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Studies on the influence of the sowing dates of a new introduced crop, the clover (Melilotus hirsutus Lipsky.) on seed yield and elements of its structure, were carried out in the experimental field of the Penza Research Institute of Agriculture in 2009-2013. We studied 7 sowing dates: the first sowing period was carried out when the physical ripeness of the soil was achieved (April 25 – May 1), the second term - when the biological ripeness of the soil occurred (May 5–10). The remaining sowing periods were carried out with an interval of 10-11 days. Winter sowing was carried out in November, at the onset of stable negative temperatures. The seeding rate is 3.5 million germinating seeds per 1 ha, the sowing method is ordinary (row 0.3 m). The soil of the experimental plot is leached chernozem of medium thickness, medium loamy. The hydrothermal coefficient (HTC) varied from 0.22 to 1.50 during the growing season May-September. On average, over three years, the most favorable conditions for the formation of seed productivity and yield of sweet clover formed during sowing in early spring and pre-winter. At these sowing dates, the seed yield for years ranged from 860-1130 kg / ha (in 2011) to 1420-1550 kg / ha (in 2010), an average of three years - 1160-1240 kg / ha and 1367 kg / ha. High yields at these sowing periods were obtained due to structural elements - plant density - 106-120 pcs / m2, plant height - 164-167 cm, the number of productive stems - 3.17 and 3.06 pcs., the number of seeds per plant - 606-638 pcs., the mass of seeds from the plant - 1.23-1.30 g. Strong correlation between elements of the structure of the crop and seed yield was revealed.
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