Influence of Cultivation Environment on Growth of Lettuce Seedlings in Artificial Light Type Plant Factory

It is necessary to optimize and homogenize the environmental conditions in plant factories. We installed sensors to observe the environmental factors in a plant factory and evaluated lettuce growth. We found that the integrated quantity of PPFD (Photosynthetic Photon Flux Density) is correlated with fresh weight of harvested leaf lettuces and that lettuce density also affects growth. There is the relationship between adjacent and central plant stocks. The influence of planting density was observed, and thinning improved the growing conditions at many planting positions. On the other hand, it was concluded that the air temperature and humidity were uniform in the plant cultivation bed and did not affect the growing condition. It was observed that the air temperature, humidity and wind speed were affected when the cultivation bed was in front of the air conditioning port. The CO2 concentration was controlled within a range that did not affect the growth.