Overseeding Eastern Gamagrass with Cool-Season Annual Grasses or Grass–Legume Mixtures

Eastern gamagrass [Tripsacum dactyloides (L.) L.] can serve as an alternative warm-season perennial forage in the southeastern United States. A 2-yr study was conducted to evaluate effects of (i) overseeding with cool-season forages and (ii) N fertilization in the spring on herbage accumulation, nutritive value, and persistence of ‘Highlander’ eastern gamagrass. Overseeding treatments included: control (no overseeding), early-maturing ‘Florida 401’ rye (Secale cereale L.), mid-maturity ‘Wrens Abruzzi’ rye, and a mixture of ‘Wrens Abruzzi’ and ‘AU Red Ace’ red clover (Trifolium pratense L.). During late spring, eastern gamagrass was fertilized with either 67 or 135 kg N ha⁻¹ to evaluate growth response following overseeding and differing N input levels. Herbage accumulation (kg dry matter [DM] ha⁻¹) and nutritive value (in vitro dry DM digestibility and crude protein) were measured during the cool- and warm-season production window. Forage canopy cover and botanical composition determinations measured persistence and compositional change during each growing season. Mob-stocking was implemented every 28 d to simulate rotational grazing. There was no effect of overseeding with cool-season annual grasses or grass–legume mixtures on seasonal eastern gamagrass herbage accumulation or persistence during the trial. Cool-season forage herbage accumulation in this study was limited. Spring N fertilization stimulated a rapid growth response in eastern gamagrass, but N-level effects dissipated as the season progressed. Results indicate that overseeding may be a viable option in eastern gamagrass swards, but given the low level of cool-season forage production observed in this study, evaluation of additional cool-season species/blends and economic viability of this system is needed.