Saturday, 15 July 2006

Nitrate-Nitrogen Dynamics in Tributaries and Riparian Wetlands of North Central Florida.

Adrienne E. Frisbee and Clark Mark. Univ of Florida, Dept of Soil and Water Science, 302 NW 2nd St, Gainesville, FL 32601

Nitrate runoff from agricultural systems is an increasing concern because of its potential effect on the health of both humans and ecosystems. Riparian systems have been shown to reduce nitrate concentrations in soil and water as a result of denitrification processes that occur under anaerobic conditions. The Santa Fe River Basin in north central Florida contains many tributaries that drain adjacent agricultural systems to the Santa Fe or New Rivers. Increasing evidence suggests that nitrate concentrations in surface and groundwater are increasing, and in some instances have exceeded EPA safe drinking water standards. In an effort to better understand the nitrate dynamics and denitrification potential of channel bed and riparian wetlands along tributaries of the Santa Fe River, a two year research investigation was established at Boston Farm-UF/IFAS Santa Fe River Beef Research Unit (SFRBRU). To better understand nitrate dynamics on the site and denitrification potential in this landscape, monitoring of two tributaries that occur on the SFRBRU was conducted. One stream is surrounded by low intensity pasture and hardwood forest, and tends to have nitrate concentrations less than 1.0 mg/l. The other tributary has nitrate concentrations that range from 7mg/L at the headwaters to 3mg/L where the tributary discharges to the Santa Fe River floodplain. The headwater of this tributary appears to be within an intensive plant nursery and then flows through low intensity improved pasture on the SFRBRU. Preliminary results indicate that along the high nitrate concentration tributary, concentrations were reduced between 67% and 28% from headwaters to discharge. If monitoring data suggests significant denitrification potential associated with wetland soils, we will make recommendations for integration of wetlands along the water courses.

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