Search Results (82)

This study is Part II of a five-year (2018–2022) field trial in western Portugal evaluating the effects of three microbial biofertilizers—Mycoshell^® (Glomus spp. + humic/fulvic acids), Kiplant iNmass^® (Azospirillum brasilense, Bacillus megaterium, Saccharomyces cerevisiae), and Kiplant All-Grip^® (Bacillus megaterium, Pseudomonas spp.)—applied at different dosages alongside two mineral fertilizer regimes, T100 (full dose) and T70 (70% of T100, alone or combined with biofertilizers), on the physiological performance of ‘Gala Redlum’ apple trees. Part I had shown that Myc4 (Mycoshell^®, 4 tablets/tree), iNM6, and iNM12 (Kiplant iNmass^®, 6 and L ha⁻¹, respectively) consistently enhanced fruit growth, yield, and selected quality traits. While Part I showed clear agronomic gains, Part II demonstrates that these improvements occurred without significant alterations in seasonal photosynthetic performance, canopy reflectance, or chlorophyll fluorescence parameters over five years, highlighting the contrast between observed yield improvements and physiological stability. Seasonal monitoring of physiological traits—including specific leaf area (SLA), chlorophyll content index (CCI), gas exchange (A_n, g_s, E, C_i), spectral indices (NDVI, OSAVI, SIPI, GM2), and chlorophyll fluorescence (OJIP). It is clear that physiological values remained largely stable across biofertilizer treatments and years. Importantly, this stability was maintained even under a 30% reduction in mineral fertilizer (T70), indicating that specific microbial biofertilizers can sustain physiological resilience under reduced nutrient inputs, thereby providing a physiological basis for the yield-enhancing effects observed and supporting their integration into fertilizer reduction strategies in Mediterranean orchards. Full article

Contamination with cadmium (Cd²⁺) poses a severe threat to the soil environment due to its toxic effect on bacteria, being of key importance to soil fertility and plant health. The present study aimed to evaluate the effect of a humic preparation, Humus Active (HA), on the structure, diversity, and functional potential of soil bacteria under conditions of cadmium stress during Zea mays cultivation. A model study was conducted to analyze the response of bacteria to soil contamination with 60 mg Cd kg⁻¹ under conditions of soil fertilization with humic acid at doses of 2 g (HA2) and 4 g (HA4) kg⁻¹ of soil. Microbiological analyses were carried out with both culture and non-culture (16S rRNA gene amplicon sequencing method) methods. Bacteria function prediction was also performed using FAPROTAX software. The study results demonstrated that Cd caused a 92% reduction in Zea mays biomass and a significant decrease (by 52%) in the abundance of organotrophic bacteria. The NGS analysis showed that it also reduced the population of the Neobacillus bacteria in the soil (by 50%), simultaneously causing an over twofold increase in the population of the Nocardioides genus bacteria. The application of HA (particularly in the HA4 dose) substantially mitigated Cd phytotoxicity. In the Cd-contaminated soil, HA4 stimulated the growth of culturable actinobacteria. The soil bacteria community was predominated by chemoheterotrophic bacteria and the nitrogen cycle bacteria, driven by tolerant, Cd²⁺-resistant bacteria from the following genera: Bacillus, Nocardioides, and Arthrobacter. The study results enable concluding that even though Humus Active does not restore the original microbiome structure, it promotes the development of a new stress-resistant bacterial community exhibiting high bioremediating potential, thereby directly translating into improved plant condition. Subsequently, humic acids provide an innovative approach that not only extends knowledge about the mechanisms behind bacterial resistance but also enables developing practical methods for diminishing cadmium mobility in the soil. Full article

Elevated ambient temperature is the primary abiotic element that possibly diminishes production and economic profitability in the chicken industry. The current study evaluated the role of dietary addition of Spirulina platensis (SP) and humic acid (HA) in mitigating the effects of acute cyclic heat stress on growth performance, meat quality, immune status, and intestinal morphology in broiler chickens. Five hundred three-day-old male Ross 308 broiler chicks (average body weight 101.42 ± 3.22 g) were assigned to five experimental groups, each with 10 replicates (10 birds per replicate). The chicks in the first group received a basal diet and were maintained in thermoneutral conditions (NEG CON). The remaining four groups received either a basal diet only (POS CON) or a basal diet added with SP (2 g/kg of feed; SP group), HA (5 g/kg of feed; HA group), or a mix of SP and HA by the same doses (SP+HA group). The four groups were exposed to acute cyclic heat stress (36 °C ± 2 °C) from the 22nd to the 25th day of age for 6 h/day. The HA group showed increased body weight and body weight gain, and improved feed conversion ratio compared with other groups (p < 0.001). The addition of SP and HA improved sensory characteristics and reduced the dripping losses of the breast muscles. The phagocytic % and phagocytic index were higher in the SP group compared with the NEG and POS CON. The serum levels of triiodothyronine and thyroxine were higher in the HA and SP+HA groups compared with the control groups. The serum concentrations of interleukin-10, complement 3, and lysozymes, as well as the liver concentrations of HSP90A and HSP90B, were higher in the SP, HA, and SP+HA groups compared with the NEG and POS CON. The duodenal villous height and width were significantly greater in the HA group compared to the other groups. Spleen histomorphology in the SP and HA groups was better than that of the POS CON. The HA group showed up-regulation in the immune expression of clusters of differentiation 3 (CD3) and 20 (CD20) proteins in the spleen tissues. In conclusion, both HA and SP, individually but not in combination, mitigated the detrimental effects of acute cyclic heat stress on growth and immunity. Humic acid addition provided the most pronounced improvements in performance and intestinal morphology. Further studies are warranted to clarify the biochemical interactions between SP and HA under different stress intensities. Full article

The co-occurrence of graphene-based nanomaterials such as reduced graphene oxide (RGO) and triclosan in agricultural soils is an emerging concern. This study investigates the impact of RGO on the formation and characteristics of bound residues (BRs) of triclosan in paddy soil using ¹⁴C-isotope tracing and LC-QTOF-MS. Results demonstrate that RGO significantly enhances the accumulation of triclosan BR in a dose-dependent manner, with the highest concentration (1.19 mg kg^–1; 57.0%) observed at 500 mg kg^–1 RGO. While the BR is primarily associated with the humin fraction (>63.8%), RGO shifts the distribution of ¹⁴C-triclosan, enhancing its retention in humin by 1.89–7.59% and in humic acid by 20.7–52.1%. RGO may increase the sequestered BR (8.8–24.7%), and it enhances the covalent BR of triclosan by increasing the proportions of both ether- (3.78–4.58%) and ester-bound (22.8–39.5%) forms. Metabolite analysis reveals limited transformation of triclosan (0.057–0.082 mg kg^–1) in BRs, with carboxylated derivatives identified as minor products. The findings indicate that RGO enhances the persistence of triclosan BRs, which may be attributed to strong adsorption and microbial inhibition, raising concerns about their potential future remobilization and entry into the food chain. This underscores the need to assess the ecological risks of nanomaterial co-contamination for soil health and sustainable agriculture. Full article

Biofertilizers are sustainable alternatives to mineral fertilizers in perennial crops, reducing the need for mineral inputs. This five-year field study evaluated three biofertilizers—Mycoshell^® (Glomus spp. + humic/fulvic acids), Kiplant iNmass^® (Azospirillum brasilense, Bacillus megaterium, and Saccharomyces cerevisiae), and Kiplant All-Grip^® (Bacillus megaterium and Pseudomonas spp.)—at different dosages alongside two mineral fertilizer regimes, T100 (full recommended dose) and T70 (70% of T100, alone or combined with biofertilizers), in an apple orchard under Mediterranean conditions. Biofertilizers maintained or increased soil nutrient availability by 5–15% and leaf N, P, K, Mg, and Zn concentrations by 5–12% compared with T100. Trees under biofertilizers, particularly Myc2 and Myc4, exhibited greater shoot growth (up to 30.4 m/year), trunk cross-sectional area (TCSA: 11.9 cm² in 2022), and canopy volume (2.21 m³), representing 10–20% increases. Selected biofertilizer treatments produced 6–7.5 kg/tree, 130–145 g average fruit weight, 66–74 mm diameter, 13.9–18.7 °Brix, and 13–18% dry matter, maintaining >90% of yield and fruit size relative to T100, with more balanced medium- and large-sized fruit distribution. Principal Component Analysis explained 66–72% of soil and leaf nutrient variance, confirming their multivariate impact. Overall, biofertilizers applied at recommended doses and timings can partially replace mineral fertilizers, sustaining productivity and quality, enhancing nutrient availability, and supporting long-term orchard sustainability. While climate remains the main driver of annual production, these findings provide evidence for integrating biofertilizers into environmentally friendly fertilization strategies. Full article

To explore strategies for the safe utilization of farmland co-contaminated with cadmium (Cd) and lead (Pb), this field study systematically evaluated the impacts of humic acid (HA) and potassium fulvate (PF) at different application rates (0, 1500, 3000, and 4500 kg·ha⁻¹) on the growth, yield, and translocation of Cd and Pb within the soil–plant system of maize (Zea mays L.). The results showed that while HA and PF did not significantly alter total soil Cd and Pb concentrations, they markedly reduced their bioavailable fractions. This mitigation of heavy metal phytotoxicity significantly promoted maize growth and yield, with the high-dose HA treatment increasing yield by a maximum of 32.9%. Both amendments dose-dependently decreased Cd and Pb concentrations, bioconcentration factors (BCF), and translocation factors (TF) in all maize tissues, particularly in the grains. At equivalent application rates, PF was slightly more effective than HA in reducing heavy metal concentrations in the grains. Notably, a significant positive correlation was observed between Cd and Pb concentrations across all plant parts, confirming a synergistic accumulation and translocation mechanism. This synergy provides a physiological explanation for the broad-spectrum immobilization efficacy of these humic substances. In conclusion, applying HA and PF presents a dual-benefit strategy for increasing yield and reducing risks in Cd- and Pb-contaminated farmlands. This study proposes a differentiated application approach: PF is the preferred option when ensuring food-grade safety is the primary goal, whereas high-dose HA is more advantageous for maximizing yield in soils with low-to-moderate contamination risk. 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

The Miradero Water Treatment Plant (MWTP) in Mayagüez, Puerto Rico, uses sodium hypochlorite (SH) as a disinfectant. However, SH reacts with humic substances present in surface water, forming disinfection by-products (DBPs) regulated by the U.S. EPA. This study evaluated whether chitosan, a biopolymer with known bactericidal properties, could reduce chlorine demand and improve disinfection. Chitosan, with a 75% degree of deacetylation and a molecular weight of 460 kDa, was solubilized in four acids (acetic, citric, hydrochloric, and L-ascorbic) and tested under two turbidity ranges (236.0 and 2556 NTU). Chlorine demand curves were generated, and coliform presence–absence (P–A) tests were performed to assess bactericidal effects. Results showed that chitosan-treated samples achieved disinfection at the breakpoint with lower SH doses. For water with a turbidity of 236.0 NTU, all chitosan-acid solutions reached the breakpoint at 3.60 mg/L of SH. At 2556 NTU, three solutions required 4.20 mg/L SH, while hydrochloric acid–chitosan required only 3.60 mg/L. All chitosan-treated samples tested negative for coliforms, while controls treated with SH alone tested positive. These findings demonstrate that chitosan enhances bacterial removal and reduces chlorine demand, potentially lowering DBP formation in water treatment. 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

Iron contamination negatively affects how plants grow and develop, and it has an analogous influence on the health of other organisms. The use of different types of organic soil amendments can be a strategy to reduce the effects of excess iron stress and limit its assimilation by plants. The aim of this experiment was to investigate the possibility of using organic material in the form of humic acids (HAs) to reduce the influence of iron contamination on the content of trace elements (TEs) in the soil. The content of iron in the soil increased linearly (by 14%) as more iron was added. The addition of humic acids to the soil also promoted an increase in soil Fe content (by 12%) in comparison to the series without HAs. The highest dose of iron resulted in a decrease in Cd (by 49%), Pb (by 29%), Cr (by 13%), and Zn (by 10%) and an increase in Mn (by 6%), Cu (by 16%), and Co (by 33%) in the soil in comparison to the object without Fe. However, the first dose of iron increased the lead content, and the first and second dose of Fe also increased the Zn content in the soil. The nickel content in the soil also increased to 500 mg Fe kg⁻¹ of soil. Thereafter, a decline was observed in the nickel content. The addition of organic material had a different influence on the content of individual TEs in the iron-contaminated soils. The most evident constraining impact of HAs pertained to the level of Cd (reducing it by 14%) and Zn in the soil (only for two of its doses). The content of other TEs in the soil after the addition of organic material was found to be higher than in the series without HAs. This was especially evident for elements such as cobalt (Co) and lead (Pb). Full article

The influence of different mineral and organic fertiliser applications on the soil organic matter (SOM) content and quality was monitored in long-term field trials. We used long-term field experiments (27 years) with a crop rotation of potatoes, winter wheat, and spring barley on cambisol soil. The treatments were as follows: an unfertilised control (Cont), sewage sludge in normal and triple doses (SS1 and SS3, respectively), farmyard manure (F1) in a conventional dose, a half dose of farmyard manure with a half dose of mineral nitrogen (F1/2 + N1/2), straw with mineral nitrogen fertiliser (N + St), and mineral nitrogen without any organic fertiliser (N). This study focused on the ability of the total and easily extractable glomalin-related soil protein (T-GRSP and EE-GRSP, respectively) and the water stability of aggregates (WSA) as indicators of long-term SOM quality changes. The results were compared with the content of humic substance fractions and the carbon in humic substances (C_HS), humic acids (C_HA), and fulvic acids (C_FA). The lowest SOM content and quality were observed in the control treatment. The highest overall SOM quality, including the degree of polymerisation (HA) and the GRSP content, was found in the F1 treatment. The organic matter in sewage sludge contributed less to the formation of stable SOM than straw. A significant correlation was found between both the EE-GRSP and the T-GRSP and the content of the C_SOM, C_HS, C_HA, and HA, but not with the C_FA. The influence of fertiliser on the GRSP content was demonstrated. However, no relationship was observed between the WSA and SOM quality, the EE-GRSP, or the T-GRSP content. Full article

The aim of this study was to determine the effect of progressive pig slurry (PS) rates, applied over a 12-year period, on the molecular composition of soil organic matter in a calcareous soil. Annual organic matter rates of PS ranged from 1.0 to 4.8 Mg ha⁻¹. Humic acids (HAs) were extracted from field plots treated with PS, including a control (no PS applied). These HAs were analysed using pyrolysis–gas chromatography–mass spectrometry. The proportions of the 122 major compounds released from the soil HAs indicated that PS stimulated humification processes, with the degree of enhancement depending on the application rate. The applied PS contained a high proportion of aliphatic compounds, but only steroids and triterpenes accumulated in the HA soil fraction, and this was only observed at low PS rates. These results suggest that the application of PS leads to a dose-dependent increase in alkyl compounds, mainly alkanes and olefins. Aromatic compounds also showed a dose-dependent increase, but not in terms of the demethoxylated compounds typical of mature humic substances found in the original soil. Instead, the increase in aromatics was observed in the form of methoxyphenols, suggesting a recent incorporation of lignin derivatives from crop residues into the HA. Full article

The application of oxidation processes, including advanced oxidation, in water treatment is one of the effective methods for eliminating risks associated with the presence of organic substances in water and those formed during chlorination. This article presents the impact of advanced oxidation in the UV + O₃ process on the content and structure of organic substances present in three natural waters with different levels of total organic carbon (TOC). The process was carried out using low-pressure and medium-pressure lamps with an irradiation time of 40 min and ozone doses of 1.5 gO₃/m³ and 5 gO₃/m³. Advanced oxidation, regardless of the type of lamp used or the ozone dose, had the greatest effect on the content of humic acids, which underwent both transformation and mineralization. The use of a low-pressure lamp resulted in an increase in the content of organic substances with the lowest molecular weight (<0.7 kDa), whereas the medium-pressure lamp led to an increase in substances with a molecular weight >1.3 kDa. Regardless of the ozone dose and the type of lamp used, the transformation of organic substances dominated over mineralization, whose efficiency reached a maximum of 44.9% and 38.4% for the low-pressure and medium-pressure lamps, respectively. The degree of organic substance transformation and the efficiency of their removal were directly proportional to the TOC content in the raw water. The use of a low-pressure UV lamp ensured higher process efficiency, which is also associated with lower energy costs. Full article

The present study highlights the possibility of using sewage sludge-derived compost (SSC) or biochar (SSB) as valuable organic amendments. Such utilization of sewage sludge fulfills the principles of a carbon farming and nature-based solution strategy (NBS). This study focused on a detailed analysis of quantitative and qualitative changes in soil C compounds (total carbon—TC, total organic carbon—TOC, humic substances—CHS, labile carbon—LC, and water extractable organic carbon—WEOC), which resulted from the application of SSC or SSB; an assessment of variability in total and available forms of N and S as biogenic components that are integrally related to the organic matter of the amendments used in the experiment; and an indication of the possible relationships between C compounds and available nutrients. The experiment was conducted under greenhouse conditions with terra rosa soil amended with SSC or SSB at different application rates (25, 50, 75, 100% by mass). Soil samples were analyzed for the abovementioned parameters using appropriate analytical methods. Regardless of the organic amendment, the values of tested parameters increased with the applied dose, with the differences being significantly greater in relation to the contents determined for the control soil. In general, the application of SSC was more favorable than SSB, which was manifested by 12–49-fold higher TOC, 6–24-fold higher total N, and 10–41-fold higher total S levels. An exception was found for the content of available sulfur, which was significantly higher in the soil fertilized with biochar. In addition, SSC contributed more humic acid carbon (12.5–24.15 g∙kg⁻¹) and labile carbon (10.34–27.37 g∙kg⁻¹). On the other hand, SSB had a greater effect on fulvic acid carbon levels (2.18–2.75 g∙kg⁻¹), which were comparable to the levels of LC (3.44–6.86 g∙kg⁻¹) and WEOC (2.56–6.28 g∙kg⁻¹). The research results highlighted the validity of processing SS into compost or biochar for further use for agricultural/reclamation purposes. Despite their different impacts on the studied soil properties, both organic amendments are important for maintaining soil health and can play a significant role in carbon farming as NBS practices. The findings allow us to conclude that the strategy of increasing the amount of C through SSC or SSB fertilization is the advisable direction in sustainable soil management. Full article

This research was carried out to determine the effects of potassium humate on the lactation performance and metabolic parameters of dairy cows during the transition period. Potassium humate was added to the concentrate feed at the following levels: (a) control (0%), (b) 0.5%, (c) 1%, (d) 1.5%, and (e) 2% humas, during the dry period from −60 to 0 days until calving. The results indicated that the total milk yield after 305 days was higher in the 0.5% group than in the 2% humic acid group. The average daily milk yield from lactation was also greater in the 0.5% group than in the 2% humic acid group. In terms of metabolic health and blood biochemistry, lymphocytes, neutrophils, monocytes, NEFAs, and BHBA were different among the treatment groups. No effects were detected on the blood physiology parameters of the calves. The IgG concentration in the colostrum and serum of calves on day 1 and 2 were higher in the 0.5% and 1% humic acid groups, respectively, than in the other groups. Overall, adding humic acid, especially at the dose of 0.5%, to the concentrate feed of dairy cows during the dry period resulted in an increased postpartum milk yield for the cows and increased serum IgG in both the cows and calves, with decreased NEFAs on the calving day and decreased postpartum BHBA for cows. Full article