Tuesday, November 14, 2006

Phosphorus Availability Along Two Small Streams in Vermont: Mapping, Characterization and Potential Mobility.

Eric Young1, Donald Ross2, Joel Tilley1, Kristen Underwood3, and Caroline Alves4. (1) Univ of Vermont, Dept of Plant & Soil Science, Hills Agricultural Building, 105 Carrigan Dr, Burlington, VT 05405, (2) University of Vermont, Dept.of Plant & Soil Sci., Hills Building Uvm, Burlington, VT 05405-0082, (3) South Mountain Consulting, 2852 S 116 Road, Bristol, VT 05443, (4) USDA/NRCS, 1193 S Brownell Rd, Suite 35, Williston, VT 05461

Phosphorus (P) mobility is a concern in watersheds draining to Lake Champlain. Soil and sediment-bound P from cropland, riparian areas, and stream banks are important P inputs to streams and the lake. The ability to estimate P loading from erosion is limited by insufficient data on soil series variability along streams, differences in P content, and processes controlling P chemistry and transport. We are performing an extensive remapping, soil sampling, and P analysis in agricultural areas along two small streams, Rugg Brook and Lewis Creek. Soils will be evaluated for NH4OAc-P and water-soluble P.  Additional studies will investigate P solubility under declining soil redox and characterize soil and water P forms. Another outcome of the research will be a high-order soils map with a GIS layer of soil P contents within series. The high order (1:3500) mapping results show that existing soil surveys (1:20000) were not accurate. At the Rugg Brook site, the soil survey completed in 1979 showed the 6 ha study area as having one soil series. The high-order map revealed five additional soil series in the same area, which comprise over two-thirds of the area. Results from the Lewis Creek site also showed several additional soil series that were not included in the original soil survey. Preliminary results indicate that the use of current soil surveys for water quality modeling in some areas may be flawed.