Analysis of the vermicomposting process and its implications for plant growth promotion under Irish conditions

Abstract

Waste is an ongoing issue, especially in Ireland. Current waste management treatments are becoming unsustainable; therefore, research on alternative methods is being conducted. This project investigates the use of vermitechnology as a possible treatment method for food waste. It involves the use of earthworms to degrade food waste in an environmentally safe manner. A system was built on-site using the earthworm species Eisenia fetida to break down food waste over a 65-day period. This work was successful in reducing the volume of food waste added to the system in a clean, economically feasible way. On the other hand, a liquid by-product produced from this technology is called ‘vermitea’(VT). Physio-chemical analysis, including pH and electrical conductivity, was carried out on VT produced on-site and from commercially sourced vermicompost (VC) prepared from a protocol designed in the lab for this project, along with nutritional analysis for potassium and phosphorus determined by UV spectroscopy. Results indicated a significant presence of physio-chemical content; after nine weeks, pH was 6.6 ± 0, electrical conductivity (EC) resulted in 755μS/cm ± 2, a salinity content of 4.3 PSU ± 0 and finally a total dissolved solid concentration of 292 mg/L ± 1. The nutritional content of the VT samples was interesting, with potassium levels increasing from approx. 500 mg/L initially to 1000 mg/L after nine weeks, compared to the control which decreased over the same time period. With respect to VT from commercially sourced VC, smaller amounts of VC may be soaked to prepare VT for sufficient nutrient concentration. Finally, the plant growth promotion potential of VT was studied through the application of VT against a leading chemical fertiliser, Miracle Gro® to a variety of arable, horticultural and pasture crops. Two types of experiments were designed, i.e. seed germination and early seedling development experiments. Overall water was seen to be the best treatment for growth in barley in germination tests with 34% germination, a root length of 1.5 cm ± 1.8 and a shoot height of 0.7 cm ± 1.1. Oat benefitted primarily form VT treatment, with 64% germination, a root length of 2.3 cm ± 1.4 and a shoot height of 1.4 cm ± 1.0. For the above crops in soil, a combination of VT and MG for barley, while VT for oat could be used. With respect to horticultural crops, VT could be added to aid in the growth of cauliflower and pea, while a combination of water and VT added to aid carrot and turnip and possibly a combination of 20 % MG and VT for tomato. Finally, in relation to a pasture crop, clover, VT aids in the germination of seeds in the initial growth stages, while MG then contributes to growth in the following growth stages in soil. Overall this technology can help in the reduction of food waste currently sent to landfill, in a safe, cost-effective manner, while producing an organic solution which may be used to aid the germination of a variety of plant species.