Capillary-Wick Irrigation Alleviates Root-Zone Drought Stress to Improve Yield and Irrigation Water Use Efficiency of Table Grapes in Arid Regions

Efficient irrigation is pivotal for viticulture in arid regions; however, solutions that simultaneously stabilize vine water status, sustain yield, and preserve fruit quality remain limited. We evaluated a microfiber-based wicking infiltration irrigation system—applied at the surface (W1) and shallow-buried at 10 cm (W2)—against drip (DI) and furrow (FI) irrigation in a two-year field trial with table grapes in northwest China. Additional wicking infiltration irrigation quota treatments (W1-2/3, W1-1/3) were also tested. The experiment combined continuous root-zone moisture and predawn leaf water potential (Ψpd) measurements with assessments of growth, berry traits, anthocyanins, and expression of related genes, synthesizing outcomes using an AHP–entropy multi-criteria framework. Wicking infiltration irrigation reduced wet–dry fluctuations, increased minimum soil moisture, and mitigated excursions to low Ψpd relative to DI and FI, indicating a more stable hydraulic environment for vines. W2 and W1-2/3 delivered the highest or near-highest yields (up to 16.5 kg per vine). Relative to DI, W2 increased IWUE by 57.9% in 2018 and 9.3% in 2019, whereas W1-2/3 increased IWUE by 155.1% and 66.0%, respectively. The AHP–EW evaluation identified W2 as the best overall integrated treatment, with the highest cumulative score across the two years (1.22), while W1-2/3 provided the strongest yield–IWUE balance under reduced irrigation. Anthocyanin accumulation and the expression of related biosynthetic genes showed year- and treatment-dependent responses; moderate water deficit was associated with enhanced anthocyanin-related responses at some developmental stages, but this effect was not consistent across seasons. These results indicate that wicking infiltration irrigation can improve grape production and irrigation efficiency under arid conditions, although its effects on berry secondary metabolism depend on seasonal and irrigation conditions.