Due to the wide range of cultivation of alfalfa and increasing the efficiency of its use in modern agriculture, it is necessary to introduce varieties of a new generation with a wide amplitude of resistance to abiotic stress factors. The development of methods for cultivating variegated alfalfa of the Dariya variety involves the use of reserves of photosynthetic activity to increase its productivity. Therefore, the aim of the research was to determine the optimal sowing period for variagated

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... alfa, at which high yields could be formed due to the better use of the photosynthetic function of plants. The experiment was conducted on the experimental field of Penza Agricultural Institute a branch of the Federal Center for Bast Crops in 2017-2019. The soil was leached chernozem (black soil). Four sowing periods were studied: the first early spring (May, 1-10), coinciding with the physical ripeness of the soil the second late spring (May, 20-30) the other two were carried out in the summer period: the third June, 1-10 and the fourth in 30 days after the previous one. The years of the research were characterized as dry. The most optimal conditions for the development of the assimilation surface of plants of the first year of life were formed in early spring crops, where the leaf area was the largest 30.5 thousand m2/ha. As the growing season decreased, a 1.5 times decrease in the leaf surface index was observed. The most intensive formation of the assimilation surface took place in 2017 and its area was 35.8...19.7 thousand m2/ha, reaching its maximum during early sowing. In the same year, the highest value of photosynthetic potential of 1001...2638 thousand m2 day/ha was noted. On average, over three years, the maximum potential of 2129.3 thousand m2day/ha was formed in plants during sowing in early spring, and the net productivity of photosynthesis was in the range from 0.87 to 0.93 g/m2 day. The highest index was established during early sowing, which contributed to the accumulation of 2.0 t/ha of dry matter.