The possibility of an earlier and more accurate prediction of protein accumulation in grains of different varieties of spring barley of steppe and Western European ecotypes was investigated. The experiments were conducted in the central part of the Voronezh region in the Research Institute of the Central Research Center “Kamennaya Steppe” in 2019–2021. Basically, a positive and high correlation was found between the nitrogen content in the soil and the elements of productivity, which allowed us to judge the importance of mineral nutrition for the formation of grain productivity of barley. In crops of barley varieties without the use of fertilizers in all phases of plant development, the production process, depending on the nitrogen content in the soil, was more intense than in variants with the use of fertilizers. With the use of fertilizers, the intensity of the production process decreased by 5.5% during tillering and by 25.0% during the earing phase. A fairly close positive correlation was noted between the indicators of stem length (r = 0.66–0.68), productive stem (r = 0.52–0.59) and yield (r = 0.78–0.79) with nitrogen content in the soil from the tillering phase to milk ripeness in both non-fertilized and fertilized variants. A positive correlation of nitrogen content in leaves with a mass of 1000 grains was revealed: r = 0.60, 0.50–0.70, respectively, in the experimental variants. In 2021, provided with moisture, the nitrogen content in the leaves in the fertilized version was 30.8% in steppe samples and 11.8% in western samples compared with the control. The efficiency of fertilizers in the conditions of arid 2019 was reduced to 7.1–8.1%. On average over the years, when analyzing the indicators of leaf diagnostics, the effectiveness of fertilizer application in steppe varieties was 20.3, 21.1 and 8.9% in the phases of tillering, earing, and milk ripeness, while in Western varieties it was significantly less – 10.4, 11.4 and 6.1%. The maximum effect of the use of fertilizers for the grain mass index per 1 m2 was obtained in the dry 2019: 27.0 and 34.7%, respectively, depending on the group of varieties (steppe and western). The indicators of protein content in grain and its vitreousness of steppe varieties significantly exceeded the indicators of Western varieties by years and variants of the experiment. It has been shown that the use of mineral fertilizers at a dose of N60P60K60 when sowing in arid conditions was effective for barley cultivation. This technique increased the yield and weight of 1000 grains due to the high accumulation of nitrogen in the leaves by the end of the growing season, which further contributed to an increased accumulation of protein in the grain and its vitreousness, especially in varieties of steppe origin.
