Response of cowpea (Vigna unguiculata) to salinity and irrigation regimes

The effects of salinity and irrigation regimes on yield, growth, and water consumption of cowpea (Vigna unguiculata) were determined in two different experiments. The first experiment focused on cowpea responses to irrigation water with six different levels of salinity (0.7, 2.0, 3.0, 4.0, 5.0, and 7.0 dS m(-1)). In the second experiment four different amounts of water (1.43, 1.0, 0.75, and 0.50 times of depleted water) were applied to cowpea plants. Seed and pod yields of cowpea decreased significantly for the soil salinity values higher than 9.0 dS m(-1). As soil salinity increased, water consumption of cowpea decreased. Therefore, the effect of salinity in lowering evapotranspiration should be considered in irrigation planning and scheduling of cowpea. Either excessive or limited water applications caused decreases in seed and pod yields of cowpea. Yield response factor (KY), from the relationships between relative evapotranspiration and relative yield decrease, were 0.98 and 0.92 for pod and seed yields, respectively. It is concluded that cowpea is tolerant to water stress in terms of seed and pod yields