Composting is a sustainable method widely used in the evaluation of organic wastes, and stabilized soil amendments and growing media can be obtained by this method. In this study, the effects of compost obtained from grape pomace on the growth and development of Dahlia variabilis “Figaro Violet” were investigated by adding 20% and 40% to the growing medium. Additionally, the interactions of different fertilization levels (EC 0.75, 1.10, and 1.85 dS m −1 ) and compost use were evaluated. According to the research findings, 40% compost + EC 1.85 dS m −1 application provided the highest values in number of flowers (5.2 pcs plant −1 ), number of leaves (64.7 pcs plant −1 ), plant fresh weight (81.0 g), plant dry weight (41.5 g), and branch thickness (7.56 mm); also, it gave the best results in phosphorus (357 mg kg −1 ), magnesium (184 mg kg −1 ), iron (0.90 mg kg −1 ), and copper (0.26 mg kg −1 ) contents. 40% compost + EC 0.75 dS m −1 application gave the highest results in terms of flower diameter (84.1 mm) and SPAD value (37.5), while it also stood out in calcium (68.2 mg kg −1 ), molybdenum (0.38 mg kg −1 ), and boron (1.49 mg kg −1 ) contents. 40% compost + EC 1.10 dS m −1 application showed the highest values in nitrogen (8.41%), potassium (709 mg kg −1 ), and manganese (2.30 mg kg −1 ) contents. The 20% compost + EC 1.10 dS m −1 application yielded the best results in plant height (38.3 cm) and root length (24.8 cm). It also resulted in earlier flowering, occurring within 39–40 days. The 20% compost + EC 0.75 dS m −1 application was superior in root fresh weight (21.5 g) and root dry weight (13.9 g). In the control treatments, only the 0% compost + EC 1.10 dS m −1 combination was distinguished by a root dry weight (15.4 g). Overall, the 40% compost and high EC (1.85 dS m −1 ) combination was found to be the most superior treatment in terms of plant growth performance, flowering characteristics, and leaf nutrient content. These results demonstrate that grape pomace can be an economical and viable alternative in ornamental plant cultivation, considering environmental sustainability and resource efficiency.
Bayram et al. (2026) studied this question.