Summer Grazing Strategies following Early-Season Grazing of Big Bluestem

Big bluestem (Andropogon gerardii Vitman) has a rapid growth phase that begins in early to mid-June in eastern Nebraska. During this rapid growth phase, rate of biomass accumulation exceeds intake rate of grazing livestock, resulting in low levels of harvest efficiency. To delay the rapid growth phase, big bluestem pasture can be grazed in mid- to late May without affecting herbage yields for the remainder of the growing season. A pasture experiment was conducted in 1999, 2000, and 2001 near Mead, NE. The objective was to determine the effect of timing and frequency of grazing big bluestem pasture, following a May grazing period, on cumulative pregrazing yields, cumulative herbage disappearance, resulting harvest efficiency, leaf/stem ratio, and stand persistence. Yield and morphological characteristics were obtained immediately before and after each grazing period, and basal cover of big bluestem was estimated annually. May grazing had no effect (P < 0.1) on cumulative pregrazing yields and resulted in an increase of cumulative herbage disappearance (3638 vs. 2673 kg ha^-1) and leaf/stem ratio (2.02 vs. 2.83) compared with paddocks with no May grazing. Grazing at the vegetative stage in June compared with the elongation stage resulted in an increase in cumulative pregrazing yields (10774 vs. 9510 kg ha^-1), cumulative herbage disappearance (4116 vs. 3194 kg ha^-1), and leaf/stem ratios (2.57 vs. 1.98). Grazing at the elongation stage in June followed by a grazing period in early August is not an advisable management strategy.