Compost and Vermicompost from Vine Pruning and Sewage Sludge as Peat Alternatives in Cucumber Seedling Production

The replacement of peat in horticultural substrates is a priority for sustainable plant production. This study evaluated compost and vermicompost, derived from vine pruning and sewage sludge, as partial peat substitutes in cucumber (Cucumis sativus L.) seedling production. Germination, early growth traits, growth efficiency indices, and leaf nutrient contents were assessed, and the relationships among variables were explored using correlation analysis and principal component analysis. Five substrates were tested: peat-perlite alone (control) and mixtures containing 10%, 20%, or 40% compost or vermicompost as peat replacements. Results showed that incorporating 10% vermicompost significantly improved germination, seedling vigor, and biomass accumulation, with performance comparable to, or exceeding, the control. In contrast, higher proportions of compost or vermicompost negatively affected germination and seedling quality. Nutrient analysis revealed that 10% vermicompost enhanced Ca and K accumulation, traits positively correlated with growth, whereas 20% compost and 20% vermicompost were associated with higher P and Mg contents but reduced seedling performance. Overall, these promising findings demonstrate that a low proportion of vermicompost (10%) is sufficient to successfully partially replace peat in cucumber seedling production, benefiting both performance and sustainability, whereas higher compost or vermicompost levels disrupt nutrient balance and limit this species’ growth.