Abstract: To investigate the effects of alternate partial rootzone drip irrigation (ADI) on the morphological characteristics and root hydraulic conductivity of apple seedlings, three irrigation modes, i.e., fixed partial rootzone drip irrigation (FDI, fixed watering on one side of the seedling root zone), controlled alternate partial rootzone drip irrigation (ADI, alternate watering on both sides of the seedling root zone), and conventional drip irrigation (CDI, watering cling to the seedling base), and three irrigation quotas, i.e., each irrigation amount of FDI and ADI was 10, 20 and 30 mm, and that of CDI was 20, 30 and 40 mm, respectively, were designed. In treatment ADI, the soil moisture content on the both sides of the root zone appeared a repeated alternation of dry and wet process; while in treatment CDI, the soil moisture content had less difference. At the same irrigation quotas, the soil moisture content at the watering sides had no significant difference under the three drip irrigation modes. At irrigation quota 30 mm, the root-shoot ratio, healthy index of seedlings, and root hydraulic conductivity in treatment ADI increased by 31.6% and 47.1%, 34.2% and 53.6%, and 9.0% and 11.0%, respectively, as compared with those in treatments CDI and FDI. The root dry mass and leaf areahad a positive linear correlation with root hydraulic conductivity. It was suggested that controlled alternate partial root-zone drip irrigationhad obvious compensatory effects on the root hydraulic conductivity of apple seedlings, improved the soil water use by the roots, benefited the equilibrated dry matter allocation in seedling organs, and markedly enhanced the root-shoot ratio and healthy index of the seedlings.

Key words: controlled alternate partial root-zone drip irrigation, root hydraulic conductivity, apple seedling, root-shoot ratio, healthy index of seedlings.