Sediment and nutrient losses from an unimproved, all-year grazed watershed
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Authors: L. B. Owens, W. M. Edwards, and R. W. Van Keuren
Date: 1989
Journal: Journal of Environmental Quality
Volume: 18
Number: 2
Pages: 232-238
Summary of Methods: Sediment losses, nutrient transport and concentrations were determined for an unimproved grassy North Appalachian watershed near Coshocton, Ohio. The site was grazed continuously for 6-years, followed by three years of summer grazing, and finally a 2-year rest period. Average monthly surface runoff and water quality from nearby unimproved pasture watershed and the wooded watershed were collected for comparison.
Article Summary / Main Points: Nutrient concentrations were low regardless of grazing level, except potassium concentrations which were higher under year-long grazing. No seasonal variation was detected. Concentrations of nitrate-N, mineral-N, potassium, calcium, magnesium, sodium and chlorine were similar to or less than the concentrations from a nearby untreated wooded watershed. As grazing pressure increased, runoff from pastures contained greater potassium, total organic-C and organic-N, and lower calcium, magnesium, and sodium concentrations. Regardless of grazing system, sediment concentrations and transport rates were greatest during July and August. Sediment concentrations and transport increased with grazing pressure, but remained well below acceptable pollution limits.
Vegetation Types: Other (includes Forest and Eastern)
MLRA Ecoregions: 114A Southern Illinois and Indiana Thin Loess and Till Plain, Eastern Part 124 Western Allegheny Plateau
Agrovoc Control Words: Riparian zones Grazing Water quality
Article Review Type: Refereed
Article Type: Documented Case History
Keywords: sediment load, pollution, stream degradation, grazing season, water quality, potassium, storm runoff
Annotation: The results from this non-replicated, 12 years study are applicable only to this riparian area and grassy or wooded pasture in Ohio. As with all grazing research results apply most directly to similar landscapes, seasons, livestock types and weather conditions. The results of the study in regard to surface runoff remaining at acceptable levels and increasing with precipitation are consistent with those from Owens et al. (1992, J Environ Qual 21: 607-613, available in the RSIS database). Owens et al. (1996, J Soil Water Conserv 51:90-94, and 1997, J Soil Water Conserv, 52:194-197, both available in the RSIS database) also found that both fencing livestock off of the riparian area and changing from year-long grazing with winter feeding to a summer grazed rotation system decreased sediment losses. Addition research with replication across space and treatments is required for this to be applicable on a larger landscape level.
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