Effects of Led Light Intensity and Carbon Dioxide Concentration on the Growth of Spinach (Spinacia oleracea L.) in a Plant Factory

Abstract

This research aimed to investigate the effects of light intensity and the carbon dioxide (CO2) concentration on spinach’s growth during vegetative stage in plant factory (PF). Two experiments were conducted with different CO2 concentration in closed chamber (500 ppm and 800 ppm). In each experiment, plants were hydroponically grown under three light intensities of 115, 140 and 160 µmol.m-2s-1. Growth’s parameters were determined at different growth stages (T30, T37 and T44 respectively to 30, 37 and 44 days after sowing). ANOVA analysis and non-parametric Kruskal analysis of variance were used to evaluate the statistical significance of the treatment effects. The results showed that, before 30 days old, the increase of light intensity was not significantly effected to the growth of plant. During later growing periods (30 days old afterward), the increase of light intensity remarkably boost up yield’s related traits such as leaf number, fresh mass and dry mass under 500ppm CO2 concentration. The combination of light intensity and CO2concentration at 800ppm showed the plant growth indicators increased significantly at the T37 and T44 stages (after 30 days old), especially at the last week of growth period, fresh weight and dry weight of plants were significantly different at the light treatment L2, increased 37% and 57.6%, respectively as compared to light treament only. The results suggested that, during latest growing period, the average light intensity of 140 µmol.m-2s-1combining with elevating CO2 concentration is an alternatively way to enhance spinach growth. The findings of this study could be helpful for growers to improve growing conditions for a better development of spinach in the indoor farming (PF)