Effects of Sowing Time and Planting Density on the Seed Yield of Soybean Cultivar, Tsukuizairai

The objective of this study was to evaluate the optimum sowing time and planting density of soybean cultivar, Tsukuizairai. Field experiments were carried out in the experimental field at Nihon University from 2012 to 2014. When Tsukuizairai were sown in May, the rate of damaged seed by stink bugs and delayed stem senescence increased. In the case of 30 cm row width and 7.5 cm intrarow spacing, marked lodging occurred in the July sowing plots due to the longer stem length and thinner stem diameter. Thus, the optimum sowing time is from June to July, and the optimum planting density is from 11.1 to 22.2 plants per m-2 for soybean cultivar, Tsukuizairai. The protein content of seeds was not affected by sowing time and planting density. However, that of Tsukuizairai was lower than that of Enrei and Tachinagaha. Thus, the subject of the Tsukuizairai cultivation is the production of high protein content seeds in the future.