[Study of some physiological characteristics of Thai soybean varieties SJ 1, SJ 2 and SJ 4 for improving yield]
Aphiphan Pookpakdi | Raweewan Siriprasert
Research was conducted between 1979-1981 to study some physiological characteristics of Thai soybean (Glycine max (L.) Merrill) varieties SJ. 1, SJ. 2 and SJ. 4 and also to determine the possibility of improving yield through cultural manipulation. The drymatter production was high during the vegetative phrase. However, vegetative growth of the three cultivars still occurred after day to floweingresulted in the increase in dry matter, node number plant height and number of branches after plants had flowered. Vegetative growth gradually decreased and completely stopped when the plants completed their flowering at 52 days after emergence (DAE). Reproductive growth started at 42 DAE and became very active after 52 DAE resulted the increase in pod number and seed weight. The response of SJ 1, 2 and 4 soybean to extended day length indicated that the critical day length of these varieties were between 13-15 hours. Extended day length up to 15 hoursrresulted in the delay in flowering and maturity. The result of the study indicated that the effective day length that could delay flowering in soybean should occurred at the basic vegetative phrase especially when unifoliate leaves or first trifoliate leaf are being expanded. This indicates that the induction phase in soybean occurred at the basic vegetative phrase. Regarding cultural practices, plant density showed large influence in soybean yield and yield components especially in SJ 4. The yield of SJ 4 increased from 173 to 1700 kg/ha when the spacing between plant increased from 50-5 cm. The number of pod per plant, and percentage of pod and flower abortion increased as density increased. However, the number of flower per mainstem number of seed per pod and 100 seed weight did not change with plant density
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