual moisture cycle covers soil thicknesses from 4 m in the steppes to 1 m in deserts. The moisture reserves accumulated in steppe soils by spring due to late autumn precipitation and melt water are intensively spent on transpiration and physical evaporation, becoming negligible by autumn. In semi-desert and desert areas, agriculture is impossible without irrigation. Moisture consumption is mainly for transpiration, so downward moisture currents predominate. All infiltrated moisture is returned to the atmosphere.

5. The effusion (deductive-effusion) type of water regime (KU less than 1) manifests itself in the steppe, especially semi-desert and desert zones with close groundwater. Characteristic is the predominance of upward flows of moisture in the soil due to its inflow through capillaries from groundwater. The upper part of the capillary fringe enters the soil layer. Soil and groundwater are allochthonous, i.e. having additional ground nutrition. The annual water cycle covers the entire soil-ground layer. With high mineralization of groundwater, easily soluble salts enter the soil and the soil becomes saline. The effusion type of water regime also appears in some regions of Belarus, mainly in Polesie. The actual effusion type is observed when the occurrence of groundwater is very close, within the soil profile. The upper boundary of the capillary fringe extends to the day surface. In this case, it is not transpiration that predominates, but physical evaporation.

6. The irrigation type is created by additionally moistening the soil with irrigation water. During irrigation, different types of water regime appear at different periods. During the irrigation period, a leaching type takes place, followed by a non-flushing and even an effusion type, that is, either ascending or descending moisture flows periodically predominate in the soil.

There are also subtypes based on the source of moisture:

Atmospheric

Ground-atmospheric

Atmospheric with additional surface

Soil-atmospheric with additional surface

Atmospheric with additional flood

Ground-atmospheric with additional flood

Thus, when peat soils are drained, the regime from leaching with atmospheric nutrition and complete saturation (swamp) is replaced by the drainage taiga type. Reclaimed soils are special types of water regime.

Each soil type is characterized by certain moisture regimes, i.e. changes in soil and hydrological conditions. It is customary to distinguish 5 humidity classes:

1) Complete saturation - the aquifer is within the soil profile for most of the growing season; humidity varies from PV to HF at the top and » PV at the bottom of the profile; the capillary fringe is located at the day surface.

2) Capillary saturation - an aquifer sometimes in the soil profile; capillary fringe within the profile; humidity - from KV to NV-VRK at the top, from PV to KV at the bottom.

3) Periodic capillary saturation - the aquifer in the profile only after snowmelt, there is a capillary fringe in the profile; humidity from KV to VRK at the top and from KV to nV at the bottom.

4) Through least saturation - in spring the soil is soaked through to the HB; there is no aquifer and capillary fringe; humidity varies from nV-VZ at the top to NV-VRK(VZ) at the bottom.

5) Non-through least saturation - in spring the soil is soaked to a certain depth to the LV, below there is always a layer with SV; Humidity within NV-EZ.

In soddy-podzolic and podzolic soils, KU is usually 1.2-1.4; wash mode. In April-July, KU is less than 1. The humidity regime is usually periodically capillary saturation. Under cultivated plants, especially perennial grasses, the thickness of the summer drying layer is up to 1 m, and grain crops use moisture up to 0.6-0.7 m. In 6-10% of cases there are droughts, and once every 3 years on soddy-podzolic soils there is an insufficient supply of moisture to plants.

Regulation of water regime is a mandatory measure in areas of intensive agriculture. At the same time, a set of techniques is carried out aimed at eliminating unfavorable conditions for water supply to plants. By artificially changing the incoming and outgoing items of the water balance, you can significantly influence the overall useful reserves of water in soils and thereby contribute to obtaining high and sustainable crop yields.

Regulation of the water regime is based on taking into account climatic and soil conditions, as well as the water needs of cultivated crops. To create optimal conditions for the growth and development of plants, it is necessary to strive to equalize the amount of moisture entering the soil with its consumption for transpiration and physical evaporation, that is, creating a moisture coefficient close to 1.

In specific soil and climatic conditions, methods of regulating the water regime have their own characteristics. Improving the water regime of poorly drained areas in the zone of sufficient and excessive moisture is facilitated by the leveling of the soil surface and the leveling of micro- and meso-depressions, in which prolonged stagnation of moisture can be observed in spring and summer.

On soils with temporary excess moisture, it is advisable to make ridges in the fall to remove excess moisture. High ridges help to increase physical evaporation, and surface water flows out of the field along the furrows. Swamp-type soils and mineral swamps require drainage reclamation - the installation of closed drainage or removal of excess moisture using an open network.

Regulation of the water regime of soils in a humid zone with a large amount of annual precipitation is not limited to drainage. In some cases, even on soddy-podzolic soils in summer there is a lack of moisture and the need for additional water. An effective means of improving the moisture supply of plants in the Non-Chernozem Zone is two-way moisture regulation, when excess moisture is removed from the fields through drainage pipes, and, if necessary, supplied to the fields through the same pipes or by sprinkling.

All methods of soil cultivation (creating a deep arable layer, improving the structural condition, increasing total porosity, loosening the subsoil horizon) increase its moisture capacity and contribute to the accumulation and preservation of productive moisture reserves in the root layer.

In zones of unstable moisture and arid areas, regulation of the water regime is aimed at maximizing the accumulation of moisture in the soil and its rational use. One of the most common methods is moisture retention of snow and melt water. For this purpose, stubble, rock-cut plants, snow banks are used... To reduce surface water runoff, fall plowing across slopes, bunding, intermittent furrowing, slitting, strip placement of crops, cellular tillage, etc. are used.

An exceptional role in the accumulation of soil moisture belongs to shelterbelts. By protecting snow from blowing away in winter, they help increase moisture reserves in a meter layer of soil by 50-80 mm by the beginning of the growing season and up to 120 mm in some years. Under the influence of forest strips, unproductive evaporation of moisture from the soil surface is reduced, which also improves the water supply of fields. Openwork and blown forest strips are the most effective.

The introduction of clean steam, especially black steam, is of great importance in improving the water regime of soils. The greatest effect of pure steam as an agrotechnical method for accumulating moisture is manifested in the steppe zone and southern forest-steppe.

Many agricultural practices contribute to the accumulation and preservation of moisture in the soil. Surface loosening of the soil in the spring or closing off moisture by harrowing allows you to avoid unnecessary losses due to physical evaporation. Post-sowing soil compaction changes the density of the surface layer of the arable horizon compared to the rest of its mass. The resulting difference in soil density causes capillary inflow of moisture from the underlying layer and promotes condensation of water vapor in the soil air. Combined with increased contact of seeds with soil particles, all the phenomena associated with rolling enhance seed germination and provide plants with water needs in early spring. The use of organic and mineral fertilizers contributes to more economical consumption of soil moisture. In vegetable growing, mulching materials are widely used to preserve moisture.

In desert and semi-desert zones, the main way to improve the water regime is irrigation. A very important issue here is the fight against unproductive consumption of soil moisture in order to prevent secondary salinization.

Conclusion. Water properties, along with climate, weather conditions, and type of ecosystem, determine the water regime of soils and, consequently, their ecological function - water supply to plants. It is known that, in relation to water, all plants can be divided into hygrophytes (living in water), hydrophytes (requiring moist soils), mesophytes (living on soils with sufficient moisture) and xerophytes growing on dry soils. It is in these requirements of plants for water that the basis of the global zonation of plants is hidden. The formation of different climatic zones with different soil water regimes leads to the growth of different plant associations on these soils. There are humid zones (tundra and forest zone of the temperate zone, tropical rain and monsoon forests, subalpine and alpine mountain zones, mountain forest belt), semiarid zones (steppe and forest-steppe, savannas in the tropics, forests and bushes of the Mediterranean type: maquis, chaparral , bush), arid regions (dry steppes, semi-deserts and deserts).

It is the soil moisture that determines the different distribution of plants within the catena, along the microrelief, in the floodplains and on the plakora (watershed). Within one landscape, the distribution of plants is associated primarily with the water regime of soils - one of their main characteristics.