The effect of tillage type and cropping system on earthworm communities, macroporosity and water infiltration

To test the assumption that changes to earthworm communities subsequently affect macroporosity and then soil water infiltration, we carried out a 3 year study of the earthworm communities in a experimental site having six experimental treatments: 2 tillage management systems and 3 cropping systems. The tillage management was either conventional (CT; annual mouldboard ploughing up to −30 cm depth) or reduced (RT; rotary harrow up to −7 cm depth). The 3 cropping systems were established to obtain a wide range of soil compaction intensities depending on the crop rotations and the rules of decision making. In the spring of 2005, the impact of these different treatments on earthworm induced macroporosity and water infiltration was studied. During the 3 years of observation, tillage management had a significant effect on bulk density (1.27 in CT and 1.49 mg m⁻³ in RT) whereas cropping system had a significant effect on bulk density in RT plots only. Tillage management did not significantly affect earthworm abundance but significantly influenced the ecological type of earthworms found in each plot (anecic were more abundant in RT). On the contrary cropping system did have a significant negative effect on earthworm abundance (104 and 129 ind. m⁻² in the less and most compacted plots, respectively). Significantly higher numbers of Aporrectodea giardi and lower numbers of Aporrectodea caliginosa were found in the most compacted plots. CT affected all classes of porosity leading to a significant decrease in the number of pores and their continuity. Only larger pores, with a diameter superior to 6 mm, however, were adversely affected by soil compaction. Tillage management did not change water infiltration, probably because the increase in macroporosity in RT plots was offset by a significant increase in soil bulk density. However, cropping system had a significant effect on water infiltration (119 vs 79 mm h⁻¹ in the less and most compacted plots, respectively). In RT plots, a significant correlation was observed between larger macropores (diameter > 6 mm) and water infiltration illustrating the potential positive effect of earthworms in these plots.     

Earthworm bioturbation stabilizes carbon in non-flooded paddy soil at the risk of increasing methane emissions under wet soil conditions

Studies on earthworms in rice-based ecosystems tend to focus on some pest species, while the potential of these important soil engineers for beneficially affecting carbon storage and cycling is widely ignored. We carried out a microcosm experiment to quantify the impact of the tropical earthworm Pheretima sp. on the C turnover in paddy soils under different conditions of water saturation and N fertilization. The soil was sampled at the lowland farm of the International Rice Research Institute (Philippines). In the absence of earthworms, soil respiration showed a distinct hump-shaped maximum at intermediate levels of water saturation (4-fold higher than in hand-dry soil) and increased 1.5-fold with increasing amounts of N fertilization. Amounts of CH₄ emitted, in contrast, were small at low to moderate soil humidity and became very high under conditions of water saturation (80-fold higher than hand-dry soil). No response to nitrogen addition was observed. Earthworms suppressed both the respiration maximum at intermediate saturation levels (by a factor of 1.4) and the stimulating impact of N fertilization (1.7-fold at maximum fertilizer level). On the other hand, earthworms strongly increased CH₄ release under conditions of high water saturation (3-fold). No consistent response of the soil microflora (bacterial abundance, soil enzymes) to earthworm activity could be established. Our findings suggest that the stabilization of soil organic C via earthworm bioturbation is confined to the range of soil humidity that allows high activity of Pheretima sp. Under conditions of intensive agriculture, the stabilizing effect of the worms may even be augmented by the fact that they offset the positive effect of N fertilization on microbial respiration. Earthworms may thus play a vital role in reducing the CO₂ flush from paddy soils after the conversion to non-flooded crops such as aerobic rice or maize. Acceleration of methane emission in very humid soils nevertheless points to a certain risk that is associated with increasing earthworm abundance in production systems that are still exposed to temporary flooding during the wet season.     

Associations between soil texture,soil water characteristics and earthworm populations in grassland

Abstract

The aim of the present study was to investigate the relationships between soil physical characteristics and earthworms in a regional-scale field study in Denmark. The earthworm populations along within-field gradients in soil texture were quantified at five field sites, representing dominant soil types of Denmark. Eleven earthworm species were found, but populations were mainly dominated by Aporrectodea tuberculata and A. longa. Despite considerable variation in soil parameters across the five study sites the results suggest that the biomass of anecic worms (or A. longa as a species) was not causally associated with the soil parameters studied. This indicates that there must be other causal factors associated with the abundance (and composition) of anecic worms that are not among the soil texture and structure parameters studied. On the other hand, soil texture (Coarse sand) was associated with the abundance of the dominant endogeic species, A. tuberculata, but not endogeic worms in general. It was hypothesized that anecic and endogeic earthworms might respond to local soil water characteristics rather than soil texture, but this hypothesis could not be confirmed with the present data.     

Effect of management practices and cropping systems on earthworm abundance and microbial activity in Sanborn Field: a 115-year-old agricultural field

Sanborn Field, an agricultural demonstration field at the University of Missouri-Columbia, has over 100 years of cropping histories and management practices implemented at this site. We examined the effect of these cropping systems and management practices on earthworm populations and microbial activity. A field experiment was conducted to characterize and quantify earthworms and to determine the microbial activity in the same selected plots. We sampled 14 plots at the site, six of which were the original plots established in 1888 with the same cropping histories and management, and eight of which had been modified over the years to accommodate changing farmer needs and scientific questions. Earthworms and soil samples were collected in the spring and fall of 1999. Aporrectodea trapezoides, Aporrectodea caliginosa, and Lumbricus terrestris were the dominant species found in this field. Lumbricus terrestris was commonly associated with the no-tillage plot at Sanborn Field. Due partly to soil moisture conditions, most of the species were found and identified during the spring. Microbial activity, as expected, was greatest during the spring. Manure, no-tillage and crop rotations that include legumes had the greatest earthworm abundance and microbial activity. In general, where no fertility treatments were added to soil or where food sources were lacking, earthworm abundance decreased significantly. The abundance of earthworms found in this field reflected the cropping history and management practices used recently and within the last 100 years. In most cases, microbial activity showed similar trends as earthworm density. However, some dynamic microbial transformations, like nitrification, do not always follow the same trend as potential soil quality biotic indicators. Earthworms, along with microbial activity, may serve as useful soil quality indicators in sustained and short-term field trials.     

An overview of some tillage impacts on earthworm population abundance and diversity — implications for functioning in soils

Conflicting reports in the literature on the effects of tillage on earthworms are reviewed in the light of their roles in agro-ecosystem functioning. Tillage can change the abundance (by 2–9 times) as well as the composition (diversity) of earthworm populations. The actual impact is dependent on soil factors, climatic conditions and the tillage operations but hitherto this information was seldom provided in research reports. The declines in earthworm population often reported in conventionally tilled soils are associated with undesirable changes in the soil environmental conditions resulting from excessive tillage. Different species of earthworm respond differently to tillage. While the abundance of the deep burrowing species (anecic) tends to decline under tillage, particularly under deep ploughing, endogeic species can actually increase in number especially when there is increased food supply. Under conservation tillage systems, earthworms can potentially play a more important role than under conventional tillage in the functioning of the farming systems because of their abilities to modify the soil physical environment and nutrient cycling. However, adoption of conservation tillage does not automatically result in an optimal earthworm population in terms of abundance and diversity. There are opportunities to introduce more beneficial species to improve the ecological performance of agro-ecosystems. More research is needed to fully understand the ecology of different earthworm species, their interactions and their potential roles in promoting more sustainable farming systems.     

Einfluß langjährig ökologischer und konventioneller Bewirtschaftung auf Regenwurmpopulationen (Lumbricidae)

Long-term effects of biological and conventional farming on earthworm populations In a long-term trial the earthworm populations of two biological farming systems, two conventional systems and one control treatment were compared. The experimental site contained a Luvisol from loess under arable land. The earthworms were investigated by handsorting three times in 1990 and 1991 after beetroot and winterwheat. The main differences within the treatments were fertilization and plant-protection management. All treatments received the same crop-rotation and a similar soil cultivation. The input of organic matter was similar in the three organically manured treatments. Significantly higher earthworm biomass, earthworm densities and presence of anecic species were found in the biological plots than in the conventional and control plots in spring and autumn of 1991. The control plot (no fertilizer during 12 years) had a similar earthworm-population as the conventional treatments. Apparently, plant protection seems to be the main factor responsible for the differences between the treatments. Nicodrilus longus, N. nocturnus, N. caliginosus and Allolobophora rosea were the dominant earthworm species in all treatments.     

Role of earthworms in regenerating soil structure after compaction in reduced tillage systems

New non-tillage or reduced tillage agricultural practises are being increasingly adopted but generally result in higher soil compaction. Due to their recognised physical influence mainly through burrow creation, it is often claimed that earthworm activity could alleviate soil compaction in these systems. To put this assumption to the test, an experimental compaction event was carried out on one plot of arable land. The abundance and biomass of earthworms were evaluated in compacted (under wheel tracks) and non-compacted (between wheel tracks) zones, seven times over a two-year period. In addition, the functional consequences of earthworm activity, defined by burrow abundance assessed in 2D and 3D and water infiltration, were measured three times over the same period. The short-term (less than three months) effects of the compaction were clear: soil bulk density increased from 1.46 to 1.57 g cm⁻³, the abundance and biomass of earthworms were greatly reduced (−40% and −70% respectively) and the number and continuity of macroporosity were lower under wheel tracks at least until a depth of 30 cm. After these initial detrimental effects, we observed a rapid recovery of earthworm populations with no statistical difference between compacted and control zones more than three months after the compaction. However, the recovery of soil functional properties linked to earthworm activity, macroporosity and water infiltration, was much slower and took between 12 and 24 months. Despite these modifications, there were no significant changes in soil bulk density with time during the two-year period. This study demonstrates that earthworms are important actors in the regeneration of compacted soil. Although the complete regeneration of compacted soil by earthworms is a slow process, agricultural practises that promote earthworm density and activity should be encouraged in reduced or minimum tillage systems.     

Earthworm populations and growth rates related to long-term crop residue and tillage management

Conventional tillage creates soil physical conditions that may restrict earthworm movement and accelerate crop residue decomposition, thus reducing the food supply for earthworms. These negative impacts may be alleviated by retaining crop residues in agroecosystems. The objective of this study was to determine the effects of various tillage and crop residue management practices on earthworm populations in the field and earthworm growth under controlled conditions. Population assessments were conducted at two long-term (15+ years) experimental sites in Québec, Canada with three tillage systems: moldboard plow/disk harrow (CT), chisel plow or disk harrow (RT) and no tillage (NT), as well as two levels of crop residue inputs (high and low). Earthworm growth was assessed in intact soil cores from both sites. In the field, earthworm populations and biomass were greater with long-term NT than CT and RT practices, but not affected by crop residue management. Laboratory growth rates of Aporrectodea turgida (Eisen) in intact soil cores were affected by tillage and residue inputs, and were positively correlated with the soil organic C pool, suggesting that tillage and residue management practices that increase the soil organic C pool provide more organic substrates for earthworm growth. The highest earthworm growth rates were in soils from RT plots with high residue input, which differed from the response of earthworm populations to tillage and residue management treatments in the field. Our results suggest that tillage-induced disturbance probably has a greater impact than food availability on earthworm populations in cool, humid agroecosystems.     

Earthworm extraction by electroshocking does not affect canopy CO2 exchange, root respiration, mycorrhizal fungal abundance or mycorrhizal fungal vitality

Electroshocking has been used to manipulate earthworm populations in agroecosystems. However, data on the effects of electroshocking on vegetation are lacking. Here we report on a field experiment with the aim to validate electroshocking as a means of manipulating earthworms without otherwise affecting the soil-plant system. We showed that there was no effect of electroshocking on canopy CO₂ exchange, root respiration or mycorrhizal fungal abundance and vitality (i.e. the proportion of mycorrhizal fungal structure which was alive). The potential for using electroshocking to manipulate earthworm populations in the field and test ecological hypotheses relating to the role of soil biodiversity in soil processes is discussed.     

Changes of pore morphology, infiltration and earthworm community in a loamy soil under different agricultural managements

Earthworm activity produces changes at different scales of soil porosity, including the mesoporosity (between 1.000 and 30 μm eq. dia.) where both water retention and near-saturated infiltration take place. At this scale, the structural changes are poorly described in temperate agricultural systems, so we do not yet fully understand how these changes occur. The present study was conducted to determine the relationships between the morphology of the mesopores, which is mainly affected by earthworm activity, and the hydrodynamic behaviour (near-saturated infiltration) of topsoil under different agricultural managements inducing a large range of earthworm populations.Investigations were carried out at the soil surface in three fields under different management practices giving rise to three different earthworm populations: a continuous maize field where pig slurry was applied, a rye-grass/maize rotation (3/1 year, respectively) also with pig slurry, and an old pasture sown with white clover and rye-grass.Pore space was quantified using a morphological approach and 2D image analysis. Undisturbed soil samples were impregnated with polyester resin containing fluorescent pigment. The images were taken under UV light, yielding a spatial resolution of 42 μm pixel⁻¹. Pores were classified according to their size (which is a function of their area) and their shape. Hydraulic conductivity K(h) was measured using a disc infiltrometer at four water potentials: −0.05, −0.2, −0.6, and −1.5 kPa. The abundance and ecological categories groups of earthworms were also investigated.Continuous soil tillage causes a decrease in both abundance and functional diversity (cf. maize compared with old pasture) when soil tillage every 4 years causes only a decrease in abundance (cf. rotation compared with old pasture). There were no relationships between total porosity and effective porosity at h=−0.05 kPa. Image analysis was useful in distinguishing the functional difference between the three managements. Fewer roots and anecic earthworms resulted in fewer effective tubular voids under maize. There were fewer packing voids in the old pasture due to cattle trampling. Greater hydraulic conductivity in the pasture phase of rotation may arise from a greater functional diversity than in the maize and absence of cattle trampling compared with the pasture. We point to some significant differences between the three types of agricultural management.A better understanding is required of the influence of agricultural management systems on pore morphology. This study provides a new methodology in which we consider the earthworm activity as well as community in order to assess the effects of agricultural management on soil structure and water movement.     

Earthworms influenced by reduced tillage,conventional tillage and energy forest in Swedish agricultural field experiments

Abstract

We compared earthworm density, depth distribution and species composition in three soil cultivation experiments including the treatments ploughless tillage and mouldboard ploughing. Sampling was done in September 2005 and for one experiment also in 1994. By yearly sampling 1995–2005, earthworms in an energy forest of Salix viminalis were compared with those in an adjacent arable field. Sampling method was digging of soil blocks and hand sorting and formalin sampling in one cultivation experiment. Both methods were used in the energy forest and arable land comparison.

In two soil cultivation experiments, highest abundances or biomass were found in ploughless tillage. Earthworm density was higher in the upper 10 cm, especially in the ploughless tillage. Earthworm density was significantly higher in the energy forest than in the arable field. Formalin sampling revealed c. 36% of the earthworm numbers found by digging in the energy forest and gave almost no earthworms in the arable field. In all treatments with soil cultivation, species living and feeding in the rhizosphere and soil dominated. One such species, Allolobophora chlorotica, was more abundant under mouldboard ploughing than ploughless tillage. Lumbricus terrestris, browsing on the surface and producing deep vertical burrows, was more common in the ploughless tillage. Species living and feeding close to the soil surface were almost only found in the energy forest, which had not been soil cultivated since 1984.

The findings support earlier studies pointing out possibilities to encourage earthworms by reduced soil cultivation. This is one of the first published studies that followed earthworm populations in an energy forest plantation during several years. Explanation of earthworm reactions to management and environmental impacts should be done with consideration of the ecology of species or species groups. Earthworm sampling by formalin must always be interpreted with caution and calibrated by digging and hand-sorting sampling.     

Effects of the earthworm Pontoscolex corethrurus on banana plants infected or not with the plant-parasitic nematode Radopholus similis

Radopholus similis is a worldwide endoparasitic nematode that greatly hampers banana (Musa acuminata, Cavendish subgroup) productivity. Earthworms are known to closely interact with above-ground and under-ground soil biota and particularly with plants and microfaunal communities. This study was aimed at investigating, under greenhouse conditions, the effects of the earthworm Pontoscolex corethrurus on banana growth and nutrient uptake, and assessing the influences of this earthworm on the development of an inoculated population of R. similis. Six-week-old tissue culture banana plants were submitted to four treatments: with P. corethrurus, R. similis, P. corethrurus+R. similis, and a control with no earthworms or nematodes. At the end of the experiment, the P. corethrurus treatments showed significantly higher leaf surface areas, shoot dry root weights, and root fresh weights than those without earthworms. This root growth enhancement probably contributed to the evident but non-significant decrease in the density of nematodes in the roots, even though earthworms did not reduce the total number of nematodes per whole root system. Moreover, the presence of earthworms slightly alleviated the severity of root damage. N bioavailability in the soil, along with N, Ca, and Mg content of banana plants, were also significantly increased in the presence of earthworms. Our results demonstrated that banana plant growth and nutrition were positively influenced by earthworms. Cropping practices that boost the development of earthworm communities in soil should therefore be promoted to enhance sustainability and to naturally alleviate nematode impact.     

Impact of five different tillage systems on soil organic carbon content and the density,biomass, and community composition of earthworms after a ten year period

To assess the impact of different types of soil tillage on the density, biomass, and community composition of earthworms, a long-term field study was performed in which soils were tilled in different ways for ten years. This study included five different types of tillage: (i) plough, (ii) grubber, (iii) disc harrow, (iv) mulch sowing, and (v) direct sowing. At the end of the experiment the earthworm density, biomass, and community composition, and the SOC (soil organic carbon) content were determined. The results show that density, biomass, and community composition of earthworm populations varied in relation to the type of soil tillage used. The density of anecic earthworm species decreased when soils were managed by conventional ploughing, relative to reduced tillage practices, whereas conversely the density of endogeic species increased. Additionally, the varying types of soil tillage influenced the abundance and biomass of different earthworm species in different ways. The density of Aporrectodea caliginosa was positively influenced by ploughing, whereas Aporrectodea longa, Lumbricus castaneus, and Satchellius mammalis showed a positive relationship to the grubber and Allolobophora chlorotica to direct sowing. We attribute these changes to modifications in the vertical distribution of SOC and varying potentials for mechanical damage of earthworms by tillage. A decrease in tillage intensity modified the vertical SOC distribution in the topsoil and consequently revealed positive effects on earthworm biodiversity, thus sustaining soil functioning.     

Zum Einfluß von obstbaulichen Bodenpflegemaßnahmen auf Lumbriciden,insbesondere Lumbricus terrestris L .

Influence of orchard soil management on lumbricids, especially Lumbricus terrestris L. In a long-term soil management experiment (apple orchard treated with cultivation methods such as grass mulch, grass harvest, straw mulch, clean cultivation) 6 plots were selected in order to study the abundance and biomass of earthworm populations. The following results were obtained: In all treatments with the exception of straw mulch L. terrestris represented the majority (60.5% on average) of the lumbricid population. Their share in the biomass amounted to 93.3%. The earthworm biomass was the highest in grass mulch; a close correlation was observed between the litter production (grass and leaves) and the biomass of L. terrestris. Added farm yard-manure on plots with grass mulch had no additional positive effect on earthworms. Although a higher earthworm biomass was found under grass mulch in comparison with straw mulch, the species diversity was higher in the latter. Clean cultivation had a highly detrimental effect on all earthworms, especially on the horizontally burrowing species. The annual nitrogen turnover by L. terrestris in mulched orchards was estimated to approx. 50 kg N/ha.     

Earthworm composition,diversity and biomass under three land use systems in south-eastern Australia

In south-eastern Australia, strips of planted native trees and shrubs (shelterbelts) are frequently established to restore ecosystem services altered by agriculture. Despite their wide use, little is known about the effects of establishing shelterbelts on soil macro invertebrates, especially earthworms, which are of major importance in soil processes. We assessed earthworm composition, diversity and biomass in three land use systems: native shelterbelts dominated by Acacia and Eucalyptus species, agricultural pastures and native remnant woodland fragments dominated by Eucalyptus blakelyi and/or Eucalyptus melliodora. Earthworm communities differed significantly among systems, with abundance, biomass and diversity greatest under pasture. Within shelterbelts we saw a shift from high earthworm biomass and density to low with increasing time after establishment. Soil edaphic variables did not correlate strongly with earthworm biomass or density, but were correlated with earthworm community composition. Overall the introduction of native woody vegetation was associated with a decline in density and biomass of earthworms, including a decrease in the relative abundance of exotic species. As such shelterbelts can be used to promote native earthworm relative abundance, which may be important for local diversity, soil function and landscape connectivity.     

Earthworm influence on carbon dioxide and nitrous oxide fluxes from an unfertilized corn agroecosystem

Earthworms modify the soil environment through their feeding, casting, and burrowing activities, which may lead to more decomposition and respiration in aerobic microsites and more denitrification in anaerobic microsites. The objective of this study was to determine whether earthworms increase CO₂ and N₂O fluxes from an unfertilized corn agroecosystem. Earthworm populations within field enclosures (2.9 m²) were reduced by repeatedly applying carbaryl insecticide, then single and mixed populations of Lumbricus terrestris L. and Aporrectodea caliginosa (Savigny) were added. Gas samples were collected once a week for 14 weeks, from June to September 2005. Carbaryl applications reduced, but did not eliminate earthworms from enclosures. The CO₂ and N₂O fluxes were affected by the sampling date, with peak gas fluxes after rainfall events. Mean CO₂ and N₂O fluxes during the study period tended to be greater from enclosures with added earthworms than the control (no earthworms added), but were not significantly affected by earthworm treatments due to the low survival rate of introduced earthworms. Better control of earthworm populations in the field is required to fully assess the impact of earthworms on CO₂ and N₂O fluxes from temperate agroecosystems.     

Earthworm populations under tropical maize cultivation: the effect of mulching with velvetbean

Earthworm populations were studied in three tropical agroecosystems of southern Mexico: improved maize with a Mucuna pruriens cover crop (MM), continuous conventional maize (CM) and pastures (P). Three replicates and six monoliths were sampled in each agroecosystem. Three earthworm species were found, two native (Balanteodrilus pearsei, Larsonidrilus orbiculatus) and one exotic (Polypheretima elongata). In all systems, the dominant species was B. pearsei, with negligible presence of the exotic species in MM and P plots. Total abundance was significantly higher in MM than in CM; and earthworm biomass was also higher in MM than in CM and P. Juveniles of both native species dominated, mainly concentrated in the top 20 cm of soil. B. pearsei and L. orbiculatus displayed different preferences (within each agroecosystem) for soil organic matter, N and temperature. Further experiments are required to investigate whether mulching with M. pruriens results in an increased earthworm abundance and biomass through a N-improvement effect or as a result of microclimatic changes and to study the extent to which earthworms and M. pruriens are synergistic in enhancing maize growth.     

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     

Crop yield and soil fertility response to reduced tillage under organic management

Conservation tillage (no-till and reduced tillage) brings many benefits with respect to soil fertility and energy use, but it also has drawbacks regarding the need for synthetic fertilizers and herbicides. Our objective was to adapt reduced tillage to organic farming by quantifying effects of tillage (plough versus chisel), fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators and crop yield. The experiment was initiated in 2002 on a Stagnic Eutric Cambisol (45% clay content) near Frick (Switzerland) where the average annual precipitation is 1000 mm. This report focuses on the conversion period and examines changes as tillage intensity was reduced. Soil samples were taken from the 0–10 and 10–20 cm depths and analysed for soil organic carbon (C_org), microbial biomass (C_mic), dehydrogenase activity (DHA) and earthworm density and biomass. Among the components tested, only tillage had any influence on these soil fertility indicators. C_org in the 0–10 cm soil layer increased by 7.4% (1.5 g C_org kg⁻¹ soil, p < 0.001) with reduced tillage between 2002 and 2005, but remained constant with conventional tillage. Similarly, C_mic was 28% higher and DHA 27% (p < 0.001) higher with reduced than with conventional tillage in the soil layer 0–10 cm. In the 10–20 cm layer, there were no significant differences for these soil parameters between the tillage treatments. Tillage had no significant effect on total earthworm density and biomass. The abundance of endogeic, horizontally burrowing adult earthworms was 70% higher under reduced than conventional tillage but their biomass was 53% lower with reduced tillage. Wheat (Triticum aestivum L.) and spelt (Triticum spelta L.) yield decreased by 14% (p < 0.001) and 8% (p < 0.05), respectively, with reduced tillage, but sunflower (Helianthus annuus L.) yield was slightly higher with reduced tillage. Slurry fertilization enhanced wheat yield by 5% (p < 0.001) compared to compost fertilization. Overall, C_org, C_mic, and DHA improved and yields showed only a small reduction with reduced tillage under organic management, but long-term effects such as weed competition remain unknown.     

Earthworm populations are stable in temperate agricultural soils receiving wood-based biochar

The application of decomposable organic residues such as manure and crop litter is generally beneficial to earthworms. There is an emerging interest in applying biochar, a carbonaceous product of pyrolysis, to temperate agricultural soils. The slow decomposition rate of biochar, which also contains ash and combustion byproducts, could be detrimental to earthworms. The objective of this study was to describe the earthworm populations in biochar-amended soils on a dairy farm in the St. Francis River watershed, Quebec, Canada. Earthworms were collected from replicated field plots under cereal production. Site A received three wood-based biochar types at two application rates(5 and 10 t ha~(-1) biochar) plus an unamended control, while Site B received wood-based biochar(7.5 t ha~(-1) biochar), dairy cattle slurry(10 t ha~(-1) manure), or a combination of the biochar and manure rates plus an unamended control. Earthworms were collected by hand sorting and formaldehyde expulsion from soil pits. Three species, Aporrectodea turgida, Aporrectodea tuberculata, and Lumbricus rubellus, were found at the sites, and Aporrectodea was the dominant genus. Biochar sources, rates, and application with dairy slurry did not affect the earthworm population, which had 52–218 individuals m~(-2) in 2010 and 4–96 individuals m~(-2) in 2011. The seasonal variation in earthworm population may be due to flooding in the spring of 2011, which apparently interfered with earthworm reproduction. The similarity in earthworm abundance and biomass in plots with and without wood-based biochar leads to the conclusion that earthworm populations are stable in biochar-amended soils in this cold, humid temperate region.