Harvest Efficiency, Forage Trampling, and Litter Decomposition of Mob Grazing

High stocking density “mob” grazing is a recent phenomenon that is being promoted by a few practitioners, but has not undergone rigorous scientific testing. Producers have claimed “mob” grazing can generate many benefits in terms of forage production and overall grassland health. The objective of this study was to determine the effect stocking density had on harvest efficiency, forage trampling, and litter decomposition. One experimental site was established in eastern South Dakota. Two separate experiments were conducted. The first experiment examined the effect of stocking density on utilization, harvest efficiency, and forage trampling. The experimental design was a completely randomized design with two replications of 5 stocking densities (50, 100, 200, 400, and 800 1,000 kg/ha of live weight). The second experiment was arranged as a 2x2x2x2 treatment design with 2 replications to examine litter decomposition. The treatments were stocking density (high or low), litter type (fresh or old), placement (surface or buried at 7.5 cm), and origin (high or low stocking litter). Treatments were applied in July and August of 2012 and 2013. Biomass samples were collected throughout July and at the beginning of August. Litter bags were placed directly post-grazing in August and collected the following May. Harvest efficiency across stocking density treatments increased linearly (P\u3c0.08), while trampling had a quadratic response (P\u3c0.05). At a 200,000 kg/ha stocking density a threshold for trampling is reached. Utilization across stocking density treatments increased linearly (P\u3c0.001). Utilization is well above the “take half, leave half” grazing recommendation. In 2012 and 2013 there was no difference in decomposition between surface samples in high and low stocking densities. Overall, the percentage of litter decomposition was less in 2013 (Buried 32% and 35%) (Surface 25% and 26%) vs. (Surface 39% and 41%) (Buried 65% and 57%) in 2012. This was likely due to drier conditions following fall 2013 than fall 2012. High stocking density “mob” grazing increased overall utilization and harvest efficiency, but did not increase litter decomposition rate. Producers with less high quality forage can utilize this grazing technique to increase overall harvest efficiency in grazing pastures. However, high stocking density “mob” grazing may not be suitable for all producers or pasture types. More long-term research is needed to evaluate if high stocking density “mob” grazing effects on plant community composition and production