Evaluating High Tunnel and Field Performance of Early Ripening Blueberry Cultivars in Central Alabama

Abstract

Rabbiteye blueberry (Vaccinium virgatum) predominantly makes up blueberry production in Alabama. These blueberries typically ripen later in the season toward the end of May and June when market prices are low. Production of southern highbush blueberries (Vaccinium corymbosum L.) has great potential to increase market price and give local growers a competitive edge by producing earlier yields. However, risk of spring frost damage will be the most limiting factor for Alabama growers and adequate frost protection will be crucial. 13 one-yr-old southern highbush cultivars grown in 2.84 L containers and 2 rabbiteye cultivars were planted under high tunnel and in open field in Apr. 2022. Blueberry plants were evaluated for berry yield, timing of first berry harvest and peak harvest, individual berry weight and soluble solid content during the 2023 growing season. The high tunnel production system increased monthly maximum air temperature by 0.9 to 5.9 °C, monthly average air temperature by 0.2 to 10 °C, and minimum monthly air temperatures by 0.3 to 0.8 °C. The high tunnel also increased monthly maximum soil temperature up to 1.4 °C higher than the field, monthly average soil temperature up to 1.7°C higher than the field, and minimum monthly soil temp by 0.3 to 11.8 °C compared to the field. Photosynthetically active radiation (PAR) at noon had an average reduction of 15.8% in the high tunnel for 2022 and an average reduction of 24.5% in the high tunnel compared to the field in 2023. All southern highbush cultivars produced first berry harvests in the month of April for both field and high tunnel locations in 2023. The two rabbiteye cultivars both produced first berry harvests in the month of May for both field and high tunnel. Total berry yield ranged from 12.74 g to 607.08 g in the high tunnel while 1.56 g to 159.49 g in field for 2023. ‘Krewer’ produced the greatest average single berry weight (3.2 g) in the high tunnel and ‘Titan’ did in the field (2.5 g). ‘Titan’ also produced berries with the greatest soluble solid content for both high tunnel and field (15.7% brix and 16.5% brix, respectively). Plant canopy volume (PCV) was 1.65 times greater in the field compared to the high tunnel in 2022, and 1.02 times greater in the high tunnel than field in 2023. Rabbiteye cultivars ‘Krewer’ and ‘Titan’ were among the cultivars with the greatest chlorophyll content values throughout the study. Growing southern highbush blueberries under high tunnel advanced blueberry bloom up to 19 days at 10%, 26 days at 50%, and 17 days at 90%, while also advancing first blueberry harvest dates up to 20 days when compared to field production and therefore may serve as a potential production system for early ripening blueberries in central Alabama.