Effects of environmental control and LED supplemental lighting on strawberry growth and yield in a subtropical climate

Abstract

We investigated the effects of environmental control and daytime LED supplemental lighting on the growth and yield of strawberries in a subtropical climate. Two strawberry cultivars, namely ‘Yotsuboshi’ and ‘Benihoppe’, were grown in three greenhouses from October to May as a forcing culture: (1) conventional greenhouse, with side vents open and no other environmental controls; (2) controlled environment (CE) greenhouse, equipped with an integrated environmental control system to cool air and growing medium using cooling devices controlled by sensor monitoring; and (3) LED greenhouse, equipped with an integrated environmental control system and LED supplemental lighting during the day. The conventional greenhouse had higher air and growing medium temperatures during the growing season than the CE or LED treatment greenhouse. Both cultivars had significantly lower aboveground dry-matter weight (TDM) and yield in the conventional treatment than in the CE or LED treatment. Yield in the CE treatment increased 2.4 and 2.0 times for ‘Yotsuboshi’ and ‘Benihoppe,’ respectively, relative to the conventional treatment. Additionally, yield in the LED treatment increased 3.1 and 2.5 times for ‘Yotsuboshi’ and ‘Benihoppe,’ respectively, relative to the conventional treatment. The marketable fruit ratio was higher in CE and LED treatments than in the conventional treatment for both cultivars. The number of fruits for both cultivars was significantly greater under the LED treatment than the conventional treatment. Clearly, daytime LED supplemental lighting further improved TDM and yield during the winter season, when cloudy weather and low solar radiation were persistent. However, during the spring season, when external solar radiation exceeded 20 MJ m−2 day−1, the enhancing effects of LED supplemental lighting on yield were limited. Supplemental lighting methods based on the amount of solar radiation available are necessary to allow maximum, high-quality strawberry fruit production in subtropical regions.