Mob and rotational grazing effects on mixed pasture forage mass, nutritive value, and species diversity

Authors: Billman, Eric; WILLIAMSON, JESSICA - Pennsylvania State University; Soder, Kathy; Andreen, Danielle (elle); SKINNER, HOWARD - Retired ARS Employee

Submitted to: Crop Science Society of America
Publication Type: Abstract Only
Publication Acceptance Date: 8/10/2020
Publication Date: 11/15/2020
Citation: Billman, E.D., Williamson, J., Soder, K.J., Andreen, D.M., Skinner, H. 2020. Mob and rotational grazing effects on mixed pasture forage mass, nutritive value, and species diversity [abstract]. Crop Science Society of America. p. 1.

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

Technical Abstract: Systems of grazing management are numerous, and known to variably affect the longevity of pastures. Two prominent systems used in the US are mob (ultra-high stocking density) grazing and rotational grazing. However, mob grazing was developed in the western US, with stark contrasts in forage species and climatic conditions than the northeastern US. Therefore, the prolonged effects of mob grazing in the Northeast are currently unknown. Objectives of this work were to compare the effects of mob and rotational grazing in the region on forage mass productivity, forage nutritive value, and species diversity in a mixed sward. This study took place over a four-year period (2015-2018) at the Pennsylvania State University Hawbecker Research Farm. Eight, 0.10-ha plots were established in 2014 as a randomized complete block with four replications, and seeded with alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), orchardgrass (Dactylis glomerata L.), narrowleaf plantain (Plantago lanceolate L.), and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort]. Mob-grazed (MOB) paddocks were grazed twice year-1, (70 – 90-day interval), and rotationally-grazed (ROT) paddocks were grazed four to six times year-1, (when sward height reached 25 cm). Cumulative pre-grazing forage mass (PGFM) of ROT paddocks was greater in three out of four years, and exceeded PGFM of MOB by 2,500 kg ha-1 at the final grazing. Within grazing season, PGFM of ROT was more consistent, varying by only 1,400 kg ha-1 compared to 2,800 kg ha-1 for MOB. Grazing system also altered species composition, with grasses and prostrate legumes declining in the MOB paddocks, and alfalfa declining in the ROT paddocks. Nutritive values were also superior in the ROT paddocks, compared to MOB. These results support ROT being more suitable for more stable, long-term productivity, stand diversity, and nutritive value, compared to MOB