Features of productivity element formation of the Diplomat soybean variety depending on sowing dates in the Amur Region

Abstract

The research goal was to determine the influence of sowing dates on the formation of productivity elements of the soybean variety Diplomat under the conditions of the Amur Region. The research was carried out in 2024 and 2025 in the experimental field of the Far Eastern State Agricultural University. The research target was the soybean variety Diplomat. The experimental design included five sowing dates: May 2, 8, 17, 25, and 30. The records and observations were conducted according to the field experiment methodology by B.A. Dospekhov and the state variety testing methodology. It was found that plant height varied from 62 to 82 cm with the maximum values recorded at the sowing dates of May 25 and 30. The lower pod attachment height in the variants of May 17 to 30 corresponded to the optimal values for mechanized harvesting (11-15 cm). The number of productive nodes proved to be a stable character (19-21 nodes) and did not depend on the sowing dates. The number of seeds per plant varied from 41 to 50 seeds reaching the maximum at May 8 sowing date. However, the largest seed weight per plant (12.0 g) was in plants of May 25 sowing date that was by 48.4% more than that of the earliest sowing date. The thousand-seed weight ranged from 203.8 to 245.3 g with the maximum value recorded from the plants of May 25 sowing date. Negative correlation was revealed between the seed (pod) number of and the thousand-seed weight which confirmed the compensatory nature of productivity formation (trade-off) under the conditions of limited resources. Seed weight per plant as an integral index of productivity was determined to the greatest extent by the seed number while the influence of height and node number was statistically insignificant.