|Franklin, Dorcas - Dory|
|GREEN, JR., J|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2006
Publication Date: 10/27/2006
Citation: Butler, D.M., Franklin, D.H., Ranells, N.N., Poore, M.H., Green, Jr., J.T. 2006. Ground cover impacts on sediemt and phosphorus export from manured riparian pastures. Journal of Environmental Quality. 35:2178-2185.
Interpretive Summary: Maintaining pasture ground cover may prevent degradation of aquatic environments. Scientists from the J. Phil Campbell Sr., Natural Resource Conservation Center, Watkinsville, GA and North Carolina State University cooperated to determine the effect of ground cover on sediment and nutrient export from areas close to streams using simulated rainfall to generate runoff. Plots were on two sites in the North Carolina Piedmont: one with 10% slope and the other with a 20% slope, both with mixed fescue/dallisgrass vegetation. Existing forage stands were modified to represent a range of ground cover levels by establishing 0% ground cover (bare ground), 45% (low cover), 70% (medium cover), and not altering high vegetative cover (95%). The average amount of runoff (rainfall not entering the soil) from bare ground was twice that observed from pastures with greater than 45% cover. Phosphorus dissolved in water and phosphorus bound to solid particles were reduced at least 31 and 82%, respectively with low, medium, and high cover. These results indicate that riparian bare areas have the potential to contribute substantial sediment (>190 lb/acre) amd phosphorus (0.6 lb/acre) to aquatic systems during heavy rainfall events, whereas export may be reduced equally well by 45% cover as by 95% cover. Producers and action agencies like USDA-NRCS can use this information to evaluate site vulnerability to potentially costly losses of water, soil, and nutrients.
Technical Abstract: Maintaining pasture ground cover may be important in preventing environmental degradation of grasslands and associated riparian areas. The objective of this work was to determine the effect of ground cover on sediment and phosphorus (P) export from pastured riparian areas under simulated rainfall events. Plots were established on two sites in the North Carolina Piedmont: a 10% slope with Appling sandy loam soils and a 20% slope with Wedowee sandy loam soils, both with mixed tall fescue (Festuca arundinacea Schreb.)/dallisgrass (Paspalum dilatatum Poir.) vegetation. Existing forage stands were modified to represent a range of ground cover levels: 0, 45, 70, and 95% (bare ground, low, medium, and high cover, respectively). Mean runoff volume from bare ground was generally twice that observed from low, medium, and high levels of cover, which were similar. For all rainfall events combined, export of dissolved reactive P was greatest (P <0.1) at bare ground and was reduced 31% at low cover, which did not differ from medium or high cover. Mean total Kjeldahl P export was greater (P <0.001) from bare ground than from other cover levels at each rainfall event. These results indicate that riparian bare areas have the potential to contribute substantial sediment (>215 kg ha-1) and P (0.7 kg P ha-1) to surface waters during heavy rainfall, whereas export may be reduced equally well by 45% cover as by 95% cover.