Comparison of heat-treated and untreated vermicompost as a peat substitute in seedling growing media for lettuce seedling growth and microbial properties.

The unique properties of vermicompost indicate that it is possible to use this organic fertilizer as a peat substitute in seedling growing media. In this study, heat-treated vermicompost (HTV) and untreated vermicompost (VC) were compared, and whether they can be used in batavia-type lettuce seedlings was examined. For this purpose, vermicomposts were added to the seedling growth media at different rates [100% peat (C), 30% VC + 70% peat (VC30), 60% VC + 40% peat (VC60), 30% HTV + 70% peat (HTV30), and 60% HTV + 40% peat (HTV60)], and their effects on the seedling growth and biological properties of the growing media were monitored in two consecutive cultivation seasons. In general, vermicompost application had positive effects on some of the biological properties of the seedling-growing media, such as urease, alkaline phosphatase, β-glycosidase, and nitrification activities, in one or both seasons. However, no clear superiority was observed between the heat-treated and untreated vermicompost in this respect. Heat treatment did not adversely affect the chemical or biological properties of vermicompost. Although some biological features, such as dehydrogenase, nitrification and the number of bacteria, were negatively affected by heat treatment, these effects were not reflected in seedling development. Regardless of heat treatment, increasing the rate of vermicompost addition to the seedling growth media resulted in elevated salinity, which adversely affected the seed emergence rate. The applications did not generally cause negative effects on other plant quality parameters.