Soil Earthworm Research Articles

New challenges in soil management

Soil management represents two important tasks that are harmonization of the soil protection with demands of the crop to be grown on the given land under prevailing farming condition. Further goals are to preserve and/or develop the soil physical, biological and chemical condition and to avoid the unfavourable changes of the soil biological activity and the soil structure. Classical authors emphasised the importance of creating proper seedbed for plants. In the physical approach, tillage was believed to play an important role in controlling soil processes. Consequently, the period of several centuries dominated by this approach is referred to as the era of crop-oriented tillage (Birkás et al., 2017). The overestimation of the importance of crop requirements resulted in damaging the soils, which inevitably led to turn to the soil-focused tillage. Since the first years of climate change, as the new trends have raised concern, tillage must be turned into a climate-focused effort with the aim of reducing climate-induced stresses through improving soil quality.
 The development of soil management has always been determined by the economical background. At the same time, deteriorating site conditions have contributed to the conception of new tillage trends by forcing producers to find new solutions (e.g. dry farming theory in the past or adaptable tillage theory nowadays). Győrffy (2009) recited the most important keywords were listed in 2001 and that seemed to be important in the future of crop production. These keywords (endeavours) were as follows:
 − Biofarming, organic farming, alternative farming, biodynamic farming, low input sustainable agriculture;
 − Mid-tech farming, sustainable agriculture, soil conservation farming, no till farming, environmentally sound, environmentally friendly, diversity farming;
 − Crop production system, integrated pest management, integrated farming, high-tech farming;
 − Site specific production, site-specific technology, spatial variable technology, satellite farming;
 − Precision farming.
 Győrffy’s prognosis proved to be realistic and the efforts mentioned above have mostly been implemented. New challenges have also appeared in soil management in relation to the last decades. The most important endeavours for the future are:
 1) Preserving climate-induced stresses endangering soils.
 2) Turn to use climate mitigation soil tillage and crop production systems.
 3) Applying soil management methods are adaptable to the different soil moisture content (over dried or wet may be quite common).
 4) Use effectual water conservation tillage.
 5) Use soil condition specific tillage depth and method.
 6) Adapting the water and soil conservation methods in irrigation.
 7) Preserving and improving soil organic matter content by tillage and crop production systems.
 8) Considering that stubble residues are matter for soil protection, humus source and earthworm’ feed.
 9) Site-specific adoption of green manure and cover crops.
 10) Applying site-adopted (precision) fertilization and crop protection. Considering the development in agriculture, new endeavours will occur before long.

Cocoa Production as Affected by Shade Tree Species and Soil Quality

Cocoa is one of the agricultural commodities that have important role and are reliable in realizing agricultural development program of Indonesia. The cocoaproduction of Indonesia tends to decrease that caused by in appropriate farming. This research aimed to evaluate the shade management to cocoa productivity and evaluating the correlation between soil quality and the cocoa production with the different shade management. This research was conducted from October 2016 until June 2017 in Kaliwining Experimental Station and Soil Laboratory of Indonesian Coffee and Cocoa Research Institute (ICCRI), Jember, Indonesia. Clones at the trial plots were Sulawesi 1 and Sulawesi 2, 10 years old, and arranged in 3 m x 3 m spacing. The design of this research was conducted by observing parameters of sample trees on cocoa field. This research used three observation plots, with shade trees of leucaena (Leucaena sp.), teak (Tectona grandis), and teak combined with krete (Cassia surithensis) shade. The results indicated that shade species affected the cocoa production. Teak shade gave higher production of cocoa (i.e 3,01 kg.tree-1) compared to other species of shade (1.83 and 1.39 kg.tree-1 for leucaena and teak and krete combination, respectively). The correlation of soil quality with cocoa production showed that soil calcium content, earthworm biomass and soil bulk density were positively correlated with the production of cocoa. Shade species greatly affected the production in combination with the soil quality.

Soil physical quality response to sugarcane straw removal in Brazil: A multi-approach assessment

Crop residues have an essential role in sustaining soil functions and the removal of sugarcane straw for bioenergy production can exacerbate the adverse impacts of mechanized harvesting on soil quality. A long-term field experiment was carried out to evaluate the effects of straw removal on soil physical quality in southern Brazil. We performed a multi-approach assessment including quantitative physical indicators (bulk density–BD; soil resistance to penetration–SRP; macroporosity–MaP; microporosity–MiP; mean weight diameter of aggregates–MWD), biological indicator (earthworm abundance), apparent electric conductivity (ECa) and visual evaluation of soil structure (VESS). In addition, VESS scores were correlated with quantitative indicators for testing its potential as a feasible integrative soil quality indicator. Straw removal rates (total removal, TR–0 Mg ha−1; high removal, HR–5 Mg ha−1; low removal, LR–10 Mg ha−1; no removal, NR–15 Mg ha−1) were arranged in a randomized block design with four repetitions. Except for MaP, straw removal for four years affected all soil physical attributes, with higher soil degradation observed in TR and HR plots. Soil moisture, earthworm abundance and ECa values were reduced by higher rates of straw removal. The VESS method was able to detect the changes in soil structural quality, and VESS scores averaged 4.5 and 3.9 for the TR and HR plots respectively, thus revealing signals of severe structural degradation. The data also showed that VESS scores correlated with quantitative indicators broadly used for soil assessments, which suggest VESS as a reliable and integrative indicator for monitoring soil structural quality in sugarcane fields. Our findings support that LR, keeping about 10 Mg ha-1 of straw on the soil surface, can be a management target to ensure the sustainability of bioenergy production.

Soil properties and earthworm dynamics affected by land use systems in western Chitwan, Nepal

Field experiments were conducted in acidic soils of Mangalpur and Fulbari Village Development Committees in western Chitwan, Nepal to study the effects of different land use systems on soil properties and earthworm dynamics. Seven land use systems (cereal based lowland, cereal based upland, vegetable farm land, fruit orchard land, pasture land, forest land and farmer’s field) were used and they were replicated four times in randomized complete block designs. Soil organic matter and total soil nitrogen were significantly higher from pasture land (4.7 % and 0.2 %) and the lowest were from farmer’s field (2.4 % and 0.1 %). However, available soil phosphorous content was significantly higher from cereal based upland (448.3 kg ha-1) and it was the lowest from forest land (13.0 kg ha-1). The highest earthworm count was observed from pasture land (10.1 numbers per trap) than others but it was the lowest from farmer’s field. There were significant positive correlations between soil organic matter content and the earthworm count (r= 0.96**) and between total soil nitrogen content and earthworm count (r= 0.80**). In contrast, a significant negative correlation was observed between earthworm count and available P (r= -0.51**). Correlation between earthworm count and silt content was positive (r= 0.68**) but between earthworm count and sand content was negative (r= -0.64**). However, there were no significant relationships of earthworm count with available K, pH, bulk density and clay content of soils. The soil organic matter, total soil nitrogen and earthworm count were higher from pasture soil than other soils. As soil organic matter, total soil N, available soil P and soil texture regulated earthworm dynamics in soils. Earthworm population may be used as a bio-indicator of soil fertility status and it can be developed as an alternative technique for soil fertility evaluation after quantification and verification from further experiments on earthworm dynamics under different land use systems.Journal of the Institute of Agriculture and Animal Science.Vol. 33-34, 2015, page: 123-128

Sheep and Goat Corralling Density Effect on Soil Properties and Weed Species Diversity of Arable Lands

The hypothesis that livestock corralling improves soil properties and weed species richness was investigated in a 2-year on-farm trial conducted in Sudan savanna agro-ecology of Ghana. The effect of three stocking densities of sheep and goats corralling (0, 70 and 140 head ha−1) on soil properties and weed species diversity was evaluated in a randomized complete block design with eight replicates. Sheep and goats weighing 27 ± 2.0 and 24 ± 1.5 kg, respectively, were corralled on fallow arable lands from 19: 00 to 06: 00 GMT hours daily for 178 nights during 2014 and 2015 cropping seasons. Soil parameters measured include pH, organic carbon (OC), total nitrogen, available phosphorus, exchangeable potassium, microbial biomass carbon, microbial biomass nitrogen, soil microbial quotient, earthworm cast, bulk density, porosity, and moisture. Soil properties and weed species diversity increased (P < 0.01) with sheep and goats corralling relative to the control. Broadleaf and sedge species were positively correlated with soil OC while the grass was positively correlated with soil OC, microbial biomass carbon, bulk density, and porosity. The results suggest that crop-livestock farmers could corral 70 head ha−1 sheep and goats for soil fertility amendment on Ferric Lixisol in Sudan savanna agro-ecology of West Africa and similar agro-ecologies.

Defining a reference system for biological indicators of agricultural soil quality in Wallonia, Belgium

Tools that will enable the assessment of agricultural soil quality and include measurements of biological indicators, such as soil respiration or nitrogen mineralisation, are increasingly in demand. Such tools require the establishment of reference systems to provide comparative ‘baseline’ or ‘normal’ values. In this study, we measured the spatial and seasonal variability of eight biological indicators (including two eco-physiological quotients) in order to establish a reference system at the regional level of Wallonia (Southern Belgium).Respiration potential, microbial biomass carbon, microbial C/N ratio, net nitrogen mineralisation, metabolic potential of soil bacteria, earthworm abundance, microbial quotient, and metabolic quotient were measured at 60 sites across contrasting agricultural regions (different soil types and climate) in both grasslands and croplands. Additionally, the same biological indicators were measured four times during the vegetation period (April, June, August, and October) in 11 cropland sites to assess seasonal variability. Reference ranges were defined for each biological indicator, based on the addition of variances (seasonal and spatial) and the calculation of cumulative distribution functions.Land use was the most useful classification variable to define a reference system in Wallonia. Two separate reference systems, one for grasslands and one for croplands, were thus appropriate for Wallonia. Sampling season had a significant effect on all biological indicators. The inclusion of seasonal variability resulted in reference ranges 1.1–5.7 times wider than ranges accounting only for spatial variability. The reference system provides a basis for a first comparative assessment of soil quality for most agricultural soils of Wallonia, independent of sampling period.

Enhancement effect of earthworm (Eisenia fetida) on acetochlor biodegradation in soil and possible mechanisms

Acetochlor is a widely used chloroacetanilide herbicide and has posed environmental risks in soil and water due to its toxicity and high leaching capacity. Earthworm represents the dominant invertebrate in soil and can promote the decomposition of organic pollutants. The effect of earthworm on acetochlor degradation in soil was studied by soil column experiment with or without acetochlor and earthworm in sterile and natural soils. The degradation capacities of drilosphere components to acetochlor were investigated by microcosm experiments. Bacterial and fungal acetochlor degraders stimulated by earthworm were identified by high-throughput sequencing. The degradation kinetics of acetochlor suggested that both indigenous microorganisms and earthworm played important roles in acetochlor degradation. Acetochlor degradation was quicker in soil with earthworms than without earthworms, with the degradation rates increased by 62.3 ± 15.2% and 9.7 ± 1.7% in sterile and natural treatments respectively. The result was related to the neutralized pH, higher enzyme activities and enhanced soil microbial community diversity and richness in the presence of earthworms. Earthworm cast was the degradation hotpot in drilosphere and exhibited better anaerobic degradation capacity in microcosm experiments. The acetochlor degradation rate of cast in anaerobic environment was 12.0 ± 0.1% quicker than that in aerobic environment. Residual acetochlor in soil conferred a long-term impairment on fungal community, and this inhibition could be repaired by earthworm. Earthworm stimulated indigenous degraders like Sphingomonas and Microascales and carried suspected intestinal degraders like Mortierella and Escherichia_coli to degradation process. Cometabolism between nutrition cycle species and degraders in casts also contributed to its faster degradation rates. The study also presented some possible anaerobic degradation species like Rhodococcus, Pseudomonas_fulva and Methylobacillus.

Listening to earthworms burrowing and roots growing - acoustic signatures of soil biological activity

We report observations of acoustic emissions (AE) from growing plant roots and burrowing earthworms in soil, as a noninvasive method for monitoring biophysical processes that modify soil structure. AE emanating from earthworm and plants root activity were linked with time-lapse imaging in glass cells. Acoustic waveguides where installed in soil columns to monitor root growth in real time (mimicking field application). The cumulative AE events were in correlation with earthworm burrow lengths and with root growth. The number of AE events recorded from the soil columns with growing maize roots were several orders of magnitude larger than AE emanating from bare soil under similar conditions. The results suggest that AE monitoring may offer a window into largely unobservable dynamics of soil biomechanical processes such as root growth or patterns of earthworm activity - both important soil structure forming processes.

Effects of agricultural management practices on soil quality: A review of long-term experiments for Europe and China

In this paper we present effects of four paired agricultural management practices (organic matter (OM) addition versus no organic matter input, no-tillage (NT) versus conventional tillage, crop rotation versus monoculture, and organic agriculture versus conventional agriculture) on five key soil quality indicators, i.e., soil organic matter (SOM) content, pH, aggregate stability, earthworms (numbers) and crop yield. We have considered organic matter addition, no-tillage, crop rotation and organic agriculture as “promising practices”; no organic matter input, conventional tillage, monoculture and conventional farming were taken as the respective references or “standard practice” (baseline). Relative effects were analysed through indicator response ratio (RR) under each paired practice. For this we considered data of 30 long-term experiments collected from 13 case study sites in Europe and China as collated in the framework of the EU-China funded iSQAPER project. These were complemented with data from 42 long-term experiments across China and 402 observations of long-term trials published in the literature. Out of these, we only considered experiments covering at least five years. The results show that OM addition favourably affected all the indicators under consideration. The most favourable effect was reported on earthworm numbers, followed by yield, SOM content and soil aggregate stability. For pH, effects depended on soil type; OM input favourably affected the pH of acidic soils, whereas no clear trend was observed under NT. NT generally led to increased aggregate stability and greater SOM content in upper soil horizons. However, the magnitude of the relative effects varied, e.g. with soil texture. No-tillage practices enhanced earthworm populations, but not where herbicides or pesticides were applied to combat weeds and pests. Overall, in this review, yield slightly decreased under NT. Crop rotation had a positive effect on SOM content and yield; rotation with ley very positively influenced earthworms’ numbers. Overall, crop rotation had little impact on soil pH and aggregate stability − depending on the type of intercrop; alternatively, rotation of arable crops only resulted in adverse effects. A clear positive trend was observed for earthworm abundance under organic agriculture. Further, organic agriculture generally resulted in increased aggregate stability and greater SOM content. Overall, no clear trend was found for pH; a decrease in yield was observed under organic agriculture in this review.

Earthworms differentially modify the microbiome of arable soils varying in residue management

Earthworms are among the most important soil ecosystem engineers. Their effects on soil structure have been well documented, however, there is limited knowledge on how earthworms in the long term affect the soil microbiome, especially in arable soils. We investigated the soil microbiome of rice (cultivated under aerobic condition) and wheat fields in two consecutive seasons after manipulating earthworms and organic amendments for 14 years. Composition of soil prokaryotes and eukaryotes were analyzed by Illumina sequencing. Molecular network analysis suggest that in mulched rice fields earthworms foster species interlinked with many others and shift the dominance of prokaryotes from Planctomycetes to Proteobacteria. In contrast, in fields where residues were incorporated into the soil earthworms shifted the dominance of prokaryotes from Proteobacteria to Planctomycetes. Further, earthworms significantly increased the Proteobacteria-to-Acidobacteria ratio, a putative indicator of high nutrient turnover. Further, the ratio of prokaryote-to-eukaryote abundance was increased by earthworms when straw was incorporated into the soil. In conclusion, the results suggest that in the long term earthworms mainly modify the structure and functioning of prokaryote rather than eukaryote communities in arable fields. The effects of earthworms on the structure of microbial communities and microbial interactions are closely linked to resource management practices. The more pronounced effects of earthworms in treatments with residues mulched as compared to incorporated into the soil suggest that earthworm effects in part were due to bioturbation, i.e. mixing straw with mineral soil.

Impact of wastewater effluent containing aged nanoparticles and other components on biological activities of the soil microbiome, Arabidopsis plants, and earthworms

The amount of engineered nanomaterials (ENMs) in the environment has been increasing due to their industrial and commercial applications. Different types of metallic nanoparticles (NPs) have been detected in effluents from wastewater treatment plants (WWTPs). The effluents have been reclaimed for crop irrigation in many arid and semi-arid areas. Here, a soil micro-ecosystem was established including a microbiome, 4 Arabidopsis thaliana plants, and 3 Eisenia fetida earthworms, for a duration of 95 days. The impact of wastewater effluent (WE) containing aged NPs was studied. WE was taken from a local WWTP and exhibited the presence of Ti, Ag, and Zn up to 97.0 ± 9.4, 27.4 ± 3.9, and 4.1 ± 3.6 µg/L, respectively, as well as the presence of nanoscale particles (1–100 nm in diameter). The plants were irrigated with WE or deionized water (DIW). After 95 days, significantly higher concentrations of extractable Ti and Zn (439.2 ± 24.4 and 9.0 ± 0.5 mg/kg, respectively) were found in WE-irrigated soil than those in DIW-irrigated soil (161.2 ± 2.1 and 4.0 ± 0.1 mg/kg). The extractable Ag concentrations did not differ significantly between the WE- and DIW-irrigated soil. Although microbial biomass carbon and nitrogen were not significantly reduced, the population distribution of the microbial communities was shifted in WE-irrigated soil compared to the control. The abundance of cyanobacteria (Cyanophyta) was increased by 12.5% in the WE-irrigated soil as manifested mainly by an increase of Trichodesmium spp., and the abundance of unknown archaea was enhanced from 26.7% in the control to 40.5% in the WE-irrigated soil. The biomasses of A. thaliana and E. fetida were not significantly changed by WE exposure. However, A. thaliana had a noticeable shortened life cycle, and corrected total cell fluorescence was much higher in the roots of WE-irrigated plants compared to the control. These impacts on the soil micro-ecosystem may have resulted from the aged NPs and/or the metal ions released from these NPs, as well as other components in the WE. Taken together, these results should help inform the reuse of WE containing aged NPs and other components in sustainable agriculture.

Individual and combined effects of herbicide tribenuron-methyl and fungicide tebuconazole on soil earthworm Eisenia fetida

Earthworms are soil engineers that alter the soil bio-physical properties to favor plant growth whereas pesticides represent a significant threat to their abundance and soil health. Thus, we investigated the toxic effects of tribenuron-methyl (TBM) and tebuconazole (TEB) on the soil earthworm, Eisenia fetida. The TBM demonstrated low toxicity to E. fetida in the contact filter paper and artificial soil tests, with median lethal concentrations (LC50) of 135.6 μg cm−2 at 48 h and 511 mg kg−1 on day 14, respectively. Similarly, TEB also showed low toxicity to E. fetida in the artificial soil test with LC50 of 287 mg kg−1 on day 14. However, TEB was highly toxic to earthworm in the contact filter paper test with LC50 of 5.7 μg cm−2 at 48 h. The mixture of two pesticides had an antagonistic effect on the earthworm. Under 0.1 LC50 of TBM and TEB, either single or combined application of pesticides induced oxidative stress and inhibited cellulase activity in early days of the earthworm exposure. However, both pesticides did not damage the earthworm DNA. Our results suggest that pesticides can negatively affect soil earthworms and provide valuable information regarding the responses of soil biological engineers to the lethal agrochemicals.

Perfluoroalkylsulfonic and carboxylic acids in earthworms (Eisenia fetida): Accumulation and effects results from spiked soils at PFAS concentrations bracketing environmental relevance

Effects of perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and perfluoroheptanoic acid (PFHpA) on earthworms (Eisenia fetida) in soils contaminated with these compounds at 0.1, 1, 10, 1,000, and 100,000 μg kg−1 dry weight, covering concentration levels found in background, biosolid–amended, and facility–surrounding soils, were investigated. Earthworms were exposed to spiked soil for 21 days. Concentrations of these compounds in earthworms after 21-d exposure ranged from below detection to 127 mg kg−1 wet weight with the rank order of PFNA > PFHxS > PFHpA > PFBS; no mortality of earthworms was observed in all treatments including controls, except PFBS at 1,000 μg kg−1 and all PFASs at 100,000 μg kg−1. The highest weight loss (29%) was observed for earthworms exposed to PFNA at 100,000 μg kg−1, which was significantly different from all other treatments except PFHpA at 100,000 μg kg−1. These results are expected to fill some data gaps in toxicity of PFASs in terrestrial environments and provide helpful information on the potential for trophic transport of PFASs from soil to higher organisms.

Do recommended doses of glyphosate-based herbicides affect soil invertebrates? Field and laboratory screening tests to risk assessment

Despite glyphosate-based herbicides are widely used in agriculture, forestry and gardens, little is known about its effects on non-target organisms. The present work evaluated the ecotoxicity of four formulated products (Roundup® Original, Trop®, Zapp® Qi 620 and Crucial®) on soil invertebrates. Screening ecotoxicity tests were carried out with soil and oat straw collected in a field experiment, besides laboratory-spiked soils. Screening tests included avoidance behaviour of earthworms (Eisenia andrei), collembolans (Folsomia candida) and isopods (Porcellio dilatatus) in single and multispecies tests; reproduction of collembolans (F. candida), and bait lamina in field. Non-avoidance behaviour was observed in standard tests (earthworms) in soil, neither in multispecies tests (earthworm + isopods) using oat straw, while for collembolans it occurred for the product Zapp® Qi 620 even at the recommended dose. Reproduction of F. candida was not impaired even at high doses in laboratory-spiked soils. Feeding activity on bait lamina test was impaired in treatment corresponding to the red label product, Crucial®. Results showed the relevance of bait lamina test on screening the impact of herbicides in the field. The findings highlight the importance of considering different formulations for the same active ingredient in risk assessment of pesticides.

Influence of metal-contamination on distribution in subcellular fractions of the earthworm (Metaphire californica) from Hunan Province, China

Earthworms have the ability to accumulate of heavy metals, however, there was few studies that addressed the metals in earthworm at subcellular levels in fields. The distributions of metals (Cd, Cu, Zn, and Pb) in subcellular fractions (cytosol, debris, and granules) of earthworm Metaphire californica were investigated. The relationship between soil metals and earthworms were analyzed to explain its high plasticity to inhabit in situ contaminated soil of Hunan Province, south China. The concentration of Cd in subcellular compartments showed the same pattern as Cu in the order of cytosol > debris > granules. The distribution of Zn and Pb in earthworms indicated a similar propensity for different subcellular fractions that ranked as granules > debris > cytosol for Zn, and granules > cytosol > debris for Pb. The internal metal concentrations in earthworms increased with the soil metals (p<0.05). Significant positive correlations were found between soil Cd and Cd concentrations in cytosol and debris (p<0.01). Moreover, the soil Pb concentration significantly influenced the Pb concentrations in cytosol and debris (p<0.01), similar to that of Cd. The soil Cu concentrations was only associated with the Cu in granules (p<0.05). Soil Zn concentrations correlated with the Zn concentrations in each subcellular fraction (p<0.05). Our results provide insights into the variations of metals partitioning in earthworms at subcellular levels and the relationships of soil metals, which could be one of the detoxification strategies to adapt the long-term contaminated environment.

Soil biota in boreal urban greenspace: Responses to plant type and age

Plant functional type influences the abundance and distribution of soil biota. With time, as root systems develop, such effects become more apparent. The relationship of plant type and time with the structure and abundance of soil microbial and invertebrate communities has been widely investigated in a variety of systems. However, much less is known about long-term soil community dynamics within the context of urban environments. In this study, we investigated how soil microbes, nematodes and earthworms respond to different plant functional types (lawns only and lawns with deciduous or evergreen trees) and park age in 41 urban parks in southern Finland. As non-urban controls we included deciduous and evergreen trees in 5 forest sites. We expected that microbial biomass and the relative abundance of fungi over bacteria would increase with time. We also expected major differences in soil microbial and nematode communities depending on vegetation: we hypothesized that i) the presence of trees, and evergreens in particular, would support a greater abundance of fungi and fungal-feeding nematodes over bacteria and bacterial-feeding nematodes and ii) the fungi to bacteria ratio would be lowest in lawns, with deciduous trees showing intermediate values. In contrast to our predictions, we showed that old deciduous trees, rather than evergreens, supported the highest fungal abundances and fungal-feeding nematodes in the soil. Consistent with our predictions, microbial biomass in urban park soils tended to increase with time, whereas – in contrast to our hypotheses – fungal-feeding nematode abundance declined. Even in the oldest parks included in the current study, microbial biomass estimates never approximated those in the minimally managed natural forests, where biomass estimates were three times higher. Anecic earthworm abundance also increased with time in urban parks, whereas abundances of fungal-feeding, plant-feeding and omnivorous nematodes, as well as those of epigeic and endogeic earthworms remained constant with time and without any distinct differences between urban parks and the control forests. Our findings highlight that although urban park soils harbor diverse soil communities and considerable microbial biomass, they are distinct from adjacent natural sites in community composition and biomass.

Different biotransformation behaviors of perfluorooctane sulfonamide in wheat (Triticum aestivum L.) from earthworms (Eisenia fetida)

Perfluorooctane sulfonamide (PFOSA) is a precursor of perfluorooctane sulfonic acid (PFOS) and can be broken down to PFOS in environment and biota. In the present work, PFOSA was spiked in soil and its biodegradation in soil, uptake and metabolism in wheat (Triticum aestivum L.) and earthworms (Eisenia fetida) were investigated. The results indicated that PFOSA could be biodegraded to highly stable PFOS, which has the same perfluorinated carbon chain length as PFOSA, by microbes in soil. PFOSA could be taken up by wheat root and earthworm from soil with higher bioaccumulation ability than PFOS. In both wheat and earthworms, PFOSA also degraded to PFOS. However, other shorter-chain perfluoroalkane sulfonates (PFSAs), including perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS), were observed in wheat, but not in soil and earthworms, suggesting that wheat displayed distinctly different degradation mechanisms to PFOSA from soil microbes and earthworms.

Herbicidal effect on the bio-indicators of soil health- A review

Soil microbial population, earth worms in soil, soil enzyme activity and organ carbon content in soil are considered as the bio indicators of soil health. They are used as indicators of soil health because of their active role in soil organic matter production, decomposition of xenobiotics and cycling of nutrients, ease of measurement and rapid response to changes in management practices. The assessment of soil health can be used to develop more sustainable crop production system. A number of herbicides have been introduced as pre and post emergence weed killer. The impact of herbicides on soil health depends on the soil type, type and concentration of herbicide used, sensitivity to non-target organisms and environmental conditions. The review elaborates the impact of herbicidal application on the biological indicators of soil health.

Chronic and reproductive toxicity of cadmium, zinc, and lead in binary and tertiary mixtures to the earthworm (Eisenia fetida)

The presence of one metal can alter the toxicity of another metal by having an additive, synergistic, or antagonistic impact. Mixed metal pollution has clear ecological consequences. The importance of use of earthworms for ecological health monitoring is recognized widely. This study investigated the effect of binary and tertiary metal mixtures on the toxicity, bioaccumulation, and reproduction of the Eisenia fetida in different South Australian soils. The end points used in this 56-day reproduction study were avoidance behavior, worm mortality, weight loss, reproduction, and metal (Cd, Zn, and Pb) bioaccumulation. The three soils (acidic, neutral, and alkaline) were spiked with selected binary and tertiary concentration mixtures that considered the soil quality guideline values, EC50 and LC50 values for Cd, Zn, and Pb obtained from the previous single metal earthworm experiments done by the authors. In acidic soil, Zn and Cd constituted the most toxic metal combination to earthworms. However, in contrast to this observation, the same metal combination was the least toxic one to earthworms in neutral and alkaline soils. For Zn and Pb spiked soils, relationships between soil and internal metal concentrations were found with R 2 = 0.63, r = 0.8, and R 2 = 0.94, p < 0.01, respectively, for Zn and Pb. This study indicates that earthworms have high tendency to bioaccumulate heavy metals in their tissues and hence serves as ecological indicators of soil heavy metal contamination. The highest bioaccumulation factor (0–9) was evident for Cd in contaminated soils. This study demonstrated the role of soil edaphic factors and metal-metal interactions in the toxicity of metal mixtures to E. fetida. In Zn and Pb binary mixture spiked acidic soil, mortality of 60% was recorded even when the Pb and Zn concentrations were below the Canada and Dutch EIL (ecological investigational levels) values. This indicates the current guideline values are not safe for mixed metal toxicity. Therefore, care must be taken when predicting metal toxicities in mixed metal contaminated soils.

Mechanism of toxicity and transformation of silver nanoparticles: Inclusive assessment in earthworm-microbe-soil-plant system

Long term and inclusive toxicity studies encompassing soil, plants, and organisms are rare in literature for AgNPs. This study examines AgNP behavior in soil-plant system through 72weeks long soil experiment, earthworm response, and plant metabolic analysis. AgNP exposed earthworms did not show reproductive failure; yet high oxidative stress and reduced protein synthesis led to significant weight loss. Such stress was highest with AgNP50 exposure. Correspondingly, the 50ppm exposure of AgNP was capable to reduce nutrient availability and microbial growth in soil. Contrary to previous reports, we demonstrated that dissolution rate of AgNP increased with time in soil. Dynamic Light Scattering and UV-VIS assessments exhibited concentration and time dependent agglomeration of AgNP in soil and aqueous media. Moreover, lab based experiments in aqueous medium revealed that significant reduction in silver availability was due to formation of Ag2S or Ag3PO4; which also greatly affected the P and S availability. Although the vegetative growth of tomato was normal, AgNP (10mgkg−1) treatment markedly upset the fruit yield. The 10mgkg−1 AgNP exposure significantly enhanced oxidative stress and Ag uptake in plants; consequently, retarded N-assimilating enzyme (glutamate synthase, glutamine synthetase, and nitrate reductase) activity by suppressing their genes in plants. Eventually, photosynthesis and CO2 assimilating efficiency were severely disrupted. These assays were vital to appreciate the true toxicity and are not well attended in most of the studies with AgNPs.