Water relations of three cowpea cultivars (Vigna unguiculata, L.)

Abstract

The effects of soil water stress imposed at different growth stages of three cowpea varieties, namely, ‘Adzuki’ (an erect type), ‘Ife Brown’ (semi erect) and ‘New Era’ (a spreading type) on growth, floral abscission and yield were investigated in the greenhouse. Stomatal density, aperture and behaviour as influenced by soil water potential was also evaluated. Root system development, grain yield, soil water content and potentials were determined in a field experiment. Soil moisture stress significantly reduced the growth and yield (34–46%) of the three cowpea cultivars. Although grain yield reduction was highest (36.8%) when stress was imposed at flowering/podding stage for ‘Ife Brown’, the variety New Era showed no reduction in yield. Floral abortion which increased with a decrease in matric potential may also be linked with imperfect aeration conditions. The choice of these cultivars for intercropping purposes should take cognisance of depth of rooting, lateral root spread, and root density, which affect water extraction at different soil depths, leaf area index, stomatal density, aperture and behaviour to decreased soil water potential all of which differed widely amongst the cultivars.