The Santa Fe River Watershed is a 3,585 square kilometer area in north-central Florida that is currently experiencing increases in surface, spring, and groundwater nitrate concentrations. Approximately 70% of the watershed consists of forested land-uses (i.e. pine plantation, forest regeneration, upland forest, and wetland). The other 30 % of the watershed consists of non-forested land-uses (i.e. row crop agriculture, improved pasture, rangeland, and urban). Dominant soil orders in the watershed include Ultisols (37 % coverage), Spodosols (26 %), and Entisols (15 %), with smaller areas of Histosols, Inceptisiols, and Alfisols. This study was designed to investigate soil nitrate distributions across the range of land-use and soil order combinations that exist in the watershed with a particular focus on comparing nitrate levels in forested versus non-forested land-uses. Soil samples were collected from over 100 sites with a stratified random sampling design from four depths (0-30, 30-60, 60-120, 120-180 cm) in five sampling events (Sept. 2003, Jan. 2004, May 2004, Jan. 2005, and May 2005). Nitrate concentrations for each event showed skewed distributions with many measurements below the detection limit, especially in samples collected from forested land-uses. In general, nitrate was highest in the 0-30 cm layer, in the Jan. 2004 event, and in Ultisols and Spodosols. In terms of land-use, nitrate was considerably lower in the forested than in the non-forested land-uses across all depths, sampling events, and soil orders. These results indicate that forested land-uses were not likely to be contributing to the elevated nitrate concentrations in surface, spring, and groundwater in this watershed.
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