Effects of Sowing Date and Planting Density on Agronomic Traits, Yield and Quality of High-protein Spring Soybean Quandou 17

In order to study the effects of different sowing dates and planting densities on the agronomic traits, yield and quality of the high-protein spring soybean variety Quandou 17 in Fujian Province, and explore the optimum sowing date and planting density, in 2024, by taking Fujian local variety Quandou 17 as the test material, the two-factor split-plot experiment design was used to set four sowing dates of February 26 (B1), March 4 (B2), March 12 (B3), and March 18 (B4) as the main factors, and five planting density treatments of 180,000 plants·hm⁻² (M1), 240,000 plants·hm⁻² (M2), 300,000 plants·hm⁻² (M3), 360,000 plants·hm⁻² (M4), and 420,000 plants·hm⁻² (M5) as the secondary factors. Then, the effects of different sowing dates and planting density treatments on the growth period, agronomic traits, quality and yield of soybean were analyzed. The results showed that Quandou 17 could mature normally at four sowing dates, with wide adaptability to the sowing dates. If the sowing date was later, the emergence of seedlings was faster, the vegetative growth period and growth period were shorter, and the reproductive growth period was longer. With the delay of sowing date, the plant height, bottom pod height, node numbers of main stem, number of effective pods per plant, grain number of single plant, kernel weight per plant, 100-seed weight and soybean yield all showed the trend of increasing first and then decreasing. The effective branch number and stem diameter showed the trend of decreasing first and then increasing. The protein content and fat content showed a decreasing trend. Under the same sowing date treatment, with the increase of planting density, the plant height, bottom pod height and node numbers of main stem showed an increasing trend, and the effective branch number, stem diameter, number of effective pods per plant, grain number of single plant, kernel weight per plant, 100-grain weight and fat content showed a decreasing trend, while the protein content and soybean yield increased first and then decreased. Based on the performance of agronomic traits, yield and quality under different seeding periods and planting densities, it could be seen that under the existing cultivation conditions in Quanzhou City, Fujian Province, the high-protein spring soybean variety Quandou 17 was suitable for being sown between March 12 and March 18. When the planting density was 240000 plants·hm⁻², the highest yield could be obtained, reaching 2837.63 kg·hm⁻². The variety could be appropriately late sown and sparsely planted, which was beneficial to the yield increase.