The present investigation was conducted to determine the feed quality of New Sudan grass varieties. On average, the highest plant height was found in Sudan grass variety Nika (274 cm) in 2019-2020. These rates in Sputnitsa and Aleksandrina were loer by 23 and 30 cm, respectevely. The yield of green matter after two cuts in the new variety Nika was 41.0 t ha -1 and 9.59 t ha -1 of hay. These rates in the recognized varieties varied in the range of 35.0-36.0 t ha -1 and 7.98-8.28 t ha -1 . The maximum protein content for varieties Nika, Sputnitsa standard and Aleksandrina were 13.72%, 11.33%, and 11.72%, respectevely. The fiber content in the air-dry matter was 25.20% in Nika, 26.01% in Sputnitsa and 26.03% in Aleksandrina. When determining the presence of metabolizable energy in sheep feed, it was found that the variety Nika contained 2.03 MJ, Aleksandrina -1.96 MJ, Sputnitsa -1.90 MJ in 1 kg of green matter. The new variety Nika also had similar maximum rate in 1 kg of hay and amounted to 8.79 MJ. Among the studied varieties of Sudan grass, the most significant amino acid content was also obtained in the variety Nika. The maximum rate of asparagine and glutamic acids in the air-dry matter of this variety was 1.84% and 1.38%, respectively. The dry matter of the variety Nika contains high level (0.5-1.0%) of the amino acids proline, glycine, alanine, valine, leucine, phenylalanine, and lysine. A significant amount of threonine, serine, isoleucine, tyrosine, and arginine amino acids (0.3-0.5%) was obtained in the air-dry matter of Sudan grass. The content of methionine and histidine amino acids in hay was low (less than 0.27%).

The goal of the research is to study new forage crops, the characteristics of their growth, development, crop formation and identifying the most promising ones for growing in the conditions of the Novgorod Region. The ecological trial of forage sorghum of North Caucasus Federal Agrarian Research Centre selection included: Echinochloa frumentacea of Stapaiz variety, Setaria italica var. mocharicum of Stamoga variety, Setaria italica subsp. italica of Stachumi 3 variety, Sudan grass of Sputnitsa, Zemlyachka, Zlata, Sofiya and Nika varieties, sweet sorghum of Galiya and Larets varieties, hybrids Silosnoe 88 and Yarik, Sorghum-sudangrass hybrids Navigator, Gvardeets, Boyarin, Barin. Hot temperature of June and July accelerated the development and growth rates of plants in July and August. On July 27, the height of sorghum crops increased to 180-210 cm; at the end of August, the studied plants reached a height of 240-270 cm. During the first ten days of September, after-grass of most sorghum species can be harvested after the first cut in the second half of July. On average, during 2020-2021 the fresh yield of Echinochloa frumentacea of Stapaiz variety reached 57.8 t/ha, Setaria italica var. mocharicum of Stamoga variety reached 33.6 t/ha, Setaria italica subsp. italica of Stachumi 3 variety reached 42.6 t/ha at the end of August. The productivity of Sudan grass during this period was 36.4-59.2 t/ha, Sorghum-sudangrass hybrids -53-74 t/ha, sweet sorghum -54.4-116.7 t/ha. During the years of the study, the seeds of Echinochloa frumentacea, Setaria italica subsp. italica and Setaria italica var. mocharicum ripened. The maximum content of crude protein in the dry matter of the mass was obtained from Setaria italica subsp. italica -9.82%. The minimum presence of crude fiber (30.3%) and the greatest number of forage units in one kilogram of feed (0.74) was found in sweet sorghum of Galiya variety. The maximum amount of metabolizable energy (9.01-9.55 MJ/kg) was obtained from sweet sorghum of Galiya variety, Sudan grass of Zemlyachka variety and Sorghum-sudangrass hybrid Navigator.

Aim of the research is to study the parameters of yield and investigate the quality of green mass, also what is of great importance is determining of the level of true heterosis of the main quantitative traits in new sorghum-sudank hybrids created on a great sterile basis at the North Caucasus Federal Agricultural Research Center. The parental forms of the new hybrids are characterized by high combining ability, a rather great and very significant level of the true heterosis, which makes it possible to obtain hybrids with a high rate of initial growth and post-abortion growth, which have high drought tolerance and give stable green mass yields in the various soil and climatic conditions. The best of them may possess a short sprouting period that includes the appearance of good brooms, which at the Gvardeets was 50 days, Boyarin-56 days. During mowing periods in these hybrids, in comparison with the average values of the parental forms, the duration of the vegetation period did not extend too much. The Fakel hybrid had a similar period of 65 days. Plant height may also depend on genotypes and is inherited with a high degree of heterosis. On the 30th day of the vegetation, the maximum plant height (82.0-86.5 cm) was obtained from hybrids Gvardeets, Boyarin, Oda and the standard Navigator. In 2018-2019 in total, for two mowing, the highest yield of green and dry mass was obtained from new sorghum-Sudan hybrids Boyarin (51.18 t/ha and 11.44 t/ha respectively), Fakel (51.42 t/ha and 11.45 t/ha), as well as the Gvardeets (47.53 t/ha and 11.03 t/ha). These combinations also exceeded the green mass of the Navigator standard by 5.94 t/ha; 6.18 t/ha and 2.29 t/ha. The level of the true geterosis of the green mass in comparison with the averaged values of the parent forms was marked by 22.6 t/ha (78.5%) for the Fakel hybrid, 16.69 t/ha (48.4%) for Boyarin and 11.80 t/ha (33.1%) of the Gvardeets. Hybrids Gvardeets and Boyarin provided the normal and at the same time the highest content of crude protein (10.38-10.54%) in absolutely dry matter. The new sorghum-Sudanese hybrid Gvardeets (Zersta 90C x Sputnitsa) was submitted to the state variety test from 2018. Hybrid Boyarin (A-63 x Sputnitsa) is preparing to transfer to some variety testing according to some value facts.

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Increasing the cultivation area of the most valuable crops, replacing unproductive varieties and hybrids with more productive ones is a significant reserve for strengthening the forage base and improving its quality. Despite the fact that the varieties and hybrids of sorghum of "North Caucasus Federal Agricultural Research Centre" breeding, which were studied in 2019-2020 in the Altai Territory, were inferior to local standards in terms of the duration of the growing season and seed yield, they significantly exceeded them in plant height, yield of green and dry matter, the content of digestible protein in 1 forage unit and metabolic energy. The average two-year rates indicate that the most significant plant height was found in the hybrid of sweet sorghum Yarik (240.5 cm) and the new sorghumsudangrass hybrid Gvardeets (247 cm). The highest yield of green and dry matter were obtained from hybrids of sweet sorghum Yarik (43.0 t/ha and 12.8 t/ha, respectively), Silosnoe 88 (43.6 t/ha and 12.4 t/ha), variety Larets (43.4 t/ha and 12.7 t/ha), undergoing state variety testing Tandem (42.9 t/ha and 12.0 t/ha), as well as the new sorghum-sudangrass hybrid Gvardeets (40.3 t/ha and 11.1 t/ha). The standard Duplet provided 25.7 t/ha of green and 8.5 t/ha of dry matter during the experimental years. In comparison with the standard, these hybrids and varieties exceeded in the content of digestible protein in 1 kg of dry feed by 13-26 g, carotene by 13.9-115.9 g, forage units by 0.01-0.02.