The biology and ecology of the earthworm Lumbricus rubellus Hoffmeister, 1843, and its effects on the turn-over of organic matter and soil are not well known. To gather this information, the ingestion and egestion rates were measured using a litterbag technique and the transport of organic matter was quantified with a newly developed method, using soil columns to which ¹⁴C labelled plant material was added. The feeding habits of the worm were positively influenced by temperature in wet soils (> -15m of water) and were negatively influenced in dry soil (< -15 m of water). The total egestion rate changed from 0.3 g.g⁻¹.day⁻¹ at 5 °C to 1.0 g.g⁻¹. day⁻¹ at 20° C in moist soil (- 5 m of water). The egestion rate at medium range temperatures, 10 and 15° C, was less affected by drought stress than at 5 and 20 °C. The egestion rate of carbon was a more stable parameter than the total egestion rate, and ranged from approximately 20 mg.g⁻¹.day⁻¹ at 5 °C, to 50 mg.g⁻¹.day⁻¹ at 20 °C. The moisture and temperature effects were apparent in the Q₁₀ of the total egestion rate and of the egestion rate of carbon. The Q₁₀ ranged from 1.66 in wet soils to 3.27 in dry soils in the 5-15 °C interval and from 1.98 to 0.32 in the 10-20 °C range. For the egestion rate of carbon, the Q₁₀ ranged from 1.92 to 3.21 and from 1.28 to 0.47, respectively. The body water content of the worm varied considerably with the soil water potential, and reached a maximum level of 5.5 kg.kg⁻¹ (dwt) between -15 metres of water and -30 metres of water. When under drought stress, worms stopped ingesting large quantities of soil, switched to a diet high in organic matter and lowered their activity. In the ¹⁴C column experiment, the total cast production was significantly related to depth. L. rubellus produced 15 % of the cast on the surface of the soil, 46 % in the 0-5 cm layer, 22 % in the 5-10 cm layer and 16 % in the 10-15 cm layer. Independent calculations from a) the uptake of ¹⁴C labelled carbon in earthworms, b) removal of litter from the surface and c) ¹⁴C label recovered from cast, showed that the worms ingested 78-82 % of the offered organic matter as shoot litter and 18-22 % as root litter. ¹⁴C originating from shoot and root litter was recovered in casts throughout the profile, indicating that the worms mixed food from all layers. The total egestion rate found in the column experiment was 5.2 times higher than was found in the litterbag technique under comparable conditions (2.34 vs 0.45 g.g⁻¹.day⁻¹). The egestion rate of carbon was similar in both techniques (37.1 vs. 46.1 mg.g⁻¹.day⁻¹, 10 °C). In preliminary litterbag trials, it was found that L. rubellus egested 15.5 mg.g⁻¹.day⁻¹ of carbon (5 °C) for each of four food types offered. The 5 °C temperature trial of the litterbag technique, showed a similar amount of carbon egested. It was concluded that the worm needed a constant amount of carbon to provide nutrients and energy, of which a part or all may originate from ingested microorganisms. Based on the distribution of cast in the profile and the feeding strategies of L. rubellus, it was concluded that this earthworm cannot be classified as an epigeic worm. A new strategy class was proposed: eurygeic worms, earthworms living in the litter-soil interface, mixing organic matter into the profile and mineral soil into the litter layer. Based on the literature and results from the present study, a computer model was developed to simulate the longterm effects of earthworms on an agricultural soil system. Simulations of the mixing of soil and organic matter in a limited-till agricultural system, showed that earthworms negatively affected the accumulation rate of surface litter and positively affected the organic matter content of the mineral soil. The model can be used to predict the trends in organic matter in soils, important in soil conservation, mine reclamation and reforestation. / Land and Food Systems, Faculty of / Graduate

This study is intended to investigate the artificial environment conditions that would favor the most effective propagation of the African night crawler.

The earthworms, Lubricus terrestris and Eisenia foetida, were used as non mammalian surrogate models to assess the immunotoxicpotential of xenobiotic to mammals. Assays were developed and optimized for detecting spreading activity and phagocytosis of rabbit red blood cell (RRBC), bacteria, and yeasts by macrophage-like coelomocytes of L. terrestris.

No description available.

No description available.

In a 28-day dietary study, Lumbricus terrestris were placed in one quart containers with soil and offered either corn (Zea mays L.), soybean (Glycine max L. Merr.) or alfalfa (Medicago sativa) leaves, corn leaves treated with a 1:1 solution of 28% N fertilizer and deionized water, corn or soybean stalks, or no addition. The worms were weighed initially and after 28 days to determine biomass production, which was used for determining food quality. Worms exhibited large weight gains when fed alfalfa or soybean leaves, intermediate weight gains when fed corn leaves treated with N, and little or no gains for the remainder of treatments. N content of the tissues was positively correlated to biomass production. These results support the hypothesis that earthworm growth is determined by food quality, particularly N content. / Department of Natural Resources

Thesis (Ph. D., Soil Science)--University of Idaho, July 2007. / Major professor: Jodi Johnson-Maynard. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

Atrazine, a member of the s-triazine herbicides, appears on the EC Red List of chemicals that cause environmental concern, with residues occurring frequently in sub-soils and aquifers world-wide. Microbial metabolism is considered to be the major mechanism of complete removal of atrazine from the soil environment. Laboratory-based studies were carried out to investigate the microbial mineralisation of atrazine in soil, and to develop novel methods for potential acceleration of breakdown. In initial investigations, simple microcosm experiments were carried out to identify the importance of different fractions (water-soluble and water-insoluble) of plant residues to the dynamics, and extent of atrazine mineralisation. The amendment of soil with different plant residue fractions initially inhibited (for the water-soluble fraction) or enhanced (for the water-insoluble fraction) dynamics of atrazine mineralisation. However, by the end of the incubation, there was no overall effect on atrazine mineralisation. This suggested that increasing the soil organic matter content may render the herbicide less bioavailable to the degrader population. Investigations carried out to determine which component of the microbial biomass was more important in atrazine mineralisation showed that substantial removal of the fungal and Gram-negative bacterial population inhibited atrazine mineralisation in the soil. Experiments to selectively enrich the soil for fungal or bacterial atrazine degraders isolated a mixed bacterial culture able to accelerate atrazine mineralisation when inoculated into soil. The effect of the presence of the earthworm Lumbricus terrestris on the indigenous atrazine degrading microflora was investigated. Results indicated that atrazine mineralisation could be accelerated, but this was not primarily due to increases in microbial biomass, but possibly due to physio-chemical changes brought about by the earthworm and subsequent alterations in atrazine bioavailability.

Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xvi, 145 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (M.A.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 68-77). Also available via Humboldt Digital Scholar.