Yield Performance of Cowpea Plant Introductions Grown in Calcareous Soils

Cowpea or southernpea (Vigna unguiculata) is an important legume crop used as a feed for livestock, as a green vegetable and for consumption of its dry beans, which provide 22% to 25% protein. The crop is very sensitive to alkaline soil conditions. When grown at a soil pH of 7.5 or higher, cowpea develops severe leaf chlorosis caused by deficiencies of iron, zinc, and manganese resulting in stunted plant growth and yield reduction. We evaluated in replicated field experiments at St. Croix, U.S. Virgin Islands, and Miami, FL, four PIs and one commercial cultivar, some of which have shown some tolerance to alkaline soils in unreplicated, seed regeneration plots of the U.S. cowpea collection. At both locations, PI 582702 had significantly higher seed protein concentration than the other PIs, averaging 28%. Alkaline soil conditions at St. Croix were severe resulting in average yield of PIs at this location being significantly lower and 69% less than that in Florida. Nevertheless, some PIs performed well at both locations. For example, PI 582605 had significantly higher yield in Florida, whereas in St. Croix, PIs 582605, 582674, and 582702 were the highest yielders. These PIs may serve as an alternative to growers or home gardeners wishing to establish a legume crop in areas where agricultural production is severely restricted by high soil alkalinity.