Note how water does not infiltrate where soil is compacted under the tire tracks. Photo credit: University of Minnesota

Soil Compaction

Soil compaction occurs when soil particles are pressed together by an applied force, reducing the pore space between the particles and damaging the structure of the soil. This is important because the structure determines the ability of a soil to hold and conduct water, nutrients, and air necessary for plant root activity.

Soil compaction is a serious problem in agricultural soils. It has become more of a problem in recent years due to increased equipment size and lack of crop rotations. In continuous monoculture, more tillage passes may be needed to control weeds and bury crop residue that could foster diseases. Increased vehicle traffic increases the potential for compaction.

 

Causes of soil compaction

• Raindrop impact is a natural cause of soilcompaction usually seen as a soil crust.
• Continuous moldboard plowing or disking at the same depth will cause serious tillage pans (compacted layers) just below the depth of tillage in some soils.
• Wheel traffic is considered the main cause of soil compaction. With increasing farm size, the window of time in which to get these operations done in a timely manner is often limited. According to the University of Minnesota, the weight of tractors has increased from less than 3 tons in the 1940's to approximately 20 tons today. This is of special concern because spring planting is often done before the soil is dry enough to support the heavy planting equipment.
• Minimal crop rotation eliminates the beneficial effects that different rooting systems have on breaking up subsoil compaction. Monoculture also increases the potential for compaction early in the season, due to more tillage activity and field traffic.

For more information,  please read

Soil Compaction, Causes, Effects and Control
University of Minnesota

Soil Compaction, Causes, Concerns and Cures
University of Wisconsin (pdf format)

Soil Compaction, Problems and Solutions
Kansas State University (pdf format)

Management to Minimize Soil Compaction - Nebraska (pdf)