Optimal feeding of field-grown plants is thought to be a key factor modifying their growth and development. Natural biostimulants, foliar fertilizers and plant growth regulators have been applied in horticultural production; however, their effect varies depending on the plant species treated, and those have been mainly cucumber, tomato, pepper, potato, and melon. The aim of the study was to evaluate the effect of preparations produced through nanotechnology on the yield and fruit quality of

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... t pepper grown under cover. The experiment comprised plants grown in three different combinations: combination I (plants treated with 2 kg ha -1 Nano Active); combination II (plants treated with 1% Nano Active Forte + 4 kg ha -1 Nano Active Forte + 2 kg ha -1 Nano Active, a single treatment carried out at the initial stage of fruit formation); and combination III (the control, where all plants were sprayed with water). The obtained results showed that Nano Active Forte foliar treatment of sweet pepper plants significantly increased fruit yield in protected cultivation. Supplementation with foliar fertilizers modified the fruit chemical composition. Application of the Nano Active Forte preparation led to an increase in dry matter content as well as in the concentrations of total sugars, vitamin C and carotenoids. Applications of Nano Active Forte and Nano Active enhanced the potassium and phosphorus contents, while the concentrations of nitrates and calcium remained at the same level regardless of the preparations used. Ke y wor d s: foliar feeding, Nano Active fertilizer, pepper fruit