Spatial distribution of livestock concentration areas and soil nutrients in pastures

Authors: Sanderson, Matt; FELDMANN, C - University Of Kiel; Schmidt, John; HERRMANN, A - University Of Kiel; TAUBE, F - Christian Albrechts University

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2009
Publication Date: 5/1/2010
Citation: Sanderson, M.A., Feldmann, C., Schmidt, J.P., Herrmann, A., Taube, F. 2010. Spatial distribution of livestock concentration areas and soil nutrients in pastures. Journal of Soil and Water Conservation. 65(3):180-189.

Interpretive Summary: Grazing livestock often congregate at waterers, feeding structures, or shaded places in pastures. Vegetation in these areas can be destroyed by trampling, and the compaction of soil reduces water infiltration and increases soil erosion, which eventually leads to more runoff water with higher nutrient levels. Our objective was to determine where livestock concentration areas occurred in pastures on grazing farms, their number and size, and the levels of soil nutrients. Our research during two years on five farms in Maryland, Pennsylvania, and New York demonstrated that feeding areas (e.g., concentrate, hay, mineral feeders) accounted for the largest amount of pasture area affected by livestock trampling and congregation. Livestock concentration areas often had higher levels of soil nutrients compared with less disturbed parts of the pasture; however, important exceptions occurred. Eroded sites sometimes had lower soil nutrient levels than less disturbed pasture areas. Most livestock concentration areas were small, isolated, and often surrounded by vegetation, which would buffer surface water runoff. The spread of these areas, however, would worsen spatial variation in soil nutrients, provide sites for weed invasion, and encourage soil erosion.

Technical Abstract: Livestock congregate at feeders, shades, or other sites in pastures, which severely disturbs soil and vegetation leading to erosion and nutrient runoff. Our objective was to determine the extent and spatial distribution of soil nutrients in livestock concentration areas in pastures. We georeferenced and measured the size of all livestock concentration areas on five farms (four grazing dairies and a beef farm) during 2 yr. Selected concentration areas were soil sampled to 0 to 5 and 0 to 15 cm (0 to 2 and 0 to 6-in) depths to compare nutrient levels with paired unaffected areas of the pasture. On two farms, we sampled three concentration areas more densely [20 to 25 samples to a 5-cm (2-in) depth distributed on each of five 100-m (328-ft) transects] to measure spatial distribution of soil nutrients. On one farm we installed runoff plots at three landscape positions at two concentration areas to measure nutrients in surface water runoff from simulated rainfall. On the five farms, concentration areas occurred most frequently at paddock gates (38% of sites), whereas feeding sites accounted for the most pasture area affected (48% of area). Most concentration areas were small (mean area 170 m**2; 1833 ft**2), isolated (mean, 91 m from a water body; 298 ft), and surrounded by vegetation, which would buffer potential surface runoff losses. Soil nutrient levels usually were higher in concentration areas than unaffected areas of the pasture; however, exceptions occured on some eroded sites. Soil within 20 to 40 m (66 to 132 ft) of concentration areas was enriched in P, which contributed to higher P concentration in the runoff compared with unaffected areas of the pasture. Unbuffered sacrifice paddocks with high or extremely high levels of soil P represented a direct threat to surface water quality though many concentration areas were buffered against this risk. Generalizations about environmental risks associated with livestock concentration areas are not straight forward but must consider location on the landscape and potential connections to emphemeral streams and vegetated areas (buffers) surrounding these concentration areas.