High Photosynthetic Photon Flux Density Differentially Improves Edible Biomass Space Use Efficacy in Edamame and Dwarf Tomato

Improving edible biomass space use efficacy (EBSUE) is important for sustainably producing edamame and dwarf tomatoes in plant factories with artificial light. Photosynthetic photon flux density (PPFD) may increase EBSUE and space use efficacy (SUE). However, no study has quantitatively explained how PPFD affects EBSUE in edamame and dwarf tomatoes. This study aimed to quantitatively validate the effects of PPFD on EBSUE in dwarf tomatoes and edamame and verify whether this effect differs between these crops. The edamame and dwarf tomato cultivars 'Enrei' and 'Micro-Tom', respectively, were cultivated under treatments with PPFDs of 300, 500, and 700 µmol m s. The results showed that the EBSUE and SUE increased with increasing PPFD in both crops. The EBSUE increased depending on the increase in SUE, the dry mass ratio of the edible part to the total plant in the edamame, and the SUE only in the dwarf tomatoes. In conclusion, a high PPFD can improve the EBSUE and SUE of edamame and dwarf tomatoes in different ways at the reproductive growth stage. The findings from this study offer valuable information on optimizing space and resource usage in plant factories with artificial light and vertical farms. Additionally, they shed light on the quantitative impact of PPFD on both EBSUE and SUE.