Earthworms affect plant growth and resistance against herbivores: A meta‐analysis

Effects of gerbil disturbance on the ecological stoichiometric characteristics and nutrient uptake and utilization of H. ammodendron

Rodent activity is an important factor that affects the growth and development of Haloxylon ammodendron. Studying the effect of rodent disturbance on plant ecological stoichiometric ratios helps evaluate the mechanism by which rodent disturbance affects plant growth and development. In this study, H. ammodendron, a dominant plant, and the gerbil, a typical rodent in the Gurbantunggut Desert, were selected as research objects. By measuring the biomass, root soil , and C: N: P ecostoichiometric ratios of the assimilated branches of H. ammodendron at different growth phases, the impact of great gerbil disturbance on the biomass, ecostoichiometric ratios, and nutrient uptake and use of H. ammodendron were investigated at different growth stages. The results showed that the gerbil disturbance increased the biomass of the aboveground part of the adult H. ammodendron. Gerbil disturbance also increased the soil N/P around the roots during the growth stage and the assimilation branch when the plants were middle-aged. In addition, this disturbance decreased the C/N value. The photosynthetic nitrogen use efficiency (PNUE) and photosynthetic phosphorus use efficiency (PPUE) of H. ammodendron during various growth periods decreased, and the absorption of total nitrogen (TN) in the soil decreased. However, soil total potassium (TK) absorption increased. The soil TN absorption capacity was weakened by gerbil disturbance. Meanwhile, the TK absorption capacity was enhanced, and the biomass of adult H. ammodendron increased. PNUE and PPUE of H. ammodendron were decreased by gerbil interference. In this study, the influence of gerbil disturbance on nutrient absorption by H. ammodendron and use of H. ammodendron was determined. This has provided a baseline for further studies on the coexistence mechanisms of gerbils and H. ammodendron.

Earthworms Enhance Crop Resistance to Insects Under Microplastic Stress by Mobilizing Physical and Chemical Defenses

To assess the ecological risk of microplastics (MPs) in agricultural systems, it is critical to simultaneously focus on MP-mediated single-organism response and different trophic-level organism interaction. Herein, we placed earthworms in soils contaminated with different concentrations (0.02% and 0.2% w/w) of polyethylene (PE) and polypropylene (PP) MPs to investigate the effect of earthworms on tomato against Helicoverpa armigera (H. armigera) under MPs stress. We found that earthworms alleviated the inhibitory effects of MPs stress on tomato growth and disrupted H. armigera growth. Compared to individual MPs exposure, earthworm incorporation significantly increased the silicon and lignin content in herbivore-damaged tomato leaves by 19.1% and 57.6%, respectively. Metabolites involved in chemical defense (chlorogenic acid) and phytohormones (jasmonic acid) were also activated by earthworm incorporation. Furthermore, earthworms effectively reduced oxidative damage induced by H. armigera via promoting antioxidant metabolism. Overall, our results suggest that utilizing earthworms to regulate above- and below-ground interactions could be a promising strategy for promoting green agriculture.

Predators control pests and increase yield across crop types and climates: a meta-analysis

Pesticides have well-documented negative consequences to control crop pests, and natural predators are alternatives and can provide an ecosystem service as biological control agents. However, there remains considerable uncertainty regarding whether such biological control can be a widely applicable solution, especially given ongoing climatic variation and climate change. Here, we performed a meta-analysis focused on field studies with natural predators to explore broadly whether and how predators might control pests and in turn increase yield. We also contrasted across studies pest suppression by a single and multiple predators and how climate influence biological control. Predators reduced pest populations by 73% on average, and increased crop yield by 25% on average. Surprisingly, the impact of predators did not depend on whether there were many or a single predator species. Precipitation seasonality was a key climatic influence on biological control: as seasonality increased, the impact of predators on pest populations increased. Taken together, the positive contribution of predators in controlling pests and increasing yield, and the consistency of such responses in the face of precipitation variability, suggest that biocontrol has the potential to be an important part of pest management and increasing food supplies as the planet precipitation patterns become increasingly variable.

Specialist reassociation and residence time modulate the evolution of defense in invasive plants: A meta-analysis

Invasive plants typically escape specialist herbivores but are often attacked by generalist herbivores in their introduced ranges. The shifting defense hypothesis suggests that this will cause invasive plants to evolve lower resistance against specialists, higher resistance against generalists, and greater tolerance to herbivore damage. However, the duration and direction of selective pressures can shape the evolutionary responses of resistance and tolerance for invasive plants. Two critical factors are (1) residence time (length of time that an invasive species has been in its introduced range) and (2) specialist herbivore reassociation (attack by purposely or accidentally introduced specialists). Yet, these two factors have not been considered simultaneously in previous quantitative syntheses. Here, we performed a meta-analysis with 367 effect sizes from 70 studies of 35 invasive plant species from native and invasive populations. We tested how the residence time of invasive plant species and specialist reassociation in their introduced ranges affected evolutionary responses of defenses against specialists and generalists, including herbivore resistance traits (physical barriers, digestibility reducers and toxins), resistance effects (performance of and damage caused by specialists or generalists) and tolerance to damage (from specialists or generalists). We found that residence time and specialist reassociation each significantly altered digestibility reducers, specialist performance, generalist damage, and tolerance to specialist damage. Furthermore, residence time and specialist reassociation strongly altered toxins and generalist performance, respectively. When we restricted consideration to invasive plant species with both longer residence times and no reassociation with specialists, invasive populations had lower resistance to specialists, similar resistance to generalists, and higher tolerance to damage from both herbivore types, compared with native populations. We conclude that the duration and direction of selective pressure shape the evolutionary responses of invasive plants. Under long-term (long residence time) and stable (no specialist reassociation) selective pressure, invasive plants generally decrease resistance to specialists and increase tolerance to generalist damage that provides mixed support for the shifting defense hypothesis.

Can antimony contamination in soil undermine the ecological contributions of earthworms?

As antimony (Sb) has been increasingly used in manufacturing industries (e.g., alloy, polymer and electronics industries), Sb contamination in the soil environment becomes widely reported and has drawn growing attention due to the toxicity of Sb to living organisms. Whether soil-dwelling organisms can tolerate Sb toxicity and maintain their ecological functions remains poorly understood. Using a cosmopolitan, ecologically important earthworm species (Eisenia fetida) as an ideal model organism, we examine the effects of Sb on the physiological, molecular and behavioural responses of earthworms to different levels of Sb contamination in soil (0, 10, 50, 100, 250 and 500 mg/kg). We found that earthworms could tolerate heavy Sb contamination (100 mg/kg) by boosting their antioxidant defence (POD and GST) and immune systems (ACP) so that their body weight and survival rate were sustained (c.f. control). However, these systems were compromised under extreme Sb contamination (500 mg/kg), leading to mortality. As such, earthworms exhibited avoidance behaviour to escape from the Sb-contaminated soil, implying the loss of their ecological contributions to the environment (e.g., increase in soil aeration and maintenance of soil structure). By measuring various types of biomarkers along a concentration gradient, this study provides a mechanistic understanding of how earthworms resist or succumb to Sb toxicity. Since extreme Sb contamination in soil (>100 mg/kg) is rarely found in nature, we are optimistic that the health and performance of earthworms are not influenced by Sb in most circumstances, but regular monitoring of Sb in soil is recommended to ensure the integrity and functioning of soil environment. Further studies are recommended to evaluate the long-term impact of Sb in the soil ecosystem through bioaccumulation and trophic transfer among soil-dwelling organisms.

Augmentation of plant biomass productivity using epigeic earthworm Perionyx excavatus and Eisenia fetida as soil nutrient facilitators

With the increasing demand for organic food production, the earthworm is used as a soil nutrient facilitator. The present study was conducted to assess the effect of epigeic earthworms Perionyx excavatus and Eisenia. fetida on soil nutrients and the consequent improvement of biomass productivity and yield of Capsicum chinense Jacq and Zea mays L. The experiment was conducted in 5 L and 15 L capacity plastic pots for C. chinense and Z. mays with 150 g and 300 g of half-decomposed cow dung, respectively. It was observed that the weekly harvest rate of ripened chili was 17.59 g, 13.91 g, and 9.24 g in P. excavatus, control, and E. fetida pot showing 26.49% higher in P. excavatus. Also, the total kernel count per corn was significantly different (F(2, 9) = 37.78, p < 0.05), with the highest kernel present in P. excavatus(333.5 ± 13.5), followed by E. fetida(261.5 ± 16.5) and control (235 ± 22). The impact of P. excavatus was more perceptible in C. chinense, indicated by higher leaf biomass (69.16%), root length (30.14%), and fruit harvest (71.03%). However, the effect of E. fetida was noticed more in Z. mays (stem length, 19.24%, stem biomass, 14.39%, root biomass, 20.9%, kernel count, 41.91%, and kernel weight, 95.07%). Enhanced plant productivity was also supported by an increasing soil nutrient turnover in organic carbon (OC) (25.76% and 23.4%), Phosphorus (P) (31.03% and 25.67%), and Potassium (K) (41.67% and 12.26) in P. excavatus and E. fetida worked soil respectively. The findings indicate that earthworms have a notable impact on plant biomass productivity by promoting the mineralization of soil nutrients and imply on possibility of organic cultivation of seasonal vegetables without using synthetic fertilizers.

Earthworm Aporrectodea molleri (oligochaeta)'s coelomic fluid-associated bacteria modify soil biochemical properties and improve maize (Zea mays L.) plant growth under abiotic stress conditions

This study evaluated the impact of Aporrectodea molleri's coelomic fluid-associated bacteria (CFB) on Zea mays L. growth and soil biochemical characteristics under abiotic stress conditions, including alkaline soil (pH = 8) and nitrogen (N), phosphate (P), and potassium (K) deficit. Compared to maize cultivated in uninoculated soil, the effect of CFB on boosting plant growth under abiotic stress was notably exceptional. Different CFB treatments increased significantly root and shoot length by 50% and 21%, respectively. Furthermore, the presence of isolates in soil resulted in a significant increase in plant fresh and dry weights (of up to 113% and 91% for roots, and up to 173% and 44% for shoots), leaf surface (78%), and steam diameter (107%). Overall, soil inoculation with CFB significantly (P < 0.05) enhanced chlorophyll and water content in the plant compared to the untreated soil. Despite the soil's alkaline condition, CFB drastically boosted soil quality by increasing nutrient availability (up to 30 ppm for N, 2 ppm for P, and 60 ppm for K) and enzyme activity (up to 1.14 μg p-NP h^-1 g^-1 for acide phosphatase, 9 μg p-NP h^-1 g^-1 for alkaline phosphatase and 40 μg NH₄-N 2 h^-1 g^-1 for urease), throughout the early stages of the growth period. Interestingly, alkaline phosphatase concentrations were substantially greater in treatments with different isolates than acid phosphatase. Furthermore, the principal component analysis showed that the inoculation with bacteria strains CFB1 Buttiauxella gaviniae and CFB3 Aeromonas hydrophila had a significantly better stimulatory stimulatory and direct influence on maize growth than the other isolates had a substantial effect on soil's biochemical features. Thus, we assumed that the beneficial contribution of earthworms in the rhizosphere might be attributed in large part to associated microorganisms.

Earthworms Drive the Effect of La2O3 Nanoparticles on Radish Taproot Metabolite Profiles and Rhizosphere Microbial Communities

To promote the sustainable and safe application of nanotechnology employing engineered nanoparticles (NPs) in agroecosystems, it is crucial to pay more attention to the NP-mediated biological response process and environmental impact assessment simultaneously. Herein, 50 mg kg^-1 La₂O₃ NPs were added to soils without and with earthworms for cherry radish growth for 50 days to investigate the response changes of metabolites in radish above- and below-ground organs and rhizosphere bacterial communities. We found that La₂O₃ NP exposure, especially with earthworms, notably increased the La bioavailability and uptake by taproots and eventually increased radish leaf sucrose content and plant biomass. The La₂O₃ NP exposure significantly altered metabolite profiles in taproot flesh and peel tissues, and particularly La₂O₃ NP exposure combined with earthworms was more conducive to La₂O₃ NPs to promote radish taproot peel to synthesize more secondary antioxidant metabolites. Moreover, compared with the control, the La₂O₃ NP exposure resulted in weaker and fewer correlations between rhizosphere bacteria and taproot metabolites, but this was recovered somewhat after the inoculation of earthworms. Altogether, our results provide novel insights into the soil-fauna-driven biological and biochemical impact of La₂O₃ NP exposure on edible root crops and the long-term environmental risks to the rhizosphere microbiota in agroecosystems.

Impaired microbial N-acyl homoserine lactone signalling increases plant resistance to aphids across variable abiotic and biotic environments

Beneficial bacteria interact with plants using signalling molecules, such as N-acyl homoserine-lactones (AHLs). Although there is evidence that these molecules affect plant responses to pathogens, few studies have examined their effect on plant-insect and microbiome interactions, especially under variable soil conditions. We investigated the effect of the AHL-producing rhizobacterium Acidovorax radicis and its AHL-negative mutant (does not produce AHLs) on modulating barley (Hordeum vulgare) plant interactions with cereal aphids (Sitobion avenae) and earthworms (Dendrobaena veneta) across variable nutrient soils. Acidovorax radicis inoculation increased plant growth and suppressed aphids, with stronger effects by the AHL-negative mutant. However, effects varied between barley cultivars and the presence of earthworms altered interaction outcomes. Bacteria-induced plant defences differed between cultivars, and aphid exposure, with pathogenesis-related and WRKY pathways partly explaining the ecological effects in the more resistant cultivars. Additionally, we observed few but specific indirect effects via the wider root microbiome where the AHL-mutant strain influenced rare OTU abundances. We conclude that bacterial AHL-signalling disruption affects plant-microbial interactions by inducing different plant pathways, leading to increased insect resistance, also mediated by the surrounding biotic and abiotic environment. Understanding the mechanisms by which beneficial bacteria can reduce insect pests is a key research area for developing effective insect pest management strategies in sustainable agriculture.

Earthworms Modulate Impacts of Soil Heterogeneity on Plant Growth at Different Spatial Scales

Soil heterogeneity (uneven distribution of soil nutrients and/or other properties) is ubiquitous in nature and can greatly affect plant growth. As earthworm activity can influence nutrient redistribution in the soil, we hypothesize that earthworms may alter the effect of soil heterogeneity on plant growth and this effect may depend on the scale of soil heterogeneity. To test these hypotheses, we grew the clonal grass Leymus chinensis in three soil treatments (heterogeneous large vs. heterogeneous small patch vs. homogeneous soil treatment) with or without earthworms [i.e., Eisenia fetida Savigny (Lumbricidae, epigeic redworm)]. In the heterogeneous treatments, the soil consisted of patches with and without 15N-labeled litter (referred to as high- and low-quality patches, respectively), and in the homogeneous treatment, the soil was an even mixture of the two types of soil patches. Biomass of L. chinensis was significantly higher in the high- than in the low-quality patches, showing the foraging response; this foraging response occurred at both scales and under both earthworm treatments. Compared to the homogeneous treatment, the heterogeneous large patch treatment increased biomass of L. chinensis without earthworms, but decreased it with earthworms. In contrast, biomass of L. chinensis in the heterogeneous small patch treatment did not differ from that in the homogeneous treatment, irrespective of earthworms. Belowground biomass was much greater in the heterogeneous small than in the heterogeneous large patch treatment without earthworms, but it did not differ between these two scale treatments with earthworms. In the heterogeneous treatments, soil 15N was greater in the high- than in the low-quality patches, but this effect became much weaker with than without earthworms, suggesting that earthworm activity homogenized the soil. We conclude that earthworms can change the impact of soil heterogeneity on plant growth via homogenizing the soil, and that this effect of earthworms varies with patch scale. Such scale-dependent interactive effects of soil heterogeneity and earthworms could be a potential mechanism modulating plant community structure and productivity.

Nutrient variation induced by rodent disturbance in Haloxylon ammodendron as a target transfer strategy

Nutrients form a link between herbivores and plant. This study explored the physiological and ecological response mechanism of Haloxylon ammodendron population to rodent disturbance in Gurbantunggut Desert from the perspective of nutrient cycle. Through field investigation, we quantified rodent disturbance intensity (DI) to H. ammodendron and analyzed the ecological response mechanism of H. ammodendron population to rodent disturbance from the perspective of plant and soil nutrient cycling and changes. The results indicated that moderate rodent DI (number of effective burrows = 3-6) was the maximum limit that can be tolerated by H. ammodendron; the threshold for optimal H. ammodendron response to rodent disturbance was mild (number of burrows = 1-3). Meanwhile, the rodent disturbance caused significant nutrient enrichment (e.g., organic carbon, available phosphorus, and available potassium) in the deeper soil (at 20-40 and 40-60 cm depth) and significantly reduced the soil total salt content (p < .05). Furthermore, as the DI increased, the branches of H. ammodendron showed significantly increased soluble total sugar, crude fiber, and total nitrogen contents (p < .05) but significantly decreased crude fat and crude protein contents (p < .05); these results are related to the nutritional target transfer strategy evolved by H. ammodendron for long-term resistance to rodent disturbance. The current study clarified the optimal disturbance model for mutually beneficial H. ammodendron-great gerbil relationship, on the basis of which the ecological response mechanism of H. ammodendron population to rodent disturbance in deserts was illustrated. The current study provides a scientific basis for the protection mechanisms of desert plants to rodent disturbance.

The impact of invertebrate decomposers on plants and soil

Soil invertebrates make significant contributions to the recycling of dead plant material across the globe. However, studies focussed on the consequences of decomposition for plant communities largely ignore soil fauna across all ecosystems, because microbes are often considered the primary agents of decay. Here, we explore the role of invertebrates as not simply facilitators of microbial decomposition, but as true decomposers, able to break down dead organic matter with their own endogenic enzymes, with direct and indirect impacts on the soil environment and plants. We recommend a holistic view of decomposition, highlighting how invertebrates and microbes act in synergy to degrade organic matter, providing ecological services that underpin plant growth and survival.

Invasive earthworms reduce chemical defense and increase herbivory and pathogen infection in native trees

Recent research shows that earthworms can alter defense traits of plants against herbivores and pathogens by affecting soil biochemistry. Yet, the effects of invasive earthworms on defense traits of native plants from previously earthworm-free ecosystems as well as the consequences for multitrophic interactions are virtually unknown.Here we use a combination of an observational study and a complementary experimental study to investigate the effects of invasive earthworms on leaf defense traits, herbivore damage and pathogen infection in two poplar tree species (Populus balsamifera and Populus tremuloides) native to North American boreal forests.Our observational study showed that earthworm invasion was associated with enhanced leaf herbivory (by leaf-chewing insects) in saplings of both tree species. However, we only detected significant shifts in the concentration of chemical defense compounds in response to earthworm invasion for P. balsamifera. Specifically, leaf phenolic concentrations, including salicinoids and catechin, were lower in P. balsamifera from earthworm-invaded sites.Our experimental study confirmed an earthworm-induced reduction in leaf defense levels in P. balsamifera for one of the defense compounds, tremulacin. The experimental study additionally showed that invasive earthworms reduced leaf dry matter content, potentially increasing leaf palatability, and enhanced susceptibility of trees to infection by a fungal pathogen, but not to aphid infestation, in the same tree species. Synthesis. Our results show that invasive earthworms can decrease the concentrations of some chemical defense compounds in P. balsamifera, which could make them susceptible to leaf-chewing insects. Such potential impacts of invasive earthworms are likely to have implications for tree survival and competition, native tree biodiversity and ecosystem functioning.

Invasive plants exert disproportionately negative allelopathic effects on the growth and physiology of the earthworm Eisenia fetida

Exotic invasive plants possess the capacity to disrupt and extirpate populations of native species. Native plants' increased sensitivity to invaders' allelochemicals is a mechanism by which this can occur. However, it is not clear whether and how the allelopathic effects of invasive plants affect members of the soil faunal community - particularly the important functional guild of earthworms. We used the model earthworm Eisenia fetida to investigate the responses to extracts from the widely invasive Asterids (Ageratina adenophora, Bidens pilosa, Erigeron annuus) and closely-related native species in a greenhouse experiment. We observed declines in body mass and respiration, and increases in oxidative and DNA damage biomarkers in the native earthworm E. fetida when grown under root and leaf extracts from these invasive plants. These effects were concentration-dependent, and worm growth and physiology was most negatively affected under the highest concentrations of leaf extracts. Most importantly, extracts from invasive plants caused significantly more negative effects on E. fetida than did extracts from native plant species, indicating allelopathy from invasive plants may inhibit earthworm physiological functioning. These results expand the domain of the novel weapons hypothesis to the earthworm guild and demonstrate the utility of E. fetida as a bioindicator for plant allelochemicals.

Bioturbation by endogeic earthworms facilitates entomopathogenic nematode movement toward herbivore-damaged maize roots

Entomopathogenic nematodes (EPNs) have been extensively studied as potential biological control agents against root-feeding crop pests. Maize roots under rootworm attack have been shown to release volatile organic compounds, such as (E)-β-caryophyllene (Eβc) that guide EPNs toward the damaging larvae. As yet, it is unknown how belowground ecosystems engineers, such as earthworms, affect the biological control capacity of EPNs by altering the root Eβc-mediated tritrophic interactions. We here asked whether and how, the presence of endogeic earthworms affects the ability of EPNs to find root-feeding larvae of the beetle Diabrotica balteata. First, we performed a field mesocosm experiment with two diverse cropping systems, and revealed that the presence of earthworms increased the EPN infection potential of larvae near maize roots. Subsequently, using climate-controlled, olfactometer-based bioassays, we confirmed that EPNs response to Eβc alone (released from dispensers) was two-fold higher in earthworm-worked soil than in earthworm-free soil. Together our results indicate that endogeic earthworms, through burrowing and casting activities, not only change soil properties in a way that improves soil fertility but may also enhance the biocontrol potential of EPNs against root feeding pests. For an ecologically-sound pest reduction in crop fields, we advocate agricultural practices that favour earthworm community structure and diversity.

Nano-enabled improvements of growth and nutritional quality in food plants driven by rhizosphere processes

With the rising global population growth and limitation of traditional agricultural technology, global crop production could not provide enough nutrients to assure adequate intake for all people. Nano-fertilizers and nano-pesticides have 20-30% higher efficacy than conventional products, which offer an effective solution to the above-mentioned problem. Rhizosphere is where plant roots, soil, and soil biota interact, and is the portal of nutrients transporting from soil into plants. The rhizosphere processes could modify the bioavailability of all nutrients and nanomaterials (NMs) before entering the food plants. However, to date, the overall rhizosphere processes regulating the behaviors and bioavailability of NMs to enhance the nutritional quality are still uncertain. In this review, a meta-analysis is conducted to quantitatively assess NMs-mediated changes in nutritional quality from food plants. Furthermore, the current knowledge and related mechanisms of the behavior and bioavailability of NMs driven by rhizosphere processes, e.g., root secretions, microbial and earthworm activities, are summarized. A series of rhizosphere processes can influence how NMs enter plants and change the biological responses, including signal transduction and nutrient absorption and transport. Moreover, future perspectives are presented to maximize the potentials of NMs applications for the enhancement of food crop production and global food security.

Assessing the risk of bias in choice of search sources for environmental meta-analyses

Results of meta-analyses are potentially valuable for informing environmental policy and practice decisions. However, selective sampling of primary studies through searches exclusively using widely used bibliographic platform(s) could bias estimates of effect sizes. Such search strategies are common in environmental evidence reviews, and if risk of bias can be detected, this would provide the first empirical evidence that comprehensiveness of searches needs to be improved. We compare the impact of using single and multiple bibliographic platform(s) searches vs more comprehensive searches on estimates of mean effect sizes. We used 137 published meta-analyses, based on multiple source searches, analyzing 9388 studies: 8095 sourced from commercially published articles; and 1293 from grey literature and unpublished data. Single-platform and multiple-platform searches missed studies in 100 and 80 of the meta-analyses, respectively: 52 and 46 meta-analyses provided larger-effect estimates; 32 and 28 meta-analyses provided smaller-effect estimates; eight and four meta-analyses provided opposite direction of estimates; and two each were unable to estimate effects due to missing all studies. Further, we found significant positive log-linear relationships between proportions of studies missed and the deviations of mean effect sizes, suggesting that as the number of studies missed increases, deviation of mean effect size is likely to expand. We also found significant differences in mean effect sizes between indexed and non-indexed studies for 35% of meta-analyses, indicating high risk of bias when the searches were restricted. We conclude that the restricted searches are likely to lead to unrepresentative samples of studies and biased estimates of true effects.

Earthworms offset straw-induced increase of greenhouse gas emission in upland rice production

Increasing water scarcity and rapid socio-economic development are driving farmers in Asia to transform traditionally flooded rice cropping systems into non-flooded crop production. The management of earthworms in non-flooded rice fields appears to be a promising strategy to support residue recycling and mitigate greenhouse gas (GHG) emissions triggered by residue amendment. We conducted a field experiment on non-flooded rainfed rice fields, with and without residue amendment. In-situ mesocosms were inoculated with endogeic earthworms (Metaphire sp.), with either low (ET1: 150 individuals m^-2), or high density (ET2: 450 individuals m^-2), and a control (ET0: no earthworms). We measured GHG emissions (methane (CH₄); nitrous oxide (N₂O); carbon dioxide (CO₂)) twice a week during the cropping season with static chambers. Effects of earthworms on yield and root growth were additionally assessed. Earthworms offset the enormous increase of CH₄ emissions induced by straw amendment (from 4.6 ± 5 to 75.3 ± 46 kg CH₄-C ha^-1 in ET0). Earthworm activity significantly reduced CH₄ release, particularly at ET2, by more than one-third (to 22 ± 15 kg CH₄-C ha^-1). In contrast, earthworm inoculation did not affect N₂O emission. Straw amendment more than doubled the global warming potential (GWP). Earthworms reduced GWP by 39% at low (ET1) and 55% at high densities (ET2). Earthworm activity reduced root mass density under conditions of straw amendment but did not affect yield. Earthworms can significantly reduce detrimental effects of rice crop residue amendment on GHG release under upland rice production. Organic carbon (C) might be preserved in earthworm casts and thereby limit C availability for CH₄ production. At the same time, earthworm activity might increase methanotrophic CH₄ consumption, due to improved soil aeration or less root exudates. Consequently, earthworms have a strong potential for regulating ecosystem functions related to rice straw decomposition, nutrient allocation and thus GHG reduction.

Microbial-Mediated Plant Growth Promotion and Pest Suppression Varies Under Climate Change

Climate change is altering the dynamics of crop pests and diseases resulting in reduced crop yields. Using beneficial soil bacterial to increase crop health is a quickly developing area in sustainable agriculture, but it is unknown if climate change or interactions with other species could alter their effect. The plant growth-promoting rhizobacterium Acidovorax radicis N35 is known to increase barley (Hordeum vulgare) plant growth under laboratory conditions, and we tested the stability of the plant-bacterial interactions when exposed to elevated carbon dioxide (CO₂) and ozone (O₃) levels while infesting the aboveground leaves with cereal aphids (Sitobion avenae) and the soil with beneficial earthworms. Acidovorax radicis N35 increased plant growth and reduced insect growth - with greatest effect in a high-stress elevated O₃ environment, but reduced effects under elevated CO₂. Earthworms promoted both plant and insect growth, but inoculation with A. radicis N35 alleviated some of the earthworm-mediated increase in pest abundance, particularly in the ambient environment. The consistency of these beneficial effects highlights the potential of exploiting local species interactions for predicting and mitigating climate change effects in managed systems. We conclude that microbial bioprotectants have high potential for benefiting agriculture via plant-growth promotion and pest suppression.

Exposure to nickel oxide nanoparticles insinuates physiological, ultrastructural and oxidative damage: A life cycle study on Eisenia fetida

Although, health and environmental hazards of Ni are ironclad; however, that of Nickle oxide nanoparticles (NiO-NPs) are still obscure. Therefore, impact of NiO-NPs exposure (0, 5, 50, 200, 500 and 1000 mg kg^-1 soil) on the earthworm (Eisenia fetida) survival (at 28th day), reproduction (at 56th day), histopathology, ultrastructures, antioxidant enzymes and oxidative DNA damage was appraised in full life cycle study. Lower concentrations of NiO-NPs (5, 50 and 200) did not influence the survival, reproduction and growth rate of adult worms significantly. However, reproduction reduced by 40-50% with 500 and 1000 mg kg^-1 exposure, which also induced oxidative stress leading to DNA damage in earthworms. Ultrastructural observation and histology of earthworms exposed to higher NiO-NPs concentrations revealed abnormalities in epithelium layer, microvilli and mitochondria with underlying pathologies of epidermis and muscles, as well as adverse effects on the gut barrier. To the best of our knowledge, this is the first study unveiling the adverse effects of NiO-NPs on a soil invertebrate (Eisenia fetida). Our findings clue towards looking extensively into the risks of NiO-NPs on soil organisms bearing agricultural and environmental significance.