Search Results (432)

Agriculture is one of the most important sectors of the global economy, but it increasingly faces sustainability challenges in meeting rising food demands. The intensive use of mineral fertilizers not only improves yields, but also causes negative environmental impacts such as increasing greenhouse gas emissions, water eutrophication, and soil degradation. To develop more sustainable solutions, the focus is on organic fertilizers, which are produced using waste and biostimulants such as amino acids. The aim of this study was to develop and characterize liquid nitrogen–calcium–magnesium fertilizers produced by decomposing dolomite with nitric acid followed by further processing and to enrich them with a powdered amino acid concentrate Naturamin-WSP and liquid extracts from digestate, a by-product of biogas production. Nutrient-rich extracts were obtained using water and potassium hydroxide solutions, with the latter proving more effective by yielding a higher organic carbon content (4495 ± 0.52 mg/L) and humic substances, which can improve soil structure. The produced fertilizers demonstrated favourable physical properties, including appropriate viscosity and density, as well as low crystallization temperatures (eutectic points from –3 to –34 °C), which are essential for storage and application in cold climates. These properties were achieved by adjusting the content of nitrogenous compounds and bioactive extracts. The results of the study show that liquid fertilizers enriched with organic matter can be an effective and more environmentally friendly alternative to mineral fertilizers, contributing to the development of the circular economy and sustainable agriculture. Full article

This article presents a review of several non-exclusive pathways for the sequestration of soil organic carbon, which can be classified into two large classical groups: the modification of plant and microbial macromolecules and the abiotic and microbial neoformation of humic substances. Classical studies have established a causal relationship between aromatic structures and the stability of soil humus (traditional hypotheses regarding lignin and aromatic microbial metabolites as primary precursors for soil organic matter). However, further evidence has emerged that underscores the significance of humification mechanisms based solely on aliphatics. The precursors may be carbohydrates, which may be transformed by the effects of fire or catalytic dehydration reactions in soil. Furthermore, humic-type structures may be formed through the condensation of unsaturated fatty acids or the alteration of aliphatic biomacromolecules, such as cutins, suberins, and non-hydrolysable plant polyesters. In addition to the intrinsic value of understanding the potential for carbon sequestration in diverse soil types, biogeochemical models of the carbon cycle necessitate the assessment of the total quantity, nature, provenance, and resilience of the sequestered organic matter. This emphasises the necessity of applying specific techniques to gain insights into their molecular structures. The application of appropriate analytical techniques to soil organic matter, including sequential chemolysis or thermal degradation combined with isotopic analysis and high-resolution mass spectrometry, derivative spectroscopy (visible and infrared), or ¹³C magnetic resonance after selective degradation, enables the simultaneous assessment of the concurrent biophysicochemical stabilisation mechanisms of C in soils. Full article

Humic acid (HA), a major component of soil organic matter, is a naturally occurring macromolecule formed through the decomposition of plant and microbial residues. Its molecular structure comprises functional groups such as carboxyl, phenolic, hydroxyl, and carbonyl functional groups, which enable HA to interact with soil particles, nutrients, and biological systems. These interactions significantly contribute to soil fertility and overall plant productivity. Functionally, HA enhances soil health by increasing cation exchange capacity, improving water retention, and promoting the formation and stabilization of soil aggregates. In addition to its role in soil conditioning, HA is essential in mitigating plant stress. It achieves this by modulating antioxidant enzyme activity, stabilizing cellular membranes, and alleviating the adverse effects of abiotic stressors such as salinity, drought, and heavy metal toxicity. This review highlights the structural characteristics of HA, its structure-based functions, and the mechanisms involved in plant stress alleviation. Additionally, we explore how HA can be modified through physical, chemical, and biological approaches to enhance its agronomic performance. These modifications are designed to improve HA agronomic efficiency by increasing nutrient bioavailability, reducing environmental losses through minimized leaching and volatilization, and supporting sustainable agricultural practices. Overall, this review underscores the multifaceted roles of HA in promoting plant resilience to environmental stress, highlighting its potential as a key agent in the development of sustainable and eco-friendly crop production systems. Full article

The purpose of this research was to determine the properties of humic acids isolated from soil samples taken from a 40-year static experiment—the experimental factors were fertilization with manure (30 t ha⁻¹; FYM) and nitrogen at rates of 40, 60 and 120 t ha⁻¹. From the soil samples (Luvisol), humic acids (HAs) were extracted and the following were determined: elemental composition, hydrophilic and hydrophobic properties and spectrometric properties in the UV–VIS and IR range. The HAs of the soil fertilized with manure and N compared to the HAs of the soil fertilized with N (without manure) were characterized by a higher degree of aliphaticity and, consequently, a higher share of hydrophilic fractions and lower values of internal oxidation. Based on the spectrometric parameters, it was indicated that the HA particles of the manure-fertilized soil are characterized by a higher share of undecomposed lignin fragments, a lower degree of humification and at the same time, a higher susceptibility to oxidation. The obtained relationships showed that the aromaticity and hydrophobicity of the HA molecules of the manure-fertilized soil can be increased at certain N doses (60 and 120 t ha⁻¹), which is particularly important in terms of the role that humic substances play in carbon sequestration. Full article

Background: Soil degradation and nutrient depletion critically impact pecan (Carya illinoinensis) production, reducing yield and soil fertility. Colloidal nutrition, a novel approach involving nano-scale nutrient formulations, could offer potential for soil restoration. Aim: This study aimed to assess the impact of colloidal nutrition on key physical, chemical, and biological soil health parameters in pecan tree cultivation. Methods: Soil from two orchards with 30-year-old pecan trees was used where different nutrition treatments were applied: conventional and colloidal. The variables considered included physical, chemical, and biological properties for the assessment of soil health indicators. Results: The colloidal treatment showed low salinity (2020: 2.04; 2021: 0.88 dS/m) and higher levels of humic acids (1.52 g C/100 g soil), available water depth (2020: 305.11, 2021: 350.00 m³/ha), and soil organic matter (2020: 2.10%; 2021: 2.11%). Furthermore, 6 of the 17 phytopathogens that were examined were not detected in the colloidal treatment. Conclusions: This study enhanced our understanding of the improvements that colloidal treatment could potentially provide to the physical, chemical, and biological aspects of soil health in pecan orchards. Full article

Agricultural greenhouse gas emissions continue to rise year after year, contributing significantly to global warming—an escalating crisis that demands urgent attention. In order to address this issue, it is crucial to investigate the relationship between greenhouse gas emissions from farmland and crop yield and quality through comprehensive regulation of the soil micro-environment by inputting water, fertilizer, gas, and heat. Therefore, we conducted field experiments in 2024 to examine the effects of different water, fertilizer, gas, and heat conditions on the yield, quality, greenhouse gas emissions, net global warming potential (NGWP), and greenhouse gas emission intensity (GHGI) of processing tomatoes in Xinjiang, China. This study established two irrigation water temperatures (T0: the local irrigation water temperature, approximately 10–15 °C; and T1: warming irrigation, 20–25 °C), two humic acid application rates (H0: 0% and H1: 0.5%, % as a percentage of total fertilizer application), and three aeration methods (A0: no aeration, A1: Venturi aerated, and A2: micro–nano aerated) during the growth period. The results showed that the number of fruits per hectare (NP), vitamin C (VC) content, titratable acidity and lycopene content were all significantly increased with increasing temperature, application of 0.5% humic acid, and aeration. Warming has little effect on GHGI, while humic acid application and aeration have significant and extremely significant effects on GHGI. The GHGI of humic acid treatment was 7.70% lower than that of H0, and the GHGI of micro–nano aeration and Venturi aeration treatment was 18.95% and 6.85% lower than that of A0, respectively. We employed a comprehensive evaluation model that focused on overall differences to assess yield, quality, economic benefits, and environmental impact (GHGI, global warming potential). The optimal strategy identified comprised 20–25 °C irrigation, micro–nano aeration, and 0.5% humic acid, which collectively achieved the highest scores in yield, quality, and emission reduction. This study establishes a theoretical and technical foundation for the sustainable and efficient production of tomatoes in the arid regions of Northern Xinjiang. Full article

Integrated soil fertility management is essential for improving soil productivity, rice yield, and nitrogen use efficiency (NUE). This study investigated the combined effects of the chemical fertilizer rate, humic acid (HA), and flue gas desulfurization gypsum (FG) on the soil chemical properties, rice yield, NUE, and nitrogen agronomic efficiency (NAE) in acidic paddy soil. The following three factors were evaluated: (1) fertilization based on farmer practices and rice nutrient requirements; (2) HA at 0 and 975 kg ha⁻¹; and (3) FG at 0, 23, and 636 kg ha⁻¹. Fertilization based on rice requirements reduced the nitrogen (N) input by 14.5% compared to farmer practices while still maintaining similar grain yields. Under farmer practice, HA enhanced total N content, cation exchange capacity (CEC), rice yield, NUE, and NAE. HA with FG (636 kg ha⁻¹) increased total organic carbon (TOC) levels, total N levels, and exchangeable ammonium nitrogen (NH₄-N), but decreased the yield. In contrast, HA combined with FG at 23 kg ha⁻¹ enhanced the soil exchangeable Ca and S levels, as well as resulting in a high rice yield (7.7 t ha⁻¹), NUE (39%), and NAE (32 kg kg⁻¹). The findings suggest that to maintain farmer fertilization practices while improving soil properties and rice yield, HA should be applied with FG (23 kg ha⁻¹). Full article

High pH, ${\mathrm{Na}}^{+}$, and $({\mathrm{CO}}_3^{2-}+{\mathrm{HCO}}_3^{-}$) are the primary characteristics of soda saline–alkali soil. Current strategies for ameliorating soda saline–alkali soil often involve the combined use of cow manure and maize straw, the addition of biochar (BC), and the inoculation of Bacillus subtilis (BS). In this study, B. subtilis-loaded biochar (BSC) was prepared using an adsorption technique. An incubation experiment was conducted. The treatments were as follows: soda saline–alkali soil amended with maize straw and cow manure (T₁), which was used as a control; T₁ supplemented with earthworms (T₂); and T₂ supplemented with BS (T₃), BC (T₄), or BSC (T₅). After a 60-day incubation, T₅ showed the most significant reduction in pH, ESP, and (${\mathrm{H}\mathrm{C}\mathrm{O}}_3^{-}$ + ${\mathrm{C}\mathrm{O}}_3^{2-}$) concentrations, with reductions of 0.24 units, 3.26%, and 120 mg kg⁻¹, respectively, compared to the T₁ treatment. The content of soil humic acid, available potassium, and available nitrogen and the activities of β-glucosidase and urease were highest in T₅, increasing by 33.5%, 70.1%, 26.1%, 19.0%, and 17.9%, respectively. Microbial sequencing analysis revealed that the Bacillus abundance in T₃ was highest during the first 45 days (2.51–3.65%), while the Bacillus abundance in T₅ peaked at 3.22% after the 60-day incubation. The soil that was cultivated for 60 days in the experiments was then used for planting alfalfa. T₅ showed the highest alfalfa aboveground biomass and peroxidase, increasing by 30.1% and 73.1%, respectively, compared with T₁. This study demonstrated that loading onto biochar is beneficial for the survival of B. subtilis in soda saline–alkali soil. When traditional organic materials are used, the combination of earthworms and B. subtilis-loaded biochar significantly alleviates the constraints of soda saline–alkali soil. Full article

Intensive industrial activities have led to severe polycyclic aromatic hydrocarbon (PAH) contamination of adjacent lands. Remediating such contaminated soil is crucial for maintaining long-term ecological health and sustainable development. This study systematically assessed the performance of a microwave-activated persulfate (MW/PS) oxidation method in remediating pyrene-contaminated soil. Under conditions of 80 °C and a persulfate concentration of 23.8 mg/g, this system achieved 85.3% pyrene degradation within 30 min, significantly outperforming both single microwave and thermal-activated persulfate (TH/PS) systems. Key factors influencing the oxidation efficiency included the temperature, persulfate and pyrene concentrations, moisture, and humic acid content. An electron paramagnetic resonance analysis confirmed the generation of reactive oxygen species, including ^•OH, SO₄^•− and ¹O₂, in the MW/PS system, while O₂^•− was exclusive to the TH/PS system. However, further experiments revealed that ¹O₂ had a negligible impact on pyrene degradation, suggesting that its role may have been overestimated in previous studies. The high MW/PS performance was attributed to the synergistic effects of both thermal and non-thermal (molecular vibration) mechanisms. Based on these findings, the pathways of pyrene degradation were proposed, with intermediate products exhibiting reduced toxicity and bioaccumulation potential. This study provides valuable insights into the application of MW/PS systems in the remediation of PAH-contaminated soils. Full article

Soil nitrate nitrogen (NO₃⁻-N) is a key indicator of agricultural non-point source pollution. The ultraviolet (UV) dual-wavelength method is widely used for NO₃⁻-N detection, but interference from complex soil organic matter affects its accuracy. This study investigated how organic matter influences NO₃⁻-N detection by optimizing UV dual-wavelength combinations. Density functional theory (DFT) calculations showed slight spectral broadening of fulvic and humic acids in the presence of NO₃⁻-N under UV spectrum. Standard solutions and soil samples were used to compare the detection performance of different wavelength pairs. The findings indicated that the dual-wavelength combination of 235 nm/275 nm is optimal rather than 220 nm/275 nm for measuring soil samples at NO₃⁻-N concentrations exceeding 5 mg·L⁻¹. The 235/275 nm method gave an average calibration coefficient of 1.57. Compared to the national standard and flow analysis methods, the average relative errors were 19.7% and 22.3% (p < 0.001), respectively, indicating its suitability for practical soil applications. These results demonstrate the method’s potential for rapid and accurate NO₃⁻-N detection in real soil samples, supporting its application in environmental monitoring and agricultural management. Full article

The structural complexity and variability of dissolved organic matter (DOM) significantly affect its binding capacity with heavy metals (HMs). This study evaluated the remediation efficacy of biochar (BC) and humic acid (HA) on Mn- and Cu-contaminated soils using four maize pot treatments: 3% BC (YB3), 6% BC (YB6), 3% BC + 1% HA (YB3H), and 6% BC + 1% HA (YB6H). The results showed that compared to the control (Y), Results showed Mn and Cu concentrations in rhizosphere soil decreased by 11.08–17.76%, while DOM content increased by 44.2–103.83%. BC enhanced DOM aromaticity and humification, further intensified by HA, leading to a more complex and stable DOM structure. PARAFAC identified four DOM components in BC (BC-DOM): C1 (fulvic-like), C2/C3 (humic-like), and C4 (protein-like), and in BC + HA (BC + H-DOM), an enhanced structural complexity with additional aromatic C–H groups was observed. 2D-COS analysis revealed that in BC-DOM, polysaccharides primarily interacted with Mn and Cu, followed by carboxylic acids and phenolic hydroxyl groups, but in BC + H-DOM, aromatic C–H groups preferentially bound Cu before polysaccharides, showing weaker affinity for Mn. These results elucidate the DOM-mediated immobilization mechanisms of BC and HA for HMs, offering insights for soil remediation and carbon sequestration strategies. Full article

Cadmium is a non-essential element for proper plant growth and development and is highly toxic to humans and animals, in part because it inters with calcium-dependent processes in living organisms. For this reason, a study was conducted to assess the potential for producing maize (Zea mays) biomass in cadmium-contaminated soil for energy purposes. The energy potential of Zea mays was evaluated by determining the heat of combustion (Q), heating value (Hv), and the amount of energy produced from the biomass. Starch, compost, fermented bark, humic acids, molecular sieve, zeolite, sepiolite, expanded clay, and calcium carbonate were assessed as substances supporting biomass production from Zea mays. The accumulation and redistribution of cadmium in the plant were also investigated. The study was conducted in a vegetation hall as part of a pot experiment. Zea mays was grown in uncontaminated soil and in soil contaminated with 15 mg Cd²⁺ kg⁻¹. A strong toxic effect of cadmium on the cultivated plants was observed, causing a 62% reduction in the biomass of aerial parts and 61% in the roots. However, it did not alter the heat of combustion and heating value of the aerial part biomass, which were 18.55 and 14.98 MJ kg⁻¹ d.m., respectively. Of the nine substances tested to support biomass production, only four (molecular sieve, compost, HumiAgra, and expanded clay) increased the yield of Zea mays grown in cadmium-contaminated soil. The molecular sieve increased aerial part biomass production by 74%, compost by 67%, expanded clay by 19%, and HumiAgra by 15%, but none of these substances completely eliminated the toxic effects of cadmium on the plant. At the same time, the bioaccumulation factor (BAF) of cadmium was higher in the roots (0.21–0.23) than in the aerial parts (0.04–0.03), with the roots showing greater bioaccumulation. Full article

The interactions between dissolved organic matter (DOM) and agrochemicals (e.g., neonicotinoid insecticides, NIs) govern the distribution, migration, and potential environmental risks of agrochemicals. However, the long-term effects of agricultural management on the DOM components and structure, as well as their further influences on the interactions between DOM and agrochemicals, remain unclear. Here, spectroscopic techniques, including Fourier transform infrared spectroscopy, two-dimensional correlation spectroscopy, and three-dimensional excitation–emission matrix fluorescence spectroscopy were employed to delve into the interaction mechanism between the DOM from citrus orchards with distinct cultivation ages (10, 30, and 50 years) and imidacloprid, which is a type of pesticide widely used in agricultural production. The findings revealed that the composition and structure of soil DOM significantly change with increasing cultivation age, characterized by an increase in humic substances and the emergence of new organic components, indicating complex biodegradation and chemical transformation processes of soil organic matter. Imidacloprid primarily interacts with fulvic acid-like fractions of DOM, and its binding affinity decreases with increasing cultivation age. Additionally, the interactions of protein-like fractions with imidacloprid occur after humic-like fractions, suggesting differential binding behaviors among DOM fractions. These results demonstrate that cultivation age significantly influences the composition and structural characteristics of soil DOM in citrus orchards, subsequently affecting its sorption capacity to imidacloprid. This study enhances the understanding of imidacloprid’s environmental behavior and provides theoretical support for the environmental risk management of neonicotinoid pesticides. Full article

Understanding soil properties that govern physicochemical and biological processes is essential for achieving high crop quality and yield. Organic matter is an important element of soil fertility and fertility in vegetable cultivation. In the process of decomposition of organic matter in the soil, humus of various quality is formed. The quality of humus depends on the content of individual acids (fulvic, humic and hymatomalanic acids) in it, which can affect the binding–chelation of heavy metals, limiting their availability to plants. The conducted studies determined the effect of adding organic matter (high peat, brown coal and wheat straw) to mineral soil on nickel detoxification in radish, its yield, nitrogen management and chloroplast pigments. The studies were conducted for three years in a greenhouse in a container system. The tested substrates were contaminated with nickel in the amount of 50, 75 and 100 mg dm⁻³. It was found that introducing organic matter into mineral soil can affect the reduction as well as the increase in nickel content in edible parts of radish. The type of organic material introduced into mineral soil as a source of organic matter has a significant impact on nickel content in radish. It was shown that nitrate reductase activity (NR) depends to a large extent on the substrate in which the plants are grown as well as on the applied dose of nickel. A similar relationship was demonstrated in the case of changes in the level of chloroplast pigments (chlorophyll a, chlorophyll b and carotenoids). Full article

In western Jilin Province, China, the presence of soda saline–alkali soil poses a significant threat to the raising of rice seedlings due to its harsh soil properties. The scarcity of suitable seedling-raising soil resources has become increasingly pronounced. A short-term soil-improvement experiment was conducted using the original saline–alkali soil sourced from the rice-growing region of Jilin Province, followed by the rice-seedling-raising test in the improved soil to identify an effective soil-improvement strategy. Four distinct treatments were established: no amendment (JCK); gypsum and straw (JCW); gypsum, straw, and sulfuric acid (JCWH); and gypsum, straw, and chemical fertilizer (JCWF). The effects of these amendment treatments on the soil physicochemical properties (pH, electrical conductivity, exchangeable sodium, total alkalinity) were evaluated, as well as the effects on soil organic carbon (SOC) and its components including humic acid carbon (HAC), and fulvic acid carbon (FAC). The results indicated that, compared to the control group, all amendment treatments effectively reduced the average soil pH by 0.53 to 0.79 units and decreased exchangeable sodium by 56.7% to 74.8%. Furthermore, the average SOC, HAC, and FAC increased by 48.3%, 89.4%, and 56.0%, respectively. Among the treatments, JCWH proved to be the most effective. After two years of improvement, the rice seedlings in the JCWH-treated soil exhibited the highest dry weight and plant height, surpassing those grown in the farmer’s seedling-raising soil. The scheme of utilizing soda saline–alkali soil for rice-seedling raising, following a short-term improvement treatment with corn straw, gypsum, and sulfuric acid (JCWH), provides technical support and an effective solution to the soil scarcity issue faced by seedling farmers in saline–alkali regions. Full article