ARS | Publication request: Grazing management effects on stream bank erosion and phosphorus delivery to a pasture stream

Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2011
Publication Date: July 1, 2011
Citation: Nellesen, S.L., Kovar, J.L., Haan, M.M., Russell, J.R. 2011. Grazing management effects on stream bank erosion and phosphorus delivery to a pasture stream. Canadian Journal of Soil Science. 91:385-395.

Interpretive Summary: To evaluate the effects of cattle grazing management on stream bank erosion and P pollution of streams, six 30-acre cool season grass pastures bisected by a stream were grazed by 15 fall-calving Angus cows and soil losses from banks were monitored. Grazing was managed in one of three ways: i.) continuous stocking with full access to the stream; ii) continuous stocking with stream access limited to a 16 x 80 foot stabilized crossing; or iii) rotational stocking. After three years, we found that stream bank erosion was higher in years with greater rainfall, and significant erosion tended to occur during the winter months more than during the actual grazing seasons. Among the treatments, pastures that were rotationally grazed were less likely to erode. In general, however, our results suggested that bank erosion and P losses to the stream were controlled by natural processes, rather than grazing management, during the first three years after establishment. The results of this work will contribute useful information to cattle producers, local environmental groups, and Cooperative Extension and NRCS personnel interested in reducing the negative effects of agricultural production on water quality.

Technical Abstract: Pasture lands may deliver significant sediment and phosphorus (P) to surface waters. To determine the effects of beef (Bos taurus) grazing practices on stream bank erosion and P losses, three treatments [rotational stocking (RS), continuous stocking with restricted stream access (CSR), and continuous stocking with unrestricted stream access (CSU)] were established in six adjacent pastures along Willow Creek in central Iowa. Bank erosion and deposition were recorded monthly from May to November of 2005-2007. Soil samples were collected by horizon to estimate P losses. Net bank erosion along the entire stream reach was higher in 2005 (-1.29 cm) and 2007 (-0.94 cm) than in 2006 (-0.30 cm), when precipitation was less. Trend analysis of monthly erosion/deposition data revealed two RS pastures with decreasing bank erosion, suggesting some response to this grazing practice. Mean P losses were lower in CSR pastures (2.0 g m-1 stream) than in RS (2.6 g m-1 stream) and CSU (3.0 g m-1 stream) pastures. Sediment and P losses tended to occur during the winter and early part of the grazing season. In general, our results suggest that bank erosion and P losses to the stream were controlled by natural processes, rather than grazing management.