During the past few decades, vertical farming has attracted a lot of interest as an alternative food production method. Vertical farms use engineered growth environments and hydroponic cultivation techniques for growing plants indoors. One of the important factors in vertical farming for the cultivation of different plants is the number of nutrients, which can be measured as electrical conductivity (EC). Studying the optimal EC is important for avoiding nutrient loss and deﬁciency in vertical farms.
In this study, the effect of ﬁve EC levels (2, 1.2, 0.9, 0.7, and 0.5 dS m−1 ) of Hoagland nutrient solution on the growth and development of basil cultivar ‘Emily’ and lettuce cultivar ‘Batavia-Caipira’ were studied. During the study, the environmental parameters were kept ﬁxed using an automatic dosing machine. The experiment was done in automatic vertical farms using the hydroponic ebb–ﬂow cultivation technique with a temperature of 20 ± 1 ◦C, relative humidity of 50–60%, the CO2 concentration of 450 ppm, pH = 6, the PPFD (photosynthetic photon ﬂux density) of 215 ± 5.5 µmol m−2 s−1, and the photoperiod of 16:8 h (day/night).
Each treatment was replicated four times. The team studied the effects on several growth parameters (including the dry and fresh weight of leaves and roots, number of leaves, and leaf area) as well as the chlorophyll and nitrogen concentration of the leaves. According to the results, the basil and lettuce growth parameters among the ﬁve treatments have been significantly higher in the treatment with EC of
1.2 and 0.9 dS m−1. These EC values are lower than the recommended EC value given as the optimum in the previous studies. However, the concentration of chlorophyll and nitrogen show different
trends and were higher in full strength of nutrient solution with EC = 2 dS m−1.
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