European Journal of Soil Biology最新文献

Lumbricids and several species of the genus Amynthas have spread over all continents and seem to be better competitors than natives in disturbed ecosystems and agricultural fields. More than half of Uruguay's 19 earthworm species recorded by 2014 are exotic. Aiming to contribute to the scarce information on earthworm ecology in the region, the objectives of this work were 1) to characterize the earthworm communities in agriculture and natural ecosystems, and 2) to assess the relationship between land use and richness of native and exotic earthworm species. Related to the latter objective, we hypothesized that the difference in the number of exotic and native species depended on the degree of disturbance, and predicted that exotic species would dominate in more disturbed soils. We sampled organic and nonorganic agricultural fields including wheat in the rotations in the South and the North-West of Uruguay. Undisturbed sites, i.e. with no recent agriculture activity, close to each sampling plot served as controls. Analyses were conducted to elucidate whether other variables, besides disturbance and location, could be influencing earthworm community structure and composition. In both locations, exotic species dominated in control plots, i.e. less or non-disturbed land, and were associated to higher N, C and soil porosity. Moreover, in the North-West, natives would dominate in terms of richness in most agriculture plots. The mean body weight was larger in the South, where there were more exotic species, than in the North-West, where there were more native species. Thirteen of the collected species had been reported for Uruguay, the four other species found, were reported for the first time in this paper: Microscolex phosphoreus and Glossodrilus parecis (natives); and Aporrectodea tuberculata and Murchieona minuscula (exotics). Finding four unrecorded species evidences the poor coverage of earthworm sampling in anthropic and natural landscapes of the country.

Earthworms are key organisms of soil ecosystems, however, the determinants of the structure and distribution of earthworm communities and their relationships with agricultural practices are not well-studied in Canada. We sampled earthworm communities from four different habitat types along a disturbance gradient: agricultural crop land, forest around crop fields (buffers), recently restored natural grassland, and forests from conservation areas. As most species living in Canada are considered exotic and because of the recent colonization of Canadian soils by mostly European species after the extinction of the native species due to the glaciation of North America during the Pleistocene, we hypothesized that the impact of agricultural practices will be similar to what is observed in Europe: for example, crop habitat showing lowest abundance, richness, and proportion of epigeic and anecic species, due to lesser soil organic matter content and higher soil disturbance. We also hypothesized that important soil variables would be associated with these habitat differences. For each habitat we sampled earthworms using a combination of two methods (quantitative + qualitative) at three replicate sites, for two years between May and July together with important environmental variables. We found lower density and diversity of earthworms in crop habitat and proportionally more epigeic species than expected. Contrary to our predictions, forest-buffer earthworm communities were more similar to crop than to forest habitats, and soil environmental variables could not explain the variations in the spatial distribution of earthworm communities. In fact, our results revealed a more homogeneous distribution of the species diversity across the habitat gradient at local scales in Southern Ontario. This was mainly associated with spatial factors, probably due to historical extinction-colonization events of earthworms in Canada and the high invasive potential of the species currently present.

Crop cultivation positively or negatively impacts soil biodiversity and associated ecological services. The push-pull technology (PPT), a climate-smart cereal-Desmodium spp.-Brachiaria spp. Companion cropping system, is known for providing nature-based solutions for pest and soil fertility challenges and has been practiced in sub-Saharan smallholder farmer fields for more than two decades. However, the extent to which this cropping system affects soil arthropod biodiversity in general and Collembola in particular is not well known. This study assessed the long-term effects of PPT on soil physicochemical properties, abundance, and diversity of Collembola communities, and soil biological quality (QBS) as indicators of soil health. Soil was collected from five maize monoculture and five push-pull smallholder farmer fields in western Kenya. Soil physicochemical properties were analysed using Walkley-Black and Bouyoucos hygrometer method. Collembola abundance and diversity were assessed following the Berlese funnel extraction method and morphological identification. Soil health was evaluated using a Collembola-based soil biological quality (QBS-c) index. Soil physicochemical properties significantly differed between push-pull and maize monoculture fields, with push-pull soils being less acidic, and having higher quantities of nitrogen and carbon. Compared to monoculture, push-pull soils had significantly higher number and diversity of Collembola, and QBS-c index values. Significant positive correlations were observed between Collembola abundance and soil pH, nitrogen, carbon, phosphorous, and electrical conductivity. This study provides experimental evidence that crop diversification through a push-pull cropping system soil legacies positively impacts Collembola abundance and diversity, serving as bioindicator of healthy soils.

Farm dairy effluents (FDE) from washing the milking parlor contain manure, urine, and chemicals and constitute a large amount of wastewater. Applying FDE as soil fertilizers to pastures can enhance forage yield and improve soil nutrient status. Since the dairy industry is increasingly attempting to maximize returns through better utilization of forage with lesser inputs, there is demand for a supply of FDE as fertilizers. Nevertheless, the impact of this practice on soil microbiota remains largely unexplored. It must be studied before large-scale soil disposal to avoid diminishing microbial diversity or enhancing pathogen abundance. This study evaluated the effects of applying lagoon-stored (Lagoon) and raw dairy effluents (Raw) at a rate of 50 kg N ha⁻¹ in four equal doses, in comparison to urea fertilization, on soil fertility and the activity, abundance, and community structure of soil microbiota. Raw was obtained after solid separation, and Lagoon corresponds to the Raw stationed in a two-lagoon system. Microbial activity was assessed as basal respiration, potentially mineralizable N, potential nitrification activity, and enzymatic activities. The catabolic activity of the microbial community was evaluated using Biolog Ecoplates™. Bacterial and fungal community composition and diversity were analyzed through amplicon sequencing of 16S rRNA and ITS2. The application of FDE benefited soil fertility and microbial activity. Lagoon had the most potent effects on soil available P and extractable K⁺, Na⁺, Mg²⁺ and Ca²⁺. Soil treated with Raw displayed higher microbial activities, such as dehydrogenase, basal respiration, urease, and potentially mineralizable N, than the other treatments. FDE did not significantly alter the microbial composition, abundance, or functional diversity. In conclusion, in this short-term trial, despite changes in soil chemical properties and microbial activity, the composition and diversity of the bacterial and fungal communities remained unaffected by FDE irrigation.

In production of cereals like maize (Zea mays L.) and barley (Hordeum vulgare L.), seeds are often treated with pesticides and/or commercial products of plant beneficial microorganisms (PBM) to reduce possible root damage from insect pests and soil borne root diseases. In a field experiment with maize and barley under conservation agriculture, we examined how such seed treatments affected the resident root and soil microbiota. The seed treatments included a pesticide mixture and different commercial products of common PBM based on the biocontrol agents (BCA) Trichoderma harzianum and Metarhizium anisopliae alone and in combination and a mix of plant growth promoting rhizobacteria (PGPR), which were compared to a negative control without seed treatment. Soil and root samples were taken at two and three sampling times during the crop cycles for barley and maize, respectively, to measure root biomass, root colonization with mycorrhizal fungi and pathogens, soil microbial communities at a general taxonomic level using biomarker fatty acids, and ecological guilds of soil nematodes. Root health was monitored with observations of the presence of insect feeding larvae and root disease symptoms, which in general showed healthy roots during the full crop cycle. Overall, most of the root and soil biota variables measured changed during the crop cycle. However, for both crops, the seed treatments had no effects on the soil and root microbiota measured, except in the case of barley root infection with Polymyxa sp., which was reduced by all treatments. In conclusion, the pesticide and PBM seed treatments evaluated in the present study for maize and barley under conservation agriculture, in general, had limited effects on the resident root and soil microbiota. However, future studies should include complementary high-resolution sequencing methods when examining non-target effects of pesticides and microbial inoculants on the root and soil microbiota.

Earthworm species interact with each other in soils, but these interactions are poorly understood. Moreover, these key soil organisms are influenced by abiotic soil components such as organic matter. Here, we investigated the influence of Allolobophora chlorotica and Aporrectodea nocturna, two earthworm species from different ecological categories, on the incorporation of organic matter, reproduction and weight change of the endogeic Aporrectodea caliginosa. Two different types of organic matter i) a compost and ii) a fresh refined organic material, both from green waste, were used. Earthworm parameters were monitored during an 8-weeks laboratory experiment using a vineyard soil in order to identify positive and negative interactions between species. Irrespective of species, earthworms interacted preferentially with smaller particles, more decomposed and with a lower C/N ratio. For an equivalent earthworm biomass, similar amount of green compost was incorporated by A. caliginosa and A. nocturna. However, A. chlorotica did not bury this material. The green compost increased the reproduction rate of A. caliginosa when associated to A. chlorotica. Moreover, the association with the epi-anecic A. nocturna increased the reproduction rate of A. caliginosa with the addition of refined organic matter (fresh material). Furthermore, in both earthworm associations, the weight loss of A. caliginosa was reduced by the addition of green compost to the soil surface. These results highlight the importance of earthworm interactions in maintaining populations, and emphasized the need of field studies to confirm these interactions, particularly in the context of soil fertility where organic amendments are often applied.

Intercropping alfalfa (Medicago sativa) with grass offers yields equal to or greater than alfalfa monoculture, improves the quality of silaged fodder, and enhances resilience to drought and other stresses. Inoculating either alfalfa monoculture or mixed cultures (with a festucoid hybrid (Festulolium pabulare)) with plant growth-promoting rhizobacteria (PGPR) could potentially enhance plant growth, yield and soil quality. A monoculture of alfalfa and three different mixed cultures of alfalfa and festucoid hybrid at ratios 1:1, 2:1, and 3:1 were sown at a seeding rate of 30 kg·ha^-1 on small-scaled field plots (3 × 10 m). The soil type was Luvisol, either uninoculated or inoculated (⁓10.5 log10 CFUm^-2) with a commercial PGPR consortium containing (Azotobacter, Sinorhizobium meliloti, Bacillus megatherium). At the end of the trial, mixed soil samples (comprising 8 probes to a depth of 10 cm) were collected, and their biological properties were determined. Mixed cultures of alfalfa with the festucoid hybrid decreased nitrification; urease was lower by 8.5 % (alfalfa:festucoid 1:1), 36.5 % (2:1), and 49.7 % (3:1) compared to alfalfa control. d-glucose-induced respiration was higher by 55.4 % (2:1) and by 23.1 % (3:1), along with a negative trend in the nitrifying Archaea abundance. Nitrososphaeria relative abundance decreased from 4.5 % (1:1) to 9.4 % (3:1) compared to the control. Inoculation indirectly affected nitrogen (N) turnover in the mixed variants by increasing urease (2:1 inoculated 49.1 % over 2:1 uninoculated; 3:1 inoculated 36.5 % over 3:1 uninoculated value) and increased the relative abundance of Nitrososphaeria (alfalfa inoculated 7.3 % and 2:1 inoculated 4.2 % over uninoculated control). Inoculation enhanced phosphatase activity (1:1 inoculated 11.4 %; 2:1 inoculated 21.8 %, 3:1 inoculated 16.2 % over respective uninoculated values), specific soil respiration (alfalfa inoculated 146 %, 1:1 inoculated 192 %, 2:1 inoculated 3 % over uninoculated values), and brought a positive tendency in copiotrophic (Actinobacteria) relative abundance (alfalfa inoculated 10.2 %, 1:1 inoculated 6.1 %, 3:1 inoculated 3.4 % over respective uninoculated values), albeit it decreased fungal biomass. An increased rate of N₂ fixation and N assimilation in variants with high alfalfa: grass ratio decreased nitrification and increased mineralization of specific substrates. Inoculation neither directly enriched the soil with the introduced PGPR taxa nor shifted soil microbial diversity. However, it did prompt tendencies in community composition changes towards a higher proportion of nitrifiers and copiotrophs. Despite multiple changes in the tested experimental variants, no significant effect on the plant biomass of harvested crops was observed during the three years.

Overusing chemical fertilizers (CFs) causes soil degradation, which can be mitigated by partially substituting CFs with green manure. This study investigated the impact of traditional vs. improved fertilization schemes that included Chinese milk vetch (CMV) on soil properties and bacterial communities in rice rhizosphere and bulk soil from plots over 12 years under fertilization. The treatments included the conventional fertilization (CF₁₀₀), CMV (22.5 t ha⁻¹) with 100 % CF (CMV + CF₁₀₀), CMV with 80 % CF (CMV + CF₈₀), CMV with 60 % CF (CMV + CF₆₀), and CMV with 40 % CF (CMV + CF₄₀). CMV + CF40 increased the soil organic matter (SOM) content in the rhizosphere (bulk) soil by 38.02 % (37.86 %) compared to CF₁₀₀ (P < 0.05). The quality index in bulk soil increased by 5.49%–8.17 % through all CF combined with CMV. The rhizosphere bacterial diversity was 1.11%–2.30 % higher, and richness was 2.87%–4.93 % higher than in bulk soil. In the bulk soil, only the CMV + CF₄₀ increased the bacterial Shannon by 0.40 %, Ace by 0.84 %, and Chao1 indice by 0.89 %. Relative abundances of Geobacter in bulk soil were by 13.90%–52.27 %, Leptospirillum by 25%–77.12 %, and Desulfobacca by 7.42%–37.85 % higher than in the rhizosphere. The stability of the rhizosphere and bulk soil bacterial communities under the CMV input was predicted by the SOM and available phosphorus contents, as indicated by the degree of bacterial average variation. The CMV + CF₄₀ was recommended as the optimal alternative rate based on local soil ecological considerations.

Restoring plant diversity is crucial to enhance soil organic carbon (SOC) storage and mitigate biodiversity loss and climate change. However, there is limited understanding of how plant diversity impacts biological SOC components and microbial communities in the short term, impeding informed agricultural management decisions. We conducted controlled experiments with various herbaceous plant mixtures to investigate the short-term effects of plant diversity on SOC components (e.g., amino sugars and lignin phenols) and associated microbial community. While soil physical and chemical properties remained relatively stable over one year, plant diversity significantly increased both microbial-derived and plant-derived carbon contents. The plant-derived carbon of two, three, and four-species mixture treatments was higher than 38 %, 59 %, and 80 %, respectively, compared to that of one species. Similarly, microbial-derived carbon increased by 68 %, 117 %, and 164 % for treatments with two, three, and four species mixtures compared to the one species treatment. While plant species richness did not influence bacterial & fungal diversity and community composition at the phylum level, it did affect community constitution at the genus level. Moreover, plant diversity decreased the total number of edges, the number of negatively related edges, and the mean degree of the fungal co-occurrence network. Hence, our results suggest that plant diversity may alter SOC composition by influencing soil microorganism interactions. The rapid response of organic carbon components to plant diversity could underpin total SOC accumulation in the long term. This study provides novel insights into how plant diversity shapes short-term SOC dynamics by influencing microbial interactions, potentially contributing to long-term SOC accumulation.

Application of organic amendments to agricultural fields often increases earthworm density and biomass. Soil pH can influence earthworm species composition, density, and biomass. However, the effects of organic amendments on these three characteristics at different soil pH value are not fully understood, especially in tropical agricultural fields. In sugarcane fields on Ishigaki Island, Okinawa Prefecture, Japan, we measured soil properties and earthworm species composition, density, and biomass at three paired sites (with and without filter cake input) in soil with low pH (pH-5 sites; pH < 5.2 without filter cake) and moderate pH (pH-6 sites; pH > 6.0 without filter cake), 12 sites in total. The fields contained Pontoscolex corethrurus (Müller, 1856), Polypheretima elongata (Perrier, 1872), and Dichogaster bolaui (Michaelsen, 1891); P. corethrurus was dominant and mean species richness was 1.2. Filter cake application increased earthworm density and biomass at the pH-5 sites but decreased them at the pH-6 sites. This discrepancy in effect might be due to how pH changed when filter cake was added. At pH near neutral, even a small change in proton content could result in a large change in soil pH. The application of filter cake did not change soil pH at the pH-5 sites, but it significantly decreased soil pH at the pH-6 sites, which might have caused the reduction of earthworm density and biomass. Overall, organic amendment affected soil physicochemical and biological properties over the short term in the subtropics, depending on the prior soil pH. Under certain soil conditions, organic amendment can improve both the physicochemical and biological properties of soil, which could improve soil ecosystem services.