Author : Edi Purwanto

Summary : Two experiments were conducted at the Department of Agronomy, University of the Philippines at Los Banos (UPLB) on October 1989-February 1990 to compare the growth and yield components of soybean cultivars BPI Sy-4, SJ-2, and UP Sy-4 at different levels of simulated drought condition. They also sought to determine the particular stage or stages of growth wherein growth and yield are most affected by drought conditions. Drought stress reduced leaf area, plant height, root dry weight, shoot dry weight, number of branches, number of pods, seed yield, seed weight, and harvest index. It increased root-shoot ratio, accelerated the rate of leaf yellowing, and shortened duration of maturity. The effect of drought stress on growth and yield of soybean was dependent on the level of drought, cultivar, and stage of growth at which stress occurred. Reduction in growth and yield of soybean was greater at higher levels of drought stress. Of the three soybean cultivars, SJ-2 had the lowest reduction in leaf area, seed yield, and weight. It also had lowest leaf yellowing and greatest root dry weight under drought conditions. Drought stress during the later reproductive stages (R4-R6) affected the seed yield more than at the other growth stages.