Dynamic water allocation for greenhouse cucumber in warming climates: Quantifying CO2-temperature synergies through multifactorial evaluation

Under future climate scenarios characterized by warming and elevated CO 2 , understanding crop water requirements and establishing sustainable production systems for cucumber ( Cucumis sativus L. ) are crucial for improving agricultural resilience and water-saving cultivation efficiency in greenhouse horticulture. To address this, a three-factor split-plot experiment with 12 treatments was conducted in 2022 Fall (F) and 2023 Spring (S) and verified in 2023 F, including two temperature levels, Tp1 (conventional chamber temperature) and Tp2 (Tp1 + 2.3℃), two CO 2 concentrations, C1 (400 ppm) and C2 (800 ppm), and three irrigation levels, I1 (75% evaporation (I 0 )), I2 (100%I 0 ) and I3 (125%I 0 ). Results showed Tp2 promoted soluble protein (SP) but inhibited above ground plant dry matter (DM), yield (Y) and irrigation water productivity (IWP) of cucumber, while C2 effectively compensated for these adverse effects of Tp2, particularly on plant height (H) at late growth stage (L-), number of stem nodes (NSN) at initial growth stage (I-) and the reducing sugar (RS). A multi-indicator comprehensive growth evaluation system based on correlation analysis was adopted to assess crop growth, and based on this system, response models were established to derive optimal irrigation intervals under different temperature and CO 2 combinations. Field verification demonstrated that the models had high accuracy, with the average difference between theoretical and field values for 8 indicators (excluding hectare profit, HP) reaching 3.0%, indicating that the established environment-matched production system can effectively optimize cucumber growth and water use efficiency, and provide a scientific basis for precision irrigation management of greenhouse cucumber under future climate change.