Sustainable use of Vinasse as a Foliar Amendment to Enhance Growth, Physiology, and Yield of Sunflower Crops (Helianthus annuus L.)

Developing high-yielding sunflower cultivars and adopting eco-friendly fertilization strategies are essential for sustaining oil crop productivity under climate change pressures. Vinasse, a nutrient-rich byproduct of the distillery industry, offers a potential eco-friendly alternative to mineral fertilizers. This study evaluated three sunflower cultivars (Sakha 53, Giza 102, and Giza 120) under foliar vinasse application (0-, 50-, and 100-mL L⁻¹) for two summer seasons (2024–2025) in south of Egypt. Application of vinasse at 50 mL L⁻¹ significantly increased seed yield (4.09 t ha⁻¹), oil yield (1.79 t ha⁻¹), and oil content (38.14%) compared with the control (p ≤ 0.05)., while higher concentrations reduced performance due to vinasse salinity and acidity. Giza 102 showed superior adaptability, achieving the highest yield and growth indices, particularly when combined with 50 mL L⁻¹ vinasse. Significant interaction effects indicated that Giza 102 treated with 50 mL L⁻¹ vinasse offered the highest agronomic potential. Path coefficient analysis revealed that Net Assimilation Rate and Crop Growth Rate had the strongest direct effects on yield. Overall, foliar vinasse application at 50 mL L⁻¹ represents a sustainable fertilization strategy to enhance sunflower growth and oil production, with Giza 102 showing the highest agronomic potential for climate-resilient cultivation. The superior productivity of Giza 102 could be attributed to its genetic constitution and its efficient interaction with the environmental conditions of the experimental site, which likely contributed to enhanced physiological performance and yield compared with the other tested cultivars.