Deficit drip irrigation enhances the comprehensive performance of late-maturing mandarin by improving fruit quality in southwest China: A multi-perspective evaluation

The response of late-maturing mandarin cultivars to stage-specific water deficit regimes remains insufficiently understood, which limits the effective implementation of deficit irrigation strategies. In this study, a two-year field experiment (2023/2024 and 2024/2025 growing seasons) was conducted with one full irrigation treatment (CTL, 100% of ETc) and twelve stage-specific deficit drip irrigation treatments (DIT). The DIT comprised mild (D20%, 80% of ETc), moderate (D40%, 60% of ETc), and severe (D60%, 40% of ETc) deficits applied during bud burst to flowering (I), young fruit (II), fruit expansion (III), and fruit maturation (IV) stages. The effects of DIT on mandarin yield, fruit quality, and water productivity (WP) were evaluated. Furthermore, a multi-stakeholder comprehensive evaluation system (involving consumers, producers, and experts/policymakers) was developed using the AHP-TOPSIS method to assess the comprehensive quality index (CQI, integrating key fruit quality attributes) and comprehensive performance score (CPS, integrating yield, quality, and WP). Results showed that III-DIT significantly enhanced key fruit quality attributes, increasing total soluble solids (TSS), titratable acidity (TA), and vitamin C (Vc) by 6.5–14.9%, 8.3–16.7%, and 3.1–22.9% compared to CTL, respectively. In contrast, yield was negatively affected by DIT during each growth stage, with sensitivity ranked as III > I > II > IV. As a result, WP decreased by 1.4–11.5% under III-DIT. However, I-D40% improved WP by 7.3–13.2%, as it markedly reduced evapotranspiration with minimal yield loss. Comprehensive evaluation revealed that III-DIT yielded the highest CQI, followed by IV-DIT, and that both strategies enhanced CPS. From a stakeholder perspective, III-D20% achieved the highest CPS for consumers, while IV-D60% was most favorable for growers. Conversely, I-DIT and II-DIT decreased CQI and CPS, suggesting that these stages are unsuitable for applying deficit irrigation. Overall, 100% of ETc during stages I and II, 80% of ETc during stage III, and 40% of ETc during stage IV emerges as an optimal irrigation regime for late-maturing mandarin to maximize comprehensive benefits. These results provide a quantitative basis for developing stage-specific precision irrigation strategies for late-maturing mandarin cultivation.