Mathew M. Haan

Grazing management effects on stream bank erosion and phosphorus delivery to a pasture stream

Nellesen, S. L., Kovar, J. L., Haan, M. M. and Russell, J. R. 2011. Grazing management effects on stream bank erosion and phosphorus delivery to a pasture stream. Can. J. Soil Sci. 91: 385-395. Pasture lands may deliver significant sediment and phosphorus (P) to surface waters. To determine the effects of beef cattle (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, USA. Erosion pins were used to record bank erosion and deposition monthly from May to November of 2005-2007. Soil samples were collected by horizon to estimate P losses. Net bank erosion/deposition and pin activity, calculated as an indicator of bank stability, differed among years and measurement periods within a given year more than among grazing management treatments. Trend analysis of the 3 yr of monthly erosion/deposition data revealed two RS pastures with decreasing bank erosion, suggesting some response to this grazing practice. Mean 3-yr P losses were lower in CSR pastures (5.0 g m-1 stream) than in RS (9.1 g m-1 stream) and CSU (12.2 g m-1 stream) pastures. Both sediment and P losses tended to occur during the winter and early part of the grazing season. In general, our results suggested that at this site bank erosion and P losses to the stream were controlled primarily by natural processes, rather than grazing management.