1. USDA‐ARS Sustainable Agricultural Systems Lab10300 Baltimore Ave., Bldg. 001BeltsvilleMD20705
2. Agricultural Analytical Services Lab.The Pennsylvania State UniversityUniversity ParkPA16802
3. Dep. of Plant ScienceThe Pennsylvania State University116 ASI BldgUniversity ParkPA16802
4. Crop Science DepNorth Carolina State University1114 Williams Hall, Campus Box 7620RaleighNC27695
5. Soil and Crop SciencesCornell University515 Bradfield HallIthacaNY14853
6. USDA‐ARS Sustainable Agricultural Systems Lab.10300 Baltimore AveBeltsvilleMD20705