Medium textured soils having a blend of sand, silt and clay particles are more likely to compact than are soils that are almost pure sand, silt or clay. Soils are most prone to compaction when the soil water status is near field capacity. Repeated cycles of freezing and thawing over the winter can be very effective in eliminating surface compaction found in the top 4 inches of soil. Grazing livestock on dry or frozen soil will not create compaction. Cracks which develop when soil is dry serve as channels for root growth and water movement to deeper depths in compacted soil.
Compaction is measured in terms of bulk density and soil strength.
Soil strength measurements are influenced by soil water content but bulk density measurements are not. Dry soils can be hard but this does not necessarily indicate that the soil is compacted. Soils that naturally have a high bulk density cannot be improved much by subsoiling. Compaction of the tilled zone can accelerate water runoff and soil erosion on steep land. Sandy soil may benefit from a small amount of compaction because drainage will be slowed.