Effects of traditional and biodynamic farmyard manure amendment on yields,soil chemical,biochemical and biological properties in a long-term field experiment

We studied the effects of applications of traditionally composted farmyard manure (FYM) and two types of biodynamically composted FYM over 9 years on soil chemical properties, microbial biomass and respiration, dehydrogenase and saccharase activities, decomposition rates and root production under grass-clover, activity and biomass of earthworms under wheat, and yields in a grass-clover, potatoes, winter wheat, field beans, spring wheat, winter rye crop rotation. The experiment was conducted near Bonn, on a Fluvisol using a randomised complete block design (n=6). Our results showed that plots which received either prepared or non-prepared FYM (30 Mg ha^–1 year^–1) had significantly increased soil pH, P and K concentrations, microbial biomass, dehydrogenase activity, decomposition (cotton strips), earthworm cast production and altered earthworm community composition than plots without FYM application. Application of FYM did not affect the soil C/N ratio, root length density, saccharase activity, microbial basal respiration, metabolic quotient and crop yields. The biodynamic preparation of FYM with fermented residues of six plant species (6 g Mg^–1 FYM) significantly decreased soil microbial basal respiration and metabolic quotient compared to non-prepared FYM or FYM prepared with only Achillea. The biodynamic preparation did not affect soil microbial biomass, dehydrogenase activity and decomposition during 62 days. However, after 100 days, decomposition was significantly faster in plots which received completely prepared FYM than in plots which received no FYM, FYM without preparations or FYM with the Achillea preparation. Furthermore, the application of completely prepared FYM led to significantly higher biomass and abundance of endogeic or anecic earthworms than in plots where non-prepared FYM was applied.     

Quantification of nitrogen excretion rates for three lumbricid earthworms using 15N

 Nitrogen excretion rates of ¹⁵N-labeled earthworms and contributions of ¹⁵N excretion products to organic (dissolved organic N) and inorganic (NH₄-N, NO₃-N) soil N pools were determined at 10  °C and 18  °C under laboratory conditions. Juvenile and adult Lumbricus terrestris L., pre-clitellate and adult Aporrectodea tuberculata (Eisen), and adult Lumbricus rubellus (Hoffmeister) were labeled with ¹⁵N by providing earthworms with ¹⁵N-labeled organic substrates for 5–6 weeks. The quantity of ¹⁵N excreted in unlabeled soil was measured after 48 h, and daily N excretion rates were calculated. N excretion rates ranged from 274.4 to 744 μg N g^–1 earthworm fresh weight day^–1, with a daily turnover of 0.3–0.9% of earthworm tissue N. The N excretion rates of juvenile L. terrestris were significantly lower than adult L. terrestris, and there was no difference in the N excretion rates of pre-clitellate and adult A. tuberculata. Extractable N pools, particularly NH₄-N, were greater in soils incubated with earthworms for 48 h than soils incubated without earthworms. Between 13 and 40% of excreted ¹⁵N was found in the ¹⁵N-mineral N (NH₄-N+NO₃-N) pool, and 13–23% was in the ¹⁵N-DON pool. Other fates of excreted ¹⁵N may have been incorporation in microbial biomass, chemical or physical protection in non-extractable N forms, or gaseous N losses. Earthworm excretion rates were combined with earthworm biomass measurements to estimate N flux from earthworm populations through excretion. Annual earthworm excretion was estimated at 41.5 kg N ha^–1 in an inorganically-fertilized corn agroecosystem, and was equivalent to 22% of crop N uptake. Our results suggest that the earthworms could contribute significantly to N cycling in corn agroecosystems through excretion processes. Received: 12 April 1999     

Microbial communities of Lumbricus terrestris L. middens: structure, activity, and changes through time in relation to earthworm presence

Background, aim, and scope  Earthworms make a major contribution to decomposition in ecosystems where they are present, mainly acting in the drilosphere, that is, galleries, burrows, casts, and middens. Earthworm middens are hot-spots of microbial activity and nutrient dynamics and represent a suitable model for studying earthworm-mediated influences on soil microbial communities by alteration of the patch structure of the microbial environment. We studied the structure and activity of the microbial communities in the soil system formed by middens of Lumbricus terrestris and the soil below and surrounding them and the role of earthworms in maintaining these structures through time. Material and methods  We set up an experiment in which middens were either left (control) or removed from their original place (translocated) and left in a nearby area free of earthworm activity for 2 months. After 1 and 2 months we sampled middens, soil below them, and surrounding soil. We analyzed the phospholipid fatty acid (PLFA) profiles and measured respiratory fluxes of CO₂ and CH₄. Results  Microbial communities of middens clearly differed from those of soil below and surrounding soil samples, showing higher bacterial and fungal PLFAs (p < 0.0001 and p < 0.01, respectively); furthermore, changes in microbial communities were stronger in control middens than in translocated middens. Moreover, gram positive and negative bacterial PLFAs were greater in translocated than control middens (p < 0.0001 and p < 0.001, respectively), as well as total organic carbon (p < 0.001). Microbial activity was higher in middens than in soil below and surrounding soil samples both for CO₂ (p < 0.0001) and CH₄ (p < 0.0001). Discussion  Soil bioturbation by the earthworm L. terrestris was strong in their middens, but there was not any effect on soil below and surrounding soil. Microbial communities of middens maintain their biomass and activity when earthworms were not present, whereas they decreased their biomass and increased their activity when earthworms were present. Conclusions  Earthworms strongly enhanced microbial activity measured as CO₂ production in middens, which indicates that there are hot spots for soil microbial dynamics and increasing habitat heterogeneity for soil microorganisms. Moreover, our data strongly support the fact that the impact of this earthworm species in this soil is restricted to their middens and increasing soil heterogeneity. Recommendations and perspectives  Our data indicate that it is not clear if earthworms enhance or depress microbial communities of middens since the microbial activity increased, but did not modify their biomass and this was not dependent on soil organic C content. These results indicate no competence for C pools between this anecic earthworm and microorganisms, which has been found for other earthworm species, mainly endogeics. Conversely, they suggest some type of facilitation due to the release of additional nutrient pools in middens when earthworms are present, through the digestion of middens' material or the addition of casts produced from other food sources.     

Manure contaminated with the antibiotic sulfadiazine impairs the abundance of nirK- and nirS-type denitrifiers in the gut of the earthworm Eisenia fetida

The antibiotic sulfadiazine (SDZ) can affect denitrifying bacteria in soil. However, effects on denitrifiers in the gut of earthworms have not been described so far. Therefore, the influence of SDZ-contaminated manure applied to soil on denitrifiers in the gut of the earthworm Eisenia fetida was assessed by quantitative polymerase chain reaction targeting genes coding for nirK- and nirS-type nitrite reductases of denitrifiers. Gut contents of Eisenia fetida contained 2.5 × 10⁶ and 5.1 × 10⁵ gene copies of nirK and nirS, respectively, after 2 weeks in soils amended with manure only. Copy numbers of nirK and nirS in gut contents from manure treatments with SDZ were up to ten times less. Overall, the data indicate a negative impact of SDZ on denitrifiers in the gut of earthworms.     

Axial and radial pressure exerted by earthworms of different ecological groups

 The aim of this study was to measure the pressures exerted by earthworms during burrowing. For this purpose we developed two methods with which to quantify the axial and radial pressure. The data were recorded with an electronic balance that was connected to a PC. Artificial earthworm burrows were used to standardize the measurements. Plexiglas tubes with diameters ranging from 2 to 6.3 mm which corresponded to the diameter of the earthworms were used. A pin was placed inside the tubes, on which the earthworms exerted a pressure by peristaltic locomotion. Only the maximum values of the pressure measurement were taken into account for evaluation, and the arithmetic mean was calculated. The measurements were conducted with Aporrectodea longa, Lumbricus terrestris, Aporrectodea caliginosa, Octolasion cyaneum, Allolobophora chlorotica, Aporrectodea rosea, Lumbricus rubellus and Dendrobaena octaedra. The species examined were classified into ecological groups. The mean axial pressures exerted by each group were in the order: epigeic (14–25 kPa), endogeic (27–39 kPa) and anecic (46–65 kPa). For the mean radial pressure the order was: epigeic (39–63 kPa), anecic (72–93 kPa) and endogeic (59–195 kPa). It was apparent from the results that radial pressure is the most important pressure with respect to the burrowing activity of earthworms. Received: 28 April 1998     

Simultaneous effects of plants and earthworms on mineralisation of 15N-labelled organic compounds adsorbed onto soil size fractions

 The simultaneous impact of three successive crops of wheat (Triticum aestivum L.) and of the earthworm (Lumbricus terrestris L.) on the mineralisation of ¹⁵N-labelled organic compounds adsorbed to different soil size fractions (sand and organic residues >50 μm; silt 50–2 μm; coarse clay 2–0.2 μm and fine clay <0.2 μm) was studied under controlled conditions in the greenhouse. Unplanted soils (UPS) were used as controls. In planted soils without earthworm (PS) total plant biomass decreased with each cropping by up to 50%. However, in planted soils with earthworms (PES) the total plant biomass loss was only 17%. This pattern was explained by the earthworm effect. Compared to the unplanted soils, the planted soils had an increased (mean +37%) mineralisation of ¹⁵N adsorbed onto fine clays and a partial transfer of ¹⁵N to silt and coarse clay. The quantities of ¹⁵N mineralised and transferred were higher in the planted soils with earthworms, indicating an amplification of the phenomenon in the presence of earthworms. The simultaneous effect of the rhizosphere and the drilosphere did not lead to increased mineralisation of N adsorbed onto coarse clays and silts but instead a greater transfer of N associated with the fine fractions towards the coarser fractions. Received: 25 April 2000     

Evolution of burrow systems after the accidental introduction of a new earthworm species into a Swiss pre-alpine meadow

 The unintentional introduction of a new earthworm species (Aporrectodea nocturna) into a Swiss pre-alpine meadow resulted in a great increase in earthworm density in the newly colonized area (386 m^–2) compared with the density observed in the natural area (273 m^–2) where an earthworm community was already present. To investigate the impact of this introduction on the burrow systems, eight soil cores (length 25 cm, diameter 16 cm) were taken (four in the colonized area and four in the natural area) and analysed with computer-assisted X-ray tomography. The resulting images were processed to obtain the 3D-skeleton reconstructions of the earthworm burrow systems. Due to high variability in these burrow systems, only slight differences were observed between the two areas. The total burrow length and the mean burrow lengths tended to be greater in the colonized area. Moreover, the distribution of pore numbers with depth showed different patterns with a maximum for depths between 10 cm and 15 cm in the colonized area and a maximum for depths between 20 cm and 25 cm in the natural area. These differences may have been related to: (1) the particular behaviour of A. nocturna, which was observed to cast at the surface in this site, and (2) the predominance of juvenile earthworms around the colonization front. These differences were sufficient to create significant effects on the continuity of the burrow systems (assessed by the number of different pathways between virtual horizontal planes) for the two areas. The colonized area was characterized by a greater pore continuity, which could have resulted in enhanced transfer properties. Received: 2 July 1999     

Can earthworms be used as bio-indicators of land-use perturbations in semi-deciduous forest?

The potential of tropical earthworms as bio-indicators of forest degradation by human-induced activities was assessed at a landscape level in the Ivory Coast. The study site covered 400 ha and was characterized by a set of land-use types along a gradient of perturbation from semi-deciduous forest, through reforestation, fallow systems to cultivated annual crops. Samples were taken on a grid at each sampling point and earthworms were hand-sorted from a 25 × 25 × 30-cm soil monolith. Results showed a potential increase in relative populations (number: +53.1%, biomass: +94.8%) of species in the earthworm communities following forest conversion. Furthermore, the impact of land-use change was higher in relation to land-use intensification in terms of earthworm populations and diversity in intermediate-disturbed systems (Multispecies plantations, old fallows). Earthworm diversity was the most sensitive response to land-use change. The species Dichogaster saliens Beddard 1893, Hyperiodrilus africanus Beddard 1891, Millsonia omodeoi Sims 1986, Dichogaster baeri Sciacchitano 1952, Dichogaster ehrhardti Michaelsen 1898, Agastrodrilus sp., Stuhlmannia palustris Omodeo and Vaillaud 1967 and, to some extent, Millsonia sp. appeared to be most sensitive to land-use change. More field and laboratory investigations are needed to find out the most efficient species to be used in bio-monitoring programmes aimed at preventing ecosystem degradation due to anthropogenic activities in the forest areas of Ivory Coast.     

不同有机物料接种蚯蚓对设施菜地土壤 培肥及作物生长的影响

设施蔬菜栽培长期施用过量化肥,往往导致土壤质量退化及作物产量降低等问题。因此,采用生态友好的农业生产方式已成为农业可持续发展的趋势。本研究在野外调控试验的第3年采集作物和土壤,研究了施用不同有机物料条件下,接种赤子爱胜蚓(Eisenia foetida)对设施菜地土壤性质和作物生长的影响。结果表明,在不同有机物料施用下接种赤子爱胜蚓均显著地提高了黄瓜和菠菜的产量,其中在施用腐熟牛粪+食用菌渣条件下接种赤子爱胜蚓效果最显著。此外,在腐熟牛粪和腐熟牛粪+食用菌渣施用条件下,接种赤子爱胜蚓显著地提高土壤的硝态氮(NO3–-N)、团聚体平均重量直径(MWD)、微生物生物量碳(MBC)、微生物生物量氮(MBN)和代谢熵(q CO2),而在施用商品有机肥的处理中,接种赤子爱胜蚓仅显著地提高了土壤NO3–-N和q CO2。本研究促进了对蚯蚓在设施农业生态系统中服务功能的理解,并为设施农业生产提供了理论基础。     

Bacteria and protozoa in soil microhabitats as affected by earthworms

The effects of incorporation of elm leaves (Ulmus glabra) into an agricultural sandy loam soil by earthworms (Lumbricus festivus) on the bacterial and protozoan populations were investigated. Three model systems consisting of soil, soil with leaves, and soil with leaves and earthworms, respectively, were compared. The total, viable, and culturable number of bacteria, the metabolic potentials of bacterial populations, and the number of protozoa and nematodes were determined in soil size fractions. Significant differences between soil fractions were shown by all assays. The highest number of microorganisms was found in microaggregates of 2–53 μm and the lowest in the <0.2μm fraction. A major part of the bacteria in the latter fraction was viable, but non-culturable, while a relatively higher number of culturable bacteria was found in the macroaggregates. The number of colony-forming units and 5-cyano-2,3-ditolyl tetrazolim chloride (CTC)-reducing bacteria explained a major part of the variation in the number of protozoa. High protozoan activity and predation thus coincided with high bacterial activity. In soil with elm leaves, fungal growth is assumed to inhibit bacterial and protozoan activity. In soil with elm leaves and earthworms, earthworm activity led to increased culturability of bacteria, activity of protozoa, number of nematodes, changed metabolic potentials of the bacteria, and decreased differences in metabolic potentials between bacterial populations in the soil fractions. The effects of earthworms can be mediated by mechanical mixing of the soil constituents and incorporation of organic matter into the soil, but as the earthworms have only consumed a minor part of the soil, priming effects are believed partly to explain the increased microbial activity. Received: 7 January 1996     

Assessing the impact of Diplocardia ornata on physical and chemical properties of compacted forest soil in microcosms

 The influence of compaction on Diplocardia ornata (Smith) burrowing and casting activities, soil aggregation, and nutrient changes in a forest soil were investigated using pot microcosms. Treatments included two levels each of compaction, organic matter, and earthworms. Both burrowing and casting activities were more abundant in uncompacted soil than in compacted soil. Bulk density decreased in microcosms of compacted soil containing D. ornata from 1.76 g cm^–3 to 1.49 g cm^–3 over the study period. The overall percent of aggregates in the same size classes in compacted soil was less than the percent of aggregates in uncompacted soil. The mean percent of aggregates in earthworm casts for size classes 0.25–1.00 mm was higher for compacted soil than for uncompacted soil. The reverse was true for aggregates in class sizes 2.00–4.00 mm. Soil compaction also affected soil microbial biomass carbon and soil inorganic N concentrations. These results indicate that the burrowing and casting activities of earthworms in compacted forest soils, as in soils of agricultural and pastured lands, can help ameliorate disturbed soils by improving aggregation, reducing bulk density, and increasing nutrient availability. Received: 1 September 1999     

Accumulation of zinc and its effects on the growth, reproduction and life cycle of Drawida willsi (Oligochaeta), a dominant earthworm in Indian crop fields

 Accumulation of Zn and its effects on the growth, reproduction and life cycle of the earthworm Drawida willsi were determined. D. willsi did not reveal any significant changes in their mass at any of the concentrations of Zn (50, 200 and 400 mg kg^–1) compared to in untreated soils. The Zn concentrations in the exposed earthworms were significantly increased, but they were able to regulate their body content of Zn within a range of 116–125 mg kg^–1 (dry wt) in 200–400 mg kg^–1 Zn-treated soil. Reproduction was significantly reduced when the Zn concentration in soil exceeded 200 mg kg^–1. The drop in reproduction at elevated concentrations of Zn apparently resulted in a delay in completion of the life cycle and a decline in the total population. Received: 9 September 1998     

Earthworm populations as affected by crop practices on clay loam soil in a Mediterranean climate

Abstract

Earthworms influence soil fertility, and their population is known to be influenced by fertilization. The objective of this study is to characterize the abundance of earthworms under three different kinds of rotation-crops (Rotation: cereals–legumes for green manure-cotton), three tillage systems (Conventional Tillage CT, Minimum Tillage MT, & No-Tillage NT) and fertilization (NP: inorganic and FYM: farmyard manure-organic). Significantly higher populations of earthworms were found under the legumes and NT system in contrast to the lowest abundance determined under the cotton and CT system. Earthworm populations benefited more from organic fertilization than from NP. Our study showed that the most important factors for earthworm abundance are the macropores and C_org under Mediterranean conditions. No-till management considerably influenced the improvement of the physical and chemical soil properties and increased the earthworm abundance.     

Significance of earthworms in stimulating soil microbial activity

 The stimulatory effect of earthworms (Lumbricus terrestris L.) on soil microbial activity was studied under microcosm-controlled conditions. The hypothesis was tested that microbial stimulation observed in the presence of a soil invertebrate would be due to the utilization of additional nutritive substances (secretion and excretion products) that it provides. Changes in microbial activity were monitored by measuring simultaneously CO₂ release and protozoan population density. The increase in CO₂ released in the presence of earthworms was found to result from both earthworm respiration and enhanced microbial respiration. The stimulation of microbial activity was confirmed by a significant increase in protozoan population density, which was 3–19 times greater in the presence of earthworms. The respiratory rate of L. terrestris was estimated to be 53 μl O₂ g^–1 h^–1. Earthworm respiration significantly correlated with individual earthworm weight, but there was no correlation between the increase in microbial respiration and earthworm weight. This finding does not support the hypothesis given above that enhanced microbial respiration is due to utilization of earthworm excreta. A new hypothesis that relationships between microbial activity and earthworms are not based on trophic links alone but also on catalytic mechanisms is proposed and discussed. Received: 26 August 1997     

Nutrient uptake in mycorrhizal plants – role of earthworms

Both arbuscular mycorrhizal fungi (AMF) and earthworms often coexist in agriculture ecosystems, but very little is known on the interactions between them. A two-compartment air gap-incorporating device was used to investigate the effects of three species of earthworm (epigeic Eisenia foetida, endogeic Aporrectodea trapezoide, and anecic Pheretima guillelmi) on AMF (Glomus intraradices) under the exclusion of plant roots, and then on maize (Zea mays L.) performance and nutrients uptake. Results showed a strong correlation between hyphal length density and subsequent plant growth and nutrient uptake. Earthworms improved soil nutrients availability in hyphal compartment (HC): E. foetida improved the concentration of soil inorganic N, A. trapezoide changed the concentration of available phosphate in the soil, and P. guillelmi changed the soil's physical properties. We found some indications that different species of earthworm and AMF might interact within the soil. Earthworms and AMF mainly acting on different nutrients create distinct niches for plants. The feeding and burrowing activities did not significantly destroy hyphal length density and made negative affect on plant performance.     

The influence of soil compaction and the removal of organic matter on two native earthworms and soil properties in an oak-hickory forest

 Earthworms may alter the physical, chemical, and biological properties of a forest soil ecosystem. Any physical manipulation of the soil ecosystem may, in turn, affect the activities and ecology of earthworms. The effects of removing organic matter (logs and forest litter) and severely compacting the soil on native earthworm species were measured in a central USA hardwood region (oak-hickory) forest in the Missouri Ozarks (USA). Soils in this region are characterized by a cherty residuum that is primarily of the Clarksville series (Loamy-skeletal, mixed, mesic Typic Paledults). Earthworms were collected from 0–15 cm depth each spring and fall for 2 years by handsorting, and densities were determined on a per meter square basis. Two native earthworm species, Diplocardia ornata and Diplocardia smithii, were dominant on this site. Organic matter removal decreased the average individual biomass of both species. However, both species responded differently to soil compaction. Soil compaction affected D. ornata adversely and D. smithii favorably. This suggested that the degree of soil compaction was not as restrictive with respect to D. smithii (2 mm diameter) as to D. ornata (5 mm diameter). Moreover, the apparently improved soil environmental conditions resulting from the remaining organic matter in compacted soil enhanced the population and growth of D. smithii. Sampling position on the landscape affected D. ornata but not D. smithii. Soil microbial biomass C and soil microbial biomass N were decreased under soil compaction when the organic matter was removed. Other factors influencing the ecology and activity of these two species will require further study. Received: 6 January 1999     

Earthworm (<Emphasis Type="Italic">Metaphire guillelmi</Emphasis>) effects on rice photosynthates distribution in the plant–soil system

An experiment was conducted to investigate the effects of earthworm (Metaphire guillelmi) activities on rice photosynthates distribution in plant–soil system through ¹⁴C pulse-labelling method. Rice was planted in pots, and maize straw was mulched on the surface with or without earthworms. Rice plants at tillering stage or heading stage were labelled with ¹⁴CO₂. Plant and soil were sampled 15 days after labelling at the tillering or heading stage and at harvest. Rice growth was inhibited by earthworms (M. guillelmi) at early stage, but the inhibition disappeared at later stage. Earthworms significantly (P < 0.01) increased the ¹⁴C percentage in root at day 15 after tillering stage labelling, but the effect disappeared at harvest. Earthworms (M. guillelmi) significantly (P < 0.01) increased the ¹⁴C percentage in root at day 15 after heading stage labelling and increased ¹⁴C percentage in soil at harvest. Earthworms decreased the percentages of total organic ¹⁴C (TO¹⁴C) present as microbial biomass ¹⁴C (MB¹⁴C) and increased the percentages of total organic ¹⁴C present as dissolved organic ¹⁴C (DO¹⁴C) at all sampling times. It is suggested that earthworms might alter the transfer of plant photosynthates from the aboveground to the belowground, and thus, soil active C pool. However, these data should be also confirmed in the field.     

Does long-term farmyard manure fertilization affect short-term nitrogen mineralization from farmyard manure?

One of the challenges in organic farming systems is to match nitrogen (N) mineralization from organic fertilizers and crop demand for N. The mineralization rate of organic N is mainly determined by the chemical composition of the organic matter being decomposed and the activity of the soil microflora. It has been shown that long-term organic fertilization can affect soil microbial biomass (MB), the microbial community structure, and the activity of enzymes involved in the decomposition of organic matter, but whether this has an impact on short-term N mineralization from recently applied organic substances is not yet clear. Here, we sampled soils from a long-term field experiment, which had either not been fertilized, or fertilized with 30 or 60 t ha⁻¹ year⁻¹ of farmyard manure (FYM) since 1989. These soil samples were used in a 10-week pot experiment with or without addition of FYM before starting (recent fertilization). At the start and end of this experiment, soil MB, microbial basal respiration, total plant N, and mineral soil N content were measured, and a simplified N balance was calculated. Although the different treatments used in the long-term experiment induced significant differences in soil MB, as well as total soil C and N contents, the total N mineralization from FYM was not significantly affected by soil fertilization history. The amount of N released from FYM and not immobilized by soil microflora was about twice as high in the soil that had been fertilized with 60 t ha⁻¹ year⁻¹ of FYM as compared with the non-fertilized soil (p < 0.05).     

Effect of passage through the intestinal tract of detritivore earthworms (Lumbricus spp.) on the number of selected Gram-negative and total bacteria

Laboratory experiments were carried out to investigate the fate of bacteria during and after passage through the intestinal tract of detritivore earthworms. Earthworms (Lumbricus spp.) were fed with cattle dung inoculated 7 days previously with one of five different Gram-negative bacteria. Bacterial concentrations were determined 2 days later in dung and soil, and in gut material from different parts of the earthworm intestinal tract. A high percentage (28–82%) of the total bacteria (epifluorescence direct counts) in the earthworm gut content was culturable. The concentration of total heterotrophic aerobic bacteria did not vary significantly among the five different bacterial additions and the non-inoculated control. In earthworm casts the number of total heterotrophs per gram dry matter (2.1×10⁹) was higher than in soil (1.7×10⁸), but lower than in the dung (1.5×10¹⁰). The test-bacteria, however, showed different survival patterns along the earthworm intestinal tract. The concentrations of Escherichia coli BJ 18 and Pseudomonas putida MM 1 and MM 11 in earthworm casts were lower than in the ingested dung, while concentrations of Enterobacter cloacae A 107 and Aeromonas hydrophila DMU 115 in dung and casts were similar. Ent. cloacae, and to aminor extent E. coli, were reduced in numbers by several orders of magnitude in the pharynx and/or crop. In the hind gut, however, the concentration of Ent. cloacae had increased to the same level as in the ingested dung, while the concentration of E. coli remained low. Our observations indicate that the bacterial flora of ingested food materials changes qualitatively and quantitatively during gut transit.     

Effect of<Emphasis Type="Italic"> Eisenia foetida</Emphasis> earthworms on mineralization kinetics,microbial biomass,enzyme activities,respiration and labile C fractions of three soils treated with a composted organic residue

The aim of this work was to assess and compare the influence of Eisenia foetida Savigny earthworms on C mineralization rate, labile C fractions (water-soluble C and water-soluble carbohydrates), microbial biomass C, and enzyme activities (dehydrogenase, urease, phosphatase and ß-glucosidase) in three soils of varying texture treated with a composted organic residue and cropped with Avena sativa L. Mineralization decreased with the addition of earthworms to the sandy and clay-loam soils, especially in sandy soil (by about 4 µg CO ₂-C g ^-1 day ^-1). There were no significant effects on the amount of CO ₂ evolved from clay soil due to the addition of E. foetida. The addition of E. foetida to sandy soil significantly decreased microbial biomass C and increased microbial metabolic quotient the qCO ₂ (CO ₂-C to biomass C ratio). The addition of E. foetida did not affect the microbial biomass or the qCO ₂ of the clay-loam and clay soils.