Soil formation and topography A Lecture By Allah Dad Khan Agri Expert KPK

1. bismillahi al r-rahmani al r-rahim

2. A
Presentation By
Mr. Allah Dad Khan Agriculture
Adviser Sohni Dharti TV KPK
Bureau

3. of geoscience and planetary
science comprising the study
of surface shape and features of
the Earth and other observable astronomical
objects including planets, moons,
and asteroids. It is also the description of
such surface shapes and features (especially
their depiction in maps). The topography of
an area could also mean the surface shape
and features themselves

12. 1.Climate and soil formation
2.Biota and soil formation
3.Parent Material and soil formation
4.Time and soil formation
5.Organisms and soil formation
6.Topography and soil formation

13. 1. Arid : Minimal leaching, slow dissolu
2. Humid: Extensive leaching, rapid Extensive
leaching, rapid dissolution dissolution
3. Cool : Active physical weathering, slow
Active physical weathering, slow chemical
weathering. Buildup of OM.
4. Warm: Strong chemical weathering, rapid
Strong chemical weathering, rapid OM
decay (nutrient cycling) OM decay (nutrient
cycling)

14. Climate is dominant factor in soil formation,
climate influence soil formation largely
through precipitation and temp and air.

15. Precipitation:
I. i. It primarily regulates the moisture air regime of the
soil and determines the leading trends in soil profile
depending upon available percolating water.
II. ii. Rainfall also affects profile development through
erosion producing thin soils on steep slopes and
deposition of soil material down hill.
III. iii. The intensity, frequency and distribution of
precipitation influence the course of soil formation.
IV. iv. With increasing moisture, nitrogen and carbon
content, clay content, aggregation, saturation capacity
and exchangeable hydrogen tend to increase.
V. v. Exchangeable base and pH value tends to decrease
with increasing moisture.

16. Temperature:
Temperature affects the velocity of chemical reactions,
which approximately doubles for every 100C increase in
temperature. It influences the organic matter
decomposition and microbial activities in soil though the
evapotranspiration phenomenon. Temperature also
determines the efficiency of rainfall. In general, with
increase in temperature the depth of weathering and clay
content show increase on the contrary nitrogen, organic
matter, silica, alumina and base alumina ratio tends to
decrease with rising temperature.

17. 1. Diversity and activity Diversity and activity
2. Plant canopy Plant canopy
a.„Root exudates promote weathering
b. Root exudates promote weathering „
c. Grasslands: Base Grasslands: Base ations
cations, humus , humus -mineral mineral
interaction (strong A horizon). interaction
(strong A horizon). „
d.Forest: Lower base saturation, less humus
a. Confers: low B.S., less incorporated OM
b. Deciduous: Higher B.S., more OM

18. A. Solid Rock
1.Basalat ( Mafic) ; High Base Saturaion
2. Granite(Felsic) : Lower Base Saturation
B. Transporated Material
1. Alluvium
2.Colluvium
c. Eolian

19. Agent Deposit
Graviy Colluvial
Water Alluvial
Marine
Lacustrine
Ice Glacial
Wind Eolian

20. Energy of water determines size of particles
transported -Flood plains, terraces (old flood
plains), deltas are rich, fertile soils
(typically) -Alluvial fans are coarser in
texture but remain productive

21. 1. Mechanical/Physical
a) Thermal expansion/contraction
b) „Freeze/thaw /Frost Widging
c) –Erosion (water, ice, wind)
d) –Biological (plant roots…)
e) Grinding of rocks/Abrasion

22. 2. Chemical
a) – Hydration
b) – Hydrolysis
c) – Acidic Decomposition
d) „Water, inorganic and organic acids
e) – Complexation Decomposition
f) „Organic acids
g) – Reductive/oxidative dissolution

23. Climate
Living Organisms
bioturbation
acid production and mineral decomposition
Time
Mineral composition
Goldich Dissolution Series
(Bowen's Reaction Series)
 Chemical Weathering Products
Clays
Metals ores
Rounding of boulders (chemical exfoliation)


24. 1. Initial – Unweathered parent material.
2. Juvenile – Weathering started but much of
the original material still Unweathered.
3. Virile – Easily weatherable mineral fairly
decomposes, clay content has increased.
4. Sensile – Decomposition reaches at final
decomposition stage only most resistance
minerals survive.
5. Final – Soil development completed under
prevailing conditions.

25. A. Recent : Little profile development (
Weakly Weathered , Little Clay movement)
Primary Minerals Present
B. Old : Well Developed Horizon
Secondary Minerals

26. The organisms living in and on the soil form distinct soil types.
Coniferous forests have acidic leaf litter that form soils classed
asinceptisols. Mixed or deciduous forests leave a larger layer of
humus, changing the elements that are either leeched or
accumulated in the soil, and thereby forming soils classed
as alfisols. Prairies have very high humus accumulation, creating
a dark, thick A horizon characteristic ofmollisols
Plant and animal activity produces humic acids that are powerful
erosion agents. Plants can physically erode as well as chemically
erode. Plants stabilize soil profiles, Animals (including man) tend
to destabilize the soil profile, increasing erosion.

27. Topography and soil formation: The prominent
types of topography designations as given in FAO
guidelines are:
1. Flat or almost flat: Land surface with slope
less than 2%
2. Undulating: Land surface with slope between
2-8%
3. Rolling: Land surface with slope between 8-
16%
4. Hilly: Land surface with slope between 16-30%
5. Steepy dissected: Land surface with slope
greater than 30%

28. 1. Warmer Drier : Less develpoped
2. Cold Wet : More Developed ,more clay
3. Shallow Soils
4. Deep Soils : Fine textured

30. Topography has a significant impact on soil formation as
it determines runoff of water, and its orientation affects
microclimate which in turn affects vegetation. For soil to
form, the parent material needs to lie relatively
undisturbed so soil horizon processes can proceed. Water
moving across the surface strips parent material away
impeding soil development. Water erosion is more
effective on steeper, un vegetated
Blue iceberg

31. 1.Transformations:Mineral weathering, OM
Mineral weathering, OM decomp
2.Translocations : Transport of inorganic and
organic material
3.Additions : OM, particles ( OM, particles
(eolian, aluvial aluvial, colluvial colluvial )
4.Losses : a. Erosión b.Leaching

32. Pedogenesis is (from the Greek pedo-, or pedon,
meaning 'soil, earth,' and genesis, meaning 'origin, birth')
be defined as the process of soil development. Late in the
19th century, scientists Hilgard in the United States and
the Russian Dukuchaev both suggested independently that
pedogenesis was principally controlled by climate and
vegetation.
This idea was based on the observation that comparable
soils developed in spatially separate areas when their
climate and vegetation were similar.

33. In the 1940s, Hans Jenny extended these ideas based on
the observations of many subsequent studies examining
the processes involved in the formation of soils. Jenny
believed that the kinds of soils that develop in a particular
area are largely determined by five interrelated
factors: climate; living organisms;parent
material; topography; and time

34. A large number of processes are responsible for the
formation of soils. This fact is evident by the large number
of different types of soils that have been classified by soil
scientists . However, at the macro-scale we can suggest
that there are five main principal pedogenic processes
acting on soils. These processes
are laterization, podzolization, calcification, salinizati
on, and gleization.

35. In this process, silica is removed while iron and alumina
remain behind in the upper surface / layers and usually
there are no well-defined horizon. Laterization is favoured
by rapid decomposition of parent rocks under climates
with high temperature and sufficient moisture for intense
leaching. Podsolization and latrization produce soils that
belong to the pedalfer (iron accumulating) group.

36. Podzolization is negative of calcification where as
calcification tends to concentrate calcium in the lower
part ‘B’ horizon podsolization reaches the entire solum.
Apart from the calcium the other bases are also removed
and the whole soil becomes distinctly acidic. Process is
mainly acid leaching.

37. It is the process of precipitation and
accumulation of calcium carbonate (CaCO3)
in some part of the profile. The
accumulation of CaCO3may result in the
development of acidic soil. Such soil
belonging to group called pedacal.

38. Salinization is a process that functions in the similar way
to calcification. It differs from calcification in that the salt
deposits occur at or very near the soil surface. Salinization
also takes place in much drier climates. Accumulation of
soluble salts under dry climate or no rainfall. Salts
accumulate on soil surface. Na+, K++, Ca++, Mg++. Soil
becomes saline due to high rate of evaporation, reclaimed
by leaching, flooding. (pH8.5) Grow salt tolerant crops,
shevri, Dhaincha.

39. It is a process of soil formation resulting in the development
of glei (or gley horizon) in the lower part of soil profile
above the parent material due to poor drainage condition
and where water logged conditions prevail such soils are
called hydromorphic soils. Gleying may be observed at any
depth depending on the depth of ground water.

40. Inversion of soil takes place in deep black cotton soils which
contain montmorillonite clay colloid (vertisol) has max
swelling shrinkage capacity. As alternate weting and
drying, expansion and contraction takes place due to
which cracks is formed. Due to crack formation A horizon
goes down and soil B horizon comes up. These are also
known as self ploughed soils. Therefore in dry farming
technique ploughing once in three years is recommended
to conserve the soil moisture and since the inversion of soil
takes place naturally there is no need of ploughing every
year.

41. It is the reverse of classification i.e. the
process of removal of CaCO3 or Ca ions from
soil by leaching.

42. Accumulation of sodium salts only like
Na2Co3 and Na2(CO3)2.

43. 1. Humification: Helps in formation of surface
layer, called Ao horizon. Its characteristics
depends upon the nature of vegetational
residue and the way it becomes decomposes
and synthesized into new organic
compounds. The percolating water passes
through this humus layer dissolves certain
organic acids affect the development of
lower A and B.

44. 2. Eluviation: Elevation means washing out. It
is a process of removal of constituents in
suspension or solution by the percolating
water from the upper to the lower layer.
Mechanical eluviation removes finer
suspended fraction of soils, producing
textural profiles by a coarse texture.

45. 3. Illuviation: The process of deposition of soil
material (Removed from the eluvial horizon)
in the lower layer is known as illuviation. The
horizons formed by this process are termed
illuvial horizons.

48. Topography generally modifies the development of soil on
a local or regional scale. Pedogenesis is primarily
influenced by topography's effect on microclimate and
drainage. Soils developing on moderate to gentle slopes
are often better drained than soils found at the bottom of
valleys. Good drainage enhances an number of pedogenic
processes of illuviation and eluviation that are
responsible for the development of soil horizons. Under
conditions of poor drainage, soils tend to be immature.

49. Steep topographic gradients inhibit the development of
soils because of erosion. Erosion can retard the
development through the continued removal of surface
sediments. Soil microclimate is also influenced by
topography. In the Northern Hemisphere, south facing
slopes tend to be warmer and drier than north facing
slopes. This difference results in the soils of the two areas
being different in terms of depth, texture, biological
activity, and soil profile development.

50. Soils tend to show a strong geographical correlation with
climate, especially at the global scale. Energy and
precipitation strongly influence physical and chemical
reactions on parent material. Climate also determines
vegetation cover which in turn influences soil
development. Precipitation also affects horizon
development factors like the translocation of dissolved
ions through the soil. As time passes, climate tends to be a
prime influence on soil properties while the influence of
parent material is less.

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