Anthropogenic Transformation of Some Properties and Composition of Gazh Gray-Brown Soils of the Ganja-Gazakh Plain

Gay gray-brown soils are distributed mainly in the foothills of the Lesser Caucasus, on the Ganja-Gazakh plain and in the lower reaches of the Araz basin. They are formed by changing volcanic rocks in hot and dry climates. In the process of erosion and soil formation, pyrite, alunitized and other sulfur-containing rocks turn into gazh, on which gray-brown gazh soils are formed. As a result of human activity, i. e. deep plowing and irrigation, these lands are being converted. It turned out that the transformation of these soils is clearly felt in the thickness of the humus layer, its distribution along the profile, quantity and composition. The thickness of the humus layer increases from 40–45 cm to 100 cm. As a result of the transformation, the length of the humus profile is constantly decreasing. Changes in the composition of humus led to an increase in the content of humic acids. Although the coefficient in the uncultivated area decreased from 1.36 to 0.80, in the irrigated area it changed from 1.70 to 0.93.

Agroecological assessment of leached chernozems with different erosion level in conditions of the slope catena at the Central Chernozemic Region

Based on the complex investigation of agroecological parameters of leached chernozems with different erosion level in conditions of the slope catena at the Central Chernozemic Region (CChR), the features of agrogenic-erosive transformation of morphogenetic, chemical and physic-chemical properties of the investigated soils at the basic levels of their structural organization are shown – depending on the degree of their erosion. The influence of the processes of surface planar erosion and intra-soil lateral migration on the content and distribution of the most problematic heavy metals (HM) – Pb, Cd is considered. The analysis of the research results has shown that the development of erosion processes in conditions of the slope type of terrain characteristic for the CChR leads to a significant transformation of the main diagnostic indicators of the agroecological state of leached chernozems, primarily to the degradation of their morphogenetic and humus profile. The significant and slope-differentiated influence of erosion processes at the level of soil elementary particles, meso- and macro-levels of the soil structural organization has been established. The processes of erosion and lateral migration change the content and profile distribution of Cd and, especially, Pb in the studied leached chernozems. In the eroded soils, there is an increase in their mobility and accumulation in the subsoil. Keywords: LEACHED CHERNOZEMS, AGROECOLOGICAL STATE, EROSION, TRANSFORMATION AND DEGRADATION, HEAVY METALS, LEAD, CADMIUM

Study of thickness of humus profiles of gray forest and chernozem soils of different terms of agricultural use in landscape shrubs of the central forest-steppe

The article presents the results of a field study of the thickness of the humus profiles of gray forest soils and podzolized chernozems of dif-ferent terms of agricultural use of soil catens of broad-leaved-forest (background) and meadow-steppe areas of the Belgorod region. The work was carried out in the spring and summer period 2018-2019. The objects of the study were different-aged arable plots with the age of agricultural development of 100 and 160 years, respectively. The steepness of the surface on the plots did not exceed 5-60. It is established that the thickness of humus profile under the influence of agricultural cultivation during 60 years has decreased by 49 cm, at that on the slopes of northern exposition this index is more expressed (33 cm) than on the slopes of southern exposition (16 cm). It is possible, to note, that with increase of age of agricultural use on slopes of northern and southern expositions the greatest thickness of humus horizon is observed on anomalous soils (72 and 65 sm accordingly). Within the background catens the soil cover is homogeneous, the second humus horizon was observed in each of the studied transects.

Geoarchaeological study of big Essentuksky 1 kurgan in Ciscaucasia, Russia

<p>The chrono-sequence of paleosols, buried under different constructions in the big kurgan Essentuksky 1 in Ciscaucasia (Stavropol region), built by people of the Maikop culture in the second quarter of the 4<sup>th</sup> millennium BC, was studied. The height of the kurgan was 5.5-6 m and diameter – more than 60 m. It had four earthen constructions and three – made of stones. We studied the composition of the material of kurgan’s constructions, paleosols buried under four earthen kurgan's constructions and the surface soil on the area adjoining to the kurgan. The macro- and micromorphological observations and set of analytical and instrumental methods were used to study the properties of soils in the chrono-sequence and composition of material from the earthen constructions. According to archaeological data, the kurgan was built for time-span from 25, but not more than 50 years. During this interval, the morphological and physicochemical properties of soils changed, namely, there was a decrease in the thickness of the humus profile and the content of organic carbon, an increase in the content of gypsum, carbon of carbonates, a shift of the area of their accumulation up the profile, and transformation of the forms of carbonate features. The percentage of the exchangeable sodium and magnesium in the composition of exchangeable bases increased and magnetic susceptibility decreased. The most “arid” properties are found in the paleosol buried last in the studied chronological sequence: the humus horizon is the lightest, the profile is most enriched in carbonates, there is the highest content of exchangeable sodium and magnesium in the composition of exchange bases, the lowest magnetic susceptibility and the maximum amount of gypsum in the second meter of the profile. During the indicated time-span of the construction of the kurgan, Haplic Chernozems Loamic changed in Calcic Chernozems Loamic. For the studied time-span, a palynological analysis revealed a decrease in forest area and an increase in the portion of grassy vegetation. In the composition of grasses, there was an increase in the proportion of steppe and xerophytic species. The climate of the studied interval (the beginning of the development of the Maikop culture in the Ciscaucasia) is characterized as drier and hotter in comparison with nowadays. The material for the earthen layers of the kurgan's constructions was taken from the gleyic horizons of the Gleysols (the lowest layer in the first and second constructions) and from the Ah and AhB horizons of the Chernozems (the overwhelming majority of the layers). This study was supported by the Russian Science Foundation, project no. 16-17-10280.</p>

Haplic chernozems humus condition of Western Bug and Styr terraced landscapes

Volyn Upland Haplic Chernozems are distributed mainly on the terrace landscapes of the Western Bug and the Styr and their tributaries (Chornohuzka, Luha, Lypa). Most of these soils are old ploughlands that have experienced various types of degradation. Haplic Chernozems are low-humus soils and they have low storages of humus substance in the 20 cm arable layer and middle storages of humus in 100 cm soil thickness. There is correlation of C humic acids to C fulvic acids within 1.2–3.3 in the humus profile. Among the various fractions of humic substances the 2nd fraction associated to Calcium dominates. A content of “free” humic acids (1rst fraction) is very low and the amount of humin is low. The optical density of humic acids ( 0,001% НА Е1 cm, 465 nm ) are high and very high. The organic matter of Volyn Upland Haplic Chernozems has some regional peculiarities. First, it caused by topographical conditions of its formation and evolution in the Holocene. Chernozems of the 1st terrace of the River Western Bug are extremely deep. They have progressive-accumulative type of humus distribution in profile, humate type of humus in upper 100 cm layer, a very high degree of organic matter humification and the same content of humic fraction associated to Calcium and lowmiddle content of 3rd fraction associated to clay minerals. The molecules of humic acids in the humus horizon of Chernozems of the 1rst terrace are better structured that indicates the older age of humus in these soils. Chernozems of the 2nd terrace above the floodplain of the River Styr are middle-deep soils. They are characterised by the regressive-accumulative type of humus distribution in profile, humate-fulvate type of humus and very high degree of organic matter humification only in 25–50 cm layer. The content of fractions associated to Calcium and clay minerals is predominantly high. Key words: Haplic Chernozems, humus, humic acids, fulvic acids, optical density, humus condition.

The evolution of podzolized and regraded chernozems in Eastern Upland Wooded Steppe of Ukraine and the ways of their development

It is indicated that podzolized and regarded chernozems in moderately humid and arid zones of Left-bank Wooded steppe with HTC 1,2–1,0 (within the valleys of the Sula and Oskil rivers) occur in high watersheds along right bedrock banks of the valleys, adjoining or being included into wooded refugiums. Being formed by the grove biogeocenosis, they have high rates of fertility. The morphological research of natural podzolized chernozems profiles showed, that the upper humus slightly-eluviated horizon, densely interweaved by roots, has coarse agronomically valuable structure, loose composition, dark-grey colour, that indicates high content of humus. It is mostly favoured by the biologically active, rich in calcium ground litter and the pristinity of soil texture. The general capacity of the humus profile is not less than 100 cm. While brining natural soils into tillage some changes of soil development conditions arise. They are: hydrothermic conditions, secondary carbonate enrichment (regradation), loosening of illuvial horizon. Under mechanical tillage the granular structure changes into a pulverescent and cloddy one, the topsoil becomes lighter because of humus loss, though the humus profile becomes 10–20 cm deeper. The analytical results indicate the sufficient differences in physicochemical and agrochemical characteristics between forest podzolized chernozems and their regradated analogs in tillage. Natural soils contain 5,7–6,5 % of humus in upper 0–35 cm layer, and up to 10,0 % in 0–15 cm layer. They also have considerable resources of hydrolyzable nitrogen. In agrogenic soils the humus content is up to 3,6 %. The humus is of a humate type both in podzolized and regarded soils. The smallest proportion of Сh.a./Сf.a is in the lower layer of humus eluviated horizon of forest soils. The level of humus loss by agrogenic soils in humus slightly-eluviated layer fluctuates from 37 % to 44 %. Dark-grey and grey forest soils lose more than half of humus content, typical chernozems – nearly 30 %, ordinary chernozems – 20 %. Regraded analogs are inferior according to the hydrolyzable nitrogen content. Positive evolutional changes in tillage, such as acidity reduction, bases saturation growth, illuvium destruction, didn’t yield expected results – resistance to degradation processes. For the development of agrogenic soils it is necessary to implement flexible complex systems of husbandry with minimal intensity of tillage, adapted to the landscape, bringing the culture of husbandry closer to natural conditions. Promising is the implementation of soil protection technologies with the maximum use of freak produce of plant growing. The integrity of soil composition and biologically active layer of mulch create the conditions, close to virgin ones, that lead to the transition of soil to natural non-degradation conditions without losing its productive functions.

Labile fractions of soil organic matter, their quantity and quality

The objective of the present paper is to contribute to the evaluation of quantity and quality of non-humified part of soil organic matter (SOM). In samples of soil organic matter from the humus profile of Šumava forest soils and forest meadows, taxonomically designated as mor and moder forms, the fractions of labile soil carbon C_cws, C_hws, C_PM and fraction of stable carbon represented by carbon of humus acids C_HA and C_FA were determined. Organic matter of samples was fractionated according to the degrees of hydrolyzability by two different methods in particle-size fractions of 2.00–0.25 mm and < 0.25 mm. The quality of labile fraction C_hws was expressed on the basis of reaction kinetics as the rate constant of biochemical oxidation K_bio and rate constant of chemical oxidation K_chem of the first order reaction from a reduction in the concentration of C-compounds. The highest values of labile forms of carbon were determined in samples with the least favorable conditions for transformation processes of SOM, and these samples also had the highest content of labile forms in hydrolyses by both methods and the most labile fractions at the same time. The degree of SOM humification was strictly indirectly proportional to the lability of SOM and its hydrolyzability. The quality of labile fraction C_hws can be expressed by both K_bio and K_chem while the sensitivity of K_bio is higher but the reproducibility of K_chem is better. K_bio corresponds with the degree of SOM transformation, K_chem with the proportion of C_PM in total C_ox.