Near-Field Deposition of Windblown Sediment during Winter.

Freeze-drying is a process that can degrade exposed aggregates lying on the soil surface in northern climate regions. Soils that undergo freeze-drying are vulnerable to wind erosion with off-site transport of windblown sediment representing both a loss of the soil resource and an environmental concern. Near-field deposition of windblown sediment was observed during the winter of 1995-1996 and 2001-2002 near Morris, MN. Windblown sediment was collected along the boundary of eroding agricultural fields that were in a conventional corn rotation. Sediment was collected by extracting snow cores adjacent to but downwind of the field boundary in March, thus deposition represents seasonal deposition resulting from windblown sediment collecting on the seasonal snowpack. Sediment deposition ranged from 1 to 150 Mg ha-1 across multiple locations. Aggregate size analysis of windblown sediment deposited downwind of the fields revealed that most of the eroded sediment was in the size range of 0.25 to 0.50 mm. Saltation-size (0.1 to 0.85 mm diameter) sediment comprised about 90% of the eroded mass. The results of this study suggests that land managers must be judicious in protecting soils from wind erosion over winter in northern climate regions.