Effect of the supplemental lighting on the growth of young plants in second nursery in tomato

The system for producing many transplants in a narrow space is necessary for low node-order pinching and high planting density cultivation. Excessive elongation of stem usually happens in high density tomato transplants during nursery stage, so the control of the plant height is necessary. We researched the effect of supplemental lighting on the growth of young plants on the second nursery. Tomato seedlings were grown in the closed nursery system using fluorescent lamps for 28 days after sowing. Seedlings transferred to the second nursery system on 17 November 2008. This system is the NFT system to which the root zone of each plant was limited separately by root barrier sheet, and plants were arranged in 12.5 × 12 cm spacing. The young plants were grown in this system for 2 weeks with supplemental lighting using ceramic metal halide lamps, with shading, and without shading and supplemental lighting. Some plants were arranged in 25 × 24 cm (low density plot). The dry matter weight of plants increased with supplemental lighting, but plant height did not chang. The height of plants was short in low density plots. Then, the effect of differences of light source on plant growth was researched. Red LED lighting reduced the stem elongation compared with the control. On the other hand, blue LED lighting increased the stem elongation a little. After second nursery, some nursery plants were grown in the NFT hydroponics system with third truss pinching and high planting density cultivation (6.25 plants m^-2). However, the yields were the same among the plants that had undergone different processing in second nursery. The supplemental lighting during second nursery was effective to increase dry weights of shoot and root, and red LED lighting was effective to suppress the plant height, and to facilitate the transplant work, but little effective to increase fruit yield.