Effect of carryover herbage on utilization of little bluestem

Numerous plant factors can affect forage utilization by grazing animals. Objectives of this 3-year study conducted at the Gudmundsen Sandhills Laboratory near Whitman, Nebraska were: (1) to determine if carryover herbage affected utilization of little bluestem (Schizachyrium scoparium (Michx.) Nash) by cattle and (2) to evaluate effects of carryover herbage removal and time of grazing on density and height of little bluestem culms. Experimental design was a split plot in space and time. Main plots were 1-ha pastures replicated 3 times and grazed once each year with 9 yearling steers for 4-7 days during mid-month in June, July, August, or October. Stocking rates were 1.1, 1.5, and 1.6 AUM ha$\sp{-1}$ in 1989, 1990, and 1991, respectively. Split plots were little bluestem plants with high densities (x = 60 dm$\sp{-2}$) of carryover culms. Thirty-six plants per pasture were treated in April 1989 as follows: (1) left intact, (2) carryover culms removed, or (3) all carryover herbage removed. Variables measured included utilization and density and height of current year and carryover culms. Carryover culms reduced utilization more than carryover leaves. Utilization was negatively related (r = $-$0.78, P $\u3c$ 0.01) to density of carryover culms across all 3 plant treatments. For plants from the intact treatment, height of carryover culms (r = $-$0.65, P $\u3c$ 0.01) and length of current year leaves (r = 0.41, P = 0.01) were also correlated to utilization. Utilization of plants from the intact treatment was not affected by time of grazing. Major changes in density and height of carryover culms for plants from the intact treatment were caused by drought conditions during 1989 and a hailstorm during 1990 and not grazing. Grazing during July and August appeared to suppress reaccumulation of culms for plants from the culm removal and total removal treatments. Time of grazing affected height of carryover culms which averaged 27, 25, 21, and 30 cm across plant treatments and years in June, July, August, and October, respectively. Management practices that reduce density and/or height of carryover culms should improve utilization of little bluestem. Following removal of carryover culms, intense grazing during July should slow culm reaccumulation and reduce average height of culms that carryover without adversely affecting plant productivity