Soil compaction (agriculture)

Soil compaction, also known as soil structure degradation/degragation, is the increase of bulk density or decrease in porosity of soil due to externally or internally applied loads. Compaction can adversely affect nearly all physical, chemical and biological properties and functions of soil. Together with soil erosion, it is regarded as the "costliest and most serious environmental problem caused by conventional agriculture."

In agriculture, soil compaction is a complex problem in which soil, crops, weather and machinery interact. External pressure due to the use of heavy machinery and inappropriate soil management can lead to the compaction of subsoil, creating impermeable layers within the soil that restrict water and nutrient cycles. This process can cause on-site effects such as reduced crop growth, yield and quality as well as off-site effects such as increased surface water run-off, soil erosion, greenhouse gas emissions, eutrophication, reduced groundwater recharge and a loss of biodiversity.

Unlike salinization or erosion, soil compaction is principally a sub-surface problem and therefore an invisible phenomenon. Special identification methods are necessary to locate, monitor and manage the problem appropriately.

Top soil compaction is considered partly reversible and its occurrence controllable. Subsoil compaction, however, is regarded as the major problem because it can be permanent, meaning the pore functions can potentially not be restored after deterioration. Since farmers in modern intensive agriculture depend on heavy machinery and therefore cannot completely avoid compaction, soil compaction management approaches focus on mitigation. Attempts to mitigate soil compaction include biological, chemical and technical approaches. Long-term public policies can tackle the underlying reasons for soil compaction. For instance, subsidies for low-tech agriculture may decrease heavy machinery use on the field, and educational programs aiming at slowing population growth can lower the pressure on agriculture caused by population size.

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