Earthworm Inoculation Research Articles

Effects of earthworm (Amynthas aspergillum) activities and cast mulching on soil evaporation

Earthworms are typical ecosystem engineers because they greatly affect the physical properties of soil in various ways. In this study, simulation experiments were performed to assess the effects of earthworms (Amynthas aspergillum) on the soil evaporation process in a subtropical region of China. Five population sizes CK (0), A1 (0), A2 (10), A3 (20), and A4 (30), four cast mulch thicknesses (0, 1, 2, and 4 cm), and four cast mulch area coverage percentages (0, 30%, 60%, and 90%) were tested with four replicates each for the different treatments. Water was applied again to the treatments until the soil water content reached 20% on day 14. The results showed that earthworms significantly increased the content of water-stable aggregates (WSA), where the WSA contents under different treatments were 35–40.6 g (P < 0.05). The soil water content decreased in the first 13 days after earthworm inoculation, before increasing gradually after adding water again. Compared with CK, the average water contents increased by 45.9–151.2 g in the earthworm treatments. When the number of added earthworms was 30, the water contents were 126.5 g in A3 and 151.2 g in A4 (P < 0.05). Different earthworm cast mulch thickness and area coverage percentages significantly reduced the cumulative evaporation (P < 0.05), where they reduced the cumulative evaporation by 31.2–63.5% and 14.5–29.8%, respectively, compared with CK. When the soil moisture was at a low level, minimal differences were observed in the evaporation rates among the treatments. Thus, the activities of earthworms can improve the soil water-holding ability and inhibit evaporation from lateritic red soil.

Earthworm community development in soils of a reclaimed steelworks

Long-term studies are essential to learn earthworm community development and soil formation post reclamation. Investigations were undertaken at a former steelworks site at Hallside, near Glasgow, UK, reclaimed in the 1990s using a mixture of colliery spoil and sewage sludge. The site was largely planted for production of short rotation coppice willow (Salix spp.). Earthworm inoculation formed a part of the restoration process. Minimal monitoring occurred in the interim, but some records of earthworm sampling existed in 2000 and 2005. This study focused on monitoring earthworms and soil properties across the site, drawing comparisons with adjacent unspoiled soil. Results showed that after 22 years, a species-rich community of earthworms (n = 16) colonized the site, with endogeic Aporrectodea caliginosa being dominant by number and anecic A. longa by mass. Across the site, earthworm community density and biomass were 208 individuals m-2 and 71 g m-2, respectively. The Shannon diversity index for earthworms was 1.89, with an evenness of 0.68. The sewage sludge increased the soil organic matter, but the stone content of the colliery spoil prevented digging in some locations. Soil chemistry had no negative effect on earthworms, but the compacted substrate did hinder water infiltration. Earthworms colonized the reclaimed site from adjacent areas, and community structure and density below well-drained, scrub-free willow, birch, and grassland were not significantly different (P > 0.05) from those of the adjacent unspoiled areas. The results show that the historical earthworm inoculation was unnecessary and badly timed. Future reclamations of similar sites can learn from this investigation.

The effect of earthworm (Eisenia foetida) on the growth of Medicago sativa

In order to study the effects of earthworms on the physiology of Medicago sativa, the effects of different numbers of earthworms (0, 2, 4, 6) on the soil organic matter, plant height, root length, biomass and soluble protein content of Medicago sativa were studied. The results showed that: compared with the control group, (1) The content of soil organic matter increased significantly with the increase of earthworm inoculation; (2)Earthworm treatment had no significant effect on the plant height and biomass of Medicago sativa; (3) Two earthworms’ inoculation significantly increased soluble protein content of Medicago sativa and promoted the growth of Medicago sativa roots; (4) The correlation analysis showed that the content of soil organic matter had a significant positive correlation with Medicago sativa plant height, and a significant negative correlation with underground dry weight. The results showed that earthworm inoculation had a positive effect on improving the yield and quality of Medicago sativa, but the specific amount of earthworm inoculation should be determined by the soil conditions, planting environment and other factors.

Effects of the earthworm Pontoscolex corethrurus on rice P nutrition and plant-available soil P in a tropical Ferralsol

We conducted a greenhouse experiment in mesocosms for 28 days to assess the effects of the endogeic earthworm Pontoscolex corethrurus on plant-available soil phosphorus (P) and rice ( Oryza sativa ) P nutrition in a Malagasy Ferralsol. To assess plant-available soil P, we determined the L-value by measuring the specific activity of P taken up from the soil by rice and by applying the isotopic dilution principle. Despite earthworm mortality, P. corethrurus significantly increased rice shoot biomass (+26%) and P nutrition (+65%), confirming that the soil used for the experiment was P-deficient. The L-value also markedly increased from 6.8 ± 0.9 to 14.2 ± 1.3 mg P mesocosm −1 in the presence of P. corethrurus . We estimated that the orthophosphate ions released due to earthworm mortality contributed to 30% of the L-value increase. We attributed the remaining 70% increase to the solubilization of native soil P during its transit through the digestive tract. Thereafter, we discussed the sources of uncertainty associated with the L-value calculation and their utilization to assess earthworm effects on P availability in further studies. • We assessed the effects of P. corethrurus ( Ponto ) on plant-available soil P. • Ponto increased rice shoot biomass (+26%) and P nutrition (+65%). • The L -value raised from 6.8 (±0.9) to 14.2 (±1.3) mg P cosm −1 in presence of Ponto . • The P release due to Ponto mortality contributes to 30% of the L -value increase. • The relevance of using L -value in earthworm inoculation experiments is discussed.

The Effects of Earthworms on Fungal Diversity and Community Structure in Farmland Soil With Returned Straw.

BackgroundTo promote the decomposition of returned straw, reduce the incidence of soil-borne diseases caused by returned straw, and accelerate the conversion of straw carbon into soil carbon, we inoculated earthworms into fields with returned straw. The earthworms accelerated straw degradation and promoted carbon conversion. However, the impact of externally inoculated earthworms on the farmland soil ecosystem, especially the structure and the function of its microbial community, remains unclear.MethodsWe analyzed the effects of straw return and earthworms on the diversity of fungal populations and the community structure of dominant fungal taxa in soil by quantifying fungal population size and community composition via PCR amplification of internal transcribed spacer genes and 18S rRNA gene sequencing.ResultsThe results showed that earthworm inoculation significantly accelerated the degradation of rice straw and promoted the conversion of straw carbon to soil carbon. Both fungal abundance and α-diversity (Sobs and Shannon indices) were higher in the plots with surface straw but without earthworms than in those inoculated with earthworms and in the CK. Principal component analysis indicated that straw return increased the diversity and the abundance of the fungal community, whereas earthworms inhibited this expansion of the fungal community caused by straw return. Interestingly, the overall differences in fungal community composition were smallest in plots with straw return, while the dominant fungal community features in plots inoculated with earthworms were closer to those of the CK.ConclusionGenerally, straw return stimulated unclassified_K_fungi, Pseudeurotium, and Fusarium with strong cellulolytic ability. In contrast, the abundances of Stachybotrys, unclassified_c_Sordariomycetes, unclassified_f_Lasiosphaeriaceae, and Schizothecium were higher in the plots inoculated with earthworms and in the CK. Furthermore, evolutionary analysis showed that the evolution of soil fungal communities tended to diverge after straw return, and the evolutionary directions of fungal species in the plots inoculated with earthworms were similar to those in the CK.

Comparative studies on physical and chemical changes during compostingof organic residues as influenced by two species of earthwormsand effective micro-organisms (EM)

An experiment was undertaken at central experimental station, Wakawali, Maharashtra to evaluate the influence of two species of earthworms and effective micro-organisms (EM)” on compositing of organic residues during July 2008 to February 2009. In order to reduce the period of composting and improve upon its quality, studies were undertaken to monitor the changes in various physical and chemical parameters governing the process of decomposition of mango leaves, cashew leaves, shivan leaves and ain leaves using Eisenia foetida and Eudrilus eugineae species of earthworms along with EM solution. It was observed that at the end of composting significantly lowest bulk density 0.38 Mg m-3 was noted in Shivan leaves inoculated with E eugineae species of earthworm.Descending order of bulk density values after the composting were observed as, Mango leaves>Cashew leaves> Ain leaves>Shivan leaves. The highest maximum water holding capacity on 150th days of composting was recorded in Shivan leaves(239.70%) and lowest in Cashew leaves(185.00%). There was reduction in pH of Mango leaves compost inoculated with earthworm species E foetida.There was a considerable reduction in electrical conductivity of all the residues after their complete decomposition. Inoculation of earthworms to all these organic residues resulted into reduction in C:N ratio with the advancement in period up to 150 days. There was significant increase in cation exchange capacity.Initially maximum CEC {36.83 c mol (p+ ) kg-1 } was recorded in Shivan leaves treated with Eudrilus eugineae and lowest CEC {23.33 c mol (p+ ) kg-1 } was noted in Cashew leaves treated with E. foetida. Similarly at the end of composting, maximum CEC{90.67 c mol (p+ ) kg-1 } was recorded in Shivan leaves treated with Eudrilus eugineae and lowest CEC {64.83 c mol (p+ ) kg-1 } was noted in Cashew leaves treated with E. foetida.

The performance of mycorrhizae, rhizobacteria, and earthworms to improve Bermuda grass (Cynodon dactylon) growth and Pb uptake in a Pb-contaminated soil.

The current study was conducted to determine the combined performance of soil micro- and macro-organisms to stimulate the growth and lead (Pb) uptake of Bermuda grass (Cynodon dactylon (L.) Persi.) in a soil polluted with Pb-mining activities. Plants were inoculated with a mixture of arbuscular mycorrhizal (AM) fungal species, plant growth-promoting rhizobacteria (PGPR) species, and epigeic earthworms (Eisenia fetida) either alone or in combination. Results demonstrated antagonistic interactions between AM fungi and PGPR or between AM fungi and earthworms on the growth of mycorrhizal plants by increasing the availability of both phosphorus (P) and Pb in the soil solution and the subsequent reduction of mycorrhizal root colonization following inoculation of PGPR or earthworms. Plant biomass was negatively correlated with soil-available Pb, but positively with the percentage of root colonization by AM fungi. Additionally, mycorrhizal root colonization was negatively correlated with soil-available P and Pb concentrations. The triple inoculation of AM fungi with PGPR and epigeic earthworms as a bioaugmentation tool could result in a synergistic interaction effect on plant Pb bioaccumulation and uptake, enhancing the efficiency of phytoremediation and eco-restoration of Pb-polluted sites. In conclusion, the use of Bermuda grass in association with functionally dissimilar soil organisms demonstrated a high effectiveness for Pb in situ phytoremediation, specifically Pb phytostabilization, to reduce Pb mobilization in the environment.

Exposure of earthworm (Eisenia fetida) to bauxite residue: Implications for future rehabilitation programmes.

Bauxite residue is typically alkaline, has high sodium content and elevated concentrations of trace elements. Effective rehabilitation strategies are needed to mitigate potential environmental risks from its disposal and storage. Increasingly, the importance of viable soil faunal populations as well as establishment of vegetation covers is recognized as key components of successful rehabilitation. Inoculation with earthworms is a strategy for accelerating mine site rehabilitation, but little is known on the effects of bauxite residue properties on earthworm survival and viability. In the current study, earthworms (Eisenia fetida) were exposed for 28days to a series of bauxite residue/soil treatments (0, 10, 25, 35, 50, 75 and 100% residue) to evaluate possible toxic effects on earthworms, investigate the bioavailability of relevant elements (e.g. As, Cr, V), and assess the risk of element transfer. Results showed that soil containing ≥25% residue (pH≥9.8; ESP≥18.5%; extractable Na≥1122mg/kg) significantly impacted survival (mortality ≥28%) and reproduction (cocoon production inhibition ≥76%) of the exposed earthworms. Alkalinity, sodicity and bioavailable Na were identified as major factors causing toxicity and some earthworms were observed to adopt compensative response (i.e. swollen body) to cope with osmotic stress. Conversely, soil containing 10% residue (pH=9.1; ESP=9.2%; extractable Na=472mg/kg) did not elicit significant toxicity at the organism level, but biomarker analysis (i.e. superoxide dismutase and catalase) in earthworm coelomocytes showed an oxidative stress. Furthermore, earthworms exposed to soil containing ≥10% residue took up and accumulated elevated concentrations of Al, As, Cr and V in comparison to the control earthworms. We concluded that earthworm inoculation could be used in future rehabilitation programmes once the key parameters responsible for toxicity are lowered below specific target values (i.e. pH=9.1, ESP=18.5%, extractable Na=1122mg/kg for Eisenia fetida). Nonetheless, trace element uptake in earthworms should be regularly monitored and the risk to the food chain further investigated.

Nutrient and Exo-Enzyme Dynamics in Organically Amended Iron Mine Spoil

The aim of this study is to restore the nutrient status of iron ore mine spoil through suitable organic interventions. This paper reports the effects of different organic manure and bio-fertilizer amendments with inoculation of the earthworm Eisenia fetida in iron mine spoil on certain chemical parameters, microbial load and soil exoenzyme activities. The mine spoil samples were collected at random from five years old spoil dump and amended with farmyard manure (FYM), poultry manure (PM) and vermimanure (VM) along with biofertilizer in different combinations. The pH, conductivity, % organic carbon, N, P, K, bacterial and fungal population with activities of soil exoenzymes amylase, cellulase and invertase were studied in organically amended mine spoil. Significant variations (p&lt;0.05) in the chemical and biological parameters were observed between treatments and days of incubation. Higher values were obtained with PM followed by FYM and VM. Earthworm inoculation enhanced the values of all the chemical parameters except % organic carbon. Bacterial population and exoenzyme activities increased significantly (p&lt;0.05) with earthworm. PM with biofertilizer was found to be the most suitable combination followed by FYM. Inoculation of Eisenia fetida could facilitate mineralization of organics resulting in higher nutrient availability, higher microbial load and exoenzyme activities required to facilitate spoil reclamation.

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.

Nitrogen supply reduces the earthworm-silicon control on rice blast disease in a Ferralsol

Revealing belowground-aboveground relationships (BAR) is essential to drive ecological processes to address agriculture dysfunctions, especially in the management of aboveground plant diseases. Earthworms are one of the most important soil organisms involved in BAR, and silicon (Si) has been identified as a crucial element regulating aboveground plant health. How earthworm-Si interactions induce BAR in poor- and rich-nutrient soil contexts is still poorly understood, despite a growing interest in agricultural sustainability. We investigated the potential of BAR induced by the earthworm-silicon interaction to control the severity of rice blast disease in a Ferralsol in Madagascar, with or without NPK fertilization. We conducted a greenhouse microcosm experiment in which we manipulated the presence of the endogeic earthworm Pontoscolex corethrurus and the fungus Pyricularia oryzae in a Ferralsol supplied or not with Si and fertilized with macronutrients (nitrogen, phosphorus and potassium, i.e., NPK). After eight weeks of growth, plant biomass, nutrition and disease severity were measured. Our results validated the hypothesis that a dual treatment of earthworm inoculation and Si fertilization in a nutrient-poor tropical soil confers a higher tolerance of rainfed rice to P. oryzae, in comparison with treatments with only earthworms or Si, providing the optimal agronomic balance between a gain in biomass (and nutrition) and a reduction in disease severity. The supply of macronutrients altered this positive BAR by favouring the phenomenon of N-induced susceptibility. The aboveground plant C:N ratio of 15 is a threshold below which any increase in N per C unit likely enhances blast disease. The role of belowground interactions to counteract agricultural dysfunctions is supported by our study. To accomplish ecological intensification and provision of ecosystem services such as disease regulation, our findings recommend replacing excessive use of macronutrient fertilizer with sustained agricultural practices promoting the development of earthworm populations, such as organic matter inputs, superficial or no tillage, and the use of cover crops or conservation agriculture.

Kitchen waste management by vermicomposting using locally available epigeic earthworm species

A large quantity of kitchen waste is generated in India which is either burnt, left in open or landfilled posing a serious problem of its safe disposal. To mitigate this problem all the kitchen waste can be converted into highly valuable nutrient rich vermicompost using the locally available epigeic earthworms. The biodegradable kitchen waste like vegetables, fruits, food waste etc can be cultured with earthworms to form the vermicompost by using vermitechnology. Since these vermicomposts are rich in nutrients which can replace the chemical fertilizers. In the present study the vermicomposting of kitchen waste has been attempted using locally available epigeic earthworm species of Jammu namely Amynthus diffringens, Metaphire houlleti and Octolasion tyrtaeum. The physico-chemical analysis of generated vermicomposts was carried out and compared with each other and with that of original soil sample that has been added in vermibeds prior to earthworm inoculation and addition of kitchen waste. The average values of macronutrients in the vermicompost produced by O. tyrtaeum were observed to be the highest among all types of vermicomposts i.e. Organic Carbon (OC)- 11.66 ± 0.34% , Nitrogen (N)- 1.17 ± 0.20%, Phosphorus (P)- 2.97 ± 0.32%, Potassium (K)- 1.18 ± 0.15%, Calcium (Ca)- 0.26 ± 0.04%, Magnesium (Mg)- 0.17 ± 0.04%.

Earthworms and Fusarium oxysporum: effect on strawberry plant growth and production

Earthworms are soil invertebrates that play an important environmental role and are often referred to as “ecosystem engineers”. These invertebrates can influence several organisms, from microscopic life forms to plants. Although many works had reported positive effects of earthworms on plant growth, studies combining these invertebrates and soil pathogens showed numerous positive interactions. Fusarium wilt is a global disease that can cause severe damage to strawberry fields. The aim of this study was to evaluate the effects of inoculation of earthworms (Lumbricus terrestris) and Fusarium wilt (Fusarium oxysporum f. sp. fragariae) in strawberry plants. This greenhouse experiment was carried out in the University of Seville School of Agricultural Engineering, Utrera City, Spain. Strawberries (Rooted cuttings) were planted in plastic pots and administered the following treatments: Control (absence of F. oxysporum f. sp. fragariae and earthworms), T1 (absence of F. oxysporum f. sp. fragariae, two L. terrestris per pot), T2 (inoculum of F. oxysporum f. sp. fragariae, absence of L. terrestris), and T3 (inoculum of F. oxysporum f. sp. fragariae and two L. terrestris). Weekly fruit production was measured for seven months. After this period the shoot fresh weight and the leaf nutrient content was measured. The results obtained showed no interaction between L. terrestris and F. oxysporum f. sp. fragariae on strawberry production. T1 treatment resulted in fruit production superior to other treatments, including the control. An absence of differences in dry shoot matter was observed with earthworm treatment, and small differences were found in the leaf nutrient content. The earthworm inoculation was unable to suppress the negative effects of Fusarium wilt in strawberry production. However, positive effects such as a reduction in the disease severity were found in the earthworm treated plants. In treatments without F. oxysporum f. sp. fragariae inoculation, the presence of earthworms increased plant productivity by 44.21 g per pot, compared with the control.

Effects of composted green waste on soil quality and tree growth on a reclaimed landfill site

The addition of composted green waste (CGW) into soil-forming materials during land reclamation can benefit tree growth by improvement of soil properties and provide an effective waste management solution. CGW addition may also assist the establishment of earthworm populations, which in turn aid soil development through their burrowing and feeding activities. An experiment was set up on a reclaimed landfill site, to measure the effects of CGW addition on soil physical and chemical quality and subsequently on the survival and growth of two tree species (Acer platanoides and Alnus cordata). A further objective was to measure the influence of earthworm (Aporrectodea longa) addition on the above. CGW addition led to significantly greater A. cordata growth (height and diameter) and increased survival rate. No benefits from CGW addition were observed on A. platanoides growth or survival, although this is likely due to soil drought conditions during establishment. CGW addition significantly increased levels of organic carbon and essential plant macro-nutrients in the reclaimed soil. Soil pH rose slightly across all treatments, with highest final pH under the control treatment. Earthworm inoculation, as used, was unsuccessful at increasing population density of A. longa. This experiment showed that CGW application can effectively improve tree establishment and soil quality on reclaimed landfill; however tree species selection is an important consideration, based on individual species tolerance and sensitivity to certain soil conditions. These findings will be informative to decisions on soil amendment and afforestation activities on similar reclaimed landfill sites.

Inoculation of an ecosystem engineer (Earthworm: Lumbricus terrestris) during experimental grassland restoration: Consequences for above and belowground soil compartments

Although soil organisms might strongly affect the dynamics and composition of natural vegetation, relatively few studies have tried to in-situ manipulate soil fauna, especially in restoration ecology. The objective of this study was thus to observe the impact of a soil ecosystem engineer (Lumbricus terrestris L.) on plant communities as well as on soil organisms (springtails) in a reclaimed floodplain previously devoid of earthworms. Within a randomized factorial design based on buried frames (depth 0.45 m), half of the quadrats (1 m2) were inoculated with 100 earthworms, the other half served as control. After one year of experiment, earthworm inoculation doubled the plant biomass and favored grass species over forbs. Both abundance and diversity of Collembola (depending on functional groups) were negatively impacted by the presence of earthworms. Using a path analysis we found that this negative impact was probably indirect and due to an earthworm effect on plant community structure and plant functional groups. We suggest in our particular case that vegetation, and more precisely plant biomass and functional traits, may be more influential than soil properties in driving Collembola assemblages. Regarding restoration, we conclude that manipulating earthworms could be an interesting tool for increasing plant productivity but may disfavor soil biodiversity and alter above-belowground linkages.

Role of earthworms in phytoremediation of cadmium (Cd) by modulating the antioxidative potential of Brassica juncea L.

Earthworms are important soil organisms known to affect soil nutrients and microbial properties. Role of earthworms in modulating the antioxidative potential of plants during phytoremediation of cadmium (Cd) was analyzed in this study. The effect of earthworms on growth, metal chelating compounds and antioxidants during accumulation of Cd was observed in 15 d old Brassica juncea seedlings. The seeds were grown under controlled conditions in plastic pots containing soil and partially decomposed cow dung (1:1). The soil was treated with different Cd concentrations i.e. 56 mg kg−1, 84 mg kg−1, 112 mg kg−1 and 140 mg kg−1 (C0, C1, C2, C3 and C4 respectively) and a set of each treatment was inoculated with earthworms. Significant improvement in growth and Cd uptake was observed after inoculation of earthworms by 28.7% in roots and 31.3% in shoots in seedlings grown in C4 concentration. Metal chelating compounds, i.e., total thiols, protein bound thiols and organic acids were also found to increase with increased Cd accumulation. The expression of genes encoding various enzymes responsible for organic acid metabolism, i.e., CS (citrate synthase), SUCLG1 (succinyl Co-A ligase,), SDH (succinate dehydrogenase), FH (fumarate hydratase) was also studied. Enhanced antioxidative potential of plants supplemented with earthworms was observed in Cd treated soils. Total antioxidative capacity (water soluble and lipid soluble antioxidants) was increased maximally by 100.6% and 139% in C4 treatment, respectively. Content of various phenolic compounds, i.e., total phenols, flavonoids, anthocyanin and polyphenols followed the same trend and were found to accumulate in metal treated soil amended with earthworms.

Characterization of microbial community succession during vermicomposting of medicinal herbal residues

Large amounts of medicinal herbal residues (MHR) are produced in the world annually due to the increasing demand for herbal products. In this study, vermicomposting was used to stabilize MHR. Four inoculating density of earthworms was studied, specifically, 0 (W1), 60 (W2), 120 (W3) and 180 (W4) earthworms per kilogram of substrate. The C:N ratios of vermicomposts in W2, W3 and W4 were less than 20 by the end of the first week, while the value for W1 was 30.92. This indicates that earthworms promote the stabilization of MHR. In the initial stage, richness and diversity of the microbial community decreased due to earthworm inoculation, and then began to increase. The dominant phyla were Proteobacteria, Bacteroidetes, Basidiomycota and Ascomycota in the substrates. The abundance of the dominant phyla varied according to earthworm density, indicating that earthworms change the microbial composition. The results suggest that MHR can be stabilized by vermicomposting.

Seabird guano and phosphorus fractionation in a rhizosphere with earthworms

Soil phosphorus (P) is a critical nutrient for plant growth and is an important determinant of vegetation development and long-term ecosystem sustainability. We investigated the effects of rhizosphere-earthworm-guano interactions on soil P dynamics in a mesocosm involving two species of native New Zealand earthworms (Megascolecidae Sp.1 and Maoridrilus transalpinus) and introduced Eisenia fetida, in the context of inputs from seabird guano and the ecological restoration of a unique coastal sandplain forest. A fully factorial experimental design included a tall fibrous liliaceous perennial plant (New Zealand flax) growing in a low P forest soil, a guano-P amendment (with and without guano-P), and earthworm inoculation (with and without species of epigeics, endogeics and anecics). Soil dehydrogenase activity, CaCl2-P, citrate-P and HCl-P were significantly modified by earthworm-guano interactions, altering the P status of the original forest soil. Furthermore, interactions between the rhizosphere and earthworms stimulated transformation of soil P and guano P; the proportional importance of soil microbial biomass P, organic-P and more soluble P fractions were substantially modified. These findings show that rhizosphere-earthworm interactions are likely to mediate the supply, chemical forms and plant-availability of P, and are likely to have an important role in successional processes and the trajectory of ecological restoration in coastal forests of New Zealand.

The Maturity and CH4, N2O, NH3 Emissions from Vermicomposting with Agricultural Waste

ABSTRACTThis study investigated the maturity and gaseous emissions from vermicomposing with agricultural waste. A vermicomposting treatment (inoculated Eisenia fetida) was conducted over a 50-day period, taking tomato stems as the processing object and using cow dung as the nutrient substrate. A thermophilic composting treatment without earthworm inoculation was operated as a control treatment. During the experiment, maturity indexes such as temperature, pH, C/N ratio, and germination index (GI) were determined and continuous measurements of earthworm biomass and CH4, N2O, and NH3 emissions were carried out. The results showed that the temperature during vermicomposting was suitable for earthworm survival, and the earthworm biomass increased from 10.0 to 63.1 kg m−3. Vermicomposting took less time on average to reach the compost maturity standard (GI 80%), and reached a higher GI (132%) in the compost product compared with the thermophilic composting treatment. Moreover, the decrease of the C/N ratio in vermicompost indicated stabilization of the waste. The activities of earthworms played a positive role in reducing gaseous emissions in vermicompost, resulting in less emissions of NH3 (12.3% NH3-N of initial nitrogen) and total greenhouse gases (8.1 kg CO2-eq/t DM) than those from thermophilic compost (24.9% NH3-N of initial nitrogen, 22.8 kg CO2-eq/t DM). Therefore, it can be concluded that vermicomposting can shorten the period required to reach compost maturity, can obtain better maturity compost, and at the same time reduce gaseous emissions. As an added advantage, the earthworms after processing could have commercial uses.

Responses of Saline Soil Properties and Cotton Growth to Different Organic Amendments

Application of organic waste to saline alkaline soils is considered to be a good practice for soil remediation. The effects of applying different organic amendments (e.g., cattle dung, vermicompost, biofertilizer) and earthworm inoculations (Eisenia fetida) on saline soils and cotton growth were investigated during 1 year of cotton cultivation. Compared to the control (applied with inorganic NPK fertilizer), applying organic amendments improved soil physicochemical properties. Biofertilizer application improved available nutrient content, reduced short-term soil electrical conductivity, and produced the highest cotton yield, whereas cattle dung and vermicompost applications resulted in higher soil organic matter content. Application of organic amendments significantly increased soil microbial biomass carbon during the flowering period, which sharply declined at harvest. This was especially true for the biofertilizer treatment, which also exhibited lower nematode abundance compared with the other organic materials. Earthworm inoculation following cattle dung application failed to significantly change soil physicochemical properties when compared to the treatments without earthworm inoculation. Results suggest that biofertilizer application to saline soil would improve soil nutrient status in the short-term, whereas cattle dung application would improve soil organic matter content and increase soil organism abundance to a greater extent. However, different strategies might be required for long-term saline soil remediation.