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Soil formation: processes

Simonson (1958) proposed that soil formation could be regarded as two major steps:

All processes are active to some degree in all soils. The balance between the combination of processes determines the ultimate nature of the soil profile.

Processes

Some of the major processes of soil formation within a pedon are summarized in the following table (Adapted from Buol et al., 1980. Soil Genesis and Classification. The Iowa State University Press, Ames).

ProcessCategoryBrief Description
EluviationTransferMovement of material out of a horizon
IlluviationTransferMovement of material out of a horizon
DecalcificationTransferReactions that remove CaCO3 from a horizon
CalcificationTransferProcesses leading to accumulation of CaCO3
DesalinizationTransferRemoval of soluble salts in a horizon
SalinizationTransferAccumulation of soluble salts in a horizon
SolonizationTransferAccumulation of sodium salts in a horizon
SolodizationTransferLeaching of sodium salts from a horizon
LeachingTransferRemoval of soluble material from the soil
LessivageTransferPhysical transfer of clay within the solum
PedoturbationTransferPhysical churning and mixing of soil material
PodzolizationTransferChemical migration of iron, aluminum, and SOM within the solum
GleizationTransferReduction of Fe3+ to Fe2+ under anaerobic conditions and transfer of Fe2+
DesilicationTransferChemical migration of silica out of the solum leaving iron and aluminum minerals behind
MelanizationTransferDarkening of A horizon material by addition and mixing of SOM
DecompositionTransferBreakdown and loss of minerals and SOM
MineralizationTransferRelease of inorganic material through decomposition of organic matter
PaludizationTransferAccumulation of organic materials under anaerobic conditions (Organic soils)

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