Genetic Horizons Research Articles

Molecular structure of humus acids in soils

AbstractThe molecular structure of humus acids remains one of the most challenging issues in the soil science. The focus of the current research lies in defining the molecular and supramolecular structure of soil humus acids. This paper provides a brief review of the current understanding of the problem and shares findings of the elemental and X‐ray structural analysis of humic and fulvic acids extracted from Chernozems and Chestnut soils in the Rostov region. This region occupies a large area of the South‐European Russia. Humic acids in the studied soils have reduced carbon content compared to average parameters for these soil types. The supramolecular organization of humic acids in three‐dimensional space contains two to four layers of condensed aromatic systems supplemented by a network of chain fragments of different regularity and length. Parameters of this structure vary for soils of different genesis and genetic horizons. However, interplanar distances are fixed in the range of 0.349 to 0.371 nm. Thickness of the carbon network band increases with the benzoidicity level of humic acids. The obtained results confirm the specific matrix structure of humic acid molecules. Considering currently available scarce data these findings are valuable and unique. Our findings are consistent with the general hypothesis about the supramolecular nature of humic substances.

Estimation of elemental composition of agricultural soils from West Azerbaijan, Iran, using mid-infrared spectral models

ABSTRACT Characterizing the elemental composition provides useful information about the weathering degree of soils. In Miandoab County, Northern Iran, this characterization was missing, and thus the objectives of this work were to evaluate the weathering degrees for the most typical soils in the area from their elemental compositions, and to estimate this elemental composition using Fourier transform infrared spectroscopy and Random Forest models. Five soil profiles, including Aridisols and Inceptisols, were selected as the most representative of the area. Major elemental oxides were determined in each genetic horizon by X-ray fluorescence, showing that these soils were at early developmental stages. Only Al2O3 and CaO were accurately estimated, with R2 values of 0.8, and out-of-bag mean square errors of 0.2 and 1.1, respectively. The other oxides were not predicted satisfactorily, probably due to small differences in their elemental compositions. Random Forest provided the important spectral bands related to the content of each element. For Al2O3, these bands were between 500 and 650 cm-1, which represent out-of-plane OH bending vibrations and Al-O gibbsite and alumino-silicate vibrations. For CaO, the most important bands are related to carbonate content. A combination of Fourier transform infrared spectra and Random Forest models can be used as a rapid and low-cost technique to estimate the elemental composition of arid and semi-arid soils of Northern Iran.

Soil Fertility Assessment of an High Natural Value Eligible Area in South-Eastern Transylvania

Abstract As low-input environmentally friendly agricultural practices are currently associated with the delivery of a wide range of public goods and socioeconomic benefits, the strategy of European Union in mitigating climate change effects, protecting environment and ensuring public health has, among others, focused around preserving the High Natural Value (HNV) areas. About a quarter of the land in Romania is potentially covered by HNV farming and eligible for associated support payments, mostly along the chain of the Carpathian Mountains. Since soil systematic data on HNV area are scarce, recent research developments currently undertake to build up a first national HNV soil data base. Soil fertility state in a HNV payment eligible area of south-eastern Transylvania was studied in seven in-depth dug profiles and seven additional shallow dug profiles. Soil samples were taken by genetic horizons as well as agrochemical samples from the upper soil layers (0-20 cm). Physical, chemical, and microbiological analyses revealed that the studied soils have a medium clayey loamy texture, good fertility and are subject to an adequate HNV management in the area, as the analytical values mostly range in favorable intervals for plant growth and nutrition. Thus, soil reaction is moderately acid up to slightly alkaline in the presence of carbonates, the soil organic matter, generally well mineralized, reaches fair levels and the high and very high cation exchange capacity ensure good conditions for plants growth and nutrition whilst nitrogen and potassium supply is adequate. Phosphorus is the only element in short supply – a situation often encountered in Romania unfertilized soils. Soil bulk density and total porosity are also favorable for root growth and spreading and plant nutrition. Microorganisms’ activity is diverse and is also adequate for plant nutrition.

Sorption properties of granulometric fractions in Haplic Cambisol developed from boulder loam

Abstract The aim of the paper was to investigate the sorption properties of granulometric fractions separated from the genetic horizons of arable Haplic Cambisol developed from boulder loams of the Middle-Polish (Riss) Glaciation, Wartanian Stadial (central Poland). Separation of granulometric fractions was made with application of the Atterberg method without the use of centrifuging and dispersing agents. The cation exchange capacity average value in cmol(+)kg−1 and % contribution in particular fractions reached: 1–0.1 mm – 2.1 (1.6%), 0.1–0.05 mm – 5.5 (4.0%), 0.05–0.02 mm – 8.5 (6.1%), 0.02–0.01 mm – 13.0 (10.1%), 0.01–0.005 mm – 16.1 (12.8%), 0.005–0.002 mm – 28.6 (20.5%) and fraction <0.002 mm – 48.7 (44.9%). Leaching of the total exchangeable bases was the largest in the 0.1–0.05 mm fraction and decreased successively with decreasing grain diameter. Sorption properties of the tested soil determine its high agricultural value and buffer properties. The cation exchange capacity of the recognised granulometric fractions successively increased with decrease of their diameter while leaching process intensity in individual fractions decreased gradually as their dimensions decreased. Calcium was the most leached cation, followed by magnesium and sodium, whereas potassium was not leached at all. Significant increase of the cation exchange capacity in fractions from carbonate horizons was mostly caused by the increased contribution of calcium, which could be released from carbonates during extraction of bases.

Typical Signs and Properties of Agricultural-Podzolic Soils of Northern Forest-Steppe

Based on the results of soil and agrochemical surveys, the state of soil fertility of agro-podzolic soils of the northern forest-steppe under conditions of intensive farming has been studied. The generalization of the soil properties of individual indicators in an amount of 44-148 values characterizing the given territory was carried out by methods of mathematical statistics. The features of the analyzed soils are discussed by dividing into two groups - fundamental and stable. The first group includes a combination of genetic horizons of the soil profile. This group also included the content of clay fraction and physical clay, the pH of the salt extract. The group of stable soil properties includes the humus content, the sum of absorbed bases and hydrolytic acidity. The results of typical soil characteristics and properties, depending on the duration and intensity of the impact of agricultural processing, their indicators are a criterion for assessing and optimizing soil conditions for crops. In this case, the actual data processed by the statistical method is more informative than the specific measurements.

Pedogenetic characterization and classification of forest soils in the Central Middle Atlas (Morocco)

The study was carried out in the forests of the Central Middle Atlas where the soils have a Mediterranean character. The forest formations found include resinous species such as on Atlas cedar ( Cedrus atlantica ) and maritime mountain pine ( Pinus pinaster ), and deciduous species of green oak ( Quercus rotundifolia ) and zeen oak (Quercus canariensis). The morphological description of soils’ genetic horizons was based on the opening of soil pedons in the forest formations composing the studied area. Then, physical and chemical characterization of the studied soils was analyzed. According to the Commission of Pedology and Soil Mapping (CPCS, 1967) principles and those of the international system of classification, nomenclature and soil mapping used by FAO (2015), three types of soils were identified as dominant in these forests, namely, the class of browned soils, iron sesquioxide soils and calcimagnesic soils. As a result, they differ in their responses to management practices, their inherent ability to deliver ecosystem services, as well as their resilience to disturbance and vulnerability to degradation.

Spatio-Temporal Dynamics of Soil Geochemical Anomalies in the Zone of Impact of Slag Residuals

The 13-year-old (from 2003 to 2016) dynamics of soil contamination for the content of heavy metals in the area of the village of Bolshoye Dumchino of the Mtsensk District in the territory adjacent to the slag dump of Mtsensk Foundry was studied. It is shown that on the territory of the placement of slag residuals a techno geochemical anomaly is formed, in which the contained heavy metals are of technogenic and genetic (natural geochemical) nature. To identify the effect of anthropogenic factor on soil pollution with heavy metals, was determined the refined enrichment factor of heavy metals (EFHM) in light gray forest soils at different distances from the slag dump, allowing to calculate the proportion of technogeneity of metals as a percentage of its total content. The technogenic origin of heavy metals as pollutants and the role of humus soil horizons in fixing these metals in the soil profile have been proven. Analysis of the results characterizing the degree of enrichment of the genetic horizons of light gray forest soils with heavy metals for the period 2003–2016 convincingly proves the effect of maximum accumulation of slag residuals in the dump on the accumulation intensity and fixation of the studied metals, both in the upper humus layer and their distribution in the profile soil. The established patterns in changing the degree of enrichment and technogenicity of heavy metals in the profile of light-gray forest soil are caused not only by the impact of the slag dump as a source of pollution, but also by the peculiarities of using the soils of the studied territories. It is shown that the toxic load for the analyzed period not only did not decrease, but even increased.

Characteristics of polycyclic aromatic hydrocarbons (PAHs) in soil horizon from high-altitude mountains in Northeastern China

Previous studies have reported that soils from high altitude mountains act as primary reservoirs of polycyclic aromatic hydrocarbons (PAHs). This study aims to investigate the spatial distribution and illuminate the behaviors of PAHs in soil profiles from Mt. Wangtiane in Northeastern China. Soil samples were collected by different soil genetic horizon rather than by depths at 10 sites, with altitudes from 1000 m to 2022 m. Results showed significantly (p < 0.05) higher concentrations of total PAHs (16 PAHs) in O-horizons (371 ± 32 to 2224 ± 207 ng g−1) than those in A- and B-horizons (362 ± 30 to 666 ± 58 ng−1 and 289 ± 23 to 571 ± 50 ng g−1, respectively). An increasing trend of PAH concentrations with altitude was observed from elevation ca. 1000 m to ca. 1800 m, but no correlation between PAH concentrations and altitude along transect was found. Total organic carbon (TOC) was strongly correlated (p < 0.05) with PAH concentrations in O-horizons but showed no relation with those in A- and B-horizons. Low molecular weight (LMW) PAHs were dominated in each soil horizon, and decreased percentage of high molecular weight (HMW) PAHs with depths in soils profiles was observed. Principle component analysis (PCA) separated O-horizons and A-/B-horizons based on PAH compositions, again suggesting different PAH compositions among soil horizons. These results reflect various processes of PAHs, including deposition, vertical motion, degradation and photolysis. This study suggests it is better to investigate characteristics of PAHs in soils by horizon rather than by depths.

Soil C:N:P stoichiometry at different altitudes in Mao'er Mountain, Guangxi, China.

We explored vertical distribution of soil organic carbon (C), nitrogen (N) and phosphorus (P) for examining the relationship between soil C:N:P stoichiometry and both altitudes and soil depths in Mao'er Mountain in Guangxi, South China. A total of ten sites from different altitudes were selected and soil genetic horizon samples were collected along soil profiles at each site. Soil organic C, N, P, pH, bulk density and particle size composition were measured. Results showed that soil C, N, C/P ratio and N/P ratio increased with the increases of altitude. Soil P concentrations and C/N ratio increased within low altitudes then decreased or with no obvious changes. Soil C, N, P, C/P and N/P ratios significantly decreased, whereas C/N ratio did not change with the increases of soil depth. Soil C and N highly coupled within horizons (CV of C/N was 4.0%) and soil P had little spatial variability (CV were 31.0% and 22.0% within altitudes and horizons, respectively). The results from redundancy analysis showed that the first two axes explained 74.8% of the variability of C:N:P stoichiometry. Soil pH, bulk density, and altitude had significant effects on C:N:P stoichiometry, whereas clay, silt, and sand had no effect.

Soil maps at a scale of 1:5000 as a source of soil databases taking soil variability into consideration: a case study from Czermin commune, S Poland

Abstract The analysis of soil spatial property variability (fuzziness) are important for the interpretation of the site-specific ecosystems not only with respect to process investigations but also for soils modelling. The objective of the study was an attempt to identify the primary parameters influencing the spatial variability of soils available without the necessity of carrying out time-consuming and costly field and laboratory research. The research was carried out in the Czermin commune. The research included the application of geostatistical methods and interpretation of source materials, including (i) digital soil-agricultural map, (ii) annex to the soil-agricultural map at a scale of 1:5000, (iii) soil quality contours and (iv) digital terrain model. The verification of field research results (test polygon) involved the performance of vertical transect soil profiles. Genetic horizon patterns and their morphological parameters were determined. Soil samples were collected for laboratory analyses, involving the determination of the basic physical soil properties. The data were analyzed using descriptive statistics and geostatistics. The database based on soil quality contours is more detailed than that based on the soil-agricultural map, because there is no loss of important data concerning the division of land. Obtaining data concerning soil type and/or agricultural usefulness complexes would require conducting a generalisation process. Nearby soil pits from 1974 and new (2015) open pits were located. Soil profile for the open pits from 2015 were described and soil samples were taken for basic physical soil properties.

Применение геофизических методов для оценки строения и свойств почв черноземного ряда

The aim of the study. To assess the potential of geophysical methods to investigate the structure and properties of chernozemic soils. Location and time of the study. The field work was carried out during June-October 2018 on the two arable soils, namely Luvic Greyzemic Chernozem (Siltic) and Haplic Phaeozem (Siltic, Colluvic, Pachic) over Haplic Phaeozem (Siltic, Luvic), in the Bugotak Hills, which is part of the Cis-Salair denudation-accumulation plain on the right side of the Ob River in the south-east of West Siberia. Methodology. Soils were studied by the standard soil and agrochemical techniques as well as by such geophysical methods as magnetometry, electrotomography and ground-penetrating radar. Soil morphology was described, and soil samples were collected from soil genetic horizons. Physical, physicochemical and chemical (altogether up to 28) properties, pertaining to soil potential and actual fertility were determined. Relationships between soil properties and geophysical parameters were studied using correlation and multiple regression analyses. Main results. The study showed that when underlying solid rock is rather close to the surface, the magnetometry cannot be used to solve urgent issues in soil science. When soil total carbon (STC) in humus-accumulating layer was high, the relationship of the decrease in electrical resistivity (ER) with the increase in STC did not work anymore. The ER was found to depend on soil texture, as the heavier soil granulomety resulted in decreased ER. This regularity allows establishing the depth of illuvial horizons in humus-accumulating soils and a fortiori texture-differentiated ones. The ER in the humus-accumulation layer of the Luvic Greyzemic Chernozem (Siltic) was estimated as 70 ohm·m, while the 0-10 cm thick soil layer after subsurface cultivator could be determined by the ER values decreased to 40-45 ohm·m. The combined use of electrotomography and ground-penetrating radar was found to be the most promising for soil studies as such combination allows estimating the thickness of the humus-accumulating layer and its lower boundary, as well as discriminating between agro-dark-humus (arable) and dark-humus horizons, establishing the depth of the illuvial horizon and the upper boundary of the carbonate horizon. Conclusion. We believe that geophysical methods can be beneficial for soil genesis research and large-scale soil mapping because of their ability to account for natural heterogeneity of spatial variation of soil potential fertility properties. Large scale soil maps provide a fortiori indispensable basis to solve many agricultural and environmental problems such as monitoring soil properties’ changes because of soil degradation due to erosion, estimating pollution degree, assessing soil nutrients’ content and calculating fertilization rates, etc. Establishing even empirical relationships between soil geophysical parameters and crop yields currently seems to be a rather ambitious task, as crop yields are mostly determined not by “basic’ soil characteristics (which may correlate with geophysical parameters), but by plant available mineral nutrients and such external factors as photosynthetically active solar radiation, precipitation, fertilizer and pesticide application.

The properties of soil as impacted by sea level rise in the dry season: A case study of Nonthaburi Province, Thailand

This study contributed to the understanding of the effect of sea level rise on soil properties in the agricultural area during the dry season and the providing of more detailed information needed to improve agricultural practices in the area. Five study sites, which located in Nonthaburi province, were selected according to the disparate distance from Chao Phraya River, comprising tropical fruit orchard (location 1 to 4) and paddy field (location 5). Soil morphology was recorded by the genetic horizon and soil samples were collected at depth of 0-15, 15-30, 30-60, 60-90 and 90-120 cm in March 2018 to analyze soil properties involving to salt affected soils, including Electrical Conductivity (ECe), Sodium Adsorption Ratio (SAR), and soil moisture. Moreover, the correlation between their soil properties was also examined by using SPSS Statistics version 22.0 at p-value < 0.05. The result divulged that all soils are deep, poorly drained, and low development. Soil textures are clayey. ECe and SAR of these soils ranged from 0.27-4.38 dS m−1 and 8.54-37.23, accordingly. The trend of soil moisture from 0-90 cm usually increased as the following depth except location 5. The relationship between ECe and SAR of these soils at 0-15, 15-30, 30-60, 60-90 and 90-120 cm revealed highly significant correlation, namely, the correlation coefficient (r) was 0.93, 0.94, 0.72, 0.77 and 0.86, respectively. These results suggest that sea level rise in the dry season influences on some properties of soil.

EFFECT OF AGROBIOLOGICAL RECLAMATION ON THE SOIL ABSORBING SOLONETS COMPLEX OF BARABA LOWLAND

The studies were conducted in the northern forest-steppe of the Baraba lowland on the territory of Novosibirsk region. The genetic profiles of crusty solonets on virgin soil and arable land were analyzed. Soil samples were selected in 2015-2016 from genetic soil horizons on the depth of 100 cm, then drilling every 20 cm to the groundwater. The effect of long-term application of agrobiological soil reclamation method on solonets profiles was studied on the experimental site. The stationary experiment was laid in 1987. The study of the morphological structure of soil profiles and the physicochemical properties of crusty solonets subjected to long-term agrobiological reclamation showed that certain changes occurred in the soil profile. The columnar structure of the solonets (illuvial) horizon was destroyed by agro-technical treatments and plant roots. In addition, under the action of agrobiological soil reclamation, the physicochemical properties of the soil changed. It was established that the concentration of calcium ions in the soil absorbing complex of the solonets (in the illuvial) horizon increased from 27.1 to 64.5%, and the content of sodium and magnesium cations decreased from 38.2 and 26.4 to 32.4 and 1.1% respectively. Solonets turned into residual type from the multi-sodium one. The effect of agrobiological soil reclamation became evident in the change of the overall medium reaction. On the virgin soil, the pH value in the solonets horizon (45-60 cm) was 9.1, while on the arable land it was only 6.5. The agrobiological method of soil reclamation not only increased the productivity of agrolandscapes, but also had a positive impact on the physicochemical properties of the solonetz soils of Baraba lowland and their genetic profile.

Spatial variability of soil organic carbon density under different land covers and soil types in a sub-humid terrestrial ecosystem

T he main objectives of the current study are i) to estimate SOC in different soil depths and to generate their spatial distribution maps, ii) to assess relationship between variation of different soil types and SOC density, iii) to determine effects of land cover types on SOC in Inebolu Watershed located in sub-humid terrestrial ecosystem. In order to determine land cover types of the study area, aster satellite image was used and five main land cover types that are bare land, sparsely vegetated area, broadleaved forest area, mixed forest area and needleleaved forest area were classified. Results indicated that soil types and land cover were two crucial influencing factors for spatial variation of SOC density. It was determined that SOC density of soil types, Vertic Haplustept ( 12.93 kg.m -2 ) was significantly higher than other soil subgroups. In this case, it can be said that main reasons of this result are indicated as soil profile depth and pedological development. In addition, when comparing the two main factors, land cover explained more of the SOC density variability and was the main controlling factor in the surface; in the subsurface, not only land cover types but also some properties of soil types such as texture, genetic horizons, soil depth have an important role on SOC density. On the other hand, it can be conclude that the combination of the soil type and land cover was a dramatically better predictor of SOC density.

Ефективність препарату «Реаком» на чорноземі звичайному за вирощування пшениці озимої

The article describes the importance of using micronutrients in the dry climate of the Southern Steppe of Ukraine on degraded soils under conditions of atmospheric pollution, violation of traditional schemes of crop rotation of crops and deficiency of organic fertilizers. The main purpose of the study, taking into account that the fertilization was carried out in a single scheme, both in terms of norms and technology, was to investigate the influence of soil ecological factors on the yield of winter wheat against the background of differentiation of the extracorporeal fertilization with the trace elements of Reakom (Zn, Cu, B, Mo, Co, P 2 O 5 , K 2 O) in a dose of 2.5 l/ha and 5 l/ha. The research was carried out on chernozem in the usual low-humus and its eroded abnormalities: weak and medium-sized, which marked the rise of carbonates due to some blurring of the upper accumulative genetic horizon and deterioration of qualitative soil fertility indices. The yield of winter wheat on chernozem was almost 1.17% higher than that of 2.5 l/ha, compared to control, whereas there was no effect on the washed offs. For application of 5l/ha Reakom at discarded crop yields increased to 13.8% on medium-chernozem. Effectiveness of the drug for foliar application of winter wheat in arid conditions on the abovementioned soil abnormalities is described by the regression equation, the use of which will allow the efficient allocation of funds when planning purchases of trace elements of trace elements.

Assessment of Soil-Water Composition Dynamics in the North Taiga Forests upon the Reduction of Industrial Air Pollution by Emissions of a Copper—Nickel Smelter

This work is aimed at assessing the dynamics of the composition of soil waters in coniferous forests subjected to air pollution from the Severonikel’ copper-nickel smelter in Murmansk oblast. The objects of investigations are the most common in boreal zone spruce forests with dwarf shrubs + green mosses and pine forests with dwarf shrubs + lichens. The results show a significant intra- (below the crowns and between the crowns) and interbiogeocenotic (spruce and pine forests) variation in the composition of atmospheric deposition and soil waters in forests under pollution. The atmospheric deposition of pollutants and leaching of their compounds from all soil genetic horizons are tens (sulfates) and hundreds (copper and nickel) times higher than in reference sites and their fluxes below the crowns are usually more intense than between the crowns. Long-term dynamics (from 1993 to 2012) demonstrate reliable trends in the reduction of concentrations and leaching of sulfates and heavy metals from the soil. The molar ratio of basic cations to aluminum (BC/Al) in soil waters from all soil horizons does not drop to the level of critical, whereas for mineral nitrogen the lowest critical level (0.2 mg/L) was exceeded in waters from all horizons at all stages of digression. It was shown that, for the early detection of exceedances of the critical level for mineral nitrogen in soil waters, an evaluation of their composition is necessary not only between the crowns, but also below them.

Change of the redox potential in the profile of light grey forest surface-gleyed soil under different anthropogenic

The results of studies of the change in redox potential in the profile of light gray forest surface-gleyed soil on variants with long-term agricultural use without applying fertilizers and mineral fertilizer system solely compared with the soil under the forest are presented. On the basis of the conducted analyzes it was established, that soil tillage without fertilizer application and with mineral fertilizer solely has a different effect on ROP in the profile. In the soil without fertilization (control) as compared to the forest a moderate oxidizing (514 mV) and slightly oxidizing (437 mV)&#x0D; processes are happening. Prolonged application of mineral fertilizers to the soil (N65R68K68) significantly reduced the redox potential of all genetic horizons compared with forest and control without fertilizers. For the given fertilizer system the highest values of ROP were obtained in arable HEgl and underarable HEgl layers: 426 mV and 416 mV&#x0D; respectively. Redox potential sharply decreases with the depth to 398-311 mV, which characterizes processes occurring in the soil profile, as weakly reducing and close to moderately reducing.

Content of Acid-Soluble Copper and Zinc in Background Soils of Komi Republic

Geochemical features of copper and zinc in soils of background landscapes of northeastern European Russia have been revealed. Soils of accumulative landscapes are enriched with copper and zinc compounds compared to those of eluvial landscapes. Humus horizons serve as a geochemical barrier for elements. Analysis of the sorption parameters of humic acids (HAs) shows that the actual content of the studied heavy metals (HMs) in soils is far from the maximum sorption capacity. The contribution of HAs to the total sorption of metals makes up 4% for copper and 21% for zinc. The distribution of HMs among the genetic horizons is more contrast in loamy automorphic soils than in sandy semihydromorphic and hydromorphic soils. Paired correlations have been revealed between the contents of copper and zinc in sandy and loamy soils, which points to the similarity of their biogeochemical migration in landscapes. An actual database has been created, which is foundational to schematic maps of the spatial distribution of elements in background soils. The geochemical assessment of the environmental status of soils has allowed establishing norms for the regional background contents of copper and zinc in taiga and tundra soils.

TAXONOMIC STRUCTURE OF PROKARYOTIC COMMUNITIES IN SOILS OF DIFFERENT BIOCLIMATIC ZONES

Using high-throughput sequencing, we performed a full-profile analysis of the taxonomic structure and diversity of prokaryotic communities of zonal soil series: sod-podzolic, dark gray, typical chernozem, brown soil, meadow-chestnut soil and solonets. Phyla Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Gemmatimonadetes, Planctomycetes, Proteobacteria and Verrucomicrobia formed up to 95% of prokaryotic communities in all studied soil horizons. Phyla Proteobacteria and Actinobacteria and archaeal phylum Thaumarchaeota dominated in all soils. We revealed the trends of changes in the representation of bacterial phyla in the soils of the zonal range from taiga to dry-steppe: a decrease of Acidobacteria and an increase of Actinobacteria in the upper horizons. The diversity indices of the prokaryotic communities of different genetic horizons of the studied soils were evaluated. In all soils, a decrease in diversity indices with the depth of the horizon was revealed. In all soils, a decrease in diversity indices with depth of the horizon was found, with a rare and slight increase in some lower horizons: structural metamorphic (BM), textural (BT) or accumulative carbonate (BCA) horizons. When examining the prokaryotic communities of soils with different genesis, no determining influence of pH and organic matter contents on the diversity indices was found. Differences in the taxonomic structure and diversity of prokaryotic communities of soils of different bioclimatic zones were presented due to a combination of factors: the difference in chemical and physical properties of soils, as well as in water and temperature conditions.

Evaluating the spatial and vertical distribution of agriculturally important nutrients — nitrogen, phosphorous and boron — in North West Iran

Soil legacy data is ubiquitous and usually contains routine soil analysis information. In Iran, like most places, legacy soil data constitutes genetic horizon soil information recorded from excavated soil profiles. Describing and sampling from each genetic horizon is assumed to be heterogeneous from site to site. Digital soil mapping (DSM) using observed data is valuable because it provides a means to exploit the available information together with leveraging commonly available information by way of environmental covariates. It creates a much more detailed view of soil at the landscape scale. The purpose of this paper is to model and map the spatial distribution of nitrogen, phosphorous and boron at four standardized depths: 0–15, 15–30, 30–60, 60–100 cm, in an area of 7300 ha in the north west of Iran, and compare different model types. To circumvent the issue of heterogeneous soil depth observations from site to site, mass-preserving soil depth function splines were used to harmonise the soil profile observed data to the aforementioned standard depths. This facilitated the spatial modelling of each of the target variables for each standard depth with the aim of creating digital soil maps. Twenty-three covariates were extracted from a publically available digital elevation model (DEM) as well as freely available Landsat 8 ETM+ imagery. The DEM-derivative covariates used in this study were divided into three main categories: i) Morphometry; ii) hydrology; and iii) lighting visibility. Both Random Forest and Cubist were assessed as candidate models for predicting each target variable. The results showed that Cubist was the most accurate method. Terrain attributes play an important role in estimating N, P, and B, while optical images do not have significant role. The most important findings of this paper in terms of environmental hazards are that the inundated regions in the west part of the study area are susceptible to boron contamination, providing future guidance for remediation.