SOYBEAN RESEARCH

differences between 60 and 80 cm ridge
width for the studied soybean traits.
Since the ridge width played a
major role in intra- and inter-specific
competition between the same and two
species for solar radiation, respectively, it
is expected that there was more shading
around soybean plant that grown in 60 or
80 cm ridge width and thereby soybean
plant suffered from mutual shading
compared to those grown in 70 cm ridge
width. Mutual shading is known to
increase the proportion of invisible
radiation, which has a specific elongating
effect upon plants (Chang, 1974). So, the
observed response in soybean plant
height that grown in 60 or 80 cm ridge
width could be primarily attributed to an
increase of internodes number and
elongation of soybean plant as a result of
increasing plant hormones.
On the other hand, soybean seed
yield and its attributes were affected
severely by the narrowest or widest ridge
width that may have cooler canopy
temperatures as a result of low light
intensity (Table 1) and retain moisture
longer which increased the probability of
foliar disease problems compared to
other ridge widths. Growth and
development of some plant species is
regulated more by synergism of
temperature and light (White and
Warrington, 1988). Clearly, number of
branches per plant, pod and seed yields
per plant and per ha, 100 seed weight and
harvest index were increased by
increasing ridge width from 60 to 70 cm
or by decreasing ridge width from 80 to
70 cm. This might be due to the
favourable soil condition created by
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spatial arrangement of ridge width (70
cm) resulting in better root development
thereby enabling soybean plants to
uptake more moisture and nutrients
meaning bigger assimilatory system and
hence more dry matter production
leading to higher economic yield.
In this concern, Leuschen et al.
(1992) reported that yields were 8 to 14
per cent greater for soybean grown in 10-
inch rows compared to soybeans grown
in 30-inch rows. Also, De Bruin and
Pedersen (2008) found a 3.7 bushel per
acre yield advantage for soybean grown
in intermediate (15 inch) rows compared
to wide rows (30 inch), the yield
advantage from intermediate row widths
was stable across fields and
environments suggesting the yield
advantage could be achieved by most
farmers. Corn plants grown in 70 cm
ridge width recorded the highest grain
yield (7.12 ton/ha) compared to the
others. These results reveal that ridge
width of 70 cm formed suitable spatial
arrangement of mixed pattern to decrease
inter and intra-specific competition
between the same and two species,
respectively, for above and underground
environmental conditions to achieve
higher economic yield of both species per
unit area compared to the others. Similar
results were obtained by Porter et al.
(1997) who revealed that an average 7.3
per cent yield advantage of corn for 20-
inch over 30-inch rows
Cropping systems: Intercepted light
intensity within soybean plants, plant
height, number of branches per plant,
pod and seed yields per plant, 100 seed
weight, harvest index, biological, straw