Neural network assessment of the effectiveness of using fulvic acids in combination with mineral fertilizers on the productivity and quality of Aficion leaf lettuce grown in vertical hydroponics

Growing demand for environmentally friendly plant products stimulates the development of closed-type urban city farms. As an innovative business model, they effectively use the limited space of megacities, providing direct access to the market. Plants are grown vertically on hydroponics with automatic environment control. To improve product quality and reduce dependence on mineral fertilizers, their partial replacement with humic stimulants was studied. An experiment was conducted with lettuce on Hoagland medium: control (water), 50% Hoagland, 100% Hoagland, and 50% Hoagland + fulvic acids (90 ppm). After completion, biomass and elemental composition were measured. The data were processed by the ChemNN neural network, which transforms the biochemical profile into the CSIelem index, indicating the optimal nutritional regime. The results of the experiment showed that the difference in biomass between 100% and 50% Hoagland was only 9%. The addition of fulvic acids to 50% Hoagland completely leveled this difference, increasing the biomass to the level of 100% Hoagland. Fulvic acids improved the absorption of macro- and microelements from the depleted environment, which was confirmed by the growth of CSIelem for these elements. At the same time, a decrease in the content of mesoelements (Ca, Mg, S) was observed. Fulvic acid additives allow reducing the share of mineral fertilizers (up to 50%) without losing yield and nutritional value. To optimize the absorption of mesoelements, additional application of calcium, magnesium and sulfur salts to the nutrient solution or through foliar feeding is recommended.