Soil compaction is becoming an increasing concern because of the increasing weight of farm equipment, and the use of heavy earth moving equipment to reclaim mined areas for agricultural purposes. If axle loads are less than 4.5 Mg (5 tons), compaction will probably not extend deeper than 30 cm (12 inches). This compaction can both increase and decrease crop yield depending on soil texture and growing season precipitation. Axle loads in excess of 9 Mg (10 tons) can cause compaction to a depth of 60 cm (24 inches) and result in significant yield decreases. Freezing and thawing, or mechanical soil loosening, may not be very effective in ameliorating deep compaction. Thus, crop yield reductions from a one-time application of heavy axle load traffic may have significant and long lasting effect on crop yield. Crop yield reductions due to soil compaction are most likely to occur on slowly drained high-clay soils.