RELATION BETWEEN PLANT-DENSITY AND YIELD COMPONENTS IN SOYBEAN PLANTS

A series of experiments were carried out to investigate the appropriate plant density to get average yield of more than 300 kg/10 a continuously and to find the yield components that contribute to higher yield, i.e. the components that tend to prevent yield reduction due to dense planting. The experiments were conducted for three years at the experimental field of Faculty of Agriculture, Tohoku University, where five determinate cultivars (Fig. 1) were grown by single planting per hill with plant density ranged from 3 to 100 hills per m2. The results are summarized as follows: 1. In general, the yield tended to increase with increase of plant density. More than 25 plants per m2 and average maximum 6.0 LAI (Leaf Area Index) were necessary to harvest more than 300 kg/10 a continuously. To obtain high and stable yield under more than 25 plants per m2, special attentions such as progresses of new cultural techniques to lodging or new cultivars with lodging resistance should be paid. 2. Relative values of most growth parameters per m2 at the density of 100 plants/m2, ranged from 2.1 to 3. 4 times larger, comparing with those at the density of 6 plants/m2. Branch and node number per m2, on the other hand, were 5.5 and 6.1 times larger respectively. Therefore the yield increase by denser planting was chiefly suggested to due to the increase of the two yield components. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.