Degree Type


Date of Award


Degree Name

Doctor of Philosophy




This study was undertaken to determine the effects of row spacing, population and planting date on the morphological characters and yield components of soybean cultivars which have indeterminate, semideterminate and determinate growth habits;Experiment I contained two indeterminates, two semideterminates and two determinates, three row spacings (69, 34 and 17 cm) and three populations (33, 63, 93 plants per m('2)). This study was conducted for two years at three locations. Experiment II contained one indeterminate, two semideterminates and one determinate, three populations (33, 63, 93 plants per m('2)) and three planting dates starting in mid-May and at three-week intervals. A 34 cm row spacing was used. A split plot design was used in both experiments;Plant height, number of nodes, lodging and height of the lowest pod increased as row spacing decreased from 69 to 34 cm. The number of branches per plant and percent stand loss decreased as row spacing decreased. There was a decrease in pods per node, but an increase in seeds per pod as row spacing decreased. The yield (per ha) increased while the yield per plant was unchanged as row width decreased. The increased yield was attributed to the greater observed plant survival in the narrower row spacings. When the plants were divided into three sections, decreased row spacings reduced the number of pods and seed yield in the lower section. As population increased plant height, lodging, height of the lowest pod and percent stand loss increased. The number of nodes, number of pods, branches and yield per plant decreased as population increased. The number of pods per node and seeds per pod also decreased as population increased;The indeterminate cultivars had a greater increase in plant height at maturity as row spacing decreased, whereas the determinate cultivars were affected more as population increased. The semideterminates and determinates had no greater yield response than the indeterminates to narrow rows;The upper section contributed approximately 28, 45, and 43 percent to the seed yield of indeterminate, semideterminate and determinate growth types, respectively, while 52, 42, and 38 percent was contributed by the middle section, respectively. The lower section contributed 20, 13 and 18 percent to the total seed yield of the three growth types, respectively;All cultivars required fewer days to flowering and the grain yield was reduced with delayed planting. The number of nodes at maturity decreased as planting was delayed, but lodging was unchanged. The upper section of the indeterminate cultivar was affected less than the semideterminate types by delayed planting.



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James Paul Shroyer



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192 pages