Vermicompost and Leachate from Sewage Sludge and Vineyard Pruning Residues: An Exploratory Assessment of Cucumber Germination and Early Seedling Growth

The sustainable management of organic residues remains a major challenge in agriculture. Vermicomposting offers an environmentally friendly strategy to convert organic waste into nutrient-rich, biologically stable biofertilizers. This exploratory study evaluated the effects of vermicompost and its leachate, produced from sewage sludge and vineyard pruning residues, on cucumber (Cucumis sativus L.) germination and 25-day early seedling growth. Treatments included a control (peat and perlite, CNT), two vermicompost doses, 20 g kg−1 and 40 g kg−1 (VC_D1 and VC_D2, respectively) and a 5% (v/v) vermicompost leachate (VC_L) applied as the sole irrigation source. Foliar nutrient contents and physicochemical properties of the substrate and leachate were determined. Germination was not significantly affected (p > 0.05), but VC_D1 promoted slightly faster and more uniform seed emergence. Growth responses were dose dependent, with VC_D1 significantly enhancing shoot biomass (approximately 15% than the CNT and VC_D2) and providing a balanced foliar nutrient profile, whereas VC_D2 significantly reduced growth, promoted excessive foliar K and P, and lower Ca, Fe, and Mn contents. VC_L enhanced foliar N accumulation but did not significantly (p > 0.05) increase biomass. Both vermicompost and its leachate were pathogen-free, with metal concentrations below regulatory limits. Overall, these findings suggest that, under the tested conditions, vermicomposting these residues can generate potentially safe amendments for cucumber seedling growth, though dose optimization is essential. This exploratory approach supports residue valorization and contributes to circular economy principles and sustainable agriculture goals.