Search Results (118)

Maize is a globally significant cereal crop, while Albic soils in Northeast China are characterized by low available phosphorus (P), poor humus (HS) quality, and constrained maize yield. The synergistic effects of P fertilization on maize yield and HS quality in these soils remain poorly understood. This three-year field experiment was conducted to determine the optimal P application rate for concurrently enhancing crop productivity and HS quality. Four P application rates were established: 0 kg P₂O₅ ha⁻¹ (no P application, P0), 40 kg P₂O₅ ha⁻¹ (low P application, LP), 80 kg P₂O₅ ha⁻¹ (moderate P application, MP), and 120 kg P₂O₅ ha⁻¹ (high P application, HP). Soil nutrients status, HS fractions, dissolved organic matter (DOM) fluorescence characteristics, and structural properties of humic acid (HA) were systematically analyzed following standard analytical procedures. Principal component analysis (PCA) and Pearson correlation analysis were integrated to facilitate comprehensive data interpretation. Results indicated that the MP treatment achieved the highest maize yield (12,257.1 kg ha⁻¹) and soil organic matter (SOM, 14.8 g kg⁻¹) content, with no further yield improvement observed under HP. The MP treatment significantly increased DOM carbon content (C_DOM, 0.350 mg L⁻¹) and its humification index (HIX, 6.80), promoting the transformation of labile DOM into stable HS. HA under MP treatment exhibited enhanced structural stability, as evidenced by a lower H/C ratio (1.72), a higher O/C ratio (0.880), and a reduced E₄/E₆ ratio, reflecting increased aromatic condensation and a greater abundance of oxygen-containing functional groups. Fourier transform infrared (FTIR) spectroscopy and differential thermal analysis (DTA) confirmed that MP improved the structural complexity and thermal stability of HA. In contrast, P0 and LP restricted nutrient availability and HS formation, whereas HP induced soil acidification (pH 5.68) and disrupted HS equilibrium. Principal component analysis (PCA) and correlation analysis revealed significant positive associations between the MP treatment and SOM, C_DOM, and maize yield. This implied that moderate P input promoted stable soil organic carbon accumulation and nutrient availability, synergistically enhancing maize productivity—consistent with the study’s core goal of optimizing P management for concurrent yield and HS quality improvement in Albic soils. Accordingly, this study concluded that moderate P application (80 kg P₂O₅ ha⁻¹) was optimal for Albic soils, synergistically enhancing both maize productivity and HS quality. These findings provided theoretical support for precise P management in sustainable agricultural systems within the Albic soil regions of Northeast China. Full article

This study shows that the structural features of humic acids reflect the specific characteristics of organic matter in permafrost soils of the southern Vitim Plateau. The region’s extracontinental climate determines the rate of decomposition, the depth of humification, and the chemical structure of humic acids. Brown forest soils (Haplic Cambisols) and sod-brownzems (Leptic Cambisols Skeletic) contain high amounts of organic carbon and total nitrogen in their upper horizons but differ in their vertical distribution. Brown forest soils are characterized by a sharp decrease in organic carbon content with depth and the presence of humus pockets enriched in carbon and exchangeable bases. Sod-brownzems contain more organic carbon with increase in acidity and base loss with depth. Both soil types retain satisfactory natural fertility. ¹³C nuclear magnetic resonance spectroscopy data reveal marked differences in the structural maturity of humic acids. Humic acids from the A horizons of brown forest soils contain an equilibrium combination of aliphatic and aromatic structures, a well-developed system of oxygen-containing groups, and moderate condensation, indicating an intermediate stage of humification. Humic acids from humus pockets are more aromatic and highly humified. They reflect an advanced stage of humification and possess high chemical stability. Humic acids from sod-brownzems also exhibit high aromaticity, which facilitates the formation of stable organomineral complexes. A comparison of the samples reveals a consistent increase in aromaticity, condensation, and stability from the A horizons of brown forest soils to the A horizons of sod-brownzems and further to humus pockets. This progression corresponds to an increase in humification and a decrease in the mobility and bioavailability of organic matter. These results confirm that the structural characteristics of humic acids are determined by soil type and formation conditions. Elemental composition revealed that humic acids from brown forest soils are characterized by the highest aromaticity and maturity, while humic acids from HA-brown forest soils-A have a less condensed structure. Humic acids from sod-brownzems occupy an intermediate position, combining high aromatization with a moderate degree of humification. Overall, the obtained elemental composition data are fully consistent with the results of ¹³C NMR spectroscopy, mutually confirming the identified structural features and the degree of transformation of soil organic matter. Full article

Soils represent the largest reservoir of organic carbon (OC) in terrestrial ecosystems, storing approximately 1500 Gt C. Forest and grassland ecosystems contribute 39% and 34% to global terrestrial carbon stocks, with soils holding about 44% and 89% of forest and grassland carbon, respectively. Land-use changes, such as the conversions between forest and grassland ecosystems, can strongly influence soil carbon accumulation, though the direction and magnitude remain uncertain. Comparative data from paired-plot studies of forest and grassland soils are still limited. In this study, we conducted pairwise comparisons of total OC and total nitrogen (TN) stocks in mature forest and climax grassland soils along a climatic and pedogenic gradient encompassing Retisols, Luvisols, and Chernozems. Relationships between OC and TN stocks (0–10 cm) and soil physicochemical properties—OC and TN contents, bulk density, pH, clay content, and humus fractional composition, as well as biological indicators—the abundance of culturable fungi and bacteria, microbial biomass carbon, potential metabolic activity, and activities of laccase and dehydrogenase, were evaluated. Strong positive correlations were found between OC and TN stocks and OC and TN contents (r = 0.62–0.99), pH (r = 0.79–0.81), clay content (r = 0.70–0.87), and the fraction of humic acids bound with calcium (r = 0.73). OC stocks also correlated strongly with dehydrogenase activity (r = 0.85–0.95). At 0–10 cm depth, OC stocks were higher in grassland soils than in forest soils by factors of 1.6–1.7 in Retisols and 1.4–1.5 in Chernozems. Similarly, TN stocks were 1.6–2.0 times greater in grasslands across all soil types. Community-level physiological profiling revealed higher potential metabolic activity in forest soils compared with grasslands, with the strongest differences in Retisols and Luvisols, while contrasts were attenuated in Chernozems. Overall, the results highlight the fundamental role of organo-mineral interactions and calcium binding in OC stabilization, as well as the likely involvement of dehydrogenase activity in the biogenic formation of calcium carbonates that contribute to this process. Full article

Heavy metal enrichment in agricultural soils can affect crop safety, ecosystem functioning, and long-term land productivity, yet farm-scale screening is often constrained by limited routine monitoring data. This study develops a GIS-based framework that combines field-scale spatial analysis with explainable machine learning to characterize and predict heavy metal enrichment on an intensively managed cereal farm in eastern Kazakhstan. Topsoil samples (0 to 20 cm) were collected from 34 fields across eight campaigns between 2020 and 2023, yielding 241 composite field–campaign observations for eight metals (Pb, Cu, Zn, Ni, Cr, Mo, Fe, and Mn) and routine soil properties (humus, pH in H₂O, and pH in KCl). Concentrations were generally low but spatially heterogeneous, with wide observed ranges for several elements (for example, Pb 0.06 to 2.20 mg kg⁻¹, Zn 0.38 to 7.00 mg kg⁻¹, and Mn 0.20 to 38.0 mg kg⁻¹). We synthesized multi-metal structure using an HMI defined as the unweighted mean of z-standardized metal concentrations, which supported field-level screening of persistent enrichment and emerging hot spots. We then trained Extreme Gradient Boosting models using only humus and pH predictors and evaluated performance with field-based spatial block cross-validation. Predictive skill was modest but nonzero for several targets, including HMI (mean R² = 0.20), indicating partial spatial transferability under conservative validation. SHAP analysis identified humus content and soil acidity as dominant contributors to HMI prediction. Overall, the workflow provides a transparent approach for field-scale screening of heavy metal enrichment and establishes a foundation for future integration with satellite-derived covariates for broader monitoring applications. Full article

Wetlands store large amounts of soil organic carbon stock (SOCS), making them crucial for global climate regulation. However, climate change, poor management, and weak protection policies threaten these stocks. To assess the contribution of different wetland types for national and international climate targets and to monitor the effectiveness of protection measures, additional research is required. Therefore, we assessed SOCS and disturbances from climate change, land use/land cover (LULC), and soil chemical composition in saline and eutrophic Ramsar sites in Serbia. Analyzing a total of 96 samples, we accounted for soil depth, reference soil group (RSG), and habitat/vegetation type. Mean SOCS in the saline site ranged from approximately 36 t·ha⁻¹ at 0–30 cm to 26 t·ha⁻¹ at 30–60 cm, whereas values were much higher for the eutrophic sites, ranging from 81 to 82 t·ha⁻¹ at 0–30 cm and 47–63 t·ha⁻¹ at 30–60 cm. Differences between groups for the whole soil columns (0–60 cm) were significant at the 0.1% level. While SOCS generally decreases with depth, it showed notable local variability, including occasional instances at deeper layers, indicating complex environmental and anthropogenic influences. Spatial mapping of soil chemistry parameters (pH, humus, P₂O₅, and K₂O) along with land use/land cover (LULC) data revealed nutrient dynamics influenced by agricultural activities. An analysis of regional climate data revealed temperature increases relative to the reference period of 1971–2000 by 0.5 °C for the decade 2001–2010 and of 1.5 °C for 2011–2020. Climate projections under the RCP4.5 and 8.5 scenarios predict further warming trends, as well as increased rainfall variability and drought risks. The results of our study contribute to quantifying the important, though variable, contribution of wetland sites to global climate regulation and show the influence of geogenic, pedogenic, and anthropogenic factors on SOCS. National policies should be adapted to safeguard these stocks and to limit negative effects from surrounding agricultural areas, as well as to develop strategies to cope with expected regional climate change effects. Full article

Soil degradation from long-term chemical fertilization poses serious challenges to the sustainability of black soil agroecosystems in Northeast China, particularly for the cultivation of medicinal plants such as Aralia continentalis Kitag. To evaluate eco-friendly alternatives, we compared decomposed leaf mulching (LM), conventional fertilization (CF), and an untreated control (CK) in a five-year field experiment. LM significantly improved soil structure by reducing bulk density by 12.8% (p < 0.05) and increasing porosity by 15.6% while enhancing organic carbon and humus fractions by 23.4% and 31.7%, respectively. These changes promoted microbial biomass carbon by 28.2% (p < 0.01) and enriched beneficial fungi such as Mortierella, which correlated with nutrient mobilization and plant growth. Fungal richness and diversity were higher under LM (+18.4% and +12.6%, respectively), whereas CF reduced evenness and favored dominance of stress-tolerant taxa. Functional predictions indicated that LM sustained saprotrophic and symbiotic guilds, while CF weakened mycorrhizal associations. Structural equation modeling identified microbial community composition as a central mediator linking soil properties, microbial diversity, and biomass (R² = 0.78), with LM exerting the strongest cascading effects. At the plant level, LM achieved the highest above- and belowground biomass, outperforming CF and CK by 26.3% and 34.5%, respectively. Overall, decomposed leaf mulching represents a sustainable strategy to restore soil quality, enhance microbial diversity, and support medicinal plant cultivation in cold-region agroecosystems. Full article

This study aimed to investigate vertical variations in dissolved organic matter (DOM) properties, humus (HS) composition, humic acid (HA) characteristics, and clay mineral dynamics, with a particular focus on the vertical distribution of HS components and mineral composition across Dark-brown, Meadow, and Paddy soil profiles. Results indicated that: (1) DOM in all three soil types was predominantly endogenous, primarily derived from microbial metabolism with minimal contributions from plant residues. (2) Vertical trends in DOM carbon content (C_DOM) were specific to soil type: in Dark-brown soil, C_DOM slightly increased from the Ap to Bt layer, followed by a sharp increase in the C layer; Meadow soil exhibited a significant decrease in C_DOM in the AB layer but remained relatively stable in other layers; Paddy soil showed a consistent decline in C_DOM with increasing depth. (3) HS and its fractions exhibited vertical variability: Paddy soil showed higher HS content in surface layers; carbon contents of water-soluble substances, HA, and humic-extracted acid (C_WSS, C_HA, and C_HE) decreased with depth in Dark-brown and Paddy soils, whereas they remained relatively stable in deeper layers of Meadow soil. (4) HA characteristics, including C/N ratio, functional groups, and aromaticity, were influenced by both depth and soil type: the Ap2 layer of Paddy soil effectively restricted the downward movement of organic matter; Fe³⁺ complexation played a key role in HA stabilization in Dark-brown soil; Meadow soil exhibited transitional HS properties. (5) Clay mineral assemblages were dominated by 2:1 type minerals (illite, smectite, illite–smectite interstratifications), showing distinct vertical weathering patterns: illite content decreased with depth due to hydrolysis, while proton-driven dissolution promoted kaolinite formation in surface layers, particularly in Dark-brown soil 2:1 minerals enhancing organic–mineral complexation in Meadow soil. The findings of this study provided a scientific basis for optimizing soil carbon pool management and offer insights into organic–mineral interactions that can enhance organic matter sequestration in agricultural soils. Full article

Forest litter plays a critical role in regulating the water balance of forest ecosystems, particularly in semi-arid regions where hydrological stability is under pressure due to climate change. This study investigates the maximum water holding capacity (MWHC) of litter layers across three ecologically distinct regions in Türkiye—Kastamonu, Kütahya, and Muğla—to evaluate how structural and physicochemical characteristics influence the maximum water holding capacity (MWHC) of litter layers. Litter samples classified into humus, fermenting debris, and needles were analyzed for MWHC, pH, electrical conductivity (EC), and total dissolved solids (TDSs). The results revealed that both the type of litter and regional ecological conditions significantly affect MWHC, with humus layers and moist environments exhibiting the highest water holding capacity. Additionally, MWHC showed moderate positive correlations with EC and TDS, highlighting the importance of chemical composition in water dynamics. The findings underscore that forest litter should be regarded as a dynamic and functional hydrological component, not merely residual biomass. This perspective is vital for sustainable watershed planning and adaptive forest management. The study supports the development of integrated management strategies aligned with the United Nations Sustainable Development Goals (SDGs), particularly SDG 6 (Clean Water and Sanitation), SDG 13 (Climate Action), and SDG 15 (Life on Land). Full article

Dissolved organic matter (DOM) exerts a significant influence on the environmental behavior of heavy metals in water. This study investigated the spatial distribution characteristics of DOM in the upper reaches of the Yangtze River and its vertical (0–10 m) binding behavior with heavy metals. The results indicated that humic acid-like substances dominated the DOM composition in the river water, exhibiting spatial variability horizontally, with a higher proportion of protein-like components observed at the depth of 8 m. The DOM showed complexation affinity (LogK) values were 4.71–6.38 for Cu²⁺ and 4.27–6.26 for Hg²⁺, with the protein-like component C3 exhibiting higher LogK values when binding with Cu²⁺ or Hg²⁺ compared to humic-like components. The LogK_Cu and LogK_Hg varied distinctly with water depth, and at 8 m depth, humus-like component C1 exhibited stronger binding affinity for Hg²⁺, whereas protein-like component C3 showed greater affinity for Cu²⁺. The 2D-FTIR-COS analysis revealed that, in the DOM-Cu complexes, DOM from surface water preferentially bound to O-H groups of carbohydrates, phenols, and carboxylic acids, while deep water DOM favored C=O groups in amides; for DOM–Hg complexes, the active binding sites varied distinctly with depth. This study provides novel insights into the migration and transformation mechanisms of heavy metals in rivers. Full article

River sludge usually contains a high content of organic matter, leading to its low strength or difficult solidification in its solidification/stabilization (S/S) treatment projects. This study selected river sludge with medium and high content of organic matter for the S/S treatment using modified curing agent (GCP) and cement (P.O). Effects of humus and curing agent on the S/S process of river sludge were investigated via analyzing physical properties, changes in organic matter, microstructure, and mineral compositions of the solidified sludge. The results showed that the increase rate of compressive strength of the solidified sludge was influenced by the content of organic matter and composition of the curing agent. The presence of humus inhibited the hydration reaction and reduced the increase rate of compressive strength of solidified sludge. Slag and phosphogypsum in GCP promoted the hydration reaction, significantly enhancing the compressive strength of the solidified sludge to 2242.24 KPa. The water content of the solidified sludge was influenced by the environmental conditions and curing agent, which could reflect the level of hydration reaction in the solidified sludge. The pH of the solidified sludge was directly affected by the humus in the sludge, with a decreasing trend during the S/S process. Decomposition of the humus in the sludge released H⁺, which reacted with OH⁻ produced by the hydration reaction via neutralization reaction. The pH of the solidified sludge was lowered, and the hydration reaction was inhibited, hindering the decrease in the water content of the solidified sludge. Therefore, the hydration reaction has an antagonistic effect on the decomposition of the humus. Microstructure analysis (SEM) confirmed that GCP could effectively solidify the organic-rich river sludge. This study provides a theoretical basis for the S/S treatment of organic-rich river sludge. Full article

Soil salinity is a major global challenge, reducing fertility and crop productivity. This study evaluated the effects of various soil management practices on the physical, chemical, and microbial properties of saline soils. Six treatments, combining loosening, ploughing, disking, and gypsum amendment, were applied to solonetzic meadow soil with high sodium levels. Soil penetration resistance was measured using a Penetronik penetrometer, while chemical analyses included pH, total salt content, calcium carbonate (CaCO₃), humus, and exchangeable cations (Na⁺, K⁺, Ca²⁺, Mg²⁺). Microbial composition was determined through DNA extraction and nanopore sequencing. The results showed that level A had the lowest penetration resistance (333 ± 200 N/m²), indicating better conditions for plant growth. Gypsum and loosening treatment significantly improved penetration resistance (141 N/m², p < 0.001), while gypsum amendment enhanced chemical properties (p < 0.05, p < 0.01, and p < 0.001). Gypsum application balanced soil parameters and influenced microbial communities. Reduced tillage favored functionally important microbial genera but did not support fungal diversity (p > 0.05). These findings highlight the effectiveness of gypsum amendment and tillage practices, like loosening and disking, in mitigating salinity stress and fostering beneficial microbial communities. Combining gypsum with these tillage methods proved most effective in enhancing soil health, offering insights for sustainable soil management in saline environments. Full article

Non-chemical methods of fertilisation and protection have been gaining importance in recent years. This trend is closely linked to current European Union (EU) agricultural policy and the growing consumer awareness of the impact of nutrition on health. Newly developed biopreparations have to be tested for their agricultural efficiency alongside a quality assessment of the resulting food. The aim of this study was to determine whether the use of newly developed microbially enriched fertilisers in organic strawberry cultivation had an effect on fruit chemical composition and heavy metal accumulation. In the research, five biopreparations (K2–K6 combinations) containing selected Bacillus strains and plant extracts were tested in 2021 and 2022 on three strawberry cultivars: ‘Honeoye’, ‘Rumba’, and ‘Vibrant’. After the vegetation period, the collected fruit samples were frozen, freeze-dried, and subjected to chemical analyses to determine the total carbon and nitrogen content, as well as the concentration of microelements (Mn, Fe), macroelements (Na, Mg, K, Ca, P) and heavy metals (Cd, Pb, Cu, and Zn). The application of the tested biopreparations did not significantly impact the total carbon content of strawberry fruit. For most of the tested traits, cultivars reacted differently to the tested preparations. A higher total nitrogen content was found for treatments treated with biopreparations, especially for the ‘Vibrant’ cultivar—ranging from 15.2 g·kg⁻¹ K2 (BacilRoots) to 16.3 g·kg⁻¹ K3 (BacilRoots + BacilExtra) and K5 (BacilRoots + BacilExtra + BacilHumus)—being about 10–18% higher than on the control object (K1). The content of sodium, phosphorus, calcium, and magnesium did not change significantly under the influence of biopreparations. The use of the K3 and K5 treatment resulted in significantly lower iron contents when compared to those of the control (strawberries sprayed with water with no biopreparations added)—respectively, by 16.1% and 17.9%. ‘Vibrant’ treated with water (control treatment) showed the highest contents of iron, copper, and zinc when compared to those treated with biopreparations. No exceedances of the permissible heavy metal content were found in the samples tested. Full article

Accurately assessing forest carbon stock (FCS) is essential for analyzing its spatial distribution and gauging the capacity of forests to sequester carbon. This research introduces a novel approach for estimating FCS by integrating multiple data sources, such as Sentinel-1 (S1) radar imagery, optical images from Sentinel-2 (S2) and Landsat 8 (L8), digital elevation modeling (DEM), and inventory data used in forest management and planning (FMP). Additionally, the estimation of FCS incorporates four key ecological features, including forest composition, primary tree species, humus thickness, and slope direction, to improve the accuracy of the estimation. Subsequently, insignificant features were eliminated using Lasso and recursive feature elimination (RFE) feature selection techniques. Three machine learning (ML) models were employed to estimate FCS: XGBoost, random forest (RF), and LightGBM. The results show that the inclusion of ecological information features improves the performance of the models. Among the models, LightGBM achieved superior performance (R² = 0.78, mean squared error (MSE) = 0.85, root mean squared error (RMSE) = 0.92, mean absolute error (MAE) = 0.58, relative RMSE (rRMSE) = 41.37%, and mean absolute percentage error (MAPE) = 30.72%), outperforming RF (R² = 0.76, MSE = 0.93, RMSE = 0.97, MAE = 0.60, rRMSE = 43.42%, and MAPE = 30.85%) and XGBoost (R² = 0.77, MSE = 0.90, RMSE = 0.95, MAE = 0.61, rRMSE = 42.66%, and MAPE = 34.61%). Full article

The paper reviews the patent descriptions of methods for obtaining humic substances and the procedures used in their industrial production. Selected humus substances, obtained using three different methods, were also examined. In the first one, humic substances were obtained due to the hydrolytic-oxidative decomposition of lignosulfonate. The second one consists of alkaline extraction from brown coal. According to the third, humus substances were extracted from digested sewage sludge. In the obtained humus substances, molecular composition, inorganic impurities, IR spectrum, gravimetric analysis, and the % shares of fulvic and humic acids were determined. The physico-chemical properties of the tested substances were also assessed. Based on the study’s results, the advantages and disadvantages of the obtained humus substances were determined, and methods for their modification to improve utility values were provided. Research on humic substances is a very important issue, especially concerning improving soil management and developing sustainable agricultural practices. They are key in improving soil structure and increasing its capacity to retain water and essential nutrients such as N, P, K, S, Ca, and Mg. In addition, humic substances are an important store of carbon in soils, which is important in the context of climate change. Full article

In recent decades, there has been a significant decrease in humus resources in the terrestrial environment, including in agriculturally used soils, due to increased mineralisation of soil organic matter (SOM). Using composting as a method for recycling lignin-cellulosic biomass, the application of innovative microbial stimulation seems reasonable for obtaining the most useful product. The aim of this study was the qualitative and quantitative analysis of humic acids during the composting of exogenous organic matter (EOM) of energy willow biomass (WBC) and biodegradable municipal waste (MSWC). Samples were collected at different maturity stages, and the following determinations were performed: total organic carbon (TOC) and total nitrogen (TN), carbon of fulvic (CFA) and humic (CHA) acids, carbon of residual fraction (CR), the elemental composition of humic acids, humification index (HR₁), and ω (oxidation) ratios. Results indicated the direction and intensity of biotransformation processes were determined by the availability of nitrogen compounds. The innovative use of microbial preparation has resulted in a more useful final product. Inoculation of lignocellulosic substrates stimulated the synthesis of humic acids, and the decomposition of the CR fraction, as well as HR₁ and ω ratios, may be used to assess the recycling efficiency. Full article