Crop models are valuable tools for exploring the responses of crops to changes in environmental factors, and have been widely used to analyze the response of crops to varying soil water content and salinity levels in extreme drought and high salinity conditions. To obtain suitable water-salt thresholds and the total irrigation amount for cotton in the arid oasis of southern Xinjiang, the AquaCrop model was calibrated and validated using measured data from 2020 and 2021 (total irrigation amount: 255–480 mm; initial soil salinity levels: 0.2–0.6%). With the same initial soil water content, when the initial soil salinity < 7 dS/m, cotton yield did not significantly change under different levels of total irrigation amount, while when the initial soil salinity was 10 dS/m, there was a significant difference in cotton yield with a total irrigation amount > 300 mm. The total irrigation amount of 375 mm is the threshold for cotton at the low-salinity treatment, while it increases to 450 mm at the high-salinity treatment. Based on cotton performance with the AquaCrop model, the threshold values of soil salinity were 7, 9.3, 8.2 and 9.3 dS/m (EC_e) during the cotton stage of seedling, squaring, flower-boll and maturity, respectively. The total irrigation amount of 450 to 500 mm could achieve a win-win scenario for both cotton yield and water use efficiency under sandy loam soil. In summary, this study can serve as a reference for regulating water and salt in arid saline-alkali regions.

An appropriate water supply strategy is imperative for obtaining tomatoes of a high yield and quality; the lack of one has caused resource wastage and quality deterioration. To determine the suitable irrigation amount and simulate daily transpiration under these optimal irrigation conditions, a two-year greenhouse cultivation experiment was conducted over 2022–2023. Commencing at anthesis, three distinct irrigation gradients were triggered and designated as irrigation controls with the lower limits set at 80% (T1), 70% (T2), and 60% (T3) of the substrate water-holding capacity. We determined the optimal irrigation amount by ranking the treatments using the TOPSIS method, balancing the tomato yield and quality. A segmented daily transpiration model under optimal irrigation conditions driven by crop and environmental factors was established using the Marquardt method and data from 2022, and the model was validated using data from 2023. The results indicated that T2 was the optimal irrigation amount, with the water use efficiency increased by 18.0%, but with a 10.9% decrease in yield, while the quality indices improved significantly. The R² values of the segmented model in the flowering and fruit-setting stage and the picking stage were 0.92 and 0.86, respectively, which could provide support for optimized water management for tomato planting in greenhouse substrate cultivation.