Effects of Partial Rootzone Irrigation on Growth and Physiological Characteristics in Apple Trees and Water Use Efficiency

We conducted an experiment to investigate the effects of partial rootzone irrigation on growth, physiological characteristics and water use efficiency on apple. We used three years 'Gala' apple trees, in which the root system was divided into four containers were used as material. There were four experiment groups of irrigation (water applied to only 1 of 4 containers, 2 of 4, 3 of 4 and 4 of 4 root zones) and three amounts of irrigation (500, 750, and 1000 ml per basin each time). Results showed that the net photosynthetic rate of the 1/4 root zone irrigation was the lowest, while the 4/4 root zone irrigation was significantly higher than the other three treatments. No differences were observed among the treatments of different irrigation amounts. At the early shoot growth stage, stomatal conductance of leaves in the 3/4 and the 4/4 root zone irrigation was higher than that of the 1/4 and the 2/4 treatments. There were no differences in stomatal conductance of shoot leaves at the later growth period. Shoot and root growth were inhibited by 1/4 and 2/4 root zone irrigation treatments and promoted by the 4/4 treatment. With increasing amounts of irrigation, different treatments showed slight effects on trunk growth. The 1/4 and 2/4 root zone irrigation treatments and the 500 ml irrigation quantity increased water use efficiency significantly. The 2/4 root zone irrigation and 750 ml irrigation were optimal for minimizing water consumption, increasing growth and enhancing the physiological characteristics of apple trees.