1. Dep. of Soil ScienceFederal Univ. of LavrasAv. Doutor Sylvio Menicucci 1001CEP 37200‐000LavrasMinas GeraisBrazil
2. USDA‐Agricultural Research ServiceNational Laboratory for Agriculture and the Environment1015 N. University Blvd.AmesIA50011‐3120
3. Dep. of AgricultureFederal Univ. of LavrasAv. Doutor Sylvio Menicucci 1001CEP 37200‐000LavrasMinas GeraisBrazil
4. Brazilian Agricultural Research Corporation (Embrapa)CEP 35700‐029Sete LagoasMinas GeraisBrazil
5. Purdue Univ.Dep. of Agricultural and Biological EngineeringWest LafayetteIN47907‐2053