Sorghum–Legume Mixtures to Improve Forage Yield and Nutritive Value in Semiarid Regions

Abstract

In a continued search for legumes to grow with forage sorghum (FS) [Sorghum bicolor (L.) Moench] in semi-arid environments, studies in 2019 and 2022 at New Mexico State University Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA, evaluated FS mixed with cowpea [Vigna unguiculata (L.) Walp.], lablab (Lablab purpureus L.), both previously evaluated, and a native legume, big-pod sesbania (Sesbania macrocarpa), for yield and nutritive value in four randomized complete blocks each year. At harvest legume proportions of approximately 15% of the dry matter yield, there were no differences in the yield (mean = 15.97 Mg ha−1, p > 0.40) or land equivalency ratio between sole FS and any mixture or among mixtures; however, the crude protein of FS+Lablab was greater than sole FS, with FS+Cowpea and FS+Sesbania intermediate (67, 77, 87, and 79 g kg−1 for sole FS, FS+Cowpea, FS+Lablab, and FS+Sesbania, respectively; 5% LSD = 14). The neutral detergent fiber digestibility of FS+Sesbania was less than all other treatments (p = 0.0266). Although the sesbania did not improve forage yield or nutritive value when grown with FS and harvested near sesbania maturity, perhaps growing with a shorter season grass and harvesting earlier may show benefit, as sesbania’s nutritive value is known to be greater at earlier stages.