Abstract:

【Objective】 To decrease the amount of irrigation and increase water use efficiency in apple orchard by improving the irrigation methods on the condition of maintaining the natural growth rate of apple trees.【Method】Effects of partial root zone alternative irrigation on growth and leaf physiological characteristics of three-year old roots of potted Gala apple trees were investigated in this study. 【Result】 Growth of new shoots and trunk diameter were retarded by the treatments of 1/4 and 2/4 root zone irrigation significantly, and that were released by increasing root zone irrigation. Leaf water potential and stomatal resistance were affected by partial root zone alternative irrigation, leaf water potential of 1/4 and 2/4 root zone irrigation was lower than that of 3/4 and 4/4 treatments, and stomatal resistance decreased with the amount of irrigation increasing significantly. Net photosynthetic Rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) of apple leaves decreased with root zone irrigation decreasing, and the extent of decreasing of transpiration rate was significantly larger than that of net photosynthetic rate, therefore, water use efficiency ( WUE ) increased. However, Pn, Tr and Gs of apple leaves were not affected by the amount of irrigation. At different growth stage, partial root zone irrigation had the same effect on Pn, Tr, Gs and WUE of apple leaves, while the highest value was shown at spring shoot growth stage. 【Conclusion】 Irrigation rate was the major factor affecting the growth of new shoots, however, leaf physiological characteristics were regulated by root zone irrigation. To maintain formal growth and development of apple trees, the root zone irrigation should not less than 50% of total root zone, the precipitation is not considered.

Key words: apple tree, root zone, alternative irrigation, growth, leaf’s physiological characteristics