The Influence of Growing Media and Periods On the Growth of Two Leafy Vegetable Seedlings In Plant Factory System

There is high consumer demand for leafy vegetables all year round in Korea due to special culinary culture, such as wrapping meat in leafy vegetables (called "ssam vegetable"). With cold winters and hot, humid summers, it is difficult to stably produce leafy vegetables all year round. In recent years, this problem has been addressed by hydroponic culture of leafy vegetables in a greenhouse or plant factory. Though small scale, about five artificial light plant factories are commercially operated in South Korea. These plant factories grow mainly leafy vegetables such as lettuce. However the hydroponic practice of raising seedling leafy vegetable has not been established in a plant factory system. This study was conducted to identify the effects of growing media and periods on the growth of leafy vegetable seedlings in an artificial light plant factory. Lettuce and pak choi were leafy vegetables studied. Two growing media—rock- wool and urethane sponge—and periods of 12, 14, and 18 days after germination were compared. As a result, the growth of both leafy vegetables seedlings was better in rock-wool than in urethane sponge because of high moisture holding ability. However, the early growth stage of seedlings was not as good because of poor rooting during germination. Germination ratio in the urethane sponge was lower because of the low water contents at the top surface of the medium. Among the three growing period treatments, the growth of seedling at 14 days was the best with respect to the aerial growth and root activity. If water content is kept more than 97% of saturation moisture capacity, the urethane sponge medium would be proper in plant factory system because of its higher germination ratio and better growth of roots.