Humus Horizon Research Articles

Variation in soil macro-fauna diversity in seven humus orders of a Parrotio-Carpinetum forest association on Chromic Cambisols of Shast-klateh area in Iran

Soil biodiversity includes organisms which spend a part or all of their life cycle on or in the soil. Among soil-dwelling animals, macro-fauna as an important group of animals have important effects on the dynamics of soil organic matter and litter decomposition process. The humus forms interact with the climatic conditions, flora, as well as soil fauna, and microbial activity. In new humus form classifications, soil organisms play an important role in separation of humus horizons from one another. The subject of this study was to determine the diversity of macro fauna for different humus forms. We determined humus forms using morphological classification, and then 69 random samples were taken from plots of 100 cm2 in area, and soil macro-fauna species were collected by hand sorting method. Two classes of humus forms, including Mull (with three humus orders, namely Dysmull, Oligomull, and Mesomull,) and Amphi (with four humus orders, namely Leptoamphi, Eumacroamphi, Eumesoamphi, and Pachyamphi) were identified. A number of 13 macro-fauna orders were identified using identification key. Among the humus orders, Shannon diversity, Simpson evenness and Margalef richness indices were the highest in Pachyamphi order. Arthropod diversity in Pachyamphi humus order was higher than those of Mull. These results showed that diversity of soil macrofauna increase by increasing the thickness of the organic horizons (OL, OF, OH), especially OH horizon.

Double-and triple-depth digging and Anthrosol formation in a medieval and modern-era city (Wrocław, SW Poland). Geoarchaeological research on past horticultural practices

Buried, humus-rich horizons, up to 0.60m thick, poor in archaeological artefacts and other anthropogenic materials, were identified during an archaeological rescue excavation conducted at monastery grounds, located near the centre of Wrocław (SW Poland). As indicated by historical sources, the monks settled in the 18th century in a suburb area, which had been used for agriculture and gardening since the Middle Ages. The paper discusses the origin of the thick humus horizon in the context of various concepts of ‘Dark earths’ formation. Three hypotheses were considered, linking the soil formation with: 1) natural pedogenesis in alluvial material, 2) ancient settlement and human activity resulting in accumulation of materials, and 3) past/modern agricultural and horticultural activities.In order to reveal the origin of this humus-rich horizon, and investigate the possible involvement of anthropogenic factors in its creation, an interdisciplinary research protocol was adopted, which involved a historical query and archaeobotanical, micromorphological, and physico-chemical soil analyses.It was argued that the studied soil, poor in archaeological artefacts, is in fact a relatively young anthropogenic soil, which had been formed by triple- and double-depth digging (Rigosol) and enrichment of the soil in certain kinds of anthropogenic material (Anthrosol), but without surface up-building typical for soils with Plaggic and Terric horizons. This led to a transformation of the original soil cover, increasing the thickness of its A horizon and adapting it for supporting gardens and orchards. These practices, which most likely took place in the late medieval and modern era period up to the 19th century, have been completely forgotten until now. In this light the discovered Rigosol-Anthrosol may be considered an artefact of horticultural/agricultural land use in the former suburbs, which were absorbed by the rapidly growing city during the last century. It is also postulated, that Rigosols (–Anthrosols) may be widespread among Dark earths in some medieval suburban and present-day urbanized areas of cities and should be investigated during archaeological research.

PECULIARITIES OF HUMUS AND NITROGEN ECOLOGICAL STATE FOR STEPPE ZONE CHERNOZEMS OF THE NORTH CAUCASUS

Purpose of the paper presented is to determine tendency and intensity for quantitative and qualitative changes in humus and nitrogen of chernozems. System approach to study natural objects is assumed as the basis for research methodology of humus and nitrogen state of soils. It is established that the depth typical values of chernozem humus horizons in the North Caucasus are 120–180 cm for South European facies of leached chernozem, 100–170 cm for modal chernozems, 70–160 cm for common chernozems, 70–120 cm for sothern chernozems; for East European facies of southern chernozems it is 55–70 cm. A distinctive ecological feature of soils is a low humus content in an arable layer, its deep distribution along the profile and. slight variability among each subtype. Nitrogen quantity in chernozems of the region variates in comparatively wide ranges: in South European facies of leached, modal and common chernozems 0,20–0,35%, in East european facies of southern chernozems 0,22–0,30%. Southern chernozems of South European facies contain least of all nitrogen 0,18–0,22%. Tota1 nitrogen composition is presented in the main with nonhydrolysed facies – 74,2–78,9%. The research materials are intended to design farming systems on the landscape basis for specialists who are busy with the problem of conservation and increase in soil fertility and environment protection. The results of research allow to realize purposeful impact on decision making to control humus and nitrogen state of soils and this will serve as the basis for conservation of bioecological potential of chernozems.

Conductive and steam-diffuse constituents of thermotransfer in different soil moisture contents: case study of the Altai Region’s soils

The goal of this study was to determine the conductive and steam-diffusive heat transfer constituents in the soil. Based on the solution of differential equation system of heat and mass transfer, the method to determine the conductive and steam-diffusive heat transfer constituents in wet soils was developed. To measure the thermophysical properties in laboratory setting, a pulse method of a two-dimensional heat source was used. The method takes into account the patterns of temperature field equalization in an unbounded medium after the heat source termination. A feature of this process is the occurrence of peak temperature at the investigated point of the medium at a given instant. In this experiment, the temperature was controlled not only at the investigated point of the medium, but also at the soil-heater interface. The proposed method was used to study the thermophysical indices of the chernozems of the Altai Region’s Priobye area (the Ob River area). The chernozem under study is of light-loamy particle-size composition; the illuvial horizon В is enriched by a sand fraction. It has been found that the soil conductive thermal diffusivity is reduced with increasing moisture content. The steam-diffusive thermal diffusivity has the extremum at the moisture close to the discontinuous capillary moisture. In humus horizons it plays a smaller role than in the mineral horizons. The thermal diffusivity determined by the steam molecule motion in the pore space of the soil exceeds the conductive thermal diffusivity two or three times. At the same time thermal steam diffusivity is more than ten time lower than the conductive constituent. Eventually, the stem molecules though dramatically accelerating the processes of heat transfer in the soil profile conduct a small amount of heat and make a weak contribution to soil thermal accumulation.

Physical parameters of Fluvisols on flooded and non-flooded terraces

Abstract The heterogeneity of soil physical properties of Fluvisols, lack of large pristine areas, and different moisture regimes on non-flooded and flooded terraces impede the possibility to find a soil profile which can serve as a baseline for estimating the impact of natural or anthropogenic factors on soil evolution. The aim of this study is to compare the pore size distribution of pristine Fluvisols on flooded and non-flooded terraces using the method of the soil water retention curve, mercury intrusion porosimetry, nitrogen adsorption isotherms, and water vapour sorption. The pore size distribution of humic horizons of pristine Fluvisols on the non-flooded terrace differs from pore size distribution of Fluvisols on the flooded terrace. The peaks of textural and structural pores are higher in the humic horizons under more humid conditions. The structural characteristics of subsoil horizons depend on soil texture and evolution stage. The peaks of textural pores at about 1 mm diminish with lowering of the soil organic content. Structureless horizons are characterized by uni-modal pore size distribution. Although the content of structural pores of the subsoil horizons of Fluvisols on the non-flooded terrace is low, these pores are represented by biopores, as the coefficient of filtration is moderately high. The difference between non-flooded and flooded profiles is well expressed by the available water storage, volume and mean radius of pores, obtained by mercury intrusion porosimetry and water desorption, which are higher in the surface horizons of frequently flooded Fluvisols.

Modeling of the development of humus horizons in soils of Crimea

Current approaches to the simulation of pedogenesis processes in time are considered. Models for the formation of humus horizon on parent rocks of different genesis in Crimea are presented. Formation rates of humus horizons have been determined, which allows developing the remediation strategies for mining dumps of mineral deposits in Crimea.

Buried humus horizons of pyrogenically transformed soils of pine forests in Western Transbaikalia.

Buried humus horizons of pyrogenically transformed soils of pine forests in Western Transbaikalia.

Soil organic matter quality and composition in a postfire Scotch pine forest in Tolyatti, Samara region

Evaluation of humus accumulation and humification rates was conducted on soils affected by surface and crown fires during 2010 forest fires near Tolyatti (Samara region, Russia). Three key soil plots were studied for estimating SOM quality changes under the forest fire effect. Total carbon and nitrogen content, as well as Сhumic acids/Cfulvic acids (Cha/Cfa) ratios, were estimated to evaluate the dynamics of soil recovery. Humic acid powders were extracted from soils and analyzed by elemental composition and 13C-NMR spectroscopy to assess changes in structure and composition. The data indicate that the burning of a forest floor and humic horizon led to humus losses and decreases in total carbon stocks and content. As a result of the fires, the content of humic acids in the pyrogenic horizon increased. Greater increases in the degree of organic matter humification were observed for surface fires than for crown fires. Fire also lead to the formation of humic acids with an increased proportion of aromatic compounds than in control soils, which indicates the degradation of carboxylic and aliphatic groups of molecules under the burning effect. This corresponds well with the decrease of the proportion of hydrogen when comparing the elemental composition of burned soil with that of mature soil.

Гумусовий стан чорноземів типових терсових місцевостей Західного Бугу та Стиру

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.

Application of magnetometry to assess distribution of dust pollution in topsoil of under-crown area of Norway spruce (Picea abies Karst.) and European beech (Fagus sylvatica L.)

Measurements of magnetic susceptibility (MS) of topsoil are used as an indicator of air derived pollutants containing magnetic particles and heavy metals. Here, we focused on the role of a single tree in the distribution of dust pollutants to topsoil under-crown area. Novelty is a dense grid (1m×1m) for magnetic susceptibility measurements, performed in under two pairs of individual Norway spruce and European beech trees located in urban forests of industrial regions. The MS measurements and chemical analyses (pH, heavy metal contents, soil C and N) were conducted on 312 soil cores. Results show differences in storage of magnetic particles and heavy metals with respect to humus type and thickness of the humic horizon. Higher MS values were measured under beech trees where stem flow was observed. Vertical and horizontal distribution of volume magnetic susceptibility values (κ) can be affected by pedogenesis and animal activity. We found high positive correlations between heavy metal contents and MS values in soil samples.

Genetic and agroindustrial features of meadow brown irrigated soils of Republic of Armenia in terms of climate change and desertification

Аbstract On the territory of the Republic of Armenia the irrigated meadow-brown soils evolve within the slightly sloping piedmont parts of the Ararat plain, in the conditions of the prolonged irrigation process and semi-hydromorphic or automorphic humidification. In this territory the primary soil formation proceeded in the conditions of the capillary ground humidification, but much later groundwater and capillary fringe detached from the soil layer and soil formation proceeded in the automorphic conditions, under the influence of irrigation. This work is dedicated to the study of the causes of degradation and desertification of irrigated meadow-brown soils of the Republic of Armenia. It is shown that the prolonged and indiscriminate use of these soils of the Ararat plain leads to the degradation and desertification. Studies show that some negative changes are observed in these soils that adversely affect agricultural crop yields. In particular, by comparing new- and old-irrigated variants, a noticeable reduction of humus content and absorbed basis is being observed in the arable layer of soils. The prolonged irrigation helped compact the soil mass at a considerable death, as well as leach or redistribute the part of products of the soil formation. The accumulation of silt fraction in the upper horizons is mainly due to the prolonged irrigation of these soils by muddy irrigation waters. In the case of prolonged and indiscriminate use the destruction of agronomically valuable structure and reduction of the content of water-stable aggregates occur in humus horizons. This paper provides suggestions of the ways for improving and increasing the fertility of these soils in the conditions of global climate change.

A comparative study of above- and below-ground parameters of healthy and declining young Norway spruce trees in a mountain area affected by air pollution

ABSTRACTThe aim of this study was to characterize possible connections between above- and below-ground parameters and the decline of Norway spruce trees in the Jeseníky Mountains of the Czech Republic – an area affected both by long-term air pollution and subjected to liming. A part of this study was dedicated to soil analysis, which showed considerable changes in the soil environment and highlighted particularly high concentrations of magnesium and calcium, exceeding optimal limits by as much as 8 and 13 times, respectively. Our results suggest that the decline of evaluated trees is primarily connected to root system development, as we found no differences between evaluated above-ground parameters for either healthy or declining trees. Tree decline related directly to low numbers of skeletal roots, root origin and higher maximal angles between skeletal roots. Declining trees had on average five skeletal roots with maximal angles between them of 173o, indicating poor mechanical stability. Regardless of tree vitality, 93% of all examined root systems were restricted to upper humus horizons with an average rooting depth of 10.2 cm. All evaluated trees showed severe root deformation into tangle, which suggests crucial influence of artificial planting on the architectural development of root systems.

Microtomographic analysis of pore space in a virgin soddy-podzolic soil

The method of X-ray microtomography was applied to study pore space of a virgin soddy-podzolic soil at the natural soil water content. The morphometric parameters of the pores of more than 100 μm in diameter were determined in the vertically oriented undisturbed soil monoliths (d = 3 cm, h = 3–4 cm) from the genetic horizons of the most differentiated part of the soil profile (the AY, AEL, EL, BEL, BT1, and BТ2 horizons). A tendency for the horizontal orientation of these pores was found in all the horizons, except for the humus (AY) horizon. Isolated vesicular pores of different sizes were abundant in the eluvial part of the profile. Numerous recent and relict phytogenic channels were found in the intraped mass of the BT2 horizon. Differently directed interfaces of structural units in the soil horizons were visualized. Cluster analysis was applied to estimate differences between the genetic horizons with respect to their textures, aggregate sizes, and shapes of pores as seen in vertical two-dimensional X-ray images.

The experience of using the rock magnetic methods for assessing the prospects of magnetic exploration in the territory of archaeological monuments of the Barabinsk forest steppe

The results of studying the magnetic properties of the components of the natural environment of the Barabinsk forest steppe accommodating the archaeological monuments dated to VI century B.C. to II century A.D. are presented. The rock magnetic model is constructed for a two-layer medium composed of modern soil and an underlying blanket substratum deposits (clay loam, sandy loam, sand). It is shown that the magnetism of the humic horizon of the soil depends on the topographic position and soil type, whereas the magnetic characteristics of the underlying substratum deposits are persistent throughout the studied territory. The ratio of the magnetic susceptibilities of the humus horizon to the substratum is K = 3–6 for the automorphic soil, K = 1–2.5 for semihydromorphic soil, and K = 0.8–1.0 for hydromorphic soil. Based on subdividing the studied territory in accordance with the values of K and the calculated amplitudes of the microanomalies of the magnetic field, the areas where application of the magnetic survey is highly promising, moderately efficient, and unpromising are outlined. The particular cases of the absence of magnetic anomalies above the archaeological objects, the false anomalies, and the chaotic patterns of the low-amplitude anomalies—all the situations when the magnetic survey is inefficient—are explained from the standpoint of the model.

MEADOW-STEPPER CHERNOZEMS (TYPICAL) OF LVOV REGION: GEOGRAPHY AND REGIONAL PECULIARITIES OF THE PROFILE CONSTRUCTION

Purpose. The available cartographic and printed materials show us the presence of meadow-steppe Chernozems (Typical) in the structure of the soil cover in Lviv region as typical zonal components. This fact cannot be considered to be completely true. The main aim of research is to reveal the true nature of the spatial mosaic of Typical Chernozems, their place in the landscape structure of the region.Data & Methods. The basis of the researches are large-scale soil maps (scale 1:10 000 and 1: 5 000) of collective farms of the Lviv region, advanced schemes of geomorphological and physic-geographical zonation of Ukraine, and materials of field and laboratory researches of the Lviv region chernozems. At the base comparative-geographical method within of the Lviv region (Pidpodilskyi natural area, Sokal-Torchynska and Syansko-Dnisterska hills, Pasmove Pobuzhya and Opillya) were selected representative of key areas. Within each of them, in the way deep trenching and soil-environmental profiles, using historical-evolutionary and genetic-morphological methods, have researched formation of the soil cover structure and modern geochemical contiguity of chernozems with other soils. In order to identify quantitative parameters of regional differences of chernozems are used complex laboratory standard methods.Results. The spatial mosaic of Typical Chernozems of Lviv region has a definite regional lithological and hydrological restriction. They are the main component of soil cover found only on the left bank-side of the Western Bug river and on the Nearpodolian natural area and to a lesser extent on the Range Pobuzhzha. These soils have been formed on well aerated loess plains. Typical Chernozems are not zonal soils in Lviv region. They hold local or island positions among zonal and a little podzolized soils. These Chernozems genetically belong to a group of leached and mycelial-calcareous Chernozems.Typical Cernozems of the Sokal plateau are mostly shallow and medium profound (53-66 cm). They have a lumpy structure and the bedding line of calcium carbonate is closer to the surface (40-45 cm) with rapid boiling. There are mole drains within the transitional humus horizon. Also, there is relatively high occurrence (70-80 cm) of segregational carbonate neoformations with the humic transition horizon of clearly tongue or pocket form in the soil profile. Morever, these soils do not have a clear-accumulative carbonate horizon. Chernozems of the Range Pobuzhya are mainly medium profound, gleyey, leached without the accumulative carbonate horizon. Chernozems of the Nearpodolian region are profound and medium profound, mycelial-calcareous, not gleyey or profound-gleyey. Also, they have a strong grain structure, mainly carbonate. Chernozems typical for terrace complexes are profound or over profound, leached and have well grained structure that makes them similar to meadow-chernozemic soils, yet they are not gleying.

Color estimation of forest-steppe soils by digital photography under laboratory conditions

Numerical values in the RGB, HSB, and L*a*b systems for the colors of structurally differentiated soils (Luvisols) in the Volga–Kama forest-steppe have been obtained using a digital camera. A high correlation has been revealed between the soil color and the content of humus in the range 0.39–6%. When the content of humus exceeds 6%, the color of humus horizon varies only slightly. A regression equation within the RRGB range from 85 to 173 has been calculated for the rapid determination of humus content in low- and medium-humus texturally differentiated soils of the Volga–Kama forest-steppe.

Trace metals in soils of the main geomorphological units in the southwestern part of Western Siberia

Total concentrations of Ti, Cr, Mn, Ni, Cu, Zn, Rb, Sr, and Pb as well as soil granulometric texture were studied for three plot sites representing different geomorphologic units of the southwestern part of Western Siberia: periphery of the upland Tobolsky Mainland, Ishim plain, Turinskaya plain. Interregional difference in the relationship by and among the content of trace elements and particle size distribution of soil horizons is established. Thus, for the soils of Turinskaya plain such interrelations are not observed. For the soils of Ishim Plain moderate negative correlation between Pb concentrations and medium silt, as well as average positive correlations between Zn and fine sand, coarse sand and Pb are found. For the soils of the high terraces of the Irtish and periphery of Tobolsky Mainland interface zone moderate positive correlations between contents of Ti, Zn, Sr and fine sand, weak positive ones between Rb and medium sand, moderate negative ones between Zn and clay, Ti, Ni, Cu, Zn, Rb, Sr, and fine dust, Ti, Cu, Zn, Rb, Sr and medium silt are observed. Consequently, properties and genesis of local parent rocks are significant factors for distribution and accumulation of trace elements in the soils of the southern taiga; at the same time, the processes of bioaccumulation in thick humus horizons of dark gray soils and chernozems apparently play an important part in accumulation and migration of trace elements in forest-steppe soils of Ishim and Turinskaya plains.

Ecosystem functions as indicators for heathland responses to nitrogen fertilisation

Anthropogenic deposition of reactive nitrogen (N) has increased during the 20th century, and is considered an important driver of shifts in ecosystem functions and biodiversity loss. The objective of the present study was to identify those ecosystem functions that best evidence a target ecosystem’s sensitivity to N deposition, taking coastal heathlands as an example. We conducted a three-year field experiment in heathlands of the island Fehmarn (Baltic Sea, North Germany), which currently are subject to a background deposition of 9kgNha−1 yr−1. We experimentally applied six levels of N fertilisation (application of 0, 2.5, 5, 10, 20, and 50kgNha−1 yr−1), and quantified the growth responses of different plant species of different life forms (dwarf shrubs, graminoids, bryophytes, lichens) as well as shifts in the C:N ratios of plant tissue and humus horizons. For an applicability of the experimental findings (in terms of heathland management and critical load assessment) fertilisation effects on response variables were visualised by calculating the treatment ‘effect sizes’. The current year’s shoot increment of the dominant dwarf shrub Calluna vulgaris proved to be the most sensitive indicator to N fertilisation. Shoot increment significantly responded to additions of ≥ 5kgNha−1 yr−1 already in the first year, whereas flower formation of Calluna vulgaris increased only in the high-N treatments. Similarly, tissue C:N ratios of vascular plants (Calluna vulgaris and the graminoids Carex arenaria and Festuca ovina agg.) only decreased in the highest N treatments (50 and 20kgNha−1 yr−1, respectively). In contrast, tissue C:N ratios of cryptogams responded more quickly and sensitively than vascular plants. For example, Cladonia spp. tissue C:N ratios responded to N additions ≥ 5kgNha−1 yr−1 in the second study year. After three years we observed an increase in cover of graminoids and a corresponding decrease of cryptogams at N fertilisation rates of ≥ 10kgNha−1 yr−1. Soil C:N ratios proved to be an inappropriate indicator for N fertilisation at least within our three-year study period. Although current critical N loads for heathlands (10−20kgNha−1 yr−1) were confirmed in our experiment, the immediate and highly sensitive response of the current year’s shoots of Calluna vulgaris suggests that at least some ecosystem functions (e.g. dwarf shrub growth) also might respond to low (i.e.<10kgNha−1 yr−1) but chronic inputs of N.

Sod-podzolic soils with a complex organic profile of the southern Vyatka River basin

The article is devoted to the morphology and substantive properties of the sod- podzolic soils with a complex organic profile having the second humus horizons and found on the southern right bank of the lower Vyatka River. The research results of the mineral and organic phases are the evidence of the relict origin of the second humus horizon as well as the evidence of profile polygenicity of the given soils. They went through two fundamentally different pedogenesis stages during the postglacial period: 1) the developmental accumulative evolution stage in the first half of the Holocene and 2) the accumulative-eluvial stage of erasing evolution including the elements of inheriting evolution in the second half of the Holocene. Keywords: granulometric composition, fractional and group composition, humus age, genesis, soil evolution

Rheological properties of typical chernozems (Kursk oblast) under different land uses

Rheological parameters of humus horizons from typical chernozems under different land use—on a virgin land (unmown steppe) and under an oak forest, long-term black fallow, and agricultural use—have been studied by the amplitude sweep method with an MCR-302 modular rheometer at water contents corresponding to swelling limit and liquid limit. From the curves of elastic and viscous moduli, the ranges of elastic and viscoelastic (plastic) behavior of soil pastes—as well as that of transition from viscoelastic to viscous behavior—have been determined. It has been shown that the rheological behavior is largely determined by the content of organic matter, which can act as a binding agent structuring the interparticle bonds and as a lubricant in the viscous-flow (plastic) state of soil pastes. Soil samples enriched with organic matter (virgin land, oak forest, forest belt) have a more plastic behavior and a higher resistance to loads. Soil samples with the lower content of organic matter (long-term fallow, plowland) are characterized by a more rigid cohesion of particles and a narrower range of load resistance. Soil pastes at the water content of liquid limit have a stronger interparticle cohesion and a more brittle behavior than at the water content of swelling limit. Methodological aspects of testing soil pastes at the constant sample thickness and the controlled normal load have been considered. For swelling soil samples, tests under controlled normal load are preferred.