Cowpea (Vigna unguiculata) is a heat-loving annual legume with excellent drought tolerance and strong nitrogen-fixing ability. It produces substantial summer biomass and develops a vigorous root system under warm conditions when cool-season legumes often perform poorly. Cowpea is therefore particularly useful in summer cover-crop mixtures following early-harvested crops. It combines especially well with warm-season grasses such as millet and sorghum-sudangrass.