Impact of water and salinity stresses on sugar beet productivity and quality under Wadi El Natrun conditions

Water scarcity and salinity are among the most critical constraints affecting sugar beet (Sultan Beta vulgaris L.) production in arid regions of Egypt. To address the dual challenges of water scarcity and salinity in arid agricultural regions, a two-year field experiment (2022/2023 and 2023/2024) was conducted in Wadi El-Natrun to assess the interactive effects of irrigation regimes (IRs 100%, 80%, and 60% of crop evapotranspiration, ETc) and saline irrigation water (2.19, 4.38, and 6.57 dS m⁻¹) under two drip irrigation systems: surface (SDI) and sub-surface (SSDI). Results demonstrated that roots yield and quality attributes (length, diameter, fresh weight, purity, and sucrose content) significantly declined (P < 0.05) with increasing salinity and water deficit while impurity levels increased. The highest marketable yield (54.75 and 54.31 t ha⁻¹ in the first and second seasons, respectively) was recorded under full irrigation (IRs 100%) with low salinity water (2.19 dS m⁻¹) using the SSDI system. Notably, the most significant values of water use efficiency (WUE) and irrigation water use efficiency (IWUE), reaching 12.36 and 12.06 kg m⁻³, were obtained at IRs 80% with low salinity under SSDI treatment. Furthermore, the lowest yield response factor (Ky = 0.14 and 0.16) was observed under the same treatment, indicating the superior capacity of the SSDI system to sustain yield under moderate water-saving conditions. In addition, these results reveal that irrigating sugar beet in sandy soils with low-salinity water (2.19 dS m^-1) at 80% of the SSDI irrigation level can increase marketable sugar beet yield by approximately 10% and effectively reduce irrigation water consumption by approximately 26% compared to the control (traditional) treatment. Furthermore, when freshwater is unavailable, using moderately saline water (S2 = 4.38 dS m^-1) under the same treatment maintains acceptable yield levels and water use efficiency, making it a suitable alternative with a limited impact on crop yield and quality of no more than 4%. This strategy provides a practical and sustainable approach to irrigation in arid environments, contributing to national efforts to conserve water, enhance food security, and achieve sustainable agriculture in reclaimed desert regions.