Integrated Use of Biostimulants and Organic Fertilizers Enhances Biomass and Yield Traits in Melon: A Case Study from Adıyaman, Türkiye

This study aimed to evaluate the effects of various biostimulants, both alone and in combination with organic fertilizers, on biomass accumulation and yield components of Cucumis melo L. Galia C8 and Kırkağaç 637 under the ecological conditions of Adıyaman, Turkey. Plants were grown in 8-liter pots and uprooted on the 30th and 60th days after planting to assess various morphological and physiological parameters in 2011. For yield parameter, experiments were carried out in open field conditions in the spring growing years of 2011 and 2013.Treatments consisted of different biostimulants Bacillus subtilis (OSU 142), Bacillus megaterium (M3), Azospirillum spp. (SP245), Bioplin, Phosfert, EM1, Bio-one, Endoroots, Sim-derma, and Spirulina sp. applied either alone or in combination with organic fertilizers (OF) (Çamlıbesi Bioactive Compost, Liquid Organic Fertilizer, and K-Humate), along with conventional fertilization (DAP + urea) and an untreated control as reference treatments. The results demonstrated significant improvements in morphological parameters, vegetative growth, and biomass production with combined applications of biostimulants and organic fertilizers. Among all treatments, Spirulina + OG and Sim-derma + OG led to the most pronounced improvements in stem diameter (up to 46%), stem length (25%), internode number (42%), root length (up to 44%), and total biomass (up to 188%) relative to the control. Biomass accumulation was assessed through two destructive harvests, revealing statistically significant differences among treatments in root, stem, leaf, and total fresh and dry weights. While no substantial difference was observed between the cultivars for some traits, interactions between cultivar and treatment were found to be statistically significant for several biomass-related traits. Total yield was calculated as 2359.16 kg/da for Galia C8 and 2283.97 kg/da for Kırkağaç 637. The average yield increased from 1441 kg/da in the first year to 3201 kg/da in the second year. Compared to the control treatments, the total yield showed an increase of 91.94% for Galia C8 and 26.75% for Kırkağaç 637. These findings suggest that integrating biostimulants with organic fertilizers can enhance melon growth, yield components, and biomass partitioning, providing a sustainable alternative to conventional fertilization practices, particularly under semi-arid conditions.