Kevin R. Butt

Utilisation of solid paper-mill sludge and spent brewery yeast as a feed for soil-dwelling earthworms

Abstract Solid paper-mill residues amounting to thousands of tonnes per annum are usually disposed of in landfill sites. However, by the addition of spent yeast from the brewing industry, the carbon to nitrogen ratio of these paper sludges can be adjusted to make them into a feed which can satisfy the requirements of earthworm growth. Using one such feed comprising a 66 : 1 mixture, by mass, of wet paper waste and dry yeast extract, the lob worm (Lumbricus terrestris) can be grown from the hatchling stage (50 mg) to maturity (3–4 g) within 90 days, with an acceptably low level of mortality. These large, soil-dwelling earthworms have potential value as agents in soil amelioration projects if they can be reared intensively, therefore their utilisation may be encouraged by using the type of superior feed described.

Combining vermiculture with traditional green waste composting systems

Freshly-shredded green waste (yard waste) was composted for 16 weeks using a mechanically-turned windrow system. The rate of organic matter stabilisation was determined by measuring the reduction in the volatile solids content of the waste. Samples of the fresh material were also vermicomposted using Eisenia andrei (Bouche) and rates of growth and reproduction obtained which were comparable to published rates for other wastes. Vermicomposting for 8 weeks produced a material with a significantly lower volatile solids content compared to composting for a similar period (P < 0.01). A combined composting and vermicomposting system was investigated by extracting partially-composted samples from the compost windrow every 2 weeks and feeding these to E. andrei. Growth and reproduction were found to be positively correlated to the volatile solids content of the waste (P < 0.01). Vermicomposting partially composted waste (2 weeks), for a further 6 weeks, reduced volatile solids content significantly more than for composting fresh waste for 8 weeks (P < 0.001). It is concluded that E. andrei is capable of attaining good rates of growth and reproduction in fresh green waste and that vermicomposting can result in a more stable material (lower volatile solids content) compared to composting. Combining vermicomposting with existing composting operations can also accelerate stabilisation compared to composting alone. The duration of pre-composting will determine the subsequent rate of growth and reproduction of E. andrei. To ensure that the vermicomposting system operates at maximum efficiency, pre-composting should be kept to a minimum, consistent with effective sanitisation of the waste.

Biological invasions in soil: DNA barcoding as a monitoring tool in a multiple taxa survey targeting European earthworms and springtails in North America

Biological invasions are increasingly recognized as a potent force altering native ecosystems worldwide. Many of the best documented cases involve the massive invasions of North America by plant and animal taxa native to Europe. In this study, we use DNA barcoding to survey the occurrence and genetic structure of two major groups of soil invertebrates in both their native and introduced ranges: Collembola and earthworms. Populations of ten species of earthworms and five species of Collembola were barcoded from both continents. Most of these species exhibited a similar genetic structure of large and stable populations in North America and Europe, a result supporting a scenario of multiple invasions. This was expected for earthworm species involved in human economic activities, but not foreseen for Collembola species de facto unintentionally introduced. This study also establishes that invasive species surveys employing DNA barcoding gain additional resolution over those based on morphology as they allow evaluation of cryptic lineages exhibiting different invasion histories.

Introduced earthworms in agricultural and reclaimed land: their ecology and influences on soil properties, plant production and other soil biota

Accidental and deliberate introductions of earthworms into agricultural and reclaimed land are natural experiments that provide opportunities to understand the attributes of successful invaders and their impacts on local biota and ecosystem processes. We consider various case studies (e.g., earthworm invasions in agricultural soils in Australia and Brazil) and deliberate introductions of earthworms into reclaimed mine sites, landfills and cutaway peat in the U.K. and Ireland. Invasions of exotic earthworms, such as European Lumbricidae in Australia, have been geographically extensive, but remain very patchy at regional and field scales. Their impacts on soil properties, plant production and other biota are therefore also likely to be patchy. Various methods have been developed to deliberately inoculate exotic earthworms into disturbed lands, with varying degrees of success. The factors controlling success are, in general, poorly understood. A broad range of impacts of invasive earthworms on soil properties (e.g., soil structure, nutrient availability, burial of surface materials, incidence of root diseases) and plant yield and quality have been reported. Less is known of the impacts of invasive earthworms on other soil fauna, but they are likely to occur due to alterations in food availability and habitat structure. Influences on other biota are likely to extend to aboveground communities as well as those belowground. Introductions of earthworms to disturbed lands can yield substantial benefits in agricultural productivity and amelioration of soil degradation. However, the potential impact of the promotion or control of such introductions on non-target biota and ecosystem processes in pristine ecosystems nearby should be considered.

Reproduction and growth of three deep-burrowing earthworms (Lumbricidae) in laboratory culture in order to assess production for soil restoration

Laboratory experiments were conducted to examine the growth and reproduction of three deep-burrowing lumbricids, Aporrectodea longa, Lumbricus terrestris, and Octolasion cyaneum. The reproductive output was recorded as 18.8, 38.0, and 32.3 cocoons per worm per year for A. longa, L. terrestris, and O. cyaneum, respectively. For the same species, maturity was reached at a mean mass of 3.9, 5.0 and 2.4 g, within 3 months from the hatchling stage by L. terrestris and within 4 months by the other two species. The hatching success of cocoons at 15 and 20°C was within the range of 70–80% for each species, except A. longa at the higher temperature, where a viability of 47% was recorded. Twenty percent of viable O. cyaneum cocoons produced twin hatchlings, compared with only one percent for A. longa and L. terrestris. A combination of these results suggests that a complete life-cycle for each species could be achieved within 6 months (L. terrestris and A. longa) or 7–8 months (O. cyaneum). Each species has particular life-cycle strategies that would aid survival and colonisation, under field conditions, if inoculated into restored soils.

The intensive production of lumbricus terrestris L. for soil amelioration

Abstract The benefits of earthworm inoculation in improving soil conditions are now well established. The main problem with this technique is that it is difficult to obtain large numbers of the most appropriate species at an economic price. At present, the only way of obtaining earthworms for soil improvement is from large scale field collection and this is laborious and expensive. Research at the Open University aims to overcome these problems by investigating ways of intensively producing Lumbricus terrestris . This paper identifies the key variables in the process and presents experimental evidence that L. terrestris can grow and reproduce all year round. Initial results indicate that by optimising the key variables of temperature and nutrition this species can be grown from cocoon to sexual maturity in less than half the time taken in the field. Furthermore, the rate of reproduction can be increased to twice the maximum rate reported by other researchers, even when the earthworms are kept at densities much higher than found in the field. It is concluded that continuous, intensive production of L. terrestris is possible and that this method of supplying earthworms for soil improvement has many advantages compared to field collection.

Inoculation of earthworms into reclaimed soils: the UK experience

Earthworms have positive effects on soil structure, therefore their incorporation during the process of soil reclamation is a sensible route towards the final restoration of a site. Over the past 20 years, 16 documented field trials have been conducted in the United Kingdom. These trials took place at locations with a number of previous uses, for example, landfill sites, steelworks and opencast mines. The species of earthworm used varied, as did the techniques used for introducing them into the soil. This paper assessed the suitability of the earthworms chosen for each trial and, more importantly, trial outcomes. The most appropriate species were not always selected (possibly due to availability) and the introduction technique was not always the most appropriate for the site. Monitoring of trials generally occurred over relatively short periods of time (possibly due to limited funding). It is evident that more recent trials were not always informed by previous events. It is suggested that work of this nature may only be viable if brought about through site-related legal obligations. Copyright

Interaction of Lumbricus terrestris L. burrows with field subdrains

The morphology of Lumbricus terrestris L. burrows was investigated in relation to subsurface tile drain position. The aim was to clarify the causes and consequences of higher densities of L. terrestris previously measuredabove the tiles at the study site. At two pairs of study pits, the plough layer was removed from a 1 m x 2 m area above the tile and at 8 m distance from it. Burrows of L. terrestris were identified at the plough pan, resident worms removed and burrows cast with dyed fibreglass resin. The resin casts were exposed in the profile, depth and length of casts measured and their connections with tiles recorded. In both above-tile pits, two cases were recorded where the cast burrow ended at the tile surface. These contacts indicate the potential importance of burrows in the conduction of water and solutes from the soil surface layers into the tiles. The mean depth of burrows was 1.0 m (se = 0.024, n = 27) above the tiles and 0.83 m (se = 0.036, n = 12) between the tiles. During adverse soil conditions such as droughts, individuals living near the tiles may gain from the shelter provided by their deeper burrows and this could partly explain the higher population densities above the tiles.

The Earthworm Inoculation Unit technique: An integrated system for cultivation and soil-inoculation of earthworms

Abstract The introduction of earthworms into degraded or newly restored land is known to promote soil improvement. Obtaining the most appropriate species in the large numbers required can be costly and time consuming using traditional techniques. Research and development of a novel approach, the Earthworm Inoculation Unit (EIU) technique, may help to overcome this. This technique combines cultivation of selected earthworms in small soil-based units, with an effective method of direct soil introduction. Successful cultivation of deep burrowing species, e.g. Lumbricus terrestris L. and Aporrectodea longa (Ude), and shallow working species, e.g. Allolobophora chlorotica (Savigny), has been achieved by optimizing environmental factors. Accelerated rates of reproduction compared with field data have been recorded. At soil-inoculation, each EIU was found to contain all three earthworm life stages, adults, cocoons and hatchlings, promoting maximum opportunity for successful colonisation. Reselts from field trials suggest, that for A. longa , the EIU technique can enhance survivorship in compacted clay soils compared with a more conventional inoculation method. Earthworm inoculation, where appropriate, should become an integral component of sustainable land restoration practice. In hostile soils, often associated with reclaimed land, the EIU technique may provide a means of ensuring long term survival for earthworm populations.

Influence of food particle size on inter- and intra-specific interactions of Allolobophora chlorotica (Savigny) and Lumbricus terrestris

The inverse relationship between the particle size of food resources and earthworm growth rate is widely recognised. The aim was to determine the effects of the particle size of food on interactions between combinations of adult and hatchling A. chlorotica and L. terrestris under laboratory conditions. Treatments were set up in 1 litre mesocosms, maintained in darkness at 15 ′ 1 °C. Separated cattle solids (SCS) were used as food either unmilled or milled to < 1 mm. The latter led to a 185 and 54 % increase in the mass of A. chlorotica and L. terrestris respectively, compared with unmilled SCS. Intra-specific competition in A. chlorotica was detected in adult and hatchling pairings. A positive inter-specific interaction was recorded with hatchling A. chlorotica and mature L. terrestris fed unmilled SCS with growth of the former significantly greater (P<0.01) than in conspecific monoculture. Clitellate A. chlorotica were only recorded in unmilled SCS treatments when paired with L. terrestris (week 18). In milled treatments, 100% maturation was achieved in monoculture and in pairings with hatchling and mature L. terrestris by week 14. The final mass of initially hatchling L. terrestris (3.23 g) fed milled SCS in monoculture was significantly greater (P<0.01) than in pairings with hatchling A. chlorotica and mature conspecifics. With unmilled SCS, lowest initially hatchling L. terrestris mean mass (1.04 g) was recorded when paired with mature conspecifics. Growth of both species was significantly enhanced by decreased food particle size and this effect was size specific. The intensity of competitive interactions was influenced by food particle size and stage of earthworm development. Results suggested a positive association between the two species and mechanisms for this are proposed.