Water scarcity is the primary constraint on the development of the potato industry in Northwest China. Improving water use efficiency (WUE) under limited water supply is, therefore, an urgent priority to promote the green and sustainable development of potato production in this region. This research was conducted from 2023 to 2024 in the rain shelter of the Agricultural Science Research Institute in Dingxi City, Gansu Province, using the potato cultivar ‘Gan Yin No. 9’ as the experimental material. Throughout the growing season, the control treatment (CK) was maintained at 75–85% of the field water capacity (FWC). Based on CK, three deficit-irrigation treatments were established: W75 (75% of the CK irrigation amount), W50 (50% of CK irrigation amount), and W25 (25% of CK irrigation amount), with three replicates per treatment. We evaluated the effects of different irrigation regimes on plant growth characteristics, physiological characteristics, tuber yield, and WUE. The results showed that the W75 treatment significantly (p < 0.05) promoted the growth of plant height and stem diameter, and significantly increased them by 8.70–10.20% and 13.03–18.70%, respectively, compared with CK. The total dry matter accumulation under W75 was significantly higher than CK (by 10.90–11.40%) and markedly higher than W50 and W25 (by 24.10–45.50%). No significant differences were observed in tuber yield, large tuber rate, and medium tuber rate between W75 and CK. Notably, W75 significantly improved WUE by 36.43–38.51% compared with CK. Overall, under the conditions of this study, W75 treatment was identified to be the optimal irrigation regime for potato cultivation, as it promoted plant growth, maintained tuber yield, and enhanced water use efficiency. This study aims to establish a definitive irrigation threshold for potato production in Northwest China. The findings provide a precise basis for formulating irrigation schedules, which can contribute to the development of water-efficient agriculture and support the sustainable development of the potato industry in the region.
Chen et al. (2026) studied this question.