Development of Practical Plant Factory with Artificial Supplemental Lighting System for the Growth of Vegetable Seedlings

Abstract

For stable mass production of vegetable seedlings with good quality, a commercial greenhouse nursery needs a supplemental lighting system that is not affected by light fluctuations under natural solar conditions. Therefore, a practical plant nursery covering a 12 × 24 m area, and using a supplemental lighting system, was developed for the growth of vegetable seedlings. The developed lighting system had 400-W mercury-free, high pressure sodium lamps with reflectors, which produced a red radiation to far-red radiation photon flux (R/FR PF) ratio of 1.1. This is similar to that of solar radiation. And over about 60 μmol m-2 s-1 of PPFD was realized for stable and healthy growth of vegetable seedlings. By using a simulation model of horizontal distribution of PPFD on two cultivation beds (each bed area: 4.6 × 22.6 m) under 100 lamps, it was found that the system had high uniformity of lighting on the two beds. Observed value of illuminance and PPFD and uniformity also satisfied the planned specifications. By repeating a seedling growth experiment using various plants in this greenhouse, it is expected that the practical and effective use of this supplemental lighting system will be possible in rainy seasons or in the late winter period.