Although only the growth of rubber was assessed in this study, improved
growth in the intercrops over the sole crop had three major implications for rubber
plantations. Firstly, the evaluation index for latex exploitation of rubber is the girth
dimension at 0.9 m height (Liyanage & Peries 1984), and it may be that the increase
in girth in the high density intercrops would have the effect of shortening the
immature growth period, with obvious benefits to farmers' income. Indeed, the
number of tappable trees (i.e. number of trees ready to be exploited for latex)
increased with planting density of banana. Secondly, the close correlation between
girth and latex yield (Thattil et al., 1991; Napitupulu, 1973) suggests that improved
yields may be obtained from rubber in the high density banana systems. However, the
early onset of tapping may limit further girth expansion (Jayasekera et aL, 1994) and
hence the capacity, for latex production in later years, with the result that farmers may
have to make a compromise between the early return and the higher yield from their
mature rubber plantations. Finally, in addition to early latex production, increased
girth dimension and tree height may result in an increase in timber production by the
time of uprooting and so provide a better incentive for replanting senile rubber.