| To investigate the suitability of regulated deficit irrigation (RDI) technology for characteristic economic crops in the Shule River Basin, an integrated water-fertilizer RDI experiment was conducted using edible sunflower (Helianthus annuus L.) as the subject of study. Three irrigation levels were established during both seedling and maturity stages: full irrigation (80%-85% θf), mild water deficit (70%-75% θf), and moderate water deficit (55%-60% θf), where θf denotes field capacity. The effects of different treatments on the growth, yield and quality of edible sunflowers were systematically analyzed. A comprehensive evaluation was conducted using a combined approach of Principal Component Analysis and Membership Function methods. The results demonstrated that dry matter accumulation in edible sunflowers followed a characteristic "S-shaped" growth curve across all treatments. The reduction in aerial dry matter accumulation became more pronounced with increasing water deficit intensity, whereas moderate water deficit significantly enhanced root dry matter accumulation. Leaf area index was consistently reduced by water deficit at all growth stages. Compared to full irrigation (CK) and moderate water deficit during the seedling stage, mild water deficit at the seedling stage improved yield, irrigation water use efficiency, and quality parameters. Mild water deficit at the maturity stage resulted in a 2.6% yield reduction compared to CK, but increased IWUE and crude protein content by 0.5% and 6.6%, respectively. The treatment combining mild water deficit at both seedling and maturity stages outperformed moderate water deficit at the maturity stage in terms of yield, IWUE, and crude protein content. Comprehensive evaluation indicated that implementing mild water deficit during both seedling and maturity stages is recommended as the optimal regulated deficit irrigation (RDI) strategy for edible sunflower cultivation in the Shule River Basin. |