T. U. ESEKHADE ET AL.
Table 4.
Mean yield performance of rubber between 1990 and 2001 as influ-
enced by cooking banana spacing within rubber avenues in an intercrop
system.
Mean annual yield rubber
(kg DRC ha–1·yr–1)
Treatment
1999 2000 2001 Mean
Rubber sole 6.7 × 3.4 m 920.7 1636.9 1736.6 1431.4
Rubber + CB (6.7 × 3.4 m) 1024 1644.6 1745.8 1471.5
Rubber + CB (4.0 × 2.0 m) 1264.8 1835.8 1937.6 1679.4
Rubber + CB (3.0 × 3.0 m) 1049.8 1782.3 1884.6 1572.2
Rubber + CB (2.0 × 2.0 m) 1015.4 1705.8 1810.8 1510.7
LSD (0.05) 20.8 60.3 43.6
Values in parenthesis are the spacings of cooking banana (CB) within the imma-
ture rubber avenues.
associated cropping system (Bekundal et al., 2000) compared to
other cropping systems. This is attributed among other things to
the reduced rate of nutrient loss ( leaching) resulting from early
shading of the surface soil by the banana plant, applied mulch-
ing materials and retention of a large quantity of the plant resi-
due after harvest. However, a lower level of K Stock was re-
corded from the intercropped plots compared to the sole. This
could be ascribed to higher uptake of K and buttressed by the
observed decline in the nutrient as the spacings of the intercrop
component narrowed. Similar observation was made (Wilson,
1985) who reported the storage of a greater proportion of K at
the fruit portion of the plant compared to the other parts. The
implication is that as the fruit are being harvested and taken
away from the farm for consumption, a large amount of K is
being exported from the field and could have some adverse
effect on the development of the rubber.
At the end of the first three years of the intercrops, the ob-
served significantly higher earthworm activities (surface cast,
biomass and abundance) in plots with cooking banana at closer
spacing (Table 2) could be as a result of shade provided by the
banana plant. Since the banana plant were at closer spacing (2 ×
2 m) within the rubber avenue, their leaves could have been
closely interlocked than those at the wider spacing (6.7 × 3.4 m
or 4 × 2 m); thus providing better shade and moisture conserva-
tion—a mechanism known to affect earthworm activities. The
higher earthworm activities observed in the plots with cooking
banana at 4 × 2 m at the sixth year sampling (maturity of plan-
tation) could be ascribed to higher organic matter content in
that plot (Table 1) resulting from the presence of banana plants
and its residue. Thus the observed higher earthworm activities
in the intercrop compared to the sole rubber is in order and its
implications on nutrient cycling and other ecosystem services
are paramount.
Rubber Tree Maturity Period
As shown in Table 3, inter-cropping shortened the maturity
(tappability) period of the rubber tree with higher percentages
of trees attaining maturity in plots with cooking banana at
closer spacings 2 × 2 m and 3 × 3 m compared to others, at five
years after planting. Theis observation could partly be attrib-
uted to improved management methods resulting from inte-
gration of banana (Esekhade et al., 2005) and the early shading
effect of the banana which may have alleviated the commonly
observed radiation induced photosynthic reduction in young
Hevea plants due to easy penetration of sun rays during the
early growth stage under sole rubber cropping system (Senevi-
rathna et al., 2003). Such shading effect is known to promote
leave production, with an associated leave area increase per
plant. Similarly, increased growth rate and dry matter accumu-
lation have been observed among rubber plants intercropped
with cassava (Esekhade, 2004).
The observed non-impairment of rubber tree growth and
maturity by cooking banana, even at closer spacings is in line
with the work of Rodrigo et al. (1997). Also the higher values
of soil nutrient stocks and biological activities in the intercrop
plots (Tables 1 and 2) may have had some positive effect on
the growth of the tree and consequently its maturity. Hauser et
al. (1997) observed a positive relation between earth worm
activeties and crop performance (growth and yield).
Dry Rubber Yield
The positive effect of the intercrops on rubber did not only
enhance the maturity (tappability) period of rubber, but also
affected the latex yield measured as dry rubber content (DRC),
compared to the sole. However, the pattern of DRC values
across the treatments did not follow the trend observed for the
maturity rate (%) of the plants, rather the highest DRC values
were consistently obtained from plots where the trees were
intercropped with cooking banana at 4 × 2 m (Table 4). This
could be due to high soil nutrient concentration under the
treatment (Table 2) aswell as soil biological activities (earth
worm) which may have influence yield. The effect of soil nu-
trient status on dry rubber content is reported by Delabarre and
serier (2002) and Esekhade et al. (2005).
Conclusion
The problem of overcoming the zero income phrase associ-
ated with rubber cultivation has necessitated the research into
the environmental and economic implication of intercropping
of rubber with other early maturing high value crops. This
study revealed that not only did intercropping of rubber with
cooking banana resulted to improve soil fertility in terms of soil
nutrient and biological activities (earth worm) but it also short-
ened the maturity period of the tree compared to the sole.
However, intercropping banana at closer spacings within the
avenue needs further investigation because of the reduction in
soil K stock. From the information gathered from the study,
intercropping with cooking banana at 4 × 2 m within the rubber
avenue ensures better rubber performance in terms of yield and
soil resources conservation.
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