Effects of regulated deficit irrigation at different growth stages on greenhouse pear-jujube quality

In order to investigate the effects of regulated deficit irrigation (RDI) on pear-jujube quality, seven-year-old pear-jujube trees in greenhouse were studied during 2005－2007. The experimental treatments included the sufficient water supply during the whole growing period (T1), low and moderate water deficits at the bud burst to leafing stage (T2), moderate water deficits at flowering to fruit set stage, fruit growth and fruit maturation stages (T3, T4, T5), respectively. The results indicated that the different deficit irrigation levels at different growth periods had significant impact on the pear-jujube quality. During the three years, water deficits treatments at the stage of Ⅰand Ⅱ had less impact on the quality of single fruit and water content of pear-jujube (P＞0.05); meanwhile enhanced, the fruit firmness by 13.7%－15.8%, and reduced the amount of organic acid and rotten fruit percentage significantly (P＜0.05) by 14.2%－18.8% and 21.0%－25.0%; and improved the soluble solid content and sugar/acid ratio rather significantly by 22.1%－24.4% and 47.8%－60.0% (P＜0.01), at the same time, shortened the fruit maturation time by 10－12 d. The water deficit treatments at the stage of Ⅲ increased the fruit firmness, fruit color, vitamin C (Vc), soluble sugar, soluble solid content and sugar/acid ratio by 22.3%, 41.9%, 27.0%, 32.1%, 38.1% and 53.3%, respectively, and meanwhile the water deficit treatments at the stage of Ⅳ improved in turn by 22.7%, 42.3%, 37.4%, 28.1%, 27.1% and 98.7%, respectively, which had the significant level (P＜0.01). The water deficit treatments at the stage of Ⅲ and Ⅳ reduced the organic acid (P＜0.05) and the fruit maturation ratio greatly (P＜0.01), and shortened the fruit maturation period by 15－20 d. At the same time, it reduced the single fruit weight and water content of pear-jujube, which had significant influence at the stage of Ⅲ (P＜0.05). The improved level for the quality of pear-jujube was stage Ⅳ＞stage Ⅲ＞stage Ⅱ ≈ stageⅠ. Through the integrated considering the impact of water deficit treatments on each indicators of pear-jujube quality, moderate water deficit treatments during the fruit maturation stage has the best results for the quality of fruit, which has important popularization value.