Crop is commonly grown in intercrop combinations
of which cereal/legumes are the most
widespread in tropical countries. The availability
of low light intensity due to shading is the critical
factor in determining legume yield in intercropping.
The experiment searches of better soybean
cultivar for intercropping. A field experiment was
conducted at the experimental farm of Khon
Kaen University in 2005. The objectives of this
study were to determine the influence of light
regimes (30% of normal light, 50% of normal light
and normal light) on the growth and yield of four
soybean cultivars (early, medium and late maturity)
under artificial shading at 35 days after seeding
until harvest in the wet and dry seasons. The
results showed that grain yield was significantly
(p < 0.05) decreased under the low light intensity
at 30% of natural light both in wet and dry season.
This was mainly due to low light intensity at 30%
of natural light decreasing the number of pods
per plant in the dry season. For cultivars, grain
yield was significantly difference (p < 0.05)
among cultivars both in the wet and dry seasons.
The cultivar KKU 74 (medium maturity) gave
maximum grain yield both in wet and dry season
under the low light at 30% of natural light. The
KKU 74 cultivar is better adapted to shading environment
than other cultivars. This was due to
the KKU 74 cultivar produced higher chlorophyll
b concentration in leaves after the plant experienced
to shading. This physiological character
can be used for soybean breeding program in
shading tolerance. Therefore, the cultivar KKU 74
had a higher potential yield advantage in intercropping
systems in which low light intensity is a
major limiting factor on grain yield.