Studies on the Increase in Protein Yield of Soybeans : I. Dry matter production of soybean varieties under late-planting culture

Abstract

The investigation was made to clarify the characteristics of dry matter production of high yielding soybean varieties as a way to increase protein yield per unit land area under late-planting culture. Soybeans were planted on late in June. High grain yields were obtained in the varieties which showed high dry matter production after the unfolding time of terminal leaves. The dry matter production after the terminal leaves unfolding time was closely related to the leaf area duration (LAD), and in the varieties which showed higher LAI than 3 that was also highly correlated to the NAR. Under the late-planting culture the growing period is shorten due to the high temperature and the short day length, consequently, the grain yield is kept at lower level, therefor, it is necessary to extend the period of vegetative growth and ripening by introduction of an indeterminate growth habit gene to the varieties. Some of Korean varieties showed high adaptability to the late-planting culture. The leaf area duration per unit grain weight was smaller in the varieties having high photosynthetic rate per unit leaf area than in the low photosynthetic varieties, so it can be considered that the high photo-synthetic varieties have high possibility to increase the yields by increase the LAD. The ratio of photosynthetate distributed to the seeds was higher than that to the pod shells in the high yielding varieties.