<p>Water scarcity and salinity are major challenges for sustainable irrigation in arid regions, particularly in greenhouse production. This study ascertained the salinity tolerance of cucumber (<i>Cucumis sativus</i> L., c.v. ‘Talisya F1’) during two growth periods, autumn-winter 2022–2023 and spring-summer 2023. Plants were exposed to four irrigation water salinity levels, including S1: &lt;3, S2: 3, S3: 6, and S4: 9 dS m^− 1 in a randomized complete block design. Key traits assessed included fruit weight (WoF), total fresh biomass (TFB), and total dry biomass (TDB). Results revealed that salinity up to 3 dS m^− 1 had minimal effects, but higher salinity significantly lowered yield and growth, up to 62.8% in TFB and 49.5% in WoF. Salinity thresholds were estimated using linear and nonlinear models. The Maas and Hoffman model identified a threshold of around 1.5 dS m^− 1, with steep yield reductions beyond it. The Van Genuchten model indicated EC₅₀ values of 6.43 dS m^− 1 for WoF and 6.02 dS m^− 1 for TDB, with strong fits (R² &gt; 0.90). A modified Van Genuchten model further improved the fit (R² &gt; 0.97) by using dual shape parameters. Further, a piecewise regression model segmented the yield response into three threshold-based phases, reflecting osmotic stress onset (T₁), physiological adaptation (T₂), and severe stress effects (T₃). For TDB, thresholds were T₁ = 1.57, T₂ = 1.71, T₃ = 6.85 dS m^− 1; for WoF, T₁ = 1.51, T₂ = 1.82, T₃ = 5.86 dS m^− 1. This model best captured the plant’s dynamic response to salinity and provides a useful framework for managing irrigation under saline conditions. These results identify clear salinity thresholds for greenhouse cucumber production and demonstrate that multi-phase modeling approaches better capture plant responses than traditional models. The findings provide a practical basis for developing adaptive irrigation strategies that account for water-quality constraints while maintaining productivity in greenhouse systems.</p>