Soil forming process

1. Soil Forming process

2. • The soil forming process are very complex
because of simultaneously operating various
chemical, mechanical and biological reactions.
• There are generally two categories of
pedogenic process involved in the formation
of well developed or mature soil ie., basis or
fundamental and specific pedogenic process.

3. • Basis or fundamental processes involved in soil
formation are additions, losses and transformation of
organic and mineral matter.
• All these processes promote horizon differentiation.

4. Basis or fundamental processes
• Additions: Materials added to the soil, such as
decomposing vegetation and organisms
(organic matter--OM), or new mineral
materials deposited by wind or water.
• Losses: Through the movement of wind or
water, or uptake by plants, soil particles (sand,
silt, clay, and OM) or chemical compounds can
be eroded, leached, or harvested from the
soil, altering the chemical and physical
makeup of the soil.

5. • Transformations: The chemical weathering of
sand and formation of clay minerals,
transformation of coarse OM into decay
resistant organic compounds (humus).
• Translocations: Movement of soil constituents
(organic or mineral) within the profile and/or
between horizons. Over time, this process is
one of the more visibly noticeable as
alterations in color, texture, and structure
become apparent.

6. Specific or pedogenic processes
• Basis or fundamental processes bring about
certain specific processes by means of a
variety of reactions like calcifictaion,
decalcifictaion,podzolizaion, laterization,
salinization, gleization and alkalization etc.

7. • Humification – is the process of
decomposition of organic matter and
synthesis of new organic substances
• Calcifictaion and gypsification are soil of
process of arid and semi arid regions and refer
to the formation and accumulation of calcium
carbonate and gypsum respecively.

8. • Eluviation - here soil particles held in
suspension, such as clay, are removed (eg.
washed away).
• Illuviation - here soil particles held in
suspension, such as clay, are accumulated (eg.
deposited).

9. • Leaching - leaching is the removal of soluable
components of the soil column. As water
washes down through the soil it can carry
away bases such as calcium, held as
exchangeable ions in clay-humus complexes,
as well as acidification through the
substitution of hydrogen ions.

10. • Podsolisation - podsolisation occurs when
strongly acid soil solutions cause the
breakdown of clay minerals.
• As a result silica, aluminium and iron form
complexes with organic substances in the soil.
These minerals are removed from the surface
zone of the soil and can accumulate in distinct
dark sub-surface layers - very evident on
inspection.
• Upland heaths and moors often contain
podsols.

11. • Gleying - gleying occurs in waterlogged, anaerobic
conditions when iron compounds are reduced and
either removed from the soil, or segregated out as
mottles or concretions in the soil. Marshy wetlands
often contain gleyed soils.
• Argillation – dispersed clay particle upper to the are
migrated from upper to the lower soil horizons
resulting a texural horizon

12. • Laterization – Process of removal of silica and
accumulation 0f sesquioxide.
• Calcification- Process of precipitation and
accumulation of calcium carbonate in soil.
• Salinization- Process of accumulation of white
crust of soluble salts of sulphates and
chlorides of Mg, K & Na.
• Alkalization - Process of accumulation of Na
on the exchange complex of soil resulting in
formation of alkali soil.
• Pedoturbation- Process of moxing in the soil
body

13. • It is important to realise also that soil types are
closely related to the shape of the landscapae - or its
'topography'. Soil scientists use this to help them
create soil maps. An experienced eye can determine
changes in underlying soil types when walking
through a landscape and observing changes in
topography (and often vegetation too).