Soil Humus Research Articles

The effect of straw on the humus state of chernozem

Abstract. The purpose of the research is to present the results of studies obtained in the long-term stationary experience of the Geographical Network of Experiments with Fertilizers of the Russian Federation on the effect of various methods of straw, crop residues and nitrogen fertilizers utilization on the humus state of leached black soil. Establish the effect of the systematic introduction of straw and crop residues on the content of total and labile humus in leached black soil, provide data on the fractional composition of humus. Methods. There were used conventional methods: total nitrogen by the method of indophenol greens, humus according to Tyurin in Simakov’s modification; fractional group composition according to Ponomareva and Plotnikova; labile carbon – by the release of humic substances during treatment with 0.1n NaOH, soil treatment with sodium pyrophosphate 0.1m Na4P2O7 (Dyakonova’s method) and hot water (Schulz’s method). Results. The results of studies obtained in a long-term stationary experiment on the study of the effect of straw and crop residues on the humus state of the soil are presented. It has been established that the annual introduction of straw and crop residues into the soil makes it possible to maintain the humus state of the leached black soil at the level of the initial content. Significant differences in the humus reserves in the arable soil layer according to the methods of utilization of organic residues were not revealed, they were assessed as very high. On a long fallow, humus reserves were high, on virgin lands they were ultra-high. The results of the studies showed that the fractional composition of fulvic acids depended on the method of using straw and stubble residues; the fractional composition of humic acids did not differ from the method of utilizing straw and stubble residues. A decrease in the content of total humus was revealed against the background of burning and removing straw and stubble, while an increase in its content was noted during the systematic plowing of post-harvest residues. Scientific novelty consists in changing the fractional-group composition of humus when using organic residues (straw, stubble) for the reproduction of soil organic matter.

Long-Term Organic Amendments Combined with Nitrogen Fertilization Regulates Soil Organic Carbon Sequestration in Calcareous Soil

Organic amendments have been widely confirmed to support soil health and agricultural sustainability. However, the effects and mechanisms of long-term organic amendments combined with chemical fertilizers on soil organic carbon (SOC) sequestration and soil macroaggregate formation are still unclear. Therefore, this study aimed to explore the interaction between soil carbon sequestration and soil agglomeration after 12 years of fertilization. Seven treatments within a field experiment were selected to conduct the research, including nitrogen (N) application by farmers, optimized N management, biochar and/or straw, manure, compost or biogas residue plus optimized N management. The results showed that the addition of organic materials significantly enhanced the SOC by 29.6–119.8% and 10.3–36.3% in 0–15 and 15–30 cm soil layers compared to N application by farmers, respectively. Meanwhile, the soil humus carbon pools in the 0–15 cm soil layer were increased by 14.7–205.2%, particularly humin carbon (HUC), which could be considered as a useful indicator of the soil carbon sequestration process. Among the organic materials, the addition of biochar was the most effective strategy due to its high aromatic carbon content that resisted biodegradation. The addition of organic materials also improved the soil labile carbon fractions, and the contents of microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC) and KMnO4-oxidizable carbon (ROC) were enhanced by 120.5%, 92.3%, 217.2% and 85.5% on average, respectively, and the amount of exchangeable Ca2+ and Mg2+ cations and Fe and Al oxides in the soil increased significantly whilst the Na+ content declined in the 0–15 cm soil layer. These indicators showed a significant correlation with the mean weight diameter (MWD). Our results revealed that the addition of organic materials could be an effective management practice to promote soil carbon sequestration and soil macroaggregate formation in calcareous soil.

Various Soil Quality Parameters and Humus Content Evolution in Conventional and Minimum Tillage Systems

An experiment was laid out on a Haplic Phaeozem (PH ha) (WRB-SR 2014) characterized by a dark colored mollic A horizon (Am), a cambic B horizon (Bv), and an accumulation calcareous illuviation horizon (Cca) of secondary calcium carbonates which occurs deeper than 125 cm (SRTS, 2012). Clay content in the first 40 cm varies between 39.4 and 42.6%, total nitrogen is 0.186%, available phosphorus soluble in the ammonium acetate lactate solution (PAL) 76 mg/kg, available potassium soluble in the same solution (KAL) 250 mg/kg, and soil reaction (pH) 6.3. The land is slightly uneven, groundwater below 5 m depth. The humus content was average in the beginning of the experimentations after which increases were noticed especially in the upper layer (5-10 cm). Soil humus content evolution following different agricultural technologies use was similar at all three studied depths, with increases in the case of minimum tillage system, but without statistically significant differences as compared to the classic one. Therefore, the various agricultural technological systems must assert the conservation and increase of soil organic matter, respectively the soil humus supply, through their technological chain links.

МИКРОБИОЛОГИЧЕСКИЕ ОСНОВЫ ПЛОДОРОДИЯ СЕРЫХ ЛЕСНЫХ ПОЧВ

The features of humus formation and manifestations of biological activity of soils are revealed. In the studied soils, the total volume of incoming phytomass is 46 kg /ha, and the underground phytomass exceeds the above-ground one by more than two times. In gray forest soils, the decomposition of cellulose during the growing season amounted to 38.2%. The distribution of organic residues entering the soil under conditions of deep freezing and slow thawing is due to the low capacity of the humus horizon and small reserves of humus in gray forest soils. However, the composition of humus is dominated by agronomically valuable fractions that provide significant stability of humic substances. The humus content is low. Catalase and urease activity has been studied from numerous soil enzymes involved in various processes of transformation of organic and mineral substances. It is shown that according to the level of catalase and urease activity in accordance with the scale of D. G. Zvyagintsev, these soils are characterized as poor. The relevance of the research is caused by the need to analyze and simulate the transformation of matter in the Selenga River-delta-Lake system.Baikal", forecasting and creating the conditions necessary to maintain sustainable soil fertility within the framework of protecting the natural environment of the unique lake. The purpose of the research was to determine the genetic properties and the associated transformation of organic substances, as well as to identify the biological activity of gray forest soils on the riverine plain adjacent to the waters of the unique Lake Baikal. The information obtained on biological activity can be used in agricultural practice in assessing soil productivity, as well as in conducting environmental monitoring.

Morphological characteristics, humus and nutrient content of recent and buried soils of the Inozemtsevo mound

The main objective of the work was to identify the evolutionary changes in the profile of recent and buried soil in the Holocene, the content of humus and the composition of mobile forms of nutrients in the solonetzol- silted black soil in the insufficiently wetted zone of Stavropol Krai. The research was carried out near the village of Inozemtsevo, Stavropol Krai. The soils of the study area are formed on marine sediments. A 1.5-metre-high grave was erected more than 5,000 years ago. At a distance of 150 metres, an incision was made on recent virgin soils. According to morphological characteristics, recent soils are medium saline fused medium powered black soils, while the buried soils evolved into weakly saline fused low powered black soils. They are distinguished by lower profile thickness and brown, rather than black, colouring. There is a BC horizon in recent soils, which is absent in paleosoils. New formation of carbonates and gypsum is noted only in recent soils in B2 and BC horizons. The organic matter content in recent soils is 5-6% and decreases 6-7 times in paleosoils in the upper horizons. Recent soils are depleted in mobile phosphorus, but enriched in mobile potassium. Differences in the content of mobile sulphur are due to some salinity of the paleosoils. In the content of mobile trace elements, the differences between the studied soils are significant, especially zinc, cobalt and molybdenum. Consequently, during the evolutionary period of 5 thousand years, the soil-absorbing complex was impoverished by these microelements.

ГРАНУЛОМЕТРИЧЕСКИЙ СОСТАВ КАК ВАЖНЫЙ ЭКОЛОГИЧЕСКИЙ ПОКАЗАТЕЛЬ ПЛОДОРОДИЯ ПОЧВ БАГАЕВСКОГО РАЙОНА

Purpose: to study the effect of granulometric texture on soil fertility, especially on the humus content and its structural state in the soils of Bagaevsky district Rostov region. Materials and methods. The studies were carried out on the soils of Bagaevsky district Rostov region. Samples were taken from the main genetic soil horizons. The granulometric texture was determined by the pipette method according to N. A. Kachinsky, and the soil structure was determined according to N. I. Savinov or granulometric (grain). Statistical data processing was carried out according to B. A. Dospekhov using the Microsoft Excel software product. Results. The main soil of Bagaevsky district is chernozems, they occupy about 64 % of the total land area of the district, chestnut soils occupy more than 26 % of the total area of the district, and floodplain soils occupy more than 7 %. The relationship with an approximation coefficient R² = 0.51 was revealed between the content of the fraction of physical clay and humus in the studied soils. Our studies of humus amount in the soils of Bagaevsky district showed that they are characterized by a very low and low content. In the studied soils, a close relationship between the structural state and the content of physical clay was determined (R² = 0.83). An analysis of soil humus status shows that the balance of organic matter is unfavorable for the prevailing part of arable land. An analysis of the research results by some authors shows that for the period from 1960 to 2021, the decrease in the humus content in arable soils of Bagaevsky district was 0.7 %. For its deficit-free balance, it is necessary to apply up to 6 t/ha of organic fertilizers. Conclusions. Our studies, combined with data analyses of studies conducted in Rostov region by a number of authors, made it possible to identify a significant effect of granulometric texture on the humus content and, as a consequence, soil fertility in general.

Humus profile specificity of chernozems of the Ob river left bank within the Priob Plateau

Purpose of the study: to identify the features of chernozem humus profiles of the river Ob left bank within the Priob plateau (south of West Siberia) and the reasons that determined their diversity. Place and time. The south of West Siberia (Topchikhinsky district of the Altai Territory), the north-eastern part of the Priobsky plateau, the steppe zone of the Pre-Altai province of the Kulundinsky-Aleysky district, the key site "Volodarka" on the eastern edge of the Porozikhinsky-Aleysky ridge (52°41-42' N and 83°38'E). Sampling was carried out annually in August. Methodology. The collection and interpretation of materials are based on the principles and rules of the systems approach and soil ecology. The objects of study were southern and ordinary chernozems confined to different parts of the Volodarka key site (according to the soil classification of 1977; these classification names of soils are used in the text; according to the new Classification of Russian Soils (2004), the soils belong to the subtype of migratory-mycelial and textural-carbonate; according to WRB-2015 they are in the reference soil group Chernozems with the qualifiers calcic and siltic). The characteristics of humus profiles were obtained using traditional methods. All methods of analytical and instrumental study of humus and its individual components were identical. Methodological features of the research include detailed sampling (every 5–10 cm or less within the visual boundaries of the horizons) in late summer and the absence of strict methods for purifying preparations from mineral impurities. In this work, the concepts of “humus” and “system of humus substances” in soils are used as synonyms. Main results. The humus profiles of the chernozems of the studied territory, currently functioning under the same conditions, have a significant variation in characteristics, representing a range of options typical for such soils (when, based on the combination of characteristics of elementary humus-forming processes - EHP - the upper part with the humification-transformation type of their structure and the lower one - with a transformation-migration type of combination of EHP), to varying degrees of structural complexity (when several parts are distinguished with different quantitative ratios of humus substances parameters with the predominance of their self-healing processes against the background of other EHP). The main characteristics of the studied buried paleosols lie within the limits peculiar to soils formed in temperature conditions optimal for humus formation, but different moisture conditions. Conclusion. A significant difference in the qualitative and quantitative characteristics of chernozem humus profiles of the Ob river left bank within the Priob Plateau is due to both the complex history of the territory development, and different levels of self-healing capabilities of the natural open self-regulating humus substance system, depending on environmental conditions during the period of its formation. During complex history of the territory development different horizons of Middle Pleistocene soils came to the surface in different places, and therefore are found within the thickness usual for mature full-profile modern soils. The advantage of using humus profiles when analyzing the state of soils and the natural environment that forms them is the possibility of conducting a more detailed analysis of the variability of properties, the use of sediments and soils of different preservation, and identifying variations in environmental parameters even in the case of very short episodes of change in one or more soil formation factors or their individual characteristics, which are shorter in duration than the characteristic time required for the formation of the trait morphological expression. The materials presented in the work and their interpretation show that the information obtained about the soil state and the environment based on the study of soil humus profiles (the characteristics of which can be the results of studying the composition and properties of humus) has not lost its significance and can be used in solving a wide range of soil science problems including monitoring soil conditions, as well as substantiating forecasts of their behavior when changing environmental operating conditions.

Spatial modelling of soil humus content using the drone-based measurements

The aim of the study was to assess the potential of spatial modeling of soil humus content through measurements with unmanned aerial vehicle (UAV), using digital relief model combined with geostatistical and regression methods. Location and time of the study. The study area was in the Middle Urals (Perm municipal district of the Perm region) in the southern taiga zone of the Central Russian province. The key area of the surveyed territory is located on the educational and scientific experimental field of the Perm State Agro-Technological University (56°34-37'N and 57°92-93'E). Soil samples were taken with a drill from a depth of 0–20 cm in May 2023. Methods. The survey data was obtained using the drone DJI mini 2 UAVS from a height of 50 m. The orthophotoplan and digital elevation model of the key site were made using the Drone Deploy software. The object of research was the soil cover of the site, represented by sod-podzolic soils. The soil humus content was determined using potassium digestion method. The UAV data processing was performed using the QGIS 3.22 system and SAGA 9 software. Spatial modeling was carried out using the geostatistical method “Ordinary Kriging” employing the Geostatistical Analyst tool of the ArcGIS 10.8 geographic information system. Results. Humus content in in the 0-20 cm soil layer varied from 0.9 to 3.0%, following normal distribution, thus allowing using the normal labels method without data transformation. The U-shape indicated a strong trend direction from north to south and from west to east. The correlation analysis showed the association of humus content with the morphometric parameters, the correlation coefficient ranging from -0.48 to 0.75. A regression equation was constructed for predicting soil humus content by using the parameters with the maximal correlation coefficients such as height (ELEV), distance to watercourses (Channel Network Distance) and relative position of the slopes (Relative Slope Position), having the correlation coefficients of 0.75, 0.75 and 0.66, respectively. This equation was found to model spatial humus with a relative divergence from Kriging interpolation of -0.6…-1.1%. Conclusions. The use of highly detailed UAV images to establish the influence of geomorphological conditions on soil properties allows not only to determine their spatial distribution, establish relationships with surface elevations, distance to watercourses, but also to simulate property changes in properties due to anthropogenic intervention, which, among other things, can enhance water erosion.

Humic and Fulvic Acids Induced Thermodynamic and Structural Instability of Tyrosinase With Antiproliferative Effect on A375 Melanoma Cancer Cell Line

Background: The tyrosinase enzyme catalysis monophenols to melanin pigments through the melanogenesis process. For this reason, various inhibitors have been studied for enzyme regulations in melanogenesis abnormalities in both the food and cosmetics industries. In this study, the effect of humic acid (Hu) and fulvic acid (Fu) on the structure, activity, and stability of mushroom tyrosinase (MT) was investigated. Methods: These two organic acids are the main components of soil humus. Assessment of the thermodynamic and structural stability of enzymes was obtained through thechemical and thermal denaturations and (8-anilino-naphthalene sulfonic acid) ANS fluorescence analysis. The Hu and Fu impact on A375 melanoma cancer cell viability was achieved by MTT assay. Findings: The results of enzyme half denaturation concentration (Cm), melting points (Tm), ΔG0 values and external fluorescence emissions in the presence of Hu and FA proved the reduction of the thermodynamic and structural stability of MT by these compounds. The anti-proliferation effects of the compounds were confirmed by the inhibitory concentrations of 50% (IC50) of 31.5 and 42.7 µM and 12.5 and µM at time points of 24 and 48 hours treatments of the A375 melanoma cell line by Hu and Fu, respectively. Conclusion: Humic and fulvic acids can be expected to contribute to advancing skin disorder science play a crucial role in tyrosinase related disorders and anti-cancer effects, and good candidates for medical applications.

Comparison of agrophysical parameters and humus content in the soil of virgin and arable land

Topicality. Currently, there is an urgent need to address the following challenges: loss of soil humus content, deterioration of soil agrophysical properties, reduction of the impact of soil agrophysical degradation, restoration and preservation of fertility. Purpose. Comparison of agrophysical parameters and humus content in the soil of virgin and arable lands and development of scientific recommendations on the formation of favourable agrophysical properties and regimes of chernozems to suspend the development of degradation processes in the soil and preserve fertility. Material and Methods. The study of ordinary chernozem was carried out in the virgin lands and experimental plots of the Erastivka Research Station of the Institute of Grain Crops of NAAS of Ukraine during 2010–2016. We studied: total humus content; structural and aggregate composition of the soil; soil structure coefficient; soil density; water resistance of agronomically valuable structural aggregates. In May, soil samples were selected at equilibrium density after mechanical tillage. Sampling was carried out from the soil profile at intervals of 5 cm, to a depth of 0–200 cm in quadruplicate according to DSTU 4287. Results. It was found that deterioration of agrophysical properties (structural and aggregate state, density, water resistance) and reduction of humus content and thickness in the humus horizon in comparison with virgin soil occurred as a result of long-term cultivation of ordinary chernozem. Conclusions. When comparing the properties of ordinary chernozem of arable land with virgin soil, we find that they are significantly degraded. Significant loss of humus and structure degradation leads to an increasing soil density and a partial loss of the ability to resist degradation. To preserve and sustainably use arable chernozems, an improved farming system should be implemented, with scientifically based crop rotations, the latest soil protection technologies, and the proper amount of organic and mineral fertilisers to increase the humus content as its main components. Key words: ordinary chernozem, soil degradation, humus content, structural and aggregate state, density, water resistance

Estimation of Potential Carbon Stocks in Mangrove Ecosystems in the Riau Islands

Global warming is characterized by high concentrations of greenhouse gas emissions, namely CO2, in the atmosphere. Mangrove ecosystems play a role in mitigating global climate change because they can absorb carbon through photosynthesis and then store it in a carbon pool, which includes Above Ground Biomass (AGB), Below Ground Biomass (BGB), litter or dead wood, and sediment. This study aimed to determine the value of biomass, carbon stocks, and CO2 sequestration in the mangrove ecosystem in the Riau Island. Carbon stocks were estimated by collecting data on AGB, BGB, and dead wood using the non-destructive allometric modeling method, and sediment sampling was carried out at 30 cm intervals until the discovery of humus soil. There are eight research stations spread across Riau Island. The results of the biomass calculation are then converted into carbon stock values and CO2 sequestration. The result showed that the mangrove ecosystem in Riau Island had a biomass value of 1854,54 tons/ha, estimated carbon stocks of 2052,78 tonsC/ha, and a CO2 sequestration of 7527,52 tonsC/ha. The mangrove ecosystem in Riau Island has an area of 79.228,91 Ha so it can store carbon reserves of 162.639.342 tonsC. The amount of CO2 can be minimized or controlled by reducing emissions and conserving forests, namely by improving mangrove management according to the function of mangrove forests.

Explore variations of DOM components in different landcover areas of riparian zone by EEM-PARAFAC and partial least squares structural equation model

Dissolved organic matter (DOM) plays key roles in species-distribution of contaminants and the biogeochemical cycle of carbon in ecosystems. Riparian zone is the representative of water-land ecotone and controls the DOM exchange between water and land. However, the variance of DOM in different landcover areas of an urban river riparian zone is unknown. In this study, fluorescence excitation-emission matrix (EEM) spectroscopy coupled with parallel factor analysis (PARAFAC) and partial least squares structural equation model (PLS-SEM) was applied to character dissolved organic matter (DOM) fractions in four types of landcover riparian areas (natural forest, artificial forest, semi-natural grassland, and cropland) of Puhe River and trace latent factors. Soil samples were collected at 0–20 cm, 20–40 cm, 40–60 cm, and 60–80 cm. The results showed that soil DOM components and humification varied between forests with grassland and cropland samples, and soil humification was obviously higher in the forest samples than that in the grassland and cropland samples. In the natural and artificial forest soils, the humic/fulvic-like were the dominant fractions of DOM, whose variations were smaller than the protein-like with soil depths. However, the tyrosine-like was the representative component in the grassland and cropland soils, whose variation was smaller than the humus substances. According to the PLS-SEM, the DOM components and humification were affected by soil physiochemical properties and DOM sources. The humification in the forest soils had a positive correlation with tryptophan-like, which derived from blended source of the autochthonous and terrigenous. Nevertheless, a positive correlation was observed between humification and humus substances, which could derive from microbial degradation of tyrosine-like, in the grassland and cropland soils. Moreover, the soil physiochemical properties were negatively related to DOM components in all soil samples, which could affect indirectly soil humification. Therefore, EEM combined with PARAFAC and PLS-SEM might be an effective method to investigate DOM fractions and trace the latent factors in different landcover areas of the riparian zone.

Тяжёлые металлы и техногенные магнитные частицы в почвах рекреационной территории города Пермь (на примере экологической тропы Чапаевская)

The work focuses on the study of soils on the territory of the Chapaevskaya ecological trail in the city of Perm (Russia). The studied soils are subject to contamination by technogenic magnetic particles and heavy metals in their composition. The forest litter of the urbanity gray humus soil formed on the eluvial-deluvial deposits is contaminated with Cd, Cu, Ni, Co, and Zn. The urbanity gray humus horizon accumulates Cu and Zn. The values of the magnetic susceptibility of the highly magnetic phase of the surface horizon are high. The maximum value of the magnetic susceptibility of the forest litter was 55.64 × 10-3 SI. The bulk content of heavy metals and Fe in the highly magnetic phase is several times higher than in the soil before magnetic separation. Keywords: POLLUTION, MAGNETIC SUSCEPTIBILITY, ENVIRONMENTAL ASSESSMENT, URBANITY GRAY HUMUS SOIL, CIS-URALS

Long-Term Effects of Organic Amendments on Carbon Stability in Clay–Organic Complex and Its Role in Soil Aggregation

Clay–organic complexes (COC) impart chemical and physical protection to soil carbon (C). In the present study, the aim was to assess the long-term effects of different organic amendments on C stability in COC, distribution of the aggregates, C concentration in the aggregates and labile organic C fractions in the inceptisols located at the research farm situated in the semi-arid sub-tropical climate of India. The results showed that the COC, the percentage of large macroaggregates (LMA) (>2 mm) and the C associated with the aggregates decreased through the soil depths, whereas the other size fractions of soil aggregates (<2 mm) showed an increasing trend. The COC was significantly higher (4.4 times) in soil treatments where farmyard manures (FYM), green manure (GM) and biofertilizers (BF) were applied together (FYM + GM + BF). The organic amendments increased the proportion of LMA over control (no application of organic amendments) to a magnitude of 83 to 101% and the C associated with LMA to a magnitude of 0.48 to 9.8% over control in surface soil. On average, the combined application of FYM, GM and BF exhibited higher C accumulation in almost all soil aggregate fractions, except microaggregates (mA), i.e., (0.25–0.053 mm) size fractions, where application of FYM alone recorded the highest value. Averaged over soil depths, the particulate organic C (POC), dissolved organic C (DOC) and potassium permanganate oxidizable C (POXC) were significantly higher under integrated organic treatments than individual amendments. The significantly higher correlation between COC and the percentage of LMA and aggregate-associated C implied their direct role in soil aggregate formation and their stability. The carbon stability, i.e., retention time of humus in soil, was significantly correlated with soil organic carbon, dissolved organic carbon, particulate organic carbon, potassium permanganate oxidizable C, C mineralization (Cmin), glomalin-related soil protein (GRSP), macroaggregate (MA)-associated C and rice equivalent yield (REY). Overall, the data suggest that the combined application of FYM + GM + BF promotes soil quality under rice–wheat rotation in inceptisols in semi-arid sub-tropical India.

The influence of trees and shrubs vegetation of sheltered forest strips on the characteristics of the steppe soil cover

The soil in forest plantations is in constant close interaction with woody and shrubby plants. It acts as a determining factor in creating optimal conditions for the existence of natural and artificially created forest communities. Modern steppe afforestation has a number of unresolved questions regarding the nature and degree of influence of tree-shrub vegetation on the soil typical for the steppe zone – ordinary chernozem, and the feasibility of creating tree-shrub ecosystems of various practical importance in the steppe conditions of Ukraine. The paper presents the results of the study of the impact of tree and shrub vegetation of forest strips on their soil cover. The content of humus, exchangeable and hydrolytic acidity of soils, acidity of salt extract from the soil in the soils of forest belts were determined іn the edaphotops of five forest strips created on the territory of the Prysamarsky International Biosphere Reserve, located in the village of Andriivka, Novomoskovsk district, Dnipropetrovsk region. The obtained data were compared with the similar results of measurements of the soil indicators of a typical for the study region of the site of the variegated-grassy-grassy-cobaceous steppe. A comparison of the humus content in the soil under tree plantations of forest strips and steppe virgin lands confirms the theory of a positive relevant effect of the forest on steppe soils and the formation of forest-improved chernozems under tree plantations in steppe conditions. The exchangeable acidity of the soils of the forest strips ranged from 0.2 to 0.8 mg-eq. per 100 g of soil, and the value of hydrolytic acidity was from 0.52 to 2.11 mg-eq. per 100 g of soil, and the maximum values ​​of both types of acidity were noted in the 20–50 cm horizon of the PP 224 oak plantation. The obtained characteristics of the soil cover of forest strips will be useful for clarifying the directions and features of the influence of tree-shrub vegetation on ordinary chernozem in the conditions of the steppe zone of Ukraine and can serve as valid arguments in making decisions regarding the creation of field-protective tree-shrub plantations within the steppe zone of Ukraine.

Spatial heterogeneity of the content and reserves of humus of virgin light gray forest soils of the south of the Tyumen region

The results of the analysis of the state of humus in virgin light gray forest soils in the south of the Tyumen region are presented. A total of 96 full profile sections were made and described, soil samples were taken for laboratory studies. The results were processed in MS Excel using the Descriptive Statistics tool. It was revealed that the subtype of light gray forest soils has a low content of humus in the upper part of the profile - 2.07±0.47 %. A sharp decrease in the humus content down the profile was established. In the A1A2 horizon, the average humus content in the sample is 1.09 % with fluctuations from 0.61 to 1.65 %. Humus formation in the studied soils is of an accumulative nature, since soils with an above-average humus content predominate in the analyzed sample. The content of total nitrogen in horizon A1 is 0.11±0.03 % at a carbon to nitrogen ratio of 11.2±1.0. Down the profile, the content of total nitrogen sharply decreases, which is associated with the leaching of water-soluble nitrogen compounds. On average, humus reserves in the A1 horizon are 38±11.7 t/ha, which is half of the reserves in the 0-100 cm layer. When light gray forest soils are involved in arable land, the nutrient regime of agricultural crops will be formed exclusively due to the A1 horizon.

Stable Carbon Isotopic Composition (δ13C) as a Proxy of Organic Matter Dynamics in Soils on the Western Shore of Lake Baikal

Abstract Assessing the main factors that control carbon dynamics in soils is an urgent problem in the context of modern climate change. The analysis of stable carbon isotope (δ13С) composition is one of the approaches to understanding this dynamics. The study was carried out in the landscapes of the southeastern slope and foothills of the Primorskii Range, characterized by contrasting physico-geographical conditions. Climatic parameters, spatial variations in the composition of stable carbon isotopes and their distribution in soil profiles, and soil physicochemical properties controlling carbon dynamics have been analyzed. The soil humus horizons formed in mountainous tundra and steppe landscapes manifest the highest δ13С values (–24.72 and –23.97…–24.75‰); whereas the lowest (–25.61…–27.18‰) values are registered in the mountainous taiga soils. Based on the calculation of linear dependence between δ13С values and the total carbon content in soil, which varies with the depth, the carbon turnover intensity was determined using the slope of linear regression. It was revealed that under the contrasting conditions of mountainous tundra and steppe landscapes, the climate (deficiency of heat and moisture) has a significant impact on the intensity of organic matter transformation, blocking the effect of edaphic (soil profile) factors. Under more favorable climatic conditions of mountainous taiga landscapes, the dynamics of organic matter in soils is controlled mainly by edaphic factors.

Preliminary Studies on How to Reduce the Effects of Salinity

Soil salinization is an important factor contributing to the deterioration of soil environment and low crop yield in arable land. In this study, the effects of five fulvic acid applications (0 (CK), 150 (T1), 300 (T2), 450 (T3), and 600 (T4) kg·ha−1) on soil physicochemical properties, humus content of each component, and cotton (Xinluzao No. 82) growth were investigated. It was confirmed that fulvic acid improved soil water-stable macroaggregates, moisture distribution, and desalinization. 0–20 cm soil relative desalinization rate was significantly increased by 2–11.75%. The pH value decreased by 0.09–0.21. The soil organic matter content was significantly increased compared to CK (p < 0.05), with 7.5–26.93% increase in organic matter content in 0–20 cm soil layer. Soil humification was increased to different degrees, with the most significant increase in humic carbon content in T3 treatment (p < 0.05). There was a significant increase in leaf area index (LAI), stem diameter, and plant height of cotton (p < 0.05). Cotton yield increased by 3.64–8.36% compared to CK (p < 0.05). Correlation analysis showed that cotton yield was significantly correlated with the soil textures of saline soils. The best improvement was achieved with 450 kg·ha−1 fulvic acid. The results of this study can provide a theoretical basis for the improvement of saline soils in arid zones to enhance crop growth and yield.

Characterization of unfrozen water in highly organic turfy soil during freeze–thaw by nuclear magnetic resonance

The unfrozen water content (ωu) is an important parameter affecting the hydrothermal-mechanical characteristics of soil and is of important significance with regard to engineering construction and environmental effects in cold regions. In this study, a widely-distributed special humus soil called turfy soil, with poor engineering geological properties, from seasonally frozen regions of northeastern China was investigated. Soil fundamental properties were determined, and ωu under various temperatures during a freeze–thaw process was measured by the nuclear magnetic resonance (NMR) method. Based on NMR theory and transverse relaxation time (T2) distribution curves, two thresholds were determined to divide the types of pore water in soil. Soil freezing characteristic curves (SFCC) of the total and pore water were drawn, and changes in the internal microstructure and pore characteristics of the soil during the freeze–thaw process were analyzed. The results showed that a drastic phase change within the soil occurs during −2 °C to −4 °C, and the freezing process can be divided into three stages. The formation of small pores and the connection of large pores make the soil looser after freeze–thaw. The division of pore water and variation in ωu show that freezing starts from large pores, while thawing starts from small pores. The capillary water content significantly decreases after freeze–thaw, and the bulk water content tends to increase. At freezing Stage I, ωu is closely related to the initial properties of the soil, whereas ωu at −3 °C almost determines the value of ωu during subsequent freeze–thaw. Finally, a ωu-power function for turfy soil was proposed, and good fitting results were obtained for both freezing and thawing soil. This work can serve as the basis of studies on soil with high organic matter content as well as soil unfrozen water content during freeze–thaw cycles in cold regions.

Effects of Applying Different Organic Materials on Grain Yield and Soil Fertility in a Double-Season Rice Cropping System

Double-cropping rice cultivation reduces soil fertility, and the extensive use of chemical fertilizers has harmful effects on both the environment and grain yield. The application of organic materials could be used as a practical strategy to maintain soil fertility and improve grain yield in a double-season rice cropping system. For this purpose, field experiments with six growing seasons over three years, from 2016 to 2018, were conducted to assess the effects of five organic materials (biochar, Chinese milk vetch, rice straw, rapeseed cake fertilizer, and manure) on the grain yield and soil fertility, aiming to save about 25% of the chemical nitrogen (N) fertilizer required for all rice growing stages. The result showed that, compared with CK (the most common dose of fertilizer in this study region; 100% chemical fertilizer without organic fertilizer), the grain yield and soil fertility of double-cropped rice were increased after applying organic fertilizers for three consecutive years. Specifically, the CRC treatment (Chinese milk vetch (10.77 t ha−1 in fresh)/rice straw (26.51 t ha−1 in fresh) + 75% chemical fertilizer) showed significantly higher rates of effective panicles (4.65–10.92%) and annual grain yield (8.00–8.82%). The total N, total phosphorus (P), total potassium (K), alkaline N, and available P content in the CRC soil were significantly increased by 11.85%, 12.22%, 15.08%, 23.32%, and 41.04%, respectively, relative to CK. The decomposition of the applied Chinese milk vetch and rice straw combined with 75% chemical fertilizer resulted in more soil humus (9.50 g kg−1), humic acid (3.19 g kg−1), fulvic acid (3.26 g kg−1), and active organic carbon (5.78 g kg−1) and a significantly higher carbon pool management index (13.5%), as well as significantly higher soil urease activity (18.10%) and acid phosphatase activity (17.64%). Therefore, in this study, Chinese milk vetch (10.77 t ha−1 in fresh) in the early rice season/rice straw (26.51 t ha−1 fresh) in the late rice season + 75% chemical fertilizer treatment was the optimal dose for the double-season rice cropping system. It resulted in higher rice yields and has the potential to be used for more sustainable soil fertility.