Evaluation of five C4 forages grasses in the tall Fescue Belt

Authors: KEYSER, PATRICK - University Of Tennessee; ZECHIEL, KATELYNN - University Of Tennessee; BATES, GARY - University Of Tennessee; Ashworth, Amanda; NAVE, RENATA - University Of Tennessee; RHINEHART, JUSTIN - University Of Tennessee; MCINTOSH, DAVID - University Of Tennessee

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2022
Publication Date: 8/24/2022
Citation: Keyser, P.D., Zechiel, K.E., Bates, G.E., Ashworth, A.J., Nave, R.L., Rhinehart, J.D., McIntosh, D.W. 2022. Evaluation of five C4 forages grasses in the tall Fescue Belt. Agronomy Journal. 114:3347-3357. https://doi.org/10.1002/agj2.21195.
DOI: https://doi.org/10.1002/agj2.21195

Interpretive Summary: Much of the forage production in the transition zone of the eastern United States is based on a cool-season perennial, tall fescue, however, as a cool-season species, it does not produce well during summer months leaving a gap in pasture productivity which could be filled by warm-season species. Therefore, we evaluated five warm-season forage options in a side-by-side grazing trial, three of which were native warm-season species (switchgrass eastern gamagrass, and a big bluestem/indiangrass blend), as well as bermudagrass and crabgrass. All five forages would improve operational drought resiliency over tall fescue through the summer although, switchgrass may be preferable in such a role. All five forage options could also contribute to alleviating impacts associated with TF toxicity. However, the three native species would allow producers to be off endophyte-infected TF by as much as 29 days sooner and, during a time when toxin levels are elevated. Overall, the three native grasses had the greatest average daily gain, total grazing days, and total gain per acre. Consequently, native warm-season grasses provided enhanced warm-season forage production while promoting drought resiliency in pasture systems.

Technical Abstract: Within the transitional zone of the eastern United States, tall fescue [TF; Schedonorus arundinaceus (Schreb.) Dumort.], a cool-season grass, consists of the preponderance of pasture systems, thereby leaving producers vulnerable to reduced summer forage production and drought. Warm-season forages can complement existing production systems by providing improved drought resiliency and summer forage production. Therefore, we evaluated five warm-season forage options in a side-by-side grazing trial: switchgrass (SW; Panicum virgatum L.), eastern gamagrass (EG; Tripsacum dactyloides L.), a big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L. Nash) blend (BBI), bermudagrass (BG; Cynodon dactylon L. Pers), and crabgrass (CG; Digitaria sanguinalis L. Scop.). Research was conducted 2014 –2016 at two locations in Tennessee: Ames and Highland Rim AgResearch and Education Centers. Weaned beef heifers (237-242 kg initial weight) grazed 1.2-ha pastures with three replications per species and location. Average daily gains (kg d-1) across locations and years were 0.62, 0.41, 0.44, 0.42, and 0.51, for BBI, BG, CG, EG, and SW, respectively. Grazing days (d ha-1) were 412, 459, 455, 664, and 617, BBI, BG, CG, EG, and SW, respectively. Total gain (kg ha-1) was 259, 186, 200, 276, and 315, BBI, BG, CG, EG, and SW, respectively. Each forage provided productive summer pasture that could complement TF, but with very modest rates of gain despite season-long crude protein (CP) averages across all years and forages of 94 (BG)-115 (CG and EG) g kg-1. Comparable range for acid detergent fiber (ADF) was 601 (CG)-680 (SW) g kg-1. Overall, BBI had the greatest ADG, with BG being the lowest. Total grazing days were greatest for EG and SW, with total gain per ha being greatest for SW, with non-native forages being lowest. Consequently, NWSGs had improved warm-season. Consequently, NWSGs provided enhanced warm-season forage production while enhancing drought resiliency in pasture systems in the TB belt.