DRIS-based evaluation of optimal nutrient ranges in sunflower under "different irrigation regimes and selenium application"

Achieving an optimal nutrient balance is fundamental to sustainable crop production, particularly for economically important oilseed crops such as sunflower (Helianthus annuus L.). In the face of increasing food demand and climate variability, strategies that improve both resource use efficiency and crop quality are becoming essential. The study examines the effect of selenium (Se) foliar application on sunflower seed and oil yield under varying levels of water stress using the diagnosis and recommendation integrated system (DRIS). Treatments included selenium concentrations (0, 5, 10, and 20 ppm) applied under full irrigation (100% WR), moderate stress (75% WR), and severe stress (50% WR) water requirement (WR). Results demonstrated that selenium application significantly enhanced seed and oil yield under water stress, particularly at 10 ppm under 75% WR. Nutrient content analysis revealed increased nitrogen (N), phosphorus (P), and potassium (K) concentrations with rising selenium levels, especially under limited water conditions. Nutrient balance indices and DRIS indices identified phosphorus as the most frequently limiting nutrient, with nutrient order often following the sequence P > N > K. Based on the reference norms for nutrient ratio interpretation, selenium application shifted nutrient ratios toward balanced or slightly excess levels, improving nutrient synchrony and physiological efficiency. The integration of selenium with deficit irrigation holds promise for optimizing nutrient balance and enhancing productivity in water-limited environments.