Short duration (≤24 h), high stocking density grazing systems (e.g., mob grazing) mimics historic prairie grazing patterns of American bison (Bison bison), and should minimize selective grazing. We compared mob [125 cow-calf pairs on either 0.65 ha for 12 h; or 1.3 ha for 24 h] vs. rotational [25 cow-calf pairs on 8.1 ha for 20 days starting in mid-May with or without 2,4-D application prior to grazing; and 15 days starting mid-April (no herbicide)] grazing systems based on forage utilization and impact to Artemisia absinthium (absinth wormwood) in a tall grass pasture of Eastern South Dakota. Grass height and density, and Artemisia absinthium patch volume were quantified pre- and post-grazing at sampling points along multiple transects. Mob grazing had >75% forage utilization, whereas rotational grazing averaged 50% (all consumption). Within a grazing season, three grazing systems suppressed Artemisia absinthium patches with rotation/spray (100% decrease) > mob (65 ± 10% decrease) > mid-May rotation (41 ± 16% decrease), whereas Artemisia absinthium patches in the mid-April rotation followed by summer rest dramatically increased in size. Artemisia absinthium patches <19,000 cm3 were browsed, whereas larger patches were trampled in mob-grazed areas, but avoided in rotational grazing. All Artemisia absinthium patches had regrowth the year following any grazing event.
Part of the book: Forage Groups