Interannual and Cultivar-Related Variation in Sunflower Productivity and Seed Quality Under Long-Term Rainfed No-Till Management in the Semi-Arid Dobrogea Region of Romania

Seasonal climatic variability represents a major constraint on sunflower (Helianthus annuus L.) production in semi-arid environments, yet interannual and cultivar-related variation under long-term no-till management remains insufficiently characterized. This study evaluated interannual and cultivar-related variation in sunflower productivity and seed quality during three consecutive growing seasons (2023–2025) under rainfed long-term no-till conditions in the Dobrogea Region of Romania. Three commercial hybrids (Averon SU, Demetra, and Helesun) were evaluated in a randomized complete block design with three replications, while agronomic management remained unchanged throughout the experimental period. Agronomic traits, yield components, and seed quality parameters were analyzed using analysis of variance, paired t-tests, Pearson’s correlation analysis, and partial redundancy analysis (RDA). Pronounced interannual climatic variability was accompanied by substantial differences in sunflower performance. Mean seed yield reached 2169.06 kg ha−1 in 2023, declined to 848.08 kg ha−1 in the drought-affected 2024 season, which had the lowest March–August precipitation total, and partially recovered to 1178.68 kg ha−1 in 2025. Similar seasonal responses were observed for plant density at harvest, seed weight per capitulum, thousand grain weight, test weight, and number of seeds per capitulum, whereas oil content remained comparatively stable (45.19–46.88%). Analysis of variance showed significant interannual variation across all evaluated traits, while significant cultivar effects were detected for plant density, number of seeds per capitulum, seed weight per capitulum, thousand grain weight, and seed yield. Partial RDA further detected a significant joint cultivar effect across the eight standardized response traits after conditioning on study year and block (F = 11.49, R2 = 0.53, exact p = 0.027). Under the specific environmental conditions observed during the three study years, interannual variation in sunflower performance was substantial; however, annual climatic conditions were not independently replicated and therefore remain confounded with year. Consequently, the observed relationships describe associations within the 2023–2025 site conditions rather than establishing a general causal ranking of climatic and cultivar effects. The results highlight the importance of improving rainfall-use efficiency and integrating cultivar selection with climate-adaptive agronomic management to increase the resilience of sunflower production in water-limited environments.