1. a Agronomy Department , Embrapa‐Soja , Caixa Postal 231, Londrina , CEP 86001–970 , PR , Brazil
2. b Soil Science Department , North Carolina State University , Raleigh , NC , 27695–7619
3. c Agronomic Division, North Carolina Department of Agriculture , Raleigh , NC , 27607–6465