Soil compaction is the result of soil particles moving closer together due to applied loads. This is measured by an increase in soil bulk density and soil strength and the end result is a reduction in large pores and an increase in small pores in the soil. Large pores decrease as a result of the rearrangement of soil particles and as points of contact between soil particles increase. Pore continuity decreases, which affects water movement through the soil, aeration of the soil and root growth. The amount of soil compaction depends on the initial soil water content, the number of passes and the soil condition.
Water acts a a lubricant and facilitates particle movement.
Under dry soil conditions less soil compaction occurs since there is less water to act as a lubricant and the suction of the water in small pores between soil particles can increase resistance to soil movement. Subsequent passes result in less compaction. To lessen the effect of traffic on subsoil compaction, manufacturers snould consider adding more axles to share the load, thereby reducing the load on individual axles. Using large diameter tyres will also reduce the compaction effect and improve mobility. To restrict soil compaction the adoption of controlled traffic is essential.