Tuesday, November 14, 2006

Seasonal Dynamics of Phosphorus Sorption and Transport in Two Ditch Soils.

David E. Ruppert1, Brian A. Needelman1, Peter J.A. Kleinman2, and Arthur L. Allen3. (1) Univ of Maryland, College Park, 1112 HJ Patterson Hall, College Park, MD 20742, (2) USDA-ARS-Pasture Systems and Watershed Mgmt Research Unit, Bldg 3702, Curtin Rd, University Park, PA 16802-3702, (3) Univ of Maryland, Eastern Shore, 30921 Martin Court, Crop and Aquaculture Bldg, Princess Anne, MD 21853

Drainage ditches are ubiquitous on Maryland’s lower Easter Shore and many drain to streams that are impaired in key water quality parameters such as phosphorus. We describe an observational experiment measuring seasonal and stormflow dynamics in ditch soil P fractions and sorption. Two ditches are continuously monitored for soil redox potential, and surface water dissolved oxygen, pH, and temperature. Cores are extracted seasonally at 20-m (0-5 cm) and 40-m (0-75 cm) intervals. Samples are horizonated and each separate horizon is characterized for water-extractable P; oxalate P, Fe, and Al; total P, C, N and S, microbial biomass C and P, and acid-volatile and chromium-reducible sulfides. Oi horizons, which contain large amounts of P, ferrihydrite and sometimes iron-monosulfides, will be compared to less active A and C horizons in their ability to sequester or release P as influenced by oxidation/reduction processes. The role of ditch soils in regulating P transport in ditches will be discussed.