Advances in Understanding Soil Degradation

Soils, the thin skin of the earth, a living body, are the basis of all highly developed life and have ensured human existence and culture since millennia. Their functions and ecosystem services are crucial for the survival of humanity. Increasing pressure on soils through overuse and mismanagement has exceeded their capacity to perform, which is considered as soil degradation. To meet the mission of the Sustainable Development Goals of the United Nations, soil degradation must be stopped and reversed. We reviewed framework conditions of soil degradation, scientific concepts of research and status and trends of their operationalization. Soil performance and degradation processes must be understood, monitored, mitigated and combated in the context of different categories and scales such as ecosystems, land and landscapes. Approaches to the assessment and monitoring of soil dynamics, degradation and desertification show inconsistencies and knowledge gaps at several levels. Concepts of soil health and ecosystem services of soil should be backed by “hard data” based on field and landscape indicators and measurements. Participatory approaches to mediate conflicting demands of stakeholders are crucial for a broad understanding of soil and its long-term sustainable use. This requires an advanced field diagnostic system of soil performance based on reliable on-site measurement technology in combination with expert-based knowledge and assessment methodologies. Strengthening field soil science is essential for progress in reducing and reversing soil degradation.

Physical soil degradation is a deterioration of the soil’s structure diminishing its functions and ecosystem services. It is mainly initiated and manifested by physical forces and processes, such as energy impacts of water, wind and mechanical pressure on soils, and it is accelerated by various kinds of anthropogenic pressure. This is a threat to meeting visions of the Sustainable Development Goals of the United Nations. We review the current state of some types of physical soil degradation, such as erosion by water, wind and tillage, soil compaction and soil sealing/land take. Despite some knowledge in research of degradation processes, gaps in knowledge and need for action exist at several levels. There is a need to understand the event-wise, stochastic character of erosion and compaction processes and the complex interaction of mechanical disturbances of soil structure with soil hydrological and biochemical processes. The implications of these processes for soil health and ecosystem functioning must be better quantified, yielding indicators, baseline values and thresholds. Progress is needed to develop simulation models of soil erosion and compaction towards complex modular models that can figure and forecast ecosystem processes. There is a demand to construct manageable decision support systems, which can help to plan and conduct zero-soil degradation projects at a landscape level. Cross-comparisons of models and strengthening the databases in terms of field laboratories and long-term experiments are essential to prevent and monitor soil degradation at different scales.

Soil degradation is an exceedance of the capacity and resiliency of soil for providing functions and ecosystem services. It is a complex ongoing phenomenon threatening humans’ livelihoods and our future on earth. Knowledge gain can help to find solutions for monitoring, preventing and combating soil degradation. In this chapter we address the essence, causes, extent, features and implications of various types of chemical and biological soil degradation. The aspects of chemical degradation, such as pollution, acidification, salinization, nutrient depletion and eutrophication are characterized shortly; for biological degradation, harm to soil microbiota and biodiversity, and soil organic matter depletion are considered. Progress in monitoring and modelling or forecasting these types of degradation is also shown. Soils of drylands, the Arctic and all man-made soils are hotspots of chemical and biological degradation. As chemical and biological degradation processes in the microscale are lingering and interacting, they need better awareness and monitoring approaches. Highly developed laboratory methods of soil chemical and biological analyses are existing, but screening methods that work under field conditions are comparatively rare. Biological soil degradation needs further evidence-based research and high-precision data for understanding and combating processes. Crucial questions such as calculation of carbon sequestration potential of agricultural soils and assessment of desertification processes should be better explored to bridge science-policy gaps.

This chapter covers the causes of soil degradation in irrigated agrolandscapes of Russia. The most significant causes are the extensive use of irrigated arable land and the unfavourable chemical composition of irrigation water. This is especially pronounced in the absence of land reclamation measures. As yet, there is no accepted classification of soil degradation due to irrigation. In this chapter, a classification for the degradation of irrigated soils was developed. Five types were proposed, divided into sub-types. Physical degradation includes the deflation and reorganisation of the soil mass. Chemical degradation suggests the unbalanced removal of biophilic elements or the excessive accumulation of harmful substances. Physico-chemical degradation manifests in negative changes in the soil absorption complex (SAC), which triggers other negative changes. Biological degradation is associated with a decreased content of organic matter in soil and unfavourable biota succession. Hydrological degradation occurs due to negative changes in the soil water regime. The degradation degree indicates how intensively the degradation processes manifest, while the speed of degradation shows the activity of negative changes over time. The nature of the degradation reflects the specificity of the degradation processes. The reversibility of degradation indicates a soil’s ability to restore its original properties. The resistance of soil to degradation is an indicator for the soil’s ability to maintain its productive and environmental functions.

Desertification factors in the dry sub-humid regions of Russia have not yet been sufficiently studied from a systemic point of view. The Northern Kulunda Steppe is a typical inner continental steppe on the southern border of the West Siberian Plain. It is an intensively used landscape and arable land covers an area of 90% of the total land surface. The main objectives of this study were (1) to evaluate existing “desertification assessment systems” based on of post-Soviet/Russian and European approaches, (2) to develop a comprehensive regionally adapted system of indicators and identify desertification processes in the Northern Kulunda Steppe and (3) to analyse the driving forces behind these and their variation in temporal scale. Based on change detection thresholds, 16 biophysical indicators and 18 socio-economic processes were analysed and assessed to produce a systematic and reliable description of the regional desertification process. To shed light on the desertification processes, regional geoecological prerequisites and the main climatic and anthropogenic factors causing desertification were determined. The results on the interdependence of causal factors were used to create a better model for describing the temporal development of desertification processes. Analysis of the indicators resulted in (1) critical discussion about the applicability of Russian and European indicator systems, (2) the identification and refined description of the desertification process, (3) a description of the relationships between factors affecting the steppe regions and the variation of driving forces on a temporal scale and (4) evidence that the desertification processes affecting the steppe regions of the south of Western Siberia lead to the adaptation of environmental and socio-economic components.

Widespread soil degradation processes (erosion, dehumidification, loss of nutrients, and acidification) have been observed in the Central Russian Plain. An environmental and economic analysis of land degradation was carried out in three regions of the Central Russian Plain (Belgorod, Tula and Lipetsk) assessing the effects of action and inaction, and analysing the soil nutrient balance. The results show that all three regions experienced an increase in ecosystem values during the 2001–2009 period in respect of the growth of forest area. At the same time, the area under cropland decreased, which was followed by growth in crop yields. This increase in productivity has not been adequately compensated for by fertilisation, which could lead to high costs for combating land degradation in the future, especially in the Tula region. Therefore, an additional analysis correlating the factors of land degradation and the soil nutrient balance was carried out for Tula. Spatial and dynamic models in Tula showed that the increase in the cultivated area was directly correlated with the increase in the area of degraded land. This could be due to the depletion of soil fertility as a result of an insufficient use of mineral and organic fertilisers. The negative balance of nutrients found in the soils of the Tula region in the 1995–2014 period was due to inappropriate management of agriculture in the region studied. In all the regions studied, from 2001 to 2009, the abandonment of a significant proportion of unprofitable arable land was identified, followed by overgrowing with woody vegetation. The increase in forested areas in these regions has increased the value of ecosystem services. Statistical modelling showed that the cost of inaction in the surveyed regions was higher than the cost of action against land degradation (6- and 30-year perspectives). Thus, the application of the action/inaction assessment method has shown that the restoration of land productivity and the maintenance of ecosystem services are economically viable.

Snowmelt erosion is the most destructive type of soil degradation in the dissected territories of Western Siberia. More than 50% of all Siberian farmlands are subject to erosion to various degrees. Issues related to the processes and consequences of soil erosion are a serious problem for both scientists and farmers. The purpose of this work is to present the main methods and devices used to define the quantity and quality of snowmelt water surface runoff and the damage caused by the snowmelt soil erosion. In Western Siberia, one of the main factors of erosion is snow cover, which forms and accumulates for up to five consecutive months. The water content in snow ranges from 65 mm in very low-snow winters to 255 mm in extremely high-snow winters. To measure soil erosion during the snowmelt, field methods were used to determine parameters such as the meltwater runoff volume, number of days with active meltwater drainage, water flow temperature and turbidity of the snowmelt waters. Diagnostic signs of the effects of soil erosion after snowmelt included the volume of the soil solid phase removed by meltwater and the change in thickness of the humus horizon. The losses from erosion after winters with different amounts of snow were: solid phase of the soil—from 1 to 11 t/ha−1, carbon—from 5 to 1000 kg−1, and nitrogen—from 1 to 55 kg−1. The described methods for studying soil erosion during the snowmelt are simple to use and do not require expensive equipment in the field.

Soil erosion caused by climate change and changes in land use increases or decreases depending on the geographic location, climate scenarios, precipitation patterns, topographic potential, and land management practices. Forf this reason, the impact of climate change on soil erosion needs to be analysed at the regional and/or local levels. Bearing in mind that climate and land use will change in the future, the purpose of this chapter is to quantify the current intensity of soil erosion, taking the Vranjska Valley (southern Serbia) as an example, to simulate soil losses for 2050 and 2100 due to changes in climate and land use, and to analyse the spatial and temporal grouping of clusters of soil loss for 2015 and 2100. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) of the sediment delivery ratio (SDR) model integrated with the EBU-POM (Eta Belgrade University-Princeton Ocean Model) regional climate model was used with the aim of quantifying erosion intensity in the Vranjska Valley region. The results of research in the Vranjska Valley region show that average erosion intensity during 2015 amounted to 5.33 t ha−1 yr−1. According to the A1B scenario, average annual soil loss is expected to fall for the two periods in the future, by 6.6% (2050) and 41.8% (2100), mainly as a result of a reduction in the rainfall erosivity factor. Measures which could protect soil effectively in the future include reforestation with drought-resistant species, soil conservation, no-till practices, and an evaluation of current erosion models.

The ground-based monitoring of dust deposition is an essential tool for the long-term evaluation of the aeolian processes involved in sediment transport in arid regions. It offers valuable insights into the spatio-temporal dynamics of the dust distribution and grants access to the deposited material for further analyses. Central Asia in general and the Aral Sea Basin, in particular, is an arid region that largely contributed to the aeolian transport of dust from natural and anthropogenic sources over long distances. The shrinking Aral Sea itself has become a global symbol for the overexploitation of limited water resources. Its artificial desiccation has led to the emergence of a new salty desert, the Aralkum. Exposed to severe wind erosion, the lake bed sediments are transported over hundreds of kilometers as white sand and dust storms, negatively affecting the Turan lowland surrounding the Aralkum. Passive dust deposition samplers were installed at 23 meteorological stations throughout the Turan lowland to monitor and evaluate the temporal and spatial dust dynamics between 2006 and 2012 and assess the grain size distribution, mineralogical and chemical properties of the deposited material. The dust deposition increased over time, which correlates with a decreasing trend in precipitation, increasing wind speeds, and a shift toward northern winds. More than 50% of all dust samples collected exceed the health-based deposition threshold, and the most intense dust storm events reached ground level deposition rates of up to 150 g m−2 per hour. The grain size analysis showed that most of the material deposited in 3 m height was part of the PM5 group with average regional grain diameters between 0.0018 and 0.0129 mm. Coarser material was deposited in spring and summer throughout the study period. The average annual grain diameter increased from 0.0019 mm in 2006 to 0.0141 mm in 2012. Quartz, calcite, and dolomite were the main mineral components in the Central Asian dust samples, and the Aralkum and Karakum samples showed the most significant similarity. A slightly different composition characterized the Kyzylkum dust, but overall all Central Asian dust samples could easily be separated from dust samples from dust source regions in Asia. The differences between the Central Asian dust sources are more pronounced on the level of their chemical composition. The Aralkum samples show a greater similarity to the samples from the Kyzylkum and samples collected in Central Xinjiang, Inner Mongolia, and the Western Sahara. Combining different analytical methods allows for a detailed characterization of the different dust source regions and can be used to track this dust over greater distances. This study showed the impact of the Aralkum, but also that the Kyzylkum is a far more active dust source. Concerning climate change and increasing aridity in the region, the aeolian dust transport will continue to increase, making a widespread monitoring program even more critical.

In the academic community, tillage has become a subject of research in environmental change as it is closely associated with the global stocks of soil carbon, the largest terrestrial organic carbon pool. However, tillage’s impacts on the soil mass are unknown and the role of tillage in the global carbon cycle is intensely debated worldwide. It is still not known how soil eroded by prior natural processes and human activities is offset by tillage, or how soil production is controlled by tillage. Using a physical tracer method, the tillage-induced flux and translocation rate of rock fragments were estimated on the Regosol hillside of the Sichuan Basin, China, where there are extensive mudstone and shale outcrops. There, we found that tillage in the fields artificially accelerates soil production by crushing bedrock to increase the soil matrix. Tilling into bedrock takes place as the soil mass is the minimum required for basic grain production. Tillage caused bedrock fragmentation and accelerated soil production/formation by increasing the soil matrix: the resultant rock fragments are incorporated into the soil layers in the Regosol areas with mudstone and shale outcrops. Our results indicate that tillage and associated tillage erosion can play a positive role in soil production, agricultural productivity, and carbon sequestration in the sloped landscapes of Sichuan, China.

The chapter presents the study of soil erosion on the arable slopes of the Crimean peninsula. The paper analyses the climatic conditionality of erosion processes. Based on an array of chronological soil data, a mathematical modelling of the formation of the humus horizon was performed. An assessment was made of the permissible rates of erosion as a criterion for managing erosion neutrality on the peninsula. Calculations based on the models developed show that, in arid regions with Kastanozems and Chernozems, the highest rates of soil formation were observed on the eroded soils of the wetter slopes with a northern exposure. Regional features of climate dynamics led to an intensification of the erosion degradation processes affecting soils and landscapes of the Crimean Peninsula. In the foothills and mountainous areas and on the southern coast of the Crimean peninsula, where a significant amount of rainfall occurs, the amount of solar radiation acts as a limiting factor. For a quantitative assessment of the rate of soil formation, the most accurate method was based on an assessment of the rate of formation of the humus horizon over time.

Soil erosion is an emerging concern threatening sustainability of forest ecosystems. In case of Japan, one of the driving forces of accelerating soil erosion is heavy deer browsing and trampling. To investigate the effect of deer and clear-cutting on soil erosion, we set up three experimental plots at a slope (24°–27°) of a forest ecosystem with high density of deer, i.e., the fenced plot [F], the non-fenced plot [NF], and the fenced + clear-cut plot [F + C]. The amounts of eroded soil, surface runoff, and loss of nutrients were measured in each experimental plot for 1 year. The amount of eroded soils were in the order of F (1.81 t ha−1 yr−1) < F + C (5.09 t ha−1 yr−1) < NF (7.71 t ha−1 yr−1), suggesting that both deer and clear-cutting accelerated soil erosion. The amount of surface runoff also increased in the order of F < F + C < NF. In addition, the bulk density increased, whereas permeability coefficient decreased in the NF plot. This result would be due to the compaction by deer trampling. The amount of eroded soils in each experimental plot positively correlated with rainfall (mm) and rainfall peak intensity (mm 10 min−1) (p < 0.01). As the rainfall and rainfall peak intensity increased, the amount of eroded soil increased proportionally in all plots. However, the erodibility to the same rainfall in three plots was different. The loss of carbon and nitrogen from the slope also increased in the order of F < F + C < NF, and most of loss (>93%) was derived from the loss of soil particles. In conclusion, we should conserve the forest ecosystems through preventing soil erosion because heavy deer browsing and trampling and clear-cutting of trees would lead to the accelerated soil erosion and loss of nutrients.

Soil compaction caused by agricultural vehicles is a global problem affecting a considerable proportion of all arable land and causing tremendous costs to farmers and society. Soil compaction reduces soil porosity and modifies pore geometry, thereby adversely affecting key soil ecological, hydrological and agronomic functions. This chapter provides an overview of current knowledge on stress propagation, soil compressive behaviour, impacts of soil compaction on soil properties and functions and recovery of soil structure after compaction, and discusses the costs of soil compaction. We provide an overview of non-destructive measurement techniques and approaches for improving description and quantification of soil compaction at spatial scales from the soil pore to the field. Finally, we discuss sensor systems for on-the-go mapping of soil compaction and provide a perspective for future development of sensor fusions for soil compaction identification and mapping.

To mitigate the harmful effects of heavy vehicle traffic and high wheeling frequency knowledge about the susceptibility of a soil against soil compaction is indispensable. Given the highly variable nature of the load bearing capacity of a soil throughout a year, this paper presents a multidimensional approach to assess soil compaction risk at the field scale, considering the spatio-temporal changes in soil strengths on the one hand side and the machinery-induced load and stress inputs on the other. At the example of two newly developed models, the field traffic model FiTraM and the spatially explicit soil compaction risk assessment model SaSCiA, this study assesses the actual soil compaction risk resulting from real field traffic activities during a complete season of silage maize cropping. For this purpose, we used GPS data recorded by all farm vehicles involved in tillage, spraying, and harvesting processes. GPS signal data served for the mapping of wheeling intensity and the calculation of the spatially distributed inputs of changing wheel load and contact area stress. These data were subsequently used for soil compaction risk modeling based upon readily available soil and weather data. Our model results indicate that nearly 95% of a field has been wheeled throughout the season, where harvest traffic at higher load contributes to more than the half of the totally wheeled area. Coupling the two models FiTraM and SaSCiA allows for estimating the spatially distributed soil compaction risk in the topsoil and the subsoil considering the single field operations. The results show that soil compaction risk varies greatly within individual fields. Thus, the need for analyzing and monitoring the effects of farm traffic on soil compaction at high spatial and temporal becomes obvious in order to sustain the diverse functions of soils.

The study provides a comparative assessment of the ecotoxicity of brownfield soil contaminated due to past environmental damage in the Northwestern region of the Russian Federation using different laboratory bioassay methods. The bioassay was carried out using Avena sativa (L.) seeds as a test plant. The contact bioassay was carried out using a natural complex of microorganisms directly present in the samples of brownfield soil, as well as in the seeds of higher plants (Triticum aestivum L.). The level of toxicity of the examined soils for microorganisms was determined based on statistically significant differences in respiratory activity between contaminated and control samples. Test parameters such as germination, root length and plant biomass were determined for phytotoxicity. The technology developed and patented by the St. Petersburg Research Center for Ecological Safety at the Russian Academy of Sciences was used as a contact bioassay in conjunction with generally accepted methods for determining acute and chronic phytotoxicity. A study of physical and chemical parameters (pH, specific conductivity, content of heavy metals and organic eco-toxicants) was carried out to assess the ecological status of the soils. The combination of the methods of bioassay and chemical analysis provided a reliable assessment of the ecological status of contaminated and brownfield soils. The proposed contact bioassay laboratory method showed high sensitivity for the soils studied. The results of two biotest systems applied in the contact bioassay (soil microorganisms and higher plants) complemented and confirmed one another. If the final ecological status cannot be detected by contact phytotoxicity for the soils containing unknown contaminants, then the chronic phytotoxicity assay should be carried out. For the reliable ecotoxicological assessment of the soil in industrial zones, it is necessary to use both eluate and contact methods in laboratory bioassays. These methods are affordable, fast and accurate and can be used at the preparatory stage of the environmental monitoring of soils from similar sites located in different zones with a temperate climate.

A procedure was developed for preparing certified reference materials (CRMs) for the composition of the matrix of natural soils containing mobile heavy metals in concentrations exceeding their background levels. The procedure for preparing soil CRMs includes sampling soil under natural conditions, drying, grinding and sieving it, mixing it thoroughly for homogenisation, preparing a water solution with pre-set concentrations of heavy metal salts, mixing the soil with a solution of heavy metal salts, and evaporating water at 105 °C. The metrological characteristics of CRMs—homogeneity and stability over time—were determined, and factors affecting the homogeneity of CRMs were revealed: the soil type and texture, the nature of the pollutant, and the pH of the metal solution. An estimate was made of how the heterogeneous distribution of different elements contributed to the error in the CRM values. The contents of copper, zinc, lead, cadmium, nickel, cobalt, and mercury in CRMs were certified in an intra-laboratory study with the participation of 57 accredited Russian laboratories.

The long-term effects of biostimulation and bioaugmentation on the ecotoxicity and biological properties of oil-contaminated soil were studied. The dynamics of the soil chemical characteristics, petroleum hydrocarbon biodegradation, toxicity to plants and crustaceans, microbial respiration and enzymatic activity were evaluated in a long-term field experiment. The highest toxicity of soils exposed to both biostimulation and bioaugmentation was found during the first year after contamination. Toxicity to plants had decreased gradually in remediated soils three years into the experiment, while the enzymatic activity of soil was strongly affected even after nine years. Both biostimulation and bioaugmentation had a positive effect on the ecotoxicity and biological activity of soil. However, much of the decontamination can be related to degradation activities of indigenous microbiota. Bioaugmentation demonstrated higher efficiency compared to activity of native microorganisms at the initial stages of remediation, while no difference between biostimulation and bioaugmentation were found later. Our results indicate that stimulating the indigenous soil microbiota by nutrients is sufficient to achieve successful bioremediation of podzolic soil.

Detailed studies of snow and soil contamination within the influence zone of the Irkutsk Aluminium Metallurgical Plant were carried out for the period of 1996–2015. The main types of atmospheric and soil pollution and the amounts and distribution area of the pollutants were described. The study revealed that within 1 km of the aluminium smelter, the maximum fluoride concentration in the snow meltwater reached 66 mg dm−3. The relationship between technogenic soil and snowpack pollution was assessed, and their effect on some soil parameters was revealed. A standard determination of technogenic loads was carried out in relation to the significant and sensitive soil parameters. The maximum level of technogenic load was obtained by determining critical points on the “load vs. effect” curve. The values of the “dose–effect” relationship can be used to determine the maximum permissible concentration (MPC) and maximum impermissible concentration (MIC) of the potentially toxic elements in the soil. The amounts of the total forms of fluoride, aluminium and sodium were, respectively, 0.66 and 0.84 g kg−1, 82 and 93 g kg−1, and 24 and 26 g kg−1 for the upper (MPC) and lower (MIC) limits. This highlights how the soil environment is polluted with these substances emitted from the Irkutsk aluminium smelter.

This paper presents the results of long-term landscape and geochemical research on the distribution of gas and dust emissions produced by aluminium plants located in the South Minusinsk basin (Khakassia, Russia). The chemical composition of solid and liquid constituents and the content of pollutants was determined in every component of the landscape. It was revealed that the main polluting elements with an anomaly index above 10 in the solid and liquid aerosol phases were F, Al, Na and Ni, compared to the solid soil phase and snow meltwater of the background. The accompanying elements were Zn, Cu, Sr, Ba, Ca, Mg, Mn, Fe and V, whose content exceeded the background levels by 2–10 times. The technogenic load of the main pollutants and their distribution in the atmosphere (snow)–soil solution–soil system were determined. The mechanisms of their primary and secondary differentiation in landscape soils were studied, and their accumulation and distribution levels in soil profile were calculated. The analysed indicators, including toxicity, showed that the main pollutant was fluorine (F). The nature of its migration and accumulation was determined to a large extent by biogeochemical, physico-chemical and geochemical barriers. The fluorine load was calculated on the basis of the maximum permissible concentrations (MPCs) of 10 mg kg−1 (load—soil content) and using cartographic maps of their surface distribution.

This chapter presents the results of a long-term study on the dynamics of calcium and strontium in soil and plants when liming with chalk-containing strontium. The ameliorant used was a conversion chalk obtained as a by-product of the production of complex fertilisers and contained 1.5% stable strontium. Four experiments were conducted to study the behaviour of Ca and Sr in the soil–plant system on acid sod-podzolic soils (Umbric Albeluvisol Abruptic). The specific goal was to trace the entire pathway of Sr from the dissolution of the ameliorant, fixation of Sr in the soil-absorbing complex, migration along the profile and finally accumulation in plants of various biological families and in various plant organs. The results showed that the 1.5% Sr contained in the conversion chalk has a high chemical activity. The complete dissolution of high doses of the chalk was achieved in 3–4 years. The migratory mobility of strontium was determined in a series of column experiments. The amount of leached Sr was found to depend on its initial content in the soils, the humus content (HA1 fraction) and the volume of washing water. It was found that the first fraction of humic acids plays a leading role in the fixation of Sr in non-limed soil, which contained about 50% of the total soil strontium. The addition of the Sr-containing chalk increased the leaching of strontium, but Sr was not completely removed from soil after multiple washings. The results showed that the accumulation of Sr in the generative and vegetative organs of plant was controlled by the barrier and barrier-free mechanisms. Strontium-free conversion chalk can be a highly effective ameliorant for reducing waste dumps generated when processing raw phosphate rocks.

This paper presents the results of a large-scale investigation into the content and distribution of potentially toxic elements in the soil throughout Central Serbia, focusing on soil types and the background limits for the most important trace elements. Pseudo-total forms of arsenic, chromium, copper, cadmium, nickel, lead and zinc were determined in 5022 surface soil samples taken using a grid system (3.3 × 3.3 km) in agricultural soil and forest throughout Central Serbia (as part of the Republic of Serbia’s national pedogeochemical research). It has been established that most of the studied territory is unpolluted. Ni, Cr and As have been found to be the largest contaminants (4.2%, 1.8%, 1.9% of samples, respectively, were above the remediation value) with predominant geochemical contamination. The background limits of trace elements in the soils of Central Serbia, calculated by the [Median + 2MAD] method, had the lowest values, between 87 and 90%. With the other two methods, TIF and in particular [Mean + 2Sdev], more approximate values were obtained, commonly between 95 and 98%. The results show that it is necessary to revise the limit values of trace elements in the legislation of the Republic of Serbia, especially for Ni and Cr, which are mainly of natural origin. In areas with a heterogeneous geological composition and with different anthropogenic impacts, a greater number of background limits should be determined for pedochemical units or for homogeneous administrative units.

Fly ash (FA) as a product of coal combustion in thermal power plants is a hazardous material that is deposited in the immediate vicinity of power plants due to its low rate of utilisation. As a result, fertile agricultural land turns into fly-ash dumps, which disperse fine ash particles around the environment, and toxic materials and salts are leached into groundwater. Revegetating fly ash dumps has proven to be the best way to stabilise the ash both physically and chemically. However, the establishment of vegetation cover at such sites is severely hampered by the unfavourable physical and chemical properties of the unweathered ash, which contains high amounts of potentially toxic elements (PTEs). This chapter provides an overview and discusses the most important issues related to the establishment of vegetation cover at FA disposal sites and the role of plants in stabilising pollutants and mitigating their negative effects as well as their role in soil formation processes. Natural vegetation plays an essential role due to its tolerance to numerous stress conditions caused by pollution and its ability to accumulate PTEs. It has been established that the use of natural plants by means of auxiliary restoration of vegetation cover with the support of appropriate agronomic practices (integrated biotechnological approach) can effectively help control the spread of PTEs and support the phytoremediation of this type of environment. The overview has revealed that ash weathering and the development of vegetation have positive effects on the physical and chemical characteristics of wet FAs. Positive changes were manifested in the morphology and texture of ash, a decrease in alkalinity and salinity, the development of horizon A due to the accumulation of organic matter and an increase in organic carbon, nitrogen, phosphorus and adsorption capacity. These changes were most pronounced in the upper layer of the FA and are important indicators of the onset of soil formation processes. It is concluded that these processes and the time elapsed after the revegetation are the main driving factors. They are extremely important for the successful ecological reclamation of fly ash disposal sites and long-term environmental protection.

The Western Balkans Region (Croatia, Bosnia and Herzegovina and Serbia) was affected by disastrous floods on a large scale in May 2014. The total flooded area occupied approximately 10,000–13,000 km2. Research results on soil and crop contamination in a flooded area of 2845 ha of agricultural land located at the confluence of the Bosna and Sava Rivers are presented in this paper. The duration of the flood was up to 22 days. The maximum height of the water in the flooded areas was three metres. In total, 62 soil samples were collected, comprising 31 soil samples from arable land, 13 samples of flood sediment and 18 samples of plant material. The soil and plant samples were analysed for the concentrations of Pb, Cd, Cr, Ni, Zn and Cu using an atomic absorption spectrophotometer. The pH of the flood sediment was alkaline. The soil pH was in the range of slightly acidic (pH H2O > 6.03) to alkaline (pH H2O 8.25). In the flood sediment and soil samples, elevated Zn concentrations (flood sediment: 102–171 mg kg−1, soil: 59.7–276 mg kg−1) and Cu concentrations (flood sediment: 41.5–58.2 mg kg−1, soil: 25.7–85.3 mg kg−1) were determined. The Ni concentration in the flood sediment was 240–295 mg kg−1, and that in the soil was 129–452 mg kg−1, which classified these soils as contaminated with Ni. The content of Cu in plant material (green fruits of peppers and tomatoes, onions, potatoes) was below the MAC (<5 mg kg−1 fresh weight) at all sites. In all the analysed vegetables and corn grown in the alkaline soil (pH in H2O 8.88–8.13), the Ni content was <5 mg kg−1 of dry matter. At all sites with slightly acidic soil (pH in H2O 6.03–6.72), the Ni content in the corn, soybean and alfalfa was >5 mg kg−1 of dry matter. Analyses of soybean, alfalfa and corn showed that in slightly acidic soils with a high concentration of Ni, and due to the changes in the redox potential of the soil, some heavy metals can dissolve and become available for absorption by plants. The results obtained showed that the floods that occurred in May 2014 have not polluted the agricultural land with the tested heavy metals. However, they slightly increased concentrations of Ni, Zn and Cu in the places where the flood sediment depth was more than 5 cm. The Ni content in the arable layer of agricultural land depended to a large extent on long-term previous floods, since it accumulated along with flood deposits and mixed with soil during agricultural work.

To this day, scientists argue about the extent and rate of accumulation of heavy metals and potentially toxic substances in the soil. Questions regarding the forms of heavy metals, their spatial distribution, solubility, plant availability, etc., are still relevant. It is known that the content of heavy metals is considerably influenced by the content and composition of soil organic matter, particle size distribution, soil pH and parent rocks, as well as redox conditions. Since 2007, the steppe soils of the Volga region have been monitored for the content of heavy metals in virgin and arable landscapes. In this work, the content of poorly soluble and mobile forms of Zn, Cu, Pb, Cd, Ni, Hg and As in 0–20 cm topsoil was determined in two types and eight subtypes of Chernozem and chestnut soils. Some differences were found in the accumulation of heavy metals between the soil types and subtypes which were studied. No changes were found in the content of poorly soluble heavy metals between the virgin and corresponding arable soil in the Volga steppes. The content of heavy metals in all the soils which were studied was below the maximum allowed concentrations. The relative content of the mobile forms of heavy metals as a percentage of the total varied from 7–25% for Cd and 0.5–2.2% for Zn and Cu. The accumulation of Pb, Cd, Ni and As in soils located near the large industrial zone showed an increasing trend. The maximum allowed concentrations of heavy metals were not exceeded in the soils studied. Also, agricultural soil management did not significantly increase the heavy metal concentrations.

The accumulation of harmful microelements in the soil can cause long-term adverse effects, while their deposition can be toxic both for people and the environment. The study of agricultural land flooded in 2014 with tailing outflow due to an accident at the tailing dump of the Stolice mine in Kostajnik (western Serbia) is focused on the contents of heavy metals (Pb, Cd, Zn, Cu, Ni, Cr and Mn) in the soils and the biological activity of these soils. The Stolice-Kostajnik mine belongs to the Zajača mining site in the Boranje area, and its mining operations ceased in 1990. Soil samples were taken from open soil profiles in the flooded and unflooded areas at fixed depths of 0–10 cm, 10–20 cm and 20–40 cm to analyse their physical and chemical properties, the content of heavy metals and the soil’s microbiological properties. The potential environmental risk and the source of heavy metals in the soils studied were determined using the enrichment factor (EF), the potential environmental risk index (RI) and statistical methods such as the principal component analysis (PCA) and the Pearson correlation matrix. Significantly higher concentrations of Pb, Zn and Cd were found in the soil that was flooded with the tailing outflow, than in the unflooded soils. Statistically significant differences were found between the total number of microflora, fungi and Azotobacter in the flooded and unflooded soils. In the flooded soil, the mean values of the enrichment factor (EF) declined in the following order: Zn > Cd > Pb > Cu > Cr > Ni. On the basis of the average value of the potential environmental risk, it was concluded that the flooded soils are classified as at high ecological risk, while the unflooded areas are classified as at low ecological risk.

Coal fly ash, a by-product of coal combustion in thermal power plants, is a fine powder made up of small, spherical, glass-like particles, the major matrix of which is ferro-alumino-silicate minerals. This review presents the detrimental and beneficial physical, chemical and biological properties of fly ash. These are a consequence of its particular chemical composition and can cause an environmental hazard, but also, under some conditions, enable it to be used in some branches of industry. Fly ash generally contains potentially dangerous and harmful heavy metals, organic pollutants and some radionuclides. Toxic concentrations of these in water, soil and air, as a consequence of ash scattering, can cause ecological problems (land degradation in the vicinity of the power plant), health problems (for human and animal respiration) and agricultural problems (harmful influence on soil, soil microorganisms and crops) in the ash dump surroundings and by leaching into watercourses and moving further into the food chain. The millions of tonnes of fly ash produced annually worldwide (about 800 Mt per year) are a major problem in many countries. Phytoremediation has been used to prevent the detrimental influences of fly ash on the environment. Grasses are suitable for cultivation on fly ash dumps as an initial, quick way to cover the ash dump and prevent ash from scattering. However, the best plant application is a mixture of grasses and legumes, due to the legumes’ ability to fix N2. When legumes are supplied with N2-fixing bacteria (fam. Rhizobiaceae), a highly effective bioinoculant, the net effect is the replacement of the mineral N fertiliser that would otherwise be required. The process of phytoremediation needs an enormous N2 content as fly ash contains little or no N. Symbiotic N2 fixation is discussed as an environmentally friendly, cost-effective method to supply crops with nitrogen. The root nodulation of the legumes can be used for an eco-toxicological evaluation of soils contaminated with fly ash heavy metals. Amendments for the effective establishment of remediation plants on ash dumps are reported in this review. Among them, the application of microorganisms (plant growth promoting rhizobacteria), alone or with the plants in this process, constitutes a more sustainable and cost-effective approach for removing heavy metals from fly ash dumps. However, nanotechnology could also help to remove heavy metals from fly ash dumps. Due to some desirable fly ash properties, primarily its alkaline pH, and some macro- and microelements, some of which are very rare, as well as the ash’s ability to transition into nanoparticles, fly ash has been used in many branches of industry, especially the construction industry and agriculture. However, around 40% of fly ash worldwide is not utilised, so the dumps this produces still require constant monitoring of their surrounding land, water and agricultural crops. Greater use of fly ash would improve the circular economy.

Soil degradation has become a significant challenge for agricultural and environmental sustainability. Continuous depletion in soil organic carbon (SOC) and nitrogen (N) in the past century has considerably affected agricultural productivity and sustainability in semiarid drylands of the inland Pacific Northwest (IPNW) of the USA. This chapter discusses linkages between soil organic matter depletion and yield decline in a winter wheat-summer fallow (WW-SF) system in the IPNW based on data obtained from a long-term study (>80 y). Studies conducted in dryland winter wheat-summer fallow (WW-SF) systems revealed a decrease in SOC and N storage in the profile. Specifically, SOC content decreased by 280 kg ha−1 yr−1 in the top 30 cm soil depth with fall burning of crop residue (FB), while it was decreased by 226 kg ha−1 yr−1 in no burning of crop residue (NB). The decline in yield was observed with a decrease in SOC and N stocks over the years, mainly due to long fallow periods between wheat crops, crop residue burning, insufficient residue returns, and intensive tillage practices. The only treatment that maintained SOC in the top 30 cm depth was manure (MN) treatment, indicating that SOC and N, added in larger amounts under this treatment, play a crucial role in SOC maintenance, crop production, and sustainability of WW-SF systems. Results of the long-term studies show a continued declining trend in SOC and nutrients under the WW-SF system, thus negatively impacting soil health, further reducing crop yield in dryland cropping in the IPNW. A decrease in SOC and N in the soil profile leads to soil degradation, affecting the sustainability of dryland WW-SF systems in the IPNW and similar agroecosystems worldwide. Cropping system intensification, residue addition, or organic amendment additions can maintain SOC and support sustainable crop production.

Soil organic matter transformations and changes were studied in hydrophysical and physical properties of Dark Chestnut soils (Kastanozems) in the dry steppes of the Trans-Volga region after 35 and 75 years of irrigation. The parameters studied included fractional groups of humic acids; balance and reserves of humus; particle size distribution; composition and distribution of soil micro- and macroaggregates; mineralogical composition; and changes in soil structural properties (aggregate stability). At the site with 75 years of irrigation, the soils with different water regimes (automorphic and hydromorphic Dark Chestnut) and different levels of groundwater were studied and compared with a non-irrigated automorphic analogue. Humus losses in the irrigated soils were found to be greater than in non-irrigated soils. The decrease in the content and reserves of humus due to irrigation was accompanied by negative changes in its qualitative composition. The results showed that long-term irrigation, especially in the hydromorphic hydrological regime, leads to an increase in the soil density, blockiness and clay content, and the degree of clay dispersion. This, in turn, led to an increase in the specific soil surface and a decrease in the total porosity. The observed soil dehumification and the compaction and destruction of the soil structure were the most dangerous degradation processes affecting the Kastanozems in the region, which reduced the efficiency of irrigated agriculture. Our results showed that even soils with a high content of stable humus, such as Kastanozems, lose their fertility and are prone to degradation with extensive, long-term, continuous irrigation. The results obtained should convince decision-makers to rethink the existing system of growing crops under irrigation in order to prevent losses of humus and the deterioration of soil physical properties, and to develop or adapt an ecologically sustainable irrigation system.

Soil types on cropland in the Volga dry steppe area were studied for changes in agrochemical properties due to long-term crop production compared to their virgin analogues (long-term non-fertilised grassland and rangeland). In cropped soils, a decline in soil fertility parameters was observed. The most intensive losses were found for Southern Chernozem, the least intensive in Typical Chernozem soils. These changes were found in the fractional composition of organic matter. In all the Chernozem soils studied (typical, ordinary, and southern), the share of humic acids decreased and the share of mobile fulvic acids increased with a negative consequence. The relative accumulation of fulvic acids was also noted due to the systematic application of mineral fertilisers. Chernozem soils also lost some of their nitrogen reserves due to cultivation. The biggest losses were observed for typical Chernozems. At the same time, a sharp decrease in the fraction of easily hydrolysable N was observed on all subtypes of Chernozem. The prolonged use of fertilisers partially compensated for the loss of phosphorus in all Chernozems studied. Changes in the agrochemical properties depended on the subtype of Chernozem. Cropping on typical Chernozems led to a decrease in the amount of exchangeable cations and a certain increase in potential acidity. At the same time, an increase in the amount of bases and a decrease in the potential acidity were noted in the arable ​​ordinary Chernozems. The cultivation of virgin Chestnut (Kastanozem) soils (in the 1950s) decreased the content of organic matter, indicating a high intensity of mineralisation of soil organic matter in the dry steppe, since the share of humic acids decreased and that of fulvic acid increased. The most intensive losses of humic compounds occurred in a meadow Chestnut soil, and the least intensive in dark Chestnut terraced soils. We conclude by commenting on the need for progress in research aimed at developing approaches and tools for productive and sustainable cropping systems, and for scientific-based monitoring and management practices on cropland to control soil carbon and stop nutrient mining.

Labile carbon fractions such as particulate organic carbon (POC) and hot-water-extractable organic carbon (HWOC) are pools of soil carbon that undergo significant transformation and could therefore serve as an indicator of changes in the quality and quantity of soil organic carbon (SOC). They represent 1–5% of the total organic matter and comprise a heterogeneous mixture of materials. The aim of this study was to assess the labile carbon pool change in relation to soil type and management. The procedure involves labile carbon extraction by separation in water or liquids with adjusted density following the aspiration of organic matter from the surface of an aqueous suspension. Our data demonstrated that the land use systems had a predominant effect on the organic matter stabilisation. This study showed that non-arable land use systems were higher in labile carbon, mostly due to lower microbiological activity. In arable soils, management practices have a significant influence on both labile fractions. Preserving the soil organic carbon would require the retention of crop residue in combination with judicious fertilisation. Our result could contribute to a better understanding of SOC fractions’ relevance in the Province of Vojvodina related to the cropping management, and could help select cropping practices for better SOC preservation.

In this chapter, the physical properties of soils were determined after forest fires in pine forests near the city of Togliatti (Russia) in 2010. The aim of the study was to assess (1) what part organic matter of pyrogenic origin played in the formation of the fire-affected clay fraction and (2) the degree of hydrophobicity of the soil under the influence of pyrogenic exposure. The soil parameters studied were the particle size distribution, solid-phase density, specific surface area, contact angle of soil wetting, soil organic matter content and air-dry moisture. Two methods of particle size distribution were compared: laser diffraction and classical sedimentation methods. The sedimentation method revealed a higher clay content due to underestimation of the density and an increase in black carbon components, rather than an actual increase in very fine earth particles. This method enabled the effect of the pseudo-fraction to be observed, when particles of organic matter, including components of black carbon, partially form a clay fraction that was not there previously. While the set of methods proposed has proven suitable to assess changes in post-fire soils, there is a need to harmonise the methods of particle size distribution. The electrophysical profiling effectively identified the vertical heterogeneity of the soil layers. The contact angle of wetting showed an increase in hydrophobicity in the upper horizons of the soil after fires, especially crown fires. These expose soil to surface runoff and thus a higher risk of erosion. Further, deeper interdisciplinary research is needed to determine soil quality and degradation risks in fire-prone forest ecosystems.

Land degradation is a serious environmental stress, which is identified and analysed through advanced remote sensing technique at a global level. Vegetal degradation, soil erosion, salinity and alkalinity, deforestation, changes in land cover are a few factors, which raise the severity of desertification and land degradation. The changes caused by these factors lower the land and food production and eventually leads to environmental and socio-economic sustainability. Periodical monitoring and observation of the factors, which are the root causes for desertification/land degradation can be evaluated through remote sensing and modelling techniques. The present chapter aims to review the various remote sensing sensors and the recent techniques in mapping desertification and land degradation processes. Remote sensing and GIS techniques serve as an aid to assess and monitor various land degradation processes, and to compare trends across spatial and temporal scales. In the future, the convergence of high-resolution data products with modern classification and modelling techniques could be explored more broadly to assess and obtain more detailed information on monitoring and modelling desertification and land degradation.

The purpose of the studies conducted under the 2015–2017 project of the Ministry of Science and Education of the Republic of Kazakhstan (“Assessment of the environmental state of the Caspian Sea northern coast soil cover”), consisted in a comprehensive assessment of the current state of the soil cover of the northern coastal zone of the Caspian Sea. The research focused on soils and soil cover on part of the northern coast of the Caspian Sea, adjacent to the modern delta of the Ural River. Soil transformation in the territory was caused both by an increased anthropogenic impact and changes in soil formation factors, associated with the decline of the Caspian Sea’s level in recent years. Materials from previous soil studies were selected and analysed to evaluate the existing knowledge in this area. Based on the obtained results, 26 soil taxonomic units, including varieties, were identified on the site. The degree of soil degradation was assessed. On the basis of the available materials, a soil map and a map of soil degradation (1:100,000 scale) were composed for the northern coast of the Caspian Sea. Until now, no similar studies had previously been implemented in the area. The study showed that, due to the fluctuation in the Caspian Sea’s level and due to climate changes such as frequent droughts and rising temperatures, soil formation processes are undergoing modification (decrease in humus and nitrogen content, increase in the content of water-soluble salts) on the northern coast of the Caspian Sea.

A rapid change in soil chemistry caused by long-term acidic deposition directly and indirectly disturbs natural habitats and ecosystem functions. The aim of this paper was to analyse long-term depositions of sulphur and nitrogen, their relationship with the soil’s chemical properties, and areas currently/potentially at risk of ecosystem degradation. Models recommended by the Convention on Long-Range Transboundary Air Pollution (CLRTAP) were applied. Critical Loads calculations were derived for acidification, eutrophication and biodiversity using the VSD model. Changes in plant diversity and soil properties of beech forests and highland grasslands were simulated using the VSD $$+$$ + PROPS model based on future air pollution and RCP 4.0 climate scenarios. The results showed areas and biological receptors with varying degrees of vulnerability and susceptibility to air pollutants, as well as identifying areas that are adversely affected by the long-term deposition of sulphur and nitrogen. Mountain forests and high mountain grasslands developed on shallow soils exhibit the highest levels of sensitivity to acidic pollutants and climate change in Eastern Serbia. To provide a background for interpreting the results of the comparative analysis on air pollution and climate change effects at regional level, process-based and spatial distribution modelling were used. Estimated critical loads on both a regional and local level indicate ecosystems’ sensitivity and potential risk of degradation, providing a good basis for planning emission reduction on a regional level and evolving adaptive management measures in situ.

The aim of the study was to characterise urban soils in central Saint Petersburg. The research was carried out in two urban parks: the Sheremetev Gardens and the Polish Gardens, both situated on the Fontanka River embankment. The soils were classified according to the Russian Soil Classification System (2001) and the WRB (2014). The chemical properties of the soils were determined using conventional techniques. The soil cover in central Saint Petersburg consists of Urbostratozems (Urbic Technosols). Profile of Urbostratozem formed from a series of filled-in organic and mineral layers that have a significant (over 10%) content of construction waste and household waste. The thickness of the anthropogenic (cultural) layer in the Sheremetev Gardens is 94–175 cm, and that in the Polish Gardens is 81–177 cm. The Urbostratozems are characterised by an alkaline reaction and a higher content of organic matter and phosphorus. The negative properties of the urban soils which were studied are increased density, significant amount of artefacts (construction debris) and local technogenic pollution by heavy metals. The concentration of Pb, Cu and Zn in anthropogenic layers exceeds the approximate permissible concentration by 1.5–10 times. The specific feature of the parks in central Saint Petersburg is the frequent presence of buried natural soils (Umbric Gleysols and Podzols) under anthropogenic strata. These soils were the main components of the natural soil cover before urbanisation. The properties of modern urban soils significantly differ from the properties of original natural soils and their modern analogues. As urban soils are polluted by heavy metals and are prone to eutrophication, the assessment and monitoring of their degradation state will be of importance.

Over the past 30 years, agricultural land in the Russian Federation has decreased by a significant area; 97 million hectares. This withdrawn arable land has become part of the fallow land that is no longer used for cropping. This land has undergone significant physical and chemical changes due to the degradation of the upper fertile horizons and the partial afforestation of the landscape. This chapter presents data on the current state and evolution of fallow land in urban St. Petersburg. The morphological and mesomorphological characteristics of soils were studied using vertical electrical resistivity sounding (VERS). An assessment was also made of changes in soil agrochemical parameters and the level of soil pollution with Zn, Cu and hydrocarbons. The negative changes in fallow urban soils were found to be due to the reduction and cessation of agrochemical and agrotechnical measures designed to maintain soil fertility and quality, which in turn resulted in a reduction in the arable area, a decline in agricultural production and an increase in the area of the degraded soils. Finally, technological measures were proposed for reclaiming fallow land of different levels of degradation. The creation of a regional centre for the restoration of fallow soils was proposed.