Vhl. Rodrigo et al., Intercropping with banana to improve fractional interception and radiation-use efficiency of immature rubber plantations, FIELD CR RE, 69(3), 2001, pp. 237-249
Intercropping provides an important means of raising not only productivity
and land-use efficiency of smallholder rubber lands, but also income genera
tion during the unproductive immature phase of the rubber tree. To evaluate
current recommendations for intercropping rubber in Sri Lanka, we assessed
the effects of a range of planting densities of banana, the most common co
mpanion crop of rubber on productivity and resource capture. In this paper,
we test the hypothesis that rubber/banana intercropping, even at high dens
ities of banana, results in an increase in biomass per unit land area and p
er crop plant due to an increase in both radiation capture and radiation-us
e efficiency. Five treatments were imposed: sole crop rubber (R); sole crop
banana (B) and three intercrop treatments comprising an additive series of
one (BR), two (BBR) and three (BBBR) rows of banana to one row of rubber.
Dry matter production in the rubber-based treatments was directly related t
o planting density, being least in the sole rubber and greatest in BBBR int
ercrop. A more than four-fold increase in dry matter across treatments deri
ved from an increase not only in light capture (270%) but also radiation-us
e efficiency (RUE, 230%). Neither R nor BR treatment, which is currently re
commended for intercropping in Sd Lanka, achieved full ground cover with fr
actional interception remaining below 40 and 50%, respectively. Fractional
interception was greatest in BBBR treatment and by the end of the measureme
nt period, total intercepted radiation was 23 and 73% greater than that in
the BBR and BR intercrops, respectively. Shade did not limit either photosy
nthesis or growth of component crops in the intercrops, even when planting
density of banana was increased three-fold. In fact, intercropping increase
d growth of both rubber and banana components suggesting that shade associa
ted with the denser intercrop canopies, moderated the microclimate and alle
viated plant stress. These results highlight the potential gains that can b
e made by intercropping and optimising planting density for improved resour
ce capture in immature rubber plantations. (C) 2001 Elsevier Science B.V. A
ll rights reserved.