Optimization of Irrigation and Potassium Application for Improved Jujube Production in arid Northwest China

The arid Northwest of China is the main production area of China's jujube, where reasonable irrigation and fertilization strategies is key to improving the quality and production of jujube trees. While current research primarily focuses on the effects of different irrigation regimes on jujube growth, there is a lack of systematic studies on the relationship between potassium application amount and jujube growth and metabolism, making it challenging to provide clear guidance for jujube fertilization strategies. This study investigated the effects of different potassium application amount (240, 180, 120, and 0 kg·hm⁻²) on the growth and production efficiency of jujube trees. The results showed that the application of potassium fertilizer improved water use efficiency of jujube trees, significantly promoted their growth, and increased transpiration rate and production efficiency with higher potassium application amount. The water-potassium transport model in the root zone and the production model of jujube trees under drip irrigation with potassium application were calibrated and validated using experimental data from four potassium application treatments. Nine orthogonal numerical experiments were designed with the irrigation volume and potassium application amount as variables. The results revealed that the irrigation volume and potassium application amount significantly influenced the growth of jujube trees (P < 0.05), with a notable interaction effect between the two. When the potassium application rate was 240 kg·hm⁻² and the irrigation volume was 180 mm, the water use efficiency of the jujube trees was optimized, aligning better with the water-saving and high-production goals of the Xinjiang region. The maximum root-uptake radius of jujube trees for soil water and potassium was 50–70 cm. Within this radius, the potassium concentration significantly decreases with increasing distance from the root system, while beyond the absorption radius, potassium infiltrates vertically into deeper soil layers along with irrigation water. An empirical formula relating the transpiration rate and production of jujube trees to irrigation volume and potassium application amount under drip irrigation conditions were established in this study, offering guidance for irrigation and potassium application strategies in arid regions.