Influence of Soil and Foliar Zinc Sulfate Treatments on Growth and Development of Cut Ornamental Sunflower

Zinc (Zn), an essential micronutrient, plays critical roles in plant growth and physiological regulation. In Helianthus annuus L., proper Zn management is necessary to support plant development and the quality parameters that affect commercial performance. However, studies evaluating different Zn treatment methods and doses simultaneously in this species remain limited. This study was conducted to determine the effects of different Zn doses applied foliarly and through the soil, as well as combinations of these treatments, on growth, quality, and post-harvest performance in Helianthus annuus F1 ‘Solano Orange Summer’. The experiment consisted of 18predefined Zn treatment regimes (ZnSO47H2O, 20% Zn), including combined treatments representing practical Zn management strategies. Within the scope of the study, flower stem length, stem thickness, flower diameter, number of leaves, branch weight, SPAD value, harvest date, and vase life parameters were evaluated. In some combinations using both foliar and soil treatments, the highest stem length was obtained in the ZF8+ZT0.5 (8mgL-1 from foliar treatment + 0.5mgL-1 from soil treatment) treatment, while branch weight increased in the ZF4+ZT1.5 (4mgL-1 from foliar treatment + 1.5mgL-1 from soil treatment) treatment. Leaf number increased in the ZF2+ZT2.5 (2mgL-1 from foliar treatment + 2.5mgL-1 from soil treatment) treatment, while the earliest harvest and longest vase life were determined in the ZF8+ZT1.0 (8mg L-1 from foliar treatment + 1.0mgL-1 from soil treatment) treatment. The SPAD value was particularly high in the ZF8 treatment (8mgL-1 via foliar treatment). It was determined that all combined Zn treatments resulted in higher branch weight and leaf number compared to the control treatment. In conclusion, this study revealed that Zn treatments have different effects on growth, quality, and post-harvest performance in cut ornamental sunflowers depending on the dose and treatment route.