EFFECTS OF PLANTING DATE AND PLANTING DENSITY ON A HIGH YIELDING SOYBEAN CULTIVAR GROWN AT DRAINED PADDY FIELD IN SANYO DISTRICT

Experiments were made in 1981, 1982 and 1984 to study the influence of planting date and planting density on vegetative growth and yield of a high yielding soybean cultivar ‘Tamahomare’ in Sanyo District, the westernmost part of the main inland. Maximum and ripened pod number per unit area and yield correlated with maximum LAI, stem dry weight per unit area and total node number per unit area, respectively. Yield increased linearly with maximum LAI increases until yield got to 596 gm-2 at 9.1 of maximum LAI. Increased vegetative growth brought about greater pod number resulting in higher yield. Grain/stem ratio was negatively correlative with vegetative growth size. Favorable weather condition of this district with high temperature and much sunshine, and well drained, fertile and less water stressing paddy field conditions, seem to have supported the growth of soybean to get high yield. Both early planting and high planting density increased vegetative growth, but yield was increased only by the former treatment. Elongated seed fillig period by early planting seems also to have contributed to the yield increase. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.