LEDs supplemental light treatment promotes flowering and increases yield of ‘Kuemsil’ strawberries

In Korea, strawberry (Fragaria × ananassa Duch.) cultivation in greenhouses is done during the period September to May. Strawberries are the most expensive in the Korean market during winter and its increased production is necessary. Strawberry productivity may be insufficient due to reduced photosynthesis caused by low light availability in winter, which can be compensated by supplemental lighting. However, because strawberries require short days and low temperatures for flower bud differentiation, increasing the day length through supplemental lighting may delay the fruit harvesting period. This study evaluated the effect of supplemental lighting provided at different stages of growth (planting (PL), first flowering (FF), and second flowering (SF) stages) on flowering and fruit yield of ‘Kuemsil’ strawberries. Untreated plants were used as the control (CT). Supplemental lighting treatments were carried out for 2 h before sunrise and 2 h after sunset. The budding and flowering of strawberries were checked every week, and fruits with minimum 80% maturity were sampled at 2- to 3-day intervals. Petiole length, leaf length, leaf width, number of leaves, and crown diameter were significantly higher in the plants under supplemental lightings than in the CT. However, flowering was delayed in PL and FF treatments during the second and third flowering periods. Fruit diameter, weight, soluble solids content, and acidity were significantly higher under supplemental lighting than in the CT. Furthermore, fruit yield and fruit grade tended to be higher under supplemental light treatments. However, PL treatment exhibited the lowest yield and fruit grade in March. These findings provide valuable data for the application of supplemental lighting in strawberry production.