Saline soils are a huge potential resource of the soil fund of the country, which may be used in agricultural production at present and in the future, if regular collection of system data on saline and solonetzic soils is arranged. The proposals of scientists for improving the monitoring of irrigated lands are aimed at the solution of this problem. Information of this kind is relevant for the development of measures to stabilize and restore soil fertility. The problems of the organization of salinization monitoring for irrigated soils in Russia are considered. The proposed approaches to its optimization are based on the integrated use of remote and terrain data and on our own research experience in Volgograd oblast. A comparative analysis of existing approaches to monitoring of saline soils in our country and abroad is given. The term of saline soils is defined. We show which soil layer should be analyzed for the presence of easily soluble salts to assign the soils, as well as solonetzes and solonetzic soils, to saline. The terrain monitoring performed by hydrogeological and reclamation parties, counting saline and saline-solonetzic soils on irrigated lands by terrain and analytical methods, should be supplemented with annual monitoring (during the spring–summer period) based on remote information for comprehensive survey. This approach will enable us to identify irrigated, rain-fed, and fallow lands in irrigation systems by satellite images; to supplement permanent terrain survey plots with sampling sites chosen by remote information; to identify areas with secondary soil salinization by the vegetation status on irrigated lands with a critical groundwater level and to take samples in them for analysis; and to reveal areas of saline-solonetzic soils on rain-fed lands and in the fields with noncritical groundwater levels by the vegetation status. All this will expand the database and characteristics of saline and saline-solonetzic soils and supplement the information obtained by hydrogeological and reclamation parties at permanent survey sites for better accounting of these soils.

Statistical analysis of 3802 samples of saline soils from different regions of Russia made possible to substantiate observations of a higher proportion of magnesium in soils containing gypsum compared to saline soils without gypsum. Gypsum is not a toxic salt and its presence does not lead to an increase in salinity. The increase of the salinity degree is mainly associated with sodium and magnesium salts, with the proportion of sodium more often than the proportion of magnesium. The article statistically substantiates that in the studied saline soils that do not contain gypsum, among the cations in the water extract (1 : 5), sodium most often dominates at any degree of salinity. The appearance of gypsum in the soil profile is accompanied by a significant increase in the proportion of magnesium. With a low and medium degree of salinity in horizons containing more than 1% gypsum, according to the median, as well as the arithmetic mean, upper quartile and maximum, the proportion of magnesium from the sum of sodium and magnesium in the water extract (1 : 5) is often more than 50%. Even at a strong and very strong degree of salinity, the proportion of magnesium in gypsum-containing horizons is significant and amounts to 43 and 31%, respectively, on the median, which is 5.8–6.7 times higher than the proportion of magnesium in gypsum-free horizons of the same degree of salinity.

Statistical analysis of 3802 samples of saline soils from different regions of Russia made it possible to substantiate preliminary conclusions about a higher proportion of magnesium in soils containing gypsum in comparison with gypsum-free saline soils. Gypsum is not a toxic salt and its presence does not cause an increase in salinity. Salinization is mainly related to sodium and magnesium salts, with the sodium percentage often exceeding the magnesium percentage. It is statistically substantiated that in the studied saline soils without gypsum, sodium often dominates among cations in the soil water extract (1 : 5) at any degree of salinity, The appearance of gypsum in the soil profile is accompanied by a significant increase in the proportion of magnesium. In slightly or moderately saline horizons with more than 1% of gypsum, the proportion of magnesium in the water extract (1 : 5) often exceeds 50% of the sum of sodium and magnesium according to the median, arithmetic mean, upper quartile, and maximum values. Even in strongly and very strongly saline soil horizons containing gypsum, the proportion of magnesium is significant with the median of 43 and 31%, respectively, which is 5.8–6.7 times higher than the proportion of magnesium in gypsum-free horizons of the same degree of salinity.

The natural conditions of the Dzhizak Steppe in the 1970s–1980s are analyzed in the article. We have compiled a series of maps for this period that reflect the natural diversity of the steppe prior to the start of its reclamation. The series of maps includes (1) a map of the lithological–geomorphologic zoning, (2) a soil map, (3) salinity maps, and (4) a map of gypsum-bearing soils. All of these maps have been compiled on a topographic map on a scale of 1 : 100 000 with aerial photography. We have identified 22 lithological–geomorphologic districts in the Dzhizak steppe assigned to five lithological–geomorphologic regions. Detailed maps of the soil salinity on a scale of 1 : 2000 were also compiled for the test plots. The series of maps is a kind of geoinformation system that characterizes the status of the soil cover in the Dzhizak steppe prior to its development. The article contains information about soil features in the delineated regions. It is shown that, prior to irrigation, the specified regions significantly differed in the history of their development, lithological structure, soil-cover pattern, the salt and gypsum content in soils, and, therefore, the reclamation properties. Analysis of the differences in the initial soil-reclamation status of the specified regions and districts enables a more reliable assessment of the advantages and disadvantages of the reclamation measures in different areas of the Dzhizak steppe when their natural features are taken into account.

A comparative assessment of the rehabilitation status of irrigated lands, which are located in different natural areas of the Volgograd Oblast, is presented for 2001–2018. It was found that during the specified period there were recorded significant changes in the condition of irrigated lands: the total irrigation area has dramatically decreased since 2001 (-31%), especially at local runoff (-44.5%), the groundwater level has decreased (the level >5 m remains on 78% of the area). Also on this background, the areas of secondary salinized soils were also decreased (-3.9%). The main problems at the present are: the presence of fallow lands and rain-fed lands initially cultivated for irrigation, the lack of drainage on the most of irrigation systems and significant areas of saline soils requiring rehabilitation. Differences in natural conditions have largely determined the current rehabilitation state of irrigated soils and the intensity of their changes. Thus, the largest areas of secondary saline soils are preserved on irrigation systems located on the initially highly saline, poorly drained soils of the Khvalyn clay plain (Pallasovka, Svetloyarsk irrigation systems). Reconstruction of a number of irrigation systems with areas of secondary saline soils gave a positive result, after which secondary saline soils on reclaimed lands were not detected (Large Volgograd, Tyazhin irrigation systems). Significant areas of saline soils can be found on irrigated lands in the distribution areas of natural saline soils and chestnut, light chestnut saline soils – in the south of the Volga Upland, in the area of the Northern Yergeni and on the Khvalyn clay plain (Gorodishуsche, Generalovskoye, Pallasovka, etc. irrigation systems). Inherent research on the Volga-Don irrigation system with the involvement of remote sensing data has shown that this system reflects the general features of the modern rehabilitation condition of irrigated lands of the Volgograd Oblast – fallow lands, lack of drainage, and widespread saline soils are specific for this area. The use of high-resolution multispectral satellite images (Landsat-8, Sentinel-2) for the purposes of detection of fallow and irrigated lands in the current season demonstrates the possibility of clarifying information on this category of land. The determination of the distribution of salinized and solonetzic soils on irrigated lands of the Volgograd Oblast by remote methods can be carried out indirectly, i. e. according to the state of vegetation: when areas of sparse vegetation cover are being identified on images, targeted routes for soil surveys and soil sampling are selected.

The article considers the history of the work of the Dokuchaev Soil Science Institute researchers in Uzbekistan, conducted jointly with soil scientists from Uzbekistan. These works were started in 1930–1940s. They were especially active during the Great Patriotic War, when the Soil Institute was evacuated to Tashkent. During these years, both Russian and Uzbek soil scientists participated in joint work. Outstanding scientists can be named among Russian researchers: V.A. Kovda, A.A. Rode, A.N. Rozanov and many others who contributed to the study of Uzbekistan soils. The work of the researchers from the Dokuchaev Soil Science Institute, performed on the basis of a station in the Hungry Steppe (Mirzacho'l) in connection with the development of saline lands during the creation of new irrigation systems in Central Asia, is analyzed in particular detail. Various work areas of the station researchers are discussed in the article: issues of ameliorative development of saline soils, salinity mapping based on remote sensing methods, detailed study of the reclaimed soils properties using chemical, micromorphological, mineralogical and other research methods for the determination of salinity and gypsum content of soils in the New Irrigation Zone (NIZ) of Hungry and Jizzakh steppes. The results of the work were presented in a series of publications. In the 1990s, cooperation was temporarily ceased, but at the beginning of the 21st century it was resumed.

The paper provides initial materials characterizing the complicated history of formation, natural soils and lithological-geomorphological conditions of the Jizzakh steppe before the beginning of reclamation development. It is shown that on the basis of soil-lithological and geomorphological zoning, the Jizzakh steppe is divided into a number of natural regions belonging to different levels (altitude levels) of the piedmont plain. In total, 22 districts have been identified within the Jizzakh steppe, including the foothill margins. On the piedmont plain itself, the regions are combined into two high-altitude levels: the upper step and the lower step or blanket zone. These two levels differ sharply in terms of drainage conditions and soil salinity. The upper level, covering the upper and middle parts of the alluvial fan, the high interconal Zaamin-Sanzar plain and the Lomakino plateau, is characterized by a weak manifestation of salinity due to relatively good drainage, except for the sloping depressions of the Lomakino plateau. In contrast to the upper level, the lower level, located in the blanket zone of the piedmont plain, is characterized by active natural salinization because of the poor drainage. The saline sediments of the Zaamin cone delta are characterized by the greatest thickness. To a lesser extent, the rocks of the Sanzar cone delta, which are drained by deep gullies, are salinized. The Khavast sloping plain is characterized by a strongly saline upper two-meter layer, with salt and gypsum content decreasing with depth. Thus, it is shown that high salinity and gypsum bearing rocks, as well as high groundwater salinity of the cone delta zone are the source of modern salt accumulation in soils of foothill Golodnostepskaya plain, as well as in soils of the cone delta zone of Djizak steppe.

The taxonomic position of dry-steppe (chestnut) soils mentioned in the books Classification and Diagnostics of Soils of the USSR (1977), Classification and Diagnostics of Soils of Russia (2004), and World Reference Base for Soil Resources (2014) is discussed. Based on the example of the soils of Mongolia, it is shown that the soils of dry steppes that formed on light nonsaline parent rocks are normally nonsaline and nonsolonetzic. The soils of Mongolian dry steppes that formed on saline rocks are saline and solonetzic. The soils with profiles that include loamy layers (even those with a predominantly light granulometric composition and formed on nonsaline rocks) normally feature signs of solonetzicity in the loamy horizons.

The article outlines the main provisions of the methodological approach to the assessment of the condition of irrigated lands in the south of the European part of Russia based on satellite imagery from Landsat-8 satellite and ground-based observations. The visual and automated methods based on it were used to decipher irrigated lands from satellite images, and their possible determination with the use of the following indicators necessary for the monitoring the state of irrigated lands was considered: (1) the area of irrigated massifs, (2) the area of a long-term fallow in irrigated massifs, (3) the area of irrigated fields under different crops, (4) the genesis of the spotting of irrigated fields due to the state of cultivated crops and soil properties. The performed work is the first step towards the establishment of the monitoring of irrigated lands based on remote sensing. The article used the optimal type and dates of surveying satellite images, developed decryption features to assess the condition of crops and the properties of irrigated soils, and developed a technology for the automated decoding of satellite images to identify the spotting of irrigated fields based on the algorithm of decision trees.

The definitions of “alkaline” and “alkaline-solonetzic soils” are given in the paper. The data on the alkaline soils distribution in the national Soil Fund and in Russian agricultural areas are represented based on the summary of materials from late XX and early XXI centuries. It is shown that the data provided in the State reports of 2016 and 2019, in the monograph “Global climate and soil cover of Russia” (2019) and in other reviewed sources do not always coincide and do not allow us to get a clear idea about the alkaline soils distribution throughout the territory of the country and within the agricultural lands. However, the most important issue is to become acquainted and evaluate methodological approaches, currently used to obtain information about the distribution and changes of alkaline and alkaline-solonetzic soils on the territory of certain regions of the country and Russia as a whole. The materials presented in the paper indicate that the data on the areas of alkaline and alkaline-solonetzic soils need to be clarified on the basis of state-of-the-art remote sensing methods and ground-based soil mapping. At the same time, it is necessary to develop and approve unified methodological approaches for consideration of alkaline and alkaline-solonetzic soils on the territory of the Russian Federation. It is noted that the areas of irrigated lands need to be independently monitored and separated from the total Soil Fund of agricultural land, as well as a separate calculation of fallow, alkaline and solonetzic soils on irrigated land.

The influence of climate aridization on soil salinity in the basins of the south of Eastern Siberia and Mongolia is considered in the article. The data characterizing the climate aridity of the basins of the south of Eastern Siberia over 50 years are analyzed. In the south of Eastern Siberia from 1955 to 2015, the increase in air temperature was higher than in the whole world. In the basins of Tuva, the increase in air temperature was 2.5–3.7 о С ; in the Minusinsk depression – 1.7–2.8 о С , in the basins of Buryatia – 1.5–1.8 о С ; the coefficient of determination for moving averages over 20 years (R 2 ) was 0.9–0.95, the changes are significant – Student's criterion 19–35. Changes in the aridity coefficient were in the range of 0.02–0.14; according to the Student criterion, they were significant (t = 7.4 – -22), while a decrease in aridization was observed in the Minusinsk depression and its growth in other regions. Thus, in general, for the studied regions, the multidirectionality of the processes of climate aridization has been ascertained. In the Minusinsk depression, despite a slight decrease in aridization, category changes (according to the classification of Lobova et al., 1977) did not occur during this period, the territory remained in the arid and subarid categories. Despite the increase in climate aridization in the basins of Tuva and Buryatia, most of them also did not show a tendency to more arid category. Nevertheless, in a number of hollows in the south of Eastern Siberia, an increase in aridization with a transition to a more arid category was observed. This applies to the Eravnensky and Barguzinsky basins of Buryatia, which switched from weakly arid to subarid, as well as to the Ubsunur basin of Tuva, which turned from arid to strongly arid. For the basins of the south of Eastern Siberia, where climate aridization was recorded, the question arose about the possible activation of the process of soil salinization. To solve this problem, materials were collected on soil salinity in the arid regions of Mongolia. It was found that an increase in climate aridity even in the extreme arid deserts of the Gobi, where parent rocks are not saline, under automorphic conditions, the soil is practically not saline (the amount of salts does not exceed 0.1%). In areas where saline Cretaceous-Paleogene red sediments are spread, automorphic soils are saline, and the amount of salts may exceed 2.5%. Thus, in extremely arid climatic conditions, salinization of automorphic soils can range from non-saline to highly saline. Under the hydromorphic conditions of the basins of the south of Eastern Siberia, as well as in Mongolia, climate aridization inevitably leads to an intensification of the salt accumulation process, therefore, in the basins of Tuva and Buryatia experiencing climate aridization, a process of soil salinization in hydromorphic landscapes should be expected.

The influence of climate aridization on soil salinity in the basins of the south of Eastern Siberia and Mongolia is considered in the article. The data characterizing the climate aridity of the basins of the south of Eastern Siberia over 50 years are analyzed. In the south of Eastern Siberia from 1955 to 2015, the increase in air temperature was higher than in the whole world. In the basins of Tuva, the increase in air temperature was 2.5–3.7 оС; in the Minusinsk depression – 1.7–2.8 оС, in the basins of Buryatia – 1.5–1.8 оС; the coefficient of determination for moving averages over 20 years (R2) was 0.9–0.95, the changes are significant – Student's criterion 19–35. Changes in the aridity coefficient were in the range of 0.02–0.14; according to the Student criterion, they were significant (t = 7.4 – -22), while a decrease in aridization was observed in the Minusinsk depression and its growth in other regions. Thus, in general, for the studied regions, the multidirectionality of the processes of climate aridization has been ascertained. In the Minusinsk depression, despite a slight decrease in aridization, category changes (according to the classification of Lobova et al., 1977) did not occur during this period, the territory remained in the arid and subarid categories. Despite the increase in climate aridization in the basins of Tuva and Buryatia, most of them also did not show a tendency to more arid category. Nevertheless, in a number of hollows in the south of Eastern Siberia, an increase in aridization with a transition to a more arid category was observed. This applies to the Eravnensky and Barguzinsky basins of Buryatia, which switched from weakly arid to subarid, as well as to the Ubsunur basin of Tuva, which turned from arid to strongly arid. For the basins of the south of Eastern Siberia, where climate aridization was recorded, the question arose about the possible activation of the process of soil salinization. To solve this problem, materials were collected on soil salinity in the arid regions of Mongolia. It was found that an increase in climate aridity even in the extreme arid deserts of the Gobi, where parent rocks are not saline, under automorphic conditions, the soil is practically not saline (the amount of salts does not exceed 0.1%). In areas where saline Cretaceous-Paleogene red sediments are spread, automorphic soils are saline, and the amount of salts may exceed 2.5%. Thus, in extremely arid climatic conditions, salinization of automorphic soils can range from non-saline to highly saline. Under the hydromorphic conditions of the basins of the south of Eastern Siberia, as well as in Mongolia, climate aridization inevitably leads to an intensification of the salt accumulation process, therefore, in the basins of Tuva and Buryatia experiencing climate aridization, a process of soil salinization in hydromorphic landscapes should be expected.

Дан краткий анализ работам сотрудников Почвенного института им.В. В. Докучаева в изучении почв Монголии в ХХ -начале ХХI в.К настоящему времени почвенный покров и почвы Монголии изучены достаточно хорошо: составлена почвенная карта М 1:2 500 000, средние, а также крупномасштабные карты на отдельные регионы Монголии.Почвенные исследования на территории Монголии были начаты Л. И. Прасоловым, который установил сходство ландшафтов Забайкалья и Северной Монголии; он впервые отметил существенные различия в свой ствах каштановых почв юга Европейской России и Монголии.Б. Б. Полынов дал описание каштановым и бурым почвам Moнголии, таким образом продолжив классификационный список почв Монголии, составленный Л. И. Прасоловым, положил начало геохимическим исследованиям Монголии; в его работах были поставлены интереснейшие проблемы дальнейшего изучения почв страны.Н. Д. Беспалов собрал большой фактический материал о почвах, ранее не описанных почвоведами.Значительным этапом в изучении своеобразия почв Монголии явились работы И. П. Герасимова и Е. М. Лавренко, имеющие большое теоретическое значение и объясняющие причины своеобразия почв Монголии.Особое место в изучении почв Монголии занимают работы Советско

A new quantitative approach to zoning of arid territories based on a new zoning climatic parameter (the sum of precipitation excesses over evaporation) and the soil-granulometric coefficient of moisture supply is proposed.

The ameliorative status of irrigated soils was estimated on the basis of reclamation cadaster data for 2001 and 2016 on 17 state irrigation systems in three nature regions of Volgograd oblast: (1) the Khvalyn clayey plain and Volga sand ridge in the Caspian Lowland, (2) the Volga and Ergeni uplands, and (3) the Volga and Don river valleys. Significant changes took place in the ameliorative status of these systems during the studied period: the total irrigation area sharply decreased (–31%), especially under irrigation by the local runoff (‒44.5%); the groundwater level became lower, and the area with deep (>5 m) groundwater table increased to 77.3%; and the areas of saline and solonetzic soils decreased by 22.9% and 19.3%, respectively. In many cases, the differences in natural conditions determined the ameliorative status of irrigated soils and the intensity of their changes. The changes were the greatest on the initially saline slightly drained soils of the Khvalyn clayey plain and the smallest in the Volga River valley. During the entire period of irrigation, some areas were subjected to secondary salinization and abandoned. Our investigations at the Raigorodsk plot of the Svetloyarsk irrigation system within the Khvalyn clayey plain in 2016 demonstrated that the soils subjected to secondary salinization in the period of maximum irrigation intensity (in 1990) are now at the stage of gradual desalinization.

This study is an attempt to quantify parameters taken into account in separation of the dry steppe soil zone. A detailed analysis of the maps of zoning, vegetation, land use, and soils has made it possible to suggest quantitative criteria of the dry steppe soil zone in Russia and to gain a better correlation between the calculated boundaries of this zone and the maps of vegetation, land use, and soils. Except for the East European Plain, boundaries of the dry steppe zone with chestnut soils do not coincide on different maps of zoning. Climatic parametersthe sum of active temperatures, the humidity factor, and the continentality coefficientare the main factors specifying the spatial pattern of soil zones and facies on the maps of zoning. Soil characteristicstexture and water-physical propertiesplay a subdominant role. It is argued that data on the texture, water-physical properties, and solonetzic properties of soils should be taken into account in separation of the dry steppe zone as the factors controlling the depth of soil moistening and the reserves of productive moisture. Together with the accumulated sum of active temperatures, they specify the development of dry steppe vegetation and, hence, the boundaries of the dry steppe soil zone. A new indicatorthe sum of monthly excesses of precipitation over evapotranspirationshould be calculated with due correction for the soil texture, solonetzic properties, and the content of carbonates. In combination with the accumulated sum of active temperatures, this indicator makes it possible to perform a detailed zoning of the area of chestnut soils on a quantitative basis and to separate cryoarid areas (cold semideserts) and semideserts with chestnut soils. Soil zones and facies determined with the use of this indicator are in good agreement with geobotanical maps and maps of land use.

A new quantitative approach to the zoning of arid territories is proposed on the basis of a new climatic parameter for zoning (the sum of precipitation exceedances over evaporation) and a soil textural water recharge coefficient.

The agrochemical properties of humus-accumulative horizons of irrigated soils on the key site of the Svetloyar irrigation system in Volgograd oblast are analyzed. The field layout before the operation of the irrigation system and a long period of irrigation resulted in redistribution of the carbonate material. Its concentration in the upper part of the soil profile amounted 5–13%, which led to the formation of a dense soil crust and alfalfa crop failure areas (mortality spots). These sites are well detected on the materials of satellite imagery. In the over-45-year period of irrigated arable land exploitation, there has been a significant decrease in the humus content in comparison to arable, nonirrigated lands. The humus content in the soils of the key sites averaged 1.23% and approached the minimum acceptable level, according to (Metodicheskie…, 2003). The soil degradation is caused by the overall low level of farming culture and the long-term use of the surface irrigation method. The content of mobile phosphorus (20–102 mg/kg) and exchangeable potassium (316–806 mg/kg) varied widely from medium to very high levels in these soils.