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

Abstract

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.