Soil compaction refers to the formation of dense layers of well packed soil, often at the bottom of the cultivated layer. The most common causes of soil compaction are tractors, harvesting equipment and implement wheels travelling over moist, loose soils. Soils tend to be more compacted deeper into the soil due to the weight of overlaying soil above. Compacted soil has smaller pores, less pore continuity and greater strength, making it less suitable for growing crops.