Effects of water stress at different stages on growth, grain yield and seed quality of cowpea genotypes

Abstract

Effects of water stress applied at three morpho-physiological growth stages, on growth, grain yield and seed quality of contrasting genotypes of cowpea (Vigna unguiculata (L) Walp) were investigated in potted experiments during the 1998 and 1999 cropping seasons. Water stress was imposed by witholding watering for three weeks at the vegetative, flowering and pod-filling growth stages and rewatered thereafter. Water stress applied at the vegetative growth stage significantly reduced growth parameters such as leaf production, branching and plant height when compared with the control and other stress treatments. Water stress at this growth stage also significantly reduced  number and weight of nodules per plant, thereby suggesting a significant decrease in N-fixation. Water stress at any growth stage significantly reduced grain yield with greater effects with stress occurring at flowering and pod-filling stages. While plant nutrients contents (especially N) were significantly decreased by water stress, nutrients composition of the harvested seeds were not appreciably affected thereby indicating that the food quality of grain was not significantly affected. The results of this study have serious implications for delayed planting of short season cowpeas. It is therefore suggested that planting should be done not latter than the 3^rd ween of August for the medium/long duration (³ 65 days) varieties and 1^st week of September for short duration (£ 60 days) varieties to increase the chances for crop to escape drought conditions during flowering and pod-filling stages.  Alternatively, drought-tolerant varieties should be grown. From the result of the present study, IT89KD-374-57, TVX L25 and IT87D-941-1 are promising as drought tolerant varieties.