EFFECTS OF IRRIGATION SYSTEMS AND ROOTSTOCKS ON WATER USE, TREE GROWTH, FRUIT QUALITY, AND MINERAL NUTRIENTS IN APPLES DURING THE THIRD AND FOURTH YEAR AFTER PLANTING

Water usage, tree growth, leaf mineral nutrients, yield, and fruit quality attributes in ‘Autumn Rose Fuji’ apple (Malus × domestica Borkh.) under five irrigation systems [Full Sprinklers (FS), Partial Root-Zone Drying Sprinklers (PRS), Full Drip (FD), Deficit Drip (DD), and Partial Root-Zone Drying Drip (PRD)] and effects of four rootstocks (‘Bud 9’, ‘RN 29’, ‘Supporter 4’, and ‘G30’) and two irrigation systems (FS and FD) on tree trunk cross sectional area (TCSA), yield, and fruit quality in ‘Pacific Gala’ were studied during the third and fourth years after planting. Trees with FS received more water than those with drip systems. ‘Autumn Rose Fuji’ trees with FS and FD had similar TCSA, but both treatments had significantly greater TCSA than those of other irrigation treatments. ‘Autumn Rose Fuji’ trees receiving FS had larger leaves than those with other treatments. ‘Autumn Rose Fuji’ trees with all drip systems had higher yield efficiencies than those with FS or PRS systems. ‘Autumn Rose Fuji’ fruit size was decreased while soluble solids concentrations (SSC) increased with PRS. ‘Autumn Rose Fuji’ fruits from trees with PRD were advanced in maturity as they had softer fruits with more advanced starch degradation pattern (SDP). In ‘Autumn Rose Fuji’, concentrations of leaf N, Mg, and Zn were lower while that of leaf K was higher in FS and FD systems. ‘Bud 9’ and ‘RN 29’ were found to be superior rootstocks for ‘Pacific Gala’. ‘Bud 9’ and ‘G30’ advanced fruit maturity of ‘Pacific Gala’ by increasing fruit color, SSC, and SDP and reducing fruit firmness. In ‘Pacific Gala’, FD irrigation increased fruit size and advanced fruit maturity by increasing SDP and reducing firmness as compared to FS system. Overall, drip irrigation at full evapotranspiration rate, calculated with inclusion of tree spacing and ground shading is advised for both ‘Fuji’ and ’Gala’ production.