Utilization of Snow and Geothermal Cold Heat for Temperature Control and Head Production in Witloof Chicory Hydroponic Forcing Culture in Summer

Abstract

Forcing culture of witloof chicory (Cichorium intybus L.) is conducted in an enclosed and dark space at a temperature of roughly 15 ℃, and the forcing space is cooled in summer. Temperature control in the forcing space for etiolated head (chicory) production was attempted using natural heat for a period of two years. Etiolated heads were obtained in the hydroponic culture of chicory roots. In 2015, air temperature in the culture room changed to roughly 21 ℃ during the hottest season because of the use of a combination of geothermal and underground water temperatures. In 2016, the average air temperature in the cooling treatment room (cooling) decreased to 16.8 ℃, and the control room (non-cooling) temperature was 22.2 ℃ during the hot season, achieved via geothermal and snow's cold heat. Quantity of cold heat supplied by snow into the culture room was four to five times higher than that of geothermal cold heat, suggesting the importance of snow's cold heat. Tightness of etiolated heads obtained in cooling was better compared to the control during the hot season. These results indicate that chicory forcing culture had been successful in an enclosed space cooled by geothermal and snow's cold heat in summer.