Peat Moss as a Suitable Substrate for Low-potassium Southern Highbush Blueberry Production

Four soil substrates—a mixture of peat moss and Kanuma soil (mixed soil), peat moss alone, Rockwool, and coir—were tested for their suitability for producing low-potassium southern highbush blueberries (Vaccinium corymbosum L. interspecific hybrid) (SHB). The characteristics of the substrates were first analyzed: peat moss and Rockwool had low cation exchange capacities, Rockwool had a high pH, and coir had high potassium content. SHB ‘Misty’ plants were transplanted into each substrate and grown under potassium-restricted conditions for 5 or 12 weeks. The 5-week restriction did not reduce the fruit potassium content, whereas the 12-week restriction reduced it by 30–45%. Although fruit quality did not differ significantly among substrates, leaf chlorosis was observed with Rockwool, and both mixed soil and coir resulted in lower yields or fewer fruits. These results suggest that peat moss is the most suitable substrate for low-potassium SHB production as it minimizes adverse effects on plant growth and fruit quality.