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Title: Grazing Management Effects on Potential Sediment and Phosphorus Loss from Streambanks

Author
item MOELLER, S - IOWA STATE UNIVERSITY
item Kovar, John
item RUSSELL, J - IOWA STATE UNIVERSITY
item HAAN, M - IOWA STATE UNIVERSITY

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/16/2006
Publication Date: 11/16/2006
Citation: Moeller, S.L., Kovar, J.L., Russell, J.R., Haan, M.M. 2006. Grazing Management Effects on Potential Sediment and Phosphorus Loss from Streambanks. In: ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-SSSA Annual Meeting, Indianapolis, Indiana, November 12-16, 2006. 2006 CD-ROM.

Interpretive Summary:

Technical Abstract: Animal grazing on lands near streams has the potential to contribute sediment and nutrients to surface waters. To minimize the impact of these systems, we must understand the interactions of grazing systems on streambank erosion. In this study, we used six 12-ha grass pastures that were bisected by a 195 m stream segment. Two replications of three management treatments [continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS)] were randomly assigned to the six pastures. Pastures were stocked with 15 fall-calving Angus cows from May to October of 2005. To estimate stream bank erosion within each of the grazing treatments, erosion pins were driven into the ground at 1-m intervals from the stream's edge to the top of the bank on both sides of the stream along 10 equidistant transects in each pasture. Pin length was measured before grazing, monthly during the grazing season, and after grazing ceased to determine sediment erosion and deposition. To determine phorphorus (P) content of the streambank soils, samples were collected less than one meter from the stream channel in each of the pastures. Three cores were collected from each pasture, divided by soil horizon, and composited for analysis. Total soil P values, in conjunction with soil bulk density and erosion pin measurements, will allow us to estimate how much P is being lost to the stream through erosion of the streambanks. Net erosion of streambanks was greatest in September from the CSU treatment, compared with either the CSR or RS management treatments. Total soil P in streambank soil samples ranged from 200 to greater than 500 mg/kg. Therefore, soil lost to erosion associated with large rainfall events could significantly increase P levels in the stream.