Excessive surface soil compaction will reduce water movement into the soil. This causes ponding of water in wheel tracks for long periods, as shown in the picture. Research has shown that the infiltration rate for a moist silt loam soil will be reduced to one-tenth when the pressure is doubled, Figure 1. Slower rates of infiltration means slower recharge of soil moisture during rainfall or surface irrigation.
Reduced infiltration will cause water ponding for longer periods following rainfall on a field with surface depressions. Once depressions are full, there will be more surface runoff because of the slower infiltration rate. On sloping land, the increased runoff will increase the risk of erosion.
Of course, all compaction isn't bad. Land that has just been plowed is generally too loose for a good seed bed. The soil is "worked," or compacted in order to get good seed/soil contact. Researchers in Sweden have determined relative crop yield versus degree of soil compactness, Figure 2. They find the normal con dition in their autumn plowed fields in spring is slightly less dense than optimum in the plow layer.
Generally, surface compaction only effects one crop year if the field is plowed before the next crop. Some soils recover from compaction as a result of freezing and thawing or wetting and drying cycles. Three tons per axle tracks on the entire field reduced yields only one year in Finland.