https://doi.org/10.37229/fsa.fja.2025.12.05

In Egypt, water scarcity represents a primary constraint on sustainable crop production. To address this challenge, the present study examined eco-friendly mitigation approaches for fennel (Foeniculum vulgare L.) subjected to water stress, focusing on the synergistic and individual effects of bio-encapsulated Lelliottia amnigena MSR-M49 and salicylic acid (SA). Two-year factorial field experiments using a split-plot design were conducted during the 2019/2020 and 2020/2021 growing seasons at the Agricultural Research Centre (ARC), Giza, Egypt. Fennel plants were subjected to three irrigation regimes: normal (15-day intervals; I₁), moderate water deficit (21-day intervals; I₂), and severe water deficit (30-day intervals; I₃). The results indicated that co-application of SA and encapsulated L. amnigena significantly enhanced boosted vegetative growth, flowering parameters, total chlorophyll (a and b), total carbohydrates, NPK nutrient uptake, and essential oil yield compared to the untreated control. This combination significantly boosted phytohormones in both seasons. While drought stress severely reduced total phenolic content by 44% under moderate stress (I₂, 80% ETc) and 70% under severe stress (I₃, 60% ETc), the combined treatment effectively restored phenolic levels, proline accumulation, and relative water content (RWC). Notably, abscisic acid (ABA) content decreased by 48.0% and 48.6% in the first and second seasons, respectively, under moderate stress (80% ETc). Furthermore, applying SA alone or combined with microencapsulated bacteria strongly reduced antioxidant enzyme activities. Under moderate water deficit, co-inoculation with L. amnigena and foliar SA demonstrated the strongest synergistic effect. Additionally, the 21-day irrigation interval proved to be the optimal regime, requiring the lowest seasonal irrigation water (mean = 2048 m³ fed⁻¹) and reducing water use by 5.8 % and 9.7% relative to the 15- and 30-day intervals, respectively, through the first season without compromising crop growth, flowering, or essential oil production. Consequently, integrating encapsulated L. amnigena with foliar SA under a 21-day irrigation schedule offers a viable agronomic strategy to optimize fennel production and water-use efficiency in arid environments.