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Title: GROUND COVER IMPACTS ON NITROGEN EXPORT FROM MANURED RIPARIAN BUFFERS.

Author
item BUTLER, D - UNIVERSITY OF GEORGIA
item RANELLS, N - NC STATE UNIVERSITY
item Franklin, Dorcas
item POORE, M - NC STATE UNIVERSITY
item GREEN, JR., J - NC STATE UNIVERSITY

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2006
Publication Date: 1/10/2007
Citation: Butler, D.M., Ranells, N.N., Franklin, D.H., Poore, M.H., Green, Jr., J.T. 2007. Ground cover impacts on nitrogen export from manured riparian buffers.Journal of Environmental Quality. 36:155-162.

Interpretive Summary: Livestock grazing in riparian areas can significantly impact water quality due to the proximity of livestock to surface waters. However, maintenance of forage ground cover may minimize the impacts of grazing while allowing farmers to utilize forages as part of a rotational grazing system. Researchers from USDA, ARS, J. Phil Campbell Sr., Natural Resource Conservation Center and North Carolina State University examined varying levels of ground cover in riparian pasture in relation to the export of nitrogen in runoff and leachate. While bare ground areas contributed large amounts of nitrogen in runoff, export of nitrogen was greatly reduced when at least 70% canopy cover was maintained. Data suggest that USDA Natural Resource Conservation Service and other land managers can utilize well-managed riparian forages for grazing while limiting the export of nitrogen to surface waters.

Technical Abstract: Maintaining ground cover of forages may reduce the export of nitrogen (N) from pastures. The objective of this work was to determine the effect of ground cover on N export from pastured riparian areas that received simulated rainfall. Plots were established on two adjacent sites in the North Carolina Piedmont: one of 10% slope with Appling sandy loam soils and a second of 20% slope with Wedowee sandy loam soils. Both sites had existing mixed tall fescue (Festuca arundinacea Schreb.) and dallisgrass (Paspalum dilatatum Poir.) vegetation. Existing forage stands were modified to represent a range of cover levels by establishing 4 cover treatments: a) 100% bare soil area (bare ground), b) 55% bare soil area with 45% ground cover (low cover), c) 30% bare soil area with 70% ground cover (medium cover), and d) not altering full vegetative cover plots (high cover). For all rain events combined, mean nitrate-N export was greatest from bare ground and was reduced by 34% at low cover, which did not differ from high cover. Mean ammonium-N export was slightly elevated (~1.37 kg N ha-1) in months when manures were applied and negligible (< 0.02 kg N ha-1) in all other months. For all rain events combined, mean export of total N was greatest from bare ground and was reduced by at least 85% at all other cover levels. Results indicated that cover and time of rainfall following grazing are important determinants of the overall impact of riparian grazing.