Drip irrigation triggered by soil matric potential improves soil water and salt environment to promote yellowhorn (Xanthoceras sorbifolium Bunge) growth in the Hexi Corridor of China

In the cultivation of yellowhorn (Xanthoceras sorbifolium Bunge), a salt-tolerant industrial crop, traditional irrigation practices exacerbated soil salinization, leading to wasted water and diminished yield. Scheduling drip irrigation by controlling soil matric potential (SMP) thresholds can effectively mitigate these problems. However, few studies have investigated the growth response of yellowhorn to the soil water and salt environment under drip irrigation triggered by SMP thresholds. A two-year field experiment was carried out in the Hexi Corridor, northwest China, during the yellowhorn growing season in 2021 and 2022. The "space for time" method was adopted, and 1-year-old and 5-year-old trees were selected to represent the young and fruit-bearing stage of yellowhorn, respectively. Five water levels by controlling SMP thresholds (−10, −20, −30, −40, and –50 kPa for young stage; −5, −10, −15, −20, and −25 kPa for fruit-bearing stage) were applied. Border irrigation (600 mm) was employed as a control. The results indicated that drip irrigation significantly increased soil moisture by 59 %–207 % and 72 %–173 %, reduced salinity (ECe) by 28 %–52 % and 3 2%–54 %, and decreased pH by 0.6 %–4.2 % and 1.1 %–4.6 % in the root zone of young and fruit-bearing yellowhorn, respectively, compared to border irrigation. Under drip irrigation, the ECe and pH in the root zone decreased with increasing SMP threshold. Higher SMP thresholds were more prone to form high-moisture environments. However, excessive moisture inhibited plant growth and yield while decreasing water use efficiency (WUE). Specifically, for the young yellowhorn, the −30 kPa reduced irrigation amount by 14 % compared to −20 kPa and no significant difference in plant growth. The −20 kPa treatment of fruit-bearing yellowhorn increased yield while improved WUE. Taking all factors into consideration, an SMP threshold of −30 kPa for the young stage and −20 kPa for the fruit-bearing stage could be employed to trigger drip irrigation while planting yellowhorn in the arid saline region.