1. a Department of Natural Resource Sciences and Landscape Architecture , H.J. Patterson Hall, University of Maryland , College Park, MD, 20742 Phone: Fax: E-mail:
2. b Department of Natural Resource Sciences and Landscape Architecture , H.J. Patterson Hall, University of Maryland , College Park, MD, 20742 Phone: Fax: E-mail:
3. c USDA-ARS , Animal Manure and By-Products Laboratory Bldg. , 007, Room 013, Beltsville Agricultural Research Center-West, Beltsville, Maryland, 20705 Phone: Fax: E-mail: