Dry Matter Yield and Nutritive Value of Cowpea and Lablab in the Southern High Plains of the USA

In addition to fixing N in the soil, legumes can be a good source of forage for livestock. The objective of this study was to assess the dry matter (DM) yield and nutritive value of two warm-season annual legumes (WSAL) as potential new forages for the Southern High Plains of the USA. Lablab bean (Lablab purpureus L.) cv Rio Verde (RV) and Rongai (RO) and cowpea [Vigna unguiculata (L.) Walp.] cv Iron and Clay (I&C) and Catjang (CATJ) were sown for two years at NMSU-Agricultural Science Center at Artesia. Legumes were harvested once in 2008 and twice in 2009 at a maturity stage that ranged from vegetative to 10% green pod. Dry matter yield and nutritive value were analyzed between years, species, and cultivar within species for first cut. Lablab had greater DM yield than cowpea in both years averaging 2.82 Mg/ha for lablab and 1.53 Mg/ha for cowpea at first cut. Among cultivars for first cut, RO had the greatest DM yield of all four cultivars (0.80, 2.26, 2.51, and 3.11 Mg/ha for CATJ, I&C, RV, and RO, respectively; SEM = 0.357). Crude protein (CP) concentration was > 200 g/kg in all legumes, but it was 28.6 g/kg greater in cowpea than lablab. Additionally, NDF and ADF concentrations were lower in cowpea than lablab. Considering the higher DM yield and reasonable nutritive value, lablab has greater potential for forage production than cowpea and could be an additional source of forage for dairy or beef cattle in Southern High Plains of the USA.