Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/1997
Publication Date: N/A
Interpretive Summary: In the piedmont region of the Southeast, high summer temperatures and water stress limits the productivity of temperate forage species. The major perennial warm-season forage that is productive from June through mid-September is bermudagrass. Its quality, however, is inadequate to support animal daily gains of much over 0.8 lb. Carostan flaccidgrass, also a C4 perennial grass, has been shown to support steer daily gains of 1.8 lb. Yield trials showed flaccidgrass to be sensitive to degree of defoliation. When defoliated from 30 to 6 in., yields averaged 9049 lb/acre vs. 6336 lb/acre when defoliated from 30 to 10 in. Defoliation at 15 to 3 in. gave yields of 6608 vs. 7779 lb/acre at 15 to 6 in. In a regional experiment, yields in North Carolina and in Georgia were highest when flaccidgrass was harvested at flowering (16,964 lb/acre in NC and 11,057 lb/acre in GA) and lowest at 8- to 1-in. defoliation (6825 and 4551 lb/acre at NC and GA, respectively). Nitrogen application rates of 160, 260, and 360 lb/acre increased nitrogen concentrations linearly in the forage. Lower yields at Georgia suggest some problem with adaptation. Flaccidgrass showed high yield potential and yield responses to nitrogen application and warrants further evaluation in the upper South.
Technical Abstract: Carostan flaccidgrass (Penniseum flaccidum Griseb.), a C4 perennial grass, has shown high quality potential, but its yield response to defoliation frequency and nitrogen fertilization has not been reported. Experiment 1 consisted of four cutting treatments of 76 cm cut to a 25-cm (76 to 25) or 15-cm (76 to 15) stubble and 38 cm cut to a 15-cm (38 to 15) or 8-cm (38 to 8) stubble and was conducted near Raleigh, NC. After year 1, defoliation at 76 to 15, compared with 76 to 25, produced highest yields (10,140 vs. 7100 kg/ha; P < 0.001). Defoliation at 38 to 8 cm compared with 38 to 15 cm resulted in higher yields (7405 vs. 8717 kg/ha; P = <0.03). Experiment 2 was conducted at Raleigh, NC (NC) and Watkinsville, GA (GA) and consisted of four defoliation treatments (20 to 5 cm, 51 to 5 cm, boot to 8 cm, and anthesis to 8 cm). Highest yields were obtained at both locations when flaccidgrass was defoliated at anthesis to 8 cm (19,010 kg/ha at NC and 12,390 kg/ha at GA) and lowest at 20 to 5 cm (7648 kg/ha at NC and 5100 kg/ha at GA). Flaccidgrass has high yield potential in NC and warrants further evaluation in the upper South.