4. Discussion
4.1. Yield advantage of intercropping
Sunflower/soybean intercrops produced more grain yield per
unit area than both sole crops, which indicates that intercropping
is more profitable than sowing a single crop (i.e. LER greater
than one, [8,26]. Over yielding observed in intercrops could be
partly explained by resource use complementarity in time and
space between different crops within intercrops [31]. Yield advantage
of intercropping was due to yield in sunflower which did not
differ from that in sole crops, while soybean yield was signifi-
cantly lower in intercrops (Table 2). Contrasting yield responses
in both crops could be explained by the differences in the canopy
structures of sole and intercrops. On the one hand, sunlight reaching
lower canopy layers would have been greater in intercropped
sunflower due to wider row spacing, thus reducing self-shading
and increasing the interception efficiency. Similar sunflower yields