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Title: SPATIAL DISTRIBUTION OF NITROGEN ON GRAZED KARST LANDSCAPES

Author
item Boyer, Douglas
item ALLOUSH, GHIATH - VIRGINIA TECH

Submitted to: The Scientific World
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2001
Publication Date: 3/15/2002
Citation: Boyer, D.G., Alloush, G.A., 2002. Spatial distribution of nitrogen on grazed karst landscapes. The Scientific World, 1(82):809-813.

Interpretive Summary: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about eighteen percent of the Region's land area. An estimated one-third of the Region's farms, cattle, and agricultural market value are located on karst terrain. Mean nitrate concentrations in several karst springs in Southeastern West Virginia exhibit a strong linear relationship with percent agricultural land cover. Development of best management practices for efficient nitrogen use and reduction of outflow of N to water from karst areas requires knowledge about nitrogen dynamics on those landscapes. We studied the terrestrial distribution of nitrogen on a grazed karst sinkhole landscape and the associated export of nitrogen in internal drainage water. Accumulation of mineralized nitrogen and carbon in the surface soil layer near sinkhole drains may be a result of transport of animal manures by hydrologic processes and by the animals themselves. Best management practices that control delivery of those byproducts to sinkhole drain areas may be the most effective strategy for protecting groundwater quality in karst areas.

Technical Abstract: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about eighteen percent of the Region's land area. An estimated one-third of the Region's farms, cattle, and agricultural market value are located on karst terrain. Mean nitrate concentrations in several karst springs in Southeastern West Virginia exhibit a strong linear relationship with percent agricultural land cover. Development of best management practices for efficient nitrogen use and reduction of outflow of N to water from karst areas requires knowledge about nitrogen dynamics on those landscapes. Water extractable NO3-N and NH4-N were measured along transects at four soil depths in two grazed sinkholes and one ungrazed, wooded sinkhole. Distribution of soil NO3-N and NH4-N were related to grazing pressure and to topographic and hydrologic redistribution of soil and fecal matter in the grazed sinkholes Karst pastures are characterized by under drainage and funneling of water and contaminants to the shallow aquifer. Control of NO3-N leaching from karst pasture may depend upon management strategies that change livestock grazing behavior in sinkholes and management strategies that reduce the opportunity for water and contaminants to quickly reach sinkhole drains.