Effects of daily light integral and photoperiod with successive harvests on basil yield, morpho-physiological characteristics, and mineral composition in vertical farming

In recent years, vertical farming is becoming increasingly popular for the production of leafy vegetables and aromatic herbs, such as basil (Ocimum basilicum L.). However, research has focused primarily on the effect of light quality levels, quantity, and photoperiod in order to define more energy-efficient basil growing protocols. Although scientists have underlined the positive response of this poliedric aromatic herb to successive harvests, this technique had not been investigated under sole source lighting with crop grown in a vertical farming cultivation. Two experiments were carried out in which the effects of two daily light integrals (DLI, 7.5 and 15 mol m–2 d–1) and three photoperiods (P, 14/10, 16/8, and 18/4 photoperiod/dark period) were evaluated in relation to two successive harvests on Genovese basil. In the first experiment, at the first cut, a DLI of 15 mol m–2 d–1 improved yield, yield parameters, and morphophysiological characteristics, but reduced incident light use efficiency (LUE), compared to a DLI of 7.5 mol m–2 d–1. At the second cut, irrespective of the DLI used, plants grown at the first cut with a DLI of 15 mol m–2 d–1 did not show significant differences in plant fresh biomass. In contrast, for plants grown at the first cut with a DLI of 7.5 mol m–2 d–1, the DLI of 15 mol m–2 d–1 used at the second cut improved yield and photosynthetic performance. Regardless of photoperiod, the cuts increased fresh biomass and DLI by 205.1% (on average), confirming how this pre-harvest factor can be used to achieve desired yield and quality from basil with potentials to enhance LUE and resource savings in the vertical cultivation.