Application of the constant soil temperature layer for energy-saving control in the local environment of greenhouse crops II. Application to strawberry cultivation during the winter season

For stable year-round production of greenhouse crops with sustainability and high profitability, it is essential to establish a system that encompasses energy-saving and year-round environmental control via the application of renewable energy resources. One such renewable energy resource is the constant soil temperature layer, which is widespread and easily accessible in agricultural fields. However, owing to the low heat capacity and conductivity of media such as soil and air, heat exchange with the constant soil temperature layer has been considered insufficient for temperature control of the entire air volume inside a greenhouse. Therefore, we utilized a novel local temperature control system based on heat exchange between the constant soil temperature layer and the ambient air surrounding greenhouse crops. In the present study, we applied this system to the elevated bed system of strawberry crops with no-heating culture during the winter season. The system, that control the ambient air temperature of strawberry crops, increased fruits yield compared with no-heating, and was estimated 45% reduction of heating load to maintain 8°C or more.