Paddock size and stocking density affect spatial heterogeneity of grazing
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Authors: M. K. Barnes, B. E. Norton, M. Maeno, and J. C. Malechek
Date: 2008
Journal: Rangeland Ecology & Management
Volume: 61
Number: 4
Pages: 380-388
Summary of Methods: The idea that spatial distribution of grazing utilization would be unaffected by a gradient in paddock size and stocking density under intensive rotational grazing management (IRG) was examined at the Utah Agriculture Experiment Station (37° 30' N; 113° W) in southwestern Utah. IRG treatments were applied representing stocking ratio densities (stocking density/stocking rate) of 16, 32, and 64 in paddocks ranging from 4 ha, 2 ha and 1 ha sized paddocks. Additionally, for grazing distribution comparison, two paddocks were managed under deferred rotation grazing (DRG). The stocking rate was held constant across all treatments (both IRG and DRG) each. Data collection included vegetation transects within each treatment to measure aboveground herbaceous plant biomass and shrub foliage along with systematic sampling of forage utilization using quadrats for determining distribution of grazing.
Article Summary / Main Points: Distribution of grazing was found to be more even across all IRG treatments compared to the DRG treatments. After the second cycle, the evenness of forage utilization in the IRG paddocks declined to levels close to the DRG paddocks. Smaller paddocks or higher stocking densities inhibited patch grazing as animals actually encounter more of the available forage. The use of this two-cycle grazing rotation proved problematic as it increased grazing intensity and did not allow for sufficient regrowth for the second cycle. All paddocks of both IRG and DRG for both years showed a weak tendency for specific locations to be used similarly, indicating perpetual patch grazing. To improve grazing distribution rotational grazing should be timed according the plant regrowth rates relative to precipitation events and not by a calendar-based schedule.
Vegetation Types: Pinyon-Juniper Woodlands (includes juniper woodlands) Ponderosa Pine Woodlands
MLRA Ecoregions: 47 Wasatch and Uinta Mountains
Agrovoc Control Words: Rotational grazing Rangelands Paddock grazing
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: deferred rotational grazing, grazing management systems, intensive rotational grazing, livestock distribution, paddock, short duration grazing, spatial heterogeneity, time control grazing
Annotation: This is a good review of the benefits and implications of subdividing large pastures into smaller paddocks intended for rotational grazing. Seasonal timing of grazing was neglected as a relevant factor in this study, leaving inconsistent and weak differences in distribution and utilization between rotational and continuous grazing management.
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