Tree Growth, Yield, Fruit Quality, and Mineral Partitioning in ‘Pacific Gala’ Apple as Affected by Rootstocks and Irrigation Methods

Abstract

ABSTRACT The objectives of this project were to study the influence of rootstocks and two irrigation systems on tree growth, fruit yield, quality at harvest, and mineral partitioning in ‘Pacific Gala’ apple trees (Malus domestica Borkh.). The rootstocks used in this study were B.9, RN-29, Supporter 4 and G.30. The irrigation regimes were drip and sprinkler. ‘Pacific Gala’ on Supporter 4 rootstocks had 47% more developing spurs than those on RN-29 and B.9 rootstocks. Trees on Supporter 4 had 12% more total limb length than those on other rootstocks. ‘Pacific Gala’ on B.9 had 8% more shoot leaf N than those on Supporter 4 and G.30 rootstocks, and 6% more spur leaf N than those on Supporter 4 rootstocks. Trees on B.9 rootstock had 29% lower spur leaf K than those on other rootstocks. Sodium, Al, Fe, Cu, and Zn in spur leaves of ‘Pacific Gala’ were unaffected by rootstocks. The total limb length and number of developing spurs were similar for trees watered with either irrigation system. Trees receiving sprinkler irrigation had 7% more P, 6% more K and Ca in shoot leaves and 17% more leaf P, 10% more K, 5% more Ca in spur leaves. Trees receiving sprinkler irrigation had 8% more fruit color than trees receiving drip irrigation. ‘Pacific Gala’ trees receiving drip irrigation used 38% less water as compared to trees receiving sprinkler irrigation. Considering growth and quality attributes, B.9 and RN-29 were found to be desirable rootstocks for ‘Pacific Gala’ under the conditions tested. Overall, trees receiving drip irrigation produced high yield and quality fruit, while using significantly less water than those under a sprinkler system.