Earthworm Populations Research Articles

Earthworm distributions are not driven by measurable soil properties. Do they really indicate soil quality?

Abundance and distribution of earthworms in agricultural fields is frequently proposed as a measure of soil quality assuming that observed patterns of abundance are in response to improved or degraded environmental conditions. However, it is not clear that earthworm abundances can be directly related to their edaphic environment, as noted in Darwin's final publication, perhaps limiting or restricting their value as indicators of ecological quality in any given field. We present results from a spatially explicit intensive survey of pastures within United Kingdom farms, looking for the main drivers of earthworm density at a range of scales. When describing spatial variability of both total and ecotype-specific earthworm abundance within any given field, the best predictor was earthworm abundance itself within 20-30 m of the sampling point; there were no consistent environmental correlates with earthworm numbers, suggesting that biological factors (e.g. colonisation rate, competition, predation, parasitism) drive or at least significantly modify earthworm distributions at this spatial level. However, at the national scale, earthworm abundance is well predicted by soil nitrate levels, density, temperature and moisture content, albeit not in a simple linear fashion. This suggests that although land can be managed at the farm scale to promote earthworm abundance and the resulting soil processes that deliver ecosystem services, within a field, earthworm distributions will remain patchy. The use of earthworms as soil quality indicators must therefore be carried out with care, ensuring that sufficient samples are taken within field to take account of variability in earthworm populations that is unrelated to soil chemical and physical properties.

Potential Impacts of Climate Change on the Toxicity of Pesticides towards Earthworms.

This review examined one of the effects of climate change that has only recently received attention, i.e., climate change impacts on the distribution and toxicity of chemical contaminants in the environment. As ecosystem engineers, earthworms are potentially threatened by the increasing use of pesticides. Increases in temperature, precipitation regime changes, and related extreme climate events can potentially affect pesticide toxicity. This review of original research articles, reviews, and governmental and intergovernmental reports focused on the interactions between toxicants and environmental parameters. The latter included temperature, moisture, acidification, hypoxia, soil carbon cycle, and soil dynamics, as altered by climate change. Dynamic interactions between climate change and contaminants can be particularly problematic for organisms since organisms have an upper and lower physiological range, resulting in impacts on their acclimatization capacity. Climate change variables such as temperature and soil moisture also have an impact on acidification. An increase in temperature will impact precipitation which might impact soil pH. Also, an increase in precipitation can result in flooding which can reduce the population of earthworms by not giving juvenile earthworms enough time to develop into reproductive adults. As an independent stressor, hypoxia can affect soil organisms, alter bioavailability, and increase the toxicity of chemicals in some cases. Climate change variables, especially temperature and soil moisture, significantly affect the bioavailability of pesticides in the soil and the growth and reproduction of earthworm species.

Reveal the metal handling and resistance of earthworm Metaphire californica with different exposure history through toxicokinetic modeling

Toxicokinetic (TK) model provides a new approach to mechanistically elucidate the natural variation of metal handling strategy by adaptive and sensitive earthworm populations. Here, TK model was applied to explore the metal handling and resistance strategy of wild Metaphire californica with different historical exposure history through a 12-day re-exposure and another 12-day elimination incubation. M. californica populations showed different kinetic strategies for non-essential metals (Cd and Pb) and essential metals (Zn and Cu), which were closely related to their exposure history. M. californica from the most serious Cd-contaminated soil showed the fastest kinetic rates of both Cd uptake (K1 = 0.78 gsoil/gworm/day) and elimination (K2 = 0.23 day−1), and also had the lowest Cd half-life (t1/2 = 3.01 day), which demonstrated the potential Cd-resistance of wild M. californica from Cd-contaminated soils. Besides, the comparative experiment showed totally different metal kinetics of laboratory Eisenia fetida from field M. californica, suggesting the impacts of distinct exposure history and species-specifical sensitivities. These findings provide a novel approach to identify and quantify resistance using TK model and also imply the risk of overlooking existing exposure background and interspecies extrapolation in eco-toxicological studies and risk assessments.

Effects of different tree species on infiltration and preferential flow in soils developing at a clayey spoil heap

Soil recovery is crucial for successful ecosystem restoration at post-mining sites. Water infiltration and preferential flow in soil are important but little studied soil characteristics. In this study, we explore effects of tree species on infiltration, geometry of preferential flows, size distribution and origin of pores, and related properties of soil. An experiment was conducted at post-mining sites developing under monocultures of three tree species (alder, oak and spruce) after lignite mining near Sokolov, Czech Republic. A key hydraulic parameter of soil, field saturated hydraulic conductivity (Ks), measured in topsoil, was highest under alder (mean value of 6.9 × 10−5 ms−1) and lowest under spruce (mean value of 1.9 × 10−5 ms−1). In subsoil, there were no significant differences in Ks between tree species. For the alder site, dye tracer tests showed that water penetrates almost uniformly to the top 15 cm of soil depth and with the greatest lateral flow. In a deeper part of the alder soil profile, preferential flow was concentrated around earthworm burrows and roots, where the two often occur together. Thin soil sections of alder soil show that earthworm casts and burrows substantially contribute to porosity around the roots (59 % of dyed worm-created structures in alder-root microsite). A similar situation was observed in oak, but preferential flows along roots started from the surface and cross section of preferential flow was smaller than in alder soil. In spruce, preferential flow was concentrated around roots and cracks in claystones and the cross section was even smaller. Comparison among the forest stands indicates that overall porosity does not correspond with infiltration of dye tracer and Ks, which seem to be more driven by pore size distribution and pore connectivity. This is consistent with larger occurrence of macropores (>300 μm) in alder. The results show that trees affect infiltration and preferential flow in soil by their specific root systems and to a large extent indirectly by effect of litter quality on earthworm populations, which then enhance macroporosity and pore connectivity.

HUBUNGAN POPULASI CACING TANAH TERHADAP C-ORGANIK DAN N-TOTAL DI LAHAN BUDIDAYA HORTIKULTURA DAN MONOKLUTUR TANAMAN KOPI DI DESA NDUARIA KECAMATAN KELIMUTU

This study aims to determine the relationship between Earthworm Population and C-organic and N-total in Horticulture and Coffee Monoculture cultivation in Nduaria Village, Kelimutu District. This research was conducted using an exploratory method that is carried out by direct observation from the observation location. How to calculate earthworms using the hand sorting method. The method commonly used for the determination of C-organic is the Walkley and Black method, while the method used for the determination of N-total is the Kjehdahl method. This method is used because it is considered simple, fast, easy to do, and requires little equipment. The results of this study indicate that in horticultural land there is no earthworm population found at all depths. Earthworm populations were found at all depths in the coffee plantation monoculture, the highest population was at a depth of 0-10 cm as many as 41 m2, Biomass was 9 g, and Biomass vs Population 0.21 m2. In horticultural fields, the highest c-organic and n-total is at a depth of 0-10 cm, the c-organic value is 3.03% (high criteria) and n-total is 0.47% (medium criteria). The close relationship between the earthworm population, biomass, and biomass versus population was positively correlated with c-organic and n-total in horticultural land and coffee monoculture.

Assessing the arsenic-saturated biochar recycling potential of vermitechnology: Insights on nutrient recovery, metal benignity, and microbial activity

Biochar mediated pollutant removal is gaining attention because of high efficiency of the process. However, effective recycling avenues of the pollutant-saturated biochars are scarce in the knowledge base; while such materials can be a new source of long-range contamination. Therefore, potential of vermitechnology for eco-friendly recycling of pollutant-loaded biochar was assessed by using arsenic-saturated native (NBC) and exfoliated (EBC) biochars as feedstocks for the first time. Interestingly, the bioavailable arsenic fractions (water soluble and exchangeable) considerably reduced by 22–44 % with concurrent increment (~8–15 %) of the recalcitrant (residual and organic bound) fractions in the biochar-based feedstocks. Consequently, ~2–3 folds removal of the total arsenic was achieved through vermicomposting. The earthworm population growth (2.5–3 folds) was also highly satisfactory in the biochar-based feedstocks. The results clearly imply that Eisenia fetida could compensate the arsenic-induced stress to microbial population and greatly augmented microbial biomass, respiration and enzyme activity by 3–12 folds. Moreover, biochar-induced alkalinity was significantly neutralized in the vermibeds, which remarkably balanced the TOC level and nutrient (N, P, and K) availability particularly in EBC + CD vermibeds. Overall, the nutrient recovery potential and arsenic removal efficiency of vermitechnology was clearly exhibited in NBC/EBC + CD (12.5:87.5) feedstocks. Hence, it is abundantly clear that vermitechnology can be a suitable option for eco-friendly recycling of pollutant-saturated sorbing agents, like biochars.

Soil quality significance of goat pens positioned on the hilltop of sloping cocoa farms in Polman-Sulawesi

Many smallholder cocoa farmers in Polman, West Sulawesi-Indonesia breed goats traditionally on hilltop of the sloped cocoa farms. The goat’s manure is deposited under the pens, not distributed on the farm. We investigated the significance of this traditional goat breeding on the hilltop of sloping cocoa farms on soil quality based on the distance from the pens along the slope direction. We selected three sloped-cocoa farms where this traditional model had been practiced for years. The farms studied had 30 to 70% slopes, clay loam to clay soil textures. Along a transect lane, 0-5, 5-10, and 10-15 meters from the pen on each farm, we measured soil bulk density, hydraulic conductivity (HC), soil organic carbon (SOC), pH, soil nitrogen, phosphorus, potassium, cation exchangeable capacity (CEC) and earthworm population. This traditional practice improved soil quality compared to the adjacent farms which were not affected by the practice (control). Soil HC, SOC, N, P, K and CEC, and earthworm population were markedly higher under this system compared to the control, especially at 0 to 5 m distance from the manure deposit. The beneficial effects of this system were limited only within 10 m from the pens, beyond which soil quality was practically similar to the control site. This traditional system may be considered as an appropriate practice for soil quality maintenance in sloping cocoa farm, but an improvement is needed for greater benefits and reduced risks through terrace construction and manure deposition every 5-10 m range along the slope.

Earthworm communities are supported by perennial bioenergy cropping systems

During the last decade a variety of perennial bioenergy crops (PECs) have been introduced into European agriculture. This study was designed to investigate the impact of various PECs on earthworm community patterns (species composition, numbers, biomass, α-diversity, life-form categories) at a landscape scale in Western Germany. The PECs investigated were cup plant (CP), tall wheatgrass (TW) and giant knotweed (GK). In total, 4 field replicates of each perennial crop were investigated at 9 study sites with the exception of CP, for which only 3 replicate sites were available. PECs were compared with silage maize as an annual bioenergy crop (AEC) and permanent grasslands (PGL). The earthworm community of the study area consisted of 13 species in total. Mean species number ranged from 2.7 (AEC) < 2.8 (GK) < 3.8 (TW) < 3.9 (PGL) < 4.2 (CP). Overall, PECs took an intermediate position between AEC and PGL concerning earthworm population data including α-diversity and community structure as indicated by Shannon-Weaver index (H’), species number and Evenness (E). There was a clear and close to significant (p < 0.1) increase in the mean total earthworm number in the range AEC (43.3 ind. m−2) – PECs (86.7 ind. m−2) – PGL (114.4 ind. m−2). Fresh earthworm biomass varied from 21.1 g m−2 (AEC) to 35.7 g m−2 (PGL) to 40.1 g m−2 (PECs), however, this difference was only significant for mean biomass of juveniles. Endogeic species were highly dominant in soils cultivated with PECs. Generalized linear mixed models revealed that soil pH, amounts of soil organic carbon and plant available soil water content were partly significant environmental driving variables for the improvement of the earthworm community in soils cultivated with PECs.

Environmental determinants of plant species diversity in organic and conventional vineyards

The factors affecting the plant biodiversity in organic (manure application) and conventional vineyards (variety “Agiorgitiko for both) in southern Greece were examined separately for each vineyard type. The index for plant biodiversity was chosen to be the Shannon one (SH). The Pearson correlation coefficients disclosed that the common factors in both vineyards types affecting the SH were the concentrations of the soil organic C and organic N, the nitrates –N, the available (Olsen) P, available Cu, exchangeable K and the CaCO3 percentage. The C/N ratio in soils affected positively and significantly the SH index in both vineyards types. That means that the supply of N is not a problem with regard to decomposition but the organic C as a source of energy can be a limiting factor to plant diversity. The earthworm population density in the two vineyards types was also a significant positive factor to the SH. The concentrations of the available Mg, Zn and ammonium-N in soils affected the SH index significantly only in the conventional vineyards although their concentrations in soils did not differ. We can conclude that chemical fertilization can also affect plant variability.

Genetic Diversity and Population Structure of Metaphire vulgaris Based on the Mitochondrial COI Gene and Microsatellites.

The earthworm species Metaphire vulgaris (a member of the Clitellata class) is widely distributed across China, and has important ecological functions and medicinal value. However, investigations into its genetic diversity and differentiation are scarce. Consequently, we evaluated the genetic diversity of five populations of M. vulgaris (GM, HD, NYYZ, QDDY, and QDY) in Yancheng, China via the mitochondrial COI gene and the novel microsatellites developed there. A total of nine haplotypes were obtained by sequencing the mitochondrial COI gene, among which NYYZ and QDDY populations had the greatest number of haplotypes (nh = 5). Further, the nucleotide diversity ranged from 0.00437 to 0.1243. The neighbor-joining trees and the TCS network of haplotypes indicated that earthworm populations within close geographical range were not genetically isolated at these small scale distances. Results of the identification of microsatellite molecular markers revealed that the allele number in 12 microsatellite loci ranged from 4 to 13. The observed heterozygosity ranged from 0.151 to 0.644, whereas the expected heterozygosity ranged from 0.213 to 0.847. The polymorphism data content of most sites was >0.5, which indicated that the designed sites had high polymorphism. Structural analysis results indicated that GM, HD, and NYYZ had similar genetic structures across the five populations. The Nei’s genetic distance between HD and NYYZ populations was the smallest (Ds = 0.0624), whereas that between HD and QDY populations was the largest (Ds = 0.2364). The UPGMA tree showed that HD were initially grouped with NYYZ, followed by GM, and then with QDDY. Furthermore, cross-species amplification tests were conducted for Metaphire guillelmi, which indicated that the presented markers were usable for this species. This study comprised a preliminary study on the genetic diversity of M. vulgaris, which provides basic data for future investigations into this species.

Impact of Litter Quality and Earthworm Populations on Seruk Spring Forest’s Soil Characteristic

Seruk spring, located in Batu, East Java, is a spring with four different Land Use Systems (LUS) in its surrounding area, comprising a mixed, a pine, an eucalypt, and a bamboo forests. Over time, there have been changes in land use around the area of Seruk Spring. This results in a decrease in the environmental quality, and even in the spring’s water discharge. As spring serves as an important part of people living in the immediate vicinity, this research aimed to determine the differences in litter quality, earthworm populations, and soil porosity at each LUS. Litter was measured in each area and analyzed in the laboratory to determine its biomass and quality. Earthworm populations and biomass were measured with the iron box method, while the soil porosity and organic matter were based on secondary data from the previous research. The correlation among all the parameters was analyzed with Principal Components Analysis (PCA) using PAST 3 software. The results showed that the bamboo forest had the most suitable land-use system around spring, based on the highest litter thickness and its quality in the area. The different qualities of each LUS provided diverse advantages for the spring ecosystem. The presence of the bamboo forest around the spring area should be conserved, to maintain the quality of the ecosystem and the sustainability of the spring area itself.

Modelling of pollutants removal in Integrated Vermifilter (IVmF) using response surface methodology

Mathematical models of vermifiltration are not only valuable tools for design and optimization of the processes, but could be also employed for output prediction and system control. In this work, Response Surface Methodology (RSM) technology has been applied to evaluate both individual effect of different parameters as well as their interaction effect simultaneously on system performance. A two stage integrated Vermifilter (IVmF) consisting of Eisenia fetida and Canna indica was developed with vertical flow (VF) system as first stage unit and horizontal flow (HF) system as second stage unit. Box-Behnken Design (BBD) model was implemented for optimization of BOD removal in treatment process. HLR, biodegradable organic strength and VF unit active layer depth were considered as the major affecting factors on performance of the filter. Subsurface flow mode was selected in operation as earthworm may not survive for long time in submerged condition. According to developed model, the optimal conditions (numerical optimization technique) for achieving maximum BOD removal for the designed system were at influent concentration of 1701.00 ​mg/L, HLR of 0.39 ​m 3 /m 2 /d 1 and active layer depth of 34.40 ​cm. Experimental BOD removal of 86.45% was obtained against predicted value of 87.08% at optimum condition. Above data can be used for the implementation of vermifiltration system in field scale with minimal deviation. Growth rate of Eisenia fetida was tracked which shows 20.29%–27.82% increase in earthworm population. Similarly, Canna indica number increased from initial number of 3 to final number 13–18 in different experimental conditions. • A RSM based BBD model was utilized to optimize the biodegradable organics removal. • Macrophyte Canna indica and earthworm Eisenia fetida worked symbiotically to remove pollutants. • 87.08% BOD was removed in optimized condition. • Earthworm number increased 20.29–27.82% and number of Canna indica increased 4–6 times.

Effect of the 32nd-year Soil Tillage and Nitrogen Fertilization on the Population and Biomass of Earthworm under Zea mays L.

The abundance and biomass of earthworms are affected by soil tillage and fertilization. This research aimed to study long-term 32nd-year soil tillage and nitrogen fertilization on the population and biomass of earthworms under Zea mays L. The research was conducted using a randomized block design (RBD) which consisted of two factors. The first factor was the soil tillage that was Intensive Tillage (IT), Minimum Tillage (MT), and No-Tillage (NT). The Second factor was nitrogen fertilization that was N0 = 0 kg N ha-1 and N1= 200 kg N ha-1. Data of earthworm population and biomass were tested using analysis of variance and continued with the least significant difference (LSD) test at the 95% significant level. The population and biomass of earthworms at MT or NT were higher than IT. The population and biomass of earthworms in the plots without fertilization were higher than those at 200 kg N ha-1. There was an interaction between the soil tillage and N fertilization on earthworm biomass observed 60 days after planting at a 0-10 cm depth. There was a positive correlation between soil pH and earthworm population and biomass before the tillage phase.

Arable fields as potential reservoirs of biodiversity: Earthworm populations increase in new leys

Managing soil to support biodiversity is important to sustain the ecosystem services provided by soils upon which society depends. There is increasing evidence that functional diversity of soil biota is important for ecosystem services, and has been degraded by intensive agriculture. Importantly, the spatial distribution of reservoirs of soil biota in and surrounding arable fields is poorly understood. In a field experiment, grass-clover ley strips were introduced into four arable fields which had been under continuous intensive/conventional arable rotation for more than 10 years. Earthworm communities in arable fields and newly established grass-clover leys, as well as field boundary land uses (hedgerows and grassy field margins), were monitored over 2 years after arable-to-ley conversions. Within 2 years, earthworm abundance in new leys was 732 ± 244 earthworms m−2, similar to that in field margin soils (619 ± 355 earthworms m−2 yr−1) and four times higher than in adjacent arable soil (185 ± 132 earthworms m−2). Relative to the arable soils, earthworm abundance under the new leys showed changes in community composition, structure and functional group, which were particularly associated with an increase in anecic earthworms; thus new leys became more similar to grassy field margins. Earthworm abundance was similar in new leys that were either connected to biodiversity reservoirs i.e. field margins and hedgerows, or not (installed earthworm barriers). This suggests that, for earthworm communities in typical arable fields, biodiversity reservoirs in adjacent field margins and hedgerows may not be critical for earthworm populations to increase. We conclude that the increase in earthworm abundance in the new leys observed over 2 years was driven by recruitment from the existing residual population in arable soils. Therefore, arable soils are also potential reservoirs of biodiversity.

Unveiling the Efficiency of Psychrophillic Aporrectodea caliginosa in Deciphering the Nutrients from Dalweed and Cow Manure with Bio-Optimization of Coprolites

There is an immense demand for vermicomposting employing psychrophilic vermiculture (Aporrectodea caliginosa) for management of wastes under the Himalayan ecosystem. Dalweed (weeds from the world-famous urban Dal Lake) and cow manure (CM) are cheaply and abundantly available bio resources in Kashmir valley. Dalweed (DW), disposed of in the heart of the city, ascribes unpleasant effects on tourism and the natural ecosystem. Initial substrate mixtures of DW and CM with different ratios (CM100, DW100, CM80:DW20, CM60:DW40, CM40:DW60 and CM20:DW80) and castings harvested were analyzed for the following parameters: pH, TOC, TN, NO3- P, K, Fe, Zn, C:N, C:P, and C:S ratio. The results of a 56day study revealed in consistency and disparity towards the bio-optimization of coprolites depending upon the type of waste residue and mixture ratio used. Treatments with medium to low dalweed residues (CM60:DW40 followed by CM80:DW20) were found to be optimum and significantly primed chemical properties of castings using A. caligenosa. C:N, C:P, and C:S ratios showed a non-linear response with maximum decrease in C:N ratio by 35%, C:P ratio by 38% in CM100, and C:S ratio by 67% in DW100. Humification ratio, humification index, and percent humic acids were changed across all the treatments with the highest respective values of 21.33 ± 1.05, 11.33 ± 0.76, and 47.83 ± 0.76 for CM60:DW40. Results also showed that the earthworm population and biomass significantly increased with the highest respective increments of 57.53% and 74.88% in CM60:DW40 over initial values. Moreover, the highest number of cocoons (95.67 ± 1.17) were recorded within CM60:DW40 and the lowest in the control (43.33 ± 1.53). Dehydrogenase and fluorescein diacetate activities were inconsistent with the highest in CM40:DW60 (64.64%) and CM20:DW80 (63.54%) respectively over the initial substrates, while highest urease activity (74.40%) was observed from CM100. The results highlight the role of A. caliginosa in sustainable transformation of CM and DW with insightful, beneficial, and priming impacts on castings for its agronomic value.

Soil quality regeneration by grass-clover leys in arable rotations compared to permanent grassland: Effects on wheat yield and resilience to drought and flooding

Intensive arable cropping depletes soil organic carbon and earthworms, leading to loss of macropores, and impaired hydrological functioning, constraining crop yields and exacerbating impacts of droughts and floods that are increasing with climate change. Grass and legume mixes traditionally grown in arable rotations (leys), are widely considered to regenerate soil functions, but there is surprisingly limited evidence of their effects on soil properties, resilience to rainfall extremes, and crop yields. Using topsoil monoliths taken from four intensively cropped arable fields, 19 month-old grass-clover ley strips in these fields, and from 3 adjacent permanent grasslands, effects on soil properties, and wheat yield in response to four-weeks of flood, drought, or ambient rain, during the stem elongation period were evaluated. Compared to arable soil, leys increased earthworm numbers, infiltration rates, macropore flow and saturated hydraulic conductivity, and reduced compaction (bulk density) resulting in improved wheat yields by 42–95 % under flood and ambient conditions. The leys showed incomplete recovery compared to permanent grassland soil, with modest gains in soil organic carbon, total nitrogen, water-holding capacity, and grain yield under drought, that were not significantly different (P > 0.05) to the arable controls. Overall, grass-clover leys regenerate earthworm populations and reverse structural degradation of intensively cultivated arable soil, facilitating adoption of no-tillage cropping to break out of the cycle of tillage-driven soil degradation. The substantial improvements in hydrological functioning by leys will help to deliver reduced flood and water pollution risks, potentially justifying payments for these ecosystem services, especially as over longer periods, leys increase soil carbon sequestration.

An Assessment of Earthworm Population Density of different Habitat Types in a Mango Cultivation Region of Palakkad District, Western Ghats

An Assessment of Earthworm Population Density of different Habitat Types in a Mango Cultivation Region of Palakkad District, Western Ghats

Earthworm species in Musa spp. plantations in Brazil and worldwide.

Bananas and plantains are major commodity/food crops that represent an important habitat for earthworms, although so far, no review is available on earthworm communities associated with banana/plantain crops worldwide. The Vale do Ribeira region is among the largest banana producing areas in Brazil, but little is known of the earthworms living there. Hence, the present study assessed earthworm populations and species in three banana plantations and adjacent Atlantic forest fragments along the Ribeira de Iguape River using standard (hand sorting) methodologies. Furthermore, we review earthworm populations reported in banana/plantain plantations worldwide. Only two species (Pontoscolex corethrurus, Amynthas gracilis) belonging to two families (Rhinodrilidae, Megascolecidae) were found in the Ribeira River valley, occurring concurrently. Abundance was low (< 13 indiv. m-2) compared with other banana plantations worldwide, that frequently surpassed 100 indiv. m-2. More than 70 studies reported earthworms from >200 banana plantations in 28 countries, and mean species richness was 2.7 per site, ranging from 1 to 10 species. Exotics predominated in most sites and P. corethrurus was the most prevalent species encountered. Overall, more than 104 species from 10 families were reported, with around 61 native and 43 exotic widespread species, mainly of the Megascolecidae, Lumbricidae and Acanthodrilidae families. Richness was highest in India (27 spp.) and the Canary Islands (25 spp.), but native species dominated only in a few countries and sites, while exotics were prevalent especially in island countries and Brazil. Lower-input practices appear to be important for earthworm communities and banana plantations can have large earthworm populations in some cases, which may be contributing to soil processes and plant production, topics that deserve further attention. However, many important banana-producing countries have not yet been evaluated, so further work is warranted, both in terms of applied ecology and biodiversity.

Three-Year Investigation of Tillage Management on the Soil Physical Environment, Earthworm Populations and Crop Yields in Croatia

The aim of this study was to determine the environmental suitability of conservation tillage systems. A 3-year experiment was conducted in Croatia, to study the effects of different tillage treatments on soil properties, with the following: deep (DC), shallow tine cultivation (SC) and ploughing (P). Soil penetration resistance (SPR) was significantly greater in P compared to DC in all three years. In 2016, it was found at 30–40 and 40–50 cm; in 2017 at 10–20 cm; in 2018 at 0–10 and 10–20 cm. However, SC was significantly greater at 20–30, 30–40 and 40–50 cm compared to P and DC in 2017. The greater surface coverage in DC and SC (&gt;30%) as compared to P (&lt;1%) provided significantly higher soil moisture content (SMC) in maize (2016) and soybean (2018). In 2017, SMC in SC was significantly lower than in P and DC. Regarding all the 3 years, the agronomic structure in DC and SC had significantly greater crumb ratio compared to P, whereas P had significantly higher dust ratio than DC and SC. Throughout the 15 measurements, DC provided the most favorable soil habitat (11 occasions out of 15). In 2017, the earthworm abundance was significantly higher in DC compared to SC. In all the three years, DC resulted the highest yield, however the difference was not significant. Higher surface coverage and SMC positively impacted the ratio of agronomic structure (decreased dust and increased crumb ratio) and earthworm abundance. It can be concluded that DC and SC provided greater soil coverage which positively affected SPR, SMC, agronomic structure and earthworm abundance as compared to P.

Effect thresholds for the earthworm Eisenia fetida: Toxicity comparison between conventional and biodegradable microplastics

Biodegradable plastics have been developed to eliminate the progressive accumulation and ever-growing threat posed by conventional fossil fuel-derived plastics. The impact of these bioplastics, particularly in an agricultural context (e.g. biopolymer mulch films), however, remains poorly understood. In this study, we compared the biotoxicity of biodegradable (polylactic acid, PLA; polypropylene carbonate, PPC) and non-degradable (polyethylene, PE) microplastics using a series of standardized bioassays using the earthworm Eisenia fetida. The responses studied included: avoidance behavior, mortality, biomass, and reproduction responses. We incubated earthworms in artificial soils amended with different concentrations of microplastic (0, 0.125, 1.25, 12.5, 125, 250, and 500 g kg−1) under laboratory conditions. This wide range allowed linear regression modeling and estimation of microplastic effect thresholds. Our results showed that microplastic concentration rather than plastic type was more important in regulating earthworm responses to soil contamination. The critical threshold for microplastic contamination was 40 g kg−1, after which earthworms exhibit microplastic avoidance behavior. A significant reduction (EC10) in number of cocoons and juvenile earthworms occurred at a concentration of 53 g kg−1 and 97 g kg−1, respectively; while no significant effect was found for survival of earthworm until levels of 500 g kg−1. Overall, the two biodegradable materials (PLA and PPC), appeared to be no more biofriendly than PE. Based on reported levels of plastic contamination in soil of up to 67 g kg−1, we conclude that microplastics are now starting to pose a threat to earthworm population. To better evaluate the risk posed by biodegradable and nondegradable plastics, further mechanistic studies on how microplastics affect earthworm behavior and the potential long-term impacts of this on soil functioning are required.