Agricultural Soils Research Articles

Biodegradation of PAEs in contaminated soil by immobilized bacterial agent and the response of indigenous bacterial community

Phthalic acid esters (PAEs) are common hazardous organic contaminants in agricultural soil. Microbial remediation is an effective and eco-friendly method for eliminating PAEs. Nevertheless, the operational mode and potential application of immobilized microorganisms in PAEs-contaminated soil are poorly understood. In this study, we prepared an immobilized bacterial agent (IBA) using a cedar biochar carrier to investigate the removal efficiency of PAEs by IBA in the soil. We found that IBA degraded 88.35% of six optimal-control PAEs, with 99.62% biodegradation of low-molecular-weight PAEs (DMP, DEP, and DBP). The findings demonstrated that the IBA achieved high efficiency and a broad-spectrum in degrading PAEs. High-throughput sequencing revealed that IBA application altered the composition of the soil bacterial community, leading to an increase in the relative abundance of PAEs-degrading bacteria (Rhodococcus). Furthermore, co-occurrence network analysis indicated that IBA promoted microbial interactions within the soil community. This study introduces an efficient method for the sustainable remediation of PAEs-contaminated soil.

Effect of straw decomposition on hexavalent chromium removal by straw: Significant roles of surface potential and dissolved organic matter

Mobility and bioavailability of hexavalent chromium (Cr(VI)) in agricultural soils are affected by interactions between Cr(VI) and returned crop straws. However, the effect of straw decomposition on Cr(VI) removal and underlying mechanisms remain unclear. In this study, Cr(VI) removal by pristine and decomposed rice/rape straws was investigated by batch experiments and a series of spectroscopies. The results showed that straw decomposition inhibited Cr(VI) removal, regardless of straw types. However, the potential mechanisms of the inhibition were distinct for the two straws. For the rice straw, a lower zeta potential after decomposition suppressed Cr(VI) sorption and subsequent reduction. In addition, less Cr(VI) was reduced by the decomposed rice straw-derived dissolved organic matter (DOM) than the pristine one. In contrast, for the rape straw, due to the increased zeta potential after decomposition, the decreased Cr(VI) removal was mainly ascribed to less Cr(VI) reduction by the rape straw-derived DOM. These results emphasized the significant roles of straw surface potential and DOM in Cr(VI) removal, depending on straw types and decomposition, which facilitate the fundamental understanding of Cr(VI) removal by straws and are helpful for predicting the environmental risk of Cr and rational straw return in Cr(VI)-contaminated fields.

Application of soil amendments to reduce the transfer of trace metal elements from contaminated soils of Lubumbashi (Democratic Republic of the Congo) to vegetables

The extraction of copper and cobalt from mines has led to the contamination of agricultural soils by trace metal elements (TMEs) (e.g. Cu: 204 to 1355 mg/kg). The mining industry is one of the sources of metal discharges into the environment, contributing to water, soil, and air contamination and causing metabolic disorders in the inhabitants of the city of Lubumbashi (R.D. Congo). This study assessed the effectiveness of organocalcareous soil improvers applied to TME-contaminated soils to reduce their transfer to plants. Following a factorial design, increasing doses of organic soil improvers (chicken droppings and sawdust) and agricultural lime were applied to the soils of three market gardens (high, medium, and low Cu contamination). The experiment was monitored for 60 days. Soil physicochemical properties (pH, TOC, and total and available copper, cobalt, lead, cadmium, and zinc (mg/kg)) were determined for the three gardens and in the vegetable biomass. The daily consumption index of the vegetables was determined based on total TME content. The results show that organocalcareous soil improvers did not promote plant growth and survival on soils with high and medium levels of copper contamination. However, on soils with low copper content, organocalcareous soil improvers improved germination and plant survival and reduced the transfer of metals from the soil to the plants. The best germination and plant survival rates were obtained with the lightly contaminated market garden. In addition, the organo-limestone amendments applied to the soils slightly increased the soil pH from acidic to slightly acidic, with pH values ranging from (5.43 ± 0.07 to 7.26 ± 0.33). The daily vegetable consumption index obtained for cobalt in the low-contaminated garden ranged from (0.029 to 0.465 mg/60 kg/day), i.e. from 0.5 to 8.45 times higher than the FAO/WHO limit, unlike the other trace metals (Cd, Cu and Pb) for which the daily consumption index found was lower than the FAO/WHO limit. Organocalcareous soil improvers can only be applied to soils with low levels of TME contamination, but for soils with medium to high levels of metal contamination, new soilless production techniques such as hydroponics or bioponics are needed.

Modulation of Cd carriers by innovative nanocomposite (Ca+Mg) and Cd-resistance microbes (Bacillus pumilus): a mechanistic approach to enhance growth and yield of rice (Oryza sativa L.).

Cadmium (Cd) is a well-known pollutant in agricultural soil, affecting human health through the food chain. To combat this issue, Ca + Mg (25 mg L-1) nanocomposite and Bacillus pumilus, either alone or combined, were applied to rice plants under Cd (5 mg kg-1, 10 mg kg-1) contamination. In our study, growth and yield traits demonstrated the beneficial influence of Ca + Mg and B. pumilus application in improving rice defense mechanism by reducing Cd stress. Combined Ca + Mg and B. pumilus application increased SPAD (15), total chlorophyll (18), chlorophyll a (11), chlorophyll b (22), and carotenoids (21%) with Cd (10 mg kg-1), compared to the application alone. Combined Ca + Mg and B. pumilus application significantly regulated MDA (15), H2O2 (13), EL (10), and O2 •- (24%) in shoots under Cd (10 mg kg-1), compared to the application alone. Cd (10 mg kg-1) increased the POD (22), SOD (21), APX (12), and CAT (13%) in shoots with combined Ca + Mg and B. pumilus application, compared to the application alone. Combined Ca + Mg and B. pumilus application significantly reduced Cd accumulation in roots (22), shoots (13), and grains (20%) under Cd (10 mg kg-1), compared to the application alone. Consequently, the combined application of Ca + Mg and B. pumilus is a sustainable solution to enhance crop production under Cd stress.

Agricultural Mitigation Strategies to Reduce the Impact of Romaine Lettuce Contamination.

Leafy greens, particularly romaine lettuce, are often associated with outbreaks due to their susceptibility to contamination from various environmental sources. This study aimed to evaluate the presence of E. coli, Salmonella, copper, nickel, zinc, and manganese in irrigation water, lettuce leaves, and agricultural soil in the Litani River Basin (LRB), Lebanon. Samples were collected from five demonstration plots employing different agricultural practices. Heavy metal concentrations were determined using atomic absorption spectrometry, while E. coli and Salmonella testing were conducted through conventional culturing techniques. The impact of E. coli contamination on seed germination and the interaction effects between E. coli and heavy metals were also examined. The study also compared the effectiveness of various irrigation systems in reducing bacterial contamination. The results demonstrated that contamination levels varied significantly across the plots and irrigation types. This variation underscores the necessity of site-specific mitigation strategies to enhance food safety. Our findings highlight the importance of selecting appropriate irrigation methods and implementing tailored agricultural practices to minimize the risk of contamination. This research provides valuable insights for optimizing agricultural practices in the LRB to ensure food safety and environmental sustainability.

Factors influencing farmers' intention to participate in the voluntary carbon market: An extended theory of planned behavior

Carbon sequestration in agricultural soils is essential for sustainable agriculture, contributing to the achievement of the Sustainable Development Goals and combating climate change. The Voluntary Carbon Market (VCM), designed to encourage farmers to implement sequestration practices, is a recent innovation in Europe, in contrast to the well-established American system. Consequently, there is limited understanding of farmers' intentions to participate. The study analyzes farmers' willingness to participate in VCM and the influencing factors through the Extended Theory of Planned Behavior (ETPB). For this purpose, data were collected from 241 Italian farmers located in the Sicily region and the partial least squares structural equation model (PLS-SEM) was applied. The results show that Attitude, Perceived Behavioral Control and Knowledge of VCM have a statistically significant influence on farmers' intention to participate in VCM. In contrast, Subjective Norms and Perceived Environmental Risk do not have a statistically significant influence. Our findings suggest that farmers' intention is strongly influenced by confidence in their capabilities and knowledge of the topic. This should guide policymakers and practitioners to offer extension services and technical assistance, helping farmers understand the potential of the VCM. Indeed, limited knowledge is a major barrier to participation in this initiative.

Evaluation of the Amount of Endophytic Bacteria Associated with Roots of Brachiaria Humidicola Cv. Humidicola (Rendle) Schweick in Relation to Ph Values, Organic Matter and Phosphorus Contents of Cattle Farm Soil

The objective of this study was to isolate endophytic bacteria from roots of Brachiaria humidicola cv. humidicola (Rendle) Schweick and to relate their presence to pH, organic matter and phosphorus contents of the soil of cattle farms located in the municipality of San Benito Abad. Soil sampling was carried out with roots of B. humicola for the isolation and counting of the population density of endophytic bacteria and soil samples were also collected for the determination of pH, organic matter and phosphorus parameters. The results found indicate that there is an amount of endophytic bacteria in roots of B. humidicola when the soil contains optimum pH values of (6.1 ± 6.98); low to moderate phosphorus content (10.8 ± 16.28 mg/kg) and low to moderate organic matter content (1.7 ± 2.31%). The presence of endophytic bacteria was observed in a range of 3.0 ± 8.0 X 106 CFU/g of roots. There is a worldwide need to establish a relationship between endophytic bacteria and soil physical-chemical quality indicator parameters to predict a change in functional diversity under physical, chemical and biological conditions of the soil ecosystem.

Distinction of facilitating effects between dissolved organic matter derived from corn straw and fulvic acid on transport of titanium dioxide nanoparticles in saturated sand: Dependent on the solution chemistry

The application of organic materials into agricultural soil introduces dissolved organic matter (DOM) into environment. The DOM derived from organic materials would significantly affect the environmental behaviors of nanoparticles. In this study, DOM extracted from corn straw (CSDOM) was characterized and its effects on the transport of titanium dioxides nanoparticles (TiO2 NPs) in porous media were evaluated and compared with those of fulvic acid (FA). The characterization of DOMs indicated marked differences in molecular properties between CSDOM and FA. Weight-average molecular weight (Mw) of CSDOM was 3139 g/mol, higher than 1185 g/mol of FA, whereas CSDOM had a lower aromaticity than FA. Three distinct scenarios of nanoparticle mobility affected by CSDOM and FA were found. Under unfavorable conditions for nanoparticles mobility (pH 4.0 with/without electrolytes, pH 7.0 with electrolytes, and pH 10.0 with CaCl2), both DOMs facilitated TiO2 NPs mobility, and FA with higher aromaticity exerted stronger enhancing effects than CSDOM. However, the promoting effects of DOM on TiO2 NPs mobility were negligible under favorable conditions (pH 10.0 without electrolytes). Under the remaining conditions (pH 7.0 without electrolytes, and pH 10.0 with NaCl), DOM could facilitate the mobility of TiO2 NPs, while there was no difference in the facilitating effects between CSDOM and FA. It could be concluded that distinction of enhancing effects between CSDOM and FA on TiO2 NPs mobility was environmental chemistry-dependent. Furthermore, aromaticity rather than Mw would be a reasonable property determining the enhancing effects of DOM derived from distinct sources on nanoparticle mobility under unfavorable conditions.

Analysis of sulfur in soil and plant digests using methane as a reaction gas for ICP-MS

Quantitation of sulfur (S) is vitally important for analysis of agricultural soil and plant samples due to the requirement of S in living organisms. Although inductively coupled plasma mass spectrometry (ICP-MS) is a commonly used and robust instrument for multi-elemental detection, S is usually analysed by ICP-optical emission spectroscopy (OES) since S quantitation poses a particular challenge for ICP-MS due to interferences on all S isotopes. The requirement for analysis by two instruments increases time and cost for sample analysis, hence analysis by one instrument is desirable. The use of reaction gases in ICP-MS can improve the performance by shifting S to a mass for detection where no interference is present. This work explored the potential of methane as a reaction gas for analysis of S in soil and plant samples to give users an alternative option to oxygen. The product ion clusters CH2SH+ were monitored (m/z 47 and 49 on ICP-MS and with mass shift of +15 from Q1 → Q2 using 32 → 47 and 34 → 49 on triple quadrupole ICP-MS). As expected, triple quadrupole ICP-MS performed better than single quadrupole ICP-MS containing a reaction cell due to the ability to preselect the m/z of choice and remove ions that may react with methane in the reaction cell. The method detection limit (MDL) was 150 mg kg−1 S for plants and 53 mg kg−1 S for soils which is fit for requirements. This is the first-time methane has been reported as a reaction gas for analysis of S and shows promising results for agricultural samples when using a triple quadrupole ICP-MS. Results compared well to those obtained via the more commonly used ICP-optical emission spectroscopy (OES) method with results <20 % for all samples. Interlaboratory comparison samples were within 2 Z-scores of the consensus mean. In the absence of ICP-MS/MS, Q-ICP-MS with detection of cluster m/z 47 was deemed to be suitable for detection of S in plant samples, with acceptable MDL (250 mg kg−1 S), acceptable precision (<20 % RSD) and <20 % variation to the reported ICP-OES result.

Isolation of Monocrotophos degrading bacterial consortium from agricultural soil for in vivo analysis of pesticide degradation.

Extensive Monocrotophos (MCP) application in agricultural soils has led to its ubiquitous accumulation in the environment. Human health can be adversely affected by chronic exposure to produce and water from such areas, causing endocrine dysfunction, birth defects, blood and nervous disorders. This study investigated the possibility of detecting Monocrotophos-degrading bacteria in soil samples taken from a cotton cultivation field in a local area. We isolated a consortium that could tolerate and neutralize Monocrotophos upto a concentration of 2000 ppm. The consortium on 16S rRNA sequencing were identified as Micrococcus luteus SBR2, Rhodococcus SBR5, Bacillus aryabhattai SBR8, Ochrobactrum intermedium SBK2. Significant tolerance of individual strains in the range of 500-5000 ppm was observed when incubating them in vitro with Monocrotophos in minimal salt medium. An analysis of the degrading genes opdA, mpd, and opd revealed plasmid borne opdA and mpd in the O.intermedium strain and B.aryabhattai strain. All the strains indicated genomic opdA and mpd whereas opd was not detected in plasmid or genomic DNA. The HPLC showed no peak at 2.5min, when individual strains were incubated with Monocrotophos. The HPLC analysis of soil samples incubated with the consortium for two weeks showed complete degradation of Monocrotophos. GC-MS analysis confirmed that Monocrotophos and its solvent cyclohexamide were degraded into non-toxic compounds such as cyclotrisiloxane compounds, acetic acid, and others. This study indicates that the expression of organophosphate hydrolyzing enzymes in the consortium can greatly contribute to the neutralization of organophosphorus compounds and also serve as a bioremediation method for agricultural soils.

Shift of microbial taxa and metabolisms relying on carbon sources of rhizodeposits and straw of Zea mays L

Decoding the fundamental taxa that decompose crop rhizodeposits (rhizo-C) and/or straw residue (straw-C) is crucial for understanding the role of plant-derived carbon (C) in driving microbial community assembly and consequent C decomposition. Here, a parallel 13C-labeling design, DNA-SIP, and metagenomics techniques were combined to separate maize rhizo-C utilizers from straw-C utilizers in agriculture soils containing both C sources. Also, by comparing bacterial utilizers and their C metabolisms in soils amended with a single C source (e.g., straw-13C only) and two C sources (e.g., straw-13C and rhizo-12C), we investigated the shift of composition and metabolisms of soil bacterial utilizers responding to C sources shift (e.g., compositional and metabolic changes of straw-13C utilizers from soil containing straw-13C to soil containing both straw-13C and rhizo-12C). We revealed i) Proteobacteria predominantly utilized rhizo-13C, while Firmicutes dominated the community specializing in straw-13C decomposition in soil containing both straw-C and rhizo-C; ii) the planted maize (i.e. rhizo-C input) changed community composition and metabolisms of straw-C utilizers, which shifted from K-strategists characterized by an enrichment of lignin-degrading genes to r-strategists which exhibited an enrichment of genes related to polysaccharide degradation. This metabolic shift of straw-C utilizer ultimately reduced straw-13C mineralization by 25.6% when maize was planted. This study identified the distinct utilizers of rhizo-C and straw-C in soils containing both C sources, and shed light on the shift of bacterial community and their metabolic activities responding to the changes of maize-derived C sources.

Effect of wildfires on mobility of metribuzine herbicide in agricultural soil

Metribuzine has been used extensively for controlling wide range of broadleaf weeds and grasses, which can lead to severe contamination of soil and groundwater. Wildfires are an important process in environment, which can be severe for many areas and could have a significant impact on the properties of the soil. The objective of this study was to investigate the effect of wildfires for the fate and transport of atrazine for agricultural soil. Miscible displacement experiments were used for the objectives. Results showed that the average distribution coefficient (Kd) obtained from metribuzine was 0.28 and 0.13 L/Kg for soils prior to and after wildfire, respectively. Results indicate that organic matter content of soil has most likely played major role on sorption of metribuzine and exhibited rate-limited sorption-desorption. In addition, sorption of metribuzine onto soil after wildfire was significantly lower which could lead to more contamination risk of groundwater resources. The results from the present study would also help in designing of effective herbicide management strategies for contaminated sites.

Quantitative release assessment for beta-lactamase-producing Escherichia coli of dairy origin into vegetables

Abstract Outbreaks of food poisoning associated with vegetables contaminated with Escherichia coli have been reported globally. This study was conducted to assess the probability of releasing beta-lactamase-producing E . coli of dairy farm origin into vegetables in Japan. A release assessment model connecting dairy farms to vegetable farms was developed. Data on the indicated diseases and antimicrobial use in dairy cattle were obtained from the agricultural insurance program in Hokkaido Prefecture between 2016 and 2019. Data on bla -harboring E . coli in cattle were obtained from the Japan Veterinary Antimicrobial Resistance Monitoring System. Microbiological field sampling was conducted at dairy and vegetable farms. Inoculation experiments in vegetables were conducted. All processes in the model simulation were iterated for 1000 times. The estimated proportion of dairy farms holding cattle with bla -harboring E . coli was 6.00% (95% CI: 4.81–7.35%). Beta-lactams were used in 71.76% (333,098/464,204 average annual cases) of indicated diseases. The estimated concentration of bla -harboring E . coli in mixed fresh manure at affected farms was 3.33 log 10 CFU/g (95% CI: 3.33–3.34). The concentrations were reduced to 0.83 (95% CI: 0.34–1.25) and −0.54 log 10 CFU/g (95% CI: −1.04 to −0.05) in soil after immature manure, and slurry spraying, respectively. The estimated concentrations in the soil of fields of radish, leafy vegetables, tomato, and spring-seeded and autumn-seeded onions at harvest were −1.99 (95% CI: −2.48 to −1.57), −2.87 (95% CI: −3.36 to −2.42), −3.82 (95% CI: −4.32 to −3.40), −5.36 (95% CI: −5.85 to −4.93), and −5.94 (95% CI: −6.43 to −5.52) log 10 CFU/g, respectively. The concentrations in the bodies of leafy green spinach and lettuce were −9.88 (95% CI: −10.38 to −9.43) and −10.91 (95% CI, −11.52 to −8.05) log 10 CFU/g, respectively. The probability of ingesting bla -harboring E . coli of dairy origin with raw vegetables in Japan was thus assessed to be very low. One Health impact statement This study applied a release assessment in the World Organisation for Animal Health framework for antimicrobial resistance risk assessment to connect the antimicrobial use for dairy cattle, manure production and vegetable farming. As vegetable is often consumed raw, the assessment is directly associated with human health. Although the environmental continuum was not explored, the reduction of the hazard on the soil of vegetable farms was considered. The study involved the engagement with dairy and vegetable farmers and the agriculture industry in understanding farming behavior and value chain. The approach in this study can be applied to the complex problems across the animal-human-environment interface.

An efficiently biological nitrogen fixation of non-native Lotus tenuis justifies its key role in the flooding Pampas (Argentina)

Forage production is a major challenge in the Salado River basin, Argentina (also denominated “Flooding Pampas”), the largest livestock raising area. The successful naturalization of the European legume Lotus tenuis (native from Mediterranean area) has been of productive and environmental relevance to the region. The main objective of this work was to quantify the efficiency of L. tenuis through its ability to fix nitrogen biologically and thus strengthening their strategic role in the region. The 15N natural abundance method was used to evaluate the Biological Nitrogen Fixation (BNF) of L. tenuis in soil plots. Non-leguminous weed species in the same plots were utilized as reference plants. Simultaneously, evaluations were carried out in the greenhouse and the relative reproducibility of the field experiments. The results showed that L. tenuis promotion was accompanied by an increase in forage quality improving the Crude Protein (CP) content and the Digestibility of Dry Matter (DDM). Moreover, its contribution to N inputs to the system through BNF in symbiosis with native rhizobia was about 80%, a highly relevant percentage for these constrained agroecosystems where the presence of native legumes is very scarce. In conclusion, this study supports the hypothesis that L. tenuis promotion plays a strategic role in ecosystem sustainability in the Salado River basin, especially in soil constrained areas. Together with previously published data, including information on ruminant management, the results obtained contribute to supporting the idea that the naturalized legume plays a strategic role in the sustainability of marginal agricultural soils.

Improved salinity tolerance in cucumber seedlings inoculated with halotolerant bacterial isolates with plant growth-promoting properties

To address salinity stress in plants in an eco-friendly manner, this study investigated the potential effects of salinity-resistant bacteria isolated from saline agricultural soils on the growth of cucumber (Cucumis sativus, cv. Royal) seedlings. A greenhouse factorial experiment was conducted based on a completely randomized design (CRD) with two factors, salinity at four levels and five bacterial treatments, with three replications (n = 3). Initially, fifty bacterial isolates were screened for their salinity and drought tolerance, phosphate solubilization activity, along with production of auxin, siderophore and hydrogen cyanide. Isolates K4, K14, K15, and C8 exhibited the highest resistance to salinity and drought stresses in vitro. Isolates C8 and K15 demonstrated the highest auxin production capacity, generating 2.95 and 2.87 µg mL− 1, respectively, and also exhibited significant siderophore production capacities (by 14% and 11%). Additionally, isolates C8 and K14 displayed greater phosphate solubilization activities, by 184.64 and 122.11 µg mL− 1, respectively. The statistical analysis revealed that the selected four potent isolates significantly enhanced all growth parameters of cucumber plants grown under salinity stress conditions for six weeks. Plant height increased by 41%, fresh and dry weights by 35% and 7%, respectively, and the leaf area index by 85%. The most effective isolate, C8, was identified as Bacillus subtilis based on the 16 S rDNA amplicon sequencing. This study demonstrated that inoculating cucumber seedlings with halotolerant bacterial isolates, such as C8 (Bacillus subtilis), possessing substantial plant growth-promoting properties significantly alleviated salinity stress by enhancing plant growth parameters. These findings suggest a promising eco-friendly strategy for improving crop productivity in saline agricultural environments.

Risk hotspots and influencing factors identification of heavy metal(loid)s in agricultural soils using spatial bivariate analysis and random forest

Heavy metal(loid)s (HMs) in agricultural soils not only affect soil function and crop security, but also pose health risks to residents. However, previous concerns have typically focused on only one aspect, neglecting the other. This lack of a comprehensive approach challenges the identification of hotspots and the prioritization of factors for effective management. To address this gap, a novel method incorporating spatial bivariate analysis with random forest was proposed to identify high-risk hotspots and the key influencing factors. A large-scale dataset containing 2995 soil samples and soil HMs (As, Cd, Cr, Cu, Mn, Ni, Pb, Sb, and Zn) was obtained from across Henan province, central China. Spatial bivariate analysis of both health risk and ecological risks revealed risk hotspots. Positive matrix factorization model was initially used to investigate potential sources. Twenty-two environmental variables were selected and input into random forest to further identify the key influencing factors impacting soil accumulation. Results of local Moran's I index indicated high-high HM clusters at the western and northern margins of the province. Hotspots of high ecological and health risk were primarily observed in Xuchang and Nanyang due to the widespread township enterprises with outdated pollution control measures. As concentration and exposure frequency dominated the non-carcinogenic and carcinogenic risks. Anthropogenic activities, particularly vehicular traffic (contributing ~37.8 % of the total heavy metals accumulation), were the dominant sources of HMs in agricultural soils. Random forest modeling indicated that soil type and PM2.5 concentrations were the most influencing natural and anthropogenic variables, respectively. Based on the above findings, control measures on traffic source should be formulated and implemented provincially; in Xuchang and Nanyang, scattered township enterprises with outdated pollution control measures should be integrated and upgraded to avoid further pollution from these sources.

Ecological risk assessment of heavy metals from application of sewage sludge on agricultural soils in Europe

AbstractThe present European Union (EU) Sewage Sludge Directive (86/278/EEC) is undergoing modifications aimed at enhancing its applicability in the agricultural sector. The Directive's existing limit values for heavy metal concentrations in soils are in the process of being revised. However, to comprehensively understand their effects on EU agricultural lands, additional evaluations are necessary. This is particularly important given that ecological risk assessments are often performed on a site‐specific basis, potentially overlooking broader regional implications. The main objective of the current work is to introduce a methodological approach to quantify the impact of sewage sludge (SS) application on agricultural soils in the EU and the United Kingdom. Concentrations of heavy metals (HMs) (Cd, Cu, Hg, Ni, Pb and Zn) in agricultural land from Land Use/Land Cover Area Frame Survey (LUCAS) 2009 topsoil database were used as a baseline. Maximum quantities of SS that can be safely applied to agricultural lands were obtained by a modeling procedure was used to determine the maximum safe quantities of SS that can be applied to agricultural lands for each country within the European Member States and the United Kingdom. Accumulation of HMs in soils was modelled by using a representative SS composition, distributed over 10 successive years at 5 Mg ha−1 year−1 rate. Ecological risk impact was assessed by using both the single ecological risk index (Er) and the integrated potential ecological risk index (RI). Maximum quantities of SS applied on agricultural soils in EU + UK were estimated to be 45 Mg ha−1 at the country level. We found that 19% of agricultural land (around 28,471,900 ha) in the EU + UK shows a higher RI than moderate risk after long time application of the representative SS. We show that the combination of the HM concentrations from the LUCAS topsoil survey and assumptions on the SS composition and soil HM partitioning can be used to define the actual and potential soil pollution rate in EU + UK. We demonstrate that the proposed methodology can be used by policymakers, farmers, regional authorities and other stakeholders, with possible adaptions based on local in‐depth soil and SS knowledge.

Multifaceted effects of microplastics on soil-plant systems: Exploring the role of particle type and plant species

Microplastics have emerged as a global environmental concern, yet their impact on terrestrial environments, particularly agricultural soils, remains underexplored. Agricultural soils, due to intensive farming, may serve as significant sinks for microplastics. This study investigated the effects of different types of microplastics—polyester microfibers, polyethylene terephthalate microfragments, and polystyrene microspheres—on soil properties and radish growth, while a complementary experiment examined the impact of polyester microfibers on the growth of lettuce and Chinese cabbage. Through both horizontal and vertical comparisons, this research comprehensively evaluated the interactions between microplastic particles and plant species in soil-plant systems. The results showed that polyester microfibers significantly affected soil bulk density, with effects varying based on planting conditions (p < 0.01). Polyethylene terephthalate microfragments and polystyrene microspheres reduced the proportion of small soil macroaggregates under radish cultivation (p < 0.01). Additionally, polystyrene microspheres significantly altered the total organic carbon stock in radish-growing soil, potentially affecting the microclimate (p < 0.01). Interestingly, polyester microfibers promoted lettuce seed germination and significantly enhanced the root biomass of Chinese cabbage (p < 0.05). Overall, the environmental effects of microplastic exposure varied depending on the type of particle and plant species, suggesting that microplastics are not always harmful to soil-plant systems and may even offer benefits in certain scenarios. Given the crucial role of soil-plant systems in terrestrial ecosystems, and their direct connection to food safety, human health, and global change, further research should explore both the positive and negative impacts of microplastics on agricultural practices.

Field assessment of Lake Erie dredged sediment for specialty crops cultivation

AbstractAnnually, approximately 1.5 million tonnes of sediment are dredged from federal navigational channels in Lake Erie. Recognizing the potential influence of Lake sediments on soil compaction, structure, water retention capacity, and aeration, this research assessed the agronomic performance of selected specialty crops under varying sediment ratios in an open‐field production system. The experimental design involved three sediment application rates: 0 tonne (100% farm soil), 0.7 tonne (90% farm soil and 10% sediment), and 7 tonnes per bed (100% sediment). Lettuces (Lactuca sativa L.) were harvested 35 days after planting, with assessments including fresh and dry weights of leaves root biomass and root length measurements. Radishes (Raphanus sativus L.) were evaluated for root length, leaf fresh weight, root fresh weight, and diameter. Tomatoes (Solanum lycopersicum L.) plants were monitored for plant height and stem diameter. Fruit harvest occurred at days 70 and 75 post‐transplant. Metrics such as total number of marketable fruits, total fruit weight, number of US grade‐1 fruits, and polar and equatorial diameters were recorded. The results revealed significant positive effects of the 7‐tonne sediment treatment on lettuce, including increased dry leaf and root biomass, root lengths, and fresh weight. Similarly, radishes exhibited enhanced weight and length when grown in beds with 7 tonnes of sediment. Tomatoes from the 7‐tonne sediment treatment displayed higher values in plant measurements and harvested fruits. Overall, the findings indicate that soils treated with Lake Erie sediment positively influence the development and production of lettuce, radishes, and tomatoes compared to untreated soils.

Isolation, screening, and identification of thermophilic lignocellulolytic fungi from agricultural soil in Vietnam

Isolation, screening, and identification of thermophilic lignocellulolytic fungi from agricultural soil in Vietnam