Responses of 'Pacific Rose'™ Apple to Partial Rootzone Drying and to Deficit Irrigation

Abstract

Summary Water resources for irrigation are becoming increasingly limited, therefore, reducing irrigation is a sensible strategy to save water and possibly improve fruit quality in apple production. We investigated plant water relations, growth, yield, and fruit quality of ‘Pacific Rose’™ apple subjected to the following irrigation treatments: commercially irrigated (CI) control, where soil was maintained near field capacity throughout the season; partial rootzone drying (PRD), where half of the irrigation volume of CI was applied to only one side of the rootzone; and no irrigation (NI), where water was withheld for the duration of the experiment. Volumetric soil water content of NI and the un-irrigated PRD side were significantly lower than CI and the irrigated PRD side from 62 days after full bloom (DAFB). Leaf water potential (ψ) of PRD was similar to CI on most occasions, whereas ψ of NI was generally lower than CI from 95 DAFB. Neither irrigation treatment significantly affected shoot growth, fruit growth, photosynthesis, and stomatal conductance. However, NI leaves discriminated significantly less against 13 CO2 late in the season. At harvest, PRD and NI had saved 0.78 and 1.56 megalitres of water per hectare compared to CI, respectively, and did not significantly reduce fruit quality or yield.