Effects of deficit irrigation at different phenological periods on yield, quality, and water productivity of Xanthoceras sorbifolium Bunge in the Horqin Sandy Land of China

In arid and semi-arid regions, improving water efficiency is imperative for the sustainable advancement of both forestry and agriculture. The water demand period for Xanthoceras sorbifolium Bunge, an economically and ecologically important tree grown in the Horqin Sandy Land of China, is unknown. This knowledge gap has hindered the development of optimized deficit irrigation (DI) schemes aimed at conserving water while maintaining yield and quality. To identify this key period and better understand the water-use dynamics of this species, we conducted a two-year field experiment (2021–2022). Eight irrigation treatments were applied across three key phenological stages: flowering (F), fruit setting to expansion (S), and fruit-expansion to maturity (M). The irrigation treatments included full-stage (FSM), two-stage (FS, FM, and SM), single-stage (F, S, and M), and no irrigation (NI). The application of DI decreased fruit yields by 8.36–58.01 % (p < 0.05), while two-stage irrigation significantly reduced water consumption and evapotranspiration compared with full-stage irrigation (p < 0.01). FS significantly improved water productivity ( WP ), irrigation water productivity ( WP I ), and fruit quality. All two-stage irrigation treatments demonstrated yield response factors ( k y ) < 1. The FS treatment reduced irrigation volume by 43.7 %, while the yield decreased by only 8.36 %, suggesting that the irrigation savings did not significantly compromise yield. In summary, the FS treatment is recommended as the most optimal irrigation schedule, followed by SM and FM, for the production of X. sorbifolium in drylands. This approach conserves water while minimally impacting productivity, thus representing a sustainable water management strategy. • Deficit irrigation (DI) should be applied during the specific critical period of water demand. • DI reduced yield by 8.36–58.01 % compared with full–stage irrigation. • DI during the flowering and fruit-setting stages reduced irrigation consumption by 43.7 %. • The yield response factor ( k y ) was 0.53 when irrigated during the flowering and fruit-setting stages.