Development of Closed-type Transplant Production System and Its Application.

The closed system is defined as a warehouse-like structure covered with opaque thermally insulated walls, multi-shelves with lamps, home-use air conditioners, and other equipments for water and CO2 supply. Environments inside the closed system are not disturbed and thus can be controlled as desired. Ventilation is restricted at minimum to minimize resource consumption and environmental pollution, and to prevent insects and/or pathogens from entering into the system. It was estimated that the initial cost for construction of the closed system per transplant could be the same as that of the open system (i.e., greenhouse). Optimally controlled environments in the closed system enhanced the growth and development of several transplants so that the production period in the closed system was reduced by 10 to 50%, compared with that in the open system.Electric energy consumption per transplant in the closed system was 0.3-0.6 MJ, and its cost was 1-2 Japanese Yen. Water and CO2 consumptions in the closed system were, respectively, about 1/15 and 1/5 of those in the open system. Transplant quality (vigor, growth uniformity, controlled flower development, etc.) was higher in the closed system than in the open system. We concluded that high quality transplants could be produced within a significantly shorter period and with less consumption of resources in the closed system than in the open system. Hence, the closed system was economically competitive over the open system for many horticultural, medicinal and other crops.