Interseeding annual warm-season grasses into pastures: Forage nutritive value and yields

Interseeding annual warm-season grasses into pastures often increases forage accumulation. Yet, impacts on nutritive value and yields remain unreported. We analyzed forage collected from five Nebraska and Kansas experiments in 2015-2016 (eight environments) for crude protein (CP), neutral detergent fiber (NDF), and in vitro organic matter digestibility (IVOMD) concentrations and yields. Each experiment subjected perennial cool-season grasses to two harvest frequencies (once at 90 d and twice at 45 and 90 d after interseeding) and four interseeded annual warm-season grass types-pearl millet [Pennisetum glaucum (L.) R. Br.], sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud) de Wet & Harlan], a sorghum-sudangrass hybrid (S. bicolor x S. bicolor var. sudanense), and an unseeded control. Across environments, 90-d CP and IVOMD concentrations increased while CP and IVOMD yields decreased in interseeded pastures when harvested twice, indicating presence of nutritive value-yield tradeoffs. Pastures interseeded with sorghum-sudangrass had greater 90-d IVOMD concentrations and CP and IVOMD yields when harvested once but only greater 90-d IVOMD concentrations when harvested twice compared to unseeded pastures. Interseeding sorghum-sudangrass provided an effective strategy to increase CP and IVOMD yields in late summer in humid environments with tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.] and in mid- and late summer in humid environments with smooth bromegrass (Bromus inermis Leyss.) and semiarid environments with western wheatgrass [Pascopyrum smithii (Rydb.) a. Love]. Interseeding annual warm-season grasses did not consistently increase CP and IVOMD yields in semiarid environments with smooth bromegrass and crested wheatgrass [Agropyrum cristatum (L.) Gaertn.].