An increase in resource capture was the principal cause of
the increased productivity in high density intercrops and on average,
radiation and water use in the BBBR intercrop increased by 73% and
140%, respectively, over the BR intercrop. Neither photosynthesis
nor respiration was affected by the increase in mutual shading at the
leaf level. Therefore, increased whole plant photosynthesis and hence
light-use efficiency resulted from the increase in leaf area per plant.
The increase in girth, of intercropped rubber was maintained
throughout the immature phase resulting in an earlier onset of
tapping in the intercrop than in the sole crop rubber. The social
implications of these findings are discussed.