As a result of the experiments carried out in 2020–2022, which were laid at the Bogdanovskoye Agricultural Enterprise LLC in the Staroshaigovsky District of the Republic of Mordovia on the alluvial soil of the Sivin River the influence of the levels of mineral nutrition and foliar feeding with liquid complex fertilizers "Agris" brand "AzotKaliy" on the morpho-biometric parameters of barley plants was established. The fertilization contributed to an increase in plant height by 4.5–9.5 cm and ear length by 0.6–1.5 cm. The highest plant height (73.0 cm), ear length (8.4 cm), grain weight per ear (0.69–0.78 g) and the weight of 1000 grains (39.6–41.7 g) was in the third variant (N60P60K60). Foliar top dressing with "Agris" brand "AzotKaliy" positively influenced the change in the height of barley plants by 2.7–5.9 cm, ear length by 0.7–1.6 cm, grain weight per ear and weight of 1000 grains. A further increase in the level of mineral nutrition (N90P90K90) and foliar fertilizing with "Agris" brand "AzotKaliy" in the amount of 6 l/ha did not contribute to a significant change in the studied parameters. Mineral fertilizers on average over three years increased the yield of barley by 14.6–5.8%, the highest values was after N60P60K60 fertilization. Foliar top dressing with "Agris" brand "AzotKaliy" increased crop yield by 0.31–0.56 t/ha, or 11.4–16.7%, depending on the level of mineral nutrition. The most favorable factors for the formation of the barley crop were after application of mineral fertilizers in the amount of N60P60K60 (3.40–3.95 t/ha) and foliar top dressing of "Agris" brand "AzotKaliy" in the amount of 4 l/ha (3 92 t/ha), this is evidenced by the data of the studied biometric indicators of plants.