Search Results (58)

The widespread occurrence of emerging mycotoxins (EMs) produced by Fusarium, Aspergillus, and Penicillium species has raised increasing concerns regarding food and feed safety. Mitigation strategies currently applied to control regulated mycotoxins in feed may also be effective in reducing contamination by EMs. This study comparatively evaluated the in vitro adsorption efficacy of two leonardites, eight natural smectites, and two modified clays (organoclays) against EMs produced by Fusarium, Aspergillus, and Penicillium spp. All materials were tested at two inclusion levels (0.1 and 0.5% w/v) under two pH conditions (pH 3 and 7), simulating the gastrointestinal environment of monogastric animals. Adsorption performance was strongly influenced by mycotoxin chemistry, adsorbent type, inclusion rate, and medium pH. Organoclays exhibited the highest and most consistent efficacy, achieving near-complete adsorption of beauvericin (BEA) and enniatins (ENNs) (>98–100%) at 0.1% (w/v), as well as high removal of mycophenolic acid (MYC. A.) and citrinin (CIT) (>90%) across both pH conditions. Natural smectites showed high but more selective adsorption, removing >90% of BEA and ENNs at low inclusion rates, while displaying limited efficacy toward fusaric acid (FA) and patulin (PAT). Leonardites demonstrated intermediate and material-dependent performance; leonardite L1 adsorbed approximately 90% of BEA at 0.1% (w/v), whereas ENN adsorption ranged from ~36% to 80% at the same inclusion rate and exceeded 90% only at higher dosages. None of the tested materials effectively adsorbed patulin (PAT) at pH 7; however, at pH 3, four smectites exhibited partial adsorption, and one trioctahedral smectite achieved more than 90% PAT adsorption under acidic conditions. Overall, organoclays displayed the broadest adsorption spectrum across structurally diverse mycotoxins, while smectites exhibited high selectivity driven by surface charge density and interlayer interactions. Leonardite-based materials showed moderate but highly variable adsorption performance, likely influenced by heterogeneity in humic functional groups and physicochemical properties. These findings highlight the need for tailored adsorbent selection or combined mitigation strategies to achieve effective mycotoxin control in the animal feed industry. Full article

Three organic soil amendments of different origins (chicken manure, fungal biomass obtained through biological fermentation, and a leonardite-based humic acid product) were applied to young chestnut trees, alongside mineral fertilizer, which when applied alone served as the control. During the second year, bud break pattern, photosynthetic activity, leaf carbohydrate concentrations, soil properties, and leaf nutrient content were evaluated across multiple sampling events. Sampling time significantly influenced most measured parameters. The addition of organic amendments accelerated bud break, influenced plant nutrient uptake, and modified soil properties. Notably, soil organic matter increased following chicken manure and fungal biomass applications, available phosphorus decreased under fungal biomass and leonardite-based humic acids (to 14.5 and 12.4 ppm, respectively, compared to 17.5 ppm in the mineral fertilizer control), and soil iron concentrations tripled under leonardite-based humic acids relative to the control. However, no significant effects were observed on photosynthetic performance or leaf carbohydrate concentrations. Discriminant and hierarchical cluster analyses revealed clear differences among amendments, with the humic acid-based product exerting distinct effects. As there are not many data available in the literature on the efficacy of organic amendments in chestnut cultivation, the present results underscore the importance of the site-specific selection of organic amendments, tailored to soil characteristics (in the present trial, an acidic soil) and specific nutritional objectives to optimize tree physiological performance. Full article

The redox activity of natural organic matter (NOM) is crucial for contaminants transformation in soils. Soil micropores (<2.5 nm) have limited accessibility for microorganisms and large NOM molecules; therefore, insoluble organic pollutants and heavy metals trapped in these micropores are usually reached by low molecular weight fractions (LMWF) of NOM. However, the mechanism of spatial electron transfer via electron shuttle of LMWF remains unclear. In this study, we separated low molecular weight fractions (LMWF < 3500 Da and LMWF < 14,000 Da) of Leonardite humic acids (LHA) and measured its acceleration of microbial ferrihydrite reduction. The results show that LMWF, as an electron shuttle, significantly accelerates the reduction in Fe (III), among which 3500-LMWF is the main fraction contributing to the acceleration. Additionally, 3D-EEM shows that quinone content was positively correlated with reduction efficiency, supporting its role as the key functional group. Based on the accelerating experiments, we determined an electron shuttling critical distance of 117.2 nm for LMWF LHA. These findings establish LMWFs as effective natural electron shuttles, providing a theoretical basis for understanding pollutant dynamics in soil micropores. Full article

The application of organic amendments and humic acids (HA) often ameliorates saline soils, but the mechanisms responsible for their positive action have never been fully clarified. HA from four different origins (Elliott soil—EHA, peat—PHA, leonardite—LHA and compost—CHA) and polyacrylic acid (PAA) were characterized by acid–base titrations and ¹H-NMR spectroscopy and tested in laboratory experiments by measuring changes in electric conductivity (EC) and pH following micro-additions of Na₂CO₃ or NaCl. The effective salinity amelioration potential (SAP_eff) of HA, which expresses the amount of Na₂CO₃ neutralized per unit weight of HA at a given pH, was calculated. PAA had the highest capacity of mitigation, corresponding to 49.9 mg Na₂CO₃ g⁻¹, followed by LHA, EHA and PHA, whose SAP_eff values were similar and only slightly lower, and with CHA having the lowest value (25.1 mg Na₂CO₃ g⁻¹ HA). All substances failed to display any effect at constant pH when NaCl was the only salt present. The dissociation of acid groups, when HA become exposed to a more alkaline pH, produces an excess of negative charges that attracts more cations within the diffuse double layer. Because of the slower diffusion of HA and their tendency to aggregate at high ionic strengths, this action reduces the osmolarity of the soil solution and therefore mitigates salinity stress. Full article

Humic substances and beneficial microorganisms are key biostimulants for sustainable agriculture and global food security in the face of climate change. Marine bacteria are emerging as a promising source of plant-beneficial microbes, tapping into a microbial diversity as immense as the oceans themselves. However, their potential, limitations, and mechanisms of action––especially in combination with other biostimulants––remain largely unexplored. In this study, we isolated the Streptomyces sp. LAP3 strain from the giant limpet Scutellastra mexicana. We evaluated the efficacy of the marine bacterium, applied alone or in combination with the humic product Leonardite hydrolate (L), in enhancing tomato performance under field conditions. Treatments included: (1) marine Streptomyces (MS), (2) Leonardite hydrolate (L), (3) both biostimulants (MS + L), and (4) a control (CTRL). We assessed growth, photosynthetic performance, antioxidant responses, and fruit yield and quality. Both biostimulants individually improved plant performance, but their combination had a significant synergistic effect, markedly boosting tomato productivity, thermotolerance, and resilience during a heatwave. Enhanced photosynthetic efficiency and antioxidant enzyme activity were associated with improved agronomic traits. These results highlight the potential of combining Streptomyces sp. LAP3 and Leonardite hydrolate as an eco-friendly strategy to increase crop productivity, strengthen stress resilience, promote sustainable agriculture, and reduce reliance on agrochemicals. Full article

Enhancing the yield and qualitative traits of horticultural crops without further hampering the environment constitutes an urgent challenge that could be addressed by implementing innovative agronomic tools, such as plant biostimulants. This study investigated the effects of three commercial biostimulants—BIO1 (fulvic/humic acids), BIO2 (leonardite-humic acids), and BIO3 (plant-based extracts)—on leaf ecophysiology, yield, and fruit quality in two raspberry cultivars, ‘Autumn Bliss’ (AB) and ‘Zeva’ (Z), grown in an open-field context, to assess their effectiveness in raspberry cultivation. Experimental activities involved two Research Years (RYs), namely, year 2023 (RY 1) and 2024 (RY 2). Leaf parameters such as chlorophyll, flavonols, anthocyanins, and the Nitrogen Balance Index (NBI) were predominantly influenced by the interaction between Treatment, Year and Cultivar factors, indicating context-dependent responses rather than direct biostimulant effects. BIO2 showed a tendency to increase yield (g plant⁻¹) and berry number plant⁻¹, particularly in RY 2 (417.50 g plant⁻¹, +33.93% vs. control). Fruit quality responses were cultivar and time-specific: BIO3 improved soluble solid content in AB (12.8 °Brix, RY 2, Intermediate Harvest) and Z (11.43 °Brix, +13.91% vs. BIO2). BIO2 reduced titratable acidity in AB (3.12 g L⁻¹) and increased pH in Z (3.02, RY 2) but also decreased °Brix in Z. These findings highlight the potential of biostimulants to modulate raspberry physiology and productivity but underscore the critical role of cultivar, environmental conditions, and specific biostimulant composition in determining the outcomes, which were found to critically depend on tailored application strategies. Full article

Leonardite (LEO), a microbial derived product rich in humic and fulvic acids, has been tested, due to its beneficial properties for health and well-being, as a feed additive, mainly in non-ruminant species. Although there are some reports of LEO supplementation in ruminants fed with high-to medium-forage based diets, there is no information available of the potential effects of LEO in ruminants fed, under sub-tropical climate conditions, with high-energy diets during long-term fattening. For this reason, the objective of the present experiment was to evaluate the effects of LEO levels inclusion in diets for feedlot lambs finished over a long-term period. For this reason, 48 Pelibuey × Katahdin lambs (initial weight = 20.09 ± 3.55 kg) were fed with a high-energy diet (88:12 concentrate to forage ratio) supplemented with LEO (with a minimum of 75% total humic acids) for 130 days as follows: (1) diet without LEO, (2) diet supplemented with 0.20% LEO, (3) diet supplemented with 0.40% LEO, and (4) diet supplemented with 0.60% LEO. For each treatment, Leonardite was incorporated with the mineral premix. Lambs were blocked by weight and housed in 24 pens (2 lambs/pen). Treatment effects were contrasted by orthogonal polynomials. The average climatic conditions that occurred during the experimental period were 31.6 ± 2.4 °C ambient temperature and 42.2 ± 8.1% relative humidity (RH). Those values of ambient temperature and RH represent a temperature humidity index (THI) of 79.07; thus, lambs were finished under high heat load conditions. The inclusion of LEO in diet did not affect dry matter intake (p ≥ 0.25) and average daily gain (p ≥ 0.21); therefore, feed to gain ratio was not affected (p ≥ 0.18). The observed to expected dietary net energy averaged 0.96 and was not affected by LEO inclusion (p ≥ 0.26). The lower efficiency (−4%) of dietary energy utilization is an expected response given the climatic conditions of high ambient heat load presented during fattening. Lambs that were slaughtered at an average weight of 49.15 ± 6.00 kg did not show differences on the variables measured for carcass traits (p ≥ 0.16), shoulder tissue composition (p ≥ 0.59), nor in visceral mass (p ≥ 0.46) by inclusion of LEO. Under the climatic conditions in which this experiment was carried out, LEO supplementation up to 0.60% in diet (equivalent to 0.45% of humic substances) did not did not help to alleviate the extra-energy expenditure used to dissipate the excessive heat and did not change the gained tissue composition of the lambs that were fed with high-energy diets during long-term period under sub-tropical climate conditions. Full article

The aim of this study was to evaluate the influence of innovative mineral–organic mixtures containing zeolite composites produced from fly ashes and lignite or leonardite on the fractional composition of soil organic matter in sandy loam soil under two-year pot experiments with maize. The fractional composition of soil organic matter (SOM) was analyzed and changes in the functional properties of soil groups were identified using the ATR-FTIR method. Changes in the content of phenolic compounds were assessed, and the potential impact of fertilizer mixtures on soil carbon stocks was investigated. The addition of these mixtures improved the stability of SOM. The application of mineral–organic mixtures significantly increased the total organic carbon (TOC) by 18% after the 2nd year of the experiment. The maximum TOC content in the soil was observed by 33% with the addition of MC3%Leo3% amendment. Nitrogen content in soil was increased by 62% with MV9%Leo6% additive, indicating increased soil fertility. The study highlighted an increase in fulvic acid carbon relative to humic acid carbon, signaling positive changes in organic matter quality. The new mineral–organic mixtures influence changes in specific functional groups (ATR-FTIR) present in the soil matrix, compared to mineral fertilization alone. The additive mixtures also contributed to an increase in soil carbon stocks, highlighting their potential for long-term improvement of soil fertility and carbon sequestration. Full article

This research was carried out to investigate the effectiveness of using organic fertilizers in improving the organic seed production process and increasing the seed quality needed in organic agriculture production. The experiment was established with organic fertilizers (farmyard manure—FYM, leonardite—L, vermicompost—VC) and the eggplant plant ’Pala-49’ variety and conducted for two years. As a result of the study, vegetative growth height varied between 52.65 and 68.06 cm, plant diameter width ranged from 51.85 to 61.20 cm, fruit height ranged from 14.67 to 21.90 cm, and fruit diameter varied between 4.73 and 6.73 cm. These differences were observed among farmyard manure (FYM), leonardite (L), and vermicompost (VC) organic fertilizer applications. In general, it was determined that the first year gave better results. In terms of parameters, the best result in all parameters was obtained from farmyard manure (FYM) organic fertilizer application. In addition, the nutrient element contents of the seed samples were found to be statistically significant. Organic applications significantly increased the nutrient element content of the seed samples according to the control. The nitrogen content varied between 0.242% and 0.271%, and the phosphorus content ranged between 0.274% and 0.456%. The highest K content was determined in farmyard manure (FYM) application in both years (0.272% and 0.309%). In contrast, Fe, Zn, and Mn contents were 35.1 mg kg⁻¹, 63.7 mg kg⁻¹, and 200.7 mg kg⁻¹ in vermicompost (VC) application in the second year, respectively. The effect of the treatments on soil available nutrient content was also found to be significant. The amount of soil available for plant nutrients was higher in the second year. Full article

In this study, the impact of leonardite as a feed additive in goldfish diets was examined, focusing on its potential to positively influence feed and water parameters, which are critical for achieving sustainable ornamental fish farming. In this study, goldfish were fed diets containing four different levels of leonardite (0%, 2%, 6%, 10%). The experiment was conducted in 12 tanks with 3 replicates per treatment and lasted for 3 months. The fish, which were provided from the Research, Production and Training Institute, with an average live weight of 0.947 ± 0.03 g and an average length of 1.12 ± 0.02 cm, were used. After 90 days, it was observed that the specific growth rates increased in correlation with the amount of leonardite in the diet, with a statistically significant difference identified (p < 0.05). In this study, which investigated the coloration of fish with leonardite added to the feed for the first time, it was determined that the color of the fish approached from yellow to orange as the amount of leonardite added to the feed increased (p < 0.05). Given the positive effects observed on pigmentation and growth in this study, it is recommended that further detailed investigations be conducted on leonardite, a natural, harmless, and cost-effective additive, using different fish species. Full article

The European Union aims to be climate neutral by 2050. To achieve this ambitious goal, net greenhouse gas emissions must be reduced by at least 55% by 2030. Post-combustion CO₂ capture methods are essential to reduce CO₂ emissions from the chemical industry, power generation, and cement plants. To reduce CO₂, it must be captured and then stored underground or converted into other valuable products. Apromising alternative for CO₂ reduction is the use of humic acid salts (HASs). This work describes a process for the preparation of potassium (HmK) and ammonium (HmA) humic acid salts from oxidized lignite (leonardite). A detailed characterization of the obtained HASs was conducted, including elemental, granulometric, and thermogravimetric analyses, as well as 1H-NMR and IR spectroscopy. Moreover, the CO₂ absorption capacity and absorption rate of HASs were experimentally investigated. The results showed that the absorption capacity of the HASs was up to 10.9 g CO₂ per kg. The CO₂ absorption rate of 30% HmA solution was found to be similar to that of 30% MEA. Additionally, HmA solution demonstrated better efficiency in CO₂ absorption than HmK. One of the issues observed during the CO₂ absorption was foaming of the solutions, which was more noticeable with HmK. Full article

In this study, two commercial products based on the main groups of contemporary biostimulants—a commercial leonardite and a seaweed extract—were tested with the objective of assessing the conditions under which they can enhance lettuce (Lactuca sativa L.) performance, particularly to determine if synergies with conventional fertilization methods can be observed. The experimental protocol was arranged as a factorial design with two factors: organic or mineral fertilization × plant biostimulant. The organic or mineral fertilization factor included five levels: two rates of a nitrogen (N) fertilizer (40 (Nmin40) and 80 (Nmin80) kg ha⁻¹ of N), the same N rates applied as an organic amendment (Norg40 and Norg80), and an unfertilized control (N0). The plant biostimulants used were a commercial leonardite (leonardite) for soil application before planting, a commercial seaweed extract (algae) for foliar application during the growing season, and a control without plant biostimulant. Leonardite significantly increased lettuce dry matter yield (DMY) compared to the control only in the first growing cycle (11.5 and 13.5 g plant⁻¹) and showed no significant interaction with conventional fertilization. It also consistently increased phosphorus (P) levels in the plant tissues. The seaweed extract did not show any effect on the plant, nor did it have any interactions with conventional fertilization regarding DMY. In contrast, with mineral fertilization, lettuce DMY increased from 8.0 and 4.0 g plant⁻¹ (N0) to 22.2 and 12.0 g plant⁻¹ (Nmin80) in the first and second growing cycles, respectively. The response to organic fertilization was lower, yet DMY still increased from 4.0 to 8.1 g plant⁻¹ in the second growing cycle. Generally, this type of plant biostimulant is tested under some form of environmental stress, where it often yields positive results. In this study, the optimal cultivation conditions maintained for the lettuce in the pots likely explain the limited response to the biostimulants. This study suggests that the product labels should more clearly indicate whether they are recommended for general cultivation conditions or specifically for situations where a particular environmental stress can be anticipated. Full article

Combining inorganic and organic soil amendments with mineral fertilizers is promising for soil quality enhancement in modern agronomy systems. In this research, four main organic components were used in fertilizer formulations: coconut coir, biochar, lignite, and leonardite (enriched with microelements, tryptophan, and bacterial metabolic products). The treatments were assigned to the completely randomized design with a control object, without any soil amendments, and with only mineral fertilization. Aboveground biomass and root characteristics of maize (root length density, mean root diameter, root surface area density, specific root length, root volume density, and root dry matter) and water retention and characteristics of soil pores were determined. Compared to the control, all fertilizer formulations applied deteriorated the water retention properties of the soil. The highest plant available water content value was obtained for the control without any fertilizers. The addition of organic fertilizer formulations consisting of coconut coir, biochar, lignite, leonardite, microelements, tryptophan, and metabolic products of Pseudomonas sp. and Bacillus subtilis did not play a significant role in improving soil physical characteristics. The lowest productivity was characterized for maize without any fertilizers and amendments. All soil organic amendments resulted in lower yields than the one with only mineral fertilization. The highest root dry matter was obtained when lignite and leonardite were used as main components. Organic amendments can be recommended for soil bioregeneration, but their main effect on maize productivity is attributed to the mineral component. Full article

Humic substances are a type of biostimulant used in greenhouse production to promote plant growth and health. Our goal was to evaluate the effect of three commercially available biostimulants containing humic and/or fulvic acids (HumaPro, FulviPro, and Micromate) on the performance and tissue nutrient concentration of Solanum lycopersicum L. ‘Bush Beefsteak’ grown in a peat-based substrate. We conducted four experiments testing application rate and fertility level (50 and 100 mg⋅L^–1 N) (Exp. 1), application rate and frequency (Exp. 2), direct Micromate incorporation into the substrate (Exp. 3), and FulviPro application method (drench vs. foliar spray) (Exp. 4). Plants were fertilized with 20N-1.3P-15.7K. Experiments 2, 3, and 4 were conducted under low fertility (50 mg⋅L^–1 N). Micromate promoted growth when applied as a weekly drench at 40 g·L⁻¹ or when incorporated into the substrate (20 g in 1 L of the substrate). Micromate-treated plants showed high P, S, and Si in the shoot and root tissues. FulviPro showed a negative effect when applied as a drench at higher rates, but foliar application increased greenness (Green Leaf Index). The negative effects of FulviPro might be due to the over-accumulation of Fe and Mn when applied as a drench. Full article

In recent years, products containing humic acids have been increasingly used in agriculture to improve soil parameters. Quantifying their impact on soil quality is, therefore, of key importance. This study seeks to evaluate the impact of the commercial humic acid product (HA) on the hydrophysical parameters of sandy and clayey soils sampled from different sites in Slovakia. Specifically, the study hypothesizes that humic amendment will enhance particle density (ρ_s), dry bulk density (ρ_d), porosity (Φ), saturated hydraulic conductivity (K_s), soil water repellency (SWR), and water retention capacity in sandy and clayey soils. The results of the laboratory measurements were analyzed using NCSS statistical software at a statistical significance of p < 0.05. In sandy soil, there was a statistically significant decrease in ρ_d and K_s and an increase in Φ and a contact angle (CA) after the application of 1 g/100 cm³ HA. At a dose of 6 g/100 cm³ HA, the values of ρ_s, ρ_d, and K_s decreased, and the Φ and CA values increased. In clayey soil, the K_s value significantly decreased by −35.5% only after the application of 6 g/100 cm³ HA. The addition of HA increased the full water capacity (FWC) and available water capacity (AWC) of clayey and sandy soils. The positive influence of HA on the studied soil parameters was experimentally confirmed, which can be beneficial, especially for their use in agricultural production. Full article