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Title: Evaluation of vermicompost from composts for agricultural and horticultural uses
Author: Roberts, Paula
ISNI:       0000 0001 3525 042X
Awarding Body: University of Wales, Bangor
Current Institution: Bangor University
Date of Award: 2006
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The EU landfill directive has imposed a challenging set of targets for the UK to reduce the amount of waste sent to landfill. This has resulted in an increased realisation that wastes can be recycled and reprocessed into valuable products. One such area that is undergoing significant development is the composting of biodegradable waste products. The primary or secondary treatment of wastes by earthworms (vermicomposting) has been proposed as a mechanism to enhance the commercial value of composts. The commercialization of these technologies, however, requires the development of stable markets and consumer confidence in the end products. Currently, in the scientific literature, there are several reports that vermicomposts enhance plant growth; however the mechanism for this enhancement is poorly understood. The first experimental chapter of this thesis presents data from an experiment into the in-vessel co-composting of Green Wastes (GW), Green waste with Paper Pulp (GW/PP), and Green waste with Biosolids (GW/SS) using Ecopod® composting process. It aimed to determine whether compost chemistry and end-use was affected by feedstock quality. Consequently, three feedstock were made by mixing green waste with paper pulp or biosolids (paper I). Vermicomposts were subsequently produced from the three Ecopod® composts. In three separate plant growth trials the presence of vermicompost significantly affected plant growth. However, not all plant species responded in the positive manner previously reported (paper II). In cereal growth, substituting inorganic fertiliser with vermicompost did not decrease yield as long as some inorganic fertiliser was present in the feeding regime. This is true for wheat and maize (paper III, appendix 2). Similarly silage grass responded much better to applications of vermicompost than to conventional composts applied at the same rate (appendix 2). Tomatoes grown in commercial growth media substituted with vermicompost did not respond in the same way as reported in previous studies; no significant yield increases were observed. Few studies report on the effect of growing medium/ fertilising regime on vitamin content of foods. With increasing interest in organic food production systems in particular, it is becoming increasingly important that we understand the effects that growing conditions have on the nutritional properties of foods. In this case there was no effect of growing medium on ascorbic acid (vitamin C) content of tomatoes (paper IV). The final chapter (paper V) was a collaborative work with A. P. Williams and investigates the effect of earthworm digestion on the survival and proliferation of E. coli 0157 in composts and soil. Litter dwelling earthworms (e. g. Dendrobaena veneta) significantly aided the lateral movement of E. coli 0157 within compost. Our results imply that whilst long-term persistence of E. coli 0157 in soil and compost may be unaffected by the presence of earthworms, digestion from worms may aid proliferation of the pathogen during initial stages of soil or compost contamination. In summary, this thesis shows that feedstock can be used to manipulate compost product quality. After vermicomposting the plant growth response is often species specific. Our failure to replicate US studies suggests that vermicompost production methods and process management may also affect end product quality. This will hinder commercialisation of the technology. Significant further work is required to identify the method by which plant growth enhancement is facilitated by vermicomposts and to what extent this is specific to a particular vermicompost production method.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available