LITTLE BLUESTEM TILLER DEFOLIATION PATTERNS UNDER CONTINUOUS AND ROTATIONAL GRAZING

Defoliation patterns of little bluestem [Schizachyrium scoparium (Mich x.) Nash] on tallgrass prairie were compared using continuous and rota tional grazing systems on six 24-ha pastures for each system over a ra nge of stocking rates (0.28 to 0.49 AU ha-1) in 1991 and 1992. We test ed the generalization that rotational grazing provides greater manager ial control over the frequency, intensity, and uniformity of tiller de foliation compared to continuous grazing. Rotational system pastures w ere subdivided into 8 paddocks with 4 grazing cycles (3-7 day graze pe riods) per grazing season. Tillers were sampled biweekly in continuous system pastures and at the beginning, midpoint, and end of each grazi ng period in rotational system pastures. Multiple regression predictio n equations were developed for grazed height, number of defoliation ev ents in a grazing season, percent of tillers defoliated per sampling p eriod (of continuous system) and grazing cycle (for rotation system), and number of defoliation events within a grazing cycle (rotational sy stem). Grazed height decreased as stocking rate increased, but was not influenced by grazing system. The number of cumulative defoliation ev ents per tiller increased with increasing stocking rate over the grazi ng season. Under similar stocking rates, a higher percentage of tiller s were defoliated during the grazing season in the continuous than in the rotational grazing system. Within both grazing systems, percentage of tillers defoliated increased with increasing stocking rates. The p ercentage of tillers defoliated biweekly in continuous system pastures was similar over the grazing season; the percentage of tillers defoli ated per cycle increased as grazing periods lengthened in rotational s ystem pastures. A large number of tillers were defoliated during the s econd half of each grazing period. Less than 10% of tillers were regra zed within a grazing cycle, even at the highest stocking rate and long est grazing period. Rotational grazing provided greater managerial con trol over the frequency and uniformity of tiller defoliation; intensit y of tiller defoliation was similar between the 2 grazing systems. We hypothesize higher range condition will be maintained over the long-te rm in rotational system pastures as little bluestem will remain more c ompetitive and productive resulting from fewer defoliation events thro ughout the grazing season.