Vertical hydroponic lettuce: Impact of organic nutrients on antioxidant phytochemicals

Biofertilizers play an important role in sustainable agriculture as they are environmentally friendly practice. Hence, the present study was conducted to investigate and compare the performance of four organic-based nutrient solutions (NSs) from fish farm waste (NS_B), humic acid (NS_C) and (NS_D), and plant source (NS_E) with an inorganic fertilizer (NS_A) as control on lettuce cv ‘Lollo bianda’ grown in a Nutrient Film Technique (NFT) Vertical hydroponic system. Plant growth parameters, yield, mineral content, phenolic content, antioxidant activity, and individual phenolic compounds have been identified and quantified in response to different NSs. Among the organic-based NSs used, NS_B and NS_E produced a slightly lower crop yield (185 and 189 g/plant) than the inorganic NS_A (211 g/plant). Organic NSs resulted in lower leaf nitrate levels in the lettuce leaf (9.5–15 mg kg⁻¹ DW) as compared to the control (189 mg kg⁻¹ DW). Notably, Organic NSs gave higher phenolic content and antioxidant activity, with the highest level in NS_C and NS_D (96.65 and 98.51 mg g⁻¹, respectively) than the control (68.48 mg g⁻¹). Chlorogenic acid, trans-ferulic, and benzoic acid levels were significantly higher, while vanillic acid and 4-hydroxy benzoic acid levels were lower in organically grown plants than those of inorganic NS. Overall, the findings provided evidence that the NS has a direct impact on the phenolic compounds content and their profile which may elucidate the mechanism of the plant response to NSs from different sources. The study offers a promising avenue for sustainable hydroponics and agricultural practices in arid environments.