Humus Horizon Research Articles

Carbon and Nitrogen Stocks and Microbial Activity of the Humus Horizon of Loamy Soils after Mass Windthrow in the Broadleaved Forest of the Kaluzhskie Zaseki Nature Reserve

Carbon and Nitrogen Stocks and Microbial Activity of the Humus Horizon of Loamy Soils after Mass Windthrow in the Broadleaved Forest of the Kaluzhskie Zaseki Nature Reserve

Влияние насаждений Quercus robur L. и Juglans rupestris Engelm. на свойства степных почв

The aim of the study has been to determine the condition of Quercus robur L. and Juglans rupestris Engelm. and their influence on the properties of segregated chernozems. The study was conducted in 2020–2021 in the steppe Crimea. The control has been a perennial grass fallow. To characterize the general condition of the trees, a 4-point scale for assessing the condition of the introduced species has been used. Standard methods have been used for soil analysis. A better preservation and a greater number of 50-year old plants in excellent and good condition have been established for Q. robur (67 и 56 %, respectively) compared to J. rupestris (48 и 42 %, respectively) in these environmental conditions, which is explained by the greater adaptive capabilities of oak as an indegenous species. Both tree crops have influenced soil properties. In their phytocenoses, a litter has been formed, more significant under J. rupestris. The dark humus horizon has also turned out to be thicker under the J. rupestris plantation (80 cm) than under the Q. robur plantation and the fallow (72 and 70 cm, respectively). Under Q. robur the soil density has been lower than under J. rupestris by 0.02–0.18 g/cm3. Under the woody plants, the soil structure has improved: the number of lumpy aggregates has decreased, and the number of agronomically valuable and granular particles has increased. The maximum coefficient of structure has been in the soil under the oaks (4.4–6.6), which exceeded the control by 2.5–4.9 times. Under the woody plants, carbonates have been significantly washed out of the soil profile, especially under J. rupestris. The pHH2O value of the alkaline soil under the woody plants has decreased by 0.2–0.4 and has been closely related to carbonate content (r = 0.83–0.91). The humus content under both species has been significantly higher than under the fallow – by 0.30–0.86 %. Afforestation has resulted in the accumulation of total forms of nutrients, to a greater extent under J. rupestris, and the C:N ratio has decreased. Tree species have stored more labile forms of nutrients in the soil. Soil desalination has been noted in the tree cenoses. Thus, J. rupestris and Q. robur are ecologically stable in the conditions of the central steppe of Crimea and can be used to increase forest cover in steppe areas. This will help improve soil fertility.

The number of seedlings from the soil seed bank of pine forests with differently dated fires near the Karabash copper smelter

We tested the hypothesis that the number of seedlings from the soil seed bank (SSB) in forests polluted by heavy metals and disturbed by recent fires decreases. It was also assumed that the consequences of pollution and fires for the soil seed bank are additive. We estimated the number of seedlings from the SSB of pine forests located near the Karabash copper smelter (KCS) (contaminated by Cu, Zn, Pb, and Cd) and from uncontaminated forests of the Ilmen State Reserve (ISR). In both areas, samples of the forest litter and humus horizon were taken from forests recently exposed to ground fires and long-term unburned forests. Samples were exhibited from June to September, conducting seven rounds of counting seedlings. Small peculiarities of the emergence of seedlings on the samples of the forest litter and the humus horizon were established. However, the regularities of the reaction of SSB to pollution and fire disturbances did not depend on the soil horizon. The number of seedlings on substrates from contaminated forests was 5–8 times lower than the number of seedlings on substrates from background forests. A decrease in the number of seedlings on polluted substrates was accompanied by an increase in the share of dicots in the total number of seedlings. The relationship between the number of seedlings and the age of fires was not found. The additivity of the consequences of pollution and fires has also not been established. Of the two types of damage, pollution and fires, the pollution factor is of leading importance for SSBs. The results indicate a low recovery capacity of the herb-shrub layer of polluted forests.

Evaluation of the soil quality using health index in temperate European conditions (Slovak Republic)

Land users and policy makers recognize importance of soil health and these types of evaluations are welcomed within sustainable land management. The aim of this study was to establish minimum and maximum values of soil health index across the breadth of agricultural used soils of Slovakia. Core objectives included (1) identifying the range of soil health benchmarks; (2) defining benchmarks for different land uses, and (3) defining benchmarks of soil health index for main groups of agricultural soils in Slovakia. These benchmarks represent the first soil health metrics of their kind in Slovakia using data from 266 locations. The soil health index (SHI) approach has been used as a quantitative tool to establish linkage between soil health and soil ecosystem services. We recorded the highest average SHI value in the very warm climatic region of the Slovak Republic, where the majority of agriculturally used arable soils (with an optimal pH value without contamination) are located. The locality with lowest SHI value is in a slightly warm area on soil used as arable soil with a very small depth of humus horizon, with by the pH value in an acidic area, and with a high content of clay. The typical SHI in humus-rich soil groups of Slovakia (Mollic Fluvisols, Chernozems and Cutanhic Luvisols) is higher contrasted with the typical SHI in other soil groups of Slovakia.

Применение моделей адсорбции при исследовании поглощения ионов никеля почвой

The aim of the presented work is to study the absorption of nickel ions by soils of the Udmurt Republic using four sorption models. Humus horizons (0–20 cm) of Albeluvisols Umbric, Leptosols Rendzinic and Phaeozems Albic soils widely distributed in Udmurtia were selected as objects of nickel adsorption research. According to the Langmuir model, good sorbents are characterized by high Amax values and low – KL, therefore, the best sorbent of nickel ions is Albeluvisols Umbric (Amax=0.0562 mol/kg, KL=2075.19 dm3/mol), and a weaker absorber is Phaeozems Albic (Amax=0.0192 mol/kg, KL=19474.48 dm3/mol), Leptosols Rendzinic occupies an intermediate position (Amax=0.0289 mol/kg, KL=14766.47 dm3/mol). The negative value of the Gibbs energy (∆G=–17.97 kJ/mol for Albeluvisols Umbric, –22.59 kJ/mol for Leptosols Rendzinic and –23.24 kJ/mol for Phaeozems Albic) indicates the spontaneous nickel adsorption by soil absorbing complex (SAC). In accordance with the Freundlich model, in all types of studied soils, the nickel ion – SAC binding energy decreases as the surface is filled, herewith the studied soils are characterized by heterogeneity of sorption centers. The approximation coefficient of the Temkin model is in the range of 0.80–0.85, therefore, the discrepancy between the experimental data of the theoretical model indicates the absence of interaction between the adsorbed particles. The Dubinin – Radushkevich model allows us to determine the nature of adsorption forces, as well as the value of the average free energy of adsorption: E=8,325 kJ/mol in Albeluvisols Umbric, 9.5477 kJ/mol in Leptosols Rendzinic and 9.6296 kJ/mol in Phaeozems Albic. Consequently, chemisorption is characteristic of all soils, and proceeds by an ion-exchange mechanism.

Analysis of organic matter stock dynamics in arable soils of Yamal: simulation experiments with the ROMUL model

The goal of this work is to analyze the dynamics of soil organic matter (SOM) in arable soils of Yamal using computational experiments with the ROMUL model. Soil temperature and moisture dynamics were simulated using the SCLISS model. The Yamal experimental station was organized in 1932. The soil is Plaggic Podzol. The thickness of humus horizon (PY) is 30 cm. Pools, kg/m2: SOM – 9.32 and 13.75; N – 0.46 and 0.66 for 0–20 and 0–30 cm respectively. Background: soddy-green-moss tundra near Salekhard. Soil: Folic Podzol: litter (O, 2 cm) and humus-accumulative (AY, 4 cm) and illuvial ferruginous (BF, 6 cm) horizons. Pools, kg/m2: SOM – 1.38 and 2.69, N – 0.03 and 0.18 for 0–2 and 2–6 cm respectively. The quantity and quality of background fall was estimated according to literature data. Clarification of the amount of fall was carried out by the method of inverse problem solving (spin-up). Peat application was simulated: starting application in the dose of 12 kg/m2 and maintenance (every 6 years) in doses 4, 8 and 12 kg/m2, N 1%. Application of mineral fertilizers, 2 variants: a) N 4 g/m2 (40 kg/ha) in peatting years and b) application of the same dose of nitrogen every year. The duration of computational experiments is 30 and 90 years. Computational experiments showed that after the starting peatting of Folic Podzol at the rate of 12 kg/m2 after 30 years, only 15% of the applied detritus remained. Maintenance peatting of 8–12 kg/m2 leads to an increase in SOM pool to 20–30 kg/m2 and excessive accumulation of detritus. Application of 4 kg/m2 of peat once every 6 years for 90 years shows the dynamics of SOM pools from Folic Podzol to Plaggic Podzol which is confirmed by field survey data. Application of mineral nitrogen (4 g/m2) once every 6 years does not affect SOM pools. Annual application of mineral N (4 g/m2) increases SOM pools due to intensified humification. This fact requires experimental verification.

Influence of Spring Burns on the Properties of Humus Horizon of Chernozem in the Southeast of Western Siberia

On the example of soils of the Basic Experimental Complex of the Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences (Tomsk), the influence of spring grass burns on the properties of the upper layer of the humus horizon of Chernozems. In the areas that burned two months ago, 1, 2, 3 and 11 years ago, a total of 56 samples (5–9 replicates) were collected. We found a considerably high stability of the controlled properties of soils (cationic-anionic composition of water extract, content of grain-size fractions and mobile compounds of a wide range of elements, total C and N, organic carbon, pH value, basicity from carbonates) to pyrogenic effects from spring grass fires. Informative indicators reflecting a significant pyrogenic impact over the past 11 years were the content of mobile Ca, Mg and Sr, as well as water-soluble Mg2+ and basicity from carbonates. Their content is higher in the soils of young (0–3 years) burnt areas relative to the old (11 year old) burnt areas and unburnt areas. Among the studied parameters, the pH value, the content of mobile Ba and Sr, and grain-size fractions of 1–5, 5–10, and 10–50 µm, had the low coefficient of variation (20%), and content of water-soluble ammonium and mobile Li and Zn had the high coefficient of variation (70%).

Study on the Factors Affecting the Humus Horizon Thickness in the Black Soil Region of Liaoning Province, China

Understanding the spatial variability and driving mechanisms of humus horizon thickness (HHT) degradation is crucial for effective soil degradation prevention in black soil regions. The study compared ordinary kriging interpolation (OK), inverse distance weighted interpolation (IDW), and regression kriging interpolation (RK) using mean error (ME), mean absolute error (MAE), root mean square error (RMSE), and relative RMSE to select the most accurate model. Environmental variables were then integrated to predict HHT characteristics. Results indicate that: (1) RK was superior to OK and IDW in characterizing HHT with the smallest ME (11.45), RMSE (14.98), MAE (11.45), and RRMSE (0.44). (2) The average annual temperature (0.29), precipitation (0.27), and digital elevation model (DEM) (0.21) were the primary factors influencing the spatial variability of HHT. (3) The HHT exhibited notable variability, with an increasing trend from the southeast towards the central and northern directions, being the thinnest in the southeast. It was thicker in the northeast and southwest regions, thicker but less dense along the southern Bohai coast, thicker yet sporadically distributed in the northwest (especially Chaoyang and Fuxin), and thick with aggregated distribution over a smaller area in the northeastern direction (e.g., Tieling). These findings provide a scientific basis for accurate soil management in Liaoning Province.

Effects of pyrophosphate-extractable aluminum, iron, and calcium on organic carbon storage in buried humic horizons of a cumulative volcanic soil profile containing charred plant fragments, Miyakonojo, Miyazaki, Japan

ABSTRACT Charred plant fragments (CPFs), having two primary types (carboxylic and phenolic functional groups) of metal-binding sites, are widely distributed in Japanese volcanic soils containing black humic acids. However, the effects of metal components on the storage of CPFs are still unknown. The aim of this study was to determine the direct and indirect effects of metal components on the CPF-carbon (CPF-C) and soil organic C (SOC) contents in four buried humic horizons (2A–5A, from 7.3 cal ka BP to AD 1471) of a cumulative volcanic soil profile (Miyakonojo, Miyazaki, Japan), employing correlation, and path analyses. Nineteen soil samples were collected from the humic horizons described above and used. Pyrophosphate-extractable aluminum (Alpy), iron (Fepy), and calcium (Capy), which are common in the soils, were selected as reactive metal components. The CPF-C content accounted for up to 15.1% of the SOC content (8.4% on average). The Alpy content was highest in all soils, mostly followed by the Fepy and then Capy contents. No consistent trends with soil age/depth were found for the accumulation levels of CPF-C, SOC, and metal components. However, there were significant correlations (p < 0.01) among the CPF-C, SOC, Alpy, Fepy, and Capy contents. The result of path analysis showed that a high correlation coefficient between the CPF-C and Fepy contents (r = 0.89, p < 0.001) was mainly explained by the direct effect of Fepy (0.84, p < 0.01) on the CPF-C content. On the other hand, in the case of SOC, a strong correlation coefficient between the SOC and Alpy contents (r = 0.93, p < 0.001) was primarily due to the direct effect of Alpy (0.74, p < 0.01) on the SOC content. The direct effects of Capy on these C contents were not important. Furthermore, significant indirect effects of the metal components on the CPF-C and SOC contents were not observed. From the results obtained, it is assumed that in Japanese volcanic soils, Fepy and Alpy contribute directly to the large accumulation and stabilization of CPF-C and SOC, respectively.

Changes in the physical properties of fallow lands during their regeneration

The change of physical and mechanical properties of soil depending on the methods of its cultivation has been studied. The experiments were carried out in the Novosibirsk region from April to September 2023. To study the structure of the soil, a soil section was made to a depth of 0.7 meters. It was determined that the soil at the experiment plots was gray forest, the thickness of the turf layer was on average 10 cm, the depth of the humus horizon 25–27 cm, a layer of sandy loam was observed under the humus layer. Fallow land cultivation was carried out by the tillage combine AKP-2.5N with MTР-80L tractor and the working width of 1.8 meters. The working body of the AKP-2.5N was made in a form of a straight rack with a blade measuring 410 mm, in addition, a small screen was installed on the rack. The unit provides for the installation of the rollers with a size of 600 mm. To determine the operating modes of the unit, studies were carried out in the soil channel. It was found that the operating speed of the unit with installed screen should be no more than 2.22 m/s or 8 km/h. The conditions of the experiment: gray forest soil, air temperature not lower than 10 0C; air humidity no more than 70%; relative humidity of at least 18%, wind speed not higher than 2 m/s; the average length of the rut is not less than 70 m and without stones on the field. It has been concluded that the most rational way to introduce fallow gray forest soils into agricultural circulation is to treat them with AKP-2.5N units with working bodies equipped with blades. After three treatments, the content of soil particles less than 10 mm is up to 93.1%, the soil absorbs moisture faster and reduces the hardness to 15 kg/cm2, which corresponds to the hardness of the soil of the field in rotation. Equations of regularity of changes in the fractional composition of soil with a size of less than 10 mm and more than 50 mm depending on the timing and number of treatments have been obtained.

Analysis and forecasting of the scale and impact of forest fires on ecosystems of Ukraine

Forest fires are one of the most significant environmental problems that have a major impact on biodiversity and climate conditions. The purpose of the study was to investigate the impact of military operations on the ground cover in the area of the Bekhy forestry, which was disturbed by fire. It was revealed that for the period 2022-2023, 15 forest fires were recorded on the territory of the Korosten forest hunting enterprise of the state enterprise “Forests of Ukraine”, while the total area covered by fires was 15.13 ha. Overall, the number of fires increased from 5 to 10, but the total area covered by fires decreased from 12.1 to 3.03 ha. At the site of fires in 2022, the pH level increased to lower horizons, with the highest values at microhills (7.55) and microdepressions (7.35). There was a slight increase in the organic carbon content in the upper humus horizon of soils (0.42% on microhills and 0.46% on microdepressions). Bekhy forestry suffered a large forest fire in May 2023, which covered an area of 1.2 ha. The fire hazard assessment of each quarter was carried out separately. In the 50th and 51st compartments, Scots pine was the most fire-prone type of plantings. The 2023 fire site also showed an increase in pH in the lower horizons, with the highest values in microhills (7.35) and microdepressions (7.55). The 2023 fire site showed a decrease in organic carbon content compared to the background sites, with minimal values in the lower parts of the soil profile (0.33% on microdepressions and 0.38% on microhills). The results of the study can be used to develop and implement environmental measures and programmes aimed at restoring forests damaged by fire

ОСОБЕННОСТИ ГУМУСНОГО СОСТОЯНИЯ ЧЕРНОЗЕМОВ ПРИ ОСВОЕНИИ ЗАЛЕЖИ

The purpose of the study is to determine the direction of change in the humus state of fallow soils in the forest-steppe zone when they are re-involved in arable land. The studies were carried out in the Kras-noyarsk forest-steppe during three growing seasons of 2015–2017 when the forb-grass deposit is replaced at the turf stage by agrocenosis of wheat and then by agrocenosis of pea-oat grass mixture. A distinctive feature of the process of involving fallow land in arable land was the chemical treatment of plants before plowing. Research has established that when the fallow is treated with herbicides and subsequent plowing, the sod horizon disappears, the amount of plant residues decreases sharply, the humus horizon differen¬tiates into arable and subarable with different densities, and blocky and dusty aggregates appear. The humus content under the long-term fallow land and during its plowing was high and amounted to 9.4–9.3 %; no decrease in humus was detected in the first two years after plowing, but the enrichment of humus with nitrogen decreased from an average to a very low level. The content of mobile humus in the soil under the long-term fallow land was 951 mg/100 g; when the fallow was plowed, it decreased to 346 mg/100 g. At the same time, the potential emission of carbon dioxide from agrochernozem increa¬sed – from 5.5 to 18.5 mg CO2 /10 g, which had an average inverse relationship with the SpO content (r = 0.56). It has been established that with intensive agrotechnical influence with the use of chemicals to destroy the turf horizon, the share of SPOs from Shumus decreases by more than 2.8 times due to its mineralization.

Spatial distribution of soil depth in relation to slope as a consequence of erosion-accumulation processes in loess lowland hills of Slovakia

Abstract In our study, we examined the influence of slope gradient on erosion processes and present soil formation and change on loess hills. We analysed data from the two study areas and found that slope gradient is a significant factor influencing soil depth as well as humus horizon thickness. At the Báb locality, we observed a negative correlation between slope gradient and soil depth (r = –0.206, p &lt; 0.05) and a negative correlation between slope gradient and humus horizon thickness (r = –0.227, p &lt; 0.01). At the Nová Vieska locality, there was a negative correlation between slope gradient and soil depth (r = –0.334, p &lt; 0.02), as well as between slope gradient and humus horizon thickness (r = –0.356, p &lt; 0.01). These findings confirm that slope gradient is a key factor influencing soil formation in loess hills, and has a significant impact on its depth and soil profile. The analysis revealed that a critical slope of 3° significantly influences soil formation, with shallower soils and a thinner humus horizon occurring on steeper slopes. Our findings have important implications for planning erosion control measures and soil management depending on the location and slope gradient. Overall, our work provides insights into soil formation processes in loess hills and contributes to a better understanding of the interactions between slope gradient and erosive processes.

Properties of psammozems of the Kama terraces above the floodplain and assessment of their sustainability to pollution by Cu and Cd

Pine forests growing on psammozems, found on sandy Kama terraces above the floodplain within the territory of Perm, encompass roughly 2 thousand hectares. The study was conducted on psammozems under the influence of advancing pollution caused by heavy metals, highlighting the significance of soil’s buffering capacity in preserving the ecosystem’s stability. It is of great interest to investigate the morphogenetic properties of psammozems and evaluate the risks linked to the accumulation of Cu and Cd in these soils through the analysis of changes in soil enzyme activity (catalase, urease, and invertase) and the occurrence of phytotoxicity. The psammozems found in the Kama region originated from periglacial sandy alluvium, which was deposited during glacial melting in the Mesozoic era. The variety of humus psammozems includes typical, podzolized, illuvial-ferruginous, and pseudofibrous subtypes. These soils are highly acidic, have a very low absorption capacity, low base saturation, and reduced activity of soil enzymes. The contents of Cu, Cd, Zn, and Pb in psammozems are notably lower compared to the regional soil clarks; however, in the underdeveloped humus horizons, the concentrations of these metals are slightly higher than in soil-forming sands. The experiment was conducted to determine the ecotoxicological load, where mixed soil samples from a 0–20 cm layer of humus psammozems were treated with solutions containing copper acetate and cadmium acetate. The application of solutions was done individually, with Cu and Cd ranging from 2.5 to 250 mg/kg of soil. Upon introducing Cu and Cd into the soil at the rate of 2.5–10 mg/kg, a decrease in invertase activity, deterioration of the physiological and biochemical parameters of the test crop (Lepidium sativum L.), along with the inhibition of Cd catalase activity, were observed.

Influence of Morphometric Relief Parameters on Soil Depth Changes and Humus Horizon Thickness in Relation to Erosion-Accumulation Processes: A Study in the Ipeľská Pahorkatina Hills, Slovakia

Abstract This study examines the spatial distribution of soil types and their susceptibility to erosion and accumulation processes in a study area in Slovakia. Field research involving 71 probes identified various soil types, with Regosols and Cutanic Luvisols being predominant. The study found that erosion-accumulation processes were detected in 69.97% of the probes, with changes observed in soil horizons. Soil analysis revealed different relations between soil depth, humus thickness, and terrain characteristics such as slope, slope length, and slope length and steepness factor (LS factor). Specifically, we confirmed a moderately strong positive correlation between soil depth and humus thickness (r = 0.597, n = 71, p &lt; 0.001). Shallow soils (0–30 cm) exhibited a very strong positive correlation between soil depth and humus horizon thickness (r = 0.978, n = 33, p &lt; 0.001). Conversely, no relationship was found in moderately deep soils (30–60 cm) (r = 0.018, n = 14, p &lt; 0.948). For deep soils, we identified a moderately strong positive correlation (r = 0.345, n = 24, p = 0.098). While slope and slope length showed relationships with soil depth and humus thickness, the LS factor did not exhibit a clear correlation. These findings underscore the importance of understanding soil dynamics in informing land management practices, especially in areas susceptible to erosion. Recommendations include continued monitoring of eroded soils and implementing erosion control measures to maintain soil health and sustainability in agricultural production amidst climate change challenges.

Features of enzymatic activity of soils in agricultural landscapes of the Vladimir high plains

The research aimed to study the enzymatic activity of grey forest soil (GF) and grey forest soil with a second humic horizon (GF SHH) depending on fertilizer systems in agricultural landscapes in the Vladimir region. The work was carried out in 2021–2023 in a stationary field experiment on two soil varieties. The following backgrounds for intensifying the use of fertilizers were studied (for rotation of a 6-field crop rotation): zero (Z) – manure 40 t/ha; intensive (I) – manure 40 t/ha + N100Р80К160; intense mineral (IM) – N350P220K390; high-intensity mineral (HIM) – N480P280K575; intensive organomineral (IOM) – N310P150K310 + manure 60 t/ha; high-intensity organomineral (VIOM) – N430P160K360 + manure 80 t/ha. Against the studied backgrounds of fertilizer use in the GF SHH, a stable trend of increasing the activity of catalase and invertase was revealed. The average activity of catalase in the soil of the second humus horizon was 23 % higher than in the GF, at the same depth (20–40 cm). The maximum catalase activity in the experiment was observed against an intense background (I) in the GF SHH: layer 0–20 cm – 2.41 ml O2/g; 20–40 cm – 1.96 ml O2/g. Invertase activity in soil with a second humus horizon at a depth of 20–40 cm is on average 30 % higher than in grey forest soil. The highest value of this indicator was observed in the soil of two soil phases against an intense background in the 0–20 cm layer – 3.50–3.55 mg of glucose/g in 40 hours. The average humus content in the second humus horizon GF SHH was at level 3,76 %, which was 33 % higher than in GF in a layer of 20–40 cm. The maximum value of this indicator in the experiment (layer 0–40 cm) was observed in GF SHH against the intensive background of fertilizer use – 4.86 %.

Scale and biometric basis of soil bioindication for apple seedlings

The studies were carried out in 2010–2022 in the Lipetsk and Tambov regions. Soil (humus horizon) was sampled from apple orchards of different ages, soil types and subtypes. For the growing season, apple seedlings of the Renet Kichunov variety from open pollination were used. With an increase in the content of physical clay in the soil from 10 to 45%, the length of seedling shoots increased from 3.5 to 15.5 cm, the total dry biomass – from 0.7 to 2.2, including leaves – from 0.3 to 1 ,0, shoots – from 0.2 to 0.6, roots – from 0.2 to 0.6 g/vessel. If the content of physical clay reaches 85%, this leads to a stop in shoot growth and a decrease in the total dry biomass. With an increase in the leached chernozem bonitet from 75 to 90 points, the height of seedlings increases from 4 to 15 cm, the total dry biomass – from 0.3 to 1.9, including leaves – from 0.1 to 0.5, shoots – from 0 .1 to 0.4, roots – from 0.1 to 1.0 g/vessel. When the age of an apple orchard changes from 1 year to 20 years, the height of apple seedlings planted on this soil decreases from 40 to 4 cm, the total dry biomass – from 6.2 to 0.6, including the mass of leaves – from 3 to 0, 3, shoots – from 1.8 to 0.2, roots – from 1.4 to 0.1 g/vessel. This allowed us to develop a biometric scale by which we can estimate the age of the soil (degree of soil fatigue) using seedlings. The obtained data make it possible to propose biometric scales for assessing changes in the granulometric composition, quality of the soil and the time it remains in the apple orchard based on the biomass of apple tree seedlings of the Renet Kichunov variety.

Pyrogenic transformation of the phosphate state of permafrost forest soils of Central and Southern Yakutia

For the first time, the phosphate state of permafrost forest post-pyrogenic polycyclic soils of Central and Southern Yakutia, formed respectively in arid and humid climates, was studied and evaluated. These soils with a polycyclic profile, formed in the transaccumulative facies of this regions of the permafrost zone, contain, in addition to the modern one, 2–3 buried humus horizons with abundant inclusion of black charcoal. These pyrogenic humus horizons are characterized by an increased content of humus, total nitrogen and phosphorus soluble in iron oxalates, exchange bases, as well as fractions of physical clay and silt compared to neighboring mineral horizons of the soil profile. At the same time, the brown soil of Southern Yakutia, formed under less severe and humid climatic conditions, compared with those of the pale soil developed under cryoarid conditions of Central Yakutia, was more biogenic, and the total content of phosphorus here was 98.0–427.2, whereas in the second soil – only 11.0–257.1 mg P2O5/100 g of soil. Organophosphates predominated in the composition of the total phosphorus of burozem, amounting to 51.8–81.3%, and in pale soil – mineral forms of phosphorus, which accounted for 52.2–78.8%. The fractional composition of mineral phosphates of both types of permafrost soils was mainly dominated by phosphates of one and a half oxides (Al-P and Fe-P), totaling 43.3–94.3%, and among the latter – Fe-P, which accounted for 34.8–87.4% of the total amount of all fractions of mineral phosphates. It is assumed that the high content of iron phosphates, and in some cases occluded aluminum-iron phosphates in the studied permafrost soils, is due to the manifestation of both cryogenic and biogenic pyrogenic ferruginization in their genesis.

Organic carbon distribution between structural and process pools in the gray forest soil of different land use

The summarized data on the content of organic carbon (Corg) in the subtypes of gray forest soils occurring on the territory of Russia was presented. It was shown that the humus horizons of virgin light-gray, typical-gray, and dark-gray forest soils contain, on average, 2.16 ± 0.67, 2.42 ± 0.61, and 3.58 ± 0.95% Сorg, respectively, while the plowing layers of arable soils contain 1.36 ± 0.40, 1.71 ± 0.40, and 2.84 ± 0.86%, respectively. Structural (particulate organic matter 0.05–2 mm in size, CPOM, and mineral-associated organic matter &lt;0.05 mm in size, CMAOM) and process (potentially mineralizable organic matter, C0, and microbial biomass, Cmic) pools were isolated in the organic matter of samples from different horizons of gray forest soils (Luvic Retic Greyzemic Phaeozems (Loamic)) under small-leaved forest and barley crop. The CPOM/CMAOM ratio in the upper soil horizons under forest and arable land was 0.60 and 0.26, respectively, and this ratio decreased with depth to 0.05 under both land uses. The sizes of the CMAOM, CPOM, C0, and Cmic pools correlated with each other and depended on the depth of the soil horizon, while the effect of land use on the pool ratios was found only for the surface horizons. The contribution of CPOM and CMAOM to the potentially mineralizable pool of organic matter in gray forest soil was 20–41 and 71–87%, respectively. According to the obtained data, the size of the C0 pool was almost equal to the annual amount of the heterotrophic CO2 emission from the soil. It was emphasized that determining of the sizes and ratios of structural and process soil organic matter pools should be important in the programs of carbon monitoring and recarbonization of agroecosystems.

Effects of root-derived organic acids on sorption of pharmaceutically active compounds in sandy topsoil

The presence and fate of pharmaceutically active compounds (PhACs) in agricultural fields are rarely investigated. The present study highlights that root-derived low-molecular-weight organic acids (LMWOAs) affect the mobility of PhACs in cultivated humic Arenosol. Sorption experiments are conducted using three PhACs characterised by different physicochemical properties: carbamazepine (CBZ), 17α-ethinylestradiol (EE2), and diclofenac-sodium (DFC). The results suggest that the adsorption of EE2 is more intense than the other two PhACs, whereas DFC and CBZ are primarily dominated by desorption. LMWOAs mainly provide additional low-energy adsorption sites for the PhACs, and slight pH changes do not significantly affect the sorption mechanism. During competitive adsorption, the high-energy sites of the adsorbents are initially occupied by EE2 owing to its high adsorption energy (∼15 kJ/mol). The new low-energy binding sites enhance the adsorption of DFC (from 8.5 % to 72.0 %) and CBZ (from 31.0 % to 70.0 %) during multicomponent adsorption. LMWOAs not only affect adsorption by modifying the pH but also provide additional binding sites that allow the PhACs to remain in the root environment for a longer period. As the concentration of LMWOAs temporarily changes, so does the availability of PhACs in the root zone. Environmental changes in the humic horizon enhance the mobility of the adsorbed PhACs, which renders them continuously available for uptake by plants, thus increasing the possibility of PhACs entering the human food chain.