Abstract
Increasing quantities of earthworm digested materials (vermicompost) are being marketed as a peat-free growth medium for amateur and professional food producers. Several studies indicate that growing tomatoes in peat mixed with low concentrations of vermicompost (10–20% by volume) produced by the earthworm Eisenea fetida increases yield of plants and marketability of fruits. Here we examined the effect of substituting commercial peat-based compost with four different vermicomposts produced by the earthworm Dendrobaena veneta. Vermicompost was added to peat-based compost at rates of 0%, 10%, 20%, 40% and 100% (v/v) and the following characteristics of tomato (Lycopersicon esculentum var. Money maker) assessed: germination, yield, marketability, fruit weight and ascorbic acid concentration. Vermicompost significantly increased germination rates (176%) and improved the marketability of fruits at 40% and 100% substitution rates due to the lower incidence of physiological disorders ('blossom end rot' and fruit cracking). Total fruit yield, marketable fruit yield, fruit number, individual fruit weight and vitamin C concentration were unaffected by the presence of vermicompost. Although vermicompost may provide a viable alternative to peat-based growth media, overall, we found little added benefit from using vermicompost. We conclude that some of the previously reported benefits of vermicompost on horticultural production may be overstated and that marketing strategies should reflect this in order to preserve consumer confidence in vermicompost products.
