Earthworm Activity Research Articles

Effect of Vermicompost on Soil Properties, Plant Growth and Environmental Sustainability: A Review

Vermicomposting, the process of converting organic waste into nutrient-rich compost through the activity of earthworms, has emerged as a promising solution to improve soil health, enhance agricultural productivity, and promote environmental sustainability. This review paper explores the effects of different doses of vermicompost on soil properties, plant growth and environmental sustainability. The application of vermicompost at varying dosages influences several soil characteristics, including nutrient availability, water retention, soil structure, and microbial activity, ultimately impacting plant growth and crop yields. Studies indicate that moderate doses of vermicompost often result in enhanced soil fertility and plant performance, while excessive application may lead to nutrient imbalances or phytotoxicity. Furthermore, vermicompost offers several environmental benefits, such as carbon sequestration, reduced dependence on synthetic fertilizers, and improved waste management. This review synthesizes findings from various studies to determine optimal dosages for specific soil types and crops, highlighting the need for region-specific guidelines. The review also identifies key research gaps and suggests directions for future studies, including long-term field trials and exploration of microbial interactions within vermicomposted soils. Ultimately, the findings emphasize the importance of balancing vermicompost doses to maximize both agricultural productivity and environmental sustainability.

A density-based method to objectively quantify earthworm activity

Earthworms are among the most important soil fauna. To exert effects on soils, they need to be active. Earthworm presence is often used as an indicator for activity, but this is not always reliable as earthworms may survive long periods of inactivity or even estivation. Other direct, reliable, and objective measurements for earthworm activity are lacking. Here, we present a novel earthworm activity measurement, based on body-density difference between actively feeding and inactive earthworms. The underlying principle is that active earthworms have a higher density as their gut is filled with soil particles, while inactive earthworms generally have an empty gut. The method therefore separates inactive earthworms from active ones by flotation. To achieve separation, a 1.08 g cm−3 sucrose solution is used. Since it is well established that earthworm activity is reduced in dry soil conditions, we set up a soil moisture gradient experiment to gain a range in earthworm activity. We tested our method on four common European earthworms (endogeic species Allolobophora chlorotica [Savigny] and Aporrectodea caliginosa [Savigny], anecic species Aporrectodea longa [Ude] and epigeic species Lumbricus rubellus [Hoffmeister]) in an experiment with three soil moisture levels (84, 126 and 168 mL kg−1) using a sandy topsoil. As additional proxy for earthworm activity, estivation was visually recorded. We found a high inter-method correlation between density-based and visually estimated earthworm activity, regardless of earthworm species and moisture treatment. Furthermore, our novel method detected inactive individuals of L. rubellus, a species without the ability of estivation. We demonstrated that our density-based method allows for easy and quick quantification of active earthworms. This method offers clear advantages over visual assessments of estivation or cast production, in particular objectivity and applicability to a wider range of species, including those that do not enter estivation.

Comparative study of fenpropathrin and its main metabolite in soil-earthworm microcosms: Toxicity, degradation, transcriptome, and oxidative stress

This study comprehensively investigated the comparative acute toxicities, degradation, transcriptome, and oxidative stress induction of fenpropathrin (FEN) and its main metabolite 3-phenoxybenzoic acid (3-PBA)in soil-earthworm microcosms. FEN degradation half-life ranged from 19.09 to 28.52 days, and the peak-shaped trends of 3-PBA were also observed in different soil types. The LC50 values of FEN and 3-PBA were 12.75 and 7.49 μg/cm2, respectively, suggesting that 3-PBA was more toxic to earthworms. Furthermore, the sub-lethal toxicities indicated that 3-PBA exerted more prominent alterations in protein content, enzyme activity, lipid peroxidation, and oxidative stress in earthworms. Additionally, integrated biomarker response evaluations indicated that 3-PBA induced more prominent sub-lethal toxicity in earthworms than FEN. Finally, exposure to FEN and 3-PBA resulted in distinct differentially expressed genes (DEGs) in earthworms. Enrichment analysis revealed that these DEGs were predominantly enriched in purine metabolism and bile secretion pathways in earthworms. Moreover, the p53 signaling pathway, cell cycle, DNA replication, drug metabolism, and pyrimidine metabolism were also enriched in earthworms after exposure to FEN and 3-PBA. These results suggested that FEN and 3-PBA induced varying toxicities in earthworms. This study highlighted the systemic differences in the toxicities, degradation, transcriptome, and oxidative stress induction between FEN and 3-PBA in soil-earthworm microcosms. Our findings could be used for a comprehensive risk assessment of FEN and 3-PBA in the soil ecosystem.

Earthworm activity reduces bacterial pathogen loads in sewage sludge.

Wastewater processing plants (WWTPs) produce large amounts of sewage sludge that are mainly disposed of on the land. This represents a health hazard due to the high loads of human bacterial pathogens (HBPs) the sludge generally contains. Vermicomposting, a mesophilic process, can reduce HBPs in organic wastes. This raises the question as to how earthworms eliminate HBPs. We aimed to determine whether earthworms reduce the levels or eliminate HBPs from sewage sludge and to establish whether the reduction/elimination occur during active (earthworm casts) or maturation (vermicompost) stages of vermicomposting. To this end, we analyzed HBPs (Escherichia coli O157, Listeria monocytogenes, Salmonella spp., and total E. coli) in sewage sludge samples from three WWTPs and the fresh earthworm casts and vermicomposts by using qPCR, to assess the impact of earthworms on reducing and/or eliminating HBPs. We did not detect either Salmonella spp. nor E. coli O157 in any of the samples. Earthworms removed or significantly reduced the amounts of E. coli and L. monocytogenes (mean relative abundances of 2.4 × 10-7 and 1.5 × 10-8 respectively) in the sewage sludge. Thus, the abundance of these HBPs was lower (or not present) in casts than in sewage sludge. This was also observed in vermicomposts (95% and 43% reduction in E. coli abundance in casts and vermicompost, respectively). Finally, our findings indicate that vermicompost derived from sewage sludge meets the requirements of organic fertilizers at least regarding the microbial pathogen content. Thus, vermicomposting seems to be a promising technique for managing municipal waste.

How the effect of earthworms on soil organic matter mineralization and stabilization is affected by litter quality and stage of soil development

Globally soil fauna consumes about half of the annual litter fall. An important question is how this activity affects the mineralization and stabilization of soil organic matter. Here we explore how much earthworms influence the decomposition of litter and the stabilization of organic matter in soils at various stages of soil development (various soil age) that are supplied with litter of various quality. The laboratory mesocosms consist of litter and a mineral layer. The mineral soils originated either from spruce and alder stands growing either on post-mining soils (young soils after about 50 years of soil development) or from soils in the close vicinity of post-mining sites (mature soils with several thousand years of soil development), the mineral soils were supplied by matching litter, the mesocosms were either without earthworms or with two individuals of earthworms. The earthworm effect showed statistically significant interaction with tree and soil age: earthworms increased respiration in both alder soils, but in spruce soils only in mature soil, while the opposite was true for young soils. In general, earthworms promoted the removal of litter from the soil surface and carbon accumulation in the mineral soil. Earthworms promoted C storage in mineral associated organic matter (MAOM), especially in young spruce soils. The results suggested that earthworm activity in young soils which were far from saturation (spruce on post-mining soils) promotes soil C sequestration by promoting C storage in MAOM, whereas earthworms in mature, C saturated soils tend to promote soil respiration. More broadly, earthworms effect on soil depends on stage of soil C saturation.

Influence of earthworms on the mobility and bioavailability of metals, metalloids and radionuclides in historically contaminated soil

While soil characteristics such as pH, cation exchange capacity and organic matter are known to influence the mobility of pollutants in soil and the transfer to vegetation, far less attention has been paid to the possible non-trophic influence of organisms on pollutant transfer to other species. When pollutants are present in a bound unavailable form in the mineral or organic fraction, they can be made available through bio-weathering and decomposition of organic material. Within this study, the impact of earthworms on the mobility of metal(loid)s and radionuclides in soil and their transfer to vegetation was evaluated and the pathways through which earthworms work were studied. Soil from a Belgian field, historically contaminated with metal(loid)s and radionuclides, was used and microcosm systems were applied to mimic the natural interactions between soil, earthworms (Lumbricus terrestris) and vegetation (Lolium perenne). Metal and radionuclide concentrations were determined in soil, pore water and grass. In addition, soil pH, (chromophoric) dissolved organic matter, the ionic composition of pore water and the soil microbial activity were analysed. In general, earthworm presence significantly increased the concentration of most pollutants in soil pore water. This could be a direct consequence of decreased soil pH and increased humification. The latter also lead to higher nutrient concentrations in pore water that were depleted in the root zone due to high accumulation by plants. Indications were found for earthworm-induced effects on the soil microbial activity. The results show that earthworm activity can increase leaching of metal(loid)s and radionuclides and enhance dispersion into the environment and transfer to other biota and the food chain. Biologically induced release or remobilization of pollutants in the soil should therefore be considered in the context of risk assessment and site management strategies.

Earthworms Transport Agents of Micro-plastic in Soil

Earthworm activity results in vermicomposting rich in vitamins, growth hormones, proteases, amylases, lipases, cellulose, chitinase, and immobilized microflora and macro and micronutrients. After the enzymes are expelled from the worms, they still break down organic materials. The benefits of using vermicomposting in agricultural production include decreased water use for irrigation, reduced pest and termite attacks, decreased weed growth, faster seed germination and rapid seedling growth and development, more fruits per plant (in vegetable crops), and more seeds produced annually (in cereal crops). Without using agrochemicals, vermicomposting and earthworms can increase horticulture output. Vermicomposting has advantages, although its application is still relatively new. This review aims to raise awareness about this particular local soil amendment.

Vermicomposting Enhances Microbial Detoxification of Sewage Sludge, Enabling Potential Application of the Treated Product in Agroecosystems

Vermicomposting offers an eco-friendly solution to managing the sewage sludge generated in wastewater treatment plants. The objective of this study was to investigate the microbial community composition, structure and functionality during the vermicomposting of sewage sludge. We analyzed samples of sewage sludge, earthworm casts and vermicompost by applying high-throughput sequencing 16S and ITS rRNA. Most of the bacterial (95%) and fungal taxa (99%) were eliminated and subsequently replaced by other microbial taxa originating from earthworms. Further changes resulted in a vermicompost with a more diverse bacterial (but not fungal) community. In addition, the earthworm activity led to an increase in bacterial and a decrease in fungal alpha diversity, resulting in greater differences in beta diversity between sewage sludge, casts and vermicompost. We also found that bacterial pathways associated with amino acid and plant hormone biosynthesis and antibiotic synthesis were enriched. Vermicomposting successfully eliminated most of the 10 human bacterial pathogens found in the sewage sludge. Simultaneously, parasitic and pathogenic fungal taxa were removed. Overall, vermicompost derived from sewage sludge is safer for disposal on land than raw sludge, particularly regarding their respective microbial compositions. This indicates that it could potentially be used as a soil organic amendment and fertilizer.

Effectivity of Earthworm (Lumbricus rubellus) Extract as Antidiarrhea Caused by Enteropathogenic Escherichia Coli

Background: Diarrhea still becomes a health problem in Indonesia with a high mortality rate among children under five years old. Antibiotics are used in the management of diarrhea caused by Enteropathogenic Escherichia coli, but it can change the intestinal microbiota in children and can cause resistance. Therefore, raw material is needed as an antibacterial.Methods: The sources of the narrative review come from Google Scholar, PubMed, and ResearchGate with keywords such as earthworm, Lumbricus rubellus, earthworm extract, antidiarrhea, and Escherichia coliResult: Earthworms (Lumbricus rubellus) have some active compounds that are useful for fibrinolytic, thrombolytic, antithrombotic, anti-inflammatory, antioxidant, and broad-spectrum antimicrobial properties. The antimicrobial activity of earthworms is due to the presence of Lumbricin-1 content where its activity against Escherichia coli has been proven by various studies.Conclusion : Earthworm (Lumbricus rubellus) extract can inhibit the growth of Escherichia coli bacteria so it has the potential to become an antidiarrheaKeywords: antidiarrheal; earthworm; Lumbricus rubellus; Lumbricin-1; Enteropathogenic Escherichia coli

Can earthworms and root traits improve plant struvite-P uptake? A field mesocosm study

The availability of conventional linear mineral phosphorus (P) fertilization will become lower as phosphate rock stocks are limited and strongly concentrated in a few locations. Therefore, we need to increase agronomic P use efficiency and find alternative, recycled, sources of P. Two possible solutions mentioned in the literature are (i) using struvite, a mineral circular P fertilizer; and (ii) making use of earthworm activity, which has been shown to increase P availability. Here, we study the interaction between these two approaches, with the hypothesis that earthworms could increase the P availability from the poorly soluble struvite. We set up a field-based mesocosm experiment in a sandy soil with a low agronomic P status with 13 different treatments combining three earthworms species (Lumbricus rubellus Hoffmeister, Aporrectodea caliginosa Savigny and A. longa Ude alone or in a threes species mixture), different P fertilizers (no P, Triple Super Phosphate (TSP) and struvite). The experiment lasted 13 months (five fertilisation-harvest cycles). We found that, in field conditions, the yield and P uptake of Lolium perenne did not differ between fertilization with struvite or TSP. Earthworms only played a minor role in explaining ryegrass P uptake compared to fertilisation. We did not see either positive nor negative interactions between earthworms and struvite, meaning that earthworms did not further increase the P availability from struvite. The equal performances of struvite and TSP are explained by an enhanced effort from plants to actively take up P through a modification of root traits. This includes increased arbuscular mycorrhizal fungi colonisation and the production of finer and longer roots. Our results show that struvite performs comparably to TSP under realistic field conditions, making it a viable alternative to phosphate rock-based fertilizers.

Vermifiltration for removal of emerging contaminant EDTA (ethylenediaminetetraacetic acid). Kinetics models for adsorption, bio- and vermidegradation

Vermifiltration is a sustainable technology that combines the action of microorganisms and earthworms to remove contaminants in wastewater. In this work, vermifiltration was used to remove the emerging contaminant, EDTA, from simulated greywater. Three types of filters were designed: Azide Filter (AF) to evaluate the adsorption process, Bio filter (BF), to evaluate adsorption plus the action of the microorganisms, and Vermi Filter (VF), to assess the previously described processes and the action of the earthworms. Each filter was filled with gravel, sand and an active layer, and VF was inoculated with 60 Eisenia fetida. The filters were operated on a batch system with recycling. Different regimes were observed: an initial rapid decrease of EDTA concentration by adsorption; a lag phase, which lasted from 7 to 18 days, and a final EDTA decrease due to biological or vermi degradation. A mathematical model was developed performing the EDTA mass balance in the system and considering a first order kinetic rate for EDTA removal. Experimental data was fitted by the model, determining kinetic constants for adsorption or degradation process, kads and kd respectively. The kads values were similar for all filters, whereas VF showed a kd 53 % higher than that of BF and AF. Earthworms survival was 85 % and, although the biomass was significantly reduced (64.8 %), there was cocoons and juveniles. Bioassays with Lactuca sativa showed no phytotoxicity of the treated wastewaters. All the systems were efficient but the VF was faster, supporting that vermifiltration is a suitable technology for treating EDTA greywater.

Compost quality, earthworm activities and microbial communities in biochar-augmented vermicomposting of dewatered activated sludge: the role of biochar particle size

Vermicomposting utilizes the synergistic effect of earthworms with microorganisms to accelerate the stabilization of organic matter in biowastes. Nevertheless, the exact mechanism behind the maturity of vermicompost and the growth of earthworms exposed to biochar of varying particle sizes remains unclear. This study presents an investigation of the effect of biochar particle size on earthworm (Eisenia fetida) survival, microbial diversity, and the quality of vermicompost products. To address these issues, pelletized dewatered sludge samples from a municipal sewage treatment plant were amended with pine-based biochar with particle sizes of 1–2 mm, 25–75 μm, 200 nm, and 60 nm as the substrate for vermicomposting. This study revealed that the addition of millimeter-scale biochar and micron-scale biochar significantly promoted the degradation of organic matter since the organic matter in the treatment with 1–2 mm biochar at the end of the vermicomposting experiment decreased by 12.6%, which was equivalent to a 1.9-fold increase compared with that of the control. Excessive nanopowdering of nanobiochar significantly affected the survival of earthworms and led to 24.4–33.3% cumulative mortality, while millimeter-scale (mm) biochar and micron-scale (μm) biochar achieved zero mortality. The findings of this study could be used for evaluating the potential impact of nanoscale biochar to earthworms and guiding biochar-augmented vermicomposting.Graphical

Biochar & fly ash amendments lower mortality and increase antioxidant activity in chlorpyrifos-exposed earthworms

The investigation presented a novel finding regarding mitigating stress induced by chlorpyrifos in Eisenia fetida by incorporating biochar derived from rice straw and fly ash as soil amendments. It was observed that phenolic compounds exhibit solubility in methanol, and the methanolic fraction exhibited notable inhibitory effects on lipid peroxidation and displayed antioxidant properties. The defence mechanism of E. fetida, comprising catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and various other enzymes, remained effective in neutralizing stressors without disruption when the earthworm was subjected to diverse chemical agents or stressful conditions. These enzymes served as indicative markers of toxicity induced by pesticide exposure, even at sublethal concentrations. The scavenging of free radicals by these enzymes ultimately safeguarded the organism. Fly ash and biochar emerged as two organic alternatives capable of alleviating stress by providing a protective mechanism. In this context, the study examined the impact of biochar and fly ash amendments on earthworm biomarkers. The mortality rate at the median lethal concentration of chlorpyrifos was reduced to less than 50% through 3% and 5% modifications. In contrast to the non-amendment group exposed to sublethal doses, the amendment group exhibited higher levels of oxidative stress and lower protein content. This observation indicated the presence of stress induced by the accumulation of free radicals, which increased in number with higher doses of chlorpyrifos. Moreover, the study highlighted the interconnected nature of total antioxidant capacity and total phenolic capacity values, with a decrease in these parameters signifying a shift in earthworm biomarkers.Graphical abstract

Endogeic earthworms mediate aggregate formation and carbon storage in an Ultisol

The role of soil fauna in the incorporation of carbon into soil aggregates of tropical soils has been understudied. We conducted a field experiment within a secondary forest and a microcosm experiment at the University of Puerto Rico in Mayagüez to test soil aggregate formation and carbon incorporation by earthworm activity. Using 13C natural abundance in vegetation and the difference in δ13C between C3 and C4 plants, carbon sources in the soil were tracked. Maize leaves (C4 carbon isotopic signal) were used to track the carbon incorporation into soil aggregates (C3 carbon isotopic signal). Earthworms and soil samples (Typic Haplohumults) were collected at 0 to 10 cm soil depth. The treatments for microcosms were: (I) soil, (II) soil + C4 leaves, (III) soil + C4 leaves + two earthworms (low density), and (IV) soil + C4 leaves + three earthworms (high density). Aggregate size classes were separated by the wet sieving method. At the study site, we found two earthworm species belonging to epigeic and endogeic ecological categories. Over six months, our field data suggested that endogeic P. corethrurus can reorganize small macroaggregates to form large macroaggregates. The microcosm experiment corroborated that P. corethrurus consumes soil and transfers soil-derived carbon from microaggregates to macroaggregates. The treatment with the highest earthworm density did not show higher carbon incorporation (0.23 g C/kg sand-free aggregates) into the soil compared to low earthworm density (0.25 g C/kg sand-free aggregates). Our results suggest that P. corethrurus prefers consuming soil-derived carbon and can translocate it from microaggregates to macroaggregates by restructuring soil aggregates.

Microplastics exert minor influence on bacterial community succession during the aging of earthworm (Lumbricus terrestris) casts

The soil microbiome, which is shaped by gut-related activities of earthworms, is affected by microplastic contamination. However, the influence of microplastics on earthworm gut and cast microbiomes has been poorly explored. Here, we investigated the influence of microplastics (1% in soil, w/w) on soil physicochemical properties and bacterial communities during gut passage and cast aging of Lumbricus terrestris. Microplastics used in agricultural film production were selected, i.e., low density polyethylene, polylactic acid and polybutylene adipate terephthalate (PBAT). Different niches, including pre-ingestion soil, gut content and aged casts (from 0 to 180 days), were studied. Results showed that microplastics possibly enhanced the gut passage-derived difference between pre-ingestion soil and fresh cast in terms of pH, ammonium, nitrate and nitrite, and dissolved organic carbon. But such effects mostly faded out after 180 days of aging. The composition, as well as the alpha and beta diversity of both the total (DNA) and active (RNA) bacterial communities were decisively shaped by their niche (R2: 0.22–0.63, p < 0.001, PERMANOVA), rather than the presence/absence or the types of MPs. Nevertheless, biomarkers indicative of PBAT treatment were identified, and functional prediction for the active community showed that bacterial communities of this treatment had higher potentials for hydrocarbon degradation (4.9–7.8 times that of the microplastic-free treatment in gut and aged casts). We also identified a “Soil-related core community” and a “Gut-related core community” (contributing to 39.2%–50.2% of the cast microbiome), which possibly neutralized microplastic impacts and maintained the structure and function of bacterial communities during the soil–gut–cast transit. Our findings indicate that the tested microplastics exerted a minor influence on the bacterial communities during the cast aging process, microplastics in aged casts might not necessarily have significant additional influence on the soil microbiome when they are incorporated into soils. Future studies testing different soils, polymers, and earthworm species, under field conditions are recommended to help enhance current knowledge of the influence of microplastics on earthworm cast microbiomes.

Vermicompost: Significance and Benefits for Agriculture

Vermicomposting is defined as the process of biodegradation and stabilization of organic materials, facilitated by the collaborative efforts of earthworms and mesophilic microorganisms. The activity of earthworms in vermicomposting results in the production of nutrient-rich vermicompost. This organic amendment is abundant in macro and micronutrients, vitamins, growth hormones, as well as enzymes like proteases, amylases, lipase, cellulase, and chitinase. Additionally, vermicompost harbors a diverse community of immobilized microflora. Even after being excreted by the worms, the enzymes in vermicompost persist in their ability to decompose organic matter, facilitating continued breakdown and nutrient release. The utilization of vermicompost in agricultural production brings forth a multitude of beneficial effects. These include decreased water requirements for irrigation, reduced susceptibility to pest and termite attacks, suppression of weed growth, and enhanced seed germination rates, accelerated growth and development of seedlings, as well as increased yield of fruits per plant in vegetable crops and a higher number of seeds per year in cereal crops. These advantages highlight the positive impact of incorporating vermicompost into agricultural practices, fostering sustainable and productive farming systems. The combination of earthworms and vermicompost presents a valuable opportunity to enhance horticultural production in a sustainable manner, reducing reliance on agrochemical inputs. Despite the numerous benefits associated with vermicompost, its widespread implementation and adoption are still relatively limited. This review aims to raise awareness and promote the understanding of this valuable local soil amendment.

Nutrient Composition of Detoxified Oil Cake from Simarouba glauca

Vermicomposting is defined as the process of biodegradation and stabilization of organic materials, facilitated by the collaborative efforts of earthworms and mesophilic microorganisms. The activity of earthworms in vermicomposting results in the production of nutrient-rich vermicompost. This organic amendment is abundant in macro and micronutrients, vitamins, growth hormones, as well as enzymes like proteases, amylases, lipase, cellulase, and chitinase. Additionally, vermicompost harbors a diverse community of immobilized microflora. Even after being excreted by the worms, the enzymes in vermicompost persist in their ability to decompose organic matter, facilitating continued breakdown and nutrient release. The utilization of vermicompost in agricultural production brings forth a multitude of beneficial effects. These include decreased water requirements for irrigation, reduced susceptibility to pest and termite attacks, suppression of weed growth, and enhanced seed germination rates, accelerated growth and development of seedlings, as well as increased yield of fruits per plant in vegetable crops and a higher number of seeds per year in cereal crops. These advantages highlight the positive impact of incorporating vermicompost into agricultural practices, fostering sustainable and productive farming systems. The combination of earthworms and vermicompost presents a valuable opportunity to enhance horticultural production in a sustainable manner, reducing reliance on agrochemical inputs. Despite the numerous benefits associated with vermicompost, its widespread implementation and adoption are still relatively limited. This review aims to raise awareness and promote the understanding of this valuable local soil amendment.

Can vermicomposting be used to process hyperaccumulator biomass in nickel agromining?

AbstractHyperaccumulator plants are a botanical curiosity that have allowed the development of agromining of metals, with a special focus on nickel. In nickel agromining, this element is recovered from ashed hyperaccumulators cultivated on metal‐rich soils. In order to explore bio‐based approaches for the decomposition of hyperaccumulator biomass and nickel recovery that do not include burning, we performed a vermicomposting experiment using the earthworm species Eisenia andrei and the biomass of Bornmuellera emarginata (which contained almost 1% of nickel). We conducted our experiment for 12 weeks and assessed the decomposition process of the hyperaccumulator biomass, changes in earthworm number and biomass, and changes in nickel concentration and mobility. Despite the initial mortality and an increase of Ni concentration in earthworm tissues, E. andrei was able to decompose B. emarginata biomass. This process also showed a massive colonization of the biomass by a fungus during the first weeks of the assay. Our results indicate that the vermicomposted hyperaccumulator biomass had a higher nickel concentration than the starting material but the diethylenetriaminepentaacetic acid‐extractable nickel decreased. At the same time, due to earthworm activity, the nickel was redistributed and diluted in the vermicompost bedding, reducing the interest of this approach for agromining, but opening the perspective of using the vermicomposted hyperaccumulator biomass as an organic amendment in nickel‐deficient crops.

Earthworms improve the rhizosphere micro-environment to mitigate the toxicity of microplastics to tomato (Solanum lycopersicum)

Microplastics (MPs) are widespread in agricultural soil, potentially threatening soil environmental quality and plant growth. However, toxicological research on MPs has mainly been limited to individual components (such as plants, microbes, and animals), without considering their interactions. Here, we examined earthworm-mediated effects on tomato growth and the rhizosphere micro-environment under MPs contamination. Earthworms (Eisenia fetida) mitigated the growth-inhibiting effect of MPs on tomato plant. Particularly, when exposed to environmentally relevant concentrations (ERC, 0.02% w/w) of MPs, the addition of earthworms significantly (p < 0.05) increased shoot and root dry weight by 12–13% and 13–14%, respectively. MPs significantly reduced (p < 0.05) soil ammonium (NH4+-N) (0.55–0.69 mg/kg), nitrate nitrogen (NO3−-N) (7.02–8.65 mg/kg) contents, and N cycle related enzyme activities (33.47–42.39 μg/h/g) by 37.7–50.9%, 22.6–37.2%, and 34.2–48.0%, respectively, while earthworms significantly enhanced (p < 0.05) inorganic N mineralization and bioavailability. Furthermore, earthworms increased bacterial network complexity, thereby enhancing the robustness of the bacterial system to resist soil MPs stress. Meanwhile, partial least squares modelling showed that earthworms significantly influenced (p < 0.01) soil nutrients, which in turn significantly affected (p < 0.01) plant growth. Therefore, the comprehensive consideration of soil ecological composition is important for assessing MPs ecological risk.

Evaluation of the variation of the GPR frequency spectra created by the activities of earthworms

The analysis and utilization of frequency spectrum in emission signals from ground penetrating radar (GPR) are essential for investigating soil characteristics and enhancing urban management. This research focuses on assessing the effectiveness of earthworm activities in improving rainwater management in regions with clay soil, where water infiltration is challenging. Specifically, we examined the impact of two earthworm species, Lumbricus terrestris and Aporrectodea caliginosa, as well as a combination of both, on the permeability of clay loam soil. To evaluate earthworm activities, a gravity-driven film flow setup with nine tanks was employed. Furthermore, we suggest utilizing the Discrete Fourier transform to analyse the frequency spectra of different data types (traces, transects, and the average of tanks) and comprehend their influence on earthworm behavior. To investigate the relationship between fluctuations in infiltration velocity and the frequency spectrum signal over time and activity position, a correlation analysis was performed using linear regression models. The goodness of fit was assessed based on the coefficient of determination (R2). For the earthworm species L1, L2, and L12, the R2 values were determined as 0.8858, 0.847, and 0.9493, respectively. These results demonstrate that the frequency domain was derived from variations in ground penetrating radar signals, and a significant correlation exists between infiltration velocity and spectra influenced by earthworm activity.