Earthworm Populations Research Articles

Influence of Oil Contamination on Physical and Biological Properties of Forest Soil After Chainsaw Use.

Forestry works using chainsaws result in up to 7 million liters of various mineral oils being soaked annually into forest soils. These substances, containing a complex mixture of polycyclic aromatic hydrocarbons (PAHs), are highly toxic. The aim of the study was to determine the effect of oil contamination with PAHs on the physical and biological properties of forest soils. The study area was located in southern Poland in the Miechów forest district. The experiment was conducted on four treatment blocks with various amounts of oil addition. The study included the determination of PAH content, dehydrogenase and urease activity, and biomass of earthworms. Physical properties were determined using the dryer method and Kopecky rings of 250 cm3 volume. The results obtained confirmed the hypothesis that oil contamination with PAHs modified the physical properties of forest soils and oil had a negative impact on enzyme activity in soil. Enzyme activity in the studied soils was negatively correlated with PAH content. Earthworm population density reflected the contamination level of oil-contaminated soils.

Effect of organic and inorganic sources of nutrients on soil fertility status of arecanut (Areca catechu) in north-east India

A study was conducted to assess the effect of three different sources of nutrients on soil fertility status in an adult arecanut (Areca catechu L.) plantation at Central Plantation Crops Research Institute, Research Centre, Guwahati, during 2008-09 and 2010-2011 in comparison with the planting time. The results revealed that the available nitrogen content was highest (332.6 and 242.3 kg/ha at 0-30 and 30-60 cm soil depth, respectively) in the soil applied with vermicompost, whereas the soils applied with chemical fertilizer recorded maximum available P and K content. However, the availability of these three major nutrients decreased with soil depth, irrespective of the sources of nutrient. Similar was in the case of organic carbon (OC) content and the soils applied with organics recorded higher value. Water holding capacity of soils was highest in organic plot over control and inorganic. Water holding capacity was significantly and positively correlated with organic carbon content but negatively correlated with bulk density of soil. Organic plots resulted almost 2.5 to 2.9 and 1.6 to 1.8 times higher earthworm population than fertilized plot and control plot respectively. Long-term application of compost improved soil physicochemical properties, available N content and also microbial population except available P and K content in soil which collectively resulted increased kernel yield of arecanut. Highest dry chali yield (4 496.9 kg/ha) of arecanut was obtained under vermicompost applied palms and was significantly higher than the chali yield of arecanut obtained under common compost and chemical fertilizer applied palms were 4 299.5 kg/ha, and 4 270.7 kg/ha, respectively.

A simple and effective method for linking field investigations of earthworms and water infiltration rate into soil at pedon‐scale

AbstractEarthworm density and activity may significantly contribute, amongst others, to soil physical properties such as water infiltration rate and permeability, and thus provide a desirable ecosystem service. In environmental field studies, investigations of the two soil physical properties are highly recommended. In practice, they are carried out separately in terms of time and space and, therefore, are typically closely connected. Therefore, the aim of this study was to test the feasibility of a combined investigation of earthworm population and infiltration rate in soil in field studies. The idea was to use an aqueous solution of allyl isothiocyanate (AITC) and a double‐ring cylinder for simultaneous measurements at the same pedon and, thus, without any spatio‐temporal deviation. Tap water was used as a control for the infiltration measurements with AITC. Another aim was to evaluate the plausibility of earthworm data received from those combined investigations. This was tested for some arable and grassland soils derived from various parent materials in W‐Germany differing in soil chemical and physical properties. Infiltration rates of AITC in soil were not significant different from tap water, neither for the different soils nor different land‐uses and at the different study sites. Earthworm population data revealed from AITC application with a double‐ring cylinder equipment were realistic and in line with previous investigations in the respected study area. Pearson correlation coefficient between earthworm biomass and infiltration rate of AITC was medium (R2= 0.363).

Agricultural management and flooding shape habitats for non-native earthworms in southern Quebec, Canada

Agricultural intensification leading to the cultivation of unmanaged field margins along rivers and streams is expected to impact soil biodiversity. Earthworm communities are typically smaller with fewer species in agricultural soils, but the effect of agriculture on earthworms could be mitigated by the more favorable soil moisture regime in riparian areas, as well as planting perennial grasses or keeping forest fragments as permanently vegetated buffers. The objective of this study was to compare earthworm community composition under contrasting land use (agricultural vs. riparian forest) ∼5m and ∼30m away from the Pike River in southern Quebec, Canada. Furthermore, we evaluated how earthworm communities were affected by management intensity, flooding, soil and vegetation patterns within these land uses. We established 4 transects at 3 sites along the Pike River representing 4 land uses (agricultural field, agricultural buffer, riparian forest fragment, upland forest fragment). Along each transect, earthworm populations and soil properties were evaluated at 5 discrete points on 4 occasions from fall 2009 to spring 2011. Vegetation cover and plant species richness were measured, and management and flooding intensity were documented through farmer surveys. Earthworm abundance and diversity were highest in a riparian forest transect (460individualsm−2, 9 species) and agricultural buffer (325individualsm−2, 10 species), and lowest in the agricultural fields with annual crop rotations and agrochemical inputs, which also had the lowest plant diversity. Redundancy analysis revealed that differences in earthworm species compositions across the study area were linked to site-specific management and flooding, represented by differences in soil moisture, vegetation diversity, and soil nutrient concentrations (dissolved organic carbon in soil solution, mineral nitrogen, extractable phosphorus). Generalized linear mixed modeling also showed that less intensively managed agricultural buffers and forest fragments with regular flooding supported higher earthworm diversity. We recommend further research on soil functions affected by earthworms in riparian areas because these non-native earthworms could affect the conservation value of unmanaged agricultural buffers and forest fragments in southern Quebec, Canada.

English

Long-term cultivation of crops has been found to cause soil physico-chemical and biological quality (SQ) degradation for sustainable agricultural production practices in Akwanga, Nigeria. Understanding the dynamics of SQ change under different land use types is desired. The present study was carried out to assess soil physico-chemical indicators (based on land evaluation approach) and biological SQ (based on agro-ecological approach) for sustainability of cereal, arable and plantation land uses and management systems. Quantitative and qualitative indicators were defined based on chronosequence of soils under different land use types: 3-month cereal cropping of Rice); 7-month root cropping (yam/cassava/vegetable intercrop); 10-year plantation (orange/pineapple orchard); and >22-year oil palm plantation. Their respective management practice is Tillage + NPK fertilization; Tillage + NPK fertilizers + Organic manure; No tillage + mulch; and no tillage + Farm yard manure + Legume cover as live mulch. Each age class was replicated at least three times and their sensitivity to change was sought. The statistical mean values of the bio-physical and chemical properties of soil quality indicators (SQI) under the various types of land use (LUT) show that the most sensitive soil quality indicators (P ≤ 0.001) were soil pH, total organic C, available phosphorus (P), CEC, bulk density, total porosity, and PWAC, and earthworm population. Moderately sensitive indicators (0.001 < P ≤ 0.01) include total N, P and K, and exchangeable K. Weaker indicators of SQ (0.01 < P ≤ 0.05) include percentage BS. Soil texture and clay/silt ratio were of no value as soil quality indicators (SQI) for these soils. SQI improvements were related to their management practices; hence LUT4 had the best SQ, followed by LUT3. The worst management was that in LUT1. Qualitative assessments based on farmers’ perception of SQ showed the following order of importance for their cropping systems: Soil organic matter, fertility, topsoil thickness, soil structure, moisture retention, earthworm abundance, compaction, soil erosion, and the incidence of weeds. Farmer observations of SQ changes were generally in good agreement with the quantitative assessments. To ensure adoption of improved management practices for more sustainable production system, qualitative soil quality information obtained from on-farm surveys should be used to supplement the quantitative data obtained through soil analyses. These would serve as effective diagnostic tools for evaluating soil quality for long-term sustainability of crop productivity Key words: Soil quality indicators, land evaluation, agro-ecological approach, guinea savanna, Nigeria.

Interactions of native and introduced earthworms with soils and plant rhizospheres in production landscapes of New Zealand

Native and exotic earthworms and plants co-exist on the margins of agricultural land in New Zealand. Remnants of native vegetation support mixed assemblages of depleted populations of native Megascolecid earthworms together with apparently increasing invasive populations of introduced Lumbricidae. We question whether the survival and viability of these earthworm populations is a function of soil preference and whether there are significant differences in terms of how the two groups are influenced by and modify soil properties and plant growth. Choice chamber and mesocosm experiments, with and without plant rhizospheres, were used to study five species of native earthworms, two of which could be identified only by DNA barcoding, and four introduced exotic species. Both natives and exotics preferred agricultural soils to a plantation forest and a native forest soil. Earthworms also modified the physico-chemistry of soils and greenhouse gas emissions, with a marked interaction with root morphology of two native species of tea tree. Lesser differences were found between native and exotic earthworms than between functional groups. It is concluded that New Zealand’s production landscapes provide novel habitats with clear benefits both to threatened species conservation and to soil ecosystem services.

Effects of agricultural management practices on earthworm populations and crop yield: validation and application of a mechanistic modelling approach

Summary There is little consensus on how agriculture will meet future food demands sustainably. Soils and their biota play a crucial role by mediating ecosystem services that support agricultural productivity. However, a multitude of site‐specific environmental factors and management practices interact to affect the ability of soil biota to perform vital functions, confounding the interpretation of results from experimental approaches. Insights can be gained through models, which integrate the physiological, biological and ecological mechanisms underpinning soil functions. We present a powerful modelling approach for predicting how agricultural management practices (pesticide applications and tillage) affect soil functioning through earthworm populations. By combining energy budgets and individual‐based simulation models, and integrating key behavioural and ecological drivers, we accurately predict population responses to pesticide applications in different climatic conditions. We use the model to analyse the ecological consequences of different weed management practices. Our results demonstrate that an important link between agricultural management (herbicide applications and zero, reduced and conventional tillage) and earthworms is the maintenance of soil organic matter (SOM). We show how zero and reduced tillage practices can increase crop yields while preserving natural ecosystem functions. This demonstrates how management practices which aim to sustain agricultural productivity should account for their effects on earthworm populations, as their proliferation stimulates agricultural productivity. Synthesis and applications. Our results indicate that conventional tillage practices have longer term effects on soil biota than pesticide control, if the pesticide has a short dissipation time. The risk of earthworm populations becoming exposed to toxic pesticides will be reduced under dry soil conditions. Similarly, an increase in soil organic matter could increase the recovery rate of earthworm populations. However, effects are not necessarily additive and the impact of different management practices on earthworms depends on their timing and the prevailing environmental conditions. Our model can be used to determine which combinations of crop management practices and climatic conditions pose least overall risk to earthworm populations. Linking our model mechanistically to crop yield models would aid the optimization of crop management systems by exploring the trade‐off between different ecosystem services.

Do alterations in mesofauna community affect earthworms?

Interactions between the saprotrophic animal groups that strongly control soil microbial activities and the functioning of detrital food webs, such as earthworms and mesofauna, are not well understood. Earthworm trophic and engineering activities strongly affect mesofauna abundance and diversity through various direct and indirect pathways. In contrast, mesofauna effects on earthworm populations are less evident; however, their importance may be high, considering the keystone significance of earthworms for the functioning of the soil system. We studied effects of a diverse mesofauna community of a deciduous forest on two earthworm species representing epigeic (Lumbricus rubellus) and endogeic (Aporrectodea caliginosa) ecological groups. In microcosms, the density of total mesofauna or its separate groups (enchytraeids, collembolans, gamasid mites) was manipulated (increased) and responses of earthworms and soil systems were recorded. A rise in mesofauna density resulted in a decrease of biomass and an increased mortality in L. rubellus, presumably due to competition with mesofauna for litter resources. In contrast, similar mesofauna manipulations promoted reproduction of A. caliginosa, suggesting a facilitated exploitation of litter resources due to increased mesofauna activities. Changes of microcosm respiration rates, litter organic matter content and microbial activities across the manipulation treatments indicate that mesofauna modify responses of soil systems in the presence of earthworms. However, similar mesofauna manipulations could induce different responses in soil systems with either epigeic or endogeic lumbricids, which suggests that earthworm/mesofauna interactions are species-specific. Thus, mesofauna impacts should be treated as a factor affecting the engineering activities of epigeic and endogeic earthworms in the soil.

Potential of waste carbide sludge addition on earthworm growth and organic matter degradation during vermicomposting of agricultural wastes

Abstract The effect of waste carbide sludge (WCS) with higher Ca content and pH buffering capacity was investigated during vermicomposting of agricultural waste. Agricultural waste mixture was prepared by mixing vegetable waste, cow dung, saw dust in (5:4:1) ratio for a total mass of 2.5 kg. In addition, 0.27 kg of dried leaves was added to all of the trials as bulking agent. Finally, the effect of WCS addition was experimented in five different trials of the same ratio of waste combinations but varying WCS concentration as following: 0.5% WCS was added in trial 1, 1% WCS in trial 2, 1.5% WCS in trial 3, 2% of WCS in trial 1 and 2.5% WCS in trial 5 respectively. Appropriate addition of WCS had no negative effects on the growth of biomass, as considerable increase of earthworm population was observed in WCS added trials as compared to the control. A maximum of 43.7% of total organic carbon reduction was observed in trial 3 when compared to all other trials. Higher biomass growth was observed in WCS added trials as compared to the control experiment proving the possibility of WCS effect on biomass growth. Total metal and micronutrient concentration was observed to increase toward the end of process.

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Soil Penetration by Earthworms and Plant Roots--Mechanical Energetics of Bioturbation of Compacted Soils.

We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip). The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

Forest successional history and earthworm legacy affect earthworm survival and performance

Introduced European and Asian earthworms, considered ecosystem engineers due to their ability to rapidly deplete leaf litter layers and alter forest floor communities and processes, continue to spread in North America. Environmental factors facilitating or limiting earthworm distributions are poorly understood. We experimentally assessed how successional age of forests in the Finger Lakes Region of New York, USA, and soil microbial communities (i.e. biotic resistance) influence earthworm communities and survival and growth of two common earthworms, Lumbricus rubellus and Dendrobaena octaedra. We used historic aerial photos and ArcGIS to establish a forest regeneration chronosequence where we surveyed earthworm communities. In addition, we collected forest soils from adjacent earthworm-invaded and earthworm-free zones, and followed survival and growth of individuals in sterilized or untreated soils over a seven week period. Our results show that both forest successional age and earthworm legacy effects influence earthworm performance. Younger forests had higher earthworm populations compared to older forests despite similar overstory tree composition, highlighting the importance of local conditions and land-use histories. Individual earthworms grew faster in soils with earthworm legacies compared to individuals in previously earthworm free soils. Contrary to our expectations, soil sterilization reduced earthworm performance, potentially through elimination of food items. Earthworms modify soil conditions, creating positive soil feedback loops favoring their own growth. Patchy earthworm distributions may be a function of earthworm preference for favorable conditions created by conspecifics, and there appears little biotic resistance to limit their spread.

Non-consumptive Effects of Native Deer on Introduced Earthworm Abundance

Chronic ungulate herbivory impacts are well documented, consistently showing changes in plant community dynamics. In contrast, indirect ungulate effects on soil biota and processes are less well understood and idiosyncratic. Evidence suggests that increased deer abundance in northeastern North American forests may facilitate invasions by non-native earthworms and non-native plants through indirect non-consumptive processes. We sampled earthworm abundance using paired open and fenced plots (experimentally excluding deer) from 2008 to 2011 at 12 sites at West Point, NY and in 2013 at 21 additional sites across four states that varied in exclosure size and age since establishment. Fencing decreased earthworm abundance at West Point and in regional surveys. At West Point, negative effects of fencing on earthworm abundance decreased with soil pH and were stronger at sites dominated by native than non-native understory vegetation. Sites dominated by native vegetation had more acidic soils and lower earthworm abundance compared to sites dominated by non-native vegetation. In the regional survey, negative effects of fencing on earthworm abundance increased with time since fences were established, but effects were not affected by exclosure size or site location. We show unforeseen indirect effects of deer exclusion on earthworm populations. Results illustrate the need to account for complex interactive effects among co-occurring stressors, such as deer, earthworms, and non-native plants. Failures to account for these interactions will result in hidden treatments, will complicate interpretation of ecological experiments, and will create difficulties in designing appropriate management strategies aimed at reducing stressor effects.

English

Earthworms are regarded as the bio-indicators of soil quality. Also, due to several beneficial ecosystem services provided by earthworms, focus has been given to earthworms in agriculture management. So, there is need of knowing the distribution of earthworms, factors affecting their distribution and modification of soil environment due to them. With the aim of characterizing earthworm distribution in Panchase area, earthworms were sampled in different aspects, land use types, depth and altitude in June and October. Soil sample was also taken to characterize the habitat preference of the earthworms. The highest earthworm population density was found in forest followed by agriculture land and grassland in both months. Also, majority of earthworms were found in top 15 cm of soil. Moisture and organic matter content were found to be major determinants of earthworm population in Panchase area. Positive and significant correlation between earthworm population and available mineral nutrients (P and K) suggests that earthworms help in mineral nutrient availability to the plants. &nbsp; Key words: Ash free dry mass, biomass, earthworm population density, Panchase area.

The effects of earthworms Eisenia spp. on microbial community are habitat dependent

The effects of earthworms Eisenia spp. on microorganisms of three different habitat soil, compost, and vermiculture were studied. Microbial communities of gut and fresh faeces of earthworms and substrates, the worms were collected from, were analysed. Microbial biomass and composition of the total microbial community were examined using phospholipid fatty acid (PLFA) biomarkers. Archaeal and bacterial communities were studied by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE). The culturing methods were used for assessment of counts, species richness and growth strategy of bacteria.In comparison with the substrates, the viable microbial biomass and the group of non-ester-linked PLFAs indicative of anaerobes were higher in both the gut and faeces of all earthworm populations. The prokaryotic community evaluated using DGGE revealed that archaeal community structure in the gut and faeces of earthworms from populations differed from that in substrates, whereas the passage through the gut had less influence on the bacterial community structure, particularly in compost and vermiculture.The counts of culturable bacteria increased due to gut passage only in forest and vermiculture populations. The fast-growing bacteria increased due to gut passage only in forest soil population. Actinobacteria (Arthrobacter, Microbacterium, Lechevalieria and Nesterenkonia) and Firmicutes (Bacillus and Paenibacillus) were generally favoured in substrates and their species richness decreased with gut passage, whereas Gammaproteobacteria (Aeromonas, Enterobacter, Pseudomonas and Salmonella) dominated in gut contents. The impact of earthworm activity on the microbial community was higher in nutrient-poor forest soil than in nutrient-rich compost and vermiculture substrates.

Invasive earthworms shape forest seed bank composition

AbstractAimTo assess how non‐native earthworm and non‐native plant invasions shape soil seed bank composition in deciduous temperate forests.LocationNew York State, USA.MethodsWe recorded earthworm density, earthworm biomass and vegetation composition in 12 deciduous forests and subsequently collected soil cores and recorded emergence of plant species from the seed bank. We used path analysis to assess direct and indirect contributions of earthworms and vegetation composition (species richness and cover of native and non‐native plants) to the species richness and abundance of emergent seedlings.ResultsHigh earthworm populations were positively associated with increased species richness and seedling density of both native and non‐native plant species emerging from the seed bank. This relationship held for all life‐form groups, although the earthworm effect was indirect for non‐native graminoid abundance. Non‐native plants were positively correlated with earthworms and while they influenced both aboveground vegetation cover and species richness, they had no direct influence on emergent abundance or species richness.Main conclusionsOur results suggest that forest seed bank composition is strongly influenced by the presence and abundance of non‐native earthworms, and only weakly influenced by non‐native plants. Forest understorey recovery from seed banks is possible following earthworm invasion, but resulting communities bear little similarity to standing vegetation. Recovery of the full desirable and typical complement of aboveground vegetation will require input to seed banks by (1) fostering seed production of existing vegetation and/or (2) planting seed of desired species. We suggest managing understorey vegetation to allow herbaceous species to set seed.

The effect of seasonal temperature on pathogen removal efficacy of vermifilter for wastewater treatment

The present study explored the effects of seasonal temperature on the treatment efficiency and pathogen removal efficacy from synthetic domestic wastewater, earthworm population characteristics and microbial population in the filter media of a lab-scale vermifilter (VF). The experimental phase lasted for one year and daily mean room temperature showed a difference of 2–16 °C between winter (Dec–Feb), spring (Mar–May), summer (Jun–Aug) and autumn (Sep–Nov) periods. The results showed that variation in ambient temperature had a significant effect on chemical oxygen demand (COD) and biochemical oxygen demand (BOD) reduction, indicator organisms and pathogen removal, earthworm population, bacterial and actinomycetes number, but had no effect on total suspended solids (TSS) removal and fungi number. The study showed that higher BOD and COD removal was accomplished during the spring and autumn period when the mean temperature was 25–27 °C. This temperature range is optimum for the earthworm species Eisenia fetida for its activity, growth and reproduction and any variation in temperature from the optimum range led to decrease in treatment efficiency and earthworm population. However, during summer, when the maximum temperature reached 38–40 °C, the indicator bacteria removal was maximum by 99.9%, Salmonella reduction by 96.9% and Escherichia coli by 99.3%. The pathogen removal efficacy of VF increases with the increase in temperature, as shown by linear regression analysis, which implied that temperature had a significant contribution to the pathogen removal efficiency of VF. Pearson coefficient of correlation (r) derived an important relationship between the seasonal temperature and treatment efficiency, pathogen removal efficacy and microbial numbers during vermifiltration.

Alleviation of take-all in wheat by the earthworm Aporrectodea caliginosa (Savigny)

Take-all, caused by the fungus Gaeumannomycesgraminis var. tritici (Ggt), can result in significant wheat (Triticumaestivum) yield losses. Previous research has suggested that earthworms may help to alleviate take-all severity, but the mechanisms are still not well understood. A pot experiment was conducted to investigate the effect of earthworms on take-all severity and crop responses for wheat grown in soils with contrasting levels of take-all suppression. The experiment consisted of eight treatment combinations composed of: two soils (suppressive and non-suppressive), with high or low quantities of added Ggt inoculum, and with or without additions of adult earthworms (Aporrectodeacaliginosa, Savigny; the predominant species in New Zealand agricultural soils). Wheat plants were grown in the pots and destructively harvested at three growth stages over the full growing season. Large differences in take-all severity were observed, depending mainly on the degree of soil suppression and amount of inoculum added. Disease severity was greatest in non-suppressive (NS) soil with high inoculum (HI) and least in suppressive soil (S) with low inoculum (LI). When disease pressure was high (i.e. NS and/or HI), earthworms were associated with an average reduction in disease severity of 25% and average increases in plant production of 10%. Earthworms had only a small effect on decomposition of the Ggt-infected wheat residue used as inoculum. Therefore, it is likely that the disease mitigating effect of earthworms was not associated with a reduction in inoculum through enhanced wheat residue decomposition, but may be due to other factors such as increased dispersion and promotion of Ggt antagonistic microbes. However, additional research is needed to test this hypothesis and evaluate other possible mechanisms of earthworm mediated suppression of take-all. The results suggest that relatively small earthworm populations (200–300m−2) may be sufficient to provide a degree of control where disease pressure is high. A positive correlation between earthworm reproductive success and suppressive soil properties was also noted and this study appears to be the first to observe this. Further work is needed under field conditions to determine if management practices that help to sustain or enhance earthworm populations (e.g. reduced tillage) can contribute to improved cultural control of take-all.

Influence of biogas digestate on density, biomass and community composition of earthworms

In recent years, the increasing number of biogas plants in operation has also led to a considerable rise in fermentative substrates, which are now widely used as agricultural fertilizers. The impact on earthworm fauna of using biogas digestate as a fertilizer has yet to be sufficiently researched. At two different tests sites, the short-term (four months after fertilization) and longer-term (three-year test period) influence of using fermented residues as a fertilizer was examined on earthworm density, biomass and community composition compared to using traditional fertilizers (cattle and pig slurry, chemical fertilizers as well as an unfertilized control). The crop grown was maize (Zea mays L.). Applying biogas digestate and slurry had a positive overall impact at both sites on earthworm density and biomass. Observing different fertilization regimes in the short term, the significantly highest earthworm density was seen where slurry had been applied. In the treatments with digestate and conventional slurry, earthworm biomass differed significantly in comparison with chemical fertilization and the untreated variant. After three years, earthworm biomass in the variants fertilized with conventional slurry and digestate tended to be higher than in the chemical fertilizer and untreated variants. Community composition was strongly influenced by the application of digestate. A decrease in the species Aporrectodearosea was accompanied by an increase in Aporrectodea caliginosa. The earthworm population was supported equally positively at both sites by the variants with conventional slurry and digestate.

Earthworm communities under boreal grass and legume bioenergy crops in pure stands and mixtures

Abstract Crop mixtures can impact soil properties through their effect on earthworm communities. Earthworm abundance and species number in a bioenergy crop mixture can therefore provide valuable information about its stability and sustainability. In the context of developing sustainable bioenergy farming methods, this experiment aimed to determine the effects of pure stands of reed canary grass (Phalaris arundinacea) (RCG), the legume forage galega (Galega orientalis) and their mixture on earthworm populations, with bare fallow controls. Twice in each growing season in 2011 and 2012, soil blocks 25 cm × 25 cm × 25 cm were extracted from each plot, earthworms were manually separated from the soil and mustard oil was used to extract those from soil underlying the block. Four earthworm species were collected: Aporrectodea caliginosa, A. rosea, Lumbricus rubellus, and L. terrestris. Earthworm abundance ranged from no individuals in bare fallow in summer 2011 to 364 individuals m−2 in galega in spring 2012. Biomass of the worms ranged from 0 to 188 g m−2 and had the same trend as abundance. Of the cropped treatments, pure galega supported the greatest earthworm numbers and biomass, although being significant only in summer. Treatment effects were weak in most sampling periods but differed between seasons and this should be investigated in future studies. Our results demonstrate that specific plant species can have positive effects on the earthworm community under certain environmental conditions, which should be considered in bioenergy cropping.