SOYBEAN RESEARCH

straw and seed yields of soybean were
recorded on the basis of experimental
plot and expressed as ton per ha.
The indicators of competitive
relationship, namely Land Equivalent
ratio (LER) (Mead and Willey, 1980),
Land Equivalent Coefficient (LEC)
(Adetiloye et al., 1983) and Aggressivity
(Agg) (Willey, 1979) were calculated as
follows.
LER = (Y ab / Y aa) + (Y ba / Y bb), where Y aa
- Pure stand yield of crop a (corn),
Y bb - Pure stand yield of crop b
(soybean), Y ab - Intercrop yield of
crop a (corn) and Y ba = Intercrop
yield of crop b (soybean).
LEC = L a x L b, where La - relative yield of
crop a (corn) and L b - relative
yield of crop b (soybean)
Agg = A ab = [Y ab / (Y aa x Z ab)] – [Y ba / (Y bb
x Z ba)] ; A ba = [Y ba / (Y bb x Z ba)] –
[Y ab / (Y aa x Z ab)], where, Y aa -
Pure stand yield of crop a (corn);
Y bb - Pure stand yield of crop b
(soybean); Y ab - Intercrop yield of
crop a (corn); Y ba - Intercrop yield
of crop b (soybean); Z ab - The
respective proportion of crop a in
the intercropping system (corn);
Z ba - The respective proportion of
crop b in the intercropping system
(soybean)
Economical benefit (US$) was
calculated as a difference between total
net returns from intercropping and solid
crops utilizing the prevailing prices of
corn grains and soybean seeds
(Anonymous, 2014) Net returns were
calculated by subtraction the sum of fixed
cost of corn plus variable costs of both
crops. Analysis of variance of the
obtained results of each season was
performed. The homogeneity test was
conducted of error mean squares and
accordingly, the combined analysis of the
two experimental seasons was also
carried out. The measured variables were
analyzed by ANOVA using MSTATC
statistical package (Freed, 1991). Mean
comparisons were performed using the
east significant differences (L.S.D) test
with a significance level of 5% (Gomez
and Gomez, 1984).
RESULTS AND DISCUSSION
Seed yield and its attributes
Ridge width: Intercepted light intensity
within soybean plants, plant height,
number of branches per plant, pod and
seed yields per plant, 100 seed weight,
biological, straw and seed yields per ha
and harvest index, as well as, corn grain
yield per ha were influenced significantly
by ridge width in the combined data
across 2013 and 2014 seasons (Tables 1, 2
and 3). Ridge width of 70 cm increased
significantly intercepted light intensity
within soybean canopy, within soybean
canopy, number of branches per plant,
pod and seed yields per plant, 100 seed
weight, biological, straw and seed yields
per ha compared to the other ridge
widths. Clearly, decreasing ridge width
from 80 to 70 cm increased biological,
straw and seed yields per ha by 7.25, 6.98
and 8.76 per cent, respectively. Also,
increasing ridge width from 60 to 70 cm
increased biological, straw and seed
yields per ha by 10.28, 8.41 and 18.69 per
cent, respectively (Tables 1, 2 and 3). It is
noticed that there were non-significant
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