Effects of row orientation and irrigation and their interaction on tomato traits and water use efficiency

This study evaluated the interactive effects of row orientation and deficit irrigation on tomato yield, fruit quality, and water use efficiency under sandy-substrate conditions in arid regions, and quantitatively assessed the comprehensive evaluation indices using the entropy weight method, the analytic hierarchy process (AHP), and the Nash equilibrium approach. A two-year, two-factor full factorial experiment was conducted in a solar greenhouse in southern Xinjiang, involving two row orientations—east–west (E–W) and north–south (N–S)—and four irrigation regimes: excessive irrigation I1 (120% ETc), full irrigation I2 (100% ETc), moderate deficit irrigation I3 (80% ETc), and severe deficit irrigation I4 (60% ETc). The results showed that the E–W orientation significantly increased tomato yield by 6.27% compared with the N–S orientation; the mean yields under E–W were 89.92 t·hm⁻ ² and 88.73 t·hm⁻ ² in 2024 and 2025, respectively, whereas the mean yield under N–S was 84.56 t·hm⁻ ² . Moderate deficit irrigation (I3) significantly improved tomato flavor and nutritional quality, with soluble solids content, vitamin C, and lycopene increasing by 18%, 38%, and 129%, respectively, while nitrate content decreased by 30%. Yield exhibited a nonlinear bell-shaped relationship with irrigation amount: excessive irrigation did not increase yield but led to greater water waste, whereas severe deficit irrigation saved water but reduced yield by 20.89% compared with full irrigation. The comprehensive evaluation indicated that the E–W orientation combined with moderate deficit irrigation (I3) was the optimal strategy for improving water–fertilizer management, achieving higher yield while increasing water use efficiency by 29% and significantly enhancing fruit quality. These findings provide a theoretical basis and practical guidance for precision water management and spatial layout optimization in protected agriculture in arid regions.