Effect of substrate type and pot size on blueberry growth and yield: first year results

Blueberry substrate production is increasing worldwide, especially in regions with mild winter climates. However, this is a new production system that needs to be studied since little information is available. Growers normally use large pots and stable substrates to maintain plants in the same pot for a long period in order to reduce labour and costs. A trial was set up in 2014 to study the influence of different substrates and pot sizes on growth and yield of 'Paloma' southern highbush blueberry plants, grown under protected cultivation. One-year-old plants were planted in two sized pots (32×24 cm/15 L and 33×33 cm/25 L) and two substrate types with different densities (200 and 140 g dm^-3) for one year. Plants were winter-pruned and all flowers removed in spring. All plant biomass was determined in three sampling dates at the beginning, middle and end of the growth cycle. Yield per plant was recorded the following spring. The experiment showed that plants thrived well in both substrates and pot sizes with an increase of 800 g in their dry matter with no significant differences regarding substrate types or volumes. Yield in 2015 was not significantly different for all treatments, with an average yield of 1.4 kg plant^-1. Since pot size and substrate were similar in this first year, prolonging the study is crucial in order to determine the long term effect of root volume and the stability of the substrate for fruit production.