Arthur Allen1, Peter J. Kleinman2, Andrew Sharpley2, Rory Maguire3, J. T. Sims4, and Bill Stout5. (1) Univ. of Maryland, E. Shore, 30921 Martin Ct/Crop & Aquaculture, Princess Anne, MD 21853, (2) USDA-ARS, Bldg. 3702, Curtin Rd., University Park, PA 16802-3702, (3) Univ of North Carolina, Dept. of Soil Science, Campus Box 7619, Raleigh, NC 27695, (4) Univ. Delaware, Dept. Plant and Soil Sciences, 531 S. College Ave, Newark, DE 19717-1303, (5) USDA-ARS, Bldg.3702, Curtin Rd., University Park, PA 16802-3702
On the Delmarva Peninsula (DP) (Delaware-Maryland-Virginia), the potential for nitrogen (N) contamination of ground and surface waters and the role of phosphorus (P) on water quality problems such as eutrophication has been documented. High losses of P in runoff are of concern relative to increasing soil P levels and the immediate proximity to the Chesapeake Bay. The Bay and its tributaries are subject to both N- and P-induced contamination since long term application of manure to agricultural soils enriches P pools which are readily available to runoff. The Total Maximum Daily Load agreement imposed in Delaware in 1997, Maryland’s Water Quality Improvement Act of 1998, and the Delaware Nutrient Management Commission in 1999 were all designed to help improve and maintain the quality of ground and surface waters, and to meet or exceed federally mandated water quality standards. These strategies dictate a change in how we apply manures to soils in areas of high animal density such as the DP where poultry litter is often applied at rates to meet crop N requirements. This practice has lead to an over application of P compared to crop requirements and a resulting enhancement in soil P. Thus, a switch from N-based to P-based nutrient management is a strategy that appears to hold promise for reducing P loads, especially on soils already high in P. Therefore, the objectives of this research were to investigate how changing from a manure nutrient management plan based on N, to one based on P, will affect P and N leaching into groundwater, as well as, affects on soil nutrient dynamics.
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