Establishment of Annual Warm-Season Grasses in Cool-Season Grass Pastures.

In recent years, pastureland has been diminishing in the central Great Plains, yet forage demand remains high.  In 2015 and 2016, we conducted experiments at six locations to evaluate effects of no-till interseeding of annual warm-season grasses on forage mass in perennial, cool-season grass pastures.  Pastures consisted of smooth bromegrass (Bromus inermis Leyss.) at Mead, NE, North Platte, NE, and Manhattan, KS; tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.] at Parsons, KS; crested wheatgrass [Agropyron cristatum (L.) Gaertn.] at Sidney, NE; and western wheatgrass [Pascopyrum smithii (Rydb.) Á. Löve] at Hays, KS.  Experiments were randomized complete block designs with a split-plot arrangement of treatments and four replications.  Treatments consisted of interseeded annual warm-season grass species (whole plots) and harvest frequencies (subplots).  Warm-season grasses were interseeded into stubble (< 5.0 cm) of cool-season grasses < 7 d after harvesting during flowering and consisted of 1) forage sorghum [Sorghum bicolor (L.) Moench]; 2) sudangrass [S. bicolor (L.) Moench subsp. drummondii (Nees ex Steud.) de Wet & Harlan]; 3) sorghum-sudangrass [S. bicolor × S. bicolor var. sudanense]; 4) pearl millet [Pennisetum glaucum (L.) R. Br.]; 5) corn (Zea mays L.); and 6) a non-seeded control.  Harvest frequencies were 1) once per year at 90 d after planting; and 2) twice per year at 45 and 90 d after planting.  Forage mass depended on year, location, interseeded species, and harvest frequency.  In general, forage sorghum, sudangrass, and sorghum-sudangrass showed the most promise for interseeding to improve forage production of perennial cool-season grass pastures.