Effects of water and nitrogen regulation on greenhouse cucumbers in North China plain

• Integrated individual weights from entropy weight method and AHP through game theory. • Identified TSS and SSC as the most essential quality indicators. • Developed a comprehensive evaluation model for cucumber production. • Determination of the optimal water-nitrogen application combination and the optimal water and nitrogen application range. Excessive irrigation and fertilization, as well as imbalance between yield and quality are prevalent issues in facility fruit and vegetable production in North China Plain. To address this issue, we conducted a two-year and three-season experiment from 2024 to 2025 to investigate the impact of different combinations of nitrogen fertilizations and irrigation amounts on total aboveground biomass, aboveground plant nitrogen accumulation, yield and quality, as well as water and nitrogen use efficiency of cucumber in a greenhouse. The optimal irrigation and fertilization for achieving the best-balanced fruit yield, quality and resource use efficiency was identified using the weighted technique for order preference by similarity to an ideal solution (TOPSIS) method. The weights in TOPSIS were estimated using the game theory that integrates the weights calculated from the subjective-weighted analytic hierarchy process and the objective-weighted entropy. Our results show that, while increasing irrigation amount enhanced total aboveground biomass (TAB), fruit yield and partial factor productivity of nitrogen (PFP n ), it reduced water use efficiency (WUE), and compromised fruit quality. We also found that optimized nitrogen application not only enhanced TAB, fruit yield, but also improved WUE, and that, total soluble solids and soluble sugar content were critical quality indicators of the cucumber. TOPSIS analysis showed that irrigating 100% of the evaporation measured from an adjustable 20cm-pan mounted 10∼15 cm above the canopy (E p-20 ) and fertilizing 360 kg·ha −1 of nitrogen achieved the highest relative closeness (Ci) in all three seasons in the two years. Further analysis indicated that irrigating 75%∼100% of E p-20 and applying 320∼370 kg·ha −1 of nitrogen can best balance yield, quality, WUE and PFP n for spring-cultivated cucumber, while for autumn-cultivated cucumber, irrigating 94%∼110% of E p-20 and applying 300∼370 kg·ha −1 of nitrogen is practically optimal. These practices not only achieved high fruit yields, but also improved fruit quality, offering an improved cultivation method for greenhouse cucumber production in the North China Plain.