Jm. Watiki et al., RADIATION INTERCEPTION AND GROWTH OF MAIZE COWPEA INTERCROP AS AFFECTED BY MAIZE PLANT-DENSITY AND COWPEA CULTIVAR/, Field crops research, 35(2), 1993, pp. 123-133
Sole and intercropped maize (Zea mays L.) and cowpea (Vigna unguiculat
a (L.) Walp.) were grown to examine how radiation interception and rad
iation-use efficiency (RUE) changed under intercropping. The work also
examined whether intercropping advantage as measured by land equivale
nt ratio (LER) was determined by the yield of the dominated cowpea cro
p. In one experiment, maize plant density was varied and in another, i
t was held constant and 15 contrasting cowpea cultivars were used. Inc
reased radiation interception by the intercrops prior to maize grain f
illing increased biomass production, particularly at the low maize den
sity. There was, however, no intercropping advantage in RUE. Radiation
-use efficiency of the combined intercrop was between that of maize an
d cowpea in sole cropping, the actual Value being determined by the pr
oportion of radiation intercepted by component crops. There was a rath
er small yield advantage of intercropping, with LER of around 1.1 at t
he two higher plant densities of maize. At the low maize density of 2.
2 plants m(-2), however, LER was less than 1.0 despite an increase in
partial LER of cowpea. Cowpea yield and partial LER varied greatly amo
ng 15 cowpea cultivars when intercropped. There were positive but weak
correlations between yield and vegetative dry matter of cowpea, and b
etween vegetative dry matter and radiation transmitted through the mai
ze canopy to the cowpea. Grain yield and partial LER of maize, on the
other hand, were similar when intercropped with different cowpea culti
vars, and hence variation in total LER reflected mostly the Variation
in partial LER of cowpea. It is concluded that maize, except when plan
ted at low densities, will dominate cowpea, and the performance of the
dominated crop (cowpea) will have most influence on total LER.