Selection of Newly Developed Artificial Medium for Lettuce Production in a Closed-type Plant Production System

Abstract

This study evaluated different media for lettuce cultivation in a closed-type plant production system. Lettuce seeds were sown in 128-cell plug trays filled with six different media, and then transplanted at 11 days after sowing in a closed-type plant production system. The used media were commercial media (urethane foam, rockwool, and Q plug), and newly developed media (PU 14-S1, TP-S1, and PU-7B). Higher values were observed for total porosity, container capacity, and air space in urethane foam and PU 14-S1. Bulk density was the greatest in the TP-S1, followed by the Q plug and rockwool. The pH and electrical conductivity (EC) of the medium ranged from 5.17 to 6.50 and 0.01 to 0.31 dS.m(-1), respectively. Germination properties were strong in the rockwool, Q plug, and PU-7B media. The initial and final growth of lettuce measured at 11 and 32 days after sowing, respectively, were the best in the Q plug medium, followed by the rockwool and TP-S1 media. These media had higher EC values than the others. The applicability of newly developed medium PU-7B was confirmed for lettuce cultivation in a closed-type plant production system when the EC of PU-7B was regulated similarly to the EC of Q plug medium.