Effects of different light intensities on lettuce growth, yield, and energy consumption optimization under uniform lighting conditions

Vertical farming is an advanced form of modern agriculture, but it involves high energy consumption when providing supplemental lighting for crops. The research designed an automated lighting detection device and explored its application in vertical farms. It comprehensively investigated the effects of different red-blue light intensities on two lettuces (<i>Lactuca sativa</i> L. cv. 'Spanish green' and 'Butterhead') varieties under highly uniform supplemental lighting conditions. The research encompasses investigations into lettuce morphological parameters, photosynthetic physiology, productivity, and energy consumption. The experimental light quality and photoperiod were set at (R/B = 4, 16 h/d), with light intensity ranging from 125 to 300 μmol/m²/s. The experiment indicates that with the increase in light intensity, the yield of both lettuce varieties also increases. Furthermore, lettuce exhibits a significant increase in leaf amplitude from day 20 to day 25 of growth. At 300 μmol/m²/s, Butterhead lettuce demonstrates optimal fresh weight and productivity ratio. As for Spanish green lettuce, the productivity ratio at 200 μmol/m²/s is only 2.11% lower than at 300 μmol/m²/s. Under the cultivation conditions of R/B = 4 and 16 h/d, a light intensity of 300 μmol/m²/s is suitable for the production of Butterhead lettuce, in comparison, a light intensity of 200 μmol/m²/s is suitable for the production of Spanish green lettuce.