Responses of 'Pacific Rose'™ apple to partial rootzone drying and to deficit irrigation

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'(TM) apple subjected to the following irrigation treatments: commercially irrigated (Cl) control, where soil was maintained near field capacity throughout the season; partial rootzone drying (PRD), where half of the irrigation volume of Cl 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 Cl and the irrigated PRD side from 62 days after full bloom (DAFB). Leaf water potential (psi) of PRD was similar to Cl on most occasions, whereas y of NI was generally lower than Cl from 95 DAFB. Neither irrigation treatment significantly affected shoot growth, fruit growth, photosynthesis, and stomatal conductance. However, NI leaves discriminated significantly less against (CO2)-C-13 late in the season. At harvest, PRD and NI had saved 0.78 and 1.56 megalitres of water per hectare compared to Cl, respectively, and did not significantly reduce fruit quality or yield.