1. USDA-ARS, US National Poultry Research Center; 950 College Station Rd. Athens GA 30606 USA
2. Univ. of British Columbia; Dep. of Civil Engineering; Vancouver British Columbia Canada
3. USDA-ARS, Food Animal Environmental System Research Unit; 230 Bennett Lane Bowling Green KY 42104 USA
4. USDA-ARS, Agroecosystem Management Research Unit; 137 Keim Hall, UNL East Campus Lincoln NE 68583 USA
5. Pennsylvania State Univ.; Dep. of Ecosystems Science and Management; 420 ASI Building University Park PA 16802 USA
6. USDA-ARS, Northwest Irrigation and Soils Research Lab.; 3793 North 3600 East Kimberly ID 83341 USA