Mob and rotational grazing long-term effects on pasture species composition

Authors: Billman, Eric; Andreen, Danielle (elle); WILLIAMSON, JESSICA - Pennsylvania State University; Soder, Kathy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/31/2019
Publication Date: 11/12/2019
Citation: Billman, E.D., Andreen, D.M., Williamson, J., Soder, K.J. 2019. Mob and rotational grazing long-term effects on pasture species composition[Abstract]. Meeting Abstract. p. 1.

Interpretive Summary: No Interpretive Summary is required for this Abstract Only. JLB.

Technical Abstract: Mob and rotational grazing offer conflicting management strategies that potentially affect long term species composition in a mixed pasture. A four-year grazing study was conducted to assess long-term effects on pasture productivity and species composition between rotational and mob grazing. In fall 2014, eight pastures were seeded with a five-species mixture containing orchardgrass (Dactylis glomerata L.), alfalfa (Medicago sativa L.), tall fescue [Schedonorous arundinaceus (Schreb.) Dumort], white clover (Trifolium repens L.), and buckhorn plantain (Plantago coronopus L.). Four pastures were subjected to rotational grazing (whenever plant height reached 25 cm) and four pastures were mob grazed (twice each year). Each pasture was grazed with Angus beef stocker calves. Subsampling for botanical separations to identify species composition was conducted in both the rotational and mob grazing paddocks when mob grazing occurred. Any other present, but non-planted species were grouped as weeds, and dead material was also quantified. At the end of four consecutive years of grazing, we observed significant P < 0.10 changes from initial species composition between mob and rotational grazed pastures. Orchardgrass (78.5%) and tall fescue (36.5%) predominated rotationally grazed systems. However, alfalfa persisted far better under mob grazing (26.2%) than rotational (0.03%). Both white clover and buckhorn plantain steadily declined to less than 5% of the stand by year 3 under both mob and rotational grazing. No differences were observed in weed composition until the final sampling (mob = 15.4%, rotational = 0.15%); more dead material was observed under mob grazing (25.7%) than rotational (4.86%) at the end of the trial. From these data, we concluded that mob and rotational grazing offer unique advantages and disadvantages to species survival, and that both methods should be practiced on an as-needed basis to best manage longevity of mixed species pastures to maintain diverse pastures.