In order to understand better what the shrinking causes, soil pores must be defined. Pore spaces, also called voids, are the portion of the soil volume not occupied by mineral or organic solids. These pores are the result of irregular shapes of particl es in the soil structure. The passage of equipment over the soil surface is generally involved in the modern agricultural reason for soil compaction. This usage creates the possibility of increased bulk densities, or increased soil compaction and destruction of t he soil structures.
Compaction reduces the porosity and increases the bulk density of soils.
Because of this, permeability is then affected and declines, making it hard for aeration and water infiltration through the soil. This can be caused by a number of agricultural activities that induce the affect on soil compaction. The worst compaction occurs when heavy eq uipment is used on the fields, compressing the subsoil, leading to subsoil compaction. Such a heavy load as this on wet soil causes deep compaction that will seriously reduce crop yields. Compaction has varying affects on crop yields.