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Table of Contentsxxx 9) Soil
MorphologyFurther Reading:
Auerswald K., H. Stanjek, J.M. Bigham. 1997. Soils and Environment: Soil Processes from Mineral to Landscape Scale, Reiskirchen, Germany, Catena.
Lal R., B.A. Stewart (eds.). 1994. Soil Processes and Water Quality. Boca Raton, FL Lewis Publishers.
Sheila R. 1989. Soil Processes: A Systematic Approach. London, New York, Routledge.
Wilding L.P., N.E. Smeck, and G.F. Hall (eds.). 1983. Pedogenesis and Soil Taxonomy. I. Concepts and Interactions. Elsevier, New York.
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This chapter lists the most important processes responsible for soil formation in an alphabetical order.
Adsorption: It occurs when the attractive forces between the
solid soil surface (adsorbent) and the solution component (adsorbate)
overcomes both the attractive forces between the solution component
and the soil solution (solvent), as well as any repulsive forces
between the soil surface and the adsorbing species.
Aggregation: Particles held
together in units of varying size and shape by physical, chemical,
and biological sub-processes. Aggregates are separated from adjoining
aggregates by surfaces of weakness.
Alkalization: Accumulation
of Na ions; formation of a natric horizon.
Audification: Accumulation
of H+ ions.
Carbonation (calcification):
Accumulation of calcium carbonate; formation of calcic or petroclacic
horizons.
Chelation: Forming complexes
with metals by organic agents. The metals are trapped in a ring
structure, which is very stable.
Compaction: The physical
reduction of the air content resulting in an increased bulk density.
Cryoturbation: Mixing of
soil by low temperatures, e.g. to disrupt horizons, to incorporate
organic matter into lower horizons, and to orient stones.
Dealkalization
(solodization): Movement of Na ions out of a section of the
profile.
Decarbonation
(decalcification): Movement of calcium carbonate out of a section
of the profile.
Decomposition: The
biochemical breakdown of mineral and organic material.
Dehydration: Loss of water
reverting the compound to the original state.
Deposition is the
sedimentation of transported material:
Accumulation of soil particles /
colluvium
Accumulation of nutrients /
increase of CEC
Relative enrichment of medium-sized
particles
Desalinization: Movement of
soluble salts out of a section of the profile.
Desilication: Movement of
silica out of a section of the profile.
Diffusion (into and out of
the soil): Air exchanges between the atmosphere and the soil under
the effects of partial pressures of mass movement.
Disaggregation: Breaking
down of aggregates.
Dispersion: The process
where soil structural elements break down in water and separate into
their constituents.
Eluviation: Movement of
material out of a section of the soil profile (literally washing away
of material); depletion of the material washed away (e.g.
sequioxides, clay minerals, organic material)
Energy influx / outflux:
Radiation absorption / reflection:
Soil temperature
Microbiological activity ->
humification ,decomposition, mineralization
Evaporation
Soil moisture
Erosion is the transport of
soil particles (and organic matter) by water or wind.
Raindrop impact causes breakdown of
soil aggregates
Soil movement / removal of the A
horizon
Smoothing or levelling of the soil
surface
Loss of nutrients / decrease of CEC
Selective particle transport
results in the relative enrichment of coarse and fine particles and
depletion of medium-sized particles
Reduced infiltration / increase in
surface runoff / reduced soil moisture
Sealing of the soil surface
Ferrugination: Development
of brown, reddish brown, and reddish soil colors.
Flocculation: It is a
process where the individual particles of clay are coagulated to form
floccular aggregates.
Gleization: It involves the
reduction of iron and its segregation into redoximorphic features, or
its removal by leaching form the gleyed horizon; process occuring in
poorly drained soil.
Humification: Formation of
humus from raw organic materials.
Hydration: Absorption of
water to form a new compound which differs only slightly from the
original state
Hydrolysis: The replacement
of cations in a mineral structure .by hydrogen ions from the soil
solution.
Illuviation: Movement of material into a section of the soil
profile (literally washing into or towards); accumulation of material
washed into (e.g. sequioxides, clay minerals, organic material)
Induration: Hardening of a
section of the profile produced in association with iron pans and
plinthite, and with other cementing agents (Si or Ca).
Infiltration: The entry of
water into the soil surface
Rainwater infiltrates in the soil
with soluble and suspended matter.
Soil moisture
Interflow (Subsurface flow,
through flow, seepage): Lateral subsurface flow.
Lessivage: Physical downward
movement of clay minerals.
Leucinization
(decoloration): Lightening the color in a section of the profile
- formation of an albic horizon.
Melanization: Darkening the
color of light-colored mineral initial unconsolidated material by
mixture and accumulation of organic matter; formation of a mollic
horizon due to incorporation of organic matter.
Mineralization: Release of
minerals in various forms during the decomposition of organic matter.
Neutralization:
Counteraction of the H+ ions.
Outflow: Loss of water from
the pedosphere to the groundwater. Loss of water and soluble
and suspended matter from the system, i.e. loss from the soil zone
(unsaturated and saturated zone) into the groundwater.
Oxidation: Formation of an
oxide or the release of electrons.
Pedoturbation: The churning
and disruption of horizon formation by biological, physical and to
some extent chemical activity, such as wetting and drying, swelling
and contraction, freezing and thawing, root pressures, animal
burrowing, acitivty of man.
Podzolization: Process by which
sequioxides are translocated in a soil profile. The soluble ferrous
iron forms ate the sites of eluviation, and the insoluble ferric iron
forms at the point of illuviation. Podzolization is a soil forming
process resulting in the genesis of Podzols.
Precipitation: Separation
and deposition of a substance in a solid form from a solution.
Reduction: Loss of oxygen
ions or acceptance of electrons.
Salinization: Accumulation
of soluble salts such as chlorides and sulphates of Ca, Mg, Na, or K.
Silication: Accumulation of
silica.
Solifluction: Slow flow of
saturated soil on a permanent frozen soil (permafrost table).
Solution: Dissolving of
minerals into solution (e.g. calcium carbonate into bicarbonate).
Surface crusting (soil
sealing): A process which results in the formation of soil crusts
on the soil surface, ranging in thickness from a few mm to perhaps as
much as 3 cm, that is much mor compact, hard and brittle, when dry,
than the material immediately beneath.
Surface runoff (overland
flow): Discharge of rainwater over the surface of the land.
Surface runoff is composed of unconcentrated and concentrated flow.
Suspension: The floating of
dispersed particles in a medium like water. It is one of the states
of particle transport of eroded sediments, especially for the smaller
and lighter particles such as clay.
Synthesis: The biochemical
formation of a new compound by combination of elements or
constituents.
Upward
movement: Movement of dissolved or suspended matter by
capillarity.
Weathering: All physical and
chemical changes produced in rocks, at or near the earth's surface,
by atmospheric agents.
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Soil is a three-dimensional body that is variable in time and space. The change of soil morphological features or soil attributes is due to processes acting continuously on soils. Processes do interact with each other, resulting in feedback reactions. For example, process x results in a soil environment that influences process y which results in a soil environment that influences process x. Soils are considered as a system or network in which interconnected processes form soil features. Because of the complexity of the soil system it is not possible to examine and descibe each process and their cause effect relationships. But it is possible to filter dominant processes in a landscape and observe their soil morphological outcome.
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