Effect of water deficiency on growth, qualities, and water use efficiency of apple in Weibei area of Shaanxi in different fruit developmental periods

[Objective] The study aims to explore the mechanism of water saving and water control methods to regulate water use efficiency of apple and to optimize the management methods of water saving, high yield, and income-increase in Weibei apple producing area. [Methods] The eight-year-old ‘Yanfu 3/T337’ apple tree was selected from the experimental station of Xi􀆳an Fruit Friend Association located at Tiefu town in the Qian County of Xianyang City, Shaanxi Province. Two irrigation levels were arranged: full irrigation (relative water content after irrigation was 75%) and slight deficit irrigation (relative water content after irrigation was 50%). There were four irrigation modes: Full irrigation at both fruit growing and expanding stages (CK), light deficit irrigation at both fruit growing and expanding stages (W1), light deficit irrigation at fruit growing and full irrigation at expanding stages (W2), and full irrigation at fruit growing and light deficit irrigation at expanding stages (W3). In order to determine the best deficit irrigation method, spring shoot growth index, fruit quality index, and fruit yield index were determined, and water use efficiency, irrigation water use efficiency, and fruit comprehensive evaluation satisfaction were calculated. [Results] (1) There were no significant differences in shoot length and leaf chlorophyll relative content (SPAD) among different irrigation modes, but the diameter of spring shoot was decreased significantly under deficit irrigation. (2) Compared with CK, the single fruit mass was significantly reduced by 10.3% under W1 treatment, the titrable acid content of fruit was significantly reduced by 14.7% under W2 treatment, and the fruit shape index and soluble solid content were not changed under the three water deficit treatments. (3) W1 treatment significantly increased the peel yellow value b* , and W2 treatment significantly increased the peel color saturation C* , but deficit treatment had no effect on the peel brightness value L* and red green value a* . (4) Compared with CK, fruit yield was decreased by 13.4% 24.7% under each treatment, but only W1 treatment reached a significant level. The fruit tree water use efficiency was increased in different degrees in each treatment, but only W1 treatment was significantly increased by 38.0%. There was no significant difference in water consumption and water use efficiency of fruit trees under each treatment. The satisfaction of fruit comprehensive evaluation was W2>CK>W3 (W1). [Conclusion] The comprehensive evaluation satisfaction of apples in Weibei area of Shaanxi Province was the highest under mild deficit in growth period and full irrigation in expansion period (W2). There was no significant change in fruit yield and single fruit mass, but fruit quality was better and water use efficiency of fruit trees was higher.