This study explores the effects of various seedling substrates on cucumber growth, focusing on their physical, chemical, and nutrient properties. Substrates were formulated with different ratios of kitchen compost, peat, rice husk, and straw. Key growth indicators, including germination rate, plant height, leaf area, root development, and biomass, were analyzed using a seedling index and fuzzy membership function. Results showed that moderate bulk density, high porosity, and optimal moisture content significantly enhanced seedling growth. Chemical properties, such as pH (5.5-7.5), low EC, and reduced chloride ion concentration, were crucial for healthy development. While alkali-hydrolyzed nitrogen, available phosphorus, and potassium were beneficial, excessive levels inhibited growth. The T2 treatment (15% kitchen compost, 45% peat, 40% rice husk) showed the best performance, offering balanced physical structure, nutrient availability, and salinity control. It promoted superior growth in leaf area, root length, and biomass while meeting local agricultural standards. This study demonstrates the potential of combining kitchen compost with agricultural waste for sustainable seedling substrates, providing insights for optimizing vegetable seedling production and enhancing the use of organic waste in agriculture. Future research should examine broader applications across various crops.