IMPACT OF DROUGHT AND EXTREME HEAT ON SUNFLOWER SEED YIELD

Abstract

Sunflower (Helianthus annuus L.) is generally considered moderately resistant to drought conditions. However, in years characterized by low rainfall and high air temperatures, significant reductions in seed yield can occur. At the Fundulea location in south eastern Romania, the year 2024 was marked by drought and extreme heat, resulting in low seed yields among the 15 tested sunflower hybrids. Yields ranged from 611 kg/ha for hybrid H5E in the ExpressSun system to 1,299 kg/ha for hybrid H10CLP in the Clearfield Plus system. In contrast, more favourable climatic conditions in 2025 led to substantially higher yields, ranging from 1,579 kg/ha for hybrid H2E (ExpressSun) to 3,046 kg/ha for hybrid H11CLP (Clearfield Plus). These results demonstrate the pronounced impact of extreme heat and drought, particularly during the flowering and seed-filling phenophases, which are the most sensitive stages of sunflower development. Stress occurring in these phases limits pollination efficiency, seed set, and oil accumulation, ultimately leading to significant yield reductions.