Dry Matter Production, Leaf Area Development, and Light Interception of Cowpea Lines with Broad and Narrow Leaflet Shape1

Abstract

Six field experiments were conducted with cowpea Vigna unguiculata L. Walp.) to determine if production could be increased by changing leaflet shape. In two trials, leaf area and light interception were measured for successive 10 cm canopy layers of two narrowleaf (NL) and two broad‐leaf (BL) lines grown at equidistant spacing. All lines reached full light interception at a leaf area index of 3, and showed similar leaf area‐light interception relationships. Dry matter production and leaf area development rates were compared for F3 populations of a cross between a BL and NL line grown at 25 cm and also 75 cm row spacings. Both populations had similar dry matter production rates and yields in two seasons, although early leaf area development was less and branching more profuse for the NL population. Light supplementation after flowering was provided to the lower canopy by placing white metal reflectors at 45° angle below widely spaced rows of 2 NL and 2 BL lines. This increased yields by 32 and 12% in April and August plantings, respectively, and increased root and nodule production, but consistent differences between NL and BL lines were not observed. All these experiments indicated that narrow leaflet shape per se would not increase the productivity of cowpeas at Ibadan.