Br. Ntare et al., PHYSIOLOGICAL DETERMINANTS OF COWPEA SEED YIELD AS AFFECTED BY PHOSPHORUS-FERTILIZER AND SOWING DATES IN INTERCROP WITH MILLET, Field crops research, 35(3), 1993, pp. 151-158
The interaction of cowpea (Vigna unguiculata (L.) Walp.) cultivars wit
h management factors and environments was analyzed in terms of paramet
ers of a simple physiological model. In one set of experiments seven c
ultivars were sown at three rates of phosphorus (P) fertilizer (0, 8 a
nd 16 kg P ha-1). In another set, five cultivars were sown on two date
s relative to sowing of millet (Pennisetum glaucum (L.) R.Br.). All ex
periments involved factorial combinations of management and cultivar t
reatments, and were conducted in 1988 and 1989 at two sites in western
Niger. Seed yield, shoot dry matter, vegetative (D(v)) and reproducti
ve (D(r)) durations were determined and crop growth rate (C) and parti
tioning (p) to seed estimated. Application of P increased seed yield b
y increasing C. As sowing was delayed from 1 to 3 weeks after the mill
et was sown, there was a reduction in seed yield due to decreases in C
. D(v) and D(r). Variation in cultivar performance across years was ma
inly a function of C and partitioning. In both experiments the C of th
e landrace Sadore Local was greater than that of other cultivars, alth
ough the partitioning to seed of this cultivar was unstable due to var
iable control of insect pest damage. It is concluded that the primary
causes of G X E interactions were differential canopy development and
insect damage effects. Therefore in the development of cowpea cultivar
s for intercropping with millet, emphasis should focus on light captur
e capabilities. Improved yields would then seem possible with most cul
tivars, providing insect damage is controlled.