Solar radiation is an important environmental factor influencing
seed yield in soybean [Glycine max (L). Merr.]. Our objective was
to analyze the response of soybean seed yield components to light
enrichment initiated at different growth stages. Light enrichment was
imposed on the indeterniinate soybean cultivars Altona and Evans
by installing wire mesh fencing on either side of the center row to
push the adjacent rows aside at different growth stages. Fences prevented
plants in the neighboring rows from encroaching on the growing
space of the center row plants. Pod number per plant and to a
lesser extent seed size accounted for variation in seed yield. Light
enrichment initiated at late vegetative or early flowering stages increased
seed yield 144 to 252%, mainly by increasing pod number.
while light enrichment beginning at early pod formation increased
seed size 8 to 23%, resulting in a 32 to 115% increase in seed yield.
Responses to light enrichment occurred proportionately across all
node positions despite the differences in the time (15-20 d) of development
of yield components at the different node positions. Although
maximum seed size may be under genetic control in soybean plants,
our results suggested seed size can still be modified by the environment
with some internal control moderating the final size of most seeds in
all pods. It indicates that plants are able to redistribute the available
resources to components not yet deterniined, in an attempt to maintain
or improve yield.