PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

The studies were carried out in 1996-2019 at the field experimental station of the Russian State Agrarian University — Moscow Timiryazev Agricultural Academy. The purpose of the research was to assess the productive longevity of various alfalfa varieties cultivated in single-species crops and mixtures with grain grasses with two and three mows per season. It was found that on well-cultivated sod-podzolic soils, alfalfa varied varieties Pastbishnaya 88 and Selena remained in the composition of herbage for 12-14 years in an amount of 35-45%. The productive longevity of red clover did not exceed three years, and white clover took part in phytocenoses in the 24th year of life, but it sharply reduced its share in the yield with a lack of moisture. Timothy grass almost completely dropped out of herbage in the 5 th year of life, and smooth brome showed high resistance when two mows per season were carried out and nitrogen was applied at a dose of 90 kg/ha. Its share in the botanical composition of herbage in the 19th year of life amounted to 71.9%, while without nitrogen it was only 23.3%. Alfalfa-grasses mixtures and single-species alfalfa crops for 12-14 years provided yields at the level of 5-6 t/ha of dry weight with two mows per season and 4-5 t/ha with three mows per season. The yield of herbage with the domination of smooth brome when applying nitrogen fertilizers even in the 15-17th years of life amounted to 4.1 and 3.6 t/ha of dry matter at two and three mows, respectively.