Improving Indoor Strawberry Production in Vertical Farming Through Enhanced Lighting and Fertilization Strategies

There is increasing interest in growing strawberries (Fragaria ×ananassa) in indoor environments such as vertical farms, as the continued sustainability of outdoor production is threatened due to reductions in arable land, labor shortages, and an increased frequency of drought. However, the optimal conditions for growing strawberries hydroponically in sole-source lighting conditions have yet to be established. The objectives of this research were to investigate the optimal lighting conditions and nutrient concentrations for strawberry production in vertical farming. In the first study, bare-root plants of two strawberry cultivars, ‘Albion’ and ‘Monterey’, were grown in an indoor vertical farm under a 22 °C air temperature and an 18-h photoperiod with 90 μmol·m−2·s−1 of blue light and 250 μmol·m−2·s−1 of red light with and without 50 μmol·m−2·s−1 of additional far-red light from light-emitting diodes. Adding far-red light increased the fruit number per plant by 36%, total fruit fresh mass by 48%, and total soluble solids content by 12% in ‘Albion’, but not ‘Monterey’. In the second study, bare root plants of strawberries ‘Monterey’ and ‘San Andreas’ were grown under a 23 °C air temperature and an 18-h photoperiod with an extended photosynthetic photon flux density of 350 μmol·m−2·s−1. Plants were subjected to four potassium to nitrogen ratios (K:N) of 1.5:1, 2.5:1, 3.5:1, and 4.5:1 in a deep-water culture hydroponic system. Increasing K:N from 1.5:1 to 4.5:1 increased the root dry mass of ‘Monterey’, but generally had little to no effect on vegetative growth in either cultivar. In addition, in both cultivars, increasing K:N from 1.5:1 to 4.5:1 decreased individual fruit size and increased titratable acidity. These results suggest that for indoor strawberry production, including far-red light in sole-source lighting can improve fruit production in some strawberry cultivars. However, increasing K:N in the hydroponic nutrient solution generally does not benefit plant growth, fruit production, and fruit quality.