Macropore

Macropores increase the hydraulic conductivity of soil, allowing water to infiltrate and drain quickly, and shallow groundwater to move relatively rapidly via lateral flow.

Macropores can also be found in soil between larger individual mineral particles such as sand or gravel.

Macropores can be formed under the influence of physical processes such as wet/dry and freeze/thaw cycles, which result in cracks and fissures of soils.

They can also be formed under biological processes where plant roots and soil organisms play an important role in their formation.

For example, plant roots create large spaces between soil aggregates with their growth and decay.

They allow free movement of water and air, influence transport of chemicals and provide habitats for soil organisms.

Connected macropores create these paths and result in the so-called preferential flows[5] in soils.

[7] This can be a concern especially to some land uses such as agricultural activities,[8] as it leads to issues regarding the effectiveness of irrigation and fertilization as well as impacts of environmental pollution.

For example, excessive nitrate converted from nitrogen fertilizers can be washed into groundwater under heavy rainfall or irrigation.

Therefore, the characteristics of these macropore networks can have significant influences on their functions in soils, especially in relation to water movement, aeration, and plant root growth.

This is particularly true to soils that are constantly subject to human disturbance, such as tilled agricultural fields where the shape and size of macropores can be altered by tillage.

[14] Compacted soils, for example in forest landings, usually have a low macropore proportion (macro-porosity) with impeded water movement.