Argillipedoturbation, sometimes referred to as self-mulching, is a process of soil mixing caused by the shrinking and swelling of the
smectite
A smectite (from ancient Greek ''σμηκτός'' smektos 'lubricated'; ''σμηκτρίς'' smektris 'walker's earth', 'fuller's earth'; rubbing earth; earth that has the property of cleaning) is a mineral mixtures of various swelling sheet sil ...
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
s contained in the soil.
It is an effect specific to soils of the
vertisol
A vertisol, or vertosol, is a soil type in which there is a high content of expansive clay minerals, many of them known as montmorillonite, that form deep cracks in drier seasons or years. In a phenomenon known as argillipedoturbation, alternat ...
ic variety, and is triggered by the constant cycles of wetting and drying
It is characterized by wide (up to ), deep ( or more) vertical cracks in the
solum
The solum (plural, sola) in soil science consists of the surface and subsoil layers that have undergone the same soil forming conditions. The base of the solum is the relatively unweathered parent material.
Solum and soils are not synonymous. Som ...
that contain differing materials from the rest of the soil layer they are found in, as well as sloughed-in surface materials.
In order for argillipedoturbation to occur, the soil must be at least 30% clay content.
The expression of argillipedoturbation depends to a large degree on the exact clay content of the soil, as well as on what other minerals make up the soil composition.
Argillipedoturbation can be strong enough that it can affect the
soil horizon
A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...
s by combining the different horizons, making them difficult to distinguish. It can also result in a gently-rolling surface referred to as
gilgai
A gilgai is a small, ephemeral lake formed from a depression in the soil surface in expanding clay soils. Additionally, the term "gilgai" is used to refer to the overall micro-relief in such areas, consisting of mounds and depressions, not just th ...
topography and in the dramatic soil inclusions known as
slickenside
In geology, a slickenside is a smoothly polished surface caused by frictional movement between rocks along a fault. This surface is typically striated with linear features, called slickenlines, in the direction of movement. Geometry of slickens ...
s.
In addition, argillipedoturbation sometimes results in a
chernozemic-like A-type horizon, or one resembling a
gleysolic order soil.
This process can also affect the distribution of rock fragments, by moving fragments at the surface to lower soil layers and vice versa.
The effects of this process are useful in agriculture, as the organic surface materials fertilize the soil and cause them to become very productive when irrigated. However, they are very difficult to plow and manage due to the high, thoroughly mixed clay content.
References
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Soil mechanics