[1] Univ Minnesota, USDA ARS, St Paul, MN 55108 USA
[2] Univ Minnesota, Dept Soil Water & Climate, St Paul, MN 55108 USA
[3] Univ Limerick, Ctr Res Colloids Soils & Waters, Limerick, Ireland
[4] Univ Bologna, Dept Agroenvironm Sci & Technol, Alma Mater Studiorum, I-40127 Bologna, Italy