Substrate production in pots has emerged as a popular method for growing highbush blueberry (Vaccinium corymbosum). However, there is limited knowledge on the best strategies for irrigation in substrate. To address this issue, a multiyear study was conducted in a retractable-roof greenhouse using ‘Legacy’ blueberry to determine an optimal combination of drip emitters (two, four, or eight emitters per pot) and irrigation set point (-2 or -4 kPa) and frequency (a single continuous pulse of up to 45 minutes or short 3-minute pulses every 15 minutes to reach container capacity). The plants were grown in 25-L pots filled with a mix of peat, coir, and perlite. Tensiometers were installed horizontally into the center of the pots to monitor the matric potential and to determine when to trigger irrigation. Irrigation was triggered automatically using a data logger and applied until the pots reached container capacity determined by small weighing lysimeters. Yield was highest in plants with eight emitters in the second year (first year of fruit production), but this difference diminished in year 3. A similar relationship was observed for aboveground biomass. Root size was also highest with eight emitters. Leachate pH and EC were mostly similar among treatments, but EC was more uniform throughout the pot with eight emitters. In contrast, the lower set point and shorter irrigation frequency decreased the ability of the pots to reach container capacity, particularly when the plants were irrigated with only two emitters per pot. Overall, the plants grew best when irrigation was triggered at -2 kPa and applied in single continuous pulses with four or eight emitters per pot.
