A deficit irrigation strategy for ‘Solar eclipse’ plum in semi-arid climates

\n Water scarcity in semi-arid regions demands irrigation strategies that enhance water use efficiency (WUE) without compromising crop productivity. This study evaluated ‘Solar Eclipse’ plum (Prunus salicina L.) production under two irrigation regimes at El Tahadi Road, Nubaryia, Egypt: control irrigation (CI), supplying 100% of crop evapotranspiration (ETc), and regulated deficit irrigation (DI), applying 50% ETc from March to June. Trees under CI achieved the highest yield (16,250 kg∙ha–1), favouring markets focused on high-volume production. However, DI reduced yield by only 16% (13,650 kg∙ha–1) while significantly improving fruit quality, including higher total soluble solids (15.8 °Brix1), phenolic content (45.6 mg GAE∙g–1), and antioxidant capacity (82.6 μmol Trolox∙g–1). The DI treatment also nearly doubled WUE and lowered production costs by 22%, enhancing resource efficiency and economic sustainability. Biochemical analysis revealed increased leaf levels of proline, abscisic acid, and anthocyanins under DI, indicating activation of stress-responsive mechanisms that maintained fruit development despite reduced water availability. Correlation analysis suggested DI enhanced WUE and fruit quality through physiological and biochemical adaptations, albeit with a modest yield reduction. Overall, this study emphasised the trade-offs between maximising yield and improving fruit quality, positioning regulated deficit irrigation as a viable, sustainable approach for ‘Solar eclipse’ plum production in semi-arid regions and provided valuable insights for those seeking to optimise WUE while maintaining both economic viability and agronomic performance.