Relationship between Yield and Vegetative Growth of Thai Soybean Varieties Grown under Different Photoperiods

Abstract

The experiment was conducted in December, 1983 at the greenhouse of the Department of Agronomy, Kasetsart University in Bangkok. Soybean varieties S.J. 2, S.J. 4,accessions KU. 3,KU.4 and KU. 5 were grown in 16 hours photoperiod for 30, 45 and 60 days before subjecting the plants to the normal photoperiod. The yield and yield components of plants which were grown in 16 hours photoperiod for 30, 45 and 60 days and the control were greatly differed from one another. The more vegetative growth the plants obtained before floral induction, the higher the yield, the number of pod per plant, and number of seed per pod. Seed size of plants which were grown under 16 hours photoperiod were significantly greater than those grown under normal photoperiod. Greater vegetative growth and increase in plant size reduced the percentage of flower and pod abortion. It was also found that yield of soybean and vegetative growth before floral induction were positively correlated (r values ranged from 0.79 – 0.94). Therefore, it can be conclusively stated that vegetative growth before flowering is one of the important factors influencing the yield of soybean.